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Rochelle Buffenstein - One of the best experts on this subject based on the ideXlab platform.
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Vascular aging in the longest-living rodent, the naked mole rat.
American journal of physiology. Heart and circulatory physiology, 2007Co-Authors: Anna Csiszar, Rochelle Buffenstein, Nazar Labinskyy, Zsuzsanna Orosz, Zhao Xiangmin, Zoltan UngvariAbstract:The naked mole rat (NMR; Heterocephalus glaber) is the longest-living rodent known [maximum lifespan potential (MLSP): >28 yr] and is a unique model of successful aging showing attenuated declines ...
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A stereotaxic atlas of the brain of the naked mole-rat (Heterocephalus glaber)
Neuroscience, 2006Co-Authors: J. Xiao, Jonathan B. Levitt, Rochelle BuffensteinAbstract:The naked mole-rat (Rodentia, Bathyergidae: Heterocephalus glaber) is a strictly subterranean eusocial mammal. These rodents show a suite of morphological and physiological adaptations, including brain specializations, to this underground milieu that they have inhabited since the early Miocene. Recently, naked mole-rats have received considerable attention as the longest living rodent known, and some of these brain specializations may be potentially important to their exceptional longevity. To serve as a basis for future brain studies, we have constructed a stereotaxic atlas of the brain of this species, labeling all major brain structures.
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The Naked Mole Rat--A New Record for the Oldest Living Rodent
Science of aging knowledge environment : SAGE KE, 2002Co-Authors: Rochelle Buffenstein, Jennifer U M JarvisAbstract:We report a new record for the world's longest-lived rodent, a male naked mole rat (Heterocephalus glaber). On the basis of his weight at capture, this animal was approximately 1 year old when collected near Mtito Andei, Kenya in July/August 1974. He died in April 2002, indicating that he lived for more than 28 years. As such, his life-span surpassed the previous longevity record for a rodent, which was held by a porcupine (Hystrix brachyura) that lived for 27 years and 4 months.
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skin morphology and its role in thermoregulation in mole rats Heterocephalus glaber and cryptomys hottentotus
Journal of Anatomy, 1998Co-Authors: Joseph T M Daly, Rochelle BuffensteinAbstract:The skin structure of 2 Bathyergid rodents, the naked mole-rat (Heterocephalus glaber) and the common mole-rat (Cryptomys hottentotus) is compared, to investigate whether thermoregulatory differences may be attributed to different skin features. Histological and ultrastructural studies of the dorsal skin of these closely related species show morphological and structural similarities but differences in the degree of skin folding, thickness of the integument and dermal infrastructure were evident. The skin of the common mole-rat conforms with expected morphological/histological arrangements that are commonly found in mammalian skin. Many features of the skin of the naked mole-rat, such as the lack of an insulating layer and the loosely folded morphological arrangement contribute to poikilothermic responses to changing temperatures of this mammal. Further evidence for poikilothermy in the naked mole-rat is indicated by the presence of pigment containing cells in the dermis, rather than the epidermis, as commonly occurs in homeotherms. Lack of fur is compensated by a thicker epidermal layer and a marked reduction in sweat glands. Differences in skin morphology thus contribute substantially to the different thermoregulatory abilities of the 2 Bathyergids. The skin morphology is related to the poor thermoinsulatory ability of the animals while simultaneously facilitating heat transfer from the environment to the animal by thigmothermy and/or other behavioural means.
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metabolic and body temperature changes during pregnancy and lactation in the naked mole rat Heterocephalus glaber
Physiological and Biochemical Zoology, 1995Co-Authors: Nicole T Urison, Rochelle BuffensteinAbstract:Naked mole rats (Heterocephalus glaber) are poikilothermic, eusocial mammals in which the single dominant female breeds continuously throughout the year, producing approximately every 76 d litters of up to 27 young, with a mean litter size of 9 ± 1. We investigated the changes in metabolic rate (n = 8) and body temperature (n = 8) in breeding naked mole rat females throughout the 10-wk gestation period and during the first week of lactation. Metabolic rate from week 2 of pregnancy to parturition (1.9 ± 0.1 mL O2 ․ g⁻¹ ․ h⁻¹) was 1.4-fold higher than that of nonreproductive animals. Oxygen consumption increased in a biphasic manner, with the nadir at week 8, similar to the O₂ consumption observed in nonpregnant and very early pregnant females and statistically no different than the high rates associated with pregnancy. Oxygen consumption was maximal during lactation (3.0 ± 0.3 mL O₂ ․ g⁻¹ ․ h⁻¹) and was 160.3% of that during the initial week of pregnancy. Body temperature in early pregnancy was similar to ...
Chris G Faulkes - One of the best experts on this subject based on the ideXlab platform.
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dna methylation clocks as a predictor for ageing and age estimation in naked mole rats Heterocephalus glaber
Aging (Albany NY), 2020Co-Authors: Robert Lowe, Vk Rakyan, Amy F Danson, Selin Yildizoglu, Frederic Saldmann, Melanie Viltard, Gerard Friedlander, Chris G FaulkesAbstract:The naked mole-rat, Heterocephalus glaber (NMR), the longest-lived rodent, is of significance and interest in the study of biomarkers for ageing. Recent breakthroughs in this field have revealed 'epigenetic clocks' that are based on the temporal accumulation of DNA methylation at specific genomic sites. Here, we validate the hypothesis of an epigenetic clock in NMRs based on changes in methylation of targeted CpG sites. We initially analysed 51 CpGs in NMR livers spanning an age range of 39-1,144 weeks and found 23 to be significantly associated with age (p<0.05). We then built a predictor of age using these sites. To test the accuracy of this model, we analysed an additional set of liver samples, and were successfully able to predict their age with a root mean squared error of 166 weeks. We also profiled skin samples with the same age range, finding a striking correlation between their predicted age versus their actual age (R=0.93), but which was lower when compared to the liver, suggesting that skin ages slower than the liver in NMRs. Our model will enable the prediction of age in wild-caught and captive NMRs of unknown age, and will be invaluable for further mechanistic studies of mammalian ageing.
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eruption rates of the mandibular incisors of naked mole rats Heterocephalus glaber
Journal of Zoology, 2006Co-Authors: B K B Berkovitz, Chris G FaulkesAbstract:Naked mole-rats Heterocephalus glaber are highly social hystricomorph rodents endemic to the arid regions of East Africa. Living entirely underground, they excavate an extensive system of tunnels with their continuously growing extra-buccal incisors. The majority of the burrow is composed of foraging tunnels, constructed in search of the underground roots and tubers that form their staple diet. Subterranean foraging imposes risks associated with not finding food, and a high energetic cost, and in addition could be limited by the rate of wear of the incisor teeth. The aim of this study was to determine eruption rates for mandibular incisors in naked mole-rats to investigate whether they showed evidence of faster eruption as an adaptation to their subterranean niche and mode of digging. Impeded eruption rates (when the teeth were left in normal occlusion) were initially determined over a period of 1 week in a group of 12 naked mole-rats kept in laboratory conditions. Unimpeded eruption rates were then monitored in the same animals by cutting one mandibular incisor free of occlusion thrice weekly, and measuring growth over a 2-week period. Mean daily impeded eruption rates were c. 228.7±17.5 μm, while mean daily unimpeded rates were higher at c. 624.7±10.4 μm. While impeded eruption rates under laboratory conditions may be an underestimate of the rates occurring in the wild, unimpeded rates (usually about twice the impeded rate) indicate the maximum potential eruption rates of the teeth and are independent of functional activity. These data are not dissimilar from those determined for laboratory rodents and lagomorphs suggesting that the naked mole-rat does not display unusual patterns of eruptive behaviour. Tooth wear resulting from their subterranean lifestyle may be offset as a limiting factor by the social behaviour of the naked mole-rat, where digging activity is distributed among a large workforce during favourable burrowing conditions.
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intracolony aggression in the eusocial naked mole rat Heterocephalus glaber
Animal Behaviour, 2001Co-Authors: F M Clarke, Chris G FaulkesAbstract:Abstract In colonies of the eusocial naked mole-rat, breeding is monopolized by one dominant female (the ‘queen’) and one to three males. Aggression in the form of shoving (prolonged pushes involving nose to nose contact) is frequently observed in captive colonies and is principally initiated by breeders. It has been suggested that shoving by queens functions primarily to suppress reproduction in subordinates (threat reduction hypothesis) or to incite work activity in nonbreeding ‘helpers’ (work conflict hypothesis). We tested predictions of both hypotheses by examining shoving in five captive colonies before and after removing breeders. Shoving was strongly associated with reproductive status. The vast majority of shoves were carried out by the queen, and to a lesser extent breeding males, and the onset of reproductive activity coincided with the onset, or greatly increased rates, of shoving. No evidence for the work conflict hypothesis was found. Queens shoved high-ranking and large colony members most, a finding that does not allow discrimination between hypotheses. Those males that posed the greatest threat to the queen's reproductive dominance, namely future breeding males, were shoved most, providing some support for the threat reduction hypothesis. However, evidence that queens targeted those females that posed the greatest threat, females that were to succeed them, was equivocal. Queen shoving may have several functions, depending on social context, in inhibiting reproduction in subordinates of both sexes, maintaining social order, and in inciting work-related behaviours in colony members, all of which ultimately increase the reproductive success of queens.
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investigation of numbers and motility of spermatozoa in reproductively active and socially suppressed males of two eusocial african mole rats the naked mole rat Heterocephalus glaber and the damaraland mole rat cryptomys damarensis
Reproduction, 1994Co-Authors: Chris G Faulkes, Jennifer U M Jarvis, S N Trowell, Nigel C BennettAbstract:Reproductive tracts and spermatozoa from reproductively active and reproductively suppressed non-breeding males from two species of eusocial African mole-rats Cryptomys damarensis and Heterocephalus glaber were examined. In two captive colonies of Heterocephalus glaber, reproductive tracts from seven non-breeding males removed from their colonies, and housed singly for 5-6 weeks to cause reproductive activation, were compared with reproductive tracts from seven non-breeding males. The body weight of the separated, reproductively active males increased significantly (P < 0.01), and the mean testis weights relative to body weight of the reproductively active males were significantly larger (P < 0.05) than those of non-breeding males. The number of spermatozoa, in one half of the reproductive tract, was higher in active males than in non-breeding males (mean +/- SEM: 8.59 x 10(6) +/- 2.69 x 10(6) versus 1.78 x 10(6) +/- 1.43 x 10(6), respectively; P < 0.05). In addition, six of the seven reproductively active males, but only two of seven non-breeding males, had motile spermatozoa. A total of 28 wild Cryptomys damarensis from two colonies were examined in the field. The testis weights relative to body weight of breeding males (n = 7) were higher than those of non-breeding males (n = 19; P < 0.01), but the number of spermatozoa did not differ significantly between the two groups (0.13 x 10(6) +/- 0.06 x 10(6), n = 7 versus 0.29 x 10(6) +/- 0.14 x 10(6), n = 21, respectively). Breeding and non-breeding males produced similar numbers of motile spermatozoa.(ABSTRACT TRUNCATED AT 250 WORDS)
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evidence that primer pheromones do not cause social suppression of reproduction in male and female naked mole rats Heterocephalus glaber
Reproduction, 1993Co-Authors: Chris G Faulkes, D H AbbottAbstract:The role of chemical cues in mediating the reproductive suppression of nonbreeding males and females in colonies of naked mole-rats (Heterocephalus glaber) was examined by comparing reproductive activation in isolated nonbreeders with that of isolated nonbreeders maintained in olfactory and gustatory contact with their parent colony. Animals were either removed from their colony and paired directly with a member of the opposite sex from the same colony, or were removed, housed singly for 40 days, and then paired with a member of the opposite sex from the same parent colony that had also been housed singly for 40 days. Approximately half of these separated animals received a daily transfer of soiled bedding and litter from their parent colony. In females, there was no significant difference between the control and bedding transfer group, in the time taken from separation to the first sustained increase of urinary progesterone above 2 ng mg-1 Cr indicative of the luteal phase of an ovarian cycle (7.8 +/- 2.6 versus 9.4 +/- 2.0 days, respectively). In both control and bedding transfer groups, singly-housed females commenced ovarian cyclicity, revealing that the presence of a male was not required for reproductive activation and ovulation. In males, concentrations of both urinary testosterone and plasma LH increased after separation from their parent colonies in both control and bedding transfer groups, to reach values equivalent to those of breeding males.(ABSTRACT TRUNCATED AT 250 WORDS)
Nigel C Bennett - One of the best experts on this subject based on the ideXlab platform.
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naked mole rats Heterocephalus glaber do not specialise on cooperative tasks
bioRxiv, 2021Co-Authors: S Siegmann, Nigel C Bennett, Daniel W. Hart, R Feitsch, Dustin J Penn, M ZoettlAbstract:It has been proposed that naked mole-rat (Heterocephalus glaber) societies resemble those of eusocial insects by showing a division of labour among non-breeding individuals. Earlier studies suggested that non-breeders belong to distinct castes that specialise permanently or temporarily on specific cooperative tasks. In contrast, recent research on naked mole-rats has shown that behavioural phenotypes are continuously distributed across non-breeders and that mole-rats exhibit considerable behavioural plasticity suggesting that individuals may not specialise permanently on work tasks. However, it is currently unclear whether individuals specialise temporarily and whether there is a sex bias in cooperative behaviour among non-breeders. Here we show that non-breeding individuals vary in overall cooperative investment, but do not specialise on specific work tasks. Within individuals, investment into specific cooperative tasks such as nest building, food carrying and burrowing are positively correlated, and there is no evidence that individuals show trade-offs between these cooperative behaviours. Non-breeding males and females do not differ in their investment in cooperative behaviours and show broadly similar age and body mass related differences in cooperative behaviours. Our results suggest that non-breeding naked mole-rats vary in their overall contribution to cooperative behaviours and that some of this variation may be explained by differences in age and body mass. Our data provide no evidence for temporary specialisation, as found among some eusocial insects, and suggests that the behavioural organisation of naked mole-rats resembles that of other cooperatively breeding vertebrates more than that of eusocial insect species.
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Cultural transmission of vocal dialect in the naked mole-rat.
Science (New York N.Y.), 2021Co-Authors: Alison J. Barker, Nigel C Bennett, Grigorii Veviurko, Daniel W. Hart, Lina Mograby, Gary R. LewinAbstract:Naked mole-rats (Heterocephalus glaber) form some of the most cooperative groups in the animal kingdom, living in multigenerational colonies under the control of a single breeding queen. Yet how they maintain this highly organized social structure is unknown. Here we show that the most common naked mole-rat vocalization, the soft chirp, is used to transmit information about group membership, creating distinctive colony dialects. Audio playback experiments demonstrate that individuals make preferential vocal responses to home colony dialects. Pups fostered in foreign colonies in early postnatal life learn the vocal dialect of their adoptive colonies, which suggests vertical transmission and flexibility of vocal signatures. Dialect integrity is partly controlled by the queen: Dialect cohesiveness decreases with queen loss and remerges only with the ascendance of a new queen.
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Changes in prolactin, cortisol and testosterone concentrations during queen succession in a colony of naked mole-rats (Heterocephalus glaber): a case study
The Science of Nature, 2019Co-Authors: Katarina Medger, Nigel C Bennett, Stefanie B. Ganswindt, Andre Ganswindt, Daniel W. HartAbstract:Colonies of naked mole-rats ( Heterocephalus glaber , NMRs) are characterised by an extreme skew in lifetime reproductive success with only one female and one to three male consorts in a colony. The rest of the individuals in a colony are reproductively suppressed and much research has been focussed on elucidating that mechanism. The dopamine system and prolactin have recently been implicated in the suppression of reproduction of subordinate NMRs. To investigate the changes in prolactin during the removal of an aged reproductive female (queen) and succession of a new queen, blood samples were collected during different stages of queen removal: before queen removal, after separation, but in olfactory contact with the queen and after the total removal of the queen. Further, plasma cortisol and testosterone concentrations were determined. The colony appeared unstable prior to queen removal as indicated by high concentrations of cortisol and testosterone and lack of successful breeding. A new queen succeeded the old queen whilst she was still in olfactory contact. The time preceding queen succession was characterised by high levels of aggression, the death of a number of individuals, high cortisol and testosterone and low prolactin concentrations. Once the older queen was removed entirely and the new queen had given birth, prolactin concentrations increased and cortisol and testosterone concentrations decreased in subordinate NMRs. The results suggest that low prolactin levels are associated with low reproductive suppression during times of colony instability due to the removal or death of a queen.
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fructose driven glycolysis supports anoxia resistance in the naked mole rat
Science, 2017Co-Authors: Thomas J Park, Jane Reznick, Bethany L Peterson, Damir Omerbasic, Nigel C Bennett, Henning P J L Kuich, Christin Zasada, Brigitte M Browe, Gregory R C Blass, Wiebke HamannAbstract:The African naked mole-rat’s (Heterocephalus glaber) social and subterranean lifestyle generates a hypoxic niche. Under experimental conditions, naked mole-rats tolerate hours of extreme hypoxia and survive 18 minutes of total oxygen deprivation (anoxia) without apparent injury. During anoxia, the naked mole-rat switches to anaerobic metabolism fueled by fructose, which is actively accumulated and metabolized to lactate in the brain. Global expression of the GLUT5 fructose transporter and high levels of ketohexokinase were identified as molecular signatures of fructose metabolism. Fructose-driven glycolytic respiration in naked mole-rat tissues avoids feedback inhibition of glycolysis via phosphofructokinase, supporting viability. The metabolic rewiring of glycolysis can circumvent the normally lethal effects of oxygen deprivation, a mechanism that could be harnessed to minimize hypoxic damage in human disease.
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a case of natural queen succession in a captive colony of naked mole rats Heterocephalus glaber
African Zoology, 2013Co-Authors: L A Van Der Westhuizen, Jennifer U M Jarvis, Nigel C BennettAbstract:Naked mole-rats occur in large colonies where usually a single queen monopolizes reproduction. Queen succession occurs from within usually as a result of aggressive encounters with subordinate females that queue for reproductive succession following colony instability, which inevitably results in death of either the queen or the challenging conspecific. We monitored a queen succession following the death of the breeding male in a colony of the naked mole-rat, Heterocephalus glaber, prior to, during as well as after replacement of the original breeding female. The response of the pituitary luteotrophs was investigated in the non-reproductive females during this period of instability by the administration of endogenous gonadotrophin releasing hormone (GnRH) and evaluating the subsequent luteinising hormone (LH) response in the blood. Larger and older non-breeding females engaged in aggressive encounters that culminated in death. The new breeding successor which arose from within the colony was a large femal...
Klas S. P. Abelson - One of the best experts on this subject based on the ideXlab platform.
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the effects of clonidine and yohimbine in the tail flick and hot plate tests in the naked mole rat Heterocephalus glaber
BMC Research Notes, 2021Co-Authors: Titus I. Kanui, Royford M Mwobobia, Klas S. P. AbelsonAbstract:Objective The naked mole rat (NMR) (Heterocephalus glaber) is increasingly considered an important biomedical research model for various conditions like hypoxic brain injury, cancer and nociception. This study was designed to investigate the effects of clonidine and yohimbine, an alpha-2 (α2) adrenoceptor agonist and antagonist respectively in the tail flick and hot plate tests. Results A significant difference in tail flick latency was noted between saline control and 30 µg/kg clonidine, which was reduced after administration of 30 µg/kg yohimbine. A significant difference in hot plate latency was also noted between saline control and 30 µg/kg clodinine during the periods 30, 45, 60, 75 and 90 min after administration, and between saline control and 10 µg/kg clonidine during 30 min after administration. The hot plate latency by 30 µg/kg clonidine was also reduced by 30 µg/kg yohimbine during 30 min after administration. Since the tail-flick and hot plate tests mediate the effects at spinal and supraspinal levels respectively, the present study indicates the presence and involvement of noradrenergic receptors in thermal antinociception at spinal and supraspinal levels of the NMR, similar to what has been found in other mammals.
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imiquimod does not elicit inflammatory responses in the skin of the naked mole rat Heterocephalus glaber
BMC Research Notes, 2020Co-Authors: Titus I. Kanui, Mosiany Letura Kisipan, Rodi O Ojoo, Klas S. P. AbelsonAbstract:Naked mole rat (Heterocephalus glaber) has recently attracted interest in biomedical research due to its exceptional longevity, cancer resistance and tolerance to potentially harmful conditions or stimuli. Given its unique attributes, this study was designed to characterize inflammatory skin reactions of this animal to topical application of imiquimod, a toll-like receptor 7 and 8 agonist that triggers psoriasis-like skin reaction. Imiquimod did not cause the expected psoriasis-like skin changes. There was no epidermal thickening and a straight epidermo-dermal boundary was maintained. There was no parakeratosis and the granular layer of epidermis was well formed. In the dermis, there was no leukocyte infiltration. This points to an exceptional nature of inflammatory/immune responses of this animal, but the mechanism could not be explained by our results. Naked mole rat could be a valuable negative model for studying psoriasis and other inflammatory skin conditions but as a prerequisite, there is need for further investigations to establish the mechanisms behind its lack of response to imiquimod.
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Investigation of the presence and antinociceptive function of muscarinic acetylcholine receptors in the African naked mole-rat (Heterocephalus glaber)
Journal of Comparative Physiology A, 2016Co-Authors: Kristine B. Jørgensen, Titus I. Kanui, Karen Krogh-jensen, Darryl S. Pickering, Klas S. P. AbelsonAbstract:The present study investigated the cholinergic system in the African naked mole-rat ( Heterocephalus glaber ) with focus on the muscarinic acetylcholine receptor subtypes M_1 and M_4. The protein sequences for the subtypes m _ 1–5 of the naked mole-rat were compared to that of the house mouse ( Mus musculus ) using basic local alignment search tool (BLAST). The presence and function of M_1 and M_4 was investigated in vivo, using the formalin test with the muscarinic receptor agonists xanomeline and VU0152100. Spinal cord tissue from the naked mole-rat was used for receptor saturation binding studies with [^3H]-N-methylscopolamine. The BLAST test revealed 95 % protein sequence homology showing the naked mole-rat to have the genetic potential to express all five muscarinic acetylcholine receptor subtypes. A significant reduction in pain behavior was demonstrated after administration of 8.4 mg/kg in the formalin test. Administration of 50 mg/kg VU0152100 resulted in a non-significant tendency towards antinociception. The antinociceptive effects were reversed by the muscarinic acetylcholine receptor antagonist atropine. Binding studies indicated presence of muscarinic acetylcholine receptors with a radioligand affinity comparable to that reported in mice. In conclusion, muscarinic acetylcholine receptor subtypes are present in the naked mole-rat and contribute to antinociception in the naked mole-rat.
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The Effects of Oxotremorine, Epibatidine, Atropine, Mecamylamine and Naloxone in the Tail-flick, Hot-plate, and Formalin Tests in the Naked Mole-rat (Heterocephalus glaber)
In vivo (Athens Greece), 2014Co-Authors: Thomas D. Dulu, Titus I. Kanui, P.k. Towett, Geoffrey M. O. Maloiy, Klas S. P. AbelsonAbstract:The naked mole-rat (Heterocephalus glaber) is a promising animal model for the study of pain mechanisms, therefore a thorough characterization of this species is essential. The aim of the present study was to establish the naked mole-rat as a model for studying the cholinergic receptor system in antinociception by investigating the involvement of muscarinic, nicotinic and opioid receptors in nociceptive tests in this species. The effects of systemic administration of the muscarinic receptor agonist oxotremorine and the nicotinic receptor agonist epibatidine were investigated in the tail-flick, the hot-plate, and the formalin tests. The effects of co-administration of the muscarinic receptor antagonist atropine, the nicotinic receptor antagonist mecamylamine, and the opioid receptor antagonist naloxone were also investigated. Oxotremorine and epibatidine induced a significant, dose-dependent antinociceptive effect in the tail-flick, hot-plate, and formalin tests, respectively. The effects of oxotremorine and epibatidine were blocked by atropine and mecamylamine, respectively. In all three nociceptive tests, naloxone in combination with oxotremorine or epibatidine enhanced the antinociceptive effects of the drugs. The present study demonstrated that stimulation of muscarinic and nicotinic receptors produces antinociceptive effects in the naked-mole rat. The reversal effect of atropine and mecamylamine suggests that this effect is mediated by cholinergic receptors. As naloxone increases the antinociceptive effects of cholinergic agonists, it is suggested that the cholinergic antinociception acts via a gateway facilitated by opioid receptor blockage; however, the precise interaction between these receptor systems needs further investigation.
Thomas J Park - One of the best experts on this subject based on the ideXlab platform.
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fructose driven glycolysis supports anoxia resistance in the naked mole rat
Science, 2017Co-Authors: Thomas J Park, Jane Reznick, Bethany L Peterson, Damir Omerbasic, Nigel C Bennett, Henning P J L Kuich, Christin Zasada, Brigitte M Browe, Gregory R C Blass, Wiebke HamannAbstract:The African naked mole-rat’s (Heterocephalus glaber) social and subterranean lifestyle generates a hypoxic niche. Under experimental conditions, naked mole-rats tolerate hours of extreme hypoxia and survive 18 minutes of total oxygen deprivation (anoxia) without apparent injury. During anoxia, the naked mole-rat switches to anaerobic metabolism fueled by fructose, which is actively accumulated and metabolized to lactate in the brain. Global expression of the GLUT5 fructose transporter and high levels of ketohexokinase were identified as molecular signatures of fructose metabolism. Fructose-driven glycolytic respiration in naked mole-rat tissues avoids feedback inhibition of glycolysis via phosphofructokinase, supporting viability. The metabolic rewiring of glycolysis can circumvent the normally lethal effects of oxygen deprivation, a mechanism that could be harnessed to minimize hypoxic damage in human disease.
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growth deficient vomeronasal organs in the naked mole rat Heterocephalus glaber
Brain Research, 2007Co-Authors: Timothy D Smith, Kunwar P Bhatnagar, John C Dennis, Edward E Morrison, Thomas J ParkAbstract:The naked mole-rat (Heterocephalus glaber) is unusual in numerous life history characteristics as well as its eusocial organization. This species demonstrates widespread sexual suppression and prominent scent marking, behaviors that have been associated with pheromonal communication involving the vomeronasal organ in other rodents. Yet, previous studies indicate that urinary signals do not mediate sexual suppression in Heterocephalus. Surprisingly, no previous studies have examined the vomeronasal organ in this species. Here, we show that Heterocephalus is unique among rodents in showing no evidence of postnatal volumetric growth in the vomeronasal neuroepithelium. Subadults from birth to weaning fell within the same volume range as adults regardless of breeding/non-breeding status of the latter. A comparison of existing ontogenetic data on other mammals suggests that the proportionally small VNOs of Heterocephalus may be explained by a deficiency in VNNE growth. Growth deficiency of the vomeronasal organ in Heterocephalus may relate to a diminished role that pheromones play in certain social interactions for this species, such as breeding suppression. In light of the unique aspects of the vomeronasal organ in Heterocephalus, comparative studies of rodents may provide a model for understanding variation of this sensory system in other mammalian orders including primates, an order which shows a range from vestigial to demonstrably functional vomeronasal organs.
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Features of visual function in the naked mole-rat Heterocephalus glaber
Journal of Comparative Physiology A, 2005Co-Authors: John R. Hetling, Monica S. Baig-silva, Christopher M. Comer, Machelle T. Pardue, Dalia Y. Samaan, Nasser M. Qtaishat, David R. Pepperberg, Thomas J ParkAbstract:The eyes and visual capacity of the naked mole-rat, Heterocephalus glaber , a subterranean rodent, were evaluated using anatomical, biochemical, and functional assays, and compared to other rodents of similar body size (mouse and gerbil). The eye is small compared to mouse, yet possesses cornea, lens, and retina with typical mammalian organization. The optic nerve cross-sectional area and fiber density are ~10% and ~50% that of gerbil, respectively. Levels per unit retinal area of 11- cis and all- trans retinal, derivatives of vitamin A associated with the visual cycle, are comparable to mouse. The corneal electroretinogram (ERG) exhibits early and late negative components that scale with flash strength; raising the body temperature of this poikilothermic animal from 30°C (normal for H. glaber ) to 37°C (normal for mouse) revealed an ERG response with typically mammalian features, but greatly attenuated and with slower kinetics. Leaving the nest chamber was a behavior correlated with light onset displayed preferentially by breeding females. Optical models of five mole-rat eyes suggest reasonable, but variable, image formation at the retina, possibly related to age. Results are consistent with amorphous light detection, possibly useful for circadian entrainment or escape behavior in the event of tunnel breeches.