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Abstract Oxidative damage is a potential physiological cost of thermoregulation during seasonal adjustments to air temperature (T a) in small mammals. Here, we hypothesized that T a affects serum thyroid hormone levels and these hormones can mediate the changes in metabolic rate and oxidative damage. Mongolian gerbils (Meriones unguiculatus) were acclimated at different T a s (5 °C, 23 °C and 37 °C) for 3 weeks. Serum tri-iodothyronine (T3) levels increased at 5 °C but decreased at 37 °C compared to the control (23 °C). Protein carbonyls increased in liver at 37 °C compared with control, however, lipid damage (malonaldehyde, MDA) in both serum and liver was unrelated to T a. After the effects of different T a s on thyroid hormone levels and oxidative damage markers were determined, we further investigate whether thyroid hormones mediated metabolic rate and oxidative damage. Another set of gerbils received 0.0036% L-thyroxin (hyperthyroid), 0.04% Methylimazol (hypothyroid) or water (control). Hypothyroid group showed a 34% reduction in resting metabolic rate (RMR) also 42% and 26% increases in MDA and liver protein carbonyl respectively, whereas hyperthyroid group had higher RMR, liver mass and superoxide dismutase (SOD) compared to control. Serum T3 or T3/T4 levels were correlated positively with RMR, liver mass, and SOD, but negatively with MDA and uncoupling protein 2 (UCP2). We concluded that high T a induced hypothyroidism, decreased RMR and increased oxidative damage, whereas low T a induced hyperthyroidism, increased RMR and unchanged oxidative damage. These data supported our hypothesis that thyroid hormones can be a cue to mediate metabolic rate and different aspects of oxidative and antioxidant activities at different T a s. Graphical abstract Unlabelled Image Highlights • Serum tri-iodothyronine level increased at 5 °C and decreased at 37 °C. • Hypothyroid led to a decrease in resting metabolic rate (RMR) but increases in malonaldehyde and liver protein carbonyl. • Hyperthyroid led to increases in RMR and superoxide dismutase but a decrease in uncoupling protein 2. • Thyroid hormones mediate RMR and oxidative, anti-oxidative balance. [ABSTRACT FROM AUTHOR]

Meriones shawi (M. shawi) is a particular semi-desert rodent known by its resistance to long periods of thirst. The aim of the present investigation is to clarify the underlying mechanisms allowing M. shawi to resist to hard conditions of dehydration. For this reason we used two different approaches: i) a morphometric study, which consists in measuring the effect of dehydration on body and kidneys weights as well as the report kidney weight/body weight, ii) By immunohistochemistry, we proceed to study the effect of dehydration on the immunoreactivity of central vasopressin (AVP) and the kidney aquaporin-2 (AQP-2) which is a channel protein that allows water to permeate across cell membranes. Our results showed both a body mass decrease accompanied by a remarkable kidneys hypertrophy. The immunohistochemical study showed a significant increase of AQP-2 immunoreactivity in the medullar part of Meriones kidneys allowing probably to Meriones a great ability to water retention. Consistently, we demonstrate that the increased AQP-2 expression occurred together with an increase in vasopressin (AVP) expression in both hypothalamic supraoptic (SON) and paraventricular nucleus (PVN), which are a major hub in the osmotic control circuitry. These various changes seen either in body weight and kidneys or at the cellular level might be the basis of peripheral control of body water homeostasis, providing to M. shawi a strong resistance against chronic dehydration. [ABSTRACT FROM AUTHOR]

Rodents of the Meriones shawii/grandis complex have been attested to in North Africa since the Middle Pleistocene and are abundant in archaeological sites. Today, they are widely spread and represent a major pest to local human populations. This complex, therefore, represents an accurate model for investigating the roles of climate change and human impact in shaping Quaternary faunal diversity and distribution. Many gray areas still exist regarding the systematics, ecology and geographical distribution of this complex, for both present and past populations. The purpose of this study is to compare modern genotyped and fossil Meriones specimens in order to 1) clarify the current systematics and distribution of the Meriones populations of the shawii/grandis complex, 2) document the taxonomic diversity in fossil Meriones from northwestern Africa, and 3) track their phenotypic and biogeographic evolution through time. To answer these questions we used geometric morphometrics on skulls (landmarks) and first upper molars (landmarks and sliding landmarks). We evidenced the existence of two morpho-groups within the M. shawii/grandis complex, with a clear geographic pattern ( M. grandis in Morocco vs. M. shawii in Algeria and Tunisia). Currently only one morpho-group, attributed to M. grandis , seems to exist in Morocco, with a small overlap with M. shawii in the most eastern part of the country. However, according to fossil data, M. shawii was also present in Atlantic Morocco during the Late Pleistocene. We have also highlighted the impact of Holocene climate change and habitat anthropization on this arid adapted group. During the Middle Holocene, a major climatic event (last interglacial optimum) seems to have induced a demographic collapse in Moroccan populations and the disappearance of the shawii clade from Morocco (except in the most eastern areas). Both species then re-expanded, benefitting from the increasing aridity and the new ecological niche driven by agriculture dispersal from the Neolithic onwards. [ABSTRACT FROM AUTHOR]

Abstract: In the present work we determined effects of a sub-chronic exposure to cadmium on some parameters of calcium and iodine metabolisms in Meriones shawi, a desert rodent species occupying the arid steppes of Tunisia and other countries. Fourteen jirds of both sex were equally divided into a control group receiving diet without cadmium and a treated group receiving cadmium in the diet during 30, 45, 60 and 90 days. At the end of each period, 5 jirds from each group were sacrificed. In cadmium-treated group, cadmium accumulation and total metallothioneins synthesis in the liver and kidneys were high and dependant on the duration of treatment. Cadmium caused significant modifications in the body weight and in the relative weights of the liver, femur and thyroids, in parallel to a decrease in calcium content in serum and in femur. Cadmium also decreased iodine content in serum and in the thyroids. Several impairments were dependant on the duration of exposure and were more pronounced at the end of the experiment. In conclusion, a sub-chronic exposure to cadmium induces perturbations in calcium and iodine metabolisms in Meriones shawi. However, effects on calcium seem to be more evident. We can conclude also that Meriones shawi is an indicator of cadmium presence in arid environments. [Copyright &y& Elsevier]

Abstract: Supraoptic (SON) and paraventricular (PVN) nuclei are part of the hypothalamic–neurohypophysial system, they constitute the main source for vasopressin and they represent also obvious examples of activity-dependent neuroglial plasticity. Certain physiological conditions such as dehydration are accompanied by a structural remodeling of the neurons, their synaptic inputs and their surrounding glia. In the present work, an adult Meriones shawi (a rodent adapted to desert life) is used as an animal model. Using GFAP and vasopressin expressions as indicators successively of astrocytes and neuronal activations, the effect of a prolonged episode of water deprivation on the SON and PVN, hypothalamus nuclei were examined. We studied the immunoreactivity of GFAP and vasopressin in various hydration states (total deprivation of drinking water for 1 and 2months compared to hydrated animals). Prolonged dehydration produces an important decrease of GFAP immunoreactivity in both SON and PVN after 1 and 2months of water restriction. This decrease is accompanied by increased vasopressin immunoreactivity following the same periods of water deprivation. These findings may explain a real communication between vasopressin neurons and their surrounding astrocytes, thus the retraction of astrocytes and their processes is accompanied by an enhancement of vasopressin neuron density and their projecting fibers in response to this osmotic stress situation. Furthermore, these data could open further investigations concerning the possible involvement of the communication between astrocytes and vasopressin neurons in both PVN and SON in the regulation of Meriones hydrous balance and resistance to dehydration. [Copyright &y& Elsevier]

Abstract: Water deprivation is a stress that has been associated with activation of several endocrine systems, including circumventricular organs of the central nervous system. The sub-comissural organ (SCO), characterized by its glycoprotein secretion called Reissner''s fiber has been suggested to play a role in the regulation of body water balance. Meriones shawi, a semi-desertic rodent characterized by its resistance to long periods of thirst was subjected to water deprivation for 1 and 3 months. Effect of water deprivation was evaluated immunohistochemically on 5-hydroxytryptamine (5-HT; serotonin) system and glycoprotein secretion of the SCO. Our findings demonstrate significant reduction of anti-Reissner''s fiber immunoreactive materials within basal and apical parts of the SCO ependymocytes. These changes seem to be the consequence of reduced control by 5-HT fibers reaching the SCO as a concomitant and significant reduction of anti-5-HT immunoreactive fibers are also observed following water deprivation. 5-HT immunoreactive reduction is seen in several regions in the brain including the neurons of origin within the dorsal raphe nucleus and the projecting supra and sub-ependymal fibers reaching the classical ependyma of the third ventricle. The extent of Reissner''s fiber and 5-HT immunoreactive changes significantly correlates with the severity of water restriction. We suggest that water deprivation causes changes of the classical ependyma and the specialized ependyma that differentiates into the SCO as well as other cirumventricular organs such as the subfornical organ and the organum vasculosum laminae terminalis known to control drinking behaviors. [Copyright &y& Elsevier]

Abstract: Antibodies directed against calcium-binding proteins (CaBPs) parvalbumin, calbindin-D28k and calretinin were used as neuronal markers to identify and characterize different principal cell types in the mammalian cochlear nucleus. For this purpose, double immunofluorescence labeling and the combination of CaBP-labeling with pan-neuronal markers were applied to analyze the CaBPs distribution in neurons of the cochlear nucleus (CN) of the Mongolian gerbil (Meriones unguiculatus) and the gray short-tailed opossum (Monodelphis domestica). Despite of the fact, that these two mammalian species are not closely related, principal cell types in the CN of the two species showed many corresponding morphological features and similarities in immunolabeling of the CaBPs. Parvalbumin seems not to be suited as a differential neuronal marker in the CN since it is expressed by almost all neurons. In contrast, calbindin and calretinin were more restricted to specific cell types and showed a mostly complementary labeling pattern. As one of the most interesting findings, calbindin and calretinin were predominantly found in subpopulations of globular bushy cells and octopus cells in the ventral CN. Such a neuron-specific CaBP-expression in subpopulations of morphologically defined cell types argues for a more refined classification of CN cell types in Meriones and Monodelphis. Additionally, other cell types (cartwheel cells, unipolar brush cells, fusiform cells) were marked with calbindin or calretinin as well. Calretinin staining was predominantly observed in auditory nerve fibers and their endings including endbulbs of Held in Meriones. Spherical bushy cells showed a different calretinin-immunolabeling in Meriones and Monodelphis. This species-specific difference may be related to adaptive differences in auditory function. [Copyright &y& Elsevier]

Summary: The secretory activity of subcommissural organ cells is controlled by various extrinsic and intrinsic factors. Lead has been recognised as a neurotoxic heavy metal, since it induces morphological and functional abnormalities in the brain. In this work, we examined the effect of lead exposure on the subcommissural organ (SCO), a brain gland known by its secretion of Reissner''s fiber (RF) in cerebro-spinal fluid. Glycoprotein secretion and serotonin (5HT) innervation of the SCO was examined after acute and chronic lead exposures in the sub-desert rodent Meriones shawi. Lead exposures were achieved by, respectively, intra-peritoneal injection of 25mg/kg body weight of lead acetate for 3 days and 0.5% of lead acetate in the drinking water over 4 months until adult age. 5HT and RF immunolabeling in the SCO revealed several serotoninergic fibers reaching the SCO and abundant secretory material. An increase in both 5HT innervation and secretory material of the SCO was recorded after both acute and chronic lead exposure. These results show that lead exposure affects the serotonergic innervation of the SCO. Moreover, the enhancement of SCO secretion suggests a role of this gland in neuroprotection and lead detoxification of the brain in Meriones shawi. [Copyright &y& Elsevier]

Abstract: A zinc containing metalloprotease, 175kDa collagenase, purified from adult female Setaria cervi showed strong cross-reactivity with sera from putatively immune (PI) individuals (unpublished observation) and induced cytotoxicity to B. malayi L3 larvae and microfilariae by ADCC mechanism [Srivastava Y, Bhandari YP, Reddy MVR, Harinath BC, Rathaur S. An adult 175kDa collagenase antigen of Setaria cervi in immunoprophylaxis against Brugia malayi. J Helminth 2004;78:347–52]. These preliminary observations suggested the immunoprotective nature of collagenase. To confirm the vaccine potential of this protease, a vaccine trial was conducted in jirds (Meriones unguiculatus) against human filarial parasite B. malayi. The vaccination resulted into a mean protection level of 75.86% and produced high level of protease neutralizing antibodies. Cytokine analysis in immune jirds sera suggested a mixed Th1/Th2 type cellular immune response whereas ELISA, immunoblotting and enzyme antibody inhibition assay revealed the presence of specific anti-collagenase antibodies. Taken together, all these results suggest that S. cervi 175kDa collagenase could form the basis of an effective molecular vaccine against human lymphatic filariasis. [Copyright &y& Elsevier]

Abstract: [(1)] The responses of body temperature (T b) daily rhythms of short photoperiod (8L:16D) acclimated fat jirds Meriones crassus, a nocturnal xeric burrowing species, to beta (propranolol, 4.5mg/kg) and alpha (prazosine, 1mg/kg) adrenergic blockade were studied. [(2)] The results of our study show that beta blockade significantly (p<0.01) increased T b values during the dark phase (24:00 and 06:00h) and shifted the acrophase. [(3)] Alpha blockade significantly (p<0.05) decreased T b values during the dark phase (24:00h) but significantly (p<0.01) also increased T b during the light phase (12:00h). [(4)] These responses are similar to those obtained for two different diurnal species inhabiting arid environments and differ from those of the nocturnal golden hamster. [Copyright &y& Elsevier]

Normative vestibulo-ocular and optokinetic reflexes (VOR and OKR) and pupil diameter were measured in young adult gerbils using infrared video-oculography with 60 Hz sampling during head-fixed binocular recordings. The pupillary light-sink technique was preferred over a single-beam retinal reflection method because its measurements were less affected by pupil size. Eye movements were generally conjugate with occasional independent saccadic movements, and independent drifting movements in the dark. The horizontal optokinetic response to sinusoidal motion of a randomly spaced white dot pattern was maximal at low velocities (5°/s), stronger temporonasally, and dropped off quickly at ∼20°/s. Constant velocity gain was near unity through 60–80°/s with a sharp drop-off. Monocular viewing revealed almost no nasotemporal optokinetic response. Pupil diameter was found to vary as a saddle function with optokinetic gain from cycle to cycle, but also have a circadian rhythm (smaller at dusk) that related inversely to mean horizontal VOR gain. Gerbils with eyes open sometimes had no optokinetic response during long stimulus periods, which then resumed after a brief vestibular stimulus. The horizontal angular VOR gain was relatively flat across 0.1–1.0 Hz and 30–120 d/s sines (phase near zero), with a mean gain of ∼0.78 in the dark, and 1.0 with the fixed pattern surround (n=15, for both raw calibrated and normalized data). Most animals also revealed a strong slow phase eye velocity asymmetry (dominant during ipsilateral rotation) in the half-cycle gain of their horizontal angular VOR response in the dark. A constant velocity horizontal optokinetic bias velocity did not change the gain or symmetry of the sinusoidal VOR response, but shifted the VOR response velocity in an additive (linear) fashion. Both cross-coupling (pitch or roll while rotating) and pseudo-OVAR (off-axis counter-rotation) stimuli generated horizontal nystagmus. The findings suggest that the gerbil, like other lateral-eyed rodents, relies on otolith cues to interpret angular motion. [Copyright &y& Elsevier]