Hypertrophy of the adrenal cortex

The human adrenal cortex in essential hypertension and in the salt-losing form of the adrenogenital syndrome and the adrenal cortex in spontaneously hypertensive rats were studied by morphometry. Under long-term functional loading hypertrophy of adrenocortical cells is the common way of increasing the mass of the cortex. The correlation between the morphological parameters of the adrenocortical structures increases in this condition. Hyperplasia along with hypertrophy has been found in man at an early age. The differences in the degree of hypertrophy of the nuclei and nucleoli may be connected with different intensity of adrenocortical function in different pathological conditions.     

Origin and identity of adrenocortical tumors in inhibin knockout mice: implications for cellular plasticity in the adrenal cortex

Inhibin knockout (Inha-/-) mice develop gonadal sex-cord tumors and--when gonadectomized--adrenocortical tumors. Previous reports demonstrated that adrenocortical tumors from Inha-/- mice produce estrogen and depend on gonadotropin signaling for initiation. Here we show that, in addition to producing estrogen, the adrenocortical tumors display a global change in cellular identity, composed of two unique cell types expressing differing arrays of genes normally restricted to theca and granulosa cells of the ovary. Many of these genes are also induced in wild-type adrenals after gonadectomy or upon chronic gonadotropin stimulation, suggesting that the adrenal cortex normally contains a population of pluripotent cells that can be driven toward an adrenal or gonadal identity given the appropriate pituitary stimuli. A central feature of this altered cellular identity is the switch from predominant expression of Gata6 (endogenous to the adrenal cortex) to Gata4, which defines cellular identity in the ovary. We show that stable transfection of Gata4 in cultured adrenocortical cells is sufficient to activate ovarian-specific genes of both theca and granulose lineages. Spatial analysis of Gata4 expression reveals a distinct pattern of localization to the supcapsular region of the adrenal, which contains undifferentiated progenitor cells that continuously populate the adrenocortical zones. Although both wild-type and Inha-/- mice display this pattern, only Inha-/- mice produce tumors composed of these Gata4-positive cells. These data suggest that Inha-/- adrenocortical tumors cells are derived from pluripotent adrenocortical progenitor cells that adopt a gonadal fate due to the convergent loss of inhibin and chronic exposure to elevated gonadotropins.     

Complex, multimodal behavioral profile of the Homer1 knockout mouse

Proteins of the Homer1 immediate early gene family have been associated with synaptogenesis and synaptic plasticity suggesting broad behavioral consequences of loss of function. This study examined the behavior of male Homer1 knockout (KO) mice compared with wild-type (WT) and heterozygous mice using a battery of 10 behavioral tests probing sensory, motor, social, emotional and learning/memory functions. KO mice showed mild somatic growth retardation, poor motor coordination, enhanced sensory reactivity and learning deficits. Heterozygous mice showed increased aggression in social interactions with conspecifics. The distribution of mGluR5 and N-methyl-D-aspartate receptors (NMDA) receptors appeared to be unaltered in the hippocampus (HIP) of Homer1 KO mice. The results indicate an extensive range of disrupted behaviors that should contribute to the understanding of the Homer1 gene in brain development and behavior.     

Caveolin-1 knockout mice have altered serum N-glycan profile and sialyltransferase tissue expression

Journal of Physiology and Biochemistry - Caveolin-1 (Cav-1) is a constitutive protein within caveolar membranes. Previous studies from our group and others indicated that Cav-1 could mediate...     

Hyperdopaminergia and altered locomotor activity in GABAB1-deficient mice

GABAB1-/- mice, which are devoid of functional GABAB receptors, consistently exhibit marked hyperlocomotion when exposed to a novel environment. Telemetry recordings now revealed that, in a familiar environment, GABAB1-/- mice display an altered pattern of circadian activity but no hyperlocomotion. This indicates that hyperlocomotion is only triggered when GABAB1-/- mice are aroused by novelty. In microdialysis experiments, GABAB1-/- mice exhibited a 2-fold increased extracellular level of dopamine in the striatum. Following D-amphetamine administration, GABAB1-/- mice released less dopamine than wild-type mice, indicative of a reduced cytoplasmic dopamine pool. The hyperdopaminergic state of GABAB1-/- mice is accompanied by molecular changes, including reduced levels of tyrosine hydroxylase mRNA, D1 receptor binding-sites and Ser40 phosphorylation of tyrosine hydroxylase. Tyrosine hydroxylase activity, tissue dopamine content and dopamine metabolism do not appear to be measurably altered. Pharmacological and electrophysiological experiments support that the hyperdopaminergic state of GABAB1-/- mice is not severe enough to inactivate dopamine D2 receptors and to disrupt D2-mediated feedback inhibition of tyrosine hydroxylase activity. The data support that loss of GABAB activity results in a sustained moderate hyperdopaminergic state, which is phenotypically revealed by contextual hyperlocomotor activity. Importantly, the presence of an inhibitory GABA tone on the dopaminergic system mediated by GABAB receptors provides an opportunity for therapeutic intervention.     

Norepinephrine transporter heterozygous knockout mice exhibit altered transport and behavior

The norepinephrine (NE) transporter (NET) regulates synaptic NE availability for noradrenergic signaling in the brain and sympathetic nervous system. Although genetic variation leading to a loss of NET expression has been implicated in psychiatric and cardiovascular disorders, complete NET deficiency has not been found in people, limiting the utility of NET knockout mice as a model for genetically driven NET dysfunction. Here, we investigate NET expression in NET heterozygous knockout male mice (NET^+/?), demonstrating that they display an approximately 50% reduction in NET protein levels. Surprisingly, these mice display no significant deficit in NET activity assessed in hippocampal and cortical synaptosomes. We found that this compensation in NET activity was due to enhanced activity of surface‐resident transporters, as opposed to surface recruitment of NET protein or compensation through other transport mechanisms, including serotonin, dopamine or organic cation transporters. We hypothesize that loss of NET protein in the NET^+/? mouse establishes an activated state of existing surface NET proteins. The NET^+/? mice exhibit increased anxiety in the open field and light–dark box and display deficits in reversal learning in the Morris water maze. These data suggest that recovery of near basal activity in NET^+/? mice appears to be insufficient to limit anxiety responses or support cognitive performance that might involve noradrenergic neurotransmission. The NET^+/? mice represent a unique model to study the loss and resultant compensatory changes in NET that may be relevant to behavior and physiology in human NET deficiency disorders .     

Molecular signatures of neurodegeneration in the cortex of PS1/PS2 double knockout mice

Background

Dimebon is an antihistamine compound with a long history of clinical use in Russia. Recently, Dimebon has been proposed to be useful for treating neurodegenerative disorders. It has demonstrated efficacy in phase II Alzheimer's disease (AD) and Huntington's disease (HD) clinical trials. The mechanisms responsible for the beneficial actions of Dimebon in AD and HD remain unclear. It has been suggested that Dimebon may act by blocking NMDA receptors or voltage-gated Ca²⁺ channels and by preventing mitochondrial permeability pore transition.

Results

We evaluated the effects of Dimebon in experiments with primary striatal neuronal cultures (MSN) from wild type (WT) mice and YAC128 HD transgenic mice. We found that Dimebon acts as an inhibitor of NMDA receptors (IC50 = 10 μM) and voltage-gated calcium channels (IC50 = 50 μM) in WT and YAC128 MSN. We further found that application of 50 μM Dimebon stabilized glutamate-induced Ca²⁺ signals in YAC128 MSN and protected cultured YAC128 MSN from glutamate-induced apoptosis. Lower concentrations of Dimebon (5 μM and 10 μM) did not stabilize glutamate-induced Ca²⁺ signals and did not exert neuroprotective effects in experiments with YAC128 MSN. Evaluation of Dimebon against a set of biochemical targets indicated that Dimebon inhibits α-Adrenergic receptors (α_1A, α_1B, α_1D, and α_2A), Histamine H₁ and H₂ receptors and Serotonin 5-HT_2c, 5-HT_5A, 5-HT₆ receptors with high affinity. Dimebon also had significant effect on a number of additional receptors.

Conclusion

Our results suggest that Ca²⁺ and mitochondria stabilizing effects may, in part, be responsible for beneficial clinical effects of Dimebon. However, the high concentrations of Dimebon required to achieve Ca²⁺ stabilizing and neuroprotective effects in our in vitro studies (50 μM) indicate that properties of Dimebon as cognitive enhancer are most likely due to potent inhibition of H1 histamine receptors. It is also possible that Dimebon acts on novel high affinity targets not present in cultured MSN preparation. Unbiased evaluation of Dimebon against a set of biochemical targets indicated that Dimebon efficiently inhibited a number of additional receptors. Potential interactions with these receptors need to be considered in interpretation of results obtained with Dimebon in clinical trials.     

P27 knockout mice: reduced myostatin in muscle and altered adipogenesis

Knockout of the P27(kip) gene, which encodes a cyclin-dependent kinase inhibitor involved in cell proliferation regulation, results in growth enhancement in mice. To investigate how p27 deficiency affected adipogenesis and myogenesis, levels of PPARgamma, C/EBPalpha, and the myogenesis inhibitor, myostatin, were measured in p27(-/-) (n=14), p27(+/-) (n=18), and p27(+/+) mice (n=11). Body weight and gastrocnemius muscle (GC) mass were increased in p27(-/-) mice (P<0.05), but there were no differences in fat depot weights, percent body fat or serum leptin concentrations among genotypes. PPARgamma, but not C/EBPalpha, was markedly increased in p27(-/-) mice (P<0.05). There was also a higher incidence of inguinal fat apoptosis (P<0.01) in p27(-/-) mice. Myostatin levels were reduced in GC muscle of p27(-/-) mice (P<0.05). These findings suggest that in p27 deficient mice, increased skeletal muscle mass is mediated in part through decreased myostatin. Although total adiposity was not changed, increased PPARgamma levels suggest an alteration in adipogenesis.     

Endothelin-1 stimulates mitotic activity in the zona glomerulosa of the rat adrenal cortex.

Subcutaneous infusion with endothelin-1 (ET-1; 30 pM min-1) for 24 h induced a 9-fold increase in the mitotic index (% of metaphase-arrested cells) of rat adrenal zona glomerulosa (ZG). Infusions with adrenocorticotrophic hormone (ACTH) angiotensin-II (ANG-II) or arginine vasopressin (AVP) (30 pM min-1/24 h) raised the ZG mitotic index 13-fold, 9-fold and 10-fold, respectively. Combined infusion with ET-1 and ACTH increased the ZG mitotic index 20-fold, while the effects of ET-1 and ANG-II or AVP were not additive. These findings suggest that ET-1 exerts a strong proliferogenic effect on the rat ZG, by a mechanism probably similar to that underlying the adrenoglomerulotrophic actions of ANG-II and AVP.     

Acylation-stimulating protein deficiency and altered adipose tissue in alternative complement pathway knockout mice

Acylation-stimulating protein (C3adesArg/ASP) is an adipokine that acts on its receptor C5L2 to stimulate triglyceride (TG) synthesis in adipose tissue. The present study investigated ASP levels in mouse models of obesity and leanness and the effect of ASP deficiency in C3 knockout (C3KO) mice on adipose tissue morphology. Plasma ASP levels in wild-type (WT) mice correlated positively with plasma nonesterified fatty acids (NEFA) (R = 0.664, P < 0.001) and total cholesterol (R = 0.515, P < 0.001). Plasma ASP was increased by 85% in obese ob/ob leptin-deficient mice and decreased in lean diacylglycerol acyltransferase 1 (DGAT1) KO mice (-54%) and C/EBPalpha(beta/beta) transgenic mice (-70%) compared with WT. Mice lacking alternative complement factor B or adipsin (FBKO or ADKO), required for ASP production, were also ASP deficient. Both FBKO and C3KO mice had delayed postprandial TG and NEFA clearance on low-fat (LF) and high-fat (HF) diets, suggesting that lack of ASP, not C3, drives the metabolic phenotype. Adipocyte size distribution in C3KO mice was polarized (increased number of both small and large cells), with decreased adipsin expression (-33% gonadal HF), DGAT1 expression (-31% to -50%) and DGAT activity (-41%). Overall, a reduction/deficiency in ASP is associated with an antiadipogenic state and ASP may provide a target for controlling fat storage.     

Defective neurogenesis in citron kinase knockout mice by altered cytokinesis and massive apoptosis

Citron-kinase (Citron-K) has been proposed by in vitro studies as a crucial effector of Rho in regulation of cytokinesis. To further investigate in vivo its biologic functions, we have inactivated Citron-K gene in mice by homologous recombination. Citron-K-/- mice grow at slower rates, are severely ataxic, and die before adulthood as a consequence of fatal seizures. Their brains display defective neurogenesis, with depletion of specific neuronal populations. These abnormalities arise during development of the central nervous system due to altered cytokinesis and massive apoptosis. Our results indicate that Citron-K is essential for cytokinesis in vivo but only in specific neuronal precursors. Moreover, they suggest a novel molecular mechanism for a subset of human malformative syndromes of the CNS.     

CDKL5 knockout leads to altered inhibitory transmission in the cerebellum of adult mice

Mutations in the X‐linked cyclin‐dependent kinase‐like 5 gene (CDKL5) are associated to severe neurodevelopmental alterations including motor symptoms. In order to elucidate the neurobiological substrate of motor symptoms in CDKL5 syndrome, we investigated the motor function, GABA and glutamate pathways in the cerebellum of CDKL5 knockout female mice. Behavioural data indicate that CDKL5‐KO mice displayed impaired motor coordination on the Rotarod test, and altered steps, as measured by the gait analysis using the CatWalk test. A higher reduction in spontaneous GABA efflux, than that in glutamate, was observed in CDKL5‐KO mouse cerebellar synaptosomes, leading to a significant increase of spontaneous glutamate/GABA efflux ratio in these animals. On the contrary, there were no differences between groups in K⁺‐evoked GABA and glutamate efflux. The anatomical analysis of cerebellar excitatory and inhibitory pathways showed a selective defect of the GABA‐related marker GAD67 in the molecular layer in CDKL5‐KO mice, while the glutamatergic marker VGLUT1 was unchanged in the same area. Fine cerebellar structural abnormalities such as a reduction of the inhibitory basket ‘net’ estimated volume and an increase of the pinceau estimated volume were also observed in CDKL5‐KO mice. Finally, the BDNF mRNA expression level in the cerebellum, but not in the hippocampus, was reduced compared with WT animals. These data suggest that CDKL5 deletion during development more markedly impairs the establishment of a correct GABAergic cerebellar network than that of glutamatergic one, leading to the behavioural symptoms associated with CDKL5 mutation.     

Ornithine decarboxylase activity in regenerating rat adrenal cortex

The activity of ornithine decarboxylase during the regenerating process of adrenal cortex was evaluated in Sprague-Dawley male rats weighing 140–180 g. In this study, 4 groups of rats were enucleated and another 4 groups were sham operated. Animals were maintained at a temperature of 23 ± 1°C and 12:12 h light:dark cycle. At 7 and 11 days post surgery, animals were sacrificed at 0600 h and 1800 h, respectively. Adrenal glands were immediately removed and assayed for ornithine decarboxylase (ODC). The enzyme activity was found to be significantly elevated in enucleated groups as compared to the sham control groups at the 7th and the 11th day of surgery. ODC activity was found to be about 2 times higher at 1800 h by the 7th day and 5 times higher at 1800 h by the 11th day of adrenal surgery when compared to the activity at 0600 h. From these results, it appears that ODC activity not only increases as the regeneration process of adrenal cortex approaches completion, but also becomes more pronounced towards the end of the light period.