Immunocytochemical and in situ hybridization detection of hypothalamic neuropeptides from postmortem unfixed rat brains

Perspectives of Pitocin administration on behavioral outcomes in the pediatric population: recent insights and future implications

Oxytocin plays an important role in the regulation of parturition as this peptide hormone promotes uterine smooth muscle contractility in gravid women undergoing labor. Here, we review the impact of Pitocin administration on behavioral outcomes in the pediatric population. Pitocin is a synthetic preparation of oxytocin widely used in the obstetric practice for the management of labor and postpartum hemorrhage. We begin by tracing the neuroanatomy of oxytocin-containing cells from an evolutionary perspective and then summarize key findings on behavioral and neural activity reported from offspring dosed with Pitocin during vaginal delivery. Finally, we discuss future directions that are experimentally tractable for understanding the developmental consequences of Pitocin administration on a small but growing subset of children worldwide. Given that fetal past experiences can shape the future behavior of the adult, further work on oxytocin signaling pathways will provide valuable references and insights for early-brain development and state-dependent regulation of behavioral outcome.

Central and Peripheral Expression of DNA Double-Strand Breaks in Human and Mouse Tissues

Mammalian cells accumulate DNA lesions when they undergo phases of the cell cycle or during normal cellular activity. In this regard, several DNA repair signaling pathways have evolved to maintain genome stability and avoid the potential acquisition of mutations. To define and further characterize the expression of DNA double-strand breaks in humans and mice, we used immunocytochemistry to localize a DNA damage signal within the spatial confines of the cell nucleus. We show that DNA double-strand breaks are abundantly expressed in postmitotic neurons of the human and mouse brain. Notably, DNA double-strand breaks are present in human hypothalamic and mouse striatal and hippocampal cells, with stable expression of the nuclear signal detected throughout the mammalian brain. Analysis of the mouse tongue, heart, and testis shows that expression of DNA double-strand breaks is only demonstrated in circumscribed populations of peripheral cells. These data suggest that levels of DNA double-strand breaks are tissue-specific with the tongue, heart and testicular tissue having different thresholds of DNA repair and DNA damage from those outlined at the brain level. Anat Rec, 301:1251-1257, 2018. © 2018 Wiley Periodicals, Inc.

Immunocytochemical localization of DNA double-strand breaks in human and rat brains

Post-mitotic neurons are particularly susceptible to DNA double-strand breaks during their relatively long lifespan. Here, we report the anatomical distribution and subcellular localization of a molecule first identified as a DNA damage checkpoint protein. Immunocytochemical analysis of 53BP1 showed that this nuclear molecule is widely expressed in adult human and rat brains. Further, we showed that 53BP1 routinely co-clusters with γ-aminobutyric acid neurons throughout the rat neuraxis. Notably, 53BP1 is only expressed in neuronal cells as the DNA damage checkpoint protein was virtually absent from glial cells. Finally, we found that human neural progenitors showed a differential index of DNA fragmentation at different stages of cellular differentiation. These data provide additional and important anatomical findings for the distribution and phenotype of DNA double-strand breaks in the mammalian brain, and suggest that DNA fragmentation is a spontaneous event routinely occurring in neural progenitors and adult neurons.

Distribution analysis of deacetylase SIRT1 in rodent and human nervous systems

Sirtuins function with other biogenic molecules to promote adaptation to caloric restriction in a broad spectrum of eukaryotic species. Sirtuin pathways also converge in the mammalian brain where they appear to protect neurons from nutrient stress. However, few anatomical studies on sirtuins (e.g., SIRT1) are available, particularly those detailing the spatial distribution and subcellular localization pattern of SIRT1 in the brain parenchyma. Here, we report the characterization of a panel of SIRT1-specific antibodies within rodent (i.e., rat and mouse) and human central nervous systems. Immunocytochemical and Western blot analyses indicate that the subcellular localization of SIRT1 is predominantly nuclear throughout the rodent brain and spinal cord. A similar subcellular distribution pattern of SIRT1 was detected in human central nervous system material. SIRT1 is ubiquitously present in areas of the brain especially susceptible to age-related neurodegenerative states (e.g., the prefrontal cortex, hippocampus and basal ganglia). Further, we show no apparent species-specific differences in the subcellular localization pattern of rodent versus human SIRT1. Finally, we identify the chemical phenotype of SIRT1-containing neurons in a number of brain sites that are strongly compromised by aging. These data provide additional and important anatomical findings for the role of SIRT1 in the mammalian brain and suggest that SIRT1 pathways are broadly distributed in neurons most susceptible to senescence injury. Activating endogenous sirtuin pathways may, therefore, offer a therapeutic approach to delay and/or treat human age-related diseases.

Expression profile of Bag 1 in the postmortem brain

Bag 1 is a protein intimately involved in signaling pathways that regulate cell survival. Here we examined the expression profile of Bag 1 in the brain to consider issues associated with the sampling of anti-apoptotic proteins in a rat model of the human postmortem process. Following a 4h postmortem interval, we analyzed the hippocampus of rats maintained at 24 or 4 degrees C storage temperatures using immunocytochemical and Western blotting techniques. Remarkably, postmortem tissue (up to 4h) showed a significant and prominent up-regulation of Bag 1 in CA1 and CA3 subfields of the hippocampal formation. Over-expression of Bag 1, however, could only be traced down to a storage temperature of 24 degrees C. These data suggest that storage temperatures, but not postmortem intervals, significantly affect the expression profile and cellular stability of Bag 1 proteins.

Autopsy at 2 months after death: brain is satisfactorily preserved for neuropathology

Disclosure of neurological disorders by neuropathological examination may be one important aim of forensic autopsies. There are insufficient data on human brain tissue preservation after prolonged postmortem periods. Here, we describe neuropathological findings in a brain of a 77-year-old woman that was fixed at autopsy 2 months after death. The body had been stored in a cooling chamber at 3 degrees C temperature. Gross inspection of the brain was satisfactorily possible. Histomorphology was excellently preserved. Many histochemical and immunohistochemical stains allowed satisfactory neuropathological evaluation of brain tissue and the diagnosis of Alzheimer's disease. Nevertheless, some immunohistochemical stainings repeatedly yielded negative or suboptimal results. We conclude that neuropathological examination of human brain tissue extracted from the skull and fixed after prolonged body storage in a cool environment is feasible for forensic diagnosis of neurological disorders even several months after death. However, in such cases the significance of negative immunohistochemical staining results must be interpreted with caution.

Blood content modulates the induction of heat shock proteins in the neurovascular network

Heat shock proteins are ubiquitous members of a family of molecular chaperones that protect various cell populations from injury. Up-regulation of heat shock proteins, particularly the 70 kDa species, bind selectively to denatured or partially damaged polypeptides that would otherwise perturb cell function and initiate cell death programs. In this regard, induction of heat shock proteins provides protection from cerebral ischemia in animal models of stroke. Endothelial cells, in particular, are intimately involved in the above protective event as these cells mount a stress response with induction of the 70 kDa heat shock protein. However, the coupling of heat shock proteins and the neurovascular response are not yet known. Here we show that blood content is an important factor in this stress response as rats devoid of blood content do not display a heat shock response in the microvasculature of the hippocampal formation. This lack of stress response, however, is reversed when rats are reperfused with exogenous rat or human blood content. We propose a new ischemic-sensing role for blood that serves to integrate information about protein-damaging conditions and heat shock protein levels in the neurovascular network. Further characterization of this sensing role could represent an attractive new approach to treatment of global ischemia and other microvascular pathologies.

Distribution of constitutively expressed MEF-2A in adult rat and human nervous systems

Myocyte enhancer factor 2A (MEF-2A) is a calcium-regulated transcription factor that promotes cell survival during nervous system development. To define and further characterize the distribution pattern of MEF-2A in the adult mammalian brain, we used a specific polyclonal antiserum against human MEF-2A to identify nuclear-localized MEF-2A protein in hippocampal and frontal cortical regions. Western blot and immunocytochemical analyses showed that MEF-2A was expressed not only in laminar structures but also in blood vessels of rat and human brains. MEF-2A was colocalized with doublecortin (DCX), a microtubule-associated protein expressed by migrating neuroblasts, in CA1 and CA2 boundaries of the hippocampus. MEF-2A was expressed heterogeneously in additional structures of the rat brain, including the striatum, thalamus, and cerebellum. Furthermore, we found a strong nuclear and diffuse MEF-2A labeling pattern in spinal cord cells of rat and human material. Finally, the neurovasculature of adult rats and humans not only showed a strong expression of MEF-2A but also labeled positive for hyperpolarization-activated, cyclic nucleotide-regulated (HCN) channels. This study further characterizes the distribution pattern of MEF-2A in the mammalian nervous system, demonstrates that MEF-2A colocalizes with DCX in selected neurons, and finds MEF-2A and HCN1 proteins in the neurovasculature network.

A neurobehavioral screening of the ckr mouse mutant: implications for an animal model of schizophrenia

A model of schizophrenia, the chakragati (ckr) mouse was serendipitously created as a result of a transgenic insertional mutation. The apparent loss-of-function of an endogenous gene produced mice that, when homozygous, displayed an abnormal circling behavior phenotype. To determine whether this phenotype could be corrected by atypical antipsychotics, we compared the effects of clozapine and olanzapine on rotational turns and hyperactivity. Both of these drugs successfully ameliorated circling behavior and hyperactivity in homozygous mice. The increased motor activity of these mutant mice was both qualitatively and quantitatively similar to that observed in wild-type animals treated with dizocilpine, an N-methyl-D-aspartate receptor antagonist that produces behaviors resembling positive symptoms of schizophrenia. Mice either homozygous or heterozygous for the mutation also displayed enlargement of the lateral ventricles, which was accompanied only in the homozygous genotype by a loss of individual myelinated axons in the striatum and agenesis of the corpus callosum. These structural brain deficits were selective in that the nigro-striatal dopamine system was normal in these homozygous mice. In addition, two types of interneurons in the neostriatum, namely those producing acetylcholine or nitric-oxide synthase were also devoid of significant structural abnormalities. These results indicate that the ckr mouse mutant could be used as a possible animal model to study the pathophysiology of schizophrenia and suggest possible strategies for treating the behavioral aspects of this brain disease.

Neuropeptide changes in the suprachiasmatic nucleus in primary hypertension indicate functional impairment of the biological clock

Abnormalities in autonomic activity resulting in disturbances of the diurnal rhythm of many physiologic processes were recently revealed in hypertensive patients. These findings suggest deteriorations in the functioning of the suprachiasmatic nucleus (SCN), which is known to be the biological clock of mammals. To test this hypothesis, we carried out an immunocytochemical study of the SCN of primary hypertension patients who had died due to myocardial infarction or brain hemorrhage, and compared them with those of individuals with a normal blood pressure who had never had any autonomic disturbances and died from myocardial infarction after chest trauma or from hypothermia. We found that the staining for the three main neuronal populations of the SCN; i.e., vasopressin, vasoactive intestinal polypeptide, and neurotensin, reduced by more than 50% in the hypertensives compared with controls. The present data indicate a serious dysregulation of the biological clock in hypertensive patients. Such a disturbance may cause a harmful hemodynamic imbalance with a negative effect on circulation, especially in the morning, when the inactivity-activity balance changes. The difficulty in adjusting from inactivity to activity might be involved in the morning clustering of cardiovascular events.

Immunodetection of Parkin protein in vertebrate and invertebrate brains: a comparative study using specific antibodies

Parkin is an intracellular protein that plays a significant role in the etiopathogenesis of autosomal recessive juvenile parkinsonism. Using immunoblot methods, we found Parkin isoforms varying from 54 to 58 kDa in rat, mouse, bird, frog and fruit-fly brains. Immunocytochemical studies carried out in rats, mice and birds demonstrated multiple cell types bearing the phenotype for Parkin throughout telencephalic, diencephalic, mesencephalic and metencephalic brain structures. While in some instances Parkin-containing neurons tended to be grouped into clusters, the majority of these labeled nerve cells were widely scattered throughout the neuraxis. The topographical distribution and organizational pattern of Parkin within major functional brain circuits was comparable in both rats and mice. However, the subcellular localization of Parkin was found to vary significantly as a function of antibody reactivity. A consistent cytoplasmic labeling for Parkin was observed in rodent tissue incubated with a polyclonal antibody raised against the human Parkin protein and having an identical amino-acid sequence with that of the rat. In contrast, rodent tissue alternately incubated with a polyclonal antibody raised against a different region of the same human Parkin protein but having 10 mismatched amino-acid sequence changes with those of the rat and mouse, resulted in nuclear labeling for Parkin in rat but not mouse neurons. This difference in epitope recognition, however, was reversed when mouse brain tissue was heated at 80 degrees C, apparently unmasking target epitopes against which the antisera were directed. Collectively, these results show a high degree of conservation in the cellular identity of Parkin in animals as different as drosophilids and mammals and points to the possibility that the biochemical specificities of Parkin, including analogous functional roles, may have been conserved during the course of evolution.

In situ hybridization with riboprobes: an overview for veterinary pathologists

In situ hybridization using nonradioactively-labeled RNA probes is a technique that combines understanding of basic molecular biology and histopathologic interpretation. Recombinant or PCR technology can be used to produce probes that hybridize with a wide variety of cellular genes and infectious agents. Hybridization conditions can be optimized for each probe/target combination.

Differential vasopressin and oxytocin innervation of the human parabrachial nucleus: no changes in Alzheimer's disease

The distribution of vasopressin and oxytocin immunoreactive fibers was examined in the pontine parabrachial nucleus of the human brain using purified polyclonal antibodies. The results revealed a striking predominance of vasopressin in this brain region. No obvious density difference, either in vasopressin or in oxytocin innervation, was found between Alzheimer's disease patients and matched controls. The present study corroborates other reports that suggest that in Alzheimer's disease the vasopressin innervation in the caudal part of the human brain is not affected.

Comparison of the number of vasopressin-producing hypothalamic neurons in rats and humans

The aim of this study was to assess the number and proportion of vasopressin-producing neurons in the hypothalamic magnocellular nuclei in rats and humans. Accurate and unbiased neuronal counts were estimated using the optical disector method. Arginine vasopressin-containing neurons were immunohistochemically visualized in formalin-fixed tissue sections. The magnocellular neurons were similar in size and morphology in both species. While the human hypothalamus contained significantly more vasopressin-containing neurons compared with the rat (36-fold increase), the proportion of vasopressin-containing neurons between species was similar. In both species, the majority of supraoptic neurons contained vasopressin, however the proportion of vasopressin-containing neurons in the human paraventricular nucleus was double that of the rat (nearly a 100-fold increase in number). These results suggest that the paraventricular nucleus contributes significantly to the release of vasopressin from the posterior pituitary in humans, whereas in rats vasopressin is mainly released by supraoptic neurons.

Loss of immunoreactivity for glial fibrillary acidic protein (GFAP) in astrocytes as a marker for profound tissue damage in substantia nigra and basal cortical areas after status epilepticus induced by pilocarpine in rat

Status epilepticus induced by pilocarpine in rats induces massive tissue damage comprising neurons and astrocytes (incomplete infarction) in substantia nigra pars reticulata (SNR) and in basal cortical areas (BCTX). Immunohistochemistry with a polyclonal antiserum and a monoclonal antibody to GFAP were used here to study the astroglial damage in these regions. Control sections showed a strong labeling for glial fibrillary acidic protein (GFAP) for both antibodies in SNR and BCTX. At 1 day after induction of seizures, labeling with the polyclonal antibodies showed diffuse increase within the lesioned areas and enhanced staining of astrocytes at the border zones. However, staining with the monoclonal antibody was abolished. At 3 days, labeling with both the polyclonal antiserum and the monoclonal antibody was severely reduced within the damaged regions. Reactive astrocytes in the surround of the infarct showed enhanced labeling with both antibodies. This combination of enhanced labeling with polyclonal antibodies and decreased labeling with the specific monoclonal antibody for GFAP can be taken as indicator for acute glial cell damage in seizures and related experimental conditions.

Induction of c-fos and CRF mRNA by MK-801 in the parvocellular paraventricular nucleus of the rat hypothalamus

The non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine maleate (MK-801) stimulates the secretion of adrenocorticotropin hormone (ACTH). As corticotropin-releasing factor (CRF) represents the primary modulator of this secretion, we tested the hypothesis that the ability of MK-801 to activate the hypothalamic-pituitary-adrenal (HPA) axis was modulated through actions at the hypothalamic level that modulate the secretion of CRF. Induction of the immediate-early gene c-fos, as well as of CRF mRNA within the paraventricular nucleus (PVN) of the rat hypothalamus, was examined following the intraperitoneally administration of MK-801 (1 mg/kg). MK-801 markedly increased the expression of Fos-like protein in parvocellular nerve cells of the PVN within 60 min of systemic treatment, and double labeling immunocytochemistry indicated that Fos was primarily localized in CRF-containing neurons of the PVN. MK-801 also significantly increased CRF biosynthesis as detected by in situ hybridization, thus suggesting that c-fos could be involved in the regulation of CRF genes. Taken together, these results suggest that MK-801 stimulates the rat HPA axis probably through the neuronal gene expression of PVN CRF. The significance of these data is discussed in terms of hypothalamic NMDA receptor blockade and subsequent transcriptional regulation of CRF by immediate-early genes.

A rapid and sensitive radioimmunohistochemical assay for quantitation of vasopressin in discrete brain regions with an anatomical resolution

Radioimmunoassay has become a widely used method to study different neuroactive substances from brain tissue extracts, but cannot provide anatomical resolution. Here we describe a simple and sensitive radioimmunohistochemical assay (RIHA) to quantify a peptide, vasopressin (VP), in discrete brain regions of rats with 3-day water deprivation. After decapitation, brains were removed, frozen with dry ice and cut into 14-microns cryostat sections which were then fixed with 4% paraformaldehyde in phosphate-buffered saline. After rinses, tissue sections were stored in a freezer until use. For RIHA, brain tissue sections were pre-incubated, and then incubated with rabbit vasopressin antibody (1:2000 dilution) for 24 h at room temperature. After rinses, sections were incubated with 125I-labeled goat antirabbit IgG (1:200 dilution) for 1 h. Specimens were processed for quantitative autoradiography after rinses and drying. RIHA with aid of a computer-assisted image analysis system revealed that the VP content was significantly reduced in the paraventricular hypothalamic nucleus (PVN) and supraoptic nucleus (SON) of rats with 3-day water deprivation, whereas a parallel in situ hybridization study further demonstrated that VP mRNAs in the PVN and SON were greatly increased. In summary, this experiment demonstrates that RIHA is a simple and powerful tool which is able to detect changes of VP in the hypothalamus of dehydrated rats. Combining this method with in situ hybridization to assess mRNA expression allows assessment of the functional significance of the peptide changes. In this case, dehydration depletes vasopressin and upregulates its synthesis. Therefore, the combined use of RIHA and in situ hybridization should have general applicability to evaluate the functional role of a peptide or neurotransmitter system in response to stimuli in a quantitative way with anatomical resolution.