Wheat germ agglutinin binding in rat primary sensory neurons: a histochemical study

Summary The binding of wheat germ agglutinin (WGA) to L5 dorsal root ganglion (DRG) cells in the rat was studied with the WGA-FITC conjugate. These cells were also examined with regard to overlap between WGA staining and choleragenoid-like immunoreactivity. The DRG cells showed varying intensity of the staining, which was confined to the cytoplasm. The majority of the small cells were heavily stained, whereas the large cells showed less or occasionally no staining. Lectin binding was observed along nerve fibres in the ganglion, and appeared to be localized to the Schwann cells and to the nodes of Ranvier. Strong staining was also observed in the area surrounding the ganglion cells and seemed to be confirned to the satellite cells. A subpopulation of the ganglion cells showed both WGA-staining and choleragenoid-like immunoreactivity. These results indicate a nonuniform affinity of WGA for different subpopulations of DRG neurons.     

Early sexual differentiation of diencephalic dopaminergic neurons of the rat in vitro

Summary Serial brain sections of female rats at late pregnancy, parturition or early lactation were immunostained for oxytocin. Immunoreactive perikarya were visible in the magnocellular nuclei in all experimental animals as well as in ovariectomized, nulliparous controls. During late pregnancy and at parturition additional immunostaining appeared in groups of perivascular neurons in the preoptic region, the lateral subcommissural nucleus, the perifornical region and scattered throughout the ventral portion of the hypothalamus. Immunostaining of almost all of these perivascular neurons disappeared by day two postpartum, while another population of oxytocin neurons, without association with blood vessels, appeared in these brain regions after parturition. Immunostaining of processes from oxytocinergic neurons in the periventricular nucleus increased markedly near parturition. Many of these processes projected toward the third ventricle. Oxytocinergic neuronal systems that are activated in late pregnancy and early postpartum may contribute to several physiological changes associated with parturition and lactation including the onset of maternal behavior.     

Directed differentiation of neural cells to hypothalamic dopaminergic neurons

Hypothalamic neurons play a key role in homeostasis, yet little is known about their differentiation. Here, we demonstrate that Shh and Bmp7 from the adjacent prechordal mesoderm govern hypothalamic neural fate, their sequential action controlling hypothalamic dopaminergic neuron generation in a Six3-dependent manner. Our data suggest a temporal distinction in the requirement for the two signals. Shh acts early to specify dopaminergic neurotransmitter phenotype. Subsequently, Bmp7 acts on cells that are ventralised by Shh, establishing aspects of hypothalamic regional identity in late-differentiating/postmitotic cells. The concerted actions of Shh and Bmp7 can direct mouse embryonic stem cell-derived neural progenitor cells to a hypothalamic dopaminergic fate ex vivo.     

Influence of sexual differentiation on striatal and limbic catecholamines

The influence of sexual differentiation of the brain on catecholamine content in the corpus striatum and limbic system was studied. Our results suggest that circulating ovary hormones during the critical period play an important role in the sexual differentiation of dopaminergic neurons in the corpus striatum and limbic system. Absence of androgenic steroids in the critical period leads to permanent alterations in the DA content of the limbic system in the male rat. Gonadectomy does not significantly alter NA levels in either of the two studied brain areas.     

Glucagon-like immunoreactivity in hypothalamic neurons of the rat

Summary Antisera specific for three different regions of pancreatic proglucagon were used to examine the distribution of such immunoreactivity in rat hypothalamus. Neurons in the supraoptic and paraventricular nuclei were immunoreactive with an antiserum against glucagon, but not with antisera directed towards the aminoterminal region of proglucagon (glicentin) or the glucagon-like peptide I sequence in the carboxyl-terminal region of proglucagon. These findings confirm a previous report of glucagon-like immunoreactivity in the supraoptic and paraventricular nuclei, but indicate that, while this material is immunochemically related to glucagon, it is not derived from a proglucagon-like precursor.     

Mercury-selenium interactions in relation to histochemical staining of mercury in the rat liver

Summary Selenium has been suggested to enhance the histochemical staining of mercury when sections of tissue are subjected to the silver-enhancement method. In the present study, histochemical staining patterns of mercury in tissue sections of rat livers were compared with the actual content of organic and inorganic Hg in the livers, in both the presence and the absence of Se. Rats were injected intravenously with 5g of Hgg^–1 body weight as methyl [²⁰³Hg] mercury chloride (MeHg) or as [²⁰³Hg]mercuric chloride (Hg²⁺). After 2h, half the rats received an additional intraperitoneal injection of 2g of Se g^–1 body weight as sodium [⁷⁵Se]selenite. All the rats were killed 1h later. Homogenized liver samples were prepared for mercury analysis by two different methods: alkaline digestion and ultrasonic disintegration. Quantitative chemical analysis based on benzene extrction of the radioactively labelled Hg compounds showed that the chemical form of mercury, either organic or inorganic, was preserved from its administration to its deposition in the liver. Light and electron microscopy demonstrated that no silver enhancement of Hg occurred when MeHg alone was present in the sections of tissue, whereas MeHg accompanied by Se induced a moderate deposition of silver grains. In contrast, sections containing Hg²⁺ alone yielded some staining, and the addition of Se increased the staining dramatically. The results of the present study show that acute selenite pretreatment is a prerequisite for the histochemical demonstration of methyl mercury, and greatly increases the staining of inorganic mercury when applying the silver-enhancement method.     

A histochemical study of catecholamines and cholinesterases in the autonomic nerves of the human minor salivary glands

Synopsis The cholinergic and adrenergic innervation of human minor sublingual buccal and labial salivary glands has been studied with histochemical techniques for localizing acetylcholinesterase and catecholamines. A rich cholinergic innervation was observed around the acini, blood vessels and some ducts of the three glands.The adrenrgic innervation, however, was virtually absent from the parenchyma although present around the blood vessels, in marked contrast to the dense parenchymal adrenergic innervation observed in the human parotid and submandibular glands. These results suggest that the autonomic nervous mechanism which regulates salivary secretion is more elaborate in the major than in the minor salivary glands.     

Effect of acute ethanol on beta-endorphin secretion from rat fetal hypothalamic neurons in primary cultures

To characterize the effect of ethanol on the hypothalamic beta-endorphin-containing neurons, rat fetal hypothalamic neurons were maintained in primary culture, and the secretion of beta-endorphin (beta-EP) was determined after ethanol challenges. Constant exposure to ethanol at doses of 6-50 mM produced a dose-dependent increase in basal secretion of beta-EP from these cultured cells. These doses of ethanol did not produce any significant effect on cell viability, DNA or protein content. The stimulated secretion of beta-EP following constant ethanol exposure is short-lasting. However, intermittent ethanol exposures maintained the ethanol stimulatory action on beta-EP secretion for a longer time. The magnitude of the beta-EP response to 50 mM ethanol is similar to that of the beta-EP response to 56 mM of potassium. Ethanol-stimulated beta-EP secretion required extracellular calcium and was blocked by a calcium channel blocker; a sodium channel blocker did not affect ethanol-stimulated secretion. These results suggest that the neuron culture system is a useful model for studying the cellular mechanisms involved in the ethanol-regulated hypothalamic opioid secretion.     

Enzyme histochemical differentiation of white adipose tissue in the rat

Subcutaneous adipose tissues from fetal and young rats were studied with enzyme histochemical techniques. Lipid staining and histological evaluation were also utilized to compare the development of a wide variety of enzyme activities to cytoplasmic lipid deposition and morphological differentiation of adipocytes. Three distinct stages of adipose-tissue differentiation were postulated. In stage III, adipocytes were morphologically differentiated (rounded, basal-lamina positive) and enzyme reactive for many enzymes. In stage II, however, adipocytes were reactive for some enzymes but were not morphologically differentiated. Stage I adipose tissue was histologically distinct from connective tissue but did not contain lipid-laden cells or enzyme-reactive cells. Stages I and II (95%) were predominant in fetuses, whereas stage III (90%) was predominant in young animals. Histochemical analysis of adipocytes in newborn rats established the metabolic competence of these cells despite their small size. These studies indicate that enzymatic differentiation of adipocytes clearly precedes morphological differentiation.     

Lectin histochemical study of olfactory neurons in the eel

Lectin histochemical studies were performed on paraffin embedded sections of the olfactory system of the eel to identify specific glycoconjugates on the surface of primary olfactory neurons. The olfactory receptors, the olfactory nerve fibres and their terminals in the bulbs were labelled with the lectins (SBA, BSA-I, BSA-I-B4 and DBA) HRP-conjugated or biotinylated. The lectin staining patterns indicate that the membrane of olfactory neurons of the eel had oligosaccharides with alpha-galactose and alpha-N-acetyl-D-galactosamine residues. These findings represent the demonstration of a molecular probe that recognizes specific sets of neurons. The identical histochemical features previously described in the olfactory neurons in amphibians suggest that these carbohydrate moieties might to related to modulation of the cell-cell interactions in the olfactory system of vertebrates.     

A pharmacokinetic approach to morphine analgesia and its relation to regional turnover of rat brain catecholamines.

Morphine concentrations in plasma and four discrete areas of the rat brain following intravenous administration, can be described by a three-compartment open model. The pharmacokinetic behavior of morphine was the same in each of the different parts of the brain. When relating this behavior to the effects of morphine on the threshold for vocalisation and vocalisation-after-discharge, it was possible to develop a pharmacokinetic model which suggests that morphine induces its analgesic effect by a change of activities in at least two neurophysiological systems.As a result of investigations of morphine-induced changes of catecholamine turnover in different parts of the brain and of the consequences of modulating central monoaminergic activity prior to morphine administration, it was suggested that one of the two neurophysiological systems could be dopaminergic. In this system morphine increases the turnover of dopamine, most probably by releasing this transmitter from limbic structures that initiate the effect of morphine on the threshold for vocalisation-afterdischarge (the emotional component of pain reactions).     

Response of rat hypothalamic perinuclear supraoptic neurons to stimulating the pituitary stalk and hippocampus

Orthodromically activated neurons (OAN) are found in the hypothalamic supraoptic area under pituitary stalk stimulation, differing in their dependence on pattern of orthodromic activation and recording site. More than a half of OAN responded to stimulation of the ventral hippocampus and response was consistently excitatory initially. Some similarity was found between the pattern of response of most OAN to pituitary stalk stimulation. Aspects of hippocampal influence on OAN taking account of their location within the supraoptic nucleus area and the perinuclear zone are examined, as well as their presumed morphofunctional connections with antidromically identified neurosecretory cells.A. A. Ukhtomskii Institute of Physiology, State University, Leningrad. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 596–604, September–October, 1990.     

Ultrastructural studies on the hypothalamic neurosecretory neurons of the rat

The spermatozoa of two closely related species of ophiuroids, Ophiocoma echinata and Ophiocoma wendti, were examined ultrastructurally. Morphologically, these spermatozoa resemble those of other non-echinoid echinoderms. The acrosomal complex, completely contained within an anterior fossa in the spherical nucleus, consists of a membrane-limited acrosomal vesicle and periacrosomal material. Events of the acrosomal reaction in O. echinata and O. wendti are presented. In both species, the reaction results in the establishment of an extracellular coat of acrosomal vesicle origin on the anterior surface of the spermatozoon. The possible role of this extracellular coat in the species-specific binding of sperm and ova is discusses. The origin of acrosomal tubule membrane is elucidated.