Mesotocin and vasotocin in the brain of the lizard Gekko gecko

Summary The distribution of mesotocin and vasotocin was studied in the brain of the lizard Gekko gecko with antisera specific for either peptide. Both mesotocinergic and vasotocinergic perikarya are found in the paraventricular and supraoptic nuclei of the hypothalamus, whereas vasotocinergic neurons are exclusively present in the bed nucleus of the stria terminalis and in a cell group of the rhombencephalon. The distributional pattern of the mesotocinergic fibers corresponds closely to that of the vasotocinergic fibers. However, throughout the entire brain the mesotocinergic innervation is less dense than the vasotocinergic innervation. No sex differences are present in the mesotocinergic fiber system.Abbreviations acc nucleus accumbens - bst bed nucleus of the stria terminalis - bv blood vessel - dB diagonal band of Broca - dc dorsal cortex - dth dorsolateral thalamic nucleus - lc lateral cortex - me median eminence - oc optic chiasma - ot optic tract - pag periaqueductal grey - pvn paraventricular nucleus - rc rhombencephalic cell group - sep septum - son supraoptic nucleus - tect mesencephalic tectum - vth ventrolateral thalamus     

Immunocytochemical localization of aminopeptidase N on the cell surface of isolated porcine thyroid follicles

Summary The ultrastructural location of aminopeptidase N on the cell surface of isolated porcine thyroid follicle cells was studied with immunocytochemistry using antibodies against intestinal aminopeptidase N and protein A-colloidal gold. Gold particles, indicating immunoreactivity, were selectively attached to the apical cell surface. Occasionally, there was a sparse labelling of the basal cell surface. In follicles kept at 4° C most gold particles at the apical cell surface appeared as clusters, with each gold particle situated at a constant distance of about 20 nm from the membrane surface. The gold particles were concentrated on the membranes of microvilli, in comparison to the smooth (intermicrovillar) portions of the apical plasma membrane. In follicles incubated at 37° C for 5–180 min gold particles were slowly internalized by predominantly smooth-surfaced micropinocytic vesicles and subsequently appeared in colloid droplets and lysosomes. Gold particles were not observed in Golgi cisternae. TSH did not appear to influence the rate of internalization. TSH-induced pseudopods were unlabelled.Our electron-microscopic observations confirm previous immunofluorescence-microscopic evidence that aminopeptidase N is selectively expressed in the apical plasma membrane domain in the thyroid follicle cell. Furthermore, aminopeptidase N appears to be distributed in microdomains within the apical plasma membrane. Earlier indications of molecular differences between the pseudopod membrane and the apical plasma membrane proper are further emphasized.This study was supported by Grant No 12X-537 from the Swedish Medical Research Council     

Immunohistochemical localization of oxytocin and vasopressin in the adrenal glands of rat,cow, hamster and guinea pig

Summary The distribution of oxytocin and vasopressin in the adrenals of rat, cow, hamster and guinea pig has been studied by use of immunohistochemical techniques. In all the species studied the adrenal cortex contained both peptides; the staining in the zona glomerulosa being more intense than that in zona fasciculata or zona reticularis. The medulla, however, showed considerable species variation. In the cow, both peptides appear to be present in the adrenergic and noradrenergic cells, though staining was particularly prominent in cortical islands interspersed within the medullary tissue. In the rat, groups of medullary cells positive for both peptides were found, though it was not possible to associate these groups with particular chromaffin cell types. In the hamster oxytocin was present only in adrenaline-containing cells, whereas vasopressin was present in all medullary cells. The guinea pig medulla, which contains only adrenaline-secreting cells, was positive for both peptides. The possibilities that vasopressin and oxytocin have an autocrine or paracrine role in functioning of the adrenal gland is discussed.     

Structure of isolated sensilla and sensory neurons in vitro: Observations on developing silkmoth antennae

Summary By combined enzymatic and mechanical treatment, it was possible to dissociate the sensory epithelium of developing antennae of male Antheraea polyphemus and A. pernyi silkmoths from the stage of separation of the antennal branches up to the early stages of cuticle deposition. Large numbers of entire developing trichoid sensilla were isolated. These are characterized by a large trichogen cell with a long apical, hair-forming process and a large nucleus. A cluster of 2–3 sensory neurons, enclosed by the thecogen cell, is situated in the basal region. The dendrites run past the nucleus of the trichogen cell into the apical process from which they protrude laterally. The nuclei of the tormogen and a 4^th enveloping cell can be distinguished near the base of the prospective hair. After further dissociation, only the neuron clusters remain, still enclosed by their thecogen cell and often attached to the antennal branch nerve via their axons. It is finally possible to disrupt the thecogen cells and the axons, leaving the sensory neurons with inner dendritic segments and axon stumps. The majority of these neurons can be expected to be olfactory.     

The superficial vascular hyaloid system in the eye of the frogs,Rana temporaria and Rana esculenta

Summary The angioarchitecture of the superficial vascular hyaloid system (membrana vasculosa retinae) of the frog eye was studied by means of scanning electron microscopy of vascular corrosion casts. The terminal vessels form a single-layered sheath intimately adjacent to the vitreal side of the avascular retina. The hyaloid system is subdivided by the ventral venous trunk into three central areas: the dorsal, the temporo-ventral, and the naso-ventral area. Toward the ora serrata, the hyaloid system is bordered by an arterial ring, and by nasal and temporal venous branches forming more or less complete hemicircles. A vascular zone composed of several tongue-like sectors establishes an inter-connection between the peripheral vascular rings and the central areas of the fundus. The arterial blood is supplied from the arterial ring. The drainage of the hyaloid system is provided via two routes: (1) the Y-shaped ventral trunk collects blood from the central areas, (2) the two peripheral venous branches drain the tongue-like sectors. The vessels within the dorsal area follow preferentially a dorso-ventral meridional direction. This densely capillarized territory corresponds in localization to the area centralis retinae. The ultrastructure of microvessels of the hyaloid system is characterized by features typical for capillaries of the central nervous system.     

Glomerular ultrastructure of the trout,Salmo gairdneri: Effects of angiotensin II and adaptation to seawater

Summary The effect of angiotensin infusion on the glomerular ultrastructure of freshwater- and seawater-adapted rainbow trout, Salmo gairdneri, has been examined by scanning and transmission electron microscopy. Adaptation of trout to seawater resulted in epithelial podocyte flattening, primary process broadening and apparent loss of foot processes in almost all glomeruli, features which were uncommon in freshwater-adapted trout. Similar changes were induced by infusion of freshwater-adapted animals with angiotensin, suggesting that the renin-angiotensin system plays a role in the modification of glomerular epithelial ultrastructure. Adaptation of trout to seawater also reduced glomerular diameter, but infusion of freshwater-adapted animals with angiotensin did not mirror this effect. Infusion of angiotensin into seawater-adapted animals increased the overall thickness of glomerular basement membrane by increasing the lamina rara interna and lamina densa. This did not occur when freshwater-adapted fish were either infused with angiotensin or adapted to seawater. These findings suggest that other humoral systems are involved in the control of glomerular diameter and basement membrane thickness as part of an integrated response to increased environmental salinity.     

In vivo binding and uptake of low-density lipoprotein-gold- and albumin-gold conjugates by parenchymal and sinusoidal cells of the fetal rat liver

Summary To elucidate the participation of fetal rat liver cells in the receptor-mediated internalization of low-density lipoproteins (LDL), rat fetuses were injected with either LDL-gold or albumin-gold conjugates. The degree of binding and uptake of LDL-gold and albumin-gold by parenchymal and sinusoidal cells of the fetal rat liver differs markedly. Endothelial cells exhibit low LDL-gold uptake. In contrast, parenchymal cells internalize LDL-gold more actively (45 ± 8 LDL conjugates/100 m² cytoplasm within 60 min). Kupffer cells exceed this value by a factor of 20. The uptake of albumin-gold by endothelial and Kupffer cells is high, whereas it is extremely low in parenchymal cells. Estradiol pretreatment causes a significant doubling (p<0.05) of the LDL-gold particle density/100 m² cytoplasm both in parenchymal and Kupffer cells, whereas estradiol has no effect on the albumin uptake. The results strongly indicate that LDL uptake by parenchymal and Kupffer cells in the fetal rat liver is mediated by estrogen-inducible receptors, which may correspond to B, E receptors in the adult liver.     

Ultrastructural localization of adenosine triphosphatase activity in HeLa cells at various stages of the cell cycle

Summary HeLa cells in a monolayer culture were synchronized to S, G₂ and mitotic phases by use of excess (2.5 mM) deoxythymidine double-block technique. The localizations of Ca⁺⁺-activated adenosine triphosphatase (ATPase) at different phases of the cell cycle were studied using light and electron-microscopic histochemical techniques, and microphotometric comparisons of the densities of reaction products. Enzyme reaction product was always localized in the endoplasmic reticulum, nuclear membrane, mitochondria and Golgi apparatus, but there were qualitative and quantitative differences related to the phases of the cell cycle. In S phase the activity was mainly concentrated in a perinuclear area of the cytoplasm whereas in G₂ and mitosis the activity was scattered throughout the cell. The total activity per cell was maximal in G₂, was less in S phase and least in mitosis. Activity in the mitochondria and endoplasmic reticulum was distinctly less in mitosis than in other phases of the cell cycle. The mitochondrial ATPase differed from the ATPase at other sites in ion dependence and sensitivity to oligomycin. The results suggest that there may be several distinct ATPases in proliferating cells.     

A morphometric and ultrastructural study of lithium-induced changes in the medullary collecting ducts of the rat kidney

Summary Rats were given a lithium-containing diet (40 mmol/kg) to Study the effect of lithium on the structure of collecting ducts from the inner stripe of the outer medulla. The results show that there is a significant increase in the volume density of collecting ducts already after one week on this diet. The volume density of both intercalated and principal cells increases, whereas the volume density of mitochondria in the cytoplasm increases in the intercalated cells only. The increased volume of both principal and intercalated cells seems to be part of a general hyperplasia and hyperactivity of the collecting duct, which may in some way be related to the effects of lithium on vasopressinmediated water transport. The specific changes in the intercalated cells may be a consequence of the effects of lithium on distal nephron potassium and hydrogen ion transport in the distal nephron.     

Reutilisation of tritiated thymidine in studies of regenerating skeletal muscle

Summary Two different aspects of tritiated thymidine (³H-Tdr) reutilisation in skeletal muscle were examined. Injection of a high dose (7 Ci/g) of ³H-Tdr into mice prior to crush injury of skeletal muscle resulted in heavy labelling (grain counts) of myotube nuclei 9 d later. In contrast, myotube nuclei were essentially unlabelled when a low dose (1 Ci/g) of ³H-Tdr was injected at similar times with respect to injury. It was concluded that labelling seen after the high dose was due to reutilisation of ³H-Tdr. (Such ³H-Tdr reutilisation can account for the results of Sloper et al. (1970) which previously supported the concept of a circulating muscle precursor cell.) When replicating muscle precursors were labelled directly with ³H-Tdr 48 h after injury, the percentages of labelled myotube nuclei and the distribution of nuclear grain counts were similar with either high or low dose.We also investigated whether the light labelling seen in regenerated myotube nuclei after 9 d, when ³H-Tdr had been injected before the onset of myogenesis (as found by McGeachie and Grounds 1987), was due to ³H-Tdr reutilisation or, alternatively, to proliferation of local cells in the wound which subsequently gave rise to muscle precursors. Labelling of myotube nuclei was compared in mice injected with ³H-Tdr either 2 h before, or 2 h after injury. In another experiment, mice were injected 12 h after injury and lesions sampled 1, 12 or 36 h later, to see whether local cells were replicating 12 h after injury, and what labelled cells subsequently entered to wound. No difference was found in myotube labelling between mice injected before or after injury, and no cells replicating locally in the wound at 12 h after injury were observed. The results clearly show that the light labelling was due to ³H-Tdr reutilisation.