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H D Dellmann

Publications and source records attributed to H D Dellmann.

At least 37 records · Page 2Linked to original sources
PubMed1984

Fine structural cytology of the rat subfornical organ during ontogenesis.

The main developmental events in the subfornical organ take place between 17 fetal days (fd) and 5 days post natum (dpn) at which time it possesses most of its mature fine structural characteristics. The surface regional characteristics of ependymal cells differentiate primarily during this time as well, while the ependymal cellular fine structure, shape and relationship with neurons and the vascularity are well established prior to birth. Undifferentiated neurons contain glycogen prior to 19 fd and then differentiate by developing processes and organelles characteristic of neurons. By 5 dpn, the various types of neurons found in the mature subfornical organ are all present, except for giant vacuolated cells. Synapses containing only electron-lucent vesicles are first present at 20 fd, those containing additional electron-dense vesicles at 3 dpn. Microglial cells are first identifiable at 17 fd, and the first protoplasmic astrocytes are recognizable at 21 fd, while fibrous astrocytes are not detectable prior to 7 dpn. By 5 dpn, the cytological elements of the subfornical organ are all in place, and further developmental changes leading to adult fine structural characteristics by 30 dpn are essentially quantitative in nature.

Animals↗
PubMed1984

Biosynthesis and axoplasmic transport of neurophysins in the hypothalamo-neurohypophysial system of Rana pipiens.

Biosynthesis, axoplasmic transport, and storage of neurophysin in the amphibian (Rana pipiens) magnocellular peptidergic neurosecretory system were studied, and the results were compared with those reported in mammals. After injection of [35S]cysteine into the preoptic recess, light microscopic autoradiography provides evidence that neurons of the preoptic nucleus (PON) synthesize cysteine-rich proteins. The time course of appearance of these [35S]cysteine-labeled proteins in different regions of the hypothalamo-neurohypophysial system was studied by slab gel autoradiography. [35S]Cysteine-labeled proteins were found in the PON less than 1 hr postinjection, whereas a major labeled protein, tentatively identified as the neurophysin, first appeared in the infundibulum and neural lobe 4 hr after the injection. In addition, the labeled neurophysin persisted in the neural lobe throughout the entire observation period of 5 days. The minimum transport rate for neurophysin was calculated as 0.9 mm/hr (22 mm/day) at 25 degrees C. Two different neurophysins (with isoelectric points (pI) 4.9 +/- 0.1, 4.6 +/- 0.1, and Mr = 23,000, 20,100) may be resolved from the neural lobe extracts by isoelectric focusing and SDS-polyacrylamide gel electrophoresis, respectively. In addition to the neurophysin peaks, two radioactive peaks with pI 5.2 and 5.8 may be detected in the preoptic nucleus and the infundibulum as early as 30 min after [35S]cysteine injection. Preliminary conversion studies suggest a putative precursor role for the pI 5.2 protein. The results indicate that in the amphibian peptidergic neurosecretory system, the synthesis of cysteine-rich neurophysin by the preoptic neurons, the transport through the infundibulum, and the storage in the neural lobe proceed similarily to their mammalian counterparts.

Animals↗
PubMed1983

Voltage-sensitive Na+ channels in the neurohypophysis of the rat as demonstrated by 125I-labelled scorpion toxin.

Fresh rat neural lobe slices were incubated in the presence of [125I] alpha-scorpion toxin (ScTX), a specific marker of Na+ channels. Quantitative electron microscope autoradiography revealed preferential, irregularly spaced labeling of the axolemma of neurosecretory axons, with a significantly higher crude specific activity than any other neuronal or non-neuronal compartment. The number of specific binding sites at the neural lobe surface was calculated to be about 23 per microns2 of axolemma.

Animals↗
PubMed1983

Preservation of fine structure in vibratome-cut sections of the central nervous system stained for light microscopy.

A technique without negative effects on tissue preservation that allows precise identification and subsequent removal of central nervous system nuclei for ultrastructural analysis is described. The procedure uses 200 microns thick Vibratome-cut sections of glutaraldehyde fixed brains. These sections are stained for 25 seconds with a methylene blue solution and stored for 4 hours in 0.2 M pH 7.4 phosphate buffer in 4% sucrose for optimal visualization at the light microscopic level. The stock solution of 1 g methylene blue and 1 g sodium borate in 100 ml of distilled water, is filtered through a Millipore filter and diluted 5:95 with distilled water immediately prior to use. Regions of specific interest are then processed for electron microscopy.

Animals↗
PubMed1982

Reversible fine structural changes in the supraoptic nucleus of the rat following intraventricular administration of colchicine.

A single low dose (3.5 micrograms or 7.0 micrograms) of colchicine injected intraventricularly into normally hydrated or dehydrated (7 or 4 days) and, subsequently, rehydrated (3 hours) rats caused a number of characteristic changes within the perikarya of the supraoptic nucleus. The temporary slow-down of axonal transport of neurosecretory granulated vesicles (NGVs) and their continued synthesis led to a perikaryal accumulation of NGVs, and changes in their electron-density are considered to be indicative of their continued maturation. In some neurons, the biosynthetic pathway appears to be interrupted or temporarily impaired as evidenced by the accumulation of material of varying electron-density and of granules within the cisternae of the rough ER. An increased number of varying types of lysosomes and phagolysosomes is indicative for the disposal of NGVs within the perikaryon. Most of them are, however, removed through resumption of axonal transport which leads to the reestablishment of pre-experimental fine structural characteristics within approximately 9 days. In the osmotically stressed groups, the fine structural changes are more pronounced but equally reversible.

Animals↗
PubMed1981

Ultrastructural effects of anteroventral third ventricle lesions on supraoptic nuclei and neural lobes of rats.

Small lesions of the tissue surrounding the anterior ventral third ventricle (AV3V) cause adipsia, but there is no compensatory antidiuretic response. Therefore, the fine structure of the supraoptic nucleus and neural lobe, the major sites of synthesis and release of antidiuretic hormone (ADH), were compared in rats rendered adipsic by AV3V lesions 3 days earlier, rats deprived of water for 3 days and rats drinking normally. In sham-lesioned rats which were deprived of water, neuronal somas in the supraoptic nucleus show signs of stimulated secretory activity. However, the neuronal somas of supraoptic nuclei of rats which did not drink because they were made adipsic by AV3V lesions resemble those of normally hydrated controls. Neural lobes of water deprived animals contain a sharply reduced number of neurosecretory granulated vesicles and reduced apposition of glial processes with the perivascular connective tissue compared to those of normally hydrated rats. In contrast, neural lobes of rats with AV3V lesions contain large accumulations of densely packed neurosecretory vesicles, as well as abundant dense bodies and multilamellar bodies which may be evidence of increased crinophagy, and they have increased interposition of glial processes between axon endings and the perivascular connective tissue. In rats with AV3V lesions the severe dehydration due to adipsia was unable to stimulate release of ADH. The accumulation of neurosecretory vesicles in the neural lobe indicates that transport of ADH to the neural lobe was not impaired in this time period, but that exocytosis of ADH-containing neurosecretory vesicles in the neural lobe was blocked.

Animals↗
PubMed1981

Pituicyte fine structure in the developing neural lobe of the rat.

The fine structure of pituicytes was investigated between 15 days of fetal life and 120 days postnatum. Prior to the penetration of neurosecretory axons into the neural lobe a uniform population of undifferentiated pituicytes is presented. Coincidental with the first appearance of neurosecretory axons in the neural lobe at 16 1/2 days of fetal life is the beginning differentiation of those pituicytes into two varieties, an active and an inactive one. The active variety predominates and has all of the morphologic characteristics of an active secretory cell, especially during axonal growth in the neural lobe; between 16 1/2 days and birth most of the undifferentiated pituicytes have differentiated into active pituicytes. The inactive variety is rarely encountered before birth; the classification as an inactive cell is based on the lack of organelles involved in secretion. After adult conditions are reached between 25 and 30 days postnatum, the active pituicytes continue to prevail in the neural lobe, although they are less active than in the developmental period as judged by morphologic criteria. The inactive pituicytes increase in number with increasing age. In addition to the pituicytes two other cells are described, microglial cells and a cell whose exact nature remains to be determined.

Aging↗
PubMed1980

Thiamine pyrophosphatase activity in the axonal smooth endoplasmic reticulum of neurosecretory neurons.

Neurosecretory cells of the supraoptic-neurohypophysial system of normal mice were investigated with the use of the cytochemical reaction for thiamine pyrophosphatase (TPPase) at the ultrastructural level. In the hypothalamic perikarya dense lead percipitates occur within the cisterns of the mature face of the Golgi apparatus, these being the cisterns that give rise to neurosecretory granules (NSG). Smooth endoplasmic reticulum is occasionally confluent with TPPase-positive Golgi cisterns. Along axons, within swellings, and within terminals distinct profiles of TPPase-positive tubules and cisterns are revealed, apparently part of a network of axonal smooth endoplasmic reticulum (AER). Some NSG appear to be confluent with AER. NSG with TPPase-positive tubular protrusions (likely vestiges of AER) are seen. Apart from reaction product (lead precipitate), the AER often contains an electron dense substance optically similar to that of NSG. TPPase-containing AER is often associated with mitochondria. Profiles of electron-lucent, precipitate-free tubules and cisterns are occasionally seen alongside reactive AER. Optimal TPPase activity in the AER occurs at pH 7.0--7.4, whereas in the Golgi complex intense marking is in the range of pH 6.0--8.5. A faint peppering of precipitate occasionally appears in the AER in controls (incubation medium without substrate), but neither in density nor in extent is this comparable to the reaction product seen after incubation in the presence of TPP. Preliminary comparison has been made between the AER revealed by the TPPase reaction, and that visualized after heavy metal impregnation according to the method of Alonso and Assenmacher (1978a). The nature of the close association between NSG and AER, and the possible roles of this membrane system in neurosecretory cells is discussed.

Animals↗
PubMed1979

Ultrastructure of the subfornical organ of the chicken (Gallus domesticus).

The SFO of the chicken is divided in half by a large central blood sinus; ventrally it is covered by a thin layer of ependyma (including tanycytes, dendrites, and axons) which connects the two lateral halves and protrudes as a midsagittal crest into the lumen of the third ventricle. The ependyma consists predominantly of tanycytes with long basal processes which terminate upon perivascular spaces. These cells have an extensive Golgi apparatus and abundant lysosomes; their cellular apices containing polyribosomes and a few vesicles frequently protrude into the ventricle. In addition to astrocytes, oligodendrocytes, and microglial cells, there is another glial cell population that is distinguished by the presence of parallel stacks or spherical to ovoid conglomerates of rough ER and their unique location, i.e., limited to areas ventral and ventral-lateral to the large blood sinus. Two types of neurons are present: neurons in which there is a paucity of granulated vesicles and occasional vacuoles in both the cytoplasm and nuclei, the second type of neuron elaborates many granulated vesicles. Numerous puncta adhaerentia are observed between adjacent neuronal perikarya and between glial processes and neuronal perikarya. Diverse axon types are found within the chicken SFO. Axo-dendritic and axo-somatic axon terminals and presynaptic axon dilations contain assorted combinations of electron-lucent and granulated vesicles of different maximal diameters. Based on the morphology of these axons, cholinergic, peptidergic, and serotoninergic fibers are described. There are two additional groups of axons whose classification awaits further investigation. The chicken SFO differs from the mammalian SFO in several respects: it possesses an ependyma with secretory and/or absorptive tanycytes predominating; it is divided midsagittally by a central blood sinus; its lateral and dorsal limits are nebulous; a previously undescribed peculiar type of glial cell is found in a limited portion of the organ; supraependymal neurons are lacking.

Animals↗
PubMed1978

Scanning and transmission electron microscopy of the subfornical organ of the grass frog (Rana pipiens).

The ventricular surface of the subfornical organ of the frog is made up of ependymal cells with numerous apical microvilli, occasional cytoplasmic protrusions and many vacuoles projecting into the lumen of the third ventricle. Between these cells dendrites of cerebrospinal fluid-contacting neurons reach the ventricle to terminate in bulbous enlargements. In addition, flask-shaped encephalo-chromaffin cells, containing granulated vesicles and aggregates of filaments in their cytoplasm, project into the cerebrospinal fluid. Surrounding the centrally located capillaries are enlarged dendrites and axons of heterogeneous morphology, some of which appear to originate within the subfornical organ, intermingled with dendrites and axons of normal structure. The glial cells in this region, especially the microglial cells, often contain large lipofuscin inclusions, suggestive of degeneration and subsequent phagocytosis of some of the enlarged dendrites and axons. The normally scarce neurosecretory peptidergic axons become more evident and form typical Herring bodies in stalk-transected animals. Neuronal perikarya of varying morphology are predominantly located peripheral to the region of enlarged dendrites and axons. Supraependymal macrophages are particularly numerous on the subfornical organ.

Animals↗
PubMed1978

Central receptor sites for angiotensin-induced drinking: a critical review.

A review of proposed sites of the dipsogenic action of angiotensin II is presented. Techniques used for such localization are critically discussed, and it is suggested that convergence of evidence from several different experimental techniques is required for localization of dipsogenic receptors. Loci suggested as such sites of action include the preoptic regions, the subfornical organ, and the tissue proximal to the optic recess of the third ventricle, including the organum vasculosum laminae terminalis. Current evidence suggests that there are at least two loci within the forebrain that possess dipsogenic receptors for angiotensin II.

Angiotensin II↗
PubMed1977

Ultrastructure of homografts of the rat median eminence into the anterior chamber of the eye.

Median eminences (MEs) were transplanted into the anterior chamber of the eye and collected at times varying between 10 and 72 days. At 10 days, all axons had degenerated leaving behind a well-vascularized epitheloid glial organ. With increasing age of the grafts, the characteristic lipid inclusions in the glial cells diminished and even disappeared, and the clear ultrastructural distinction between ependymal (tanycytes) and other glial cells became difficult or even impossible. In both the perikarya and perivascular terminals, an increased number of membrane-bounded, pleomorphic, electron-dense granulated vesicles occurred, the significance of which is unknown. Regrafting of these transplants into various hypothalamic and hypophysial sites is expected to yield information on the function of the glial cells of the ME.

Animals↗
PubMed1977

Better epoxy resin embedding for electron microscopy at low relative humidity.

In the absence of other factors known to influence sectioning properties, high environmental relative humidity is shown to yield poorly embedded tissue. Humidity-related effects are avoided if the following embedding precedure is used; impregnate tissues using the following solutions 1) 70% alcohol - 5 minutes, 2) 95% alcohol - 2 x 15 minutes, 3) absolute alcohol - 3 x 20 minutes, 4) acetone - 2 x 15 minutes, 5) 1:1 mixture of acetone-epoxy resin (DDSA, 63.4 g; Araldite 502, 5.6 g; Epon 812, 39.4 g; DMP-30, 2.6 g) - 1 hour, 6) acetone-epoxy resin 1:3 - 1 hour, 7) epoxy resin - 1 hour; complete the preparation of blocks as follows 8) when tissues have been oriented in epoxy resin in flat embedding molds, place molds in one evacuated vacuum desiccator 10 cm above a 2 cm layer of Drierite for 24 hours at room temperature, 9) raise temperature to 60 C and maintain for 3 days to cure resin.

Animals↗
PubMed1976

Regional differences in the morphology of the rat subfornical organ.

Based upon scanning and transmission electron microscopy 3 regions are distinguished in the rat subfornical organ. The rostral region is dominated by nerve fibers interspersed with relatively few neurons and glial cells. Squamous to low cuboidal ependymal cells with flat ventricular surfaces bearing a few short microvilli line the center of this region; laterally, ciliated cuboidal ependymal cells predominate. The central region occupies the largest area of the organ and contains most of the neuronal perikarya and glial cells. Many perikarya and neuronal processes are located immediately underneath the ependymal surface. A dense capillary network with wide pericapillary spaces permeates the tissue. In the rostral two-thirds of this region the ependymal cells are either squamous or cuboidal, sometimes with slightly bulging ventricular surfaces bearing longer microvilli. Here supraependymal neurons are particularly numerous. The caudal one-third of the central region is characterized by squamous, cuboidal and columnar ependymal cells whose hemispherical ventricular surfaces are studded with long microvilli and occasional cilia and vesicular protrusions. The caudal region, like the rostral region, is dominated by nerve fibers between which neuronal perikarya and glial cells are present. At this level the choroid plexus is attached to the SFO through highly vascularized pial connective tissue. It is the major point of penetration of the SFO's capillary plexus. The possible significance of these observations and their importance in experimental interventions are discussed.

Animals↗