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Biomedical subjects

M Castel

Publications and source records attributed to M Castel.

31 records · Page 2Linked to original sources
PubMed1977

Pseudopodia formation by neurosecretory granules.

Ultrastrucal studies of the mouse neurohypophysis, under various experimental conditions, revealed a number of neurosecretory granules (NSG) bearing single pseudopodia-like protrusions. Some NSG adhered to the axolemma via pseudopodia; other NSG, distant from the axolemma, budded electron lucent microvesicles from the tip of the pseudopod. Pseudopodia counts were made on electron micrographs, and calculated as a percentage of the NSG population. In neural lobes from intact mice, small numbers of pseudopodia were observed (0.3%); the count increased significantly after injections of large doses of horseradish peroxidase (HRP) (9.4--14.5%); hypertonic saline augmented the count, as did histamine. In vitro incubation experiments with isolated neural lobes in Krebs Ringer revealed concomitant pseudopodia formation and elevated vasopressin release (measured by antidiuretic bioassay) in the presence of HRP and di-butyryl cyclic AMP respectively. Histamine and excess potassium also increased hormone secretion, but did not induce pseudopodia formation in vitro; pseudopodia were observed neither in controls, nor in the presence of ineffective secretagogues. It is suggested that the pseudopod may represent the active site on the granule membrane. Different ultrastructural images of granule release suggest that several modes of hormone release may be operative in the neurohypophysis. The role of HRP in pseudopodia formation and vasopressin release is enigmatic.

Animals↗
PubMed1976

Ultrastructural immunohistochemical localization of vasopressin in the hypothalamic-neurohypophysial system of three murids.

Vasopressin was immunohistochemically localized at the electron microscopic (EM) level in the hypothalamic-neurohypophysial system (HNS) of three murids. Antiserum to vasopressin was produced in rabbits injected with lysine vasopressin (LVP) conjugated to egg albumin (EA), anti-EA being precipitated prior to staining. Sternberger's unlabeled antibody peroxidase technique was employed, immunoreactivity being designated by peroxidase-anti-peroxidase (PAP) molecules and electron opacity. Immunoreactive neurosecretory granules (NSG) were found in the perikarya of the supraoptic nucleus (SON) in all three murids investigated, although far more profusely in the two wild strains. Immunoreactive axonal NSG were observed in the inner and outer zones of the median eminence (ME), and within most of the axons and terminals in the neurohypophysis. The concentration of primary serum effective for staining the SON (1:10-1:50) was far higher than that required for the ME and the neurohypophysis (1:500-1:1,200). Anti-LVP also induced electron opacity of granules in cells of the pars intermedia (PI). Discussion centers of the significance of immunoreactive NSG in the neurosecretory (NS) perikarya, on the possibility of an extragranular pool of hormone, and on speculation about the electron opacity of the PI granules.

Animals↗
PubMed1976

Ultrastructure of region of a low safety factor in inhomogeneous giant axon of the cockroach.

1. The structure of the ventral giant axons of the cockroach at the level of ganglion T3 was studied by means of light and electron microscopy. 2. From serial sections and cobalt injections, the axons diameter was found to range between 40 and 60 mum at the caudal end of ganglion T3; toward the center of T3 they narrow to 20-40 mum, and again expand to 30-45 mum anteriorly in ganglion T3. 3. Each giant axon sends off several branches, 1-15 mum in diameter, into the neuropil. The giant axons and the bases of their branches are enveloped by cytoplasmic processes of glial cells. The periaxonal space is about 100-200 A. 4. Distally the branches are devoid of glial envelopes and the extracellular space between the branches and other axonal profiles is about 200 A. Terminals with presumptive chemical synapses on the giant axon branches were found. Clear vesicles, 300-400 A in diameter, are seen clustered together. The width of the supposedly synaptic gap is about 100 A. 5. In some areas the branches and other axonal profiles form close appositions.

Animals↗
PubMed1975

The ultrastructure of normal and glycerol treated muscle in the ghost crab, Ocypode cursor.

The ultrastructure of normal and glycerol treated fibers of the closer muscle of the ghost crab, Ocypode cursor, was studiedmthe muscle is composed of presumably phasic (short sarcomeres) and tonic (long sarcomeres) fibers, the latter greatly predominating. Horseradish peroxidase (HRP) was used as an extracellular tracer to delineate the tubular system (TS), and to determine to what extent this system becomes detached from the extracellular space as a result of glycerol treatment. Sarcolemmal clefts invade deeply into the muscle at Z-lines and I-bands; tubules invaginate into the muscle from the clefts and from the surface sarcolemma at the Z-lines, A-I overlaps and A-bands. A tubules are in frequent diadic or tetradic contact with the sarcoplasmic reticulum (SR), whereas Z tubules appear to be randomly associated with SR, terminal cisterns (TC) and Z-line fibrils. When HRP was administered to normal muscle, black reaction product was found adjacent to the outer surface of the sarcolemma, within the clefts and within profiles of the TS throughout the tissue. In glycerol treated muscle peripheral vacuolation frequently occurred; black reaction product penetrated only as far as the vacuoles and into dilated Z-line tubules, but was virtually absent from the rest of the TS. This lack of continuity between the extracellular space and the A tubules indicated disruption or constriction of the A tubules as a result of glycerol treatment, although Z tubule contact with the extracellular space appeared unimpaired. These findings provide ultrastructural correlates of the electrophysiological changes produced by glycerol treatment of the closer muscle of the ghost crab (Papir, 1973), namely, interference with excitation-contraction (e-c) coupling. The random association of the Z tubules with SR and TC, and their resistance to disruption by glycerol treatment, tend to endorse the claims that the Z tubules in crustacean muscle are not directly involved in e-c coupling (Brandt et al., 1965; Peachey, 1967; Selverston, 1967).

Animals↗
PubMedDate not supplied

Immunocytochemical identification of dynorphin-containing vesicles in Brattleboro rats.

Vasopressin and its carrier protein, vasopressin-associated neurophysin, are co-packaged together with an opioid peptide, dynorphin, into 160 nm diameter neurosecretory vesicles in the normal rat hypothalamo-neurohypophysial system. The homozygous Brattleboro rat lacks vasopressin and vasopressin-associated neurophysin, but contains substantial amounts of dynorphin in the vasopressin-deficient neurosecretory cells. We used post-embedding electron microscopic immunocytochemistry to determine the subcellular location of dynorphin in Brattleboro rats. The results show that dynorphin is present within 100 nm neurosecretory vesicles in homozygous Brattleboro cell bodies and axons, and within 160 nm vesicles in heterozygous (control) neurosecretory cell bodies and axons. Oxytocin-associated neurophysin is present in a separate population of magnocellular neurons in both homozygous and heterozygous rats, and is contained within 160 nm vesicles in both cases. Therefore, the absence of synthesis of the vasopressin prohormone results in a dramatic reduction of neurosecretory vesicle size, despite the continued synthesis and packaging of dynorphin peptides.

Animals↗
PubMedDate not supplied

Microsporidian infection in the cyst wall of Trematode metacercariae encysted in fish.

Microsporidian infection is reported in Liza ramada (Risso), Mugilidae, from Bardawil Lagoon, Mediterranean coast of Sinai, in the fibroblasts of the metacercarial capsule of Heterophyes heterophyes (Siebold). Infection of the metacercarial cyst resulted in an hypertrophy of the cyst wall and degeneration and eventual death of the encapsulated metacercaria.

Animals↗
PubMedDate not supplied

[Environment of invasive breast carcinoma. Morphological and epidemiological study].

In a retrospective study, the authors have observed different types among 180 breast invasive carcinomas, their environment and their epidemiology. Tumors consisted in 158 invasive ductal carcinomas, 11 invasive lobular carcinomas and 11 special forms. The benign environment was divided in 3 groups: no epithelial lesion (1/5 cases), "mastosis simple" (3/5) (elementary lesions more or less associated, exceptionally isolated, diffuse or focal), the last, 1/5, corresponded to a "mastosis complex" defined as the significant association of the same elementary lesions (minimum 3 to 4), diffuse, with some degree of dysplasia and always an intraductal hyperplasia, of any type. The confrontation of these environments with carcinoma types and grades and with some epidemiological data allowed: 1) To opposite intraductal hyperplasias, mainly "mastosis complex", to other environments; 2) to discuss a) "mastosis complex" position in relation to cancer, b) an eventual lobular origin for precancerous lesions and c) individualization of epidemiological factors in relation to development of malignant tumors.

Adenocarcinoma↗