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Biomedical subjects

M Abraham

Publications and source records attributed to M Abraham.

At least 73 records · Page 4Linked to original sources
PubMed1984

The cellular envelope of oocytes in teleosts.

Structural and functional relationships between oocytes and their envelopes were studied by means of electron microscopy in several teleost species after injection of live fish with horseradish peroxidase. The marker first appeared in the capillaries and the pericapillary spaces of the ovarian stroma. It then entered the collagen-filled spaces between the granulosa and theca cells; these spaces are in direct connection with the pericapillary spaces. The marker penetrated between the follicle cells and into the channels of the zona radiata surrounding the microvilli which traverse these channels. The marker was never found inside the microvilli or in the follicle cells; finally, it reached the surface of the oocytes and was internalized via micropinocytosis. Six stages in the course of folliculogenesis were observed, determined by (1) the formation of follicular and thecal cellular layers and a collagen-filled space between them, (2) the development of microvilli of oocytal and follicular origin, (3) the differentiation of the vitelline envelope and the pore channels, (4) pinocytotic activity of the oocytes, and (5) rapid growth of the oocyte and its envelopes during vitellogenesis.

Animals↗
PubMed1982

Extravascular circulation in the pituitary of Mugil cephalus (Teleostei).

Extravascular circulation in the pituitary of Mugil cephalus was investigated by injecting live fish with horseradish peroxidase and studying the distribution of the enzyme in the gland. The principal components of the extravascular circulatory system are the pericapillary spaces, and, arising from them, the interlobular and circumhypophyseal spaces. Extensions of these spaces penetrate the glandular parenchyma of the pars distalis, where they merge with pericellular spaces. In the neurohypophysis, pericapillary spaces are connected to the periaxonal spaces. Capillaries penetrating from the proximal neurohypophysis into the pars distalis are accompanied by neurosecretory axons. These axons form a mass of tissue which is limited near the capillaries by the pericapillary spaces and near the adenohypophysis by the interlobular spaces. Toward the interior of the adenohypophysis the amount of nervous tissue accompanying the capillaries progressively diminishes, thus reducing the distance between pericapillary and interlobular spaces. Within the pars distalis, the neurosecretory axons accompanying the capillaries are sparse, and the secretory and stellate cells are mostly located directly adjacent to the pericapillary spaces. In the neurointermediate lobe, interlobular spaces outline the neuro-adenohypophyseal boundary. The relationship between extravascular spaces and hormone-secreting cells varies in the different regions of the adenohypophysis depending upon the type of neurosecretory innervation in the respective region. In the regions of prolactin and gonadotropin cells, where neurosecretory axons are in direct contact with the secretory cells, the hormone-secreting and stellate cells are adjacent to the pericapillary spaces. In the regions of ACTH and STH cells, secretory and stellate cells are found adjacent to the interlobular spaces, which are interposed between the cells and the neurosecretory axons.

Animals↗
PubMed1981

Prenatal assessment of fetal outcome by amniotic fluid C-peptide levels in pregnant diabetic women.

Amniotic fluid C-peptide (AFCP), insulin, and glucose levels were measured in 33 diabetic and 126 nondiabetic pregnant women at greater than or equal to 36 weeks' gestation. Levels of AFCP distinguished diabetic from nondiabetic patients more reliably than amniotic fluid (AF) insulin or glucose. Levels of AFCP in diabetic patients correlated well with infant birth weight adjusted for gestational age (large for gestational age greater than adequate for gestational age), degree of diabetic control (fair to poor control greater than good control), or diabetogenic infant morbidity, but did not correlate with classes of diabetes within the limits of the population studied. We conclude that AFCP is a useful prognostic index for predicting fetal outcome in diabetic pregnancies. A level of AFCP of greater than or equal to 1.0 pmoles/ml is associated with an increased risk of macrosomia in infants of diabetic mothers.

Adult↗
PubMed1981

Amniotic fluid C-peptide as an index for intrauterine fetal growth.

Amniotic fluid C-peptide (AFCP) was monitored as an indicator of the amount of insulin secreted by the fetus in utero. Levels of amniotic fluid and cord blood C-peptide, insulin, and glucose were measured in 103 nondiabetic infants at greater than or equal to 36 weeks's gestation. Infants were grouped according to birth weight and gestational age at delivery, as follows: small gestational age (SGA, less than or equal to 10%, n = 11), average for gestational age (AGA, 10% to 90%, n = 75), large for gestational age (LGA, greater than 90%, n = 17). AFCP correlated best with infant weight-gestational age percentile classification: low AFCP in SGA infants and high AFCP in LGA infants. The data from this study suggest that a persistently low production of insulin by SGA fetuses and a high production of insulin by LGA fetuses may lead to the different intrauterine growth rates observed.

Amniotic Fluid↗
PubMed1980

Bacilliform inclusions in cells of the proximal pars distalis in the pituitary of four species of Tilapia (Teleostei).

Thin sections and replicas of freeze-etched pituitaries from six species of the teleostean family of Cichlidae were studied by electron microscopy. Four species belonging to the genus Tilapia exhibit rod-like structures, i.e., "bacilliform inclusions" (BI), about 1-2 micrometer in length in cells of the proximal pars distalis. The BI are found either isolated or fused in small groups. They are enclosed in an envelope similar to that of secretory granules. Both the BI and the secretory granules give a positive PAS-reaction.

Animals↗
PubMed1980

The blood-testis barrier in Aphanius dispar (Teleostei).

Thin sections of normal testes from the cyprinodont Aphanius dispar were studied by electron microscopy after intravascular injection of live specimens with horseradish peroxidase. The intercellular space in the spermatogenic cysts is marked differently by the tracer according to the degree of differentiation of the germ cells. Spermatogonia and gonocytes undergoing meiosis are surrounded by a dark band of the marker. This band gradually disappears during spermiogenesis. In cysts containing ripe spermatozoa, the marker penetrates a short distance between the bases of adjoining Sertoli cells bordering the cysts, but is arrested by tight junctional complexes near the lumian of the cysts. The tight junctions between the Sertoli cells provide a permeability barrier between the vascular spaces of the stroma and the lumina of ripe cysts.

Animals↗
PubMed1980

Distribution of Vibrio parahaemolyticus in finfish harvested from Porto Novo (S. India) environs: a seasonal study.

A seasonal survey was undertaken to elucidate the incidence of Vibrio parahaemolyticus in freshly caught and market samples of fish collected from five distinct locales near Porto Novo. Vibrio parahaemolyticus was isolated from 35.6 and 40.6% of freshly harvested fishes from the estuary and mangroves, respectively, while only 3.9% of freshly caught specimens originating from the Bay of Bengal were positive for the pathogen. Isolation rates of 46.8% for fishes from the landing site and 40.6% for fishes from the fish market were recorded. Vibrio parahaemolyticus was more readily recovered from market samples of fish (44%) compared with freshly caught brackish water fishes (37.5%). Incidence of V. parahaemolyticus was higher during summer (March-July) than in other seasons.

Animals↗
PubMed1979

Freeze-etch study of the teleostean pituitary.

The structure of membranes in the pituitary of several teleostean species was studied with the freeze-etching technique. Nuclear pore density is higher in hormone-secreting than in stellate cells, suggesting a higher rate of nucleo-cytoplasmic interactions in the secretory cells. The perinuclear endoplasmic reticulum (ER) in the MAS-secreting cells has a large number of fenestrae, whereas in the ER whorls of the prolactin-secreting cells the fenestration occurs only rarely. Three different types of membrane specializations are described, presumably related to exo-endocytotic events at the level of the plasmalemma.

Animals↗
PubMed1979

[Netilmicin and tobramycin: comparative evaluation of pharmacokinetics, nephrotoxicity, and therapeutic efficacy in animal studies (author's transl)].

Pharmacokinetics, nephrotoxicity, and therapeutic efficacy of (2S-cis)-4-O-[3-amino-6-(aminomethyl)-3,4-dihydro-2H-pyran-2-yl]-2-deoxy-6-O-[3-deoxy-4-C-methyl-3-(methyl-amino)-beta-L-arabinopyranosyl]-N1-ethyl-D-streptamine sulfate (netilmicin) and tobramycin were investigated in rats. The excretion rates of tubular cells and of the urinary enzyme malic dehydrogenase served as parameter of nephrotoxicity. Both compounds were, similar to other aminoglycosides, tubulotoxic within the range of dosages used for human therapy. Netilmicin, however, produced less renal damage than did tobramycin in all dosages applied. Pharmacokinetic studies revealed lower renal concentrations of netilmicin after repetitive administration. Experimental chemotherapy of the chronic E. coli pyelonephritis in rats with both aminoglycosides resulted in a significant reduction of the renal bacterial counts. In spite of approximately identical serum concentration curves and in vitro activity, especially the low dosage of netilmicin led to more favourable therapeutic results than equal doses of tobramycin. These animal experiments suggest higher renal tolerance and efficacy of netilmicin.

Animals↗
PubMed1978

Separation of rat pituitary thyrotrophic cells.

A method for the enrichment of live thyrotrophic pituitary cells is described. Pituitary glands of young male rats were removed into Earle's solution and dispersed in a 0.1% trypsin solution containing 0.5% bovine serum albumin, pH 7.2. Nylon fibres (25 microgram) were used for the separation of the thyrotrophic cells, by stringing them across a plastic frame which fitted a plastic Petri dish containing the cell suspension. The fibres were washed with light petroleum (b.p. 60--80 degree C) and carbon tetrachloride, hydrolysed with 3 M-HCL for 30 min at room temperature and washed with distilled water and phosphate-buffered saline (pH 7.2). The fibres were treated with thyrotrophin releasing hormone (TRH) alone or in the presence of soluble carbodiimide solution. After incubation for 1 h at room temperature, the fibres were transferred to a new Earle's medium and cells were released from the fibres by plucking them with a needle. The separated thyrotrophic cells were identified by radioimmunoassay and by electron microscopy. Using the above-mentioned methods, enrichment of thyrotrophic cells was obtained. Thus, the amounts of TSH, prolactin, LH and GH released, during 2 h of incubation, by 1.5 x 10(6) unseparated cells were 6.8 +/- 0.65, 4.1 +/- 0.47, 4.8 +/- 0.52 and 5.2 +/- 0.68 microgram respectively, while the same number of purified thyrotrophic cells released 76.1 +/- 0.42, 1.2 +/- 0.3, 0.6 +/- 0.35 and 1.6 +/- 0.22 microgram of the same hormones (means +/- S.E.M.).

Animals↗
PubMed1977

The pituitary of Aphanius dispar (Rüppell) from hypersaline marshes and freshwater. II. Ultrastructure of the rostral pars distalis.

An ultrastructural study of the rostral pars distalis of the pituitary of Aphanius dispar specimens taken from freshwater or hypersaline marshes revealed significant structural differences which indicate higher activity of the prolactin cells in the hypotonic medium. Prolactin cells from freshwater specimens had larger secretory granules, a higher amount of endoplasmic reticulum, and expanded intercellular spaces with many secretory lakes. These cells contained an unusual cytoplasmic structure, consisting of twisted canals with vesicular lumina, connected to the endoplasmic reticulum of the cell. This structure is about 1-2 micron in diameter. Stellate cells are characterized by extracellular spacing junctions which are particularly noticeable at the confluence of the interstellate cell canaliculi and the pericapillary space.

Animals↗
PubMed1976

The extravascular channel system in the rostral pituitary of Mugil cephalus (Teleostei) as revealed by use of horseradish peroxidase.

The interlobular spaces, separating the neuro- and the adenohypophysis can be visualized in the pituitary of the Grey Mullet by using the horseradish peroxidase technique. On the one hand, these spaces communicate with the pericapillary spaces. On the other, they are linked with the pericellular spaces in the adenohypophysis and the periaxonal spaces in the neurohypophysis, thus providing a pathway for the exchange of metabolites and hormones between blood system, epithelial cells and the terminal region of the neurosecretory axons. The interlobular spaces branch off between the tips of the corticotrop cells and form a network adjacent to the adeno- and neurohypophyseal interface. It is possible that branches of this network penetrate into the interior of the corticotrops. The probable role of the network is to permit close contact between neurosecretory hormones and the corticotrops and also to enable the corticotrop hormone to reach the capillaries.

Animals↗