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Biomedical subjects

A Porte

Publications and source records attributed to A Porte.

At least 37 records · Page 2Linked to original sources
PubMed1983

[Absence of dopaminergic receptor sites identified with (H3)-spiroperidol in the intermediate lobe of the rabbit pituitary gland].

Dopaminergic receptors were sought in the intermediate lobe of the pituitary gland by measuring specific 3H-spiroperidol binding. This approach enabled the identification of specific sites in the Mouse neurointermediate lobe. In contrast, no such sites seem to exist in the Rabbit intermediate lobe. However, in the latter species, numerous 3H-spiroperidol binding sites were detected in the anterior lobe. These observations tally with immunocytochemical data showing the absence of catecholaminergic innervation from the Rabbit intermediate lobe and explain why dopamine has no effect on alpha MSH release from the perifused gland. A new mode of regulation of melanotrophic function, not based on inhibitory dopaminergic control, must be envisaged in Leporidae.

Animals↗
PubMed1982

Effects of experimental hypo- or hypernatremia on the fine structure of the pars intermedia of the murine pituitary. A morphometric study.

Quantified ultrastructural observations of the pars intermedia (PI) of the murine hypophysis enable evaluation and kinetic study of relatively fine secretory changes in the gland. Changes in volume of rER and newly formed dense secretory granules (Golgi granules) appear to best translate functional variations in the PI, as shown by the morphological effects of drugs affecting the dopaminergic control of the gland. Our morphometric results show that the PI is stimulated, but only briefly (no longer than 8-12 days), by both salt-loading and Na deprivation. However, the PI displays different secretory patterns in salt-loaded and Na-deprived mice; moreover, bromocriptine, which abolishes PI stimulation in Na-deprived mice, has only a slight inhibitory effect in salt-treated animals. Thus, it appears that the stimulation of the PI under both experimental conditions is triggered by different mechanisms. These results underline the plurifactorial control of the PI and show that the gland may have complex effects on hydromineral regulation.

Animals↗
PubMed1982

[Myocardiopathy with lipid overload and leukocyte palmityl carnitine transferase (PCT) deficiency].

Histological changes of the skeletal muscle with moderate fatty infiltration and varied abnormalities of the muscle fibres and conjunctivo-vascular tissue were demonstrated in three adult patients with apparently primary cardiomyopathy with dilatation. Leukocyte PCT activity was decreased and plasma carnitine was increased. In two cases, postmortem cardiac biopsy showed a massive accumulation of lipids and an intense progressive fibrosis dissociating the atrial and ventricular cardiac fibres. A disturbance of lipid metabolism could be the cause of this cardiac and skeletal muscle disease, but the reduced PCT activity could be a sign of more diffuse myocardial disease as suggested by the fibrous lesions and vascular abnormalities observed in our cases. These cases emphasise the value of routine investigation of PCT activity in primary cardiomyopathy and of ultrastructural studies of skeletal muscle, even in the absence of clinical involvement, which may show relatively severe changes reflecting the state of the myocardium.

Acyltransferases↗
PubMed1981

Fine structure and cytochemistry of the mammalian pars intermedia.

Various cytophysiological aspects of the pars intermedia of the pituitary are discussed. Cells containing melanocyte-stimulating hormone (MSH) have been studied under normal and experimental conditions. They react to variations in ionic equilibrium, but without any clear correlation with natraemia and osmotic blood pressure. The MSH-cell stimulation in hypernatraemic mice, which is not inhibited by bromocriptine, seems more specific than the stimulation in hyponatraemic mice, which is blocked by bromocriptine. The existence of a corticotropic cell system has been clearly demonstrated in the mouse (where it is particularly obvious), in the rat and in the cat but its significance is not clear. Although very poorly vascularized, the pars intermedia is rapidly invaded by tracer protein (horseradish peroxidase) injected either intravenously or intracerebroventricularly. The hypophysial cleft rapidly stores the tracer which can be resorbed by macrophagic epithelial cells lying free in the colloid contained in the cleft. Horseradish peroxidase lingers in the pars intermedia but is rapidly eliminated from the other hypophysial lobes after intraventricular (third ventricle) injection. Diffuse innervation of the pars intermedia applies to both glandular (MSH and ACTH) and non-glandular (epithelial and stellate) cells. While aminergic innervation of the pars intermedia is obvious, cholinergic innervation has not been demonstrated ultrastructurally or histochemically. Peptidergic fibres only occasionally penetrate marginal areas of the pars intermedia and seldom establish synaptic contacts with glandular cells. A specific relationship might exist between the pars intermedia and oxytocin fibres in view of the marginal distribution of the latter in the neural lobe. Numerous stellate cells of the pars intermedia react intensely with antiserum to gliofibrillar acid protein, indicating their astrocyte nature, which reinforces the idea of an analogy between the folliculo-stellate system of the hypophysis and the glial cells.

Adrenocorticotropic Hormone↗
PubMed1981

B-cells of the synovial membrane. III. Relationship with the specific collagenous structure of the intimal interstitium in the mouse.

An ultrastructural study of the synovial membrane in mice revealed that, in addition to specific polypeptide-producing secretory cells (B-cells), the intima is characterized by a specific differentiation of the interstitium adjacent to the synovial cavity. Scattered collagen fibrils are embedded in a fine fibrillar material, which often appears as cross-striated strands resembling long-spacing-collagen (periodicity from 90 to 120 nm). Similar material was found along the synovial cavity in the rat, guinea pig, rabbit and man. The close relationship between this material and B-cells observed in the mouse suggests that the maintenance of the specialized intimal interstitium may depend on the secretory function of B-cells.

Animals↗
PubMed1981

Ultrastructural study of electrophysiologically identified neurones in the paraventricular nucleus of the rat.

The ultrastructural characterization of electrophysiologically identified neurones of the rat paraventricular hypothalamic nucleus was performed with extracellular labelling technique. The extracellularly recorded neurons are labelled with an electrophoretic deposit of alcian blue contained in the recording micropipette. The neurone thus labelled takes on a dark and shrunken appearance which enables its detection among neighbouring cells without, however, concealing its main morphological characteristics. 1) Spontaneously firing neurones, invaded by an antidromic action potential elicited by electrical stimulation of the neurohypophysis, were identified as magnocellular cells containing dense-cored vesicles of 200-250 nm in diameter. Dense-cored vesicles were not found in the antidromically activated neurones devoid of spontaneous activity. 2) Trans-synaptically activated neurones in the PVN or in its dorso-lateral edge were small cells devoid of dense secretory vesicles. 3) PV neurones in which neurohypophysial stimulation evoked no response, contained small, dense vesicles (100 nm in diameter) comparable with those found in parvocellular peptidergic neurones.

Action Potentials↗
PubMed1981

Light and electron microscopic study of ear cartilage in a case of relapsing polychondritis evolving under corticoid treatment.

Light and electron microscope studies of the ear cartilage in a patient with relapsing polychondritis (RP) under corticoid treatment are reported. Unilateral auricular deformation evolved without inflammatory epidoses and the lesions consisted mainly of marginal erosions filled with fine collagen fibrils and containing degenerating perichondrial cells in their basal parts. Degenerative cells were scattered throughout the perichondrium, but cartilage erosions only occurred when numerous cells were affected in a same area. Cartilage outside the eroded zones did not seem to be modified. Cartilage lesions thus appear to be a result of a chondrocyte renewal defect leading to loss of proteoglycans and elastic fibers, with only collagen remaining. These data suggest that inflammation is probably not the initial pathogenic process responsible for cartilage injury in RP, but that a metabolic defect in perichondrial cells might be involved.

Adrenal Cortex Hormones↗
PubMed1980

Unusual familial cardiomyopathy with storage of intermediate filaments in the cardiac muscular cells.

Unusual histological and ultrastructural changes in cardiac muscle cells have been found in 3 brothers with progressive myocardial deficiency. Histologically, this cardiomyopathy was characterized by massive storage of PAS-negative proteinaceous material in most cardiac muscle cells. The electron microscope showed that this material consisted of sinuous filaments, 7-10 nm in diameter, similar to the intermediate filaments normally present in cardiac muscle cells. Filament storage coincided with the disintegration of neighbouring myofibrils, with particular change in Z bands giving rise to rod-like bodies and more complex structures formed by the association of Z band material and sarcoplasmic reticulum (SR) tubules. Filament storage and myofibrillar disintegration always occurred in areas where the SR developed and involuted extensively. Relatively high glycogen accumulation also occurred, in close relation to the SR changes. Discrete SR proliferation, glycogen overload and filament deposits were observed in a few skeletal fibres. These observations suggest that disturbance in the metabolism of desmin (protein subunit of intermediate filaments and a fundamental component of Z bands) might be involved in this type of cardiomyopathy. The influence of a chronic defect in calcium regulation might also be envisaged in view of the marked SR abnormalities.

Adult↗
PubMed1980

Biochemical and ultrastructural studies of cultured rat astroglial cells: effect of brain extract and dibutyryl cyclic AMP on glial fibrillary acidic protein and glial filaments.

The growth of astroglial cells in primary cultures derived from newborn rat cerebral hemispheres was investigated in the absence and in the presence of newborn rat brain extract or dBcAMP. The parameters chosen were the content of DNA, total protein, and glial fibrillary acidic protein (GFA) as well as the morphologic development of gliofilaments. During the entire culture period the DNA content increased in control culture indicating a continuous cell division, whereas the cells stopped dividing after 14 or 4 days of treatment with either brain extract or dBcAMP respectively. In contrast, a constant increase of total protein was found in both control and treated cultures. Since cell divisions had stopped in treated cultures, the increase in total protein in these cultures indicates growth of the individual cells. The GFA levels increased progressively and similarly in control cultures and in cultures treated with brain extract. The values in the treated cultures remained slightly higher than those in controls. Conversely, immediately after the addition of dBcAMP a sudden increase in GFA protein occurred and the amounts were statistically significantly different from those of the controls. The GFA levels were expressed relative to total protein indicating that GFA constitutes an increasing amount of the total protein of the individual cells during culture. The changes in the amount of GFA was shown to parallel the morphologic development of gliofilaments. Indeed, when the level of GFA increased a progressive accumulation of gliofilaments was observed. The results obtained were discussed in relation to the astrocytic maturation.

Animals↗
PubMed1979

Modifications in the sarcoplasmic reticulum and subcellular calcium distribution in skeletal muscle in a case of Westphal's disease (hypokalemic periodic paralysis).

In a case of hypokalemic periodic paralysis with characteristic alterations of the sarcoplasmic reticulum (SR) in the skeletal muscle, subcellular calcium re-partition, as revealed with the pyroantimonate technique, appears disturbed during paralysis. Pyroantimonate precipitates, normally concentrated in the terminal cisternae of the SR, were localized in the T tubules, whereas the terminal cisternae appeared empty. The increase (about 14%) in muscular calcium during paralysis may result from the accumulation of calcium in the extracellular compartment (T tubules). Defects in calcium uptake and storage by the SR may be involved in the pathogenesis of the periodic paralysis syndrome.

Adolescent↗
PubMed1979

Embryonic development and secretory differentiation in the pars tuberalis of the mouse hypophysis.

The pars tuberalis (PT) of the mouse, like that of other mammals, consists mainly of glandular cells rich in glycogen and peculiar to this lobe. In the mouse, the glandular cells are characterized by large, dense secretory vesicles (up to 300 nm in diameter), the abundance of which indicates a marked secretory activity. The PT develops from a distinct antero-ventral area of Rathke's pouch. The border between the anlagen of the PT and the pars distalis is formed by Atwell's recessus which represents the access for the vessels afferent to the pars distalis. The pedicle of Rathke's pouch is incorporated into the PT anlage, thus contributing to its formation. The entire PT anlage is characterized by glycogen accumulation from the commencement of its formation and persisting in the adult tuberal lobe. Secretory differentiation of the glandular cells of the PT occurs at day 12 of gestation, preceding that of all other adenohypophysial cell types. The secretory features of these cells (development of ergastoplasm and Golgi apparatus, abundance of dense secretory vesicles) appear at an early stage of the enbryonic life (14 days) comparable to those of mature cells. These results confirm earlier observations in the foetal rat where hypophysial secretion also begins in the PT. The existence of peculiar glandular cells speaks in favour of a specific but still unknown function of the PT during foetal and adult life.

Animals↗