Biomedical subjects
Publications and source records attributed to M Karasek.
Data are presented which indicate an influence of the pineal gland on the adenohypophysis and the effects of some adenohypophyseal hormones on the pineal gland, suggesting the existence of a reciprocal relationship between these two glands.
The effects of hypophysectomy and prolactin administration on the ultrastructure of rat pinealocytes were studied by means of morphometric analysis. Hypophysectomy resulted in an increase in the Golgi apparatus and dense-core vesicles and a decrease in the granular endoplasmic reticulum, lysosomes and lipid droplets. Prolactin administration induced an increase in the granular endoplasmic reticulum and in the vacuoles which contained a flocculent material. Administration of prolactin to hypophysectomized rats raised the lowered levels of granular endoplasmic reticulum and lipid droplets to control values and caused an increase in vacuoles containing a flocculent material. Although hypophysectomy appeared to diminish the general activity of pinealocytes, it stimulated the neurosecretory-like secretory process Golgi apparatus-dense-core vesicles), whereas prolactin appeared to stimulate the ependymal-like secretory process (granular endoplasmic reticulum-vacuoles containing a flocculent material).
The ultrastructure of the pinealocytes of Snell dwarf mice (dw/dw) was examined morphometrically and compared with that of both phenotypically normal (dw/+ or +/+) animals of the same strain and dwarf mice with ectopic pituitary grafts. Ultrastructural features characteristic of diminished activity of the pinealocytes were observed in dwarf mice as compared with controls. Ectopic pituitary grafts induced morphological signs of activation of the pinealocytes in this mutant. The results of the present study demonstrate the influence of the adenohypophysis on the pineal gland and these data, together with the known influence of the pineal gland on the adenohypophysis, support the existence of a reciprocal relationship between these two glands.
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The numbers of Golgi profiles, dense-core vesicles, vacuoles containing a flocculent material, lysosomes, lipid droplets, 'synaptic' ribbons and microtubular sheaves were counted in the rat pinealocytes in the last 5 days of pregnancy. The numbers of Golgi profiles and dense-core vesicles increase at days 21 and 22, while numbers of LYS and LD increase the day before parturition. On the contrary, the number of VFC decreases in the final day of pregnancy. The results of the present study suggest that the pineal gland may play a subtle role in pregnancy.
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The dense-core vesicles and 'synaptic' ribbons were counted in Djungarian hamster pinealocytes after superior cervical ganglionectomy. Sympathectomy caused a decrease in the number of dense-core vesicles in pinealocytes, suggesting diminished secretory activity of these cells. An increase in the number of 'synaptic' ribbons after superior cervical ganglionectomy supports the hypothesis that adrenergic innervation of the pineal gland influences the level of 'synaptic' ribbon formation.
An analysis of more than 75000 electron micrographs from 84 intact control and 167 experimental male rats divided into 11 groups subjected to various treatments, was performed in the present study, a special attention being paid to the relation of cytoplasmic organelles to the processes of synthesis and secretion of pinealocytes. From these observations the following conclusions have been drawn: 1. specific pineal cells - the pinealocytes - show several attributes of metabolically active endocrine cells; 2. at least two probably intimately related secretory processes are present in the rat pinealocytes; 3. several cytoplasmic structures may be involved in the secretory mechanism of the rat pinealocytes.
Pinealocytes of female pigs were studied electron-microscopically and compared with those of other mammals. A prominent Golgi apparatus forming dense-cored vesicles was widely dispersed in the cytoplasm of the cell body. A very characteristic feature of the pig pinealocytes was the presence of membrane-bounded bodies showing wide variations in internal structure. Possible roles of the dense-cored vesicles and membrane-bounded bodies in secretory processes of pinealocytes are discussed.
In this study we report the demonstration of receptors for 1,25-(OH)2 vitamin D3 in fresh and cultured human skin. Cultured fibroblasts grown from infant foreskin exhibit a binding site which by Scatchard analysis had a Kd for [3H]1,25-(OH)2D3 of 0.2 nM and an Nmax of approximately 40 fmol/mg cytosol protein. On sucrose density gradients the receptor sediments at 3.2S. Receptors could also be identified in skin biopsies from adult patients when assayed either in fresh epidermis or cultured keratinocytes and dermal fibroblasts. The human receptors are similar to rodent receptors assessed in classical target organs such as intestine, bone and kidney. The findings that receptors can be measured in cultured human skin after several arterial passages indicates that skin biopsy may provide a means of assessing the 1,25-(OH)2D3 receptor status of patients.
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