Manuel Alvarez-Uría

Morphometric Analysis of the Synaptic Ribbons and Nerve Vesicles of the Cat Pineal Gland After Electrical Stimulation of the Superior Cervical Ganglia

The nerve vesicles and synaptic ribbons were quantified in the cat pineal gland after electricl stimulation of the pineal sympathetic nerve fibers. It has been shown that the bilateral electrical stimulation of the preganglionic fibers innervating the superior cervical ganglia (SCG) markedly reduces the number of dense cores of small dark vesicles (SDV) and on the other hand modifies the number and shape of the large dark vesicles (LDV). An increase in the number of the synaptic ribbons after stimulation of the SCG supports the hypothesis that the numerical reduction of dense cores of nerve vesicles in the cat pineal gland influences the level of synaptic ribbon formation.

An ultrastructural study of myoepithelium maturation during postnatal development of the hamster Harderian gland

SummaryThis study reports the ultrastructural cell modifications in the myoepithelium of the Harderian gland during the postnatal development of the Syrian hamster. Tissues were obtained from male and female hamsters at days 1, 3, 5, 7, 10, 12, 15, 17, 20, 27, 37, 46 and 90 after birth, and processed for transmission electron microscopy. Electron microscopy was coupled with point counting methods to quantitate changes in several subcellular organelles during the course of myoepithelial cell maturation. The myoepithelial cells in this gland remained immature at birth. The earliest age of development when organized bundles of microfilaments were observed was 7 days. By the 12th day, the myoepithelial cells had developed most of their specific characteristics and resembled the mature form. Myoepithelial cells mature synchronously with each other and with the secretory cells. No undifferentiated myoepithelial cells were found in adult glands. In addition to epithelial and myoepithelial cells, the secretory endpieces of the adult hamster Harderian gland contain a third cell type which resembles the myoepithelial cell in shape and has an extremely electron-lucent cytoplasm lacking microfilament bundles.

Effects of superior cervical preganglionectomy on nerve vesicles and synaptic ribbons in the cat pineal gland

Previous studies have shown that bilateral preganglionectomy of the superior cervical ganglia (SCGp) modifies the nerve vesicles and synaptic ribbons in the cat pineal gland. In the present study the nerve vesicles (NV) and synaptic ribbons (SR) were analyzed morphometrically after chronic preganglionectomy of the pineal sympathetic nerve fibers. It was shown that bilateral sympathectomy of the preganglionic fibers innervating the superior cervical ganglia (SCG) markedly reduces the number of dense cores of small dark vesicles (SDV) and, on the other hand, modifies the number and shape of the large dark vesicles (LDV). An increase in the number of the synaptic ribbons after chronic preganglionectomy of the SCG supports the hypothesis that the numerical reduction of dense cores of nerve vesicles in the cat pineal gland influences the level of synaptic ribbon formation.

The magnocellular neurosecretory system of the hamster hypothalamus : an ultrastructural and morphometric study during lifetime

A quantitative study regarding the age-related changes occurring in the nucleus and the somatic organelles of neurosecretory magnocellular neurons of the hypothalamo neurohypophyseal system (HNS) was carried out in the hamster at six age-points during animal life. The magnocellular cells of both parts of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of male Syrian hamsters between 3 and 30 months of age were examined ultrastructurally. Cells of all age groups present the same morphological ultrastructure. Standard manual morphometric techniques are used to calculate the following parameters related directly or indirectly with cellular activity: nuclear area, nucleolar area, nuclear invagination index and volumetric fractions of some intracellular structures (Golgi apparatus, mitochondria, rough endoplasmic reticulum and lipofuscin). With respect to the cell nucleus, the parameters are not modified during aging. No significant differences in the volume density of subcellular components, except lipofuscin, were detected at the age groups studies. However, there is a positive linear trend among all parameters and age except for the rough endoplasmic reticulum. Our results suggest maintenance of the synthetic activity of the magnocellular neurons in the hamster during aging but in no case an increase in their metabolic activity.

Quantitative ultrastructural evidences suggest no age-related changes in biosynthesis and processing within parvocellular cells of the paraventricular nucleus in hamsters

The parvocellular neurons of the parvocellular division of the paraventricular nucleus (PVPA) were studied in hamsters at six point ages (from 3 to 30 months old). Standard manual morphometric techniques were used to obtain data of parvocellular activity including nuclear and nucleolar size, as well as the percentage of the cell occupied by Golgi apparatus (GA), mitochondria and rough endoplasmic reticulum (RER). Other directly age-related parameters like amounts of nuclear invagination and lipofuscin have also been studied. No significant differences in the measured subcellular components were detected among groups studied, except slight increases in lipofuscin. No age-related changes were found in the synthesizing apparatus, but a significant decrease in the cell area was observed in older groups. This finding could suggest a reduction in absolute terms in the protein synthesis of the parvocellular neurons during aging. Ultrastructural morphometric observations in parvocellular neurons are discussed in relation to synthesizing activity and hormone production during aging.

Effects of ovariectomy and ageing on the structure and ultrastructure of the female Syrian hamster Harderian gland: a stereological analysis.

The effects of ovariectomy and ageing on the structure and ultrastructure of the Syrian hamster Harderian gland were investigated by techniques of quantitative stereology. Tissues were obtained from intact 6-month-old, sham-operated 6-month-old, ovariectomized 6-month-old, intact 18-month-old and ovariectomized 18-month-old female hamsters. Glands from both ovariectomized and aged hamsters showed comparable qualitative and quantitative characteristics. They showed histological alterations that included thinning of the tubule walls, lowering of luminal porphyrins, invasion of lumina by neutrophils and the occurrence of interstitial porphyrins. Glands from both ovariectomized and aged hamsters showed statistically significant differences from control animals in relation to numerical density and cellular size. Finally, quantitative studies with the electron microscope revealed significant decreases in the volume densities of the cytoplasmic organelles concerned with secretion. These results support the hypotheses that the secretory activity of the female hamster Harderian gland is influenced, directly or indirectly, by ovarian hormones, and that many of the age-related modifications of the Harderian gland reflect alterations in ovarian function.

Circadian changes in synaptic ribbons and spherules in pinealocytes of the Syrian hamster (Mesocricetus auratus).

SummaryIn the present study, “synaptic” ribbons were studied morphologically and quantitatively in hamster pineal gland. The number of ribbons and spherules of hamster pinealocytes was counted over a 24-h period. The 24-h variations in the quantity of “synaptic” ribbons were found to parallel fluctuations in pineal melatonin concentrations. No significant circadian changes were observed for “synaptic” spherules, indicating different roles for these two structures.

Ultrastructure of the “smooth endoplasmic reticulum cell” in the nucleus recessus lateralis of Salmo gairdneri Richardson

SummaryThe fine structure of one of the cellular components of the nucleus recessus lateralis of trout is described. These cells have an enormously developed smooth endoplasmic reticulum which makes their identification easy. The relationship of this cell type with the ventricular cavity, neighbouring cells and the presence of synaptic contacts with these cells are also described.

The Pineal Gland of Mammals: Some Open Morphological Questions

The pineal gland derives from the dorsal wall of the diencephalon and presents a varied structure in the different vertebrate species. In fish, amphibians and reptiles the ultrastructure of its main cell type, the pinealocyte, is similar to that of photoreceptor cells of the vertebrate retina and to the sensory organs of invertebrates that respond directly to light.

The dorso-lateral recess of the hypothalamic ventricle in neonatal rats

SummaryLight and electron microscopy of the hypothalamic ventricle in neonatal rats demonstrate morphological specializations of the ventricular wall at the level of the premammillary region of the third ventricle. The morphological features are: (1) A ventricular recess that we have called the “hypothalamic dorso-lateral recess” (HDR). (2) The presence of intraventricular capillaries near the dorsolateral recess. (3) The HDR possessing a specialized ependymal lining; this consists of non-ciliated cells with short microvilli and bleb-like processes. (4) The existence of cerebrospinal fluid-contacting neurons within the HDR. (5) The presence of numerous phagocytic supraependymal cells. The HDR is not found in adult rats. This indicates that the dorso-lateral recess may play a physiological role during development.