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Biomedical subjects

M Davidoff

Publications and source records attributed to M Davidoff.

At least 55 records · Page 3Linked to original sources
PubMed1980

Steroid hormone binding receptors in the rat kidney.

The studies were done on 93 Wistar rats of both sexes. Binding capacity and affinity for 3H-estradiol were determined biochemically in the cytosol fraction of renal homogenates. Free cytoplasmic estrogen binding sites were demonstrated in a portion of the females (Kd 5.2-17.8 x 10(-10) mol/l): in 33.3% of normal animals, in 54.6% 3-4 days after ovariectomy, and in 25% 17-18 days after ovariectomy. The investigation of females which received estradiol or testosterone replacement after castration, as well as of uncastrated or castrated males, led to negative results. Thaw-mounted autoradiography was used to study the retention of radioactivity from 3H-estradiol or 3H-testosterone in normal and castrated animals and in animals which received corresponding hormone replacement after castration. In all animals, specific silver granules were found in the cytoplasm and nucleus of proximal tubules cells from the S1 and S2 segments of juxtamedullary nephrons, particularly in the females. Only a few silver granules were observed in the S segments; some cells in males were marked by a heavy nuclear accumulation of silver granules following the injection of 3H-testosterone. In the distal tubules, only isolated silver granules were found in some cells. Somewhat more radioactivity was found in the cytoplasm of the cells of the collecting ducts in the inner medullary zone.

Animals↗
PubMed1978

Cytochemical localization of acid phosphatase and adenosine triphosphatase in some avian mechanoreceptors.

Ultrastructural distribution of acid phosphatase and adenosine triphosphatase was studied in the receptor elements of HERBST and GRANDRY sensory corpuscles. Acid phosphatase activity was established in the elements of smooth and rough endoplasmic reticulum of perineural capsule cells, as well as in the secondary lysosomes of all cell types. Particular interest was paid on the activity of myelin-like dense bodies and some clear core vesicles belonging to the axoplasm of receptor nerve fibres. Adenosine triphosphatase activity was established on the membranes of receptor structures and pinocytotic vesicles. More deposits of electron dense material were localized on the axolemma of the non-myelinated portions of the receptor nerve fibres. The functional significance and importance of the both enzymes in the receptor structures was discussed.

Acid Phosphatase↗
PubMed1978

[Uptake of peroxidase by activated nerve cells of the hypothalamus (author's transl)].

After thirst or adrenalectomy followed by dehydration electron microscopy reveals an activation and an increased uptake of peroxidase in the nerve cells of the supraoptic, paraventricular, ventromedial and praemamillar nuclei. The amount of peroxidase which is taken up runs parallel with the activation of the corresponding nerve cells. After rehydratation the activity of the nerve cells and the uptake of peroxidase decrease. The incorporation of the enzyme by the nerve cells differs depending on the region investigated: After thirst peroxidase is taken up especially by the nerve cells of the supraoptic and paraventricular nuclei. After adrenalectomy, however, this is true for the ventromedial and praemamillar nucleus. In the magnocellular nuclei peroxidase is preferentially incorporated by the perikarya, whereas in the parvocellular nuclei the uptake of the enzyme predominates in the dendrites. Within the nerve cells peroxidase is only seen in heterophagic bodies. The ependyma above the paraventricular nucleus takes up peroxidase in low amounts via the cell membrane which borders the III. ventricle; high amounts are incorporated by the lateral and basal plasmalemma.

Animals↗
PubMed1977

[The ultrastructure of Langhans cells in pathologic human placentas (author's transl)].

In electron microscopic observations on the villous cytotrophoblast in pathologic human placentas we find, besides a general increase of the amount of Langhans cells, significant ultrastructural differences according to the different diseases in pregnancy. Diabetes mellitus: the most striking observations are small, extremely electron dense mitochondria and a lot of intracellular filaments in a hydropic cytoplasm. Rh-incompatibility: according to the stage of placental damage the Langhans cells show a different structure. In light cases we find hydrolic cells with normal mitochondria as well as swollen ones. The plasmalemm shows a lot of foldings and dentations with the syncytium. In serious cases of rh-incompatibility the Langhans cells cover the trophoblastic basal membrane completely. Their electron density is even higher than that of the syncytium. Characteristic lysosomes appear. In the most serious cases the syncytium is completely destroyed and maximal hydropic Langhans cells cover the villi. EPH-gestosis: the Langhans cells show different phases of differentiation, but no other characteristic criteria. The importance of the Langhans cells for the regeneration of the syncytotrophoblast is discussed. Mitochondria and rough endoplasmic reticulum are obviously not formed in the syncytium but they must be regenerated by taking up Langhans cells by syncytial fusion.

Blood Group Incompatibility↗
PubMed1977

Eliminating the gap in flexor tendon surgery. A new method of suture.

A new method of tendon suture has been designed to eliminate the development of a gap when tension is applied to the repair. It has been demonstrated to resist distraction at relatively high tensions on cadaveric tendon. The possible advantages of the technique are discussed.

Humans↗
PubMed1976

On the vegetative network of guinea pig thoracic spinal cord.

A dense AChE-positive network was visualized by light microscopy in the thoracic spinal cord of grown-up guinea pigs of both sexes (bodyweight 250-300 g). This network connects in a horizontal and vertical direction the preganglionic sympathetic nuclei (n. intermediolateralis pars principalis (ILp), n. intermediolateralis pars funicularis (ILf), n intercalatus spinals (IC), n. intercalatus pars paraependymalis (ICpe), (Petras and Cummings, 1972) all along the thoracic spinal cord. In addition to AChE activity, the bundles of fibers of this network also show a strong formaldehyde-induced NA fluorescence. Electron microscopy demonstrated granular vesicles in the cytoplasm of ILp cells. The surface of the ILp and IC neurons is almost entirely covered with synaptic bottons which have clear and granulated synaptic vesicles. The bundles of fibers consists of parallel myelin-free axones and dendrites. On their cource the axones form varicosities. In the varicosities and in the synaptic enlargements there are also clear and granulated (40-100 nm) vesicles. The probable origin of the vegetative network fibers of guinea pig thoracic spinal cord is discussed.

Acetylcholinesterase↗
PubMed1976

On the histochemistry of N-acetyl-beta-D-glucosaminidase in rat central nervous system.

The optimal conditions for histochemical demonstration of NAG activity in the cerebrum, diencephalon, midbrain, cerebellum, medulla oblangata, and spinal cord were studied in a series of 37 Wistar rats of either sex. The following more important results were obtained: Each CNS zone required a definite methodlogical approach. Optimal fixation for most structures was achieved after 2 h treatment with formol-calcium and subsequent immersion of tissue blocks in formol-calcium 0,88 M saccharose. By this fixation technique it was possible to preserve high enzyme activity and good tissue structure. Only for the large pyramidal cells of the cerebral cortex the method of Holt provided optimal fixation. Formol-calcium-saccharose mixture and pure 0,88 M saccharose produced the opposide osmotic effect on nervous tissue previously fixed with formol-calcium: the former induced tissue shrinkage, the latter edema. The use of hexazonium p-rosaniline coupler prompted preliminary alcohol treatment of sections and introduction of 0.1 M acetate buffer in the incubation solution. Acetate buffer concentrations lower than 0.2 M diminished the diffuse cytoplasmic coloration and permitted a clear-cut demonstration of the lysosomal reaction. Ample information on the distribution of NAG activity in the CNS was obtained by using fast garnet GBC coupler and 0.1 M citrate buffer. Manganese chloride in a 0.2 mM concentration activates the reaction. The distribution of NAG reaction product in the cells of the different sections of the CNS was studied. The distribution of NAG reaction product in the cells of the different sections of the CNS was studied. The neurons, glial cells, and blood vessels showed positive reaction. Strongest activity was reported for the neurons of the supraoptic and paraventricular necleus, the epithelial cells of the chorioid plexus, nucleus ruber of the mesencephalon, and the vascular wall pericytes.

Acetylglucosaminidase↗
PubMed1975

[The postnatal development of the hypoglossal nucleus in the rat].

Using light and electron microscopy the neurons, glial cells and capillaries in hypoglossal nucleus of the rats have been examined up to 20 days after birth. The neuronal nuclei are usually situated ecentrically. The mitochondria and extensively developed Golgi-zones occupy the perinuclear region. The microtubules and lysosomes become more numerous with aging. At the earliest periods rough endoplasmic reticulum (ER) occupies the neuronal periphery, whereas after 14th day it is extended to the perinuclear region also. The ER forms elongated and concentric lamellated bodies and subsurface cisternae. At this time nucleolus like bodies are also numerous in the cytoplasm. After 4th and 6th days the extensive growth of dendrites, containing many cell organelles, and axons rich in microtubules are observed. Only at the birthday do neurons contain glycogen deposit. After 1st day the glycogen leaves the pericaryon, but it persists a long time in the neuronal processes. The symmetrical and asymmetrical contacts are characteristic for the examined period. The axo-somatic and axo-dendritic synapses are more abundant, but "double synapses" are also established. More synaptic boutons possess besides synaptic vesicles dense-core vesicles at the earlier periods. The quantity of asymmetric synapses increases with differentiation. Extensive cell degeneration has been established between 8 and 18th days. At 4 and 6 days the glial cells penetrate from subependymal layer and they have satellite neuronal position. This is more pronounced between 14 and 18 days when the oligodendrocytes are more numerous and active. At the same time fibrous astrocyte like cells are appeared. Microglial cells were not observed. Capillary differentiation, expressed by changes of the endothelial cells, pericytes and connective tissue cells, continues after birth also.

Animals↗