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Biomedical subjects

M S Davidoff

Publications and source records attributed to M S Davidoff.

45 records · Page 3Linked to original sources
PubMed1982

The fate of newly synthesized proteins in nerve and glial cells following nerve injury as shown by electron microscope radioautography.

Following peripheral crush of hypoglossal nerve the fate of newly synthesizing proteins in corresponding nerve and glial cells was traced out using light and high resolution radioautography after intraventricular injection of 3H-leucine. Radioautographic analysis was applied on the normal and chromatolytic neurons and their glial surroundings 45 min after injection of labelled precursor. Both chromatolytic neurons and surrounding glia showed higher incorporation of labelled proteins than those of control nerve and glial cells. Relative specific radioactivity (RSR) of ergastoplasm and lysosomes were increased in the chromatolytic neurons, whereas RSR of nuclei, mitochondria and Golgi apparatus were decreased. Contrary to neurons, RSR of corresponding compartments in experimental glial cells except lysosomes showed reciprocal values in comparison with control glial cells. The higher RSR of mitochondria and Golgi apparatus in experimental glial cells depended mostly on the astrocytes, whereas those of nuclei and lysosomes were related first of all with microglial cells. These findings are correlated with present concepts of the complex interdependency between neurons and glia in which mutual regulatory controls and influences are exerted.

Animals↗
PubMedDate not supplied

Processing of testicular biopsies--fixed in Stieve's solution--for visualization of substance P- and methionine-enkephalin-like immunoreactivity in Leydig cells.

In the present report a schedule for processing testicular biopsies fixed in Stieve's solution is described which is suitable for modern immunocytochemical techniques. By means of this procedure the existence of immunoreactivity in Leydig cells can be demonstrated using antisera against substance P and methionine-enkephalin.

Biopsy↗
PubMedDate not supplied

Neuron-specific enolase-like immunoreactivity in human Leydig cells.

Using the peroxidase anti-peroxidase immunocytochemical technique, neuron-specific enolase (NSE)-like immunoreactivity (NSE-LI) was revealed in Leydig cells of adult human testes at the light microscopic level. Differences in the NSE staining intensity were observed between the individual Leydig cells, separate cell groups within a testis and between the testes of individual patients. Together with the already established substance P-like immunoreactivity (SP-LI), the results obtained provided further evidence for the possible neuroectodermal origin of human Leydig cells and their presumable relation to the APUD- or the Diffuse Neuroendocrine System (DNES).

Adult↗
PubMedDate not supplied

Substance P-induced inhibition of Leydig cell steroidogenesis in primary culture.

The effect of substance P (SP) on hamster Leydig cell steroidogenesis in primary culture was investigated. Purified Leydig cells were cultured with or without SP for 24 h. The levels of testosterone and progesterone in the culture media were 174 +/- 20 pg ml-1 and 105 +/- 12 pg ml-1, respectively. In the presence of SP (10(-7) mol l-1), testosterone concentration significantly decreased to 123 +/- 19 pg ml-1, e.g. with 29.3%. By contrast, at the concentration used, SP had no effect on progesterone secretion. The possible molecular mechanism of the SP action on Leydig cell function was discussed. The reported results indicate that SP can modulate Leydig cell steroidogenesis in culture.

Animals↗
PubMedDate not supplied

Combination of alkaline phosphatase anti-alkaline phosphatase (APAAP)- and avidin-biotin-alkaline phosphatase complex (ABAP)-techniques for amplification of immunocytochemical staining of human testicular tissue.

An amplification procedure was developed for the visualization of antigens in human testis using monoclonal antibodies against desmin and vimentin. The technique combines the high sensitive and specific APAAP- and ABAP-methods. Depending on the quality of the antibodies used and the processing of the material prior to the immunocytochemical staining the amplification technique may be applied either as a single APAAP and ABAP- or as a double APAAP and ABAP-combination. Especially after the double amplification reaction a distinct increase of the staining intensity of the vimentin- (in Sertoli cells, myofibroblasts of the lamina propria, and fibroblasts of the interstitium) and desmin- (in myofibroblasts of the lamina propria and smooth muscle cells of the blood vessels) like immunoreactivity was observed. If different diazonium salts were used for the visualization of the alkaline phosphatase activity (e.g. Fast Red TR Salt, Fast Blue BB Salt) desmin- and vimentin-like immunoreactivity can be demonstrated in the same tissue section in a double sequential staining approach. For double staining, the alkaline phosphatase technique may be combined successfully with a technique or a combination that uses peroxidase as a marker.

Alkaline Phosphatase↗
PubMedDate not supplied

Neuroendocrine characteristics of human Leydig cell tumours.

The neuroendocrine nature of a subset of Leydig cells has already been established. The present investigation deals with neuroendocrine characteristics of Leydig tumour cells. A number of neuroendocrine and neuronal markers were demonstrated in Leydig cell tumours of 7 men aged 25-41 years. The following substances were immunocytochemically tested in Leydig tumour cells: the monoamine-synthesizing enzymes tyrosine hydroxylase and aromatic L-amino acid decarboxylase, the indoleamine serotonin, the calcium-binding protein parvalbumin, the microtubule associated protein-2, neurofilament protein 200, synaptophysin, neuron specific enolase, substance P and neuronal nitric oxide synthase (NOS). Compared to the normal interstitial cells beyond the tumours, all neoplastic cells showed a significantly weaker immunoreactivity for nerve cell markers as well as for testosterone and cyclic guanosine monophosphate (cGMP), which is usually accumulated by nitric oxide (NO). This provides evidence for a certain dedifferentiation of Leydig tumour cells. However, these results suggest that tumourous development of Leydig cells does not include loss of neuronal phenotype. Moreover, on the assumption that 'neuronal' Leydig cells exist beside 'non-neuronal' ones in normal testicular tissue, we propose the hypothesis that 'neuronal' Leydig cells can transform to tumour cells.

Adult↗
PubMedDate not supplied

In vitro effects of substance P and arginine-vasopressin on testosterone production in Leydig cells of short and long photoperiodic hamsters.

The aim of the present study was to determine the interaction between substance P (SP) and arginine-vasopressin (AVP) on basal and LH-stimulated testosterone production by Leydig cells isolated from hamsters kept under long or short days (LD-hamsters, SD-hamsters, respectively). SP inhibited the testosterone production of Leydig cells, its effect being more pronounced in the case of LH-stimulated steroidogenesis in LD-hamsters. Similarly, the addition of AVP to the culture medium resulted in a diminution of basal, as well as LH-stimulated testosterone secretions. When Leydig cells were co-incubated with SP (10(-7) M) and AVP (10(-7) M), a strong inhibition of the testosterone production by 50-60% was established in LD-animals. However, even within the experimental circumstances in SD-hamsters, the modulation of testosterone production by SP and AVP was evident. The reported results suggest that there is an interference of two regulatory pathways, namely photoperiodic dependence and paracrine control of testicular steroidogenesis in hamsters.

Animals↗