Biomedical subjects

R P Engelhardt

Publications and source records attributed to R P Engelhardt.

5 recordsLinked to original sources

PubMed1989

[Gonadal opioids and testicular function].

A review is presented on the occurrence of opioid systems within mammalian testes at different stages of sexual development. Identification of the messenger ribonucleic acid sequences (mRNA) related to the three opioid precursor families and as well as characterization and localization of their main derivates may account for the importance of such systems within reproductive tissues. These data are supported by experimental in vivo and in vitro studies giving evidence that opioid peptides are produced locally and may exert paracrine and/or autocrine effects within the testes.

Animals↗

PubMed1988

Nuclear protein transitions in cuttle-fish spermiogenesis: immunocytochemical localization of a protein specific for the spermatid stage.

The changes in basic nuclear proteins throughout cuttle-fish spermiogenesis were investigated both by immunocytochemical procedures and by isolation of late spermatid nuclei (by virtue of their resistance to sonication). Antibodies were raised in rabbits to a protein, named protein T, isolated from testis chromatin. The anti-protein T immune serum was found to recognize protein T and not histones from the testis. Immunoperoxidase staining of sections or of smears of testis with anti-protein T antibodies showed that protein T appears in the nuclei of round spermatids, is abundant in elongating spermatid nuclei, but cannot be detected in elongated spermatids. Nuclei from these elongated spermatids were isolated by sonication treatment of testis cells. A protein, named protein Sp, with the characteristic mobility of a protamine, was isolated from elongated spermatid nuclei. This protein has the same mobility as the protamine present in mature spermatozoa. Taken together, the results indicate that in cuttle-fish, nuclear protein transitions involve the replacement of histones by a spermatid-specific protein (protein T), which is replaced at the end of elongation of the nucleus by a protamine (protein Sp). Thus, spermiogenesis of the cuttle-fish (and perhaps of other cephalopods), shows two basic nuclear protein transitions, which are similar to the transitions observed in higher vertebrates such as mammals.

Animals↗

PubMed1986

Immunohistochemical localization of enkephalinlike peptides during testicular development in rats.

The distribution of opioid peptides is of interest in the rat testes, because the presence of opiate binding sites strongly supports the hypothesis of paracrine function for these peptidergic factors. Testes of Wistar albino rats between birth and adult stage were examined immunocytochemically for enkephalins, dynorphin, and alpha neoendorphin. The presence of immunoreactive enkephalinlike substances was visualized in both interstitial tissue and seminiferous tubules, but no staining was observed for dynorphin or neoendorphin. In interstitial tissue the material stained in Leydig cells raised after birth, declined at day 12, and increased again between day 22 and day 35 of life. From day 35 till adult stage we observed again a slight decrease of immunostaining. In seminiferous tubules, intense immunostaining was observed in stem spermatogonia until day 7 of life. After this period the presence of immunoreactive enkephalinlike material was detected, mainly in some spermatogonia and peritubular primary spermatocytes. These data suggest a possible implication of enkephalinlike peptides in spermatogonesis.

Animals↗

PubMed1982

Immunohistochemical demonstration of a CCK-like peptide in the nervous system of a marine annelid worm, Nereis diversicolor O.F. Müller.

Perikarya and nerve fibers containing a substance immunologically related to CCK-8 were detected in the nervous system of Nereis, a marine annelid worm. The most noteworthy immunostaining was seen in cell bodies, localized at the periphery of the brain, within nuclei 5, 6, 7, 9, 10, 13, 14, 15, 17, 20, 23-24. Immunoreactive fibers were also found in the neuropile without any particular grouping. Numerous other "positive" perikarya occur in the medioventral portion of the ventral nerve cord, and in the ventral and dorsal parts of the suboesophageal ganglion. In addition to the cell bodies in the cerebral external layer, immunoreactive axons were abundantly observed in the connectives between the ganglia. Moreover, our results demonstrate CCK-like staining in neurons showing variations in size and shape, and in affinity for paraldehyde fuchsin. The present results support the hypothesis that this peptide may exert a role as neurotransmitter or neuromodulator in annelids.

Animals↗

PubMedDate not supplied

Immunohistochemical localization of enkephalins in adult rat testis: evidence for a gonadotrophin control.

The recent detection of immunoreactive POMC derived peptides in the male reproductive tract raised the possibility that these hormones might regulate reproductive function. In addition, a variety of studies suggested that POMC derived peptides have paracrine effects in the testis. In this present study, after HCG addition to the organ culture medium, Sertoli cells cytoplasma became immunoreactive with the enkephalins antisera.

Animals↗