Biomedical subjects

R M Lechan

Publications and source records attributed to R M Lechan.

At least 91 records · Page 5Linked to original sources

PubMed1986

Immunolocalization of the thyrotropin-releasing hormone prohormone in the rat central nervous system.

The distribution of immunoreactive TRH prohormone in the rat central nervous system was studied by immunocytochemistry using an antiserum raised against a synthetic decapeptide hypothesized to represent a portion of the mammalian TRH precursor protein. Reaction product was identified in several regions of the brain in a distribution typical of that previously described for the tripeptide. In contrast to TRH, however, immunoreactive pro-TRH was largely confined to neuronal perikarya and only rarely seen in axons or axon terminals. In addition, immunoreactive pro-TRH was present in portions of the telencephalon and brainstem where TRH has not previously been described in neurons by immunocytochemistry. These studies indicate that in most regions of the brain the TRH prohormone is rapidly processed within the cell soma and not during axonal transport, and raise the possibility that in certain regions of the brain processing of the prohormone may be to non-TRH peptides, which may be of biological importance.

Animals↗

PubMed1986

Amyotrophic lateral sclerosis: thyrotropin-releasing hormone and histidyl proline diketopiperazine in the spinal cord and cerebrospinal fluid.

In spinal cords from seven amyotrophic lateral sclerosis (ALS) patients and four controls, we found no difference in thyrotropin-releasing hormone (TRH) concentration relative to protein content, but there was a reduction per tissue wet weight in ALS. Immunohistochemical localization of TRH in ALS cord was unaltered. Histidyl proline diketopiperazine (HisPro-DKP), a possible metabolite of TRH, was significantly elevated per protein content in ALS. CSF levels of TRH and HisPro-DKP were unchanged. These findings suggest that TRH neurons are not primarily affected in ALS, but TRH and tissue protein are lost together as the disease progresses.

Aged↗

PubMed1985

Immunohistochemical localization in the rat brain of the precursor for thyrotropin-releasing hormone.

A rabbit antiserum to a peptide sequence present in the precursor for thyrotropin-releasing hormone (proTRH), deduced from cloned amphibian-skin complementary DNA, was raised by immunization with the synthetic decapeptide Cys-Lys-Arg-Gln-His-Pro-Gly-Lys-Arg-Cys (proTRH-SH). Immunohistochemical studies on rat brain tissue showed staining of neuronal perikarya in the parvicellular division of the paraventricular nucleus of the hypothalamus and the raphe complex of the medulla, identical to that already described for thyrotropin-releasing hormone (TRH). Immunostaining was abolished by preincubation with proTRH-SH (10(-6)M) but not TRH (10(-5)M). Both TRH precursor and TRH were located in neurons of the paraventricular nucleus. However, in contrast to the findings for TRH, no staining was observed in axon terminals of the median eminence. These results suggest that a TRH precursor analogous to that reported in frog skin is present in the rat brain and that TRH in the mammalian central nervous system is a product of ribosomal biosynthesis.

Animals↗

PubMed1985

Thyrotropin releasing hormone but not histidyl-proline diketopiperazine is depleted from rat spinal cord following 5,7-dihydroxytryptamine treatment.

Histidyl-proline diketopiperazine (His-Pro DKP) has been proposed as a metabolite of thyrotropin releasing hormone (TRH). Since spinal cord TRH arises from serotoninergic (5-HT) neurons in the brainstem, a 5-HT neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), was injected into the lateral ventricle of 7 rats, and the levels of TRH and His-Pro DKP in the spinal cord were studied 5 weeks later. In comparison to the saline treated controls, 5,7-DHT treated animals showed marked depletion of TRH throughout the spinal cord, especially in the lumbosacral area where almost 90% disappeared, (0.28 +/- 0.02 vs. 2.46 +/- 0.01 ng/mg protein; P less than 0.0001). In contrast, His-Pro DKP showed no significant change in any region. Since 5,7-DHT lowers spinal cord TRH by destroying TRH perikarya in the medulla, we conclude that spinal cord His-Pro DKP is not derived from the same neurons as TRH.

5,7-Dihydroxytryptamine↗

PubMed1985

Immunoreactive neuronal pathways of growth hormone-releasing hormone (GRH) in the brain and pituitary of the teleost Gadus morhua.

Using an antiserum directed against the C-terminus of hGRH(1-44)NH2 and another recognizing the mid portion to C-terminal of hGRH(1-40)OH, we identify two immunocytochemically distinct GRH-immunoreactive systems in the brain of the codfish, Gadus morhua. The antiserum directed against GRF(1-44)NH2 stains cell bodies exclusively in the rostral pars distalis. The other antiserum immunoreactive with GRF(1-40)OH reacts with a population of parvocellular and magnocellular neuronal cell bodies in the hypothalamus and with two major axonal pathways which project toward the median eminence and terminate primarily in the pars nervosa. These results indicate the presence of at least two forms of hGRH-like peptides in the teleost which may have different roles in the regulation of pituitary function.

Animals↗

PubMed1985

Multiple forms of human pancreatic growth hormone releasing factor-like immunoreactivity in teleost brain and pituitary.

Two anatomically distinct neuronal GRF systems in the brain-pituitary of the teleost codfish (Gadus morhua), immunohistochemically localized by use of antisera directed against hpGRF1-44NH2 and hpGRF1-40OH are described. Chromatographic analysis additionally revealed the presence of three molecular variants of immunoreactive hpGRF1-44NH2, two of which differ from the authentic human material. However, all three forms released GH from rat pituitary cells in dispersed culture. These findings indicate that hpGRF is highly conserved in nature and suggest that peptides closely related to this human hypothalamic releasing hormone regulate the teleost pituitary.

Animals↗

PubMed1984

Distribution of immunoreactive growth hormone releasing factor(1-44)NH2 in the tuberoinfundibular system of the rhesus monkey.

Using an antiserum which reacts with the carboxyl terminus of GRF(1-44)NH2, the distribution of immunoreactive growth hormone releasing factor (GRF) in the rhesus monkey hypothalamus was delineated by peroxidase immunocytochemistry. Immunoreactive material was present in dense terminal fields in the median eminence closely associated with portal capillaries but in a location distinct from that noted for immunoreactive thyrotropin-releasing hormone (TRH) or somatostatin. GRF-immunoreactive cell bodies were identified in the arcuate nucleus and ventromedial nucleus. These studies provide evidence for the presence of GRF(1-44)NH2 in the primate brain and demonstrate that in the hypothalamus it is localized exclusively in cells and fibers corresponding to the tuberoinfundibular system.

Animals↗

PubMed1984

The distribution of thyrotropin-releasing hormone (TRH) in the rhesus monkey spinal cord.

The distribution of thyrotropin-releasing hormone (TRH) in the Rhesus monkey spinal cord was studied using a highly specific antibody to TRH and the indirect peroxidase-antiperoxidase technique. TRH-positive fibers were found at all levels of the spinal cord and were in greatest concentration in the ventral gray, intermediolateral column and central gray. All motor nuclear groups in lamina IX of the ventral gray were innervated by TRH, frequently in close association with perikarya of alpha-motoneurons. The motor nuclei in the lumbar cord were the most heavily stained and contrasted to the minimal staining in the retrodorsolateral nuclear groups of the cervical, thoracic and sacral cord. Within the intermediolateral column, which contains the majority of preganglionic sympathetic neurons, TRH terminal fields reached their highest density between T2-T4 and T12-L2. Other preganglionic neurons including the nucleus intercalatus spinalis and the dorsal commissural nucleus were also densely innervated. These studies demonstrate the preferential distribution of TRH in the monkey spinal cord to regions containing alpha-motoneurons and preganglionic neurons and indicate that TRH may play an important role in the regulation of motor function and in the autonomic nervous system.

Animals↗

PubMed1984

Ontogeny of thyrotropin-releasing hormone and histidyl proline diketopiperazine in the rat central nervous system and pancreas.

The ontogeny of TRH and of a proposed TRH metabolite, histidyl proline diketopiperazine (His-Pro DKP), was determined in the rat central nervous system and pancreas as a means of studying the interrelationship of these peptides. Various regions of the rat brain, spinal cord, and pancreas were dissected from animals ranging in age from prenatal day 17 to adult. The tissues were extracted for TRH and His-Pro DKP, and tissue levels of the two peptides were measured by specific RIAs. We found increasing TRH levels in the hypothalamus, spinal cord, and multiple extrahypothalamic brain regions in the developing rat [e.g. from 21 +/- 3 (+/- SE) pg/hypothalamus on prenatal day 17 to 2606 +/- 296 pg/hypothalamus in the adult]. In the rat pancreas, however, TRH levels initially increased from 354 +/- 37 pg/pancreas on prenatal day 21 to 749 +/- 68 pg/pancreas on postnatal day 7, but from day 7 to adulthood, the TRH content fell dramatically, being undetectable in the adult rat pancreas. The His-Pro DKP content increased in nearly all tissues studied, with peak values occurring on postnatal days 10 and 28 and in the adult. There was little apparent correlation, however, between the anatomical distribution and ontogeny of TRH compared with those of His-Pro DKP. We conclude that His-Pro DKP and TRH have widespread distributions involving the hypothalamus, extrahypothalamic brain, spinal cord, and pancreas in the developing rat. TRH and His-Pro DKP, however, have differing patterns of ontogeny in the rat, suggesting that His-Pro DKP may be derived from sources other than just TRH.

Animals↗

PubMed1983

Evidence that spinal cord thyrotropin-releasing hormone is independent of the paraventricular nucleus.

To determine whether neuronal perikarya containing thyrotropin-releasing hormone (TRH) in the paraventricular nucleus project to the spinal cord, this region of the hypothalamus was ablated by a midline electrolytic lesion and the spinal cord assayed for its content of TRH. In contrast to the marked diminution of TRH in the median eminence, there was no significant change in the TRH content in the spinal cord. These results indicate the absence of significant afferent input of TRH-containing perikarya in the paraventricular nucleus to the spinal cord.

Animals↗

PubMed1983

Prosomatostatin-specific antigen in rat brain: localization by immunocytochemical staining with an antiserum to a synthetic sequence of preprosomatostatin.

Using an antiserum to a 15-amino acid synthetic peptide corresponding to amino acids 63-77 of rat preprosomatostatin (rat somatostatin cryptic peptide, RSCP), we have compared the distribution of immunoreactive RSCP (IR-RSCP) with that of immunoreactive somatostatin-14 in the rat brain. IR-RSCP was present in neuronal cell bodies, processes, and axon terminals in the hypothalamic tuberoinfundibular system as well as in diverse regions of the central nervous system in an identical distribution to immunoreactive somatostatin. These observations indicate that in neurons the somatostatin prohormone or the NH2-terminal extension peptide of somatostatin-28 (or both) is stored and transported intracellularly along with somatostatin 14. In addition, the presence of IR-RSCP in nerve terminals suggests that this material may be secreted as a hormone or neuromodulator and may serve as a biologic marker of somatostatin secretion.

Amino Acid Sequence↗

PubMed1983

Acrolein: a fixative for immunocytochemical localization of peptides in the central nervous system.

Acrolein was examined as an alternative fixative to formaldehyde for immunocytochemical localization of neuropeptides in the rat brain. A brief (5 min) vascular perfusion with a 5% acrolein solution allowed the identification of thyrotropin-releasing hormone (TRH), vasoactive intestinal peptide (VIP), somatostatin (SRIF), neurotensin (NT), methionine enkephalin (Menk), adrenocorticotropic hormone (ACTH), tyrosine hydroxylase (TH), and luteinizing hormone-releasing hormone (LHRH) in fibers and perikarya within the central nervous system of the rat using the peroxidase-antiperoxidase (PAP) technique. Acrolein appears to be particularly valuable for immunocytochemistry, as it 1) stabilizes heterogeneous peptides and proteins rapidly and effectively, 2) retains antigenicity, and 3) preserves morphological detail.

Acrolein↗

PubMed1983

Distribution of immunoreactive human growth hormone-like material and thyrotropin-releasing hormone in the rat central nervous system: evidence for their coexistence in the same neurons.

The distribution of a substance with human GH (hCG)-like immunoreactivity was studied in the rat brain after rapid fixation with acrolein. Using this method of tissue preparation, the hGH-like material (hGH-LM) was found in several hypothalamic and extrahypothalamic regions of the brain and extended into the spinal cord and posterior pituitary. On serial sections, the distribution of the hGH-LM was observed to be identical to that of TRH throughout the neuraxis. Sequential immunostaining of the hGH-LM and TRH in the same tissue section revealed the coexistence of these two peptides in the same neuronal cell bodies in the hypothalamus and brain stem and in beaded processes in all regions of the central nervous system studied. These findings demonstrate the intimate association between the hGH-LM and TRH in the central nervous system and raise the possibility that the hGH-LM forms part of a precursor hormone from which TRH is derived.

Animals↗

PubMed1982

The tuberoinfundibular system of the rat as demonstrated by immunohistochemical localization of retrogradely transported wheat germ agglutinin (WGA) from the median eminence.

The origin of neuronal perikarya which project to the external zone of the median eminence (the tuberoinfundibular neuronal system) was determined in the rat after injection or diffusion of wheat germ agglutinin (WGA) into the median eminence. The retrogradely transported lectin was detected in neurons using an immunohistochemical method based on the peroxidase-antiperoxidase technique. Immunoreactive cell bodies were found both in hypothalamic and extrahypothalamic regions. Within the hypothalamus, the majority of peroxidase-positive cells were present in the dorsomedial and basolateral portions of the arcuate nucleus, regions of the periventricular nucleus, and the preoptic region, particularly at the level of the organum vasculosum of the lamina terminalis (OVLT). Within the extrahypothalamic regions, WGA-positive perikarya were found in the diagonal band of Broca, the region of the medical septum and the brainstem. Only rare cells were labeled in the ventromedial nucleus of the hypothalamus and no cells were labeled in any region of the amygdala. These data demonstrate that neurons with afferent projections to the median eminence are more widely distributed in the rat brain than previously recognized and therefore, that the concept of the tuberoinfundibular neuronal system must be expanded.

Animals↗

PubMed1982

Immunohistochemical localization of human growth hormone-like material in the median eminence of the rat: light and electron microscopic observations.

Using the peroxidase-antiperoxidase pre-embedding technique for immunoelectron microscopy, human growth hormone (hGH)-like material was demonstrated in large, dense core vesicles in axon terminals in the hypothalamic median eminence of the rat. The close association of immunoreactive terminals with fenestrated capillaries of the portal plexus, suggests that the hGH-like material is contained within the tuberoinfundibular neuronal system and may be a hypophysiotropic hormone.

Animals↗

PubMed1982

Immunohistochemical localization of thyrotropin-releasing hormone in the rat hypothalamus and pituitary.

The distribution of immunoreactive TRH in the rat hypothalamus and pituitary was demonstrated using the peroxidase-antiperoxidase technique after rapid fixation of the rat brain with 5% acrolein. Widespread reaction product was identified in neuronal processes throughout the hypothalamus, with dense labeling in the median eminence, dorsomedial nucleus, parvocellular division of the paraventricular nucleus, perifornical region, periventricular nucleus, and organum vasculosum of the lamina terminalis. A striking accumulation of immunoreactive TRH was also noted throughout the posterior pituitary, where fibers appeared to terminate in grape-like swellings. Peroxidase-positive perikarya were best seen after colchicine pretreatment and were distributed in many regions of the hypothalamus. The greatest density of immunoreactive neurons was in the suprachiasmatic preoptic nucleus, parvocellular subdivision of the paraventricular nucleus, perifornical region, dorsomedial nucleus, and baso-lateral hypothalamus. These data are consistent with the role of TRH as a hypophysiotropic hormone, a regulator of the posterior pituitary, and a neurotransmitter or neuromodulator of neurons in other regions of the hypothalamus.

Animals↗

PubMed1981

Immunohistochemical localization of retrogradely and anterogradely transported wheat germ agglutinin (WGA) within the central nervous system of the rat: application to immunostaining of a second antigen within the same neuron.

Immunohistochemical localization of retrogradely transported wheat germ agglutinin (WGA) is proposed as a sensitive histochemical technique to identify point to point connections within regions of the central nervous system. Injections of WGA into the median eminence of the hypothalamus and the caudate-putamen complex, respectively, were performed to illustrate that this material is rapidly transported over long distances and accumulates within the cytoplasm of neuronal perikarya and their processes. The applicability of this technique to identification of a second antigen within immunoreactive-WGA-labeled neurons is also demonstrated by sequential immunostaining of tyrosine hydroxylase within dopamine-containing cells of the mesencephalon, ipsilateral to an injection in the caudate-putamen complex. This technique is of use in characterizing bioaminergic neurons in the central nervous system and may also be of use in characterizing peptidergic neurons.

Animals↗

PubMed1981

Immunohistochemical identification of a novel substance with human growth hormone-like immunoreactivity in rat brain.

Through use of an antiserum directed against hGH, an immunoreactive hGH-like material has been identified in the rat brain by peroxidase immunohistochemistry. Peroxidase-positive material was found in beaded, neuronal fibers in the external zone of the median eminence, lateral septum, and organum vasculosum of the lamina terminalis and was unaffected by prior hypophysectomy. After pretreatment with intraventricular colchicine, numerous immunoreactive neuronal cell bodies were visualized within the parvocellular medial division of the paraventricular nucleus, periventricular nucleus, dorsomedial nucleus, lateral hypothalamus, and preoptic area. Immunohistochemical staining was completely abolished by preincubation of the antiserum with 10(-6) M hGH, the 20,000 mol wt variant of hGH. hGH dimer, core peptide 20-64/135-167, proteolytically derived hGH fragments 1-134 and 147-91, and human placental lactogen. There was no diminution in staining after preincubation with hGH N-terminal fragment 1-43, hGH C-terminal fragment 171-191, rat GH, rat or human PRL, and numerous other neuropeptides and anterior pituitary hormones. Bilateral electrolytic ablation of the paraventricular nucleus area caused a loss of immunostaining in the median eminence. These results indicate the presence of a hitherto undescribed intrinsic neuronal system in rat brain that contains a substance bearing immunological similarity to the midportion of the hGH molecule and to human placental lactogen. It is proposed that this substance is part of a tuberoinfundibular neuronal system deriving from the parvocellular medial division of the paraventricular nucleus-immunoreactive perikarya and may, therefore, be involved in hypophysial regulation. It may also act as a neuromodulator of limbic lobe structures and other hypothalamic regions.

Animals↗