GABA-immunoreactive structures in rat kidney

We examined the distribution of gamma-aminobutyric acid-like immunoreactivity (GABA-LI) in the rat kidney by light and electron microscopy. In vibratome sections, GABA-LI was present in both the renal medulla and cortex. The inner stripe of the outer medulla was most heavily and almost homogeneously labeled, whereas GABA-LI in the cortex was mainly confined only to some tubules. GABA-positive structures involved the epithelial cells of the thin and the thick ascending limbs of the loop of Henle, the connecting tubules, and the collecting ducts. In GABA-positive connecting tubules and collecting ducts the immunoreactivity was present in the cytoplasm of about half of the epithelial cells. As revealed by electron microscopy, the labeled cells in the collecting tubules were the light (principal) cells. No GABA-LI occurred in neuronal structures. These findings are consistent with the presence of a non-neuronal GABA system in the rat kidney. Furthermore, the specific distribution of GABA in the tubular epithelium suggests a functional significance of this amino acid in tubular transport processes.

An efficient enzyme immunoassay for glutamate using glutaraldehyde coupling of the hapten to microtiter plates

In order to coat microtiter plates for enzyme immunoassays (EIAs), amino acids and other haptens are usually coupled to larger protein molecules. The formation of such conjugates is not always reproducible. This may lead to inconsistent hapten-protein stoichiometries, unfavorable orientation of the hapten on the protein and/or well-to-well variation in the concentration of the available hapten. In the assay described here the excitatory amino acid (EAA) Glu is coupled directly to polystyrene microtiter wells with GA. Each step of the assay was tested for maximum efficiency. The resulting EIA with Glu as a competitor gave excellent reproducibility (coefficient of variation = 5.87%), an EC50 of 2.02 X 10(-5) M and a detection limit of 1.26 X 10(-6) M. This EIA method is generally useful for a variety of antisera to amino acids and small peptides and a wide range of competing substances. It can be used to characterize the conformational requirements for antigen binding, to assay for glutamate or to identify compounds with glutamate-like structure in unknown solutions.

Alternative processing of androgen-binding protein RNA transcripts in fetal rat liver. Identification of a transcript formed by trans splicing

Androgens and their nuclear receptor regulate genes necessary for development of the male phenotype, a process that is thought to be modulated by extracellular androgen carrier proteins. Two of these carrier proteins, testicular androgen-binding protein (ABP) and plasma sex hormone-binding globulin (SHBG), are encoded by the same gene, but differ in glycosylation and possibly amino acid sequence. To investigate ABP-SHBG gene expression in fetal rat liver, we analyzed RNA transcripts and expressed protein. These studies demonstrated a transient expression of ABP in hepatocytes during the time of testosterone-dependent differentiation of the Wolffian duct. Analysis of cDNA clones derived from fetal rat liver cDNA libraries identified two cDNAs encoded by the ABP-SHBG gene that represented alternatively spliced RNAs. One cDNA had an alternate exon 1, suggesting the function of another promoter in fetal liver. This cDNA also lacked testicular exon 6 DNA, an alteration that implicates the encoded protein in regulatory functions. The other cDNA represented a fused transcript of the ABP-SHBG gene (exons 1-5) and the histidine decarboxylase (HDC) gene, encoding a Mr 98,000 precursor protein. The two domains were joined at splice junctions of the ABP-SHBG and HDC genes, which were localized to rat chromosomes 10 and 3, respectively. Our results indicate that the joining of the two domains was by a trans (donor and acceptor)-splicing mechanism. Data from Northern hybridization experiments suggest the fusion transcript is present in fetal liver RNA. Polymerase chain reaction experiments with fetal liver cDNA further support the existence of an ABP-HDC fusion transcript, as well as the other alternate mRNA. Moreover, a Mr 93,000 immunoreactive protein was transiently expressed in fetal liver during the time of ABP and HDC gene expression. Expression of the fusion cDNA in COS cells yielded HDC activity and the predicted size protein (Mr = 93,000) on Western immunoblots.

Colchicine enhances mRNAs encoding the precursor of calcitonin gene-related peptide in brainstem motoneurons

Hybridization signals indicating mRNAs encoding the precursor of calcitonin gene-related peptide (CGRP) and CGRP immunoreactivity were detected on parallel sections containing brainstem motor nuclei using in situ hybridization histochemistry and immunohistochemistry. In untreated and saline-injected rats the motoneurons in the hypoglossal, facial motor nuclei and in the ambiguus nucleus showed weak to moderate hybridization signals. In these motoneurons CGRP immunoreactivity was restricted to the Nissl bodies of the perikarya. Twenty-four and 42 hours after intracerebroventricular colchicine injection the intensity of both the hybridization signal and the immunoreaction product increased. The distribution of CGRP immunoreactivity changed from discrete perikaryal localization to diffuse reaction in the perikarya and along the proximal dendritic tree. Motoneurons in the rest of the brainstem motor nuclei (VIth, Vth, IVth and IIIrd) of untreated and saline-injected rats showed neither hybridization signal nor CGRP immunoreactivity. After intracerebroventricular injection of colchicine these motoneurons showed both hybridization signal and CGRP immunoreactivity. In all nuclei the size of motoneurons decreased and their Nissl structure changed to an amorphous basophilic mass following colchicine treatment.

Plasticity of GABA- and glutamate-containing terminals in the mouse thalamic ventrobasal complex deprived of vibrissal afferents: an immunogold-electron microscopic study

GABA and glutamate immunogold staining demonstrated that nerve cells of the thalamic ventrobasal complex (VB) of mice were positive exclusively for glutamate. None of the neuronal perikarya reacted the GABA antibody. By using alternate thin sections of the normal VB, it was also shown that large "specific" somatosensory and small corticothalamic terminals, both of which contained spherical synaptic vesicles, exhibited only glutamate-like immunoreactivity. A third axonal type, containing flat-ovoid synaptic vesicles, stained only for GABA. Seventy-five days after coagulation of the vibrissal follicles in newborn mice, a characteristic multiplication of GABA positive axon terminals was observed. In addition, it was demonstrated that, similarly to modified cortical endings (Hámori et al., J. Comp. Neurol. 254:166-183, '86), many GABA positive terminals appeared as specific afferent endings, replacing the missing "specific" vibrissal afferents. This finding shows a remarkable plasticity of inhibitory GABA axons during developmental synaptogenesis and provides further evidence that the size, location, and the type of attachment of presynaptic terminals are dependent on their postsynaptic target.

The androgen-binding protein gene is expressed in male and female rat brain

Extracellular androgen-binding proteins (ABP) are thought to modulate the regulatory functions of androgens and the trans-acting nuclear androgen receptor. Testicular ABP and plasma sex hormone-binding globulin (SHBG), which is produced in liver, are encoded by the same gene. We have now found that the ABP-SHBG gene is also expressed in male and female rat brain. Immunoreactive ABP was found to be present in neuronal cell bodies throughout the brain as well as in fibers of the hypothalamic median eminence. The highest concentrations of immunoreactive cell bodies were located in the supraoptic and paraventricular nuclei. Likewise, ABP mRNA was present in all brain regions examined. Analysis of cDNA clones representing brain ABP mRNAs revealed amino acid sequence differences in brain and testicular ABPs. The protein encoded by an alternatively processed RNA has sequence characteristics suggesting that the protein could act as a competitior of ABP binding to cell surface receptors. These data and gene-sequencing experiments indicate that a specific ABP gene promoter is used for transcription initiation in brain. ABP may function in brain as an androgen carrier protein; however, in view of the widespread presence of ABP and ABP mRNA in brain, the protein may have a much broader, yet unknown, function.

Immunogold electron microscopic demonstration of glutamate and GABA in normal and deafferented cerebellar cortex: correlation between transmitter content and synaptic vesicle size

Selective labeling of mossy fiber terminals and parallel fibers was obtained in rat cerebellar cortex by a glutamate antibody produced and characterized by Hepler et al. The high-resolution electron microscopic immunogold demonstration of this amino acid offered the possibility of determining the size and shape of synaptic vesicles in glutamate-positive mossy endings. Mossy terminals that stained with the glutamate antibody formed two distinct populations, one with spherical synaptic vesicles with an average diameter of 34.0 nm (more than 90% of all mossy fiber endings) and one with pleomorphic and smaller synaptic vesicles which had an average diameter of 28.5 nm. We present experimental evidence that the mossy terminals with large round vesicles are of extracerebellar origin, whereas those with small pleomorphic synaptic vesicles are endings of nucleocortical fibers. The presence of two distinct classes of gamma-aminobutyric acid (GABA)-containing axon terminals within cerebellar glomeruli has also been demonstrated; those originating from the cerebellar nuclei contain large (36.2 nm) synaptic vesicles, whereas the majority of GABA-stained axon terminals that are of local (cortical) origin contain small (29.1 nm) synaptic vesicles. It therefore appears that, at least in the case of glutamate and GABA, morphological characterization of the axon terminals based on the size and shape of synaptic vesicles is not a reliable indicator of their functional nature (i.e., whether they are excitatory or inhibitory); convincing evidence for the identity of the transmitter can be obtained only by electron microscopic immunostaining procedures. Our results also suggest the existence of both inhibitory and excitatory feedback from cerebellar nuclei to cerebellar cortex.

Antibodies to glutamate and aspartate recognize non-endogenous ligands for excitatory amino acid receptors

Antisera raised against glutaraldehyde conjugates of glutamate (Glu) and aspartate (Asp) with hemocyanin proved highly specific for their respective unconjugated amino acid haptens when tested in immunocytochemical blocking experiments on sections of the rat spinal cord. In addition, immunocytochemical staining by the Glu antiserum was effectively blocked by quisqualate but not by kainate or N-methyl-D-aspartate (NMDA); staining with the Asp antiserum was effectively blocked by kainate, to a lesser extent by quisqualate, and was not affected by NMDA. These results may be explained by assuming that the specific binding regions of the antibodies tested share certain recognition characteristics with endogenous binding sites or receptors for excitatory amino acids and their agonists.

Termination patterns of calcitonin gene-related peptide-immunoreactive nerve fibers in the dorsal horn of the human spinal cord

CGRP-immunoreactive varicose nerve fibers displayed three kinds of termination patterns in the cervical, thoracic and lumbar segments of the human spinal cord. Bundles of immunoreactive fibers formed a loose network in lamina I. A homogenous band of immunoreactive fibers filled lamina II. Multiple bundles of CGRP-positive fibers coursed through the superficial laminae towards deep portions of the grey matter. In the lumbar segments, in contrast to the cervical and thoracic segments, the bundles could be followed deep into the dorsal funiculus. Bundles of varicose immunoreactive fibers were seen to twine around the dendrites of neurons located in lamina I, in the dorsal funiculus of the lumbar segments and deep in the dorsal horn (laminae III-V). The corresponding types of large and medium-sized neurons were found in silver impregnated adjacent spinal cord sections. It is suggested that neurons in the above locations preferentially receive multiple contacts from CGRP-containing nerve fibers along their extensive dendritic arborizations (CGRP-target neurons).

Development of neurotransmitter systems in the mouse embryo following acute ethanol exposure: a histological and immunocytochemical study

Acute maternal ethanol administration to C57B1/6J mice on gestational day 7 (GD7) results in facial and brain abnormalities similar to those reported in human fetal alcohol syndrome (FAS). Using this model, we assessed the damage to brain structures using histological methods and changes in developing neurotransmitter systems with immunocytochemistry. Cholinergic neurons in the forebrain were stained with a monoclonal antibody to choline acetyltransferase (ChAT). Catecholaminergic neurons in the midbrain and serotoninergic neurons in the hindbrain were stained with polyclonal antisera to tyrosine hydroxylase (TH) and serotonin (5-HT), respectively. Forebrain deficiencies, including loss of midline structures (olfactory bulbs, midline septation, medial septal area) and deficits in lateral and dorsal regions (neostriatum and cerebral cortex) were found in both GD14 embryos and GD18 fetuses. In severely affected offspring, complete loss of the septal region resulted in conjoined lateral ventricles and a reduction in the thickness of the ventricular zone surrounding the single ventricle, as well as a severe loss of ChAT neurons which would normally be located in this territory. However, no consistent changes were seen in the distribution or size of TH or 5-HT neuronal cell groups in the midbrain and hindbrain. These differences in effects on specific neurotransmitter systems reflect the fact that the forebrain is most severely affected by early ethanol administration, whereas the hindbrain is relatively spared. Such differential effects could produce an imbalance in developing neurotransmitter systems in the embryonic and fetal brain, which could explain some of the functional deficits observed in children with FAS.

Combined retrograde tracing and immunocytochemical identification of luteinizing hormone-releasing hormone- and somatostatin-containing neurons projecting to the median eminence of the rat

LHRH and somatostatin or somatotropin-release inhibiting factor (SRIF) are produced by neurons whose cell bodies are located in telencephalic and diencephalic regions in the rat. Many, but not all, of these neurons project to the external zone of the median eminence (ME), where the peptides are released from the nerve terminals into hypophysial portal vessels. In the present study, we identified these neurons by in vivo injection of a retrograde tracer, the lectin wheat germ agglutinin (WGA), into the external zone of the ME. Subsequently, colchicine was given into the lateral ventricle 10-24 h after the WGA injection. The animals were killed 24-48 h after the WGA injection. Vibratome sections of the brains were stained for both WGA and LHRH or SRIF with a dual immunocytochemical technique. Approximately 70% of the LHRH neurons in the septum and the anterior hypothalamus and about 70% of the SRIF neurons in the medial preoptic area, the anterior periventricular area, and the paraventricular nucleus were double labeled, indicating that they projected to the ME. None of the SRIF neurons in the ventromedial and arcuate nuclei were labeled with WGA. Double labeled LHRH cells were either smooth and fusiform or spiny. WGA-accumulating LHRH or SRIF perikarya were intermixed with single labeled LHRH or SRIF cells, which apparently did not project to the ME. The results indicate that there are at least two populations of LHRH neurons in the preoptic-septal region and two populations of SRIF neurons in the medial preoptic and anterior periventricular areas and the paraventricular nucleus of the rat brain: one with access to the portal capillaries of the ME and, therefore, functionally related to the regulation of the pituitary, and another without access to portal capillaries, perhaps functionally related to intracerebral neurotransmission or modulation. Moreover, some hypophysiotropic LHRH and SRIF neurons may have axon collaterals reaching multiple targets within the central nervous system.

Ontogeny of cholinergic neurons in the mouse forebrain

The development of cholinergic neurons in the mouse forebrain was studied by immunocytochemistry with a monoclonal antibody to choline acetyltransferase (ChAT), the rate-limiting enzyme for acetylcholine synthesis. Since this antibody stained dividing cells in ventricular germinal zones as well as differentiating neurons, likely routes of migration could be inferred on the basis of the location of immunoreactive (IR) cells at different gestational ages. Germinal zones for cholinergic cells were observed in all ventricular zones of the forebrain with the ventral zones generating the earliest cells by gestational day 13.5 (GD13.5). On GD14, ChAT IR cells were visible in the germinal zones of the eye, olfactory ventricle, anterior horn, and dorsolateral aspect of the lateral ventricle, lateral ganglionic eminence, ventro- and dorsolateral third ventricle, and in the pineal anlage (epiphysis). ChAT IR neurons continued to develop in these and additional germinal zones on GD15, including the medial, dorsal, and dorsomedial walls of the lateral ventricle, and the medial and dorsal ganglionic eminence. On GD16, ChAT IR neurons were located in the prelimbic, pyriform, and parietal cortices and the lamina terminalis, and a cluster of IR cells was observed in the ventricular zone of the caudatopallial angle. On GD17-18, neurons in the anterior olfactory nucleus, olfactory tubercle, horizontal and vertical nucleus of the diagonal band, and medial septal nucleus stained more darkly and were multipolar, whereas immature bipolar neurons appeared to continue their migration into the hippocampus and along major fiber tracts, such as the corpus callosum, external capsule, fornix and anterior commissure. This study provides a comprehensive view of the zones of origin, probable routes of migration, and final destination of cholinergic neurons in the mouse forebrain.

Identification of hypophysiotropic luteinizing hormone-releasing hormone (LHRH) neurons by combined retrograde labeling and immunocytochemistry

The decapeptide luteinizing hormone-releasing hormone (LHRH) is produced by telencephalic and diencephalic neurons and transported to the median eminence (ME). After having been released from nerve terminals, it is carried by the hypophysial portal vessels to the anterior pituitary, where it stimulates the production and release of luteinizing hormone (LH) and follicle stimulating hormone (FSH). Those LHRH neurons which project to the ME represent the final common pathway for the regulation of the pituitary/gonadal axis. We identified these neurons by injecting a retrograde tracer, the lectin wheat germ agglutinin (WGA), into the external zone of the ME. Eight to 24 hours later colchicine was given into the lateral ventricle and 24-48 hours after the WGA injection the animals were sacrificed. Vibratome sections of the brains were stained simultaneously for WGA and LHRH with a dual immunocytochemical technique. Approximately 70% of the LHRH neurons in the septum and the anterior hypothalamus were double-labeled, indicating that they projected to the ME. Double labeled LHRH cells were either smooth, fusiform or "spiny". WGA-accumulating LHRH perikarya were intermixed with single-labeled LHRH cells. The remaining 30% of the LHRH neurons which were not labeled with WGA appeared to project to different hypothalamic and extrahypothalamic areas of the brain. Our results suggest that there are at least two populations of LHRH neurons, one with access to the portal capillaries of the ME and functionally related to the regulation of the pituitary, and one without access to capillaries of the ME, functionally probably related to intracerebral neurotransmission or modulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental expression of an androgen-regulated epididymal protein

Acidic epididymal glycoprotein (AEG), an androgen-regulated secretory protein of rat epididymis, was quantitated by RIA in epididymal extracts of rats of increasing age. Although detectable at 1 day of age, significant concentrations of AEG were not measured until 20 days; concentrations increased steadily, so that by 120 days of age, AEG represented 10% of total soluble protein. AEG mRNA was detected by Northern blot analysis of RNA from epididymides of 5-day-old animals and rapidly increased in amount between 20 and 35 days, reaching a maximum at 45 days. Using immunohistochemistry, AEG was localized in epididymal epithelial cells at 1 day of age. The number of cells staining for AEG increased markedly after 15 days. At 120 days, the immunoreactivity was predominantly localized to the lumen of the epithelial duct. To delineate factors that may influence AEG expression in the developing epididymis, we measured concentrations of androgen and androgen receptor mRNA in tissue extracts prepared from animals of various ages. Androgen receptor mRNA was detectable in epididymal extracts isolated from 1- to 90-day-old animals. Epididymal androgen concentrations were high at all ages (range, 6.0-31.2 ng/g tissue). The marked increase in AEG mRNA concentration at 20 days of age was not associated with an increase in either androgen or androgen receptor mRNA concentrations, suggesting that other factors may be necessary for AEG expression.

The androgen-binding protein gene is expressed in CD1 mouse testis

Androgen-binding protein (ABP) is a testicular Sertoli cell secretory protein that acts as a carrier of androgen in the male reproductive tract. ABP has been characterized from a wide range of animal species, including man, rabbit and rat. However, it has been widely accepted that mice do not produce testicular ABP. We have used immunological and molecular biological techniques to demonstrate that the ABP gene is expressed in the CD1 mouse. Steroid-binding, radioimmunoassay and immunocytochemical studies demonstrated that ABP is present in mouse testis and epididymis, but at 1/50 to 1/25 the level of rat epididymis. A 1.7 kilobase mRNA, homologous with rat ABP cDNA, was identified in mouse testis and Sertoli cells by Northern blot hybridization, but at a much lower level than in the rat. An ABP cDNA was isolated from a mouse testis cDNA library and encoded a protein (403 residues) with 89% of the amino acid residues identical to rat ABP, including a signal peptide. Our results indicate that ABP is expressed in the mouse and past failures to detect androgen-binding activity were due to the low level of ABP protein.

Identification and immunocytochemical localization of a new thyrotropin-releasing hormone precursor in rat brain

Antisera were raised to a tridecapeptide, Ser-Asp-Val-Thr-Lys-Arg-Gln-His-Pro-Gly-Arg-Arg-Phe, that was synthesized based on the sequence (residues 166-178) of a proposed cDNA for pro-TRH reported by Lechan et al. With this antiserum, immunostaining of Western blots of rat brain extracts revealed two major proteins with mol wt (Mr = 39,000 and 52,000) considerably larger than that of the largest protein (Mr = 29,000) that could be encoded by the cDNA of Lechan et al. Because these observations suggested the possibility of novel TRH precursors, we studied the immunocytochemical distribution of pro-TRH (39-52K) in rat brain. Our anatomical findings were 4-fold. 1) The distributions of 29K pro-TRH and 39-52K pro-TRH are not identical. 2) TRH is found only in regions containing 29K pro-TRH, 39-52K pro-TRH, or both. 3) There are regions that contain both 29K pro-TRH and 39-52K pro-TRH, but no TRH. 4) Regions containing only 39-52K pro-TRH do not contain 29K pro-TRH mRNA as mapped by Segerson et al. From these electrophoretic and anatomical observations, we postulate the existence of at least one and possibly two additional precursors that can be processed to TRH in rat brain.

Immunocytochemical localization of the gonadotropin-releasing hormone-associated peptide portion of the LHRH precursor in the hypothalamus and extrahypothalamic regions of the rat central nervous system

The gonadotropin-releasing hormone-associated peptide (GAP) of the LHRH precursor and the decapeptide LHRH were localized in the rat brain by immunocytochemistry in 12- to 18-day-old animals, by use of thick Vibratome sections and nickel intensification of the diaminobenzidine-reaction product. Our results indicate that the GAP portion of the LHRH precursor is present in the same population of neurons that contain LHRH in the rat brain. An important difference observed was that the GAP antiserum, in contrast to LHRH antisera, stained several perikarya in the medial basal hypothalamus. GAP-immunoreactive perikarya were observed in the following regions: the olfactory bulb and tubercle, diagonal band of Broca, medial septum, medial preoptic and suprachiasmatic areas, anterior and lateral hypothalamus, and several regions of the hippocampus. In addition to the preoptico-terminal and the septo-preoptico-infundibular pathways, we also observed GAP-immunopositive processes in several major tracts and areas of the brain, including the amygdala, stria terminals, stria medullaris thalami, fasciculus retroflexus, stria longitudinalis medialis, periventricular plexus, periaqueductal gray of the mesencephalon and extra-cerebral regions, such as the nervus terminalis and its associated ganglion. These results confirm the specificity of previous immunocytochemical results obtained with antisera to LHRH. The presence of GAP immunoreactivity in nerve terminals of the rat brain indicates that GAP or a GAP-like peptide is located in the proper site to serve as a hypophysiotropic substance and/or as a neurotransmitter or neuromodulator.

Characterization of metorphamide-like immunoreactivity in the zona incerta and lateral hypothalamus: co-localization with alpha-melanocyte-stimulating hormone-like immunoreactivity

Double-staining in either vibratome or paraffin sections using contrasting chromogens revealed an alpha-melanocyte-stimulating hormone (alpha-MSH)-containing cell group in the arcuate nucleus, a metorphamide-containing cell group in the paraventricular hypothalamus, and an extensive group of magnocellular perikarya in the zona incerta (ZI) and the lateral hypothalamus (LH) that appeared to contain both antigens. Staining of adjacent paraffin sections also suggested that most (and perhaps all) of the magnocellular perikarya in the ZI and LH that contained metorphamide-like immunoreactivity also contained alpha-MSH-like immunoreactivity. Metorphamide-like immunoreactivity in the ZI and the LH was abolished by absorption of the antiserum with metorphamide but was unaffected by absorption with alpha-MSH. alpha-MSH-like immunoreactivity in the ZI and LH was abolished by absorption of the antiserum with alpha-MSH but was unaffected by absorption with metorphamide. Antisera directed against [Met5]-enkephalin (Met-ENK), [Met5]-enkephalin-Arg6,Gly7,Leu8 (ENK-8), [Met5]-enkephalin-Arg6,Phe7 (ENK-7), neuropeptide Y, and FMRF-amide did not stain magnocellular perikarya in the ZI and LH. Pretreatment of paraffin sections with trypsin resulted in the appearance of [Met5]-enkephalin-Arg6-like immunoreactivity in the ZI and LH. Pretreatment of paraffin sections with trypsin did not reveal any occult Met-ENK-, ENK-7- or ENK-8-like immunoreactivity in either the ZI or the LH. These observations indicate that magnocellular neurons in the ZI and LH contain both a metorphamide-like and an alpha-MSH-like peptide but do not express either the preproenkephalin or the prepro-opiomelanocortin48 gene.

Influence of estrogens on mouse uterine epidermal growth factor precursor protein and messenger ribonucleic acid

Estrogens stimulate the in vivo proliferation of epithelial cells of the mouse uterus. The cumulative evidence from several earlier studies suggests that the mitogenic effect of estrogens is mediated indirectly through a polypeptide growth factor. The primary focus of the present investigation was to determine whether an epidermal growth factor (EGF)-related polypeptide originates in the uterus of the immature or adult mouse under normal or altered estrogen status. Hybridization experiments revealed the presence of the 4.7-kilobase prepro-EGF mRNA in uteri of immature CD-1 mice. The level of this mRNA was augmented at least 2-fold in immature mice treated for 4 days with estrogen, but levels remained markedly low compared to those in submaxillary gland or kidney. Two preparations of pooled uterine luminal fluid from estrogen-treated immature mice contained EGF immunoreactivity (1.2 and 1.7 ng/ml) that was stable in response to acid (50 mM acetic acid) and heat. Negligible EGF (less than 20 pg/uterus) was detected in acid extracts of uteri from ovariectomized or cycling adult mice. After injection of 17 beta-estradiol (0.2 or 2.0 micrograms, ip), the levels of acid-extractable uterine EGF in ovariectomized adult mice up to 48 h after treatment were not different from those obtained with vehicle alone. Immunolocalization of EGF in the mouse uterus was demonstrated only after paraffin sections were first briefly treated with pronase. Staining was observed along the borders of luminal and glandular epithelial cells, especially at the apical region of the cells. Some staining was also observed in the myometrium; stromal cells were negative. Synthesis of the reactive material was apparently estrogen independent, since localization was retained in uteri of both ovariectomized and immature mice. Immunoblots of preparations of membranes from uterine homogenates or epithelial cells revealed a band at mol wt of about 130,000, which, along with other findings of the present study, suggests that EGF occurs predominantly as the membrane-bound precursor form in this organ, as has been previously shown for the kidney. Although the biological role of the precursor in the uterus is not known, we speculate that estrogens function in an autocrine circuit by stimulating processing of the membrane-bound EGF precursor. EGF elaborated by this mechanism might conceivably react with known complementary receptors on uterine epithelial cells to stimulate proliferation.

The Pro-LHRH system of the rat brain. Effects of changes in the endocrine background

The gonadotropin-releasing hormone-associated peptide (GAP) and luteinizing hormone-releasing hormone (LHRH) portions of the LHRH precursor were localized by immunocytochemistry in prepubertal female rats, in adult female rats at different stages of the estrous cycle, and in ovariectomized rats. Our results indicate that GAP is present in the same population of neurons as LHRH in the rat brain. These results confirm the specificity of previous immunocytochemical studies which used antisera to LHRH alone. The endocrine status of the animal was demonstrated to affect the immunocytochemical appearance of the GAP system. The number of GAP immunopositive cells and terminals is highest during diestrus II and lowest on the day of estrus, suggesting either a role in and/or a dependence upon the endocrine changes associated with the estrous cycle. Ovariectomy results in a gradual decrease in GAP immunoreactivity in the median eminence. This observation, in concert with other recent studies, suggests that ovarian factors may be acting to maintain the LHRH system and that ovariectomy may result in decreased synthesis and/or processing of the LHRH system and that ovariectomy may result in decreased synthesis and/or processing of the LHRH precursor.

New data on the immunocytochemical localization of thyrotropin-releasing hormone in the rat central nervous system

An antiserum raised against the synthetic tripeptide pyroglutamyl-histidyl-proline (free acid) was used to localize thyrotropin-releasing hormone (TRH) in the rat central nervous system (CNS) by immunocytochemistry. The distribution of TRH-immunoreactive structures was similar to that reported earlier; i.e., most of the TRH-containing perikarya were located in the parvicellular part of the hypothalamic paraventricular nucleus, the suprachiasmatic portion of the preoptic nucleus, the dorsomedial nucleus, the lateral basal hypothalamus, and the raphe nuclei. Several new locations for TRH-immunoreactive neurons were also observed, including the glomerular layer of the olfactory bulb, the anterior olfactory nuclei, the diagonal band of Broca, the septal nuclei, the sexually dimorphic nucleus of the preoptic area, the reticular thalamic nucleus, the lateral reticular nucleus of the medulla oblongata, and the central gray matter of the mesencephalon. Immunoreactive fibers were seen in the median eminence, the organum vasculosum of the lamina terminalis, the lateral septal nucleus, the medial habenula, the dorsal and ventral parabrachial nuclei, the nucleus of the solitary tract, around the motor nuclei of the cranial nerves, the dorsal vagal complex, and in the reticular formation of the brainstem. In the spinal cord, no immunoreactive perikarya were observed. Immunoreactive processes were present in the lateral funiculus of the white matter and in laminae V-X in the gray matter. Dense terminal-like structures were seen around spinal motor neurons. The distribution of TRH-immunoreactive structures in the CNS suggests that TRH functions both as a neuroendocrine regulator in the hypothalamus and as a neurotransmitter or neuromodulator throughout the CNS.

Expression of ras proto-oncogenes in the Dunning R3327 rat prostatic adenocarcinoma system

Steady-state levels of c-Ha-ras mRNA were measured in eight sublines of the Dunning R3327 rat prostatic adenocarcinoma. As a control, normal dorsal prostate tissue was studied. Increased expression of c-Ha-ras is associated with tumor progression in one lineage of the Dunning R3327 system (H to AT1 to MAT-Lu and MAT-Ly-Lu). Here ras mRNA increases as the tumor advances from androgen dependence and a high degree of differentiation to an anaplastic aneuploid phenotype with high metastatic potential. However, in the other Dunning lineage (H to HI to HI-F to AT3), expression of c-Ha-ras is variable and does not correlate with tumor progression. Immunocytochemistry showed that levels of the c-Ha-ras p21 protein paralleled steady-state mRNA levels in variants. Transfection assays, using NIH/3T3 cells, suggested that the ras loci were not activated in the R3327 tumors. Levels of c-Ki-ras mRNA were also measured in the Dunning tumors; these did not correlate with tumor progression in either lineage. Expression of N-ras mRNA was not detected in the Dunning tumors.

Characterization of antisera to glutamate and aspartate

Antisera were raised in rabbits against glutamate (Glu) and aspartate (Asp) conjugated to the invertebrate carrier protein hemocyanin (HC) with glutaraldehyde (GA). The antisera were characterized by testing their immunocytochemical staining properties on sections cut at the level of the ventral cochlear nucleus (VCN) from fixed brains of normal rats after absorption with conjugates of compounds structurally similar and biologically relevant to Glu and Asp. Optimal staining with Glu antiserum was obtained at a dilution of 1:10,000 and was completely blocked by 303 micrograms/ml of the Glu-HC conjugate. No crossreactivity with any of 11 compounds tested was observed. Optimal staining with the Asp antiserum was obtained at 1:8000 dilution and was completely blocked by 225 micrograms/ml of the Asp-HC conjugate. Of 10 compounds tested for crossreactivity, only L-asparagine demonstrated a measurable (about 10%) crossreactivity with the Asp antiserum. The specificity of the two antisera was also tested by immunoblot analysis against 11 compounds conjugated to HC with GA. Listed in order of staining intensity, from greatest to least, conjugates that reacted with the Glu antiserum were Glu greater than Gly-Glu greater than Asp-Glu = Asp greater than N-carbamyl (NC)-Glu greater than Asn = Gln = GABA. Conjugates that reacted with the Asp antiserum, in order of decreasing staining intensity, were Asp greater than Glu-Asp = Asn greater than Gly-Asp greater than Glu. No other compounds tested for crossreactivity reacted with the two antisera in the immunoblot analysis. Glu-like immunoreactivity in rat dorsal root ganglia and somatosensory cortex, and the comparative distribution of Glu- and Asp-like immunoreactivities in the latter tissue, are presented as examples of staining patterns obtained with the two antisera.

Immunocytochemical localization of inhibin in rat and human reproductive tissues

Recently, the structures of two forms of inhibin present in human follicular fluid were elucidated from the corresponding cDNA sequences. Using specific antisera generated against the alpha-chain common to both forms, we have examined the cellular localization of inhibin in the male and female rat gonads and in human placental tissue. Specific alpha-inhibin immunoreactivity was localized within the Sertoli cells of a number of tubules in each testes section. However, other adjacent tubules were unstained suggesting a stage-specific production of inhibin. Intense immunostaining was observed in the granulosa cells of ovarian follicles at various stages but not in the thecal cells. Immunostaining was present in the human placenta and limited to the cytotrophoblast cells, suggesting a role of inhibin during pregnancy. The present study demonstrates the probable site of production of inhibin in the gonads and placenta and further implicates this important factor as a key regulator of reproductive functions.