The ubiquitin pathway in Parkinson's disease.
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Amino Acid Sequence↗
Biomedical subjects
E Mezey
Publications and source records attributed to E Mezey.
Ontogeny of vesicular monoamine transporter mRNAs VMAT1 and VMAT2. II. Expression in neural crest derivatives and their target sites in the rat.
We used in situ hybridization histochemistry to study the expression of the two vesicular monoamine transporters (VMAT1 and VMAT2) during embryonic development in the rat. In the adult rat VMAT2 is present exclusively in neuronal tissues and VMAT1 is present in the adrenal medulla and in certain intestinal endocrine cells. We found that both transporter molecules are more widely expressed during development. We demonstrate a complete overlap of the two VMAT mRNAs in the sympathetic nervous system between E13 and E21 days. In addition, VMAT2 (and to some extent VMAT1) mRNA is expressed in ganglionic cells of the parasympathetic nervous system and in cranial ganglia (trigeminal, vestibular and spiral ganglia) between E12 and E21. The sensory neurons of the dorsal root ganglia, which are also neural crest derivatives, express VMAT2 mRNA (E11-E21), exclusively. Both VMAT mRNAs are found in the developing GI system, but in different cells. VMAT1 mRNA was detected in organs of the endocrine system (pituitary gland, adrenal gland, testis, seminal vesicle), some connective tissue cells, and the thymus. We observed expression of both VMAT mRNAs in two separate cell groups in the placenta (E8-E10). Based on their distribution during development we suggest that monoamines, released in a controlled fashion, might affect migration and differentiation of neural crest derivatives.
Adrenal Medulla↗
Ontogeny of vesicular monoamine transporter mRNAs VMAT1 and VMAT2. I. The developing rat central nervous system.
We used in situ hybridization histochemistry to study the expression of the mRNA of the two vesicular monoamine transporters (VMAT1 and VMAT2) during embryonic and postnatal development of the central nervous system (CNS) in the rat. In the adult rat, VMAT2 mRNA is present exclusively in monoaminergic cell groups of the CNS and VMAT1 mRNA was reported to be present in the adrenal medulla and certain intestinal epithelial cells. In contrast to the above, the expression of VMAT1 mRNA has previously never been detected in the central nervous system. This study shows the first evidence that both transporter molecules are expressed in CNS during ontogenesis. We here demonstrate four main expression patterns detected during development: 1. VMAT2 mRNA expression in monoaminergic neurons of the brainstem beginning as early as embryonic day E13. 2. Expression of VMAT2 mRNA in all major sensory relay nuclei of central nervous system. 3. Co-expression of VMAT1 and VMAT2 mRNA in most limbic structures, basal ganglia, as well as in some hypothalamic nuclei. 4. Exclusive expression of VMAT1 mRNA in the neocortical subventricular zone, in the amygdala at early (E15-18) and late (P1-P28) timepoints, the granular cell layer of cerebellum, and in several brainstem motor nuclei. Based on their distribution during development we suggest that monoamines, released in a controlled fashion, might affect wiring of sensory and also motor circuits. VMAT1 mRNA expression may reflect a specific effect of monoamines in glial differentiation and cerebellar granule cell migration and/or differentiation.
Aging↗
Transdifferentiation of rat hepatic stellate cells results in leptin expression.
Leptin is a peptide hormone that appears critical in regulating Fat metabolism. Recently, circulating leptin levels were reported higher in patients with alcoholic cirrhosis. In health, hepatic stellate cells store retinoids, but following liver injury they transdifferentiate into myofibroblast-like cells with loss of the retinoid stores. Leptin expression was demonstrated by detection of leptin mRNA by RT-PCR analysis and by immunohistochemistry viewed with confocal microscopy in transdifferentiated stellate cells after 14 days, or more, of culture. Leptin expression was not found in freshly isolated quiescent stellate cells. Leptin expression was not demonstrated in freshly isolated or cultured Kupffer cells. Treatment of activated stellate cells with either 1 microM retionic acid or 10 microM retinol acetate resulted in the inhibition of leptin mRNA expression. The observation that activated stellate cells in culture can express leptin has implications for understanding adipocyte biology in liver disease and treatment of malnutrition in cirrhotics.
Animals↗
Hypoalgesia in mice with a targeted deletion of the tachykinin 1 gene.
The tachykinin neuropeptides, substance P and substance K, are produced in nociceptive primary sensory neurons and in many brain regions involved in pain signaling. However, the precise role and importance of these neuropeptides in pain responses has been debated. We now show that mice that cannot produce these peptides display no significant pain responses following formalin injection and have an increased pain threshold in the hotplate test. On the other hand, the mutant mice react normally in the tail flick assay and acetic acid-induced writhing tests. These results demonstrate that substance P and/or substance K have essential functions in specific responses to pain.
Acetic Acid↗
Effect of dihydrotestosterone on turnover of alcohol dehydrogenase in rat hepatocyte culture.
Dihydrotestosterone decreased alcohol dehydrogenase (ADH) activity and enzyme-protein in rat hepatocytes in culture. This effect was observed after the hepatocytes had been exposed to dihydrotestosterone for 3 days at concentrations of 0.5 micromol/L or higher. Dihydrotestosterone did not decrease alcohol dehydrogenase messenger RNA (mRNA) but, rather, resulted in small increases in ADH mRNA after 3 days of exposure. To further determine the mechanism for the effects of dihydrotestosterone in decreasing the enzyme, the turnover of ADH was determined after incorporation of [3H]-leucine into the enzyme protein. Dihydrotestosterone did not alter the initial 2-hour incorporation of [3H]-leucine into the enzyme protein. Dihydrotestosterone, however, resulted in an increase in the fractional rate of degradation (Kd) of the enzyme from 0.12 +/- 0.013 to 0.23 +/- 0.004 per hour (P < .001) accompanied by a much smaller increase in the fractional rate of synthesis (Ks) from 0.12 +/- 0.028 to 0.17 +/- 0.031 per hour (P > .05). Hence, the mechanism for the fall in ADH in the presence of dihydrotestosterone is an increase in enzyme degradation which is not accompanied by a sufficient increase in enzyme synthesis.
Alcohol Dehydrogenase↗
Dietary fat and alcoholic liver disease.
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Animals↗
Localization and dynamic regulation of biogenic amine transporters in the mammalian central nervous system.
The monoamines, serotonin, dopamine, norepinephrine, epinephrine and histamine, play a critical role in the function of the hypothalamic-pituitary-adrenal axis and in the integration of information in sensory, limbic, and motor systems. The primary mechanism for termination of monoaminergic neurotransmission is through reuptake of released neurotransmitter by Na+, CI-dependent plasma membrane transporters. A second family of transporters packages monoamines into synaptic and secretory vesicles by exchange of protons. Identification of those cells which express these two families of neurotransmitter transporters is an initial step in understanding what adaptive strategies cells expressing monoamine transporters use to establish the appropriate level of transport activity and thus attain the appropriate efficiency of monoamine storage and clearance. The most recent advances in this field have yielded several surprises about their function, cellular and subcellular localization, and regulation, suggesting that these molecules are not static and most likely are the most important determinants of extracellular levels of monoamines. Here, information on the localization of mRNAs for these transporters in rodent and human brain is summarized along with immunohistochemical information at the light and electron microscopic levels. Regulation of transporters at the mRNA level by manipulation in rodents and differences in transporter site densities by tomographic techniques as an index of regulation in human disease and addictive states are also reviewed. These studies have highlighted the presence of monoamine neurotransmitter transporters in neurons but not in glia in situ. The norepinephrine transporter is present in all cells which are both tyrosine hydroxylase (TH)- and dopamine beta-hydroxylase-positive but not in those cells which are TH- and phenyl-N-methyltransferase-positive, suggesting that epinephrine cells may have their own, unique transporter. In most dopaminergic cells, dopamine transporter mRNA completely overlaps with TH mRNA-positive neurons. However, there are areas in which there is a lack of one to one correspondence. The serotonin transporter (5-HTT) mRNA is found in all raphe nuclei and in the hypothalamic dorsomedial nucleus where the 5-HTT mRNA is dramatically reduced following immobilization stress. The vesicular monoamine transporter 2 (VMAT2) is present in all monoaminergic neurons including epinephrine- and histamine-synthesizing cells. Immunohistochemistry demonstrates that the plasma membrane transporters are present along axons, soma, and dendrites. Subcellular localization of DAT by electron microscopy suggests that these transporters are not at the synaptic density but are confined to perisynaptic areas, implying that dopamine diffuses away from the synapse and that contribution of diffusion to dopamine signalling may vary between brain regions. Interestingly, the presence of VMAT2 in vesicles underlying dendrites, axons, and soma suggests that monoamines may be released at these cellular domains. An understanding of the regulation of transporter function may have important therapeutic consequences for neuroendocrine function in stress and psychiatric disorders.
Amino Acid Sequence↗
Expression of the CB1 and CB2 receptor messenger RNAs during embryonic development in the rat.
We mapped the distribution of CB1 and CB2 receptor messenger RNAs in the developing rat to gain insight into how cannabinoids may affect embryogenesis. In situ hybridization histochemistry studies were done using riboprobes specific for CB1 or CB2 receptor messenger RNAs. We found that CB1 and CB2 receptor messenger RNAs are expressed in the placental cone and in the smooth muscle of the maternal uterus at the earliest gestational periods studied [from eight days of gestation (E8) through E12]. In the embryo, as early as E11, CB1 receptor messenger RNA is expressed in some cells of the neural tube and, at later embryological stages (from E15 to E21), in several distinct structures within the central nervous system. In addition, high levels of CB1 receptor messenger RNA were also found in areas of the peripheral nervous system such as the sympathetic and parasympathetic ganglia, in the retina and in the enteric ganglia of the gastrointestinal tract. In addition to neural structures, high levels of the CB1 receptor messenger RNA were also present in two endocrine organs, the thyroid gland and the adrenal gland. On the other hand, CB2 receptor messenger RNA is expressed exclusively in the liver of the embryo as early as E13. The region-specific expression of CB1 and CB2 receptor messenger RNAs suggests that these receptors have a functional role during embryogenesis.
Animals↗
Serotonin transporter messenger RNA in the developing rat brain: early expression in serotonergic neurons and transient expression in non-serotonergic neurons.
Serotonin has been shown to affect the development of the mammalian nervous system. The serotonin transporter is a major factor in regulating extracellular serotonin levels. Using in situ hybridization histochemistry the rat serotonin transporter messenger RNA was localized during embryogenesis, the first four weeks postnatally and adulthood. Three general classes of serotonin transporter messenger RNA expression patterns were observed: (i) early detection with continued expression through adult age, (ii) transient expression colocalized with vesicular monoamine transporter 2 messenger RNA but with no detectable tryptophan hydroxylase immunoreactivity, and (iii) transient expression in the apparent absence of both vesicular monoamine transporter 2 messenger RNA and tryptophan hydroxylase immunoreactivity. For example, hybridization for serotonin transporter messenger RNA was strong in serotonin cell body-containing areas beginning early in gestation, and remained intense through adulthood. Immunoreactivity for tryptophan hydroxylase, the rate-limiting enzyme in serotonin synthesis, was completely overlapping with the presence of serotonin transporter messenger RNA in raphe nuclei postnatally. Sensory relay systems including the ventrobasal nucleus (somatosensory), lateral and medial geniculate nuclei (visual and auditory, respectively) as well as trigeminal, cochlear and solitary nuclei were representative of the second class of observations. In general, the limbic system expressed serotonin transporter messenger RNA in the third pattern with various limbic structures differing in the timing of expression. Septum, olfactory areas and the developing hippocampus contained serotonin transporter messenger RNA early in the developing brain. Other regions such as cingulate and frontopolar cortex exhibited hybridization peri- and postnatally, respectively. Several hypothalamic nuclei and pituitary transiently expressed serotonin transporter messenger RNA either postnatally or perinatally, respectively. If the observed patterns correlate with functional protein expression, distinct classes of serotonin transporter messenger RNA expression may reflect different functional roles for the serotonin transporter and serotonin, itself. Since the serotonin transporter is a target for a number of addictive substances including cocaine and amphetamine derivatives as well as antidepressants, transient expression of the serotonin transporter might suggest a window of vulnerability of associated cells to fetal drug exposure. Re-uptake, storage and re-release from non-serotonergic neurons might serve as a feedback mechanism from target neurons to serotonergic neurons. Alternatively, the transient expression of serotonin transporter messenger RNA may reflect critical periods important for tight regulation of extracellular serotonin in several brain regions, and may indicate previously unappreciated roles for serotonin as a developmental cue.
Aging↗
Regulation of dopamine transporter mRNA levels in the central nervous system.
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Animals↗
Alpha synuclein in neurodegenerative disorders: murderer or accomplice?
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Amyotrophic Lateral Sclerosis↗
Alpha synuclein is present in Lewy bodies in sporadic Parkinson's disease.
A missense mutation in the human alpha synuclein gene was recently identified in some cases of familial Parkinson's disease (FPD). We have developed an antibody that recognizes the C-terminal 12 amino acids of the human alpha synuclein protein and have demonstrated that alpha synuclein is an abundant component of the Lewy bodies found within the degenerating neurons of patients with Parkinson's disease (PD). The presence of alpha synuclein in Lewy bodies of sporadic PD patients suggests a central role for alpha synuclein in the pathogenesis of PD.
Aged↗
Substance P receptor expression in intestinal epithelium in clostridium difficile toxin A enteritis in rats.
We previously reported that the inflammatory effects of Clostridium difficile toxin A on rat intestine can be significantly inhibited with a specific neurokinin-1 receptor (NK-1R) antagonist. In this study we investigated the localization and expression of NK-1R mRNA and protein in rat intestine by in situ hybridization, Northern blot analysis, and immunohistochemistry, respectively, after exposure to toxin A. Northern blot analysis showed increased mucosal levels of NK-1R mRNA starting 30 min after toxin A administration. In situ hybridization showed that toxin A increased NK-1R mRNA expression in intestinal epithelial cells after 30, 120, and 180 min. In rats pretreated with the NK-1R antagonist CP-96345 the increase in NK-1R mRNA levels after exposure to toxin A was inhibited, indicating that NK-1R upregulation is substance P (SP) dependent. One hour after exposure to toxin A many of the intestinal epithelial cells showed staining for NK-1R compared with controls. Specific 125I-SP binding to purified epithelial cell membranes obtained from ileum exposed to toxin A for 15 min was increased twofold over control and persisted for 4 h. This report provides evidence that NK-1R expression is increased in the intestinal epithelium shortly after exposure to toxin A and may be important in toxin A-induced inflammation.
Animals↗
Dopamine produced by the stomach may act as a paracrine/autocrine hormone in the rat.
Dopamine (DA) has been suggested to be a protective factor in the gastrointestinal tract but neither a source of DA nor its exact targets of action have been identified. In this study, we demonstrate high levels of DA (and DOPA) which persist after chemical sympathectomy in the gastric juice of rats. Immunostaining and in situ hybridization histochemistry reveal the presence of tyrosine hydroxylase (TH), DA transporter and vesicular monamine transporters in the acid-producing parietal cells. Like DA, TH enzyme activity remains after chemical sympathectomy. We also demonstrate active reuptake and storage of DA that indicates a regulated release of this neurohormone from parietal cells. DA D1b receptor mRNA is the most abundant DA receptor subtype in gastric and duodenal epithelium. Therefore, we suggest that selective DA D1b receptor agonists may be useful adjuncts in the treatment of duodenal and gastric ulcers. Gastric epithelia possess the hallmarks of functional DA neuroendocrine cells, suggesting that DA has an important role in self-protective mechanisms of the gastrointestinal tract. These findings should allow elucidation of DA role in normal and disease states in the stomach and duodenum.
Animals↗
The localization of messenger ribonucleic acids for somatostatin receptors 1, 2, and 3 in rat testis.
Somatostatin (SRIF) exerts multiple inhibitory actions throughout the body by binding to specific SRIF receptors (sst). In recent years, five subtypes of SRIF receptors (sst1-5) have been cloned. In this study, 35S-labeled complementary RNA probes were used for in situ hybridization to localize the sst1-5 messenger RNAs (mRNAs) in the rat testis and examine the changes in their distribution during the cycle of the seminiferous epithelium. We found that sst 1-3 mRNAs were visualized in rat testes and were mainly localized within the seminiferous tubules. The signal for sst3 mRNA was also found in interstitial cells. sst4 and 5 mRNAs were not detected in rat testes with the method used in this study. In Sertoli cells, the most intense labeling for sst1 and 3 mRNAs was in stages IV-VII of the cycle of the seminiferous epithelium, which coincided with the lowest labeling intensity for sst2. In germ cells, sst1-3 mRNAs showed similar patterns of distribution. In these cells, sst1-3 mRNA was not observed at the early steps of spermatogenesis. Positive signals for sst1-3 mRNAs were first apparent in the pachytene spermatocytes at stage VII and last until stage XII and in the diplotene spermatocyte at stage XIII. Positive signals for sst1-3 were also detected in round spermatids at stages I-VIII. Labeling of spermatids dramatically decreased at stage IX, when these cells began their elongating changes. The presence of three sst in testis suggests that SRIF may play an essential role in testicular function.
Animals↗
Cell specific expression of the sst2A and sst5 somatostatin receptors in the rat anterior pituitary.
Somatostatin (SRIF), originally described as a hypothalamic hormone that inhibits the release of growth hormone was subsequently shown to inhibit the secretion of multiple pituitary hormones. Five genes encoding six different SRIF receptors (sst1, 2A, 2B, 3, 4 and 5) have been cloned and mRNAs for all five are expressed in the anterior pituitary. We used double immunostaining to determine which cells in the anterior pituitary bear sst2A and sst5 receptors. Our results show that these two receptors are widely distributed in the pituitary gland and are both present in a large percentage of GH cells. In addition, sst5 occurs in a small population of corticotrophs and a large percentage of lactotrophs whereas sst2A is found in only a few lactotrophs but a large number of corticotrophs. The sst2A receptor is also expressed in about a third of the gonadotrophs and thyrotrophs. Interestingly, sst2A and sst5 receptors colocalize in a small percentage of cells, most likely somatotrophs demonstrating that the same cells can contain multiple sst receptor subtypes. These results indicate that sst subtype specific analogs are likely to be useful for the selective regulation of individual pituitary hormones.
Animals↗
Gastrin-producing endocrine cells: a novel source of histamine in the rat stomach.
Gastrin and histamine both potently stimulate secretion of acid into the gastric lumen. How these agents interact and how their release is controlled is poorly understood. Therefore, we decided to look for histamine in the antral portion of the rat stomach where the gastrin-producing G cells are located. We used immunocytochemical methods to visualize histamine, histidine decarboxylase (HDC, the enzyme that converts histidine to histamine), and the type 1 vesicular monoamine transporter (VMAT1, the protein responsible for moving histamine into vesicles for storage and release). We were surprised to find that histamine, HDC, and VMAT1 were all present in G cells. Our results suggest that G cells synthesize and secrete gastrin and histamine. Whether histamine acts in concert with gastrin to stimulate acid secretion, or functions as an autocrine inhibitor of gastrin release remains to be seen.
Animals↗