Search PubMed⌕ Search

Biomedical subjects

F L Margolis

Publications and source records attributed to F L Margolis.

At least 73 records · Page 4Linked to original sources
PubMed1990

Expression of catfish amino acid taste receptors in Xenopus oocytes.

We demonstrate that poly (A+)RNA isolated from catfish barbels directs the expression of functional amino acid taste receptors in the Xenopus oocyte. The activity of these receptors is monitored in ovo by the two electrode voltage clamp technique. Specific conductance changes recorded in response to amino acid stimulation are analogous to those recorded electrophysiologically from intact catfish barbels. These responses exhibit specificity, reproducibility, rapid onset and termination, and desensitization to repetitive stimulation. A functional assay system that encompasses the full complement of transduction events from the ligand-receptor interaction to subsequent conductance changes is necessary to identify molecular components responsible for these events. Our results demonstrate that the Xenopus oocyte can be used to characterize and identify clones coding for amino acid taste receptors analogous to its use in studying receptor molecules for other neuroactive compounds.

Amino Acids↗
PubMed1990

Transneuronal regulation of neuronal specific gene expression in the mouse olfactory bulb.

Peripheral afferent denervation (deafferentation) of the rodent main olfactory bulb produces a marked decrease in tyrosine hydroxylase (TH) activity and immunoreactivity in a population of juxtaglomerular dopaminergic neurons. Preservation of activity and immunostaining for aromatic L-amino acid decarboxylase implies that these cells do not die, but change phenotype. We now report that the steady-state level of TH mRNA markedly decreases in the adult mouse olfactory bulb in response to deafferentation. This reduction is permanent following intranasal irrigation with 0.17 M zinc sulphate (ZnSO4) but reversible following deafferentation produced by intranasal irrigation with 0.7% Triton X-100. The initial declines in TH activity, protein and mRNA of dopaminergic juxtaglomerular neurons observed after Triton X-100 treatment are all reversible as the steady-state level of TH mRNA gradually returns to control levels. Steady-state levels of mRNA for olfactory marker protein (OMP), a protein found in high concentrations in olfactory receptor neurons and their processes which innervate the olfactory bulb, were also monitored following deafferentation. Following treatment with either ZnSO4 or Triton X-100, the pattern of changes in steady-state levels of OMP mRNA was similar to that observed for TH. The steady-state level of PEP19 mRNA, a peptide previously localized to granule cells in the olfactory bulb, was not altered by deafferentation. These data indicate selective and parallel regulation of TH and OMP message and protein levels following deafferentation.

Afferent Pathways↗
PubMed1990

Cellular localization of carnosine-like and anserine-like immunoreactivities in rodent and avian central nervous system.

Aminoacylhistidine dipeptides are present in the nervous tissue of many species. The olfactory mucosa and bulb of many vertebrates are rich in carnosine (beta-alanyl-L-histidine). Two related dipeptides homocarnosine (gamma-aminobutyryl-L-histidine) and anserine (beta-alanyl-N-methyl-L-histidine) are present in the CNS of mammals and birds, respectively. This manuscript describes the production, characterization and use in immunolocalization studies of antisera directed against carnosine and anserine. The anserine antiserum is highly specific for anserine while the carnosine antiserum cross-reacts with all three dipeptides. The differential specificity of the antisera, coupled with chemical characterization of the dipeptide composition of various brain regions, has permitted assignment of the cellular localization of the various dipeptides. Immunocytochemical localization of anserine has not been previously reported. Carnosine immunoreactivity in the olfactory system is restricted to the mature neurons in the olfactory mucosa, their axons and synaptic terminations in the glomerular layer of the olfactory bulb. Similar reactivity is seen in the accessory olfactory system. Astrocytes and cerebellar Bergmann glia seem to account for all the non-olfactory carnosine-like immunoreactive staining in the rodent brain. In contrast, in the avian CNS where anserine is chemically abundant, anserine-like immunoreactivity is widespread and apparently exclusively associated with glial cells. Thus, the olfactory receptor neurons appear to be the only neuronal population that expresses carnosine. Elsewhere in the CNS the aminoacylhistidine dipeptides are associated with various populations of glia.

Animals↗
PubMed1990

Use of reverse transcriptase polymerase chain reaction to monitor expression of intronless genes.

Our data demonstrate the use of the reverse transcriptase polymerase chain reaction (RT-PCR) technique to study mRNA expression of genes that are devoid of introns. We have developed conditions that eliminate the false positives that can result from any preexisting DNA and that could confuse the interpretation of results. This modification (DNase pretreatment under specified conditions) ensures that the product resulting from RT-PCR is due to amplification of cDNA that has been synthesized during the reverse transcriptase reaction. Our results illustrate and emphasize the importance of including both a DNase pretreatment and a minus RT control. Using this modified procedure, our data illustrate clearly the ability of this protocol to demonstrate the presence of very low levels of olfactory marker protein (OMP) mRNA in three non-olfactory rat brain regions (cerebellum, thalamus/hypothalamus and cerebral hemispheres) where OMP mRNA was previously unknown. These data confirm a prior report of the ectopic expression of OMP immunoreactivity in these locations and indicate for the first time the "illegitimate" expression of extremely low levels of OMP mRNA in a non-neural tissue. Finally, this modification of the RT-PCR procedure will now permit the study of expression of specific, rare, mRNA molecules in the absence of any prior knowledge of the structure of their genes of origin.

Animals↗
PubMed1989

Biochemical and immunocytochemical characterization of olfactory marker protein in the rodent central nervous system.

Olfactory marker protein (OMP), previously thought to be expressed only by olfactory receptor neurons and their processes, was localized anatomically with immunocytochemical techniques to a number of brain regions in three rodent species, the mouse, rat, and hamster. In addition, the amount of antigen was quantified by radioimmunoassay (RIA) and characterized by an immunoblot procedure. In all three species the antigen could be detected immunocytochemically in the preoptic region and hypothalamus. The rat did not exhibit immunostaining in any other brain region. However, in the mouse neuronal labelling was observed throughout the neural axis, including cellular labelling in the bed nucleus of the anterior commissure, the median preoptic nucleus, the bed nucleus of the stria terminalis, the periventricular region, the anterior parvicellular subnucleus of the paraventricular nucleus, around the dorsomedial hypothalamic nucleus (pars compacta), the subincertal region, the arcuate nucleus, the anterior cortical nucleus of the amygdala, the suprageniculate nucleus, the lateral lemniscal nuclei, the lateraldorsal and lateralventral central gray, the posterior aspects of the commissural and marginal nuclei of the inferior colliculus, the paragenule nucleus, the A-5 region, the area postrema, the ventromedial nucleus of the solitary tract, area X, the spinal trigeminal nucleus (pars zonale), and superficial laminae of the spinal cord. The hamster displayed a different pattern of labelling including cells in the periventricular gray, the pontine reticular tegmental nucleus, the A-5 region, the medial vestibular complex, the prepositus hypoglossal nucleus, the parvicellular reticular nucleus, the lateral paragigantocellular nucleus, the raphe obscuras, the lateral reticular nucleus, and the lateral nucleus of the cerebellum. Immunostaining was seen in fibers within the red nucleus and within mossy fibers of the cerebellum. OMP levels could only be quantified by radioimmunoassay in the olfactory bulb of the three species and in the hamster cerebellum where they were 1/1,000 of those determined in the olfactory bulb. The authenticity of OMP measured in the RIA and detected immunocytochemically was verified by a double-antibody immunoisolation/immunodetection procedure, which confirmed that the antigen being visualized had the molecular properties expected for OMP. In summary, these experiments demonstrate that authentic OMP exists in small groups of neurons in many areas of the central nervous system.

Animals↗
PubMed1989

The expression of the growth associated protein B50/GAP43 in the olfactory system of neonatal and adult rats.

B50/GAP43 is a neuron-specific phosphoprotein whose expression is associated with neural development and synaptic plasticity. Its postnatal ontogeny was investigated in the primary olfactory pathway of the rat using immunohistochemical methods. The unique ability of the olfactory neuroepithelium to generate new neurons from a population of precursor cells present in the basal cell layer of this tissue makes it a valuable model in the study of neural development. In newborn rats B50/GAP43 is present throughout the entire population of olfactory receptor neurons. These cells are stained throughout, from the ciliated dendritic knob to their axon terminals in the bulb. This appears to be the first example of unambiguous B50/GAP43 expression in dendritic processes. With increasing age the distribution of this protein becomes progressively restricted to a subpopulation of olfactory neurons. Comparison of the expression of B50/GAP43 and the olfactory marker protein (OMP), a polypeptide only present in mature olfactory neurons, revealed that during postnatal development of the olfactory system these 2 proteins are expressed in a nearly reciprocal fashion. In adult animals (3.5 months-6 months of age), B50/GAP43-positive cells are exclusively present adjacent to the basal cell layer of the neuroepithelium. Basal cells appear to be unstained. The region of the epithelium containing the B50/GAP43-positive cells is virtually devoid of OMP-positive neurons. A significant fraction of these B50/GAP43-containing cells bear dendritic and neuritic processes. However, these cells do not express olfactory cilia. It is probable that the olfactory neurons expressing the growth-associated B50/GAP43 protein may correspond to a particular subset of olfactory neurons at an intermediate state of maturation.

Animals↗
PubMed1988

Differential afferent regulation of dopaminergic and GABAergic neurons in the mouse main olfactory bulb.

Peripheral deafferentation of the mouse main olfactory bulb following intranasal irrigation with ZnSO4 produced profound decreases in tyrosine hydroxylase activity and immunoreactivity in intrinsic dopamine neurons normally localized to the juxtaglomerular region of the bulb. In contrast, only modest alterations in GABA-immunoreactivity and glutamic acid decarboxylase (GAD) activity were observed in the same region. In fact, when GAD activity was expressed per mg tissue, a reflection of enzyme concentration, no changes in activity were observed 3 weeks postlesion and only relatively modest decreases in specific activity were found following long survival times (4 months). When the data were expressed per bulb, as an indication of the total amount of enzyme present, GAD activity and bulb weight exhibited similar reductions. Olfactory marker protein levels, determined as an indication of the completeness of the deafferentation, were at or below the limits of detection in all lesioned mice. These data indicate that afferent regulation of transmitter expression in the juxtaglomerular neurons of the olfactory system is phenotype specific.

Afferent Pathways↗
PubMed1987

Molecular cloning and sequencing of a cDNA for olfactory marker protein.

cDNA clones corresponding to mRNA for rat olfactory marker protein (OMP) were isolated from a cDNA library. The library was constructed from olfactory mucosa poly(A)+ RNA enriched for OMP mRNA and cloned into a pBR322-derived plasmid, pMG5. OMP cDNA clones were detected by using a 17-base oligonucleotide probe that contained all 16 possible sequences coding for a known partial amino acid sequence of rat OMP. The identity of these clones was confirmed by hybrid-selected translation and nucleotide sequencing. The sequence of one clone was determined and contained the complete OMP coding region of 486 nucleotides followed by 1630 nucleotides of the 3' untranslated region. The 3' untranslated region included the polyadenylylation signal 16 nucleotides upstream of the poly(A) tail. No other ATG-initiated open reading frame larger than 20 codons was present in register. RNA blot analysis of olfactory mucosa poly(A)+ RNA using this clone as a probe indicated that the level of OMP mRNA, but not its size, declined significantly within a few days following olfactory bulbectomy. OMP mRNA was not detected in 14 nonolfactory rat tissues. Surprisingly, a small amount of OMP mRNA was observed in olfactory bulb. The presence of OMP mRNA in olfactory bulb was confirmed by in vitro translation and immunoprecipitation. These results suggest either that a previously undescribed population of neurons in the olfactory bulb synthesize OMP or that OMP mRNA is transported to the bulb by axonal transport.

Amino Acid Sequence↗
PubMed1987

Monoclonal antibodies to mammalian carnosine synthetase.

A set of mouse monoclonal antibodies has been generated against rabbit muscle carnosine synthetase. The immunoreactivity of these antibodies has been characterized using an immunoassay that permits the separation and direct measurement of the synthetase activity on a second antibody bead complex. Four IgG monoclonal antibodies bind the carnosine synthetase activity from muscle of all mammals tested (mouse, rat, rabbit, cow, dog, and monkey) but not that from chicken muscle. This indicates the mammalian enzymes share epitopes that are absent from the avian enzyme. In addition, relative tissue levels of synthetase activity can be quantified with this immunoassay. Thus, high levels of carnosine synthetase activity are immunoprecipitated from the olfactory tissues of both rat and rabbit. Synthetase activity is generally lower in other tissues (muscle, brain, heart, liver, and gut). Nevertheless, the cross-reactivity of the synthetase from several tissues (olfactory mucosa, muscle, brain, gut, heart, and liver) of a single species indicates the enzyme protein contains similar epitopes in these tissues. Immunoaffinity purification of this low-abundance, unstable enzyme should now be possible for subsequent studies of structure and regulation.

Animals↗
PubMed1986

Amino acid sequence of a unique neuronal protein: rat olfactory marker protein.

A neuron-specific protein, the olfactory marker protein (OMP), has been sequenced. This was achieved by gas phase sequencing of peptides isolated by HPLC following chemical and enzymatic cleavages of the intact rat protein. The amino terminus of the intact protein is acetylated. This has been determined by fast atom bombardment mass spectrometry of the amino terminal dodecapeptide isolated following BrCN cleavage of the OMP. Comparison of the sequence reported here with over 3000 protein sequences stored in the NBRF protein data base indicates no significant homology with any previously sequenced protein. This, coupled with the occurrence of OMP only in mature olfactory neurons of many vertebrate species, suggests that this protein has a olfactory neurons of many vertebrate species, suggests that this protein has a unique function in the metabolism of these neurons.

Acetylation↗
PubMed1985

Olfactory neuron-specific protein is translated from a large poly(A)+ mRNA.

Poly(A)+ mRNA was isolated from rat olfactory mucosa and translated in a rabbit reticulocyte cell-free protein synthesizing system. Olfactory marker protein (OMP) of Mr 18,500 was faithfully produced by this system upon addition of mucosal mRNA. The protein was identified by radioimmunoprecipitation with specific anti-OMP serum and by competitive displacement of the radioactive product with authentic OMP. In addition, the immunoprecipitated product comigrated with OMP on NaDodSO4/polyacrylamide gels and on HPLC. In vitro synthesized OMP represented 0.5% of the total translational products. Total olfactory mucosal poly(A)+ mRNA is approximately 1.5-21 kilobases in size, as determined by denaturing agarose gels. Translational assays of gel-fractionated poly(A)+ mRNA demonstrated that OMP mRNA occurs in the 2.5- to 3.4-kilobase range. An mRNA of this size could code for a protein significantly larger than OMP. Since the in vitro synthesized OMP is indistinguishable in size from OMP isolated from tissue, our data indicate that OMP is synthesized directly without the intermediate formation of a larger polypeptide precursor. Thus, OMP mRNA contains untranslated regions that are four to five times larger than the coding region.

Animals↗
PubMed1985

Carnosine synthesis in olfactory tissue during ontogeny: effect of exogenous beta-alanine.

Carnosine has now been demonstrated by chemical analysis to be present in rat olfactory mucosa on day 16 of gestation. The tissue content of this dipeptide then increases progressively during fetal and postnatal life. Radioactive carnosine can be isolated from cultured embryonic rat olfactory mucosa incubated with [14C]beta-alanine as early as 13-14 days of gestation. The amount of incorporation also increases progressively with the initial age of the explant and with time in culture indicating in vitro maturation of the carnosine synthesis capability of olfactory tissue. To test whether the level of beta-alanine was limiting the synthesis of carnosine, we evaluated the effect of elevated beta-alanine levels on tissue carnosine content. Exogenous beta-alanine caused an increase in the tissue content of carnosine at several ages in vivo and in vitro. In adult animals this increase was observed in olfactory bulb, olfactory mucosa, and skeletal muscle. However, there was no associated alteration in carnosine synthetase activity. In addition, the different half-lives of carnosine in olfactory tissue and muscle seemed unaltered, arguing against any effect on degradative enzymes. Thus, tissue carnosine levels are regulated, at least in part, by substrate availability. The early appearance of carnosine synthetic capacity during prenatal development indicates that this enzyme activity should be a valuable aid in studying early events in olfactory neuron maturation.

Age Factors↗
PubMed1984

Enhanced carnosine (beta-alanyl-L-histidine) breakdown and histamine metabolism following treatment with compound 48/80.

We have previously suggested that carnosine may serve as a reservoir for histidine to be used as a source of histamine in the trauma response of rats. In this study we report the effect of stimulation of histamine-forming capacity by compound 48/80 on muscle carnosinase (C'ASE) and histidine decarboxylase (HDC) activities as well as on muscle carnosine and histamine concentrations. Male rats (180 g) were injected i.p. with 5 mg/kg bw of compound 48/80 and C'ASE and HDC activities as well as carnosine, histidine and histamine concentrations were monitored over a 72 h period post-injection. This treatment resulted in an 120% increase in muscle HDC activity and an 110% increase in muscle histamine concentration at 15 min post-injection, followed by an 80% increase in muscle C'ASE activity at 1 h and a 100% reduction in muscle carnosine concentration at 24 h post-injection when compared to control animals injected with 0.9% saline. Histidine concentration was not affected by treatment. The time frame of response, a rapid increase in muscle HDC activity and in muscle histamine concentration followed by an increase in muscle C'ASE activity and a later decrease in muscle carnosine concentration, suggests that carnosine is hydrolysed to liberate histidine and that carnosine, as a reservoir for histidine, is mobilized to maintain a constant muscle concentration of histidine for histamine synthesis.

Animals↗
PubMed1984

Substance P and catecholaminergic expression in neurons of the hamster main olfactory bulb.

A coordinated series of immunohistochemical and biochemical analyses have been conducted in the hamster to examine the dependence of substance P and tyrosine hydroxylase (TH) expression by second-order olfactory neurons, and the level of dopamine in the main olfactory bulb (MOB), on the integrity of carnosine- and olfactory marker protein (OMP)-containing primary afferent neurons. Substance P-like immunoreactivity (SPLI) is localized in external tufted cells and centrifugal afferents of the MOB; TH immunoreactivity has a wider distribution, in external tufted, middle tufted, periglomerular, and deep short-axon cells as well as in centrifugal afferents. To characterize the SPLI, this material was isolated by guanidine-HCl extraction and passage over a C18 SEP-PAK. The SPLI coelutes on HPLC with authentic substance P and, following oxidation, coelutes with substance P sulfoxide. It is sensitive to alpha-chymotrypsin and is resistant to trypsin. Thus, the SPLI in the MOB behaves as authentic substance P. Intranasal irrigation with 0.17 M ZnSO4 results in peripheral deafferentiation of the MOB for up to 8 months as evidenced by a persistent loss of OMP immunoreactivity and shrinkage of the olfactory nerve layer and glomeruli. By these criteria, the vomeronasal inputs to the accessory olfactory bulb are not destroyed and the spared vomeronasal receptor neurons do not innervate the vacated peripheral projection field in the MOB. The loss of peripheral inputs to the MOB is accompanied by marked and parallel reductions in the incidences of SPLI- and TH-positive second-order neurons despite an increase in the density of neuronal somata in the glomerular layer. Biochemical quantifications following peripheral deafferentation also demonstrate significant decreases of both substance P and dopamine, together with the expected decrease of carnosine. In contrast, the SPLI and the TH and serotoninlike immunoreactivities in centrifugal afferents as well as the TH immunoreactivity in deep interneurons do not appear to be reduced, and the MOB content of norepinephrine in centrifugal afferents is unaffected. These results collectively indicate that the loss of inputs from the primary olfactory receptor neurons can reduce the levels of at least two different, putatively neuroactive compounds (substance P and dopamine) in at least three classes of second-order neurons (external tufted, middle tufted, and periglomerular cells). The control of central neuron phenotype by the peripheral olfactory neurons thus appears to be a phenomenon of broad influence. It may play a role in processing chemosensory information as well as offering a system in which to study neuronal plasticit

Animals↗
PubMed1984

Inherited differences in mouse kidney carnosinase activity.

Carnosinase is a peptidase which cleaves B-alanyl-L-histidine (carnosine) and closely related dipeptides. Its activity in kidney cytosol of various mouse strains varies more than 50-fold. The highest activity occurs in random-bred CD-1 and inbred NZB/BINJ mice, while it is barely detectable in BALB/cJ, C57BL/6J, and AU/SsJ among others. Carnosinase is immunologically and enzymologically identical in all high-activity strains. This is the first report of quantitative interstrain differences in carnosinase activity. No other peptidase activity has been reported which exhibits the same strain distribution shown here. In matings and backcrosses between the NZB/BINJ and the BALB/cJ strains, the levels of kidney carnosinase activity in the progeny behave as a classical Mendelian trait.

Animals↗
PubMed1984

Perireceptor and receptor events in vertebrate olfaction.

In this article we have summarized the basic information which identifies several key issues in the study of perireceptor and receptor events in vertebrate olfaction. We have emphasized the biophysical and biochemical data which have established a pivotal role for the olfactory mucus in the access of odorants to receptor sites as well as their clearance from the micro-environment. In addition, based on initial reports in the literature, we have postulated that the uptake of odorants by cells in the olfactory epithelium and their subsequent enzymatic degradation is an important mechanism in odorant removal. Hence, the pre- and post-interactive events in vertebrate olfaction play a key role in molecular recognition, sensory transduction and receptor desensitization. Study of the primary events in vertebrate olfaction is an increasingly active area of research in neurobiology. Application of contemporary techniques in cell and molecular biology as well as biochemistry and cellular biophysics is yielding new insights into the process and into establishing new hypotheses to be tested.

Animals↗
PubMed1984

Olfactory bulb dopamine neurons survive deafferentation-induced loss of tyrosine hydroxylase.

Peripheral deafferentation of the rodent olfactory bulb results in loss of dopamine content, tyrosine hydroxylase activity and immunocytochemical staining for tyrosine hydroxylase in juxtaglomerular dopamine neurons. Reinnervation of the bulb by afferent neurons results in the return of all parameters to control levels suggesting that the dopamine neurons did not degenerate but that the expression of tyrosine hydroxylase enzyme was transneuronally regulated in a static population of juxtaglomerular cells. To evaluate this possibility, we determined the activity and immunocytochemical localization of the second enzyme in the dopamine biosynthetic pathway, DOPA decarboxylase. At a time when tyrosine hydroxylase activity was reduced to 25% of control values, DOPA decarboxylase activity in the lesioned bulb was maintained at about 65% of that in the unlesioned bulb. Immunocytochemical staining with antibodies to both enzymes, performed sequentially in the same sections, demonstrated that in the unlesioned bulb tyrosine hydroxylase and DOPA decarboxylase are co-localized in the same population of juxtaglomerular neurons. Similar results were obtained in adjacent sections each stained with one of the two antibodies. In contrast, in the deafferented bulb, about three times as many neurons were stained with DOPA decarboxylase as with tyrosine hydroxylase antibodies. The DOPA decarboxylase activity measurements and immunocytochemistry argue for the continued presence, in the lesioned olfactory bulb, of a population of tyrosine hydroxylase deficient dopamine neurons. The data suggest that olfactory receptor cell innervation transneuronally regulates the expression of tyrosine hydroxylase by mechanisms separate from those controlling the levels of DOPA decarboxylase.

Afferent Pathways↗