Biomedical subjects

M D Bates

Publications and source records attributed to M D Bates.

At least 19 recordsLinked to original sources

PubMed2002

Aberrant cytokine production by peripheral blood mononuclear cells in recurrent pregnancy loss?

BACKGROUND: Successful pregnancy may depend on a Th2-type cytokine response, whilst, conversely, a poor pregnancy outcome may be associated with an increase in Th1 cytokines and a concomitant decrease in Th2 cytokines. This prospective study was designed to elucidate whether a failure of the cytokine shift pre-dated miscarriage and was therefore likely to be an aetiological factor in recurrent pregnancy loss (RPL). METHODS: Cytokine production by stimulated peripheral blood mononuclear cells from 46 pregnant women who had previously suffered idiopathic RPL during early pregnancy was compared with 25 gestationally age-matched pregnant controls and 11 non-pregnant women. RESULTS: Production of IFN-gamma was lower in pregnant than in non-pregnant women and even lower in RPL pregnant women (P = 0.0191). IL-10 was increased in pregnant women compared with non-pregnant controls, and further increased in RPL patients (P = 0.026). IL-4 was also increased in women with RPL (P = 0.0001). No differences in IFN-gamma, IL-10 or IL-4 secretion were observed in RPL patients who subsequently miscarried compared with those who successfully completed the pregnancy. RPL women with a successful reproductive outcome had similar concentrations of TNF-alpha to pregnant women, RPL women who subsequently miscarried had significantly lower levels than either pregnant women (P = 0.02) or non-pregnant controls (P = 0.0004). CONCLUSIONS: Contrary to our hypothesis, the cytokine shift, which appears to characterize normal pregnancy, was accentuated rather than diminished in RPL pregnant women.

Abortion, Habitual↗

PubMed2001

Two CCAAT boxes in a novel inverted repeat motif are required for Hlx homeobox gene expression.

Hlx is a homeobox transcription factor gene required for normal intestinal and hepatic growth in development. We previously found high sequence identity and 17 conserved consensus cis-regulatory/transcription factor binding elements in the mouse and human Hlx 5' regions. A 594 bp sequence in the Hlx 5' region possessing the same activity in driving luciferase expression as larger Hlx 5' sequences had three segments each necessary but not sufficient for luciferase expression in NIH 3T3 cells (which express Hlx). Nine of the conserved putative regulatory elements are positioned within these segments, including two CCAAT boxes on opposite strands within a conserved 44 bp inverted repeat sequence. To test the hypothesis that these elements are required for promoter activity, we compared the reporter expression activity of segments containing mutations of these elements with activity of the parent Hlx promoter sequence. We found that mutation of either CCAAT box or a conserved AP-2 site resulted in a significant decrease in promoter activity. Restoration of the inverted repeat with complementary mutations of both CCAAT boxes did not restore activity. Further, mutation of other portions of the inverted repeat did not affect promoter activity. Mutation of other elements had no effect on promoter activity.

Animals↗

PubMed2001

Peritoneal fluid concentrations of interleukin-4 in relation to the presence of endometriosis, its stage and the phase of the menstrual cycle.

BACKGROUND: Interleukin-4 (IL-4) is a cytokine with both stimulatory and inhibitory effects on the inflammatory system such as macrophage inhibition and T-cell activation. It is known to regulate several monocyte functions, including inhibition of the synthesis of cytokines such as IL-1, IL-6 and TNF-alpha as well as potentiating IL-8. METHOD: In an attempt to clarify the association between IL-4 and endometriosis, we measured the concentration of IL-4 in the peritoneal fluid of 52 women; 24 with endometriosis and 28 with no endometriosis, controlling for the phase of the cycle and the stage of disease. RESULTS: There was no difference in the concentrations of IL-4 between women with (n=28) and without endometriosis (n=24). No difference was found between the IL-4 concentrations in women with different stages of endometriosis. Levels of IL-4 did not show a difference according to the phase of the cycle in either group. CONCLUSION: Our results indicate no association between peritoneal fluid levels of IL-4 and endometriosis and hence suggest that IL-4 is not involved in the pathogenesis of endometriosis.

Ascitic Fluid↗

PubMed2000

Structural and functional characterization of the mouse Hlx homeobox gene.

Hlx is a mesenchymally expressed homeobox transcription factor gene that is essential for normal intestinal and hepatic development in the mouse. Here we report further characterization of the mouse Hlx gene, including an additional 3.7 kb of 5' sequence as well as the sequence of the three introns. Comparison of the sequence of the mouse Hlx gene 5' to the coding region with that of the human gene revealed multiple regions of high conservation. Neither the mouse nor the human gene contained a TATA box, and ribonuclease protection studies defined heterogeneous transcription start sites for the mouse gene. A number of consensus transcription factor binding sites were conserved between the mouse and human Hlx genes both within and outside of the highly conserved regions. Reporter constructs containing 4.2 or 1.4 kb of mouse 5' sequence showed active expression in cell lines that express Hlx. Further characterization of the mouse Hlx gene will provide insight into the developmental regulation of the mouse digestive system.

3T3 Cells↗

PubMed2000

Factors affecting metamotivational reversals during motor task performance.

Reversal theory proposes that the individual's psychological state constantly switches between metamotivational state pairs (such as Apter's 1982 telic-paratelic pair). Three factors are thought to affect reversals: frustration, contingent event, and satiation. Only a few studies have directly investigated these factors in sports contexts, and evidence is needed to assess support for these factors. In a laboratory setting, 24 participants performed a telic and a paratelic version of a dart-throwing task for 10 min. Participants were free to change from one task version to another as they wished, and reasons for any task changes were solicited. Task changes, indicative of reversals, were observed in 11 participants, and these were reported as due to satiation or frustration but not to contingent events. These findings may inform the structure of sessions on skill development but require confirmation in actual sports contexts.

Achievement↗

PubMed1999

Leukocytes in semen from men with spinal cord injuries.

OBJECTIVE: To assess the leukocyte populations in semen samples from men with spinal cord injuries (SCIs) and their relation to sperm motility. DESIGN: Cross-sectional study. SETTING: A joint spinal cord injury and fertility clinic at an academic tertiary referral center for fertility treatment and a university-based department of immunology. PATIENT(S): Nine men with chronic SCIs and seven healthy sperm donors as controls. INTERVENTION(S): Semen samples were obtained by electroejaculation from men with SCIs and by masturbation from donors. MAIN OUTCOME MEASURE(S): Leukocyte populations determined by immunohistochemical techniques, bacteriologic assessment of urine, and sperm density and motility. RESULT(S): The most cellular specimens were antegrade specimens obtained from men with SCIs and coexisting urinary tract infections. The highest proportion of leukocytes occurred in retrograde samples from men with SCIs and urinary tract infections. The most predominant leukocytes in all specimens were granulocytes. Infection increased the number of T cells and the degree of cell activation. There was no significant correlation between leukocyte populations and total motile sperm counts. CONCLUSION(S): Increased numbers of leukocytes in semen samples from men with SCIs are the result of urinary tract infections. The reduced sperm motility seen in men with SCIs does not correlate with the numbers of leukocytes; therefore, other factors also contribute to the semen abnormalities in these patients.

Adult↗

PubMed1998

Biliary atresia: pathogenesis and treatment.

Biliary atresia is a disorder of infants in which there is obliteration or discontinuity of the extrahepatic biliary system, resulting in obstruction of bile flow. Untreated, the resulting cholestasis leads to progressive conjugated hyperbilirubinemia, cirrhosis, and hepatic failure. Biliary atresia has an incidence of approximately one in 10,000 live births worldwide. Evidence to date supports a number of pathogenic mechanisms for the development of biliary atresia. An infectious cause, such as by a virus, would seem most pausible in many cases. The clinical observation that biliary atresia is rarely encountered in premature infants would support an agent acting late in gestation. However, no infectious or toxic agent has been conclusively implicated in biliary atresia. Genetic mechanisms likely play important roles, even regarding susceptibility to other specific causes, but no gene whose altered function would result in obstruction or atresia of the biliary tree has been identified. The variety of clinical presentations support the notion that the proposed mechanisms are not mutually exclusive but may play roles individually or in combination in certain patients. Biliary atresia, when untreated, is fatal within 2 years, with a median survival of 8 months. The natural history of biliary atresia has been favorably altered by the Kasai portoenterostomy. Approximately 25 to 35% of patients who undergo a Kasai portoenterostomy will survive more than 10 years without liver transplantation. One third of the patients drain bile but develop complications of cirrhosis and require liver transplantation before age 10. For the remaining one third of patients, bile flow is inadequate following portoenterostomy and the children develop progressive fibrosis and cirrhosis. The portoenterostomy should be done before there is irreversible sclerosis of the intrahepatic bile ducts. Consequently, a prompt evaluation is indicated for any infant older than 14 days with jaundice to determine if conjugated hyperbilirubinemia is present. If infectious, metabolic, endocrine disorders are unlikely and if the child has findings consistent with biliary atresia, then exploratory laparotomy and intraoperative cholangiogram should be done expeditiously by a surgeon who has experience doing the Kasai portoenteostomy. Biliary atresia represents the most common indication for pediatric liver transplantation, representing more than 50% of cases in most series. Transplantation is indicated when symptoms of end stage liver disease occur, including recurrent cholangitis, progressive jaundice, portal hypertension complications, ascites, decreased synthetic function, and growth/nutritional failure.

Bile Ducts, Intrahepatic↗

PubMed1993

Elevation of cAMP is required for down-regulation, but not agonist-induced desensitization, of endogenous dopamine D1 receptors in opossum kidney cells. Studies in cells that stably express a rat cAMP phosphodiesterase (rPDE3) cDNA.

D1 dopamine receptors stimulate cAMP accumulation in opossum kidney (OK) cells, but this response is attenuated by pretreatment with dopamine. Dopamine pretreatment also causes a reduction in D1 dopamine receptor number. We transfected OK cells with a rat cAMP phosphodiesterase cDNA (rPDE3) in order to determine the contribution of elevations of cAMP to those two phenomena. Wild-type (WT) OK cells were compared to three clones (C, H, and N) which demonstrated stable expression of the rPDE3 phenotype and genotype, rPDE3 RNA expression was confirmed in clones C, H, and N (but not in WT-OK cells) by reverse transcriptase-polymerase chain reaction. A functional rPDE3 phenotype was demonstrated in that dopamine-responsive cAMP accumulation was absent in clones C, H, and N in intact cells, but could be restored by preincubation with cAMP phosphodiesterase inhibitors, or by using washed membranes from those clones. All three clones had increased cAMP phosphodiesterase activity when compared to WT-OK cells (approximately 100% increase), and blunted or absent dopamine (1 microM)-induced protein kinase A activation. After pretreatment with dopamine (1 microM) for 1 h, clones C, H, and N desensitized equally well as WT-OK cells (approximately 40-50% reduction in maximal increase in cAMP). In contrast, down-regulation of D1 dopamine receptors was blunted for clone C (20% receptor loss) and absent for clones H and N, when compared to a 45% loss of receptors for WT-OK cells. These findings suggest that in OK cells pretreated with 1 microM dopamine (i) cAMP accumulation is not necessary for dopamine-induced desensitization, but (ii) is necessary for down-regulation of D1 dopamine receptors, and (iii) that the down-regulation and desensitization processes may be differentially regulated.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1992

Location and molecular cloning of D1 dopamine receptor.

Recently, our laboratory has purified the D1 dopamine receptor 6600 fold to near homogeneity from digitonin solubilized rat striatal membranes using sequential affinity, ion exchange, lectin, and size exclusion chromatographies. The resulting receptor preparations still retained ligand binding activity (-11,000 pmol [3H]SCH 23390 bound per mg/protein) and appeared as a single band at 70-80 kDa on SDS-PAGE. In order to learn more about the sequence and structure of this protein, we recently cloned the gene for a human CNS D1 dopamine receptor. This gene has an open reading frame of 1388 nucleotides and encoded for a protein with a deduced amino acid sequence of 446 residues. When expressed in mammalian cells the cloned D1 receptor had all the ligand binding properties expected for a D1 receptor (SCH 23390 > cis flupenthixol > raclopride and SKF 38393 > apomorphine > dopamine > quinpirole). The cloned D1 receptor was found to stimulate adenylyl cyclase but not phospholipase C. The message for this D1 dopamine receptor was found in caudate, putamen, frontal cortex, and hippocampus, but not in substantia nigra, heart, or kidney. These accomplishments now will allow the pursuit of biochemical studies of the receptor protein as well as investigations into structure/function relationship of the receptor using a molecular biological techniques.

Amino Acid Sequence↗

PubMed1992

The renal dopamine receptors.

Dopamine is an endogenous catecholamine that modulates many functions including behavior, movement, nerve conduction, hormone synthesis and release, blood pressure, and ion fluxes. Dopamine receptors in the brain have been classically divided into D1 and D2 subtypes, based on pharmacological data. However, molecular biology techniques have identified many more dopamine receptor subtypes. Several of the receptors cloned from the brain correspond to the classically described D1 and D2 receptors. Several D1 receptor subtypes have been cloned (D1A, D1B, and D5) and are each coupled to the stimulation of adenylyl cyclase. The D2 receptor has two isoforms, a shorter form, composed of 415 amino acids, is termed the D2short receptor. The long form, called the D2long receptor, is composed of 444 amino acids; both are coupled to the inhibition of adenylyl cyclase. The D3 and D4 receptors are closely related to, but clearly distinct from, the D2 receptor. They have not yet been linked to adenylyl cyclase activity. Outside of the central nervous system, the peripheral dopamine receptors have been classified into the DA1 and DA2 subtypes, on the basis of synaptic localization. The pharmacological properties of DA1 receptors roughly approximate those of D1 and D5 receptors, whereas those of DA2 receptors approximate those of D2 receptors. A renal dopamine receptor with some pharmacological features of the D2 receptor but not linked to adenylyl cyclase has been described in the renal cortex and inner medulla. In the inner medulla, this D2-like receptor, termed DA2k, is linked to stimulation of prostaglandin E2 production, apparently due to stimulation of phospholipase A2. Of the cloned dopamine receptors, only the mRNA of the D3 receptor has been reported in the kidney. The DA1 receptor in the kidney is associated with renal vasodilation and an increase in electrolyte excretion. The DA1-related vasodilation and inhibition of electrolyte transport is mediated by cAMP. The role of renal DA2 receptors remains to be clarified. Although DA1 and DA2 receptors may act in concert to decrease transport in the renal proximal convoluted tubule, the overall function of DA2 receptors may be actually the opposite of those noted for DA1 receptors. Dopamine has been postulated to act as an intrarenal natriuretic hormone. Moreover, an aberrant renal dopaminergic system may play a role in the pathogenesis of some forms of hypertension. A decreased renal production of dopamine and/or a defective transduction of the dopamine signal is/are present in some animal models of experimental hypertension as well as in some forms of human essential hypertension.

Humans↗

PubMed1991

Desensitization of DA1 dopamine receptors coupled to adenylyl cyclase in opossum kidney cells.

Peripheral dopamine receptors are classified as DA1 and DA2 receptors, similar to but distinct from central D1 and D2 receptors. Here we report the characterization of DA1 dopamine receptors in the opossum kidney (OK) cell line, which possesses properties of renal proximal tubule cells. OK cell membranes contain 248 +/- 12 fmol [125I]Sch 23982 binding sites/mg protein, which possess pharmacological properties appropriate for a DA1 receptor. Dopamine stimulates adenylyl cyclase via these receptors 4.3 +/- 0.4-fold (50% effective concentration = 4.0 +/- 0.7 microM). The responsiveness of this signaling system is regulated by agonist exposure. Exposure of these cells to dopamine leads to a rapid and profound desensitization of DA1-receptor-stimulated adenylyl cyclase that appears to be independent of the slower downregulation of DA1 receptors. Treatment of cells with 8-bromoadenosine 3',5'-cyclic monophosphate also desensitizes dopamine-stimulated adenylyl cyclase but in a fashion qualitatively and quantitatively distinct from that induced by agonist exposure. These data suggest that the cellular machinery for both homologous and heterologous desensitization of the DA1-receptor response exists in OK cells. Thus OK cells provide a model system for the study of the peripheral actions of dopamine at DA1 receptors and the regulation of these receptors.

Adenylyl Cyclases↗

PubMed1991

Molecular characterization of G-protein coupled receptors: isolation and cloning of a D1 dopamine receptor.

This article summarizes the recent progress our laboratory has made in understanding the molecular characteristics of the D1 dopamine receptor. The D1 dopamine receptor from rat striatum has been purified to near homogeneity using a combination of several chromatographic steps. Furthermore, the gene for the human D1 dopamine receptor has been cloned, sequenced, and expressed. The cloned receptor has all the pharmacologic and biochemical properties of the classical D1 receptor coupled to adenylyl cyclase which has been previously described in the central nervous system.

Amino Acid Sequence↗

PubMed1991

Regulation of responsiveness at D2 dopamine receptors by receptor desensitization and adenylyl cyclase sensitization.

The regulation of cellular responsiveness to dopamine via the D2 dopamine receptor was investigated in mouse fibroblast Ltk-cells stably expressing the rat D2-short receptor [Nature (Lond.) 336:783-787 (1988)]. Dopamine inhibited forskolin-stimulated cAMP levels in these cells (half-maximal inhibition at 3.9 +/- 1.1 nM), and the inhibition by dopamine was blocked by D2 antagonists and was pertussis toxin sensitive. Treatment of these cells with the D2 agonist quinpirole (1 microM) resulted in desensitization of dopaminergic inhibition of forskolin-stimulated cAMP accumulation, with a approximately 4-fold decrease in the potency of dopamine after 1 hr of treatment. No significant changes in total cellular D2 receptor concentrations were observed, even after prolonged agonist treatment. At longer time points, basal and forskolin-stimulated cellular cAMP levels were increased in treated cells. The effect of D2 agonist treatment on membrane adenylyl cyclase (EC 4.6.1.1) activity was examined. Basal and forskolin- and prostaglandin E1-stimulated adenylyl cyclase activities were increased by quinpirole treatment for 24 hr. This sensitization of adenylyl cyclase was blocked by the presence of a D2 antagonist. Pertussis toxin pretreatment blocked the sensitization of adenylyl cyclase by quinpirole, although pertussis toxin also caused increased adenylyl cyclase activity on its own. Sensitization was not dependent upon dopaminergic inhibition of intracellular cAMP levels, because quinpirole treatment in the presence of membrane-permeable cAMP analogs or 3-isobutyl-1-methylxanthine (an inhibitor of cAMP phosphodiesterase) resulted in greater sensitization of adenylyl cyclase activity than quinpirole treatment alone. These results suggest that, in this model system, responsiveness to dopamine via the D2 receptor is regulated by both desensitization of receptor function and sensitization of the stimulatory adenylyl cyclase pathway.

Adenylyl Cyclases↗

PubMed1990

Molecular cloning and expression of the gene for a human D1 dopamine receptor.

The diverse physiological actions of dopamine are mediated by its interaction with two basic types of G protein-coupled receptor, D1 and D2, which stimulate and inhibit, respectively, the enzyme adenylyl cyclase. Alterations in the number or activity of these receptors may be a contributory factor in diseases such as Parkinson's disease and schizophrenia. Here we describe the isolation and characterization of the gene encoding a human D1 dopamine receptor. The coding region of this gene is intronless, unlike the gene encoding the D2 dopamine receptor. The D1 receptor gene encodes a protein of 446 amino acids having a predicted relative molecular mass of 49,300 and a transmembrane topology similar to that of other G protein-coupled receptors. Transient or stable expression of the cloned gene in host cells established specific ligand binding and functional activity characteristic of a D1 dopamine receptor coupled to stimulation of adenylyl cyclase. Northern blot analysis and in situ hybridization revealed that the messenger RNA for this receptor is most abundant in caudate, nucleus accumbens and olfactory tubercle, with little or no mRNA detectable in substantia nigra, liver, kidney, or heart. Several observations from this work in conjunction with results from other studies are consistent with the idea that other D1 dopamine receptor subtypes may exist.

Amino Acid Sequence↗

PubMed1990

Dopamine receptor subtypes: beyond the D1/D2 classification.

The D1/D2 dopamine receptor classification is widely accepted. However, intense investigative efforts over the last several years using pharmacological, biochemical and behavioral approaches have produced results that are increasingly difficult to reconcile with the existence of only two dopamine receptor subtypes. Recent developments, including cloning of the cDNAs and/or genes for several members of the large family of G-protein-coupled receptors, have revealed that heterogeneity in the pharmacological or biochemical characteristics of individual receptors often indicates the presence of previously unsuspected molecular subtypes. In this article, Marc Caron and colleagues have assembled the main lines of evidence that suggest the presence of several novel subtypes for both D1 and D2 dopamine receptors and predict that molecular cloning will, in the near future, confirm their existence.

Animals↗

PubMed1990

Molecular characterization of dopamine receptors.

The D1 and D2 dopamine receptors have been biochemically characterized using specific probes based on the subtype selective antagonists SCH 23390 and spiperone, respectively. The D2 dopamine receptor was identified from several tissues by photoaffinity labeling and was purified from bovine anterior pituitary to homogeneity using a combination of affinity, lectin and hydroxylapatite chromatography. A complementary DNA (cDNA) encoding a rat brain D2 dopamine receptor has been cloned via low stringency hybridization using a portion of the beta 2-adrenergic receptor gene as a probe. Photoaffinity crosslinking and affinity chromatography have also been used to identify and purify the rat brain D1 dopamine receptor.

Affinity Labels↗

PubMed1990

In vitro effects of primaquine and primaquine metabolites on exoerythrocytic stages of Plasmodium berghei.

The antimalarial activities of primaquine and its metabolites against exoerythrocytic (EE) stages of Plasmodium berghei in vitro were compared with their abilities to spontaneously generate activated oxygen. A quantitative relationship between the number of sporozoites and the number of EE merozoites produced was established. The reduction in the number of merozoites was used as an assay of drug activity. The ED50 of primaquine, 3.7-3.9 x 10(-6) M, was the concentration of drug that reduced the number of merozoites to 50% of controls. Several of the primaquine metabolites were much more potent than primaquine, with ED50s as low as 2 x 10(-7) M. Metabolites containing the 4-amino-1-methylbutyl side chain were most effective in vitro. Superoxide generation was measured for the various metabolites. In general, superoxide generation did not correlate with antimalarial activity. However, for the 3 metabolites with 4-amino-1-methylbutyl side chains, there was a correlation between superoxide generation and antimalarial activity.

Animals↗

PubMed1988

Protective immunity to malaria: studies with cloned lines of Plasmodium chabaudi chabaudi in CBA/Ca mice. III. Protective and suppressive responses induced by immunization with purified antigens.

The protective effect of affinity purified antigen has been investigated in an experimental model for malaria which shows a well marked recrudescence of parasitaemia, a feature of the disease in man. A monoclonal antibody (MoAb) recognizing an epitope common to two genetically distinct cloned lines of Plasmodium chabaudi (AS and CB), was used to purify a Mr250,000 polymorphic schizont antigen (PSA) from these parasites. The purified preparations were then examined for the presence of specific and cross-reactive epitopes by immunoprecipitation with a panel of MoAb raised against P. chabaudi AS. When tested previously on smears of parasitized blood by immunofluorescence, or against lysates of parasitized erythrocytes by immunoprecipitation, most of these MoAb had been found to be AS specific. When either AS or CB affinity purified Mr250,000 PSA was used as the target, these same MoAb immunoprecipitated both antigens, and in some cases, a number of associated polypeptides (AP) which copurify with the Mr250,000 PSA. Subsequently, mice were immunized with either the purified AS or CB antigens in Freund's complete adjuvant (FCA). Prechallenge sera were compared by indirect immunofluorescence and immunoprecipitation. Sera from mice immunized with AS antigen reacted strongly with AS and cross-reacted with CB parasite preparations. Pre-challenge serum from CB antigen immunized mice reacted well with CB, but only faintly with AS preparations. In mice immunized with the AS antigen and then challenged with either AS or CB parasites, the initial parasitaemias were delayed in appearance and the height of the peak parasitaemia reduced, an effect which was most pronounced after challenge with homologous parasites. Only homologous challenge of the mice immunized with CB antigen produced statistically significant modification of the initial parasitaemia. In the immunized mice challenged with homologous parasites, the delayed appearance and slightly reduced peak of the primary parasitaemia was associated with delayed resolution of the patent parasitaemia and significant enhancement of the recrudescence.

Animals↗