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Biomedical subjects

G R Brown

Publications and source records attributed to G R Brown.

At least 37 records · Page 2Linked to original sources
PubMed1998

Short-term regulation of insulin gene transcription by glucose.

Whereas short-term regulation of insulin biosynthesis at the level of translation is well accepted, glucose-dependent transcriptional control is still believed to be a long-term effect occurring after more than 2 hr of glucose stimulation. Because pancreatic beta cells are exposed to elevated glucose levels for minutes rather than hours after food uptake, we hypothesized the existence of a short-term transcriptional control. By studying the dynamics of newly synthesized (prepro)insulin RNA and by employing on-line monitoring of gene expression in single, insulin-producing cells, we were able to provide convincing evidence that insulin gene transcription indeed is affected by glucose within minutes. Exposure of insulinoma cells and isolated pancreatic islets to elevated glucose for only 15 min resulted in a 2- to 5-fold elevation in (prepro)insulin mRNA levels within 60-90 min. Similarly, insulin promoter-driven green fluorescent protein expression in single insulin-producing cells was significantly enhanced after transient glucose stimulation. Thus, short-term signaling, such as that involved in insulin secretion, also may regulate insulin gene transcription.

Animals↗
PubMed1998

Lymphoid hyperplasia, CD45RBhigh to CD45RBlow T-cell imbalance, and suppression of Type I diabetes mellitus result from TNF blockade in NOD-->NOD-scid adoptive T cell transfer.

Sustained antibody-mediated inhibition of tumor necrosis factor (TNF) activity offers protection against Type I (insulin-dependent) diabetes mellitus in non-obese diabetic (NOD) mice. The mechanism of this effect, however, has remained obscure: TNFalpha might be required for the development of specific immune responses to islet antigens or it could directly participate in destruction of beta cells. In this study, autoimmune destruction of beta cells was initiated in NOD-severe combined immunodeficient (scid) mice by transfer of NOD splenic T-cells to induce diabetes. The blockade of TNFalpha activity was achieved during a narrow window of time after transfer. Transient inhibition of TNFalpha greatly reduced the number of islet lymphocytes and the incidence of diabetes in recipients of prediabetic NOD spleen cells. Protection extended beyond the interval of effective TNF blockade. Furthermore, the protective effect was only observed if cells were obtained from 6-week-old donors. The suppression of autoimmunity was reversible in the context of adoptive transfer as indicated by the transfer of splenocytes from the primary recipient to a second NOD-scid host led to a diabetic outcome. The blockade of TNFalpha was accompanied by a considerable increase in spleen size and doubling of the total splenocyte count, suggesting that TNFalpha might normally eliminate a transplanted T-cell subset within the recipients. Further analysis showed an increase in the absolute count of CD4 + T cells and pronounced distortion of the CD45RBhigh to CD45RBlow ratio, with a relative augmentation in the CD45RBlow count in the spleen. TNFalpha appears to regulate the number and subtype distribution of a transplanted T cell population.

Adoptive Transfer↗
PubMed1998

Acupuncture: a review of its history, theories, and indications.

BACKGROUND: The National Institutes of Health recently recommended acupuncture as an effective tool for the treatment of various health problems. Acupuncture is an old technique but has been popular in the United States only since 1972. Its history, theories, and indications are not well known to the medical community. METHODS: We reviewed the literature to gather information on the history, techniques, physiology, indications, adverse effects, and opposing views to acupuncture. RESULTS: The mechanism by which acupuncture works involves neurotransmitters and adrenocorticotropic hormones. It appears to be effective in the treatment of pain, nausea, and drug detoxification and in stroke victims. Studies suggest acupuncture is no more effective than placebo. Acupuncture side effects have rarely been reported. CONCLUSIONS: Acupuncture appears to be a safe and effective alternative medical therapy for certain health problems. More controlled research is necessary to better understand the range of its clinical application.

Acupuncture Therapy↗
PubMed1998

Organization and distribution of a Sau3A tandem repeated DNA sequence in Picea (Pinaceae) species.

Repeated DNA families contribute to the large genomes of coniferous trees but are poorly characterized. We report the analysis of a 142 bp tandem repeated DNA sequence identified by the restriction enzyme Sau3A and found in approximately 20,000 copies in Picea glauca. Southern hybridization indicated that the repeated DNA family is specific to the genus, was amplified early in its evolution, and has undergone little structural alteration over evolutionary time. Fluorescence in situ hybridization localized arrays of the Sau3A repeating element to the centromeric regions of different subsets of the metaphase chromosomes of P. glauca and the closely related Picea sitchensis, suggesting that mechanisms leading to the intragenomic movement of arrays may be more active than those leading to mutation of the repeating elements themselves. Unambiguous identification of P. glauca and P. sitchensis chromosomes was made possible by co-localizing the Sau3A tandem repeats and the genes encoding the 5S and 18S-5.8S-26S ribosomal RNAs.

Base Sequence↗
PubMed1997

Parallel changes in nuclear and cytosolic calcium in mouse pancreatic beta-cells.

In the neuroendocrine pancreatic beta-cell, elevations in intracellular Ca2+ lead to insulin secretion and the initiation of gene transcription. However, the relationship between cytosolic and nuclear Ca2+ in these cells is unknown. The Ca2+ permeability of the nuclear membrane would therefore determine if Ca2+ could play a direct role in Ca2+-dependent nuclear processes. Using confocal fluorescence microscopy with the ratiometric Ca2+ indicator indo-1 and carefully correcting for compartmentalized indicator, we now demonstrate that there is no difference between the nuclear Ca2+ concentration and the cytosolic Ca2+ concentration ([Ca2+]c) in the resting beta-cell. Slow Ca2+ oscillations induced by glucose, fast oscillations induced by glucagon-like peptide-1 and responses to potassium and carbachol all indicate that changes in cytosolic Ca2+ are reflected within the nucleus. We conclude that there are no restrictions on Ca2+ entry into the nucleus of the pancreatic beta-cell subsequent to increases in [Ca2+]c. This implies that any signal involved in increasing [Ca2+]c, and thereby insulin release, may also promote nuclear Ca2+-induced gene transcription.

Animals↗
PubMed1997

Adenoviral vectors given intravenously to immunocompromised mice yield stable transduction of the colonic epithelium.

BACKGROUND & AIMS: Adenoviral vectors have been used for gene transfer in the liver but not for gene transfer in intestinal tissue. The aim of this study was to show that in selectively immunocompromised mice injected intravenously with a recombinant adenovirus, higher levels of a reporter gene are expressed in the colon than in the liver. METHODS: Adenovirus encoding beta-galactosidase was injected intravenously in lethally irradiated B6D2F1 mice that had received syngeneic B6D2F1 bone marrow and spleen cell transplants, in athymic mice, in mice treated with 2-chlorodeoxyadenosine, or in normal mice. Enzymatic assays and polymerase chain reaction analysis were performed on colonic tissue obtained months after transduction. Colonic tissues were also stained for beta-galactosidase. RESULTS: Intravenous adenoviral administration yielded long-term expression of a foreign gene in liver and colonic epithelium in transiently immunocompromised recipients. Histological analysis suggested that stem cell transfection and integration of the foreign gene may have occurred insofar as crypts and colonic epithelial cells in immunocompromised animals stained positive for beta-galactosidase months after virus administration. In polymerase chain reaction analysis, the transverse and distal colon of syngeneic bone marrow transplant recipients showed long-term retention of beta-galactosidase gene. CONCLUSIONS: Long-term transduction of colonic epithelial cells is observed after administration of adenoviral vectors by an intravenous route in selectively immunocompromised mice.

Adenoviridae↗
PubMed1997

Effects of altering testosterone in early infancy on social behaviour in captive yearling rhesus monkeys.

Thirteen male and twenty female rhesus monkeys (Macaca mulatta), aged 9-12 months, living as members of long term captive social groups, were observed in order to quantify sex differences in a variety of behaviour patterns. Six males had been treated with a GnRH agonist (Meterelin: M) during their first six postnatal months, in order to block the surge of testosterone which occurs at this time. Ten females had been treated with testosterone (T) during their first six months, in order to mimic the postnatal T surge seen in males. The remaining 7 males and 10 females acted as control subjects. Marked sex differences were measured in frequencies of play and socio-sexual behaviour in these juvenile monkeys. However, neither M nor T treatments produced any significant changes in frequencies of these behaviour patterns. Although M-treated males showed a tendency (p < 0.1) to groom others for longer periods than control males, and control females tended to spend more time alone than T-treated females, we were unable to measure any significant (p < 0.05) effects of either M- or T-treatment upon affiliative behaviour in juvenile rhesus monkeys. We conclude, therefore, that the postnatal T surge in male rhesus monkeys does not affect development of sexually dimorphic and associated patterns of behaviour. Presumably, organisational effects of T upon these behaviour patterns must be completed before birth in this species.

Animals↗
PubMed1997

Sertindole hydrochloride: a novel antipsychotic medication with a favorable side effect profile.

Forty percent of all long-term care hospitalization days are accounted for by patients with schizophrenia. New approaches to managing this disorder are needed, including improved efficacy and better tolerability to enhance compliance with treatment. Sertindole hydrochloride is a novel antipsychotic medication soon to be available in the United States and Canada. As part of multisite phase II and III studies, we studied effects of this medication in five patients with chronic schizophrenia and examined the side effect profile. With more than 30 patient-months of exposure, sertindole treatment was not associated with neurologic side effects and was well tolerated in all patients studied. No evidence of hematologic abnormalities was found. Serial electrocardiograms revealed slight increases in QTc that were not considered clinically significant and did not lead to discontinuance of treatment. While data from larger samples are needed, in this small population sertindol hydrochloride was tolerated well with no evidence of acute neurologic side effects associated with traditional treatments for schizophrenia. Individuals with schizophrenia may benefit from enhanced compliance with treatment and a possible reduction in hospitalizations in the future.

Adult↗
PubMed1997

Adenovirus-mediated blockade of lymphotoxin-beta inhibits the induction of contact sensitivity in mice.

Lymphotoxin-beta is a newly recognized member of the tumor necrosis factor ligand family. Recent studies have suggested a role for this cytokine in delayed-type hypersensitivity responses. To determine whether lymphotoxin-beta contributes to the development of contact sensitivity, we utilized an inhibitor protein that can effectively block binding of lymphotoxin-beta to its receptor. An adenoviral vector was created that encodes for a lymphotoxin-beta inhibitor protein consisting of the extracellular domain of the lymphotoxin-beta receptor fused to IgG heavy chain. Intravenous injection of the recombinant virus into BALB/c mice yielded plasma levels of inhibitor protein > 500 micrograms that persisted for 1 week. Mice treated in this manner were compared with control animals injected with adenovirus encoding beta-galactosidase, with respect to their ability to mount contact sensitivity responses to epicutaneously applied dinitro-fluorobenzene. Mice transduced with the lymphotoxin-beta inhibitor prior to the induction of contact sensitivity showed significantly suppressed ear swelling responses. By contrast, mice treated with the lymphotoxin-beta inhibitor prior to the elicitation of contact sensitivity showed no change in ear swelling responses in comparison to controls. These findings indicate that lymphotoxin-beta plays an important role in the afferent phase of the contact sensitivity response.

Adenoviridae↗
PubMed1996

Synthesis and activity of a novel series of 3-biarylquinuclidine squalene synthase inhibitors.

Quinuclidines with a 3-biaryl substituent are a new class of potent, orally active squalene synthase (SQS) inhibitors. Variants around these rigid structures indicate key structural requirements for cationic SQS inhibitors. Thus the lower in vitro potency found for quinuclidines bearing 3-substituents, which did not overlay the biphenyl group of 3-(biphenyl-4-yl)-3-hydroxyquinuclidine (2) (IC50 = 16 nM, rat microsomal SQS), implied a directional requirement for the 3-substituent. Similarly, the lower potency of the 3-terphenyl analogue 6 (IC50 = 370 nM) indicated size constraints for this substituent. In compounds with a linking group between the quinuclidine and biphenyl ring, linking groups of lower lipophilicity were less well tolerated (e.g., 17, CH2CH2, IC50 = 5 nM vs 19, NHCO, IC50 = 1.2 microM). Replacement of the distal phenyl ring of 2 with a more polar pyridine heterocycle caused a reduction in in vitro potency. In general, good in vivo activity in the rat was restricted to 3-hydroxy analogues, with the 3-[4-(pyrid-4-yl)phenyl] derivative 39 (IC50 = 161 nM) showing the best inhibition (following oral dosing) of cholesterol biosynthesis from mevalonate (ED50 = 2.7 mg/kg).

Animals↗
PubMed1996

Inhibition of squalene synthase of rat liver by novel 3' substituted quinuclidines.

Squalene synthase (SQS) is a key enzyme in the biosynthetic pathway for cholesterol and is a target for improved agents to lower plasma levels of low-density lipoprotein (LDL). A series of novel 3' substituted quinuclidines have been discovered as inhibitors of the rat liver microsomal enzyme. In this study, we demonstrate the inhibitory effects in vitro and in vivo, of two examples of the series. When microsomes were preincubated with compounds, before addition of substrate, both 3-(biphenyl-4-yl)quinuclidine (BPQ) and 3-(biphenyl-4-yl)-3-hydroxyquinuclidine (BPQ-OH) were found to cause biphasic inhibition of the enzyme with apparent inhibition constants (K'i) for the sensitive phases of 12 nM and 15 nM, respectively. The K'i values for the insensitive phases were 1.8 microM and 2.9 microM, respectively. The two examples inhibited equally both steps of the SQS-catalysed reaction, as shown by parallel inhibition of 3H+ release and labelled squalene formation from [1-3H]farnesyl pyrophosphate (FPP). BPQ and BPQ-OH were shown to be inhibitors of hepatic sterol synthesis from mevalonate with ED50 values of 10.6 and 7.1 mg/kg, respectively, after acute oral administration to the rat. BPQ-OH was chosen for further study and, to determine its selectivity of effect on the mevalonate pathway in vivo, the effect of a dose of 70 mg/kg on the pattern of labelled mevalonate incorporation into the various lipid fractions of the rat liver was examined. As expected, the incorporation into squalene and sterol products was inhibited by about 70%. An appearance of label in fractions corresponding to farnesyl and geranylgeranylpyrophosphates, as well as the corresponding alcohols, was observed in treated but not control animals. In addition, the administration of compound resulted in the appearance of peaks of mevalonate-derived radioactivity in an acidic fraction believed to represent metabolites of farnesol. Such results are consistent with inhibition of the mevalonate pathway at, and not before, SQS. In contrast, there was a significant increase in the incorporation of labelled mevalonate into ubiquinone 10, and the synthesis of dolichols was apparently unchanged. The results suggest a specific effect of BPQ-OH on rat liver SQS. The compound is, therefore, an interesting lead for further investigation of this class of compounds.

Animals↗
PubMed1996

Inhibition of squalene synthase in vitro by 3-(biphenyl-4-yl)-quinuclidine.

Squalene synthase (SQS) catalyses a step following the final branch in the pathway of cholesterol biosynthesis. Inhibition of this enzyme, therefore, is an approach for the treatment of atherosclerosis with the potential for low side effects. We have characterised the inhibition of rat liver microsomal SQS by 3-(biphenyl-4-yl)quinuclidine (BPQ). BPQ follows slow binding kinetics in that the rate of accumulation of product decreases with time if the inhibitor is added when the assay is started. Preincubation of BPQ and SQS leads to a biphasic dose-response where accumulation of product is linear with time only for the sensitive phase. When the farnesyl pyrophosphate (FPP) substrate is present at 19.6 microM, approximately 77% of the SQS activity is sensitive to the inhibitor (vOs) and the remainder is insensitive (vOi). The apparent inhibition constants (K'i values) are respectively K'is = 4.5 nM and K'ii = 1300 nM. Similar biphasic behaviour is exhibited by other inhibitors and in microsomes prepared from human and marmoset liver. As the concentration of FPP is reduced below 19.6 microM, there is a decrease in the relative contribution from vOi. Conversely, the value of K'is for BPQ remains constant when the FPP concentration is changed, showing noncompetitive kinetics with respect to this substrate. Possible causes of the observed kinetics are discussed. Inhibition by BPQ is said to follow tight binding kinetics because the value of K'is is similar to the concentration of inhibitor binding sites. Thus, to avoid an artefactual variation in potency when the enzyme concentration is varied, it is necessary to allow for the effects of depletion of free inhibitor. Furthermore, estimates of potency that average activity across the two phases are influenced by the relative contributions of each phase. These contributions differ according to the FPP concentration and the species used as the source of microsomes. Thus, it is necessary to separate the phases to compare measurements made in different experiments. Our observations indicate that careful experimental design and data analysis are required to characterise the kinetics of SQS inhibitors.

Animals↗
PubMed1996

Personality characteristics and sexual functioning of 188 cross-dressing men.

The literature on cross-dressing men has been primarily limited to self-identified patients at psychiatric clinics who are in distress. To understand the personality trait characteristics and sexual functioning of nonpatient cross-dressers, 188 non-treatment-seeking male cross-dressers completed the NEO Personality Inventory (NEO-PI) and the Derogatis Sexual Functioning Inventory (DSFI). Respondents were classified as transvestites (TV; N = 83), transgenderists (TG; N = 61), or transsexuals (TS; N = 44) based on self-report and the nature of their cross-gender activities (e.g., use of female hormones, desire for sex reassignment, and amount of time spent in female role). These diagnostic groups did not differ on the five broad personality domains of the NEO-PI, but TS men scored higher than TV and TG men on the Aesthetics facet scale of Openness to Experience (O). In terms of the DSFI scales, TS men reported lower sexual drive than TV and TG men, and TS and TG men exhibited greater psychiatric symptoms and feminine gender role, and poorer body image than TV men. Upon exclusion of a group of 49 respondents who previously sought treatment for psychological problems, no significant differences emerged among the three diagnostic groups on the NEO-PI domain and facet scales. Consideration of the DSFI scales showed that TS men experienced less sexual drive, more psychiatric symptoms, and a greater feminine gender role than TV or TG men. This study suggests that cross-dressers not seen for clinical reasons are virtually indistinguishable from non-cross-dressing men using a measure of personality traits, a sexual functioning inventory, and measures of psychological distress. These results emphasize the importance of using clinical significance criteria as required by DSM-IV guidelines before diagnosing men who cross-dress with an axis I disorder.

Adult↗
PubMed1995

Regulation of neurite outgrowth from differentiated human neuroepithelial cells: a comparison of the activities of prothrombin and thrombin.

The mechanism by which thrombin and prothrombin control neurite retraction was studied in Ad12E1HER10 human neuroepithelial cells. Morphological changes in differentiated cells were apparent within minutes of the addition of very low concentrations of thrombin (3 pM). Higher concentrations (2 nM) of prothrombin were required to elicit a similar response. Doses of thrombin and prothrombin sufficient to cause neurite retraction stimulated protein tyrosine kinase activity. Protein tyrosine kinase activation also correlated positively with thrombin- and prothrombin-induced phosphoinositide 3-kinase activation and InsP6 dephosphorylation. However, thrombin-stimulated Ins(1,4,5)P3 generation and intracellular Ca2+ mobilization only occurred at concentrations in excess of those needed to induce retraction. No fluctuations in Ins(1,4,5)P3 were detected after stimulation with prothrombin, and no rapid synchronized release of Ca2+ was observed, even at very high concentrations. Prothrombin did, however, cause small oscillations in the intracellular Ca2+ concentration, similar to those produced by low concentrations of thrombin, after approximately 30 min. We conclude that prothrombin- and thrombin-induced neurite retractions are not dependent on PtdIns(4,5)P2 and Ca2+ mobilization, but are more probably mediated through an effector mechanism involving protein tyrosine kinase activation. No intracellular Ca2+ mobilization, protein tyrosine kinase activity or neurite retraction was observed after treatment of cells with proteolytically inactive mutant thrombin (S205-->A). Prothrombin-mediated intracellular Ca2+ mobilization and neurite retraction were inhibited by hirudin, which was shown to interact with thrombin but not prothrombin. It is concluded that cleavage of prothrombin to thrombin is a necessary prerequisite for biological activity on differentiated Ad12E1HER10 cells and that differences in agonist concentration are capable of coupling the thrombin receptor to different pathways within the cell.

Blotting, Western↗
PubMed1995

A novel approach to dual-acting thromboxane receptor antagonist/synthase inhibitors based on the link of 1,3-dioxane-thromboxane receptor antagonists and -thromboxane synthase inhibitors.

A new class of dual-acting racemic thromboxane receptor antagonist/thromboxane synthase inhibitors is reported, based on the novel approach of linking the known thromboxane synthase inhibitors (TXSI) dazoxiben (2) or isbogrel (11) (separately) to thromboxane receptor antagonists (TXRA) from the 1,3-dioxane series, such as ICI 192605 (10). Dual activity was observed in vitro with inhibition of human microsomal thromboxane synthase in the range IC50 = 0.01-1.0 microM and receptor antagonist activity by inhibition of U46619-induced human platelet aggregation in the range pA2 = 5.5-7.0. The in vitro results also showed that very large groups could be tolerated at the selected substitution positions of the TXRA and TXSI components. Oral activity was observed in ex vivo tests in both rats and dogs at a dose of 10 mg/kg. Thus, (E)-7-[4-[[4-[(2SR,4SR,5RS)-5-[(Z)-5-carboxypent -2-enyl]-4-(2- hydroxyphenyl)-1,3-dioxan-2-yl]-benzyl]oxy]phenyl]-7-(3-pyridyl)he pt-6- enoic acid (110) was both an antagonist (pA2 = 6.7) and a synthase inhibitor (IC50 = 0.02 microM). On oral dosing (10 mg/kg) to rats and dogs, 110 showed significant TXRA activity [concentration ratio > 64 (rat, 3 h) and > 59 +/- 11.3 (dog, 2 h) vs ex vivo U46619-induced platelet aggregation]. Inhibition of thromboxane synthase at the respective time points in these experiments was 81 +/- 4.4% (rat) and 69 +/- 4.8% (dog).

Animals↗
PubMed1995

CD27-CD27 ligand/CD70 interactions enhance alloantigen-induced proliferation and cytolytic activity in CD8+ T lymphocytes.

To study the role of CD27-CD27 ligand (CD27L)/CD70 interactions in the generation of murine allospecific T cell responses, SF9 cells or cell membranes expressing recombinant human CD70 were added to in vitro MLC containing C57BL/6 (H-2b) responder cells and class I and II MHC disparate H-2b/d stimulator cells. Alloantigen-specific CTL generation, CD8+ T cell proliferation, and levels of N-alpha-benzyloxycarbonyl-L-lysine thiobenzyl esterase activity were enhanced in the presence of human CD27L/CD70 expressed on SF9 cell membranes. Enhancement of CD8+ T cell responses occurred in the absence of any discernible effects on CD4+ T cell proliferation or IL-2 responses. Additional studies demonstrated that CD27L/CD70-expressing membranes enhanced proliferative responses to class I MHC differences but had no effect on proliferative responses to class II MHC disparities. Enhancement of allospecific CTL generation was also observed when CD27L/CD70-expressing membranes were added only during the last 24 to 48 h of 5-day MLC. Thus, the present studies suggest that CD27-CD27L/CD70 interactions can selectively enhance differentiation of Ag-specific CD8+ T cell effector mechanisms under conditions in which Th cell responses are not altered.

Animals↗
PubMed1995

Dual-acting thromboxane receptor antagonist/synthase inhibitors: synthesis and biological properties of [2-substituted-4-(3-pyridyl)-1,3-dioxan-5-yl] alkenoic acids.

The design, synthesis, and pharmacology of a new class of compounds possessing both thromboxane receptor antagonist and thromboxane synthase inhibitory properties are described. Replacement of the phenol group of the known thromboxane antagonist series 4(Z)-6-[(4RS,5SR)-4-(2-hydroxyphenyl)-1,3-dioxan-5-yl] hex-4-enoic acid by a 3-pyridyl group led to a series of compounds, 5, which were potent thromboxane synthase inhibitors and weak thromboxane antagonists. Further modifications at the dioxane C2 position led to compounds, 7, which were potent dual-acting agents. In the case of compound 7w, the dual activity was shown to reside almost exclusively in the (-)-enantiomer, 7x. Following oral dosing to rats and dogs, 7x (3 mg/kg) displayed significant dual activity over a period of at least 8 h.

Animals↗