Biomedical subjects

M E Brown

Publications and source records attributed to M E Brown.

At least 19 recordsLinked to original sources

PubMed2001

Light differentially regulates cell division and the mRNA abundance of pea nucleolin during de-etiolation.

The abundance of plant nucleolin mRNA is regulated during de-etiolation by phytochrome. A close correlation between the mRNA abundance of nucleolin and mitosis has also been previously reported. These results raised the question of whether the effects of light on nucleolin mRNA expression were a consequence of light effects on mitosis. To test this we compared the kinetics of light-mediated increases in cell proliferation with that of light-mediated changes in the abundance of nucleolin mRNA using plumules of dark-grown pea (Pisum sativum) seedlings. These experiments show that S-phase increases 9 h after a red light pulse, followed by M-phase increases in the plumule leaves at 12 h post-irradiation, a time course consistent with separately measured kinetics of red light-induced increases in the expression of cell cycle-regulated genes. These increases in cell cycle-regulated genes are photoreversible, implying that the light-induced increases in cell proliferation are, like nucleolin mRNA expression, regulated via phytochrome. Red light stimulates increases in the mRNA for nucleolin at 6 h post-irradiation, prior to any cell proliferation changes and concurrent with the reported timing of phytochrome-mediated increases of rRNA abundance. After a green light pulse, nucleolin mRNA levels increase without increasing S-phase or M-phase. Studies in animals and yeast indicate that nucleolin plays a significant role in ribosome biosynthesis. Consistent with this function, pea nucleolin can rescue nucleolin deletion mutants of yeast that are defective in rRNA synthesis. Our data show that during de-etiolation, the increased expression of nucleolin mRNA is more directly regulated by light than by mitosis.

Cell Cycle↗

PubMed2000

A PPxY motif within the VP40 protein of Ebola virus interacts physically and functionally with a ubiquitin ligase: implications for filovirus budding.

VP40, the putative matrix protein of both Ebola and Marburg viruses, possesses a conserved proline-rich motif (PY motif) at its N terminus. We demonstrate that the VP40 protein can mediate its own release from mammalian cells, and that the PY motif is important for this self-exocytosis (budding) function. In addition, we used Western-ligand blotting to demonstrate that the PY motif of VP40 can mediate interactions with specific cellular proteins that have type I WW-domains, including the mammalian ubiquitin ligase, Nedd4. Single point mutations that disrupted the PY motif of VP40 abolished the PY/WW-domain interactions. Significantly, the full-length VP40 protein was shown to interact both physically and functionally with full-length Rsp5, a ubiquitin ligase of yeast and homolog of Nedd4. The VP40 protein was multiubiquitinated by Rsp5 in a PY-dependent manner in an in vitro ubiquitination assay. These data demonstrate that the VP40 protein of Ebola virus possesses a PY motif that is functionally similar to those described previously for Gag and M proteins of specific retroviruses and rhabdoviruses, respectively. Last, these studies imply that VP40 likely plays an important role in filovirus budding, and that budding of retroviruses, rhabdoviruses, and filoviruses may proceed via analogous mechanisms.

Amino Acid Motifs↗

PubMed2000

WW- and SH3-domain interactions with Epstein-Barr virus LMP2A.

Epstein-Barr virus (EBV) is a human herpesvirus which establishes a lifelong latent infection in B lymphocytes. Latent membrane protein 2A (LMP2A) is expressed in both humans with EBV latent infection and EBV immortalized cell lines grown in culture. Previous studies have shown that the amino terminal domain of LMP2A, which contains eight tyrosines, associates with a variety of cellular proteins via SH2-phosphotyrosine interactions. Also contained within the LMP2A amino terminal domain are five proline-rich regions, three of which possess the PxxP core consensus sequence required for interacting with SH3 domains and two of which possess the PPxY core consensus sequence (PY motif) required for interacting with class I type WW domains. In the current study, the ability of LMP2A to interact with either modular SH3 or WW domains was investigated. The results of these studies indicate that the two LMP2A PY motifs interact strongly with representative class I WW domains, but not with representative class II WW domains. In contrast, no interactions were detected between LMP2A and any of the five different SH3 domains tested. These data demonstrate that a subset of the conserved proline-rich motifs within the amino terminus of LMP2A can potentially mediate interactions with cellular proteins and may play a role in EBV-mediated latency and/or transformation.

Amino Acid Sequence↗

PubMed2000

Enhancement of the dense-core vesicle secretory cycle by glucocorticoid differentiation of PC12 cells: characteristics of rapid exocytosis and endocytosis.

The secretory cycle of dense-core vesicles (DCVs) in physiologically stimulated patch-clamped PC12 cells was analyzed using both amperometry and capacitance measurements. Untreated cells had low or undetectable Ca currents and sparse secretory responses to short depolarizations. Dexamethasone (5 microM) treatment for 5-7 d tripled Ca current magnitude and dramatically increased quantal secretion in response to depolarization with action potentials. Such cells expressed L-, N-, and P-type Ca channels, and depolarization evoked rapid catecholamine secretion recorded as amperometric spikes; the average latency was approximately 50 msec. These spikes were much smaller and shorter than those of primary adrenal chromaffin cells, reflecting the smaller size of DCVs in PC12 cells. Depolarizing pulse trains also elicited a rapid increase in membrane capacitance corresponding to exocytosis in differentiated but not in naïve cells. On termination of stimulation, membrane capacitance declined within 20 sec to baseline indicative of rapid endocytosis (RE). RE did not take place when secretion was stimulated in the presence of Ba or Sr, indicating that RE is Ca-specific. RE was blocked when either anti-dynamin antibodies or the pleckstrin homology domain of dynamin-1 was loaded into the cell via the patch pipette. These studies indicate that neuroendocrine differentiation of PC12 cells with glucocorticoids enhances the development of the excitable membrane and increases the coupling between Ca channels and vesicle release sites, leading to rapid exocytosis and endocytosis. Slow catecholamine secretion in undifferentiated cells may be caused in part by a lack of localized secretory machinery rather than being an intrinsic property of dense-core vesicles.

Animals↗

PubMed2000

Evidence for crystalline water and ammonia ices on Pluto's satellite charon.

Observations have resolved the satellite Charon from its parent planet Pluto, giving separate spectra of the two objects from 1.0 to 2.5 micrometers. The spectrum of Charon is found to be different from that of Pluto, with water ice in crystalline form covering most of the surface of the satellite. In addition, an absorption feature in Charon's spectrum suggests the presence of ammonia ices. Ammonia ice-water ice mixtures have been proposed as the cause of flowlike features observed on the surfaces of many icy satellites. The existence of such ices on Charon may indicate geological activity in the satellite's past.

Ammonia↗

PubMed2000

Preliminary report on the results of the second phase of a round- robin endotoxin assay study using cotton dust.

In an on-going endotoxin assay study, a two-part interlaboratory endotoxin assay study has been completed. The purpose of the study was to compare the variation in assay results between different laboratories, and, if the variation was high, to see if a common protocol would reduce the variation. In both parts of the study, membrane filters laden with the same approximate amount and type of cotton dust were sent for analysis to laboratories that "routinely" perform endotoxin analyses. First, each of these laboratories performed the analysis using the methodology common to its laboratory. In the second part of the study, membrane filters with cotton dust were again sent to the same laboratories where the analyses were performed as before but with a common extraction protocol. The preliminary results from the first phase of the study have been collected and showed that intra-laboratory variations were small, but large and significant interlaboratory variation was observed. The results were reported elsewhere. The preliminary results from the second part of the study consisting of the data currently collected are presented here. Again, intra-laboratory variations were small, but, also again, large and significant inter-laboratory variation was observed. However, in this part of the study, the range between the highest and lowest average results was narrower than in the first part of the study. Influence of the assay kit type was examined. The variation within assay kit type was small but significant differences in results were observed between assay kit types. The findings suggest that endotoxin concentration in samples can be ranked within laboratories, but not necessarily between laboratories. However, some of the variation between laboratories has been reduced by a common extraction protocol which suggests the possibility of further standardization that may lead to better comparability between laboratories.

Air Pollution, Indoor↗

PubMed2000

Importance of photoperiodic signal quality to entrainment of the circannual reproductive rhythm of the ewe.

An endogenous circannual rhythm drives the seasonal reproductive cycle of a broad spectrum of species. This rhythm is synchronized to the seasons (i.e., entrained) by photoperiod, which acts by regulating the circadian pattern of melatonin secretion from the pineal gland. Prior work has revealed that melatonin patterns secreted in spring/summer entrain the circannual rhythm of reproductive neuroendocrine activity in sheep, whereas secretions in winter do not. The goal of this study was to determine if inability of the winter-melatonin pattern to entrain the rhythm is due to the specific melatonin pattern secreted in winter or to the stage of the circannual rhythm at that time of year. Either a summer- or a winter-melatonin pattern was infused for 70 days into pinealectomized ewes, centered around the summer solstice, when an effective stimulus readily entrains the rhythm. The ewes were ovariectomized and treated with constant-release estradiol implants, and circannual cycles of reproductive neuroendocrine activity were monitored by serum LH concentrations. Only the summer-melatonin pattern entrained the circannual reproductive rhythm. The inability of the winter pattern to do so indicates that the mere presence of a circadian melatonin pattern, in itself, is insufficient for entrainment. Rather, the characteristics of the melatonin pattern, in particular a pattern that mimics the photoperiodic signals of summer, determines entrainment of the circannual rhythm of reproductive neuroendocrine activity in the ewe.

Animals↗

PubMed2000

Prostaglandins mediate the endotoxin-induced suppression of pulsatile gonadotropin-releasing hormone and luteinizing hormone secretion in the ewe.

Five experiments were conducted to test the hypothesis that PGs mediate the endotoxin-induced inhibition of pulsatile GnRH and LH secretion in the ewe. Our approach was to test whether the PG synthesis inhibitor, flurbiprofen, could reverse the inhibitory effects of endotoxin on pulsatile LH and GnRH secretion in ovariectomized ewes. Exp 1-4 were cross-over experiments in which ewes received either flurbiprofen or vehicle 2 weeks apart. Jugular blood samples were taken for LH analysis throughout a 9-h experimental period. Depending on the specific purpose of the experiment, flurbiprofen or vehicle was administered after 3.5 h, followed by endotoxin, vehicle, or ovarian steroids (estradiol plus progesterone) at 4 h. In Exp 1, flurbiprofen reversed the endotoxin-induced suppression of mean serum LH concentrations and the elevation of body temperature. In Exp 2, flurbiprofen prevented the endotoxin-induced inhibition of pulsatile LH secretion and stimulation of fever, reduced the stimulation of plasma cortisol and progesterone, but did not affect the rise in circulating tumor necrosis factor-alpha. In Exp 3, flurbiprofen in the absence of endotoxin had no effect on pulsatile LH secretion. In Exp 4, flurbiprofen failed to prevent suppression of pulsatile LH secretion induced by luteal phase levels of the ovarian steroids progesterone and estradiol, which produce a nonimmune suppression of gonadotropin secretion. In Exp 5, flurbiprofen prevented the endotoxin-induced inhibition of pulsatile GnRH release into pituitary portal blood. Our finding that this PG synthesis inhibitor reverses the inhibitory effect of endotoxin leads to the conclusion that PGs mediate the suppressive effects of this immune/inflammatory challenge on pulsatile GnRH and LH secretion.

Animals↗

PubMed1999

Pharmaceutical applications of the Prout-Tompkins rate equation.

More than 50 years ago, a paper by E.G. Prout and F.C. Tompkins was published in the Transactions of the Faraday Society. The paper dealt with the kinetics of the thermal decomposition of crystals of potassium permanganate, and suggested a rate equation, which has become known as the Prout-Tompkins equation, for use in the kinetic analysis of solid state reactions. The paper has been extensively cited in the literature. Applications of the Prout-Tompkins equation in pharmaceutical stability studies are reviewed in this short review.

Algorithms↗

PubMed1998

Hunger in an adult patient population.

CONTEXT: Although clinical observations suggest that some patients experience hunger and food insecurity, there are limited data on the prevalence of hunger in adult patients. OBJECTIVE: To determine the prevalence of hunger and food insecurity in adult patients at an urban county hospital. DESIGN: Cross-sectional survey conducted in 1997. PATIENTS: The primary survey included all patients aged 18 years or older who were admitted to the medicine, surgery, and neurology services during a 2-week period, and all patients who attended the hospital's general medicine clinic during 1 week. A second survey included primary care patients who received insulin from the hospital pharmacy during a 1-month period. MAIN OUTCOME MEASURES: Rates of hunger and food insecurity. RESULTS: Of 709 eligible patients, 567 (participation rate, 80%) were interviewed in either the clinic (n=281) or hospital (n=286). An additional 170 patients who received insulin were interviewed by telephone (response rate, 75%). Of the primary sample, 68 (12%) respondents reported not having enough food, 75 (13%) reported not eating for an entire day, and 77 (14%) reported going hungry but not eating because they could not afford food. A total of 222 (40%) had received food stamps in the previous year and of those, 113 (50%) had their food stamps reduced or eliminated. Recipients whose food stamps had been eliminated or reduced were more likely to report not having enough food (18% vs 13%, P=.006), not eating for a whole day (20% vs 16%, P=.01), going hungry but not eating (20% vs 16%, P=.08), and cutting down on the size of meals or skipping meals (33% vs 27%, P=.01). In multivariate analysis, independent predictors of hunger included an annual income of less than $10000 (odds ratio [OR], 7.55; 95% CI, 3.01-18.92), drug use (OR, 3.56; 95% CI, 1.46-8.66), and a reduction in food stamp benefits (OR, 1.73; 95% CI, 1.01-2.96). Predictors of food insecurity included an annual income of less than $10000 (OR, 4.12; 95% confidence interval [CI], 1.98-8.58), drug use (OR, 2.11; 95% CI, 1.66-5.08), and a reduction in food stamps (OR, 2.02; 95% CI, 1.23-3.32). In addition, 103 (61%) patients in the sample of diabetics reported hypoglycemic reactions; 32 (31%) of these were attributed to inability to afford food. CONCLUSION: Hunger and food insecurity are common among patients seeking care at an urban county hospital.

Adult↗

PubMed1998

Monitoring the consequences of uninsurance: a review of methodologies.

The proportion of the United States population without health insurance continues to grow. How will this affect the health of the nation? Prior research suggests that the uninsured are at risk for poor health outcomes. They use fewer medical services and have higher mortality rates than do insured persons. The episodic nature of uninsurance and its prevalence among disadvantaged groups makes it difficult to ascertain the health effects of uninsurance. The goal of this review is to assist researchers and policy makers in choosing methodologies to assess the effects of uninsurance. It provides a compendium of methods that have been used to examine the health consequences of uninsurance, the populations in which these methods have been used, and the strengths and weaknesses of different approaches. The review highlights the need for more longitudinal studies that focus on community-based samples of the uninsured.

Adult↗

PubMed1998

Systemic challenge with endotoxin stimulates corticotropin-releasing hormone and arginine vasopressin secretion into hypophyseal portal blood: coincidence with gonadotropin-releasing hormone suppression.

We tested the hypothesis that systemic immune/inflammatory challenge (endotoxin) activates the neuroendocrine stress axis centrally by stimulating the secretion of CRH and arginine vasopressin (AVP) into hypophyseal portal blood. In addition, we examined the temporal association between this stimulation of the stress neuropeptides and the inhibition of pulsatile GnRH and LH secretion. Using alert, normally behaving ewes, hypophyseal portal and peripheral blood were sampled simultaneously at 10-min intervals for 14 h. Temperature was monitored remotely by telemetry at the same interval. Endotoxin (400 ng/kg, i.v. bolus) or saline as a control was injected after a 4-h baseline period. Portal blood was assayed for CRH, AVP, and GnRH, and peripheral blood was assayed for cortisol, progesterone, and LH. In controls, hypophyseal portal CRH and AVP remained just above or at assay sensitivity, and cortisol showed a regular rhythmic pattern unaffected by saline and typical of basal secretion. In contrast, endotoxin potently stimulated CRH and AVP secretion into portal blood, and cortisol and progesterone into peripheral blood. Both CRH and AVP generally rose and fell simultaneously, although the peak of the AVP response was approximately 10-fold greater than that of CRH. The AVP in portal blood was not due to recirculation of hormone secreted into the peripheral circulation by the posterior pituitary gland, because the AVP increase in peripheral blood was negligible relative to the marked increase in portal blood. The stimulation of CRH and AVP coincided with significant suppression of GnRH and LH pulsatile secretion in these same ewes and with the generation of fever. We conclude that endotoxin induces central activation of the neuroendocrine stress axis, stimulating both CRH and AVP release into the hypophyseal portal blood of conscious, normally behaving ewes. This response is temporally coupled to inhibition of pulsatile GnRH and LH release as well as with stimulation of adrenal cortisol and progesterone secretion and generation of fever.

Animals↗

PubMed1998

Build consensus and develop collaborative practice guidelines.

With differing treatment guidelines available from many sources, collaborating advanced practice nurses and physicians at this facility recognized the need for one clear, acceptable set. Survey results show that clinicians incorporate all or most of the guidelines into practice (91%).

Ambulatory Care↗

PubMed1997

The response of Jupiter's magnetosphere to an outburst on Io.

A 6-month-long monitoring campaign of the Io plasma torus and neutral cloud was conducted to determine the characteristics of their interaction. During the observations, a large outburst of material from Io-inferred to be caused by the eruption of a volcanic plume on Io-caused a transient increase in the neutral cloud and plasma torus masses. The response of the plasma torus to this outburst shows that the interaction between Io and Jupiter's magnetosphere is stabilized by a feedback mechanism in which increases in the plasma torus mass cause a nonlinear increase in loss from the plasma torus, limiting plasma buildup.

Atmosphere↗

PubMed1996

Analysis of basic fibroblast growth factor in rats with inherited retinal degeneration.

In RCS rats, photoreceptors degenerate between postnatal days 20 and 60, secondary to a genetic defect expressed in the neonatal retinal pigmented epithelium (RPE). Previous work has shown delay of the photoreceptor degeneration in this model by intraocular injection of basic fibroblast growth factor (bFGF). Evidence is presented here, from bFGF immunostaining and Northern analysis of bFGF mRNA, for reduced bFGF expression in uncultured RPE of dystrophic RCS pups. It is also shown that in the mutant eyes angiogenesis in the underlying choroid, which normally occurs between postnatal days 7 and 10, is markedly delayed, with irregular distribution of vessels, consistent with a reduction in this known angiogenesis factor. Mutational analysis of the bFGF transcript and gene by denaturing gradient gel electrophoresis and Southern analysis did not, however, reveal abnormalities in the coding sequence of this gene in RCS rats.

Animals↗

PubMed1996

Do patients use marijuana as an antidepressant?

Several lines of evidence suggest that cannabis may have antidepressant effects. However, methodologic limitations in available studies make the results difficult to interpret. We review this literature and present five cases in which the evidence seems particularly clear that marijuana produced a direct antidepressant effect. If true, these observations argue that many patients may use marijuana to "self-treat" depressive symptoms.

Adolescent↗

PubMed1996

The secretion of active recombinant human gastric lipase by Saccharomyces cerevisiae.

The expression of the complete human gastric lipase (HGL) gene in Saceharomyces cerevisiae grown in defined medium resulted in the secretion of active recombinant HGL (rec.HGL) to levels of up to approximately 11 mg/liter. Of the total measurable HGL activity, 90% was detected by assaying intact cells, suggesting that the majority of rec.HGL produced was secreted but stayed attached to the cell wall. The remaining 10% was present in the growth medium and from this source active rec.HGL was purified 300-fold by a combination of hydrophobic interaction and ion-exchange chromatography. Rec.HGL migrated on reduced SDS-PAGE as three bands with estimated molecular masses of 47,45, and 43 kDa. All three forms cross-reacted with an antibody raised to natural HGL and their treatment with Endo H showed them to be N-linked glycosylation variants of a single polypeptide. The 47-kDa species was isolated using lentil lectin Sepharose 4B and shown to possess a specific activity comparable to that of the natural enzyme. Rec.HGL had an acid pH activity optimum using either tributyrin or olive oil as substrate and did not lose activity if incubated in the presence of pepsin at pH 2.0. These results demonstrate that HGL secreted by Saccharomyces cerevisiae retained those properties of the natural enzyme required for its use in the treatment of pancreatic insufficiency.

Chromatography, Agarose↗

PubMed1996

Protein-bound and unbound forms of plasma cortisol in piglets after castration at seven or 14 days of age.

Male piglets from seven litters were used to evaluate the long-term effects of castration and age at castration on the concentrations of cortisol and its distribution in peripheral plasma. The piglets were allotted to one of three groups of 12 animals according to whether they had been castrated at seven or 14 days old or left intact. The animals were weighed and blood samples were collected from the anterior vena cava at three, seven, 10, 14, 17, 21, 28, 35 and 42 days of age. The plasma concentrations of albumin, total protein, cortisol, and the percentage distribution of cortisol among corticosteroid binding globulin-bound (CBG-bound), albumin-bound and unbound forms, were determined. Castration at seven or 14 days of age had no effect on any of the parameters measured. In all the piglets, the percentage of unbound cortisol decreased (P < 0.001) from 24.5 to 11.6 per cent over the period of sampling. The percentage of CBG-bound cortisol increased (P < 0.001) from 19 per cent on day 17 to 47 per cent on day 21, and albumin-bound cortisol declined from 61 to 37 per cent over the same period. These results agree with previous findings of age-related changes in the percentage distribution of cortisol in the piglet and demonstrate that these patterns are unaffected by castration.

Age Factors↗