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Biomedical subjects

D R Brown

Publications and source records attributed to D R Brown.

At least 343 records · Page 19Linked to original sources
PubMed1987

Retinopathy of prematurity. Risk factors in a five-year cohort of critically ill premature neonates.

We studied the importance of exposure to an elevated partial pressure of carbon dioxide (PCO2) in the development of scarring retinopathy of prematurity (SROP) in a cohort of 92 neonates with chronic lung disease (greater than or equal to 14 days of respiratory therapy, greater than or equal to 30 days of oxygen therapy, and greater than or equal to 70 days in the hospital), 31 of whom had SROP. This cohort was chosen to avoid confounding prolonged respiratory failure with the presence of SROP and because such a cohort was expected to contain approximately 85% of all patients with SROP. Patients with SROP had a lower PCO2 and spent more time on a respirator at higher respirator pressures during the first 70 days of life. In addition, infants with SROP had a lower mean arterial pressure and had a higher prevalence of seizures (97% vs 43%) and intraventricular hemorrhage (52% vs 26%). We conclude that an elevated PCO2 is not associated with SROP in this group of critically ill premature neonates but that the presence of a seizure disorder or an intraventricular hemorrhage is strongly associated with SROP.

Blood Pressure↗
PubMed1987

Stressful life events, social support networks, and the physical and mental health of urban black adults.

The direct and the buffering effects of social support networks have been documented, but few studies have examined their health outcomes for blacks and, specifically, the differences in physical and mental health. This study uses six measures of social support to examine the relationships of social support to health outcomes for black males and females. The data are from a community sample of 451 urban black adults. Results show significant differences by sex according to source of social support and particular health outcomes. Number of nearby relatives and perceived social support have direct and buffering effects, respectively, on mental health for black females, but no significant influences emerge for black males. On the other hand, the number of confidants for black males and the degree of religiosity among black females were inversely related to physical health, suggesting differences in conceptual models of social support for mental and physical health.

Adult↗
PubMed1987

Responses to excess dietary magnesium as affected by experimental Eimeria acervulina infection or by dietary ammonium chloride ingestion in the chick.

Three experiments were conducted to investigate the effect of experimental Eimeria acervulina infection on excess Mg ingestion in the chick and to investigate the effect of NH4Cl addition to the diet on the coccidiosis X Mg interaction. Two Mg sources were evaluated, MgO and MgSO4 X 7H2O. Gain, efficiency of feed utilization, bone ash percent (BAP), bone Ca and duodenal pH were lower in coccidiosis-infected chicks than in uninfected chicks. However, bone P and bone Mg levels were higher as a result of the coccidial infection. Bone Mg levels were higher and bone Ca levels and BAP were lower in chicks fed excess dietary Mg, either as the oxide or sulfate forms. Gain and feed efficiency of chicks fed excess Mg, as MgO but not as MgSO4 X 7H2O, were lower than in chicks fed the basal level of Mg. Coccidiosis X Mg interactions were observed in bone Mg and bone Ca concentration data; bone Mg uptake was greater when high dietary Mg and the coccidial infection were in combination. In some instances, a similar interactive effect was observed in bone Ca concentration data; bone Ca loss tended to be greater as a result of the combination of high dietary Mg and the coccidial infection.

Ammonium Chloride↗
PubMed1987

Cloning of the filamentous hemagglutinin of Bordetella pertussis and its expression in Escherichia coli.

Bordetella pertussis UT25 DNA was cloned into the kanamycin resistance gene of cosmid pCP13 to construct a genomic library in Escherichia coli LE392. One clone containing plasmid pDB441 expressed the filamentous hemagglutinin (FHA) as identified by protein immunoblots with the use of rabbit anti-B. pertussis antiserum, rabbit anti-FHA antiserum, and a monoclonal antibody to FHA. FHA is a protein of 220 to 210 kilodaltons, but the immunoreactive FHA, as expressed in E. coli, was larger than that expressed in B. pertussis, suggesting that there was a difference in the processing of this protein between these two bacteria. The fha gene was mapped to a 6.5-kilobase pair DNA fragment by the use of various restriction endonucleases. The kanamycin resistance gene of pCP13 was found to provide the promoter function but probably not the translation start signal for the fha gene. Conjugative transfer of pDB441 to B. pertussis BP353, a transposon Tn5-induced FHA mutant, increased the expression of the FHA over that seen with wild-type B. pertussis.

Antigens, Bacterial↗
PubMed1987

Psychological monitoring of overtraining and staleness.

It is widely agreed that overtraining should be employed in order to achieve peak performance but it is also recognised that overtraining can actually produce decrements in performance. The challenge appears to be one of monitoring stress indicators in the athlete in order to titrate the training stimulus and prevent the onset of staleness. The present paper summarises a ten-year research effort in which the mood states of competitive swimmers have been monitored at intervals ranging from 2-4 weeks during individual seasons for the period 1975-1986. The training cycle has always involved the indoor season which extends from September to March and the athletes who served as subjects were 200 female and 200 male competitive swimmers. The results indicate that mood state disturbances increased in a dose-response manner as the training stimulus increased and that these mood disturbances fell to baseline levels with reduction of the training load. Whilst these results have been obtained in a realistic setting devoid of experimental manipulation, it is apparent that monitoring of mood state provides a potential method of preventing staleness.

Affect↗
PubMed1987

Post-prandial compositional changes of fluid- and particle-associated ruminal microorganisms.

Two ruminally cannulated cows were fed a diet containing 65% alfalfa haylage and 35% concentrate every 12 h. During two collection periods, whole ruminal contents were sampled before feeding, when feed not eaten was removed (1 h after initiation of feeding) and 1, 2, 3, 4, 6, 8, 10 and 12 h after removal. At each sampling, fluid-associated microorganisms were obtained by straining whole ruminal contents through eight layers of cheesecloth. A portion of the particle-associated population was obtained by chilling squeezed particles before seven successive extractions with saline solution. Microbial ash concentrations ranged from 9.9 to 16.6% of dry matter, with differences due to population (P less than .01) and to time after feeding for both fluid- (P less than .05) and particle-associated (P less than .01) microorganisms. Within 1 h after initiation of feeding, N decreased (P less than .05) from a pre-feeding concentration of 9.5% of organic matter to 7.7% for fluid-associated microorganisms, and from 9.2 to 6.7% for particle-associated microorganisms. Both populations did not return to pre-feeding concentrations until 6 h after feed removal. Nucleic acid concentrations decreased (P less than .05) in both populations after feeding, and did not return to pre-feeding concentrations until 6 h for fluid-associated and 4 h for particle-associated microorganisms. Nucleic acid-to-N ratios were higher (P less than .01) in the fluid- than particle-associated organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effect of dietary buffer additions on gain, efficiency, duodenal pH, and copper concentration in liver of Eimeria acervulina-infected chicks.

Three experiments were conducted with broiler chicks to investigate the effect of dietary additions of NaHCO3(1%), A1(OH)3(.5%), kaolin(1%), A1(OH)2NaCO3(.23%), CaCO3(.37%), and MgO(1%) on gain, efficiency, duodenal pH, and liver Cu concentration of Eimeria acervulina-infected chicks. Experimental coccidial infection consistently reduced chick gain, efficiency, and duodenal pH, but it increased liver Cu concentration of chicks fed excess Cu. Sodium bicarbonate addition improved chick gain and efficiency slightly, whereas the MgO addition reduced these performance criteria. Sodium bicarbonate improved gain more in coccidiosis-infected chicks than in uninfected chicks, but it failed to alleviate, to any extent, the coccidiosis-induced liver Cu increase of the duodenal pH decrease.

Animals↗
PubMed1986

Clinical studies with recombinant-DNA-derived methionyl human growth hormone in growth hormone deficient children.

Thirty-six children with growth hormone deficiency were treated for up to 48 months with methionyl human growth hormone (hGH) synthesised by DNA recombinant methods. The growth rate for these children increased from 3.2 +/- 1.1 cm/yr to 10.5 +/- 2.2 cm/yr (mean +/- SD). This was similar to the effect of pituitary hGH in ten GH deficient children, 3.8 +/- 1.0 to 10.1 +/- 1.1 cm/yr. Serum somatomedin C rose from 0.26 +/- 0.23 U/ml to 0.79 +/- 0.53 U/ml after 6 months of methionyl-hGH therapy, similar to the effect of pituitary hGH. The incidence of antibody formation to methionyl-hGH was higher than that observed with pituitary hGH (Kabi) but poor growth was observed only in the one patient on methionyl-hGH who acquired high-titre high-binding-capacity antibodies to hGH. No consistent changes in levels of antibodies to Escherichia coli proteins were detected. No other allergic manifestations or systemic side-effects were demonstrable.

Adolescent↗
PubMed1986

Early suckling and prolonged breast-feeding.

We determined the duration of breast-feeding for 362 full-term infants of middle- and upper-class mothers. The median duration of breast-feeding was five months for infants whose mothers elected to postpone physical contact (n = 94), four months for infants whose mothers elected early physical contact but later suckling (n = 82), and 8.5 months for infants whose mothers elected to suckle during early contact (n = 186). The rate of decline of breast-feeding was significantly slower for infants who were suckled early than for those who were first suckled later. The association between early suckling and prolonged breast-feeding was not affected by the infant's gender or maternal parity.

Birth Order↗
PubMed1986

Pain threshold changes in adjuvant-induced inflammation: a possible model of chronic pain in the mouse.

A chronic hyperalgesic condition was induced in mice by the injection of Freund's complete adjuvant (FCA) into the lower lumbar region or directly into the hind footpads. Although little or no visible inflammation was observed after a single intradermal injection of FCA into the lower lumbar area of rats or mice, significant alterations in nociceptive thresholds occurred in each species as determined by decreases in response latency in tail-flick and hot-plate assays. Unilateral intraplantar administration of FCA in mice resulted in visible inflammation in the area of the tibiotarsal (ankle) joint. Changes in the response latency to a noxious stimulus in the areas surrounding the inflamed joint were similar to those observed in non-inflamed limbs, suggesting that changes in sensitivity to noxious stimuli were not merely the result of local hypersensitivity of the inflamed tissue, but may also be due to alterations in nociception at the level of the central nervous system (CNS). When the chronic inflammatory condition induced in the mouse tibiotarsal joint was evaluated by histological and morphological techniques, it was found to have the same characteristics as described in the early stages of FCA-induced arthritis in rats. The similarities between the response to FCA in rat and mouse suggest that injection of FCA in mice may prove to be a useful model for the study of chronic pain in mice as well as in rats.

Adjuvants, Immunologic↗
PubMed1986

Regioselective inhibition of benzo(a)pyrene metabolism by corticosterone in comparison with metyrapone and alpha-naphthoflavone.

Corticosterone was investigated for its ability to inhibit benzo(a)pyrene (BaP) metabolism and was compared to metyrapone and alpha-naphthoflavone. Corticosterone inhibited aryl hydrocarbon hydroxylase (AHH) activity nonlinearly in hepatic microsomes from uninduced, phenobarbital-induced, or 3-methylcholanthrene-induced rats. When compared to the classic inhibitors metyrapone and alpha-naphthoflavone, corticosterone had inhibitory properties similar to each. Metabolism of BaP to dihydrodiols was inhibited at the K-region by corticosterone only in uninduced microsomes. Dihydrodiol formation at the Bay region, which leads to the putative ultimate carcinogen, was not affected by corticosterone in uninduced or phenobarbital-induced microsomes but stimulated in 3-methylcholanthrene-induced microsomes. These findings suggest that corticosterone regioselectively inhibits cytochrome P-450 mediated oxidation of BaP to less mutagenic metabolites while stimulating the formation of highly mutagenic products.

Animals↗
PubMed1986

Lung metabolism of benzo[a]pyrene in rats treated with p-xylene and/or ethanol.

The metabolism of benzo[a]pyrene (BaP) may be altered by xenobiotic compounds. The effects of p-xylene and ethanol on the lung metabolism of BaP were studied. p-Xylene was administered by ip injection at doses ranging from 0.1 to 1.0 g/kg (1:1 in soybean oil). Ethanol was administered po at 5 g/kg (40% w/v). Rats given p-xylene, ethanol, or p-xylene and ethanol were sacrificed 1 h after treatment. Additional time points of 15 min, 30 min, 4 h, and 24 h after p-xylene (1 g/kg) were examined. 3-Hydroxy-BaP (3-OH) formation was measured fluorometrically as aryl hydrocarbon hydroxylase activity (AHH) in lung microsomes. p-Xylene (1 g/kg) inhibited the formation of 3-OH BaP 40% at 15 min, 27% at 30 min, 43% at 1 h, and 39% at 4 h after treatment. Inhibition of AHH activity was still present 24 h after dosing (41%). AHH activity was inhibited 27% and 46% at 0.5 mg/kg and 1.0 mg/kg p-xylene (1 h), respectively, while the lowest dose (0.1 mg/kg) did not change activity. Analysis of the major metabolites of BaP by high-performance liquid chromatography (HPLC) demonstrated that the formation of 3-OH and 4,5-diol BaP were inhibited 32% and 50%, respectively, in lung microsomes prepared 24 h after a single injection of p-xylene (1 g/kg). None of the other metabolites analyzed were changed by p-xylene. Ethanol had no effect on 3-OH BaP formation during a 1-h treatment. A combined dose of ethanol and p-xylene moderately inhibited 3-OH BaP formation. These findings indicate that BaP detoxication (i.e., 3-OH formation) in rat lung is selectively inhibited by p-xylene but not ethanol. Ethanol appears to modify the inhibitory effect of p-xylene.

Animals↗
PubMed1986

Combined premedical-medical programmes: programme structure and student outcomes at four universities.

Many American universities now support combined premedical-medical programmes which shorten and integrate the education of doctors. This paper reviews combined baccalaureate-MD programmes at four institutions: Boston University, the City College of New York, The University of Michigan-Ann Arbor, and the University of Missouri-Kansas City. In comparison to most US medical schools, the combined programmes have admitted and educated larger portions of women students. In addition, some have had large proportions of graduates choosing primary-care careers.

Boston↗
PubMed1986

Secretagogue-induced changes in membrane calcium permeability in chicken and chinchilla ileal mucosa. Selective inhibition by loperamide.

Substance P (SP), neurotensin (NT), bombesin (BB), serotonin (5HT), and carbamylcholine (CCH) transiently increase electrogenic anion secretion in chinchilla and chicken ileum. SP and CCH also transiently inhibit amiloride-sensitive Na/H exchange in isolated chicken enterocytes. Loperamide (LP) inhibits the short-circuit current responses caused by SP, NT, and BB, but not those caused by CCH, 5HT, Ca ionophore, or cyclic nucleotides. Similarly, LP inhibits the effects of SP, but not those of CCH, on Na/H exchange. LP inhibition of the SP effects was further studied in isolated chicken enterocytes. CCH and SP transiently increased cytosolic Ca activity by 20-50 nmol/liter, but only the response to SP was inhibited by LP (10(-5) M) and by the absence of extracellular Ca. We conclude SP and CCH effects on intestinal electrolyte transport are mediated by increasing enterocyte Ca activity and LP specifically inhibits peptide hormone-activated Ca entry by an opiate receptor-independent mechanism.

Amiloride↗
PubMed1986

Excess supplemental choline for swine.

Seven experiments were conducted with 280 crossbred pigs to investigate the effect of excess choline on rate and efficiency of gain of weanling, growing and finishing swine Choline additions were made to a conventional corn-soybean meal diet. Daily gain of weanling pigs was reduced slightly by 6,000 ppm excess choline compared with 0, 500, 1,000, 2,000 or 4,000 ppm excess choline. Excess supplemental choline (2,000 ppm) fed throughout the weanling, growing and finishing (121 to 126 d) phases of growth reduced (P less than .08) daily gain but it did not affect (P greater than .10) feed utilization. The 2,000-ppm choline addition, however, did not affect (P less than .10) pig gain when fed only during the growing and finishing stages of growth (68 to 86 d). Excess choline should be avoided in swine diets if maximum rate of gain is to be achieved.

Animals↗
PubMed1986

Dietary cimetidine and copper in Eimeria acervulina-infected chicks.

The effects of varying levels of cimetidine (N"-cyano-N-methyl-N'-(2-[(5-methylimidazol-4-yl)methylthio]-ethyl ) guanidine) on Eimeria acervulina (duodenal coccidiosis)-induced changes in gain, efficiency, duodenal pH, and liver copper concentration of chicks were investigated. In a preliminary trial, gain, efficiency, and duodenal pH were significantly reduced in chicks inoculated one time with 1 X 10(6) sporulated oocysts. Dietary addition of 121 ppm monensin (2-[5-ethyltetrahydro-5-[tetrahydro-3-methyl-5-[tetrahydro-6-hydro xy-6- (hydroxymethyl)-3,5-dimethyl-2H-pyran-2-yl]-2-furyl]-2-furyl]-9-hydroxy- beta-methoxy-alpha, gamma, 2,8-tetramethyl-1,6-dioxaspiro[4.5]decane-7-butyric acid) prevented these coccidiosis-induced aberrations. In subsequent trials, growth rate, feed efficiency, and duodenal pH were reduced by E. acervulina infection, but were unaffected (P greater than 0.10) by dietary addition of 0.01% cimetidine. Linear depressions (P less than 0.05) in gain and efficiency, however, were observed from 0.05 and 0.10% cimetidine additions. Dietary addition of 500 ppm copper increased liver copper levels thirtyfold (P less than 0.01) after 2 weeks. Significant coccidiosis X copper interactions were detected in gain, efficiency, duodenal pH reduction, and liver copper elevation of chicks repeatedly inoculated with 4 X 10(5) sporulated E. acervulina oocysts. Coccidiosis increased liver copper levels (P less than 0.01) of chicks fed excess copper an additional threefold compared with uninfected chicks fed excess copper. Dietary additions of 0.01, 0.05 or 0.10% cimetidine were ineffective in preventing coccidiosis-associated performance and duodenal pH depressions as well as the coccidiosis-induced liver copper elevation. Apparently, host response to cimetidine is minor in comparison to effects of coccidia on duodenal pH. Increased copper solubility at low duodenal pH may explain high tissue copper levels and enhanced copper toxicity due to coccidiosis.

Animals↗