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Biomedical subjects

A A Johnson

Publications and source records attributed to A A Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1994

The pulmonary effect of nitric oxide synthase inhibition following endotoxemia in a swine model.

OBJECTIVE: To evaluate the pulmonary effect of treatment with N-nitro-L-arginine methyl ester (NAME) with and without inhaled nitric oxide (NO) in a swine model of endotoxemia. DESIGN: Randomized controlled trial. SETTING: Laboratory. INTERVENTIONS: Following a 20-minute intravenous infusion of Escherichia coli lipopolysaccharide (LPS) (200 micrograms/kg), animals were resuscitated with saline solution (1 mL/kg per minute) and observed for 3 hours while mechanically ventilated (fraction of inspired oxygen [FIO2], 0.6; tidal volume, 12 mL/kg; positive end-expiratory pressure, 5 cm H2O). Group 1 (LPS, n = 6) received no additional treatment; group 2 (NAME, n = 5) received NAME (3 mg/kg per hour) for the last 2 hours; group 3 (NO, n = 6) received NAME (3 mg/kg per hour) and inhaled NO (40 ppm) for the last 2 hours; and group 4 (control, n = 5) received only saline solution without LPS. MAIN OUTCOME MEASURES: Cardiopulmonary variables and blood gases were measured serially. The multiple inert gas elimination technique was performed at 3 hours. The wet-to-dry lung weight ratio was measured following necropsy. RESULTS: Administration of LPS resulted in pulmonary arterial hypertension, pulmonary edema, and hypoxemia with increased ventilation perfusion ratio mismatching. None of these changes were attenuated by NAME treatment alone but all were significantly improved by the simultaneous administration of inhaled NO. CONCLUSIONS: Systemic NO synthase inhibition failed to restore hypoxic pulmonary vasoconstriction following LPS administration. The deleterious effects of endotoxemia on pulmonary function can be improved by inhaled NO but not by systemic inhibition of NO synthase.

Administration, Inhalation↗
PubMed1994

The effects of pentoxifylline on pulmonary function following smoke inhalation.

Bronchopulmonary injury secondary to smoke inhalation is a significant comorbid factor following major thermal trauma. The present study evaluates the effects of pentoxifylline (PTX) on pulmonary function in an ovine model of inhalation injury. Following smoke exposure to produce a moderate inhalation injury, 16 animals were divided into two groups. Group 1 animals (n = 8) were untreated; Group 2 animals (n = 8) were treated continuously with pentoxifylline following smoke exposure. The animals were observed in the unintubated, awake state for 48 hr. Cardiopulmonary variables and blood gases were measured serially. Ventilation perfusion distribution (VA/Q), analyzed using the multiple inert gas elimination technique, and bronchoalveolar lavage (BAL) were performed at 48 hr. The wet to dry lung weight ratio was measured following necropsy. In Group 2, the progressive hypoxemia observed following smoke inhalation was attenuated with less VA/Q mismatching than in Group 1 (P < 0.05). Pulmonary hypertension secondary to increased vascular resistance was also attenuated in Group 2 (P < 0.05). In BAL fluid, polymorphonuclear leukocytes, total protein content, and conjugated dienes were less in Group 2 than in Group 1 (P < 0.05). Plasma-conjugated diene levels were also lower in Group 2 at 48 hr. Extravascular lung water and decrease in lung compliance were greater in Group 1. There was less morphologic evidence of airway injury in Group 2 compared to Group 1. The improvement of pulmonary function following treatment with PTX suggests that this agent may be useful in the management of smoke inhalation injury.

Animals↗
PubMed1994

Prenatal predictors of performance on the Brazelton Neonatal Behavioral Assessment Scale.

The present study presents a prospective analysis of the interrelationships among prenatal medical, nutritional (dietary and biochemical) and behavioral determinants of Brazelton performance. Previous researchers (Scanlon 1984, Lester and Brazelton 1984) have raised questions regarding the relative roles of medical factors, nutrition, ponderal index and other behavioral factors in neonatal performance on the BNBAS. Four hundred sixty-seven predominantly Black nulliparous women and their neonates in Washington, D.C. who were enrolled in the study by the 20th week of gestation were subjects. Results of univariate tests of significant (P < 0.01) association between independent variables and Brazelton clusters from scores measured on day 2 are presented. The 26 behavioral items were summarized into 6 clusters as done in similar studies by linearizing measures made on a curvilinear scale and taking the mean. The 6 behavioral clusters are habituation, motor, orientation, range of states, regulation of states, and autonomic. Results of 16 reflex tests are used to define a seventh reflex cluster. Independent variables included demographic, lifestyle, nutritional, medical, ponderal index, and psychosocial measures. Several psychosocial variables, including stress, anxiety and partner interaction were associated with the behavioral clusters. Nutritional variables were associated with BNBAS habituation, motor, orientation, reflex score and autonomic responses. An analysis of co-variance was performed to determine the joint effect of the above variables on the variation in the Brazelton performance on the seven cluster scores. Five of the seven models (orientation, motor, range of states, autonomic, and reflex scores) were significant predictors of the outcome variables.

Adolescent↗
PubMed1994

Maternal stress and pregnancy outcomes in a prenatal clinic population.

A two-fold decrease in the incidence of infant low birth weight, from 20.6% to 8.3%, occurred in Africa American women enrolled from 1985 to 1988 in this interdisciplinary research project conducted in an urban prenatal clinic. Nutritional, biochemical, medical, psychosocial, lifestyle, and environmental data were collected by trained Africa American interviewers. Several instruments were administered to the mother to specify the stress construct and assess body image, the social support network, and other psychosocial variables. The reduction in the incidence of low birth weight in an urban Africa American low income population admitted to the Howard University Hospital is attributed to the mediation of maternal stress by project personnel, in effect, providing an additional support system through the caring, sensitive environment provided by the project clinical staff, who met the women at each of their clinic-scheduled appointments. Women with a positive self attitude and higher self esteem were more likely to be delivered infants at term; the number of persons in the mother's social support network was directly correlated with her infant's gestational age. Maternal serum concentrations of the antioxidant vitamins, vitamin E and ascorbic acid, and the free radical scavenger, uric acid, were significantly correlated with serum folate and blood urea nitrogen. An hypothesis of low birth weight is presented.

Adolescent↗
PubMed1994

Deoxyribonucleic acid, ribonucleic acid, and protein in the placentas of normal and selected complicated pregnancies.

Placenta from uncomplicated term pregnancies resulting in the birth of male infants weighing between 2900 and 3800 grams were analyzed for deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein content. The mothers of the infants all had pre-pregnancy weights within +/- 15 percent expected body weight for body frame, according to the Metropolitan Life Tables. There were no significant differences, as regards the content of DNA, RNA and protein, between the placental cotyledons. Nine placenta from mothers giving birth to growth retarded infants were analyzed along with the placenta from six mothers with insulin dependent diabetes mellitus. A trend suggesting less DNA in the placenta of the severely growth retarded (symmetric) infants when compared with placenta from the normal pregnancies was not noted in the less severely growth retarded (asymmetric) infants. The placenta from the infants of diabetic pregnancies contained DNA and RNA in amounts similar to that found in normal pregnancy placenta but the protein content was greater.

Birth Weight↗
PubMed1994

Multiple factors as mediators of the reduced incidence of low birth weight in an urban clinic population.

A five year prospective observational study was initiated in 1985 at Howard University to describe the nutritional, clinical, dietary, lifestyle, environmental, and socioeconomic characteristics of women who enrolled in the hospital prenatal clinic. The participants were nulliparous, between the ages of 18 and 35 years, free of diabetes and abnormal hemoglobins (sickle cell disease, thalassemia, and hemoglobin C), and had been admitted prior to the 29th week of gestation. During the three year period from 1985-1988, the incidence of low birth weight (LBW) in 239 deliveries to project participants was 8.3%, whereas that of women simultaneously enrolled in the prenatal clinic with the same eligibility requirements, but not recruited for the research project, was 21.9% (P = 0.001). The incidence of LBW in infants of African American women with these eligibility requirements who were delivered by private physicians but were not enrolled in the project, was 6.3%. The reduction in LBW of infants delivered to participants in this study is attributed to the enhanced social and psychological support by project staff during their pregnancies. The caring, sensitive demeanor of the research project staff may have empowered the participants to (a) give greater compliance (91 vs. 70%) in the ingestion of the routine physician-prescribed vitamin/mineral supplement, which provided nutrients low (less than 70% of the 1989 RDAs) in their customary diets, such as folate, pyridoxine, iron, zinc, and magnesium and (b) show greater accountability in keeping prenatal clinic appointments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Dietary intakes, anthropometric measurements and pregnancy outcomes.

The relationships of maternal prenatal dietary intakes and anthropometric measurements to pregnancy outcomes were investigated in a prospective observational study of urban African American women. The 322 subjects, a subset of the 744 women recruited for the study using purposive sampling, were all nulliparous, free of diabetes mellitus and abnormal hemoglobins, and delivered term, singleton infants. Sociodemographic data and monthly quantitative 24-hour food recalls were collected by trained interviewers. Maternal anthropometric measurements were obtained from the subjects' hospital records. Pregnancy outcome data were obtained by physical examinations of the newborn infants by the project pediatrician. With the exception of vitamin C, average maternal dietary intakes were within the ranges of intakes obtained in previous studies. Mean intakes of protein, vitamins A and C, thiamin, riboflavin, and niacin exceeded the 1989 RDA, while those of food energy, vitamin B-6, folate, calcium, iron, magnesium, and zinc were below the RDA. Underweight prior to pregnancy and low pregnancy weight gains were found among 12.9% and 44.4% of the subjects respectively. Dietary intakes were not significantly correlated with pregnancy outcomes. Maternal anthropometric measurements significantly correlated with pregnancy outcomes included delivery weight, pregnancy weight gain, weekly weight gain, prepregnancy weight, net weight gain, height, prepregnancy body mass index, and % ideal prepregnancy body weight (P < 0.05). Using the stepwise selection procedure in multiple regression analysis, delivery weight, % ideal prepregnancy body weight, and prepregnancy body mass index were selected as being predictive of infant birth weight. It was concluded that anthropometric measurements were better nutritional predictors of pregnancy outcome than dietary intake.

Adolescent↗
PubMed1994

Biochemical profile of African American women during three trimesters of pregnancy and at delivery.

The data presented are the results from a prospective observational study which was conducted to investigate the effects of nutrition and other related factors on the outcome of pregnancy in nulliparous African American women 16-35 years old. Fasting blood samples were collected from the women during the first, second and third trimesters of pregnancy. At delivery, both maternal and cord samples were collected. Biochemical variables such as, serum folate, vitamin B12, ascorbic acid, vitamin E, ferritin, selected minerals as well as complete blood count (CBC) and red cell folate were analyzed in the blood samples. The concentrations of hematocrit, hemoglobin, white blood cells, red blood cells and vitamin B12 were below the reference non-pregnant ranges throughout gestation. Maternal concentrations of folate and vitamin E increased sequentially with increased gestational age. Serum ferritin, during the third trimester, declined to 58% of the first trimester concentration. Maternal levels of ferritin at delivery were one third of the values found in the infant (cord) sample. Cord levels of folate, ascorbic acid and vitamin B12 were higher than the concentrations in the maternal delivery samples. The data suggest that among this group of pregnant women, major physiological changes, such as plasma volume expansion which alters blood chemistry and maternal to fetal transfer of nutrients, were similar to the findings of other investigators. In this population however, the findings for serum and whole blood folate are contrary to those reported by other researchers, and the sequential increase in the maternal concentration of the vitamin during pregnancy could be attributed to the use of vitamin supplements.

Adolescent↗
PubMed1994

Pica in an urban environment.

The practice of pica, the compulsive ingestion of nonfood substances over a sustained period of time, was studied in 553 African American women who were admitted to prenatal clinics in Washington, D.C. Dietary, biochemical, and psychosocial correlates of the pica practices of a subset of this urban population are presented in this paper. Geophagia, compulsive eating of clay or dirt, was not observed in these women; pagophagia, or the ingestion of large quantities of ice and freezer frost, was self reported in 8.1% of the women, who consumed 1/2 to 2 cups a day from 1 to 7 days per week. Serum ferritin concentrations of pica women were significantly lower during the second and third trimesters of pregnancy; the average values for three trimesters of pregnancy for both ferritin and mean corpuscular hemoglobin were significantly lower in pica women than their nonpica counterparts (P = 0.0001 and P = 0.017, respectively). Although not significantly different, the iron (66 vs. 84% RDA) and calcium (60 vs. 75% RDA) contents of the diets of pica women were less those of nonpica women. Gestational age, body length, and body weight were not different, but head circumferences of infants delivered to pica women who consumed freezer frost and/or ice were smaller than those of nonpica women (P = 0.012). The hypothesis is presented that pica in African American women may be a mediator of stress, acting through the immune system. The size of the social support network of pica women was significantly less than that of nonpica women.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Selected lifestyle practices in urban African American women--relationships to pregnancy outcome, dietary intakes and anthropometric measurements.

The relationships of selected lifestyle factors (cigarette smoking, consumption of alcoholic beverages, recreational drug use, and exercise during pregnancy), all self-reported, to pregnancy outcomes, dietary intake during pregnancy, and maternal anthropometric measurements, were investigated in a group of urban African American pregnant women. The 234 subjects were aged 16-35 years and were free of diabetes and abnormal hemoglobins. The lifestyle data were collected by trained interviewers during the subjects' prenatal clinic visits, and the dietary data by monthly, quantitative 24-hour food recalls conducted during these same visits. Maternal anthropometric measurements were obtained from the subjects' hospital records, and pregnancy outcome data during physical examinations of the newborn infants. Both cigarette smoking and drug use were associated with significantly lower mean birth weight, length, and head circumference, while exercise was associated with a significantly higher mean birth weight, and head circumference (P < 0.05). Drug use during pregnancy was associated with a significantly higher intake of vitamin C, and a significantly lower intake of iron; while women reporting drug use before pregnancy had significantly higher mean intakes of food energy, protein, total and saturated fat, and zinc. Prepregnancy weight, percent ideal prepregnancy body weight, prepregnancy body mass index, and delivery weight were significantly lower among those reporting drug use before pregnancy. Multiple regression analyses indicated that smoking explained a relatively small proportion of the variance in infant birth weight compared with delivery weight and percent of ideal prepregnancy body weight.

Adolescent↗
PubMed1994

Relationships of serum illicit drug concentrations during pregnancy to maternal nutritional status.

Findings reported are for a subset of African American subjects, residing in the urban area of Washington, D. C., who participated in a Program Project designed to study nutrition, other factors, and the outcome of pregnancy. Fasting blood samples, drawn during each trimester of pregnancy and at delivery, were screened for concentrations of cocaine, phencyclidine (PCP) and marijuana. Since substance abusers are expected to consume inadequate diets, these samples were also analyzed for serum folate, vitamin B12, ferritin and ascorbic acid. Data for these biochemical variables were compared for subjects whose serum values for drugs were either above or below the drug screening threshold concentrations established by ADAMHA/NIDA. Pearson's correlations were used to determine relationships between pregnancy outcome variables and maternal serum drug concentrations. Blood samples drawn at delivery showed higher maternal: cord ratios (mean +/- SEM) for marijuana (3.3 +/- 2.2) and PCP (2.9 +/- 1.0) than for cocaine (1.0 +/- 0.2). The subjects whose serum values were above the ADAMHA/NIDA ranges for marijuana, PCP and cocaine had concentrations of folate and ferritin that were significantly less than those of subjects with lower serum drug levels (P < or = 0.05). High maternal serum concentrations of illicit drugs were accompanied by a significant increase in leukocyte count (P < or = 0.05). The level of maternal cocaine during the third trimester was inversely correlated with birthweight (r = -0.29; n = 52; P = 0.038) and head circumference (r = -0.28; n = 52; P = 0.047).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Maternal low level lead and pregnancy outcomes.

We examined the relationship between the concentrations of blood lead and pregnancy outcomes in a subset of 349 African American women who enrolled in the program project, "Nutrition, Other Factors, and the Outcome of Pregnancy." Vitamin-mineral supplement users had significantly higher serum levels of ascorbic acid and vitamin E. Also, in supplement users, there were significantly lower mean concentrations of maternal blood lead. Inverse correlations were found between maternal levels of lead and the antioxidant vitamins, vitamin E and ascorbic acid. In addition, significant Pearson's correlations were observed between maternal blood lead levels and the following variables: positive correlations with calcium, phosphorus, mean corpuscular volume; inverse correlations with gestational age, Ponderal Index, infant orientation, and hematologic values. In the total subset, the three trimester sample means for maternal blood lead concentrations were not significantly different for mothers of infants who weighed less than 2500 g (low birth weight) and those who were delivered infants who weighed 2500 g or more. Clinically, nutrition may play a role in the reduction of potentially adverse effects from lead during pregnancy, i.e. protection of the fetus against lead toxicity and/or free radical damage through the antioxidant actions of vitamin E and ascorbic acid. Even when maternal blood lead levels are within the so-called "safe" range, maternal/use of a vitamin supplement supplying vitamin E and ascorbic acid during pregnancy may offer protection.

Adolescent↗
PubMed1994

Nutrition, genital tract infection, hematologic values, and premature rupture of membranes among African American Women.

Using a prospective comparative design, African American gravidae with and without genital tract infection were assessed with respect to dietary intakes, serum nutrient values, hematologic values, and pregnancy outcomes. Intakes of ascorbic acid, vitamin A, protein, and iron were the dietary variables while levels of ascorbic acid, protein, albumin, globulin, and ferritin were the variables measured in serum. The hematologic variables included hemoglobin, hematocrit, and red and white blood cell counts. Pregnancy outcome was defined on the basis of premature rupture of the membranes (PROM), and infant birth weight, birth length, gestational age, and head circumference. The sample consisted of 335 nulliparous women who were between 16-35 years of age, 96 of whom had genital tract infection based on laboratory reports. Findings indicated no significant differences between the mean dietary intakes as well as serum values of the infected and non-infected women, and no difference in the incidence of PROM. However, non-infected women had a better mean hematologic profile than the infected gravidae during pregnancy. Also, for the non-infected group, there were significant relationships between head circumference and protein consumption (P = .015) and serum ferritin (P = .05). For the infected women, the relationship between the hemoglobin and hematocrit measurements obtained at the first prenatal visit and infant birth weight, birth length and head circumference were statistically significant.

Adolescent↗
PubMed1994

Prenatal substance abuse and pregnancy outcomes among African American women.

Subjects in this prospective observational study were 467 nulliparous women, ages 16-35, recruited at the prenatal clinics of a university hospital and a public hospital. Using a purposive sampling approach, and entry questionnaire and a series of psychosocial instruments were administered throughout the pregnancy course to assess stress, anxiety, body image, self-esteem, pregnancy symptoms, locus of control, and partner's interaction. Several pregnancy outcome measures were determined after delivery. Brazelton neonatal behavioral assessments were performed two days after birth of infants delivered to the maternal subjects. Self-reported substance abuse data were obtained from the entry questionnaire and the medical intake records, with usage characterized in terms of occurrence prior to and/or during pregnancy. Illicit drug users during pregnancy had lower self-esteem, greater stress, more pregnancy symptoms, a more negative pre-pregnancy body image and less favorable interactions with their partners. T test results show that infants of smokers had smaller head circumferences, shorter body length, and less optimal Brazelton orientation performance. Infants of illicit drug users had smaller head circumferences and shorter body lengths.

Adolescent↗
PubMed1994

The effect of inhaled nitric oxide on smoke inhalation injury in an ovine model.

Smoke inhalation is a significant comorbid factor in thermal trauma. The effect of inhaled nitric oxide (NO) on smoke inhalation injury was evaluated in an ovine model. Following smoke exposure, group 1 animals (n = 9) spontaneously breathed room air, and group 2 animals (n = 8) breathed 20 parts per million of NO in air for 48 hours. Cardiopulmonary variables and blood gases were serially measured; bronchoalveolar lavage (BAL) was performed and wet-to-dry lung weight ratios (W/D) determined at 48 hours. Pulmonary vasoconstriction following smoke inhalation was significantly attenuated by inhaled NO (p < 0.05), which exerted no apparent effect on the systemic circulation. In group 2, the serial decline in pulmonary oxygenation was less than in group 1, consistent with a smaller physiologic shunt (p < 0.05). There were no significant differences in W/D, lung compliance, BAL fluid analysis results, or histologic evaluation findings between the two groups. These results suggest that inhaled NO exerted beneficial effects on pulmonary arterial hypertension and oxygenation following smoke inhalation without apparent amelioration of airway inflammation.

Administration, Inhalation↗
PubMed1994

The effect of inhaled nitric oxide on pulmonary ventilation-perfusion matching following smoke inhalation injury.

BACKGROUND: We previously reported that inhaled nitric oxide (NO) improved pulmonary function following smoke inhalation. This study evaluates the physiologic mechanism by which inhaled NO improves pulmonary function in an ovine model. METHODS: Forty-eight hours following wood smoke exposure to produce a moderate inhalation injury, 12 animals were anesthetized and mechanically ventilated (FIO2, 0.40; tidal volume, 15 mL/kg; PEEP, 5 cm H2O) for 3 hours. For the first and third hours, each animal was ventilated without NO: for the second hour, all animals were ventilated with 40 ppm NO. Cardiopulmonary variables and blood gases were measured every 30 minutes. The multiple inert gas elimination technique (MIGET) was performed during the latter 30 minutes of each hour. The data were analyzed by ANOVA. RESULTS: Pulmonary arterial hypertension and hypoxemia following smoke inhalation were significantly attenuated by inhaled NO compared with the values without NO (p < 0.05, ANOVA). Smoke inhalation resulted in a significant increase in blood flow distribution to low VA/Q areas (VA/Q < 0.10) with increased VA/Q dispersion. These changes were only partially attenuated by the use of inhaled NO. The SF6 (sulfur hexafluoride) retention ratio was also decreased by inhaled NO. Peak inspiratory pressures and pulmonary resistance values were not affected by inhaled NO. CONCLUSIONS: Inhaled NO moderately improved VA/Q mismatching following smoke inhalation by causing selective pulmonary vasodilation of ventilated areas in the absence of bronchodilation. This modest effect appears to be limited by the severe inflammatory changes that occur as a consequence of smoke exposure.

Analysis of Variance↗
PubMed1994

Effect of inhaled nitric oxide on pulmonary function after sepsis in a swine model.

BACKGROUND: Inhaled nitric oxide (NO) has been shown to improve sepsis induced pulmonary dysfunction. This study evaluated the mechanism by which inhaled NO improves pulmonary function in a porcine sepsis model. METHODS: After an infusion of Escherichia coli lipopolysaccharide (LPS, 200 micrograms/kg), animals were resuscitated with saline solution (1 ml/kg/min) and observed for 3 hours while mechanically ventilated (fraction of inspired oxygen, 0.6; tidal volume, 12 ml/kg; positive end-expiratory pressure, 5 cm H2O). Group 1 (LPS, n = 6) received no additional treatment. Group 2 (NO, n = 6) received inhaled NO (40 ppm) for the last 2 hours. Group 3 (control, n = 5) received only saline solution without LPS. Cardiopulmonary variables and blood gases were measured serially. Multiple inert gas elimination technique was performed at 3 hours. Wet to dry lung weight ratio was measured after necropsy. RESULTS: Lipopolysaccharide resulted in pulmonary arterial hypertension, pulmonary edema, and hypoxemia. Multiple inert gas elimination technique analysis indicated a significant increase in blood flow to true shunt and high ventilation perfusion distribution (VA/Q) areas with an increased dispersion of VA/Q distribution. All of these changes were significantly attenuated by NO. CONCLUSIONS: Inhaled NO significantly improved LPS induced VA/Q mismatching by decreasing both true shunt and high VA/Q areas, by decreasing pulmonary edema, and by redistributing blood flow from true shunt to ventilated areas.

Administration, Inhalation↗