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Biomedical subjects

R A Lawrence

Publications and source records attributed to R A Lawrence.

At least 109 records · Page 6Linked to original sources
PubMed1988

Glutathione concentrations in rat lung bronchoalveolar lavage fluid: effects of hyperoxia.

Glutathione concentrations were measured in rat bronchoalveolar lavage fluid (BALF) obtained from normal rats and rats exposed to a fraction of inspired oxygen (FiO2) of 0.8 for up to 5 days. We also perturbed rat lung glutathione concentrations by administering the compound diisopropylidene acetone (phorone) to a separate group of animals and correlated changes in BALF glutathione with changes in lung tissue glutathione. We found that reduced glutathione is present in normal rat BALF but glutathione disulfide is extremely low. Increases in lung tissue glutathione concentration and in BALF glutathione concentration occurred after 5 days of exposure to hyperoxia. Animals treated with phorone exhibited decreases in lung glutathione concentration two hours after dosing and increases in lung glutathione concentration 24 hours after dosing. Rat BALF obtained from phorone-treated animals at 2 or 24 hours after administration revealed that changes in BALF glutathione concentrations reflected changes in lung tissue glutathione concentration. The presence of glutathione in lung lavage fluid suggests that the compound could be playing an extracellular role in the lung, either as an antioxidant or as a coenzyme for other glutathione-related enzymatic reactions.

Animals↗
PubMed1987

Rat lung glutathione release: response to oxidative stress and selenium deficiency.

We performed experiments to characterize the glutathione-dependent metabolism occurring during tert-butyl hydroperoxide infusion in isolated perfused rat lungs and to examine the effect of selenium deficiency on this metabolism. Selenium deficiency resulted in decreased lung glutathione peroxidase activity but normal glutathione reductase activity and glutathione content. Infusion of the hydroperoxide into control lungs caused a proportional increase in tissue glutathione disulfide (GSSG) concentration and release of GSSG into the perfusate up to an infusion rate of 250 nmol of tert-butyl hydroperoxide X min-1 X 100 g body wt-1. Infusion rates greater than this resulted in continued rise of tissue GSSG concentrations but GSSG release into the perfusate plateaued. Infusion of tert-butyl hydroperoxide into selenium-deficient rat lungs resulted in much lower concentrations of tissue GSSG and GSSG release into the perfusate; however, release in the selenium-deficient rat lung was also found to be saturable at infusion rates of 450 nmol of tert-butyl hydroperoxide X min-1 X 100 g of body wt-1. Selenium deficiency in the rat decreases the rate of reduction of infused tert-butyl hydroperoxide by glutathione and may predispose the lung to free radical damage.

Animals↗
PubMed1987

Maternal disease as a consideration in lactation management.

Breastfeeding for mothers with chronic medical conditions presents important medical decisions for the primary physician. The issues need to be considered in light of the chronic disease, the physiological process of lactation, and the individual Mother for whom breastfeeding is very important. Management plans need to be based on adequate information and coordinated by the mother's physician and the pediatrician.

Breast Feeding↗
PubMed1987

Effects of copper deficiency on carbon tetrachloride-induced lipid peroxidation.

To investigate the hypothesis that copper deficiency in the rat could result in increased susceptibility to CCl4-induced lipid peroxidation caused by decreased free radical defenses, we performed a series of experiments administering CCl4 to copper-deficient and control rats. Peroxidation after CCl4 administration was monitored by measuring the evolution of expired ethane in closed metabolic chambers. Rats were fed one of two copper-deficient diets based on either evaporated milk or powdered milk. Compared with control values, liver copper content, liver superoxide dismutase activity, and plasma ceruloplasmin level were significantly decreased in copper-deficient rats fed either of the diets. Liver glutathione peroxidase activity was also decreased in the copper-deficient rats fed the evaporated milk diet. Ethane evolution was markedly increased in both copper-deficient groups as compared with their controls. Copper deficiency was also found to produce increases in hepatic iron concentrations, but normal rats loaded with iron dextran to increase hepatic iron concentrations into a range similar to that found in the copper-deficient rats did not exhibit increased ethane evolution after CCl4 administration. Copper deficiency in the rat results in increased CCl4-induced lipid peroxidation.

Animals↗
PubMed1987

The management of lactation as a physiologic process.

Lactation is the physiologic completion of the reproductive cycle. The breast is ready to provide complete nourishment for the newborn and the normal infant has all the necessary reflexes. Mother, however, must learn to adopt her actions to complement the physiologic process for successful milk production.

Breast↗
PubMed1986

Cultural values and biomedical knowledge: choices in infant feeding. Analysis of a survey.

This paper presents a study of 313 parturient women and considers their choices to bottle or breast feed. It examines demographic and cultural factors statistically and focuses on the effect of knowledge or ignorance of benefits of either method of infant feeding. Most women are found to have some biomedical knowledge of the benefits of breast feeding. The choice of bottle or breast feeding is closely associated with several demographic factors and a number of cultural ideas. Women who bottle feed see some of their dietary and other health related practices as barriers to breast feeding. It recommends that health practitioners who decide that individual women and/or their infants may benefit from breast feeding, should engage in a dialogue with the women. Such a dialogue should focus, not so much on information, but on the woman's views about her dietary and other health practices. If the woman is given compelling health reasons she may see herself as capable of changing some practices long enough to breast feed.

Adolescent↗
PubMed1986

Effects of bacterial endotoxin on protecting copper-deficient rats from hyperoxia.

The administration of very low doses of bacterial endotoxin protects rats during exposure to hyperoxia and is associated with the induction of lung antioxidant enzyme activities. Copper-deficient rats have increased susceptibility to O2 toxicity, which may be related to their decreased lung superoxide dismutase activity (SOD) or decreased plasma ceruloplasmin concentrations. To determine whether endotoxin can protect against hyperoxia in this susceptible model, we exposed copper-deficient and control rats to a fractional inspiratory concentration of O2 greater than 0.95 for 96 h after pretreatment with 500 micrograms/kg of bacterial endotoxin or phosphate-buffered saline (PBS). Mortality in the copper-deficient and control rats given PBS and exposed to O2 for 96 h was 100%. Copper-deficient rats died significantly earlier during the exposure than controls. No mortality occurred in either group treated with endotoxin and hyperoxia despite the decreased activity of copper-dependent enzymes in the copper-deficient rats. Copper-deficient rats treated with endotoxin and exposed to hyperoxia did increase lung Cu-Zn-SOD activity, but activity remained below levels found in air-exposed controls. Mn-SOD activity was found to be induced above air-exposed controls in the copper-deficient rats treated with endotoxin and exposed to hyperoxia. Hyperoxic exposure resulted in a marked increase in plasma ceruloplasmin concentrations in the control rats, but no increases in ceruloplasmin occurred in the copper-deficient animals. Endotoxin protects copper-deficient rats from hyperoxia despite their decreased lung Cu-Zn-SOD activity, and decreased plasma ceruloplasmin.

Animals↗
PubMed1986

Interactions of adolescent mothers and their 1-year-old children.

It is unclear why the school-aged children of adolescent mothers have more cognitive and behavioral problems than those of adult mothers. To clarify why these children have problems and when during their lives they develop, the relationship between adolescent maternal age and the nature of the behavioral interaction between mothers and their children was studied in the laboratory. Thirty lower socioeconomic status mothers who were 15.5 years to 20 years of age and their 9- to 12-month-old children were videotaped for 20 minutes. Rating scales were developed to score the videotapes. There were significant correlations indicating that younger mothers tended to show less acceptance (r = .63; P less than .001), less cooperation (r = .57; P less than .001), less accessibility (r = .51; P less than .003), less sensitivity (r = .46; P less than .006), and more negative verbal communication (r = .32; P less than .047) than older adolescent mothers. Younger maternal age was also associated with more overall negative interaction between mother and child (r = .35; P less than .032) and with less child-initiated social contact with the mother (r = .32; P less than .050). We conclude that over the relatively narrow age range younger adolescent maternal age is related to less favorable mothering behaviors in the laboratory when the children are 9 to 12 months of age.

Adolescent↗
PubMed1984

A pocket calculator program for Duncan's New Multiple Range Test and analysis of variance.

A program for the TI-59 calculator to be used in analysis of variance and testing of significance of differences between each mean and every other mean by Duncan's New Multiple Range Test is presented. The test is both simple and powerful for data involving more than two treatment groups in a completely random design. Up to six groups with any number of replicates may be analyzed with this program.

Analysis of Variance↗
PubMed1984

Enhanced pulmonary toxicity in copper-deficient rats exposed to hyperoxia.

The antioxidant enzyme superoxide dismutase (SOD) found in the cytosol of eucaryotic cells and the plasma protein ceruloplasmin are copper containing proteins though to be important in providing protection from oxygen toxicity. To investigate the hypothesis that copper deficiency in the rat could result in decreased lung SOD activity and plasma ceruloplasmin concentration resulting in increased susceptibility to O2 lung damage, we performed a series of experiments exposing copper-deficient and control rats to normobaric and hyperbaric hyperoxia. Lung SOD activity in the copper-deficient rats was found to be 56% of control and ceruloplasmin content was 6% of control. The copper-deficient rats exhibited increased mortality and enhanced pulmonary toxicity as evidenced by increased pathologic damage and lung edema during the normobaric exposure to 85% O2. Copper-deficient animals also showed increased susceptibility to a hyperbaric exposure of 4 ata of 100% O2 with a decreased time of survival. The copper-deficient rat represents a new model for the study of oxidant injury.

Animals↗
PubMed1984

Glutathione peroxidase, superoxide dismutase, and glutathione S-transferase activities in human lung.

Glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and glutathione S-transferase activities were measured in lung tissue obtained from 7 patients receiving resectional surgery because of localized lung tumors. Human-lung-soluble fractions were also fractionated on Sephadex G-150-S columns, and GSH-Px activity was measured using hydrogen peroxide and cumene hydroperoxide as substrates to investigate the presence of non-selenium-dependent GSH-Px activity. The amount of SOD activity was found to be similar to the amount of activity present in rat lung. Glutathione S-transferase activity was 3 times greater in human lung than that in rat lung. Selenium-dependent GSH-Px activity was much lower in human lung than that in rat lung (less than 30%), and no evidence of non-selenium-dependent glutathione peroxidase activity was found in human lung using gel filtration techniques. We conclude that human lung differs from rat lung in some antioxidant enzymatic defense mechanisms, and that selenium deficiency could result in marked decreases in the ability of human lung to detoxify organic hydroperoxides.

Animals↗
PubMed1984

Endotoxin protects selenium-deficient rats from hyperoxia.

Rats treated with low doses of bacterial endotoxin have been shown to be protected from oxygen poisoning under normobaric conditions. Induction of lung activity of the antioxidant enzymes glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) has been reported to occur with endotoxin administration. GSH-Px is a selenoenzyme and selenium-deficient rats have decreased lung GSH-Px activity and enhanced lung toxicity during a hyperoxic exposure. To determine whether bacterial endotoxin administration can provide protection for animals with decreased antioxidant defenses, selenium-deficient and control rats received daily intraperitoneal injections of 250 micrograms/kg bacterial endotoxin or phosphate-buffered saline (PBS) during normobaric exposure to greater than 95% O2. Both groups of animals were protected from hyperoxia by bacterial endotoxin administration despite the extremely low lung GSH-Px activity in the selenium-deficient rats. GSH-Px, SOD, or CAT activities were not induced in the selenium-deficient rats by 48 hr (the time when the selenium-deficient rats treated with PBS began to die). In the selenium-deficient rat, mechanisms other than enzyme induction appear to be providing early protection from hyperoxia.

Animals↗
PubMed1984

Adolescent mothers and their infants.

It is unclear why children of adolescent mothers experience more developmental problems than children of adult mothers. There has been minimal systematic investigation of whether there is a relationship between the young age of the mother and her mothering behaviors. Our data fail to demonstrate any relationship between adolescent maternal age and the counts of maternal behaviors three days following birth. Seventy-five normal primiparous mothers less than 20 years old were videotaped with their normal infants for ten minutes in a standardized laboratory setting during the three days following birth. The frequency of maternal behaviors was counted from the videotapes by trained observers. Future studies of primiparous adolescent mothers should consider the effects of maternal race/culture and socioeconomic status on their mothering behaviors. The relationship between adolescent maternal age and the vocalizations expressed by the mother to her infant should also be explored further.

Adolescent↗
PubMed1984

Esophageal function after repair of esophageal atresia.

The results of this study demonstrate that there is abnormal esophageal function in patients who have undergone repair of esophageal atresia. The diagnostic tests used may be too sensitive as the abnormalities demonstrated have little clinical relevance. In addition, there was an inverse relationship between signs and symptoms of esophageal dysfunction and the age of the child. The abnormalities are probably intrinsic and only secondarily affected by surgical treatment. Increased tension at the gastroesophageal junction is a likely factor in the production of gastroesophageal reflux. Esophageal dysfunction does not necessarily lead to detrimental gastroesophageal reflux with the sequela of repeated respiratory infections, failure to gain weight or esophageal stricture. Only patients who have such signs or symptoms need to undergo evaluation of esophageal function to determine if there is an abnormality. The results of the studies then document the need for an antireflux procedure.

Child↗
PubMed1983

Non-selenium-dependent glutathione peroxidase activity in rat lung: association with lung glutathione S-transferase activity and the effects of hyperoxia.

To determine if non-selenium-dependent glutathione peroxidase (Non-Se GSH-Px) activity is present in rat lung, we fractionated rat lung soluble fractions from rats fed a selenium-deficient or control diet and measured glutathione peroxidase activity with both cumene hydroperoxide and hydrogen peroxide as substrates. We also measured glutathione S-transferase (GSH S-transferase) activity in the fractions with 1-chloro-2,4-dinitrobenzene as substrate. Non-Se GSH-Px activity was present (about 34% of total GSH-Px activity), and the peak present in the gel filtration chromatogram coeluted with the GSH S-transferase peak. We then measured GSH S-transferase activity in lung-soluble fractions from rats exposed to room air or 85% O2 for 5 days. Lung GSH S-transferase activity was increased in the oxygen-exposed animals when compared to the air-exposed controls. The increase in GSH S-transferase activity could represent the induction of lung non-Se GSH-Px activity.

Animals↗