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Biomedical subjects

B H Johnson

Publications and source records attributed to B H Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1983

Community networking for improved services to children with chronic illnesses and their families.

The authors describe a program, developed under the auspices of the Association for the Care of Children's Health (ACCH), that focuses on community networking among children with chronic illnesses and their families. The program rests on two beliefs: (a) that a network can successfully focus on the generic needs of children with chronic or handicapping conditions and of their families; and (b) that a network can improve care by enhancing coordinating collaboration among existing services without creating new ones. Efforts of the past two years have centered on three specific areas: preparation and dissemination of written materials; creation of new links among families, health and education professionals, organizations, associations, and community institutions; and training in networking techniques. ACCH has prepared two pamphlets for families, schools, and health professionals on community issues and on hospitalization. In addition, a demonstration model for community networking has been established in the Houston/Galveston area. Finally, training programs in the skills of community networking have been established. Work is beginning to replicate the community networking model through other ACCH regional affiliates.

Child↗
PubMed1983

Influence of adrenocorticotropin upon milk production, milk constituents, and endocrine measures of dairy cows.

Ten lactating Holstein cows were injected intramuscularly with either 200 IU of adrenocorticotropin or saline every 6 h for 42 h. Blood concentrations of corticosteroids, glucose, sodium, and potassium, and milk yield and constituents were measured before, during, and after the injection period. Mean corticosteroid increased eightfold for adrenocorticotropin 1 h after first injection, remained significantly higher than controls during the injection period, and then decreased to preinjection concentrations 13 h after last injection. Mean milk yields were similar at 8 h after first injection, then decreased for adrenocorticotropin during the injection period. Increases in glucose concentrations accompanied suppression of milk yield for adrenocorticotropin. After injections glucose concentrations returned to preinjection concentrations at 13 h after last injection whereas milk yield for adrenocorticotropin remained suppressed for several milkings. Milk protein yields decreased for adrenocorticotropin during and after the injection period. Fat percentage for adrenocorticotropin increased though fat yield was unaffected. Concentrations of somatic cells in milk were unchanged by adrenocorticotropin treatment, but sodium was increased and potassium decreased during injection. Mammary gland function in lactating dairy cows may be affected adversely by exaggerated increases of concentrations of corticosteroids in blood.

Adrenal Cortex Hormones↗
PubMed1983

Influence of herd relocation upon production and endocrine traits of dairy cows.

Effects of potential stress encountered by two Holstein herds relocated into a new double-six herringbone parlor and free-stall facility were studied by evaluating alterations of milk yield and fat percentage, mastitis status, corticosteroids, and heat detection. One-half of one herd (18 cows) was moved 100 m to new facilities (Merged), and the remaining 18 cows were maintained in their original tie-stall barn (Control). The same day, the second herd of 50 cows (Moved) was transported via stock trailer 7 km to new facilities. Milk yield by Merged and Moved cows was decreased at first milking, but subsequent milk yields were similar to yields prerelocation. Milk fat percentage was decreased for only 3 days for Moved cows but was unchanged for Merged cows. Across groups, older cows and cows in late lactation tended to have greatest decreases in milk yield. Corticosteroids in serum were increased in Merged cows for only 2 days after relocation. No changes in milk somatic cell count or percentage heats detected were associated with relocation. Detrimental effects of herd relocation were slight and indicate that dairy herds can be moved without adversely affecting production traits.

Adrenal Cortex Hormones↗
PubMed1983

Effects of halothane, isoflurane, enflurane, thiopental, and fentanyl on blood gas values in rats exposed to hypoxia.

In rats pretreated with phenobarbital breathing 10% oxygen, subanesthetic doses of halothane, isoflurane, enflurane, thiopental, and fentanyl caused hepatic injury. Because hypoxia per se can produce such injury, we hypothesized that the anesthetic-induced injury resulted from increased hypoxemia secondary to respiratory depression. Male Sprague-Dawley rats were pretreated with phenobarbital; half of the rats were fed and the other half were deprived of food for the 24 h before study. Isoflurane anesthesia was given for the placement of a catheter into the femoral artery. After 1 h of recovery, the rats were exposed to 10% oxygen. Control samples were obtained and halothane, isoflurane, enflurane, thiopental, or fentanyl was administered. Rats given food had higher PaCO2 and lower pH values than starved rats. Also, arterial oxygen saturation (SaO2) tended to be lower in rats given food. At concentrations of 0.15-0.2 MAC or higher, halothane, isoflurane, and enflurane slightly increased PaCO2 values relative to values for a control group exposed only to hypoxia. However, SaO2 and PaO2 did not show significant drug-induced changes. Fentanyl transiently decreased PaO2 and SaO2. Thiopental caused no changes. Thus, we conclude that subanesthetic doses of anesthetics may depress the ventilatory response to hypoxia but that this depression is inconsistent and appears to be too small to cause hepatic damage.

Anesthetics↗
PubMed1983

Hepatic injury induced by anesthetic agents in rats.

Recent studies on rats pretreated with phenobarbital indicate that anesthetic agents may produce hepatic injury even when metabolism of the anesthetic is almost negligible. This implies that anesthesia per se may cause hepatic injury. To evaluate this possibility, we determined the amount of hepatic injury produced by halothane, enflurane, isoflurane, thiopental, and fentanyl in rats pretreated with phenobarbital. Anesthetics were administered in doses ranging from 0.04-1.1 MAC (or their equivalent for thiopental or fentanyl) and were given with 10% oxygen for 2 h. Liver specimens taken 24 h later were examined microscopically for hepatic injury. At concentrations of 5-40% of MAC, all anesthetics produced more hepatic injury than did control conditions (i.e., exposure to only 10% oxygen for 2 h). There were no systematic differences among agents, nor did starvation before anesthetic exposure produce a difference among agents. Therefore, mechanisms other than anesthetic metabolism are needed to explain hepatic injury produced by anesthetic agents.

Anesthetics↗
PubMed1983

Effect of oxygen concentration, hyperthermia, and choice of vendor on anesthetic-induced hepatic injury in rats.

Although hypoxic rats exposed to anesthetics may develop hepatic injury, divergent results have been obtained. These discrepancies might be due to different levels of hypoxia, hypothermia, or choice of vendor. Male Sprague-Dawley rats purchased from Zivic-Miller were pretreated with phenobarbital for 4 days. After 24 h without phenobarbital, they were exposed to 2 h of hypoxia and halothane, enflurane, isoflurane, thiopental, or fentanyl. Rectal temperature was kept between 36.5 degrees C and 38.5 degrees C. All agents given in 10% oxygen produced more hepatic injury than did control conditions (exposure to 10% oxygen alone) (P less than 0.01). Only halothane given in 12% and 14% oxygen produced hepatic injury. No agent given in 20% or 100% oxygen demonstrated hepatotoxicity. In a separate study, rectal temperatures were kept between 32 degrees C and 34 degrees C during 2 h of exposure to 0.3 MAC halothane, enflurane, or isoflurane in 10% oxygen. Hypothermia prevented hepatotoxicity by enflurane and isoflurane, but not by halothane. Finally, although livers of rats obtained from Zivic-Miller were injured, specific pathogen-free rats from Charles River were not injured or were less injured by enflurane, thiopental, or fentanyl. Apparently, minor changes in experimental conditions can substantially affect results; hepatic hypoxia per se, anesthetic metabolism (especially that of halothane), and perhaps anesthesia itself may produce hepatic injury.

Anesthetics↗
PubMed1983

MAC values of thiopental and fentanyl in rats.

A comparison of the effects of thiopental or fentanyl with those of inhaled anesthetics requires the establishment of a comparable level of anesthetic potency. Accordingly, using the response of male Sprague-Dawley rats to tail-clamping, we determined the ED50S for thiopental and fentanyl. Half of the rats were pretreated with phenobarbital. After subcutaneous injection of various doses of thiopental or fentanyl, each rat was tested for movement in response to tail-clamping at 15-min intervals for 2 h. In untreated rats, the maximal effect of thiopental (i.e., the lowest ED50 value was 107 +/- 10 mg/kg, mean +/- SEM) occurred 75 min after injection. Although higher values were found at other times, differences from the nadir were relatively small. In rats pretreated with phenobarbital, the lowest value (130 +/- 8 mg/kg) occurred at 60 min. The lowest ED50S for fentanyl (52 +/- 7 micrograms/kg for control rats, and 73 +/- 14 micrograms/kg for pretreated rats) were found at 15 min.

Anesthesia, Intravenous↗
PubMed1982

Suppression of luteinizing hormone and testosterone secretion in bulls following adrenocorticotropin hormone treatment.

The present investigation was conducted to evaluate the inhibitory effects of adrenal corticosteroids on testosterone production by the bull testis. Administration of a single i.v. dose of adrenocorticotropic hormone (ACTH; 80 IU) resulted in a corticosteroid peak which lasted approximately 6 h. During this 6 h period, no episodic increases in secretion of LH or testosterone were initiated and basal concentrations of testosterone were suppressed (P less than 0.05) below control values. Episodic secretion of LH and testosterone resumed 6--7 h after ACTH when concentrations of serum corticosteroids had returned to basal levels. These results suggest that ACTH-induced increases in serum corticosteroids suppress the episodic secretion of LH, resulting in a suppression of testosterone secretion by the bull testis.

Adrenal Cortex Hormones↗
PubMed1982

A noninvasive in vivo method of assessing the kinetics of halothane metabolism in humans.

The authors describe a noninvasive method of estimating the kinetic constants that characterize metabolism of inhaled anesthetics in humans. Ten healthy male volunteers breathed subanesthetic concentrations of halothane and isoflurane in a fixed inspired ratio of 20:1. Isoflurane served as a marker that identified changes in uptake in nonmetabolizing depots. Each study progressed through nine 30-min levels (numbered 0-8). At each level, inspired concentrations of both halothane and isoflurane were doubled, and alveolar concentrations and uptakes were determined. Clearance (uptake/alveolar concentration) of isoflurane remained constant over a range of concentrations of 0.00006 to 0.008%. In contrast, clearance of halothane decreased as the alveolar concentration increased from 0.0007 to 0.13%. On this basis, the authors assumed that the clearance of halothane was a combination of linear clearance to depots and saturable metabolism, the former proportional to the clearance of isoflurane, and the latter attributable to a Michaelis-Menten process. Applying such a model to halothane, they estimated the mean (+/- SE) Vmax (the composite maximum rate of metabolism) to be 0.79 +/- 0.09 ml . min-1 . individual-1, and the Km (the composite concentration at which half-saturation of enzymes occurs) to be 0.029 +/- 0.003%. This model provides a significantly better data fit than that provided by two simpler submodels, one of which assumes that all clearance is linear, and the other of which allows a part of clearance to be saturable but ignores the isoflurane marker data. The value of 0.029% for Km indicates that a wide range of clinical anesthetic concentrations will produce similar rates of metabolism; that metabolism will proceed at near maximum rates during the first several minutes of recovery; and that most metabolism probably occurs after, rather than during, anesthesia.

Adult↗
PubMed1982

Effect of feeding wet brewers grains to beef heifers on wintering performance, serum selenium and reproductive performance.

Wet brewers grains (WBG) were evaluated as a feed source for growing Angus heifers (201 kg, 313 d of age) during a 112-d wintering trial. Effects on growth, feed efficiency, serum Se and first breeding performance were examined. Three replications of four heifers each were fed the following diets: (1) corn silage with no protein supplement (CSNS); (2) corn silage plus 33.8% of the diet dry matter (DM) from WBG (CSWBG), and (3) WBG, corn and fescue hay at 62.2, 10.8 and 26.1% of diet DM, respectively (WBGCH). Average daily gains for heifers fed CSNS, CSWBG and WBGCH were .50, .73 and .56 kg/head (P less than .05), and DM:gain ratios were 9.52, 6.34 and 6.13 (P less than .05), respectively. Serum Se concentrations were higher (P less than .01) in heifers fed diets containing WBG than in heifers fed CSNS. Serum Se concentrations were also influenced by sampling time (P less than .01) and the diet x sampling time interaction (P less than .05). At the end of the trial, serum Se concentrations were .050, .085 and .105 ppm (P less than .01), respectively, for heifers on the three dietary treatments. Following a 66-d breeding period, 12 of 12 heifers fed CSNS and WBGCH diets and 10 of 12 heifers fed CSWBG were diagnosed pregnant and subsequently calved.

Animals↗
PubMed1982

Genetic parameters for testes size and sperm number in Hereford bulls.

Paternal half-sib heritability and genetic correlation estimates were obtained utilizing data from 578 Hereford bulls from 66 sires. Bulls were maintained in three lines (weaning weight, postweaning gain and control) of an ongoing selection project. Growth performance traits studied were adjusted 205-d weaning weight, 365-d weight, individual feed efficiency, sonoray fat thickness and postweaning gain. Heritability estimates for these traits were .15 +/- .17, .33 +/- .19, .46 +/- .21, .28 +/- .18 and .52 +/- .21, respectively. Scrotal measurements taken were circumference of both testes and length and diameter of right testis at 205 and 365 d of age. Heritability estimates were .08 +/- .20, .07 +/- .20 and .28 +/- .24 at 205 d, and .44 +/- .24, .16 +/- .21 and .40 +/- .24 at 365 d, respectively. Excised testes traits, circumference, right testis length, diameter and weight, total sperm in the testes and sperm/gram of testes had heritability estimates of .21 +/- .26, .19 +/- .26, .02 +/- .24, .63 +/- .27, .14 +/- .21 and -.13 +/- .18, respectively. Genetic correlations of scrotal measurements at 205 d with scrotal measurements at 365 d and excised testes traits were negative. Scrotal measurements at 365 d had high positive genetic correlations with excised testes size, weight and total sperm. These relationships suggest that selection for increase of scrotal size at 365 d should increase testes size and weight and sperm numbers. Genetic correlations of weights and gain with scrotal measurements at 365 d and excised testes characteristics were moderate to high, in a favorable direction. Genetic correlations of testes traits with feed efficiency were essentially zero, while those with fat thickness were moderately positive. These results suggest that increasing testes size should not adversely affect growth performance traits except through the reduction in selection intensity.

Animals↗
PubMed1982

Hypoxia per se can produce hepatic damage without death in rats.

To evaluate the importance of hypoxia itself on halothane-induced hepatic injury in the rat, the question of whether hypoxia could injure the liver without causing death was investigated. Male Sprague-Dawley rats pretreated with phenobarbital (1 mg/ml of drinking water, 4 days) and deprived of food for 24 hours were exposed to 6%, 7%, 8%, or 10% inspired oxygen with 0%, 5%, or 7.5% carbon dioxide for 2 hours. Several rats died when given 6% oxygen with 0% or 7.5% carbon dioxide, but all other rats survived. Without carbon dioxide, oxygen at a concentration of 7% or 8% produced more injury than did room air, and 6% oxygen produced the most severe damage. These results demonstrate that in rats hypoxia per se may be an important factor in causing hepatic damage.

Animals↗
PubMed1982

Hypoxia may be more important than reductive metabolism in halothane-induced hepatic injury.

To evaluate the relative importance of halothane metabolism and liver hypoxia in the occurrence of hepatic injury, the injury produced in hypoxic rats exposed to identical MAC hours of halothane but at various concentrations of halothane was compared. Groups of male Sprague-Dawley rats were pretreated with phenobarbital for 4 days, and 24 hours later they were exposed to 10 hours of 10% oxygen and concomitantly 0.2 MAC hours of halothane at the following anesthetic concentrations: 0.02% for 10 hours, 0.1% for 2 hours, 0.5% for 24 minutes, or 2.5% for 4.8 minutes. A control group received only 10% oxygen for 10 hours. Liver specimens taken 24 hours later demonstrated concentration-dependent damage; high concentrations given briefly produced more damage than lower concentrations given for long periods. As hepatic clearance of halothane by metabolism appears to be a saturable phenomenon, these results suggest that hypoxia per se may be more important than halothane metabolism in causing liver damage.

Animals↗
PubMed1982

Postanesthetic hepatic injury in rats: influence of alterations in hepatic blood flow, surgery, and anesthesia time.

Hepatic injury was measured in enzyme-induced rats following ligation of the hepatic artery performed under anesthesia with thiamylal, halothane, enflurane, or isoflurane. The influence of surgical site was determined by performing upper abdominal (sham ligation), lower abdominal, and peripheral surgery on rats anesthetized with halothane. The effect of anesthesia time was evaluated by continuing halothane anesthesia for 1, 2, or 4 hours after upper abdominal (sham ligation) surgery. Centrilobular necrosis did not occur in enzyme-induced rats anesthetized with thiamylal, isoflurane, or enflurane, or in halothane-anesthetized animals that had not undergone enzyme induction. When halothane was the anesthetic, hepatic injury was significant after both the sham operation and ligation of the hepatic artery, and hepatic injury was directly related to anesthesia time. Lower abdominal surgery and the sham operation were associated with comparable hepatic damage, which was more than that occurring after peripheral surgery.

Abdomen↗
PubMed1981

Minimum alveolar concentrations and oil/gas partition coefficients of four anesthetic isomers.

We determined the minimum alveolar concentration (MAC) of four structural isomers having the empirical formula C3H2F5CIO in dogs. MAC for three of the four isomers (including isoflurane and enflurane) ranged from 1.41 to 2.67 (volumes per cent at one atmosphere pressure). The olive oil/gas partition coefficients at 37 degrees C for these isomers ranged from 90.8 to 96.6. In contrast, MAC for the fourth isomer, compound 485, was 12.53 per cent atm. However, the oil/gas partition coefficient for that compound was 25.8. These results suggest that isomer 485, despite its high MAC, does not deviate strikingly from the established correlation between anesthetic potency and lipid solubility.

Anesthetics↗