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Biomedical subjects

J Roberts

Publications and source records attributed to J Roberts.

At least 469 records · Page 26Linked to original sources
PubMed1988

Effects of dietary-fish-oil feeding on muscle growth and damage in the rat.

1. Giving diets containing 100 g fully-refined, non-hydrogenated fish oil/kg to rats caused substantial modification of skeletal-muscle-membrane fatty acid composition compared with control animals fed on an equivalent diet containing 100 g maize oil/kg. 2. Total muscle arachidonic acid (20:4 omega 6) was reduced from 138 (SD 25) mg/g total fatty acids to 15 (SD 2) mg/g and phospholipid arachidonic acid content showed equivalent changes. 3. Reduction in muscle arachidonic acid content had no influence on the growth of individual muscles. 4. Variation in muscle fatty acid composition exacerbated the response of muscle to calcium-induced damage assessed by efflux of intracellular creatine kinase (EC 2.7.3.2). 5. It is concluded that metabolites of arachidonic acid are unlikely to be primary controlling factors of muscle growth or specific mediators of muscle sarcolemmal damage leading to enzyme efflux.

Aging↗
PubMed1988

Metabolism of nephrotoxic isopropylcyclohexane in male Fischer 344 rats.

The metabolism of isopropylcyclohexane and associated renal pathology were evaluated in male Fischer 344 rats exposed by oral gavage. The rats experienced moderate proximal tubular damage similar to that produced by acyclic, branched-chain hydrocarbons. The urinary metabolites of isopropylcyclohexane included cis-4-isopropylcyclohexanol, trans-4-isopropylcyclohexanol, 2-cyclohexylpropanoic acid, 2-cyclohexyl-1,3-propanediol, 2t-hydroxy-4t-isopropylcyclohexanol, 2c-hydroxy-4c-isopropyl-cyclohexanol, and 2c-hydroxy-4t-isopropylcyclohexanol. The extent and preferred sites of oxidative metabolism of nephrotoxic hydrocarbons could potentially prove useful in elucidating the pathogenic mechanisms.

Administration, Oral↗
PubMed1988

Effects of age on neurotransmission at the cardiac sympathetic neuroeffector junction.

The effect of age on the capacity of the right cardiac sympathetic nerve to release norepinephrine (NE) into perfusion effluent (NE overflow) was studied in hearts isolated from male Fischer 344 rats at 6, 12 and 24 months of age. The hearts were perfused through an aortic cannula with Krebs-Ringer solution and the cardiac sympathetic nerve was stimulated electrically with supra-maximal voltage at frequencies of stimulation that produced 20%, 50% or 80% of maximal NE overflow at each age. The content of NE in the perfusion effluent was measured by electro-chemical detection after alumina extraction and high-performance liquid chromatography separation. The NE overflow was significantly lower in hearts of 12- and 24-month-old animals compared to hearts from 6-month-old animals at each frequency of stimulation. In addition the frequency of stimulation necessary to produce 50% or 80% of maximal NE overflow was significantly greater in heart preparations from both 12- and 24-month-old animals compared to preparations from 6-month-old animals. Perfusion with cocaine (10(-6) M) significantly increased the quantity of NE in the effluent after nerve stimulation only in hearts from 12- and 24-month-old animals. Nevertheless, NE overflow remained significantly lower than that observed in hearts of 6-month-old animals. The results suggest that the capacity of the cardiac sympathetic nerve to release NE is diminished in 12- and 24-month-old animals. Furthermore, in these age groups an increase in neuronal uptake appears to reduce further the quantity of NE made available to the heart. These changes seem to occur by middle age and persist to senescence.

Aging↗
PubMed1988

Characterization of the acute clinical illness associated with human immunodeficiency virus infection.

The clinical and serologic features and immune status of 39 homosexual men who had seroconversion to human immunodeficiency virus positivity were compared with 26 homosexual men who remained seronegative during a six-month period. An acute clinical illness occurred in 92.3% of seroconverted subjects and 40% of controls. The duration of illness was significantly greater in the seroconverters than the controls (10 + 4.4 days). A general practitioner was consulted by 87.2% of the seroconverters because of the illness, including 12.8% who were admitted to hospital, compared with 20% of controls. The most frequently reported symptoms in the seroconversion group were fever (76.9%); lethargy and malaise (66.7%); anorexia, sore throat, and myalgias (56.4% each); headaches and arthralgias (48.7% each); weight loss (46.2%); swollen glands (43.5%); retro-orbital pain (38.5%); and dehydration and nausea (30.8% each). Lymphadenopathy developed in 75% of seroconverters compared with 4% of controls. Changes in T-cell subsets were not found in controls, but the number of T4+ cells and the T4+/T8+ ratio decreased significantly in seroconverters.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Pharmacodynamic basis for altered drug action in the elderly.

The elderly have the highest incidence of medical and psychiatric disorders. These conditions frequently occur simultaneously and are often chronic, lasting the lifetime of the individual. Consequently, the elderly require more medications than do younger patients. Consumption of over-the-counter drugs is considerable among the aged. There is considerable evidence that the elderly patient in most cases responds differently to drugs than do young adults. Many factors contribute to these differences. Among them are reduced protein binding, reduced biotransformation, diminished renal elimination, changes in receptor density or affinity, or both, diminished receptor adaptability, changes in the coupling between receptors and effector systems, impairment of responding organs resulting from the pathologic state, reduction in the reactivity of homeostatic mechanisms, and the aging process itself. These components may have different weight, depending on the drug and the individual considered. Because of the physiologic age-related changes in the distribution and elimination of drugs and in the sensitivity to medications, adverse side effects develop frequently in the elderly. Accordingly, dosages and dosage intervals must be adjusted carefully. In addition, since the elderly often take multiple medications, they frequently experience ADRs. Psychotropic drugs are often involved in such interactions and cause twice the incidence of side effects in elderly patients as they do in younger patients. Drug-nutrient and drug-drug interactions, programs to enhance patient compliance, and sociogenic factors should be taken into account in any well-designed dose regimen for the elderly. Physician awareness of problems that exist in the elderly population's use of drugs is essential if rational drug therapy for the aged is to evolve. The proper use of drugs in the elderly largely depends on taking into account both the pharmacokinetic and the pharmacodynamic properties of the drug and how these parameters are altered with age; such information can be obtained only by investigating drug action in older people.

Aged↗
PubMed1988

Diagnostic accuracy of fever as a measure of postoperative pulmonary complications.

Various prevalence rates have been estimated for pulmonary complications after abdominal surgery, and fever has been thought to be a diagnostic indicator. This study quantifies the diagnostic accuracy of fever as a measure of postoperative pulmonary complications and includes the sensitivity, specificity, and positive and negative predictive values. Assessments using fever and chest x-ray film were determined for 270 patients after elective intra-abdominal surgery in three hospitals with six practicing surgeons in a Southern Ontario city. With use of reliable chest x-ray reports indicating lung pathologic findings as positive for pulmonary complication, the prevalence of a positive finding was 57%. The prevalence of a fever (temperature greater than or equal to 38 degrees C) was 40%. The sensitivity and negative predictive value of fever were slightly below 50%, and the specificity and positive predictive value of fever was 68% and 66% respectively. Fever was an accurate indicator of x-ray evidence of atelectasis in only 56% of the subjects. Therefore, neither the presence nor the absence of fever can assure clinicians of the presence or absence of a postoperative pathologic pulmonary complication such as atelectasis.

Abdomen↗
PubMed1987

Superoxide dismutase-like activities of copper(II) complexes tested in serum.

The superoxide dismutase-like activities of a series of coordination complexes of copper were evaluated and compared to the activities of bovine erythrocyte superoxide dismutase (superoxide: superoxide oxidoreductase, EC 1.15.1.1) in serum using the nitroblue tetrazolium chloride (NBT)-reduction assay and electron paramagnetic resonance (EPR) spectroscopy. A 40% inhibition was observed for the initial rate of the NBT reduction by superoxide dismutase in serum, but more than 40% inhibition was achieved with CuSO4, Cu(II)-dimethylglyoxime, Cu(II)-3,8-dimethyl-4,7-diazadeca-3,7-dienediamide, Cu2[N,N'-(2-(O-hydroxy-benzhydrylidene)amino)ethyl]2-1,2-ethane dia mine), Cu(II)-(diisopropylsalicylate)2, Cu(II)-(p-bromo-benzoate)2, Cu(II)-(nicotinate)2 and Cu(II)-(1,2-diamino-2-methylpropane)2. The electron paramagnetic resonance technique of spin trapping was used to detect the formation of superoxide (O2-.) and other free radicals in the xanthine-xanthine oxidase system under a variety of conditions. Addition of the spin trapping agent 5,5-dimethylpyrroline 1-oxide (DMPO) to the xanthine-xanthine oxidase system in fetal bovine serum produced the O2-.-spin adduct of DMPO (herein referred to as superoxide spin adduct, DMPO-OOH) as the well known short-lived nitroxyl whose characteristic EPR spectrum was recorded before its rapid decay to undetectable levels. The hydroxyl radical (HO.) adduct of the spin trap DMPO (herein referred to as DMPO-OH) was detected to a very small extent. When CuSO4, or the test complexes of copper, were added to the xanthine-xanthine oxidase system in serum containing the spin trap, the yield of DMPO-OOH was negligible. In addition to their superoxide dismutase-like activity, CuSO4 and the copper complexes also behaved as Fenton-type catalysts as seen by the accumulation of varying amounts of the hydroxyl spin adduct DMPO-OH. Both the Fenton-type catalysis and the superoxide dismutase-like action of these compounds were lost when a chelator such as EDTA was included in the xanthine-xanthine oxidase incubation mixture. Addition of superoxide dismutase instead of the copper compounds to this enzyme system abolished the formation of superoxide adduct DMPO-OOH, and no hydroxyl adduct DMPO-OH was detected. This effect of superoxide dismutase remained unaltered by EDTA.

Animals↗
PubMed1987

Transcutaneous oxygen monitoring and retinopathy of prematurity.

This study was performed to determine whether the use of continuous tcPO2 monitoring could reduce the incidence of ROP in preterm infants receiving oxygen therapy. Two hundred and ninety-six infants with birth weights less than or equal to 1300 grams were randomly assigned to a continuous monitoring (CM) or a standard care (SC) group. CM infants had tcPO2 monitored continuously as long as they required supplemental oxygen while SC infants had tcPO2 monitored only during the more acute state of their illness. Management of both groups was otherwise identical. One hundred and one of 148 infants in the CM and 113 of 148 patients in the SC groups survived. Mean birth weights and gestational age were similar in both groups. Duration of mechanical ventilation and oxygen therapy was also similar. The overall incidence of ROP was 51% in the CM and 59% in the SC group. As birth weight for infants greater than or equal to 1000 grams increased a higher risk for developing ROP was noted in the SC group. Four infants in the CM and 5 in the SC group developed cicatricial ROP. These results suggest that continuous tcPO2 monitoring may reduce the incidence of ROP in infants with birth weights greater than 1000 grams, but not in the smaller infants in whom this complication occurs more frequently and is more severe.

Birth Weight↗
PubMed1987

Erythrocyte biochemistry of the grey-headed fruit bat (Pteropus poliocephalus).

1. Several haematological and biochemical parameters were measured in the erythrocytes of the grey-headed fruit bat. 2. The level of 2,3-diphosphoglycerate was almost twice that found in human erythrocytes. Similarly pyruvate kinase activity was more than twice that of man. 3. The activities of other enzymes of the glycolytic pathway were similar to those found in man. 4. The level of reduced glutathione (GSH) and the GSH regeneration rate in the erythrocytes of the bat were comparable to those found in man.

2,3-Diphosphoglycerate↗
PubMed1987

The metabolism of t-butylcyclohexane in Fischer-344 male rats with hyaline droplet nephropathy.

The molecule t-butylcyclohexane is one of the first examples of a branched alkyl group attached to a hydrocarbon ring shown to be capable of producing renal damage at the corticomedullary junction of male rats. A metabolic study of t-butylcyclohexane yielded the following urinary metabolites: trans-4-t-butylcyclohexanol, 2c-hydroxy-4t-t-butylcyclohexanol, 2-methyl-2-cyclohexylpropanoic acid, 2c-hydroxy-4c-t-butylcyclohexanol, 2-methyl-2-cyclohexyl-1,3-propanediol, 2t-hydroxy-4t-t-butylcyclohexanol, and cis -4-t-butylcyclohexanol. As with other hydrocarbons of similar molecular weight that induce nephropathy in male rats, preferential sites of oxidative metabolism were observed that could potentially be related to the pathogenesis.

Animals↗
PubMed1987

Retinopathy of prematurity. A randomized, prospective trial of transcutaneous oxygen monitoring.

To determine whether the use of continuous transcutaneous oxygen monitoring (tcPO2) could reduce the incidence of retinopathy of prematurity (ROP) in pre-term infants receiving oxygen therapy, a randomized, prospective trial of constant monitoring using the transcutaneous oxygen monitor versus intermittent monitoring of oxygen was performed on a population of premature infants at very high risk for the development of ROP. Two hundred ninety-six infants were randomly assigned to either a constantly monitored (CM) or standard care (SC) group. CM infants had tcPO2 monitored continuously as long as they required supplemental oxygen, whereas SC infants had tcPO2 monitored only during the more acute state of their illness. Management of both groups was otherwise identical. One hundred one of 148 infants in the CM group and 113 of 148 in the SC group survived. The overall incidence of ROP was 51% in the CM group and 59% in the SC group (no significant difference). In infants over 1000 g birthweight, as the weight increased there was increasing risk of developing ROP in the SC group. The odds ratio for the ROPsc:ROPcm reached 7.6 in infants between 1200 and 1300 g in infants with Apgar scores greater than or equal to 8 at 5 minutes. The incidence of cicatricial ROP was similar in both groups: four in the CM and five in the SC group.

Blood Gas Monitoring, Transcutaneous↗
PubMed1987

Organophosphate poisoning.

Organophosphate insecticides have become increasingly popular for agricultural, industrial, and home use and represent a significant potential health risk. We have reviewed the history, pathophysiology, clinical presentation, laboratory findings, differential diagnosis, therapy, and complications of toxic exposure to organophosphates. Promp recognition and aggressive treatment of acute intoxication are essential in order to minimize the morbidity and mortality from these potentially lethal compounds.

Diagnosis, Differential↗