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Biomedical subjects

J S McDonald

Publications and source records attributed to J S McDonald.

At least 19 recordsLinked to original sources
PubMed1992

Frequency of reisolation of Staphylococcus aureus from multiple sequential milk samples.

Bacterial cultures were performed on multiple sequential composite samples of milk from 1,172 cows in 9 dairy herds. If the initial diagnosis of Staphylococcus aureus infection was based on the first positive culture, an average of 37.8% of subsequent cultures on the same cows were negative for S aureus. However, if the initial diagnosis of S aureus infection was confirmed by 2 or 2 of 3 sequential positive cultures and any conversions from S aureus positive to negative were confirmed by 2 or 2 of 3 sequential negative cultures, then only 17.0% converted to a negative diagnosis. Conversion of cows from S aureus culture-positive to -negative varied between herds; 8.1 to 69% for single cultures and 0.0 to greater than 40% for confirmed cultures.

Animals↗
PubMed1992

Cell swelling, blebbing, and death are dependent on ATP depletion and independent of calcium during chemical hypoxia in a glial cell line (ROC-1).

The morphological and biochemical changes that occur during chemical hypoxic injury in a neural cell line were studied in the presence and absence of calcium. Oligodendroglial-glioma hybrid cells (ROC-1) were subjected to inhibitors of glycolytic and oxidative ATP synthesis (chemical hypoxia). Complete respiratory inhibition depleted [ATP] to less than 5% of control by 4 min. Blebs appeared on the cell surfaces and cells began to swell within a few minutes of ATP depletion. A 200% increase in cell volume and bleb coalescence preceded irreversible cell injury (lactate dehydrogenase release) which began at approximately 20 min with 50% cell death by 40 min. In energized cells an equivalent degree of osmotic swelling induced by ouabain inhibition of the Na+, K(+)-ATPase pump did not produce blebbing or cell death. Partial inhibition of respiration decreased [ATP] to approximately 10% of control by 40 min. Blebbing and swelling began at 40 min and bleb coalescence preceded plasma membrane disruption which began at approximately 55 min. ATP depletion, blebbing, swelling, and death followed similar time courses in the presence or absence of extracellular calcium ([Ca2+]e). Intracellular calcium ([Ca2+]i) was measured using fura-2. In calcium-containing medium metabolic inhibition caused a transient increase in resting [Ca2+]i (100 +/- 17 nM) followed by a low steady-state level preceding plasma membrane disruption. Following deenergization in calcium-free medium, [Ca2+]i remained below 60 nM throughout injury and death. These data suggest that decreased ATP initiates a sequence of events including bleb formation and cell swelling that lead to irreversible cell injury in the absence of large increases in [Ca2+]i.

Adenosine Triphosphate↗
PubMed1992

Role of spinal opioid receptors in the antinociceptive interactions between intrathecal morphine and bupivacaine.

In studies on the clinical management of pain, a combination of morphine and bupivacaine is more effective than either of them alone in producing analgesia. The present study was designed to examine the effect of bupivacaine on morphine-induced antinociception as measured by the tail-flick test in the rat. To understand the basis of this interaction, the effect of bupivacaine on the binding of opioid ligands to their spinal opioid receptors in the rat also was investigated. Intrathecal administration of 5, 20, or 50 micrograms bupivacaine significantly potentiated the antinociception produced by intrathecal administration of 10 micrograms morphine. There was more than a 10-fold increase in the area under the curve (AUC0-60 min) for morphine-induced antinociception in the presence of bupivacaine. At higher doses of morphine (20 micrograms), bupivacaine was not very effective, increased AUC0-60 min for antinociception by only about 25%, and in fact significantly decreased the total duration of morphine-induced antinociception. Radioreceptor assays done with rat spinal cord membrane preparations revealed that bupivacaine (0.1-10 nM) inhibited the binding of specific ligands to mu-receptors but increased the binding to delta- and kappa-receptors. The authors conclude that the facilitation of morphine-induced antinociception by bupivacaine may be associated with a conformational change in the spinal opioid receptors induced by bupivacaine. Although increasing the binding of morphine to kappa-opioid receptors is the most prominent effect, the binding of opioid ligands to all spinal receptors is inhibited at high doses of bupivacaine.

Analgesics↗
PubMed1991

Evaluating the human engineering of microprocessor-controlled operating room devices.

Although human engineering features are widely appreciated as a potential cause of operating room incidents, evaluating the human engineering features of devices is not widely understood. Standards, guidelines, laboratory and field testing, and engineering discipline are all proposed methods for improving the human engineering of devices. New microprocessor technology offers designers great flexibility in the design of devices, but this flexibility is often coupled with complexity and more elaborate user interaction. Guidelines and standards usually do not capture these features of new equipment, in part because technology improvements occur faster than meaningful guidelines can be developed. Professional human engineering of new devices relies on a broad, user-centered approach to design and evaluation. Used in the framework of current knowledge about human operator performance, these techniques offer guidance to new equipment designers and to purchasers and users of these devices.

Anesthesiology↗
PubMed1991

Modulation of mu, kappa and delta opioid receptors in the rat brain by isoflurane and enflurane.

This study was done to investigate whether inhalational anesthetics modulated the binding of specific ligands to opioid receptors in the brain of the rat. The effect of isoflurane and enflurane on the binding of specific ligands to various subtypes of opioid receptors in vitro was studied. Isoflurane inhibited the binding of [3H]naloxone to opioid receptors by 50% in the spinal cord, midbrain and cortex at 22, 49 and 50 mM, respectively. Enflurane was more potent than isoflurane in inhibiting the binding of [3H]naloxone. Scatchard analysis of the binding of [3H]naloxone, done in the presence of therapeutic level (5 mM) of isoflurane, suggested that it did not affect the KD (1.3 nM) but decreased the Bmax by 41% in the cortex. Isoflurane and enflurane, at large doses (30-50 mM), inhibited the binding of [3H]ethylketo-cyclazocine (EKC) to kappa receptors in midbrain, cortex and spinal cord. At a smaller dose (5 mM), they increased the binding of EKC in spinal cord. The binding of the analogs of enkephalin [3H]DSTLE(Tyr-D-Ser-Gly-Phe-Leu-Thr-enkephalin) to delta receptors and [3H]DAGO (Tyr-D-Ala-Gly-Methyl-Phe-Glyol-enkephalin) to mu receptors in the midbrain and cortex was inhibited by isoflurane at a significantly smaller concentration than the binding of [3H]naloxone, indicating that the binding of peptides was more susceptible to the inhibition by inhalational anesthetics than the binding of alkaloids, such as naloxone or EKC. These results suggest that the modulation of opioid receptors by inhalational anesthetics is a function of both the nature of the ligand and the tissue used for the receptor binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗
PubMed1991

Differential effects of intrathecal midazolam on morphine-induced antinociception in the rat: role of spinal opioid receptors.

The antinociceptive effects of an intrathecally administered benzodiazepine agonist midazolam, alone and in combination with morphine, were examined in the rat by using the tail-flick test. The duration of antinociceptive effect produced by midazolam was significantly less (P less than 0.05) than that produced by morphine. Low doses of midazolam (10 micrograms) and morphine (10 micrograms) produced a synergistic effect in prolonging antinociceptive effect. However, at higher doses (20 or 30 micrograms), these drugs reduced the extent of antinociception produced by each other. Naloxone administration prevented antinociception produced by these drugs, indicating interactions between midazolam and opioid receptors. Midazolam had dual effects on the binding of opioid ligands to the spinal opioid receptors. At low dose, it potentiated the displacement of [3H]naloxone by morphine. At higher doses, midazolam inhibited the binding of opioid ligands to their spinal receptors in the following order: kappa greater than delta greater than mu. These results indicate that differential antinociceptive effects of midazolam on morphine-induced antinociception involve interaction of this benzodiazepine with spinal opioid receptors.

Animals↗
PubMed1991

Performance of residents in anesthesiology as related to measures of personality and interests.

79 male and 16 female residents in anesthesiology at six training centers took the California Psychological Inventory (CPI) and Strong Interest Inventory (SII) in Year 1 and were rated for performance two years later. Descriptively, the total sample scored highest on CPI scales for Dominance, Social Presence, and Achievement via Independence, and on SII scales for investigative, mathematical, and medical science interests. Scores from a four-scale CPI cluster of Empathy. Socialization, Achievement via Conformance, and Achievement via Independence correlated .39 with ratings for men and .31 with ratings for women. In another sample of 20 residents, the cluster score correlated .30 with ratings gathered three years after testing. These findings, consonant with prior research, suggest that attributes such as empathy, strong internalization of pronormative values, and the ability to work well within either structured or open settings are conducive to superior performance in the specialty.

Achievement↗
PubMed1990

A second time-study of the anaesthetist's intraoperative period.

This second time-study of the anaesthetist's intraoperative period was conducted at The Ohio State University Hospitals. The study involved a total of 30 anaesthetic procedures. The activities of the anaesthetists were videotaped and analysed independently by three reviewers. Unlike our previous study, the present study was performed at a time when automatic noninvasive arterial pressure monitors, automatic ventilators and patient breathing circuit disconnect alarms were in use. The greatest amount of intraoperative time of the anaesthetist (59.1%) was spent monitoring the patient directly (44.8%) or indirectly (14.3%) via patient monitors. This represented an increase from our previous study attributable to the increased use of technology in the operating room. The anaesthetist still spent about 10-12% of his/her time completing patient records.

Anesthesia↗
PubMed1990

Performance studies of an enzyme-linked immunosorbent assay for detecting Staphylococcus aureus antibody in bovine milk.

An enzyme-linked immunosorbent assay (ELISA) for detecting Staphylococcus aureus antibody in bovine milk samples was examined for repeatability. A set of 51 bovine milk samples from 4 universities with confirmed culture results was assembled, and a panel of 30 milk samples was randomly selected. When the selected panel was tested at the collection laboratory, there was 97% agreement between the ELISA and the culture test. The panel was tested with the ELISA by the 4 university laboratories. Results were scored by both visual and optical density reader methods. When compared to reference ELISA results, the university laboratory ELISA results showed an agreement of 99.8% for negative samples, 98% for positive samples, and 99% for all samples. Additional studies on 19 milk samples that cultured positive for bacteria other than S. aureus showed 100% specificity. Overall comparison of ELISA and culture results showed high agreement between the 2 techniques. Disagreement appeared to result from explainable differences in antibody and bacterial levels and not from errors in either of the 2 techniques.

Animals↗
PubMed1990

Thoughts on the management of chronic facial, head, and neck pain.

As previously stated in this paper, the therapeutic goal in the management of patients with chronic pain conditions in the face, head and neck is management and rehabilitation, striving for a 50 percent decrease in pain, a 50 percent increase in function and mobility, and a 50 percent decrease in medication with the elimination of agents with an addicting potential. These results will best be obtained through proper diagnosis and utilization of the aforementioned techniques in an interdisciplinary fashion as has been described.

Analgesics↗
PubMed1989

Pretreatment with paracetamol inhibits metabolism of enflurane in rats.

We studied the interaction between paracetamol (acetaminophen U.S.P.) and enflurane. Sixteen rats were assigned to four groups (n = 4) to receive: paracetamol 7.5 mg/100 g body weight; paracetamol plus 1% enflurane; 1% enflurane alone, or no treatment (controls). Animals were killed 6 h later. A second series of 16 were treated identically, but were killed after 24 h. Measurements were made of fluoride concentrations in serum, liver and urine (indicators of biotransformation of enflurane), paracetamol concentrations in urine, pathological changes in liver samples, and concentrations of the enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum. Pretreatment with paracetamol significantly decreased urinary fluoride at 6 and 24 h after exposure to enflurane, but decreased fluoride concentrations in serum and liver only at 6 h after exposure to enflurane. Paracetamol concentrations in urine did not change after exposure to enflurane. Exposure to paracetamol alone increased AST and ALT. At 24 h after exposure to enflurane, serum concentrations of enzymes in rats pretreated with paracetamol were similar to those of control rats. Pretreatment with paracetamol may therefore inhibit metabolism of enflurane. Although no hepatic damage was observed, the increased in AST and ALT suggested subclinical liver damage in rats given only paracetamol.

Acetaminophen↗
PubMed1989

Differences between handwritten and automatic blood pressure records.

Comparison of 46 handwritten and electromechanically generated blood pressure records revealed substantial differences between the recordings. The highest automated record pressures exceeded the highest pressures found in corresponding handwritten records. Similarly, the lowest pressures from automated records were lower than those from handwritten records. Seventeen records (37%) had at least three automatic blood pressure determinations with values substantially in excess of the most extreme values recorded by hand. No handwritten record contained a diastolic pressure above 110 mmHg. Discrepancies between handwritten and automatic records may arise from one or more causes. Among these are readings captured automatically but not observed by the anesthesiologist, faulty reconstruction of handwritten records from memory, and bias in favor of less controversial values.

Adult↗
PubMed1989

A comparison of enflurane with alfentanil anaesthesia for gynaecological surgery.

Forty patients undergoing gynaecological surgery were randomly assigned to receive either alfentanil and thiopentone for induction of anaesthesia, followed by alfentanil-N2O/O2 (60%/40%) for maintenance of anaesthesia, or low-dose fentanyl and thiopentone, followed by enflurane-N2O/O2 (60%/40%). More patients given enflurane developed a tachycardia (P less than 0.03) and 20% decreases in systolic and diastolic blood pressure. Times to recovery were significantly shorter after alfentanil than after enflurane. Plasma concentrations of alfentanil during induction suggested that haemodynamic and catecholamine responses were either less than, or did not differ from, baseline levels when the plasma concentration of the drug exceeded 150 ng ml-1. At extubation and the beginning of spontaneous breathing, the plasma concentration was 278 +/- 129 ng ml-1. Values for pharmacokinetic parameters of alfentanil were as follows: clearance, 5.2 +/- 2.0 ml kg-1 min-1; volume of distribution, 0.63 +/- 0.20 1 kg-1; and elimination half-life, 96.9 +/- 52.5 min. Two patients who had extended surgery had significantly lower plasma clearance of alfentanil and increased half-life. The authors conclude that the alfentanil technique was preferable to maintenance with enflurane.

Adult↗