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Biomedical subjects

M Herbert

Publications and source records attributed to M Herbert.

At least 19 recordsLinked to original sources
PubMed1995

Effect of amlodipine, atenolol and their combination on myocardial ischemia during treadmill exercise and ambulatory monitoring. Canadian Amlodipine/Atenolol in Silent Ischemia Study (CASIS) Investigators.

OBJECTIVES: This study compared the effects of amlodipine, atenolol and their combination on ischemia during treadmill testing and 48-h ambulatory monitoring. BACKGROUND: It is not known whether anti-ischemic drugs exert similar effects on ischemia during ambulatory monitoring and exercise treadmill testing. METHODS: Patients with stable coronary artery disease and ischemia during treadmill testing and ambulatory monitoring were randomized to receive amlodipine (n = 51) or atenolol (n = 49). Each group underwent a counterbalanced, crossover evaluation of single drug and placebo, followed by evaluation of the combination. RESULTS: Amlodipine and the combination prolonged exercise time to 0.1-mV ST segment depression by 29% and 34%, respectively (p < 0.001) versus 3% for atenolol (p = NS). During ambulatory monitoring, the frequency of ischemic episodes decreased by 28% with amlodipine (p = 0.083 [NS]), by 57% with atenolol (p < 0.001) and by 72% with the combination (p < 0.05 vs. both single drugs; p < 0.001 vs. placebo). Suppression of ischemia during exercise testing and ambulatory monitoring was similar in patients with and without exercise-induced angina. Exercise time to angina improved by 29% with amlodipine (p < 0.01), by 16% with atenolol (p < 0.05) and by 39% with the combination (p < 0.005 vs. placebo, atenolol and amlodipine). In patients with angina, total exercise time improved by 16% with amlodipine (p < 0.001), by 4% with atenolol (p = NS) and by 19% with the combination (p < 0.05 vs. placebo and either single drug). In those patients without angina, no therapy significantly improved total exercise time. CONCLUSIONS: Ischemia during treadmill testing was more effectively suppressed by amlodipine, whereas ischemia during ambulatory monitoring was more effectively suppressed by atenolol. The combination was more effective than either single drug in both settings.

Amlodipine↗
PubMed1995

Intradiscal pressure measurements above an instrumented fusion. A cadaveric study.

STUDY DESIGN: An in vitro study to determine the intradiscal pressure changes during flexion in levels above a simulated fusion was performed. OBJECTIVES: To determine if intradiscal pressure increases more during flexion in discs above an instrumented spinal segment compared to an uninstrumented segment. SUMMARY OF BACKGROUND DATA: The progressive degeneration of intervertebral discs adjacent to a fused or fixed segment is a phenomenon that is noted but poorly understood. Intuitively, the degeneration appears to be a function of altered biomechanics of the motion segments in the spine. METHODS: Two intervertebral disc levels were evaluated, L3-L4 and L4-L5 from each of six fresh frozen cadaver spines. Pressure measurements were taken with the spine uninstrumented, with bilateral pedicle screw-rod instrumentation from L5 to S1, and with bilateral pedicle screw-rod instrumentation from L4 to S1. Pressure measurements were accomplished with Millar Mikro-Tip pressure transducers. The transducers were placed within the nucleus pulposus of L3-L4 and L4-L5 intervertebral discs. Pressure data were recorded by computer data acquisition. The pressure data were compared by intervertebral level and by the effects of added instrumentation. RESULTS: In general, the addition of instrumentation significantly affected the intradiscal pressure in the levels above a simulated fusion. The intradiscal pressure increased as the amount of levels involved in the simulated fusion increased. The intradiscal pressure increased as flexion motion increased. A greater increase was seen at the L4-L5 level than the L3-L4 level. When L5-S1 fixation was added, the intradiscal pressure increased. When L4-S1 fixation was added, the intradiscal pressure further increased. CONCLUSION: This study demonstrated increasing intradiscal pressures during flexion.

Aged↗
PubMed1995

The fate of long-standing intraperitoneal gallstone in the rat.

Gallstones are occasionally spilled into the peritoneal cavity during open and laparoscopic cholecystectomy. Using the rat model, we investigated the long term effect of such retained intraperitoneal gallstones. During a follow-up period of one year, no systemic deleterious outcome could be attributed to the presence of the implanted gallstones except for mild local effects. Based on the rat model we conclude that reasonable effort should be made in order to retrieve an escaped gallstone, but there is no justification whatsoever for a conversion of the laparoscopic procedure to an open laparotomy only for the purpose of retrieving a lost stone.

Animals↗
PubMed1995

Mitotic activity during preimplantation development of human embryos.

The rate of cell division of human embryos in vitro was estimated throughout the preimplantation period. Seventy-five human embryos were assessed by performing nuclei counts on whole mount preparations at 24 h intervals between day 2 and day 6 of development. The results indicate that the cell doubling time increases after the first two division cycles. The mean (+/- SEM) doubling time between day 2 and day 6 was 31 +/- 2.51 h. At the end of the designated culture periods, embryos were exposed to a microtubule disrupting agent, which caused the nuclei to arrest in metaphase. Thus, a profile of the mitotic activity at given stages of development was obtained. The numbers of actively dividing cells were frequently lower than anticipated, indicating that nuclei counts cannot be directly correlated with continuing mitotic activity.

Blastocyst↗
PubMed1992

Upstream curved sequences influence the initiation of transcription at the Escherichia coli galactose operon.

The two overlapping promoters that control mRNA synthesis at the galactose operon contain three phased stretches of adenine residues, located around positions -84.5, -74 and -63, with respect ot the start of the P1 promoter. As a result, the corresponding DNA sequence is bent, an anomaly that is relieved by the addition of small concentrations of drugs like distamycin A or netropsin. By abortive initiation assays performed on several DNA fragments derived from the wild-type promoter or from various mutants we show that the curved sequence increases the strength of the P1 promoter. In the absence of cyclic AMP (cAMP) and of the corresponding receptor protein (CRP), the upstream curved sequences enhance the rate of isomerization from the closed to the open complex at P1. This effect is abolished when distamycin A is bound in the bent region. In the presence of cAMP-CRP, a more drastic change is observed: activation of the gal P1 promoter takes place at a different formal step, depending whether the upstream curved sequence is present or not (enhancement of the rate of conversion from a closed to an open complex instead of an increase in the affinity of the enzyme during closed complex formation). These data, together with previous results obtained with other mutants of the gal control region, suggest that several closed complexes corresponding to different nucleoprotein arrangements are formed during open complex formation at gal P1, in the presence of CRP.

Base Sequence↗
PubMed1992

Psychomotor testing and the ability to perform an anastomosis in junior surgical trainees.

Ten junior surgical trainees underwent objective testing of manual dexterity and visuospatial ability and were required to carry out five consecutive anastomoses on fresh porcine jejunum. Anastomoses were scored by a single observer and a cumulative error score (CES) derived for each procedure. In the first anastomosis there was little correlation between the psychomotor test results and the anastomosis scores. In subsequent trials there were significant negative correlations between aspects of manual dexterity and the CES. Over the five anastomoses there were significant negative correlations between improvement and manual dexterity, but there was a positive correlation between improvement and visuospatial ability (rs = 0.76, P < 0.005). Visuospatial skills are more important than pure motor ability in predicting the capacity to perform an anastomosis and tests of manual dexterity may be misleading in this context.

Adult↗
PubMed1992

Optimism, coping, psychological distress, and high-risk sexual behavior among men at risk for acquired immunodeficiency syndrome (AIDS).

In a cohort of gay men responding to the threat of acquired immunodeficiency syndrome (AIDS), dispositional optimism was associated with less distress, less avoidant coping, positive attitudes as a coping strategy, and fewer AIDS-related concerns. Men who knew they were seropositive for human immunodeficiency virus (HIV) were significantly more optimistic about not developing AIDS than men who knew they were seronegative for HIV. This AIDS-specific optimism was related to higher perceived control over AIDS and to active coping among seropositive men only and to health behaviors in both serostatus groups. There was no relation of optimism to risk-related sexual behavior. It is concluded that optimism is psychologically adaptive without necessarily compromising health behavior. It is also concluded that it is useful to distinguish between event-based optimistic expectations and dispositional optimism.

AIDS Serodiagnosis↗
PubMed1989

Comparison of intradermal and intramuscular hepatitis B vaccination in university students.

Antibody levels following intradermal and intramuscular hepatitis B vaccination were compared in a group of university students matched for age and sex. Intradermal vaccination gave satisfactory antibody levels in females, but much lower levels than by the intramuscular route and an unacceptable failure rate in men. The cost implications of introducing a selective vaccination policy in health care workers are discussed.

Adult↗
PubMed1989

[The value of immunofluorescence on frozen sections and immunoperoxidase methods on paraffin sections with different types of glomerulonephritis comparative study].

171 kidney biopsies were tested with the peroxidase- antiperoxidase (PAP)-method on paraffin sections. A comparison of the PAP-results with corresponding ones for the immunofluorescence method (IMF) on frozen sections was possible in 131 of the biopsies. When results of the 2 techniques were compared, outcomes showed a very strong accordance for both methods in tissues of postinfectious and perimembraneous GN an a strong accordance in mesangioproliferative GN tissue. In membrano-proliferative GN the immunopathological findings were more readily delinated with the PAP-method than with IMF. Cases involving IgA-nephritis, focal sclerosis and lupus nephritis with smaller deposits did not show consistant reactivity in the PAP-method as compared with IMF. 40 kidney biopsies, not examined by IMF, were diagnosed as GN by light microscopy and could be shown in 29 cases to contain evidence of an immune pathogenesis with the PAP-method.

Biopsy↗
PubMed1988

Comparison of ioxaglate with diatrizoate in angiography of the internal mammary artery.

To compare ioxaglate with the traditional agent diatrizoate, 44 patients scheduled to undergo coronary angiography that included internal mammary artery (IMA) visualization were entered into a randomized double blind-parallel design protocol. Complete data were collected on 32 out of 44. Four patients were withdrawn because of angiographically normal coronary arteries; seven, because of unsuccessful IMA cannulation; and one, because of an anaphylaxis-like reaction to ioxaglate. No other serious adverse effects were seen with either agent. The major endpoints were patient and physician assessments of discomfort, rated independently on a 4-point scale. Ioxaglate caused significantly less discomfort (n = 17, median rating of "mild discomfort") than did diatrizoate (n = 15, median rating of "severe discomfort"; P less than 0.01); this effect was independent of patient sex, the number of injections, and the volume of dye injected. Radiographic quality was good with both agents. We conclude that ioxaglate is much better tolerated than diatrizoate during angiography of the IMA.

Diatrizoate↗