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Biomedical subjects

A W Kimball

Publications and source records attributed to A W Kimball.

At least 19 recordsLinked to original sources
PubMed1997

D2-like dopamine receptor density in Tourette syndrome measured by PET.

UNLABELLED: Tourette syndrome (TS) is a chronic neurologic disorder characterized by the presence of involuntary motor and phonic tics. There is evidence that TS is associated with an abnormality of the dopaminergic system, involving postsynaptic D2 receptors. We tested the hypothesis that D2-like dopamine receptors are elevated in TS. METHODS: Twenty-nine adult patients with TS were studied by PET imaging with [11C]3-N-methylspiperone ([11C]NMSP). Two methods of data analysis were used. The first was a caudate-to-cerebellar ratio, measured at 45 min. The second method, applied in 20 subjects, was a two-PET scan procedure. Both used high specific activity [11C]NMSP, but the second scan was preceded by a dose of unlabeled haloperidol, which partially occupied the D2-like dopamine receptors. This was done to provide an absolute measure of receptor density (Bmax). All patients were compared to age- and sex-matched controls. RESULTS: Neither group showed significant differences from their control group in caudate-to-cerebellar ratio. However, the two-PET scan Bmax measurement demonstrated that 4 of the 20 patients had significantly elevated D2-like receptors. In this group of 20 patients, multiple linear regression analysis revealed a trend between the severity of vocal tics and Bmax values. This Bmax measure also revealed a significant (p < 0.05) association with performance on the Wisconsin Card Sorting Test. CONCLUSION: These findings suggest that not all patients with TS have an abnormality of D2-like receptors, but a subgroup of TS subjects has a significant D2-like dopamine receptor elevation. These findings also support the importance of applying a more quantitative method for Bmax determination to PET imaging analysis. The Bmax findings in the subgroup do not exclude an effect of intrasynaptic dopamine competition, but this effect may be less likely due to the high affinity of [11C]NMSP.

Adult↗
PubMed1995

Response to acute ozone exposure in healthy men. Results of a screening procedure.

We screened 64 healthy, nonsmoking men, 18 to 35 yr old, for their sensitivity to 0.35 ppm ozone (O3) administered for 130 to 150 min with intermittent exercise. The changes in FVC, FEV1, AND FEF25-75 (p < 0.0001) immediately after O3 exposure varied widely among subjects. Histograms of the percentage changes in FVC and FEV1 did not differ from a unimodal, skewed (gamma) distribution (p = 0.99 and p = 0.17, respectively); the changes in FEF25-75 tended to deviate from a gamma distribution (p = 0.055). To adjust FEF25-75 for the confounding effects of O3 on FVC, we used multiple linear regression analysis with contemporaneous FVC as a covariable, analysis of a subgroup of nine subjects whose O3-induced FVC changes were < or = 5%, and volume correction of FEF25-75 for any changes in FVC after exposure. These analyses showed reductions in FEF25-75 unexplained by and following a different time course than the O3-induced changes in FVC. In 26 subjects also exposed to filtered air, significant effects of O3 on respiratory frequency (p < 0.004) and tidal volume (p < 0.0007) correlated weakly with FVC changes. The results confirm the wide variability in spirometric responsiveness among individuals to O3 and suggest that intrinsic narrowing of the small airways may be a significant component of the functional response.

Adolescent↗
PubMed1994

Enzyme-linked fluorescent detection for automated multiplex DNA sequencing.

Initiatives to sequence DNA on a large scale have created a need for increased throughput and decreased costs. One scheme for increasing throughput, multiplex sequencing, involves the processing of a mixture of sequencing templates followed by sequential hybridization to reveal the individual sequence ladders on a membrane. Because multiplex sequencing has not been fully automated, and has not seemed automatable, few sequencing efforts have attempted to exploit it. We describe here a scheme for the automation of multiplex sequencing. Probe hybridized to target DNA is detected via spatially localized enzyme-linked fluorescence. Light output is high enough that imaging is possible with simple instrumentation. Direct imaging within an automated hybridization apparatus is made feasible so that the entire process will be automatic once a multiplex membrane is produced. The technique has the potential to increase severalfold the throughput of automated sequencing instruments required for sequencing the human genome.

Base Sequence↗
PubMed1993

A randomized trial of three oral contraceptives: comparison of bleeding patterns by contraceptive types and steroid levels.

OBJECTIVE: Our purpose was to determine the relationship between bioavailability of contraceptive steroids and bleeding patterns. STUDY DESIGN: A randomized clinical trial evaluated 192 women on 50 micrograms of ethinyl estradiol and 1.0 mg of norethindrone (OC1), 35 micrograms ethinyl estradiol and 1.0 mg of norethindrone (OC2), and 35 micrograms ethinyl estradiol and 0.5 mg norethindrone (OC3) over nine cycles. RESULTS: Intermenstrual bleeding rates were higher for OC3 when compared with OC1 (p = 0.01). The number of intermenstrual bleeding days was highest for OC3 (p = 0.001) and higher for OC2 when compared with OC1 (p < 0.006). The onset of withdrawal bleeding occurred faster in OC3 patients (p < 0.02). Bioavailability of both contraceptive steroids as measured by baseline values and 1-hour slopes did not correlate with bleeding patterns at 3, 6, and 9 months of use. CONCLUSION: These data suggest that differences in biologic responses associated with pill use cannot be explained solely on the basis of these particular hormone measurements.

Biological Availability↗
PubMed1992

Alcohol consumption regression models for distinguishing between beverage type effects and beverage preference effects.

In relating health outcomes to alcohol consumption, several investigators have evaluated differences among beverage types, but there is no consistency with respect to models used for this purpose. Furthermore, beverage type effects and beverage preference effects have not been evaluated simultaneously. In this report, the authors propose regression models which permit the simultaneous evaluation of beverage type (congener dose response) effects and beverage preference (sociobehavioral) effects. The presence of sociobehavioral effects can be established even if the variables responsible for them have not been measured or identified. The models are applied to a data set from 589 women who participated in an oral contraceptive study at the Johns Hopkins University (Baltimore, Maryland) in 1988-1989.

Adolescent↗
PubMed1992

Nonlinear modeling of alcohol consumption for analysis of beverage type effects and beverage preference effects.

In a previous report (Kimball and Friedman, Am J Epidemiol, 1992;135:1279-86), linear models for relating health outcomes to alcohol consumption were proposed for differentiating between beverage type effects and beverage preference effects. The models were applied to data relating serum high density lipoprotein cholesterol to alcohol consumption. In this report, those models are extended to the nonlinear case and are applied to data from the 1982 Maryland Hypertension Survey relating systolic blood pressure to alcohol consumption.

Adolescent↗
PubMed1992

Epidural versus general anesthesia, ambient operating room temperature, and patient age as predictors of inadvertent hypothermia.

To elucidate the multifactorial nature of perioperative changes in body temperature, the influence of several clinical variables, including anesthetic technique, ambient operating room temperature, and age, were evaluated. Perioperative oral sublingual temperatures were measured in 97 patients undergoing lower extremity vascular surgery randomized to receive either general (GA) or epidural (EA) anesthesia. Surgery and anesthesia were performed in operating rooms (OR) with a relatively warm mean ambient temperature (24.5 +/- 0.4 degrees C) (GA, n = 30; EA, n = 33) or relatively cold mean ambient temperature (21.3 +/- 0.3 degrees C) (GA, n = 21; EA, n = 13). Patients were 35-94 yr old, with a mean age of 64.5 +/- 1.1 yr. A regression analysis was performed to determine the variables that correlated with intraoperative decrease in temperature and postoperative rewarming rate. The major correlates of greater intraoperative decrease in temperature were 1) GA (P = 0.003); 2) cold ambient OR temperature (P = 0.07); and 3) advancing patient age (P = 0.03). There was significant interaction between ambient OR temperature and type of anesthesia (P = 0.03): there was a greater intraoperative decrease in temperature with GA compared to EA in a cold OR but a similar decrease with GA and EA in a warm OR. The data also suggest an interaction between type of anesthesia and patient age (P = 0.06), showing a greater decrease in temperature with GA compared to EA in the younger patients, but a similar decrease between GA and EA in older patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Existence of multiple peaks in plasma ethinyl estradiol and norethindrone after oral administration of a contraceptive pill.

Previous measurements of plasma ethinyl estradiol (EE2) and norethindrone (NE) over 24 h after oral administration of a contraceptive pill have demonstrated a single steroid peak occurring 1-2 h after pill ingestion, with a gradual decline over the next 22 h. In the present study plasma concentrations of EE2 and NE were measured 0, 0.5, 0.75, 1, 2, 4, 12, and 24 h after oral ingestion of a contraceptive pill containing 35 micrograms EE2 and 1 mg NE at 0, 3, 6, and 9 months of use in 58 normal healthy women. Contrary to previous reports, analysis of the 464 steroid curves (58 subjects x 4 time periods x 2 steroids) revealed the presence of multiple hormone peaks. Two peaks of EE2 were identified in 44.8% of women during the first pill cycle and in 75.9%, 55.2%, and 67.2% of women after 3, 6, and 9 months of pill use. Two hormone peaks of NE were observed in 29.3% of women during the first cycle and in 36.2%, 50%, and 44.8% at 3, 6, and 9 months, respectively. Existence of these multiple peaks at the frequency observed has not previously been reported. Further quantification of the frequency and magnitude of these peaks could be helpful in explaining differences in biological responses associated with pill use.

Adult↗
PubMed1991

Oral contraceptives and antithrombin III: variations by dosage and ABO blood group.

A randomized clinical trial of oral contraceptives evaluated 67 women on a regimen of 50 micrograms ethinyl estradiol and 1.0 mg norethindrone, 61 women on a regimen of 35 micrograms ethinyl estradiol and 1.0 mg norethindrone, and 64 women on a regimen of 35 micrograms ethinyl estradiol and 0.5 mg norethindrone. ABO blood group type was determined in all women. At baseline and at 3, 6, and 9 months, plasma antithrombin III levels, by both an immunologic and an activity method, and selected plasma levels of the contraceptive steroids were measured. Antithrombin III levels for all oral contraceptive groups combined decreased from baseline by 19.7% and 28.8% for the immunologic and activity methods, respectively. Analysis of interrelationships among antithrombin III by activity method, oral contraceptive type, and ABO blood group showed larger declines in antithrombin III for type O women using the highest estrogen dose preparation (31.6%) and for non-type O women using the lowest progestin dose preparation (38.9%). Plasma levels of contraceptive steroids also were related to changes in the most extreme levels of antithrombin III.

ABO Blood-Group System↗
PubMed1990

Halothane alters the oxygen consumption-oxygen delivery relationship compared with conscious state.

The authors' objectives were as follows: 1) to characterize for the first time the relationship between whole body O2 delivery (DO2) and O2 consumption (VO2) in adult conscious dogs; and 2) to asses the effects of the inhalational anesthetic, halothane, on that relationship. DO2 was varied over a wide range in chronically instrumented dogs by gradual inflation and deflation of a hydraulic occluder implanted around the thoracic inferior vena cava to alter venous return and cardiac output. VO2 was measured at different values of DO2 in dogs in the fully conscious state and again during halothane anesthesia. A "binning" technique indicated that halothane decreased VO2 (P less than 0.01) at any given value of DO2 over a broad range of VO2. A two-line piecewise linear regression analysis technique indicated that halothane decreased (P less than 0.01) the critical O2 delivery (COD) from 20 +/- 3 to 10 +/- 1 ml.kg-1.min-1 and increased (P less than 0.01) O2 extraction at COD from 31 +/- 3 to 40 +/- 2%. However, the DO2-VO2 plots measured in both conscious and halothane-anesthetized dogs did not exhibit a discrete discontinuity but rather were closely fit (correlation coefficient = 0.98) by an exponential equation of the following form: O2 extraction = B1.(1 - exp (-DO2/B2))/DO2, where B1 is the delivery-independent estimate of VO2 and B2 is the "delivery constant," i.e., the DO2 associated with a VO2 equal to 63% of B1. Halothane decreased B1 (P less than 0.01) from 5.3 +/- 0.1 to 3.9 +/- 0.1 ml.kg-1.min-1 and decreased B2 (P less than 0.01) from 5.6 +/- 0.3 to 3.6 +/- 0.3 ml.kg-1.min-1 compared with that measured in conscious dogs. Thus, compared with the conscious state, halothane anesthesia alters the fundamental relationship between DO2 and VO2 and may have a beneficial effect on tissue oxygenation at low values of DO2.

Animals↗
PubMed1989

Alcohol and traffic safety: a sensitivity analysis of data from composite sources.

Risk factors associated with single-vehicle driver fatalities are explored in a sensitivity analysis of data from composite sources. Information on fatalities was taken from the Federal Accident Reporting System data base for 1976-1981. Characteristics of the driving population were given by the 1973 National Roadside Breath Testing Survey (Wolfe 1974). Using Bayes theorem and logistic regression analysis, the effect of changing driver characteristics on the probability of a fatality was explored. The method used is proposed for a case-control study in which the controls may not accurately represent the population from which the cases were drawn. Risk factors identified are generally in agreement with previous reports.

Accidents, Traffic↗
PubMed1989

Oral contraceptives and lipids and lipoproteins: Part II--Relationship to plasma steroid levels and outlier status.

A randomized clinical trial of oral contraceptives evaluated 67 women on 50 ug ethinyl estradiol (EE) and 1.0 mg norethindrone (NE), 61 women on 35 ug EE and 1.0 mg NE, and 64 women on 35 ug EE and 0.5 mg NE. At baseline, three, six and nine months, lipids and lipoproteins were measured as well as selected plasma determinations of the contraceptive steroids. Data was related to change in outlier status for lipids/lipoproteins (less than 10th percentile for high-density lipoprotein cholesterol and apolipoprotein A-1, greater than 90th percentile for all others). Women on the lowest dose preparation had the smallest trend towards outlier status for high-density lipoprotein cholesterol and apolipoprotein A-1. An increase over the time period of the study in the initial slope (one hour level minus zero hour level over time) of NE and a decrease in the initial slope of EE was associated with a shift to outlier status for low-density lipoprotein cholesterol. A number of other relationships were also shown. Use of the techniques described might assist in identifying sub-groups of women at risk for adverse cardiovascular sequelae associated with oral contraceptive use.

Adolescent↗
PubMed1989

Oral contraceptives and lipids and lipoproteins: Part I--Variations in mean levels by oral contraceptive type.

A randomized clinical trial of oral contraceptives evaluated 67 women on 50 micrograms ethinyl estradiol (EE) and 1.0 mg norethindrone (NE), 61 women on 35 micrograms EE and 1.0 mg NE, and 64 women on 35 micrograms EE and 0.5 mg NE. Fasting lipids and lipoproteins were measured at baseline, three, six and nine months. All groups showed an increase in plasma total cholesterol, triglycerides, low-density lipoprotein/apolipoprotein B and apolipoprotein A-1. The group taking the preparation with 0.5 mg of NE was the only one to result in an elevation of high-density lipoprotein cholesterol; the other two groups showed declines in the mean levels of this lipoprotein over the study time period. Mean changes in lipid/lipoprotein levels associated with oral contraceptive use appear to be at least partially related to the doses of the contraceptive steroids.

Adolescent↗
PubMed1989

Cause-specific actuarial survival analysis: a useful method for reporting survival data in men with clinically localized carcinoma of the prostate.

The primary objective of this retrospective 15-year survival analysis of 57 men with clinical stage B1 carcinoma of the prostate undergoing radical prostatectomy between 1951 and 1963 is to compute the cause-specific curve for these men and argue why it is a useful method to report survival data in men with clinically localized prostatic cancer. Historically, survival following radical prostatectomy and radiotherapy has been reported using all cause survival analysis. Cause-specific survival focuses on the impact of a disease process on survival, since men dying of causes unrelated to carcinoma of the prostate are considered lost to followup as of date of death of such unrelated causes. Cause-specific survival analysis reduces the impact of age, medical condition and other risk factors on survival rates. The cause-specific 15-year actuarial survival rate in our patients was 86 per cent. The 95 per cent confidence interval for this 15-year survival rate was 76.9 to 90.1 per cent. Based upon this series of patients with clinical stage B1 carcinoma of the prostate who undergo radical prostatectomy one may state that the chance of death of carcinoma of the prostate within 15 years of surgery averages 14 +/- 5 per cent. The cause-specific survival curve reached a plateau at 10 years, indicating that most men who survive 10 years are cured of the disease. With the Cox model regression analysis, mortality in this series was related positively to age at operation when the outcome variable was death of all causes (p equals 0.003) but it was unrelated to age when the outcome variable was prostate cancer mortality (p equals 0.85). Cause-specific survival rates are a more precise indicator of the impact of a therapeutic modality on survival and, therefore, they are useful to report survival data in men with localized carcinoma of the prostate and other disease when death from competing causes is an important consideration.

Actuarial Analysis↗
PubMed1988

The interaction of alcohol consumption and oral contraceptive use on lipids and lipoproteins.

Oral contraceptive (OC) use and alcohol consumption have been shown to alter the levels of lipids and lipoproteins in the blood. The effect of alcohol consumption on levels of total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, LDL-B, Apo-A1, the ratio of HDL cholesterol/total cholesterol, HDL cholesterol/LDL cholesterol, and the ratio of LDL cholesterol/LDL-B among normal healthy young women before initiation of oral contraceptives and after six months of oral contraceptive use are both described. Of primary interest is the mediating effect of alcohol consumption on the association between steroid usage and blood lipid values. At baseline, ethanol consumption was found to be positively associated with triglycerides, HDL-C, and Apo-A1 and negatively associated with LDL-C/LDL-B. After adjustment for several covariables, alcohol consumption was found to be positively associated with the increases in triglycerides and in Apo-A1 observed at 3 and 6 months after initiation of OCs. Since these two parameters are believed to have opposite relationships to cardiovascular disease, the effect of alcohol consumption remains uncertain.

Adult↗
PubMed1988

Measures of and tests for net improvement in clinical trials, PhD.

For clinical trials in which the outcome variable is trichotomous (regression, no change, improvement), a measure of net improvement in health status is proposed. Test statistics are derived for the null hypothesis of zero net improvement in a single patient group and for the null hypothesis of no difference in net improvement between two groups. The methods are applied to a clinical trial that evaluated the effect of argon laser photocoagulation in patients with macular edema in branch vein occlusion.

Clinical Trials as Topic↗
PubMed1988

Prostate specific antigen in the preoperative and postoperative evaluation of localized prostatic cancer treated with radical prostatectomy.

The usefulness of prostate specific antigen to predict final pathological stage was studied in 178 consecutive patients. Prostate specific antigen was determined preoperatively in all patients by a monoclonal immunoradiometric assay. All pathological specimens were examined for capsular penetration, seminal vesicle involvement and lymph node involvement. Prostate specific antigen correlated directly with capsular penetration (p less than 0.002), seminal vesicle involvement (p less than 0.02) and lymph node involvement (p less than 0.05). However the diagnostic accuracy of an elevated serum antigen level on an individual basis was only 55 per cent for capsular penetration and 50 per cent for seminal vesicle involvement and lymph node involvement. With a log-linear regression model, the half-life of prostate specific antigen was calculated to be 3.15 +/- 0.09 days. From the equation PSA (t) equals PSA (2) e[-0.2197(t-2)], prostate specific antigen can be used to detect residual cancer on day t in the immediate postoperative period. With respect to long-term followup, 127 patients have been monitored for longer than 2 months postoperatively with prostate specific antigen (mean followup 2 years, range 2 months to 8.6 years). Of the 101 patients who had favorable pathological findings at operation (organ-confined cancer or capsular penetration only) 92 (91 per cent) had a followup antigen concentration in the female range (0.0 to 0.2 ng. per ml.), whereas only 5 of 26 men (19 per cent) with either seminal vesicle involvement or lymph node involvement had an antigen value that was less than 0.2 ng. per ml. All patients with a documented clinical recurrence (8 of 127, 6 per cent) had an elevated followup serum prostate specific antigen concentration. These findings suggest that preoperative levels of prostate specific antigen are not sufficiently reliable to predict final pathological stage on an individual basis in patients with early prostatic cancer, and that the antigen is a sensitive tumor marker for the detection of residual disease after radical prostatectomy and subsequent recurrence of tumor on long-term followup.

Adenocarcinoma↗