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Biomedical subjects

B J Skipper

Publications and source records attributed to B J Skipper.

At least 73 records · Page 4Linked to original sources
PubMed1985

Statistical significance tests for autoradiographic data.

The purpose of this paper is to develop statistical methods that take radiation spread into account in analyzing data from different autoradiographic experiments. The method uses the probability circle analysis of Salpeter and McHenry (1973) to obtain the probable source of each radioactive emission and the circle and point counting method of Williams (1969) to estimate the relative area occupied by each cellular site. Two levels of analysis are presented. The first level of analysis is concerned with estimating relative activities and standard errors for cellular items that are larger than the probability circle. The second level of analysis involves estimating relative activities and standard errors for cellular sites that are smaller than the probability circle and are therefore observed in circles containing another item such as cytoplasmic matrix. Two different tests of hypotheses are discussed. The first null hypothesis is that the radioactivity is randomly distributed among the cellular sites. The second null hypothesis is that there is no difference between two different treatments in the relative activities for a given site.

Animals↗
PubMed1985

Lung cancer risk and vitamin A consumption in New Mexico.

The association between dietary intake of vitamin A and lung cancer risk was examined in a population-based, case-control study of 447 patients and 759 control subjects in New Mexico. A food frequency interview was used to measure usual consumption of total vitamin A retinol, preformed vitamin A, and carotene. With all respondents combined, the odds ratios for lung cancer increased as intakes of total vitamin A and carotene declined but did not vary with intake of preformed vitamin A. When the subjects were stratified by ethnic group, Hispanic or non-Hispanic (Anglo) white, significant effects of vitamin A consumption were limited to the Anglos. In the Anglos, the protective effects of total vitamin A and carotene consumption were present in males and females, but varied strongly with cigarette smoking habits. In Anglo smokers, significant increases in the odds ratios with declining intake were observed in former but not in current smokers. Among the former smokers, significant effects of total vitamin A and carotene consumption were present only in those who had stopped smoking for 6 to 15 yr. Limitation of the protective effect of vitamin A and carotene consumption to past smokers has important implications for the design of clinical trials and for cancer control strategies.

Aged↗
PubMed1985

Cigarette smoking and lung cancer in 'Hispanic' whites and other whites in New Mexico.

A population-based case-control study of lung cancer was performed in New Mexico to explain the differing patterns of lung cancer occurrence in the state's "Hispanic" Whites and other Whites. From 1980 through 1982, interviews were completed with 521 cases and 769 controls. In the male controls, the prevalence of current and previous cigarette usage was similar in the two ethnic groups, but Hispanics smoked fewer cigarettes daily. In the female controls, a lower percentage of Hispanics had ever smoked and their usual consumption was less than that of other White women. Older Hispanic female smokers had used hand-rolled cigarettes for an average of 8.8 years, whereas other White women of the same age had used this type for less than one-half year. Both stratified and multiple logistic analysis showed comparable risks of lung cancer in Hispanic White and other White smokers. There was no evidence of interaction between ethnicity and cigarette smoking. These analyses imply that the differences in lung cancer incidence between New Mexico's Hispanic Whites and other Whites are largely explained by the patterns of cigarette smoking of these two groups.

Adult↗
PubMed1984

Ordering decision and clinic cost variation among resident physicians.

Physicians vary considerably in the services they order for their patients. We examined ordering variation among 47 resident physicians during 4,991 continuity clinic visits with patients who had specific, chronic medical problems. We ranked the physicians by their average charge per visit and grouped them into three equal categories. High-charge physicians averaged $164 per visit, medium-charge $124 and low-charge $97. In comparing the frequencies with which physicians in each group ordered a wide array of specific laboratory tests, x-ray studies, medications and miscellaneous items, we found that ordering variation among the physician groups was not confined to certain decisions or categories of services. High-charge physicians ordered a little more of nearly every item or service. Although the magnitude of ordering variation for each item was small, the sum over many items was great, suggesting that cost-containment efforts may have to focus on the "little ticket" decision-making style of expensive physicians.

Cost Control↗
PubMed1984

Pneumococcal-induced pulmonary leukostasis and hemodynamic changes: role of complement and granulocytes.

In the present study we investigated the cardiopulmonary dysfunction caused by systemic pneumococcal (PNC) disease. We studied the hemodynamic and hematologic effects of intravascular challenge with nonviable PNC in normal, granulocyte-depleted, and genetically C3-deficient dogs. In normal dogs PNC administration caused a decrease in cardiac output (CO) of 58% (p less than 0.001), an increase in pulmonary vascular resistance (PVR) of 151% (p less than 0.02), and an increase in systemic vascular resistance (SVR) of 72% (p less than 0.02). The PNC challenge also caused significant decreases in both circulating granulocytes (-73%; p less than 0.02) and platelets (-58%; p less than 0.02). Histologic examination revealed granulocyte plugging within small pulmonary vessels. PNC challenge in granulocyte-depleted and C3-deficient dogs resulted in hemodynamic and hematologic changes that were not significantly different from those seen in normal PNC-challenged animals. Infusion of PNC-activated plasma resulted in hematologic changes that were not significantly different from those seen in PNC-challenged animals. Infusion of plasma treated with ethylenediamenetetraacetic acid (EDTA) prior to PNC incubation induced the same hematologic alterations but the hemodynamic response was less pronounced. To control for PNC constituents not removed by centrifugation and filtration, saline was incubated with PNC. After the PNC was removed, infusion of the saline induced no significant hemodynamic changes, although profound granulocytopenia occurred. We conclude that an intact complement system, but not normal numbers of circulating granulocytes, is essential to PNC-induced hemodynamic changes. PNC generates a plasma factor in vitro that does not require an intact complement system or cellular machinery to induce granulocytopenia without hemodynamic effect.

Animals↗
PubMed1984

Isokinetic muscle imbalance and knee-joint injuries. A prospective blind study.

One hundred and seventy-two randomly selected high-school football players underwent pre-season isokinetic muscle-testing to determine if there was any relationship between an imbalance in thigh-muscle function and the occurrence of knee injuries. Strength, power, power-endurance, and time to maximum tension were measured for the quadriceps and hamstring muscle groups for both lower extremities of each athlete. The resulting values were utilized to see if a difference of 10 per cent or more between the right and left extremities or between the mean and actual hamstring-to-quadriceps ratio of the individual extremity would result in more knee injuries. No such relationship was found.

Adolescent↗
PubMed1983

Bovine carotid artery heterografts versus polytetrafluoroethylene grafts. A prospective, randomized study.

A prospective, randomized comparison of BCAH and PTFE vascular access grafts resulted in no statistically significant difference when analyzed for survival rates of complications, types of complications, reasons for failure, and clot salvageability. The results in diabetic patients were similar to those in nondiabetic patients. The majority of retrospective studies and subjective experiences favor PTFE grafts over BCAHs. The explanation may be part that BCAH preceded PTFE grafts into clinical use, and inexperience in the operating room and in the dialysis unit had an effect on BCAH results. A review of impressions of the graft materials indicated a decided preference for PTFE grafts.

Adolescent↗
PubMed1983

Impact of a cost-containment educational program on housestaff ambulatory clinic charges.

A cost-containment project was established to determine if a broad educational program that coupled clinical logic with feedback of charges to internal medicine residents in an ambulatory clinic setting could alter behavior. The project was evaluated by comparing charge data from a preintervention comparison year with charge data from the intervention year. Decreases in charges for laboratory procedures occurred in six of the seven diagnostic categories during intervention and were significant (t-test) for four categories. Regression analysis evaluated the influence of the intervention and 12 other variables on charges and demonstrated that the intervention was associated with a mean reduction of lab charges of $ 6.30 (p less than 0.0001) and a mean reduction of total encounter charges of $ 10.36 (p less than 0.01). We conclude that our educational program resulted in a decrease in mean laboratory changes and total charges for ambulatory encounters.

Awareness↗
PubMed1983

Comparison of family medicine and internal medicine: charges for continuing ambulatory care.

The authors compared charges for ambulatory and continuing patient care prescribed by residents in internal medicine and family medicine. An analysis of covariance showed that the charges per encounter in internal medicine were $38.83 greater than charges in family medicine after accounting for differences such as patient age, diagnosis, and severity of condition. However, family practitioners scheduled patient encounters more frequently. The median number of days between encounters was 30 for family medicine and 60 for internal medicine. The duration of medical care for each patient (up to 18 months was possible) and the summation of encounter charges over that duration of medical care were evaluated. Because only two out of eight duration-of-medical-care categories were significantly less in family medicine, the differences in charges between the specialties essentially disappeared. Comparative studies which consider only charges per encounter potentially have a large bias.

Analysis of Variance↗
PubMed1983

Immunological and microbiological studies of midtrimester amniotic fluid.

Midtrimester amniotic fluids (MAF) from 73 women undergoing an amniocentesis were studied. The mean immunoglobin G (IgG) level was 34 +/- 14 mg/dl, which is higher than that reported in the third trimester. The maternal serum:MAF IgG ratio was 29 suggesting the blood:MAF barrier is less restrictive than others like the blood:cerebrospinal fluid barrier. Antibodies to herpes simplex virus (HSV) type 1 were detected in 78% of the MAF and the maternal serum:MAF HSV antibody titer ratio was 33. Antibodies to cytomegalovirus (CMV) were found in 84% of the MAF and the maternal serum:MAF CMV antibody titer ration was 40. Whenever either antibody was detected in the maternal serum it was also found in the MAF. No viruses, bacteria, mycoplasma, fungi and chlamyidae were isolated from MAF.

Amniotic Fluid↗
PubMed1980

Effects of active shortening on tension development of rabbit papillary muscle.

Duration and intensity of force development have been shown to be less during active muscle shortening than during isometric contraction. The purpose of this study was to compare force developed during controlled shortening with that predicted by the Frank-Starling relation. Paillary muscles from the right ventricles of rabbits were arranged for isometric tension recording, and isometric contractions were recorded at several lengths. The muscles were then permitted to shorten at velocities of 0.2--6 mm/s, shortening beginning 150--200 ms after the stimulus. Length-tension-time curves constructed from the isometric contractions were used to determine predicted shortening tension (Pp), which was compared with actual tension during shortening (Ps) at corresponding times and lengths. Ps was significantly less than Pp and the ratio Ps/Pp decreased with increasing velocity of shortening. The decrease in Ps/Pp was directly related to the duration of shortening (P less than 0.001), suggesting that the fall of shortening tension reflected both the Hill force-velocity relation and shortening deactivation.

Animals↗
PubMed1977

Biological activity of dilute isoproterenol solution stored for long periods in plastic bags.

The effect of long-term storage in polyvinyl chloride bags on the biological activity and the chemical stability of isoproterenol was studied. A freshly prepared solution of isoproterenol, isoproterenol solution stored for six months and isoproterenol stored for 30 months were infused into the coronary circulation of 14 isolated rabbit hearts; heart rates were determined. Spectrophotometric studies to determine stability at various pH levels were also done. Aging of the solutions at pH 4 and at a concentration of 4 microgram/ml caused no significant impairment of their potency. Solutions above pH 6 were unstable.

Animals↗
PubMedDate not supplied

The influence of ethnicity on use of herbal remedies in elderly Hispanics and non-Hispanic whites.

OBJECTIVE: To compare the use of herbal remedies between elderly, self-identified Hispanics and non-Hispanic whites (NHW). DESIGN: Cross-sectional, interviewer-administered survey. PATIENTS/SETTING: 186 patients, 65 years and older, at a university-based, ambulatory, senior health center. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Differences in herbal use patterns between Hispanic and NHW participants. Main outcome measures were participants' use of herbal remedies, types of remedies used, medical reason for use, age, sex, Hispanic or NHW ethnicity, income, and education. RESULTS: Overall, 61% of patients had used an herbal remedy at some time in their lives. A larger proportion of Hispanic subjects used herbal remedies than did NHW subjects (77% versus 47%, respectively). Hispanic subjects preferred to use the raw herb in a tea, whereas NHW subjects preferred processed herbs in a capsule or tablet form. Significantly more Hispanic subjects grew or gathered their own herbs and received their information about herbs from a family member than did NHW subjects. Few subjects in either ethnic group received their information about herbal remedies from an allopathic provider. For both groups, the herbs most often used were yerba buena, manzanilla, poleo, osha, and alhucema. The top perceived medical problems that herbs were used for were health care maintenance, dyspepsia, upper respiratory infection, skin problems, and anxiety/nerves/insomnia. CONCLUSION: Ethnicity was related to the frequency of herbal use, the choice and preferred form of herb, and the source of knowledge of herbal remedies. Hispanic culture may account for the observed differences.

Aged↗
PubMedDate not supplied

A study of respiratory illnesses in infants and nitrogen dioxide exposure.

Toxicologic and epidemiologic studies have elevated concern that exposure to nitrogen dioxide (NO2) in outdoor and indoor air may increase the frequency and severity of respiratory infections. We have developed and implemented a prospective cohort study to test the hypothesis that exposure to NO2 increases the incidence and severity of respiratory infections during the first 18 mo of life. This study, which was based on extensive pilot research, was designed to address the potential limitations of misclassification, confounding, and inadequate power. Enrollment of 1,315 subjects has been completed. This paper reviews the methods used in the study, characteristics of the enrolled subjects, NO2 concentrations in the homes of study participants, and rates of illness occurrence.

Air Pollution, Indoor↗
PubMedDate not supplied

Persistence of high-risk sexual activity among homosexual men in an area of low incidence of the acquired immunodeficiency syndrome.

Before 1985 only five cases of the acquired immunodeficiency syndrome (AIDS) had been diagnosed in New Mexico, and there was no information regarding prevalence of antibody to the human immunodeficiency virus (HIV). Of 166 gay and bisexual men tested in 1985 in New Mexico, 20% were found to have antibody to HIV. Of 153 responding participants, 107 (70%) reported practicing receptive anal intercourse in the last 12 months, and only 13% of the 107 reported the regular use of condoms. High-risk sexual activity may have persisted in part because of underestimation of the local risk of acquiring HIV infection. Voluntary serologic testing and education of members of high-risk groups should be stressed in areas where the incidences of AIDS and of seropositivity to HIV are low but where high-risk sexual activity may still be prevalent.

Acquired Immunodeficiency Syndrome↗