Search PubMed⌕ Search

Biomedical subjects

J M Mitchell

Publications and source records attributed to J M Mitchell.

At least 19 recordsLinked to original sources
PubMed1996

Urinary excretion profiles of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol in humans after single smoked doses of marijuana.

Interpretation of marijuana-positive urine tests requires an understanding of the excretion pattern of marijuana metabolites in humans. However, limited urinary excretion data from controlled clinical studies of marijuana use are available. In this study, six subjects smoked a single marijuana cigarette (placebo, 1.75% delta 9-tetrahydrocannabinol [THC], or 3.55% THC) each week while residing on the clinical ward of the Addiction Research Center. Individual urine specimens were collected for 7 days after drug administration and analyzed for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH) by gas chromatography-mass spectrometry (GC-MS) with a limit of detection of 0.5 ng/mL. Substantial intersubject variability in patterns of THCCOOH excretion was noted between subjects and between doses. Mean THCCOOH concentrations in the first urine collections were 47 +/- 22.3 ng/mL and 75.3 +/- 48.9 ng/mL after the 1.75 and 3.55% THC cigarettes, respectively. Mean peak urine THCCOOH concentrations averaged 89.8 +/- 31.9 ng/mL and 153.4 +/- 49.2 ng/mL after smoking of approximately 15.8 mg and 33.8 mg THC, respectively. The mean times of peak urine concentration were 7.7 +/- 0.8 h after the 1.75% THC and 13.9 +/- 3.5 h after the 3.55% THC dose. Mean GC-MS THCCOOH detection times for the last positive urine sample after the smoking of a single 1.75 or 3.55% THC cigarette were 33.7 +/- 9.2 h and 88.6 +/- 9.5 h, respectively, when a 15-ng/mL cutoff concentration was used. An average of 93.9 +/- 24.5 micrograms THCCOOH (range, 34.6-171.6 micrograms) was excreted by each subject during the 7-day period after smoking of a single 1.75% THC cigarette. The average amount of THCCOOH excreted in the same time period after the high dose was 197.4 +/- 33.6 micrograms (range, 107.5-305.0 micrograms). This represented an average of only 0.54 +/- 0.14% and 0.53 +/- 0.09% of the original amount of THC in the low-and high-dose cigarettes, respectively. These data provide a detailed complication of THCCOOH concentrations in urine after administration of marijuana that may aid in the interpretation of urine cannabinoid results.

Adult↗
PubMed1995

Short fourth toes in Rett syndrome: a biological indicator.

Classic Rett syndrome is now well-known as a non-dysmorphic developmental disorder almost certainly of genetic origin. Short 4th toe (uni- or bi-lateral) is inherited as an autosomal dominant with 27% penetrance and is found also in certain dysmorphic syndromes. Having observed the anomaly in several Rett cases, we examined a cohort of classic Rett people at advisory clinics and all the residents in an adult learning disabled hospital in order to determine the significance of the association. Among the Rett clinic group 28 of 137 showed the anomaly (20%). Among the heterogeneous hospital group it was found in 19 of 526 people, 9 of 206 females (4%) and 10 of 320 males (3%). Rett syndrome was present in 7% of all the women (14 of 206 women). Four of the Rett women showed the toe anomaly (28% of the Rett cases). The anomaly was found in 4 men and 4 women with Down syndrome, representing 16% (8 of 49). Diagnoses in other men with the anomaly included foetal alcohol syndrome, toxoplasmosis, 18/2 translocation and birth injury. The only other woman with the anomaly was profoundly disabled with short limbs. The strong positive association of the anomaly with Rett syndrome and Down syndrome throws new light on the developmental processes affected by these diseases.

Brain↗
PubMed1995

Ownership and utilization of MR imagers in the Commonwealth of Virginia.

PURPOSE: To assess distribution, operation, and ownership of magnetic resonance (MR) imagers in Virginia in 1991. MATERIALS AND METHODS: Questionnaires regarding ownership, location, hours of operation, annual throughput, sources and amounts of revenue, and expenses were mailed to identified providers. Data, specifically regarding ownership and location, were analyzed. RESULTS: Staff from 95% of MR facilities responded. Most facilities were located in and around major metropolitan areas. Population density per imager ranged from one per 76,000 to one per 222,000 persons. Imagers in larger metropolitan areas were operated for longer hours with higher revenues and greater expenses than were those in lower-population-density areas. Imagers owned by physicians in a position to self-refer had the highest patient throughput, the most revenue, and a much lower percentage of revenues from Medicare and Medicaid than did other ownership types. CONCLUSION: Patient access to MR services in Virginia is inhomogeneous. Important aspects of utilization are location and ownership. Ownership by physicians who can self-refer is associated with higher use, greater overall revenues, and less service to the poor and elderly.

Costs and Cost Analysis↗
PubMed1994

The prevalence of polycystic ovaries on ultrasound scanning in a population of randomly selected women.

Polycystic ovaries (PCO) diagnosed by ultrasound have been commonly reported amongst healthy women. The study aimed to determine the prevalence of PCO in a population of women from the community, and to relate it to clinical and endocrinological data. Twelve hundred women chosen randomly from electoral rolls were invited to take part in the study. Two hundred and fifty five women (21%) who met eligibility criteria greed to participate and 183 women 916%) finally completed the study. Seventy two women did not attend. An ultrasound scan and blood tests were taken on day 5-9 of their menstrual cycles. Data about their menstrual periods and reproductive history was collected. The prevalence of PCO was 21% (39 of 183). No differences existed between women with PCO and normal ovaries with respect to uterine size, body mass index, luteinizing hormone levels, serum hormone binding globulin levels and fertility status. Hirsutism (Ferriman Gallwey score > 7), elevated testosterone levels and irregular menstrual cycles were significantly more frequent amongst women with PCO. Mean ovarian volume was larger in women with PCO irrespective of the use of hormonal contraception. Fifty nine per cent of women with PCO had irregular menstrual cycles or elevated Ferriman Gallwey scores or both. There was no detectable effect of PCO on parity or miscarriage although only 70% of women with PCO had evidence of an adequate ovulation compared to 95% of women with normal ovaries.

Female↗
PubMed1994

Lowering the federally mandated cannabinoid immunoassay cutoff increases true-positive results.

Proposed changes to the Health and Human Services Guidelines for forensic urine drug testing will lower the required cannabinoid immunoassay cutoff concentration from 100 to 50 micrograms/L. We investigated the effect of this change on the sensitivity, specificity, and efficiency of eight cannabinoid immunoassays: Syva Emit d.a.u. 100; Syva Emit II 100; Syva Emit d.a.u. 50; Syva Emit II 50; Roche Abuscreen Online; Roche Abuscreen radioimmunoassay; Diagnostic Reagents; and Abbott ADx. All specimens also were assayed by gas chromatography/mass spectrometry. Lowering the cutoff concentration from 100 to 50 micrograms/L increased efficiencies and sensitivities for all immunoassays, with minor decreases in specificity (1.0-2.6%). There was a 23.2-53.6% increase in the number of true-positive specimens identified. Thus, lowering the cannabinoid immunoassay cutoff concentration from 100 to 50 micrograms/L resulted in detection of a substantial number of additional true-positive specimens, with an accompanying small increase in unconfirmed positive results.

Cannabinoids↗
PubMed1993

Augmented femoral venous return.

We present a technique of femoral cardiopulmonary bypass that allows excellent venous drainage. This is accomplished by augmenting the venous return with a centrifugal pump.

Blood Circulation↗
PubMed1993

Thickness of tissues intervening between the transducer and fetus and models for fetal exposure calculations in transvaginal sonography.

In transvaginal scanning the tissues intervening between the fetus and transducer are relatively thin. The average thickness in the first trimester is 25 mm and reduces to 15 mm by the third trimester; the minimum thicknesses are 14 and 8 mm, respectively. Two models are proposed for calculating exposure in transvaginal scanning. The models are considered in terms of the overlying tissues and the target tissues. A fixed path, constant attenuation of 0.3 dB/MHz describes the properties of the overlying tissues throughout pregnancy. In the model used in first-trimester scanning, the target tissues of the embryo/fetus are considered to have properties similar to those of soft tissues, and they attenuate the energy at the same rate as the overlying tissues. In the model used in second- and third-trimester scanning, the bony structures of the fetus are the target tissues. These reflect 30% of the incident energy and attenuate all of the transmitted energy at their surface.

Extraembryonic Membranes↗
PubMed1993

Validity testing of the EZ-SCREEN cannabinoid test.

Recently, a number of "quick tests" became available for use in on-site drug testing. These tests offer advantages in simplicity, ease of performance, and rapid access to test results. However, there is a paucity of data on the validity of these tests for the detection of drugs of abuse. This report describes a validity study of the EZ-SCREEN cannabinoid test for the detection of cannabinoids in urine. Three healthy, male volunteers with a history of marijuana use participated in the study. Each subject smoked 1, 2, or 4 marijuana cigarettes (2.6% THC) on each test day. Urine samples were collected and incorporated into a specimen set consisting of 178 clinical urine samples, 72 urine samples containing known amounts of drug, and 50 drug-free urine samples. The specimen set was randomized and analyzed under blind conditions by the EZ-SCREEN test and by GC/MS for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH). Results were interpreted independently by three readers. Concordance analysis was performed by comparison of results of the EZ-SCREEN test with GC/MS. The EZ-SCREEN test was highly sensitive and produced positive results at a standard THCCOOH concentration of 5 ng/mL. While showing high sensitivity to THCCOOH, the assay demonstrated low cross-reactivity with delta 9-tetrahydrocannabinol (THC) and other cannabinoids. No false-positive results were recorded with 50 drug-free urine samples, but one reader recorded eight undecided results. Overall agreement between the three readers for the EZ-Screen results was approximately 80%. Delayed readings and photocopy readings tended to be less accurate than readings obtained at 3 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Consequences of physicians' ownership of health care facilities--joint ventures in radiation therapy.

BACKGROUND: Physicians are increasingly the owners of health care facilities to which they refer patients for services but at which they do not practice. We studied such ownership arrangements, known as "joint ventures," in the field of radiation therapy, examining their effects on access, use of services, costs, and quality. METHODS: Because 44 percent of free-standing facilities providing radiation therapy in Florida in 1989 were joint ventures, as compared with 7 percent elsewhere (95 percent confidence interval, 3 to 10 percent), we compared data for Florida with comparable data for the remainder of the United States. We also compared radiation-therapy facilities in Florida that were established as joint ventures with those that were not. Since most data were derived from entire populations rather than from samples, any differences found were of necessity statistically significant. RESULTS: No joint-venture facilities providing radiation therapy were located in inner-city neighborhoods or rural areas, but 11 percent of other free-standing facilities and hospital-based facilities were located in such areas. Among free-standing facilities, joint ventures received 39 percent of their revenues from patients with well-paying insurance coverage, as compared with 31 percent for facilities that were not joint ventures (P < 0.01). The frequency and costs of radiation-therapy treatments at free-standing centers were 40 to 60 percent higher in Florida than in the rest of the United States; there was no below-average use of radiation therapy at hospitals or higher cancer rates that explained the higher rates of use or higher costs in Florida. Radiation physicists at joint-venture facilities (the principal personnel involved in quality control other than physicians) spent 18 percent less time with each patient over the course of treatment than did their counterparts at free-standing facilities that were not joint ventures (P < 0.05). Mortality among patients with cancer in Florida was not lower than the U.S. average, even though joint ventures are much more common in that state. CONCLUSIONS: Joint ventures in radiation therapy appear to have adverse effects on patients' access to care. They also appear to increase the use of services and costs substantially. Some indicators show that joint ventures cause either no improvement in quality or a decline. Our results add to the evidence indicating that physicians' self-referral generally has negative consequences. We recommend legislation to ban ownership of joint ventures by referring physicians. Such legislation needs to be carefully designed in order to achieve its objectives and forestall new, financially abusive arrangements.

Ambulatory Care Facilities↗
PubMed1992

Physician ownership of physical therapy services. Effects on charges, utilization, profits, and service characteristics.

OBJECTIVE: To evaluate the effects of physician ownership of freestanding physical therapy and rehabilitation facilities on utilization, charges, profits, and three measures of service characteristics for physical therapy treatments. DESIGN: Statistical comparison by physician joint venture ownership status of freestanding physical therapy and comprehensive rehabilitation facilities providing physical therapy treatments in Florida. PARTICIPANTS: A total of 118 outpatient physical therapy facilities and 63 outpatient comprehensive rehabilitation facilities providing services in Florida during 1989. The data from the facilities were collected under a legislative mandate. MAIN OUTCOME MEASURES: Visits per patient, average revenue per patient, percent operating income, percent markup, profits per patient, licensed therapist time per visit, and licensed and nonlicensed medical worker time per visit. RESULTS: Visits per patient were 39% to 45% higher in joint venture facilities. Both gross and net revenue per patient were 30% to 40% higher in facilities owned by referring physicians. Percent operating income and percent markup were significantly higher in joint venture physical therapy and rehabilitation facilities. Licensed physical therapists and licensed therapist assistants employed in non-joint venture facilities spend about 60% more time per visit treating physical therapy patients than licensed therapists and licensed therapist assistants working in joint venture facilities. Joint ventures also generate more of their revenues from patients with well-paying insurance. CONCLUSION: Our results indicate that utilization, charges per patient, and profits are higher when physical therapy and rehabilitation facilities are owned by referring physicians. With respect to service characteristics, joint venture firms employ proportionately fewer licensed therapists and licensed therapist assistants to perform physical therapy, so that licensed professionals employed in joint venture businesses spend significantly less time per visit treating patients. These results should be of interest to the medical profession, third-party payers, and policymakers, all of whom are concerned about the consequences of physician self-referral arrangements.

Conflict of Interest↗
PubMed1992

New evidence of the prevalence and scope of physician joint ventures.

Physician ownership of health care businesses (outside their own practice) to which they refer patients has attracted considerable attention in the medical literature, in the media, and from federal and state policymakers. Despite the concerns raised about these ownership arrangements, known as joint ventures, the prevalence and scope of joint ventures involving physicians is not well documented. This report examines the prevalence and scope of physician joint ventures in Florida based on data collected under a legislative mandate. Our results indicate that physician ownership of health care businesses providing diagnostic testing or other ancillary services is common in Florida. While this conclusion is based on our comprehensive survey of health care businesses in Florida, it is at least indicative that such arrangements are likely to occur elsewhere. We find that at least 40% of Florida physicians involved in direct patient care have an investment interest in a health care business to which they may refer their patients for services; over 91% of the physician owners are concentrated in specialties that may refer patients for services. About 40% of the physician investors have a financial interest in diagnostic imaging centers. The estimates reported here indicate that the proportion of referring physicians involved in direct patient care who participate in joint ventures is much higher than previous estimates suggest.

Data Collection↗
PubMed1992

Inhibitory effect of topical application of a green tea polyphenol fraction on tumor initiation and promotion in mouse skin.

A green tea polyphenol fraction was evaluated for its ability to inhibit tumor initiation by polycyclic aromatic hydrocarbons and tumor promotion by a phorbol ester in the skin of CD-1 mice. Topical application of the green tea polyphenol fraction inhibited benzo[a]pyrene- and 7,12-dimethylbenz[a]-anthracene-induced tumor initiation as well as 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion. Topical application of the green tea polyphenol fraction also inhibited TPA-induced inflammation, ornithine decarboxylase activity, hyperplasia and hydrogen peroxide formation. Studies with individual polyphenolic compounds in green tea indicated that topical application of (-)-epigallocatechin gallate, (-)-epigallocatechin and (-)-epicatechin gallate inhibited TPA-induced inflammation in mouse epidermis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

Continuous retrograde blood cardioplegia.

We present a technique of myocardial protection using retrograde cold blood cardioplegia. This safe and simple method allows excellent continuous and homogeneous cooling of the heart during the ischemic period in all types of open heart operations.

Cardiac Surgical Procedures↗