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Biomedical subjects

A M Tucker

Publications and source records attributed to A M Tucker.

At least 19 recordsLinked to original sources
PubMed2000

Transformation of Rickettsia prowazekii to erythromycin resistance encoded by the Escherichia coli ereB gene.

Rickettsia prowazekii, the etiologic agent of epidemic typhus, is an obligate, intracytoplasmic, parasitic bacterium. Recently, the transformation of this bacterium via electroporation has been reported. However, in these studies identification of transformants was dependent upon either selection of an R. prowazekii rpoB chromosomal mutation imparting rifampin resistance or expression of the green fluorescent protein and flow cytometric analysis. In this paper we describe the expression in R. prowazekii of the Escherichia coli ereB gene. This gene codes for an erythromycin esterase that cleaves erythromycin. To the best of our knowledge, this is the first report of the expression of a nonrickettsial, antibiotic-selectable gene in R. prowazekii. The availability of a positive selection for rickettsial transformants is an important step in the characterization of genetic analysis systems in the rickettsiae.

Animals↗
PubMed1998

The development of a risk-adjusted capitation payment system: the Maryland Medicaid model.

This article describes the risk-adjusted payment methodology employed by the Maryland Medicaid program to pay managed care organizations. It also presents an empirical simulation analysis using claims data from 230,000 Maryland Medicaid recipients. This simulation suggests that the new payment model will help adjust for adverse or favorable selection. The article is intended for a wide audience, including state and national policy makers concerned with the design of managed care Medicaid programs and actuaries, analysts, and researchers involved in the design and implementation of risk-adjusted capitation payment systems.

Ambulatory Care↗
PubMed1998

Smokeless tobacco, reaction time, and strength in athletes.

PURPOSE: This study investigated the effects of smokeless tobacco on reaction time and strength in a group of Division III athletes. METHODS: Athletes were tested for simple and choice reaction time, maximum voluntary force, and maximum rate of force generation of the knee extensors on a KinCom dynamometer at 250 degrees.s-1. Smokeless tobacco-using athletes (N = 20) were tested while both using and after abstaining from smokeless tobacco. Another group of athletes (N = 20) who did not use smokeless tobacco served as a control group. RESULTS: Simple and complex reaction times were not affected by smokeless tobacco use or abstention. In the simple reaction time test, maximum voluntary knee extensor force was higher in the smokeless tobacco-using group while abstaining (P < 0.05). Maximum rate of force generation in the simple reaction time test was not statistically different between the conditions. In the choice reaction test, both strength parameters (maximum force and maximum rate of force generation) were higher in the user group while abstaining (P < 0.05) compared with the using condition. The strength parameter measurements in the control group were not statistically different from the tobacco-using group, while either using or abstaining. CONCLUSIONS: We conclude that smokeless tobacco use has no effect on reaction time but may detrimentally influence maximum voluntary force and maximum rate of force generation.

Adolescent↗
PubMed1998

Transformation of Rickettsia prowazekii to rifampin resistance.

Rickettsia prowazekii, the causative agent of epidemic typhus, is an obligate intracellular parasitic bacterium that grows directly within the cytoplasm of the eucaryotic host cell. The absence of techniques for genetic manipulation hampers the study of this organism's unique biology and pathogenic mechanisms. To establish the feasibility of genetic manipulation in this organism, we identified a specific mutation in the rickettsial rpoB gene that confers resistance to rifampin and used it to demonstrate allelic exchange in R. prowazekii. Comparison of the rpoB sequences from the rifampin-sensitive (Rifs) Madrid E strain and a rifampin-resistant (Rifr) mutant identified a single point mutation that results in an arginine-to-lysine change at position 546 of the R. prowazekii RNA polymerase beta subunit. A plasmid containing this mutation and two additional silent mutations created in codons flanking the Lys-546 codon was introduced into the Rifs Madrid E strain of R. prowazekii by electroporation, and in the presence of rifampin, resistant rickettsiae were selected. Transformation, via homologous recombination, was demonstrated by DNA sequencing of PCR products containing the three mutations in the Rifr region of rickettsial rpoB. This is the first successful demonstration of genetic transformation of Rickettsia prowazekii and represents the initial step in the establishment of a genetic system in this obligate intracellular pathogen.

Amino Acid Sequence↗
PubMed1997

Common soccer injuries. Diagnosis, treatment and rehabilitation.

Soccer is a game with worldwide appeal. Increasing numbers of participants are members of all age groups and skill levels. The game presents to the sports medicine practitioner a wide variety of musculoskeletal and medical problems. Soccer injuries increase in frequency as the age of participant increases, with a low incidence of injury in preadolescent players. Musculoskeletal injuries most commonly affect the lower extremities and include contusions, acute and chronic musculotendinous strains, and ligamentous injuries to the knee and ankle. Most injuries are minor and respond to analgesics, therapy modalities and exercise therapy. Groin pain is a common problem and particularly prevalent among soccer players owing to the game's specific stresses. Other less common but important injuries include facial trauma, mild brain injury (concussion) and heat-related injury. Team physicians, athletic trainers and physical therapists need to possess a basic understanding of the most common injuries and problems in order to maximise safe participation for their athletes.

Ankle Injuries↗
PubMed1996

Profiling primary care physician resource use: examining the application of case mix adjustment.

Growing emphasis on managed care has led to increased interest in physician practice profiling. Standardized techniques for conducting profiling are not yet well established. One particularly challenging methodologic issue, case mix adjustment, is explored here using actual cost profiles derived from primary care physicians at two independent practice association (IPA)-model health maintenance organizations (HMOs). Specifically, this article examines how the ambulatory care group case mix methodology can be applied to profiling and illustrates that it provides more depth of information with which to assess performance than does standard demographic adjustment alone. This analysis suggests both the potential and methodologic limitations of profiling at the individual physician level.

Ambulatory Care↗
PubMed1996

Role of plasminogen activator inhibitor in the reciprocal regulation of bovine aortic endothelial and smooth muscle cell migration by TGF-beta 1.

Vascular endothelial and smooth muscle cells exhibit reciprocal migratory responses after transforming growth factor (TGF)-beta 1 treatment. Endothelial cells exhibit a decreased migratory rate and smooth muscle cells exhibit an increased migratory rate. Previous studies have demonstrated increases in extracellular matrix and integrin synthesis and expression in response to TGF-beta 1. In this report, we illustrate the roles of plasminogen activator inhibitor in modulating the migratory rates in these two cell types. Endothelial cells appear to require a proteolytic phenotype for rapid migration, whereas vascular smooth muscle cells appear to require an anti-proteolytic phenotype. Modulation of proteinase/anti-proteinase activity ratios was accomplished via TGF-beta 1 induction, addition of exogenous plasminogen activator inhibitor, addition of anti-catalytic antibodies directed against urokinase plasminogen activator, overexpression of plasminogen activator inhibitor utilizing stable transfectants, and the use of vitronectin as a substratum. The reciprocal migratory behaviors exhibited by these two vascular cell types in response to TGF-beta 1 is discussed in the context that these two vascular cell types utilize distinct adhesive and signaling pathways in their interactions with extracellular matrix components and responsiveness to proteolytic activity.

Animals↗
PubMed1994

Shoulder pain in a football player.

A 19-yr-old college football player presents with a 1.5-yr history of right shoulder pain and associated easy fatigability of the right arm. The history is significant for an automobile accident 3 yr prior to presentation in which the right shoulder struck the dashboard of the car. An extensive workup proved unremarkable. Treatment included multiple trials of anti-inflammatory medication and extensive physical therapy without benefit. The patient underwent a first rib resection for thoracic outlet syndrome with significant relief of symptoms. Thoracic outlet syndrome (TOS) may mimic other more common causes of shoulder and arm symptoms. Diagnosis may be difficult as tests are often nonconfirmatory. Conservative treatment usually is adequate. In resistant cases, surgery may be indicated.

Accidents, Traffic↗
PubMed1992

Realizing the potential of practice pattern profiling.

In January 1992, the Physician Payment Review Commission held a conference to learn about the appropriateness of present uses of profiling of practice patterns, and to identify what will be required to realize the full potential of this technique in the future. The conference addressed the data needs of profiling, the development of valid and relevant profiles, the impact of profiles on medical practice, and controversies surrounding public access to profiling information and the uses to which profiling has been put. This paper, based in part on that conference, reviews the basic concepts that underlie profiling and describes the roles that profiling can play in quality improvement, assessment of provider performance, and utilization review. It uses case studies to illustrate the types of problems that have arisen in actual usage and discusses what will be required to resolve them. The final section describes the roles that profiling can play in achieving the goals of health care reform, and concludes with what is needed in data and infrastructure development to improve the quality and usefulness of profiling.

Data Collection↗
PubMed1988

Phenotypic modulation of endothelial cells by transforming growth factor-beta depends upon the composition and organization of the extracellular matrix.

Transforming growth factor beta (TGF-beta) is angiogenic in vivo. In vitro, endothelial cell proliferation is inhibited by TGF-beta. We have correlated this inhibitory effect with an increase in cellular fibronectin synthesis and deposition in a two-dimensional culture system using specific matrix coatings. The inhibitory effect was mimicked by addition of soluble fibronectin to cultures. In contrast, TGF-beta was found to elicit the formation of tube-like structures (mimicking angiogenesis) when microvascular endothelial cells were grown in three-dimensional collagen gels. In this culture system TGF-beta elicited rapid extensive formation of complex, branching, tube-like structures, while cell proliferation was not inhibited. These data confirm and support the hypothesis that TGF-beta is angiogenic and may exert some of its effects through modulation of matrix synthesis and are consistent with the hypothesis that the organization of the extracellular environment influences cellular responses to this "panregulin."

Angiogenesis Inducing Agents↗
PubMed1988

Disenrollment patterns in Medicare HMOs: a preliminary analysis.

This paper examines disenrollment patterns of 17 Medicare Competition Demonstration HMOs during 1984. Characteristics of HMO disenrollees for a sample of Medicare beneficiaries from two surveys conducted in early 1985 and 1986 are also examined. These data provide a preliminary, descriptive analysis of the nature and the implications of Medicare HMO disenrollment.

Data Collection↗
PubMed1984

The role of the accessory and main olfactory systems in maternal behavior of the primiparous rat.

The objective of this study was to analyze the respective roles of the main and accessory olfactory systems in the development of maternal behavior in the primiparous Wistar rat. Females underwent one of the following treatments: vomeronasal nerve section (VN), irrigation of nasal cavities with 5% ZnSO4 solution (ZN), surgical control, saline irrigation control, and normal control. Surgical or first irrigation were done before mating occurred. Irrigations were done every 7 days thereafter. The dams and their litters were observed from the day the litter was born (Day 1) through Day 16. Pup weights and temperatures were recorded daily. Home cages were checked daily for changes in nest location and number of times pups were found out of the nest. Retrieving tests were conducted on Days 4, 7, 10, and 13. The following behavioral items were observed: number of pup retrievals , number of times mother nosed or licked pups, percentage of litter returned to nest by end of test, dam self-grooming, dam climbing or rising, and dam digging or burrowing in shavings. The VN dams and their litters were not significantly different from the control dams and their litters on any of the measures taken. The ZN dams and their litters were not significantly different from their controls on all measures except for pup body temperature which was slightly lower from Day 13 through day 16 and pup body weight which was slightly lower from Day 12 through Day 16. Since these differences are very small, they do not seem to indicate a serious deficiency in maternal behavior. The results indicate that adequate maternal behavior develops with either of the two systems intact.

Animals↗
PubMed1977

Self-assessment of hearing impairment: test of the expanded hearing ability scale questionnaire on hearing impaired adults in England.

The National Center for Health Statistics developed a questionnaire for self-assessment of hearing impairment which has been widely tested in the United States. The performance of this questionnaire was tested on a sample of 131 people in England, known to have hearing impairment and gave results very similar to those obtained in the United States. These results are compared with a randomly selected sample from the general population. Characteristics of the hearing ability scale derived from the questionnaire are discussed and some suggestions made for a modified version of the questionnaire. The relationship between the average pure tone threshold and the score derived from the hearing ability scale questionnaire is described and takes the form of a bounded relationship with scale score indicating the minimum threshold level.

Adolescent↗
PubMed1974

Patients' attitudes to the provision of medical care from a health centre.

A one in 20 sample of patients aged 18 and over registered at a health centre in Sidmouth were interviewed in their homes. Information about their personal characteristics was related to patients' use of the centre. A majority of patients found the facilities satisfactory and approved of the health-centre concept. Suggestions for improvements were also obtained.

Consumer Behavior↗