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Biomedical subjects

T E Powers

Publications and source records attributed to T E Powers.

At least 19 recordsLinked to original sources
PubMed2000

Prior knee injury and risk of future hospitalization and discharge from military service.

BACKGROUND: Athletic capability is paramount for survival in military basic training and successful service. Orthopedic conditions are common reasons for hospitalization and premature discharge of military recruits. Medical fitness for military service is determined through a medical examination. Individuals medically disqualified may receive a waiver to enter the service on a case-by-case basis. This study was carried out to determine how individuals with a medical waiver for knee problems compared to recruits without a history of knee injury regarding hospitalization and military discharge. METHODS: Two hundred eighty-one enlisted recruits with a history of a waiver for a knee condition were considered high risk. The comparison group was 843 recruits without prior knee pathology. Comparisons were made using frequency and chi-square analyses, relative risk estimates, and survival analyses. RESULTS: Individuals in the high-risk group were 1.4 (CI 1.0, 2.1) times more likely to be hospitalized for any diagnoses and 8.0 (CI 2. 1, 29.9) times more likely to be hospitalized for a knee condition than those in the comparison group. Individuals with a knee waiver were 2.1 (CI 1.3, 3.5) times more likely to be prematurely discharged, and 14.0 (CI 4.6, 39.6) times more likely to be discharged for a knee-related condition than those in the comparison group. CONCLUSION: Unfavorable outcomes were more likely in recruits disqualified initially and granted a waiver than in recruits without a history of knee injury. Military service requires intense physical activity; therefore, further research should be conducted to limit knee-related morbidity, especially in those with a prior history of knee injury.

Adolescent↗
PubMed1994

Random-effects linear regression meta-analysis models with application to the nitrogen dioxide health effects studies.

As the field of epidemiology grows and multiple studies of the same topic are more frequently available, increased focus is placed on quantitative methods for synthesis of results to yield an overall conclusion. A major difficulty encountered in practice has been the lack of convenient methodology for addressing groups of studies which are similar, but not exactly alike, in features which may affect study results. The age group from which subjects were selected, the general health of subjects when selected, and the specific health endpoint examined are examples of such features. Some previous investigators have addressed the problem using iterative techniques, although most have opted for simpler models which assume that differences in the studies do not appreciably affect the outcome under investigation. That is, he studies are taken to be homogeneous in that the underlying effect being investigated is the same in each study. This paper presents a random-effects linear regression technique which allows differences in the individual study features. The proposed methodology does not require iterative or other complicated procedures, making it more readily accessible to the applied researcher. We demonstrate this technique on a set of studies of the health effects of indoor NO2 exposure in children. It is seen that odds ratios from these studies vary considerably according to subject age, the study location, and the health endpoint considered. A simple synthesis which does not account for these differences may be misleading.

Air Pollutants, Occupational↗
PubMed1990

Pharmacokinetics and the dosage regimen of antimicrobial agents.

Some consider antimicrobial therapy an art rather than a science. The drug concentration at the site of infection is often assumed to be a major factor in predicting efficacy and high serum concentrations are assumed to have an advantage by increasing the amount of drug that diffuses into the various body tissues and fluids. Pharmacokinetic studies, along with pharmacodynamic studies, remain to be an important and essential portion of the data base needed for the determination of a proper dosage regimen for antimicrobial agents prior to clinical trials. Additional studies are needed to define the influence of the post antibiotic effect and post antibiotic leukocyte enhancement, as well as the subminimal and supraminimal inhibitory concentrations, on establishing the proper dosage regimen. It is recommended that the insert for a prescription antimicrobial agent should contain pharmacokinetic parameters, such as volume of distribution, t1/2 and body clearances.

Animals↗
PubMed1987

Tissue concentrations and pharmacokinetics of florfenicol in male veal calves given repeated doses.

The pharmacokinetic disposition of florfenicol was studied in male veal calves given 11 mg of florfenicol/kg of body weight, IV and 11 mg of florfenicol/kg PO every 12 hours for 7 doses. After florfenicol administration IV, the median elimination half-life was 222.8 minutes, whereas the median half-life of the distribution phase was 7.94 minutes. Median body clearance and apparent volume of distribution were 2.87 ml/kg/min and 0.907 L/kg, respectively. After florfenicol administration, PO, there was a wide variation in the calculated half-life, which was attributed to variation in the rate of florfenicol absorption. The half-life was 167.4 to 534.9 minutes after the first oral dose and 190 to 808.8 minutes after the seventh dose. The median bioavailability after the first oral dose was 0.8888. Peak and trough concentrations of florfenicol were increased after subsequent doses were administered, compared with those after the first oral dose. The percentage of protein binding in serum from one adult cow was 22% to 26%. Florfenicol concentrations in tissues and body fluids of male veal calves were studied after the seventh dose of 11 mg of florfenicol/kg. High concentrations of florfenicol were measured in the urine, kidney, and bile. Low concentrations were measured in the brain, CSF, and aqueous humor. Concentrations in all other tissues and fluids studied were similar to the concurrent serum concentration.

Administration, Oral↗
PubMed1987

Single- and repeat-dose pharmacokinetic studies of chloramphenicol in horses: values and limitations of pharmacokinetic studies in predicting dosage regimens.

A single-dose pharmacokinetic study of chloramphenicol in propylene glycol was done in 6 horses after 22 mg/kg was administered IV. Serum drug concentrations obtained at various predetermined intervals were determined by an electroncapture gas-chromatographic technique. The time-concentration data were described by a 2-compartment open model, and various pharmacokinetic variables were estimated. The median elimination rate constant was estimated to be -0.0185 minute-1 (-0.0225 to -0.0148 minute-1), and the median half-life was 37.36 minutes (30.74 to 46.90 minutes). The median apparent volume of distribution and total body clearance were 1.46 L/kg (1.13 to 1.60 L/kg) and 25.56 ml/kg/min (23.66 to 32.21 ml/kg/min), respectively. On the basis of these data, single- and repeat-dose kinetic studies were done in another group of 6 animals. The drug was administered at a dosage of 22 mg/kg every 4 hours for 3 days. Blood samples were obtained for pharmacokinetic studies after the first and the last doses were given. The half-life, volume of distribution, and total body clearance did not change significantly (Wilcoxon signed rank test) after 3 days of therapy with chloramphenicol. The IV dose schedule for treating bacterial infections with organisms of different sensitivities has been determined from the estimates of the pharmacokinetic variables. The limitations of calculating the dose schedules for chloramphenicol on the basis of pharmacokinetic variables in horses are discussed.

Animals↗
PubMed1986

Pharmacokinetics of florfenicol in veal calves.

The pharmacokinetic disposition of florfenicol was described in veal calves after administration of a single 22-mg/kg dose intravenously, orally after a 12-h fast and orally 5 min post feeding. Both serum concentrations and urinary excretion were studied. After intravenous administration the median elimination half-life was 171.9 min while the half-life of the distribution phase was 5.9 min. The median body clearance (Cl) and apparent volume of distribution (Vz) were 2.85 ml/kg/min and 0.78 l/kg, respectively. Following oral administration the median bio-availability (f) was 0.88 for calves dosed after a 12-h fast and 0.65 for calves dosed 5 min post feeding. Calves given the oral doses had a complex absorption pattern with delayed absorption. Slightly more than 50% of the administered dose both orally and intravenously was recovered as unchanged florfenicol in the urine by 30 h.

Administration, Oral↗
PubMed1984

Clearance of penicillin G in the newborn calf.

Sodium penicillin G was administered intravenously (4545 IU/kg) to calves on the day of birth (12-24 h old) and at 5, 10, and 15 days of age. Serum was collected at varying intervals for 120 min after injection and analysed for penicillin G. The mean total body clearance (ClB) of penicillin G on the day of birth was 2.98 ml/min/kg compared to 4.83 ml/min/kg at 5 days, 3.11 ml/min/kg at 10 days and 4.65 ml/min/kg at 15 days of age. Clearances at 5 and 15 days were significantly (P less than or equal to 0.05) higher than on the day of birth. The half-life (t1/2 beta), however, did not change significantly over the 15-day period of the study. These results indicate that the newborn calf has an appreciable ability to excrete penicillin G before it is 24 h old, and that total body clearance of the antibiotic increases rapidly in the immediate postnatal period.

Aging↗
PubMed1984

Standardization of an experimental disease model of Streptococcus zooepidemicus in the equine.

A reproducible experimental disease model in horses using Streptococcus zooepidemicus was developed. An intravenous challenge dose of 1 X 10(10) colony-forming units (CFU), followed 24 h later with another challenge of 1 X 10(8) CFU of Strep. zooepidemicus produced the desired disease model. The disease was characterized by depression, pyrexia, anorexia, abnormal lung sounds, inflammation of joints, moderate to severe lameness, gradual loss of condition and emaciation. The effects of the disease on hematology, serum chemical profile and different protein fractions were studied. The disease state had no effect on serum glucose, sodium, potassium, chloride, urea nitrogen, creatinine, uric acid, calcium, phosphorus and enzymes SGOT or SGPT. However, the alkaline phosphatase showed a gradual decline. The serum iron levels dropped markedly and remained low to the last day of observations (post-infection day, PID 13). On serum protein electrophoresis, the albumin showed a gradual decrease; whereas, alpha II, beta and gamma globulin levels rose suggesting an immune response. The elevation of rectal temperatures and white blood cell counts related well with clinical observations. The serum iron levels proved very helpful in predicting the severity of clinical signs and often dropped before the onset of clinical signs and pyrexia.

Animals↗
PubMed1984

A health index to evaluate clinically a beta-hemolytic streptococcal infectious disease model in the horse.

Quantification of the clinical manifestations of a disease has been a serious problem particularly as related to clinical trials or drug efficacy studies. Historically, this quantification has been limited to categorizing each patient into one of three or four groups, e.g. worse, no improvement, improved. This problem becomes serious when an investigation utilizes an experimentally induced animal disease model. A health index, which quantifies the clinical state of horses which have an experimentally induced beta-hemolytic streptococcal infection, is described. Aspects of experimental design and statistical analysis are also discussed in relationship to the use of the index for drug efficacy studies.

Animals↗
PubMed1983

Experimental Streptococcus equi infection in the horse: correlation with in vivo and in vitro immune responses.

Fourteen young outbred horses, divided into 2 groups on the basis of 18- or 24-hour skin-test reactions to Streptococcus equi, were inoculated nasopharyngeally with virulent S equi. Animals (n = 6, group I) with evidence of previous exposure to S equi (positive dermal response and existing serum antibodies), with one exception, developed minimal or no signs of disease after inoculation. In contrast, S equi skin-test negative and seronegative horses (n = 8, group II) developed predictable and severe clinical signs of infection after their inoculation, including shedding of the organism from nasal discharges and ruptured mandibular lymph nodes. Results of the present study indicate that resistance to virulent S equi infection is correlated with existing humoral and cellular immune responses to streptococcal antigens. In susceptible horses, recovery from infection was accompanied by the appearance of humoral antibodies and the acquisition of a positive skin-test response to S equi antigens.

Animals↗
PubMed1981

A study on renal function in the Indian buffalo (Bubalus bubalis).

Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) in buffalo species (Bubalus bubalis) were estimated using a single injection technique. The total body clearances of inulin and para-aminohippuric acid (PAH) served as estimates of GFR and ERPF, respectively. Inulin and PAH were administered to animals as a single i.v. bolus. The time-concentration curves were determined for each compound. Three mathematical models were applied to the data. The two compartment model gave the best fit to the data. The single compartment model gave slightly higher values, but could be used in clinical and certain research situations to estimate renal functions when it is not practical to take large number of samples.

Animals↗
PubMed1980

Pharmacotherapeutics of newer penicillins and cephalosporins.

The beta-lactam group of compounds includes a large number of biologically active substances. Some are important as antibiotics (penicillin and cephalosporins) or antibiotic precursors (6-aminopenicillanic acid) and some are important due to their inhibitory action on several beta-lactamases. The pharmacologic features of these compounds are discussed on the basis of their structure, mechanism of action, pharmacokinetics, therapeutics, toxicologic properties, interaction, and incompatibilities.

Animals↗
PubMed1980

Statistical considerations in clinical field evaluation of drugs.

Statistical problems associated with clinical field evaluation of drugs are many. The Food and Drug Administration requires that the safety and efficacy of a drug must be shown in adequate and well-controlled clinical investigations. From a statistical point of view, safety and efficacy must be precisely defined, and a quantitative method must be developed to measure these properties. It is proposed that efficacy be defined in both the therapeutic and pharmacologic aspects. Further, to measure therapeutic efficacy, it is suggested that an appropriate health index be used. This index would provide information regarding degree of improvement and also the time course of improvement. To measure or evaluate pharmacologic efficacy, it is suggested that kinetic studies be done to compare half-lives, volumes of distribution, and any other relevant kinetic parameter(s).

Animals↗
PubMed1980

Trimethoprim and sulfadiazine: experimental infection of Beagles.

The purpose in the present study was to determine whether the commercial combination of trimethoprim (TMP) and sulfadiazine (SDZ) tribrissen (TRI) was more effective than either of the components for treating experimentally induced infection of Streptococcus zooepidemicus. Two dose levels of each were given subcutaneously for treatment, and their effectiveness was compared with that of sulfadimethoxine (SDM) in terms of (i) clinical manifestations, (ii) hematologic changes, (iii) blood culture examinations, and (iv) tissue culture examinations. According to these four measurements, the combination TMP/SDZ was more effective than either of the components. This effect was observed at the two dosages of TRI (30 and 15 mg/kg). The higher dosage, however, was more effective as demonstrated by three of the measurements. Alone, TMP and SDZ were not effective, but SDM treatment was effective in this model.

Animals↗