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Biomedical subjects

R Henderson

Publications and source records attributed to R Henderson.

270 records · Page 15Linked to original sources
PubMedDate not supplied

MRC image processing programs.

Digital image processing is an essential step in the determination of macromolecular structures by electron microscopy. Centrally important procedures are the averaging of many images of the subunit to improve the signal, the correction for various transfer functions, and the generation of a three-dimensional map from a set of two-dimensional projections. The detailed way in which these computational procedures are best carried out depends on the symmetry of the object and the type of specimen preparation. Over many years a large set of programs has been written by various members of the Laboratory of Molecular Biology for processing images of two-dimensional crystals and of particles with helical or icosahedral symmetry. The philosophy has been to write stand-alone programs and the whole system is given coherence by the adoption of standard formats for the storage and interchange of different kinds of data. This paper describes the current state of the programs.

Bacteriophage T4↗
PubMedDate not supplied

High dietary NaCl early in development enhances mean arterial pressure of adult rats.

We investigated the long-term influence of early dietary NaCl on adult mean arterial pressure (MAP) and heart rate (HR), assessed continuously for 7 weeks when fed water and chow containing 1% NaCl (weeks 1, 4, 7), 0% NaCl (weeks 2-3), and 3% NaCl (weeks 5-6) while on a 12:12 light/dark cycle. Subjects were offspring of female Sprague-Dawley rats fed solid chow consisting of either 0.1% (basal), 1% (intermediate), or 3% (high) NaCl throughout pregnancy and lactation. After weaning on postnatal day (PD) 21, offspring were fed the same NaCl diet of their mother until PD 30, at which time all offspring were given Purina 5001 diet (1% NaCl) as their solid chow. On PD 60, 22 adult male offspring (eight basals, six intermediates, eight highs) were implanted with an aortic electronic sensor for transmitting blood-pressure signals by telemetry. MAP and HR varied significantly across the 7-week testing period in association with dietary NaCl levels. The three perinatal salt groups had similar HR levels on normal 1% NaCl chow. However, HR increased in all groups during 0% NaCl and decreased in all groups during 3% NaCl. In contrast, the average MAP levels were significantly greater in the highs compared to both the intermediate and basal groups during both dark and light periods. MAP increased in high and basal groups during both 0% and 3%; however, the increase was more pronounced in the highs. In conclusion, exposure to high levels of dietary NaCl early in development led to a persistent increase in MAP in adulthood.

Animals↗
PubMedDate not supplied

Incidence of non-Hodgkin lymphoma in kidney and heart transplant recipients.

Organ transplant recipients receive immunosuppressive drugs to prevent graft rejection. This treatment has been associated with higher rates of non-Hodgkin lymphoma (NHL) than in the general population. We assessed the incidence of NHL in a multicentre study of 45,141 kidney transplant patients and 7634 heart transplant recipients. The NHL rate was especially high during the first post-transplant year among both kidney transplant recipients (101 cases vs 2.7 expected in general population; 224 per 10(5)) and heart transplant recipients (93 vs 0.6 expected; 1218 per 10(5)). The incidence was lower in subsequent years (43 and 371 per 10(5) in kidney and heart transplant recipients). During the first year the NHL incidence was higher in North America than in Europe (relative risk 2.12 [95% CI 1.55-2.89]). There were also significant increases in risk for patients who received rejection prophylaxis with antilymphocyte antibodies (1.80 [1.31-2.46]) and in those who received both cyclosporin and azathioprine rather than another immunosuppressive combination (1.47 [1.03-2.08]). This study quantified the risk of NHL after kidney or heart transplantation. It suggests that the risk of NHL is related to the aggressiveness of the immunosuppressive regimen.

Adolescent↗
PubMedDate not supplied

Preparation of cryoprecipitated factor VIII concentrates.

Factors affecting the yield of factor VIII in cryoprecipitate have been investigated in the context of a blood component program. Both in vitro and in vivo measurements were used to assess the effects of critical variables on the yield of factor VIII activity. Variables such as anticoagulant, plastic bag, mixing during collection, and platelet contamination had no significant effect on yield of factor VIII activity in cryoprecipitate. Among the most critical factors affecting yield were storage time of whole blood and procedures for freezing, thawing, and reconstitution. The following procedures were found to assure a 60 per cent recovery of factor VIII in cryoprecipitate: 1)processing of whole blood within six hours of collection; 2)use of a technique to freeze plasma within 30 minutes either in a -70 C ethanol bath or -85 C freezer; 3)rapid thawing (1 1/2 hour or less) in a 4 C circulating water bath; 4)centrifugation at 4,500 X g for 10 minutes at 4 C followed by draining of the supernatant in a 4 C cold room; 5) storage of the precipitate at -20 C until ready for use; 6) thawing in a 37 C water bath for at least 15 minutes followed by addition of 20 ml of 0.15 M saline for a 20 minute period at room temperature, and gentle mixing before pooling units for transfusion. The recovery of factor VIII in cryoprecipitate appears to be limited to about 65 per cent by its solubility in plasma at 4 C. Therefore, further effort to increase the amount available for treatment should involve improving the supply of plasma for its preparation and decreasing the cost of processing.

Blood Cell Count↗
PubMedDate not supplied

Coagulation factor activity in platelet concentrates.

Coagulation factor activity in platelet concentrates stored under different condtions was investigated. At both 22 C and 4 C, coagulation factors, II, VII, IX, X, XI, and XII and fibrinogen were well maintained up to 72 hours. Factor V activity declined slightly in platelet concentrates stored at 4 C (to 78% at 72 hours), but fell to 47 per cent activity in platelets stored at 22 C. Factor VIII activity declined to approximately 68 per cent of normal activity by 72 hours at both 22 C and 4 C. Agitation did not make a difference in levels of coagulation factors. While the decline in Factor V was clearly more pronounced in platelet concentrates than in platelet-poor plasma from the same units, the decline in Factor VIII was decreased by the presence of platelets. Platelet concentrates are a source of coagulation factor activity which should be considered in a component program.

Blood Coagulation Factors↗
PubMedDate not supplied

The effect of induced reflections on human arterial waveforms.

1. External compression of the human brachial artery results in waveform reflection. 2. Resonant waves are found superimposed on the original blood pressure signal. 3. The mechanism may be likened to the operation of an organ pipe with reflections at both ends of an arterial segment. 4. This has implications for measurements in arteries where external pressure is applied.

Adult↗
PubMedDate not supplied

Computer-compatible patient contour plotter.

The use of a compact, mobile, relatively inexpensive electromechanical patient-contouring mechanism is described. The system utilizes a Numonics Model 224 graphics digitizer suspended over the patient. The digital X and Y coordinates of the patient contour in either of multiple, parallel transverse, or sagittal planes are inherently accurate to within +/-0.25 mm over a total reading are of 60X90 cm. Display features include the interface to an analog 11-in.X17-in. X-Y plotter with a variable scale-down factor for those contours which would otherwise be larger than the plotting surface. The system is easy to use and may also be readily interfaced for on-line entry of patient contours to calculator- or minicomputer-based treatment-planning systems.

Computers↗
PubMedDate not supplied

The need for policy and risk analysis--the Department of Energy experience.

Reduction of major risks to the public and workers is a top priority of all federal agencies. Given current and future budget realities, agencies cannot attempt to address all risks simultaneously nor to address certain relatively lower risk activities as rapidly as some would like. The assumptions and judgments inherent in using risk analysis in the absence of data, however, have to be clearly stated. What is needed is an integrated risk assessment and management process that meets the current and future needs of the government, as well as of stakeholders. Yet there have been many questions raised regarding risk assessment: our ability to define the risks on a specific substance or site basis and in a systematic way; methodology questions about identifying and assessing diverse hazards and risks as well as uncertainties in the estimates, data gaps, and concern over the quality of information; and the fact that "who" performs the risk assessment matters. Knowing these controversies surrounding risk and the use of risk-based approach, the Department of Energy (DOE) requested the National Academy of Sciences-National Research Council to determine whether and how risk and risk-based decisions could be incorporated into a major federal program, the DOE's Office of Environmental Management. The report identified the major obstacles, issues, and barriers to implementing a risk-based management approach. The report concluded that the use of risk-based approach could help compare outcomes, build consensus, and gain early public involvement to include cultural, socioeconomic, historical, and religious values, if its purposes and limitations are well defined. A status of the DOE's ability to implement the recommendations presented in the report on the use of risk assessment in a major federal program and the adoption of principles for using risk analysis will be given.

Government Agencies↗
PubMedDate not supplied

Efficacy of strength training in prepubescent to early postpubescent males and females: effects of gender and maturity.

There has been considerable debate concerning the benefits of children participating in weight training programs. With the potential benefits of such training in specific rehabilitation regimens, the safety/efficacy of weight training is a topic in need of scientific study. Fifty-two experimental and 39 control subjects participated in this study. A 2 x 2 x 2 (gender by treatment by Tanner stage) ANOVA was used to examine pre- to post-test differences in six strength measures, eight anthropometric measures, five motor performance measures, and one flexibility measure associated with participation in a 12-week progressive resistance programme. In addition, safety of the weight training programme was examined. For strength differences, there were two significant main effects favouring strength gains in males and four favouring the experimental group. For anthropometric changes, 3-way interactions occurred that were not easily explained. However, the predominant main effect was treatment; the experimental group generally experienced gains in body segment girths with decreases in skinfold thickness. For motor performance, the experimental group had greater improvements in three of five parameters. The experimental group also had significantly greater gains in flexibility. The weight training programme was associated with only one injury. These findings support the general observation that physical benefits can be gained safely by children who participate in a weight training programme.

Adolescent↗
PubMedDate not supplied

The effect of a closed formulary on prescription drug use and costs.

This study examines the effect of a closed formulary on pharmaceutical use and spending. We compared an employer plan that implemented a closed formulary in July 1997 to a control group with an open formulary, for the nine months preceding and following implementation of the formulary. When controlling for age, gender, and chronic disease score, the closed formulary was associated with significantly lower increases in utilization and expenditures, a higher prior authorization rate, and a reduced rate of continuation with chronic medications in the nine months following its implementation. These findings have implications for the design of prescription drug benefits.

Adult↗
PubMedDate not supplied

Sonography for fluid collections in the leg.

Ultrasound may be used in the diagnosis and follow-up of fluid collections in the soft tissues of the leg. As in all parts of the body, anatomy dictates the fundamental sonographic approach. It is suggested that an examination carried out following the guidelines above will ensure a thorough and replicable study.

Edema↗
PubMedDate not supplied

Assessment of satisfaction with computer training in a healthcare setting.

The use of computers in healthcare settings has become increasingly common. However, issues of training and training assessment have received scant attention. The main aim of the current study was to assess the use of consumer satisfaction data for evaluation and development of computer training packages in healthcare settings. One hundred and thirty-six randomly selected people completed a brief satisfaction questionnaire at the completion of computer training. The effects of different teachers, course duration, course complexity, and changes in satisfaction over time were examined. The use of a customer satisfaction approach to training evaluation is discussed.

Computer User Training↗