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Biomedical subjects

R A Jenkins

Publications and source records attributed to R A Jenkins.

At least 37 records · Page 2Linked to original sources
PubMed1995

Incentives and disincentives to participate in prophylactic HIV vaccine research.

An anonymous cross-sectional paper-and-pencil survey was used to assess incentives and disincentives to participate in a Phase I preventive human immunodeficiency virus (HIV) vaccine trial in a potential Thai target population. A total of 255 persons employed in health care service and research settings completed questionnaires after attending informational briefings regarding the proposed vaccine product and the planned trial procedures. Willingness to participate was related to self-perceived benefits from joining a preventive vaccine trial, as well as to concerns about product safety and social discrimination that might result from participation. The distinction between positive results of enzyme-linked immunosorbent assay from vaccine administration and positivity from HIV infection was unclear for many participants. Men were more willing to participate than women, and there was a trend toward greater willingness to participate in those who were less educated. Preparations for preventive vaccine trials may be more successful if they emphasize personal benefits of trial participation, clearly address safety issues, and consider ways to prevent social discrimination against participants.

AIDS Vaccines↗
PubMed1993

Cognitive distraction and relaxation training for the control of side effects due to cancer chemotherapy.

Sixty cancer chemotherapy patients were randomly assigned to one of six conditions formed by a 3(cognitive distraction, relaxation training, no intervention) x 2(high anxiety, low anxiety) factorial design. All patients were followed for five consecutive chemotherapy sessions. Outcome measures included patient reports, nurse observations, and physiological indices. Results indicated that distraction patients reported less nausea prior to chemotherapy and lower systolic blood pressures after chemotherapy than controls. Relaxation training patients reported less nausea prior to chemotherapy and exhibited lower systolic and diastolic blood pressures after chemotherapy than control patients. There were no significant differences between distraction and relaxation training patients on any measure. Patients with high initial levels of anxiety exhibited continually elevated levels of distress throughout the chemotherapy experience; however, anxiety level did not interact with the effectiveness of the treatment interventions. Overall, the data support the use of both cognitive distraction and relaxation training for reducing the distress of chemotherapy with both high and low-anxiety patients and suggest that at least some of the effects of relaxation training can be achieved with distraction alone.

Adult↗
PubMed1993

Neuropsychiatric morbidity in early HIV disease: implications for military occupational function.

The Military Medical Consortium for Applied Retroviral Research Program's (MMCARR) Behavioral Medicine Human Immunodeficiency Virus (HIV) Research component is conducting a tri-service, comprehensive, and longitudinal research study in military HIV-infected personnel at all stages of infection. Identification of neuropsychiatric and psychosocial outcomes and their determinants will help the military minimize the impact of the HIV epidemic on military readiness and function. Neuropsychiatric and psychosocial findings are among the most common complications seen in early HIV disease and among the most likely to have an adverse impact on military readiness and function. The study has demonstrated that the average HIV-infected service person experiences at least transient military occupational difficulty following notification of HIV status. More than 15% at any given time have levels of clinical or subclinical anxiety or depression that are referrable for mental health intervention. Ten per cent of study subjects have a current major mood disorder and 5% have a psychoactive substance use disorder. Finally, 17% of study subjects have experienced serious suicidal ideation or behaviours at least once since notification of seropositivity. Fortunately, however, data also indicate at least partial effectiveness of current primary, secondary and tertiary preventive efforts. Only about 1% of Air Force HIV-infected persons are discharged for psychiatric reasons prior to eventual medical discharge. Further, a large majority of active-duty patients demonstrate solid military occupational and social performance. Though military HIV neurobehavioural research is still in progress, preliminary data identify social support and pre-HIV psychiatric predisposition as important factors associated with current neuropsychiatric status.

Aerospace Medicine↗
PubMed1992

Effectiveness of biofeedback and relaxation training in reducing the side effects of cancer chemotherapy.

Assessed the effectiveness of electromyographic (EMG) and skin-temperature (ST) biofeedback and relaxation training (RT) in reducing the aversiveness of cancer chemotherapy. Eighty-one cancer patients, equated on several individual-difference variables, were randomized to one of six groups formed by a 3 (EMG Biofeedback, ST Biofeedback, No Biofeedback) x 2 (RT, No RT) factorial design. Outcome was assessed with physiological, patient-reported, and nurse-reported indices taken over five consecutive chemotherapy treatments. RT patients showed decreases in nausea and anxiety during chemotherapy and physiological arousal after chemotherapy. EMG and ST biofeedback reduced some indices of physiological arousal but had no other effects on chemotherapy side effects. These findings suggest that RT can be effective in reducing the adverse consequences of chemotherapy and that the positive effects found for biofeedback in prior research were due to the RT that was given with the biofeedback, not to the biofeedback alone.

Adolescent↗
PubMed1991

Four sites in the acceptor helix and one site in the variable pocket of tRNA(Ala) determine the molecule's acceptor identity.

The structural features that determine tRNA(Ala) acceptor identity have been studied with amber-suppressor tRNAs in Escherichia coli cells. Previous work established that a wobble pair composed of guanosine at position 3 and uridine at position 70 (G3-U70) in the acceptor helix of tRNA(Ala) is a determinant of the molecule's acceptor identity. We show that additional determinants are located at three other sites in the acceptor helix and at one site in the variable pocket of tRNA(Ala). These latter determinants are less important than G3.U70 since their individual alterations in mutants of tRNA(Ala) have smaller degrading effects on the functions of the molecules, and subsets of the determinants, when combined with G3.U70, are sufficient to switch the identities of several other tRNAs to that of tRNA(Ala). Other workers are using fragments of the tRNA(Ala) acceptor helix to study the molecule's acceptor identity. Our demonstration that the variable pocket contributes to tRNA(Ala) acceptor identity means that such fragments do not faithfully replicate the structure-function relationship of the cellular process.

Anticodon↗
PubMed1991

Rapid determination of nucleotides that define tRNA(Gly) acceptor identity.

Expression of the genetic code depends on the recognition of specific tRNAs by the enzymes that aminoacylate them. A computer comparison of tRNA sequences coupled with analysis of mutant nonsense-suppressor tRNAs has revealed the structural features that distinguish the acceptor identity of Escherichia coli tRNA(Gly) from tRNAs that accept phenylalanine, arginine, lysine, and glutamine. On replacement of several nucleotides in the acceptor stem and anticodon of the latter tRNAs with tRNA(Gly)-derived residues, the resulting molecules acquired a tRNA(Gly) identity.

Anticodon↗
PubMed1991

Preparing patients for cancer chemotherapy: effect of coping preparation and relaxation interventions.

Sixty cancer chemotherapy patients were randomly assigned to one of four treatments: (a) relaxation training with guided relaxation imagery (RT), (b) general coping preparation package (PREP), (c) both RT and PREP, or (d) routine clinic treatment only. All patients were assessed on self-report, nurse observation, family observation, and physiological measures and were followed for five sequential chemotherapy treatments. Results indicate that the PREP intervention increased patients' knowledge of the disease and its treatment, reduced anticipatory side effects, reduced negative affect, and improved general coping. RT patients showed some decrease in negative affect and vomiting, but not as great as in past studies. The data suggest that a relatively simple, one-session coping preparation intervention can reduce many different types of distress associated with cancer chemotherapy and may be more effective than often-used behavioral relaxation procedures.

Adaptation, Psychological↗
PubMed1990

Nucleotides that determine Escherichia coli tRNA(Arg) and tRNA(Lys) acceptor identities revealed by analyses of mutant opal and amber suppressor tRNAs.

We have constructed an opal suppressor system in Escherichia coli to complement an existing amber suppressor system to study the structural basis of tRNA acceptor identity, particularly the role of middle anticodon nucleotide at position 35. The opal suppressor tRNA contains a UCA anticodon and the mRNA of the suppressed protein (which is easily purified and sequenced) contains a UGA nonsense triplet. Opal suppressor tRNAs of two tRNA(Arg) isoacceptor sequences each gave arginine in the suppressed protein, while the corresponding amber suppressors with U35 in their CUA anticodons each gave arginine plus a second amino acid in the suppressed protein. Since C35 but not U35 is present in the anticodon of wild-type tRNA(Arg) molecules, while the first anticodon position contains either C34 or U34, these results establish that C35 contributes to tRNA(Arg) acceptor identity. Initial characterizations of opal suppressor tRNA(Arg) mutants by suppression efficiency measurements suggest that the fourth nucleotide from the 3' end of tRNA(Arg) (A73 or G73 in different isoacceptors) also contributes to tRNA(Arg) acceptor identity. Wild-type and mutant versions of opal and amber tRNA(Lys) suppressors were examined, revealing that U35 and A73 are important determinants of tRNA(Lys) acceptor identity. Several possibilities are discussed for the general significance of having tRNA acceptor identity in the same positions in different tRNA acceptor types, as exemplified by positions 35 and 73 in tRNA(Arg) and tRNA(Lys).

Anticodon↗
PubMed1988

Cognitive appraisals in cancer patients.

Coping with cancer was examined using interviews with outpatient subjects in a correlational design. Specific attention was given to the relationships between cognitive appraisals and various aspects of adjustment. Appraisals were selected in accord with Lazarus' (1980) model of coping. The primary appraisal of perceived life threat appeared negatively related to adjustment. The primary appraisal process also appeared to involve multiple, simultaneous appraisals. Several secondary appraisals emerged as correlates of adjustment: perceived personal control, God-control, and chance-control, along with perceived control over emotional reactions. Overall, cognitive appraisals appeared to be modest predictors of adjustment.

Adaptation, Psychological↗
PubMed1985

The acute effects of cigarette smoke exposure on experimental skin flaps.

Random vascular patterned caudally based McFarlane-type skin flaps were elevated in groups of Fischer 344 rats. Groups of rats were then acutely exposed on an intermittent basis to smoke generated from well-characterized research filter cigarettes. Previously developed smoke inhalation exposure protocols were employed using a Maddox-ORNL inhalation exposure system. Rats that continued smoke exposure following surgery showed a significantly greater mean percent area of flap necrosis compared with sham-exposed groups or control groups not exposed. The possible pathogenesis of this observation as well as considerations and correlations with chronic human smokers are discussed. Increased risks of flap necrosis by smoking in the perioperative period are suggested by this study.

Animals↗
PubMed1984

Plasma nicotine and cotinine in tobacco smoke exposed beagle dogs.

Nicotine and cotinine have been determined in plasma samples from 87 beagle dogs chronically exposed to cigarette smoke with three different levels of nicotine. An additional 18 sham-exposed animals were included in the study as controls. Smoke was administered to the animals through permanent tracheostomas via cuffed tracheostomy tubes and was generated from reference cigarettes under standard puffing parameters by ADL-II smoking machines. The dogs were exposed for an average of 2 years prior to sample collection. The results from blood samples collected at specific intervals in the daily exposure schedules indicate that nicotine may be useful as a relative index of smoke exposure. At elevated exposure levels, average blood concentrations were related to the number of cigarettes smoked as well as the nicotine delivery of the cigarette. Cotinine was found to increase more slowly than nicotine and was also metabolized more rapidly than in humans. Overall, the study affords an examination of the relationship of plasma nicotine and cotinine with estimated nicotine exposure.

Animals↗
PubMed1983

Evidence for the lack of actin involvement in mitosis and in the contractile process in Spirostomum teres.

Studies using actin decoration techniques and electron microscopy have failed to show the presence of actin in the ciliate Spirostomum teres. The internal and external membranes of dividing cells were made permeable by treatment with Triton. The myosin subfragment S-1 was introduced into the cells for incubation under conditions suitable for actin decoration. Arrowhead decoration of microfilaments was not observed within dividing micronuclei or in cytoplasmic filament bundles. However, using similar procedures, the brush border of mouse small intestine yielded clearly decorated microfilaments. A spectrophotometric DNase I inhibition assay specific for G-actin demonstrated that the level of actin in S. teres extracts was less than 0.06% of the total soluble protein and confirms the observations made using the decoration procedures. On the basis of this work, it appears that actin does not play a significant part in either mitotic chromosome movement or contractility in S. teres.

Actins↗
PubMed1977

Stomatogenic events accompanying binary fission in Blepharisma.

Stomatogenesis was studied in the heterotrich ciliate Blepharisma japonicum stained with protargol. During binary fission not only is a new oral apparatus made for the posterior daughter, but the already existing oral apparatus of the parent cell is reorganized, i.e., partially disassembled and then subsequently reassembled to provide a functional feeding apparatus for the anterior daughter cell. These morphogenetic events, requiring 2 1/2 to 3 hr, are complete by the time the anterior and posterior daughters separate. In preparation for division, an oral anlage is formed by the rapid proliferation of kinetosomes along 4-5 stomatogenic kinetics directly subtending the cytostome. This field of randomly oriented kinetosomes ultimately gives rise to the feeding apparatus of the posterior daughter cell. Early in division, the oral anlage separates into 2 longitudinal fields of kinetosomes: one is destined to give rise to the undulating membrane and the other forms the adoral zone of membranelles. Shorly after the anlage is established posterior to the cytostome, reorganization of the existing functional mouth is initiated. The morphologic changes associated with this dedifferentiation-redifferentiation sequence lead to the formation of an oral apparatus for the anterior daughter and cannot be distinguished from those characteristically seen during physiologic reorganization.

Animals↗