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Biomedical subjects

I Bell

Publications and source records attributed to I Bell.

18 recordsLinked to original sources
PubMed2001

Down-modulation of the costimulatory molecule, CD28, is a conserved activity of multiple SIV Nefs and is dependent on histidine 196 of Nef.

In this study Nef proteins derived from simian immunodeficiency virus (SIV) and human immunodeficiency virus (HIV) were compared to assess their abilities to down-modulate the cell surface levels of the T-cell costimulatory molecule CD28. We demonstrate that in addition to Nef derived from the prototypic SIVmac239, Nef proteins encoded by the pathogenic SIVsmmPBj molecular clone and the SIVsmmB670 isolate also down-modulate cell surface CD28. In contrast, Nef proteins derived from HIV failed to down-modulate CD28. We have also identified H196 as a critical residue which influences the capacity of SIVmac Nef to down-modulate CD28. Nef derived from SIVmacJ5 failed to down-modulate cell surface CD28, whereas a Q196H substitution mutant of SIVmacJ5 Nef was able to down-modulate cell surface CD28. Conversely, substitution of H196 to Q196 in SIVmac239 Nef resulted in a mutant that had minimal effect on cell surface CD28 expression, despite retaining the capacity to down-modulate cell surface CD3epsilon. H196 lies immediately adjacent to a documented di-leucine endocytic motif and mutation of this motif also abrogated the ability of SIVmac239 Nef to down-modulate CD28. These findings demonstrate that down-modulation of the costimulatory molecule, CD28, and clonotypic TCR/CD3 complex are conserved attributes of SIV Nef.

Animals↗
PubMed2000

The T-cell receptor zeta chain contains two homologous domains with which simian immunodeficiency virus Nef interacts and mediates down-modulation.

We have recently demonstrated that simian immunodeficiency virus (SIV) Nef binds to the zeta chain of the T-cell receptor (TCR), leading to its down-modulation from T-cell surfaces (I. Bell, C. Ashman, J. Maughan, E. Hooker, F. Cook, and T. A. Reinhart, J. Gen. Virol. 79:2717-2727, 1998). Using a panel of human as well as rhesus macaque TCR zeta cytoplasmic domain mutants, we have identified in this report two linear peptides in the cytoplasmic domain of TCR zeta which independently interact with SIV Nef. Each SIV Nef interaction domain was sufficient in the absence of the other for interaction with SIV Nef in a yeast two-hybrid assay. In parallel, we demonstrated that Nef down-modulation of CD8-TCR zeta fusion proteins containing full-length or truncated portions of the TCR zeta cytoplasmic domain occurs in transiently transfected 293T cells. Furthermore, using proteins expressed in Escherichia coli, a glutathione S-transferase-Nef fusion protein coprecipitated histidine-tagged portions of the TCR zeta cytoplasmic domain which contained SNID-1 or SNID-2. The peptides targeted by SIV Nef, YNELNL and YSEIGMKGERRR, are portions of the first and second of three immunoreceptor tyrosine-based activation motifs which are important in signal transduction, thymocyte development, and TCR biogenesis. These results demonstrate that SIV Nef binds to two distinct domains on TCR zeta in the absence of other T-cell-specific factors, and that interaction with either domain is sufficient to cause down-modulation of TCR zeta.

Amino Acid Sequence↗
PubMed1999

The association of energy intake bias with psychological scores of women.

OBJECTIVE: Assess the association between reporting bias of dietary energy intake and the behavioral and psychological profiles in women. DESIGN: At baseline a series of questionnaires were administered to 37 women, (the Marlowe-Crowne Social Desirability Scale, Weinberger Adjustment Inventory (WAI), the Eating Disorder Inventory (EDI), the Restraint Scale and Sorensen-Stunkard's silhouettes). Subjects received training on how to record dietary records. Subjects recorded three days of dietary records to measure energy intake (EI) during a study to determine total energy expenditure (TEE) using doubly labeled water. Reporting accuracy (RA = EI/TEE x 100) was determined for each subject. Statistical analysis of the data used a mixed effects model accounting for within subject variability to determine if the psychological scores were associated with reporting accuracy. SETTING AND SUBJECT: Women were recruited with local advertisements in Tucson, Arizona. The women had a mean ( +/- 1 s.d.) age of 43.6 +/- 9.3 yrs, body mass index (BMI) of 28.7 +/- 8.5 kg/m2 and total body fat (%TBF) of 31.9 +/- 7.3%. RESULTS: Age and %TBF were significantly and inversely associated with RA. Furthermore, Social Desirability was negatively associated with RA. Body dissatisfaction and associating a smaller body size than one's own as being more healthy were also associated with a lower RA. CONCLUSIONS: These results suggest that Social Desirability and self image of body shape are associated with RA. Modifications in subject training may reduce the effect of these factors on RA.

Adult↗
PubMed1998

Repressive and defensive coping styles predict resting plasma endorphin levels in the elderly.

Jamner, L.D., Schwartz, G.E., 1986, Psychosom. Med. 48, 211-223, have proposed that repressive and defensive coping are associated with greater central endogenous opioid activity. They reasoned that high-defensive (HD) participants' attenuated distress, increased pain tolerances, attenuated somatic symptomatology, and accentuated reports of positive emotions are consistent with actions of centrally active opioid peptides. The present study assessed plasma beta-endorphin (END) levels, Marlowe Crowne Social Desirability Scale (MCSD), and Taylor Manifest Anxiety Scale (TMAS) scores in men (n = 6) and women (n = 20) between the ages of 59 and 79. Contrary to predictions, HD had lower plasma endorphin levels than did low-defensive (LD) participants. Raw MCSD scores correlated negatively with endorphin levels. Findings were significant for women only, which may have been due to the small sample of men. The results are discussed as they related to the hypothesis that defensiveness involves alteration of central opioid systems.

Adaptation, Psychological↗
PubMed1998

Association of simian immunodeficiency virus Nef with the T-cell receptor (TCR) zeta chain leads to TCR down-modulation.

The Nef protein of simian immunodeficiency virus (SIV) is dispensable for replication in established T-cell lines but essential for high level virus replication in the adult host, though the mechanism by which Nef contributes to this has remained unclear. We demonstrate here that SIV Nef binds to the zeta chain of the T-cell receptor (TCR). SIV Nef proteins that interact with TCR zeta in a yeast two-hybrid system also reduce T-cell surface expression levels of TCR alphabeta, CD3 and CD4. These findings are the first demonstration that Nef can bind directly to a component of the TCR-CD3 complex and modulate its surface expression.

Animals↗
PubMed1996

Traumatic memory characteristics: a cross-validated mediational model of response to rape among employed women.

In a cross-validated mediational model, the authors examined characteristics of memories formed in response to rape and other intense unpleasant and pleasant experiences. Data were responses to a mailed survey of women medical center and university employees. Measurement models of memory and symptom factors and a structural model with pathways among cognitive appraisal, emotional valence, memory characteristics, and health outcomes were developed in Sample 1 (N = 1,307) and confirmed in Sample 2 (N = 2,142). Rape had substantial direct effects on 2 memory factors (Clarity and Affect) and indirect effects through the construal of victimization. Rape was associated with memories described as more emotionally intense but less clear and coherent and less often thought of or talked about. Most effects on physical symptoms were nonsignificant. Implications of findings for neurohormonal and multiple representation models of emotional memory and to cognitive avoidance are discussed.

Adolescent↗
PubMed1993

Profiling. Less impertinence, more partnership.

Health profiling is a central aspect of health visiting practice, writes Ian Bell. Here he describes the development of a profiling tool for use with all age groups to enable accurate assessment of clients' health needs.

Adolescent↗
PubMed1990

Magnitude of diotic summation in speech-in-noise tasks: performance region and appropriate baseline.

The diotic summation effect is one of the three types of binaural advantage for perceiving speech-in-noise. Using a within-subject design in normally-hearing subjects having no significant noise exposure, we examined its magnitude. The average advantage was +5%, at an overall performance level of 70-80% rising to +9% when an appropriate control was used to exclude order effects introduced by the within-subject design. Diotic summation is an important component of the advantage to be derived from presentation to two ears, but the size of the binaural advantage obtained depends critically on the particular monotic baseline chosen for comparison. The methodological problems of demonstrating binaural advantages (as in binaural aiding studies) are discussed.

Adult↗
PubMed1990

Asymmetrical auditory probe evoked potentials during REM and NREM sleep.

Two experiments were conducted to evaluate interhemispheric differences in late auditory evoked potentials (AEPs) during rapid-eye-movement (REM), Stage 2, and Stage 4 sleep. In the first study, 1,000-Hz stimuli [80 db (SPL)] were presented binaurally at a rate of 1/1.1 s. Analyses of variance were computed on the absolute difference in the amplitude of right and left evoked responses. N1 AEPs were significantly more asymmetrical in Stage 4 sleep compared to either REM or Stage 2 sleep. A second study was conducted with a wider topographical electrode distribution. This study used both a long and a short interstimulus interval with 500-Hz 80-db SPL tone pips. The absolute difference in the amplitude of right and left AEPs was compared across sleep stage. Asymmetries were larger in Stage 4 sleep than in either REM or Stage 2. Examination of these data indicated relative hemispheric balance in REM and Stage 2 sleep with largest asymmetries in Stage 4. The results do not support the view that REM and non-REM sleep stages are associated with differential activation of the two cerebral hemispheres. Rather, they suggest that the sleep cycle is characterized by variations in the degree of asymmetry. Asymmetries in Stage 4 sleep were not consistently in favor of the left hemisphere.

Adolescent↗
PubMed1988

A peak detector program for event-related potentials.

A computer program, developed for peak detection of averaged evoked potential waveforms, is described. The program is able to automatically score up to 200 data files in a single session. The user is asked to define intervals (windows) in which a maximum peak is to be detected. The program can optionally search each EEG channel or a single 'reference' channel from which all other channels will be compared. The mean amplitude of several data points can also be computed within a particular window. When evoked potentials are particularly noisy, it is possible to estimate the 'signal' in the higher frequency background 'noise'. Because the program is written in BASIC, it can be readily transferred to many different computer systems.

Arousal↗
PubMed1988

Electrophysiological monitoring during acoustic neuroma and other posterior fossa surgery.

Techniques used to monitor the function of the seventh and eighth cranial nerves during acoustic neuroma and other posterior fossa surgery are reviewed. The auditory brainstem response (ABR), electrocochleogram (ECochG) and direct recording from the auditory nerve (CNAP) were compared. The best technique is the ECochG, although in many cases, the CNAP should be used as a back-up technique. The CNAP is especially useful for the identification of the auditory nerve. Both can provide real-time feedback on the physiological integrity of the auditory nerve. The ABR may be helpful in monitoring brainstem function. For some procedures, optimal monitoring requires the combined recording of all three techniques. Monopolar constant-voltage intracranial stimulation of the facial nerve is helpful for the identification and preservation of the facial nerve. Audio monitoring of spontaneous electromyographic activity provides real-time feedback on the effect of surgical manipulation of the nerve. Monitoring of ephaptic transmission in the facial nerve during microvascular decompression for hemifacial spasm aids in the identification of the offending vessel.

Action Potentials↗
PubMed1987

Estimation of auditory threshold during sleep using brainstem auditory-evoked potentials.

The brainstem auditory-evoked potential (BAEP) is often employed to determine auditory threshold in subjects who are unable to complete traditional behavioural testing. These responses are usually recorded during natural or drug-induced sleep. The effects of sleep on the BAEP threshold have however not been determined. BAEPs were recorded in 8 young adults in wakefulness and during natural sleep. Click stimuli were presented through a hearing aid device at either 0, 5, 10, 20 or 30 dB above the behavioural threshold. The amplitude of wave V decreased and its latency increased with decreases in stimulus intensity. The BAEP waveform was invariant in sleep. The overall mean BAEP threshold was approximately 16 dB above that determined by behavioural methods. This did not significantly vary in the sleeping subject.

Adult↗
PubMed1985

Subtle neuropsychological deficits in patients with good recovery after closed head injury.

This study demonstrates residual mental deficits in patients who have apparently recovered after closed head injury. Twenty closed head injury patients were compared to 20 normal control subjects matched for age, sex, handedness, education, language, and IQ. All received a series of neuropsychological tests. Discriminant function analysis significantly differentiated the two groups. Correct classification of individuals as having suffered a head injury or not was 85%. The head injury patients did have primary impairment on tests of divided attention. Litigation was not a factor. We propose that this impairment of information processing reflects residual brain damage secondary to the closed head injury.

Adult↗
PubMed1980

A brief communication on bone conduction artefacts.

The various factors which may be involved in the incorrect measurement of bone-conduction threshold are outlined. One of these factors, airborne radiation from the vibrator, has been investigated for three Radioear vibrators, the B70A, B71 and B72. The results indicate that false bone-conduction threshold values could arise, due to the airborne radiation component, mainly with the B72 vibrator.

Audiometry↗