Biomedical subjects

John Taylor

Publications and source records attributed to John Taylor.

42 records · Page 3Linked to original sources

PubMed2002

rTMS to the supplementary motor area disrupts bimanual coordination.

Bimanual coordination tasks form an essential part of our behaviour. One brain region thought to be involved in bimanual coordination is the supplementary motor area (SMA). We used repetitive transcranial magnetic stimulation (rTMS) at 1 Hz for 5 min to create a temporary virtual lesion of the rostral portion of the human SMA immediately prior to performance of a goal-directed bimanual coordination task. In two control conditions, participants underwent sham stimulation or stimulation over the primary motor cortex (MI). The experimental task was to open a drawer with the left hand, catch a ball with the right hand, and reinsert the ball into the drawer through an aperture just big enough for the ball to pass through, again with the right hand. Hence, the actions of one hand depend upon the actions of the other. We calculated time intervals between the successive component actions of one hand (unimanual intervals) and actions of both hands (bimanual intervals) and analyzed these intervals separately. Interestingly, none of the unimanual intervals were affected by the rTMS, but the variability of a critical bimanual interval--the time between the left hand opening the drawer and the right hand starting to move to catch the ball--was increased by rTMS over the rostral parts of the SMA. No such effect was seen following rTMS over MI or after sham rTMS. Our results suggest that the rostral parts of the SMA play an important role in aspects of functional bimanual tasks, which involve tight temporal coordination between different motor actions of the two hands.

Adult↗

PubMed2002

Parameters of human hepatitis delta virus genome replication: the quantity, quality, and intracellular distribution of viral proteins and RNA.

Assembly of hepatitis delta virus (HDV) in infected human hepatocytes involves association of the 1,679- nucleotide single-stranded genomic RNA (deltaRNA) with multiple copies of both small and large forms of the delta protein (deltaAg) to form a ribonucleoprotein particle which in turn interacts with envelope proteins of the natural helper virus, hepatitis B virus. Subsequently, for initiation of a new round of replication, the amount of small deltaAg within the assembled HDV particle is both necessary and sufficient. Quantitative assays were used in order to better understand just how much deltaAg is needed. The molar ratio of deltaAg species to genomic deltaRNA in assembled HDV particles was approximately 200. Next, this ratio was determined for cells under several different experimental situations in which HDV genome replication was occurring. These included replication in woodchuck liver and also in mouse liver and skeletal muscle, as well as replication in stably and transiently transfected cultured human hepatoblastoma cells. Surprisingly, in almost all these situations the molar ratios were comparable to that observed for HDV particles. This was true for different times after the initiation of replication and was independent of whether or not virus assembly was occurring. Cell fractionation combined with quantitative assays was used to test whether the majority of deltaAg and deltaRNA were colocalized during HDV replication in transfected cells. The cytoplasmic fraction contained the majority of deltaAg and genomic deltaRNA. Finally, the quality of deltaAg and deltaRNA, especially at relatively late times after the initiation of replication, was examined by using reverse transcription-PCR, cloning, and sequencing through the entire deltaAg open reading frame. When virus assembly and spread were not possible, 20% or less of the predicted deltaAg would have been able to support HDV replication. In summary, an examination of the quantity, quality and intracellular distribution of deltaAg and deltaRNA in several different experimental systems has provided a better understanding of the parameters associated with the initiation, maintenance, and ultimate decline of HDV genome replication.

Animals↗

PubMed2002

Carotid endarterectomy and race: do clinical indications and patient preferences account for differences?

BACKGROUND AND PURPOSE: Carotid endarterectomy (CE) has been proved to reduce the risk of stroke for certain patients, but black patients are less likely than whites to receive CE. The purpose of this work was to determine the importance of clinical indications and patient preferences in predicting the use of carotid angiography and CE in a racially stratified sample of patients. METHODS: Between 1997 and 1999, 708 patients with at least 1 carotid artery containing a >/=50% stenosis were enrolled (617 whites, 91 blacks) from 5 Veteran Affairs Medical Centers. Patient interviews were conducted at the time of the index carotid ultrasound, and each patient was followed up for 6 months to determine clinical events and receipt of carotid angiography or CE. RESULTS: Black and white patients were similar in terms of age, sex, education level, and social support. More black than white patients received ultrasound for a completed stroke (36% versus 13%), and fewer black patients were classified as asymptomatic (56% versus 70%) or as having had a TIA (8% versus 17%; P<0.001). Health-related quality of life scores, trust in physician, and medical comorbidity scores were similar for black and white patients. Black patients expressed higher aversion to CE than white patients (31% versus 15% in the highest aversion quartile for blacks and whites, respectively; P=0.01). During follow-up, 20% of white patients and 14% of black patients received CE (P=0.19). In adjusted analyses, only patient clinical status as it relates to the indication for CE and site were associated with receipt of CE. CONCLUSIONS: Contrary to prior research, patient's race was not associated with receipt of invasive carotid imaging or CE for older male veterans. These findings persist after controlling for patient preferences, comorbid illness, and quality of life. For patients enrolled in an equal-access health care system, clinical status was the primary determinant of the receipt of CE.

Black or African American↗

PubMed2002

The relationship between age and depressive symptoms: a test of competing explanatory and suppression influences.

OBJECTIVE: The objective is to examine competing explanatory and suppression influences on a negative, linear association between age and depressive symptoms. METHODS: Two samples were used: a community sample of physically disabled individuals and a comparison sample matched on age, sex, and area of residence. RESULTS: Fewer economic hardships and fewer experiences of negative interpersonal exchanges among older disabled and nondisabled respondents account for the negative relationship between age and depressive symptoms. Higher scores on a composite measure of religiosity among older disabled adults also account for part of the negative age effect. Conversely, a lower sense of mastery among older respondents in both samples suppresses the size of the negative age slope. DISCUSSION: Findings are discussed in terms of stress process and socioemotional selectivity theories, which predict that personal and social arrangements influence the experience of emotions differentially across the life course.

Adult↗

PubMedDate not supplied

Subfield variations in hippocampal processing-components of a spatial navigation system.

The hippocampus is a part of the brain strongly linked to spatial exploration. Within it exist 'place cells' which fire preferentially when an animal is in certain regions of physical space. Recent research has shown that these place cells and their corresponding representations of space behave differently in the CA3 and CA1 subfields of the hippocampus. We review this research and show, by simulation, that these differences can be explained by a combination of known physiological features of the hippocampus and proposed variations in the rate of synaptic plasticity and connection strength between different information pathways. We suggest possible reasons for these differences, namely use of the CA1 cell field for current spatial exploration, and CA3 for longer term spatial memory.

Algorithms↗

PubMedDate not supplied

Perspectives of relatives and health care workers on care of terminally ill patients in the UK.

Two parallel questionnaires were used to explore perceptions of healthcare workers (HCWs) and the relatives of terminally ill patients on the quality of care received by the patients. There was general agreement between the two groups of respondents in most of the assessed areas. The relatives, however were more satisfied with the control of pain and psychological symptoms than the HCWs, and the HCWs perceived the control of diarrhea, skin problems, and swallowing problems more positively than did the relatives. There also was some variation between the two groups in their perception of the care received by the relatives during visits at the hospital, with the relatives' group being more positive. Although HCWs reported that time to deal with patients and their families was inadequate, the relatives' group was generally satisfied with the standards in place.

Caregivers↗