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Biomedical subjects

J Larkin

Publications and source records attributed to J Larkin.

At least 19 recordsLinked to original sources
PubMed1996

Polyunsaturation in cell membranes and lipid bilayers and its effects on membrane proteins.

The effect of variation of the degree of cis-unsaturation on cell membrane protein functioning was investigated using a model lipid bilayer system and protein kinase C (PKC). This protein is a key element of signal transduction. Furthermore it is representative of a class of extrinsic membrane proteins that show lipid dependent interactions with cell membranes. To test for dependence of activity on the phospholipid unsaturation, experiments were devised using a vesicle assay system consisting of phosphatidylcholine (PC) and phosphatidylserine (PS) in which the unsaturation was systematically varied. Highly purified PKC alpha and epsilon were obtained using the baculovirus-insect cell expression system. It was shown that increased PC unsaturation elevated the activity of PKC alpha. By contrast, increasing the unsaturation of PS decreased the activity of PKC alpha, and to a lesser extent PKC epsilon. This result immediately rules out any single lipid bilayer physical parameter, such as lipid order, underlying the effect. It is proposed that while PC unsaturation effects are explainable on the basis of a contribution to membrane surface curvature stress, the effects of PS unsaturation may be due to specific protein-lipid interactions. Overall, the results indicate that altered phospholipid unsaturation in cell membranes that occurs in certain disease states such as chronic alcoholism, or by dietary manipulations, are likely to have profound effects on signal transduction pathways involving PKC and similar proteins.

Animals↗
PubMed1996

Breathing, sleep state, and rectal temperature oscillations.

Overheating may cause terminal apnoea and cot death. Rectal temperature and breathing patterns were examined in normal infants at home during the first 6 months of life. Twenty one infants had continuous overnight rectal temperature and breathing recordings for 429 nights (mean 20.4 nights, range 7-30) spaced over the first six months of life. Periods when breathing was 'regular' were directly marked on single night records. Sleep state was determined from respiratory variables. 'Regular' breathing was a reliable marker of 'quiet' sleep (specificity 93%). The duration of 'quiet' sleep increased from 6 to 22 minutes from two weeks to three months of age and then remained static, as did the proportion of sleep spent in the quiet phase (9% to 34%). Rectal temperature fell during 66% of quiet sleep and usually rose during rapid eye movement (REM) sleep. The drop in rectal temperature was maximal at the start of quiet sleep, whereas the maximum rise during REM sleep was reached after 10 to 15 minutes. Oscillations in rectal temperature are associated with changes in sleep and breathing state. The maturation of rectal temperature patterns during the first six months of life are closely related to a maturation of sleep state and breathing patterns.

Aging↗
PubMed1995

Apnoea detection: human performance and reliability of a computer algorithm.

We examined the consistency of apnoea recognition between three human experts. The hypothesis was that computer detection of apnoea could emulate human expert apnoea recognition. The aim was to detect apnoeas with the highest possible accuracy from a single breathing signal, by both human experts and computer. Three human experts independently examined recordings of breathing wave-form from overnight sleep studies from 10 infants aged 3-17 weeks. All apnoeas of 5 s or more were identified and reviewed. However, there still remained 10% disagreement. A computer apnoea detector was implemented. An algorithm analysed statistical properties of the signal to find breathing pauses. Optimal performance was 1% missed apnoeas (compared with the agreed apnoeas identified by the three experts) and 29% false detections. This computer algorithm reliably identified most apnoeas but did not replace the human expert.

Algorithms↗
PubMed1994

Infant home apnoea monitors in Christchurch: an audit.

AIM: To audit parental perception of the apnoea monitor service given to neonatal graduates and infants surviving an apparent life threatening event in Christchurch. METHODS: Seventy-five of 103 sets of parents (74%), who had monitored their infants, between November 1990 and November 1992, were interviewed using a structured telephone questionnaire (apparent life threatening event (ALTE) n = 44, significant recurrent apnoea (NNU) n = 31. RESULTS: Anxiety present in most parents (83%) was relieved by monitoring (89%). Parents (97%) were satisfied with the instruction in monitor use. Eighty-nine percent had good contact with the technician, 73% called her to solve a problem. Most parents (84%) thought that initial instruction in cardiopulmonary resuscitation (CPR) was adequate. Sixty-eight percent would have liked a refresher course which only 7% of NNU and 22% of ALTE parents received. Sixty percent of parents had at least one significant alarm. Nine percent performed CPR to abort an apnoea. Ten percent of parents would have liked to monitor their child longer. CONCLUSIONS: Apnoea monitoring allays parental anxiety and may save the lives of a few infants. A technician is essential to coordinate all aspects of the service. Improvements could be made to instruction for cardiopulmonary resuscitation.

Anxiety↗
PubMed1994

Miscellaneous neurologic, cardiac, pulmonary, and metabolic disorders with rheumatic manifestations.

The First International Workshop on Hypertrophic Osteoarthropathy crystallized the current knowledge of this puzzling syndrome. Cytokine release by large thrombocytes in the periphery is the favored etiology, although specific therapy remains unavailable. An article on the rheumatologic consequences of alcohol is reviewed, along with a number of case reports of joint problems in rare skin and metabolic diseases. Understanding the mechanisms of rarities, including rheumatic fever, interleukin-2-induced arthritis, and a unique "menstrual arthritis" might give insight into the etiology of more common arthropathies.

Alcoholism↗
PubMed1990

The beta-tubulin gene family in Zea mays: two differentially expressed beta-tubulin genes.

Maize beta-tubulins are encoded by a large multigene family with at least nine members, as determined by Southern blot analysis. Two expressed genes, represented by the beta 1 genomic clone and the beta 2 cDNA clone, were examined in this study. The two genes encode beta-tubulins which show 94% sequence identity at the amino acid level. Maize beta 1 transcript levels were highest in seedling root tip and tissue culture cells, which are both rapidly dividing tissues. No transcripts were detected in non-dividing leaf tissue. In contrast, beta 2 transcripts were present at relatively high levels in tissue culture cells and at lower levels in seedling root tip and leaf tissue. The electrophoretic mobility of the beta 2 polypeptide was examined in relation to the constellation of beta-tubulin polypeptides on two-dimensional gel western blots of a maize pollen total protein extract. No evidence for post-translational modification of the beta-tubulin polypeptides was found in pollen.

Base Sequence↗
PubMed1990

Human T-cell lymphotropic virus-type I.

HTLV-I is a retrovirus now identified as the etiologic agent of two diverse disease processes: ATLL, an aggressive T-cell malignancy; and TSP/HAM, a chronic progressive myelopathy. Transmission can occur horizontally through blood transfusions, IV drug abuse and sexual intercourse. Vertical transmission may also occur. Available diagnostic modalities are serologic in nature and include the EIA and the more specific confirmatory assays WIB and RIPA. These studies are thus far suboptimal in terms of sensitivity and specificity, and await refinement. DNA amplification by the polymerase chain reaction seems to hold the most immediate diagnostic promise for the future. AZT apparently is not useful clinically, and current treatment is only palliative in nature. The diverse diseases caused by HTLV-I underscore the insidious nature of the Retroviridae family. These subtle cell-associated pathogens will undoubtedly be shown to play a significant role in other disease processes of uncertain etiology.

HTLV-I Infections↗
PubMed1987

Factors influencing one's ability to adapt to chronic illness.

The disease course in chronic illness may be subtle and accompanied by irreversible changes that have to be managed. Once the immediacy of the illness has been dealt with, the patient may face a future full of uncertainties related to illness recurrence, further disease progression, and perhaps even death. Thus the long-term implications of chronic illness necessitate multiple accommodations on the part of the patient, the family, and society. To aid in one's ability to deal with a chronic illness such factors as care, technology, family relationships, developmental level, cultural values and beliefs, communication, and economics need to be considered. An understanding of how each of these factors affects chronic illness can facilitate the appropriate development and initiation of options for adaptation to the illness.

Adaptation, Psychological↗
PubMed1983

The dexamethasone suppression test as a predictor of antidepressant response.

There is some evidence to suggest that dexamethasone suppression test (DST) results obtained prior to treatment for depression might aid in selecting the proper type of antidepressant medication. Forty endogenously depressed outpatients were evaluated with the DST and 12 (30%) were identified as nonsuppressors. All patients were then treated with desipramine (150-350 mg/day). Plasma concentrations of desipramine were monitored to assure that therapeutic levels were achieved. At 5 weeks of treatment, patients were characterized as treatment responders or nonresponders on the basis of change in Hamilton Depression Scale scores.

Adolescent↗
PubMed1980

DALE--a system for developing computer-aided biomedical experiments.

The implementation of new computer-aided biomedical experiments usually requires a high level of computing expertise and a significant amount of time. Acquiring this knowledge and devoting the necessary time may result in the inefficient use of a researcher's own particular skills. A number of software aids for laboratory experimentation have been developed, but it is considered that none adequately satisfies the user's requirements. DALE (direct access to laboratory equipment) has been designed as a user-oriented software system, and consists of a menu-based interactive subsystem, with which experiments are defined, and a table-driven interpreter to execute the experiment. Little computing knowledge or development time is required to implement new experiments, and experience has indicated that DALE is a useful tool for biomedical experimentation.

Computers↗
PubMed1980

An analysis of the performance of a variable venturi-type oxygen mask.

The theoretical performance of the Hudson Multivent mask is considered. A method is described of determining the flow-weighted mean inspired oxygen concentration produced by the mask. Using this method, it was found that the inspired oxygen concentration was predictable only at the 24% setting using the recommended flow rates, but that increasing the supplied-oxygen flow rates above the recommended levels resulted in the return of predictable function. At settings above 30% predictable function was found to be unlikely, whatever the supplied oxygen flow rate. Recommendations are made regarding the use of this device.

Humans↗