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Biomedical subjects

M B Walker

Publications and source records attributed to M B Walker.

At least 19 recordsLinked to original sources
PubMed2000

Incidence and prevention of epithelial growth within the interface after laser in situ keratomileusis.

PURPOSE: To analyze the incidence of epithelial growth within the interface after laser in situ keratomileusis (LASIK) and describe a technique that may prevent its occurrence. METHODS: Results were reviewed for all LASIK procedures performed by two surgeons using identical surgical technique with either the Automated Corneal Shaper or Hansatome microkeratome. After laser ablation, the bed and posterior surface of the flap were irrigated with 0.2 microM filtered basic salt solution, and the surfaces were swept with lint-free sponges to clear the interface of epithelial and other debris. An aspirating lid speculum connected to suction was used to evacuate irrigation fluid and debris from the field. After the flap was smoothed into position, a bandage contact lens was used for the first day after surgery to prevent lifting of the flap edge during blinking. RESULTS: Seven hundred eighty-three eyes of 419 patients had primary LASIK, and 108 eyes had LASIK reoperation. Three eyes developed epithelial growth within the interface, with a minimum of 3 months of follow-up. The interface opacity appeared within 1 month of surgery in all three eyes. Two epithelial nests were small (1.0 and 1.5 mm in diameter, respectively) and did not increase in size on subsequent visits. Neither peripheral epithelial nest affected best-corrected visual acuity or caused any other sequelae. One ingrowth occurred early postoperatively in a case with a donut-shaped flap and was eliminated by transepithelial photorefractive keratectomy (PRK). CONCLUSION: Irrigating, wiping the stromal interface with sponges. aspirating irrigation fluid and debris with a suctioning lid speculum, and use of a bandage contact lens for the first day after surgery during LASIK and LASIK enhancement may markedly reduce the incidence of epithelial growth within the interface.

Acetates↗
PubMed1999

The maize tha4 gene functions in sec-independent protein transport in chloroplasts and is related to hcf106, tatA, and tatB.

Proteins are translocated across the chloroplast thylakoid membrane by a variety of mechanisms. Some proteins engage a translocation machinery that is derived from the bacterial Sec export system and require an interaction with a chloroplast-localized SecA homologue. Other proteins engage a machinery that is SecA-independent, but requires a transmembrane pH gradient. Recently, a counterpart to this Delta pH mechanism was discovered in bacteria. Genetic studies revealed that one maize protein involved in this mechanism, HCF106, is related in both structure and function to the bacterial tatA and tatB gene products. We describe here the mutant phenotype and molecular cloning of a second maize gene that functions in the Delta pH mechanism. This gene, thylakoid assembly 4 (tha4), is required specifically for the translocation of proteins that engage the Delta pH pathway. The sequence of the tha4 gene product resembles those of the maize hcf106 gene and the bacterial tatA and tatB genes. Sequence comparisons suggest that tha4 more closely resembles tatA, and hcf106 more closely resembles tatB. These findings support the notion that this sec-independent translocation mechanism has been highly conserved during the evolution of eucaryotic organelles from bacterial endosymbionts.

Amino Acid Sequence↗
PubMed1999

Molecular cloning of the maize gene crp1 reveals similarity between regulators of mitochondrial and chloroplast gene expression.

The maize nuclear gene crp1 is required for the translation of the chloroplast petA and petD mRNAs and for the processing of the petD mRNA from a polycistronic precursor. In order to understand the biochemical role of the crp1 gene product and the interconnections between chloroplast translation and RNA metabolism, the crp1 gene and cDNA were cloned. The predicted crp1 gene product (CRP1) is related to nuclear genes in fungi that play an analogous role in mitochondrial gene expression, suggesting an underlying mechanistic similarity. Analysis of double mutants that lack both chloroplast ribosomes and crp1 function indicated that CRP1 activates a site-specific endoribonuclease independently of any role it plays in translation. Antibodies prepared to recombinant CRP1 were used to demonstrate that CRP1 is localized to the chloroplast stroma and that it is a component of a multisubunit complex. The CRP1 complex is not associated detectably with either chloroplast membranes or chloroplast ribosomes. Models for CRP1 function and its relationship to other activators of organellar translation are discussed.

Amino Acid Sequence↗
PubMed1999

Psychological factors can predict the response to primary chemotherapy in patients with locally advanced breast cancer.

This study evaluated the possible value of psychological variables in predicting clinical and pathological response to primary chemotherapy. 96 women with newly diagnosed large, or locally advanced, breast cancer (T2 > 4 cm, T3, T4, N2 and M0) participated in a prospective, randomised trial to evaluate the effects of relaxation training with guided imagery and L-arginine on response to primary chemotherapy. Before the first of six cycles of primary chemotherapy, women were assessed using the Hospital Anxiety and Depression Scale (HADS) and the Eysenck Personality Questionnaire (EPQ). The primary outcomes were clinical response (evaluated using standard International Union Against Cancer (UICC) criteria) and pathological response (graded by means of a previously published 5-point scale) following primary chemotherapy. Stepwise linear regressions were used to estimate the predictive value of age, menopausal status, clinical nodal status, tumour size at diagnosis, oestrogen receptor status, dietary supplementation (L-arginine versus placebo), personality (EPQ-L scores), mood (HADS scores) and a psychological intervention. HADS depression score was a significant independent predictor of pathological response to chemotherapy. HADS anxiety score was a significant independent predictor of clinical response. Because the original tumour size before chemotherapy (also a significant predictor of clinical and pathological responses) was taken into account in the analyses, the results cannot be explained in terms of psychobiological factors related to tumour size. This study supports the importance of psychological factors as independent predictors of response to primary chemotherapy in patients with breast cancer. If they can be replicated, these findings have major implications for the management of women with breast cancer. Psychological factors need to be assessed and evaluated in future trials of chemotherapy.

Adult↗
PubMed1999

Psychological, clinical and pathological effects of relaxation training and guided imagery during primary chemotherapy.

The diagnosis and treatment of breast cancer are stressful, and stress may be associated with a poorer response to chemotherapy. There is a need, therefore, to develop and evaluate interventions that might enhance quality of life and, possibly, improve treatment response. The effects of relaxation combined with guided imagery (visualizing host defences destroying tumour cells) on quality of life and response to primary chemotherapy, to date, have not been adequately evaluated. Ninety-six women with newly diagnosed large or locally advanced breast cancer (T2 > 4 cm, T3, T4, or TxN2 and M0) took part in a prospective, randomized controlled trial. Patients were randomized following diagnosis to a control condition (standard care) or to the experimental condition (standard care plus relaxation training and imagery). Psychometric tests to evaluate mood and quality of life were carried out before each of the six cycles of chemotherapy and 3 weeks after cycle 6: tests of personality and coping strategy were carried out prior to cycles one and six. Clinical response to chemotherapy was evaluated after six cycles of chemotherapy using standard UICC criteria and pathological response was assessed from the tissue removed at surgery. As hypothesized, patients in the experimental group were more relaxed and easy going during the study (Mood Rating Scale). Quality of life was better in the experimental group (Global Self-assessment and Rotterdam Symptom Checklist). The intervention also reduced emotional suppression (Courtauld Emotional Control Scale). The incidence of clinically significant mood disturbance was very low and the incidence in the two groups was similar. Finally, although the groups did not differ for clinical or pathological response to chemotherapy, imagery ratings were correlated with clinical response. These simple, inexpensive and beneficial interventions should be offered to patients wishing to improve quality of life during primary chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

Extraversion and exercise addiction.

Extraversion has been suggested as a factor associated with addiction. This claim was tested in relation to exercise addiction. Twelve exercise addicts were compared with 12 nonaddicted individuals who were committed to regular exercise and with 12 nonexercising individuals drawn from the same student population. Addicted exercisers did not differ from nonaddicted exercisers in extraversion, although exercisers as a group were more extraverted than nonexercisers. The results are interpreted as evidence against the claim that extraversion is a component of the addictive personality profile.

Adolescent↗
PubMed1997

The psychological and psychiatric effects of rIL-2 therapy: a controlled clinical trial.

It has been suggested that recombinant interleukin-2 (rIL-2) may cause pyschological and psychiatric problems, although the effects of rIL-2 on its own have not been well documented. To evaluate these effects, 17 patients with advanced colorectal cancer took part in a randomised, parallel group study of rIL-2 with chemotherapy (5-fluorouracil and leucovorin) versus chemotherapy alone. Patients were assessed regularly by means of various psychometric tests including the Hospital Anxiety and Depression Scale, the Mood Rating Scale, the Mini-Mental State Examination, the Digit Symbol Substitution Test, the Trail-Making Test and the Benton Revised Visual Retention Test. Rigorous discontinuation criteria were applied to ensure that the effect of time-related variables did not influence the results. Compared with patients who were given chemotherapy alone, patients receiving immunochemotherapy reported reduced energy, impaired confidence, higher depressed mood and more confusion. Immunochemotherapy was rated as more distressing than chemotherapy alone and patients reported a greater incidence of appetite impairment, weight loss, poor concentration and fever. Cognitive assessments indicated that brain dysfunction can be caused by rIL-2. Compared with the control group, patients receiving immunochemotherapy showed significant impairment on Trail Making Test B and the Digit Symbol Substitution Test. One patient developed repeated transient psychotic episodes associated with rIL-2 infusions and another regularly became confused. These effects were not due to sleep deprivation or pyrexia. Treatment with rIL-2 should not be discarded on psychosocial grounds, although in each case the psychological morbidity and adverse effects on quality of life need to be balanced carefully against potential therapeutic benefits.

Antimetabolites, Antineoplastic↗
PubMed1997

Cognitive performance and mood after a weekend on call in a surgical unit.

BACKGROUND: Considerable interest and concern have been expressed about junior doctors' hours. This study was carried out to evaluate the emotional and cognitive effects of a weekend on call in a surgical ward. METHODS: Ten surgical house officers were assessed, in counterbalanced design, on four Monday mornings, twice after a weekend off duty and twice after a weekend on call. Cognitive functioning was assessed using the Cognitive Drug Research computerized cognitive assessment system, and emotional state was evaluated by means of the Aberdeen Mood Rating Scale. RESULTS: Following a weekend on call, significant impairment in concentration, speed and power was observed, and the doctors felt less confident, less energetic and more confused. Impaired attention, working memory, long-term memory and confusion were most closely correlated with number of hours worked on Sunday, and tiredness and confusion were related to number of hours slept. CONCLUSION: A weekend on call has significant deleterious effects on cognitive performance and mood. The findings have implications for staffing levels and the design of duty rosters.

Affect↗
PubMed1996

The cognitive effects of recombinant interleukin-2 (rIL-2) therapy: a controlled clinical trial using computerised assessments.

It has been suggested that patients undergoing treatment with recombinant interleukin-2 (rIL-2) may develop cognitive impairment. To evaluate these effects, 17 patients with advanced colorectal cancer took part in a randomised, parallel group study of rIL-2 with chemotherapy (5-fluorouracil and leucovorin) and chemotherapy alone. Assessments were carried out daily whilst patients were in hospital and regularly between cycles of treatment using state-of-the-art computerised cognitive assessment, as well as traditional psychometric tests. Rigorous discontinuation criteria were applied to ensure that the effect of time-related variables did not influence the results. One patient developed repeated transient psychotic episodes associated with rIL-2 infusions and another regularly became confused. Computerised cognitive assessments revealed that immunochemotherapy produced significant impairment in various tasks, especially reaction time, picture recognition and vigilance. These effects were not due to sleep deprivation or pyrexia. For most patients, cognitive functioning was restored to the baseline level within 10 days following the cessation of rIL-2. In conclusion, during infusions of rIL-2, some patients experience severe confusion and amnesia which resembles some of the major cognitive impairments associated with dementias such as Alzheimer's disease. Computerised cognitive assessment using the Cognitive Drug Research system provides a feasible, sensitive and reliable method of evaluating cognitive changes in patients with cancer. It could usefully be included in quality of life assessments in clinical trials where treatment-related cognitive changes need to be evaluated.

Aged↗
PubMed1996

Conformity in the Asch task as a function of age.

The social conformity paradigm of Asch (1956) was replicated to investigate the relationship between age and conformist behavior. One hundred ten Australian school children and adolescents between 3 and 17 years of age participated in the study. Each participant was placed in the position of being a minority of 1 against a wrong but unanimous majority of 3. The results indicate that conformity decreases with age in perceptually unambiguous tasks. Conflicting evidence from earlier studies can be attributed to task ambiguity in those studies.

Adolescent↗
PubMed1996

Height and weight measurements of Ibadan school children.

Height and weight measurements were carried out on three groups of Nigerian primary school children aged 6-12 years, in and around Ibadan. A total of 1,192 children was examined from three social classes as follows: (1) the educated elite group (n = 444); (2) the urban low socio-economic group (n = 366), and (3) the rural village group (n = 382). The school children from the educated elite group had the highest mean height and weight values while the school children from the rural group had the lowest values and the urban low socio-economic came in between the two. In the children of the educated elite class, mean heights and weights were higher than those of the international reference population (though not significantly so) only at ages 6-9 years. Malnutrition as indicated by wasting and stunting was prevalent among both rural and urban low socio-economic school children. The prevalence of wasting was 75.9% among the rural school children, while it was 62.5% among the urban low socio-economic children. The prevalence of stunting was 79.1% among the rural school children, while it was 62.9% among the urban low socio-economic school children. Neither stunting nor wasting was observed among the children of the elite educated group. This study has demonstrated that there has been no change with time in the pattern of differences of height and weight with respect to school children of various social classes.

Age Distribution↗
PubMed1994

A chicken achaete-scute homolog (CASH-1) is expressed in a temporally and spatially discrete manner in the developing nervous system.

We have identified a basic helix-loop-helix encoding cDNA from embryonic chicken retina which shares sequence similarity with the achaete-scute family of genes of Drosophila. The deduced amino acid sequence of this chicken achaete-scute homolog (CASH-1) is identical, over the region encoding the basic helix-loop-helix domain, to the recently identified mammalian achaete-scute homolog (MASH-1) and to the Xenopus homolog (XASH1), and 70% identical, over the same region, to Drosophila achaete-scute complex members. The expression of CASH-1 is restricted to subsets of neuronal progenitor cells in the developing chicken nervous system, similar in distribution to that reported for MASH-1 and XASH1. In addition, in situ localization in the retina reveals a dynamic character of expression of the gene in a particular region of the CNS, and suggests that the expression of CASH-1 may be important in defining a particular stage in the progenitor cell necessary for the differentiation of particular neuronal phenotypes.

Amino Acid Sequence↗
PubMed1994

The use of pulmonary artery catheters in intensive care: time for reappraisal?

The precise role of the pulmonary artery catheter (PAC) in reducing the morbidity and mortality of intensive care patients remains uncertain. Future studies of the different patient groups who possibly benefit from their use may well require multicentre trials in order to include sufficient numbers and produce significant conclusions. This would suggest a need for a consensus opinion on how PACs are actually used to obtain the different physiological variables which can influence patient management. A questionnaire was designed to assess the degree of conformity of PAC use in intensive care; the questions were derived from a Medline search and considered by the authors to represent a cross-section of the different aspects and potential errors of PAC use. A postal questionnaire was sent from a District General Hospital to 42 adult Intensive Care Units (ICUs) requesting information on the use of PACs in each ICU. The reply rate was 93%, with all but one of the respondents using PACs. The questionnaire obtained information in different areas of PAC use: 1. General usage of PACs. 2. Measurement of patient height and weight. 3. Confirmation of position of PAC tip. 4. Measurement of pulmonary artery wedge pressure (PAWP). 5. Measurement of cardiac output (CO). 6. Derived values. 7. Monitoring for PAC-related sepsis. The results of the questionnaire demonstrated a considerable lack of standardisation in the use of PACs in the United Kingdom.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization, Swan-Ganz↗
PubMed1993

Associative priming in perceptual identification: effects of prime-processing requirements.

Three experiments assessed the effects of prime-processing instructions on associative priming in word identification and episodic memory for primes. In Experiment 1, groups instructed to read the prime silently or generate silently an associate of the prime showed a larger accuracy benefit for related over unrelated targets than did a group that decided whether an asterisk was to the right or left of the prime. The asterisk-search group showed a weaker repetition effect on a subsequent identification test of primes, indicating that the weaker priming in this group was a result of poorer perceptual processing. On a cued-recall test for primes, the generate group was superior to the other groups. In Experiment 2, we found that with weak prime-target associations, priming was comparable for read and generate groups and stronger than estimated for a guessing strategy, on the basis of single predictions made from each prime by an additional group. In Experiment 3, we demonstrated that the read and generate instructions produced similar mispriming and inhibitory effects. The results suggest that the depths of prime-processing manipulations do not have parallel effects on priming and episodic memory, and that associative priming in word identification, as in other tasks, may involve an expectancy process.

Adult↗