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Biomedical subjects

M A White

Publications and source records attributed to M A White.

At least 73 records · Page 4Linked to original sources
PubMed1994

Biological monitoring of occupational cobalt exposure in the United Kingdom.

The determination of urinary cobalt levels has been shown to be of value in the monitoring of occupational exposure and absorption of the metal. A rapid atomic absorption spectrophotometric method for measuring cobalt in urine is described, which has been used for biological monitoring of exposed workers from different occupational groups. Highest urine cobalt concentrations were associated with the handling of cobalt containing powders in the chemical industry (median 93 nmol/mmol creatinine) and hard metal manufacture (median 19 nmol/mmol creatinine). Significant urinary excretion of cobalt was also associated with hard metal finishing and tool making activities (median 17 nmol/mmol creatinine). The study confirms the usefulness of biological monitoring in assessing the uptake of cobalt and control of exposure.

Chemical Industry↗
PubMed1994

Analysis of meiotic recombination events near a recombination hotspot in the yeast Saccharomyces cerevisiae.

The region of yeast chromosome III between the HIS4 and LEU2 genes has an unusually high frequency of meiotic recombination. In order to determine the pattern of cross-over and gene conversion events, we constructed a strain with a number of heterozygous markers in this 25-kb interval. We found that very high levels of recombination are localized to regions of DNA near HIS4. In addition, analysis of the patterns of co-conversion of adjacent markers suggests that there is more than one initiation site contributing to recombination of HIS4.

Chromosomes, Fungal↗
PubMed1994

Family dynamics during the third trimester of pregnancy in Denmark.

Family dynamics in Danish families during the third trimester of pregnancy were explored in relation to family structure, parity, mother-father differences, and normative versus delayed childbearing. There were differences between married and cohabiting families, first- and second-time expectant parents, mothers and fathers, and between normative and delayed first-time expectant parents. For married couples to have better family dynamics than cohabiting couples is surprising for Denmark where both marriage and cohabitation are examples of a nuclear family lifestyle. A dual-path model is conceptualized as a nursing strategy to support the couples' interrelationship during their role transition.

Adolescent↗
PubMed1994

Ras partners.

Explore the source record for details and available documents.

Animals↗
PubMed1994

Family dynamics and infant temperament in Danish families.

Transition to parenthood involves the fine balance of family dynamics which both affect, and are affected by, the infant's temperament. The purpose of this study was to investigate changes in family dynamics over the transition to parenthood and the relationship of family dynamics to infant temperament. A sample of 99 families in Odense, Denmark, completed the Family Dynamics Measure in the third trimester of pregnancy and again when the infant was 8-9 months old. At this second time, the mothers also completed the Revised Infant Temperament Questionnaire. Overall we found small changes, although always in a negative direction, in family dynamics over this transition. The largest change was an increase in perceived role conflict reported by both mothers and fathers. Mothers reported more role conflict than fathers. Positive family dynamics were related to infant rhythmicity.

Adult↗
PubMed1993

Transcription factors are required for the meiotic recombination hotspot at the HIS4 locus in Saccharomyces cerevisiae.

The full activity of a recombination initiation site located 5' of HIS4 requires the binding of the transcription factors RAP1, BAS1, and BAS2. Two RAP1 binding sites can substitute for the wild-type initiation site. A 51-bp region of telomeric DNA inserted upstream of either HIS4 or ARG4 very strongly stimulates recombination. We suggest that the ability of transcription factors to induce recombination is a consequence of an altered chromatin structure that favors the entry of proteins that initiate recombination, rather than an effect of these factors on transcription.

Base Sequence↗
PubMed1993

Analysis of soybean chloroplast DNA replication by two-dimensional gel electrophoresis.

Chloroplast DNA replication was studied in the green, autotrophic suspension culture line SB-1 of Glycine max. Three regions (restriction fragments Sac I 14.5, Pvu II 4.1 and Pvu II 14.8) on the plastome were identified that displayed significantly higher template activity in in vitro DNA replication assays than all other cloned restriction fragments of the organelle genome, suggesting that these clones contain sequences that are able to direct initiation of DNA replication in vitro. In order to confirm that the potential in vitro origin sites are functional in vivo as well, replication intermediates were analyzed by two-dimensional gel electrophoresis using cloned restriction fragments as probes. The two Pvu II fragments that supported deoxynucleotide incorporation in vitro apparently do not contain a functional in vivo replication origin since replication intermediates from these areas of the plastome represent only fork structures. The Sac I 14.5 chloroplast DNA fragment, on the other hand, showed intermediates consistent with a replication bubble originating within its borders, which is indicative of an active in vivo origin. Closer examination of cloned Sac I 14.5 sub-fragments confirmed high template activity in vitro for two, S/B 5 and S/B 3, which also seem to contain origin sites utilized in vivo as determined by two-dimensional gel electrophoresis. The types of replication intermediate patterns obtained for these sub-fragments are consistent with the double D-loop model for chloroplast DNA replication with both origins being located in the large unique region of the plastome [17, 18]. This is the first report of a chloroplast DNA replication origin in higher plants that has been directly tested for in vivo function.

Cell-Free System↗
PubMed1993

Genetic evidence that the meiotic recombination hotspot at the HIS4 locus of Saccharomyces cerevisiae does not represent a site for a symmetrically processed double-strand break.

In the yeast Saccharomyces cerevisiae, the binding of the Rap1 protein to a site located between the 5' end of the HIS4 gene and the 3' end of BIK1 stimulates meiotic recombination at both flanking loci. By using strains that contain mutations located in HIS4 and BIK1, we found that most recombination events stimulated by the binding of Rap1 involve HIS4 or BIK1, rather than bidirectional events including both loci. The patterns of aberrant segregation indicate that most of the Rap1-stimulated recombination events do not represent the symmetric processing of a double-strand DNA break located at the Rap1-binding site.

Alleles↗
PubMed1992

Analysis of a gene conversion gradient at the HIS4 locus in Saccharomyces cerevisiae.

Heteroduplexes formed between genes on homologous chromosomes are intermediates in meiotic recombination. In the HIS4 gene of Saccharomyces cerevisiae, most mutant alleles at the 5' end of the gene have a higher rate of meiotic recombination (gene conversion) than mutant alleles at the 3' end of the gene. Such gradients are usually interpreted as indicating a higher frequency of heteroduplex formation at the high conversion end of the gene. We present evidence indicating that the gradient of conversion at HIS4 primarily reflects the direction of mismatch repair rather than the frequency of heteroduplex formation. We also identify a site located between the 5' end of HIS4 and the 3' end of BIK1 that stimulates heteroduplex formation at HIS4 and BIK1.

Alleles↗
PubMed1992

The slump test.

The Slump Test is an inexpensive, easily administered assessment tool that can help record qualitative changes in sitting in an objective manner. Objective data are useful to document treatment efficacy over time. Over the past 2 years, the Slump Test has been administered at our clinic to a varied population with respect to age, neuromuscular condition, and functional abilities. At the time of this writing, more than 200 children have had the Slump Test administered as part of their assessment protocol. Most of these children have been between the ages of 3 and 8 years; have cerebral palsy, decreased trunk control, and limb spasticity; and are dependent on a wheelchair or aide for ambulation. In conclusion, the picture representation and objective data obtained from the Slump Test along with a qualitative description of sitting have provided us with a useful means of assessing change over time.

Cerebral Palsy↗
PubMed1991

DNA-binding protein RAP1 stimulates meiotic recombination at the HIS4 locus in yeast.

In the yeast Saccharomyces cerevisiae, as in other eukaryotes, some regions of the genome have a much higher rate of meiotic recombination than others. We show below that the binding of the RAP1 protein to a site upstream of the HIS4 gene is necessary for a high rate of meiotic (but not mitotic) recombination at this locus. A mutation in the RAP1 binding site at HIS4 results in a decrease in recombination; overproduction of RAP1 causes an increase in recombination at HIS4 above wild-type levels.

Base Sequence↗
PubMed1991

Family dynamics and infant temperament in urban Iceland.

Pregnancy is a time of transition and crisis when many families are challenged with the addition of an infant. Studies of this challenge are unknown for Icelandic families. The purpose of this study was to investigate the effects of pregnancy and the young infant on family dynamics and the relationship between family dynamics and the infant's developing temperament. Fifty families completed the Family Dynamics Measure during the third trimester of pregnancy and when the infant was eight months old. Mothers also completed the Revised Infant Temperament Questionnaire. Mothers perceived a decrease in role reciprocity across this transition. More stable organized families had more rhythmic infants. There was no association between family structure and either family dynamics or infant temperament. After the birth of the child, fathers perceived more role reciprocity while mothers perceived more individuation and mutuality. Mothers of second infants reported greater individuation than mothers with first infants.

Family↗
PubMed1990

On the role of knowledge of results in motor learning: exploring the guidance hypothesis.

Recent work on the role of knowledge of results (KR) in motor learning has challenged some traditional assumptions. In particular, the guidance hypothesis suggests that there is a detriment to learning when KR guides the learner toward correct performance. Three experiments that explored this hypothesis are reported here. These experiments contrasted the effects of relative frequency of guidance versus the relative frequency of KR. According to the guidance hypothesis, it was predicted that parallel effects of the relative frequency manipulation on motor learning and performance would result under guided and KR conditions. The movement task was a reciprocal timing task that was either paced by a metronome (Experiment 1) or augmented by auditory KR (Experiments 2 and 3). The results of Experiments 1 and 3 revealed a number of parallel effects, thus providing support for the guidance hypothesis. The contrast of Experiments 1 and 2 resulted in a number of dissociable effects, however. These findings are discussed in relation to the potential guiding properties of KR and their impact on motor performance and learning.

Journal Article↗
PubMed1990

Family dynamics during pregnancy.

Pregnancy as a transition in family life is perceived as a crisis by many families. Sociodemographic characteristics of families during pregnancy can serve as important sources of information to nurses in drawing out family strengths and providing assistance during this crisis. Family dynamics were measured in 160 women in the third trimester of pregnancy. Half were in their first pregnancy and half were in their second pregnancy. The research question addressed the relationship between family dynamics and several sociodemographic characteristics. Statistically significant relationships were found between the sociodemographic variables of marital and social status, and several dimensions of family dynamics. Families in which couples were married and who enjoyed a higher social status had more positive family dynamics in the dimensions of individuation, stability, flexibility, mutuality and communication. Race, maternal age and parity were not related to level of family dynamics. Strengths in families who have more positive dynamics may be explained by availability of resources, their expertise in using the system, societal approval of marriage and internal family support from the husband. It is essential for nursing care to include systematic family assessment, socialization in effectively using the health care system and individualized family guidance.

Adolescent↗
PubMed1990

Donor cornea procurement: six-year review of the role of the eye bank in South Australia.

The Lions Eye Bank of South Australia was established six years ago and has collected corneas from 790 donors. The consent rate is currently 82% of requests made. Two-thirds of donors have been male, with mean donor age/year varying from 54 to 64 years (range two to 93 years). Cardiovascular and respiratory diseases, trauma and haemorrhage account for 80% of all donor deaths. Mean death to enucleation time is five hours. Corneas assessed as being of excellent or very good quality are released preferentially from the bank; those with central endothelial cell counts of less than 1500 cells/mm2 are discarded. Fewer than 1% of donors have returned a positive result for HIV or hepatitis B. Of the 1580 corneas collected by the bank, 863 (55%) have been used for transplantation with a primary non-function rate of 0.46%. The evolving policies, logistics of operation and methodologies employed by the bank are described in detail.

Adolescent↗
PubMed1989

Palindromic sequences in heteroduplex DNA inhibit mismatch repair in yeast.

Although single heterozygous markers in yeast usually segregate during meiosis in a 2:2 ratio, abberant 3:1 segregations occur quite frequently as a result of gene-conversion events. A second type of aberrant segregation, post-meiotic segregation, results from the segregation of two genotypes from a single haploid spore; in yeast such events are detected as sectored spore colonies and usually occur rarely. Post-meiotic segregation is thought to result from the replication of heteroduplex DNA formed during meiotic recombination. We report here that if the heteroduplex includes a palindromic insertion sequence, a high frequency of post-meiotic segregation results. This suggests that palindromic insertions are poorly repaired, which may be the result of hairpin-loop formation that affects the efficiency of repair of heteroduplex DNA.

Base Sequence↗
PubMed1989

Leukocytes in the graft bed associated with corneal graft failure. Analysis by immunohistology and actuarial graft survival.

Immunohistochemical staining analysis using monoclonal antibodies was performed on 107 recipient corneas removed at graft. There were significantly more infiltrating cells bearing one or more of the leukocyte-common antigen, class II major histocompatibility complex antigens, various myeloid-lineage markers, and a peripheral T cell marker, in the graft beds of those recipients who subsequently lost a corneal graft than there were in the graft beds of those for whom the outcome was successful. The hypothesis that large numbers of leukocytes in the recipient graft bed would be correlated with subsequent graft failure was examined by actuarial graft survival analysis. Recipients whose corneas contained fewer than 50 leukocyte-common antigen-positive cells/mm2 of corneal stroma showed a 3-year actuarial graft survival of 83%, compared with 39% in those whose corneas contained more than 50 such cells/mm2. The corneal leukocyte count was a particularly useful prognostic indicator of outcome in those patients judged clinically to be at risk of graft failure.

Actuarial Analysis↗