Biomedical subjects
Publications and source records attributed to M A White.
Several investigators have reported that transcription stimulates some types of mitotic recombination in the yeast Saccharomyces cerevisiae. We find that mutations that reduce the rate of transcription of the yeast HIS4 gene in vegetative cells reduce the frequency of mitotic, but not meiotic, recombination events.
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.
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.
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.
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.
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.
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.
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.
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.
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The nature of behaviors during sleep onset latency (SOL) at night bedtime was studied in a group of 40 hospitalized children ages 3 to 8 years whose parents did not room-in. Research questions were: (a) What is the nature of behaviors during sleep onset latency of young children whose parents do not room-in? and (b) How are these behaviors related to family structure, social status, age, gender, previous hospitalizations, and number of days hospitalized? Child subjects were observed using the Senders, Signals, and Receivers (SSR) computer-compatible system to measure SOL, distress, and self-soothing behaviors for 2-3 consecutive nights. The median falling asleep time was 26 minutes. Variations in SOL and self-soothing behaviors were not significantly related to family structure, social status, gender, age, length of hospitalization, night of hospitalization, or previous hospitalizations. Greater distress behaviors were, however, significantly related to children of two-parent families and those from middle social status.
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We have examined the potential use of salivary cadmium measurements for the biological monitoring of occupational cadmium exposure, paying particular attention to the contamination risks associated with such measurements. We have developed a method for the direct determination of cadmium in saliva by graphite furnace atomic absorption spectrophotometry, which minimizes the risk of contamination during sample preparation and analysis. The limit of detection is 0.6 nmoll-1, which is sufficiently sensitive to discriminate between unexposed and occupationally exposed individuals. The method has been employed to measure cadmium levels in saliva samples collected by two different methods from an unexposed population, a group of ex-workers previously exposed to cadmium (Group 1), and two groups of currently exposed workers (Groups 2 and 3). Salivary cadmium levels were significantly raised in both of the groups of currently exposed individuals (group 2 median (Md) = 17 nmoll-1, group 3 Md = 70 nmoll-1, p greater than 0.0001), and in past workers with previous long-term exposure (Group 1 Md = 2.5 nmoll-1, p greater than 0.001) when compared with an unexposed population. The results suggest that the measurement of salivary cadmium may reflect recent exposure to the metal. However, considerable care must be taken in collecting samples because a risk of contamination during sampling is apparent with procedures commonly used for saliva collection, and for this reason the applicability of such measurements for biological monitoring is limited.
A strategy to promote night sleep was tested in 94 hospitalized 3- to 8-year-old children. Parents were not present at bedtime with the first three of four groups of children who: listened to a parent-recorded story, a stranger-recorded story, or did not listen to a recorded story. The fourth group had parents present at bedtime and the children did not listen to a recorded story. Hypotheses were tested with three dependent variables: a) length of sleep onset latency (SOL), b) incidence of distress, and c) self-soothing behaviors. Length of SOL on Night 2, adjusted for Night 1 length of SOL and observer, showed significant treatment effects. The parent-recorded story group had significantly longer SOL than the other three groups. The group with parents present at bedtime had significantly longer SOL than the no-story group which was not significantly different from the stranger-recorded story group. Distress behaviors on Night 2, adjusted for distress on Night 1, age, and observer, showed significant differences between groups. The parent-recorded story group had a higher incidence of distress behaviors than the other groups; the difference between the parent-recorded and the stranger-recorded group was significant. No significant differences between groups were seen in self-soothing behaviors.