Biomedical subjects

S M Williams

Publications and source records attributed to S M Williams.

At least 109 records · Page 6Linked to original sources

PubMed1997

Inattentive and hyperactive behaviors and driving offenses in adolescence.

OBJECTIVE: The associations between symptoms of attention-deficit hyperactivity disorder (ADHD), conduct disorder, anxiety, or depression and no disorder in relation to driving offenses were examined in 916 adolescents. METHOD: Self-report and parent report were used to assess a birth cohort of New Zealand adolescents' mental health status at age 15 years. Adolescents who scored 1.5 SD above the mean on the DSM-III total ADHD symptom scale were identified as reporting significant ADHD symptomatology. Self-report data and official traffic conviction records were used to identify adolescents who had committed driving offenses between ages 15 and 18 years. RESULTS: ADHD symptomatology and conduct disorder were strongly associated with driving offenses. ADHD symptomatology in females was significantly associated with driving offenses and more traffic crashes compared with other disorder or no disorder. CONCLUSIONS: Adolescents with a history of ADHD and conduct problems are significantly more likely than their peers to commit traffic offenses. Research in ADHD and risky driving should include female adolescents, as those with attentional difficulties are at a high risk for being involved in traffic crashes than females who do not experience attentional difficulties.

Adolescent↗

PubMed1997

Why is sudden infant death syndrome more common at weekends? The New Zealand National Cot Death Study Group.

OBJECTIVES: To determine whether the prevalence of known risk factors and the magnitude of their association with sudden infant death syndrome (SIDS) differed between weekends and weekdays. METHOD: A large nationwide case-control study, comparing interview data for 393 cases with 1591 controls. RESULTS: Sudden infant death syndrome occurred more often at weekends, more deaths occurring on Sunday than on any other day of the week. Significant interaction effects were found between weekends and sharing a room with an adult and the parents going to a party. After adjustment for confounders, room sharing was less protective at the weekends (odds ratio (OR) = 0.66, 95% confidence interval (CI) 0.43 to 1.03) than it was on weekdays (OR = 0.41, 95% CI 0.30 to 0.57) using not room sharing and weekdays as the reference group. Although the likelihood of SIDS after a party was higher at weekends (OR = 2.47, 95% CI 1.11 to 5.47) than on weekdays (OR = 0.55, 95% CI 0.21 to 1.37), few cases were reported. Being Maori (OR = 3.35, 95% CI 1.75 to 6.43) or the child of an unmarried mother (OR = 3.91, 95% CI 2.20 to 6.92) were risk factors for SIDS occurring on Sundays. CONCLUSIONS: The increase in SIDS at weekends may be explained in part by the lesser protective effect of sharing a bedroom with an adult at that time. It may also be related to social activities that occur at weekends.

Case-Control Studies↗

PubMed1996

High density of an SAR-associated motif differentiates heterochromatin from euchromatin.

Heterochromatin is an important component of eukaryotic chromosomes, comprising a significant portion of the total DNA in genomes. Despite its prevalence, long-standing cytological descriptions, and predominant composition of tandemly repeated DNA, no general theory unites heterochromatic with its functions. In an attempt to identify heterochromatic sequence tags, we have analysed heterochromatic sequences from Drosophila melanogaster for the presence of motifs that are known to define regions that anchor the chromosomal DNA to the scaffold (scaffold attachment regions or SARs). The SARs of Drosophila melanogaster are characterized by the presence of a small conserved sequence (the A-box) that is clustered in overall A + T-rich regions. In comparing heterochromatic and euchromatic sequences we find that heterochromatic regions are several-fold enriched for these operationally defined SARs. This high density of SAR-associated sequences not only serves as a molecular tag for heterochromatin but also suggests a hypothesis for its special properties.

Animals↗

PubMed1996

The distribution of theta-class glutathione S-transferases in the liver and lung of mouse, rat and human.

Two murine Theta-class glutathione S-transferases (GSTs), mGSTT1 and mGSTT2, have been cloned and sequenced. The murine cDNAs, together with the published sequences of the rat and human enzymes, were used to design oligonucleotide probes in order to determine the distribution of mRNA for these enzymes in the liver and lung of rat, mouse and human. The mRNA distribution was compared with that of enzyme protein determined with an antibody to rat GSTT2-2. Both the antibody and the oligonucleotide probes gave the same distribution patterns. Both enzymes were present at significantly higher concentrations in mouse tissues than in rat or human tissues. In mouse liver, both enzymes were localized in specific cell types and in nuclei. Although the distribution of GSTT2-2 in rat liver was similar to that seen in the mouse, GSTT1-1 was not localized in a specific cell type or in the nuclei of either rat or human liver. In the lungs, very high concentrations of the Theta enzymes were present in mouse-lung Clara cells and ciliated cells, with much lower levels in the Clara cells only of rat lung. Low levels of human transferase GSTT1-1 were detected in a small number of Clara cells and ciliated cells at the alveolar/ bronchiolar junction. The relative activities between species, and the cellular and sub-cellular distribution within the liver and lungs of each species, provides an explanation for the species-specificity of methylene chloride, a mouse-specific carcinogen activated by glutathione S-transferase GSTT1-1.

Animals↗

PubMed1996

Infant room-sharing and prone sleep position in sudden infant death syndrome. New Zealand Cot Death Study Group.

BACKGROUND: There is evidence that the risk of sudden infant death syndrome is lower among ethnic groups in which parents generally share a room with the infant for sleeping. We investigated whether the presence of other family members in the infant's sleeping room affects the risk of the sudden infant death syndrome. METHODS: The case-control study covered a region with 78% of all births in New Zealand during 1987-90. Home interviews were completed with parents of 393 (81.0% of total) babies who died from the sudden infant death syndrome aged 28 days to 1 year and 1592 (88.4% of total) controls, selected from all hospital births in the study region. FINDINGS: The relative risk of sudden infant death for sharing the room with one or more adults compared with not sharing was 0.19 (95% CI 0.08-0.45) for sharing at night during the last 2 weeks and 0.27 (0.17-0.41) for sharing in the last sleep, after control for other confounders. Sharing the room with one or more children did not affect the relative risk (1.25 [0.86-1.82] for sharing during last 2 weeks; 1.29 [0.85-1.94] for sharing in last sleep). There was a significant interaction (p = 0.033) between not sharing the room with an adult and prone sleep position in the last sleep. Compared with infants sharing the room with an adult and not prone, the multivariate relative risk was 16.99 (10.43-27.69) for infants not sharing with an adult and prone, 3.28 (2.06-5.23) for infants sharing the room and prone, and 2.60 (1.58-4.30) for infants not sharing the room and not prone. The interaction between adult room-sharing and prone sleep position suggests that both exposures may affect the risk of sudden infant death syndrome through a common mechanism. INTERPRETATION: We recommend that infants sleep in the same bedroom as their parents at night to reduce the risk of sudden infant death syndrome.

Adult↗

PubMed1996

Progestogen-only oral contraceptives and risk of breast cancer in New Zealand.

Little is known about the influence of progestogen-only oral contraceptives on a woman's risk of breast cancer. This issue was examined in a national population-based case-control study in New Zealand. A total of 891 women aged 25 to 54 years with a first diagnosis of breast cancer and 1,864 control subjects, randomly selected from the electoral rolls, were interviewed. Use of progestogen-only pills was reported by 8.7 percent of all control subjects (and by 17.3 percent of those aged 25 to 34 years). The relative risk (RR) of breast cancer in women who had ever used progestogen-only pills was estimated to be 1.1 (95 percent confidence interval [CI] = 0.73-1.5). In women aged 25 to 34 years, the RR was 2.3 (CI = 1.2-4.3). Women who had started using progestogen-only pills within the last 10 years were at increased risk of breast cancer (RR = 1.6, CI = 1.0-2.4), whereas those who had first used them earlier were at significantly reduced risk (RR = 0.44, CI = 0.22-0.90). These findings are similar to results for depot medroxyprogesterone acetate, and a possible analogy with the influence of pregnancy is also suggested.

Adult↗

PubMed1996

Sudden infant death syndrome: insulation from bedding and clothing and its effect modifiers. The National Cot Death Study Group.

BACKGROUND: Thermal stress related to excessive insulation from bedding and clothing has been postulated to be associated with sudden infant death syndrome (SIDS). METHODS: The parents of 393 (81%) of the infants who died of SIDS in the post neonatal period were interviewed at home. Interviews were also completed with the parents of 1592 (88.4% of total) controls, a representative sample of all hospital births. The study was conducted in regions of the North and South Island of New Zealand in which 78% of all New Zealand births occurred in 1987-1990. Temperatures for the infant's bedroom estimated from the outside temperature and a model were used to predict the appropriate insulation for lower critical temperature (temperature below which the metabolic rate is likely to increase). RESULTS: Sudden infant death syndrome was associated with extra thermal insulation of > 2 tog above the lower critical value, the odds ratio (OR) was 1.70 (95% confidence interval [Cl] : 1.3-2.20) after adjusting for season. After adjusting for a number of confounding factors the CR was reduced to 1.35 (95% Cl: 0.97-1.87). Also associated with SIDS was too little thermal insulation OR = 1.67(95% Cl: 1.13-2.48; and 2.63 (95% Cl: 1.61-4.30) when adjustments were made for the confounding factors. The interaction effect between infants sleeping prone and >2 tog extra thermal insulation was significant (OR = 6.07, 95% Cl: 3.83-9.60). Infants with too little thermal insulation were at increased risk if they were not tightly wrapped (OR = 3.81, 95% Cl: 2.04-7.09). There were also small additive interaction effects if the mother smoked and the infants had > 2 tog extra thermal insulation, or they were ill and had > 4 tog extra insulation. Interaction effects between thermal insulation and other factors were not significant. CONCLUSION: More thermal insulation than was necessary to maintain the lower critical temperature increased the risk of SIDS primarily among infants in the prone sleep position, and to a lesser degree in infants whose mothers smoked and in infants who were unwell.

Bedding and Linens↗

PubMed1996

Temperature and the sudden infant death syndrome.

The relationship between the days on which sudden infant death syndrome (SIDS) occurred and daily minimum and average temperature was examined for five regions of New Zealand for a three-year period beginning on 1st November 1987. There was a marked winter excess of SIDS. After adjusting for season the temperature on the days preceding SIDS deaths were negatively associated with SIDS, but the effect was not statistically significant. Further analysis, using data from the New Zealand Cot Death Study, a nation-wide case-control study was based on the mean temperature 2 to 5 days before death for the cases or a nominated day for the controls. Statistically significant interaction effects between temperature and sleep position, and temperature and the age of the infant were found. A mean temperature 2-5 days beforehand 2.5 degrees C below that on the day of death or the nominated day increased the risk of SIDS in those sleeping prone by 1.17 [95% CI 0.95 to 1.43] and in those sleeping on their side or back by 0.96 [95% CI 0.77 to 1.19]. In the same circumstances the odds ratio (OR) for infants aged 3 months or less would increase by 0.98 [95% CI 0.80 to 1.19] and that for infants older than 3 months by 1.20 [95 CI 0.97 to 1.49]. The statistically significant negative association between temperature a few days before death and SIDS has been reported previously. Most of the effect of temperature can be attributed to seasonal variations, and minor fluctuations in day to day temperatures make only a very small contribution to SIDS.

Case-Control Studies↗

PubMed1996

Symptoms, sweating and reactivity of infants who die of SIDS compared with community controls. New Zealand National Cot Death Study Group.

OBJECTIVE: To describe the symptoms of illness reported by the parents of infants who have died of sudden infant death syndrome (SIDS) compared with those reported by community controls. METHODOLOGY: A nationwide case-control study involving regions of New Zealand with 78% of all births between 1987 and 1990. Home interviews were completed with parents of 393 (81% of total) infants who died from SIDS in the post neonatal age group, and 1592 (88.4% of total) controls who were a representative sample of all hospital births in the study region. RESULTS: Symptoms of infection were common in both cases and controls, but were not significantly different. Infants dying of SIDS, however, were likely to have symptoms suggestive of more severe illness in the 2 days before death (odds ratio [OR] = 3.02, 95% confidence interval [CI] 1.69-5.38). After adjusting for potential confounding this was still statistically significant (adjusted OR 2.36, 95% Cl 1.14-4.90). Also, babies dying of SIDS were more likely to have been less reactive to their environment in the 2 weeks before death compared with the controls (univariate OR 0.88, 95% Cl 0.55- 1.39, adjusted OR 0.55, 95% CI 0.29-0.88). 'Drenching' sweats at least weekly were reported for 15.6% of case infants compared with 5.9% of control infants (adjusted OR 2.12, 95% CI 1.53-3.39). Forty per cent of these infants had this symptom in the first 4 weeks of life when it was also associated with a significantly raised risk of SIDS. Apnoea lasting more than 20 s was reported for 13.2% of case infants compared with 5.3% of control infants (adjusted OR 1.93, 95% CI 1.17-3.17). Similarly, 71.8% of case infants' faces were reported to never turn red while awake compared to 49.8% of control infants (adjusted OR 2.98, 95% CI 2.19-4.07). CONCLUSIONS: Only a small number (6.4%) of babies who die of SIDS have symptoms of serious illness in the 2 days before death. There is support for the hypothesis that there is a group of babies dying of SIDS who have subtle abnormalities in autonomic control or arousal ability.

Apnea↗

PubMed1996

Growth and the sudden infant death syndrome.

OBJECTIVE: To compare the growth curves based on measurements of body weight for male and female infants dying of sudden infant death syndrome (SIDS) with those of male and female controls. METHODS: The data were drawn from a large case control study of SIDS carried out in New Zealand between 1987 and 1990. RESULTS: The mean birthweight for the cases was 3049 g and for the controls 3526 g. The mean growth curves for the male and female controls were close to the 50th centile of growth charts used in New Zealand. The growth curve for the male cases diverged from that of the controls, being closer to the 25th percentile. The differences between the female cases and controls were less pronounced. The differences in weekly weight increments derived from the curves for the cases and controls for nine 4-week periods were not statistically significant after taking into account race, manner of feeding and maternal smoking for any 4-week period. CONCLUSIONS: SIDS cases were lighter at birth, but their growth velocity was normal postnatally.

Body Weight↗

PubMed1996

A potential danger of bedclothes covering the face.

Investigations of infants dying unexpectedly have reported up to 28% being found completely under bedding. No detailed physiological studies looking at the possibilities of asphyxia in this situation are available. The aim was to determine the potential for asphyxia under different types and thicknesses of bedding. A mechanical model of a 3-month-old infant's respiratory system was used. Bedding was positioned over the head in a supine position, and inspired carbon dioxide recorded. With a fixed respiratory rate and tidal volume, carbon dioxide accumulation increased with increasing layers of blankets. Up to 8.3% inspired carbon dioxide was recorded with more than four layers of blankets. A cotton sheet between the face and blankets reduced the accumulation by half. An infant found dead under bedding may have been exposed to an asphyxial stress. Suffocation from rebreathing trapped, expired gases can be a cause of death in this situation.

Asphyxia↗

PubMed1996

Distribution of blood lead levels in a birth cohort of New Zealanders at age 21.

Little is known about lead exposure in the general population of young adults. In this study, whole blood lead concentration (PbB) was determined in a sample of the Dunedin Multidisciplinary Health and Development Study, a well-documented birth cohort of New Zealanders aged 21 years in 1993-1994. PbB in those who consented to venipuncture at 21 years of age (n = 779; 411 males, 368 females) was compared to PbB for the same cohort at age 11 years. The PbB at age 21 ranged from 0.4 to 56 micrograms/dl with a geometric mean of 4.5 micrograms/dl (95% CI, 4.3-4.7 micrograms/dl). Only three individuals had a PbB above 30 micrograms/dl. Males had significantly higher PbB than females (geometric mean 6.0 vs. 3.2 micrograms/dl; p < 0.0001). The PbB at age 21 was 53% lower than in the same individuals at age 11 (geometric mean 4.8 vs. 10.2 micrograms/dl; p < 0.001; n = 480) and the correlation between corresponding values was weak (r = 0.19; p < 0.001). PbB at age 21 showed significant associations with high risk occupational activities, recreational exposure, domicile close to a main road, smoking, and male sex. Blood lead concentrations continue to fall in New Zealand, but occupational and recreational activities remain a significant source of lead exposure.

Adult↗

PubMed1995

The effect of adaptive mutagenesis on genetic variation at a linked, neutral locus.

Based on recent studies in single-celled organisms, it has been argued that a fitness benefit associated with a mutation will increase the probability of that mutation occurring. This increase is independent of mutation rates at other loci and is called adaptive mutagenesis. We modeled the effect of adaptive mutagenesis on populations of haploid organisms with adaptive mutation rates ranging from 0 to 1 x 10(-5). Allele frequencies at the selected locus and a neutral linked locus were tracked. We also observed the amount of linkage disequilibrium during the selective sweep and the final heterozygosity after the sweep. The presence of adaptive mutagenesis increases the number of genetic backgrounds carrying the new fitter allele, making the outcomes more representative of the population before the selection. Therefore, more neutral genetic variation is preserved in simulations with adaptive mutagenesis than in those without it due to hitchhiking. Since adaptive mutagenesis is time-dependent, it can generate mutants when other mechanisms of mutation cannot. In addition, adaptive mutagenesis has the potential to confound both phylogeny construction and the detection of natural selection from patterns of nucleotide variation.

Adaptation, Physiological↗

PubMed1995

Models of adolescent psychopathology: childhood risk and the transition to adulthood.

OBJECTIVE: To examine the relationship between DSM-III disorder in adolescence (age 15 years) and DSM-III-R disorder in early adulthood (age 18 years), in relation to a history of behavior problems or disorder, other family and individual characteristics, and events commonly associated with the transition to adulthood. METHOD: The sample came from a New Zealand birth cohort selected from the general population. Data were obtained from ages 3 to 18 years for 890 of those enrolled. RESULTS: For both males and females, disorder at age 15 was strongly predicted by histories of early mental health problems. However, neither those histories, background characteristics, nor the experience of adolescent transition events modified the strength of association between disorder at ages 15 and 18 years. In childhood, after adjusting for histories of behavior problems, parental separations and (for boys) poor social competence remained independent predictors of disorder at age 15. Overall, boys appeared more vulnerable and those from socially disadvantaged backgrounds in early childhood had an elevated risk of disorder at age 18. After adjusting for disorder at age 15, adolescent unemployment remained an independent predictor of disorder at age 18 for both males and females. CONCLUSIONS: This study modeled the continuity of disorder across the adolescent transition period and, after taking earlier disorder into account, identified clear predictors of later disorder. This is the first step in the process of developing more effective interventions to reduce the risk of mental health disorders.

Adolescent↗

PubMed1995

Care frames: interactive units of health-care delivery.

Describes a way of characterizing the progress of a patient into and out of acute care. Presents a model of the process which resulted from a study of the interface between tertiary care and resettlement in the home community in a single health district. After discussion of the problems relating to patient discharge as described in the literature, briefly describes the origins of and setting for the study. The method of data collection (through documentary analysis, individual and group interview and case study) involved over 100 staff and patients on both sides of the interface. Does not present the substantive findings in detail, as these remain confidential to the organizations involved. However, outlines the process whereby the data gave rise to a model of patient progress and discusses in detail the essential feature of that model--the care frame--both as a theoretical entity and as a basis for practical action. Concludes with a demonstration of how the care-frame model can be used to manage the interface between successive phases in the provision of care and, especially, how it helps to define and manage the interface between acute care and care in the home community.

Continuity of Patient Care↗

PubMed1995

Antenatal and intrapartum factors associated with sudden infant death syndrome in the New Zealand Cot Death Study.

OBJECTIVE: To describe the relationship between antenatal and intrapartum factors and sudden infant death syndrome (SIDS). METHODOLOGY: The New Zealand Cot Death Study was a 3 year case-control study, with 485 infants who died from SIDS in the postneonatal period and 1800 randomly selected control infants. Data were obtained from obstetric records, parental interview and community nursing records. RESULTS: This study confirms many of the antenatal and intrapartum risk factors for SIDS noted in studies from both the southern and northern hemispheres. After controlling for potential confounders, such as occupational group and marital status, significant inverse effects were noted for interpregnancy interval, birthweight and gestation. Other factors that retained a significantly increased risk of SIDS were: increasing parity, bacteriological evidence of urinary tract infection (UTI) (adjusted odds ratio 1.73, 95% CI 1.10-2.73); smoking antenatally (AdjOR 2.14, 95% CI 1.61-2.84); less than six antenatal checks attended (AdjOR 1.84, 95% CI 1.19-2.84); second stage of labour less than 16 min (AdjOR 2.06, 95% CI 1.35-3.14) and multiple birth (AdjOR 3.23, 95% CI 1.70-6.02). No interaction was observed between maternal haemoglobin and antenatal smoking. Interactions were tested for and not found between antenatal smoking and three antenatal risk factors (UTI, short second stage of labour and number of antenatal appointments). The only significant interaction between these three factors and three modifiable postnatal risk factors (prone sleeping, bed sharing and bottle feeding) was between bed sharing and fewer antenatal appointments. The risk of SIDS associated with bed sharing was greater among those whose mothers had fewer antenatal appointments. CONCLUSIONS: Although many of the previously identified antenatal and intrapartum risk factors for SIDS are confirmed, the risks of SIDS associated with obstetric factors are in general considerably lower than the risks associated with the four modifiable postnatal risk factors.

Case-Control Studies↗

PubMed1995

Spacing requirements for transcription activation by Escherichia coli FNR protein.

We cloned a consensus DNA site for the Escherichia coli FNR protein at different locations upstream of the E. coli melR promoter. FNR can activate transcription initiation at the melR promoter when the FNR binding site is centered around 41, 61, 71, 82, and 92 bp upstream from the transcription start. The SF73 positive control amino acid substitution in FNR interfered with transcription activation by FNR in each case. In contrast, the GA85 positive control substitution reduced activation only at the promoter, where the FNR binding site is 41 bp upstream of the transcript start. The SF73 substitution appears to identify an activating region of FNR that is important for transcription activation at promoters that differ in architecture. Experiments with oriented heterodimers showed that this activating region is functional in the upstream subunit of the FNR dimer at the promoter where FNR binds around 41 bp from the transcript start and in the downstream subunit at the promoters where FNR binds farther upstream.

Bacterial Proteins↗

PubMed1995

Sudden infant death syndrome in New Zealand: are risk scores useful? New Zealand National Cot Death Study Group.

STUDY OBJECTIVE: To evaluate the Christchurch, Invercargill, Dunedin (CID) and Oxford record linkage study (ORLS) risk scores in five regions of New Zealand and examine the effect of risk factors for sudden infant death syndrome (SIDS), such as prone sleeping position, maternal smoking, breast feeding, measures of illness, the use of antenatal classes, community health care, and medical services on a high and low risk group delineated by the CID score. DESIGN: This was a case-control study of infants dying of SIDS. SETTING: Both the cases and controls were born in one of five health districts in New Zealand and their parents were interviewed between 1 November 1987 and 31 October 1990. PARTICIPANTS: The cases were 485 infants who died of SIDS. The controls were a random sample drawn from the same five regions in which the cases were born, chosen so that their age on the day on which they were interviewed was similar to the age at death of the cases. Risk scores were calculated for 387 case and 1579 controls. MEASUREMENTS AND MAIN RESULTS: Using the recommended cut off points the sensitivity and specificity of the CID and ORLS were found to be similar to those described for other samples. The differences among the regions were significant. There was, however, no evidence that the association between SIDS and the risk factors considered was different in the high and low risk groups delineated by the CID score. The relative attributable risk for smoking was 32.3% in the high risk group. The excess risk that could be attributed to a different prevalence of any of the other risk factors in the high risk group was small when compared with the low risk group. CONCLUSIONS: Health care resources should be spent on promoting and evaluating good child care practices for all, rather than identifying and promoting special interventions for those in the high risk category.

Breast Feeding↗