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Biomedical subjects

S M Williams

Publications and source records attributed to S M Williams.

At least 37 records · Page 2Linked to original sources

The smell map: commonality of odour perception confirmed.

We have examined the repeatability of a perceptual space, or smell map, initially developed in a sample of 20 people. A total of 110 normosmic people performed similarity ratings for pairs of the 11 commonly encountered odours used in the previous study. Multidimensional scaling was again used to analyse the relationships between odours. Some individual plots and an archetype, generated using the data from all participants, produced results similar to the previous study, confirming the ability to obtain reproducible results using a different tester and different participants. Exploration of the source space, that is, the spatial distribution of the individual plots relative to each other, suggests that the current model explains about 50% of the variation between subjects for the two-dimensional solution and 57% for the three-dimensional solution.

Adolescent↗

Association studies of neurotransmitter gene polymorphisms in alcoholic Caucasians.

Ethanol enhances mesolimbic/cortical dopamine activity in reward and reinforcement circuits. We investigated the hypothesis that risk for alcoholism may be mediated by genes for neurotransmitters associated with the dopamine reward system as well as genes for enzymes involved in ethanol metabolism. DNA was extracted from brain tissue collected at autopsy from pathologically characterized alcoholics and controls. PCR-based assays showed that alcoholism was associated with polymorphisms of the dopamine D2 receptor (DRD2) TaqI B (P = .029) and the GABAA-beta2 subunit C1412T (P = .012) genes, but not with the glutamate receptor subunit gene NMDAR2B (366C/G), the serotonin transporter gene (5HTTL-PR), the dopamine transporter gene DAT1(SLC6A3), the dopamine D2 receptor gene DRD2 TaqI A, or the GABAA alpha1(A15G), alpha6(T1519C), and gamma2(G3145A) subunit genes. The glial glutamate transporter gene EAAT2 polymorphism G603A was associated with alcoholic cirrhosis (P = .048). The genotype for the most active alcohol dehydrogenase enzyme ADH1C was associated with a lower risk of alcoholism (P = .026) and was less prevalent in alcoholics with DRD2TaqIA2/A2 (P = .047), GABAA-beta2 1412C/C (P = .01), or EAAT2 603G/A (P = .022) genotypes. Combined DRD2TaqI A or B with GABAA-beta2 or EAAT2 G603A genotypes may have a concerted influence in the predisposition to alcoholism.

Alcoholism↗

Body composition of 4- and 5-year-old New Zealand girls: a DXA study of initial adiposity and subsequent 4-year fat change.

BACKGROUND: Dual-energy X-ray information (DXA) quantitating body fat mass and percentage fat in healthy children of preschool age is scarce. OBJECTIVE: To study the initial variability in body composition and subsequent longitudinal changes in absolute fat mass (kg) and relative adiposity (fat percentage) in a sample of contemporary young New Zealand girls. DESIGN: Cross-sectional study with a longitudinal component. SETTING: University research unit. SUBJECTS: A total of 89 Caucasian girls aged 4-5 y were recruited by advertisement at baseline and 4-y changes in body composition were evaluated in 23 of these girls. METHODS: Total body composition was measured by DXA, height and weight by anthropometry. RESULTS: Baseline values for fat mass varied more than values for lean mass or bone mass. Girls from the upper third of our fat percentage distribution (% fat >19.2%) had more than twice the fat mass (5.34 vs 2.31 kg, P<0.001) of those from the lowest third (% fat &<15.4%). The percentage gain in fat mass over 4 y (124 (95% CI 90-163) also exceeded the percentage gain of lean mass (55 (95% CI 51-59). In data adjusted for age and height, 63.5% of the variance in percentage body fat at time 2 was explained by fat mass at time one. CONCLUSIONS: In girls, the trajectory of fat gain appears to be established at a young age. Our results support the view that body fatness tracks strongly before puberty. Since preventing the accumulation of excessive fat is preferable to reduction of existing excessive fat stores, it is important to put in place strategies to limit excessive fat gain early in life.

Absorptiometry, Photon↗

Does circadian variation in risk factors for sudden infant death syndrome (SIDS) suggest there are two (or more) SIDS subtypes?

UNLABELLED: Sudden infant death syndrome (SIDS) is known to occur more frequently at night. In two studies it has now been shown that a prone sleep position is more strongly associated with SIDS occurring during the day, whereas night-time deaths are more strongly associated with maternal smoking and illness. CONCLUSION: This variation, although unexplained, does suggest at least two SIDS subtypes: one related to sleep position and possibly a thermal mechanism, and one related to an uncontrolled inflammatory response to infection predominantly occurring at night. In addition, there are probably other mechanisms that do not show a circadian variation.

Body Temperature↗

Spinal overload: a concern for obese children and adolescents?

Heavy children require stronger bones than leaner children. The present cross-sectional observational study was undertaken to examine the magnitude of compensatory increases in the spinal bone mineral content (BMC) and area shown by overweight and obese children and adolescents. Vertebral area and BMC of lumbar vertebrae L2-L4 were measured by dual-energy X-ray absorptiometry in 202 boys and 160 girls aged 3-19 years. Subjects were categorized as of normal weight, overweight or obese using international cutoffs for body mass index. Compared with children of healthy weight our overweight and obese children had lower vertebral BMC for their bone area, body height, body weight and pubertal development: ratios and 95% CI for overweight and obese groups were 0.92 (95% CI 0.87-0.97) and 0.88 (95% CI 0.80-0.96) for girls and 0.96 (95% CI 0.91-1.02, NS) and 0.87 (95% CI 0.78-0.96) for boys, respectively. Spinal area was low in overweight and obese girls compared with girls of healthy weight but overweight and obese boys had enlarged their vertebral area appropriately for their increased body size. We conclude that during growth overweight and obese children do not increase their spinal BMC to fully compensate for their excessive weight. Limiting excessive adiposity in childhood and adolescence should help to avoid excessive loading and stresses on the lumbar spine.

Adaptation, Physiological↗

How many children remain fracture-free during growth? a longitudinal study of children and adolescents participating in the Dunedin Multidisciplinary Health and Development Study.

While much is known regarding the incidence and pattern of fractures during growth, information is sparse as to how many children fracture repeatedly and how many remain fracture-free during growth. The Dunedin Multidisciplinary Health and Development Study, a birth cohort, whose members were questioned regularly throughout growth (at ages 5, 7, 9, 11, 13, 15 and 18 years) concerning injuries including fractures, has provided a unique opportunity to answer these questions. Life-table analysis showed that approximately half the children remained fracture-free throughout growth [girls 60.1%, (95% CI 54.7-65.0) and boys 49.3% (95% CI 44.0-54.4)]. Data on fracture history, for participants seen at every phase, was available for 601 members through to the age of 18 years (61.1% of the cohort seen at age 5 years). Two hundred and ninety-one of these 601 participants reported 498 fractures, with 172 sustaining a single fracture, and 119 more than one fracture (15.8% girls and 23.4% boys). The most common site of fracture was the wrist/forearm (24.1% of all fractures). We conclude that although bone fractures are a common adverse event in childhood, half of all children remain fracture-free throughout growth.

Adolescent↗

Assessment of three levels of folic acid on serum folate and plasma homocysteine: a randomised placebo-controlled double-blind dietary intervention trial.

OBJECTIVE: To determine the minimum effective dose of folic acid required to appreciably increase serum folate and to produce a significant reduction in plasma total homocysteine (tHcy). DESIGN: Double-blind, randomised placebo-controlled intervention trial. SETTING: Community-based project in a New Zealand city. SUBJECTS: Seventy free living men and women with tHcy> or =10 micromol/l. Mean age (range) was 58 (29-90) y. INTERVENTIONS: Daily consumption over 4 weeks of 20 g breakfast cereal either unfortified (placebo) or fortified with 100, 200 or 300 microg folic acid. Dietary intake was determined by weighed diet records and consumption of commercially fortified products was avoided. MAIN OUTCOME MEASURES: Plasma tHcy and serum folate concentrations. RESULTS: Average serum folate concentrations (95% CI) increased significantly in the treatment groups relative to the control group by 28(9-51)%, 60(37-87)% and 79(51-114)% for supplementation with 100, 200 and 300 microg folic acid, respectively. A reduction in tHcy was observed, being 16(8-22)%, 12(4-18)% and 17(9-24)% in the three treatment groups, respectively. CONCLUSIONS: A regular intake of as little as 100 microg folic acid per day was sufficient to lower tHcy in persons at the upper end of the normal range for tHcy. Low-level fortification may also be appropriate for lowering the risk of neural tube defects given that, when aggregated from all sources, the total intake of folic acid may be sufficiently high to adequately improve the folate status of young women.

Adult↗

Heterosis of growth and reproductive traits in fowl.

Long-term divergent selection for high (HH) and low (LL) BW at 56 d of age in White Plymouth Rock chickens resulted in deviations from a typical chronological timeline for reproductive development. Line HH chickens of the 42nd generation of selection (S(42)) were heavier at 28, 56, 168, and 266 d of age, as well as at sexual maturity than those from line LL of the same generation, and commenced egg production at a younger age (188 d vs. 217 d). Once the LL chickens reached sexual maturity, 99.5% of their ovulations resulted in normal oviposits, in contrast to 94.6% for HH females. Heterosis, as measured by differences of F(1) progeny from the parental lines, can have a positive or negative sign. Although negative heterosis does not imply inferiority, results may be confusing because, depending on the trait, positive or negative can biologically be the phenotype that is preferred. Heterosis was calculated using coefficients of variation and means for reciprocal crosses from S(41) parents of the selected lines. Growth and reproductive traits were measured in this experiment. In almost all cases, heterosis calculated using coefficients of variation had a narrower range of magnitudes.

Animals↗

Articular mobility in Maori and European New Zealanders.

OBJECTIVES: To determine the prevalence of hypermobility and of the hypermobility syndrome (HMS) in Maori and European New Zealanders. METHODS: The prevalences of generalized hypermobility (Beighton's score > or = 4), of hypermobility at individual sites and of HMS were determined in 804 Maori and European subjects. Musculoskeletal system (MSS) manifestations were documented in all subjects by personal interview and an MSS examination. Radiographs were obtained where appropriate. RESULTS: The percentage of hypermobile subjects was 6.2 for Maori (9.0 for females and 2.2 for males) and 4.0 for Europeans (5.6 and 1.9). Hypermobility was more prevalent in females (P=0.0001). Hypermobility of the elbow was more prevalent in Maori (P=0.003) and hyperextension of the fifth finger and apposition of thumb to forearm were more prevalent in females (P<0.001). HMS was present in two of 41 (4.9%, 95% confidence interval 0.6-17.6%) hypermobile subjects. Both were Maori females and therefore 2/23 hypermobile Maori females (8.7%, 1.1-31.4%) had HMS. CONCLUSION: The prevalence of hypermobility in Maori is similar to that in European New Zealanders and Caucasians elsewhere. Larger studies are necessary to determine the prevalence of HMS in Maori, particularly Maori females.

Adolescent↗

Were NZ's structural changes to the welfare state in the early 1990s associated with a measurable increase in oral health inequalities among children?

OBJECTIVE: To test the hypothesis that the 1990-91 social and economic policy changes in New Zealand were associated with a subsequent increase in socioeconomic and ethnic inequalities in the dental caries experience of five-year-old children. METHOD: Dental caries data from the School Dental Service treating the greater Wellington area were analysed for the period 1995-2000. Multivariate models were developed for deciduous caries prevalence (logistic regression) and severity (negative binomial regression). RESULTS: In the years 1995, 1996, 1997, 1998, 1999 and 2000, complete data were available for 2,627, 3,335, 4,404, 4,155, 3,154 and 2,804 children, respectively. Ethnic and socio-economic differences in caries prevalence and severity were substantial and persistent during the observation period. Where caries severity was concerned, there was a significant interaction between time and Maori ethnicity, indicating that (on average) the oral health of Maori children deteriorated in comparison to their European counterparts. CONCLUSIONS: The early-1990s social and economic policy changes were associated with an apparent widening of ethnic inequalities in caries severity among five-year-old children. IMPLICATIONS: Economic rationalism appears to have oral health disadvantages for non-European children. Before implementation of proposed major social and economic policy changes, policymakers should consider their health implications.

Child↗

Are risk factors for sudden infant death syndrome different at night?

AIMS: To determine whether the risk factors for SIDS occurring at night were different from those occurring during the day. METHODS: Large, nationwide case-control study, with data for 369 cases and 1558 controls in New Zealand. RESULTS: Two thirds of SIDS deaths occurred at night (between 10 pm and 7 30 am). The odds ratio (95% CI) for prone sleep position was 3.86 (2.67 to 5.59) for deaths occurring at night and 7.25 (4.52 to 11.63) for deaths occurring during the day; the difference was significant. The odds ratio for maternal smoking for deaths occurring at night was 2.28 (1.52 to 3.42) and that for the day 1.27 (0.79 to 2.03); that for the mother being single was 2.69 (1.29 to 3.99) for a night time death and 1.25 (0.76 to 2.04) for a daytime death. Both interactions were significant. The interactions between time of death and bed sharing, not sleeping in a cot or bassinet, Maori ethnicity, late timing of antenatal care, binge drinking, cannabis use, and illness in the baby were also significant, or almost so. All were more strongly associated with SIDS occurring at night. CONCLUSIONS: Prone sleep position was more strongly associated with SIDS occurring during the day, whereas night time deaths were more strongly associated with maternal smoking and measures of social deprivation.

Age Distribution↗

Macroscopic assessment of pulmonary fine needle aspiration biopsies: correlation with cytological diagnostic yield.

Fine needle aspiration biopsy (FNAB) is widely used in the diagnosis of pulmonary neoplasia. Previous studies have advocated the use of immediate cytological review at the time of biopsy to reduce the number of needle passes performed, whilst stating that in the absence of this, simple macroscopic assessment of sample quality was used. This latter practice is widespread, but there is no data regarding its accuracy or the level of intra-observer consistency. We assessed the degree of correlation between a macroscopic grading of the FNAB sample at the time of lung biopsy by the radiologist performing the procedure and subsequent diagnostic yield. 45 consecutive patients in whom pulmonary neoplastic disease was strongly suspected were included. Macroscopic sample appearances were graded on a five-point scale from 1 (blood with no particulate material) to 5 (solid tissue pieces). The positivity rate increased stepwise along with macroscopic grading from 50% for samples graded 1 to 100% for samples graded 5. Grouping the predominately haemorrhagic samples (graded 1-2) together and comparing them with the particulate samples (graded 3-5) demonstrates a statistically significant difference in diagnostic yield (p<0.001). This small study shows that a simple macroscopic grading of pulmonary FNAB samples can provide a good indication of likely cytological diagnostic yield and that radiologists can develop a degree of consistency in their assessment. In the absence of direct cytological input, this may provide a basis for decisions on the number of passes performed.

Adult↗

A new lump.

Explore the source record for details and available documents.

Arachnoid Cysts↗

Partial- or full-mouth approaches to assessing the prevalence of and risk factors for periodontal disease in young adults.

BACKGROUND: While partial-mouth recording is often used in epidemiological studies of periodontal disease because of the efficiencies afforded in data collection, there has been no investigation of the extent to which information is lost in studies of young adults using the combined attachment loss (CAL) approach. METHODS: A random sample of 25- and 26-year-olds was periodontally examined at 3 sites per tooth in all 4 quadrants. The analysis obtained full-mouth prevalence estimates for gingival recession (GR), probing depth (PD), and CAL. The half-mouth analyses took 3 forms: 1) estimates from each of the left and right sides were obtained and compared; 2) estimates were obtained separately and compared for quadrants 1 and 3 (upper right and lower left), and quadrants 2 and 4 (upper left and lower right); and 3) estimates were obtained from a diagonal half-mouth count, whereby quadrants 1 and 3 were analyzed for study participants whose identification number was odd, and quadrants 2 and 4 were analyzed for the remainder. The utility of the half-mouth and full-mouth approaches in analytical epidemiology was examined by estimating the strength of the association between periodontitis prevalence and smoking, male gender, and episodic use of dental care. RESULTS: Of the 169 participants examined, 100 (59.2%) were female, 54 (32.0%) were smokers, and 78 (46.2%) were episodic dental visitors. The difference in prevalence estimates obtained from the different methods was considerably greater for GR than for PD and CAL. The unadjusted odds ratio (OR) for the prevalence of 1 or more teeth with > or = mm of CAL among smokers was 2.3 (95% confidence interval [CI] 1.0, 5.3) using the full data set and 2.4 (95% CI 0.9, 6.1) using the diagonal half-mouth approach. Similarly close odds ratios were observed for males and, to a lesser extent, for episodic dental visitors. CONCLUSIONS: Wherever possible, full-mouth data should be collected for descriptive epidemiological studies of periodontal disease, but where resource and time constraints mean that half-mouth examinations must be used, analytical studies of periodontitis should not be unduly affected by the loss of information. However, where the primary focus of the latter is upon gingival recession, the full-mouth design should be used in order to capture all relevant information, and attention should be directed to making economies in other areas of the data collection process.

Adult↗

The effect of hormone replacement therapy on cardiovascular risk factors in type 2 diabetes: a randomized controlled trial.

BACKGROUND: Postmenopausal women with diabetes are at high risk for cardiovascular disease, compared with their nondiabetic counterparts. Combined continuous hormone replacement therapy (HRT) is associated with improvements in serum lipoprotein levels in nondiabetic women; however, the effect in women with diabetes has not been determined. We evaluated the effect of combined continuous HRT on lipoprotein and coagulation factor concentrations and glycemic control in postmenopausal women with type 2 diabetes mellitus. METHODS: In a randomized controlled crossover study, 61 subjects received combined continuous HRT or placebo. Each treatment phase was of 6 months' duration, with an 8-week washout phase between treatment phases. RESULTS: Total cholesterol concentration decreased by 7% (95% confidence interval [CI], 4%-11%) during HRT. For low-density lipoprotein concentration, the mean decrease with HRT was 12% (95% CI, 6%-17%). Apolipoprotein B levels decreased in keeping with the reduction in low-density lipoprotein cholesterol concentrations. There were no significant changes in concentrations of high-density lipoprotein, its subfractions, or triglycerides. Lipoprotein(a) and fibrinogen concentrations were reduced by 21% (95% CI, 10%-31%) and 8% (95% CI, 2%-13%), respectively, with HRT. Fructosamine concentrations declined by 5% (95% CI, 2%-9%) during HRT. CONCLUSIONS: In postmenopausal women with type 2 diabetes mellitus, combined continuous HRT has beneficial effects on lipoprotein concentrations and improves some markers of coagulation and glycemic control.

Aged↗

Haplotype diversity and linkage disequilibrium at human G6PD: recent origin of alleles that confer malarial resistance.

The frequencies of low-activity alleles of glucose-6-phosphate dehydrogenase in humans are highly correlated with the prevalence of malaria. These "deficiency" alleles are thought to provide reduced risk from infection by the Plasmodium parasite and are maintained at high frequency despite the hemopathologies that they cause. Haplotype analysis of "A-" and "Med" mutations at this locus indicates that they have evolved independently and have increased in frequency at a rate that is too rapid to be explained by random genetic drift. Statistical modeling indicates that the A- allele arose within the past 3840 to 11,760 years and the Med allele arose within the past 1600 to 6640 years. These results support the hypothesis that malaria has had a major impact on humans only since the introduction of agriculture within the past 10,000 years and provide a striking example of the signature of selection on the human genome.

Africa↗

Why we see things the way we do: evidence for a wholly empirical strategy of vision.

Many otherwise puzzling aspects of the way we see brightness, colour, orientation and motion can be understood in wholly empirical terms. The evidence reviewed here leads to the conclusion that visual percepts are based on patterns of reflex neural activity shaped entirely by the past success (or failure) of visually guided behaviour in response to the same or a similar retinal stimulus. As a result, the images we see accord with what the sources of the stimuli have typically turned out to be, rather than with the physical properties of the relevant objects. If vision does indeed depend upon this operational strategy to generate optimally useful perceptions of inevitably ambiguous stimuli, then the underlying neurobiological processes will eventually need to be understood within this conceptual framework.

Animals↗