Biomedical subjects
S M Williams
Publications and source records attributed to S M Williams.
A group test of auditory lateral advantage.
It is possible to demonstrate the right-sided advantage for speech in a group. This is achieved by playing simultaneous messages over two loudspeakers rather than over headphones. The effect was shown with pre-cued report order in a small (N = 14) and a large (N = 40) group. The effect was larger for the small group. This result argued against an attentional interpretation of the advantage.
Factor analysis of the Edinburgh Handedness Inventory.
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Mammography in women under age 30: is there clinical benefit?
With the increasing utilization of mammography, young women under age 30 are being referred for mammographic examination more frequently. A review of the mammograms of 76 patients, aged 18-29 years, was conducted to evaluate the clinical utility of the examination in this age group, for whom the probability of malignancy is quite low and the risk of radiation carcinogenesis may not be negligible. In 74% of patients referred for study of a palpable mass, no mass was evident on mammograms. When a mass was seen, the radiographic features did not influence clinical management. Radiologists should inform their clinical colleagues regarding the risks and limitations of mammography in women under age 30 and encourage more frequent utilization of ancillary diagnostic procedures including sonography and diagnostic aspiration.
Breast cancer: a challenge to Nebraska physicians.
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Sister chromatid exchange and the evolution of rDNA spacer length.
The structures of rDNA spacers from several species have been characterized and virtually all have internally repeated sequences. Different numbers of these internal repeats are responsible for most spacer length variation. Because unequal recombination between these internal repeats will cause new length variation, while unequal exchange between rDNA copies will homogenize the variants, we modeled the interaction of these two processes. Two models were used to simulate both types of unequal exchange at the sister chromatid level. Both models indicate that a narrow range of relative recombination frequencies is required to produce levels of variability comparable to those published. One model puts a lower limit on the number of internal repeats, and the other puts both a lower and upper limit on the number of repeats. The model with both maximum and minimum constraints produces a distribution closer to actual spacer distributions. These results imply that small changes in recombination rates can generate the differences in numbers of length variants observed in different species.
Homogenization of geographical variants at the nontranscribed spacer of rDNA in Drosophila mercatorum.
rDNA nontranscribed spacer (NTS) lengths of Drosophila mercatorum have been measured in individuals from several geographic regions. Individuals from the different geographic subpopulations share some length fragments but are in general distinct. The length differences, both within and between individuals, arise from different copy numbers of a 250-bp repeating unit that is localized to one part of the NTS. In addition to the length differences caused by the 250-bp repeat, there is a Y chromosome (male)-specific length variant elsewhere in the NTS that is approximately 70 bp shorter than the NTS fragment from the X chromosome. Sexual dimorphism seems to be present in all Drosophila. Also, D. mercatorum has fewer NTS length variants per individual than does D. melanogaster while possessing comparable levels of restriction-site polymorphism. The mechanisms that may cause this pattern of variation are selection, gene conversion, and unequal recombination.
The maintenance of polymorphism owing to differences in developmental time and competition.
The effect of developmental time on the maintenance of an enzyme polymorphism is analyzed under the assumption that competition exists for a reproductively essential resource. Specifically, in laboratory vials Drosophila compete for oviposition and pupation sites. This system of competition serves as a prototype for the model with late-eclosing individuals being excluded from the reproductive pool. Two mating behaviors are modelled: (i) mating is with individuals from only the same cohort group and occurs only once, and (ii) mating is with all individuals that have eclosed up to that time and occurs daily. Numerical analyses are done on both mating structures using data from Drosophila mercatorum. The simulations show that mating structure and initial conditions do not affect the equilibrium genotype frequencies, but that slight changes in the level of competition can dramatically alter the equilibrium values.
Clinical application of in vitro studies for barium-enema examination following colorectal biopsy.
A total of 150 colorectal biopsies were performed in 71 patients and correlated with the barium-enema examination (BE). The investigation was divided into two parts. In the first part, involving 19 patients, the depth of each biopsy specimen was determined histologically prior to BE and potential complications related to the biopsy-BE sequence were evaluated. In the second part, involving all 71 patients, the depth of biopsy specimens taken from various colon lesions was determined histologically without regard to the timing of BE. The results confirm previous in vitro findings in pigs and dogs, namely: (a) BE may be performed without delay following a superficial biopsy, but should not be performed until at least 6 days after a deep biopsy; (b) transcolonoscopic biopsies are likely to be superficial, while transproctoscopic biopsies have the potential to be deep; and (c) BE should be delayed at least 6 days following polypectomy or polyp biopsy performed with electrosurgery.
Fistula following continent ileostomy.
A patient who developed a fistula secondary to Marlex mesh in the nipple valve of a continent ileostomy is reported. Etiology and management of fistula following continent ileostomy are discussed. Fistula formation should be recognized as a potential hazard of the use of prosthetic material to stabilize the nipple valve of a continent ileostomy.
Radiologic features of multinodular lymphoma of the colon.
The colon is frequently involved in patients with systemic malignant lymphoma and may be the site of initial clinical presentation. Multiple nodules are one of the manifestations of colonic lymphoma. In an effort to determine the most useful and characteristic features, the radiographic findings in 23 patients with multinodular colonic lymphoma were reviewed. The most characteristic radiographic features were identified: (1) variably sized, smooth, sessile nodules with an average diameter of 7 mm; (2) a cecal mass larger than 3 cm; (3) distortion of the haustra ; (4) incomplete evacuation of barium; and (5) involvement of the stomach, small bowel, or spleen. Less common were irregular, pedunculated, or filiform nodules and occasional umbilication . The differential diagnosis includes gastrointestinal polyposis, benign lymphoid hyperplasia, and inflammatory bowel disease. The radiologist may be the first to suggest the correct diagnosis when lymphoma patients present with multiple colonic nodules.
Superiority of the left cerebral hemisphere in word recognition with nonverbal central fixation.
The right visual-field advantage for bilateral presentation put forward by McKeever and Huling was investigated. The central-fixation task was varied so that in one condition this task was nonverbal. Results gave some support for scanning-type explanations in this paradigm but over-all favoured Kinsbourne's activation-and-priming account.
Some developmental and behavioural characteristics of seven-year-old children with delayed speech development.
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Blood pressure in a cohort of Dunedin seven year olds.
Blood pressure, pulse measurements, socio-economic status, and anthropometric data were recorded in 982 children within approximately one month of their seventh birthdays. The means, standard deviations, and 95th centiles are reported for systolic, diastolic phase IV, and diastolic phase V blood pressure. There was no significant difference between the socio-economic levels for any measure of blood pressure. Systolic blood pressure was slightly but significantly higher in boys than in girls; this difference disappeared after correction for height. There were small but significant correlations between blood pressure and pulse rate, weight, height, arm circumference, triceps skinfold thickness, and indices of obesity and body size. After adjustment for weight, the associations of systolic blood pressure with height, body mass index, and arm circumference were no longer significant.
The identity of bovine liver "nothing dehydrogenase".
An assay system was developed which allowed the partial purification of the substrate for beef liver nothing dehydrogenase. This was also found to be a substrate for lactate dehydrogenase (LDH). Using electrophoretic separations of purified LDH and beef liver extracts, nothing dehydrogenase was determined to be primarily the H4 isoenzyme of LDH. The nothing dehydrogenase phenomena was also observed with highly-purified, commercially-obtained LDH.
Protein deficiency: effects on lung mechanics and the accumulation of collagen and elastin in rat lung.
Groups of weanling (approximately 50 g) or young adult (approximately 300 g) rats were fed ad libitum casein-based diets varying in protein content from 4 to 16%. A group was also fed the 16% protein diet in an amount on a daily basis restricted to that consumed by the protein-deficient group (4% protein). The rats were fed the diets for either 4 weeks (weanling) or 6 weeks (adults). Protein-deficient or "food-restricted" rats (whether weanling or adults) were smaller and had smaller lungs than rats fed ad libitum the diets containing 16% protein. The lung elastin content was more resistant to dietary manipulation than was the lung collagen content. Lung collagen was significantly decreased in both weanling and adult rats fed the 4% protein diet. In weanling rats, pressure-volume relationships derived from saline-filled lungs (analyzed by exponential curve-fitting methods) suggested that lungs from food-restricted rats may be less compliant than lungs from rats fed the control diet ad libitum. When expressed in absolute terms, lungs from protein-deficient rats also appeared to be less compliant than normal rats; however, on a relative basis (percentage of volume at a given recoil pressure or the expression of volume on a weight basis) differences in compliance were less apparent. It is proposed that in weanling rats the differences in lung composition and compliance are the result of retarded lung growth and perhaps development.
Developmental language delay from three to seven years and its significance for low intelligence and reading difficulties at age seven.
A large sample of Dunedin (New Zealand) children was assessed at three, five and seven years to study the prevalence and stability of language delay, and to investigate the association between language delay at each age and low intelligence and reading problems at age seven. The prevalence of specific comprehension delay, specific expressive delay, and general language delay varied from 2.0 to 4.3 per cent. General language delays were the most stable. Every type of language delay at each age, particularly earlier, general and stable delay was associated with a significantly higher prevalence of low intelligence or reading difficulties at age seven than among the total sample.
Work in progress: transverse striations of the esophagus: association with gastroesophageal reflux.
Transverse mucosal ridging of the esophagus may be demonstrated on double-contrast esophagrams as transverse striations. A case review of 44 patients who had transverse striations was performed to evaluate the significance of the striations with respect to gastroesophageal reflux. Gastroesophageal reflux was significantly more common among patients who had transverse striations than it was in the general population who had been referred for the barium meal. This does not imply that all patients with transverse striations or with reflux at fluoroscopy have esophagitis. However, recognition of transverse striations should prompt careful evaluation for reflux and associated complications in symptomatic patients.