Search PubMed⌕ Search

Biomedical subjects

J G Williams

Publications and source records attributed to J G Williams.

At least 91 records · Page 5Linked to original sources
PubMed1994

Comparison of stable isotopes and radioisotopes in the measurement of iron absorption in healthy women.

1. Stable isotope methods are being used to investigate the absorption of dietary iron. In order to be certain that this new methodology is accurate, we have compared results obtained using stable isotopes and inductively coupled plasma mass spectrometry with those determined using a radioisotope and whole body counting. 2. The stable isotope 54Fe (2.8 mg) was given to 10 healthy non-pregnant women. Six women received the isotope in aqueous form, and four took it with a meat meal. The 54Fe served as a carrier for 10 ng of the radioisotope 59Fe. An ampoule (200 micrograms) of the isotope 57Fe or 58Fe was then given intravenously, and in serum samples taken over the next 10 h the ratios of the stable iron isotopes were measured by inductively coupled plasma mass spectrometry and the oral iron absorption was calculated. This was then compared with the results obtained by using a whole body counter to measure (on day 0 and day 14) the gamma-activity emitted by the radioisotope. 3. The mean iron absorption measured by both methods ranged from 8% to 45%. Measurement of the post-absorptive serum enrichment of the stable isotopes provided estimates of absorption from both aqueous and food iron which were similar to that yielded by whole body counting, the mean difference being -1.5% (95% confidence interval -5.2 to 2.1%). Absorption estimated by stable isotopes exhibited the same inverse relationship with the serum ferritin level (body iron stores) to that known to exist with whole body counting.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Visual search strategies in experienced and inexperienced soccer players.

This study investigated skill-based differences in anticipation and visual search strategy within open-play situations in soccer. Experienced (n = 15) and inexperienced (n = 15) subjects were required to anticipate pass destination from filmed soccer sequences viewed on a large 3-m x 3-m video projection screen. MANCOVA showed that experienced soccer players demonstrated superior anticipatory performance. Univariate analyses revealed between-group differences in speed of response but not in response accuracy. Also, inexperienced players fixated more frequently on the ball and the player passing the ball, whereas experienced players fixated on peripheral aspects of the display, such as the positions and movements of other players. The experienced group fixated on significantly more locations than their inexperienced counterparts. Further differences were noted in search rate, with experienced players exhibiting more fixations of shorter duration. The experienced group's higher search rate contradicted previous research. However, this resulted from using 11 on 11 film sequences, which were never previously used in visual search research. The increased frequency of eye fixations was regarded as being more advantageous for anticipating pass destination during open play in soccer. Finally, a number of practical implications were highlighted.

Adult↗
PubMed1994

Fistulas in ano: endoanal ultrasonographic assessment assists decision making for surgery.

Eighteen patients with a clinical impression of a complex fistula in ano, had anal endosonography to delineate the anatomy of the fistula track and identify associated areas of sepsis. The clinical impression of a complex fistula was refuted by endosonography and subsequent surgical exploration in two cases. Horseshoe tracks were identified in nine (50%) patients and fluid collections, not evident on clinical examination were identified in eight (45%) patients. Accurate identification of the internal opening with a 7 MHz transducer was possible in two (11%) cases. External sphincter damage was evident in four (22%) patients. Surgical findings matched endosonographic appearances in all but one case (94%). Anal endosonography is an accurate and minimally invasive method of delineating the relation of fistula tracks to the anal sphincters and identifying deep areas of sepsis in relation to such fistulas.

Adult↗
PubMed1994

Prevalence of dyspepsia: the epidemiology of overlapping symptoms.

Studies of the epidemiology of dyspepsia have been complicated by the use of different symptom definitions, subject populations and time frames of investigation. Published figures for the prevalence of dyspepsia vary from 20% to 40%, of which perhaps only a quarter can be attributed to peptic ulcer disease. General practitioners see only a fraction of the dyspepsia within the community, the majority of which is either ignored or treated by self-medication. However, dyspepsia still accounts for about 3-4% of all general practice consultations and for about 14% of all patients attending. In about half of all cases, even extensive investigation reveals no underlying organic lesion. There has been much recent interest in the clinical value of grouping dyspeptic symptoms into particular subtypes. These have been called ulcer-like, dysmotility-like and reflux-like. Although these patterns have descriptive value, there is no evidence that they result from discrete pathophysiological processes. Indeed, studies both in general practice and in the community show a large degree of overlap between them.

Dyspepsia↗
PubMed1994

Physicians' attitudes toward a new gynecological examination gown.

Gynecologists' attitudes toward an examination gown found in previous studies to reduce patients' distress during examination were investigated. Twenty-six gynecologists in four cities volunteered to use the new examination gown and complete a questionnaire evaluating the gown for adequacy of design and perceived patient comfort. Participants rated the gown positively overall. Favorability ratings were highly correlated with ratings of the structural adequacy of the gown for performing the breast, back, and pelvic exams. Favorability was also highly correlated with physicians' perceptions of the patients' comfort with the gown. The new gynecological examination gown is well accepted by gynecologists. It appears that gynecologists are open to changes in examination procedures that do not interfere with the exam and increase patient comfort. This new gown offers a strategy for decreasing patient distress during examination, which may reduce delay in seeking examinations.

Attitude of Health Personnel↗
PubMed1994

Situational influences on cues used to judge intoxication.

Subjects' perceptions of cues used to judge intoxication across different drinking settings were investigated. College students (N = 40) were presented with 12 one-paragraph scenarios, four for each of three types of drinking expectancy: tension reduction, social disinhibition and physical impairment. Pilot testing confirmed that the scenarios accurately represented these different expectancies. Subjects rated the importance of 18 cues to intoxication for judging intoxication in each of the 12 scenarios. Results indicated that 15 of the 18 cues were perceived to be differentially important in the three types of situations. These results suggest that subjects apply cues to intoxication differently in different situations.

Adolescent↗
PubMed1994

Validity of a perceived exertion scale for children: a pilot study.

The purpose of this study was to examine the validity of a recently developed rating scale of perceived exertion, the Children's Effort Rating Table (CERT), for controlling exercise intensity in young children. 16 children (M age = 9.9 yr., SD = 1.2) performed three separate exercise tests on a mechanically braked cycle ergometer. Stage I (response protocol) consisted of a graded test with heart rate and perceived effort rating recorded in response to specified steady-state work outputs. Stage II (production protocol) examined subjects' ability to produce work outputs corresponding to levels 5, 7, and 9 of the CERT. This protocol was repeated on a further occasion (Stage III) to assess the reliability of the findings. Pearson correlations between ratings and heart rate (0.76) and ratings and work output (0.75) highlight the potential of the scale as a valid measure of exercise intensity. Also, the work rates produced by subjects in Stage II correlated 0.89 with those predicted from Stage I; however, analysis of variance showed that work output was significantly lower in Stage II than predicted. Finally, an intraclass correlation of 0.91 between Stages II and III suggests that the scale gave a reliable estimate of exercise intensity of children. The findings from this pilot study suggest that children's perceptions of effort might be used to guide intensity of exercise during structured activity classes.

Attitude↗
PubMed1994

CERT: a perceived exertion scale for young children.

This paper describes the rationale for the Children's Effort Rating Table (CERT) designed for assessing perceived exertion by children aged 6 to 9 years. This device is similar to Borg's Rating of Perceived Exertion (RPE) which is internationally recognized and currently used in conjunction with standard metabolic measures in a wide range of settings where exercise is prescribed and the intensity of various forms of physical activity is regulated by adults. We devised CERT for use in our research on the development of perception of effort by younger children. Some validation research on CERT has been completed.

Arousal↗
PubMed1993

Regulation of Dictyostelium morphogenesis by cAMP-dependent protein kinase.

During formation of the Dictyostelium slug extracellular cAMP signals direct the differentiation of prespore cells and DIF, a chlorinated hexaphenone, induces the differentiation of prestalk cells. At culmination the slug transforms into a fruiting body, composed of a stalk supporting a ball of spores. A dominant inhibitor of cAMP-dependent protein kinase (PKA) expressed under the control of a prestalk-specific promoter blocks the differentiation of prestalk cells into stalk cells. Analysis of a gene specifically expressed in stalk cells suggests that PKA acts to remove a repressor that prevents the premature induction of stalk cell differentiation by DIF during slug migration. PKA is also necessary for the morphogenetic movement of prestalk cells at culmination. Expression of the PKA inhibitor under control of a prespore-specific promoter blocks the accumulation of prespore mRNA sequences and prevents terminal spore cell differentiation. Thus PKA is essential for progression along both pathways of terminal differentiation but with different mechanisms of action. On the stalk cell pathway it acts to regulate the action of DIF while on the spore cell pathway PKA itself seems to act as the inducer of spore cell maturation. Ammonia, the extracellular signal which regulates the entry into culmination, acts by controlling the intracellular concentration of cAMP and thus exerts its effects via PKA. The fact that PKA is necessary for both prespore and spore gene expression leads us to postulate the existence of a signalling mechanism which converts the progressive rise in cAMP concentration during development into discrete, PKA-regulated gene activation events.

Animals↗
PubMed1993

Genetic mapping of mutations using phenotypic pools and mapped RAPD markers.

Genetic markers facilitate the study of inheritance and the cloning of genes by genetic approaches. Molecular markers detect differences in DNA sequence, and are thus less ambiguous than phenotypic markers, which require gene expression. We have demonstrated a molecular approach to the mapping of mutant genes using RAPD markers and pooling of individuals based on phenotype. To map genes by phenotypic pooling a strain carrying a mutation is crossed to a strain that is homozygous for the wild-type allele of the corresponding gene. A set of primers corresponding to mapped RAPDs distributed throughout the genome and in coupling phase with respect to the wild type parent is then used to amplify DNA from wild type and mutant pools of F2 individuals. Linkage between the mutant gene and the RAPD markers is visualized by the absence of the corresponding RAPD DNA bands in the mutant pool. We developed a mathematical model for calculating the probability of linkage between RAPDs and target genes and we successfully tested this approach with the model plant Arabidopsis thaliana.

Arabidopsis↗
PubMed1993

Activation of the prespore and spore cell pathway of Dictyostelium differentiation by cAMP-dependent protein kinase and evidence for its upstream regulation by ammonia.

Expression of a dominant inhibitor of the Dictyostelium cAMP-dependent protein kinase in prespore cells blocks their differentiation into spore cells. The resultant structures comprise a normal stalk supporting a bolus of cells that fail to express a sporulation-specific gene and that show greatly reduced levels of expression of several prespore-specific genes. The latter result suggests that in addition to activating spore formation, the cAMP-dependent protein kinase may play a role in initial prespore cell differentiation. Development of the strain expressing the dominant inhibitor is hypersensitive to the inhibitory effects of ammonia, the molecule that is believed to repress entry into culmination during normal development. This result supports a model whereby a decrease in ambient ammonia concentration at culmination acts to elevate intracellular cAMP and hence induce terminal differentiation.

Ammonia↗
PubMed1993

Interferon-gamma: a key immunoregulatory lymphokine.

Interferon-gamma is an important component of numerous host responses to inflammatory insults. Data from in vitro and animal studies suggest that this agent may have clinical uses in immunocompromised patients who are at increased risk for infectious complications. In addition to reviewing our current understanding of the in vitro and in vivo actions of interferon-gamma, this article cautions that the potential for adverse reactions exists when interferon-gamma is administered to an immunologically competent host.

Endothelium, Vascular↗