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Biomedical subjects

S Williams

Publications and source records attributed to S Williams.

At least 811 records · Page 45Linked to original sources
PubMedDate not supplied

Time-resolved fluorescence resonance energy transfer studies of DNA bending in double-stranded oligonucleotides and in DNA-protein complexes.

Time-resolved Förster resonance energy transfer (trFRET) has been used to obtain interdye distance distributions. These distributions give the most probable distance as well as a parameter, sigma, that characterize the width of the distribution. This latter parameter contains information not only on the flexibility of the dyes tethered to macromolecules, but on the flexibility of the macromolecules. Both the most probable interdye distance as well as sigma provide insight into DNA static bending and DNA flexibility. Time-resolved fluorescence anisotropy and static anisotropy measurements can be combined to provide a measure of the cone angle within which the tethered dyes appear to wobble. When this motion is an order of magnitude faster than the average lifetime that characterizes transfer, an average value of the dipolar orientational parameter kappa2 can be calculated for various mutual dye orientations. The resulting kappa2 distribution is very much narrower than the limiting values of 0 and 4, allowing more precise distances and distance changes to be determined. Static and time-resolved fluorescence data can be combined to constrain the analyses of DNA-protein kinetics to provide thermodynamic parameters for binding and for conformational changes along a reaction coordinate. The parameter sigma can be used to model multiple DNA-protein complexes with varying DNA bend angles in a global fitting of trFRET data. Such a global fitting approach has shown how the range of bends in single base DNA variants, when bound by the TATA binding protein (TBP), can be understood in terms of two limiting forms. Time-resolved FRET, combined with steady-state FRET, can be used to show not only how osmolytes affect the binding of DNA to proteins, but also how DNA bending depends on osmolyte concentration in the DNA-protein complexes.

DNA↗
PubMedDate not supplied

Membrane phospholipids and adrenergic receptor function.

We have reviewed the effects on adrenergic receptors by membrane phospholipid alterations secondary to oxidative stress and phospholipases' activity. Experimental evidences indicate that the function of both alpha- and beta-adrenoceptors is regulated by their phospholipid microdomain; however, the underlying mechanism is still undefined. No information seems to be available on the influence of phospholipids on alpha 2-adrenoceptors and on all adrenoceptors' subtypes. Thus, further studies are necessary to clarify the role of membrane phospholipids in regulating the function of each member of the adrenergic receptor superfamily.

Animals↗
PubMedDate not supplied

Peripheral neuroepithelioma with ganglion cells: report of two cases and review of the literature.

Peripheral neuroepitheliomas, also known as peripheral primitive neuroectodermal tumors, are by definition primitive embryonal lesions generally composed of poorly differentiated neuroectodermal elements. We have examined two cases that paradoxically contain extensive foci of ganglionic differentiation similar to that of ganglioneuroblastoma, in addition to primitive elements. One tumor arose from the chest wall of an 8-year-old male and the other from the abdominal wall of a 15-year-old male. Differentiation into a mature ganglionic phenotype was confirmed by immunohistochemistry in one case. Rare peripheral neuroepitheliomas have a capacity for maturation that is not generally appreciated. These lesions should not be confused with ganglioneuroblastomas, which are genotypically unrelated neoplasms.

Adolescent↗
PubMedDate not supplied

In vivo and in vitro effects of insulin-like growth factor-I (IGF-I) on femoral mRNA expression in old rats.

The in vivo response of bone to IGF-I infusion in a marrow ablation model and the effect of IGF-I on bone marrow stromal cells in vitro was evaluated. IGF-I (25 ng/day), infused directly into femur, stimulated the expression of alkaline phosphatase, procollagen alpha 1 (I) and osteopontin mRNA, while osteocalcin mRNA was not affected. The dose dependency to IGF-I was bi-phasic, with stimulation at 25 and 50 ng but not at 150 ng/day. The effect of IGF-I was observed in the aged but not in the adult rat femur. However, the elevated mRNA levels in old bones with IGF-I treatment were still below those observed in adult bones. The effect of IGF-I was also examined in cultured stromal cells. IGF-I (50 ng/ml) stimulates the expression of alkaline phosphatase, procollagen alpha 1 (I), osteopontin and osteocalcin mRNA in stromal cells from both adult and old rats. These results suggest that the lack of response of adult bone to IGF-I in vivo was not due to the impaired response of the stromal cells to IGF-I. Differences in the responses of stromal cells from adult and old animals were noted. In the presence of serum (10%), stromal cells from adult rats were stimulated to synthesize DNA at lower levels of IGF-I than stromal cells from old animals. Our results show that IGF-I can stimulate mRNA expression of osteoblast markers in vivo in aged rats in a marrow ablation model and enhance DNA synthesis and gene expression in cultured marrow stromal cells from old rats. Thus, it is possible that exogenous IGF-I could be beneficial in treating age-associated osteopenia.

Aging↗
PubMedDate not supplied

[Arm motion analysis: a new method and its clinical application].

AIM: An investigation into the objective criteria of shoulder mobility possesses special meaning for diagnostic documentation, the evaluation of therapy and the effects of rehabilitation in the treatment of diseases of the shoulder. In order to ascertain the criteria which characterise shoulder mobility, it is necessary to have a tool available that is objective, comparable and allows the complexity, variability and range of motion to be recorded. Motion analysis represents one such standard procedure used to measure joint movement. METHOD: Accordingly, a marker- based motion analysis of the wrist and elbow, a marker-based three-dimensional motion analysis system for the upper extremities was developed. We evaluated 10 healthy subjects without shoulder conditions and 8 patients with impingement syndrome (7 operative, 1 conservative therapy). RESULTS: The healthy subjects revealed a reproducible motion curve for the specific motion tested. The curves were defined as the normal standard and we used them for comparative purposes. In the treatment group, an improvement of the 3D range of motion could be documented for the affected shoulder following rehabilitation. CONCLUSION: It can be stated that this newly developed marker-based procedure for the three-dimensional motion analysis is suitable for recording complex unconstrained movements. This was found to be more relevant for the assessment of the ability of patients to manage the physical demands of daily living than traditional clinical tests. Furthermore, the information gained from motion analysis of the upper extremities will play a valuable role in the future for quality control during diagnosis and treatment, as well as for the design of shoulder rehabilitation programs.

Adult↗
PubMedDate not supplied

Early influences on the secular change in adult height between the parents and children of the 1958 birth cohort.

The present account is of data available from the 1958 British national birth cohort and its follow-up to the age of 23 years. It shows an increase in adult height between the cohort members and their parents, amounting to an average 1.2 +/- 0.11 (SEM) cm between the daughters and their mothers and 3.0 +/- 0.12 cm between the sons and their fathers. Factors in early life which contributed jointly to a significant increase in adult height included, as well as sex and parental height, birthweight and maternal pre-pregnant weight, while increasing gestational age had a negative effect. Overall these factors accounted for 71% of the variance of the cohort members' height. Measuring the intergenerational difference between individual pairs of sons and father and daughters and mothers allows to some extent for social and genetic influences. This showed that the size of the difference was increased by increasing intrauterine growth rate, and falling paternal social class. These findings demonstrate again the lifelong influence on offspring of circumstances pertaining at their birth and explain why it may take more than one generation to overcome the effects of childhood disadvantage.

Adolescent↗
PubMedDate not supplied

Anthropometry in adolescent girls in Kingston, Jamaica.

There is little information on the nutritional status of adolescents in developing countries. In particular there is a lack of data concerning black adolescents. We measured height, weight, and triceps and subscapular skinfolds in 452 13-14-year-old girls, randomly selected from those attending nine schools in Kingston, Jamaica. The girls' heights and body mass indices were appropriate for their age. This suggests that undernutrition was not a significant problem in this population. However, the girls' skinfolds were smaller than the US references, both those for the total population and those for blacks only. The fat pattern (triceps/subscapular ratio) was similar to that reported for adult black women in the United States. It is possible that the levels of fat in the references are not appropriate for this population. Data from other black populations are needed for comparison.

Adolescent↗
PubMedDate not supplied

Risk of germ cell malignancy in children with XY intersex versus isolated cryptorchidism by immunohistochemistry.

The risk of subsequent development of testicular germ cell neoplasia is related to presence of underlying developmental defects such as cryptorchidism, in which the risk is around 0.5%, and XY intersex with abdominal testes, in which the risk may be as high as 20-25%. We examined the hypothesis that the increased risk of germ cell malignancy in intersex testes with Y chromosome was a direct consequence of an abnormal increase in number of PLAP/CD117+ immature germ cells into postnatal life. Archival cases of uncomplicated cryptorchidism (CO) and XY intersex (INT) were identified and anonymized, and a subgroup of aged-matched cases had sections immunostained with placental alkaline phosphatase (PLAP) and CD117. From a total of 89 intersex and 105 cryptorchid cases identified, a power calculation to detect a 20% difference in expression between groups (alpha = 0.05, power = 80%) determined that 18 intersex and 36 cryptorchid cases were required. Thus, 58 cases were examined, median age 3 (range birth-11) years, including 39 CO and 19 INT. The prevalence of any PLAP+ germ cells was 2/39 (5.1%) versus 3/19 (15.7%), respectively. (Z = 1.4, p = 0.17). In contrast, 94% of cases showed presence of any CD117+ germ cells, but the frequency of CD117+ cells was not significantly different between groups (t = 0.56, p = 0.58). CD117 and PLAP identify different populations of germ cells in pediatric testes. The extent of increased risk of malignancy in XY INT is not simply related to increased numbers of immature PLAP+/CD117+ germ cells present; additional factors play a pathogenic role.

Adolescent↗
PubMedDate not supplied

Imaging characteristics of a small germanium camera.

A high purity germanium gamma-camera has been developed and is currently being evaluated. This camera incorporates unique performance parameters such as a 2 mm full-width spatial response function with rejection of multiple-scatter in the detector, a 2.2% FWHM energy resolution for 99 mTc, a 180 nsec paralyzable dead-time, and a 2 mu sec non-paralyzable dead-time. Imaging studies demonstrate the superior capabilities of this instrument.

Animals↗
PubMedDate not supplied

Indications for aortography. Radiography after blunt chest trauma: a reassessment of the radiographic findings associated with traumatic rupture of the aorta.

Indications for aortography in truncal trauma patients have expanded as reports of radiographic findings associated with traumatic rupture of the aorta (TRA) have proliferated. By studying to what extent these findings also occurred in trauma patients without TRA, we determined the utility of these findings in selecting patients for aortography. The detection of nine radiographic findings associated with TRA was tabulated in 173 patients undergoing arch aortography to rule out TRA from 1975 to 1980. Twenty-five of these had TRA. All patients with TRA under age 65 had a widened mediastinum (WM); this was the only finding that taken alone correlated significantly with TRA (P = 0.001). Only two of six patients with TRA over 65 had a WM. Other findings such as hemothorax, fracture of ribs 1 or 2, pulmonary contusion, or multiple rib fracture were more likely to be found in patients without TRA. Formal radiographic interpretation by staff radiologists detected more radiographic abnormalities than physicians caring for the patient emergencly, who had access to a junior radiology resident. However, these physicians were as successful as staff radiologists in detecting WM when it was associated with TRA. A widened mediastinum is the best single criterion for aortography in young trauma patients; all elderly persons with severe truncal trauma should probably have aortography even in the absence of mediastinal widening. Radiologic consultation is important for complete detection of thoracic pathology in trauma patients, but in this study late interpretation of more subtle findings did not detect additional patients with TRA.

Adolescent↗