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Biomedical subjects

S Alva

Publications and source records attributed to S Alva.

10 recordsLinked to original sources
PubMed2000

Familial moyamoya disease in Caucasians.

There are few reports of moyamoya disease (MMD) in the Caucasian population and even fewer descriptions of the natural history of the disease. The study reports a 12-year follow-up of two white male siblings with MMD. Although both brothers had a persistently abnormal electroencephalogram and a learning disorder, the siblings recovered on aspirin and antiepileptic therapy with minimal neurologic residua. The occurrence of MMD in these siblings contributes to the evidence that MMD has a hereditary basis in Caucasians, as well as the Japanese. Even with the use of conservative measures, children may still have persistent yet minor cerebrovascular insults. In addition to the two patients discussed, this study reviewed the literature on all cases of MMD reported within families. Future follow-up studies are required to determine the natural history and the appropriate medical and surgical management of MMD.

Child↗
PubMed1998

Maternal education and child health: is there a strong causal relationship?

Using data from the first round of Demographic and Health Surveys for 22 developing countries, we examine the effect of maternal education on three markers of child health: infant mortality, children's height-for-age, and immunization status. In contrast to other studies, we argue that although there is a strong correlation between maternal education and markers of child health, a causal relationship is far from established. Education acts as a proxy for the socioeconomic status of the family and geographic area of residence. Introducing controls for husband's education and access to piped water and toilet attenuate the impact of maternal education on infant mortality and children's height-for-age. This effect is further reduced by controlling for area of residence through the use of fixed-effects models. In the final model, maternal education has a statistically significant impact on infant mortality and height-for-age in only a handful of countries. In contrast, maternal education remains statistically significant for children's immunization status in about one-half of the countries even after individual-level and community-level controls are introduced.

Child Welfare↗
PubMed1995

Riboflavin: a potential material for molecular electronics applications.

Riboflavin (Rbf), the simplest manifestation of the isoalloxazine ring, undergoes redox reactions during biochemical processes. The redox reaction can be simulated under electrochemical conditions. The two oxidation states of the isoalloxazine molecule have different optical properties. Rbf embedded in a polyurethane matrix has been shown to undergo colour change on application of an external electric field. Rbf has been modified to form TARbf and TPRbf--the amphiphilic analogues for the convenience of forming ordered two-dimensional organization. The modification has been found to leave native characteristics of Rbf undisturbed. TPRbf forms monolayers at the air-water interface with a collapse pressure of 10 mNm-1.

Electrochemistry↗
PubMed1991

Glucose oxidase immobilized electrode for potentiometric estimation of glucose.

Glucose oxidase has been immobilized onto a thin platinum strip, by co-crosslinking with bovine serum albumin and glutaraldehyde. The retention of redox characteristics of glucose oxidase has been verified by cyclic voltammetry. The activity of the immobilized enzyme reduces to a quarter of its value when the enzyme is in solution but improves when coimmobilized with 1 M urea. The potentiometric response builds up and remains stable after 100 s. It is sensitive to the thickness of the immobilizing matrix. pH and temperature. An improvement in the performance of the electrode has been achieved by co-immobilizing 2 M urea and metal ions such as Mg2+ and Mn2+. The presence of Cu has been proved to be detrimental. The electrode has been calibrated in the 0.1-5.0 mM glucose concentration range. It gives a stable response for more than 50 independent assays and can be stored for 60 days without significant loss of function.

Biosensing Techniques↗
PubMed1979

Distribution of ATPase in isolated human spermatozoa nuclei: a high resolution cytochemical study.

The presence of ATPase activity was demonstrated in isolated nuclei of human spermatozoa by high resolution cytochemical methods. The Wachstein and Meisell technique as modified by Marchesi and Palade was used. ATPase activity was identified as dense and irregularly distributed granules confined to the exposed surface of spermatozoa nuclei. Within the nucleus the reaction product appeared as electron dense precipitates randomly distributed. Control experiments were negative. Deposits of lead phosphate specifically restricted to the exposed surface of nuclei were interpreted as an indication of a glucose-6-phosphatase and/or phosphohydrolase activity. Whether this activity is located in remnants of the inner leaflet of the nuclear envelope is not known. The presence of the enzyme activity within the nucleus is thought to be related to aerobic ATP synthesis previously suggested. If so, this function may be involved in establishing and/or maintaining the highly complex structural organization of spermatozoa nuclei.

Adenosine Triphosphatases↗
PubMedDate not supplied

Cytoplasmic estradiol binding sites in testis of fertile and infertile men.

Free cytoplasmic estradiol receptor was determined in testicular biopsies from six adults showing various primary testicular disorders, and in testicular tissue obtained at autopsy from 18 males of various ages. Estradiol receptors were found in all cases examined. Receptor concentration varied during testicular maturation and from one patient to another. The presence of the receptor at an early stage of development and the changes observed in its concentration during testicular maturation and dysfunction support the idea that estradiol may play, through its receptor interaction, an important role in the regulation of testicular steroidogenesis during postnatal human development.

Adult↗