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Biomedical subjects

J Stevenson

Publications and source records attributed to J Stevenson.

251 records · Page 14Linked to original sources
PubMed1967

The characterization and properties of castaprenol-11, -12 and -13 from the leaves of Aesculus hippocastanum (horse chestnut).

The isolation and purification of a mixture of cis-trans-polyprenols from the leaves of Aesculus hippocastanum (horse chestnut) are described. Results of studies involving mass spectrometry, nuclear magnetic resonance, infrared spectroscopy, micro-hydrogenation and ozonolytic degradation show the mixture to be made up of undecaprenol, dodecaprenol and tridecaprenol with dodecaprenol predominating. Each of the prenols contains three trans internal isoprene residues and a cis ;OH-terminal' isoprene residue. They differ from each other only in the number of cis internal isoprene residues. The trivial names castaprenol-11, castaprenol-12 and castaprenol-13 are proposed to describe these compounds. Gas-liquid-chromatographic and reversed-phase partition thin-layer chromatographic evidence suggest the presence in the mixture of small quantities of castaprenol-10 also.

Acetates↗
PubMed1966

The specific requirement for sodium chloride for the active uptake of L-glutamate by Halobacterium salinarium.

1. Uptake of l-glutamate by Halobacterium salinarium is dependent on high concentrations of sodium chloride in the environment. When the sodium chloride is replaced by isomolar concentrations of potassium chloride, sodium acetate or potassium acetate, only negligible uptake occurs. 2. Most of the glutamate taken up can be shown to be in the cells in the free state and at a concentration of at least 50 times that in the medium. Sodium chloride is therefore required for an active transport of the glutamate into the cells. 3. The question whether sodium chloride is essential for the actual migration of glutamate across the cell envelope or for the mechanism supplying energy for this migration is discussed on the basis of experiments on endogenous respiration and with inhibitors.

Acetates↗
PubMedDate not supplied

MP-RAGE subtraction venography: a new technique.

Preliminary evaluation of a new magnetic resonance (MR) venography technique was performed with data sets from five patients undergoing MR imaging of the brain before and after intravenous administration of gadopentetate dimeglumine. Before contrast agent injection, the patients were imaged with MP-RAGE (magnetization-prepared rapid gradient-echo) and axial turbo T2-weighted sequences. After contrast agent injection, the MP-RAGE sequence was repeated. Images were post-processed with an algorithm that calculates, on a pixel-by-pixel basis, the absolute value of signal intensity of each postcontrast MP-RAGE partition minus that of each precontrast MP-RAGE partition. These subtracted partitions were then subjected to a standard maximum-intensity-projection algorithm to obtain the venogram. In all cases, the new method afforded a high-resolution venogram with clear depiction of venous sinus anatomy. Cortical venous anatomy was also clearly depicted.

Cerebral Veins↗
PubMedDate not supplied

Cognitive sequelae of severe malaria with impaired consciousness.

Although cerebral malaria is the most common acute encephalopathy arising in children in Africa little is known of its effect upon the longer-term cognitive development of survivors. In Kenya, we compared the performance of 87 survivors of severe malaria with impaired consciousness to matched community controls on a wide range of tasks, not less than 42 months post illness episode. The presence of cognitive impairment was then related to both the pattern of symptoms at the time of the acute illness and the presence of gross neurological impairment on discharge. Significant group differences were found in areas of cognitive functioning suggestive of widespread impairment in the development of the ability to initiate, plan and carry out tasks (the executive functions). On tasks of more discrete cognitive skills (information processing) there were no significant group differences, although impaired performance was found more frequently in the severe malaria group. The odds ratio associated with the development of cognitive impairment following severe malaria with impaired consciousness was found to be 4.48 (95% CI 1.22, 16.47). A combination of 4 signs (coma, hypoglycaemia, seizures, and absence of hyperpyrexia) proved to have greater accuracy than the presence of gross neurological sequelae in predicting cognitive impairment (95% vs 93% specificity, 67% vs 58% sensitivity).

Child↗
PubMedDate not supplied

Drug-like index: a new approach to measure drug-like compounds and their diversity.

Combinatorial organic synthesis (combinatorial chemistry or CC) and ultrahigh-throughput screening (UHTS) are speeding up drug discovery by increasing capacity for making and screening large numbers of compounds. However, a key problem is to select the smaller set of "representative" compounds from a virtual library to make or screen. Our approach is to select drug-like as well as structurally diverse compounds. The compounds, which are not very drug-like, are less taken into account or excluded even if they contribute to the diversity of the collection. Hence, the first step in the compound selection is to rank compounds in drug-like "degree". To quantify the drug-like "degree", drug-like index (DLI) is introduced in this paper. A compound's DLI is calculated based upon the knowledge derived from known drugs selected from Comprehensive Medicinal Chemistry (CMC) database. The paper describes the way of this knowledge base is formed and the procedure for selecting drug-like compounds.

Algorithms↗
PubMedDate not supplied

Changes in fertility relative to starting, stopping, and spacing behaviors in a migrating Mennonite community, 1775-1889.

Fertility change over time in a migrating Mennonite church congregation is reconstructed through genealogies developed from church registries of vital events during 1725-1924. The congregation was located in Prussia from 1725-1821, in Russia from 1822-1874, and in Kansas, U.S.A., from 1875-1924. Age-specific marital fertility rates were relatively low and usually peaked for women aged 25-29. Total fertility rates ranged from 1.19 to 5.29. These relatively low figures for a natural fertility population may partly reflect underreporting of births and deaths of infants, but it also reflects the heterogeneity in fertility evident for this population. Some women had many children while others were having either few or none. This pattern changed twice. Fertility was lowest during residence late in Prussia and early in Russia, peaked during residence late in Russia, and has decreased slightly for women born in the United States.

Birth Intervals↗
PubMedDate not supplied

Sex differences in the etiology of aggressive and nonaggressive antisocial behavior: results from two twin studies.

Recent theory and results from twin and adoption studies of children and adolescents suggest greater genetic influence on aggressive as compared to nonaggressive antisocial behavior. In addition, quantitative or qualitative differences in the etiology of these behaviors in males and females have been indicated in the literature. The Child Behavior Checklist was completed by the parents of 1022 Swedish twin pairs aged 7-9 years and of 501 British twin pairs aged 8-16 years. Genetic factors influenced aggressive antisocial behavior to a far greater extent than nonaggressive antisocial behavior, which was also significantly influenced by the shared environment. There was a significant sex difference in the etiology of nonaggressive antisocial behavior. Bivariate analyses supported the conclusion that the etiologies of aggressive and nonaggressive antisocial behavior differ for males and females.

Adolescent↗
PubMedDate not supplied

Genetic and environmental covariation between verbal and nonverbal cognitive development in infancy.

Despite cognitive neuroscience's emphasis on the modularity of cognitive processes, multivariate genetic research indicates that the same genetic factors largely affect diverse cognitive abilities, at least from middle childhood onward. We explored this issue for verbal and nonverbal cognitive development in infancy in a study of 1,937 pairs of same-sex 2-year-old twins born in England and Wales in 1994. The twins were assessed by having their parents use a measure of productive vocabulary (the MacArthur Communicative Development Inventory) and a novel measure of nonverbal cognitive abilities (Parent Report of Children's Ability). Verbal and nonverbal development correlated .42. A multivariate genetic analysis indicated that genetic factors were responsible for less than half of this phenotypic correlation. Moreover, the genetic correlation between verbal and nonverbal abilities was only .30, which indicates that genetic effects on verbal and nonverbal abilities are largely independent in infancy. These multivariate genetic results suggest that genetic effects on cognitive abilities are modular early in development and then become increasingly molar. The implications of this result for theories of cognitive development are discussed.

Age Factors↗
PubMedDate not supplied

Which three-year-olds attend preschool facilities?

In an epidemiological survey of a total population of three-year-old children living in a London borough, information was obtained on the behaviour, development and social characteristics of 828 children. Details were extracted from the registers of 27 preschool facilities in the borough (a residential nursery, day nurseries, play groups and nursery schools and classes) on all children attending over an 18-month period. The patterns of attendance and factors influencing attendance of about 3000 children are discussed. The comparison of children attending facilities in the original sample of 828 with the total sample shows that those children most in need are not over-represented in these preschool groups.

Child Behavior Disorders↗
PubMedDate not supplied

Measuring the quality of service in the community.

This paper describes a joint project carried out by clinical psychologists and senior trusts managers to identify and measure consumer outcomes across a range of community services. The outcomes identified have been written into service contracts, and the outcome data are collected on a regular basis and used to inform management decisions.

Community Health Services↗
PubMedDate not supplied

Schedules for Clinical Assessment in Neuropsychiatry (SCAN): introduction to WV's mental health community.

The Schedules for Clinical Assessment in Neuropsychiatry (SCAN) is a semi-structured clinical interview used by trained clinicians to assess and diagnose psychiatric disorders among adults. The SCAN core is the Present State Examination (PSE) which has been developed and tested globally during the past four decades with good validity and reliability. The SCAN was developed within the framework of the World Health Organization (WHO) and the National Institute of Mental Health (NIMH) Joint Project on Diagnosis and Classification of Mental Disorders, Alcohol and Related Problems (1). The use of the SCAN gives the flexibility to diagnose mental disorders based on the current International Classification of Disease (ICD), Diagnostic and Statistical Manual (DSM) systems or other diagnostic systems that may develop in the future. A major purpose of the SCAN is to allow comparisons of psychiatric diagnoses to be made across the world.

Adult↗