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Biomedical subjects

A M John

Publications and source records attributed to A M John.

15 recordsLinked to original sources
PubMed2003

A focus group investigation into young children's understanding of mental health and their views on appropriate services for their age group.

BACKGROUND: Children's views about mental health and concurrent service provision are under researched areas. Yet there is concern regarding appropriate service development to meet the increasing mental health needs of children and young people. Recent government policy underlines the need for collaborative work with consumers in service development. METHOD: This was a qualitative study designed to explore 10- and 11-year-old children's understanding of the concept of mental health and their opinions regarding an appropriate service for their age group. Two focus groups were conducted with 10- and 11-year-old children and the data was analysed using Interpretative Phenomenological Analysis. RESULTS: The participants showed a sophisticated understanding of mental health. The participants thought that school-based services would not be appropriate for their age group. CONCLUSION: The participants demonstrated that their level of understanding and interest qualifies them for a place in discussions about services for their age group. Collaborative work with children and young people in line with government policy in this area is necessary for appropriate service development.

Child↗
PubMed2000

A search for evidence of somatic mutations in the NF1 gene.

Neurofibromatosis type I (NF1) is an autosomal dominant disorder affecting 1 in 3000 people. The NF1 gene is located on chromosome 17q11.2, spans 350 kb of genomic DNA, and contains 60 exons. A major phenotypic feature of the disease is the widespread occurrence of benign dermal and plexiform neurofibromas. Genetic and biochemical data support the hypothesis that NF1 acts as a tumour suppressor gene. Molecular analysis of a number of NF1 specific tumours has shown the inactivation of both NF1 alleles during tumourigenesis, in accordance with Knudson's "two hit" hypothesis. We have studied 82 tumours from 45 NF1 patients. Two separate strategies were used in this study to search for the somatic changes involved in the formation of NF1 tumours. First, evidence of loss of heterozygosity (LOH) of the NF1 gene region was investigated, and, second, a screen for the presence of sequence alterations was conducted on a large panel of DNA derived from matched blood/tumour pairs. In this study, the largest of its kind to date, we found that 12% of the tumours (10/82) exhibited LOH; previous studies have detected LOH in 3-36% of the neurofibromas examined. In addition, an SSCP/HA mutation screen identified five novel NF1 germline and two somatic mutations. In a plexiform neurofibroma from an NF1 patient, mutations in both NF1 alleles have been characterised.

Chromosome Mapping↗
PubMed1991

A model of HIV-1 transmission for urban areas of Africa.

A model of the transmission dynamics of HIV-1, appropriate to urban areas of Africa, is presented and its behaviour explored through numerical studies. The model is a two-sex model with age-dependent demographic and behavioural parameters. Adults are classified by age, sex, risk group, and epidemiologic status. HIV-1 is transmitted to adults heterosexually, and to infants and children vertically and parenterally. Numerical studies show that, while AIDS will slow population growth, growth rates do not become negative for reasonable parameter values. The sex and age patterns of infection are explored, as is the potential economic impact of changes in the sex and age composition of the population.

Africa↗
PubMed1991

Disease in changing populations: growth and disequilibrium.

This paper examines simple age-structured models of childhood disease epidemiology, focusing on nonstationary populations which characterize LDCs. An age-structured model of childhood disease epidemiology for nonstationary populations is formulated which incorporates explicit scaling assumptions with respect both to time and to population density. The static equilibrium properties and the dynamic local stability of the model are analyzed, as are the effects of random variability due to fluctuations in demographic structure. We determine the consequences of population growth rate for: the critical level of immunization needed to eradicate an endemic disease, the transient epidemic period, the return time which measures the stability of departures from epidemiological equilibrium, and the power spectrum of epidemiological fluctuations and combined demographic-epidemiological fluctuations. Growing populations are found to be significantly different from stationary ones in each of these characteristics. The policy implications of these findings are discussed.

Age Factors↗
PubMed1991

The psychological effects of disaster work: implications for disaster planning.

The paper focuses on the psychological consequences of disaster work. The issue of identifying staff who may be more vulnerable to psychological distress is discussed as is the need for services to plan psychological screening and support for staff who will be exposed to the trauma of dealing with the aftermath of disasters. It is concluded that active steps need to be taken to incorporate psychological aspects into disaster planning. Specifically, attention should be paid to staff selection, training, use of resources, supervision, debriefing, counselling and feedback.

Counseling↗
PubMed1990

Endemic disease in host populations with fully specified demography.

This study explores the epidemiology of an aerogenically transmitted infectious disease following an S.I.R. pattern in a host population with completely specified age-specified maternity and mortality schedules. A fully age-structured demographic-epidemiologic model is developed, and its demographic and epidemiologic behaviour is explored in numerical studies. The impact of variations in host population demographic structure upon the effect of immunization programs is also studied.

Age Factors↗
PubMed1989

Incidence and duration of breast-feeding in Mexican-American infants, 1970-1982.

The Mexican-American component of the Hispanic Health and Nutrition Examination Survey (HHANES-MA) was used to examine the breast-feeding behavior of 2402 infants born between 1970 and 1982. The proportion of infants ever breast-fed increased substantially in recent years. Weighted proportions were 30.7% for 1970-1974, 38.1% for 1975-1978, and 47.6% for 1979-1982. By use of logistic regression models, children born into households with a college-educated head were shown to be more likely to be breast-fed than were other children; breast-feeding was also positively associated with birth weight. Infants in households for which the preferred interview language was Spanish were more likely to be breast-fed than were infants living in households for which the interview was conducted in English. Analysis of the factors influencing the distribution of weaning times among infants was less definitive because reported weaning times are heaped on multiples of 3 mo. The gathering of current-status, or status quo, information on infant feeding is urged for data collection in future studies.

Birth Weight↗
PubMed1985

Calculation of age-specific fertility schedules from tabulations of parity in two censuses.

The mathematics of stable populations recently has been generalized to cover populations with time-varying fertility and mortality by a modification incorporating the sum of age-varying growth rates in place of the fixed growth rate of a stable population. Equations that characterize nonstable populations apply to any cohort-like phenomenon with a measurable property that cumulates gains or losses through time. In particular, the equations fit the relation between a population's average parity at a given age and age-specific fertility rates previously experienced at lower ages. Techniques devised to derive an intercensal life table from single-year age distributions in two censuses are adapted to estimate accurate intercensal fertility schedules from distributions of parity by age of woman in two censuses. Birth-order specific fertility schedules are also estimated.

Adolescent↗
PubMed1981

Amino acid requirements of growing mice: arginine, lysine, tryptophan and phenylalanine.

Linear programmed diets designed to maximize the use of proteins and to minimize the use of free (1-) amino acids, and containing five dietary levels of each amino acid under test, were fed to weanling crossbred Carworth Farms No. 1 x Swiss mice in 14-day growth trials. Arginine dietary levels were 0.1, 0.2, 0.3, 0.4 and 0.7%; lysine: 0.2, 0.3, 0.4, 0.5 and 1.0%; tryptophan: 0.03, 0.07, 0.10, 0.13 and 0.17%; and phenylalanine: 0.10, 0.25, 0.40, 0.55 and 0.89%. Growth, feed consumption and regression-adjusted growth rates indicated the following minimum requirements: arginine less than 0.1% and probably zero, lysine 0.4%, tryptophan 0.1% and phenylalanine 0.4%. The AIN '76 reference diet was included in each amino acid test and resulted in superior growth and feed utilization. It was postulated that the greater content of free amino acids in our diets may have affected the efficiency of feed utilization adversely.

Amino Acids, Essential↗
PubMed1979

Protein nutrition of Tenebrio molitor L. XX. Growth response of larvae to graded levels of amino acids.

Larvae of Tenebrio molitor L;, Gembloux strain, race F, having an average initial weight of 10 mg were reared for 4 weeks at 27 +/- 0.25 degrees C and 65 +/- 5% relative humidity on diets containing an amino-acid mixture resembling the composition of larval tissues; Each of 14 amino acids was tested individually at levels of 0, 10, 20, 50, 100 and 200% of the amount found in larval tissues, while the concentration of other amino acids remained constant. Diets were maintained isonitrogenous at 1.6% nitrogen with supplementary glutamic acid, glycine, serine and tyrosine; Maximum fresh weight gains and dry weights were achieved by larvae fed reference levels of all essential amino acids except phenylalanine, threonine and tryptophan. Maximum growth was achieved by larvae fed 50% of the phenylalanine level found in larval tissues, Threonine and tryptophan were the limiting amino acids in this study and are probably required in the diet in excess of twice the concentration occuring in larval tissues, Probable ranges for quantitative amino-acid requirements of T. molitor were determined and suggestions were made for improving the nutritional adequacy of the amino-acid mixture.

Amino Acids↗
PubMed1976

Amino acid requirements of the growing mouse.

Using diets based on rat amino acid requirements, containing 2.0% nitrogen and 4.1 digestible kcal/g, the dietary levels of ten essential amino acids required for normal post-weaning growth of Swiss X Carworth Farms No. 1 crossbred mice were estimated. The response criteria used were growth rate, dry matter intake, energy and protein contents of body weight gain, protein efficiency ratio and apparent biological value. Maximum responses were obtained when the dietary dry matter contained less than or equal 0.3% arginine, 0.2% histidine, 0.4% isoleucine, 0.7% leucine, less than or equal 0.4% lysine, 0.5% methionine, less than or equal 0.4% phenylalanine, 0.4% threonine, less than or equal 0.1% tryptophan and 0.5% valine.

Amino Acids↗