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Biomedical subjects

F Davidson

Publications and source records attributed to F Davidson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Production of fruits and vegetables at the homestead is an important source of vitamin A among women in rural Bangladesh.

BACKGROUND: Vitamin A deficiency is considered to be an important public health problem in Bangladesh. A universal biannual distribution of high-dose vitamin A capsules has been in place for over the past two decades. This supplementation has been beneficial for preschool children. Bangladesh has been exploring more sustainable approaches for all segments of the population. To support this initiative, Helen Keller International has implemented a homegardening promotion project since 1993. This project is executed on a large scale and currently reaches an estimated 244,000 families. METHODS: This paper presents data from 7341 women of reproductive age which were collected as part of the baseline census of a community monitoring system whose objective is to track progress and measure the impact of home-gardening activities. RESULTS: Vitamin A intake in this population derived almost entirely from the consumption of fruits and vegetables. Logistic regression analyses showed that maternal vitamin A intake was determined by qualitative indicators of homestead gardens (type of home garden, the total quantity of provitamin A-rich food produced and the number of fruits and vegetables varieties grown in the garden) after adjusting for socio-economic status. CONCLUSIONS: These results indicate that traditional production of provitamin A-rich fruits and vegetables in the homestead may provide a valuable contribution to vitamin A intake in communities where alternative dietary sources of vitamin A are scarce.

Agriculture↗
PubMed1995

Molecular epidemiology of an outbreak of infection with hepatitis C virus in recipients of anti-D immunoglobulin.

In a retrospective investigation of possible transmission of hepatitis C virus (HCV) by anti-rhesus D immunoglobulin (anti-D) in 1977, we compared variants infecting anti-D recipients in Ireland of one of the implicated batches with those of epidemiologically unrelated HCV-infected individuals. All 100 of the recipients of the batch investigated to date were infected with a single genotype (type 1), consistent with a single-source outbreak, whereas a wider range of genotypes (1, 2, and 3) were found in anti-HCV positive individuals from Ireland infected by different routes. Nucleotide sequences from a 222 base fragment from the NS-5 region of the genome amplified from stored aliquots of the implicated batch closely matched those detected in anti-D recipients 17 years after the transmission event. This study shows the value of molecular epidemiological techniques for identifying distant sources of infection, and for the epidemiological investigation of the current distribution and transmission of HCV in different populations.

Antibodies, Anti-Idiotypic↗
PubMed1995

Survey of major genotypes and subtypes of hepatitis C virus using RFLP of sequences amplified from the 5' non-coding region.

A method is described for identifying different genotypes of hepatitis C virus (HCV) by restriction endonuclease cleavage of sequences amplified by PCR from the 5' non-coding region. Using the enzymes HaeIII-RsaI and HinfI-MvaI, followed by cleavage with BstU1 or ScrFI, it was possible to identify and distinguish HCV genotypes 1a, 1b, 2a, 2b, 3a, 3b, 4, 5 and 6. The method was used to investigate the prevalence of these genotypes in 723 blood donors in 15 countries, the largest survey to date, and one which covered a wide range of geographical regions (Europe, America, Africa and Asia). These results, combined with a review of the existing literature, indicate the existence of several distinct regional patterns of HCV genotype distribution, and provide the framework for future detailed epidemiological investigations of HCV transmission.

Blood Donors↗
PubMed1995

Variation of the hepatitis C virus 5' non-coding region: implications for secondary structure, virus detection and typing. The International HCV Collaborative Study Group.

Variation in the 5' non-coding region (5'NCR) of hepatitis C virus (HCV) was investigated in detail by comparing 314 5'NCR sequences of viruses of genotypes 1 to 6. Evidence was obtained for the existence of associations between particular 5'NCR sequence motifs and virus types and subtypes. No recombination was observed between the 5'NCR and coding regions of different genotypes, implying that the sequence of subgenomic regions such as the 5'NCR can be used to deduce virus genotype. The distribution of polymorphic sites within the 5'NCR is used to propose improved oligonucleotide primers for virus detection and quantification that would be equally efficient in detecting RNA of different virus genotypes. The accuracy of two different genotyping methods (RFLP and the line probe assay) based on analysis of sequence polymorphisms in the 5'NCR is predicted from the sequences surveyed to be 97% and 83% respectively for types 1 to 6, with higher accuracies for distinguishing between subtypes 1a/1b, 2a/2b or 3a/3b. Several sites of genotype-specific polymorphism were covariant and maintained the base pairings required for a secondary structure model of the 5'NCR. Other sites of variation suggest minor modifications to this model and have implications for the probable functions of the 5'NCR.

Base Composition↗
PubMed1995

The distribution of hepatitis C virus genotypes in Turkish patients.

The distribution of hepatitis C virus (HCV) genotypes was investigated in 89 HCV-infected Turkish patients. Blood samples were collected from haemodialysis patients (n = 45), chronic liver disease (CLD) patients (n = 38), acute non-A, non-B (NANB) hepatitis patients (n = 2) and blood donors (n = 4). HCV RNA sequences were amplified in the 5' non-coding region and were typed by restriction fragment length polymorphism analysis. The predominant genotype was 1b (75.3%), followed by 1a (19.1%), 2 (3.4%) and 4 (2.2%). While there was no significant difference in the distribution of HCV genotypes with respect to age, sex, transfusion history, alanine aminotransferase levels or liver histology (in the CLD group), type 1a-infected patients were younger than type 1b-infected patients (P < 0.05) in the haemodialysis group. Serological reactivity to recombinant HCV proteins was assessed in 58 samples using the Chiron RIBA-2 assay. The reactivity of samples from patients infected with type 1b with 5-1-1 and c100 antigens was significantly lower (P < 0.05) than the reactivity of samples from those infected with type 1a. These results, together with the results of two previous studies, indicate that HCV genotypes 1, 2, 3 and 4 are prevalent in different frequencies in the Turkish population. Determination of the genotype distribution of HCV in a geographical area may provide important clues for studying the epidemiology, transmission and pathogenesis of HCV-related diseases and may also aid in improving serological assays to detect HCV infection.

Adult↗
PubMed1995

Hepatitis C virus variants and the role of genotyping.

Hepatitis C virus demonstrates considerable divergence in nucleotide sequence. This variation may affect virus detection, disease outcome, and the effectiveness of interferon treatment. For example, infection with genotype 1 is associated with a lower response rate to interferon treatment. Hepatitis C virus can be classified into six distinct types, comprising at least 74 different subtypes. Both types and subtypes are subject to geographical differences in distribution, presumably reflecting the epidemiological history of the virus. However, because this history may be blurred by migration and by commerce in blood products between regions, screening and typing assays must recognize both the major indigenous and more exotic virus genotypes. Little information exists about the role of virus sequence variation in screening for hepatitis C virus antibodies, but there is some evidence that the reactivity of current serological screening assays for hepatitis C virus is genotype dependent. In the future, screening assays may need to include antigens specific for different virus types or may need to be designed with regard to the particular types found in a certain area. Antigenic variation may also mean that an effective vaccine needs to be multivalent to protect against all genotypes present in a given region. There are several polymerase chain reaction-based methods of distinguishing between hepatitis C virus variants. These methods must be continually updated, however, as new sequence variants are discovered. Alternative genotyping assays are based on the host's serological response to virus infection, but these cannot distinguish between virus subtypes and are unsuitable for immunocompromised patients. As more countries are sampled, it is likely that more genotypes will be identified and this may help elucidate the origins of hepatitis C virus. Detailed epidemiological studies may delineate past and current routes of transmission.

Enzyme-Linked Immunosorbent Assay↗
PubMed1994

A portable dual energy x-ray absorptiometry technique for the measurement of bone mineral in preterm infants.

A dual energy x-ray absorptiometry technique has been developed for the measurement of bone mineral in preterm infants. Two films are taken of the infant's forearm using a standard mobile x-ray set on the ward at two x-ray energies. Included in the field of view is a double step wedge made of aluminum and Perspex. The images are digitized by viewing them on a light box with a TV camera. The bone mineral content in the forearm can then be mapped by the measurement of light intensity in matching pixels of the two films and comparison with the intensities in the step wedge. The bone mineral concentration in the radius, expressed as bone mineral per unit length (mg/mm), is calculated. The technique has been tested using phantoms of calcium hydroxylapatite set in a tissue equivalent material and in Perspex. It has been shown that the reproducibility of the technique is approximately 7% and that there is a systematic underestimate of bone mineral of about 17%. The technique has been shown to be linear up to a bone mineral concentration of 8 mg.mm-1. Longitudinal studies for 14 infants that show an initial 6-wk period of demineralization after birth with a subsequent mineralization phase are reported.

Absorptiometry, Photon↗
PubMed1993

Ifs and butts.

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Attitude to Health↗
PubMed1989

Validation of an automatic crackle (rale) counter.

Crackles are commonly used in clinical decision-making, and in certain diseases the number of crackles reflects the severity of the illness. Auditory crackle estimations are subjective; crackle counting from time amplitude plots of sound (called time-expanded waveforms) is more objective but is cumbersome. We devised a computer-based system to count crackles automatically. One hundred samples of lung sounds from 41 subjects were recorded using an electret microphone air-coupled to the chest wall. Interobserver agreement in estimating the number of crackles per breath was high (r = 0.88, p less than 0.001), and these counts were significantly correlated with counts made of spikelike deflections seen on time-expanded waveform analysis (r = 0.78, p less than 0.001). The automatic crackle counting correlated with the physician counts (r = 0.74, p less than 0.001). The average number of crackles counted per breath was greater by visual inspiration (8.8) and by automatic analysis (7.8) than it was by the physician observers (5.8). Reasons for the discrepancies include the fact that there are no absolute criteria for crackles and that rapidly occurring crackles are difficult to count by ear. Counting crackles by computer-based methods is feasible and can improve noninvasive cardiopulmonary diagnosis.

Asbestosis↗
PubMed1985

The pill does not cause 'thrush'.

Contraceptive method, presence or absence of genital candidosis and other genital infections or conditions were recorded in 1363 new patients attending three different genitourinary medical clinics. Genital candidosis was present in 28% but was not associated with oral contraceptive usage; it seemed more likely to be associated with other genital disorders, especially non-specific infection and viral infections.

Candidiasis, Vulvovaginal↗
PubMed1984

Structure of murine complement component C3. II. Nucleotide sequence of cloned complementary DNA coding for the alpha chain.

From the inserts of two recombinant plasmids isolated from a murine liver cDNA library, the nucleotide sequence coding for the C3 alpha chain was obtained and the corresponding amino acid sequence was derived. The alpha chain portion of the mRNA is 2979 nucleotides long, specifying a polypeptide of 993 amino acids. The molecular weight of the alpha chain, in the absence of carbohydrate, was calculated from the sequence data to be 112,933. Two possible carbohydrate attachment sites were predicted at residues 269 (Asn) and 947 (Asn). In addition, the positions for two putative factor I cleavage sites were predicted from a comparison with the cleavage sites in the human C3 alpha chain. The C3 alpha chain contains 24 cysteine residues, 10 of these clustered in the C-terminal 175 amino acids of the alpha chain. Together with the accompanying report (Lundwall, A, Wetsel, R.A., Domdey, H., Tack, B.F., and Fey, G.H. (1984) J. Biol. Chem. 259, 13851-13856), this study completes the nucleotide and amino acid structure of the murine precursor prepro-C3 molecule.

Amino Acid Sequence↗
PubMed1984

[Study of the process of alcoholism in young persons using cluster analysis].

An epidemiological survey was carried out among high school students of 3 French regions. Their use of drugs (alcohol, tobacco, psychotropic drugs, illicit drugs) was studied, as well as their self-perception of personality, relations inside and outside the family, school performance, and lifestyle. Different aspects of drinking were considered: regularity of intake, quantity absorbed, inebriation. The use of alcoholic drinks together with psychotropic substances was studied. A cluster analysis applied to adolescent personality self-perception revealed 10 different personality types (5 for the boys; 5 for the girls). The social, family, and relational characteristics of each personality type are described. The correlations between personality self-perception and liquor use allow us to define 3 profiles of heavy drinkers.

Achievement↗