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Biomedical subjects

S West

Publications and source records attributed to S West.

At least 19 recordsLinked to original sources
PubMed1992

Multiple nucleic acid labeling and rainbow detection.

A method which allows discrete nucleic acid sequences to be detected with differently colored hybridization signals on the same blot involving only a single hybridization step is described. Nucleic acid probes labeled with digoxigenin, fluorescein, or biotin are hybridized simultaneously to immobilized target nucleic acids. Differential colorimetric detection is carried out in consecutive alkaline phosphatase-based immunoassays with one of three 3-hydroxy-2-naphthoic acid anilide phosphate/diazonium salt combinations as substrate. Each label is visualized by a different color precipitate (green, red, and blue) directly on the membrane. We demonstrate the use of this method in multicolor plasmid mapping, detection of different genomic sequences on a single Southern blot, discrimination of transcription levels in a Northern blot, and colony screening. Advantages and limitations of the method, as well as further applications, are discussed.

Alkaline Phosphatase↗
PubMed1992

Low-level visual processing of biological motion.

Biological motion displays depict a moving human figure by means of just a few isolated points of light attached to the major joints of the body. Naive observers readily interpret the moving pattern of dots as representing a human figure, despite the complete absence of form cues. This paper reports a series of experiments which investigated the visual processes underlying the phenomenon. Results suggest that (i) the effect relies upon responses in low-level motion-detecting processes, which operate over short temporal and spatial intervals and respond to local modulations in image intensity; and (ii) the effect does not involve hierarchical visual analysis of motion components, nor does it require the presence of dots which move in rigid relation to each other. Instead, movements of the extremities are crucial. Data are inconsistent with current theoretical treatments.

Humans↗
PubMed1992

Herbal medicine use, Epstein-Barr virus, and risk of nasopharyngeal carcinoma.

Herbal medicine use is thought to be linked to nasopharyngeal carcinoma (NPC) either through its ability to reactivate the Epstein-Barr virus (EBV) or through a direct promoting effect on EBV-transformed cells. To investigate this, 104 histologically confirmed NPC cases and 205 matched controls were studied in The Philippines. Blood was collected to assess antibody titers against EBV, and an interview was administered which elicited information concerning herbal medicine use and other risk factors for NPC. Subjects strongly positive for anti-EBV antibodies (Epstein-Barr nuclear antigen [EBNA]) (titers greater than or equal to 1:80) were at a 21-fold excess risk of disease (95% confidence interval, 8.4, 51.8). Herbal medicine use was also associated with NPC (relative risk, 2.5; 95% confidence interval, 1.4, 4.5). Associations persisted after adjustment for education, smoking, Chinese ancestry, and consumption of salted fish. Exposure to herbal medicines among subjects testing negative/weakly positive for anti-EBNA antibodies was not associated with an elevation in risk (relative risk, 0.6), strong positivity to anti-EBNA antibodies in the absence of herbal medicine use was associated with a significant 16-fold excess risk of disease, and exposure to herbal medicines among subjects testing strongly positive for anti-EBNA antibodies was associated with a significant 49-fold excess risk of NPC when cases were compared to controls. Similar results were obtained when other serological measures of EBV exposure were used. Anti-EBV antibody titers were elevated in herbal medicine users compared to nonusers among cases but not among control subjects. This suggests that, if herbal medicines interact with EBV in the development of NPC, they do not do so by reactivating EBV infection but rather through a direct proliferative effect on EBV-transformed cells. Although the interaction between EBV and herbal medicines is biologically plausible, larger, more detailed studies need to be conducted to validate this preliminary finding.

Antibodies, Viral↗
PubMed1992

The long-term effects of visible light on the eye.

The relationship between exposure to sunlight and senile cataract, age-related macular degeneration, pterygium, and climatic droplet keratopathy was examined in 838 watermen who work on the Chesapeake Bay. The presence and severity of lenticular, corneal, and macular changes were assessed by either clinical examination or from stereo macular photographs. From detailed exposure histories, ocular exposure was estimated for three bands of visible radiation-violet (400 to 450 nm), blue (400 to 500 nm), or all visible (400 to 700 nm)-as well as for UV-A (320 to 340 nm) and UV-B (290 to 320 nm). The results with each band of visible radiation were similar. Neither cortical nor nuclear cataract was associated with ocular exposure to blue or all visible radiation, but pterygium and climatic droplet keratopathy were more common with higher exposures. Compared with age-matched controls, patients with advanced age-related macular degeneration (geographic atrophy or disciform scarring) had significantly higher exposure to blue or visible light over the preceding 20 years (odds ratio, 1.36 [1.00 to 1.85]) but were not different in respect to exposure to UV-A or UV-B. These data suggest that high levels of exposure to blue or visible light may cause ocular damage, especially later in life, and may be related to the development of age-related macular degeneration.

Adult↗
PubMed1992

Trachoma and flies. Individual vs environmental risk factors.

The risk of active trachoma in children appears to be higher in association with flies in the environment. However, a measure of fly density that could consistently be related to an increased risk of trachoma is unknown. In a survey of six villages in a hyperendemic area of Tanzania, a comparison was made between the number of flies on the faces (face-fly scores) of children and the number of household flies around the main doorways (household-fly scores). The risk of trachoma associated with each measure was evaluated after adjusting for the age and sex of the child. A multiple logistic regression model demonstrated that the presence of flies on the face was consistently associated with increased risk of trachoma, and that number of flies on the face is a superior predictor in terms of ease of measurement and strength of association than is number of household flies.

Age Factors↗
PubMed1992

Household decisions among the Gogo people of Tanzania: determining the roles of men, women and the community in implementing a trachoma prevention program.

An epidemiological survey in rural Tanzania indicated that the rate of trachoma was elevated in children whose faces were unclean. To aid in designing a health education program to increase face washing, a descriptive village study was done to determine water use patterns, attitudes towards face washing, responsibility for child hygiene, and decision making processes in the household and community. The study found that mothers were responsible for both water use and the health and cleanliness of the children. However, health education could not be directed at the women alone because the decision to change behavior had to be sanctioned by the husband in the household, and the community as a whole. The final health campaign was designed to be compatible with the accepted patterns of decision making. This case study, as well as others which focus on women's groups as change agents, suggests several factors such as male migration and local authority structures which health planners may need to assess when designing health programs.

Attitude to Health↗
PubMed1992

Epidemiology of trachoma in Bebedouro State of São Paulo, Brazil: prevalence and risk factors.

Trachoma was considered to have been 'eradicated' from the state of São Paulo, Brazil, until 1982 when a number of new cases of trachoma were reported in preschool children in Bebedouro, a small town in northwestern São Paulo. A household survey was undertaken to assess the prevalence and epidemiological characteristics of trachoma. A total of 2939 people of all ages was examined having been selected from a two-stage probalilistic household sampling frame based on census data. Overall, 7.2% of the population had evidence of one or more signs of trachoma and 2.1% had inflammatory trachoma. Inflammatory trachoma was more common in children aged one to ten years, especially in the peripheral urban and rural areas, and was more common in boys. The presence of chlamydia was confirmed by direct fluorescent antibody cytology. No cases of blindness due to trachoma were seen. A number of socioeconomic and hygiene variables were studied in order to determine the independent risk factors for trachoma in a household. Variables significantly associated with the occurrence of trachoma in the household were the number of children in the house aged one to ten years, the 'per capita' water consumption, the frequency of garbage collections, source of water, and the educational level of the head of household. Clustering of trachoma in different parts of this community was entirely explained by the concentration of households with these characteristics.

Adolescent↗
PubMed1992

An abbreviated assessment of ocular exposure to ultraviolet radiation.

Individual behaviour has a very large effect on determining the exposure of the eye to solar radiation. To be able to examine the relationship between ocular exposure to ambient ultraviolet radiation and ocular disease, a model was developed previously that assessed cumulative ocular exposure from individual information on work and leisure activities. In this paper, we present a simplified version of the model that uses data on exposure during the middle of the day (9 a.m. to 3 p.m. solar time) during the northern 'summer' months (April to September). The ocular exposure determined by the simplified model is highly correlated with the full model (r = 0.98) and the simplified model predicts 62% of the total ocular exposure. This model should be useful for future epidemiologic studies of sun exposure and eye disease.

Adolescent↗
PubMed1992

The natural history of endemic trachoma: a longitudinal study.

A longitudinal study of trachoma was conducted among 100 members of nine families living in a hyperendemic area of Tanzania. Family members were examined for trachoma every three months for one year and conjunctival specimens were collected for antigen detection, which was performed either by direct fluorescent antibody cytologic analysis or enzyme immunoassay. The serovar specificity of tear antibodies was determined. Overall, young children tended to form a core of those with persistent, often severe, disease who consistently shed Chlamydia. These children are a potential source of infection in their family. Chlamydia could be identified early in the course of presumed recently acquired infections, but not later in resolving infections. This temporal change may account for the discrepancies between demonstrable organisms and clinical disease seen in cross-sectional studies. Several children were identified who did not develop trachoma despite having Chlamydia identified in conjunctival scrapings. Their ability to resist infection may offer clues for vaccine development. The study of serovar specificity is consistent with the intrafamily transmission of trachoma, but was confounded by the large family size and the potential for separate transmission units to occur within large extended families. These observations give further understanding of the natural history and kinetics of the transmission of trachoma that should be of use in developing and evaluating intervention studies.

Adolescent↗
PubMed1991

Diagnosis of Chlamydia trachomatis eye infection in Tanzania by polymerase chain reaction/enzyme immunoassay.

Detection of Chlamydia trachomatis eye infection is largely unsatisfactory by standard laboratory methods. A polymerase chain reaction/enzyme immunoassay (PCR-EIA) that had previously been successful for diagnosis of genital C trachomatis infection was compared with direct antibody immunofluorescence (DFA) for detection of the organism in conjunctival scrapes. 234 Tanzanian children aged 1-7 years living in a village that had had no previous trachoma control programme were classified clinically as having no sign of trachoma (0) n = 97, follicular trachoma (TF) n = 100, or intense inflammatory trachoma with or without TF (TI +/- TF) n = 37. PCR-EIA detected C trachomatis in 24%, 54%, and 95% of subjects, respectively, compared with elementary body (EB) detection by DFA of 1%, 28%, and 60%, respectively. Overall prevalence of chlamydial eye infection was 22% by DFA compared with 48% by PCR-EIA. Of subjects with chlamydial DNA at pretreatment, 103 (92%) had no detectable chlamydial DNA at the end of 4 weeks of ocular tetracycline. The findings show that PCR-EIA is likely to affect trachoma diagnosis and epidemiology because of the increased sensitivity for detection of C trachomatis in all clinical groups; the less stringent requirements for specimen collection and transport make this method suitable for field use. Moreover, the semi-quantitative aspect of PCR-EIA may be useful for monitoring a decrease in chlamydial DNA after treatment.

Administration, Topical↗
PubMed1991

Central and peripheral nervous system demyelination after infection with Mycoplasma pneumonia: evidence of an autoimmune process.

We have reported a unique case of multiple central and peripheral nervous system abnormalities after a serologically documented infection due to Mycoplasma pneumoniae. The evidence suggests that this organism is capable of causing demyelination, probably through an autoimmune process. This case may help to provide further insight into the pathogenetic mechanisms involved in other demyelinating diseases in which the triggering exogenous agent is unknown. Certainly this case demonstrated that both central and peripheral nervous system demyelination can occur and that patients with M pneumoniae infections should be observed closely for possible development of neurologic symptoms.

Adult↗
PubMed1991

Longitudinal study of the microbiology of endemic trachoma.

A longitudinal study of trachoma in 100 members of nine Tanzanian families was conducted to assess the sources of variation in the laboratory identification of trachoma and the changes that might occur over time. Multiple conjunctival swabs were collected every 3 months for 1 year and examined by direct fluorescent-antibody cytology (DFA), enzyme immunoassay, or microimmunofluorescence serology for tear antichlamydial antibodies. DFA specimens collected 5 min apart had a discordance rate of 10% and this is attributable to sampling variation. DFA specimens collected 2 days or more apart show a 25% discordance rate. This suggests a biologic variation in shedding in addition to sampling variation. Good correlation existed between the DFA and the enzyme immunoassay. Tear serology was quite specific in predicting the presence of clinical disease and correlated with the other two antigen detection tests, although it does not seem to offer any practical advantages. These studies indicate that there is considerable variation in the shedding of chlamydia by people living in trachoma-endemic areas.

Adolescent↗
PubMed1990

A multiple-staining procedure for the detection of different DNA fragments on a single blot.

We have developed a method that implies the use of a particular type of substrate which can be used in combination with alkaline phosphatase in detecting nucleic acid on filters. The method allows the detection of several different nucleic acid sequences on a single filter. In consecutive steps, the target DNA molecules are hybridized with different digoxigenin-labeled DNA probes. After each hybridization step, digoxigenin is detected with an antibody-alkaline phosphatase conjugate. This enzyme is subsequently visualized by a color reaction using different 2-hydroxy-3-naphthoic acid anilide (naphthol AS) phosphates as substrates in combination with varying diazonium salts. The multiple-staining procedure is based on the fact that the probe DNA-antibody complex can be removed while the color precipitate remains stably bound at its place on the filter. This allows several repeated hybridizations with other digoxigenin-labeled probes followed by antibody detection and color reaction with other naphthol AS phosphate-diazonium salt combinations. Aside from the ability to simultaneously visualize different target DNAs on a single filter, this new method provides several important features that are more powerful than the conventional 5-bromo-4-chloro-3-indolyl phosphate-nitro blue tetrazolium (BCIP-NBT) color reaction for alkaline phosphatase. The colors are more stable and brilliant than BCIP-NBT; their development is faster, the resolution of closely spaced bands is greater, and the background is much lower. The detection limit for alkaline phosphates is as good as with BCIP-NBT (0.1 pg of DNA). One major advantage is the simplicity of removing the colors by ethanol incubation. In this paper, the method is described using the example of Southern blotted DNA fragments.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1990

Association of nonmelanoma skin cancer and actinic keratosis with cumulative solar ultraviolet exposure in Maryland watermen.

To establish the relationship between ultraviolet-B radiation and squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and actinic keratosis (AK), a cross-sectional prevalence survey was performed in a sample of 808 white, male watermen 30 years of age and older residing in the Eastern Shore of Maryland. A measure of personal cumulative ultraviolet-B exposure was determined for each subject from data collected through interviews and field and laboratory measurements. A personal interview elicited skin type, medication history, and other factors. Clinical diagnoses and histologic confirmation were done for current and previously removed skin tumors. The ratio of subjects with SCC to subjects with BCC was approximately 1:1; however, the ratio of BCC to SCC was 1.25:1 because BCC cases were more prone to multiple lesions. Watermen with SCC or AK but not BCC had higher average annual ultraviolet-B doses than age-matched controls. This was particularly marked in watermen younger than 60 years of age. Logistic regression showed that an older age, childhood freckling, and blue eyes significantly increased the risk of the development of all three types of skin tumor. Ease of sunburning was associated with BCC and AK, but not with SCC. Watermen in the upper quartile of cumulative ultraviolet-B exposure had a 2.5 times higher risk for the development of SCC when compared with the lower 3 quartiles. This suggests that high levels of ultraviolet-B exposure are important in SCC occurrence. The risk of AK developing was 1.5 times higher for those whose cumulative ultraviolet-B exposure exceeded the median. The relationship of BCC to cumulative ultraviolet-B exposure was not clear and this suggests that different etiologic mechanisms operate for SCC and BCC.

Adult↗