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Biomedical subjects

C E Taylor

Publications and source records attributed to C E Taylor.

At least 19 recordsLinked to original sources
PubMed2001

Microstructure determination of AOT + phenol organogels utilizing small-angle X-ray scattering and atomic force microscopy.

Dry reverse micelles of the anionic twin-tailed surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) dissolved in nonpolar solvents spontaneously form an organogel when p-chlorophenol is added in a 1:1 AOT:phenol molar ratio. The solvents used were benzene, toluene, m-xylene, 2,2,4-trimethylpentane (isooctane), decane, dodecane, tetradecane, hexadecane, and 2,6,10,14-tetramethylpentadecane (TMPD). The proposed microstructure of the gel is based on strands of stacked phenols linked to AOT through hydrogen bonding. Small-angle X-ray scattering (SAXS) spectra of the organogels suggest a characteristic length scale for these phenol-AOT strands that is independent of concentration but dependent on the chemical nature of the nonpolar solvent used. Correlation lengths determined from the SAXS spectra indicate that the strands self-assemble into fibers. Direct visualization of the gel in its native state is accomplished by using tapping mode atomic force microscopy (AFM). It is shown that these organogels consist of fiber bundle assemblies. The SAXS and AFM data reinforce the theory of a molecular architecture consisting of three length scales-AOT/phenolic strands (ca. 2 nm in diameter) that self-assemble into fibers (ca. 10 nm in diameter), which then aggregate into fiber bundles (ca. 20-100 nm in diameter) and form the organogel.

Chlorophenols↗
PubMed2001

DNA analysis of transferred sperm reveals significant levels of gene flow between molecular forms of Anopheles gambiae.

Anopheles gambiae populations in west Africa are complex, being composed of multiple, sympatric subpopulations. Recent studies have failed to reveal significant genetic differences among subpopulations, stimulating a debate regarding the levels of gene flow among them. The observed homogeneity may be the consequence of substantial contemporary gene flow or it may be that reproductive isolation is complete, but too recent for the accumulation of significant levels of genic divergence. Here, we report the results of a study estimating contemporary levels of gene flow between An. gambiae subpopulations by analysing females and transferred sperm removed from their reproductive systems. A total of 251 female and associated sperm extracts was analysed from a single site in Mali. Two molecular forms of An. gambiae, the M- and S-forms, occurred in sympatry at this site. Overall, we found very strong positive assortative mating within forms, however, we did observe significant hybridization between forms. In the M subpopulation 2/195 females (1.03%) contained sperm from S-form males and in 55 S-form females we found one female containing M-form sperm (1.82%). We also identified a mated M xS hybrid adult female. From mating frequencies, we estimate the Nem between the M- and S-form at 16.8, and from the adult hybrid frequency at 5.6. These values are consistent with our earlier estimate, based on FST for 21 microsatellite loci in which Nem = 5.8. We conclude that the general lack of genetic divergence between the M and S subpopulations of An. gambiae can be explained entirely by contemporary gene flow.

Animals↗
PubMed2001

Smoking cessation in China: findings from the 1996 national prevalence survey.

OBJECTIVES: To describe patterns of smoking and smoking cessation in China within the context of the stages of change model, using data from the 1996 national prevalence survey. DESIGN: A cross sectional survey was carried out using the 145 preselected disease surveillance points, which provide a representative sample for the entire country. A standardised questionnaire on smoking was interviewer administered. SETTING: The country of China. SUBJECTS: 122,220 people aged 15-69 years. MAINTENANCE MEASURES: Smoking cessation patterns, as defined by smoking status (current or former) and stage of change (precontemplation, contemplation, and action). RESULTS: The sample included 45,995 ever smokers of whom 4336 had quit. About 72% of current smokers reported not intending to give up their smoking behaviour, and about 16% of current smokers said they intended to do so, but have not taken any action. Of all ever smokers, the percentage of former smokers was 9.5%, and 12% of current smokers had quit at least once, but relapsed by the time of the survey. The patterns were similar in men and women with regard to the stated intent to quit. Among males, the percentage of former smokers increased with age but the percentage intending to quit was constant at about 15% across age strata. The most common reason for quitting was illness. Participants with a university education were more likely to have made an attempt to quit. CONCLUSIONS: The percentage of smokers contemplating quitting was low in China in 1996. The study shows that smokers in China must be mobilised to contemplate quitting and then to take action.

Adolescent↗
PubMed2000

Respiratory viral infections in primary immune deficiencies: significance and relevance to clinical outcome in a single BMT unit.

Respiratory viral infections are major causes of morbidity and mortality in children with SCID and other primary immunodeficiencies who require BMT. Twenty-two of 73 (30%) such children were admitted with respiratory viral infections, of whom 13/22 (59%) died. All viruses were detected in nasopharyngeal aspirate (NPA). Virus was only found in BAL in those with LRTI. Eleven of 22 (50%) had paramyxovirus infections, all with severe viral pneumonitis which worsened post BMT. Five of 11 (45.5%) survived overall. All 11 received aerosolised ribavirin; five of 11 received additional inhaled immunoglobulin and corticosteroid. Three of 5 (60%) survived compared with two of six (33.3%) not thus treated. Three of 22 (13.6%) had adenoviruses; one died of disseminated disease, including pneumonia despite intravenous ribavirin. Eleven patients had rhinovirus detected; nine of 11 (82%) were asymptomatic or coryzal and survived. Two patients with additional severe lung pathologies had LRT rhinovirus and died. All patients received intravenous immunoglobulin. No treatments resulted in viral clearance without successful T cell engraftment. Respiratory viruses, particularly paramyxoviruses and adenoviruses are common, significant pathogens in these patients, significantly worsening outcome of BMT. NPA is an ideal specimen for diagnosis and monitoring of infection. Aggressive treatments may reduce viral replication and damage. Nebulised immunoglobulin and corticosteroid in LRTI may improve respiratory function and outcome.

Adenoviridae Infections↗
PubMed2000

Micronutrients and infectious diseases: thoughts on integration of mechanistic approaches into micronutrient research.

Results of field and laboratory studies provide convincing evidence that micronutrient deficiencies contribute to the mortality and morbidity of infectious diseases. Despite encouraging results in large trials, understanding the mechanisms by which micronutrients contribute to the outcome of the encounter between an individual and an infectious agent requires additional hypothesis-driven research. Presumably, such understanding should lead to translational studies with targeted nutritional therapy. Although these mechanistic studies are varied and complex, they must be done systematically and should include examination of the mechanisms by which micronutrients affect host-pathogen interactions, development of appropriate animal models and reliable methods for the assessment of micronutrient levels, and translation of the results of basic research findings into clinical studies. Moving the frontiers of micronutrient research from the laboratory to the field will be challenging. However, sound scientific research should lead toward better human health.

Communicable Diseases↗
PubMed2000

Effects of compression on language evolution.

For many adaptive complex systems information about the environment is not simply recorded in a look-up table, but is rather encoded in a theory, schema, or model, which compresses information. The grammar of a language can be viewed as such a schema or theory. In a prior study [Teal et al., 1999] we proposed several conjectures about the learning and evolution of language that should follow from these observations: (C1) compression aids in generalization; (C2) compression occurs more easily in a "smooth," as opposed to a "rugged," problem space: and (C3) constraints from compression make it likely that natural languages evolve towards smooth string spaces. This previous work found general, if not complete support for these three conjectures. Here we build on that study to clarify the relationship between Minimum Description Length (MDL) and error in our model and examine evolution of certain languages in more detail. Our results suggest a fourth conjecture: that all else being equal, (C4) more complex languages change more rapidly during evolution.

Algorithms↗
PubMed1999

Smoking in China: findings of the 1996 National Prevalence Survey.

CONTEXT: As the world's largest producer and consumer of tobacco products, China bears a large proportion of the global burden of smoking-related disease and may be experiencing a tobacco epidemic. OBJECTIVE: To develop an evidence-based approach supporting tobacco control initiatives in China. DESIGN AND SETTING: A population-based survey consisting of a 52-item questionnaire that included information on demographics, smoking history, smoking-related knowledge and attitudes, cessation, passive smoke exposure, and health status was administered in 145 disease surveillance points in the 30 provinces of China from March through July 1996. PARTICIPANTS: A nationally representative random sample of 128766 persons aged 15 to 69 years were asked to participate; 120298 (93.8%) provided data and were included in the final analysis. About two thirds of those sampled were from rural areas and one third were from urban areas. MAIN OUTCOME MEASURES: Current smoking patterns and attitudes; changes in smoking patterns and attitudes compared with results of a previous national survey conducted in 1984. RESULTS: A total of 41187 respondents smoked at least 1 cigarette per day, accounting for 34.1% of the total number of respondents, an increase of 3.4 percentage points since 1984. Current smoking continues to be prevalent among more men (63%) than women (3.8%). Age at smoking initiation declined by about 3 years for both men and women (from 28 to 25 years). Only a minority of smokers recognized that lung cancer (36%) and heart disease (4%) can be caused by smoking. Of the nonsmokers, 53.5% were exposed to environmental tobacco smoke at least 15 minutes per day on more than 1 day per week. Respondents were generally supportive of tobacco control measures. CONCLUSION: The high rates of smoking in men found in this study signal an urgent need for smoking prevention and cessation efforts; tobacco control initiatives are needed to maintain or decrease the currently low smoking prevalence in women.

Adolescent↗
PubMed1998

Complexities in the genetic structure of Anopheles gambiae populations in west Africa as revealed by microsatellite DNA analysis.

Chromosomal forms of Anopheles gambiae, given the informal designations Bamako, Mopti, and Savannah, have been recognized by the presence or absence of four paracentric inversions on chromosome 2. Studies of karyotype frequencies at sites where the forms occur in sympatry have led to the suggestion that these forms represent species. We conducted a study of the genetic structure of populations of An. gambiae from two villages in Mali, west Africa. Populations at each site were composed of the Bamako and Mopti forms and the sibling species, Anopheles arabiensis. Karyotypes were determined for each individual mosquito and genotypes at 21 microsatellite loci determined. A number of the microsatellites have been physically mapped to polytene chromosomes, making it possible to select loci based on their position relative to the inversions used to define forms. We found that the chromosomal forms differ at all loci on chromosome 2, but there were few differences for loci on other chromosomes. Geographic variation was small. Gene flow appears to vary among different regions within the genome, being lowest on chromosome 2, probably due to hitchhiking with the inversions. We conclude that the majority of observed genetic divergence between chromosomal forms can be explained by forces that need not involve reproductive isolation, although reproductive isolation is not ruled out. We found low levels of gene flow between the sibling species Anopheles gambiae and Anopheles arabiensis, similar to estimates based on observed frequencies of hybrid karyotypes in natural populations.

Africa, Western↗
PubMed1998

Mark-release-recapture experiments with Anopheles gambiae s.l. in Banambani Village, Mali, to determine population size and structure.

Mark-release-recapture experiments with Anopheles gambiae s.l. were performed during the wet seasons of 1993 and 1994 in Banambani, Mali. All recaptured mosquitoes were identified to species by PCR analysis and, when possible, by chromosomal analysis to chromosomal form. Two species of the An. gambiae complex were present: An. gambiae s.s. and An. arabiensis; their ratio differed greatly from one year to the next. Three chromosomal forms of An. gambiae s.s. were found--Bamako, Savanna and Mopti. The drier 1993 was characterized by a high frequency of An. arabiensis and of the Mopti chromosomal forms of An. gambiae s.s. These trends were consistent with large-scale geographical patterns of abundance along a precipitation gradient. We observed no difference in dispersal between the two species, nor among the chromosomal forms of An. gambiae s.s. Therefore, in this situation at least, it is reasonable to group such data on the An. gambiae complex as a whole for analysis. Population size of An. gambiae s.l. females in the village was estimated to be 9000-11,000 in 1993 and 28,000 in 1994. The corresponding numbers were somewhat higher when independently-derived values of daily survival were used. These were consistent with estimates of effective population size obtained from patterns of gene frequency change.

Animals↗
PubMed1998

Multicenter evaluation of the Amplicor Enterovirus PCR test with cerebrospinal fluid from patients with aseptic meningitis. The European Union Concerted Action on Viral Meningitis and Encephalitis.

The Amplicor Enterovirus PCR test was compared with viral culture for the detection of enteroviruses in cerebrospinal fluid (CSF) specimens. In a multicenter study in which nine laboratories participated, a total of 476 CSF specimens were collected from patients with suspected aseptic meningitis. Sixty-eight samples were positive by PCR (14.4%), whereas 49 samples were positive by culture (10.4%), demonstrating that the Amplicor Enterovirus PCR test was significantly more sensitive than culture (P < 0.001). After discrepancy analysis the sensitivity and specificity of the Amplicor Enterovirus PCR test obtained by using viral culture as the "gold standard" were 85.7 and 93.9%, respectively. Our results with the CSF specimens collected in different countries demonstrate that the Amplicor test is capable of detecting a large variety of enterovirus serotypes and epidemiologically unrelated isolates in CSF specimens from patients with aseptic meningitis. The Amplicor Enterovirus PCR test is a rapid assay which can be routinely performed with CSF samples and is an important improvement for the rapid diagnosis of enteroviral meningitis.

Cerebrospinal Fluid↗
PubMed1998

Parainfluenza virus and respiratory syncytial virus infection in infants undergoing bone marrow transplantation for severe combined immunodeficiency.

Respiratory syncytial virus and parainfluenza virus infection carry a poor prognosis in severe combined immunodeficiency (SCID), particularly if the viral load is high. Patients with high viral load develop severe pneumonitis at engraftment which may possibly be modulated by immunotherapy, including high dose nebulised corticosteroids. Further work is required to develop effective treatment for this severe condition.

Antiviral Agents↗
PubMed1997

Correlation between the detection of viral DNA by the polymerase chain reaction in peripheral blood leukocytes and serological responses to human herpesvirus 6, human herpesvirus 7, and cytomegalovirus in renal allograft recipients.

Diagnosis of significant infections by human herpesvirus 6 (HHV6) and 7 (HHV7) in transplant patients has proved difficult because both viruses are ubiquitous and can cause persistent infections in their hosts. The significance of viral DNA detected in peripheral blood leukocytes (PBLs; DNAemia) by PCR is therefore unclear. The interpretation of serological results is complicated by the fact that both primary and secondary infections with other herpesviruses may be associated with a concurrent antibody response to HHV6. Fifty-four renal allograft recipients were studied prospectively and their serological response to HHV6, HHV7 and CMV were compared with the detection of viral DNAemia from the homologous and heterologous viruses. Serum and heparinished blood samples were collected prospectively from 54 renal allograft recipients. DNA was extracted from PBLs and tested for the presence of HHV6, HHV7 and CMV DNA by PCR. Antibodies to HHV6 and HHV7 were measured by an indirect immunofluorescence test and to CMV by an anticomplement immunofluorescence (ACIF) test. CMV IgM antibodies were detected by a commercial enzyme immunoassay. CMV and HHV7 DNAemia were each significantly associated with serological responses to the homologous virus but no such association was found for HHV6 DNAemia. However, patients with consecutively positive DNAemia to any of the viruses (including HHV6) were more likely to have a homologous serological response. Patients who had detectable CMV IgM without a concurrent rise in CMV antibodies were significantly less likely to have CMV DNAemia (odds ratio = 0.16; 95% CI 0.02-0.9). CMV IgM antibodies may be associated with HHV6 or HHV7 DNAemia (odds ratio 2.3; 95% CI 0.5-15). This serological profile may reflect a crossreactive response to HHV6, HHV7 or other herpesviruses. CMV IgM should not be used in isolation for the diagnosis of CMV infection or disease in this group of patients.

Adolescent↗
PubMed1997

Ethical dilemmas in current planning for polio eradication.

Intensification of polio eradication efforts worldwide raises concerns about costs and benefits for poor countries. A major argument for global funding is the high benefit-cost ratio of eradication; however, financial benefits are greatest for rich countries. By contrast, the greatest costs are borne by poor countries; the Pan American Health Organization has estimated that host countries bore 80% of costs for polio eradication in the Americas. The 1988 World Health Assembly resolution setting up the Polio Eradication Initiative carried the proviso that programs should strengthen health infrastructures. Drastic cuts in donor funding for health make this commitment even more important. Two international evaluations have reported both positive and negative effects of polio and Expanded Programme on Immunization programs on the functioning and sustainability of primary health care. Negative effects were greatest in poor countries with many other diseases of public health importance. If poor countries are expected to divert funds from their own urgent priorities, donors should make solid commitments to long-term support for sustainable health development.

Developed Countries↗