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D C Barker

Publications and source records attributed to D C Barker.

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

Prospects for childhood immunization registries in public health assessment and assurance: initial observations from the All Kids Count initiative projects.

This article offers an overview of selected evaluation findings from the initial implementation year of the Robert Wood Johnson Foundation's All Kids Count childhood immunization initiative in which demonstration projects were funded to develop community-based immunization registry and follow-up systems in 14 sites throughout the United States. The basic components of these systems, the process through which these registries were developed, efforts to secure the participation of private sector providers, the prospects for system success at the community level, and the potential for these immunization programs to influence other aspects of primary health care for children are addressed.

Health Services Accessibility↗
PubMed1996

Identification of the C-terminal region of 70 kDa heat shock protein from Leishmania (Viannia) braziliensis as a target for the humoral immune response.

A Leishmania (Viannia) braziliensis (Lb) promastigote cDNA library in lambda gt11 was screened with patients' sera with the aim of identifying antigens specifically related to mucocutaneous leishmaniasis (MCL). One of the clones isolated, 133P, consistently reacted with MCL sera; it was sequenced and found to encode the C-terminal three-quarters of a protein belonging to the highly conserved Hsp70 family. Since Hsp70 proteins from different species tend to be less conserved through the C-terminal end, it was predicted that this region would be more antigenic and was likely to bear the discriminatory epitopes. In order to test this hypothesis, the N- and C-terminal halves of the polypeptide encoded by 133P, 133P-N and 133P-C, respectively, were expressed in Escherichia coli. Immunoblotting analysis demonstrated that 133P-C reacted more strongly with a pool of MCL sera than 133P-N, and both recombinant proteins reacted faintly with pools of cutaneous (CL) and visceral (VL) leishmaniasis sera. These results confirmed the predicted epitope location in the C-terminal region. The 133P-C fragment was also expressed as a fusion protein with glutathione-S-transferase (GST-133P-C), affinity-purified with glutathione-agarose and tested by ELISA with individual sera. From 46 Lb-infected patients, 41 sera (89%) were positive, no cross-reactivity was observed with healthy, Trypanosoma cruzior L. amazonensis-infected individuals. Despite a relatively high cross-reactivity with VL sera, the enhanced humoral response of MCL as compared with CL patients might be interesting for studies on disease aggravation.

Amino Acid Sequence↗
PubMed1996

Physician service to the underserved: implications for affirmative action in medical education.

Affirmative action is under increasing scrutiny. In medicine, the observation that minority physicians disproportionately serve minority patients has been one rationale for affirmative action. Using two large physician surveys, we find that minority and women physicians are much more likely to serve minority, poor, and Medicaid populations. Weaker, but significant association exists between physician and patient socioeconomic background. Service patterns are sustained over time and are generally consistent with physician career preferences. Ending affirmative action in medicine may imperil access to care. Results do not support affirmative action based on economic disadvantage instead of race, ethnicity, and sex.

Adult↗
PubMed1995

The RFLP analysis of the beta-tubulin gene region in New World Leishmania.

We have examined the similarities and differences in the organization of tubulin genes in New World Leishmania by restriction endonuclease digestion of genomic DNA and Southern blot analysis, using heterologous and homologous tubulin gene probes. As judged by the hybridization pattern and the restriction fragment length polymorphism (RFLP), there were large differences in both the restriction and hybridization patterns of the beta-tubulin sequences between stocks of the mexicana and braziliensis complexes. There were similarities in the hybridization patterns of different species of the mexicana complex. In contrast, a high heterogeneity was found between species of the braziliensis complex which includes intraspecific variation. The results suggest that this polymorphism may be associated with random mutations. The same analysis gave evidence of large differences in the beta-tubulin gene restriction pattern between New and Old World Leishmania. This variation in the beta-tubulin gene region was sufficient to distinguish between New and Old World Leishmania groups and between stocks of the mexicana and braziliensis complexes.

Animals↗
PubMed1995

Plasticity of gp63 gene organization in Leishmania (Viannia) braziliensis and Leishmania (Viannia) peruviana.

The genomic organization of gp63 genes in 4 and 7 isolates of Leishmania braziliensis and L. peruviana, respectively was studied by RFLP analysis with 3 restriction enzymes (Bgl I, Sal I and Apa I). Our results showed a marked polymorphism among isolates. Some characters were specific to L. braziliensis or to L. peruviana, and others specific to the respective biogeographical populations of L. peruviana. The average minimum copy number of gp63 genes was found to be higher in L. braziliensis (71) than in L. peruviana (46), suggesting that deletion of gp63 genes might be partially involved in the size decrease of the chromosome bearing gp63 genes, observed between those 2 species (from 700 to 610 kb). Our results may suggest the existence of at least 2 arrays of heterologous gp63 repeats, varying in relative copy number between L. braziliensis and L. peruviana, and among isolates of the latter species. Rearrangement of the gp63 genes was observed during long-term in vitro maintenance of a reference strain of L. braziliensis. These observations document the existence of a dynamic gp63 gene organization in Leishmania of the braziliensis complex.

Animals↗
PubMed1994

The polymerase chain reaction can reveal the occurrence of naturally mixed infections with Leishmania parasites.

On isolation and characterization of Leishmania parasites from Sudanese patients with visceral leishmaniasis (VL), four cases of mixed infections were found. Three of those cases were from the Eastern Sudan focus of VL. In one case the patient was found to be concomitantly infected with Leishmania donovani and Leishmania aethiopica, while the remaining three patients possessed mixed infections of Leishmania donovani and Leishmania major. Mixed infections were identified by PCR amplification of Leishmania kinetoplast DNA (kDNA) from parasites in culture or in original patient aspirate material and, additionally in the former cases by isoenzyme electrophoresis. In those cases where parasite culture was successful, PCR also demonstrated the rapidity with which one Leishmania species was eliminated from culture during continuous passage.

Animals↗
PubMed1994

Identification and diagnosis of Leishmania mexicana complex isolates by polymerase chain reaction.

Following cloning of Leishmania (L.) amazonensis kinetoplast DNA two recombinant clones were identified: one specific for L. (L.) amazonensis and the other specific for L. (L.) amazonensis and closely related isolates. DNA sequences from these clones were compared with those of other kinetoplastids and oligonucleotide primers were designed to be used in the polymerase chain reaction. A pair of these primers has been shown not only to be highly specific for L. mexicana complex isolates but can also be used to distinguish between L. (L.) mexicana and L. (L.) amazonensis isolates. These primers have been tested with water-lysed cultures, crude DNA extracts from human patients, potential host reservoirs, sandfly vectors and with cell pellets after isoenzyme characterization. The results of these tests indicate that the primers can be used specifically in the presence of excess host DNA originating from the majority of South American countries.

Animals↗
PubMed1994

1044 women with migraine: the effect of environmental stimuli.

This study initiated by a self-help migraine group investigated disability caused by visual environmental stimuli, e.g. glare, flicker, pattern and color. One thousand forty-four women with migraine completed the self-report questionnaire on visual environmental stimuli reported in earlier studies to precipitate or aggravate migraine. One hundred twenty-one female controls were obtained from general practice and hospital out-patients. The responses of the classical, common and non-migraine groups were compared. Women with classical migraine expressed greater disability than those with common migraine or controls both in respect of number of visual sensitivities reported (P < 0.0001) and severity of consequences of such stimuli (P < 0.0001). This study indicated differences between classical and common migraine outside of the attack phase apart from aura. Reported range of sensitivities for the migraineurs peaked between the ages of 46-60 years. A high level of unrealized disability caused by visual environmental stimuli was thus identified in hitherto unexplored self-help groups.

Adolescent↗
PubMed1993

A small chromosome of Leishmania (Viannia) braziliensis contains multicopy sequences which are complex specific.

Orthogonal Field Alternating Gel Electrophoresis (OFAGE) has been used to show a band of approximately 260 kb which is stained intensely with ethidium bromide in Leishmania (V.) braziliensis stock M2903. This small chromosome (sc-2903), as well as a 50 kb and a 200 kb chromosome seen in L. (L.) mexicana and L. (L.) amazonensis, respectively, are stably maintained and linear. When used as a hybridisation probe, sc-2903 showed homology to large chromosomal DNA bands and to a multiplicity of genomic fragments in all braziliensis stocks tested, indicating either different sequences, different copy numbers or both but no hybridisation to mexicana stocks. It is possible that these sequences are present in all members of the braziliensis complex and are not related to LD1 or any other previously published small chromosome sequences. However, at least one clone isolated from a sc-2903 library recognised genomic DNA of stocks belonging to the braziliensis, mexicana and donovani complexes. Our results suggest that the clone carries sequence(s) that are repeated and shared between stocks of different complexes but with a variable genomic distribution.

Animals↗
PubMed1993

The prevalence of headache and migraine in atopic children: an epidemiological study in general practice.

The lifetime prevalence of headache and migraine was assessed in an unselected sample of atopic (asthma, eczema or rhinitis) children in a general practice population of known socio-economic and age/sex composition. Maternal migraine was also recorded. The prevalence of both headache and migraine was significantly and proportionally higher in children with atopic disorders compared to those without. Childhood migraine was associated with atopy and the association was strongest with rhinitis. Rhinitis in children was associated with maternal migraine. A history of atopy (especially rhinitis) supports the diagnosis of migraine in young children with paroxysmal headaches.

Child↗
PubMed1993

A comparative study of diagnosis by the polymerase chain reaction and by current clinical methods using biopsies from Colombian patients with suspected leishmaniasis.

The results of a preliminary trial are reported in which the diagnostic value of a Polymerase Chain Reaction (PCR) specific for Leishmania of the subgenus Viannia was compared with that of currently recommended methods. These methods were microscopic examination of dermal scrapings, in vitro culture of both patient biopsies and aspirates, an in vitro culture of hamster aspirates following inoculation with patient biopsies. The tests were performed on biopsies of Colombian patients with leishmaniasis or with nonleishmanial ethiologies. The outcome of this trial was that PCR was consistently more sensitive than any of the four currently recommended methods of diagnosis, an gave results much faster than the three culture-based methods. Clinical specificity did not match the absolute specificity obtained in the laboratory when tested against purified kDNAs from various Leishmania species. This is thought to be due to the small sample size and to possible subclinical presence of the parasite in the population. The results nevertheless show that, given a more extensive trial directed at clinical validation, PCR can provide the means for early and rapid diagnosis of leishmaniasis. This should reduce morbidity and treatment costs. Further improvements to the method, its introduction in endemic settings and its possible further clinical uses are also discussed.

Adolescent↗
PubMed1992

Diagnosis of New World leishmaniasis: specific detection of species of the Leishmania braziliensis complex by amplification of kinetoplast DNA.

We have sequenced single kinetoplast DNA minicircles from three species and part of a minicircle from the fourth major species within the Leishmania braziliensis complex. Alignment of these sequences with each other and with those of other kinetoplastids allowed the selection of a pair of oligonucleotides suitable as primers in a polymerase chain reaction which is highly specific for the Leishmania braziliensis complex. The reaction is capable of detecting less than one femtogramme of kinetoplast DNA. It has been tested with crude specimens from South American leishmaniasis patients, potential wild animal reservoirs and sandfly vectors. The tests indicate that these primers are suitable for diagnosis of leishmaniasis and potentially useful in epidemiological surveys.

Animals↗
PubMed1992

Rapid and sensitive detection of Leishmania kinetoplast DNA from spleen and blood samples of kala-azar patients.

Following sequence analysis of a Leishmania donovani kinetoplast DNA (kDNA) minicircle, we have developed synthetic oligonucleotides for use in the polymerase chain reaction (PCR). With these primers, we have amplified L. donovani kDNA from splenic aspirates and blood samples taken from kala-azar patients. Treatment of the samples for PCR requires only limited DNA purification by lysis in SDS, digestion with proteinase K, phenol extraction and ethanol precipitation of the resulting nucleic acid. We have obtained amplified product routinely with DNA prepared from the equivalent of 2.5-25 microliters of splenic aspirate or of 50-500 microliters of blood from infected patients. In dilution experiments a visible product has been obtained on amplification of DNA from the equivalent of 2.5 x 10(-7) microliters of splenic material. We therefore propose the amplification of L. donovani kDNA by PCR as a rapid and highly sensitive method for the diagnosis of kala-azar.

Animals↗
PubMed1991

Medical educators' views on medical education reform.

To determine whether medical educators perceive a need for change in medical student education, we analyzed data from a 1989 survey of 1369 respondents from all US schools of allopathic medicine. Except for basic sciences faculty, a majority of educators stated that "fundamental changes" are needed in medical student education in the United States. Nearly three fourths of deans and associated deans reported the need for "fundamental changes" or "thorough reform." At least 79% of educators voiced support for six specific reforms, such as rewarding teaching excellence and increasing clinical education in ambulatory and community settings. While slight majorities supported reducing class size and centralizing governance, substantial proportions stated that they would "work against" such reforms. Most educators reported that a broad base of support within the school would be essential for change. The survey suggests a restlessness among the leaders of medical education.

Attitude of Health Personnel↗
PubMed1990

Correlation of Pityosporum ovale density with clinical severity of seborrheic dermatitis as assessed by a simplified technique.

One hundred patients with facial seborrheic dermatitis and 42 control subjects were studied. The number of periodic acid-Schiff-positive Pityosporum ovale yeast cells in skin scrapings per high-power field were counted and designated 1 + to 4 +. Our data indicate a correlation between the density of P. ovale and the clinical severity of seborrheic dermatitis, both before and after therapy with a precipitated sulfur/salicyclic acid shampoo. The data support the concept that yeast contributes to the pathogenesis of seborrheic dermatitis.

Administration, Cutaneous↗