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Biomedical subjects

D J Sexton

Publications and source records attributed to D J Sexton.

124 records · Page 7Linked to original sources
PubMed1976

Rocky Mountain spotted fever in Mississippi: survey for spotted fever antibodies in dogs and for spotted fever group reckettsiae in dog ticks.

During epidemiologic studies of Rocky Mountain Spotted Fever in Mississippi in 1973, dogs were surveyed for antibodies tp spotted fever group antigens and for tick parasites infected with rickettsiae of the spotted fever group. Fifty-three (46%) of 116 serum samples had complement-fixing antibody titers greater than or equal to 1:8 as compared to only one (5%) of 21 samples from a group of dogs obtained from metropolitan Chicage. Fifty-two per cent of the dogs tested from Mississippi had microagglutinating antibodies titers greater than or equal to 1:8; 9% of dogs from Chicago had similar titers. Rickettsia rickettsii was demonstrated in only one (0.8%) of 129 Dermacentor variabilis removed from Mississippi dogs. Quite unexpectedly, 167 (18.9%) of 884 Rhipicephalus sanguineus taken from these dogs contained spotted fever group rickettsiae.

Agglutination Tests↗
PubMed1975

Clinical and epidemiologic features of Rocky Mountain spotted fever in Mississippi, 1933-1973.

During the period 1933-1973, 169 cases of Rocky Mountain spotted fever (RMSF) were either reported by physicians or detected in a retrospective survey of hospitals and practicing physicians in Mississippi. The epidemiologic characteristics of 119 cases and the clinical features of 75 serologically confirmed cases are summarized in this communication and compared with other published reviews of RMSF. Although the percentage of reported fatal cases decreased overall since 1950, 9 of 49 reported cases (18%) in Mississippi were fatal during the period 1969-1972. The yearly number of reported cases of RMSF in Mississippi increased fourfold from 1970-1973. In the past 40 years, only 5 cases of RMSF have been reported from the Mississippi delta, a flat agricultural region that includes over one fourth of the total population of the state.

Adolescent↗
PubMed1975

Rhipicephalus sanguineus: vector of a new spotted fever group rickettsia in the United States.

A rickettsia related to but distinct from the spotted fever agent, Rickettsia rickettsii, has been detected in 167 (18.9%) of 884 Rhipicephalus sanguineus taken off dogs in central and northern Mississippi. The organisms could readily be isolated in male meadow voles (Microtus pennsylvanicus), where it produced massive infections in the tissues of tunica vaginalis. It was practically nonpathogenic for male guinea pigs, although inoculation of these animals with infected tunica vaginalis of voles afforded in 30 of 38 instances solid immunity to challenge with virulent R. rickettsii. The Rhipicephalus rickettsia grew well in monolayers of chicken embryo fibroblast, Vero, mouse L, and HeLa cells. Cytopathogenic effects were minimal unless large concentrations of rickettsiae were used as inocula. It also could be established in embryonated hen eggs but only after injection of massive doses of L cell-propagated organisms. Serological tests (complement fixation, microagglutination and/or micro immunofluorescence) indicated that the newly described Rickettsia belongs to the spotted fever group but differs from R. rickettsii, R. akari, and R. conorii. Antigenic differences were also demonstrated by direct fluorescence microscopy as well as by vaccine potency and mouse-toxin neutralization tests.

Animals↗
PubMed1975

Human-to-human transmission of Pseudomonas pseudomallei.

Melioidosis, the clinical manifestation of infection with Pseudomonas pseudomallei, has occurred infrequently in American citizens; almost all reported cases have been in Vietnam veterans, usually associated with respiratory disease. A Vietnam veteran from Mississippi developed chronic prostatitis, with no other clinical manifestations, during service in Vietnam, and P. pseudomallei was isolated from prostatic secretions 2 years after his return to the United States. The patient had had sexual contact with four women including his wife since his return from Vietnam. Vaginal and cervical cultures and serum samples were obtained from the four women, and serum samples and cultures of semen were obtained from the patient. Vaginal swabs and semen cultures were negative for P. pseudomallei. The patient and his wife had hemagglutination titers (greater than 640) diagnostic of P. pseudominallei infection. This occurrence of venereal transmission is the first report of person-to-person spread of P. pseudomallei infection.

Adult↗
PubMedDate not supplied

A nonoccupational outbreak of inorganic mercury vapor poisoning.

An outbreak of inorganic mercury vapor poisoning involving 12 people occurred in a trailer park in Mississippi in 1973-74. For information concerning levels of mercury in hair and blood of humans with short-term exposures, these individuals were observed for as long as 10 months after the end of their exposures, and the amount of mercury in their blood and scalp hair was serially measured. Specimens were also obtained from nonexposed individuals in the trailer park. Inorganic mercury was measured in 1-cm segments of hair samples obtained both 6 and 9 months after termination of exposure. Over a 3-month period, the peak amount of inorganic mercury per gram of hair shifted in position from 7 cm to 13 cm from the scalp. The average mercury concentration in newly formed hair (the 4 cm of hair closest to the scalp) decreased fourfold over the same time period. Surface contamination of exposed hair by exogenous mercury also occurred. Levels of inorganic mercury in blood from exposed individuals ranged from 183 to 620 ng/ml and fell to levels similar to those of controls 4 to 6 months after ending exposure. The source of the outbreak was metallic mercury spilled on rugs. Attempts to remove the mercury failed and actually dispersed the metal over a larger surface area. Air mercury levels as high as 1.0 mg/m3 of air were found in one of the contaminated house trailers. Rugs or carpets contaminated with metallic mercury are a significant health risk.

Accidents, Home↗
PubMedDate not supplied

Spotted fever group rickettsial infections in Australia.

More than four decades ago, Rickettsia australis was discovered to be the etiologic agent of Queensland tick typhus (QTT), yet many unanswered questions persist about the ecology, epidemiology, and clinical features of this disease. We review 46 previously published cases of QTT along with 16 cases discovered by active surveillance. QTT is usually a mild disease. Patients often have regional lymphadenopathy and eschars. Some have vesicular rashes. Because clinical features overlap, serologic tests are necessary to distinguish QTT from other endemic Australian rickettsial diseases (scrub and murine typhus). Only two tick vectors of R. australis have been identified: Ixodes holocyclus and Ixodes tasmani. Until rickettsiae are isolated from patients in Victoria and Tasmania, it remains unproven that spotted fever group infections in these locations are due to R. australis. However, available serologic, epidemiologic, and clinical data suggest that QTT is not confined to the area in which R. australis was first isolated (Queensland); rather, it occurs along a 3,200-km span of eastern coastal Australia, from tropical to temperate climates.

Adolescent↗
PubMedDate not supplied

A spectrophotometric glutathione S-transferase assay displaying alpha-class selectivity utilizing 1-p-chlorophenyl-4,4-dimethyl-5-diethylamino-1-penten-3- one hydrobromide.

The conjugation of 1-p-chlorophenyl-4,4-dimethyl-5-diethylamino-1-penten-3- one hydrobromide (CDDP), a Mannich base of an alpha,beta-unsaturated ketone, to glutathione is catalyzed selectively by alpha-class glutathione S-transferase. The reaction of CDDP with glutathione can be monitored continuously by following the conjugation-dependent decrease in absorbance of CDDP at 307 nm. The Km and Vmax for CDDP with alpha-class glutathione S-transferase from horse liver were determined to be 226 microM and 14.6 mumol/(min.mg), respectively. CDDP is the first example of an alpha-class glutathione S-transferase selective substrate that monitors the glutathione conjugation activity, rather than the glutathione peroxidase activity of the enzyme.

Chlorobenzenes↗
PubMedDate not supplied

Platelet glutathione transport: characteristics and evidence for regulation by intraplatelet thiol status.

The present study demonstrates the carrier-mediated uptake of intact glutathione (GSH) by human platelets. Platelet GSH uptake was characterized as being Na+ independent and saturable. The KM, apparent and Vmax, apparent for GSH uptake in platelet plasma membrane vesicles were 28.0 +/- 8.4 microM and 263.5 +/- 28.5 pmol/min per mg protein, respectively. The transport was inhibited by GSH analogs and enhanced by KCl-induced membrane depolarization. GSH transport may be regulated by the intracellular thiol status, since the depletion of intraplatelet GSH with 100 microM 1-chloro-2,4-dinitrobenzene (CDNB) increased GSH uptake by approximately 40%. The KM, apparent and Vmax, apparent for GSH uptake in intact platelets changed from 99.5 +/- 15 microM and 42 +/- 7.5 pmol/min per 10(9) platelets, respectively, to 33.7 +/- 6.7 microM and 21.5 +/- 6.9 pmol/min per 10(9) platelets, respectively, on reducing intraplatelet GSH with 100 microM CDNB.

Biological Transport↗
PubMedDate not supplied

Dual infection with Ehrlichia chaffeensis and a spotted fever group rickettsia: a case report.

Well-documented cases of simultaneous human infection with more than one tick-borne pathogen are rare. To our knowledge only two dual infections have been reported: simultaneous human infection with the agent of human granulocytic ehrlichiosis and Borrelia burgdorferi and simultaneous human infection with B. burgdorferi and Babesia microti (1-2). Rocky Mountain spotted fever has long been known to be endemic in North Carolina; cases of human ehrlichial infection were recognized there soon after Ehrlichia chaffeensis was recognized as an important cause of tick-borne disease in the southeastern United States. Because both Rocky Mountain spotted fever and ehrlichiosis are prevalent in North Carolina, occasional cases of simultaneous human infection by rickettsial and ehrlichial agents would not be surprising; however, no such cases seem to have been reported.

Adult↗
PubMedDate not supplied

The impact of antimicrobial resistance on empiric antibiotic selection and antimicrobial use in clinical practice.

The prevalence of antimicrobial resistance may vary dramatically between countries and regions and even among different patient populations and between hospitals in the same community. In light of these variations, physicians in practice must make a clinical judgment about the likely pathogen(s) involved in the infectious process. They should have access to up-to-date data on the antimicrobial resistance pattern of commonly encountered pathogens. Such data should be subdivided and analyzed for isolates from community as opposed to hospitalized patients. The data on intensive care units patients and from special groups of patients, such as those undergoing dialysis, organ transplant recipients, or cancer patients receiving chemotherapy, should also be made available to practicing physicians. When antimicrobial resistance is considered to be probable or highly likely, or if empirical therapy has failed, a concerted effort should be made to make a microbiologic diagnosis which will ultimately reduce the cost, simplify therapy and improve the outcome over treatment that is solely empirically based.

Anti-Bacterial Agents↗