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Biomedical subjects

A Burke

Publications and source records attributed to A Burke.

At least 55 records · Page 3Linked to original sources
PubMed1994

Persistence of replicating coxsackievirus B3 in the athymic murine heart is associated with development of myocarditic lesions.

Coxsackievirus B3 (CVB3)-induced myocarditis was studied in euthymic (nu/+) and athymic (nu/nu) C3H/HeN (H-2k) mice. Mice were inoculated intraperitoneally with 10(6) p.f.u. of CVB3 (Nancy strain) and sacrificed at intervals up to 92 days post-inoculation (p.i.). Viraemia peaked at day 2 to 3 p.i. and ceased at day 5 to 7 p.i. in a synchronized manner in both sets of mice. Very few infectious particles were detected in the blood of nu/nu mice after day 14 p.i. In nu/nu mice, CVB3 persisted in myocardial tissue with constant titres between 2.7 +/- 1.9 x 10(4) and 7.6 +/- 5.2 x 10(4) p.f.u./mg from day 3 to 92 p.i., which were comparable to those of nu/+ mice in the acute phase. In nu/+ mice, the virus was recovered from all animals examined by day 11 p.i. and from three out of 13 mice between days 14 and 21 p.i., yet no virus was recovered from nu/+ mice at day 42 p.i. In nu/nu mice, sense and antisense RNA for CVB3 was detected in the myocardial tissue up to day 42 p.i. by in situ hybridization and up to day 92 p.i. by reverse transcriptase-PCR. Neither sense nor antisense RNA was detected after day 21 p.i. in nu/+ mice with the same techniques. Myocardial tissue damage was analysed morphologically. At day 92 p.i., the area of myocardial injury peaked at 23% of the section in nu/nu mice. In contrast, less than 0.6% of tissue sections contained lesions in nu/+ mice. A neutralizing antibody response to CVB3 was observed in both nu/nu and nu/+ mice. The mean titre of neutralizing antibody was significantly higher at day 21 p.i. in nu/+ mice, but similar at day 42 p.i. with nu/nu and nu/+ mice. Perforin-producing natural killer-like cells, which are considered to play an important role in causing acute myocarditic lesions in immunocompetent mice, were found in the lesions of nu/nu mice persistently infected with CVB3. Prolonged tumour necrosis factor-alpha mRNA synthesis detected in nu/nu mice appears to reflect the continuous activation of macrophages, which extend phagocytic reactions to virus-infected myocytes. These immunological results suggested that the host immune response devoid of antigen-specific T cell function is not sufficient to terminate CVB3 infection in nu/nu mice. Also, it appears that competent cellular immunity, on the whole, plays a role in curing rather than in aggravating myocarditis in nu+mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

The management of constipation in end-stage disease.

A rectal examination may be considered an invasive intervention in a frail patient, but it is preferable to a blanket approach to treatment, which may be ineffective or do more harm than good, for example, giving antidiarroeals when the diarrhoea is spurious secondary to impaction, or continuing to soften soft faeces when in fact a stimulant laxative is required. The rectal examination can be modified to a gentle inspection. It should not need to be performed repeatedly if the regular regimen is altered according to the findings. This approach prevents the need for routine suppositories, enemas or manual evacuation. However, on the occasions that the above measures are unsuccessful, an enema may need to be employed. Microlax (containing osmotic agents such as sorbitol) is relatively well tolerated. Intractable cases may require a Clezy enema (a large volume enema that is prepared by a hospital pharmacist and contains the softeners: Paraffin oil 30 mL, Glycerine 30 mL, Enema soap 30 mL, and olive oil 60 mL, made up to 400 mL with water). If manual evacuation is contemplated, a pre-medication with midazolam 5 mg subcutaneously will give short sedation for this procedure.

Cathartics↗
PubMed1993

Massive covert infection of helper T lymphocytes and macrophages by HIV during the incubation period of AIDS.

Animal and human lentiviruses elude host defences by establishing covert infections and eventually cause disease through cumulative losses of cells that die with activation of viral gene expression. We used polymerase chain reaction in situ double-label methods to determine how many CD4+ lymphocytes are latently infected by human immunodeficiency virus (HIV) in patient lymph nodes and whether the pool of infected cells is large enough to account for immune depletion through continual activation of viral gene expression and attrition of cells responding to antigens. We discovered an extraordinarily large number of latently infected CD4+ lymphocytes and macrophages throughout the lymphoid system from early to late stages of infection, and confirmed the extracellular association of HIV with follicular dendritic cells. Follicular dendritic cells may transmit infection to cells as they migrate through lymphoid follicles. Latently infected lymphocytes and macrophages constitute an intracellular reservoir large enough ultimately to contribute to much of the immune depletion in AIDS, and represent a difficult problem that must be resolved in developing effective treatments and protective vaccine.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Analysis of human immunodeficiency virus-infected tissues by amplification and in situ hybridization reveals latent and permissive infections at single-cell resolution.

Latent and productive viral infections are at the extremes of the spectrum of virus-cell interactions that are thought to play a major role in the ability of such important human pathogens as human immunodeficiency virus (HIV) to elude host defenses and cause disease. The recent development of PCR-based methods to amplify target sequences in individual cells in routinely fixed tissues affords opportunities to directly examine the subtle and covert virus-cell relationships at the latent end of the spectrum that are inaccessible to analysis by conventional in situ hybridization techniques. We have now used PCR in situ with in situ hybridization to document latent and permissive HIV infection in routinely fixed and paraffin-embedded tissue. In one of the first specimens we examined, a tumor biopsy from an HIV-infected individual, we found many of the lymphocytes and lymphocytes infiltrating the tumor had HIV DNA that was detectable only by PCR in situ. The fraction of positive cells varied regionally, but there were foci where most of the cells contained HIV DNA. Most of these lymphocytes and macrophages are latently infected, as we could detect HIV RNA in fewer than one in a thousand of these cells. We also detected HIV RNA, surprisingly, in 6% of the tumor cells, where the number of copies of viral RNA per cell was equivalent to productively infected cell lines. The alternative states of HIV-gene expression and high local concentration of latently infected lymphocytes and monocytes revealed by these studies conceptually supports models of lentiviral pathogenesis that attribute persistence to the reservoir of latently infected cells and disease to the consequences of viral-gene expression in this population. The magnitude of infection of lymphocytes documented in this report is also consistent with the emerging view that HIV infection per se could contribute substantially to depletion of immune cells in AIDS.

Adenocarcinoma↗
PubMed1993

Inhibition of HIV infection by flavanoids.

Of a variety of flavanoids, the flavans were generally more effective than flavones and flavanones in selective inhibition of HIV-1, HIV-2 or SIV infection. Studies of their effects on the binding of sCD4 and antibody to gp120 indicated that the effective compounds interact irreversibly with gp120 to inactive virus infectivity and block infection.

CD4 Antigens↗
PubMed1993

Intestinal bile acid malabsorption in cystic fibrosis.

This study aimed at examining the mechanisms participating in excessive faecal bile acid loss in cystic fibrosis. The study was designed to define the relation between faecal fat and faecal bile acid loss in patients with and without cystic fibrosis related liver disease; to assess terminal ileal bile acid absorption by a seven day whole body retention of selenium labelled homotaurocholic acid (SeHCAT); and to determine if small intestinal bacterial overgrowth contributes to faecal bile acid loss. The study population comprised 40 patients (27 men; median age 18 years) with cystic fibrosis (n = 8) and without (n = 32) liver disease and eight control subjects. Faecal bile acid excretion was significantly higher in cystic fibrosis patients without liver disease compared with control subjects (mean (SEM) 21.5 (2.4) and 7.3 (1.2) micromoles/kg/24 hours respectively; p < 0.01) and patients with liver disease (7.9 (1.3) micromoles/kg/24 hours; p < 0.01). No correlation was found between faecal fat (g fat/24 hours) and faecal bile acid (micromoles 24 hours) excretion. Eight (33%) of cystic fibrosis patients had seven day SeHCAT retention < 10% (normal retention > 20%). SeHCAT retention in cystic fibrosis patients with liver disease was comparable with control subjects (30.0 (SEM) 8.3% v 36.8 (5.9)%; p = NS) while SeHCAT retention in cystic fibrosis patients who did not have liver disease was significantly reduced (19.9 (3.8); p < 0.05). Although evidence of small bowel bacterial overgrowth was present in 40% of patients no relation was found between breath hydrogen excretion, faecal fat, and faecal bile acid loss. The results are consistent with the presence of an abnormality in terminal ideal function in patients with cystic fibrosis who do not have liver disease and that a defect in the ileal absorption of bile acids may be a contributory factor to excessive faecal bile acid loss. Faecal bile acid loss in cystic fibrosis is unrelated to the presence of intraluminal fat or intestinal bacterial overgrowth.

Adolescent↗
PubMed1992

Susceptibility of an emetine-resistant mutant of Entamoeba histolytica to multiple drugs and to channel blockers.

Previously a cloned emetine-resistant mutant of the protozoal parasite Entamoeba histolytica was shown to overexpress a gene for an ameba homolog of the mammalian P-glycoprotein, a plasma membrane pump that removes hydrophobic drugs from multidrug-resistant tumor cells. Three sets of experiments were performed to better characterize the multidrug-resistant phenotype of the emetine-resistant amebae. First, the emetine resistance of the mutant amebae was reversed by concentrations of calcium and sodium channel blockers effective in reversing drug resistance by multidrug-resistant tumor cells, but it was reversed only in the presence of very high concentrations of the tricyclic antidepressants. Second, the mutant amebae showed cross-resistance to antiamebic drugs used to treat luminal infection (iodoquinol and diloxanide) but were not cross-resistant to drugs used to treat invasive disease (chloroquine and metronidazole). Third, when amebae were loaded with radiolabeled emetine, the mutant parasites released the drug at approximately 1.6 times the rate of the wild-type organisms. We conclude that the emetine-resistant E. histolytica parasites have some but not all the features of the multidrug-resistant phenotype.

Animals↗
PubMed1992

Remembering emotional events.

Recent experiments have implied that emotional arousal causes a narrowing of attention and, therefore, impoverished memory encoding. In contrast, other studies have found that emotional arousal enhances memory for all aspects of an event. We report two experiments investigating whether these differing results are due to the different retention intervals employed in past studies or to their different categorization schemes for the to-be-remembered material. Our results indicate a small role for retention interval in moderating emotion's effects on memory. However, emotion had markedly different impacts on different types of material: Emotion improved memory for gist and basic-level visual information and for plot-irrelevant details associated, both temporally and spatially, with the event's center. In contrast, emotion undermined memory for details not associated with the event's center. The mechanisms for emotion's effects are discussed.

Adult↗
PubMed1991

Diarrheal disease during Operation Desert Shield.

BACKGROUND: Under combat conditions infectious disease can become a major threat to military forces. During Operation Desert Shield, there were numerous outbreaks of diarrhea among the U.S. forces. To evaluate the causes of and risk factors for diarrheal disease, we collected clinical and epidemiologic data from U.S. troops stationed in northeastern Saudi Arabia. METHODS: Between September and December 1990, stool cultures for enteric pathogens were obtained from 432 military personnel who presented with diarrhea, cramps, vomiting, or hematochezia. In addition, a questionnaire was administered to 2022 soldiers in U.S. military units located in various regions of Saudi Arabia. RESULTS: A bacterial enteric pathogen was identified in 49.5 percent of the troops with gastroenteritis. Enterotoxigenic Escherichia coli and Shigella sonnei were the most common bacterial pathogens. Of 125 E. coli infections, 39 percent were resistant to trimethoprim-sulfamethoxazole, 63 percent to tetracycline, and 48 percent to ampicillin. Of 113 shigella infections, 85 percent were resistant to trimethoprim-sulfamethoxazole, 68 percent to tetracycline, and 21 percent to ampicillin. All bacterial isolates were sensitive to norfloxacin and ciprofloxacin. After an average of two months in Saudi Arabia, 57 percent of the surveyed troops had at least one episode of diarrhea, and 20 percent reported that they were temporarily unable to carry out their duties because of diarrheal symptoms. Vomiting was infrequently reported as a primary symptom, but of 11 military personnel in whom vomiting was a major symptom, 9 (82 percent) had serologic evidence of infection with the Norwalk virus. CONCLUSIONS: Gastroenteritis caused by enterotoxigenic E. coli and shigella resistant to a number of drugs was a major problem that frequently interfered with the duties of U.S. troops during Operation Desert Shield.

Adolescent↗
PubMed1991

The inhibitory activity of a peptide derivative against the growth of simian immunodeficiency virus in C8166 cells.

The peptide derivative Ro 31-8959 is a potent and selective inhibitor of the aspartic proteinases encoded by HIV-1 and HIV-2 and it arrests the growth of both viruses in cell culture. We have demonstrated similar effects against the simian immunodeficiency virus SIVmac251 in the human T-cell line, C8166 (ED50 = 6nM) with a therapeutic index of 4,500. The antiviral activity of Ro 31-8959 was 250 and 22 times greater than that of ddI and ddC, respectively. The mode of action was confirmed by accumulation of the polyprotein p55 with concomitant reduction of the cleavage product, p27, and by the production of immature virions.

Animals↗
PubMed1991

Spreading the message. Building a general consensus on the environment.

In communicating an environmental message to society at large, it is useful to distinguish between decision-makers and the general public. The influence of decision-makers on public debates is as significant as their ability to implement decisions; in democratic societies, the two functions are inseparable. Proceeding from an environmental consensus, physicians can provide a source of impartial medical/ecological wisdom, and serve as mediators of public debates. For those purposes, a network of physicians and/or scientists can be useful; three examples are provided. Communicating to the general public can only be achieved economically through the mass news media, which operate under conditions very different from those of physicians and scientists. There is considerable room for improvement in environmental journalism, and physicians can make a useful contribution to any such process. It is an important issue, since the mass media constitute the 'ecology textbook' of the general public.

Ecology↗
PubMed1990

Hemangiomas of the heart. A clinicopathologic study of ten cases.

The clinical and histopathologic features of 10 cardiac hemangiomas are presented. The patients' ages ranged from 2 weeks to 65 years (mean: 32 years). Eight patients had no other cardiovascular abnormalities, one was associated with intra-atrial lipoma, and one was associated with an anomalous origin of the left coronary artery. One patient had other hemangiomas of the oral cavity and small intestine. The tumors presented as pericardial effusion (2), sudden death (2), shortness of breath (1), incidental finding on chest X-ray (1), asymptomatic murmur (1), syncope (1), and incidental finding at autopsy (2). Location of the tumors included the right ventricle (4), left ventricle (3), atrial septum (2), and right atrium (1). All six tumors presenting in life were resected successfully, one requiring placement of a synthetic graft. Cardiac hemangiomas are usually sporadic; presenting symptoms depend on location in the heart; arrhythmias or sudden death can occur if the tumor is present in the basal region of the ventricular septum; surgical resection is feasible in other locations.

Adolescent↗
PubMed1989

The effects of method of presenting health plan information on HMO enrollment by Medicaid beneficiaries.

Marketing strategies are critical for enhancing HMO enrollments among Medicaid beneficiaries when they are provided a choice of health plans. This study examined one component of marketing HMOs--the method of communicating the HMO's attributes. The purpose of the analysis was to determine if characteristics of Medicaid beneficiaries who enroll in HMOs vary by method of communicating information about health plan options. Data were analyzed from the marketing component of California's Prepaid Health Research, Evaluation, and Demonstration (PHRED) project. Five communication methods are examined in the article: brochure, film, county eligibility worker presentation, state representative presentation, and HMO representative presentation. The analysis reveals that each communication method is most effective with a different type of beneficiary. No single consumer characteristic is related to HMO enrollment across all five methods, although lack of a private physician and dissatisfaction with a current provider are associated with choice in four methods. Film is the best method for attracting persons who have an ongoing relationship with a provider.

Adult↗