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Biomedical subjects

R A Larsen

Publications and source records attributed to R A Larsen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Itraconazole treatment of disseminated histoplasmosis in patients with the acquired immunodeficiency syndrome. AIDS Clinical Trial Group.

PURPOSE: Amphotericin B has been the treatment of choice for disseminated histoplasmosis in patients with acquired immunodeficiency syndrome (AIDS). Oral antifungal agents would be welcome alternatives to standard treatment of disseminated histoplasmosis in less severe cases. The purpose of this study was to assess the efficacy and safety of itraconazole therapy in patients with AIDS and disseminated histoplasmosis. PATIENTS AND METHODS: This was a multicenter, open-label, nonrandomized prospective trial conducted in university hospitals of the AIDS Clinical Trial Group. All patients had AIDS and first episodes of disseminated histoplasmosis. Patients with central nervous system involvement or with severe clinical manifestations were excluded. Patients were treated with itraconazole BID by mouth 300 mg for 3 days and then 200 mg BID for 12 weeks. Resolution of clinical findings, clearance of positive cultures, and drug tolerance were the main outcome measurements. A secondary objective was effect of therapy on Histoplasma capsulatum var capsulatum antigen levels. RESULTS: Of 59 evaluable patients, 50 (85%) responded to therapy. Five patients withdrew because of progressive infection, 1 died of a presumed pulmonary embolus within the first week of therapy without improvement, 2 withdrew because of toxicity, and 1 was lost to follow-up after week 2 of therapy. Patients with moderately severe clinical (fever > 39.5 degrees C or Karnofsky score < 60) or laboratory abnormalities (alkaline phosphatase > 5 times normal or albumin < 3 g/dL) at baseline tended to respond more poorly than did other patients. Resolution of complaints of fever and improvement in fatigue occurred after a median of 3 and 6 weeks, respectively, and weight gain after 2 weeks. Fungemia cleared after a median of 1 week. H capsulatum var capsulatum antigen cleared from the urine and serum at rates of 0.2 and 0.3 units per week, respectively. CONCLUSIONS: Itraconazole is safe and effective induction therapy for mild disseminated histoplasmosis in patients with AIDS, offering an alternative to amphotericin B in such cases. Patients with moderately severe or severe histoplasmosis should first be treated with amphotericin B and then may be switched to itraconazole after achieving clinical improvement.

AIDS-Related Opportunistic Infections↗
PubMed1995

Characterization of the exbBD operon of Escherichia coli and the role of ExbB and ExbD in TonB function and stability.

TonB protein appears to couple the electrochemical potential of the cytoplasmic membrane to active transport across the essentially unenergized outer membrane of gram-negative bacteria. ExbB protein has been identified as an auxiliary protein in this process. In this paper we show that ExbD protein, encoded by an adjacent gene in the exb cluster at 65', was also required for TonB-dependent energy transduction and, like ExbB, was required for the stability of TonB. The phenotypes of exbB exbD+ strains were essentially indistinguishable from the phenotypes of exbB+ exbD strains. Mutations in either gene resulted in the degradation of TonB protein and in decreased, but not entirely absent, sensitivities to colicins B and Ia and to bacteriophage phi 80. Evidence that the absence of ExbB or ExbD differentially affected the half-lives of newly synthesized and steady-state TonB was obtained. In the absence of ExbB or ExbD, newly synthesized TonB was degraded with a half-life of 5 to 10 min, while the half-life of TonB under steady-state conditions was significantly longer, approximately 30 min. These results were consistent with the idea that ExbB and ExbD play roles in the assembly of TonB into an energy-transducing complex. While interaction between TonB and ExbD was suggested by the effect of ExbD on TonB stability, interaction of ExbD with TonB was detected by neither in vivo cross-linking assays nor genetic tests for competition. Assays of a chromosomally encoded exbD::phoA fusion showed that exbB and exbD were transcribed as an operon, such that ExbD-PhoA levels in an exbB::Tn10 strain were reduced to 4% of the levels observed in an exbB+ strain under iron-limiting conditions. Residual ExbD-PhoA expression in an exbB::Tn10 strain was not iron regulated and may have originated from within the Tn10 element in exbB.

Alkaline Phosphatase↗
PubMed1994

Treatment of coccidioidomycosis with SCH 39304.

A new oral triazole antifungal, SCH 39304, was administered to 54 patients with progressive infections due to Coccidioides immitis from six collaborating centers. Patients were grouped according to site of infection including chronic pulmonary (25), bone/joint (17) and skin/soft tissue (12). The median age was 40 years; 83% were male, 52% white, 13% HIV-infected and 35% had failed previous therapy. The majority of patients were treated with either 100 mg or 200 mg day-1. One patient on renal dialysis received 300 mg day-1. Baseline abnormalities were reassessed for evidence of efficacy every 4 months and expressed in a standardized scoring system. Cumulative overall response rates at 4, 8 and 12 months were 7%, 36% and 66% respectively. Twelve month response rates by disease were 77% (pulmonary), 62% (skin/soft tissue) and 31% (bone/joint). Fifteen patients failed therapy although seven of these were still on treatment when the study was discontinued. Two failed due to toxicity. Possible symptoms or signs of toxicity occurred in 24 (44%) patients and were generally mild. SCH 39304 is an effective and well tolerated therapy for progressive forms of coccidioidomycosis.

Administration, Oral↗
PubMed1994

Evaluation of neurosyphilis in human immunodeficiency virus-infected individuals.

The diagnosis of neurosyphilis in patients infected with the human immunodeficiency virus (HIV) remains problematic. We examined the use of the Treponema pallidum hemagglutination (TPHA) index and quantitative tests of CSF by means of microhemagglutination-T. pallidum for diagnosis of neurosyphilis in 58 HIV-infected persons with latent syphilis who had not recently received therapy for syphilis. Five patients (9%) had reactive CSF VDRL tests and thus had proven neurosyphilis. For 13 patients (22%), CSF findings were normal and revealed no evidence of neurosyphilis. For 40 patients (69%), abnormal CSF findings were characteristic of neurosyphilis, but their CSF VDRL tests were nonreactive. Twenty-five of the 40 patients with possible neurosyphilis had pleocytosis and elevated CSF levels of protein and/or IgG. Five (12.5%) of these 40 patients had positive TPHA indices that indicated intrathecal antitreponemal antibody production, a finding that provided greater support for the diagnosis of active neurosyphilis. With use of the TPHA index, patients with CSF abnormalities can be better classified in regard to their need for therapy for neurosyphilis.

Adult↗
PubMed1994

Fluconazole combined with flucytosine for treatment of cryptococcal meningitis in patients with AIDS.

Treatment of cryptococcal meningitis with amphotericin B or fluconazole is often unsuccessful; in only 35%-40% of cases do CSF cultures become negative by 10 weeks after initiation of such therapy. We conducted a prospective, open-label clinical trial involving persons with AIDS to determine whether the rate of clinical success would improve when fluconazole (400 mg daily) was combined with flucytosine (150 mg/kg daily). At the conclusion of 10 weeks of therapy, 75% (95% confidence interval, 58%-87%) of 32 subjects' CSF cultures were negative. The Kaplan-Meier estimate of clinical success at 10 weeks was 63% (95% confidence interval, 48%-82%). The median time to negativity of the CSF culture was 23 days. Toxic side effects that were sufficiently severe to lead to the withdrawal of flucytosine were observed in nine subjects (28%). In this pilot study of fluconazole combined with flucytosine, the rate of clinical success at 10 weeks was greater than that previously reported with regard to the use of fluconazole alone or amphotericin B alone.

AIDS-Related Opportunistic Infections↗
PubMed1994

Partial suppression of an Escherichia coli TonB transmembrane domain mutation (delta V17) by a missense mutation in ExbB.

Active transport of vitamin B12 and Fe(III)-siderophore complexes across the outer membrane of Escherichia coli appears to be dependent upon the ability of the TonB protein to couple cytoplasmic membrane-generated protonmotive force to outer membrane receptors. TonB is supported in this role by an auxiliary protein, ExbB, which, in addition to stabilizing TonB against the activities of endogenous envelope proteases, directly contributes to the energy transduction process. The topological partitioning of TonB and ExbB to either side of the cytoplasmic membrane restricts the sites of interaction between these proteins primarily to their transmembrane domains. In this study, deletion of valine 17 within the aminoterminal transmembrane anchor of TonB resulted in complete loss of TonB activity, as well as loss of detectable in vivo crosslinking into a 59 kDa complex believed to contain ExbB. The delta V17 mutation had no effect on TonB export. The loss of crosslinking appeared to reflect conformational changes in the TonB/ExbB pair rather than loss of interaction since ExbB was still required for some stabilization of TonB delta V17. Molecular modeling suggested that the delta V17 mutation caused a significant change in the predicted conserved face of the TonB amino-terminal membrane anchor. TonB delta V17 was unable to achieve the 23 kDa proteinase K-resistant form in lysed sphaeroplasts that is characteristic of active TonB. Wild-type TonB also failed to achieve the proteinase K-resistant configuration when ExbB was absent. Taken together these results suggested that the delta V17 mutation interrupted productive TonB-ExbB interactions. The apparent ability to crosslink to ExbB as well as a limited ability to transduce energy were restored by a second mutation (A39E) in or near the first predicted transmembrane domain of the ExbB protein. Consistent with the weak suppression, a 23 kDa proteinase K-resistant form of TonB delta V17 was not observed in the presence of ExbBA39E. Neither the ExbBA39E allele nor the absence of ExbB affected TonB or TonB delta V17 export. Unlike the tonB delta V17 mutation, the exbBA39E mutation did not greatly alter a modelled ExbB transmembrane domain structure. Furthermore, the suppressor ExbBA39E functioned normally with wild-type TonB, suggesting that the suppressor was not allele specific. Contrary to expectations, the TonB delta V17, ExbBA39E pair resulted in a TonB with a greatly reduced half-life (approximately 10 min). These results together with protease susceptibility studies suggest that ExbB functions by modulating the conformation of TonB.

Amino Acid Sequence↗
PubMed1993

Fluconazole therapy for coccidioidal meningitis. The NIAID-Mycoses Study Group.

OBJECTIVE: To determine the efficacy and safety of fluconazole treatment of coccidioidal meningitis. DESIGN: Uncontrolled clinical trial. SETTING: Four university-based treatment centers in California, Arizona, and Texas. Most therapy was conducted without hospitalization. PATIENTS: Fifty consecutive patients with active coccidioidal meningitis, of which 47 (94%) were evaluable. Twenty-five patients had received no previous treatment for their meningitis, and nine had coinfection with human immunodeficiency virus (HIV). INTERVENTION: Fluconazole was administered in an oral dose of 400 mg once per day for up to 4 years (median, 37 months) in responding patients. Concurrent therapy with another antifungal agent was prohibited. MEASUREMENTS: Predefined assessment of infection-related abnormalities was done at the time of enrollment and was repeated at least every 4 months during treatment. Elimination of 40% or more of baseline abnormalities was considered a response. RESULTS: Thirty-seven of 47 (79%; 95% CI, 61% to 90%) evaluable patients responded to treatment. Response rates were similar for patients with and without previous therapy, for patients with and without concomitant HIV infection, and for patients with and without pre-existing hydrocephalus. Most improvement occurred within 4 to 8 months after starting treatment. Patient symptoms resolved more quickly than did cerebrospinal fluid abnormalities. In 15 of 20 responding patients followed for 20 months or more, residual low-level cerebrospinal fluid abnormalities remained throughout therapy. No patient discontinued therapy because of drug-related side effects, although confusion developed in two patients that resolved when the dose of fluconazole was reduced. CONCLUSION: Fluconazole therapy is often effective in suppressing coccidioidal meningitis.

AIDS-Related Opportunistic Infections↗
PubMed1993

Catastrophic visual loss due to Cryptococcus neoformans meningitis.

We have reviewed our experience with 17 of our own patients with cryptococcal meningitis and 32 cases from the literature. Although this complication is an uncommon event, patients with cryptococcal meningitis may develop visual loss in the absence of other ocular lesions (endophthalmitis or cryptococcomas in the visual pathway) that could explain the visual symptoms. There are 2 distinct patterns of visual loss: rapid visual loss and slow visual loss. Rapid visual loss is characterized by onset of profound visual loss over a period as short as 12 hours before or early in the course of therapy and a clinical syndrome that is strongly suggestive of optic neuritis. Direct invasion of the optic nerve by C. neoformans is demonstrated by cases in this and other reports. Slow visual loss is characterized by slow but progressive visual loss which typically begins later during therapy and may be due to the effects of increased intracranial pressure. While the initial deficit may be mild, patients with slow visual loss can progress to severe visual loss over weeks to months. The only factors that appear to predict either pattern of visual loss are the presence of papilledema, an elevated CSF opening pressure, and a positive CSF India ink preparation. In the 25 visual loss patients for whom data were available for all 3 items, 10 (40%) were positive for all 3, as opposed to only 4 of 114 (3.5%) from a reference group of cryptococcal meningitis patients without visual loss (p < 0.00001). The only therapeutic measures with any degree of consistent success were those directed at reducing intracranial pressure. When begun early and used aggressively, such therapy halted and sometimes even reversed the course of visual loss, particularly in the slow visual loss group. Corticosteroids did not appear to be of value in the small number of patients who received them.

Adolescent↗
PubMed1993

The conserved proline-rich motif is not essential for energy transduction by Escherichia coli TonB protein.

TonB protein functions as an energy transducer, coupling cytoplasmic membrane electrochemical potential to the active transport of vitamin B12 and Fe(III)-siderophore complexes across the outer membrane of Escherichia coli and other Gram-negative bacteria. Accumulated evidence indicates that TonB is anchored in the cytoplasm, but spans the periplasmic space to interact physically with outer membrane receptors. It has been presumed that this ability is caused by a conserved (Glu-Pro)n-(Lys-Pro)m repeat motif, predicted to assume a rigid, linear conformation of sufficient length to reach the outer membrane. Based on in vitro studies with synthetic peptides and purified FhuA outer membrane receptor, it has been suggested that this region contains a site that directly binds outer membrane receptors and is essential for energy transduction. We have found a TonB lacking the (Glu-Pro)n-(Lys-Pro)m repeat motif (TonB delta(66-100)). TonB delta(66-100) is fully capable of irreversible phi 80 adsorption, except under physiological circumstances where the periplasmic space is expanded. Based on the ability of TonB delta(66-100) to interact with outer membrane receptors and components of the energy transduction apparatus under normal physiological conditions, it is evident that the TonB proline-rich region has no role in energy transduction other than to provide a physical extension sufficient to reach the outer membrane.

Amino Acid Sequence↗
PubMed1992

Control of alkaline phosphatase activity in C3H10T1/2 cells: role of retinoic acid and cell density.

The enzyme alkaline phosphatase (AP) has been shown to be lost or inappropriately expressed during carcinogenesis in some tissues. Because retinoic acid (RA) appears to play a role in the normal regulation of the enzyme (RA up-regulates AP in a variety of cell types) we have suggested that altered AP expression in some cancers may be caused by a defect in the ability of the cells to respond normally to retinoid. We have begun to use the chemically transformable mouse embryo fibroblast cell, C3H10T1/2, to investigate this possibility. In this initial study we characterized AP regulation in normal C3H10T1/2 cells and show that: (1) 10(-7) M RA increases AP activity within 3-4 h in serum-free medium; (2) serum inhibits short-term induction (0-8 h) in a concentration-dependent manner (10% serum causes complete inhibition); (3) during long-term RA exposure (24 h and 48 h), induction can be detected in serum-containing medium; (4) AP induction is dose related at RA concentrations from 10(-10) M to 10(-6) M in serum-free medium; (5) 10(-5) M RA is ineffective at inducing AP in serum-free medium during 8 h but is the most effective concentration in serum-containing medium during 24 h and 48 h exposures; (6) AP inducibility by RA requires near-confluent cell densities; and (7) when cultures become confluent, cells become constitutive for AP and no longer require RA for enzyme expression. The effects of serum and cell density on AP inducibility by RA and implications of the RA up-regulation of AP for teratogenesis are discussed.

Alkaline Phosphatase↗
PubMed1992

Tuberculous meningitis in patients with and without human immunodeficiency virus infection.

OBJECTIVE: To characterize the symptoms, signs, laboratory findings, and outcome of culture-proven meningitis due to Mycobacterium tuberculosis in patients with and without human immunodeficiency virus (HIV) infection. DESIGN: Retrospective chart review. SETTING: Urban public general hospital in the United States. PATIENTS: Fifteen patients with and 16 without HIV infection. MEASUREMENTS: Demographics, symptoms, physical exam findings, serum sodium, complete blood cell count, CD4+ cell count, cerebrospinal fluid findings, imaging data, and in-hospital mortality. MAIN RESULTS: Symptoms, signs, chest radiograph appearance, cerebrospinal fluid cell counts and chemistries, and mortality were similar in both groups (p = NS). Median CD4+ cell counts were lower in HIV-infected patients (median 99/mm3, range 7 to 251, versus 384/mm3, range 171 to 724 in those without HIV infection, p = 0.007). Intracerebral mass lesions were more common in the HIV-infected group (60% versus 14% in the uninfected group, p = 0.01), although the presence of a mass did not correlate with focal neurologic deficits, altered level of consciousness, or mortality. CONCLUSION: With the exception of an increased incidence of intracerebral mass lesions in HIV-infected individuals, HIV infection appears to have little impact on the findings and in-hospital mortality of tuberculous meningitis.

AIDS-Related Opportunistic Infections↗
PubMed1992

Prevalence of neurosyphilis in human immunodeficiency virus-infected patients with latent syphilis.

PURPOSE: A prospective study was done to determine the prevalence of confirmed neurosyphilis (cerebrospinal fluid [CSF] Venereal Disease Research Laboratory [VDRL]-reactive) in human immunodeficiency virus (HIV)-infected patients with latent syphilis (reactive serum rapid plasma reagin [RPR] and microhemagglutination-Treponema pallidum [MHA-TP]). PATIENTS AND METHODS: All HIV-infected patients seen for their first visit at the Los Angeles County/University of Southern California Medical Center AIDS Clinic from June through December 1990 were screened for latent syphilis. Those with reactive serum RPRs and MHA-TPs who had not received recent (within 6 months) therapy for syphilis were offered diagnostic CSF sampling. RESULTS: A total of 312 patients were screened, of whom 71 (22.8%) had reactive serum RPRs and MHA-TPs. Thirty-three of these patients (47%) had diagnostic CSF sampling (26 refused lumbar puncture or were lost to follow-up; 12 had had recent therapy for syphilis and thus did not have CSF sampling). Among the 33 patients who had CSF sampling, 20 (60.6%) had normal CSF profiles (white blood cell count less than 8/mm3; protein less than 0.60 g/L; glucose greater than 2.8 mmol/L) and nonreactive CSF VDRLs. Ten of the 33 patients (30.3%) had abnormal CSF profiles and nonreactive CSF VDRLs, and three of 33 (9.1%) had reactive CSF VDRLs. CONCLUSIONS: Asymptomatic neurosyphilis was found in 9.1% of our patient population undergoing CSF sampling, giving a 1.0% prevalence of CSF VDRL-reactive neurosyphilis in the population we screened. The abnormal CSF findings may have been due to either nonreactive CSF VDRL neurosyphilis, central nervous system infection with HIV, or infection with some unrecognized agent.

Adult↗
PubMed1992

Abdominal angiostrongyliasis mimicking acute appendicitis and Meckel's diverticulum: report of a case in the United States and review.

Two cases of children with abdominal angiostrongyliasis acquired within the United States are reported. The index patient presented with complaints consistent with appendicitis, but at surgery findings were thought to represent an atypical presentation of a Meckel's diverticulum. His sole sibling (sister) had eosinophilia, no other intestinal parasites on fecal examination, and a positive serologic test, all suggesting infection with Angiostrongylus costaricensis. Because infections with this parasite are not known to result from human-to-human transmission, his sister's infection represents a second case.

Acute Disease↗
PubMed1992

Randomized trial of meatal care with silver sulfadiazine cream for the prevention of catheter-associated bacteriuria.

A randomized, controlled, prospective clinical trial involving 696 hospitalized patients was undertaken to determine the effectiveness of 1% silver sulfadiazine cream applied twice daily to the urethral meatus in preventing transurethral catheter-associated bacteriuria. The overall incidence of bacteriuria was 11.4% (38/332) in the treated group and 13.2% (48/364) in the untreated group (P = .56; odds ratio, 0.85; 95% confidence interval, 0.53-1.37). Cox proportional hazards analysis identified female sex, lack of antibiotic use, and a positive initial meatal culture (but not treatment randomization or lack of urinemeter use) as independent variables associated with an increased risk of bacteriuria. Survival curve analysis of subgroups stratified by sex and antibiotic use failed to detect an effect of silver sulfadiazine on the rate of bacteriuria. Meatal care with silver sulfadiazine cream did not prevent the development of catheter-associated bacteriuria in short-term catheterized patients.

Administration, Topical↗