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Biomedical subjects

B Efron

Publications and source records attributed to B Efron.

16 recordsLinked to original sources
PubMed1999

Resistance mutations to zidovudine and saquinavir in patients receiving zidovudine plus saquinavir or zidovudine and zalcitabine plus saquinavir in AIDS clinical trials group 229.

The relationships among treatment regimens, plasma human immunodeficiency virus (HIV) RNA levels, and resistance mutations to saquinavir (codons 48 and 90) and zidovudine (codon 215) were examined in a cohort of 144 patients from the AIDS Clinical Trials Group 229 study. After 24-40 weeks of therapy, no patients who had received the two-drug combination (zidovudine plus saquinavir) had only codon 48 mutations, 45.8% had only codon 90 mutations, and 8.3% had both codon 48 and 90 mutations. Mutations developed by patients who had received the three-drug combination (zidovudine and zalcitabine plus saquinavir) were codon 48 alone in 1.4%, codon 90 alone in 33.3%, and both codons 48 and 90 in 4.2%. The difference between the groups showed a trend toward reduced mutations with three versus two drugs but did not reach significance (P=.11, two-sided chi2). Higher baseline HIV RNA levels correlated with the development of protease mutations. Mutations at codon 215 were present in 82% of all patients at baseline and in 87% after therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Clinical resistance patterns and responses to two sequential protease inhibitor regimens in saquinavir and reverse transcriptase inhibitor-experienced persons.

The efficacy of sequential protease inhibitor therapy was studied in 16 human immunodeficiency virus (HIV) 1-infected persons in whom saquinavir with multiple nucleoside reverse transcriptase (RT) inhibitors (NRTI) had failed. Nelfinavir plus two NRTIs (new or continued) resulted in minimal (0.59 log RNA copies/mL) and transient (8 weeks) suppression of plasma HIV RNA levels. Rapid failure was surprisingly associated with baseline presence of protease gene mutation L90M (P=.04) in the absence of D30N and with RT mutations D67N (P<.01), K70R/S (P=.02), and K219Q/W/R/E (P<.01). Ten patients were subsequently switched to indinavir plus nevirapine and 2 NRTIs, resulting in a median 1.62 log reduction in plasma HIV RNA, with 3 patients maintaining 400 copies/mL for 24 weeks. These results suggest that nelfinavir may have limited utility after saquinavir failure, particularly without potent concomitant therapy. Combining an NRTI with a new protease inhibitor for rescue may improve response.

Adult↗
PubMed1997

A predictive morphometric model for the obstructive sleep apnea syndrome.

BACKGROUND: Mathematical formulas have been used to clinically predict whether patients will develop the obstructive sleep apnea syndrome (OSAS). However, these models do not take into account the disproportionate craniofacial anatomy that accompanies OSAS independently of obesity. OBJECTIVE: To determine the accuracy of a morphometric model, which combines measurements of the oral cavity with body mass index and neck circumference, in predicting whether a patient has OSAS. DESIGN: 6-month prospective study. SETTING: University-based tertiary referral sleep clinic and research center. PARTICIPANTS: 300 consecutive patients evaluated for sleep disorders for the first time. MEASUREMENTS: Body mass index, neck circumference, and oral cavity measurements were obtained, and a model value was calculated for each patient. Polysomnography was used to determine the number of abnormal respiratory events that occurred during sleep. Sleep apnea was defined as more than five episodes of apnea or hypopnea per hour of sleep. RESULTS: The morphometric model had a sensitivity of 97.6% (95% CI, 95% to 98.9%), a specificity of 100% (CI 92% to 100%), a positive predictive value of 100% (CI, 98.5% to 100%), and a negative predictive value of 88.5% (CI, 77% to 95%). No significant discrepancies were revealed in tests of intermeasurer and test-retest reliability. CONCLUSIONS: The morphometric model provides a rapid, accurate, and reproducible method for predicting whether patients in an ambulatory setting have OSAS. The model may be clinically useful as a screening tool for OSAS rather than as a replacement for polysomnography.

Adolescent↗
PubMed1997

Effect of therapeutic immunization with recombinant gp160 HIV-1 vaccine on HIV-1 proviral DNA and plasma RNA: relationship to cellular immune responses.

Therapeutic vaccination has been proposed as a strategy to augment immune mechanisms to control viral replication and slow clinical progression of HIV infection to disease. Following recombinant gp160 (r-gp160) immunization in three clinical trials, plasma HIV-1 RNA and cellular proviral DNA were assessed by quantitative polymerase chain reaction (PCR) in 76 HIV-seropositive subjects with CD4+ T cell counts > or = 300/mm3. Immunization increased HIV-specific cellular immune responses (e.g., cytotoxic T lymphocyte [CTL] activities, lymphocyte proliferative responses); however, there were no significant effects of immunization or cellular immune responses on measures of plasma RNA or cellular DNA viral load.

AIDS Vaccines↗
PubMed1997

Risk for retinitis in patients with AIDS can be assessed by quantitation of threshold levels of cytomegalovirus DNA burden in blood.

Cytomegalovirus (CMV) retinitis in patients infected with human immunodeficiency virus (HIV) is a significant clinical problem. Seventy-five patients with CD4 T cell counts <100/mm3 were monitored prospectively every 2 months for CMV DNA burden. The target for DNA amplification was a 162-bp fragment from the CMV immediate early gene. CMV DNA burden, at levels of > or =320 in white blood cells or > or =32 in plasma (P = .001), particularly when sustained (P = .005 and .008, respectively), distinguished patients who developed retinitis from those who remained free of disease. Progression to retinitis was not consistently accompanied by increases in CMV burden, indicating that quantitation of CMV burden beyond threshold levels is not necessary to predict risk for development of retinitis. Virus isolation from WBC, but not urine, was also significantly associated with risk for retinitis (P = .001).

Acquired Immunodeficiency Syndrome↗
PubMed1997

Circadian rhythms and enhanced athletic performance in the National Football League.

Circadian rhythms produce daily changes in critical elements of athletic performance. We explored the significance of performing at different circadian times in the National Football League (NFL) over the last 25 seasons. West Coast (WC) NFL teams should have a circadian advantage over East Coast (EC) teams during Monday Night Football (MNF) games because WC teams are essentially playing closer to the proposed peak athletic performance time of day. Retrospective data analysis was applied to all games involving WC versus EC teams playing on MNF with start times of 9:00 p.m. Eastern Standard Time (EST) from the 1970-1994 seasons. Logistic regression analysis of win-loss records relative to point spreads and home-field advantage was examined. West Coast teams win more often (p < 0.01) and by more points per game than EC teams. West Coast teams are performing significantly (p < 0.01) better than is predicted by the Las Vegas odds (the point spread). This apparent advantage enhances home-field advantage for WC teams and essentially eliminates the beneficial effects of home-field advantage for EC teams during MNF games. These results support the presence of an enhancement of athletic performance at certain circadian times of the day.

Circadian Rhythm↗
PubMed1996

Bootstrap confidence levels for phylogenetic trees.

Evolutionary trees are often estimated from DNA or RNA sequence data. How much confidence should we have in the estimated trees? In 1985, Felsenstein [Felsenstein, J. (1985) Evolution 39, 783-791] suggested the use of the bootstrap to answer this question. Felsenstein's method, which in concept is a straightforward application of the bootstrap, is widely used, but has been criticized as biased in the genetics literature. This paper concerns the use of the bootstrap in the tree problem. We show that Felsenstein's method is not biased, but that it can be corrected to better agree with standard ideas of confidence levels and hypothesis testing. These corrections can be made by using the more elaborate bootstrap method presented here, at the expense of considerably more computation.

Animals↗
PubMed1996

Bootstrap confidence levels for phylogenetic trees.

Evolutionary trees are often estimated from DNA or RNA sequence data. How much confidence should we have in the estimated trees? In 1985, Felsenstein [Felsenstein, J. (1985) Evolution 39, 783-791] suggested the use of the bootstrap to answer this question. Felsenstein's method, which in concept is a straightforward application of the bootstrap, is widely used, but has been criticized as biased in the genetics literature. This paper concerns the use of the bootstrap in the tree problem. We show that Felsenstein's method is not biased, but that it can be corrected to better agree with standard ideas of confidence levels and hypothesis testing. These corrections can be made by using the more elaborate bootstrap method presented here, at the expense of considerably more computation.

Algorithms↗
PubMed1996

The effect of high-dose saquinavir on viral load and CD4+ T-cell counts in HIV-infected patients.

OBJECTIVE: To evaluate the efficacy and safety of high-dose therapy with the human immunodeficiency virus (HIV) protease inhibitor saquinavir and to establish the duration of the effect of this therapy. DESIGN: Open-label study. SETTING: Clinical research referral center. PATIENTS: 40 adults with human immunodeficiency virus type 1 (HIV-1) infection and CD4+ T-cell counts of 200 to 500 cells/mm3. INTERVENTION: Monotherapy with 3600 mg or 7200 mg of saquinavir per day, in six divided doses, for 24 weeks. MEASUREMENTS: Patients were monitored for adverse events and were evaluated monthly for CD4+ T-cell count, HIV-1 viral load (as measured by reverse transcriptase polymerase chain reaction [PCR] for plasma HIV RNA levels), immune-complex-disassociated p24 antigen levels, peripheral blood mononuclear cell viral DNA levels (as measured by PCR), and resistance mutations to saquinavir. Quantitative peripheral blood mononuclear cell cultures were also done every 2 months. RESULTS: The low-dose saquinavir regimen (3600 mg/d) resulted in a maximal mean decrease in plasma HIV RNA levels of 1.06 log RNA copies/mL of plasma and a mean maximal increase in CD4 counts of 72 cells/mm3. At week 24, the plasma HIV RNA level remained 0.48 log RNA copies/mL of plasma lower than baseline (P < 0.001) and the CD4 count remained 31 cells/mm3 higher than baseline (P = 0.165). The high-dose saquinavir regimen (7200 mg/d) produced a mean maximal decrease in the plasma HIV RNA level of 1.34 log RNA copies/mL of plasma and a mean maximal increase in CD4 count of 121 cells/mm3. At week 24, the plasma HIV RNA level remained 0.85 log RNA copies/mL of plasma lower than baseline (P < 0.001) and the CD4 count remained 82 cells/mm3 higher than baseline (P = 0.002). The high-dose regimen produced a greater reduction in plasma HIV RNA level (P = 0.08), a greater reduction in peripheral blood mononuclear cell cultures (P = 0.008), and a greater increase in CD4 count (P = 0.002) than did the low-dose regimen. Higher plasma drug concentrations in individual patients correlated with greater reductions in plasma HIV RNA levels over the two doses. Nine patients receiving the low-dose regimen and four patients receiving the high-dose regimen developed key saquinavir resistance mutations. Adverse reactions, most commonly gastrointestinal problems and elevated serum aminotransferase levels, were more common in patients receiving the high-dose regimen, but most adverse events were mild and all were reversible. CONCLUSION: Saquinavir is a potent antiviral agent that has a favorable toxicity profile at high doses. Higher doses produce a greater and more durable suppression of viral load and elevation in CD4+ T-cell counts and may delay the development of resistance mutations. Therapy with high-dose saquinavir alone or in combination with other antiretroviral agents should be investigated further.

Adult↗
PubMed1994

Didanosine resistance in HIV-infected patients switched from zidovudine to didanosine monotherapy.

OBJECTIVE: To determine the frequency and pattern of development of specific drug resistance mutations for human immunodeficiency virus (HIV) reverse transcriptase in patients switched from zidovudine to didanosine therapy and to examine the relation of the didanosine resistance mutation at codon 74 of the HIV reverse-transcriptase gene to CD4+ T-cell changes and virus burden. DESIGN: Retrospective analysis of all patients enrolled at Stanford University in protocols where patients were switched from zidovudine to didanosine monotherapy. SETTING: A university hospital. PATIENTS: 64 patients infected with HIV who were switched from zidovudine to didanosine monotherapy. Patients had the acquired immunodeficiency syndrome (AIDS), AIDS-related complex, or were asymptomatic (mean [+/- SD] starting CD4+ T-cell count of 129 +/- 88 cells/mm3). MEASUREMENTS: Serial serum specimens were tested for the didanosine resistance mutation at codon 74 of the HIV reverse-transcriptase gene and for a zidovudine resistance mutation at codon 215 using selective polymerase chain reactions (PCR). Serum HIV RNA levels were determined by quantitative PCR. CD4+ T-cell counts were determined at serial time points. RESULTS: By 24 weeks of didanosine therapy, the proportion of patients with the didanosine resistance mutation at codon 74 increased from 0% to 56% (36 of 64). In contrast, the proportion of patients with the zidovudine resistance mutation at codon 215 decreased from 84% at the start to 59% after 24 weeks of didanosine therapy (a 25% decrease, 95% lower CI, 15%; P < 0.0001). Patients who developed the codon 74 mutation had a greater decrease in CD4+ T cells after the development of the mutation than did patients without the mutation (P < 0.001). In addition, after 24 weeks of didanosine, patients who developed the codon 74 mutation had a greater serum HIV RNA burden than patients who remained wild type (did not have the mutation) at codon 74 (225,000 compared with 82,400 HIV RNA copies/mL serum; P = 0.01). CONCLUSIONS: Among patients infected with HIV who had advanced disease and were switched from zidovudine to didanosine therapy, more than one half developed the didanosine resistance mutation at codon 74 by 24 weeks of didanosine therapy. Patients who developed the codon 74 mutation had a greater decline in CD4+ T cells after the development of the mutation and had a greater serum virus burden than did patients without the codon 74 mutation.

CD4-Positive T-Lymphocytes↗
PubMed1989

Prognostic indicators of laparotomy findings in clinical stage I-II supradiaphragmatic Hodgkin's disease.

Between July 1968 and July 1986, 915 patients with clinical stage (CS) I and II Hodgkin's disease limited to sites above the diaphragm underwent laparotomy and splenectomy at Stanford University. Fifteen percent were CS I, of whom 76% had cervical/supraclavicular disease, 13% axillary disease, and 9% mediastinal presentations. CS I patients were more likely to be male, were significantly older, and were significantly less likely to have nodular sclerosis (NS) histology than CS II patients. Twenty percent of CS I patients and 30% of CS II patients were pathologically upstaged. No CS I patients were upstaged to pathological stage (PS) IV. Univariate and multivariate analyses of presenting clinical characteristics were performed to predict staging laparotomy findings. CS I women, CS I patients with mediastinal-only disease, and CS I men with either lymphocyte predominance or interfollicular histologies were at low risk for having disease below the diaphragm (5%) or requiring chemotherapy (0%). CS II women who were less than 27 years old and had only two or three sites of disease were also at low risk for upstaging (9%) or requiring chemotherapy (2%). Mixed cellularity histology and male gender were associated with increased risk for subdiaphragmatic disease and require laparotomy; the presence of systemic symptoms was not correlated with laparotomy findings. These results confirm the importance of performing staging laparotomy for the majority of patients who present with supradiaphragmatic Hodgkin's disease if treatment programs are based on the presence and extent of subdiaphragmatic disease. Selected subgroups are at low risk for subdiaphragmatic disease and might be spared laparotomy if they are treated with mantle, paraaortic, and splenic irradiation.

Adolescent↗
PubMed1978

Radiation-induced inhibition of compensatory renal growth in the weanling mouse kidney.

Weanling mice were given 500, 1,000, 1,500, or 2,000 rads single-fraction renal irradiation immediately following unilateral nephrectomy and sacrificed 3 days or 3, 6, 12, or 24 weeks later. Inhibition of compensatory renal growth was related to both radiation dose and time following treatment; it was transient following 500 and 1,000 rads but persisted following 1,500 and 2,000 rads. Renal growth was inhibited more than body growth. These studies indicate that the weanling mouse kidney is more sensitive to radiation-induced inhibition of compensatory renal growth than adult mice or other rodents.

Adaptation, Physiological↗
PubMed1975

The possible prognostic usefulness of assessing serum proteins and cholesterol in malignancy.

Serial measurement of serum proteins, albumin, and cholesterol levels was used in attempt to assess the course and prognosis in cancer patients. This assessment is based on the fact that their declines followed first order kinetics and that these patients usually died when their levels were lower than half the initial levels. Two categories of cancer patients were identified: those in whom the initial measurements of serum albumin or cholersterol, taken soon after diagnosis, were declining (Group I), and those who showed such a decline as they entered an advanced or terminal phase (Group II). Group I included cancer of the stomach, kidney, lung (adenocarcinoma and squamous cell carcinoma), oral cavity, large intestine, breast (40%), bladder, ovary (70%), pancreas, and prostate; leukemia (acute myeloid and lymphocytic); and Hodgkin's disease (60%), all of which accounted for approximately 90% of the major causes of cancer deaths. Group II included Hodgkin's disease (40%), and cancer of the ovary (30%) and breast (60%), all of which accounted for 10% of the major causes of cancer deaths.

Adenocarcinoma↗