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Biomedical subjects

M B Weiss

Publications and source records attributed to M B Weiss.

At least 19 recordsLinked to original sources
PubMed2006

Persistent mismatch repair deficiency following targeted correction of hMLH1.

The use of gene therapy to correct mutated or lost gene function for the treatment of human cancers has been an active, yet problematic area of biomedical research. Many technical difficulties, including efficient tissue-specific delivery, integration site specificity and general toxicity, are being addressed. Little is known, however, about the genetic and phenotypic stability that accompanies a successful gene-specific targeting event in a cancer cell. This question was addressed following the creation of a colon cancer cell line in which a mutated hMLH1 gene was corrected via targeted homologous recombination. This correction resulted in the expression of wild-type hMLH1 protein, restoration of the hPMS2 protein and mismatch repair (MMR) proficiency. One of two hMLH1-corrected clones, however, was found to retain defects in MMR activity. These cells continued to express the corrected hMLH1 protein, but had lost expression of another MMR protein, hMSH6. DNA sequence analysis of the hMSH6 gene revealed biallelic expansions of a cytosine repeat region in exon 5 that result in frameshifts leading to premature stop codons. These findings suggest that, similar to acquired drug resistance, the presence of genetically heterogeneous cancer cell populations or acquisition of compensatory mutations can result in 'resistance' to gene replacement therapy.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Circulating endothelial cells are elevated in patients with type 2 diabetes mellitus independently of HbA(1)c.

AIMS/HYPOTHESIS: Patients with diabetes mellitus are well known to be at high risk for vascular disease. Circulating endothelial cells (CECs) have been reported to be an ex vivo indicator of vascular injury. We investigated the presence of CECs in the peripheral blood of 25 patients with diabetes mellitus and in nine non-diabetic control donors. METHODS: Endothelial cells were isolated from peripheral blood with anti-CD-146-coated immunomagnetic Dynabeads, and were stained with acridine orange dye and counted by fluorescence microscopy. The cells were also stained for von Willebrand factor and Ulex europaeus lectin 1. RESULTS: Patients with diabetes mellitus had an elevated number of CECs (mean 69+/-30 cells/ml, range 35-126) compared with healthy controls (mean 10+/-5 cells/ml, range 3-18) (p<0.001). The increase in CECs did not correlate with the levels of HbA(1)c. Circulating endothelial cell numbers were elevated regardless of glucose levels, suggesting that, even with control of glucose levels, there is increased endothelial cell sloughing. CONCLUSIONS: Our study suggests that the higher number of CECs in patients with type 2 diabetes may reflect ongoing vascular injury that is not directly dependent on glucose control.

Adult↗
PubMed1999

Influence of pre-PTCA strategy and initial PTCA result in patients with multivessel disease: the Bypass Angioplasty Revascularization Investigation (BARI).

BACKGROUND: In PTCA patients with multivessel coronary artery disease, incomplete revascularization (IR) is the result of both pre-PTCA strategy and initial lesion outcome. The unique contribution of these components on long-term patient outcome is uncertain. METHODS AND RESULTS: From the Bypass Angioplasty Revascularization Investigation (BARI), 2047 patients who underwent first-time PTCA were evaluated. Before enrollment, all significant lesions were assessed by the PTCA operator for clinical importance and intention to dilate. Complete revascularization (CR) was defined as successful dilatation of all clinically relevant lesions. Planned CR was indicated in 65% of all patients. More lesions were intended for PTCA in these patients compared with those with planned IR (2.8 versus 2.1). Successful dilatation of all intended lesions occurred in 45% of patients with planned CR versus 56% with planned IR (P<0. 001). In multivariable analysis, planned IR (versus planned CR), initial lesions attempted (not all versus all intended lesions attempted), and initial lesion outcome (not all versus all attempted lesions successful) were unrelated to 5-year risk of cardiac death or death/myocardial infarction but were all independently related to risk of CABG. CONCLUSIONS: Overall, a pre-PTCA strategy of IR in BARI-like patients appears comparable to a strategy of CR except for a higher need for CABG. Whether the use of new devices may attenuate the elevated risk of CABG in patients with multivessel disease and planned IR remains to be determined.

Aged↗
PubMed1996

Adverse effects of enalapril in the Studies of Left Ventricular Dysfunction (SOLVD). SOLVD Investigators.

In the Studies of Left Ventricular Dysfunction (LVD), enalapril or placebo was administered in a double-blind fashion to 6797 participants with ejection fraction < or = 0.35. During 40 months' average follow-up, 28.1% of participants randomized to enalapril reported side effects compared with 16.0% in the placebo group (p < 0.0001). Enalapril use was associated with a higher rate of symptoms related to hypotension (14.8% vs 7.1%, p < 0.0001), azotemia (3.8% vs 1.6%, p < 0.0001), cough (5.0% vs 2.0%, p < 0.0001), fatigue (5.8% vs 3.5%, p < 0.0001), hyperkalemia (1.2% vs 0.4%, p = 0.0002), and angioedema (0.4% vs 0.1%, p < 0.05). Side effects resulted in discontinuation of blinded therapy in 15.2% of the enalapril group compared with 8.6% in the placebo group (p < 0.0001). Thus enalapril is well tolerated by patients with LVD; however, hypotension, azotemia, cough, fatigue, and other side effects result in discontinuation of therapy in a significant minority of patients.

Aged↗
PubMed1995

Patterns of medication use in patients with heart failure: a report from the Registry of Studies of Left Ventricular Dysfunction (SOLVD).

To determine patterns of medication use based on clinical variables in patients with heart failure, we analyzed data from 5,999 patients participating in the Registry of Studies of Left Ventricular Dysfunction (SOLVD). The Registry comprised a broad spectrum of patients with heart failure, including some with predominantly diastolic dysfunction. Drug use was determined in a population cross-sectional manner at the time of identification (74% hospitalized). The median number of drugs per patient was four, with diuretics taken by 62%, digitalis by 45%, angiotensin-converting enzyme inhibitors (ACE-I) by 32%, calcium channel blockers by 36%, antiarrhythmics by 22%, and beta-blockers by 18%. Only 18% were on the combination of ACE-I, diuretic, and digitalis. Stratification for diagnosis, heart failure symptoms, and ejection fractions demonstrated that triple-drug therapy (digitalis, diuretic, and ACE-I) was common only in those with ejection fractions less than .20 and several signs or symptoms of heart failure. Older patients were taking diuretics frequently (73% of patients older than 70 years of age), and our European center used fewer drugs overall, while prescribing digitalis about half as frequently as North American clinics. These data serve as the baseline for analysis of evolving therapeutic practice in patients with heart failure.

Aged↗
PubMed1994

Tolerability of enalapril initiation by patients with left ventricular dysfunction: results of the medication challenge phase of the Studies of Left Ventricular Dysfunction.

Although converting-enzyme inhibitors are useful for the treatment of congestive heart failure (CHF), there are concerns about adverse reactions especially on initiation of therapy. In the Studies of Left Ventricular Dysfunction, enalapril, 2.5 mg twice per day was given on an open-label outpatient basis for 7 days (mean 6.1, range 2 to 7, and median 7) as a prerandomization drug challenge to 7487 patients with left ventricular dysfunction (ejection fraction < or = 0.35). Four hundred forty-four (5.93%) patients reported side effects, including symptoms attributed to hypotension (in 166 patients [2.2%]). The majority (346 [77.9%] of 444 and 129 [77.7%] of 166 with symptoms attributed to hypotension) of patients who reported side effects were willing to participate in the study and to continue receiving enalapril. Thus only 98 (1.3%) of 7487 patients (0.5% because of symptoms attributed to hypotension) were not willing to continue because of side effects. Women and patients of CHF class III or IV were more likely to report side effects. In conclusion, enalapril is well tolerated by patients with left ventricular dysfunction; treatment can be initiated on an outpatient basis in the majority of patients.

Enalapril↗
PubMed1994

Adjunctive thrombolytic therapy during angioplasty for ischemic rest angina. Results of the TAUSA Trial. TAUSA Investigators. Thrombolysis and Angioplasty in Unstable Angina trial.

BACKGROUND: Acute closure is increased after angioplasty in unstable angina, and adjunctive intracoronary thrombolytic therapy has been used successfully to increase angiographic success. The role of prophylactic thrombolytic therapy during angioplasty in unstable angina is unknown. METHODS AND RESULTS: Four hundred sixty-nine patients with ischemic rest pain with or without a recent (< 1 month) infarction were randomized in double-blind fashion to intracoronary urokinase or placebo. Randomization was carried out in two sequential phases. In phase I, 257 patients were randomized to 250,000 U of urokinase or placebo given in divided doses at the time of angioplasty. In phase II, 212 patients were randomized to 500,000 U of urokinase or placebo in divided doses. All patients were pretreated with aspirin, and activated clotting times were followed to maintain them at > 300 seconds during angioplasty. Angiographic end points of thrombus after angioplasty were insignificantly decreased by urokinase (30 [13.8%] versus 41 [18.0%] with placebo; P = NS). Acute closure, on the other hand, was increased with urokinase (23 [10.2%] versus 10 [4.3%] with placebo; P < .02). The difference in acute closure between urokinase and placebo was more striking at the higher dose of urokinase (P < .04) than in phase I at the lower urokinase dose (P = NS). Adverse in-hospital clinical end points (ischemia, infarction, or emergency coronary artery bypass surgery) were also increased with urokinase versus placebo (30 [12.9%] versus 15 [6.3%], respectively; P < .02). Angiographic and clinical end points were worse with urokinase in unstable angina without recent infarction than with angioplasty after a recent infarction. CONCLUSIONS: Adjunctive urokinase given prophylactically during angioplasty for ischemic rest angina as administered in this trial is associated with adverse angiographic and clinical events. These detrimental effects may be related to hemorrhagic dissection, lack of intimal sealing, or procoagulant or platelet-activating effects of urokinase.

Angina, Unstable↗
PubMed1992

Origin of all three coronary arteries from separate ostia in the right sinus of Valsalva: a rarely reported coronary artery anomaly.

Anomalous origin of the circumflex and left anterior descending coronary arteries from separate ostia in the right sinus of Valsalva is a rarely reported phenomenon. Few clinical details concerning patients with this anomaly are available in the literature. Angiographic and clinical data in an adult patient with this finding are reported here.

Cardiac Catheterization↗
PubMed1992

Left main coronary artery aneurysm following percutaneous transluminal angioplasty: a report of a case and review of the literature.

Since its introduction in 1977, the number of PTCAs and its indications have grown. Along with more frequent usage, newer complications have been reported. Aneurysm of left main coronary artery is rare. This report describes the formation of a new non-obstructing aneurysm in the left main coronary artery after PTCA of left circumflex artery. The patient has had 7 yr of follow-up with a benign clinical course.

Angina, Unstable↗
PubMed1992

Reversible late potentials due to ischemia.

The role of ischemia in the development of reversible late potentials was assessed in 19 patients undergoing percutaneous transluminal coronary angioplasty. Signal-averaged electrocardiograms were performed before angioplasty, during ischemia caused by balloon inflation and after angioplasty. Five of 19 patients developed late potentials that reverted to normal after angioplasty. Age, sex, ejection fraction, left ventricular end diastolic pressure, vessels involved, and extent of myocardium in jeopardy did not predict the development of late potentials. Patients with a prior history of myocardial infarction were more likely to develop late potentials. Therefore, patients with prior myocardial infarction appear more likely to develop the substrate for reentrant ventricular tachycardia during periods of ischemia.

Angioplasty, Balloon, Coronary↗
PubMed1988

Cardiopulmonary exercise testing. The clinical value of gas exchange data.

Cardiopulmonary exercise testing is a noninvasive tool whose clinical value is not yet widely recognized. The technique involves breath-by-breath measurement of respiratory gas exchange during a symptom-limited exercise test, with determination of maximal oxygen uptake and anaerobic threshold. These measurements serve as objective, reproducible indices of exercise capacity that can be applied to the management of various clinical problems. In addition, by permitting simultaneous assessment of circulatory and ventilatory reserves, the test can be especially helpful in the differential diagnosis of exertional dyspnea and fatigue. This paper reviews the physiology of gas exchange, the limitations of standard exercise tests, and the methodology and clinical applications of cardiopulmonary exercise testing.

Carbon Dioxide↗
PubMed1985

Monoclonal antibody identification of mononuclear cells in endomyocardial biopsy specimens from a patient with rheumatic carditis.

A 17-year-old woman with rheumatic carditis underwent endomyocardial biopsy both prior to and following treatment with prednisone and aspirin. Frozen sections from the endomyocardial biopsy specimens were studied with monoclonal antibodies by an indirect immunofluorescence technique to define the composition of the inflammatory infiltrate in the myocardium and to determine whether the composition of the infiltrate is distinctive and diagnostically useful. The specimen from the initial biopsy contained a heterogeneous infiltrate composed of T lymphocytes, macrophages, B lymphocytes, and mast cells. T lymphocytes predominated, and the ratio of T-helper to T-cytotoxic/suppressor cells was 2.0. Following treatment the overall cellularity of the infiltrate was diminished, but the infiltrate remained heterogeneous; T cells predominated, and the T-helper to T-cytotoxic/suppressor ratio was reversed, to 0.59. The composition of the inflammatory infiltrate in this case of rheumatic carditis distinguishes it immunologically from other "idiopathic," presumably virus-associated, forms of myocarditis.

Adolescent↗