Search PubMed⌕ Search

Biomedical subjects

R Simon

Publications and source records attributed to R Simon.

At least 307 records · Page 17Linked to original sources
PubMed1990

Diastolic dysfunction during acute cardiac allograft rejection.

Left ventricular diastolic function was evaluated in 41 heart transplant patients during acute rejection by an analysis of echocardiograms and surgically implanted intramyocardial tantalum markers. In 35 patients, isovolumic relaxation time was calculated from M-mode tracings selected from two-dimensional echocardiographic recordings. A total of 84 biopsy findings of no rejection, moderate rejection, and severe acute rejection after treatment were correlated with measurements of isovolumic relaxation time. In six patients, end-diastolic volume, end-systolic volume, stroke volume, ejection fraction, and peak filling rate were obtained from biplanar cineradiographic images of intramyocardial markers. Data from 11 prerejection periods were compared with those of moderate acute rejection. All echocardiograms and marker images were analyzed without previous knowledge of biopsy findings. At times of acute rejection, isovolumic relaxation time decreased from 107 to 65 msec (p less than 0.01) and returned to 98 msec after immunosuppressive therapy. Ejection fraction and end-systolic volume did not change significantly with acute rejection, whereas stroke volume decreased from 76 to 67 ml (p less than 0.05). In contrast to the effects on systolic function, episodes of acute rejection were accompanied by a decrease in end-diastolic volume from 166 to 153 ml (p less than 0.01) and a reduction in peak filling rate from 514 to 460 ml/sec (p less than 0.05). These data suggest that acute cardiac rejection is associated with relative preservation of left ventricular systolic performance but with alterations in diastolic dynamics similar to those seen in "restrictive" cardiomyopathy.

Acute Disease↗
PubMed1989

[Churg-Strauss syndrome].

The Churg-Strauss syndrome is part of the necrotizing vasculitis group of diseases. Its clinical diagnosis rests on the occurrence of a severe asthma followed, more or less closely, by systemic manifestations that are predominantly neurological, cutaneous, gastrointestinal and cardiovascular. To these must be added pulmonary infiltrates, eosinophilia and increase in serum IgE's. Three histological criteria (necrotizing vasculitis of the small vessels, perivascular infiltration with numerous eosinophils and extravascular granulomas) enable this anatomico-clinical syndrome to be identified, but the granuloma component is frequently missing and the existence of borderline states, notably with periarteritis nodosa, is unquestionable. Corticosteroids and immunodepressants have transformed the prognosis of the Churg-Strauss syndrome, while its physiopathological mechanism remains mysterious.

Churg-Strauss Syndrome↗
PubMed1989

The specific NMDA receptor antagonist AP-7 attenuates focal ischemic brain injury.

Pharmacologic blockade of excitatory amino acid receptors, especially the N-methyl-D-aspartate-preferring subclass of glutamate receptors, has been shown to reduce neuronal damage in models of global cerebral ischemia followed by reperfusion. The pharmacologic blockade at the NMDA receptor attenuates infarct size following permanent focal vascular occlusion in brain. Functional recovery is improved as well. These effects were seen with treatment begun 15 min following the stroke.

2-Amino-5-phosphonovalerate↗
PubMed1989

New derivatives of transposon Tn5 suitable for mobilization of replicons, generation of operon fusions and induction of genes in gram-negative bacteria.

Three types of new variants of the broad-host-range transposon Tn5 are described. (i) Tn5-mob derivatives with the new selective resistance (R) markers GmR, SpR and TcR facilitate the efficient mobilization of replicons within a wide range of Gram-negative bacteria. (ii) Promoter probe transposons carry the promoterless reporter genes lacZ, nptII, or luc, and NmR, GmR or TcR as selective markers. These transposons can be used to generate transcriptional fusions upon insertion, thus facilitating accurate determinations of gene expression. (iii) Tn5-P-out derivatives carry the npt- or tac-promoter reading out from the transposon, and TcR, NmR or GmR genes. These variants allow the constitutive expression of downstream genes. The new Tn5 variants are available on mobilizable Escherichia coli vectors suitable as suicidal carriers for transposon mutagenesis of non-E. coli recipients and some on a phage lambda mutant to be used for transposon mutagenesis in E. coli.

Base Sequence↗
PubMed1989

Flexible regression models with cubic splines.

We describe the use of cubic splines in regression models to represent the relationship between the response variable and a vector of covariates. This simple method can help prevent the problems that result from inappropriate linearity assumptions. We compare restricted cubic spline regression to non-parametric procedures for characterizing the relationship between age and survival in the Stanford Heart Transplant data. We also provide an illustrative example in cancer therapeutics.

Adult↗
PubMed1989

Intracoronary nisoldipine: effects on acute myocardial ischemia during coronary angioplasty.

The effects on ischemic myocardium of 0.05 mg nisoldipine given by intracoronary injection were studied in 22 patients subjected to percutaneous transluminal coronary angioplasty. The angioplasty balloon was inflated for periods of 60 seconds. During the occlusion period, pulmonary wedge pressure was measured, an intracoronary epicardial ECG recorded, and ventricular volumes and ejection fraction were determined by means of digital subtraction angiography. After the intracoronary administration of nisoldipine, the onset of the rise in diastolic filling pressure was slightly delayed from 29 to 36 seconds. While affecting neither the rise in filling pressure nor the increase in end-diastolic and end-systolic volumes after 60 seconds of ischemia, nisoldipine delayed the occurrence (from 13 to 33 seconds; p less than 0.005) and reduced the extent (from 1.5 to 0.6 mV; p less than 0.001) of ischemic ST elevation in the intracoronary ECG. After nisoldipine, anginal symptoms were clearly reduced during the ischemic phase in the majority of patients. These findings suggest that intracoronary pretreatment with nisoldipine leads to a regional protection of ischemic myocardium without any appreciable effect on ischemia-induced myocardial dysfunction.

Angioplasty, Balloon, Coronary↗
PubMed1989

Optimal two-stage designs for phase II clinical trials.

The primary objective of a phase II clinical trial of a new drug or regimen is to determine whether it has sufficient biological activity against the disease under study to warrant more extensive development. Such trials are often conducted in a multi-institution setting where designs of more than two stages are difficult to manage. This paper presents two-stage designs that are optimal in the sense that the expected sample size is minimized if the regimen has low activity subject to constraints upon the size of the type 1 and type 2 errors. Two-stage designs which minimize the maximum sample size are also determined. Optimum and "minimax" designs for a range of design parameters are tabulated. These designs can also be used for pilot studies of new regimens where toxicity is the endpoint of interest.

Drug Evaluation↗
PubMed1989

Left ventricular function, tricuspid incompetence, and incidence of coronary artery disease late after orthotopic heart transplantation.

Functional results and data concerning the incidence and severity of graft atherosclerosis (GASC) and tricuspid incompetence (TI) in the intermediate term after orthotopic heart transplantation (HTX) are still striking. We examined 92 patients 1, 2, and 3 years after HTX by right and left heart catheterization in order to evaluate pump function, the status of the coronary arteries and the extend of TI, using a double indicator thermodilation technique. Mean left ventricular volumes and ejection fraction were normal 1 and 2 years post-transplant. The incidence of GASC was 8/87 (9.2%) at 1, and 11/92 (12%) at 2 years. It was more frequent (16%) in patients with preexisting coronary artery disease (IHD) than in patients with underlying dilative cardiomyopathy (DCM) (11%). At the end of the 1st postoperative year, 62% of patients were free of TI, whereas only 38% had normal valve function 2 years posttransplant. In 9/14 (64%) of patients, consecutively assessed at 1 and 2 years, TI had increased between both investigations. Preoperative haemodynamics, the number of endomyocardial biopsies and rejection episodes as well as preoperative cardiac size did not correlate with TI. Left ventricular volumes and ejection fraction are normal in the intermediate term after HTX. The incidence of GASC was less than 10% at 1 year and did not significantly increase thereafter. TI is a frequent and yet unexplained finding after HTX showing a considerable tendency to increase with time, but with little or not haemodynamic consequence.

Adult↗
PubMed1989

Effects of the N-methyl-D-aspartate receptor blocker MK-801 on neurologic function after experimental brain injury.

Pharmacologic inhibition of excitatory amino acid (EAA) neurotransmission attenuates cell death in models of global and focal ischemia and hypoglycemia and improves neurologic outcome after experimental traumatic spinal cord injury. The present study examined the effects of the noncompetitive N-methyl-D-aspartate (NMDA) receptor blocker MK-801 on cardiovascular and neurologic function after experimental fluid-percussion (FP) brain injury in the rat. Animals received either an intravenous bolus of MK-801 (1 mg/kg) or saline (equal volume) 15 min prior to FP brain injury or 15 min following FP brain injury. MK-801 pretreatment significantly improved postinjury cardiovascular variables and attenuated postinjury neurologic dysfunction. Postinjury treatment with MK-801 also significantly improved cardiovascular variables, but had little effect on postinjury neurologic scores. These results suggest that EAA neurotransmitters may be involved in the pathophysiological sequelae of traumatic brain injury and that noncompetitive blockade of the NMDA receptor prior to brain injury may reduce EAA-induced damage and limit neurologic dysfunction.

Amino Acids↗
PubMed1989

The prevalence and management of pain in patients with AIDS: a review of 134 cases.

In light of the lack of any prior systematic evaluations of the prevalence and types of pain syndromes and treatments found in patients with AIDS, a chart review study was undertaken to evaluate this issue. Fifty-two of 96 charts reviewed (54%) had at least one note on nonprocedural pain or analgesic prescription. Although chest pain was the most prevalent pain location (22%), presumably because of the high incidence of Pneumocystis carinii pneumonia, other possible AIDS-related entities, such as peripheral neuropathy and thrombophlebitis, were also found. No specific AIDS syndromes could be identified that were related to a higher incidence of pain. Nearly one-third of patients with pain received codeine (31%), others received acetaminophen (27%), and 17% of patients received acetaminophen and oxycodone HCl. Specific pain management interventions must be evaluated and applied to control the nontrivial occurrence of pain in patients who have AIDS symptoms that may be overlooked by the physician given the overwhelming disease process.

Acquired Immunodeficiency Syndrome↗