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P Benjamin

Publications and source records attributed to P Benjamin.

At least 19 recordsLinked to original sources
PubMed2001

Interaction between the unphosphorylated receptor with high affinity for IgE and Lyn kinase.

Chinese hamster ovary fibroblasts previously transfected with the high affinity receptor for IgE (FcepsilonRI) were further transfected with the alpha subunit of the receptor for interleukin 2 (Tac) or with chimeric constructs in which the cytoplasmic domain of Tac was replaced with the C-terminal cytoplasmic domain of either the beta subunit or the gamma subunit of FcepsilonRI. Whereas native Tac failed to affect the aggregation-induced phosphorylation of FcepsilonRI, both chimeric constructs substantially inhibited this reaction. Alternatively, the FcepsilonRI-bearing fibroblasts were transfected with two chimeric constructs in which the cytoplasmic domain of Tac was replaced with a modified short form of Lyn kinase. The Lyn in both of the chimeric constructs had been mutated to remove the sites that are normally myristoylated and palmitoylated, respectively; one of the constructs had in addition been altered to be catalytically inactive. The catalytically active construct enhanced, and the inactive construct inhibited, aggregation-induced phosphorylation of the receptors. All of the chimeric constructs were largely distributed outside the detergent resistant microdomains, and whereas aggregation caused them to move to the domains in part, their aggregation was neither necessary nor enhanced their effects. These results and others indicate that the receptor and Lyn interact through protein-protein interactions that neither are dependent upon either the post-translational modification of the kinase with lipid moieties nor result exclusively from their co-localization in specialized membrane domains.

Adenosine Triphosphate↗
PubMed1999

Left superior vena cava to the left atrium: do we have to change the traditional approach?

Left superior vena cava (LSVC) to the left atrium is a rare congenital cardiac complex, which may appear as an isolated anomaly, or as part of more complex cardiac anomalies. Traditionally, an intraatrial baffle was the preferred surgical technique. Although this technique has proved reliable and successful, acute ligation and extracardiac repair are simpler and easier solutions, requiring less myocardial ischemic time. We present 3 patients who underwent simple ligation and discuss the literature for other extracardiac options of surgical repair. Our patients had short transient congestion in the left upper part of their body that resolved completely after a few weeks, without further complications. We believe that either acute ligation or extracardiac repair is a much simpler yet effective solution to divert the left caval flow to the lesser circulation.

Adult↗
PubMed1998

[Transcatheter closure of atrial septal defects: initial clinical applications].

The incidence of congenital heart defects is 0.8% of liveborn infants. Of these 13% are ostium secundum atrial septal defects (ASD) which can be successfully repaired by open heart surgery with less than 1% mortality. However, morbidity associated with cardiac surgery is universal. Transcatheter closure of ASDs was introduced 2 decades ago to decrease surgical complications, hospital stay and cost. Few devices have undergone clinical trials but all of them have been associated with instances of failure and complications. The most important mechanism for acute failure was selection of cases with too large a defect or selection of a defective device. In the past decade great progress has been made with the aid of transesophageal echocardiography (TEE) and modifications of the device. We present our experience in our first 5 patients. They ranged in age from 4 to 27 years; the ASD diameter was 11-15 mm and the device diameter was 17-33 mm. All transcatheter closures were performed on the same day without any complications, and all patients were discharged home after 2 days of hospitalization. We conclude that transcatheter occlusion of ASDs up to 15 mm is feasible, relatively safe and effective. This transcatheter method appears to be a viable alternative to surgery for some patients with secundum atrial septal defects.

Adolescent↗
PubMed1995

Elevated conversion of alpha-2-macroglobulin to the complexed form in gingival crevicular fluid from adult periodontitis patients.

The broad spectrum protease inhibitor, alpha 2-macgrolobulin (alpha 2M), is one of the host's principal regulators of both endogenous and exogenous proteases and is likely to have an important role in the regulation of proteolytic activity at inflammatory sites. We have determined the amount of complexed (com alpha 2M) and total alpha 2M (tot alpha 2M) in gingival crevicular fluid (GCF) harvested from shallow and deep sites in adult periodontitis (AP) patients (n = 21). An ELISA technique was developed to measure both forms of alpha 2M in the same sample utilizing a monoclonal antibody (MAb) specific for the complexed form. In addition, protease activity towards human serum albumin (Prot1), transferrin (Prot2) and N alpha-benzoyl-L-arginine 7-amido-4-methylcoumarin-hydrochloride (BAAMc; Prot3) were determined in a second GCF sample from the same site. Plasma alpha 2M concentrations were only positively correlated (p = 0.0163) with GCF tot alpha 2M from highly inflamed sites. We observed a significant positive correlation between tot alpha 2M and proteolytic activity in GCF from deep sites but not from shallow sites (Prot1: p = 0.002; Prot2: p = 0.005). A similar correlation between tot alpha 2M and proteolytic activity was found at highly inflamed sites (Prot1: p = 0.014; Prot2: p = 0.002). A very high proportion of the tot alpha 2M in GCF was in the complexed form at both shallow (71.14% +/- 29.13) and deep sites (68.17% +/- 28.5) Com alpha 2M was positively correlated with proteolytic activity only in deep sites (Prot1: p = 0.015; Prot2: p = 0.031). Our results suggest that the concentration of tot alpha 2M in the gingival crevice is positively associated with the amount of proteolytic activity at the site and that protease activities in GCF may only partly explain the high percentage conversion alpha 2M to the complexed form. The high level of alpha 2M inactivation in GCF from AP patients reported here may have significance not only in view of its role as a broad spectrum protease inhibitor but also through the differential effects of native vs complexed alpha 2M on the regulation of immune responses.

Adult↗
PubMed1995

Characterization of an invasive phenotype associated with enteroaggregative Escherichia coli.

Enteroaggregative Escherichia coli (EAggEc) strains are associated with persistent diarrhea in children in the developing world and exhibit a classic aggregative phenotype. We have demonstrated that EAggEc strains isolated from children with persistent diarrhea in Brazil, Bangladesh, and Pakistan also have the potential to be internalized by HeLa cells in the gentamicin protection assay. We have confirmed this phenomenon with transmission electron micrographs of bacteria engulfed by HeLa cells. We examined the mechanisms by which this process occurs. Staurosporine inhibited internalization of EAggEc strain 162 by 50% at a concentration of 0.1 microM. Genistein inhibited internalization of this same organism by 50% at a concentration of 50 microM. Cytochalasin D inhibited internalization by 50% at a concentration of 1 microgram/ml. Staurosporine, genistein, and cytochalasin D inhibited the internalization of EAggEc strain 162 by HeLa cells in a dose-dependent manner. These data suggest that active cell processes such as signal transduction by protein kinase and/or tyrosine kinase may be involved in the internalization of EAggEc strain 162 by HeLa cells and that actin filaments and cytoskeletal structure may be important for this process.

Alkaloids↗
PubMed1993

Production and characterisation of monoclonal antibodies to the principle sonicate antigens of Porphyromonas gingivalis w50.

Protein antigens from whole cell sonicates of Porphyromonas gingivalis W50, previously shown to be discriminatory antigens for patients with adult periodontitis, were purified using SDS-PAGE. Electroeluted proteins were used to immunize mice for the production of monoclonal antibodies (mAbs). A combination of enzyme-linked immunosorbent assay (ELISA) and Western blotting were used to screen hybridoma supernatants for mAbs. MAbs were successfully raised against M(r) 115,000, M(r) 55,000 and M(r) 47,000 antigens together with a second M(r) 55,000 polypeptide which was a contaminant of the M(r) 55,000 antigen. No immunological cross-reactivity was found between these four proteins. The mAbs were used to examine the distribution of these antigens among fifteen P. gingivalis strains together with related oral bacteria using immunostaining of dot blots and Western blots. The antigens were confined to P. gingivalis with the M(r) 115,000 and M(r) 47,000 antigens being present in all strains tested. The distribution of the M(r) 55,000 antigens were slightly more restricted: one M(r) 55,000 (outer membrane location) was present in nine of the fifteen P. gingivalis strains tested, while the other M(r) 55,000 (location unknown) was only absent from one strain. Whole cell ELISA demonstrated that the M(r) 115,000 and the outer membrane M(r) 55,000 antigen possess epitopes which are located on the surface of the bacterium.

Adult↗
PubMed1990

Cerebral embolization from an inferior vena cava thrombus in tetralogy of Fallot.

Cerebrovascular accident (CVA) complicating cyanotic congenital heart disease (CCHD) is most frequently attributed to cerebral venous thrombosis, only rarely to in situ cerebral arterial thrombosis. Cerebrovascular accident due to paradoxical embolization from an inferior vena cava (IVC) thrombus in a patient with tetralogy of Fallot (TF) is described. This case is the first antemortem documentation of a venous embolic source that caused paradoxical embolization to the brain in a patient with CCHD, and illustrates the importance of noninvasive screening for a venous source of emboli in these patients.

Child, Preschool↗
PubMed1986

Two-dimensional echocardiographic analysis of proximal left main coronary artery in humans.

The left main coronary artery (LMCA) was evaluated in 100 consecutive patients (88 men and 12 women; mean age 63 years) with anginal syndrome, all in New York Heart Association classes II and III. Each patient underwent two-dimensional echocardiography (2DE) from the parasternal short-axis and apical four-chamber views. Coronary angiography was subsequently performed within 24 hours. The LMCA was directly measured by 2DE and coronary angiography at its widest point. Each echocardiogram was blindly evaluated for LMCA aneurysm or obstruction. Eight patients (8%) were excluded because of inadequate visualization of the LMCA. The mean 2DE measurement was 4.4 +/- 0.9 mm vs 4.2 +/- 0.8 mm on coronary angiography (r = 0.86). Atherosclerotic aneurysms of the LMCA were correctly diagnosed in two patients by 2DE. LMCA stenosis (greater than 50%) was found in 11 patients on coronary angiography; three of them had ostial or proximal lesions, three had middle lesions, and five had distal lesions. 2DE correctly diagnosed all three ostial lesions, two of three middle lesions, but only two of five distal lesions. In four patients, dense echoes in the LMCA caused a false positive diagnosis. It was concluded that: the LMCA can be visualized and correctly measured by 2DE; atherosclerotic aneurysms can be detected; and 2DE is yet unable to screen patients for LMCA lesions; however, 2DE is a promising method for evaluating proximal and especially ostial LMCA stenosis.

Adult↗
PubMed1984

Diagnosis of pulmonic regurgitation by contrast echocardiography.

In order to determine whether pulmonic regurgitation (PR) can be reliably diagnosed using contrast echocardiography, we studied 24 subjects using echocardiography during intravenous injections of 5% dextrose solution. Twelve were without PR, and twelve had PR (10 after intracardiac repair of tetralogy of Fallot, one after a Brock procedure for pulmonic stenosis, and one after insertion of a right ventricle-pulmonary artery conduit for pseudo truncus arteriosus). Two blinded independent observers correctly diagnosed PR in all patients when it was present, and correctly excluded it in 11 of 12 of the patients without PR. They disagreed in one patient who had an unusual contrast pattern during diastole. Four postoperative patients had PR by contrast echocardiography despite the absence of a cardiac murmur at the time of their study. We conclude that contrast echocardiography is a safe, simple, sensitive, and specific method for diagnosing PR. Some methodologic suggestions and limitations of the method are discussed.

Adolescent↗
PubMed1983

Diagnosing tricuspid regurgitation by direct imaging of the regurgitant flow in the right atrium using contrast echocardiography.

To determine whether tricuspid regurgitation (TR) can be diagnosed by direct imaging of regurgitant flow in the right atrium (RA) using contrast echocardiography, echocardiography was performed in 35 patients using peripheral intravenous injections of 5% dextrose solution. Fifteen patients had TR judged by v-wave synchronous contrast appearance on the inferior vena cava echogram (a previously validated method for diagnosing TR), 5 of whom had clinically obvious TR. Twenty patients had no TR on inferior vena cava contrast echocardiography, 9 of whom were normal volunteers. On subsequent blind review, 13 of the 15 patients with TR were correctly identified on the basis of the regurgitant contrast flow just posterior to the tricuspid valve in the RA. Of the 20 without TR, 19 were correctly identified and there was 1 false-positive result. Using different criteria for the diagnosis (insisting on imaging of flow across the tricuspid valve in systole), another blinded observer correctly diagnosed only 8 of the 15 patients as having TR, but had no false-positive results. To avoid false-positive results, it is important to realize that there are 2 regions where retrograde flow can normally be seen in the RA: (1) briefly at the onset of systole coincident with tricuspid valve closure, and (2) in the posterior RA, as distinct from the anterior RA area just behind the tricuspid valve where TR is diagnosed in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Initiation of DNA replication in vitro by a DNA-membrane complex extracted from Bacillus subtilis.

Initiation of DNA replication has been observed in vitro with a DNA-membrane complex extracted from Bacillus subtilis. Antibiotics known to interfere with various aspects of initiation inhibited DNA synthesis significantly in vitro, whereas a mutant resistant to one inhibitor failed to respond to its presence. The inhibitory effects occurred primarily when the immediate RNA precursors (ribonucleoside triphosphates) were present in the assay solution but not significantly when the precursors were omitted. Complexes extracted from a temperature-sensitive initiation mutant were almost incapable of synthesizing DNA at the restrictive temperature but displayed extensive synthesis at the permissive temperature. A strong indication of semiconservative DNA synthesis was obtained in vitro after density-shift experiments involving incubation of the complex with a heavy-density DNA precursor, followed by neutral and alkaline CsCl density gradient centrifugation. A significant amount of chain elongation or repair (or both) was also observed.

Aminoglycosides↗
PubMed1982

Replication of a low-copy-number plasmid by a plasmid DNA-membrane complex extracted from minicells of Escherichia coli.

A DNA-membrane complex was extracted from minicells of an Escherichia coli mutant harboring a "miniplasmid" derivative (11.2 kilobases) of the low-copynumber plasmid RK2 (56 kilobases). The complex contained various species of supercoiled and intermediate forms of plasmid DNA, of which approximately 20% was bound firmly to the membrane after centrifugation in a CsCl density gradient. The plasmid DNA-membrane complex synthesized new plasmid DNA without the addition of exogenous template, enzymes, or other proteins. DNA synthesis appeared to proceed semi-conservatively, was dependent on the four deoxynucleoside triphosphates, partially dependent on ribonucleoside triphosphates, and was sensitive to rifampin, an antibiotic known to inhibit initiation of replication. Novobiocin and nalidixic acid also inhibited synthesis, as did the omission of ATP, N-Ethylmaleimide, an inhibitor of DNA polymerase II and III activity, but not DNA polymerase I activity, also partially inhibited the synthetic reaction, as did chloramphenicol. The plasmid DNA synthetic product was analyzed by alkaline sucrose and dye-CsCl gradient centrifugation, as well as by agarose gel electrophoresis. In each case, the product consisted of parental and intermediate forms of plasmid DNA. Some chromosomal DNA was also synthesized by a contaminating bacterial DNA-membrane complex, but this synthesis was rifampin insensitive and could be separated from plasmid DNA synthesis.

Cell Membrane↗