PubMed Health⌕ Search

Biomedical subjects

J Berman

Publications and source records attributed to J Berman.

At least 19 recordsLinked to original sources
PubMed1992

Role of mast cell chymase in the extracellular processing of big-endothelin-1 to endothelin-1 in the perfused rat lung.

Previous studies of endothelin-1 (ET) synthesis have shown that some cultured endothelial cells secrete an intermediate product, big-endothelin-1 (bigET), suggesting that the processing of secreted bigET to ET may be physiologically significant. In this study, two pertinent ET converting enzyme activities, mast cell chymase I (EC 3.4.21.39) and a phosphoramidon-sensitive, neutral metalloprotease, were identified in a rat lung particulate fraction. We perfused rat lungs with bigET and chymostatin or phosphoramidon to study the relevance of these two proteases to the processing of extracellular bigET in vivo. Addition of compound 48/80 (a compound which activates mast cells, causing degranulation and release of chymase) to the perfusion buffer greatly increased hydrolysis of exogenously added bigET to ET. ET formation was inhibited completely by 32 microM chymostatin, whereas inhibition by 50 microM phosphoramidon was incomplete and variable. Perfusate histamine levels were used to monitor the extent of mast cell degranulation, and inhibition of ET production by phosphoramidon was attributed to inhibition of degranulation, per se. There was a direct correlation between perfusate ET and histamine levels in both control and phosphoramidon-treated (but not chymostatin-treated) lungs. Our results suggest that chymase from lung mast cells is capable of physiologically relevant extracellular processing by bigET to ET in the perfused rat lung.

Animals↗
PubMed1992

Rapid optimization of enzyme substrates using defined substrate mixtures.

A strategy is described for the rapid optimization of kcat/Km for protease substrates. Selected positions of a given peptide substrate sequence are varied through synthesis with mixtures of amino acids. Incubation of the resulting peptide mixture with the enzyme of interest and analysis by high pressure liquid chromatography provides a direct measure of analogs with enhanced kcat/Km. High performance liquid chromatography/continuous flow fast atom bombardment mass spectrometry is used to assign structure to each peak in the chromatogram. As an example of the utility and efficiency of "substrate mapping" we describe optimization of the collagenase substrate Dnp-Pro-Leu-Gly-Leu-Trp-Ala-D-Arg-NH2 (where Dnp is dinitrophenyl) at the P'1 and P'2 positions. Six different mixtures were prepared for evaluation, representing the synthesis of 128 different synthetic substrates. "Substrate mapping" has led to Dnp-Pro-Leu-Gly-Cys(Me)-His-Ala-D-Arg-NH2, a substrate that possesses a 10-fold better kcat/Km than Dnp-Pro-Leu-Gly-Leu-Trp-Ala-D-Arg-NH2.

Amino Acid Sequence↗
PubMed1992

Chlamydomonas reinhardtii telomere repeats form unstable structures involving guanine-guanine base pairs.

Unusual DNA structures involving four guanines in a planar formation (guanine tetrads) are formed by guanine-rich (G-rich) telomere DNA and other G-rich sequences (reviewed in (1)) and may be important in the structure and function of telomeres. These structures result from intrastrand and/or interstrand Hoogsteen base pairs between the guanines. We used the telomeric repeat of Chlamydomonas reinhardtii, TTTTAGGG, which contains 3 guanines and has a long interguanine A + T tract, to determine whether these sequences can form intrastrand and interstrand guanine tetrads. We have found that ss (TTTTAGGG)4 can form intrastrand guanine tetrads that are less stable than those formed by more G-rich telomere sequences. They are not only more stable, but also more compact, they are more stable in the presence of K+ than they are in the presence of Na+. While ds oligonucleotides with ss 3' overhangs of (TTTTAGGG)2 can be observed to associate as dimers, formation of this interstrand guanine tetrad structure occurs to a very limited extent and requires very high G-strand concentration, high ionic strength, and at least 49 hours of incubation. Our results suggest that, if telomere dimerization occurs in vivo, it would require factors in addition to the TTTTAGGG telomere sequence.

Animals↗
PubMed1992

Improving clinical teaching. Evaluation of a national dissemination program.

This study assessed a dissemination approach to improve clinical teaching. We hypothesized that (1) physicians from a variety of institutions nationwide could be trained to conduct teaching improvement seminars for faculty colleagues; (2) such seminars would be perceived as highly useful; (3) pre/post self-evaluations by faculty participants and evaluations of faculty participants by house staff/students would indicate improved teaching performance. Selected medical faculty completed 1 month of facilitator training at the Stanford Faculty Development Program, Palo Alto, Calif. They then delivered teaching improvement seminars for other faculty. From 1986 to 1988, 12 facilitators from 12 institutions trained 107 faculty at their home institutions in their initial seminar series. Their seminars were rated as highly useful by participants. Both faculty self-assessments and house staff/student ratings indicated improved teaching performance. We concluded that this dissemination approach provides one possible mechanism for ongoing teaching improvement within institutions across the country.

Education, Medical, Undergraduate↗
PubMed1992

Yeast telomere repeat sequence (TRS) improves circular plasmid segregation, and TRS plasmid segregation involves the RAP1 gene product.

Telomere repeat sequences (TRSs) can dramatically improve the segregation of unstable circular autonomously replicating sequence (ARS) plasmids in Saccharomyces cerevisiae. Deletion analysis demonstrated that yeast TRSs, which conform to the general sequence (C(1-3)A)n, are able to stabilize circular ARS plasmids. A number of TRS clones of different primary sequence and C(1-3)A tract length confer the plasmid stabilization phenotype. TRS sequences do not appear to improve plasmid replication efficiency, as determined by plasmid copy number analysis and functional assays for ARS activity. Pedigree analysis confirms that TRS-containing plasmids are missegregated at low frequency and that missegregated TRS-containing plasmids, like ARS plasmids, are preferentially retained by the mother cell. Plasmids stabilized by TRSs have properties that distinguish them from centromere-containing plasmids and 2 microns-based recombinant plasmids. Linear ARS plasmids, which include two TRS tracts at their termini, segregate inefficiently, while circular plasmids with one or two TRS tracts segregate efficiently, suggesting that plasmid topology or TRS accessibility interferes with TRS segregation function on linear plasmids. In strains carrying the temperature-sensitive mutant alleles rap1grc4 and rap1-5, TRS plasmids are not stable at the semipermissive temperature, suggesting that RAP1 protein is involved in TRS plasmid stability. In Schizosaccharomyces pombe, an ARS plasmid was stabilized by the addition of S. pombe telomere sequence, suggesting that the ability to improve the segregation of ARS plasmids is a general property of telomere repeats.

Alleles↗
PubMed1992

Enhanced angiogenesis and growth of collaterals by in vivo administration of recombinant basic fibroblast growth factor in a rabbit model of acute lower limb ischemia: dose-response effect of basic fibroblast growth factor.

The purpose of this study was to evaluate the effects of exogenous recombinant basic fibroblast growth factor (bFGF) on angiogenesis in severely ischemic tissue beds. We used a two-stage procedure to produce severe ischemia of the hindlimb of 34 New Zealand rabbits. The ischemic hindlimb received intramuscular injection of saline (group A), 1 microgram bFGF (group B), or 3 micrograms bFGF (group C), daily for 2 weeks. Tissue perfusion, skeletal muscle infarction, angiogenesis, and collateral growth were assessed by angiography, transcutaneous oximetry (TcPO2), quantitative spectrophotometric assay of triphenyltetrazolium chloride reduction in muscle, capillary density (capillaries per square millimeter), and capillary per muscle fiber ratio. There were no significant differences in baseline TcPO2 among the three groups for both thigh and calf measurements. Angiography revealed extensive perfusion of the left hindlimb in all the assessed bFGF treated animals. Both thigh and calf TcPO2 values showed a significant increase in all groups over the 14 days ischemia was induced (p less than 0.0001), but the two treatment groups exhibited a much more rapid rise in TcPO2 than the control group (p less than 0.0001). The capillaries per square millimeter and capillaries per muscle fiber ratios were significantly increased in all posttreatment measurements for all animals that received bFGF. The treatment groups with bFGF had a significant (p = 0.025) increase in thigh muscle viability compared with controls based on triphenyltetrazolium chloride reduction. Whereas there was evidence of muscle infarction in both the thighs of groups A and B, there was none in group C.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1992

Aortoenteric fistula.

Aortoenteric fistula is a rare but deadly medical emergency. Primary fistulas occur between the native aorta and the intestinal tract. Secondary fistulas occur between an aortic graft and the gastrointestinal tract. Patients often present with a "herald bleed," followed by massive gastrointestinal hemorrhage. Sepsis and abdominal pain in a patient who has had an aortic graft may also indicate the formation of a fistula. Prompt intervention is imperative; the mortality rate is 100 percent if the condition is left untreated. In clinically stable patients with a herald bleed, evaluation usually consists of endoscopy in an operating room. Computed tomographic scanning is useful for patients with signs of sepsis; scans showing an aortic graft surrounded by inflammation and abscess formation may indicate fistula formation. Clinically unstable patients require immediate laparotomy. Even in surgically treated patients, the mortality rate is approximately 60 percent.

Aortic Diseases↗
PubMed1991

Alternative, simultaneous complex I mitochondrial DNA mutations in Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy has been linked to a mitochondrial DNA mutation at position 11,778 in the ND-4 gene in 50% of families. Three alternative mutations in Complex I genes at positions 4,216 (ND-1), 4,917 (ND-2), and 13,708 (ND-5) were discovered in 11,778- Leber families. The 4,917 and 13,708 mutations appear pathogenetically significant and were observed in 36% (4,917 mutation) and 43% (13,708 mutation) of 11,778- Leber probands. Multiple, simultaneous mutations were noted. Mutation of distinct, functionally related Complex I genes is the central pathogenetic feature of Leber's hereditary optic neuropathy.

Amino Acid Sequence↗
PubMed1991

Biomedical applications of high-performance liquid chromatography-mass spectrometry with continuous-flow fast atom bombardment.

This report describes the application of high-performance liquid chromatography combined with continuous-flow fast atom bombardment mass spectrometry to analytical problems in the biomedical laboratory. Applications include the compound-specific detection of diagnostic acylcarnitines in human urine, the separation and analysis of acyl-coenzyme A thioesters, and qualitative studies on complex mixtures of modified peptides (dansyl and dinitrophenyl derivatives). For each of these applications standard analytical columns (3.9 mm I.D.) and 1 ml/min flow-rates were employed with post-column stream splitting (1:100) before mass spectrometry. Various mobile phase compositions and solvent gradients were employed. The addition of 1-5% glycerol to the mobile phase was shown to have little effect on the chromatography. For all compounds studied (acylcarnitines, acyl-coenzyme A thioesters, and derivatized peptides) molecular weight information was obtained and sufficient sensitivity was achieved to allow unambiguous identification of trace components in complex mixtures.

Acyl Coenzyme A↗
PubMed1991

Determination of enzyme specificity in a complex mixture of peptide substrates by N-terminal sequence analysis.

A method has been developed to determine preferred residue substitutions in the P' position of peptide substrates for proteolytic enzymes. The method has been validated with four different enzymes; the angiotensin I-converting enzyme, atrial dipeptidyl carboxyhydrolase, bacterial dipeptidyl carboxyhydrolase, and meprin A. A mixture of N-acylated potential peptide-substrates for each of the enzymes was prepared in a single synthesis procedure on the same solid-phase synthesis resin. The peptides were identical in all residue positions except the P' position to be studied, into which numerous amino acid residues were incorporated on a theoretical equimolar basis. After cleavage and extraction of the peptides from the resin, no attempt was made to purify them individually; the exact concentration of each peptide in the mixture was determined by quantitative amino acid analysis. Incubation of an enzyme with its peptide-substrate mixture at [S] much less than Km yielded peptide hydrolytic products with newly exposed N-termini. The identity and amount of each hydrolysis product was determined by automated N-terminal sequence analysis. One cycle of sequencing revealed preferred amino acid substitutions in the P'1 position, two cycles the P'2 position, and so forth. Comparison of the rates of production of the various products indicates the preferred substitution in that particular P' position. New information on the substrate specificities of each of the enzymes tested was obtained and it is clear that this approach can be applied to any protease with a defined (or suspected) point of cleavage in a peptide substrate.

Amino Acid Sequence↗
PubMed1991

Evidence against a role for aspartyl proteases in intracellular processing of big endothelin.

CPAE endothelial cells were cultured in the presence of pepstatin, NH4Cl, or chloroquine in order to assess their effects on the secretion of endothelin-1 (ET-1). The first of these is an inhibitor of aspartyl proteases and the last two are known to neutralize acidic intracellular compartments. The pepstatin was encapsulated into liposomes to aid in its uptake, and uptake was confirmed by measuring the residual aspartyl protease activity in washed, lysed cells. Pepstatin had no effect (less than 5%) on the secretion of ET-1, 25 mM NH4Cl decreased secretion by 30-47%, and 25 microM chloroquine increased secretion by 37-79%. In contrast, each of these reagents is known to inhibit lysosomal degradation of intracellular proteins by 75-90%. Additionally, big ET was shown to be a very poor substrate, in terms of kcat/Km values, for aspartyl proteases. The rate constants were less than 10(4) M-1 s-1, which is approximately 1% of the value for the best substrates. The data, therefore, do not support a role for aspartyl proteases in the formation of ET-1. Similar to chloroquine, 0.5 microM monensin increased the secretion of ET-1 by 40-60%. Both of these reagents have previously been shown to increase the rate of constitutive secretion of peptides by affecting their partitioning between packaging into storage granules and constitutive secretion. The results would therefore provide supportive evidence for the existence of a storage form of ET-1 in endothelial cells.

Ammonium Chloride↗
PubMed1991

Sump catheter drainage of parotid abscess: an alternative to surgery.

It is a clinical challenge to distinguish patients with parotid abscesses from those with acute sialadenitis. A case of parotid abscess is presented in which a CT scan with intravenous contrast enhancement localized the abscess cavity and guided its aspiration and drainage with an indwelling catheter. By using this percutaneous technique, the need for early surgical intervention by incision and drainage was eliminated. The dense overlying parotid fascia and position of the deep parotid lobe make differentiating between these two clinical entities difficult. Parotid abscesses are readily apparent on computerized tomographic (CT) scanning evaluation with intravenous contrast enhancement, presenting as discrete fluid-filled areas unlike the amorphous appearance of acute sialadenitis. CT scanning with intravenous contrast enhancement has been the preferred radiographic study of choice for evaluating parotid masses or parapharyngeal masses. The treatment of a patient with acute sialadenitis differs from that of a patient with a parotid abscess. Patients with acute sialadenitis will usually respond to vigorous intravenous (IV) hydration, use of sialagogues and appropriate antibiotic coverage. Following a period of conservative treatment with antibiotics and warm soaks, patients with parotid abscesses will usually undergo an incision and drainage procedure, and later, parotidectomy. A case of parotid abscess is presented in which a CT scan with intravenous contrast enhancement localized the abscess cavity and guided its aspiration and drainage with an indwelling catheter. Percutaneous drainage of parapharyngeal abscesses guided by CT has been previously described by Cole. By using this percutaneous technique, the need for early surgical intervention by incision and drainage was eliminated.

Abscess↗
PubMed1990

A paraprosthetic-enteric fistula associated with a duodenal tumor.

An unusual etiology and presentation of a paraprosthetic-enteric fistula is reported involving a duodenal tumor. Review of the possible mechanisms of graft-enteric fistula formation and diagnostic evaluation is presented. Initial insertion of an extraanatomic bypass followed by graft excision was performed in the present case and is encouraged in hemodynamically stable patients. Additionally, resection of the eroded duodenum with end-to-end anastomosis was performed in order to restore intestinal continuity.

Aged↗
PubMed1990

Chlamydomonas telomere sequences are A+T-rich but contain three consecutive G-C base pairs.

We have isolated telomeric DNA and telomere-associated sequences from Chlamydomonas reinhardtii. The terminal telomere sequences of the green alga Chlamydomonas are composed of (TTTTAGGG)n repeats that are similar, but not identical, to those of the higher plant Arabidopsis thaliana. We demonstrate that these repeats are telomeric by their preferential sensitivity to nuclease Bal-31 digestion, their similarity to A. thaliana telomeres, their orientation relative to the end of the chromosome, and the methods used for their isolation. Five independent telomere clones were isolated, and three of these clones include closely related telomere-associated sequences. One of these telomere-associated sequences hybridizes to a number of genomic fragments sensitive to digestion with the exonuclease Bal-31. Like telomere sequences from other organisms, the C. reinhardtii telomeres display a bias for guanine and thymine nucleotides on the 3'-end strand. However, the sequence of Chlamydomonas telomeres is more A + T-rich than any other known telomere sequence. We propose that the common feature of all known telomere is the frequent occurrence of tracts of three or more adjacent guanine residues.

Adenine↗
PubMed1990

Effects of acute lower limb ischemia on femoral venous efflux.

Revascularization of an acutely ischemic limb may lead to the development of a reperfusion syndrome, characterized by acidosis, hyperkalemia, myoglobinuria, and disseminated intravascular coagulation. The authors evaluated the components of the femoral venous efflux after reperfusion of an acutely ischemic limb in both an experimental model and in a small clinical series.

Animals↗
PubMed1990

The effect of alpha blockade on iontophoresis-induced ocular shedding of latent HSV-1 W in different host animals.

Previous studies demonstrated that non-specific beta blockade promoted ocular shedding of latent HSV-1 in the mouse and rabbit iontophoresis models. The present study examined the effect of topical alpha blockers, thymoxamine and corynanthine, on reactivation and induced ocular shedding of latent HSV-1 W in different host animals. Latent trigeminal ganglionic infection was established in Balb/c mice and New Zealand rabbits following corneal inoculation with HSV-1 W strain, and later confirmed by co-cultivation. Treatment with coded eye drops (thymoxamine, corynanthine or BSS was begun one day prior to iontophoresis induction and continued BID OU for 5 days. Reactivation and recovery of latent HSV-1 was determined by daily ocular swabs, and characteristic HSV-1 cytopathic effect in Vero cells. In Balb/c mice, topical administration of thymoxamine 0.5% or corynanthine 5% significantly reduced the number of virus-positive eyes, virus-positive mice, and total virus-positive swabs per experiment, whereas the inhibitory effect was minimal in NZ rabbits. We conclude that alpha blockade may alter the reactivation signal that is mediated via the adrenergic system, and that different host factors (as expressed in different species) may play an important role in this process.

Administration, Topical↗