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Biomedical subjects

R Greenberg

Publications and source records attributed to R Greenberg.

At least 19 recordsLinked to original sources
PubMed1992

P amylase is always greater than S in spot urine of normal subjects. Diagnostic implications.

Single random samples of urine were collected from 50 control subjects; 27 patients with chronic pancreatitis; 19 with acute pancreatitis; 6 with acute on chronic pancreatitis; five in the recovery phase of acute attack; four patients with pseudocysts. Salivary (S) and pancreatic (P) amylase values were measured by cellulose acetate electrophoresis. The P amylase values always exceeded those of S amylase in the control specimens. In acute pancreatitis, both the lower and upper levels of total and P amylase were considerably higher than in the controls, and these high values tended to return to normal during the recovery phase of acute pancreatitis. The S amylase values were often very low or undetectable during the acute phase. Values for P amylase exceeded control values in patients with pseudocysts even in the presence of chronic pancreatitis. In chronic calcific pancreatitis, S amylase was higher than P amylase. We conclude that P amylase is always greater than S amylase in normal urine specimens, and a change in this pattern may be helpful in diagnosing various forms of pancreatitis.

Amylases↗
PubMed1992

Escherichia coli resistant to ampicillin/sulbactam.

Escherichia coli strains resistant to ampicillin/sulbactam from hospitals in 4 different geographic locations were examined with respect to type and amount of beta-lactamase produced. A total of 5 strains was examined from each region. The isoelectric points of all of the involved beta-lactamases were 5.4, corresponding to TEM-1. Km and Vmax values of the beta-lactamases among the clinical isolates resembled those from the control TEM-1 strain. In an 18-hour broth culture the highly resistant isolates produced 3 times more beta-lactamase as compared to the ampicillin/sulbactam-susceptible isolates. However, the highly resistant strains contained approximately the same amount of plasmid DNA (size of > 6,500 bp) as the susceptible isolates. In transformation experiments, both the resistance and the degree of resistance appeared to have been transferable by plasmids. The mechanism for resistance is likely to be a baseline overproduction of TEM-1 beta-lactamase due to either an alteration in the control of gene expression or simply to an increase in the number of copies of the beta-lactamase gene in the plasmids.

Ampicillin↗
PubMed1992

A research-based reconsideration of the psychoanalytic theory of dreaming.

We present a brief review of sleep research which, when combined with psychoanalytic experience, has led to the hypothesis that REM sleep and dreaming serve the function of adaptation by the process of integration of information. We then report the results of a study of dreams, based on this hypothesis. We studied dreams and their relation to waking mental activity and found a correlation between problems in manifest dreams and those in pre- and postsleep waking life. Dreams can be understood on the basis of problems that appear in them. We also found evidence for a relation between the solution of problems in dreams and the fate of those problems the next day. We discuss these findings in relation to some of the controversies about dreaming, and then present suggestions for future research.

Dreams↗
PubMed1992

Phase II study of estramustine and vinblastine, two microtubule inhibitors, in hormone-refractory prostate cancer.

PURPOSE: Estramustine phosphate (EMP) and vinblastine are two microtubule inhibitors with distinct molecular targets and at least additive antimicrotubule effects in vitro. Their modest single-agent activities in hormone-refractory prostate cancer, nonoverlapping toxicities, and lack of cross-resistance prompted a phase II trial in hormone-refractory prostate cancer. PATIENTS AND METHODS: Thirty-six assessable patients at the Fox Chase Cancer Center and seven Fox Chase Cancer Center Network institutions were treated with oral EMP 600 mg/m2 on days 1 to 42 and vinblastine 4 mg/m2 intravenously (IV) once a week for 6 weeks. Courses were repeated every 8 weeks. Response assessment was based on a change in serum prostate-specific antigen (PSA) levels and was correlated with change in pain scores. RESULTS: PSA decreased from baseline by at least 50% in 22 patients (61.1%) and by > or = 75% in eight patients (22.2%). A 50% or more decrease in PSA on three successive 2-week measurements together with an improved or stable pain score, performance status, and measurable soft tissue disease (if present) was required for a partial response (PR), which occurred in 11 patients for an overall response rate of 30.5% (95% confidence interval, 15.6% to 45.6%). In seven patients with measurable nonosseous disease, there was one PR (14%) and one minor response (MR). In 28 patients with assessable pain, major pain responses occurred in 12 (42.9%). PSA response (> or = 50% decrease times three measurements) was predictive of major pain response with a 93.7% specificity, a 50% sensitivity, and a positive predictive value of 85.7%. CONCLUSION: We conclude that EMP and vinblastine is an active combination in hormone-refractory prostate cancer.

Aged↗
PubMed1991

Replication-defective missense mutations within the terminal protein and spacer/intron regions of the polymerase gene of human hepatitis B virus.

We have analyzed 11 independent mutations located at various domains of the polymerase gene (pol) of human hepatitis B virus. Surprisingly, one of the two missense mutants within the spacer/intron region appears to be lethal. This result further defines the N-terminal limit of the reverse transcriptase domain. Alternatively, it suggests the potential existence of a novel domain with an unknown function. Two missense mutations within the terminal protein (TP) domain appear to be replication-defective as well, suggesting a functionally essential role of the TP domain in DNA replication.

Blotting, Northern↗
PubMed1991

The carboxyl-terminal region of human interferon gamma is important for biological activity: mutagenic and NMR analysis.

Deletion of nine amino acids from the carboxyl terminus of human IFN gamma (residues 138--146; LFRGRRASQ) resulted in a 7-fold increase in specific antiviral activity. Similar increases in receptor binding affinity were seen. Deletion of residues 136 and 137 (QM) had little additional effect, but removal of Ser135 resulted in a sharp drop in antiviral activity. Further removal of residues 133 and 134 (KR) lowered antiviral activity to 1% of the peak value. Comparison of the proton NMR spectra of selected deletions down to residue 132 showed that there was no significant change in the core protein structure. Deletions down to residue 125 had the same antiviral activity as those to 132, but changes could now be seen in the aromatic proton NMR spectrum of this shorter derivative. Substitution of the homologous murine sequence between residues 124 and 130 (human SPAAKTG; murine LPESSLR) resulted in only a small decrease in antiviral activity, further suggesting that the precise sequence in this region was not critical for activity. Ser135 was substituted with a number of other amino acids with little or no change in activity. The importance of the residues between 131 and 134 for biological activity was corroborated by mutagenesis, although some substitutions in this region were tolerated.

Animals↗
PubMed1991

Very high affinity interaction of DPI 201-106 and BDF 8784 enantiomers with the phenylalkylamine-sensitive Ca2(+)-channel in Drosophila head membranes.

1. Piperazinylindoles (DPI 201-106, BDF 8784), drugs known to act on voltage-dependent Na(+)-channels, bind with very high affinity to a Ca2(+)-channel-associated phenylalkylamine receptor in Drosophila melanogaster head membranes. These compounds and (+)-tetrandrine, a naturally occurring Ca2(+)-antagonist, were the most selective inhibitors for phenylalkylamine-labelled Drosophila Ca2(+)-channels compared to mammalian L-type Ca2(+)-channels. 2. Replacement of the cyano group by a methyl group in (+)-DPI 201-106 ((+)-BDF 8784) increases the IC50 value for inhibition of phenylalkylamine labelling of Drosophila Ca2(+)-channels from 0.29 to 2.1 nM but decreases the IC50 value for inhibition of phenylalkylamine labelling of mammalian skeletal muscle Ca2(+)-channels from 3480 to 49 nM. 3. DPI 201-106 enantiomers completely block (at 0.1 microM) phenylalkylamine photolabelling of a 136 K polypeptide in Drosophila head membranes whereas 10 microM aconitine or lidocaine are without effect. 4. Assessment of the Ca2(+)-antagonist effects of the substituted DPI 201-106 enantiomers in K(+)-depolarized taenia strips from guinea-pig caecum yielded pA2 values of 6.33 +/- 0.07 for (-)-BDF 8784 and 6.99 +/- 0.17 for (+)-BDF 8784, respectively. 5. Piperazinylindoles, previously believed to act nonspecifically on voltage-dependent mammalian L-type Ca2(+)-channels, therefore have stereoselectivity for a novel binding site and chemical selectivity unrelated to local anaesthetic activity. 6. It is proposed that a very high affinity piperazinylindole-selective site is coupled to the phenylalkylamine receptor of Drosophila Ca2(+)-channels. These sites are still present on mammalian L-type Ca2(+)-channels but have lower affinity and/or are less tightly coupled to phenylalkylamine receptors on the alpha 1-subunit.

Affinity Labels↗
PubMed1990

Value of electrophysiologic testing in patients with previous myocardial infarction and nonsustained ventricular tachycardia. Philadelphia Arrhythmia Group.

Previous studies of the value of electrophysiologic studies in patients with nonsustained ventricular tachycardia (VT) have been hampered by the inclusion of a small number of patients with various types of heart disease. This retrospective study was designed to assess the value of programmed stimulation in 205 asymptomatic patients who had had an acute myocardial infarction greater than 1 month before study. Inclusion was based on 24-hour Holter monitoring during which patients had to manifest greater than or equal to 3 consecutive ventricular beats at a rate greater than 135 beats/min. Forty-seven (23%) patients had normal, 70 (34%) mildly impaired and 88 (43%) severely impaired left ventricular function. Programmed stimulation, using up to 3 extrastimuli, was used in each. Seventy-five patients (36%) were noninducible, 59 (29%) had nonsustained VT (less than 30 seconds), 67 (33%) had sustained monomorphic VT and 4 (2%) had either polymorphic VT or ventricular fibrillation. Eighty-two patients were not treated with antiarrhythmic drugs, 57 others were placed on a program selected empirically and 66 had therapy guided by electrophysiologic testing. Satisfactory follow-up information was gathered in 187 of the 205 patients, with a mean follow-up of 18 months. One hundred forty-two patients are alive and well, 39 had sustained VT or sudden death and 6 others had a cardiac death. Only left ventricular function discriminated those who had a sustained arrhythmia or died from those who did not. Thus, programmed stimulation did not have independent predictive value in patients with nonsustained VT. However, definitive conclusions can be reached only with a large prospective study carried out in untreated patients.

Anti-Arrhythmia Agents↗
PubMed1990

Cytoplasmic and periplasmic expression of a highly basic protein, human interleukin 4, in Escherichia coli.

Human IL-4 (hIL-4) has been cloned from a human T cell line based on its homology to the murine IL-4 cDNA sequence. We have compared cytoplasmic and extra-cytoplasmic expression of this basic protein in Escherichia coli using various combinations of promoters, replicons and host strains. Strains producing a cytoplasmic product were most successful at heterologous protein expression, producing up to 500 mg/l of an inactive aggregated form of the protein. The biological activity of the protein could be restored by refolding the protein with guanidine hydrochloride and glutathione giving a specific activity identical to that of IL-4 derived from CHO cell lines stably transformed with an hIL-4 expression plasmid. Strains designed to secrete human IL-4 into the periplasmic space produced far less protein (approximately 5 mg/l). However, a significant fraction of this protein was detected in the culture medium. This fraction appeared to be soluble after ultracentrifugation, and demonstrated high specific activity without refolding. Leakage of heterologous protein into the culture medium may be a viable way to recover biologically active products without relying on the denaturation and refolding in vitro that can, at times, yield incorrectly folded gene product.

Amino Acid Sequence↗
PubMed1990

Exploiting the cell membrane for the production of heterologous proteins in Escherichia coli.

The bacterial membrane serves both as a cell organelle and as a barrier for segregating the metabolically active cytoplasm from the extracellular milieu. Thus we can use plasmid vectors designed to produce a hybrid protein containing an efficient signal peptide coupled to the amino terminus of the cloned heterologous protein (secretion cloning vectors) for the production of proteins which are insoluble, proteolytically sensitive, or bacteriocidal when produced in the cytoplasm of Escherichia coli. We demonstrate that human granulocyte-macrophage colony stimulating factor can be isolated as an active species only after transport into the bacterial periplasm. Production of the protein in the bacterial cytoplasm is bacteriocidal. We also demonstrate that biologically active human interleukin 4 appears only after transport of the protein into the bacterial growth medium. The protein forms membrane-associated aggregates in the cytoplasm, and demonstrates an active but nonnative conformation when expressed in the periplasm. This may correlate with the affinity of the interleukin 4 molecule for negatively charged macromolecules, including bacterial membrane components and bacterial lipopolysaccharides, which may alter the folding pathway inside the cell.

Animals↗
PubMed1989

Safety of endoscopy in the immediate postoperative period following gastric anastomosis.

The safety of gastrointestinal endoscopy in the immediate postoperative period following partial gastrectomy was assessed in ten dogs. Endoscopy was performed preoperatively and at 1, 2, 3, and 7 days postoperatively. The mean pressures required to perform an adequate endoscopy varied from 17 to 20 mm Hg. Following partial gastrectomy, the abdominal wall was closed with a zipper to facilitate inspection of the gastric anastomosis. No leakage of air or intra-abdominal abscesses were seen following endoscopy. The results of this study suggest that endoscopy can be safely performed in the immediate postgastrectomy period.

Animals↗
PubMed1989

Gastroenterology, diagnosis-related groups, and age.

Hospitals are now being reimbursed by a prospective Diagnosis-Related Group (DRG) classification system. There have been no major changes in the Federal Medicare DRG classification system since its inception 5 years ago. In this project, we analyzed all gastrointestinal (GI) medicine admissions by age and resource utilization at a large academic medical center. Total hospital costs for the 3,598 GI patients (January 1, 1985, through December 31, 1987) were $18,460,604. Although DRG reimbursement for all patients for the 3-year period would have generated an aggregate profit of $957,760, four out of five age categories of patients 65 years of age and above would have generated losses; the highest loss was for patients 85 years and over, at $2,235 per patient. Older GI patients (i.e., 65 years and over) had higher hospital costs, longer lengths of stay, more diagnoses and procedures per patient, and a higher mortality rate than younger patients. Both intensive care unit (ICU) and blood utilization rose with age. Thus, older GI patients consumed a disproportionately larger share of hospital resources. Our study suggests that the current DRG reimbursement scheme may be inequitable relative to the older GI medicine patient; financial disincentives from DRGs may affect elderly patients' access to and quality of care in the future.

Academic Medical Centers↗
PubMed1988

Accessibility and mobility of lysine residues in beta-lactoglobulin.

N epsilon-[2H6]Isopropyllysyl-beta-lactoglobulin was prepared by reductive alkylation of beta-lactoglobulin with [2H6]acetone and NaBH4 to provide a 2H (NMR) probe for the study of lysine involvement in lipid-protein interactions. Amino acid analysis showed 80% of the protein's 15 lysine residues to be labeled. Unmodified lysine residues were located through peptide maps produced from CNBr, tryptic, and chymotryptic digests of the labeled protein. Lys47 was not modified; Lys135,138,141, located along an amphipathic helical rod, were each partially unmodified. All other lysine residues were at least 90% modified. Average correlation times calculated from 2H NMR spectra were 20 and 320 ps for 8.7 and 3.3 residues, respectively, in 6 M guanidine hydrochloride; in nondenaturing solution, values of 70 and 320 ps were obtained for 6.5 and 3.2 residues, respectively, with the remaining 2.3 modified residues not observed, suggesting that side chains of lysine residues in unordered or flexible regions were more mobile than those in stable periodic structures. 2H NMR spectra of the protein complexed with dipalmitoylphosphatidylcholine confirmed the extrinsic membrane protein type behavior of beta-lactoglobulin previously reported from 31P NMR studies of the phospholipids complexed with beta-lactoglobulin. Although no physiological function has yet been identified, comparison of these results with the X-ray structure [Papiz et al. (1986) Nature (London) 324, 383-385] supports the hypothesis that residues not accessible for modification may help to stabilize the cone-shaped beta-barrel thought to contain binding sites for small lipid-soluble molecules.

Amino Acid Sequence↗
PubMed1988

Effects of reductive alkylation on peptide retention times.

Reductive alkylation of primary amino groups is used to introduce nuclear magnetic resonance or radioactive probes into proteins. Because of electrostatic and conformational effects, reductive alkylation is not always complete. We describe herein a rapid high-performance liquid chromatographic method for separating and quantitating mixtures of native and reductively alkylated peptides. Small synthetic peptides were chosen to illustrate the effects of methylation and isopropylation of primary amino groups on chromatographic retention times. Mixtures of unmodified and reductively methylated or isopropylated peptides (Gly-Leu-Tyr, Gly-Gly-Lys-Arg, Arg-Lys-Asp-Val-Tyr and Pro-Gly-Lys-Ala-Arg) could be separated. Chromatography was on a 5-micron, 25 cm x 0.4 I.D., C18 reversed-phase column with 0.1% trifluoroacetic acid in a 10 to 80% linear gradient of acetonitrile in water, a system appropriate for protein digests. The relative concentrations of native, and singly and doubly alkylated peptide were determined as well as the effective retention coefficients for dimethyl and isopropyl groups. The method shows promise for the peptide mapping of partially alkylated proteins.

Alkylation↗