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Biomedical subjects

E Rosenberg

Publications and source records attributed to E Rosenberg.

At least 19 recordsLinked to original sources
PubMed1992

Mutation and mapping of genes involved in production of the antibiotic TA in Myxococcus xanthus.

Transposition of TnV and Tn5lac into Myxococcus xanthus yielded 8,381 kanamycin-resistant mutants that were tested for antibiotic TA production. Twenty-four of the mutants were nonproducers of TA (less than 0.4 ng/ml), and 3 produced a higher level (2.5 micrograms/ml) than the parent strain (1.5 micrograms/ml). For most of the strains, there was 100% cotransduction between kanamycin resistance and the altered TA phenotype. Southern blot analysis of restriction digests of the mutant DNA indicated that the transposons were inserted at different sites on the M. xanthus chromosome. The TA genes were mapped by cotransduction between pairs of mutants following replacement of the initial insert of one of the pair with the tetracycline resistance transposon Tn5-132. Nine of the 13 nonproducers tested were linked over a 36-kb stretch of the chromosome. There was no linkage between one of the overproducers and any of the nonproducers tested.

Anti-Bacterial Agents↗
PubMed1992

Use of Tn5lac to study expression of genes required for production of the antibiotic TA.

The beta-galactosidase activities arising from Tn5lac insertions in several genes required for antibiotic TA production were measured under different growth conditions. In all of the non-TA-producing mutants, the beta-galactosidase specific activity was higher when the cells were grown in nutrient-limited 0.5CTS medium (0.5% Casitone plus alanine, serine, and glucose) than in rich 2CT medium (2% Casitone). One of the mutants, 420, had low beta-galactosidase specific activity in both media. The other seven mutants containing inserts in genes essential for TA production had specific activities of 139 to 367 U/mg of protein in 0.5CTS medium and 11 to 48 U/mg of protein in 2CT medium. The beta-galactosidase specific activities of two strains, 1030 and 420, increased during exponential growth in 0.5CTS medium. The beta-galactosidase specific activities of both strains increased greatly when the cells were grown in the presence of magnesium phosphate, which traps ammonium ions. The Tn5lac insertions in 1030 and 420 were used to screen for mutants with increased levels of transcription. An N-methyl-N'-nitro-N-nitrosoguanidine-induced mutation in 1030 that mapped 17 kb from the omega 1010 insert increased the specific activity of beta-galactosidase 21 times in 2CT medium. The regulatory mutation appears to release the repression caused by 2CT medium. A UV-induced mutation in 420 increased the beta-galactosidase specific activity 1.4 to 2.4 times. Medium conditions that affect the transcription of TA genes are discussed in terms of enhanced antibiotic TA production.

Anti-Bacterial Agents↗
PubMed1992

Hunger: a hospital survey.

Patients at a New York City municipal hospital were surveyed in 1985 and 1989 to ascertain the extent of hunger and its possible correlates. Twenty-two percent (22%) of the 382 subjects in 1985 and 23% of the 332 subjects in 1989 experienced hunger. Hunger was related significantly to homelessness, social isolation and the physical inability to buy and/or prepare food. Between 1985 and 1989, there was a large increase in the use of institutional resources for food; a decline in reliance on Food Stamps; and an increase in household density. Inpatients were found to be poorer than outpatients, and to rely more heavily upon soup kitchens. Practice, policy and research implications are noted.

Food Deprivation↗
PubMed1992

Transcriptional and posttranscriptional control of connexin mRNAs in periportal and pericentral rat hepatocytes.

Distinct patterns of expression of gap junction, or connexin, mRNAs were observed in periportal vs. pericentral hepatocytes. The two cellular fractions (isolated from rat livers by perfusion) were more than 90% parenchymal, as determined by flow cytometry for a hepatocyte-specific marker. The periportal and pericentral fractions were identifiable due to enrichment in enzymatic activities previously shown to be differentially expressed in the respective regions of liver. Northern blot analyses revealed that mRNA encoding connexin 26 was 2.8 times more abundant in the periportal than in the pericentral cells, while connexin 32 mRNA was equally distributed. Messenger RNA from each fraction was radiolabeled in order to compare the relative abundance of the connexin mRNAs in each fraction. The ratio of connexin 26 to connexin 32 mRNA in the portal fraction was about 0.085, and in the central fraction about 0.038. Connexin 26 mRNA was transcribed, however, at a faster rate than connexin 32 mRNA by nuclei isolated from both cellular fractions. Connexin 26 mRNA was transcribed at 3.9 times the rate in nuclei from the periportal than from the pericentral cells. These data suggest that while the zonation of connexin 26 mRNA synthesis in liver appears to be controlled transcriptionally, posttranscriptional regulatory mechanisms determine the relative abundance of the connexin mRNAs.

Animals↗
PubMed1991

Testing various methods of introducing health charts into medical records in family medicine units.

OBJECTIVE: To test three methods of introducing health charts into the medical records of six family medicine units. DESIGN: Quasi-experiment. PARTICIPANTS: The staff physicians and family medicine residents in all six units and the nurses in two units. INTERVENTIONS: Group 1 (minimal intervention): health charts, a user's guide and one training session. Group 2 (intermediate intervention): same intervention as for group 1 plus two feedback sessions at 3 and 6 months. Group 3 (maximum intervention): same intervention as for group 2 plus promotion of the team concept (nurses were included). The intervention phase lasted from September 1987 to August 1988. OUTCOME MEASURES: The frequency with which the health charts were used, the item scores of each preventive care activity and the overall unit scores. Data were gathered through chart audits at baseline and at the end of the intervention phase. RESULTS: The frequency with which the health charts were used varied from 3.9% to 26.9%. The greatest increases in item scores were observed in the use of mammography (20.0%), counselling on lifestyle (19.4%) and breast examination (17.2%). Although the overall improvement in the unit scores was statistically significant (p less than 0.05) the hypothesis of an increasing gradient of effect across the three intervention groups could not be tested because of the variation in scores across the units. CONCLUSION: Health charts and other similar tools are useful; however, they are not sufficient to change practice behaviours. The support of a "champion" on the health care team might well be a determining factor of success for the delivery of preventive services in primary care practice.

Adult↗
PubMed1991

Comparison of sensitivity for human cytomegalovirus of the polymerase chain reaction, traditional tube culture and shell vial assay by sequential dilutions of infected cell lines.

Although traditional tube culture (TTC) is still considered by many as the 'gold standard' for the laboratory diagnosis of human cytomegalovirus (HCMV), the shell vial assay (SVA) offers greater speed of detection. This technique utilizes immunofluorescence (IF) to detect early or immediate early nuclear antigens (IEA). The detection capabilities of these two tests were compared with the polymerase chain reaction (PCR), a technique that amplifies enzymatically selected DNA target sequences. Serial dilutions of crude culture harvests from 2 HCMV strains, Towne and a clinical urine isolate, were made up to 1:1 000,000. Ten-microliters aliquots of the original sample and each dilution were tested by PCR, TTC and SVA. For PCR, the nested-primer approach was used. Outer primers delimited a 721-bp sequence contained within the 2nd to 4th exons of the immediate-early protein. Inner nest primers delimited a 167-bp sequence in the third exon, detected by a 32P-labelled probe. The results show that: (1) control samples which contained all PCR reagents but no DNA were uniformly negative; (2) radiolabelled-probe detection (RPD) of PCR products is, on average, 100 x more sensitive than detection by ethidium bromide; (3) PCR is, on average, 100 x more sensitive than evaluation of cytopathic effect (CPE) in the TTC; (4) the predictive value of a negative SVA result is low compared to PCR.

Base Sequence↗
PubMed1991

Basic medical physiology: the whole is more than the sum of its parts.

In this article we examine the role of basic medical physiology in medical school education. We discuss the historical background, courses in this subject, and methods of teaching it. We conclude that the teaching of medical physiology should emphasize the study of organ systems and of the intact body. The techniques should emphasize meticulous observation, the posing of hypotheses, and the subsequent testing of the hypotheses, i.e., the use of the method used successfully in research. Students should learn the power of the experimental approach and to appreciate the immense variability possible in responses in complex organisms. They should also learn that principles of statistical probability applied logically can detect important differences in data that may be obscured by this variability. They should learn that there are no rigid answers when studying an individual and that they must continue to learn throughout their lives.

Animals↗
PubMed1990

Human natural killer cells express Na+ channels. A pharmacologic flow cytometric study.

Voltage-gated excitability of purified human NK cells was studied by using flow cytometry and the voltage-sensitive dye, oxonol. Highly purified human NK cells (CD16 = 95 +/- 1%) from normal volunteers were prepared by using a negative panning technique. The Na(+)-channel agonists batrachotoxin (BTX) (1 to 4 microM) and veratridine (Ver) (100 to 400 microM) depolarized a population of highly purified human NK cells as determined by flow cytometry. BTX and Ver responses were concentration-, time-, temperature-, and Na(+)-dependent. The Na+ channel antagonist tetrodotoxin (1 microM) blocked BTX and Ver responses. Ver (100 microM) produced significant inhibition of cytotoxicity when purified NK cells were incubated with K562 tumor target cells in a 4-h 51Cr release cytotoxicity assay. The effect was blocked by tetrodotoxin. These results strongly suggest presence of functional Na+ channels in NK cells. Activation of voltage-dependent Na+ channels depolarizes cells and reduces their in vitro cytotoxic function.

Batrachotoxins↗
PubMed1990

Role of autocide AMI in development of Myxococcus xanthus.

A new developmental mutant of Myxococcus xanthus has been isolated by screening TnV insertion mutants for AMI-dependent development in submerged culture. This mutant (ER304) aggregated and sporulated on agar surfaces but required at least 3.8 micrograms of autocide AMI per ml for development in submerged cultures. Spore rescue of ER304 was obtained with the saturated, monounsaturated, and diunsaturated fatty acid fractions of AMI, with specific activities of 68, 115, and 700 U/mg, respectively. In addition, several model fatty acids were capable of rescuing sporulation of ER304; however, there was no correlation between specific lytic activity observed in vegetative cultures and specific rescue activity. Rescue of ER304 was effected during the first ca. 12 h after the initiation of starvation conditions; after this time, addition of AMI or model fatty acids killed the cells. Supernatant fluids of ER304 rescued development in dsg mutants (e.g., DK3260) in submerged cultures, but dsg mutant supernatant fluids were incapable of rescuing ER304 development. The data presented in this article support the idea that the primary mechanism of rescue by AMI is not via lysis, although developmental lysis may be an indirect result of the rescue event. A membrane permeability model is presented to explain the role of autocides in early developmental events in wild-type strains and in the aggregation and sporulation rescue of developmental mutants ER304 and DK3260.

DNA Transposable Elements↗
PubMed1990

Statistical models for evaluating the penetrating ability of endodontic instruments.

An in vitro study was conducted to evaluate the penetrating ability of hand instruments (No. 10 K-file and "Pathfinder") and an automated device with a No. 08 (Canal Finder System) file in 270 extracted curved and narrow molar roots. The roots were randomly allocated to six groups, each one corresponding to a different permutation of the three instruments. The experiment was performed in three sequential stages, and Stages II and III were undertaken only in roots where no apical penetration was achieved in the previous stage(s). Statistical models were designed to fit the resulting clinical data. The No. 08 Canal Finder System and No. 10 K-file proved to be similar in their penetrating ability in Stage I (with estimated probabilities of 71.1% and 68.8%, respectively). The No. 08 Canal Finder was found to be the most efficient in Stage II and especially in Stage III, with a probability of penetration of 20.7%, compared with 9.8% for the "Pathfinder" and 7.4% for the No. 10 K-file.

Dental Pulp Cavity↗
PubMed1990

Blood pressure response to exercise in normotensive and hypertensive young men.

We attempted to determine the optimal cut-off value of blood pressure defining a hypertensive response to exercise testing in 90 asymptomatic Israeli candidates for flight training with casual resting blood pressure of 140/90 mm Hg or more, and 72 age-matched normotensive controls tested in the Israel Air Force Aeromedical Center. Exercise testing (Bruce protocol) was performed using a calibrated Quinton Treadmill and a Hewlett Packard 151711-A three-channel ECG recording system. Recordings were made at 3-min intervals. At 3 min of exercise 12/87 (14%) of the hypertensive subjects had a SBP of greater than or equal to 210, compared to only 1/71 (1%) of the control group (relative risk 14). At 12 min of exercise 27/51 (53%) of the hypertensives and 9/55 (16%) of the controls had similar elevations of SBP (relative risk 3.3). At 6 min of exercise 11/87 (13%) of hypertensives had SBP greater than or equal to 220, whereas none of the normal controls had SBPs elevated to that degree. We concluded that an increase in SBP to 210 mm Hg or more after 3 min or to 220 mm Hg after 6 min of exercise testing by the Bruce protocol best separates the hypertensive group from the control group. This occurs at the expense of sensitivity. Only appropriate longitudinal studies can compare the degree to which various definitions of the hypertensive response to exercise will predict future hypertension.

Adolescent↗
PubMed1989

Effect of adhesive antibiotic TA on plaque and gingivitis in man.

The adhesive antibiotic TA was applied to the dento-gingival junction of 8 human volunteers, suffering from moderate to severe gingivitis. 2 diametrically opposed quadrants of the mouth received 4 applications of 0.1 mg TA, while the other 2 quadrants were treated with a placebo and served as controls. The plaque index, gingival index and bleeding index were scored periodically for 2 weeks and in 4 patients for up to 30 days. The TA-treated quadrants showed a rapid decrease in all 3 indices following 2 treatments. A further improvement was observed with the 3rd and 4th treatments. 30 days after the onset of the experiment and 23 days after the last application, the indices were still considerably lower than the initial values.

Adult↗
PubMed1989

Guided tissue regeneration in the treatment of furcation defects in mandibular molars. A clinical study of degree III involvements.

The present investigation was designed to evaluate the regenerative potential of the periodontal tissues in degree III furcation defects at mandibular molars using a treatment procedure based on the principle of guided tissue regeneration. The patient sample included 21 patients, 26-65 years of age, who presented periodontal lesions in the right and left molar regions including "through and through" furcation defects. After an initial examination, each patient was subjected to a series of full-mouth scaling and root planing. 2-3 months later, they were recalled for a baseline examination. The furcation-involved molars were randomly assigned in each patient to either a test or a control treatment procedure. The test procedure included the elevation of muco-periosteal flaps at the buccal and lingual aspects of the molars. Granulation tissue was removed and the exposed root surfaces were debrided and planed. The width and the height of the entrance openings to the furcation defects were assessed. A teflon membrane was adjusted to cover the entrances to the defects (buccal and lingual) and was retained in the manner described by Pontoriero et al. (1988). The flaps were repositioned on the outer surface of the membrane and secured by sutures which were removed after 10 days. Following surgery, the patients were instructed to rinse the mouth twice daily for 4 weeks with chlorhexidine gluconate. The membranes were removed after a healing period of 1-2 months. A surgical procedure identical to the test procedure was performed in the control tooth regions with the exception of the placement of membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Autocide AMI rescues development in dsg mutants of Myxococcus xanthus.

Low concentrations of autocide AMI rescued aggregation and sporulation in the dsg mutant class of Myxococcus xanthus but were incapable of rescuing asg, bsg, or csg mutants. AMI-induced spores of dsg mutants were resistant to heat and sonication and germinated when plated on nutrient-rich agar. AMI accelerated aggregation and sporulation and increased the final spore number in submerged cultures of a wild-type strain of M. xanthus. Development of M. xanthus was accompanied by release of a fluorescent material (emission maximum, 438 nm) into the supernatant fluid. The release of this material began early and continued throughout development. All Spo- mutant strains tested released significantly reduced levels of this material. These levels were increased in the presence of AMI in all Spo- mutant classes, most dramatically in the dsg mutants.

DNA, Bacterial↗
PubMed1989

Sporulation of Myxococcus xanthus in liquid shake flask cultures.

When suspended in a liquid starvation medium, exponentially growing Myxococcus xanthus sporulated within 3 days. These myxospores were similar to spores developed within fruiting bodies, as determined by electron microscopy and the production of spore-specific protein S. This liquid sporulation system may be useful as a means of preparing large quantities of myxospores and extracellular fluid for biochemical studies, including isolation of chemical signals produced during the sporulation process.

Bacteriological Techniques↗
PubMed1989

Cell-density-dependent lysis and sporulation of Myxococcus xanthus in agarose microbeads.

Vegetative cells of Myxococcus xanthus were immobilized in 25-microns-diameter agarose microbeads and incubated in either growth medium or sporulation buffer. In growth medium, the cells multiplied, glided to the periphery, and then filled the beads. In sporulation buffer, up to 90% of the cells lysed and ca. 50% of the surviving cells formed resistant spores. A strong correlation between sporulation and cell lysis was observed; both phenomena were cell density dependent. Sporulation proficiency was a function of the average number of cells within the bead at the time that sporulation conditions were imposed. A minimum of ca. 4 cells per microbead was necessary for efficient lysis and sporulation to proceed. Increasing this number accelerated the lysis and sporulation process. No lysis occurred when an average of 0.4 cell was entrapped per bead. Entrapping an average of 1.7 cells per bead resulted in 46% lysis and 3% sporulation of survivors, whereas entrapping an average of 4.2 cells per bead yielded 82% lysis and 44% sporulation of the surviving cells. Sporulation and lysis also depended upon the cell density in the culture as a whole. The existence of these two independent cell density parameters (cells per bead and cells per milliliter) suggests that at least two separate cell density signals play a role in controlling sporulation in M. xanthus.

Cell Survival↗