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J W Roberts

Publications and source records attributed to J W Roberts.

At least 19 recordsLinked to original sources
PubMed1995

Kinetics of RNA polymerase initiation and pausing at the lambda late gene promoter in vivo.

We have measured the kinetics of transcription initiation and pausing by Escherichia coli RNA polymerase (RNAP) at the bacteriophage lambda late promoter, pR's, in growing cells. RNAP initiating transcription from pR' pauses after transcribing 16 or 17 nucleotides, and escape from this pause could in theory be the rate-limiting step in promoter function. We tested this hypothesis by analyzing pausing and non-pausing variants of both the pR' promoter segment and a more active mutant version of pR'; we measured reporter gene expression and used KMnO4 footprinting to measure directly occupancy of the promoter and pause sites in growing cells. We find that RNAP paused at +16/+17 does not limit expression of pR'. However, RNAP paused at +16/+17 does limit expression from the more active promoter by impeding formation of open complex. Therefore, the activity of the late gene regulatory protein Q to suppress the early pause, in addition to its antitermination activity, is unlikely to be important in phage gene expression.

Bacteriophage lambda↗
PubMed1995

Putting prevention into practice. Impact of a multifaceted physician education program on preventive services in the inner city.

BACKGROUND: Physicians' prevention practices often differ from guidelines published by national authorities. Effective preventive services are most needed in inner city settings that suffer disproportionately from preventable diseases. This study examined the impact of a multifaceted physician prevention education program on the provision of preventive services in an inner city municipal hospital. METHODS: The study used a controlled intervention comparative design at two inner city municipal hospitals--Harlem Hospital Center, New York, NY (intervention site) and Kings County Hospital, Brooklyn, NY (comparison site)--serving predominantly African-American patient populations. The intervention site received prototype materials for physicians, patients, and the office setting from the US Public Health Service's Put Prevention Into Practice campaign and a series of prevention lectures from November 1991 through April 1992. Change in physician prevention practices and knowledge was assessed by self-administered questionnaires and change in patients' reports of preventive services received was assessed by structured interviews. RESULTS: Physicians at Harlem Hospital Center reported a greater postintervention increase in prevention practices and demonstrated a greater increase in prevention knowledge in comparison with physicians at Kings County Hospital. Patients at Harlem Hospital Center reported receiving increased preventive services from physicians after the intervention, while patients at Kings County Hospital did not report any significant change in preventive services received. CONCLUSIONS: A multifaceted physician education program using prototype materials from the Put Prevention Into Practice campaign with prevention lectures significantly increased the prevention knowledge and practices reported by physicians and the preventive services reported received by patients at an inner city municipal hospital.

Adult↗
PubMed1995

Transluminal extraction catheter atherectomy in long saphenous vein grafts.

Lesions in distal coronary vasculature present unique problems for catheter-based interventions. We report two cases of attempted transluminal extraction catheter (TEC) atherectomy for very distal lesions in long circular saphenous vein grafts. One case succeeded with a simple modification of the TEC device; another failed because of excessive tortuosity in the proximal graft. This experience helps define the potential and limitations of TEC.

Aged↗
PubMed1995

Exposure of children to pollutants in house dust and indoor air.

This review summarizes occurrence and exposure studies for pollutants in house dust and related indoor air exposures. A standard sampling method and control methods to reduce these exposures are discussed, including recommendations for future research. Infants and toddlers receive a broad and significant range of exposures to lead, pesticides, PAHs, allergens, and VOCs in house dust and indoor air. Carpet dust in eight Columbus and nine Seattle homes contained concentrations of potentially carcinogenic PAHs ranging from 3 to 290 micrograms/g, of lead from 250 to 2250 micrograms/g, and of PCBs from 210 to 1900 ng/g. Dust collected from ten used sofas in Seattle averaged 16.3, 37.2, and 229 micrograms/g for dust mite allergen, cat allergen, and lead, respectively; dust samples showed mutagenic activity. Biological and chemical pollutants in indoor dust and air have been associated with lead poisoning, cancer, allergy, asthma, damage to the nervous system, and sick building symptoms. The 11% of toddlers who have pica tend to have the highest exposures and risks. Further, the exposure of toddlers to lead via the dust pathway can be greater than by other routes. Standard method ASTM 5438.94 for sampling house dust has been used to characterize current and chronic exposure of toddlers in epidemiological studies. The accumulation of dust, dust mites, and tracked-in soil in old carpets, sofas, and mattresses appears to be a major source of exposure to lead, pesticides, allergens, PAHs, and VOCs. Remodeling and energy conservation can reduce ventilation and increase relative humidity, dust, dust mites, molds, VOCs, and other indoor air pollutants. The U.S. faces large and increasing costs from asthma and allergy. Asthma incidence in the U.S. has increased from 0.5% in 1930 to 8%-12% in 1991. Asthma hospitalization rates for children are increasing at the rate of 4%/yr in the U.S. and 14%/yr in Seattle. Such hospital visits would be rare with effective diagnosis, patient education, and control of home exposures. Asthma was estimated to cost $6.2 billion in 1990; hospital visits of children in Seattle cost $2,526,000 in 1993. Forty percent of the U.S. population has been sensitized to allergens; one in three homes has high relative humidity, which favors dust mites, molds, allergies, asthma, and other respiratory diseases. Reducing indoor allergens can reduce costs, severity, and the risk of being sensitized and developing allergic disease. Use of volunteer Master Home Environmentalists to do free in-home surveys and education in Seattle may reduce immediate health costs from allergens as well as long-term risks from lead, carcinogens, and home chemicals.(ABSTRACT TRUNCATED AT 400 WORDS)

Air Pollutants↗
PubMed1995

Transanal excision of rectal carcinoma.

Twenty-two men and 16 women with a mean age of 67 years were treated for rectal carcinoma by transanal excision. Patients presented with rectal bleeding (63%), change in bowel habits (11%), rectal pain (4%), or were asymptomatic and discovered on screening proctosigmoidoscopy (22%). The tumors were located from the anal verge to 8 cm proximally and ranged in size from 1 to 4 cm. Pathologic findings included adenocarcinoma (92%), squamous cell carcinoma (4%), and cloacogenic carcinoma (4%). Postoperative hospitalization averaged two days (0 to 29 days). One patient died of a perioperative myocardial infarction for an operative mortality of 3 per cent. Morbidity was 7 per cent and included urinary retention and pneumonia. Postoperative radiation therapy was administered to 11 patients with either undifferentiated tumors or invasion into the muscularis propria. Follow-up in these 38 patients averaged 30 months. One patient died of metastatic carcinoma, and two patients developed local recurrence that was treated successfully by a low anterior resection or abdominoperineal resection. Transanal excision of rectal carcinoma can be performed in properly selected patients with good overall survival and local control.

Adenocarcinoma↗
PubMed1994

Determination of intrinsic transcription termination efficiency by RNA polymerase elongation rate.

Transcription terminators recognized by several RNA polymerases include a DNA segment encoding uridine-rich RNA and, for bacterial RNA polymerase, a hairpin loop located immediately upstream. Here, mutationally altered Escherichia coli RNA polymerase enzymes that have different termination efficiencies were used to show that the extent of transcription through the uridine-rich encoding segment is controlled by the substrate concentration of nucleoside triphosphate. This result implies that the rate of elongation determines the probability of transcript release. Moreover, the position of release sites suggests an important spatial relation between the RNA hairpin and the boundary of the terminator.

Base Sequence↗
PubMed1993

Use of Prograf (FK 506) as rescue therapy for refractory rejection after liver transplantation. US Multicenter FK 506 Liver Study Group.

This report describes the clinical characteristics and demographics of patients enrolled into this rescue trial for patients experiencing refractory rejection after liver transplantation. Actuarial graft and patient survival at 12 months postconversion was 50% and 72%, respectively. Actual treatment success at 3 months postconversion was 70%. Karnofsky scores and liver function tests were significantly improved for patients continuing on therapy indicating clinical benefit in these patients. The safety profile of FK 506 is acceptable for such a high-risk group of patients. These preliminary clinical results support the conclusion that FK 506 can effectively control and reverse refractory rejection in a majority of liver transplantation patients.

Acute Disease↗
PubMed1992

The phage lambda gene Q transcription antiterminator binds DNA in the late gene promoter as it modifies RNA polymerase.

The bacteriophage lambda gene Q transcription antiterminator modifies RNA polymerase during an extended pause in elongation at nt +16 and +17 of the phage late gene promoter transcript. We show here that Q binds a specific DNA site between the -10 and -35 elements of the promoter as it interacts with the enzyme. We show that the pause must reflect a specialized elongation structure that is receptive to modification by Q, because Q does not bind to RNA polymerase stopped artificially after transcribing 16 nt of mutant DNA that does not encode the natural pause. Footprinting shows that RNA polymerase in the paused complex makes distinctive interactions with DNA in the region where Q binds; binding of Q, in turn, changes the footprint both at the Q-binding site and in the transcription bubble. Binding of Q to the paused transcription complex is stabilized by the transcription factor NusA, as expected from the dependence of lambda Q-mediated antitermination on NusA.

Bacteriophage lambda↗
PubMed1992

What are the contraindications for laparoscopic cholecystectomy?

Acute cholecystitis, morbid obesity, and previous upper abdominal surgery have been reported as relative contraindications to laparoscopic cholecystectomy. An analysis of 706 laparoscopic cholecystectomies performed at our institution was undertaken to determine if these relative contraindications led to increased morbidity, an increased rate of conversion to the open technique, or longer operating time. One hundred ninety-seven patients demonstrated one or more relative contraindications to laparoscopic cholecystectomy. Morbidity was not increased in patients with these risk factors, but conversion to open cholecystectomy was required in a greater percentage of patients with acute cholecystitis. We favor an attempt at laparoscopic cholecystectomy in patients with these risk factors; however, they should be counseled as to the increased risk of conversion to open cholecystectomy in the presence of acute cholecystitis.

Abdomen↗
PubMed1992

Evidence of genetic heterogeneity among the nondystrophic myotonias.

Recent in vitro electrophysiologic studies have demonstrated abnormal sodium channel gating in muscle from patients with Thomsen's disease and have called the chloride hypothesis into question. Abnormal sodium channel function, like myotonia, is a feature common to Thomsen's disease and several myotonias that are genetically linked to a chromosome-17q sodium channel locus. We present a pedigree segregating an allele for Thomsen's disease that is unlinked to this sodium channel locus, thus constituting evidence of genetic heterogeneity among the nondystrophic myotonias.

Child↗
PubMed1991

Rho-dependent transcription termination. Characterization of the requirement for cytidine in the nascent transcript.

By substituting template segments encoding AU-rich, GU-rich, and CA-rich transcripts for natural sequences upstream of the phage lambda rho-dependent tR1 termination site, we demonstrate that cytidines are required in the upstream RNA for rho-dependent termination to occur. These results are extended through in vitro mutagenesis of a template encoding an inactive AU-rich upstream sequence: certain mutant templates encoding new cytidines are able to activate rho-dependent termination. Cytidines must be dispersed over a region of the transcript in order for rho to be activated, although no specific pattern of cytidines appears to be required. The results show that no local clustering or regular spacing of cytidines is necessary and that cytidines are not used as a "ruler" to determine the location of termination sites. Rho is somewhat sensitive to the relative positions of cytidines since slightly different nascent transcripts activate rho termination activity to various degrees. A model is presented in which hexameric rho binds 78 nucleotides of contiguous RNA in a primary site, such that each monomer interacts with at least one cytidine somewhere in the 13 nucleotides allotted to the monomeric primary site.

Bacteriophage lambda↗
PubMed1991

Open versus laparoscopic cholecystectomy. A comparison of postoperative pulmonary function.

Upper abdominal surgery is associated with characteristic changes in pulmonary function which increase the risk of lower lobe atelectasis. Sixteen patients undergoing open cholecystectomy and 20 patients undergoing laparoscopic cholecystectomy were prospectively evaluated by pulmonary function tests (forced vital capacity [FVC], forced expiratory volume [FEV-1], and forced expiratory flow [FEF] 25% to 75%) before operation and on the morning after surgery to determine if the laparoscopic technique lessens the pulmonary risk. Fraction of the baseline pulmonary function was calculated by dividing the postoperative pulmonary function by the preoperative pulmonary function and multiplying by 100%. Postoperative FVC measured 52% of preoperative function for open cholecystectomy and 73% for laparoscopic cholecystectomy (p = 0.002). Postoperative FEV-1 measured 53% of baseline function for open cholecystectomy and 72% for laparoscopic cholecystectomy (p = 0.006). Postoperative FEF 25% to 75% measured 53% for open cholecystectomy and 81% for laparoscopic cholecystectomy (p = 0.07). It is concluded that laparoscopic cholecystectomy offers improved pulmonary function compared to the open technique.

Adult↗
PubMed1991

Characterization of the late-gene regulatory region of phage 21.

A segment of Escherichia coli bacteriophage 21 DNA encoding the late-gene regulator, Q21, and the late-gene leader RNA segment was sequenced; its structure is similar to those of the related phages lambda and 82. The leader RNA is about 45 nucleotides long and consists essentially entirely of sequences encoding the p-independent terminator that is the putative target of the antitermination activity of Q21. Like the corresponding regions of lambda and 82, the 21 late-gene promoter segment encodes an early transcription pause in vitro, at about nucleotide 18, during which Q21 presumably acts to modify RNA polymerase. The 21 Q gene, cloned in isolation, is active on the late-gene leader segment in trans, and its purified product is active as an antiterminator in vitro; Q21 represents a third late-gene antiterminator, in addition to those of lambda and 82. There is little evident similarity in the primary sequences of the three Q genes.

Amino Acid Sequence↗
PubMed1991

Paramyotonia congenita and hyperkalemic periodic paralysis map to the same sodium-channel gene locus.

Paramyotonia congenita (PC), an autosomal dominant muscle disease, shares some clinical and electrophysiological similarities with another myotonic muscle disorder, hyperkalemic periodic paralysis (HYPP). However, clinical and electrophysiologic differences allow differentiation of the two disorders. The HYPP locus was recently shown to be linked to a skeletal muscle sodium-channel gene probe. We now report that PC maps to the same locus (LOD score 4.4, theta = 0 at assumed penetrance of .95). These linkage results, coupled with physiological data demonstrating abnormal sodium-channel function in patients with PC, implicate a sodium-channel gene as an important candidate for the site of mutation responsible for PC. Furthermore, this is strong evidence for the hypothesis that PC and HYPP are allelic disorders.

DNA Probes↗