A plasmid vector for isolation of strong promoters in Escherichia coli

In order to isolate very strong promoters from bacteria and bacteriophage a plasmid named pProm was constructed. It possesses an origin (ORI) for replication in Gram-negative bacteria, an ORI for replication in Gram-positive bacteria, a promoterless ampicillin resistance gene with a multiple cloning site (MCS) in the position formerly occupied by the ampicillin promoter, a tetracycline resistance gene for selection in Gram-negative bacteria and a chloramphenicol resistance gene for selection in Gram-positive bacteria. Insertion in the MCS of DNA fragments of Staphylococcus aureus bacteriophages resulted in isolation of several clones very resistant to ampicillin. The DNA fragments inserted in these recombinant plasmids were sequenced and all of them contained putative promoter motifs. Direct measurement of the penicillinase activity indicated that one of the isolated promoters could be included within a group of the stronger known prokaryotic promoters. According to these results pProm is a powerful tool to perform studies on promoter strength and for industrial applications.

Specialists achieve better outcomes than generalists for lung cancer surgery

OBJECTIVE

A push toward care provided by generalists as opposed to specialists has occurred in the health-care marketplace despite a lack of provider specific outcome data. The objective of this study was to determine whether the outcome of patients undergoing lung cancer surgery is different between general surgeons (GSs) and thoracic surgeons (TSs).

DESIGN

Examination of data from a state-wide severity-adjusted administrative hospital discharge database.

SETTING/PARTICIPANTS

Patients undergoing lung cancer resection in all nonfederal acute care hospitals within South Carolina.

MAIN OUTCOME MEASURES

Mortality by specialty adjusted for case mix.

RESULTS

From 1991 to 1995, 1,720 resections for lung cancer were performed in South Carolina. One hundred thirty-seven cases were excluded because surgeons did not meet the predefined criteria for board certification, leaving 1,583 resections for analysis. One-half of lobectomies and nearly 60% of pneumonectomies were performed by GSs. Patients were similar in age, sex, gender, race, and the proportion in each severity of illness subclass. Mortality was significantly higher in patients who underwent lobectomy by GSs vs TSs (5.3% vs 3.0%; p<0.05) and in patients with extreme comorbidities (43.6% vs 25.4%; p=0.03) or age >65 years (7.4% vs 3.5%; p<0.05). Seventy percent of TSs performed > 10 cases in the series, whereas 75% of GSs performed <10 (p=0.05). Logistic regression analysis failed to identify any significant variable that might explain the mortality differences between TSs and GSs.

CONCLUSION

Mortality is lower for lung cancer resection when the surgery is performed by a TS.

Evidence of genetic heterogeneity in a BALB/c mouse colony as determined by DNA fingerprinting

A genetic monitoring of the BALB/c mouse foundation colony in our animal facility was carried out. The techniques of choice were skin grafting, coat colour test, flow cytometric analysis for H2 antigens (loci H2-D and H2-A), electrophoretic analysis of isoenzymes (loci Idh1, Pep3, Es3 and Mod1), PCR-amplified microsatellites (loci Igh-V, Ngfg, Plau, Crp, Igh, D16Mit5, D3Mit49 and D17Mit16) and DNA fingerprinting (multilocus probes 33.6, 33.15 and (CAC)5). No evidence of genetic contamination was found, ruling out the possibility of an outcross with AKR, the other albino strain maintained at the facility. Nevertheless, DNA fingerprint patterns revealed evidence of genetic heterogeneity in four out of nine lines of the nucleus colony, interpreted as minisatellite mutations favoured for a single line system with more than 40 generations of separation from the ancestral pair. These mice are mainly used in cancer and immunological research within the institute.

Papillomaviruses in human skin warts and their incidence in an Argentine population

Human papillomavirus genomic types present in human warts of an Argentine population were studied. HPV DNA from single warts was obtained using an alkaline extraction procedure that resulted in a clean DNA preparation, which could be analyzed with several endonucleases. This method was used to isolate and insert the HPV DNAs of two genomic types into the Bam HI site of the pBR322 plasmid. Restriction maps of both HPV DNAs were constructed. According to these maps, one of the genomic variations was identical to HPV1a and the other to HPV2a. The incidence of HPV2 and of HPV1 in different types of skin warts was studied by a dot blot hybridization assay. Twenty-two out of 28 common warts were positive for HPV2 and negative for HPV1; four were positive for HPV1 and negative for HPV2 and two were negative for both. Five out of six plantar warts were positive for HPV1, and one was negative for both. Three out of seven filiform warts were positive for HPV2, three were positive for both probes, and one was negative for both. Southern blot analysis of HPV2 positive samples indicated that 80% were HPV2a and 20% another subtype not yet characterized. All plantar warts contained HPV1a. Msp I/Hpa II restriction analysis confirms previous results indicating that HPV1a DNA is partially methylated, while no evidence of methylation was found for HPV2a DNA.

The effect of organic solvents on the activation and the activity of spinach chloroplast fructose-1,6-bisphosphatase

A two-stage assay was used to study the effect of organic solvents on the activation of and the catalysis by chloroplast fructose-1,6-bisphosphatase. Irrespective of chemical structure, all the organic solvents tested had a dual effect on the enzyme. In the activation they stimulated and inhibited at low and high concentrations, respectively, in a process that required dithiothreitol, fructose 1,6-bisphosphate, and Ca2+. Conversely, organic solvents inhibited catalysis. The enhancement in fructose-1,6-bisphosphatase activity did not arise from a change in the molecular weight of the enzyme and correlated positively with the hydrophobic character of the organic solvent. In the presence of 2-propanol, all the activation constants for modulators (fructose 1,6-bisphosphate, a2+, thioredoxin-f) were lower than in a strictly aqueous medium. Monothiols were also functional in the activation of chloroplast fructose-1,6-bisphosphatase, although they were less effective than dithiols. Sulfhydryl compounds decreased the concentration of fructose 1,6-bisphosphate required for the activation of the enzyme, and 2-propanol lowered this requirement further. Arrhenius plots were nonlinear for the enzyme activation and linear for the hydrolytic step. The anomalous temperature dependence of the chloroplast fructose-1,6-bisphosphatase activation was indicative of a cooperative process. The data obtained in this study indicate that the concerted activation of chloroplast fructose-1,6-bisphosphatase is favored in a medium less polar than water.

Regulation of the activation of chloroplast fructose-1,6-bisphosphatase: inhibition by spermidine and spermine

The activation of chloroplast fructose-1,6-bisphosphatase by fructose-1,6-bisphosphate, Ca2+, DTT and chloroplast thioredoxin-f is prevented by either spermidine or spermine; on the contrary, other amino compounds do not replace polyamines in this reversible effect. On the other hand, neither spermidine nor spermine modify the catalysis of chloroplast fructose-1,6-bisphosphatase. The effect of spermidine, but not the effect of spermine, is reversed by increasing the concentration of Ca2+ in the activation; higher concentrations of Fructose-1,6-bisphosphate or thioredoxin-f do not restore the control activity. The present results suggest that other regulatory mechanisms may control the activation of fructose-1,6-bisphosphatase in chloroplasts.