Adhesion properties of mutants of Staphylococcus aureus defective in fibronectin-binding proteins and studies on the expression of fnb genes

Staphylococcus aureus 8325-4 has the potential to express two distinct cell wall-associated fibronectin-binding proteins called FnBPA and FnBPB. In order to test if both proteins are expressed in S. aureus and if both are required for promoting bacterial adhesion to fibronectin-coated surfaces, insertion mutations were isolated in each gene. A DNA fragment encoding tetracycline resistance was inserted into fnbA and a fragment encoding erythromycin resistance was inserted into fnbB. A double fnbAfnbB mutant was also constructed. The fnbA and fnbB single mutants showed no significant reduction in their adhesion to polymethylmethacrylate coverslips that had been coated in vitro with fibronectin. However, the double mutant was completely defective in adhesion. Monospecific antibodies directed against the non-conserved N-terminal regions of both proteins confirmed the lack of expression of FnBPs in the mutant strains. Wild-type fnbA and fnbB genes cloned seperately on a multicopy plasmid were each able to restore fully the adhesion-defective phenotype of the 8325-4 fnbAfnbB mutant. This demonstrates that both fnb genes are expressed in S. aureus and that both contribute to the ability of strain 8325-4 to adhere to fibronectin-coated surfaces. The double mutant was also defective in adhesion to coverslips that had been removed from tissue cages implanted subcutaneously in guinea-pigs, which suggests that fibronectin is important in promoting attachment of S. aureus to biomaterial in vivo.     

Two-year follow-up of directly-observed intermittent regimens for smear-positive pulmonary tuberculosis in China

SETTING: The tuberculosis component of the Infectious and Endemic Disease Control Project in the People's Republic of China is the largest single tuberculosis control project in the world using directly-observed therapy and standardized intermittent regimens. OBJECTIVE: To determine the two-year relapse and mortality rates following completion of treatment. DESIGN: A prospective cohort study of 649 cases cured in this project. The 306 new and 343 retreatment cases were treated under field conditions with 2H3R3Z3S3/4H3R3 and 2H3R3Z3E3S3/6H3R3E3, respectively. Following treatment completion, two sputum samples were collected every six months for two years and examined for acid-fast bacilli. Causes of death were identified. RESULTS: The two-year relapse rates for new and retreatment cases were 3.3% and 5.6%, respectively. Retreatment cases with delayed sputum conversion had a greater risk for subsequent relapse. The two-year mortality rate for new and retreatment cases was 3.3% and 8.5%, respectively. The higher mortality rate in retreatment cases was not attributable to relapse of disease, but rather to non-infectious sequelae of tuberculosis. CONCLUSION: The use of directly-observed intermittent regimens is effective in permanently removing infectious tuberculosis cases from the community.     

Molecular events including p53 and k-ras alterations in the in vitro progression of a human colorectal adenoma cell line to an adenocarcinoma

The aim of the current study was to identify genetic abnormalities in human colorectal adenoma and carcinoma derived cell lines, and to determine whether the genetic changes which occur in vitro are relevant to the in vivo situation. Loss of 1p(33-35) region was shown to be the most common chromosome 1 abnormality and loss of heterozygosity (LOH) of the DCC gene and/or adjacent sequences was detected in all adenoma derived cells as well as the carcinoma cell lines. The level of p53 protein was also investigated as increased cellular p53 protein had previously been associated with mutation of the p53 gene. A further aim was to investigate genetic changes in our in vitro model of tumour progression, where the adenoma derived PC/AA cell line has previously been converted in vitro to two distinct tumorigenic phenotypes, producing either an adenocarcinoma or a mucinous carcinoma in athymic nude mice. Progression to the adenocarcinoma phenotype was shown to involve a specific chromosome 1 rearrangement, loss of both normal copies of chromosome 18 (although DCC gene sequences were retained), loss of the remaining wild type allele of k-ras resulting in homozygosity for the k-ras codon 12 mutation and increased cellular p53 protein as detected by SDS-PAGE Western blotting. The increase in p53 protein was shown not to be due to the acquisition of a mutation in the p53 gene. Interestingly, progression of the adenoma derived PC/AA cell line to the mucinous malignant phenotype did not involve any of these molecular rearrangements, suggesting that different genetically distinct pathways are involved in colorectal carcinogenesis. These studies show that the genetic changes in our in vitro model of human colorectal tumour progression are similar to those observed in in vivo studies.     

Endogenous oncornaviral DNA sequences: evidence for two classes of viral DNA sequences in guinea pig cells

The nature of the endogenous viral DNA sequences in guinea pig cells was studied by hybridization. A segment of the viral RNA (r-VRNA) hybridizing to abundant (or reiterated) DNA sequences (R-VDNA) was isolated by recycling to a Cot of 300. The hybridization of the recycled VRNA, as well as the total VRNA, was followed by determining their kinetics and by Wetmur-Davidson analysis. The kinetics of hybridization of total VRNA were complex, did not follow a second-order kinetics, and revealed two slopes by Wetmur-Davidson analysis. The recycled RNA, on the other hand, had a second-order reaction rate expected of the hybridization between a single species of RNA and DNA sequences and yielded a single straight line in a Wetmur-Davidson plot. The Cot1/2 and slope of the recycled r-VRNA was almost identical to that of the abundant VDNA sequences obtained from the hybridization data of the total VRNA. Guinea pig 28S rRNA with or without recycling was used in monitoring hybridization rate. The kinetics of hybridization of 28S RNA followed a second-order reaction and produced a single straight line by Wetmur-Davidson plot, with a second-order reassociation rate constant of 9.6 x 10(-3) liters/mol-s, a Cot1/2 of 104 mol-s/liter, and reiteration frequency of 146. There was no difference in the kinetics of hybridization of 28S RNA before and after recycling. These experiments showed that guinea pig cells contain two classes of VDNA sequences. (i) R-VDNA sequences with a second-order reassociation rate constant of 8.2 x 10(-4) liters/mol-s, a Cot1/2 of 1,219 mol-s/liter, and a reiteration frequency of 12 represent 37.5% of the viral genome. (ii) Unique VDNA sequences with a second-order reassociation rate constant of 1.2 x 10(-4) liters/mol-s, a Cot1/2 of 7,692 mol-s/liter, and a reiteration frequency of 2 represent 62.5% of the viral genome.     

Diagnosis and pathophysiology of paradoxical embolism

A review of the experience with 134 consecutive patients with germinal cell testicular neoplasia indicates that definitively accurate staging of the malignancy at presentation is the single most important prognostic factor. Nearly two-thirds of the patients with all types of germinal malignancies survived or died of other causes and the highest survival rates were seen among patients with earlier stages of seminoma. In recent years patients with all types of germinal malignancies of the testis have been treated by radical retroperitoneal lymphadenectomy with enhancement of survivals. Patients with seminoma and non-seminomatous tumors exhibited increased survival rates with node dissection. In 66 consecutive lymphadenectomies the complication rate was less than 14 per cent, with only 1 death related to the operation. Retroperitoneal lymphadenectomy not only affords therapeutic advantage but also provides an opportunity for accurate surgical staging of disease and allows for rational decision relative to additional treatment, radiation therapy or chemotherapy.     

ISDMS—a scientific data management system

This paper describes the design and development of the Idaho National Engineering Laboratory Scientific Data Mangement System (ISDMS). The ISDMS is an integrated system providing organization, processing, control and retrieval of scientific time series data in a large laboratory environment using Control Data Corporation (CDC) computers. Data reformatting, graphics, data manipulation, data management, engineering analysis and general utility functions are offered to engineers, scientists, and other end users. The ISDMS usage has grown steadily since its first release into production status in early 1979. The current configuration is well received by the user community and meets most requirements for studying and analysing data in a scientific environment.