Functional analysis of heterologous holin proteins in a lambdaDeltaS genetic background.

Holins are small hydrophobic proteins causing non-specific membrane lesions at the end of bacteriophage multiplication, to promote access of the murein hydrolase to their substrate. We have established a lambdaDeltaS genetic system, which enables functional expression of holins from various phages in an isogenic phage lambda background, and allows qualitative evaluation of their ability to support lysis of Escherichia coli cells. Synthesis of Holins is under control of native lambda transcription and translation initiation signals, and the temperature-sensitive CIts857 repressor. A number of different holins were tested in this study. The opposing action of phage lambda S105 and S107 holin variants in lysis timing could be confirmed, whereas we found evidence for a functionally non-homologous dual translational start motif in the Listeria phage Hol500 holin, i.e., the Hol500-96 polypeptide starting at Met-1 revealed a more distinct lytic activity as compared to the shorter product Hol500-93. The largest holin known, HolTW from a Staphylococcus aureus phage, revealed an early lysis phenotype in the lambdaDeltaSthf background, which conferred a plaque forming defect due to premature lysis. Mutant analysis revealed that an altered C-terminus and/or a V52L substitution were sufficient to delay lysis and enable plaque formation. These results suggest that the extensively charged HolTW C-terminus may be important in regulation of lysis timing. The gene 17.5 product of E. coli phage T7 was found to support sudden, saltatory cell lysis in the lambdaDeltaSthf background, which clearly confirms its holin character. In conclusion, lambdaDeltaSthf offers a useful genetic tool for studying the structure-function relationship of the extremely heterogeneous group of holin protein orthologs.

Analysis of plasmid pMZ1 from Micromonospora zionensis.

Plasmid pMZ1, isolated from Micromonospora zionensis, was also able to replicate by the rolling circle mechanism in Micromonospora melanosporea and Streptomyces lividans. Southern hybridisation experiments with probe prepared from pMZ1 and immobilised M. zionesis DNA fragments separated on pulsed-field gel electrophoresis, indicated that the plasmid is present in the progenitor strain in both integrated and autonomous states. Thiostrepton resistant derivatives of pMZ1 plasmid, pMZS25 and pMZS34, were used to study conjugal transfer in M. melanosporea and S. lividans. A 3.4 kb NcoI-MluI fragment from pMZ1 cloned in pIJ702 (plasmid pIJNM3) was shown to be sufficient to promote plasmid transfer and pock formation in S. lividans.

[Problems in the treatment and care of bronchogenic carcinoma]. / Neki problemi lecenja i zbrinjavanja bronhogenog karcinomo.

At the Military Medical Academy about 400-500 patients are hospitalised yearly due to bronchogenic carcinoma which represents about 35-40% of all hospitalized patients. Within a five-year period (1983-1987) there have been examined and treated 887 patients, 406 military and the rest socially insured from Belgrade, Serbia Proper and other regions of Yugoslavia. All types of antitumorous therapy have been applied depending on histologic type and degree of spreading of the disease. After completion of active antitumorous therapy patients were followed up and controlled examinations were performed at the out-patient service with symptomatic therapy at home and temporary hospitalization at the M.M.A. More than 300 patients were hospitalised in the terminal stage of the diseases for general care and symptomamic therapy for approximately 30 days.

[Late detection of bronchogenic carcinoma]. / Problem kasnog otkrivanja bronhogenog karcinoma.

The retrospective analysis of 1781 patients with bronchogenous carcinoma treated at the Institute of Pulmonary Diseases of the Military Medical Academy within the period 1971-1980 is presented. In 86% cases the disease was discovered according to symptoms because of which the patients had consulted physicians. The time between the onset and the detection of the disease was more than 3 months in the majority of patients and more than 6 months in one third of the patients. In the largest number of patients the disease was detected late when chances for successful intervention were diminished. Only in one third of the patients the disease was localized. Aiming to early detection of bronchogenous carcinoma it is essential to have good knowledge of symptoms both by patients and primary care physicians.