Immunoelectron microscopic study of the distribution of porin on outer membranes of rat heart mitochondria

The distribution of porin on the outer membranes of rat heart mitochondria has been studied by means of immunogold labelling with antibodies to the N-terminal part of the human protein. It was found that only a minority of isolated, unfixed mitochondria are labelled by these antibodies, with the gold particles frequently organized in threads or bands. Extensive immunogold labelling is frequently observed on regions of outer membranes stripped away from mitochondria and on regions separating two mitochondrial compartments whose cristae display different configurations (possibly representing two mitoplasts covered by a common outer membrane). Also, pairs of connected mitochondria are sometimes heavily labelled in the neck regions, which may represent the junctions involved in electrical communication between mitochondria in cardiac tissue.     

General and primary thermoresistance in genetically differing variants of murine neuroblastoma

General and primary thermoresistance of mouse neuroblastoma clonal cell lines derived from N18A subline was studied: the N18A1 clonal cell line was not treated by heat, the NTR1 was obtained by one-step selection for resistance to the long action of the temperature 40 degrees C, the NHSR1 was obtained by multistep selection for resistance to short-time treatment at 44 degrees C. The NHSR1 clonal line was shown to have higher general and primary thermoresistance by comparison with that of N18A1 cells. The NTR1 cell line, capable of unlimited proliferation at 40 degrees C, did not differ in general resistance but displayed a slower primary resistance compared to that in the N18A1 cells. Cells of all the three clones were found to be capable of temporary increasing in primary thermoresistance, i.e. hardening. A possible contribution of the primary resistance into the general one in cells of all the selected clones has been discussed.     

Chromosomal rearrangements with a common breakpoint at 6p23 in five cases of myeloid leukemia

Rearrangement of the short arm of chromosome 6 with a breakpoint at 6p23 was found in five patients with myeloid leukemia. Three of them had different morphological variants of AML (M2, M3, M4) and two blastic crisis of Ph1 negative and Ph1 positive CML. Identical translocation, t(6;9)(p23;q34), was revealed in two patients. One of them had AML (M2), the other blastic crisis of Ph1 negative CML. The blast cells of the last patient were morphologically similar to those in the M2 variant of AML. Translocation (6;9)(p23;q34) was also detected in two AML patients of Rowley and Potter (1976). The role of the breakpoint at 6p23 in myeloid malignancies needs further investigation.     

Characteristics of the post-radiation reaction of hematopoietic tissue with adrenaline use

It was shown that the administration of adrenaline before or after X-irradiation intensified the recovery of mouse haemopoiesis. When adrenaline was administered before irradiation the survival of CFUs (endo- and exo-tests) increased and the bone marrow cellularity and the spleen weight were restored more rapidly than those of the controls. With adrenaline administered after irradiation, the survival of endo-CFUs increased, the bone marrow cellularity was restored and the spleen weight increased.     

Cystic fibrosis mutations and associated haplotypes in Bulgaria – a comparative population genetic study

We present data on the population genetics of cystic fibrosis (CF) in Bulgaria, obtained by comprehensive mutation analysis and the construction of intragenic microsatellite haplotypes. The sample of 262 CF alleles analysed is representative of the patients diagnosed during the period of referral and of the three main ethnic groups in the country. ΔF508 accounted for 100% of Gypsy CF alleles, which thus differed significantly from both Bulgarians and ethnic Turks. In Bulgarian and Turkish CF patients, 92% of the mutant alleles were identified, yielding a total of 25 different mutations, of which only 7 occurred at frequencies higher than 1%. The findings were compared to other European populations and to the distribution of phenylketonuria mutations. Genetic distances and population trees demonstrated that in the south-eastern tip of Europe, the overall distribution of CF mutations and polymorphic haplotypes is very close to that of Mediterranean populations, with a high frequency of N1303K and G542X, a large number of rare mutations and a prevalence of the 23 31 13 haplotype in association with ΔF508. These findings are consistent with a main role for the Neolithic expansion in the shaping of the CF mutation spectrum in Bulgaria and southern Europe. Received: 1 September 1996     

Electron microscopic findings on reversion of Listeria L-forms

Reversion in L-forms of Listeria monocytogenes was studied with the use of electron microscopy. In the culture undergoing the process of reversion cells differing in size, form and the electron density of the cytoplasm were present. The process of reversion was characterized by the increase of cytoplasmic density, the decrease of nucleoid, the appearance of fibrillary material of medium electron density on the membrane surface and the longitudinal elongation of the cell. The cell wall of the revertants was thinner and its outer layer with greater electron density was less pronounced than in the initial culture.