Microbial colonization and succession in the large intestine of newborn infants during their stay with mothers at the maternity hospital]

Formation of microflora in the large intestine of 5-day old infants was studied in one of the Moscow maternity homes. The up-to-date procedures for isolation and identification of aerobic and anaerobic organisms were used in the study and the findings were processed on a computer. In the newborns of the maternity home of the "mother-infant" type there was observed colonization of the large intestine with aerobic and anaerobic organisms. A wave-like dynamics in the formation of the symbiotic microflora was revealed. It reflected the phenomenon of the microbial succession in the infants. The attempts to detect microbial interference between the species colonizing the large intestine showed that it was extremely rare in the 5-day old infants. This was likely the reason of the low intestine resistance to the colonization in the newborns which in its turn defined the frequent colonization of the intestine mucosa with S. aureus and the organisms of the Klebsiella, Enterobacter and Citrobacter group.     

Cholesteryl hemisuccinate's inductive effect on membrane rigidization regarding both, its remodelling of the cells' surface receptor pattern and its decreasing the natural killer susceptibility of K-562 cells.

The relationship of changes in membrane fluidity to natural killer susceptibility of K-562 target cells was investigated. Membrane rigidization was performed by the chemical modulator cholesteryl hemisuccinate. Steady-state fluorescence polarization measurements of the diphenyl hexatriene labelled, modified K-562 cells revealed that cholesteryl hemisuccinate increased the structural order of the hydrophobic region of membranes in a dose dependent way. Investigation of natural killer susceptibility followed by 51Cr release assay indicated that modified cells are less sensitive to natural killer attack. To elucidate whether surface structures such as transferrin and lectin receptors are associated with the altered susceptibility, the surface density of these receptors was followed by (I-125)-transferrin binding assay and quantitative immunofluorescence. We found that the number of transferrin and concanavalin A receptors increased by a factor of 2.44 and 2.00, respectively, whereas that of the wheat germ agglutinin receptor failed to exhibit any changes upon rigidization. From the results we concluded that i the membrane structural order does influence the natural killer susceptibility, ii changes in membrane structural order result in alteration of the number of cell surface transferrin and lectin receptors, iii however, no direct relationship seems to exist between these two events.     

Protein truncation is required for the activation of the c-myb proto-oncogene.

The protein product of the v-myb oncogene of avian myeloblastosis virus, v-Myb, differs from its normal cellular counterpart, c-Myb, by (i) expression under the control of a strong viral long terminal repeat, (ii) truncation of both its amino and carboxyl termini, (iii) replacement of these termini by virally encoded residues, and (iv) substitution of 11 amino acid residues. We had previously shown that neither the virally encoded termini nor the amino acid substitutions are required for transformation by v-Myb. We have now constructed avian retroviruses that express full-length or singly truncated forms of c-Myb and have tested them for the transformation of chicken bone marrow cells. We conclude that truncation of either the amino or carboxyl terminus of c-Myb is sufficient for transformation. In contrast, the overexpression of full-length c-Myb does not result in transformation. We have also shown that the amino acid substitutions of v-Myb by themselves are not sufficient for the activation of c-Myb. Rather, the presence of either the normal amino or carboxyl terminus of c-Myb can suppress transformation when fused to v-Myb. Cells transformed by c-Myb proteins truncated at either their amino or carboxyl terminus appear to be granulated promyelocytes that express the Mim-1 protein. Cells transformed by a doubly truncated c-Myb protein are not granulated but do express the Mim-1 protein, in contrast to monoblasts transformed by v-Myb that neither contain granules nor express Mim-1. These results suggest that various alterations of c-Myb itself may determine the lineage of differentiating hematopoietic cells.     

Intrachromosomal rearrangements fusing L-myc and rlf in small-cell lung cancer.

Chromosomal abnormalities affecting proto-oncogenes are frequently detected in human cancer. Oncogenes of the myc family are activated in several types of tumors as a result of gene amplification or chromosomal translocation. We have recently found the L-myc gene involved in a gene fusion in small-cell lung cancer (SCLC). This results in a chimeric protein with amino-terminal sequences from a novel gene named rif joined to L-myc. Here we present a preliminary structural characterization of the rlf-L-myc fusion gene, which has been found only in cells with an amplified L-myc gene. In addition, we have used somatic cell hybrids to assign the normal rlf locus to the same chromosome (chromosome 1) on which L-myc resides. Finally, we have been able to establish a physical linkage between rif and L-myc with pulsed-field gel electrophoresis. Our results demonstrate that normal rlf and L-myc genes are separated by less than 800 kb of DNA. Thus, the rlf-L-myc gene fusions are due to similar but not identical intrachromosomal rearrangements at 1p32. The presence of independent genetic lesions that cause the formation of identical chimeric rlf-L-myc proteins suggests a role for the fusion protein in the development of these tumors.     

A chicken beta-actin gene can complement a disruption of the Saccharomyces cerevisiae ACT1 gene.

Recently it was demonstrated that beta-actin can be produced in Saccharomyces cerevisiae by using the expression plasmid pY beta actin (R. Karlsson, Gene 68:249-258, 1988), and several site-specific mutants are now being produced in a protein engineering study. To establish a system with which recombinant actin mutants can be tested in vivo and thus enable a correlation to be made with functional effects observed in vitro, a yeast strain lacking endogenous yeast actin and expressing exclusively beta-actin was constructed. This strain is viable but has an altered morphology and a slow-growth phenotype and is temperature sensitive to the point of lethality at 37 degrees C.     

The function of selenocysteine synthase and SELB in the synthesis and incorporation of selenocysteine.

The selAB operon codes for the proteins selenocysteine synthase and SELB which catalyse the synthesis and cotranslational insertion of selenocysteine into protein. This communication deals with the biochemical characterisation of these proteins and in particular with their specific interaction with the selenocysteine-incorporating tRNA(Sec). Selenocysteine synthase catalyses the synthesis of selenocysteyl-tRNA(Sec) from seryl-tRNA(Sec) in a pyridoxal phosphate-dependent reaction mechanism. The enzyme specifically recognizes the tRNA(Sec) molecule; a cooperative interaction between the tRNA binding site and the catalytically active pyridoxal phosphate site is suggested. SELB is an EF-Tu-like protein which specifically complexes selenocysteyl-tRNA(Sec). Interaction with the selenol group of the side chain of the aminoacylated residue is a prerequisite for the formation of a stable SELB.tRNA complex. Mechanistically, this provides the biochemical basis for the exclusive selection of selenocysteyl-tRNA(Sec) in the decoding step of a selenocysteine-specific UGA triplet.     

Biphasic changes in leukocytes induced by strenuous exercise

Seven healthy male volunteers participated in short- (STR, 1.7 km), middle- (MTR, 4.8 km) and long- (LTR, 10.5 km) term runs at a speed close to their maximum. A prompt mobilization of white cells, and lymphocytes in particular, appeared following the exercise. The initial increase in the number of lymphocytes was succeeded by a significant decrease [(P less than 0.03) lymphopenial], which on average was 32%-39% of the pre-exercise values in all groups. A close correlation was found between the initial increase in plasma cortisol concentration after exercise and the subsequent lymphopenia. A modest enhancement in the number of granulocytes immediately after the exercise was accompanied by a comprehensive increase in polymorphonuclear (PMN) elastase concentration accounting for 78.6%, SEM 16.3%, 140.7%, SEM 31.8% and 241.3%, SEM 48.1% in the STR, MTR and LTR groups. No correlation was found between granulocyte number and the plasma PMN elastase concentration. A delayed granulocytosis was noted in all subjects, reaching a peak between 2 and 4 h after the exercise. The magnitude of the granulocytosis varied among subjects and peak values of the number of circulating granulocytes were found to be 5.7 x 10(9) cells.l-1, SEM 0.5, 6.7 x 10(9) cells.l-1, SEM 0.6 and 8.8 x 10(9) cells.l-1, SEM 0.5 in STR, MTR and LTR respectively, whereas the mean baseline value was 3.6 x 10(9) cells.l-1, SEM 0.4. The neutrophilic granulocytosis was not accompanied by a corresponding enhancement in PMN elastase concentration. The plasma cortisol concentration reached a peak 30 min after exercise and declined below the control level in 4 h. Neither the initial increase, nor the subsequent decrease in plasma cortisol concentration were found to be essential for the magnitude of the delayed leukocytosis.     

Physiological effects of micropauses in isometric handgrip exercise

The physiological response to continuous and intermittent handgrip exercise was evaluated. Three experiments were performed until exhaustion at 25% of maximal voluntary contraction (MVC): experiment 1, continuous handgrip (CH) (n = 8); experiment 2, intermittent handgrip with 10-s rest pause every 3 min (IH) (n = 8); and experiment 3, as IH but with electrical stimulation (ES) of the forearm extensors in the pauses (IHES) (n = 4). Before, during, and after exercise, recordings were made of heart rate (HR), arterial blood pressure (BP), exercising forearm blood flow, and concentrations of potassium [K+] and lactate [La-] in venous blood from both arms. The electromyogram (EMG) of the exercising forearm extensors and perceived exertion were monitored during exercise. Before and up to 24 h after exercise, observations were made of MVC, of force response to electrical stimulation and of the EMG response to a 10-s test contraction (handgrip) at 25% of the initial MVC. Maximal endurance time (tlim) was significantly longer in IH (23.1 min) than in CH (16.2 min). The ES had no significant effect on tlim. During exercise, no significant differences were seen between CH and IH in blood flow, venous [K+] and [La-], or EMG response. The HR and BP increased at the same rate in CH and IH but, because of the longer duration of IH, the levels at exhaustion were higher in this protocol. The subjects reported less subjective fatigue in IH. During recovery, return to normal MVC was slower after CH (24 h) than after IH (4 h).(ABSTRACT TRUNCATED AT 250 WORDS)     

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids

Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1, n = 16 in study 2), running (n = 16 in study 1 and n = 16 in study 2) and control (n = 17 in study 1 and n = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9-10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%-85% of the maximal oxygen consumption (VO2max) using portable heart rate metres and the mean heart rate was 156-157 beats.min-1 in the training groups. In the pooled data of the two studies the mean increase in the VO2max (in ml.min-1.kg-1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase in VO2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9-10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.     

Calcitonin gene-related peptide and its mRNA in pulmonary neuroendocrine cells and ganglia.

The occurrence of calcitonin gene-related peptide (CGRP) and it's mRNA was studied in lungs of rats and piglets using in situ hybridization with two synthetic oligonucleotide probes followed by immunocytochemistry (ICC). CGRP mRNA was present in pulmonary neuroendocrine cells (PNEC) of both the solitary type and cluster type (neuroepithelial body; NEB) at all levels of the airway epithelium from bronchi to alveoli. The distribution of labelled cells was similar to that previously described with ICC. The 44-mer probe provided stronger hybridization signal than the 34-mer and the two combined increased labelling slightly. Formalin fixation reduced labelling and tended to increase background. Labelling for CGRP mRNA was evenly distributed over the cytoplasm, whereas CGRP-like immunoreactivity (LI) usually was of highest intensity toward the base of the PNEC, suggesting basal accumulation of synthesized peptide. CGRP-LI was also observed in occasional rat ganglia and in some, but not all, piglet ganglia. These local neurons may contribute to the CGRP fibers of airways and vasculature, and could theoretically bridge their dendrites and axons between NEB and the effector organ (e.g. artery or arteriole) thus accomplishing a function similar to the postulated axon reflex.