Regulation of three beta-tubulin mRNAs during rat brain development.

The nucleotide sequence of a complete rat brain beta-tubulin T beta 15 has been determined from three overlapping cDNA clones. The overall length of the T beta 15 sequence is 1589 bp and shows between 84.5% and 88.6% homology within the coding region as compared with chick and human beta-tubulin sequences. On the other hand, the 3'-non-coding region is highly divergent. Comparison of the derived amino acid sequences from different species demonstrates that the amino acid changes are not randomly distributed, but rather there are several conserved and two highly variable regions common to beta-tubulin polypeptides from various sources. The T beta 15 sequence encodes a dominant neuronal 1.8-kb beta-tubulin mRNA species. Two other minor beta-tubulin mRNA species of 2.6 and 2.9 kb are present in rat brain. By using two synthetic oligonucleotide probes complementary to the carboxyl-terminal divergent region and to the amino-terminal conserved region, we have shown that the three mRNAs are distinct species, which are developmentally regulated. The level of the 1.8-kb mRNA species increases till the age of 12 days thereafter its level decreases. The 2.9-kb mRNA is an early neuronal mRNA species, while the 2.6-kb mRNA is a late neuronal species which is detected at 30 days of rat brain development. The data illustrate that there is a differential expression of the beta-tubulin multigene family during rat brain development which may suggest different functions for the various beta-tubulin isotopes.     

Brain tubulin and actin cDNA sequences: isolation of recombinant plasmids

Rat brain mRNA enriched for tubulin and actin sequences was used to prepare double stranded cDNA. A library of recombinant clones was constructed by inserting the dsDNA into the Pst1 site of pBR322 plasmid and transformation of E. coli chi 1776 host. Clones bearing sequences coding for tubulin and actin were identified and characterized.     

Evidence for active water transport in a corn root preparation

Summary Water flow was measured in aZea mays root preparation consisting of a segment from which the central part had been excised. It was shown that water flow had two components, one osmotic and one non-osmotic. The non-osmotic flow was inhibited by cyanide. No correlation was found between water flow and solute flow. These findings suggest that active water transport occurred in the root preparation. The mechanism of such water movement is discussed.     

Neuronal polarity: targeting of microtubule components into axons and dendrites

The functional polarity of nerve cells depends on the outgrowth of both axons and dendrites. These processes, which were distinguished by morphological and physiological criteria, have been shown in recent years to differ in molecular composition, including their cytoskeleton. The asymmetric distribution of cytoskeletal elements and, particularly, the segregation of microtubule-associated proteins by their differential transport, may play an important role in the assembly of distinct microtubules in the two neuronal domains. An additional mechanism to achieve this subcellular localization is the transport of specific mRNAs to allow the local synthesis of specific proteins close to their functional site. This may endow the cell with a rapid mechanism for the regulation of synthesis under special conditions, which may be important during neuronal development and plasticity.     

Comprehensive radionuclide lung imaging in preventive mass screening of industrial workers]

The results of a combined roentgenoradionuclide investigation of the lungs were studied in 45 persons at risk of developing chronic nonspecific pulmonary diseases, diagnosed in a mass screening of 3000 workers at an industrial enterprise. The results of fluorographic, roentgenoscopic and roentgenographic investigations of the lungs, roentgenopneumopolygraphy and radionuclide investigation of lung perfusion (pulmoscintigraphy with 99mTc-labeled albumin macroaggregates) were compared. During this combined investigation the signs of nonspecific pulmonary diseases were diagnosed in 40% of the patients, changes of the pulmonary blood flow--in 71%, changes of ventilation--in all the examinees. A conclusion was made of the necessity of additional combined investigation of patients belonging to risk groups, identified during mass screenings.