Alternative splicing of fibronectin pre-mRNA at two distinct regions, termed ED-A and IIICS, was investigated with human adult and fetal tissues by the nuclease S1 protection assay. A clear tissue specificity was observed in the splicing pattern at the ED-A region. More ED-A+ than ED-A- mRNAs were identified in lung, whereas ED-A- mRNAs were predominantly expressed in liver. Endometrium contained nearly equal amounts of ED-A+ and ED-A- mRNAs. The splicing pattern at the ED-A region was also different between adult and fetal liver but not between adult and fetal lung. Tissue type specific splicing was also observed at the IIICS region. Although the mRNA species containing the complete IIICS sequence comprised 40-65% of the total fibronectin mRNAs irrespective of tissue types, expression of the mRNA species lacking a part or all of the IIICS sequence was more pronounced in adult liver than in other tissues including fetal liver. These results strongly suggest that the alternative splicing of fibronectin pre-mRNA in vivo is regulated in a tissue type specific manner at both the ED-A and IIICS regions and that it is developmentally regulated in liver but not in lung. On the basis of these and other observations reported previously, a possibility that a part of the fibronectins synthesized and secreted by hepatocytes is deposited in the tissue matrix is discussed.

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The cold tolerance of Cylas formicarius from five islands in the southwest of Japan was studied. The thermal threshold of the reproductive activity of adults tended to be lower and the supercooling point of the pupae was a little higher for the Okinawa-Honto population than for the others. The cold tolerance of the adult weevils was slightly accelerated by cold acclimation to 15°C for 4 d. Reproductive diapause induced under 10L : 14D increased cold tolerance significantly. Therefore, the cold tolerance of adult weevils would be accelerated by both cold acclimation at decreasing temperatures from autumn to winter and reproductive diapause induced by short daytime hours. When considering the increased cold-tolerence of C. formicarius through such mechanisms together with the temperature conditions in winter at the northern edge of its distribution area in the USA, C. formicarius probably has the capability to survive in the coastal zone of the Pacific Ocean in southern and central Japan.

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