We examined somatic mutations of the adenomatous polyposis coli (APC) gene in 63 colorectal tumors (16 adenomas and 47 carcinomas) developed in familial adenomatous polyposis (FAP) and non-FAP patients. In addition to loss of heterozygosity (LOH) at the APC locus in 30 tumors, 43 other somatic mutations were detected. Twenty-one of them were point mutations; 16 nonsense and two missense mutations, and three occurred in introns at the splicing site. Twenty-two tumors had frameshift mutations due to deletion or insertion; nineteen of them were deletions of one to 31 bp and three were a 1-bp insertion. One tumor had a 1-bp deletion in an intron near the splicing site. Hence, 41 (95%) of 43 mutations resulted in truncation of the APC protein. Over 60% of the somatic mutations in the APC gene were clustered within a small region of exon 15, designated as MCR (mutation cluster region), which accounted for less than 10% of the coding region. Combining these data and the results of LOH, more than 80% of tumors (14 adenomas and 39 carcinomas) had at least one mutation in the APC gene, of which more than 60% (9 adenomas and 23 carcinomas) had two mutations. These results strongly suggest that somatic mutations of the APC gene are associated with development of a great majority of colorectal tumors.

A simple method of identifying the initial slope of the stress-strain curve (i.e., Young's modulus of the soft tissue) by introducing the pipette aspiration technique is presented. The tissue was assumed to be isotropic and macroscopically homogeneous. Numerical simulations by the linear finite element analysis were performed for the axisymmetric model to survey the effects of friction at the tissue-pipette contact boundary, pipette cross-sectional geometry, relative size of the specimen to the pipette, and the layered inhomogeneity of the specimen tissue. The friction at the contact region had little effect on the measurement of Young's modulus. The configuration of the pipette was shown to affect the measurement for small pipette wall thickness. The measurement also depended on the relative size of the specimen to the pipette for relatively small specimens. The extent of the region contributing to the measurement was roughly twice the inside radius of the pipette. In this region, the maximum stress did not exceed the level of the aspiration pressure, with only minor exceptional locations. Calculation of strain energy components indicated that the major contributions to the deformation under pipette aspiration were by the normal extension and shear deformation in pipette axial direction. Experimental verification of the present method for the isotropic, homogeneous artificial material is also presented.

To investigate genetic features of esophageal cancer, we have examined 93 squamous cell carcinomas of the esophagus for loss of heterozygosity (LOH), using 41 restriction fragment length polymorphism (RFLP) markers representing all autosomal chromosomes. Allelic losses at frequencies of at least 30% were observed at loci on chromosomal arms 3p (35%), 3q (30%), 5q (36%), 9p (57%), 9q (60%), 10p (33%), 13q (43%), 17p (62%), 17q (46%), 18q (38%), 19q (32%), and 21q (37%). These results suggest that several putative tumor suppressor genes, in addition to the cyclin D and TP53 genes that are sometimes mutated in esophageal carcinomas, may be associated with development and/or progression of esophageal cancer. By a comparison of LOH on each chromosomal arm with clinicopathological parameters, we have found a significant correlation between LOH on 19q and regional lymph node metastases. Interestingly, the frequency of LOH on 17q was significantly higher in tumors in female patients (12 of 14 cases) than in those in male patients (20 of 56 cases) (P = 0.0009 by Fisher's exact test). Furthermore, we examined for mutations of the APC gene on chromosome arm 5q. Screening of nearly one third of the APC coding region, including the MCR (mutation cluster region), revealed no alterations. Therefore, although allelic loss at the APC locus is frequent in squamous cell carcinomas of the esophagus, it is likely that a gene on 5q other than APC is involved in esophageal tumorigenesis.

The mechanism of the through-thickness gas leakage of carbon ber-reinforced plastics (CFRP) laminates is investigated in view of propellant leaks for composite tanks of reusable launch vehicles. In this study analysis of leakage caused by the existence of matrix cracks acting as the chain of leakage paths is developed under the simple assumption that conductance for leakage is a function of crack-opening displacements. The analytical results in consideration of mechanical and thermal loads are compared with experimental results, which are measured as helium gas leaks through carbon ber-reinforced plastics laminates containing matrix cracks at room temperature. Good agreement between the analytical and experimental data is con rmed. Numerical analysis based on the proposed method can be used to evaluate the in uence of mechanical loads on propellant leak through CFRP cross-ply laminates. The analytical calculations show that the increase of propellant leakage can be caused by the enlargement of crack-opening displacements caused by mechanical and thermal loads, increase of crack density, and decrease of temperature.

We report here the result of a screening for germ-line mutations in the adenomatous polyposis coli (APC) gene in 61 new familial adenomatous polyposis (FAP) patients as well as a summary of the results of 150 patients. Examination of the entire coding region of the APC gene, based on a ribonuclease protection assay coupled with the polymerase chain reaction (PCR), disclosed mutations that were considered to cause significant defects in the APC product in 97 of 150 unrelated FAP patients. Our findings revealed the following characteristics of the germ-line mutations of APC: 1) the great majority of the mutations were found to truncate the APC product; 2) almost all of the mutations were located within the first half of the coding region; 3) no correlation was observed between the locations of germ-line mutations and extracolonic manifestations in FAP patients; 4) more than 80% of base substitutions in the APC gene were from cytosine to other nucleotides, nearly one-third of which occurred at the GpG site. Our results provide information helpful to an understanding of the APC gene and will also contribute to presymptomatic diagnosis of members in FAP families.

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The Turcot syndrome (TS) is a rare, probably autosomal recessive, disorder characterized by development of primary neuroepithelial tumors of the central nervous system (CNS) and numerous adenomatous colorectal polyps. To examine the possible involvement of mutations of the APC gene, which is responsible for familial adenomatous polyposis (FAP), in Turcot syndrome, we examined DNAs from TS patients for alterations in this gene by means of ribonuclease protection analysis. Germ-line APC mutations were detected in each of three unrelated cases of TS, and additional (somatic) mutations were observed in colonic adenomas that had developed in one of these patients. However, no somatic mutations in APC were found among 91 neuroepithelial tumors (medulloblastoma, glioblastoma, astrocytoma, and oligodendroglioma), whether sporadic or associated with TS. These results suggest that the APC gene is associated with pathogenesis of one feature of TS, but that at least one other gene is responsible for the genesis of neuroepithelial tumors in the CNS.

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