DNA sequence analysis of spontaneous mutations at the aprt locus of hamster cells.

To determine the nature of spontaneous mutational events in cellular genes in hamster cells, mutant adenine phosphoribosyltransferase (aprt) genes were cloned and the regions to which we mapped alterations were sequenced. A variety of nucleotide changes were found to occur in the 12 mutant genes analyzed. Most mutations were simple base-pair substitutions-transitions (both G X C----A X T and A X T----G X C) and transversions. The only multiple mutation was a simple transition next to a single-base-pair insertion. Of the 12 mutations, 4 were more complex, involving small deletions or duplications. Two of these were similar to previously described deletions in that they occurred between short direct sequence repeats. No hot spots were detected. Three independent mutations were characterized at one restriction endonuclease site, although no other mutations were detected in the nucleotides surrounding this site in other mutant strains. At a functional level, sequence changes were either in exons (resulting in missense and, in one instance, nonsense mutations) or at splicing sites.     

Stimulation of pancreatic secretory process in the rat by low-molecular weight proteinase inhibitor

Oral application of a single dose of a new synthetic proteinase inhibitor Camostate (Foy-305) in male Wistar rats was carried out together with studies of in vitro amino acid incorporation followed by separation of proteins by two-dimensional gel electrophoresis. The aim of this experiment was to analyze changes produced by the inhibitor in total protein and individual enzyme biosynthesis. Administration of 100 mg/kg Foy-305 resulted in significant inhibition of total pancreatic protein synthesis, without changes in fractional rates for individual enzymes. 50 mg/kg Foy-305 induced a 10-fold elevation of cholecystokinin (CCK) levels in serum; this persisted for 3 h and led to a significant increase in the total rate of protein synthesis with peak values at 6 and 9 h (78% and 84% above control levels, respectively), returning to control by 15 h. Changes in fractional rates of synthesis occurred with a latency of 6 h and were restricted to amylase and the anionic form of trypsinogen and chymotrypsinogen. Amylase biosynthesis decreased by about 40% from control levels at 9 h to return to control levels by 15 h. Increased synthesis of trypsinogen and chymotrypsinogen was observed; this was also phasic. The results show similar enzyme-specific regulation as previously described for exogenous CCK stimulation and for the adaptation of the pancreas to diets enriched in protein. They demonstrate the effectiveness of pulsatory endogenous hormone release in the regulation of protein synthesis.     

Linking of the human immunoglobulin VK and JKCK regions by chromosomal walking.

The linking of the human VK and JKCK gene regions (abbreviations in ref. 1) by chromosomal walking is reported. Hybridization experiments with the DNA of a somatic cell hybrid containing the region between JKCK and the telomer show that none of the major VK gene clusters is located downstream of CK. The distance between the VK and JK genes was found to be 23 kb. The JK proximal VK gene is the B3 gene which is the only representative of subgroup IV in the genome. This gene and the neighbouring B2 gene (accompanying paper) are arranged in opposite orientation to JKCK and can therefore rearrange only by an inversion mechanism. This finding is used, together with previous data, to delineate the rearrangement processes in the Burkitt lymphoma derived cell line BL21 as comprising an inversion in the first and a deletion in the second step.     

An antioxidant prevents and reverses calcium-induced uncoupling of rat liver mitochondria

Accumulation of Ca2+ by rat liver mitochondria in the presence of inorganic phosphate results in spontaneous activation of respiration accompanied by a progressive loss of the accumulated cation. The lipid peroxidation inhibitor, ionol, completely prevents and reverses the Ca2+/phosphate-induced loss of accumulated Ca2+ and restores the respiration to state 4 level without having any effect on the rate of Ca2+ accumulation and respiration in the presence of an uncoupler. No correlation between the ionol-dependent loss of Ca2+ and the formation of malonic dialdehyde in mitochondria was found. The measurements of delta psi across the inner mitochondrial membrane during a progressive loss of Ca2+ suggest that the Ca2+/phosphate-induced "uncoupling" is mainly due to the appearance of electrogenic fluxes (but not Ca2+ cycling) which is under control of some products of initial steps of lipid peroxidation.     

Mesodermal metamerism in the teleost, Oryzias latipes (the medaka)

Previous studies of the metameric pattern in mesodermal tissues of chick, mouse, turtle, and amphibian embryos have indicated that segmental characteristics exist along the entire length of the embryo. This paper describes this phenomenon in a fish embryo, for some differences in the cranial segmental plan exist between the anamniote and the amniote embryos hitherto studied. Embryos of the cyprinodont, Oryzias latipes, were fixed at various times, the examined by means of stereo scanning electron microscopy. As in other vertebrate embryos, the first indication of mesodermal metamerism in this fish embryo is the occurrence of somitomeres, which are orderly, tandemly arranged units of uncondensed mesenchymal cells in the paraxial mesoderm. As many as ten somitomeres can be observed caudal to the last formed somite to the elongating tail region. In addition, 7 somitomeres are present rostral to the first definitive somite, which is segment number eight. As in other vertebrate embryos examined, somitomeres in Oryzias embryos are circular, bilaminar arrays of paraxial mesoderm that form before any indications of segmentation can be seen with the light microscope. In the trunk region these mesodermal units condense to give rise to definitive somites, but in the head they eventually disperse. Despite a fundamentally different mode of gastrulation and a relatively small number of cells in the newly formed somitomeres, cranial segmentation in Oryzias embryos was found to be more similar in number to the metameric pattern of the embryos of the bird, reptile, and mammal than to the situation found in the two amphibians studied thus far.     

Nuclear DNA analysis of koilocytic and premalignant lesions of the uterine cervix.

Cervical biopsy samples were taken from 79 patients who had various grades of cervical intraepithelial neoplasia or who showed evidence, in the form of koilocytosis, of human papillomavirus infection of the uterine cervix and from 10 women with normal cervices. The DNA content of the cells in the samples was analysed by flow cytometry. Analysis of the data obtained showed that the biopsy samples from women with cervical intraepithelial neoplasia and human papillomavirus lesions contained significantly more dividing cells (31.2% of cells from human papillomavirus lesions with no cervical intraepithelial neoplasia and 33.06%, 29.89%, and 31.76% of cells from cervical intraepithelial neoplasia grades I, II, and III, respectively) than those from women with normal cervices (21.6%). The proportion of aneuploid samples from the group who showed evidence of human papillomavirus infection only (18.2%) did not differ significantly from the group with cervical intraepithelial neoplasia grade III (21.2%). Aneuploidy and an increased rate of cellular proliferation are recognised characteristics of malignancy. These results therefore support the view that human papillomavirus plays an important part in the aetiology of cervical carcinoma and are relevant to the clinical management of patients.