Increased transversions in a novel mutator colon cancer cell line

We describe a novel mutator phenotype in the Vaco411 colon cancer cell line which increases the spontaneous mutation rate 10-100-fold over background. This mutator results primarily in transversion base substitutions which are found infrequently in repair competent cells. Of the four possible types of transversions, only three were principally recovered. Spontaneous mutations recovered also included transitions and large deletions, but very few frameshifts were recovered. When compared to known mismatch repair defective colon cancer mutators, the distribution of mutations in Vaco411 is significantly different. Consistent with this difference, Vaco411 extracts are proficient in assays of mismatch repair. The Vaco411 mutator appears to be novel, and is not an obvious human homologue of any of the previously characterized bacterial or yeast transversion phenotypes. Several hypotheses by which this mutator may produce transversions are presented.     

Juvenile Tillaux fracture simulating syndesmosis separation: a case report

Determination of proliferative activity of non-Hodgkin's lymphomas (NHL), aimed at improving the prediction of their clinical behavior, has gained considerable attention in the recent years. Flow cytometry has allowed rapid measurement of the cellular DNA content in terms of ploidy and proliferative activity. Flow cytometric DNA analysis was performed on paraffin embedded biopsy specimens taken from 125 patients with NHL. In 90 of them, proliferative index (PI) could be accurately measured and correlated with histology grade of the Working Formulation (WF). Intermediate and high grade NHL (54 patients) were analyzed together as HG-NHL. With the discrimination point for PI of 10%, the survival of high and low proliferative lymphomas was compared in the whole NHL group and within the WF prognostic groups. The median PI was 5% in LG (low grade) NHL and 10% in HG (high grade) NHL group. Acturial survival in NHL with high proliferative activity (39 patients) was 31% at 5 years and 15% at 10 years, and in NHL with low proliferative activity (51 patients) 53% and 18%, respectively (p = 0.002). In HG-NHL, survival at 5 years for low proliferative cases was 55% and for high proliferative cases 28% (p = 0.065), whereas in the LG-NHL group it was 54% and 28%, respectively (p = 0.059). The survival at 10 years was nearly equal in all groups. Proliferative index was associated with the overall survival of NHL in the whole group, as well as within the LG and HG prognostic categories. PI could differentiate more and less aggressive NHLs both within LG-NHL and HG-NHL. A tendency of survival curves toward continuous relapse was observed in low proliferative NHL and a tendency toward "plateau" in high proliferative NHL, irrespective of the histology grade.     

Inflammatory breast carcinoma incidence and survival: the surveillance, epidemiology, and end results program of the National Cancer Institute, 1975-1992

BACKGROUND: Little is known about the cause of inflammatory breast carcinoma (IBC), the most aggressive form of breast cancer. To the authors' knowledge, no studies have investigated whether IBC risk factors are different from those for breast carcinoma overall, and there has been only one report of IBC incidence and survival patterns. METHODS: The authors used data from the Surveillance, Epidemiology, and End Results program of the National Cancer Institute for the period 1975-1992 to calculate age-adjusted incidence and survival rates for 913 white and 121 African American women with IBC involving dermal invasion of lymphatic ducts and 166,375 white and 13,674 African American women with other types of breast carcinoma (non-IBC). RESULTS: Between 1975-1977 and 1990-1992, IBC incidence doubled, increasing among whites from 0.3 to 0.7 cases per 100,000 person-years and among African Americans from 0.6 to 1.1 cases. However, rates for African Americans varied due to the small numbers of IBC cases. The twofold increase in IBC incidence was higher than that observed for non-IBC during the same period (27% for African Americans and 25% for whites). IBC patients were significantly younger at diagnosis than non-IBC patients; and among both IBC and non-IBC patients, African Americans were younger than whites. Overall survival was significantly worse for IBC patients than for non-IBC patients and for African Americans than for whites. Among whites, 3-year survival improved more for IBC patients than for non-IBC patients between 1975-1979 and 1988-1992, increasing from 32% to 42% for IBC patients (P=0.0001) and from 80% to 85% for non-IBC patients (P=0.0001). CONCLUSIONS: The disparities observed in incidence trends and age at diagnosis, particularly according to race, highlight the need for further investigation of the differences between IBC and non-IBC incidence.     

Overnight normalization of glucose concentrations improves hepatic but not extrahepatic insulin action in subjects with type 2 diabetes mellitus

Subjects with poorly controlled type 2 diabetes are both hyperglycemic and insulin resistant. To determine whether short term restoration of normoglycemia improves insulin action, hyperinsulinemic (approximately 300 pmol/L) euglycemic clamps were performed in diabetic subjects after either overnight infusion of saline or overnight infusion of insulin in amounts sufficient to maintain euglycemia throughout the night. Fasting glucose concentrations (5.2 +/- 0.2 vs. 11.9 +/- 1.4 mmol/L; P < 0.01) and rates of endogenous glucose production (13.0 +/- 1.1 vs. 18.6 +/- 1.6 mumol/kg.min; P < 0.05) were both lower after overnight insulin than overnight saline. Insulin-induced stimulation of glucose uptake (to 34.9 +/- 6.8 vs. 28.8 +/- 3.4 mumol/kg.min; P = 0.2) and inhibition of free fatty acids (to 0.13 +/- 0.03 vs. 0.12 +/- 0.04 mmol/L; P = 0.6) did not differ after overnight saline and overnight insulin. In contrast, endogenous glucose production during the final hour of the hyperinsulinemic clamps (i.e. when glucose concentrations were the same) remained higher (P = 0.05) after overnight saline than after overnight insulin (5.5 +/- 1.5 vs. 0.02 +/- 1.4 mumol/kg.min). Thus, acute restoration of euglycemia by means of an overnight insulin infusion improves hepatic (and perhaps renal) but not extrahepatic insulin action.     

Topographic assessment of irregular astigmatism after photorefractive keratectomy

OBJECTIVE: To correlate new quantitative topographic indexes of corneal irregular astigmatism to best spectacle-corrected visual acuity (BSCVA) following excimer laser photorefractive keratectomy (PRK). SETTING: Department of Ophthalmology, LSU Eye Center, and Refractive Surgery Center of the South, Ear, Nose & Throat Hospital, New Orleans, Louisiana; Manhattan Eye, Ear and Throat Hospital, New York, New York, USA. METHODS: Videokeratography data (TMS-1) were obtained preoperatively and 1, 3, 6, 12, 18, and 24 months postoperatively from 100 eyes having PRK for low to mild myopia. Algorithms measured fine local irregularity with the surface regularity index (SRIp), varifocality with the coefficient of variation of corneal power (CVPp), and central islands with the elevation/depression magnitude (EDM). RESULTS: The SRIp and CVPp increased after surgery and remained significantly higher than the preoperative levels throughout the 24 month follow-up (P < .05). The increase in EDM was significant from 1 to 6 months (P < .05) but not thereafter. Multiple regression analysis revealed that variables having a statistically significant relationship with postoperative BSCVA were CVPp and EDM at 1 month, CVPp at 3 months, and CVPp, haze, and age at 6 months. No statistically significant correlation between any measures of irregular astigmatism and BSCVA was found after 1 year of follow-up. CONCLUSION: The quantitative measures used in this study are sensitive methods by which irregular astigmatism after keratorefractive procedures can be classified, evaluated, and compared.     

Structure of alpha-lytic protease complexed with its pro region

While the majority of proteins fold rapidly and spontaneously to their native states, the extracellular bacterial protease alpha-lytic protease (alphaLP) has a t(1/2) for folding of approximately 2,000 years, corresponding to a folding barrier of 30 kcal mol(-1). AlphaLP is synthesized as a pro-enzyme where its pro region (Pro) acts as a foldase to stabilize the transition state for the folding reaction. Pro also functions as a potent folding catalyst when supplied as a separate polypeptide chain, accelerating the rate of alphaLP folding by a factor of 3 x 10(9). In the absence of Pro, alphaLP folds only partially to a stable molten globule-like intermediate state. Addition of Pro to this intermediate leads to rapid formation of native alphaLP. Here we report the crystal structures of Pro and of the non-covalent inhibitory complex between Pro and native alphaLP. The C-shaped Pro surrounds the C-terminal beta-barrel domain of the folded protease, forming a large complementary interface. Regions of extensive hydration in the interface explain how Pro binds tightly to the native state, yet even more tightly to the folding transition state. Based on structural and functional data we propose that a specific structural element in alphaLP is largely responsible for the folding barrier and suggest how Pro can overcome this barrier.     

Nonsurgical infarctectomy in acute experimental myocardial infarction

This study examines whether a catheter mounted left intraventricular balloon may prevent left ventricular (LV) dysfunction following acute experimental myocardial infarction. In 10 anesthetized pigs, multiple coronary arterial ligations were applied around the apex of the heart. LV end-diastolic pressure (LVEDP), aortic flow (AF), and LV long and short axis fractional shortening (FS) were measured before and at 15 min intervals after ligations. At the 60th min after ligation, the LV long axis FS and AF decreased by 7.2 +/- 2.6% (p < 0.05) and 13.25 +/- 2.68% (p < 0.01), respectively, and the LVEDP increased by 4.3 +/- 1.1 mm Hg (p < 0.01) while no change was noted in the LV short axis FS. An intraventricular catheter mounted nonpulsating balloon was positioned over the endocardium of the infarcted area at the LV apex. Inflation of the nonpulsating balloon to an optimal volume, which was found to be equal to 8-10% of the LV end-diastolic volume, resulted in a reduction (by 3.8 +/- 1.2 mm Hg, p < 0.01) of the already increased LVEDP and in an increase (by 6.6 +/- 2.1%, p < 0.05) in the LV short axis FS while no statistically significant change was noted in the AF and LV long axis FS. It is concluded that an intraventricular catheter mounted balloon patch positioned over the endocardium of the infarcted area may ameliorate early LV dysfunction, possibly by interfering with the functional geometry of the LV contraction.     

Phylogenetic and physiological diversity of sulphate-reducing bacteria isolated from a salt marsh sediment

Xenopus blastula cells activate different mesodermal genes as a concentration-dependent response to activin, which behaves like a morphogen. To understand how cells recognize morphogen concentration, we have bound naturally labeled activin to cells and related this to choice of gene activation. We find that the increasing occupancy of a single receptor type can cause cells to switch gene expression. Cells sense ligand concentration by the absolute number of occupied receptors per cell (100 and 300 molecules of bound activin induce Xbra and Xgsc, respectively, i.e., 2% and 6% of the total receptors) and not by a ratio of occupied to unoccupied receptors. The long duration of occupancy explains a previously described ratchet effect. Our results suggest a new concept of morphogen gradient formation and interpretation that is particularly well suited to the needs of early development.     

Sialic acid-depleted red cells following acute myocardial infarction

A reduction of red cell SA in patients following acute myocardial infarction is reported and the effects of SA-depleted red cells on cardiac index and alveolar capillary blood flow in the dog are described. The mean red cell SA in 26 patients following acute myocardial infarction was 0.021 +/- 0.001 compared with a mean of 0.031 +/- 0.002 mumol./0.1 ml RBC in 12 normal subjects (p less than 0.01). In five dogs injected with neuraminidase, an enzyme which removes SA from the red cell membrane, a 43% decrease in mean cardiac index from 2.3 +/- 0.22 to 1.3 +/- 0.16 (p less than 0.01) occurred. In films of the pulmonary microcircuation the mean widths of typical alveolar capillary beds decreased 42.6% +/- 5% (p less than 0.01). In three other dogs, autotransfusion with SA-depleted stored blood resulted in a 25% decrease in mean cardiac index from 2.0 +/- 0.21 to 1.5 +/- 0.21 (p less than 0.2), and a 21.7% +/- 0.9% (p less than 0.01) decrease in mean widths of typical alveolar capillary beds. We conclude that a reduction of red cell SA follows acute myocardial infarction and that SA-depleted red cells decrease cardiac index and alveolar capillary blood flow in the dogs.     

Specific inhibition of hepatic fatty acid synthesis exerted by dietary linoleate and linolenate in essential fatty acid adequate rats

Dietary linoleate and linolenate were investigated for their ability to specifically inhibit liver and adipose tissue lipogenesis in meal-fed (access to food 900-1,200 hr), essential fatty acid (EFA) adequate rats. Supplementing a high carbohydrate diet containing 2.5% safflower oil with 3% palmitate 16:0, oleate 18:1, or linoleate 18:2 did not affect in vivo liver or adipose tissue fatty acid synthesis. However, 18:2 addition to the basal diet did result in a significant (P less than 0.05) decline of liver fatty acid synthetase (FAS) and glucose-6-phosphate dehydrogenase (G6PD) activities. When the safflower oil content of the basal diet was reduced to 1%, the addition of 3% 18:2 or linolenate 18:3 significantly (P less than 0.05) depressed hepatic FAS, G6PD, and in vivo fatty acid synthesis by 50%. Addition of 18:1 caused no depression in hepatic FAS activity but did result in a significant (P less than 0.05) decline in liver G6PD activity and fatty acid synthesis which was intermediate between basal and basal +18:2- or +18:3-fed animals. Adipose tissue rates of lipogenesis were completely unaffected by dietary fatty acid supplementation. Similarly, the addition of 3 or 5% 18:3 to a basal diet for only one meal resulted in no change in lipogenesis relative to that in animals fed the basal diet. The data indicate that, like rats fed EFA-deficient diets, dietary 18:2 and 18:3 exert a specific capacity to depress rat liver FAS and G6PD activities and rate of fatty acid synthesis.