Different rate of chromosome breakage in human fibroblast strains after storage in liquid nitrogen.

Cytogenetic investigation was carried out on fibroblasts stored in liquid nitrogen during a period of 7-99 months. Cell strains were from 9 individuals, 2 of whom were affected by xeroderma pigmentosum group C (XPC), and 2 XPC heterozygotes. In cell samples from 3 normal subjects and from 1 patient, high frequencies of abnormal mitoses were observed at the first passage after thawing, which returned to normal values after a few subcultures. The most frequent lesions were chromosome gaps and breaks. The cells damaged the most were those from one XP patient. These findings indicate that cells from some individuals are hypersensitive to clastogenic factors acting during freezing and thawing procedures. This sensitivity could be related to the genetic constitution, although the XP homozygous condition is not an essential or sufficient factor.     

Gamma-ray and hydrogen peroxide induction of gene amplification in hamster cells deficient in DNA double strand break repair

To investigate the role of DNA double strand breaks (DSBs) and of their repair in gene amplification, we analyzed this process in the V3 Chinese hamster cell line and in the parental line AA8, after exposure to gamma-rays and to hydrogen peroxide (H2O2). V3 is defective in DSB repair because of a mutation in the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) gene, a gene involved in the non-homologous end-joining pathway. As a measure of gene amplification we used the frequency of colonies resistant to N-(phosphonacetyl)-L-aspartate (PALA), since in rodent cells PALA resistance is mainly achieved through the amplification of the CAD (carbamyl-P-synthetase, aspartate transcarbamylase, dihydro-orotase) gene. After treatment with different doses of gamma-rays and of H2O2, we found a dose related increase in the frequency of gene amplification and of chromosome aberrations. When the same doses of damaging agents were used, these increments were higher in V3 than in AA8. These results indicate that DSBs that are not efficiently repaired can be responsible for the induction of gene amplification. H2O2 stimulates gene amplification as well as gamma-rays, however, at similar levels of amplification induction, chromosome damage was about 50% lower. This suggests that gene amplification can be induced by H2O2 through pathways alternative to a direct DNA damage. Stimulation of gene amplification by H2O2, which is one of the products of the aerobic metabolism, supports the hypothesis that cellular metabolic products themselves can be a source of genome instability.     

Complementation studies in cells from patients affected by trichothiodystrophy with normal or enhanced UV photosensitivity

A normal level of UV-induced DNA-repair synthesis (UDS) was observed in fibroblasts from a patient affected by trichothiodystrophy (TTD) without photosensitivity. This finding indicates that the hypersensitivity to UV light and the reduced UDS due to the presence of xeroderma pigmentosum complementation group D mutation (XP-D), described in photosensitive TTD patients, are not constantly associated with TTD. Complementation analysis in heterokaryons, obtained by fusion of repair-proficient with repair-deficient TTD cells, demonstrates that cells from the patient showing normal photosensitivity are able to restore UDS in UV-hypersensitive TTD cells.     

Kinetics of veratridine action on Na channels of skeletal muscle

Veratridine bath-applied to frog muscle makes inactivation of INa incomplete during a depolarizing voltage-clamp pulse and leads to a persistent veratridine-induced Na tail current. During repetitive depolarizations, the size of successive tail currents grows to a plateau and then gradually decreases. When pulsing is stopped, the tail current declines to zero with a time constant of approximately 3 s. Higher rates of stimulation result in a faster build-up of the tail current and a larger maximum value. I propose that veratridine binds only to open channels and, when bound, prevents normal fast inactivation and rapid shutting of the channel on return to rest. Veratridine-modified channels are also subject to a "slow" inactivation during long depolarizations or extended pulse trains. At rest, veratridine unbinds with a time constant of approximately 3 s. Three tests confirm these hypotheses: (a) the time course of the development of veratridine-induced tail currents parallels a running time integral of gNa during the pulse; (b) inactivating prepulses reduce the ability to evoke tails, and the voltage dependence of this reduction parallels the voltage dependence of h infinity; (c) chloramine-T, N-bromoacetamide, and scorpion toxin, agents that decrease inactivation in Na channels, each greatly enhance the tail currents and alter the time course of the appearance of the tails as predicted by the hypothesis. Veratridine-modified channels shut during hyperpolarizations from -90 mV and reopen on repolarization to -90 mV, a process that resembles normal activation gating. Veratridine appears to bind more rapidly during larger depolarizations.     

Wheat germ agglutinin treatment of follicle cell-free mouse oocytes inhibits fertilization

Controversy exists whether treatment of follicle cell-free oocytes with wheat germ agglutinin (WGA) prevents fertilization. Lack of inhibition in one case has led to the suggestion that acrosin may not be a zona lysin. To re-examine the effect of the WGA, the zona pellucida of follicle cell-free mouse oocytes was made more resistant to proteinase digestion by treatment with 10 or 50 μg/ml WGA. Such WGA-treated oocytes showed decreased fertilizability when washed to remove excess WGA and incubated with capacitated spermatozoa. Oocyte cleavage was used as an end point, because a large number of spermatozoa adhered to the eggs after WGA treatment, making observation of sperm penetration and pronucleus formation unreliable. Resistance to proteinase digestion increased, and the fertilizability decreased with the higher amount of WGA. The action of WGA was most likely not mediated by a direct effect on sperm motility, sperm acrosin activity, sperm binding to the zona pellucida, or oocyte cleavage. WGA did not affect the acrosome reaction of guinea pig spermatozoa. These data show that WGA treatment of follicle cell-free mouse oocytes results in decreased fertilizability, possibly by rendering the zona pellucida more resistant to sperm proteinase digestion.     

Greffes de cornée automatisées par laser femtoseconde optimisé et système de contrôle aberrométrique

We present a first evaluation of the results of the GRECO project which aims to conceive and realise an innovative device for ocular surgery by ultrafast pulse laser optimised for corneal grafting.     

Apoptotic index or a combination of Bax/Bcl-2 expression correlate with survival after resection of pancreatic adenocarcinoma

In the present study, the prognostic impact of factors involved in the apoptosis pathway were tested on 67 consecutive patients treated with surgical resection. Included in the study were all patients resected for pancreatic adenocarcinoma from 1988 to 2003. Expression analysis for p53, Bax, and Bcl-2 were performed by immunohistochemical staining. Apoptotic cells were identified by the TUNEL method. These data were correlated with survival. Sixty-seven tumor specimens were included in the study. A strong positive correlation was recorded between p53 overexpression and Bax expression levels (P < 0.001). By univariate analysis, overall survival seemed to be improved with Bcl-2 and Bax expression (respectively, P = 0.0379 and 0.0311). The median survival time in patients with low apoptotic index was better versus those with a high index (P = 0.0127). Lymph node involvement was the only clinico-pathologic parameter that significantly correlated with overall survival (P = 0.0202). By a multivariate Cox regression analysis, the only immunohistochemical parameter that influenced overall survival was the apoptotic index (P = 0.040). Tumor's overexpression of both Bax and Bcl-2 resulted the strongest independent prognostic factor (P = 0.013). This is the first study to report a statistically significant association of apoptosis to overall survival for pancreatic cancer patients treated with surgical resection. The contemporary overexpression of Bax and Bcl-2 represents the strongest prognostic factor.     

The biological threat to U.S. water supplies: Toward a national water security policy

In addition to providing potable drinking water, U.S. water systems are critical to the maintenance of many vital public services, such as fire suppression and power generation. Disruption of these systems would produce severe public health and safety risks, as well as considerable economic losses. Thus, water systems have been designated as critical to national security by the U.S. government. Previous outbreaks of waterborne disease have demonstrated the vulnerability of both the water supply and the public's health to biological contamination of drinking water. Such experiences suggest that a biological attack, or even a credible threat of an attack, on water infrastructure could seriously jeopardize the public's health, its confidence, and the economic vitality of a community. Despite these recognized vulnerabilities, protecting water supplies from a deliberate biological attack has not been sufficiently addressed. Action in this area has suffered from a lack of scientific understanding of the true vulnerability of water supplies to intentional contamination with bioweapons, insufficient tools for detecting biological agents, and a lack of funds to implement security improvements. Much of what is needed to address the vulnerability of the national water supply falls outside the influence of individual utilities. This includes developing a national research agenda to appropriately identify and characterize waterborne threats and making funds available to implement security improvements.