Effects of fasting and gender on ochratoxin A toxicokinetics in F344 rats.

Ochratoxin A (OTA) is a mycotoxin that causes renal tumors in rats, particularly in males. In previous kinetic studies performed in fed conditions (Vettorazzi et al., 2008), mature F344 male rats presented a significantly lower OTA bioavailability than females and young animals. The objective of the present study was to evaluate two factors which could explain this different kinetic profile: the presence of food and the male-specific protein alpha-2u-globulin. Therefore, a 24h kinetic study has been performed in rats under fasting conditions. Food ingestion has been controlled in both sexes during two months. The presence of alpha-2u-globulin in the urine has been analyzed with SDS-gradient mini-gel electrophoresis. Fasting tends to increase the maximum OTA plasma concentrations and the rate of absorption. The relative bioavailability is significantly increased under fasting conditions only in males. Mature males consumed a higher amount of food but, as the OTA dose administered, it was proportional to body weight. The reason why the OTA bioavailability is more affected in presence of food only in males is unclear. Several possibilities, such as differences in gastric emptying, OTA-food interactions and the involvement of alpha-2u-globulin are discussed.

Inhibition of bone resorption by alendronate and risedronate does not require osteoclast apoptosis.

Bisphosphonate inhibition of bone resorption was proposed to be due to osteoclast apoptosis. We tested this hypothesis for both the N-containing bisphosphonates alendronate and risedronate, which inhibit farnesyldiphosphate synthase and thus protein isoprenylation, and for clodronate and etidronate, which are metabolized to adenosine triphosphate (ATP) analogs. We found, in dose-response studies, that alendronate and risedronate inhibit bone resorption (in pit assays) at doses tenfold lower than those reducing osteoclast number. At an N-bisphosphonate dose that inhibited resorption and induced apoptosis, the antiapoptotic caspase inhibitor, Z-VAD-FMK, maintained osteoclast (Oc) number but did not prevent inhibition of resorption. Furthermore, when cells were treated with either alendronate alone or in combination with Z-VAD-FMK for 24 or 48 h, subsequent addition of geranylgeraniol, which restores geranylgeranylation, returned bone resorption to control levels. On the other hand, Z-VAD-FMK did block etidronate and clodronate inhibition of resorption. Moreover, in cells treated with etidronate, but not alendronate or risedronate, Z-VAD-FMK also prevented actin disruption, an early sign of osteoclast inhibition by bisphosphonates. These observations indicate that, whereas induction of apoptosis plays a major role in etidronate and clodronate inhibition of resorption, alendronate and risedronate suppression of bone resorption is independent of their effects on apoptosis.

Does the cleaning technique influence the durability of the <9F flexible ureteroscope?

BACKGROUND AND PURPOSE: The fragility of the <9F flexible ureteroscope limits its availability to general urology practice. The purpose of this study was to determine whether the technique used to clean the flexible ureteroscope or the number of persons handling the instrument during the cleaning process influenced endoscope breakage or deterioration during regular endourologic use. PATIENTS AND METHODS: A new Olympus URF/P3 flexible 7.5F ureteroscope was used for each of two 30-day study periods during which a single surgeon used the endoscope for a variety of upper urinary tract procedures. During the first 30-day period (Group 1), the endoscope was leak-proof-pressure tested and cleaned by the endourology support team using the Steris 20 (peroxyacetic acid 35%) technique. During the second 30-day period (Group 2), the endoscope was leak-proof tested and cleaned only by the surgeon using the Cidex (glutaraldehyde 2.4%) technique. A record was kept for each ureteroscopic case to document the patient position, access technique, time the endoscope was in the urinary tract, instruments passed through the ureteroscope, and the maximum irrigant pressure used. In addition, a record was made of the number of broken fibers, the degree of flexion and deflexion of the endoscope, and the problems encountered with the endoscope during the case. RESULTS: The two study groups were similar in terms of the total number of cases performed, the mean time the endoscope was in the urinary tract per case, the access approach used, and the use of the ureteral access sheath and ancillary equipment. In Group 2, the endoscope was used for a longer total time (618 minutes v 457 minutes), and access to a lower pole calix was more than twice as common as in Group 1. This may explain why more broken fibers were noted in the instrument used in Group 2 over the study period (eight v four broken fibers) than in Group 1. The only breakage occurred as a result of the surgeon accidentally activating the laser probe inside the working channel of the endoscope in Group 2. CONCLUSION: The technique and number of personnel involved in the maintenance and cleaning of the flexible ureteroscope does not have a significant effect on the durability and function of these instruments. It is the arduous demands of the endourologic procedure that influence the durability of these fragile endoscopes.

Bisphosphonates act directly on the osteoclast to induce caspase cleavage of mst1 kinase during apoptosis. A link between inhibition of the mevalonate pathway and regulation of an apoptosis-promoting kinase.

Bisphosphonates (BPs) include potent inhibitors of bone resorption used to treat osteoporosis and other bone diseases. BPs directly or indirectly induce apoptosis in osteoclasts, the bone resorbing cells, and this may play a role in inhibition of bone resorption. Little is known about downstream mediators of apoptosis in osteoclasts, which are difficult to culture. Using purified osteoclasts, we examined the effects of alendronate, risedronate, pamidronate, etidronate, and clodronate on apoptosis and signaling kinases. All BPs induce caspase-dependent formation of pyknotic nuclei and cleavage of Mammalian Sterile 20-like (Mst) kinase 1 to form the active 34-kDa species associated with apoptosis. Withdrawal of serum and of macrophage colony stimulating factor, necessary for survival of purified osteoclasts, or treatment with staurosporine also induce apoptosis and caspase cleavage of Mst1. Consistent with their inhibition of the mevalonate pathway, apoptosis and cleavage of Mst1 kinase induced by alendronate, risedronate, and lovastatin, but not clodronate, are blocked by geranylgeraniol, a precursor of geranylgeranyl diphosphate. Together these findings suggest that BPs act directly on the osteoclast to induce apoptosis and that caspase cleavage of Mst1 kinase is part of the apoptotic pathway. For alendronate and risedronate, these events seem to be downstream of inhibition of geranylgeranylation.

Purification and characterization of recombinant catalase-peroxidase, which confers isoniazid sensitivity in Mycobacterium tuberculosis.

The Mycobacterium tuberculosis katG gene encodes a dual-function enzyme called catalase-peroxidase, which confers sensitivity in M. tuberculosis to isonicotinic acid hydrazide. We have constructed a system for the high level expression of a recombinant form of this enzyme by amplifying the katG gene from the pYZ56 construct (1) and subcloning into a vector suitable for expression in Escherichia coli. The resulting plasmid, pTBCP, produced the catalase-peroxidase in large quantities, corresponding to 30% of total cell protein. The enzyme has been purified to homogeneity and appears to be a dimer in the native form. Using either hydrogen peroxide or t-butyl hydroperoxide and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) as substrates, kcat and Km values have been obtained for both catalatic and peroxidatic activities, respectively. The availability of significant quantities of an active, folded, recombinant form of M. tuberculosis catalase-peroxidase should thus facilitate future studies of its role in drug activation and antibiotic resistance.

The effect of smoking cessation on pulmonary function: a 30-month follow-up of two smoking cessation clinics.

To obtain further information about the effects of cessation of smoking on pulmonary function, we followed subjects who attended 2 smoking cessation clinics during a period of 30 months. This paper reports the results from 15 persons who succeeded in stopping smoking for the full 30-month period and from 42 who did not succeed for more than one month. Testing included a respiratory questionnaire, spirometry, and the single-breath N2 test. Standardized methods, the same equipment, and the same experienced personnel were used throughout the study. We found that forced vital capacity, one-second forced expiratory volume, closing volume as a percentage of vital capacity, closing capacity as a percentage of total lung capacity, and the slope of the alveolar plateau of the single-breath N2 test all improved significantly in the subjects who stopped smoking. This improvement continued for as long as 6 to 8 months, and then remained stable. There was no sex difference in the response to smoking cessation, nor could we find a threshold of function below which cessation did not result in improvement. On the contrary, those subjects with the greatest impairment initially showed the greatest improvement. Respiratory symptoms virtually disappeared in those who stopped smoking. Subjects who continued to smoke showed an initial improvement in some function tests, probably due to a marked decrease in consumption, but no significant improvement during the whole period. We concluded from this study that cessation of smoking results in definite improvement in pulmonary function, that there is greater improvement in persons who begin with impaired function than in those whose function is initially normal, that respiratory symptoms disappear rapidly.

The effect of smoking cessation and modification on lung function.

The purpose of this study was to obtain more information about the effect on lung function of stopping smoking or of modifying the smoking habit and to determine the time course of change. We followed a group of 75 cigarette smokers who attended a smoking cessation clinic in May 1973, using a respiratory symptom questionnaire, spirometry, closing volumes, and the slope of the alveolar plateau of the single-breath nitrogen test. Subjects were tested before stopping smoking and at 1, 3, 6, and 12 months after the initial testing. We found a significant (P less than 0.05) improvement in closing volume as a percentage of vital capacity and closing capacity as a percentage of total lung capacity at 6 and 12 months and in the slope of the alveolar plateau at 1, 6, and 12 months in those who stopped smoking. There was also a dramatic decrease in respiratory symptoms in those who stopped smoking, a moderate decrease in those who reduced their consumption by at least 25 per cent, and very little change in those who did not appreciably modify their smoking consumption.