Genetic analysis of double-strand break repair in Escherichia coli

We had reported that a double-strand gap (ca. 300 bp long) in a duplex DNA is repaired through gene conversion copying a homologous duplex in a recB21 recC22 sbcA23 strain of Escherichia coli, as predicted on the basis of the double-strand break repair models. We have now examined various mutants for this repair capacity. (i) The recE159 mutation abolishes the reaction in the recB21C22 sbcA23 background. This result is consistent with the hypothesis that exonuclease VIII exposes a 3'-ended single strand from a double-strand break. (ii) Two recA alleles, including a complete deletion, fail to block the repair in this recBC sbcA background. (iii) Mutations in two more SOS-inducible genes, recN and recQ, do not decrease the repair. In addition, a lexA (Ind-) mutation, which blocks SOS induction, does not block the reaction. (iv) The recJ, recF, recO, and recR gene functions are nonessential in this background. (v) The RecBCD enzyme does not abolish the gap repair. We then examined genetic backgrounds other than recBC sbcA, in which the RecE pathway is not active. We failed to detect the double-strand gap repair in a rec+, a recA1, or a recB21 C22 strain, nor did we find the gap repair activity in a recD mutant or in a recB21 C22 sbcB15 sbcC201 mutant. We also failed to detect conservative repair of a simple double-strand break, which was made by restriction cleavage of an inserted linker oligonucleotide, in these backgrounds. We conclude that the RecBCD, RecBCD-, and RecF pathways cannot promote conservative double-strand break repair as the RecE and lambda Red pathways can.     

Hair analysis for drugs of abuse. VI. The excretion of methoxyphenamine and methamphetamine into beards of human subjects

The excretion of methoxyphenamine (MOP) and methamphetamine (MA) into beards has been studied. Six healthy male subjects orally took 50 mg of MOP at a single dose and 7 doses for a successive 7 days. Their beard hairs were collected by an electric shaver every morning until MOP disappeared from the beard. After washing with 0.1% SDS, the beard samples were extracted with methanol-5 N HCl (20:1) under ultra-sonication for 1 h and the solution was kept overnight. MOP in the extract was determined by GC/MS using deuterium labelled MOP as an internal standard after trifluoroacetyl-derivatization. The drug concentrations in beard and the reproducibility of analysis were compared with the three procedures, unwashed, 0.1% SDS (wash I) and the additional ethanol (wash II) wash. The drug concentration in beard after SDS wash was 0.5-2.5 ng/mg lower than that in unwashed beard during the first 5-6 days. The drug concentration in beard after ethanol wash was much lower than that in the unwashed beard. The drug excreted into beard was detected 10 approximately 12 days for a single dose and 12-14 days for 7 doses after the last dosage at the cut off level of 1 ng/mg. On the contrary, the drug excreted in urine was not detected after more than 3 days after use. O-Desmethyl MOP, a major metabolite of MOP, was also detected in beard. The procedures were applied to the detection of MA in beard of MA abusers. It was realized that a beard sample was more useful than a urine sample assuming a longer detection.     

Local anaesthetic bupivacaine alters function of sarcoplasmic reticulum and sarcolemmal vesicles from rabbit masseter muscle

The effects of local anaesthetics, bupivacaine and lidocaine, on Ca2+ flux behaviour of sarcoplasmic reticulum and on sarcolemmal functions were studied in the rabbit masseter muscle. The experiments were performed on sarcoplasmic reticulum and sarcolemmal vesicles prepared at 1 to 10 days after injection of local anaesthetics or saline into masseter muscle as well as on sarcoplasmic reticulum vesicles prepared from non-treated rabbits (for assessment of the effect on in vitro incubation with local anaesthetics). Bupivacaine potently reduced the efficiency of active sarcoplasmic reticulum Ca2+ transport as evaluated by coupling ratio (Ca2+ transported/ATP hydrolyzed, in the presence of oxalate) at 3 days after the injection; there was only a slight degree of uncoupling of Ca2+ transport from ATP hydrolysis with lidocaine injection. Bupivacaine but not lidocaine, at 3 days after injection, decreased both the apparent permeability of sarcoplasmic reticulum vesicles to Ca2+, determined by measuring net efflux of Ca2+ after stopping pump-mediated fluxes, and the steady-state Ca2+ load in sarcoplasmic reticulum, but had no effect on overall turnover of the Ca2+ATPase. The effects of bupivacaine on apparent sarcoplasmic reticulum Ca2+ permeability and steady-state Ca2+ load were inhibited by a Ca2+ antagonist verapamil. The reduction of Ca2+ uptake of sarcoplasmic reticulum and the protective effect of verapamil were reproduced in unfractionated homogenates prepared at 3 days after bupivacaine injection. In vitro exposure of sarcoplasmic reticulum vesicles to bupivacaine (0.5 to 50 mM) reduced steady-state Ca2+ load in a dose-dependent manner. The observed effect elicited by bupivacaine (25 mM) was partially protected by procaine, an inhibitor of Ca2(+)-induced Ca2+ release from sarcoplasmic reticulum, or by specific closure of the sarcoplasmic reticulum Ca2+ release channel by ryanodine, suggesting the possibility that in vitro exposure of sarcoplasmic reticulum vesicles to bupivacaine may produce an increase in apparent permeability of sarcoplasmic reticulum to Ca2+. In sarcolemma, bupivacaine reduced Na+,K(+)-ATPase and Na(+)-Ca2+ exchange activities at 3 days after injection; the effects on sarcolemmal vesicles were prevented by verapamil. These results suggest that although the effects elicited by bupivacaine injection and the in vitro exposure to bupivacaine on steady-state Ca2+ load of sarcoplasmic reticulum vesicles were similar, the membrane properties of the vesicles from bupivacaine-treated masseter muscles and those from normal untreated muscles may not be the same, which indicates that pure bupivacaine effect is due partly by an effect on ryanodine- and procaine-sensitive Ca2+ channels.(ABSTRACT TRUNCATED AT 400 WORDS)     

Scanning electron microscopy of the myosin-coated surface of polystyrene beads in a force-movement assay system for ATP-dependent actin-myosin sliding

An outbreak of Cryptosporidiosis occurred over three months in a British Columbia community, peaking in December 1990. Results of the case-control study and illness surveys support the hypothesis that transmission occurred in a public children's pool at the local recreation centre. Analysis using lab-confirmed cases revealed a matched odds ratio of 4.5 [95% CI 0.97, 20.83], and using clinical cases an unmatched odds ratio of 12.8 [95% CI 3.68, 46.77], associated with swimming in the children's pool within two weeks prior to onset of illness. Other risk factors were not significant. Attack rates in various groups of children's pool users ranged from 8% to 78%. The children's pool was closed for steam cleaning and disinfection. Unusually frequent defecations including liquid stools had occurred before and during the outbreak. Improvements were instituted for removal of feces and superchlorination of pool water.     

Liquid viscosities and densities of HFC-134a+glycol mixtures

Liquid viscosity and density of six binary mixtures of HFC-134a with glycols [ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (400), and polypropylene glycol (2000)] have been measured in the temperature range from 273 to 333 K. The viscosity was measured by a rolling-ball viscometer calibrated with standard liquids of viscosities and densities (JS5, JS10, JS20, and JS50). The density was measured with a glass pycnometer. The uncertainties of the measurements were estimated to be less than 3.4 % for viscosity and 0.04 % for density, respectively. An equation is given to represent the obtained viscosity values as a function of weight fraction and temperature.     

Lack of carcinogenicity of medium-viscosity liquid paraffin given in the diet to F344 rats

The carcinogenicity of medium-viscosity liquid paraffin was examined in Fischer 344 rats. Groups of 50 males and 50 females were given the material at dietary doses of 0 (control), 2.5 or 5% for 104 wk. Slight increases in food consumption and body weight were observed in both sexes of the 5% group. However, no significant differences between the control and treated groups were noted with regard to clinical signs, mortality and haematology findings. A variety of tumours developed in all groups, including the control group, but all the neoplastic lesions were histologically similar to those known to occur spontaneously in F344 rats, and no statistically significant increase in the incidence of any tumour type was found for either sex in the treated groups. Granulomatous inflammation in the mesenteric lymph nodes, considered to be a reaction to paraffin absorption, was observed with similar incidence and severity in both sexes of the 2.5 and 5% groups. Thus, it is concluded that under the present experimental conditions, the high dose, about 2000-200,000 times higher than the current temporary acceptable daily intake, does not have any carcinogenic potential in F344 rats. Furthermore, granulomatous inflammation observed in mesenteric lymph nodes were not associated with any development of neoplastic lesions.     

Three-dimensional motion of the upper cervical spine in rheumatoid arthritis

Rheumatoid arthritis frequently contributes to instability of the upper cervical spine. Rotational instability of the upper cervical spine was evaluated in rheumatoid arthritis patients using biplanar x-ray photogrammetry. Three-dimensional cervical motion and the instantaneous axis of rotation of the atlas relative to the axis were evaluated in normal and rheumatoid arthritis patients during axial rotation in the horizontal plane. Anterior atlantoaxial subluxation did not increase during axial head rotation in either the atlantoaxial subluxation or the vertical subluxation groups, while the instantaneous axes of rotation were distributed posteriorly in the dens in the RA-normal group, but were widely scattered in the atlantoaxial subluxation group.     

Auditory middle latency responses in patients with epilepsy

Middle latency auditory responses (MLRs) were studied in 55 normal subjects and 49 epileptic patients. We evaluated the function of the auditory system and of the temporal lobe in epileptic patients using MLRs. (1) The patients with epilepsy had significantly prolonged Pa and Nb latencies and the significantly increased amplitude of Pa-Nb component. (2) The prolongation and the increase of MLR components in latency and amplitude were more obvious in patients with intractable epilepsy than patients without intractable epilepsy. (3) The difference between left and right sides was larger in epileptic patients than normal subjects. (4) Epileptic patients with polypharmacy had reduced amplitude of Pa-Nb component and prolonged latency of Pa component than patients with monotherapy. Antiepileptic drugs (AEDs) appeared to decrease the amplitude of Pa-Nb component. It was supposed that the enhancement of amplitude of Pa-Nb component represented the abnormality of central nerve system in epileptic patients, in part.     

Simulation and experimental analyses of electromagnetic transients behaviors of lightning surge on vertical conductors

Simulation of very fast surge phenomena in a three-dimensional (3-D) structure requires a method based on Maxwell's equations, such as the finite-difference time-domain (FDTD) method or the method of moments, because circuit-equation-based methods cannot handle the phenomena. This paper uses a method of thin-wire representation of the vertical conductor system for the FDTD method which is suitable for the 3-D surge simulation. The thin-wire representation is indispensable to simulate electromagnetic surges on wires or steel frames in which the radius is smaller than a discretized space step used in the FDTD simulation. In this paper, a general surge analysis program named the virtual surge test lab based on the Maxwell's equations formulated by the FDTD method, is used to simulate the surge phenomena of a vertical conductor, including the effects of horizontal wave incidence and vertical wave incidence. Experimental results on the reduced scale model have been presented in order to compare among the simulation results by the FDTD method and the results using numerical electromagnetic code based on the MoM.