Substrate masking: binding of RNA by EGTA-inactivated micrococcal nuclease results in artifactual inhibition of RNA processing reactions

Inhibition of an RNA processing reaction after treatment with the Ca2(+)-dependent micrococcal nuclease (MN) is often used as a criterion for the presence of a required RNA or ribonucleoprotein component in the system. Following MN digestion, the nuclease is inactivated with EGTA and radiolabeled substrate is added to assay for remaining RNA processing activity. We found previously that inhibition of RNA processing by MN need not involve RNA hydrolysis: EGTA-inactivated MN can suppress RNA processing if the assay is performed in the absence of carrier RNA. We now demonstrate both by native gel electrophoresis and by nitrocellulose filter retention that EGTA-inactivated MN forms a complex with free RNA which can be dissociated by addition of synthetic polynucleotides or heparin. In the absence of Ca2+, nuclease binds to precursor tRNA with an apparent KD congruent to 1.4 x 10(-6) M, comparable to its reported affinity for DNA. In an assay for endonucleolytic tRNA maturation, inactivated MN bound to radiolabeled pre-tRNA physically blocks the sites of endonuclease cleavage and prevents tRNA processing. We call this phenomenon 'substrate masking'. Addition of excess carrier RNA competes with pre-tRNA for MN binding and restores normal processing.

Single-step labeling of DNA using restriction endonucleases and T4 polynucleotide kinase

DNA restriction fragments can be end-labeled in a combined digestion and labeling reaction with restriction endonuclease plus T4 polynucleotide kinase, omitting a dephosphorylation step. Both pBR322 and phage lambda DNA digests are efficiently labeled in one step, one tube and one incubation.

Passive protection of mice, goats, and monkeys against Japanese encephalitis with monoclonal antibodies

Six monoclonal antibodies (McAbs) against Japanese encephalitis virus (JEV) were tested for passive protection in JEV-infected mice, goats, and rhesus monkeys. mG9 and nG2 had no protective effect; mG3 and 2D2 had some protective effect, but not sufficient to be of therapeutic significance; and 2H4 and 2F2 had excellent protective efficacy in mice even 120 hr after infection when most of the mice in the virus control group were sick. The mixture of 2H4, 2F2, mC3 (M-McAb), and their F(ab')2 fragments showed excellent protection in mice, goats, and monkeys and was safe. The protective effects of McAbs correlated with their neutralization titers, but cytotoxicity-mediated activities also played a role in protection.

A method of evaluating inspector's performance differences and job requirements

Large individual differences are among the most consistent findings in the study of industrial inspection. From a statistical point of view, a large proportion of the variation in inspection performance is attributed to this individual factor. Based on the conclusions obtained from the review of previous papers, the relations between subjects' cognitive factors and inspection performance were shown to be in need of further exploration. The objective of this paper is to introduce a method that can explore this large proportion of variation by concentrating on individuals' cognitive attributes and how each contributes to the efficiency and effectiveness of inspection performance. In an experiment, three inspection tasks and 11 cognitive pretests were included. Through factor analysis and Pearson correlations, some significant predictive relationships were found. The findings can be applied to set up selection criteria as well as training schemes for industrial inspectors.

Defibrillation current and impedance are determinants of defibrillation energy requirements

The relationship between various electrical descriptors of shocks for cardiac defibrillation is incompletely understood. Defibrillating energy, current, impedance and pulse duration were measured in 18 dogs. They were subject to repeated fibrillation--defibrillation through epicardial patches, with shocks of preset energy and voltage and variable pulse duration, impedance and peak current. Current and energy requirements for defibrillation were calculated. Energy requirements were positively correlated with pulse duration and interelectrode impedance (r = .70, P less than 0.01). Correcting for heart weight, these correlations were no longer present. However, peak current was correlated with energy requirements both before (r = -0.62, P less than 0.05) and after (r = 0.76, P less than 0.01) correcting for heart weight, with energy requirement decreasing as peak current/g heart increased. Current requirements were significantly less variable between animals than energy requirements (.027 +/- .012 joules/g vs .016 +/- .003 Amps/g), suggesting that current per unit heart weight may be a better descriptor than energy for the ability to defibrillate.

Novel mechanisms for maturation of chloroplast transfer RNA precursors

Despite the prokaryotic origins of chloroplasts, a plant chloroplast tRNA precursor is processed in a homologous in vitro system by a pathway distinct from that observed in Escherichia coli, but identical to that utilized for maturation of nuclear pre-tRNAs. The mature tRNA 5' terminus is generated by the site-specific endonucleolytic cleavage of an RNase P (or P-type) activity. The 3' end is likewise produced by a single precise endonucleolytic cut at the 3' terminus of the encoded tRNA domain. This is the first complete structural characterization of an organellar tRNA processing system using a homologous substrate. In contrast to eubacterial RNase P, chloroplast RNase P does not appear to contain an RNA subunit. The chloroplast activity bands with bulk protein at 1.28 g/ml in CsCI density gradients, whereas E.coli RNase P bands as ribonucleoprotein at 1.73 g/ml. Chloroplast RNase P activity survives treatment with micrococcal nuclease (MN) at levels 10- to 100-fold higher than those required to totally inactivate the E.coli enzyme. The chloroplast system is sensitive to a suppression of tRNA processing, caused by binding of inactive MN to pre-tRNA substrate, which is readily overcome by addition of carrier RNA to the assay.

Dose finding double-blind clinical trial with praziquantel in schistosomiasis japonica patients

A double-blind clinical trial with praziquantel was carried out. A total of 400 cases was treated with four different dosages, namely, 60, 50, 40 and 30 mg/kg body weight of praziquantel. The drug was given in one day divided into two doses. Identical placebo tablets were used to make up a total of 60 mg/kg. Tolerance was good in all with the exception of one case suffering from asthmatic attack with papule rashes over large area of the body surface. 394 patients were able to be followed up parasitologically six months post-treatment. 79.8%, 71.7%, 78.8% and 70.1% of the patients were negative in the groups with the total dose of 60, 50, 40 and 30 mg/kg respectively. The cure rates as well as the side effects were similar for the four groups. The efficacy was lower than that reported by other authors and the possibility of reinfection was incriminated. In villages with few snails the negative hatching rates in aforementioned four groups were 89.1%, 91.1%, 88.9% and 81.8%, while in villages with abundant snails the rates were 68.2%, 46.5%, 66.7% and 54.8%. The difference between the two areas was statistically significant. Higher efficacy was observed in adults with an average cure rate of 80.0% than in children under 15 years of age, the average cure rate being 57.1%.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical trial on furapyrimidone in filariasis

A clinical trial was carried out with furapyrimidone in treating 51 patients with B. malayi, 159 with W. bancrofti and eight with D. perstans using different dosage schedules. Two hundred and fifty-seven cases of Malayan and bancroftian filariasis were treated with hetrazan for comparison. The results based on the microfilaricidal effects suggest that furapyrimidone possesses similar therapeutic effects of hetrazan on Malayan filariasis at eight-month follow-up, and higher incidences of microfilarial disappearance of W. bancrofti infection (81.3%) at six-month follow-up. The drug was also effective against D. perstans. The side effects consisted of fever and irritation of the digestive tract. Fever may be related to allergic reaction of foreign protein from the dead or dying parasites. The side reactions are similar to those of hetrazan and usually not serious. Comparing the efficacies and side effects of furapyrimidone with different dosage schedules the authors recommend regimens of 15 to 20 mg/kg/day for six days in treating Malayan filariasis and 20 mg/kg/day for seven days in treating bancroftian filariasis.