The acceleration of cosmic-ray protons in the supernova remnant RX J1713.7-3946.

Protons with energies up to approximately 10(15) eV are the main component of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking. Electrons are known to be accelerated to cosmic-ray energies in supernova remnants, and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (pi(0)), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in gamma-rays with a particular spectral-energy distribution. Here we report the observation of cascade showers of optical photons resulting from gamma-rays at energies of approximately 10(12) eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.

High-affinity binding of hemimethylated oriC by Escherichia coli membranes is mediated by a multiprotein system that includes SeqA and a newly identified factor, SeqB.

The binding of hemimethylated oriC to Escherichia coli membranes has been implicated in the prevention of premature reinitiation at newly replicated chromosomal origins in a reaction that involves the SeqA protein. We describe the resolution of the membrane-associated oriC-binding activity into two fractions, both of which are required for the high-affinity binding of hemimethylated oriC. The active component in one fraction is identified as SeqA. The active component of the second fraction is a previously undescribed protein factor, SeqB. The reconstituted system reproduced the salient characteristics of the membrane-associated binding activity, suggesting that the membrane-associated oriC-binding machinery of E. coli is likely to be a multiprotein system that includes the SeqA and SeqB proteins.

[Assessment of proliferative cell nuclear antigen expression and clinical prognosis in gastric malignant lymphoma].

Clinicopathological study was performed in 15 resected cases of gastric malignant lymphoma. The clinicopathological features were as follows. 1) In 6 of 15 cases, the tumor was located in the upper part of the stomach. 2) Lymph node metastasis was observed in 5 of 12 cases. 3) In 3 of 15 cases, multiple tumorous lesions were noted. We also studied the relationship between PCNA expression and clinical prognosis in 10 cases, specimens of which were well preserved, out of 15 cases. About 500 nuclei immunohistochemically stained by PCNA monoclonal antibody were counted, and results were expressed by positive cell ratio (PCNA labelling index LI%). In conclusion, 1) the positive cases of lymph node metastasis showed a tendency for PCNA LI to increase compared with the negative cases. 2) The recurrent cases showed a tendency for increased PCNA LI compared with the cases without recurrence. 3) Cases with more than 60% of PCNA LI tended to have a poor prognosis compared with those of less than 60%.

Metabolism of gemcitabine in rat and dog.

1. The metabolism of 14C-gemcitabine in the male rat has been studied after intravenous administration of a single dose (10 mg/kg) or five doses (1 mg/kg/day) of 14C-gemcitabine. The metabolism in male dog has been studied after only single dosing. The effects of gemcitabine on hepatic drug-metabolizing enzymes in rat has also been studied. 2. The concentration of gemcitabine in the plasma was 11.84 micrograms/ml at 5 min, and then rapidly decreased after a single administration to rat. A deaminated uracil analogue of gemcitabine progressively increased with time. Gemcitabine and the uracil metabolite accounted for 80.0 and 11.8% of the radioactive dose in the 0-24-h urine samples respectively. Gemcitabine was the major component identified in lung, liver and kidney at 5 min after administration. 3. After repeated administration to rat, metabolites in the plasma and tissues were not remarkably different from those found after a single administration. 4. After a single administration to dog, the plasma concentration of gemcitabine was 12.39 micrograms/ml at 5 min. Gemcitabine and the uracil metabolite accounted for 8.3 and 71.8% of the dose in the 0-24-h urine samples respectively. 5. No differences were observed in enzymatic activities per whole liver between the gemcitabine-treated and control rat.

Characterization of the Escherichia coli membrane domain responsible for binding oriC DNA.

It has previously been shown that hemimethylated DNA from the Escherichia coli replication origin (oriC) binds with high specificity to membrane fractions isolated from disrupted cells. In this article, the membrane localization of oriC-binding activity was studied by subjecting crude membrane preparations to successive cycles of sedimentation and flotation gradient analysis. This revealed that approximately two-thirds of the membrane-associated oriC-binding activity of the cell was not associated with the outer membrane fraction as previously suggested but was recovered instead in a unique membrane fraction (OCB1) whose buoyant density and protein profile differed from those of both inner and outer membranes. The specific activity of oriC binding in OCB1 was approximately fivefold higher than the activity of the isolated outer membrane peak. It is likely that membrane fraction OCB1 includes the membrane domain responsible for the binding of hemimethylated oriC to the cell envelope in intact cells.

[Studies on the pharmacokinetics of BMY-28100 (I)].

The pharmacokinetics of BMY-28100 have been studied in rats and monkeys upon oral administration of 14C-BMY-28100. 1. In rats administered with BMY-28100 at a single oral dose of 20 mg/kg, the peak blood level of the drug was 6.30 micrograms equiv./ml at 1 hour after administration. Blood levels declined biphasically, thereafter. The AUC value was 37.0 micrograms equiv..hr/ml, and was 97% of that observed after intravenous administration. This suggests that BMY-28100 is absorbed at a high absorption rate from the gastro-intestinal tract. 2. In monkeys administered with a single oral dose of 20 mg/kg, the peak blood level was 4.26 micrograms equiv./ml at 3 hours after administration. Thereafter, blood levels declined biphasically as did in rats. The AUC was 38.9 micrograms equiv..hr/ml, which is similar to that observed in rats. 3. Urinary and fecal excretion after 20 mg/kg oral administration were 60.9% and 38.1%, respectively, in rats, and 40.3% and 51.2%, respectively, in monkeys. 4. Although absorption from gastro-intestinal tract was delayed by food intake, this did not affect the total amount absorbed in rats. 5. The absorption rates were similar in rats administered with 20 and 60 mg/kg, while a lower rate was obtained with 200 mg/kg. 6. In rats, biliary excretion was 28.5% of dose administered. Thirty-nine percent of the biliary radioactivity was reabsorbed from the intestinal tract. 7. No differences between sexes were observed in absorption and excretion in rats administered with the drug at 20 mg/kg orally. 8. In rats administered with 20 mg/kg, the radioactivity distributed rapidly to the whole body. High levels of radioactivity were found in gastro-intestinal tract, kidney, urinary bladder, aorta and liver. The radioactivity was removed rapidly from the tissues. Autoradiograms of the whole body were consistent with the measured tissue distribution. Relatively high levels of radioactivity were found in aorta, fascia, and ligament at 0.5, 1, 6, and 24 hours. 9. In vivo protein binding, which increased with time after administration, was 56.8 to 73.5% in rat and 36.3 to 58.6% in monkey. The in vitro protein binding at 0.4 to 50 micrograms/ml of drug concentration was 50.0 to 54.7% in rat, 32.3 to 35.0% in monkey, and 33.4 to 36.3% in human. 10. A stability test of 14C-BMY-28100 in plasma solution showed that the drug decomposed gradually into relatively polar compound(s). At 8 and 24 hours, the proportions of unchanged 14C-BMY-28100 were 53.2% and 5.9%, respectively.

[Studies on the pharmacokinetics of BMY-28100 (II)].

Studies were done in rats on placental transfer and excretion into milk of 14C-BMY-28100 upon single oral administration. Studies on absorption, distribution and excretion of 14C-BMY-28100 were also done upon multiple dosing. 1. Fetal tissue concentration of the drug reached a maximum at 6 hours after dosing on day 18 of gestation. The highest concentration observed was only 0.56 microgram equiv./g in fetal kidney; The transfer of radioactivity into the fetus was low. Similar results were obtained from whole body autoradiograms performed in rats on day 12 and day 18 of gestation. 2. Concentrations of radioactivity in milk reached a maximum of 0.60 microgram equiv./ml at 1 hour after administration, and gradually decreased thereafter. The maximum concentration in milk was 10% of the plasma concentration measured at the same time. 3. In the multiple oral administration study, 24 hours blood levels of radioactivity rose progressively with each dose, and reached a level 3.8 times higher than that observed with single dosing by the final (21st) administration. Tissue concentrations were relatively high in aorta, kidney and large intestine as were found upon single administration. However, the ratios of these levels between multiple and single dosing were lower than those observed in blood; 1.7, 3.6 and 2.9 for aorta, kidney and large intestine, respectively. Urinary and fecal excretion were constant after the 2nd administration.

Disposition and metabolism of [14C]-amezinium metilsulfate in rats.

Disposition and metabolism of [14C]-amezinium metilsulfate (4-amino-6-methoxy-1-phenylpyridazinium methylsulfate, Risumic) were systematically studied in rats after intravenous (5 mg/kg) or oral (20, 100 mg/kg) administration. After oral administration at 20 mg/kg, blood level reached the maximum (Cmax) of 0.65 microgram eq/ml at 3 h (tmax) and decreased with t1/2 of 8.1 h. Levels in plasma and most tissues elevated to the Cmax at 3 h. The liver level was the highest (61 times as high as plasma level) of all examined tissues. Most tissue levels decreased thereafter essentially in parallel with plasma levels. The findings by whole-body autoradiography essentially agreed with those by radiometry. In lactating rats, milk levels were virtually similar to plasma levels. [14C]-Amezinium metilsulfate radioactivity in fetus and fetal blood was around 0.3 microgram eq/g, being about 1/10 level of maternal plasma level. About 24, 72 and 42% were excreted in urine, feces and bile, respectively. Re-absorption of biliary metabolites accounted for about 31%, being about 13% of orally given [14C]-amezinium metilsulfate. Plasma and aorta contained unchanged amezinium and glucuronide of hydroxyl amezinium MIII. In the brain, the major metabolite was O-demethyl amezinium MV and unchanged drug was not detected. Urinary metabolites were largely MIII glucuronide and the unchanged drug. Biliary metabolite was found composed mostly from MIII glucuronide. In feces, MIII and the unchanged amezinium were found. MIII and its glucuronide were novel metabolites which were identified by thin-layer chromatography and mass spectrometry.

Leptomycins A and B, new antifungal antibiotics. I. Taxonomy of the producing strain and their fermentation, purification and characterization.

A strain of Streptomyces was found to produce new antifungal antibiotics. The active compounds were purified and separated into two substances named leptomycin A and B by high performance liquid chromatography. The molecular formulae of leptomycins A and B are C32H46O6 and C33H48O6 respectively, and physicochemical and biological properties of them are very similar to each other. Leptomycins A and B exhibit strong inhibitory activity against Schizosaccharomyces and Mucor.