[Inhibition of growth and metastases of lung carcinoma in C57BL/6 mice by Corynebacterium parvum and its antitumor mechanism]

Cocrynebacterium parvum (CP) was injected around the tumor and tumor cells were inoculated subcutaneously with activated peritoneal macrophages. The effects on the growth and metastases of Lewis lung carcinoma in C57BL/6 mice were observed. Experimental results indicated that CP had significant inhibitory effect on the tumor growth and lung metastases. The cytotoxic effects of activated peritoneal macrophages in mice on target tumor cells (L5178Y) in vitro were studied with the technique of 3H-TdR assay. The proliferation of tumor cells was markedly inhibited by the activated peritoneal macrophages of CP. Experiments showed that the antitumor mechanism of CP was the mediation via activated cytotoxic macrophages. These results indicated that CP is an effective immunostimulant. These findings will provide a scientific basis for the clinical treatment of the primary and metastatic lung carcinoma.

Angiogenin depresses aortic smooth muscle cell cAMP by a pertussis toxin sensitive mechanism

Angiogenin transiently depresses the cAMP level of rat aortic smooth muscle cells. The dose response is similar to angiogenin activation of the inositol-specific phospholipase C in this cell line [Moore, F. & Riordan, J.F. (1989) Biochemistry. Submitted]. The time course showed a maximal depression (28%) in cAMP at 2 min, followed by a return to that of unstimulated cells by 3.5 min. Angiogenin also inhibited isoproterenol stimulated cAMP formation, but the percentage depression in cAMP (9%) was less than that in cells treated with angiogenin alone (28%). In contrast angiogenin enhanced forskolin stimulation of adenylate cyclase, an effect previously linked with agonist activation of protein kinase C. The effect of angiogenin on cellular cAMP was abolished by pre-incubation with pertussis toxin. Angiogenin had no effect on cellular cGMP. These results are consistent with activation of adenylate cyclase Gi following exposure of the cells to angiogenin and provide further evidence for interaction between cellular signalling pathways.

[A study of acute toxicity of mitoxantrone]

Acute toxicity of mitoxantrone (DHAQ) synthetized by Department of Organic Chemistry, School of Pharmacy, WCUMS was studied in mice and dogs. The toxic effects were compared with those of adriamycin (ADR). The LD50 were 6.6 +/- 1.3 and 7.1 +/- 1.6 mg/kg DHAQ, 7.9 +/- 2.1 and 10.7 +/- 2.2 mg/kg ADR (P = 0.95) respectively on observation with a single dose i.v. and i.p., for 21 days in Kunming mice. The toxicity appeared to be delayed with DHAQ and ADR. The earliest death occurred on 4th day after treatment in mice. In the third week still a few died. There were obvious decreases in WBC counts in the peripheral blood of mice receiving either 1-2.5 mg/kg DHAQ or 2.5-5 mg/kg ADR with a single dose i.p.. The WBC count could return to normality after 3 weeks with the withdrawal of the drugs. On electron microscopic examination of myocardial samples from mice 4 days after a single dose of 20 mg/kg DHAQ i.p., mitochondria swelling and vacuoles formation in some cells were shown. Besides the above-mentioned changes, some myocytes exhibited disorientation and loss of myofilaments in the mice which received equivalent dose of ADR. In dogs anaesthetized a temporary falling of blood pressure and slowing of heart rate were observed following 5-10 mg/kg DHAQ i.p.. When a dose of 50-100 mg/kg was given, the blood pressure dropped continuously until death.

Correlation of dietary aflatoxin B1 levels with excretion of aflatoxin M1 in human urine

Corn and peanut oil (total, 253 samples) were collected from 32 households in Fushui county of the Guangxi autonomous region of the People's Republic of China, where high liver cancer incidence has been reported, every day over a period of 1 week and analyzed for aflatoxin B1 (AFB). A total of 252 urine samples were collected simultaneously from the residents in the households which were shown to have consumed AFB and were analyzed for aflatoxin M1 (AFM) by a competitive direct enzyme-linked immunosorbent assay. A good correlation between total dietary AFB intake and total AFM excretion in human urine was observed during a 3-day study. A regression equation of 0.143 plus 0.0135 multiplied by the amount of AFB consumed was observed. Between 1.23 and 2.18% of dietary AFB was found to be present as AFM in human urine. A good correlation was also observed between the AFB concentration in corn and the AFM concentration in human urine. The results suggest that analysis of AFM in urine by enzyme-linked immunosorbent assay could be used as an index for human exposure of AFB in an extensive epidemiological study.

Studies on optic nerve of Lipotes vexillifer-structure, fiber count and diameter spectrum

Four optic nerves obtained from two Lipotes Vexillifer have been studied with the aid of electron microscope. The fiber diameter spectra of all the four optic nerves are unimodal. The diameters of fibers range from 0.35 to 7.45 microns with the highest frequency at 1.5 microns. T test indicates there is no significant difference in fiber density and fiber diameter between the central and peripheral regions of the optic nerve. The ratio of axon diameter to the total fiber diameter is 0.6 +/- 0.02 (p less than 0.05). The examination of four optic nerves indicates a mean count of 78,900 fibers; none of unmyelinated fibers have been seen. The shapes of the cross sections of fibers are very irregular. The myelin sheaths of some nerve fibers are very thick while those of some others are thinner.

Recent advances in anther culture of Hevea brasiliensis (Muell.-Arg.)

The yield of pollen embryoids from cultured Hevea anthers was increased 4 fold by optimizing the proportion of ammonium nitrate to potassium nitrate in the dedifferentiation medium. For optimal differentiation of pollen embryoids, kinetin, 2,4-D and α-naphtalene acetic acid are required. Anther culture for 50 days on the dedifferentiation medium is a prerequisite for the selective development of calli and embryoids from microspores.The determination of chromosome numbers in embryoids, plantlets and regenerated trees reveals that they originate from (poly)haploid pollen grains (n=2x=18). Aneuploid, triploid (3x=27) and tetraploid (4x=36) cells were encountered in increasing frequencies as the embryoids and plants developed. A few haploid cells with 9 chromosomes were consistently observed. Buds from shoots with mixoploid chromosome numbers can be grafted and the change in the chromosome constitution of the developing new shoots followed.