我国东南沿海地区的AM真菌Ⅳ.四个我国新记录种

本文报道了采自我国山东、福建、广西和海南四省土壤中的四种ＡＭ真菌新记录种：１．两型球囊霉ＧｌｏｍｕｓｄｉｍｏｒｐｈｉｃｕｍＢｏｙｅｔｃｈｋｏ＆Ｔｅｗａｒｉ;２．多产球囊霉ＧｌｏｍｕｓｆｅｃｕｎｄｉｓｐｏｒｕｍＳｃｈｅｎｃｋ＆Ｓｍｉｔｈ;３．亮色盾巨孢囊霉ＳｃｕｔｅｌｏｓｐｏｒａｆｕｌｇｉｄａＫｏｓｋｅ＆Ｗａｌｋｅｒ;４．网纹盾巨孢囊霉Ｓｃｕｔｅｌｏｓｐｏｒａｒｅｔｉｃｕｌａｔａ（Ｋｏｓｋｅ,Ｍｉｌｅｒ＆Ｗａｌｋｅｒ）Ｗａｌｋｅｒ＆Ｓａｎｄｅｒｓ。文中详细描述了其形态特征和生境状况。     

Nucleotide metabolism and nucleic acid synthesis in mouse thymocytes.

Nucleotide pool sizes, DNA polymerizing enzymes, and DNA synthesis were studied in mouse thymocytes over a 24-hr period of culture in Marbrook chambers. The initial rate of cell division was high with an average mitotic index of 1.6%/hr for 12 hr, followed by a decline to 0.14%/hr at 24 hr. The decline in DNA synthesis was not closely correlated with the activities of DNA-dependent DNA polymerases-α or -β or with the activity of terminal deoxynucleotidyl transferase. The amounts of several ribo- and deoxyribonucleotides per thymocyte were measured using high performance liquid chromatography and DNA polymerase. Pool sizes of ATP, GTP, dATP, and dTTP were less than 10% of pool sizes commonly observed in mammalian cells. The rates of DNA and RNA synthesis in thymocytes may be critically affected by minor changes in the availability of nucleotides. Cultures of thymocytes serve as useful experimental systems for investigation of nucleotide and nucleic acid metabolism during lymphoid differentiation.     

Elevated plasma vasopressin in cardiomyopathic hamsters

Hamsters of the BIO 14.6 strain characteristically develop cardiomyopathy as they age, and hamsters of this strain have overt signs of heart failure by 11 months of age. Plasma levels of the posterior pituitary hormone arginine-vasopressin (AVP) were found to be elevated (approximately 2-fold) in 11 month old BIO 14.6 hamsters, compared to age-matched hamsters of a control strain. AVP appeared inappropriately elevated in these animals, since they were neither hyperosmotic nor markedly hypotensive. The elevated levels of AVP observed in these animals appears to contribute to vasomotor tone, since intravenous adminstration of a specific antagonist of the vasoconstrictor action of AVP [d(CH₂)₅Ome(TYR)AVP] elicited a fall in arterial pressure (9±2 mm Hg, n=6, p<0.05). The AVP antagonist had no effect on arterial pressure in hamsters of a control strain, and vehicle administration had no effect on arterial pressure in either strain. These data indicate that inappropriately elevated levels of AVP contribute to the cardiovascular state of myopathic hamsters. Since elevated plasma AVP has been noted in human congestive heart failure, these results suggest that AVP may contribute to the cardiovascular status during congestive heart failure.     

Activatin of guanylate cyclase during the oxidation of arylamine carcinogens.

When added alone, the arylamine procarcinogens N-acetyl-aminofluorene, 4-acetyl-aminobiphenyl or their N-hydroxy derivatives failed to alter partially purified soluble guanylate cyclase from rat liver or particulate guanylate cyclase activity from colonic mucosa. However, addition of linoleic acid hydroperoxide to the enzyme preparation in the presence N-OH-acetyl-aminofluorene or N-OH-acetyl-aminobiphenyl significantly increased guanylate cyclase activity. With linoleic acid hydroperoxide plus N-OH-acetyl-aminofluorene, both the activation of hepatic guanylate cyclase and the formation of the carcinogen oxidation product 2-nitrosofluorene required hematin but not molecular O₂. Both processes were inhibited by ascorbic acid. These data strongly imply that guanylate cyclase activation was dependent upon hematin catalyzed oxidation of N-OH-acetyl-aminofluorene by the lipid peroxide. The results provide the first evidence that guanylate cyclase activation can occur during the conversion of a procarcinogen to a more reactive chemical species, and thereby emphasize the importance of examining carcinogen interaction with the GC system under conditions which permit such chemical conversion.