Patterns of psychiatric consultation in a Chinese general hospital

The authors conducted a study of psychiatric consultation in a Chinese general hospital. Seventy-five inpatients (0.74% of the patients in the hospital) were referred by different services over a 1-year period. Internal medicine referred the most patients, and organic brain syndromes were the most common diagnoses. Depression was not a frequent diagnosis, but neurasthenia was a fairly common one. None of the referred patients had a diagnosis of alcoholism, drug abuse, or personality disorder. The authors compare these data with those of Western studies and discuss the possible factors influencing psychiatric consultation in China.

In vivo mapping of DNA topoisomerase II-specific cleavage sites on SV40 chromatin

The antitumor drug, m-AMSA (4'-(9-acridinylamino)-methanesulfon-m-anisidide), is known to interfere with the breakage-reunion reaction of mammalian DNA topoisomerase II by blocking the enzyme-DNA complex in its putative cleavable state. Treatment of SV40 virus infected monkey cells with m-AMSA resulted in both single- and double-stranded breaks on SV40 viral chromatin. These strand breaks are unusual because they are covalently associated with protein. Immunoprecipitation results suggest that the covalently linked protein is DNA topoisomerase II. These results are consistent with the proposal that the drug action in vivo involves the stabilization of a cleavable complex between topoisomerase II and DNA in chromatin. Mapping of these double-stranded breaks on SV40 viral DNA revealed multiple topoisomerase II cleavage sites. A major topoisomerase II cleavage site was preferentially induced during late infection and was mapped in the DNAase I hypersensitive region of SV40 chromatin.

Isolation of stable preinitiation, initiation, and elongation complexes from RNA polymerase II-directed transcription

Distinct RNA polymerase II transcription preinitiation, initiation, and elongation complexes can be formed in vitro on cloned adenovirus 2 DNA sequences containing the major late promoter. These transcription complexes are stable and can be rapidly isolated by gel filtration of HeLa whole cell extracts. In the absence of exogenous nucleotides and under appropriate salt conditions, a stable but transcriptionally incomplete preinitiation complex is formed. When this complex is incubated in the presence of adenosine or deoxyadenosine triphosphates, the beta-gamma phosphodiester bond is hydrolyzed, and RNA polymerase II joins the complex, thereby converting it into a stable initiation complex capable of forming (but prior to the formation of) the first phosphodiester bond. When this complex is isolated and incubated in the presence of all four nucleoside triphosphates, it is converted into an elongation complex that then permits the synthesis of phosphodiester bonds and the correct run-off transcript. A limiting transcription component is sequestered in the preinitiation complex. This factor is released upon elongation and can reassociate with new DNA templates during subsequent rounds of initiation. Therefore, class II genes do not appear to form activated transcription units stable for multiple rounds of transcription; rather, their transcriptional activity may be controlled in part by regulating the association of transcription factors at each initiation event.

Nonintercalative antitumor drugs interfere with the breakage-reunion reaction of mammalian DNA topoisomerase II

Many intercalative antitumor drugs have been shown to cleave DNA indirectly through their specific effect on the stabilization of a cleavable complex formed between mammalian DNA topoisomerase II and DNA (Nelson, E.M., Tewey, K.M., and Liu, L.F. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 1361-1365). Antitumor epipodophyllotoxins (VP-16 and VM-26) which do not intercalate DNA can similarly induce protein-linked DNA breaks in cultured mammalian cells. In vitro studies using purified mammalian DNA topoisomerase II show that epipodophyllotoxins interfere with the breakage-reunion reaction of mammalian DNA topoisomerase II by stabilizing a cleavable complex. Treatment of this stabilized cleavable complex with protein denaturants results in DNA strand breaks and the covalent linking of a topoisomerase subunit to the 5'-end of the broken DNA. Furthermore, epipodophyllotoxins also inhibit the strand-passing activity of mammalian DNA topoisomerase II, presumably as a result of drug-enzyme interaction. The agreement between the in vivo and in vitro studies suggests that mammalian DNA topoisomerase II is a drug target in vivo. The similarity between the effect of epipodophyllotoxins on mammalian DNA topoisomerase II and the effect of nalidixic acid on Escherichia coli DNA gyrase suggests that the cytotoxic action of epipodophyllotoxins may be analogous to the bactericidal action of nalidixic acid.

Adriamycin-induced DNA damage mediated by mammalian DNA topoisomerase II

Adriamycin (doxorubicin), a potent antitumor drug in clinical use, interacts with nucleic acids and cell membranes, but the molecular basis for its antitumor activity is unknown. Similar to a number of intercalative antitumor drugs and nonintercalative epipodophyllotoxins (VP-16 and VM-26), adriamycin has been shown to induce single- and double-strand breaks in DNA. These strand breaks are unusual because a covalently bound protein appears to be associated with each broken phosphodiester bond. In studies in vitro, mammalian DNA topoisomerase II mediates DNA damage by adriamycin and other related antitumor drugs.

Isolation of an active transcription initiation complex from HeLa cell-free extract

A two-step procedure has been developed for the formation of RNA polymerase II transcription initiation and elongation complexes. Initiation complexes are rapidly formed in HeLa cell-free extract supplemented with a DNA template containing the adenovirus 2 major late promoter and ATP. Assembly of transcription components required for correct initiation is absolutely dependent on specific eukaryotic promoter sequences. Sarkosyl-sensitive transcription initiation complexes are rapidly converted to Sarkosyl-resistant elongation complexes when supplemented with the remaining nucleoside triphosphates. The 60S initiation complex can be extensively purified by glycerol gradient centrifugation and is easily separated from free RNA polymerase II and free DNA template. Recovery of this stable complex is greater than 90%. Specific transcription cannot be detected if the DNA template is subsequently added to gradient fractions containing HeLa cell-free extract components alone. This suggests that the DNA templates promote the specific assembly of RNA polymerase II and transcription factors required for accurate initiation. Since conversion of purified initiation complexes to elongation complexes can occur without additional HeLa cell components, the presence of transcription components required for initiation and elongation in a single complex is indicated.

Homologous globin cell-free transcription system with comparison of heterologous factors

Mouse erythroleukemia (MEL) cells provide a useful model system to examine the regulation of globin gene expression. MEL cells ordinarily do not express globin genes, but in the presence of inducers, such as dimethyl sulfoxide or hexamethylene bisacetamide, they mimic erythroid differentiation. We have developed a cell-free transcription system from uninduced MEL cells to determine the requirements for mRNA synthesis. The MEL system directs accurate transcription of adenovirus type 2 major late DNA and mouse betamaj-globin with an efficiency comparable to those of HeLa and KB cell extracts. Using the procedure of Matsui et al. (T. Matsui, J. Segall, P.A. Weil, and R.G. Roeder, J. Biol. Chem. 255:11992-11996, 1980), we have isolated three active fractions from both MEL and HeLa cell extracts which are required for accurate transcription and have shown that equivalent fractions from MEL and HeLa cell extracts are interchangeable. Our findings suggest that the components required for initiation of transcription are similar in different cell types, at least to the extent that they can be assayed in these in vitro systems.

Cleavage of DNA by mammalian DNA topoisomerase II

Using the P4 unknotting assay, DNA topoisomerase II has been purified from several mammalian cells. Similar to prokaryotic DNA gyrase, mammalian DNA topoisomerase II can cleave double-stranded DNA and be trapped as a covalent protein-DNA complex. This cleavage reaction requires protein denaturant treatment of the topoisomerase II-DNA complex and is reversible with respect to salt and temperature. The product after reversal of the cleavage reaction remains supertwisted, suggesting that the two ends of the putatively broken DNA are held tightly by the topoisomerase. Alternatively, the enzyme-DNA interaction is noncovalent, and the covalent linking of topoisomerase to DNA is induced by the protein denaturant. Detailed characterization of the cleavage products has revealed that topoisomerase II cuts DNA with a four-base stagger and is covalently linked to the protruding 5'-phosphoryl ends of each broken DNA strand. Calf thymus DNA topoisomerase II cuts SV40 DNA at multiple and specific sites. However, no sequence homology has been found among the cleavage sites as determined by direct nucleotide-sequencing studies.

Attachment and ingestion of mycoplasmas by mouse macrophages. II. Scanning electron microscopic observations

Mycoplasmas adhere closely to the central region of the surface of mouse peritoneal macrophages in vitro. They do not appear connected to each other or the macrophage membrane, and they induce no change in the surface of the cell. After addition of antimycoplasma antibody, mycoplasmas show interconnections and the cell shows an increase occurrence of ruffled membrane and folding over the mycoplasmas. Large and small lacunae appear in the membrane at sites other than those taking in organisms, and the cell develops a diffusely granular appearance. These changes are associated with an increase in pinocytosis of horseradish peroxidase that is 85% above controls. Five minutes after addition of antibody, the macrophage appears contracted and engorged and has persistent membrane changes consisting of pits, openings, and membrane folds. Trypsin causes slow ingestion of surface mycoplasmas without the obvious membrane folding over organisms but with evidence of a predominantly invaginating process of phagocytosis. The macrophage surface has numerous microprojections, but is does not have the granular appearance seen after addition of antibody. Trypsin and Mycoplasma pulmonis antigen do not enhance macrophage pinocytic rates. (Am J Pathol 87:347-358, 1977).

Down's syndrome with X0/XY mosaicism

A 5-month-old Chinese infant with combined Down's syndrome and X0/XY mosaicism is presented. The phenotypical features of mongolism are classical and unmodified. The somatic effects of X0/XY mosaicism is that of incomplete masculinization with short phallus, hypospadias, bifid scrotum, urogenital sinus, and bilateral extra-abdominal infantile testicles. These features together with the absence of internal female organs and signs of Turner's syndrome in this patient are different from the previous reported cases of mixed gonadal dysgenesis.

Structure of the red fluorescence band in chloroplasts

Using Weber's method of "matrix analysis" for the estimation of the number of fluorescent species contributing to the emission of a sample, it is shown that the fluorescence(1) band in spinach chloroplast fragments at room temperature originates in two species of chlorophyll a. Emission spectra obtained upon excitation with different wavelengths of light (preferentially absorbed in chlorophyll a or b) are presented. Upon cooling to - 196 degrees C, the fluorescence efficiency increases about twentyfold. Two additional bands, that now appear at 696 and 735 mmicro, suggest the participation of four molecular species. Emission spectra observed at different concentrations of chloroplast fragments with excitation in chlorophyll a and b and excitation spectra for different concentrations of chloroplast fragments and measurements at 685 and 760 mmicro are presented. Two of the four emission bands may belong to pigment system I and two to system II. The 685, 696, and 738 mmicro bands respond differently to temperature changes. In the -196 degrees C to -150 degrees C range, the intensity of the 685 mmicro band remains constant, and that of the 696 mmicro band decreases twice as fast as that of the 738 mmicro band.