Interaction of the DNA untwisting enzyme with the SV40 nucleoprotein complex.

The SV40 nucleoprotein complex which was isolated from infected CV-1 cells did not possess an active DNA untwisting enzyme. The superhelix density of the DNA in the chromatin complex was unchanged after treatment with purified rat liver DNA untwisting enzyme. However, in the presence of ethidium bromide (1 microgram/ml) the superhelix density was changed. Moreover, the nicked intermediate in the DNA untwisting reaction could be detected using the chromatin DNA as a substrate. These results show that the DNA in the SV40 chromatin which is accessible to the DNA untwisting enzyme is under no topological strain.     

The staging and treatment of epithelial ovarian cancer.

Recent advances in the staging of ovarian cancer have suggested that many patients with apparently localized (stage I or II) disease have occult dissemination within the abdomen. Approximately 20% of patients classified at laparotomy as having stage I or II ovarian cancer are found by lymphangiography to have abnormal retroperitoneal lymph nodes. In many other patients advanced disease is also detected by peritonescopy; with this technique metastases are often discovered on the undersurface of the right diaphragm. These findings may help explain the high rates of recurrence after surgical resection or pelvic irradiation, or both, in patients with localized disease. Studies are in progress to determine whether modification of the radiotherapy field to include the right diaphragm will improve survival. Along with improved staging, histologic grading of the degree of anaplasia of the tumour tissue may permit more precise determination of prognosis and therefore better design of therapy. Adjuvant radiotherapy has not yet been shown to improve the survival of patients with stage I disease, but the 5-year survival of patients with stage II disease is greater for those receiving postoperative radiotherapy than for those undergoing surgery alone. For most patients with advanced disease radiotherapy is palliative only and carries a high risk of long-term complications. Numerous chemotherapeutic agents used singly can produce an objective response by tumour. Preliminary data suggest that combination chemotherapy can increase the rate of objective response, but a longer follow-up period is necessary to determine whether this form of therapy can improve survival.     

Incorporation of N-acetyl-D-glucosamine from UDP-N-acetyl-D-glucosamine by isolated membranes of Bacillus subtilis. Identification of undecaprenyl poly(N-acetylglucosaminyl pyrophosphate).

Membrane isolated from Bacillus subtilis strain 168 incorporated GlcNAc from UDP-GlcNAc directly onto undecaprenyl phosphate via transphosphorylation and subsequent transglucosylations. Chain lengths of 6, 4, and 1 units of GlcNAc were found. Approximately 80% of the isotope incorporated was extracted into chloroform:methanol (2:1 v/v), and could be distinguished from the undecaprenyl disaccharide cell wall intermediate by a different elution pattern on DEAE-cellulose (acetate form). The GlcNAc-lipid(s) were eluted from a similar column in chloroform:methanol:water (10:10:3, v/v) with 6 mM NH4COOH indicating a pyrophosphate linkage between the lipid and the GlcNAc. The GlcNAc-lipid(s) were not degraded by conditions which completely deacylated [32P]glyceryl phospholipids, but were rapidly hydrolyzed by mild acid treatment (0.005 N HCl, 90 degrees) with the release of oligosaccharide phosphate (typical of sugars linked to undecaprenyl pyrophosphate). Catalytic hydrogenation of the GlcNAc-lipid(s) resulted in the release of water-soluble sugar phosphate. Under these same conditions, undecaprenyl pyrophosphate and undecaprenyl disaccharide cell wall intermediate were similarly effected while [32P]glyceryl phospholipids remained intact. The formation of GlcNAc-lipid(s) in vitro was inhibited if membranes were prepared from cells previously treated with bacitracin. Thus, the GlcNAc-lipid(s) has the properties of undecaprenyl poly(N-acetylglucosaminyl pyrophosphate) and may represent a new synthetic role of the polyisoprenyl lipid in B. subtilis.     

Poliovirus aggregates and their survival in water.

Inactivation of aggregated poliovirus by bromine is characterized by a continuously decreasing reaction rate. Poliovirus released from infected cells in these experiments by alternate freezing and thawing in water without electrolytes has always been aggregated. The aggregates persist even on 7,000-fold dilution in ion-free water. Virus similarly released into phosphate-buffered saline solution may be well dispersed, but it aggregates when sedimented into a salt-free sucrose gradient or when it is diluted as little as 10-fold in water. Large one-step dilutions of dispersed virus in water remain dispersed. Aggregated virus was not dispersed by one-step dilution (7,000-fold) in distilled or untreated lake water but was dispersed if phosphate-buffered saline or clarified secondary sewage plant effluent was used as diluent. Dispersed virus aggregates at all dilutions in alum-treated, finished water from the city filter plant. This may be the result of complex formation with insoluble material rather than virion-virion aggregation. A simple procedure is described for rendering a very dilute suspension of mixed virion aggregates into a three-part spectrum of sizes.     

Aerobic respiration in mutants of Escherichia coli accumulating quinone analogues of ubiquinone.

The ability of three naturally occurring analogues of ubiquinone to function in aerobic respiration in Escherichia coli has been studied. The compounds, which differ from ubiquinone in terms of the substituents on the quinone ring, accumulate in the cytoplasmic membranes of ubiE-, ubiF- and ubiG- mutants. One of the analogues (2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone, NMQ), which lacks the 5-methoxyl group of the benzoquinone ring of ubiquinone promoted the oxidation of NADH, D-lactate and alpha-glycerophosphate but not succinate. Electron transport supported by MMQ was found to be coupled to phosphorylation. In contrast, 2-octaprenyl-6-methoxy-1,4-benzoquinone, which lacks both the 3-methyl and 5-methoxyl groups of ubiquinone, and 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone, in which the 5-methoxyl group of ubiquinone is replaced by an hydroxyl group, were virtually inactive in the oxidases tested. The ability of MMQ to function in respiration in isolated membranes is consistent with the findings that the growth rate and yield of a ubiF- strain, unlike other ubi- strains, were only slightly lower than those of a ubiF+ strain. The fact that MMQ is active in some but not all oxidases provides further support for the concept that the quinones link the individual dehydrogenases to the respiratory chain and that each dehydrogenase has specific structural requirements for quinone acceptors.     

The effect of phenylephrine on excretion of fluid and electrolytes by the parotid and mandibular glands of the rat

The effect has been investigated of the alpha-adrenergic agonist, phenylephrine, on excretion of water and electrolytes (Na, K, and HCO3) by the parotid and mandibular glands of the rat. In the mandibular glands the agonist was as effective as acetylcholine (or parasympathetic nerve stimulation) in stimulating secretion, and the electrolyte excretory patterns seen in the two modes of stimulation were similar. In the parotid gland, phenylephrine was only one-fifth as potent as acetylcholine (or parasympathetic nerve stimulation) in evoking a secretory response but, when due allowance for flow rate differences is made, the electrolyte excretion patterns were similar. In both glands the secretory response to phenylephrine was totally different, in magnitude and in electrolyte excretion pattern, to that evoked by the beta-adrenergic agonist, isoprenaline. It is concluded, as has already been established for secretion of exportable protein, that alpha-adrenergic agonists have very similar effects to muscarinic agonists both on endpiece and on duct cells and that these actions are completely different from those evoked by activation of beta-adrenergic receptors.