Effects of substrate branching characteristics on kinetics of enzymatic depolymerization of mixed linear and branched polysaccharides: II. Amylose/glycogen alpha-amylolysis

Enzymatic depolymerization of polysaccharides with alpha-amylase has been studied in mixed aqueous dimethylsulfoxide (DMSO)/water solvents. Polysaccharide substrate chemical compositions, configurational structures, and bonding pattersn are known to affect observed enzymatic reaction kinetics. The branching structures of polysaccharides and their effects on the kinetic mechanisms of depolymerization reactions via endo-acting hydrolyzing enzyme was studied via size exclusion chromatography coupled to low angle laser light scattering (SEC/LALLS). The glycogen branching structure is a heterogeneously distributed "cluster" structure rather than a homogeneously distributed "treelike" structure. The action pattern of alpha-amylase on glycogen, which is composed of highly branched clusters, as end-products, has a "pseudo-exo-attack" in contrast to an expected "endoattack" as seen in the hydrolysis of amylose or amylopectin substrates. These effects of branched substrates for mixed amylose/glycogen alpha-amylolysis have been predicted and demonstrated by both experimental and theoretical analysis using the kinetic model presented in this report. The "lumped" kinetic model employed, assumes that the enzyme simultaneously attacks both linear and branched substrates. In general, excellent agreement between the model predictions and the experimental observations, both qualitatively and quantitatively, was obtained. (c) 1995 John Wiley & Sons, Inc.     

The centric region of the X chromosome rDNA functions in male meiotic pairing in Drosophila melanogaster

In Drosophila melanogaster males, sex chromosome pairing at meiosis is ensured by so-called pairing site(s) located discretely in the centric heterochromatin. The property of the pairing sites is not well understood. Recently, an hypothesis has been proposed that 240 bp repeats in the nontranscribed spacer region of rDNA function as the pairing sites in male meiosis. However, considerable cytogenetic evidence exists that is contrary to this hypothesis. Hence, the question is whether the chromosomal rDNA clusters, in which a high copy number of 240 bp repeats exists, are involved in the pairing. In order to resolve the problem we X-rayed Drosophila carrying the X chromosome inversion In(1)sc ^V2L sc ^8R and generated free, mini-X chromosomes carrying a substantial amount of rDNA. We defined cytogenetically the size of the mini-chromosomes and studied their meiotic behavior. Our results demonstrate that the heterochromatin at the distal end of the inversion, whose length is approximately 0.4 times that of the fourth chromosome, includes a meiotic pairing site in the male. We discuss the cytological location of the pairing site and the possible role of rDNA in meiotic pairing.     

Chaperone SecB: Conformational changes demonstrated by circular dichroism

The chaperone SecB, which is involved in protein export inEscherichia coli, is shown by circular dichroism measurements to contain a high content of-pleated sheets. Prediction of the secondary structure of SecB is in good agreement with the observed content of-sheet. In accordance with the previous studies in which changes in conformation were assessed indirectly [Randall (1992),Science 257, 241–245], here we show that the conformation of SecB changes with the concentration of salt in the milieu and also when SecB interacts with a peptide ligand.Abbreviations ANS 1-anilino-naphthalene-8-sulfonate - CD circular dichroism - NMR nuclear magnetic resonance - CCA convex constraint analysis     

Proton nuclear magnetic resonance spectroscopy of isolated rabbit fundic glands

1H-nuclear magnetic resonance spectroscopy (NMR) was adapted to isolated rabbit fundic glands and identification made of compounds responsible for several observed spectral resonances. A minimum gland concentration of 0.5 mg dry weight or 5 mg wet weight per 0.5 ml was needed for adequate signal-to-noise ratio. At physiological temperature and pH, the glands demonstrated reproducible spectra, stability for accumulation times greater than 30 min and responsiveness to histamine stimulation, as measured by oxygen consumption and aminopyrine uptake. The relatively anaerobic conditions favored use of proton compared to phosphorus NMR, since 1H-NMR allowed significantly shorter spectral accumulation times and therefore did not compromise glandular viability to the same extent as 31P-NMR. The most conspicuous resonance in the gland spectrum was assigned to the -N+(CH3)3 protons of choline and related compounds. In membrane-free lysates, several components of the signal were resolvable and assigned to choline, phosphatidylcholine, phosphocholine and L-alpha-glycerophosphocholine. Thin-layer chromatography verified that phosphatidylcholine and phosphatidylethanolamine were the major phospholipids present in gland lipid. Presumably, they represent the source of the surface-active phospholipids present in gastric juice, which may play a role in gastric cytoprotection.     

Effects of external loading on short term power output in children and young male adults

The effects of external loading, in the form of small weights distributed evenly over the limbs and torso, on physical performance and power output have been studied during vertical jumping in 10 children and four young adults and the results compared with maximal cycling. The results show under control (unloaded) conditions the absolute peak power output (W) achieved by children and adults was 572 W (45%) and 765 W (25%) respectively higher in cycling than jumping. The addition of weights during jumping served only to increase this difference. External loading produced a linear decrease of W in both groups of subjects. The reduction in W was entirely due to a decrease of take-off velocity (VT). The relationship between VT and added weights (delta wt) could be described by the equations: VT (ms-1) = 1.91 - 0.042 delta wt (kg); r = -0.96 (children); VT (ms-1) = 2.49 - 0.021 delta wt (kg); r = -0.99 (adults). Thus, contrary to the recent work of Caiozzo and Kyle (1980) which involved stair-climbing, body size and speed of movement in children and young adults would appear to be optimally matched for the production of lifting work during vertical jumping. External loading reduces the generation of power output immediately prior to take-off of a maximal jump from a force platform.     

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.     

Rallinyssus sorae sp. n. (Acari: Dermanyssidae: rhinonyssinae) from the nasal passages of the sora, Porzana carolina (Aves: Rallidae)

Rallinyssus sorae sp. n. is described from the nasal turbinates of the sora, Porzana carolina, collected in Maryland and Ohio. The new species is most similar to Rallinyssus verheyeni Fain but differs in number of setae on the female ventral opisthosoma, structure of the fixed and movable digits of the male and female chelicerae, chaetotaxy of legs I to IV, and presence of a sternal plate in the male. The taxonomy and host-parasite relationships of the various species of Rallinyssus are discussed.     

Effectiveness of out-of-hours biochemistry investigations.

A survey was carried out of doctors who used their out-of-hours biochemistry service to find out why requests for investigations were made, how often the results altered patient management, and whether they could define areas where investigations were unproductive. Of 107 questionnaires distributed, 147 (88%) were completed. In 86% the requests were for diagnosis or immediate patient management and in 35% the results actually altered management. Senior clinical staff were more efficient than their juniors in instigating biochemical investigations that proved to be effective. In no instance where the clinical staff predicted that it was unlikely that the results would alter management was management altered. It is suggested that joint reviews of case notes by junior and senior clinical staff would prove to be the most appropriate way to increase the effectiveness and efficiency of clinical investigation.