Flow profiles and wall shear stress distribution at a hemodialysis venous anastomosis: preliminary study

The phasic velocity field in the vicinity of the venous anastomosis in a hemodialysis angioaccess arteriovenous fistula loop graft (AVLG) is investigated employing a laser Doppler anemometer (LDA) system. Detailed LDA velocity profiles are obtained by sectional survey performed in a transparent, elastic flow model which was fabricated to represent the geometry of the AVLG system under physiological pressure and flow waveforms. The geometry of the flow model was based on a silicone rubber cast obtained from an experimental dog model. In the present study, detailed distribution of velocity profiles is obtained. The distribution of wall shear stress in the model is computed from the slope of the local velocity profiles near the wall. The relationship between the results obtained by flow visualization and the LDA measurement is discussed.     

The P-M Hybrid Dysgenesis Cline in Eastern Australian Drosophila melanogaster: Discrete P, Q and M Regions Are Nearly Contiguous

The dramatic latitudinal cline in P-M hybrid dysgenesis characteristics along the east coast of Australia is not smooth. Tests of recent collections of Drosophila melanogaster from the southeastern coast define the previously described cline as comprising three discrete, apparently contiguous regions of P, Q and M phenotypes, respectively. Northern populations from Cairns (16.9°SLat) to Ourimbah (33.4°SLat) are phenotypically P; populations from Wollongong (34.4°SLat) to Eden (37.1°SLat) are Q; and populations from Genoa (37.5°SLat) to Cygnet (43.2°SLat) are M. The decline in P activity from northern Queensland (55-60% gonadal dysgenesis (GD) in cross A) to mid-New South Wales (20-30% GD in cross A) is gradual; proceeding south, there then is a sharp drop to Q populations (<10% GD in crosses A and A*). This drop in P activity occurs in only 150 km, across the urban and suburban area of Sydney. Q populations are then found south to Eden, but Genoa, only about 50 km further southeast, is clearly M (48% GD in cross A*), as are two populations further south. The two discontinuities in the P-M cline do not correspond to obvious climatic differences along the coast, nor to obvious barriers to dispersal of D. melanogaster. The cline has apparently not moved between 1983 and 1985-1986.     

Connective tissue influences on the expression of epithelial cell-surface antigens

Summary Adult mice were found to show regional variation in the epithelial expression of some molecules of the blood-group antigen series. To investigate connective tissue influences on such differences, heterotypic recombinants of epithelia and connective tissues from various regions were prepared and examined using monoclonal antibodies directed against bloodgroup antigens H and Le^y. The results indicate that epithelia may maintain a preexisting regionally specific pattern following recombination but that, in some recombinant matches, the connective tissue is capable of signalling redirection of the pattern of expression towards that typical of the epithelium with which it is normally associated.This work was supported by NIH-NIDR RO1-DEO-5190     

柚花头香化学成分的研究(一)

本文首次报道柚花的香气成分。作者利用憎水性树脂XAD-4吸附柚鲜花的头香,并以毛细管气相色谱和毛细管气相色谱-质谱-计算机联用方法研究头香的化学组分,分离鉴定了17个已知化学成分。它们是芳樟醇、β-蒎烯、β-水芹烯、橙花叔醇等。     

Some physicochemical properties of rice mitochondrial DNA

Summary Certain physicochemical properties of rice mitochondrial DNA (mtDNA) were determined. Certain low-molecular-weight mtDNA bands were found in addition to the major mtDNA band. Rice mtDNA appeared in the electron microscope as a collection of linear molecules with heterogeneous length in the range of 1–156 kb. The major distribution area was 60–105 kb. A small fraction (less than 5%) of rice mtDNA was found in the form of a circular molecule. Some molecules had the appearance of being supercoiled. Replication fork structures were found in both circular and linear mtDNA molecules. In one rice species, Jin Nante, 15 different circular molecules were found. Rice mtDNA was digested with different restriction enzymes. The total molecular weight of rice mtDNA was calculated to be about 300 kb according to the data of restriction enzyme digestion and electron microscopy.     

Velocity distribution on the membrane of a tank-treading red blood cell

The kinematics of an area-conserving tank-treading disk-shaped red blood cell membrane is studied using the stream function method suggested by Secomb and Skalak (Q. Jl Mech. appl. Math. 35, Pt 2, 233–247, 1982). Two simple area-conserving velocity fields are superimposed to satisfy the continuity condition at the curved edges of the disk. A differential equation for the trajectory of any material point of the membrane is derived. The requirement of synchrony of the cycle for all membrane points leads to an integral equation which determines a magnitude function. An approximate solution is made possible by assuming small trajectory deflections.     

Homologous plasmid recombination is elevated in immortally transformed cells.

The levels of intramolecular plasmid recombination, following transfection of a plasmid substrate for homologous recombination into normal and immortally transformed cells, have been examined by two independent assays. In the first assay, recovered plasmid was tested for DNA rearrangements which regenerate a functional neomycin resistance gene from two overlapping fragments. Following transformation of bacteria, frequencies of recombinationlike events were determined from the ratio of neomycin-resistant (recombinant) colonies to ampicillin-resistant colonies (indicating total plasmid recovery). Such events, yielding predominantly deletions between the directly repeated sequences, were substantially more frequent in five immortal cell lines than in any of three normal diploid cell strains tested. Effects of plasmid replication or interaction with T antigen and of bacterially mediated rejoining of linear molecules generated in mammalian cells were excluded by appropriate controls. The second assay used limited coamplification of a control segment of plasmid DNA, and of the predicted recombinant DNA region, primed by two sets of flanking oligonucleotides. Each amplified band was quantitated by reference to a near-linear standard curve generated concurrently, and recombination frequencies were determined from the ratio of recombinant/control DNA regions. The results confirmed that recombinant DNA structures were generated within human cells at direct repeats in the transfected plasmid and were markedly more abundant in an immortal cell line than in the diploid normal cells from which that line was derived.     

Scavenging effect of extracts of green tea and natural antioxidants on active oxygen radicals

With the use of the spin trapping methods, the scavenging effects of the extracts of green tea and other natural foods are studied. In stimulated polymorphonuclear leukocytes (PMN) system, water extract fraction 6 (F6) from green tea and green tea polyphenols (GTP) have the strongest scavenging effect on the active oxygen radicals, much stronger than vitamin C (Vc) and vitamin E (VE). Rosemary antioxidants (RA) and Curcumin (Cur) have weaker scavenging effects than Vc, but stronger than VE. In Fenton Reaction, Cur has the strongest scavenging effect (69%) on hydroxyl radicals. In irradiation, riboflavin system F6(74%) and GTP(72%) have very strong scavenging effects that are weaker than Vc, but much stronger than VE (23%). With the use of spin probe oxymetry, the oxygen consumption in respiratory burst of stimulated PMN were measured when the antioxidants existed in these systems. The results demonstrated that these antioxidants did not affect the respiratory burst of human polymorphonuclear leukocytes stimulated with PMA.