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At least 595 records · Page 33Linked to original sources
PubMed1997

Morphometric analysis of neointimal formation in murine cardiac grafts: III. Dissociation of intestitial fibrosis from neointimal formation.

BACKGROUND: This study examined the relationship between transplant vascular sclerosis (TVS) and tissue fibrosis, features of chronic rejection that can develop rapidly in accepted heterotopic murine cardiac allografts. METHODS: The rate of development of interstitial fibrosis or TVS development was determined by computerized analysis of tissue sections from DBA/2-->C57BL/6 heterotopic cardiac allografts after immunosuppression with gallium nitrate. RESULTS: In accepted cardiac allografts, neointimal fibrosis developed by 30 days after transplant, whereas TVS was minimal by day 30, and maximal by day 60. Variable levels of fibrosis were found throughout the allografts. DBA/2-->DBA/2 cardiac isografts never displayed TVS in this time period, but displayed allograft-like fibrosis within 60 days of transplantation. CONCLUSIONS: Interstitial fibrosis can be dissociated from the TVS development in this experimental model of chronic cardiac allograft rejection. Apparently, it is caused, at least in part, by alloantigen-independent factors other than TVS-related tissue ischemia.

Animals↗
PubMed1983

Differential protein synthesis in Candida albicans during blastospore formation at 24.5 degrees C and during germ tube formation at 37 degrees C.

To identify proteins synthesized during blastospore to germ tube transformation in Candida albicans, membrane and cytoplasmic protein fractions labelled with 14C were analysed by SDS-PAGE and autoradiography. Four cytoplasmic proteins were detected in pulse-labelled lysates prepared from cells forming blastospores and germ tubes at 37 degrees C, but not in pulse-labelled lysates prepared from cells forming blastospores at 24.5 degrees C. Three proteins detectable in 24.5 degrees C lysates were diminished in 37 degrees C lysates.

Autoradiography↗
PubMed1985

Formation of a hexagonal lattice structure by an R-form lipopolysaccharide of Klebsiella: relationship between lattice formation and uniform salt forms.

Various uniform salt forms of an R-form lipopolysaccharide (LPS) extracted from Klebsiella strain LEN-111 (O3-:K1-) were prepared and their ultrastructure was examined. The LPS, which was extracted by the phenol-water method, freed from contamination with RNA by treatment with RNase, and precipitated by addition of two volumes of 10 mM MgCl2-ethanol, was used as the original preparation for uniform salt forms. The original LPS preparation formed a hexagonal lattice structure with a lattice constant of 14.9 +/- 0.2 nm. The LPS after electrodialysis retained the ability to form a hexagonal lattice structure, although its lattice constant was large (18.7 +/- 0.5 nm) and the lattice structure of the electrodialyzed LPS was labile at pH 8.0 in contrast to that of the original LPS preparation. The magnesium salt form of the LPS formed essentially the same ordered hexagonal lattice structure (lattice constant of 15.0 +/- 0.2 nm) as that of the original LPS preparation. The calcium and ammonium salt forms formed a hexagonal lattice structure, but the lattice constants of the calcium and ammonium salt forms were larger (18.6 +/- 0.6 nm and 19.3 +/- 0.4 nm, respectively) than that of the magnesium salt form. The sodium and potassium salt forms consisted of freely branching ribbon-like structures with an average width of 13 nm and an average thickness of 9 nm. The triethylamine salt form consisted principally of short rods (10 nm X 9-13 nm).

Calcium↗
PubMed1988

Formation of a hexagonal lattice structure by an R-form lipopolysaccharide of Klebsiella: effect of various divalent cations on the lattice formation.

The R-form lipopolysaccharide from Klebsiella pneumoniae strain LEN-111 (O3-:K1-), from which cationic material had been removed by electrodialysis, was previously shown to form a hexagonal lattice structure with the lattice constant of 14 to 15 nm when suspended in 50 mM tris(hydroxymethyl)aminomethane buffer at pH 8.5 containing 10 mM Mg2+. Under this experimental condition, effects of other divalent metal cations on the hexagonal assembly of the electrodialyzed LPS were compared with that of Mg2+. The Zn2+, Hg2+, Cu2+, and Ni2+ could produce essentially the same hexagonal lattice structure with the lattice constant of 14.5 to 15.0 nm as that formed with Mg2+. The Cd2+, Co2+, and Fe2+ produced the hexagonal lattice structure with the lattice constant of 15.5 to 16.0 nm, and Ba2+, Sr2+, and Ca2+ produced that with the lattice constant of 18 to 19 nm. In addition, the hexagonal lattice structures formed with the latter three cations were less orderly than those formed with the other cations. When the higher concentrations of Ba2+, Sr2+, and Ca2+ were used, the lattice constants were not shortened. The length of lattice constants of the hexagonal lattice structures formed with the divalent cations did not relate to the quantity of the cations bound to the LPS. Among the divalent cations tested, Hg2+ was bound to the LPS in the smallest amount (its atomic ratio to P, 0.07), and Zn2+ and Fe2+ were bound in very large amounts (their atomic ratios to P, 2.94 and 8.28, respectively).

Cations, Divalent↗
PubMed1995

Pattern formation in the mammalian forebrain: striatal patch and matrix neurons intermix prior to compartment formation.

The striatum of the mammalian forebrain is divided into two compartments: the patches and the matrix. Neurons of the patch compartment in the rat striatum become postmitotic earlier in neurogenesis than neurons of the matrix compartment. The selective adhesion of patch neurons to one another has been suggested previously to be an important developmental mechanism of striatal compartmentation. We asked if the selective adhesion of patch neurons is expressed before or after the migration of the majority of the matrix neurons into the striatum. Patch neurons were labelled in vivo by a fluorescent retrograde tracer injected into the substantia nigra on embryonic day 19, which almost exclusively labelled patch neurons. Matrix neurons were labelled with a maternal injection of bromodeoxyuridine at embryonic day 18. When animals were killed at embryonic day 20, the majority of the retrogradely labelled patch neurons were intermixed with the bromodeoxyuridine-labelled matrix neurons, although there appeared to be clustering of some of the patch neurons. However, by postnatal day 2 there was a complete segregation of the clusters of the retrogradely labelled patch neurons from the bromodeoxyuridine-labelled matrix neurons in the striatum. This process was modelled in vitro. The patch and matrix compartments were labelled in vivo at embryonic day 13 and 18 respectively, with different birthdate markers ([3H]thymidine or bromodeoxyuridine). At embryonic day 20 the striatal tissue was removed, dissociated and reaggregated in suspension cultures. After 1 day in vitro, labelled patch and matrix neurons were randomly intermixed within the reaggregates. Examination of the cultures at 2.5 and 4 days in vitro revealed clumping of the labelled patch neurons towards the centres of the reaggregates. Over this same period, the labelled matrix neurons did not clump and were dispersed towards the periphery of the reaggregates. The results suggest that patch neuron adhesiveness may appear relatively soon after these neurons become postmitotic, but that this adhesiveness is unable to overcome the initial force produced by the massive migration of matrix neurons into the striatum. We hypothesize that a migratory phase of embryonic striatal development exists, when fated patch and matrix neurons intermix. After this migratory phase, patch neuron adhesiveness can produce the mature segregation of the striatal compartments.

Aging↗
PubMed1987

Nitrates do not affect prostacyclin formation by rat arteries: this is unrelated to increased vascular prostacyclin formation with age.

The question of whether vasodilator nitrates act by releasing prostacyclin is controversial. Since the ability of blood vessels to form prostacyclin changes with age, we have investigated whether this may explain the discrepancies in the literature. It does not, since isosorbide dinitrate or glyceryl trinitrate incubated with rat aorta or vena cava from male Wistar rats had little or no effect on the release of prostacyclin, measured as 6-keto-PGF1 alpha. We confirm that the aorta produces substantially more prostacyclin than the vena cava. The arterial production of prostacyclin was greater in rats weighing 350-400 g than in those weighing 116-152 g, but the production by the veins was similar in both groups.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Formation of Polyesters by Pseudomonas oleovorans: Effect of Substrates on Formation and Composition of Poly-(R)-3-Hydroxyalkanoates and Poly-(R)-3-Hydroxyalkenoates.

Pseudomonas oleovorans grows on C(6) to C(12)n-alkanes and 1-alkenes. These substrates are oxidized to the corresponding fatty acids, which are oxidized further via the beta-oxidation pathway, yielding shorter fatty acids which have lost one or more C(2) units. P. oleovorans normally utilizes beta-oxidation pathway intermediates for growth, but in this paper we show that the intermediate 3-hydroxy fatty acids can also be polymerized to intracellular poly-(R)-3-hydroxyalkanoates (PHAs) when the medium contains limiting amounts of essential elements, such as nitrogen. The monomer composition of these polyesters is a reflection of the substrates used for growth of P. oleovorans. The largest monomer found in PHAs always contained as many C atoms as did the n-alkane used as a substrate. Monomers which were shorter by one or more C(2) units were also observed. Thus, for C-even substrates, only C-even monomers were found, the smallest being (R)-3-hydroxyhexanoate. For C-odd substrates, only C-odd monomers were found, with (R)-3-hydroxyheptanoate as the smallest monomer. 1-Alkenes were also incorporated into PHAs, albeit less efficiently and with lower yields than n-alkanes. These PHAs contained both saturated and unsaturated monomers, apparently because the 1-alkene substrates could be oxidized to carboxylic acids at either the saturated or the unsaturated ends. Up to 55% of the PHA monomers contained terminal double bonds when P. oleovorans was grown on 1-alkenes. The degree of unsaturation of PHAs could be modulated by varying the ratio of alkenes to alkanes in the growth medium. Since 1-alkenes were also shortened before being polymerized, as was the case for n-alkanes, copolymers which varied with respect to both monomer chain length and the percentage of terminal double bonds were formed during nitrogen-limited growth of P. oleovorans on 1-alkenes. Such polymers are expected to be useful for future chemical modifications.

Journal Article↗
PubMed1976

Specialized transduction of D-serine deaminase genes: formation of lysogens that yield high lambda-d dsd/lambda ratios and formation of a dimeric lambda-d dsd.

We have obtained two classes of double lysogens that on induction yield higher titers of lambda-d dsd transducing phage than of helper phage. One class was obtained by lysogenization of strain EM6116 (dsddelta attlambdadelta HfrC) with lambda-dsd type 2 (dsdC+ dsdO+ dsdA+, head-tail substitution). In the absence of either a normal attlambda or the homology of a chromosomal dsd region, the transducing phage integrated at other sites, at least one of which, in strain EM6177, is near the origin of HfrC. On induction, strain EM6177 yields a phage burst of 20 to 50 with a lambdadsd:lambda ratio of 10(4):1. The asnychronously high yield of lambda dsd is attributed to an efficiency of excision greater than that of lambda. The other class was obtained by lysogenization of strain EM1407 (dsdA attlambda+) with lambda-dsd type 2 (dsdO6 dsdA, partial deletion of dsdC). The DNA of mature lambda-dsd type 2 is a complete dimer. It lacks nearly all the phage late genes and b2 and carries about five bacterial genes. It could not be packaged as a monomer but is just within the packaging size limit as a dimer. Models for the derivation of these lambda dsd phages and the high-yielding lysogens are presented.

Chromosome Mapping↗