Active contractions of ureteral segments

The first step in the analysis of the biomechanics of any organ is to obtain its constitutive equation. In pursuit of a constitutive equation describing the peristalsis of the ureter, we measured the relationship between the length of the muscle, the velocity of contraction, and the active tension development of isolated ureter segments. The results of length-tension measurements (giving the maximum tension developed in isometric contraction of a ureter segment of specific length) were similar to those obtained by previous investigators and reflected the behavior of length-tension relationship for other smooth muscles. Two aspects of the force-velocity relationship of the ureter were examined: the effect of releasing the ureter at different times after stimulation, and that at different levels of afterload. Measurements were analyzed using the hyperbolic Hill's equation in the form T/T0 = (1-v/v0) (l + cv/v0)-1 where v is the velocity of contraction, v0 is the velocity of contraction when T = 0, T is the tension in the muscle after release, T0 is the tension in the muscle immediately prior to release, and c is the dimensionless constant. The results of force-velocity measurements showed that the so-called "maximum" velocity v0, is the largest if the tension is released at a time of contraction, early in the rise portion of the contraction cycle. Further, if tension is released from an isometric contraction at a fixed time in the rise portion of the contraction cycle, the largest value of v0 is obtained when the muscle length is in the range of 0.85-0.90 Lmax. Interestingly, the in vivo length of the ureter lies also in this range, 0.85-0.90 Lmax.     

The polypeptide structure and assembly of Ly-2/3 heterodimers

Mild reduction of mature, thymic Ly-2/3 heterodimers of M _r 67 000 resulted in dissociation into three individual polypeptide chains, , , and , of respective M _r values 38000, 35000, and 30000. The and chains were both immunoprecipitated by a monoclonal antibody directed to the Ly-2.1 epitope whereas the Ly-3.1 antibody bound only the chain. The possibility that the and chains of each heterodimer established their interchain links within a labile precursor protein in which a and segments were fused was considered but discounted by the finding that in mice heterozygous for both Ly-2 and Ly-3 loci, the Ly-2 product of one chromosome was not exclusively joined to Ly-3 structures coded by the same chromosome. By utilizing ionic detergents which selectively alter the charge of intrinsic membrane proteins, both Ly-2 and Ly-3 polypeptides were shown to have membrane insertion sites. It is suggested that as a consequence of their likely synthesis on membrane-bound polysomes, newly synthesized Ly-2 and Ly-3 structures accumulate within the same subcellular compartment — the membranes of the rough endoplasmic reticulum. Their elevated concentration within this space may facilitate a low affinity binding interaction between Ly-2 and Ly-3 which is later stabilized by interchain disulfide bond formation.Abbreviations used in this paper BSA bovine serum albumin - DOC sodium deoxycholate - DTT dithiothreitol - HA hemagglutinin - HTAB hexadecyltrimethylammonium bromide - RER rough endoplasmic reticulum - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - TX100 Triton X-100     

Quantitative Assessment of Factors Affecting the Recovery of Indigenous and Released Thermophilic Bacteria from Compost

Thermophilic actinomycetes and bacilli were recovered from mushroom compost by conventional dilution plating and sedimentation chamber-Andersen sampler methods. Excessive growth of thermophilic bacilli on dilution plates accounted for the poor recovery and limited diversity of actinomycete colonies, and this result was largely unaffected by the use of modified extraction procedures and diluents. Assessment of the actinomycete population was more successfully achieved by applying the sedimentation chamber method, by using selective media, or both. Background resistance of the compost microflora to selective agents (kanamycin, novobiocin, tetracycline, thiostrepton, and NaCl) was extremely varied, but both actinomycetes and bacilli were particularly sensitive to tetracycline. The selective isolation of Thermoactinomyces spp. and Thermomonospora chromogena by novobiocin and kanamycin, respectively, was shown to be reproducible, and the use of high concentrations of kanamycin resulted in the isolation of a novel group of unidentified thermophilic actinomycetes. Comparison of nonselective nutrient media demonstrated that the nutrient-rich protoplast regeneration medium R5 was surprisingly efficient for actinomycete recovery. This medium was found to be particularly appropriate for the recovery of Saccharomonospora viridis BD125, introduced as spores into both sterile and fresh samples of mushroom compost. This stable pigmented variant of the S. viridis strains indigenous to compost was released at concentrations of up to 10⁷ spores g of compost⁻¹ in order to provide information for future experiments on the release and recovery of genetically manipulated strains. The detection limits for this strain were in the region of 10² g⁻¹ from sterilized compost but only 10⁵ g⁻¹ from nonsterile compost. These figures correspond to mean recovery efficiencies of approximately 70% (sterilized compost) and 53% (fresh compost) of viable spores released. Further improvements in the detection and recovery of S. viridis strains released into compost should be achieved by the introduction of selectable markers developed from this information on the antibiotic resistance profile of the indigenous compost microflora.     

Mouse/human chimeric anti-HIV-1 gp120 antibody to the principal neutralizing determinant: Tolerability and pharmacokinetics in cynomolgus monkeys,Macaca fascicularis

In preparing for testing a pharmaceutical grade preparation of chimeric (mouse/human) antibody CGP 47 439 in HIV-1 infected individuals, it was administered toMacaca fascicularis (cynomolgus) monkeys to study tolerability, immunogenicity and pharmacokinetics. Four groups of monkeys, three males and three females per group, received respectively four infusions of 0, 1.43, 4.3, and 14.3 mg of CGP 47 4391 kg body weight at one-week intervals. The chimeric antibody induced no fever, was tolerated well throughout the 50-day observation period, elicited no tissue damage and no anti-antibody response. The pharmacokinetic profile was similar at all dose levels with a mean T_1/2 of 14.2 h (range 11.8–19.3 h) and a mean T_1/2 of 172.6h (range 137.2–220.5h). Following four successive antibody infusions serum concentrations of CGP 47 439 increased without reaching a steady state, and its measured concentrations were comparable to the simulated values. Collectively the study has provided safety and pharmacokinetic data that would allow human studies with this antibody in AIDS patients.     

Production and purification of recombinant human interleukin-5 from yeast and baculovirus expression systems

A cDNA for human interleukin-5 (hIL-5) was created from the hIL-5 gene using site-directed mutagenesis to splice out the introns in vitro. This cDNA was expressed in yeast and baculovirus systems, utilizing in both cases an in-frame fusion to the pre sequence of the alpha-mating-type factor to direct secretion. The highest level of production was achieved from Sf9 cells using a baculovirus vector in serum-containing medium (2.7 mg/l), whereas in serum-free medium ten times less hIL-5 was produced. In the yeast system much lower levels of hIL-5 were produced (12.5 micrograms/l). Recombinant hIL-5 was purified to homogeneity from serum-free baculovirus cultures. The rhIL-5 consisted of a 30-kDa homodimer linked by disulfide bridging. The purified recombinant protein had a specific activity on murine BCL1 cells of 1.5 x 10(4) U/mg, of 3 x 10(5) U/mg in the murine eosinophil differentiation factor assay, and 2.4 x 10(7) U/mg in a human peripheral eosinophil maintenance assay.     

Gas chromatographic/mass spectrometric analysis of specific isomers of polychlorodibenzofurans

The gas chromatographic/mass spectrometric characteristics of 26 congeners of polychlorinated dibenzofurans, previously characterized by specific synthetic routes and by standard spectroscopic techniques, have been evaluated. The electron impact mass spectra are not particularly isomer-specific, though 2,3,7,8-tetrachlorodibenzofuran is distinguishable on this basis from the three other tetrachloro isomers investigated in this work. Positive ion methane chemical ionization mass spectra do show a greater degree of isomer distinction, and are reasonably reproducible. Electron attachment negative ion spectral characteristics are also presented. Preliminary results on negative ion chemical ionization mass spectra, obtained using methane plus small amounts of oxygen as reagent gas, are reported.     

Human land use promotes the abundance and diversity of exotic species on Caribbean islands

Human land use causes major changes in species abundance and composition, yet native and exotic species can exhibit different responses to land use change. Native populations generally decline in human‐impacted habitats while exotic species often benefit. In this study, we assessed the effects of human land use on exotic and native reptile diversity, including functional diversity, which relates to the range of habitat use strategies in biotic communities. We surveyed 114 reptile communities from localities that varied in habitat structure and human impact level on two Caribbean islands, and calculated species richness, overall abundance, and evenness for every plot. Functional diversity indices were calculated using published trait data, which enabled us to detect signs of trait filtering associated with impacted habitats. Our results show that environmental variation among sampling plots was explained by two Principal Component Analysis (PCA) ordination axes related to habitat structure (i.e., forest or nonforest) and human impact level (i.e., addition of man‐made constructions such as roads and buildings). Several diversity indices were significantly correlated with the two PCA axes, but exotic and native species showed opposing responses. Native species reached the highest abundance in forests, while exotic species were absent in this habitat. Human impact was associated with an increase in exotic abundance and species richness, while native species showed no significant associations. Functional diversity was highest in nonforested environments on both islands, and further increased on St. Martin with the establishment of functionally unique exotic species in nonforested habitat. Habitat structure, rather than human impact, proved to be an important agent for environmental filtering of traits, causing divergent functional trait values across forested and nonforested environments. Our results illustrate the importance of considering various elements of land use when studying its impact on species diversity and the establishment and spread of exotic species.