Supporters and survivors: the people without AIDS.

Over the past 10 years the AIDS crisis has produced a large volume of writing. Much of this is documentary. Dozens of studies of AIDS from various clinical and political perspectives have been complemented by just as many published diaries, autobiographies, novels, plays, and poems. A few of these works have risen to the surface not only as extraordinarily valuable testimonies to the changes AIDS has wrought in individual and collective life but also as first-rate literary works, worth reading because beyond their immediate purposes they articulate with extraordinary lucidity and compassion some deep truths about the human--and the modern--condition. Paul Monette's Borrowed Time is among the most distinctive of those. It speaks not only for the community of people with AIDS and those who support them but for a generation.     

Prostaglandin synthesis and release by subpopulations of rat alveolar macrophages

Alveolar macrophages are the primary phagocytic cell of lung, but are also capable of a variety of other functions, which include initiating or modulating inflammatory and immune responses through the production of soluble mediators. One such group of mediators is the eicosanoids. Further, recent data indicate that alveolar macrophages are not functionally homogeneous, but are heterogeneous with several subpopulations that differ both morphologically and functionally. Considering the apparent importance of prostaglandin synthesis and release in inflammatory and immune responses, the current study was undertaken to determine whether alveolar macrophage subpopulations differ in their ability to synthesize and release prostaglandin (PG) E, PGI2, and thromboxane A2 after stimulation by calcium ionophore A23187, zymosan, or aggregated IgG. Alveolar macrophages were harvested by bronchoalveolar lavage and were separated into 18 density-defined fractions. Density-defined alveolar macrophages (DD-AM) showed marked heterogeneity in prostaglandin synthesis and release. Maximal PGE synthesis and release was seen as a single peak after calcium ionophore A23187 and zymosan stimulation. In contrast, two peaks in PGE synthesis were seen after aggregated IgG stimulation. PGI2 synthesis was seen as a single peak generated by different DD-AM after calcium ionophore A23187 and zymosan. In contrast, aggregated IgG stimulation of subpopulations exhibited uniform synthesis and release of PGI2. Thromboxane A2 synthesis and release was maximal from a broad range of various DD-AM after calcium ionophore A23187, zymosan, and aggregated IgG stimulation. The results demonstrate that DD-AM are heterogeneous in ability to synthesize and release prostaglandins which is dependent on the stimuli. Therefore, specific subpopulations of alveolar macrophages may be central to the control of the pulmonary inflammatory response through specific eicosanoid synthesis and release.     

Foraminifera may structure meiobenthic communities

The cosmopolitan benthic foraminiferan, Ammonia beccarii, is a fervent microfloral predator which often forms densely-populated 2–4 cm² aggregates in the field. Sediments within aggregate patches become extensively pelletized, mucus bound and depleted in microfloral food. On a West German Wattenmeer mudflat, copepodite and naupliar densities of a predominant harpacticoid copepod, Amphiascoides limicola, were significantly depressed in sediments containing>100 A. beccarii·3 cm^-2 suggesting a possible foraminiferal: copepod amensalism. Therefore, I cultured A. beccarii and A. limicola separately in sediment microcosms and then tested if A. limicola's seemingly negative reaction to sediments containing A. beccarii occurs under controlled conditions, how various life stages of A. limicola are affected, and what the repulsive mechanisms of A. beccarii may be. In natural field sediments seeded with a latin-square dispersion of sterile sediment patches containing 0 or 100 A. beccarii, mean A. limicola naupliar and copepodite densities were 2 to 6 times lower in Ammonia-rich patches than Ammonia-poor patches (i.e. patches containing <100 A. beccarii·3 cm^-2). Choice experiments directly testing potential A. beccarii inhibitory mechanisms were conducted with A. limicola copepodites: Cubic microcosms containing a latin-square patch dispersion of (1) sterile sediments (SS) seeded with 100 A. beccarii (low microflora), (2) SS bound with sterile mucus (0.0001%) (low microflora), (3) SS seeded with pelletized sediments (high microflora), and (4) SS seeded with mucus and pellets (high microflora), showed that copepodites colonized 12 & 3, but 1 & 4 were not significantly different. Mucus addition by itself, in the absence of pelletization and microflora, strongly facilitated colonization—as did addition of microfloral-rich pelletized sediments. Pelletization and mucousbinding combined, but with low microflora, were least attractive to A. limicola. Pelletization and mucous-binding combined, but with high microflora, were more attractive to A. limicola than its complement, but not significantly so. Thus A. beccarii's inhibition of A. limicola is probably not caused by sediment pelletization and simple mucous exudates but by local microfloral depletion within aggregate foraminiferal patches.Contribution No 774 of the Belle W. Baruch Institute for Marine Biology and Coastal Research     

Intergeneric somatic hybrid plants of Citrus sinensis cv. Hamlin and Poncirus trifoliata cv. Flying Dragon

Intergeneric somatic hybrid plants between Hamlin sweet orange [Citrus sinensis (L.) Osbeck] and Flying Dragon trifoliate orange (Poncirus trifoliata Raf.) were regenerated following protoplast fusion. Hamlin protoplasts, isolated from an habituated embryogenic suspension culture, were fused chemically with Flying Dragon protoplasts isolated from juvenile leaf tissue. The hybrid selection scheme was based on complementation of the regenerative ability of the Hamlin protoplasts with the subsequent expression of the trifoliate leaf character of Flying Dragon. Hybrid plants were regenerated via somatic embryogenesis and multiplied organogenically. Hybrid morphology was intermediate to that of the parents. Chromosome counts indicated that the hybrids were allotetraploids (2n=4x=36). Malate dehydrogenase (MDH) isozyme patterns confirmed the hybrid nature of the regenerated plants. These genetically unique somatic hybrid plants will be evaluated for citrus rootstock potential. The cell fusion, selection, and regeneration scheme developed herein should provide a general means to expand the germplasm base of cultivated Citrus by intergeneric hybridization with related sexually incompatible genera.Abbreviations MDH malate dehydrogenase - CTV citrus tristeza virus - MT Murashige and Tucker basal medium - BH3 protoplast culture medium, Grosser and Chandler, 1987 - PEG polyethylene glycol - GA3 giberellic acid - BA N-(phenylmethyl)-1 H-purin-6-amine - HCl hydrochloric acid Florida Agricultural Experiment Station Journal Series No. 7972     

Pteroylpolyglutamate hydrolase from human jejunal brush borders. Purification and characterization

Pteroylpolyglutamate hydrolase was solubilized with Triton X-100 from human jejunal mucosal brush borders and purified approximately 5,000-fold using organomercurial affinity chromatography, DEAE-cellulose chromatography, and gel filtration. The apparent molecular weight of the purified enzyme in the Triton micelle was estimated as 700,000 using Bio-Gel A-1.5m gel filtration. Sodium dodecyl sulfate/urea-polyacrylamide gel electrophoresis followed by Coomassie stain demonstrated two polypeptide bands at 145,000 and 115,000 daltons. The purified enzyme had an isoelectric point of 7.2, was maximally active at pH 5.5, and was stable above pH 6.5 and at temperatures up to 65 degrees C for at least 90 min. Human jejunal brush-border pteroylpolyglutamate hydrolase is an exopeptidase which liberated [14C]Glu as the sole labeled product of PteGlu2[14C]Glue (where PteGlun represents pteroylpolyglutamate), failed to liberate a radioactive product from PteGlu2[14C]GluLeu2, and released all possible labeled PteGlun products during incubation with Pte[14C]GluGlu6 with the accumulation of Pte[14C]Glu. PteGlu2, PteGlu3, and PteGlu7 were substrates, each with Km = 0.6 microM, whereas PteGlu was a weak inhibitor of the hydrolysis of PteGlu3 with Ki = 20 microM. Components of the pteroyl moiety, Glu, and short chain Glun in alpha or gamma linkages were not inhibitory. The enzyme was activated by Zn2+ or Co2+. The properties of brush-border pteroylpolyglutamate hydrolase are different from those described for the soluble intracellular pteroylpolyglutamate hydrolase in other species and in human mucosa, yet are consistent with previous data on the process of hydrolysis of PteGlun in the intact human intestine.     

Overinitiation of chromosome and plasmid replication in a dna Acos mutant of Escherichia coli K12. Evidence for dnaA-dnaB interactions

The dnaAcos mutations are phenotypic suppressors of dnaAts46 that are co-transduced with dnaA, render the cell cold sensitive, and cause an excess of chromosome replication relative to cell mass when the cells are shifted from 42 degrees C to 32 degrees C. We have used pulse labelling and DNA-DNA hybridization to follow the effect of a temperature shift on the replication of the chromosome and of the plasmids pSC101, RTF-Tc, and lambda dv in such strains. After a shift of a dnaAcos strain from 42 degrees C to 32 degrees C (non-permissive temperature), initiation of the chromosome and replication of the plasmid pSC101 are stimulated, while the dnaA-independent plasmid RTF-Tc is not affected. The presence of pSC101 does not affect the level of overinitiation of the chromosome. The presence of lambda dv suppresses the cold sensitivity of dnaAcos mutants and allows the cells to grow at both 32 degrees C and 42 degrees C. The presence of lambda dv suppresses the overinitiation of chromosome and of pSC101 replication at 32 degrees C. Previous reports had shown that these suppressions involve an interaction between the dnaA product and the lambda P protein, which is also known to interact with dnaB. We show here that the mutant prophage P1 bac-crr, which produces high levels of a dnaB analogue, suppresses the dnaAcos phenotype, while wild type P1 does not. These results suggest that initiation involves interactions between the dnaA and dnaB products.     

Differentiation properties of pure populations of human dystrophic muscle cells

The interpretation of the majority of studies of Duchenne muscular dystrophy (DMD) has been complicated by the heterogeneous composition of the cultures used. In addition to muscle cells, muscle tissue contains adipocytes and fibroblasts and the proportion of these cell types varies, especially in disease states. To overcome this problem we developed culture conditions which permitted isolation and characterization of pure populations of clonally derived human muscle cells [1, 2]. Here we report the successful application of these methods to muscle cells from biopsies of individuals with diagnosed DMD. The normal and mutant human muscle cells were used in experiments of muscle differentiation in the same manner as cell lines. Frozen-stored cells were thawed, plated in a series of replicate plates, and allowed to differentiate under similar culture conditions. Yet, in contrast with cell lines, the cells were karyotypically normal, not altered by adaptation to long-term culture, and had a finite lifespan. We have systematically analysed specific properties of the normal and DMD muscle cells which differentiated in culture. The kinetics and extent of myoblast fusion, myotube morphology, and the accumulation and distribution of membrane acetylcholine receptors were monitored. In addition, the isozyme composition of creatine kinase and its intracellular and extracellular distribution were determined. Our results indicate that DMD muscle cells are fully capable of initiating myogenesis in culture and do not differ from normal muscle in several important parameters of differentiation.