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.     

cDNA and protein sequence of a major pea seed albumin (PA 2 : Mr≈26 000)

Summary Pea albumin 2 (PA2:M_r26000) is a major component of the albumin fraction derived from aqueous salt extracts of pea seed. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and chromatography on DEAE-Sephacel resolve PA2 into two closely related components (PA2a and PA2b). A cDNA clone coding for one of these components has been sequenced and the deduced amino acid sequence compared with partial, chemically-determined sequences for cyanogen bromide peptides from both PA2 components. Complete amino acid sequences were obtained for the C-terminal peptides. The PA2 molecule of 230 amino acids contains four imperfect repeat sequences each of approximately 57 amino acids in length.The combined sequence data, together with a comparison of PA2-related polypeptides produced in vitro and in vivo, indicate that PA2 is synthesized without a signal sequence and does not undergo significant post-translational modification. Although both forms of PA2 contain Asn-X-Thr consensus sequences, neither form is glycosylated. Accumulation of PA2 contributes approximately 11% of the sulfur-amino acids in pea seeds (cysteine plus methionine equals 2.6 residues percent). Suppression of levels of PA2 polypeptides and their mRNAs in developing seeds of sulfur-deficient plants is less marked than that for legumin, in spite of the lower content of sulfur-amino acids in legumin.     

Escherichia coli integration host factor bends the DNA at the ends of IS1 and in an insertion hotspot with multiple IHF binding sites.

The integration host factor of Escherichia coli (IHF) is a small, histone-like protein which participates in the integration of bacteriophage lambda into the E. coli chromosome and in a number of regulatory processes. Our recent footprinting analysis has shown that IHF binds specifically to the ends of the transposable element IS1, as well as to several sites within a short segment of the plasmid pBR322. We have extended our studies of the binding of the IHF molecule to these sites in vitro using a gel retardation assay. We report here that IHF bends the DNA upon binding, as judged from the strong cyclic dependence of the protein-induced mobility shift on the position of the binding site. Using cloned, synthetic ends of IS1 as substrates, we have found that some mutations within the conserved bases of the IHF consensus binding sequence abolish binding, and that alterations of the flanking sequences can greatly reduce IHF binding. The presence of multiple IHF sites on a single DNA fragment increases binding very little, indicating that IHF does not bind cooperatively in this complex. We discuss the possibility that DNA bending is related to the role IHF plays in forming and stabilizing nucleoprotein complexes, and suggest that bending at the IHF sites may be important to its diverse effects in the cell.     

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     

Growth characteristics and ion contents of non-selected and salt-selected callus lines of highbush blueberry (Vacdnium corymbosum) cultivars Blue Crop and Denise Blue

Non-selected and sodium chloride selected callus lines of Vacdnium corymbosum L.cv Blue Crop and cv. Denise Blue were grown on media supplemented with 0–100 mM NaCl. For both cultivars, fresh weight and dry weight yields were greater in selected lines on all levels of NaCl. Selected lines of Blue Crop displayed better growth than selected lines of Denise Blue at most concentrations of NaCl. Internal Na⁺ and Cl^– concentrations in selected and non-selected lines of both cultivars increased as external concentration was raised. However, selected lines of Blue Crop and Denise Blue accumulated more Na⁺ and Cl^– than non-selected lines. Selected lines of both cultivars maintained higher levels of K⁺ than non-selected lines on all external NaCl levels. Selected lines of Blue Crop had higher levels of Na⁺ and Cl^– than that of Denise Blue. The results suggest Na⁺ and Cl^– accumulation could be a mechanism allowing better growth in selected lines at moderate salinity levels (50–75 mM NaCl).     

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