Pneumocystis carinii shows DNA homology with the ustomycetous red yeast fungi

Pneumocystis carinii causes life-threatening pneumonia in T-lymphocyte-immunodeficient subjects in transplant and oncology units or with acquired immune deficiency syndrome (AIDS). Recent DNA homology studies show P. carinii to be a fungus. To investigate the biology and epidemiology of this parasite further, we elected to determine for it a more precise taxonomic assignment within the fungal kingdom. We screened a wide range of organisms representing the major orders of fungi using DNA amplification and subsequently sequenced a portion of the mitochondrial gene encoding the large subunit ribosomal RNA. Our data show that the opportunistic pulmonary pathogen P. carinii is closely related to the ustomycetous red yeast fungi, a group which includes organisms that are extensively distributed throughout the environment and which release many widely dispersed airborne spores.     

The spectrophotometric determination of nanomole quantities of chloride in plant tissue

The determination of Cl- in plant tissues was investigated by FeSCN2+ spectrophotometry following SCN- displacement from Hg(SCN)2 by Cl-. The calibration curve was nonlinear, but consistent and reproducible. As little as 10 nmol Cl- could be measured. There was no obvious interference in color development by water-soluble components in plant tissues. Values obtained by this method were in close agreement with those obtained potentiometrically and by coulometric titration.     

Effect of Plant Species and Environmental Conditions on Ice Nucleation Activity of Pseudomonas syringae on Leaves

Selected plant species and environmental conditions were investigated for their influences on expression of ice nucleation activity by 15 Pseudomonas syringae strains grown on plants in constant-temperature growth chamber studies. Ice nucleation frequencies (INFs), the fraction of cells that expressed ice nucleation at −5 or −9°C, of individual strains varied greatly, both on plants and in culture. This suggests that the probability of frost injury, which is proportional to the number of ice nuclei on leaf surfaces, is strongly determined by the particular bacterial strains that are present on a leaf surface. The INFs of strains were generally higher when they were grown on plants than when they were grown in culture. In addition, INFs in culture did not correlate closely with INFs on plants, suggesting that frost injury prediction should be based on INF measurements of cells grown on plants rather than in culture. The relative INFs of individual strains varied with plant host and environment. However, none of seven plant species tested optimized the INFs of all 15 strains. Similarly, incubation for 48 h at near 100% relative humidity with short photoperiods did not always decrease the INF when compared with a 72 h, 40% relative humidity, long-photoperiod incubation. Pathogenic strains on susceptible hosts were not associated with higher or lower INFs relative to their INFs on nonsusceptible plant species. The ice nucleation activity of individual bacterial strains on plants therefore appears to be controlled by complex and interacting factors such as strain genotype, environment, and host plant species.     

Circular dichroism of platelet factor 4

The circular dichroism of platelet factor 4 was investigated and it was found to contain 15% alpha-helix, 25% beta-structure, and the rest of the molecule in unordered conformation. In the presence of heparin, no change in the circular dichroism was observed, suggesting no significant changes in the secondary structure of platelet factor 4 when heparin binds. The CD spectrum of platelet factor 4 was also investigated in the presence of increasing concentrations of guanidine hydrochloride. A two-state transition was observed with midpoints at 0.125 and 2.0 M guanidine hydrochloride. Based on gel filtration studies, the first unfolding transition was correlated with the dissociation of the tetrameric structure. This first unfolding domain was not observed in the presence of heparin, suggesting that heparin stabilizes the tetrameric structure. The second unfolding transition corresponds to the disruption of the overall secondary structure which is generally observed with most proteins. It is concluded that a relatively weak force of attraction holds the tetrameric structure of platelet factor 4 and the dissociation of the subunits is accompanied by loss of some helical secondary structure.     

Studies on the genus Fontinalis (Musci: Fontinalaceae)

Fontinalis welchiana, a new species in the concave-leaved group ofFontinalis restricted to Arkansas, Missouri, and Illinois, differs fromF. novaeangliae by its slender size, dimorphic leaves, erect and strongly concave branch leaves, and lightly papillose exostome with ventral lamellae that are strongly rounded at the corners.Fontinalis allenii is a synonym ofF. antipyretica var.oreganensis.     

Effect of long-term Intralipid administration in mice

Intralipid was administered intravenously to mice at a level of 2 g kg-1 day-1 for 23 days. No alterations in phagocytic index, liver or spleen size were observed in the chronically injected mice as compared with control mice that received saline injections. Tissue distribution of 0.45 micron multilamellar liposomes of egg phosphatidylcholine:cholesterol (2:1) was similar in mice that had been chronically injected with Intralipid to that in control mice. Mice chronically given the same total amount of phospholipid in the form of 0.2 micron liposomes of phosphatidylcholine:cholesterol (2:1) rather than as a lipid-triglyceride emulsion showed altered tissue distribution of entrapped label with decreased liver uptake and increased splenic uptake, which is indicative of reticuloendothelial blockade. Tissue distribution of [14C]dipalmitoylphosphatidylcholine Intralipid was compared with that of [14C]dipalmitoylphosphatidylcholine 0.2 micron MLV of phosphatidylcholine:cholesterol (2:1). Intralipid was taken up 2- to 3-fold less by liver and 5- to 10-fold less by spleen than liposomes. Blood levels of Intralipid were higher than those of liposomes. [14C]dipalmitoylphosphatidylcholine Intralipid was eliminated from the body at a faster rate than [14C]dipalmitoylphosphatidylcholine liposomes. The lack of reticuloendothelial blockade caused by Intralipid as compared with liposomes appears to be related to its diminished uptake into reticuloendothelial tissues. This diminished uptake may be related to differences in apolipoprotein uptake of Intralipid, which is primarily in the form of a phospholipid monolayer, and liposomes, which have their phospholipid organized into a bilayer.     

The structure of the basement membrane of human lymph node high endothelial venules: An ultrastructural, histochemical and immunocytochemical study

Summary The structure of the basement membrane of the high endothelium of reactive human lymph nodes was investigated by techniques selective for carbohydrates (periodic acid-Schiff; critical electrolyte concentration staining with Alcian Blue; lectin histochemistry), specific proteins (immunohistochemistry for laminin and fibronectin) and by conventional techniques of light and transmission electron microscopy. Adjacent small lymphocytes were assigned to B and T cell subsets by use of monoclonal antibodies and they were analysed for non-specific esterase,-glucuronidase,-N-acetylglucaminidase and proteolytic activities. The basement membranes were shown to be distinctive and to contain three layers, of differing laminin, glycosaminoglycan and glycoprotein oligosaccharide content. Certain lymphocytes (probably T) contained enzymes potentially able to degrade some components of these basement membranes.     

Hexavalent capsomers of herpes simplex virus type 2: symmetry, shape, dimensions, and oligomeric status

The structures of the hexavalent capsomers of herpes simplex virus type 2 were analyzed by negative staining electron microscopy of capsomer patches derived from partially disrupted nucleocapsids. Optimally computer-averaged images were formed for each of the three classes of capsomer distinguished by their respective positions on the surface of the icosahedral capsid with a triangulation number of 16; in projection, each capsomer exhibited unequivocal sixfold symmetry. According to correspondence analysis of our set of capsomer images, no significant structural differences were detected among the three classes of capsomers, as visualized under these conditions. Taking into account information from images of freeze-dried, platinum-shadowed nucleocapsid fragments, it was established that each hexavalent capsomer is a hexamer of the 155-kilodalton major capsid protein. The capsomer has the form of a sixfold hollow cone approximately 12 nm in diameter and approximately 15 nm in depth, whose axial channel tapers in width from the outside towards the inner capsid surface.     

Transient response of forests to CO2-induced climate change: simulation modeling experiments in eastern North America

Summary The temporal response of forests to CO₂-induced climate changes was examined for eastern North America. A forest stand simulation model was used with the assumption that climate will change at a constant rate as atmospheric CO₂ doubles, and then as CO₂ doubles again. Before being used to project future vegetation trends, the simulation model FORENA was verified by its ability to reproduce long, temporal sequences of plant community change recorded by fossil pollen and by its ability to reproduce today's vegetation. The simulated effects of changing monthly temperature and precipitation included a distinctive dieback of extant trees at most locations, with only partial recovery of biomass in areas of today's temperate deciduous forest. In the southern portion of today's deciduous-coniferous transition forests the simulated dieback was indistinct and recovery by deciduous tree species was rapid. In more northerly transition areas, the dieback not only was clearly expressed, but occurred twice, when new dominant species replaced extant conifers, then were themselves replaced, as climate change continued. Boreal conifers also underwent diebacks and were replaced by deciduous hardwoods more slowly in the north than in the south. Transient responses in species composition and carbon storage continued as much as 300 years after simulated climate changes ceased.Environmental Sciences Division Publication No. 2625     

Promoter recognition by Escherichia coli RNA polymerase. Effects of substitutions in the spacer DNA separating the -10 and -35 regions

A family of variants of the PRM promoter of lambda phage was constructed, bearing nine base pair substitutions in a stretch of the spacer DNA separating the contacted -10 and -35 regions. The substituted sequences were chosen for their potential to adopt structures different from those of average B-form DNA and thus to affect the interaction of RNA polymerase with the two contacted regions. Characterization of the promoters in vitro and in vivo provides additional support for the lack of specific contacts in the substituted spacer region and shows that a small change in the relative rotational orientation of the -10 and -35 regions is inconsequential to promoter function. However, a 2-3-fold reduction in promoter activity is observed with promoters bearing substitutions of nonalternating dG-dC base pairs in either orientation. This corroborates other studies indicating the anomalous behavior of such sequences and suggests that the structure of the spacer DNA can modulate promoter recognition.