Partial characterization of a Trypanosoma cruzi-released decomplementing factor

Trypanosoma cruzi releases a factor (SCAF) when grown in vitro which decomplements normal mouse, human, and guinea pig sera. The production and potency of SCAF was dependent on the density of cultured parasites, parasite viability and proliferative capacity, and duration of culture. The in vitro interaction between SCAF and serum complement (C') occurred rapidly and was complete within 30 min of mixing. The administration of SCAF to normal mice resulted in up to 50% reduction in hemolytic C' activity, whereas SCAF had no effect on the C' levels in mice infected wit T. cruzi for more than 10 days. The active moiety of SCAF was shown to be a nonproteinaceous substance(s) with a molecular weight of approximately 23,000 daltons.     

Diel vertical migration in Mesocyclops edax: implications for predation rate estimates

The diel migration patterns of Mesocyclops edax and its preyin a small lake were followed in two studies separated by approximatelyone year. Gut contents of the predators were examined and selectivityindices calculated at each depth at 0100 h during 1980. Thethree principal zooplankton prey found in the guts of M. edaxwere Keratella, Kellicottia, and Bosmina. The predator and allthree major prey species exhibited unique and different dielvertical distribution and migration patterns. The complex natureof the spatio-temporal variation in prey density to which M.edax is exposed, demonstrates the dangers of using selectivityindices without knowledge of the distribution patterns of bothpredator and prey. An increase in vertebrate predation pressurefrom one year to the next is thought to be responsible for anincrease in the abundance of small zooplankton species, thedisappearance of two out of three of the large zooplankton species,and the onset of a pronounced nocturnal migration pattern inthe third large species. ¹Present address: Biology Department, Williams Hall #31, LehighUniversity, Bethlehem, PA 18015, USA     

Stereospecific activity of 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine and comparison of analogs in the degranulation of platelets and neutrophils

1-O-Hexadecyl-2-O-acetyl-$\text{sn}$-glycero-3-phosphocholine (platelet activating factor) stimulated the degranulation of rabbit platelets and human neutrophils, whereas the enantiomer, 3-O-hexadecyl-2-O-acetyl-$\text{sn}$-glycero-1-phosphocholine, was inactive. The analogs compared had the following relative potencies in degranulating platelets and neutrophils: 1-O-hexadecyl-2-O-acetyl-$\text{sn}$-glycero-3-phosphocholine > 1-O-hexadecyl-2-O-ethyl-$\text{sn}$-glycero-3-phosphocholine >$\text{rac}$-1-O-octadecyl-2-O-ethylglycero-3-phosphocholine = 1-O-hexadecyl-2-O-methyl-$\text{sn}$-glycero-3-phosphocholine >$\text{rac}$-1-O-dodecyl-2-O-ethyl-glycero-3-phosphocholine. The deacetylated compound, 1-O-hexadecyl-2-lyso-$\text{sn}$-glycero-3-phosphocholine, and 1-O-hexadecyl-2,2-dimethylpropanediol-3-phosphocholine were inactive. The active analogs selectively desensitized the response to each other in the neutrophils. It is suggested that these compounds may activate cells through interaction with a stereospecific receptor.     

Mouse DNA methylase: methylation of native DNA.

An improved method of purification of DNA methylase from Krebs II ascites cells is reported. The enzyme sediments at 8.3 S on glycerol-gradients and a major band on SDS polyacrylamide gel electrophoresis has a molecular weight of 184 000. Aggregation occurs at low salt and this may interfere with enzymic activity. The preferred double stranded DNA substrate is that rendered partially unmethylated by an in vitro repair mechanism or by isolation from methionine starved cells. Methylation of native partially methylated DNA is favoured under conditions of low salt and high temperature; conditions which encourage 'breathing' of the DNA. Methylation of native, unmethylated DNA also involves breathing but results in formation of a salt resistant tight binding complex between the enzyme and the DNA.     

Optimum interaction of sterol side chains with phosphatidylcholine.

The specificity of the interaction between the cholesterol side chain and egg phosphatidylcholine was precisely defined by examining the effect of three new analogues of cholesterol with modified side chains on the ordering of two steroid spin labels in liposomes. The complete side chain of cholesterol was shown to be required for maximum ordering. Sterols with side chains shorter or longer than cholesterol caused significantly less ordering.     

Presence of two forms of fumarase (fumarate hydratase E.C. 4.2.1.2) in mammalian cells: Immunological characterization and genetic analysis in somatic cell hybrids. Confirmation of the assignment of a gene necessary for the enzyme expression to human chromosome 1

Two major forms of fumarate hydratase have been resolved in extracts prepared from a wide variety of mammalian cells by electrophoresis. Fractionation experiments with human and mouse cells suggest that one form (the slower migrating) is localized in the mitochondria, whereas the other form is predominant in the cytoplasm. Analysis of the segregation of the enzyme forms in human-mouse somatic cell hybrids indicates that a gene(s) necessary for the expression of both forms can be assigned to human chromosome 1 (confirmation of a previous assignment by van Someren et al., 1974). Electrophoretic analysis suggests that the two forms may be interrelated. Furthermore, they both exhibit identical reactivity toward anti-fumarate hydratase antiserum. It is suggested that a modification of one form may occur in vivo and that the modification may be important in determining the intracellular localization of the enzyme.     

Isolation and detailed characterization of human cell lines resistant to -threo-chloramphenicol

The isolation and characterization of chloramphenicol resistant derivatives of the human cell line HeLa B is described. Growth of resistant lines was unaffected in the presence of 100 μg/ml -threo-chloramphenicol, whereas growth of the parental cells was inhibited at 12.5 μg/ml. The incorporation of [³⁵S]methionine into mitochondrial protein of intact resistant cells continued normally in the presence of 100 μg/ml chloramphenicol (cytoplasmic protein synthesis was blocked by addition of 50 μg/ml emetine). Under these conditions the electrophoretic profile of labelled, presumptive mitochondrially-made proteins was similar to that of the parental cell line labelled in the absence of chloramphenicol. The cell lines selected in the presence of chloramphenicol also showed increased resistance to some other inhibitors of mitochondrial protein synthesis, e.g. carbomycin and mikamycin. [¹⁴C]Chloramphenicol was found to have normal access to the interior of resistant cells and it is therefore unlikely that resistance results from altered cell permeability. No modification of the drug by acetylation or glucuronide conjugation mechanisms was observed. The possibilities remain that resistance is mediated by altered permeability of the mitochondrial membrane, or from modification to a component of the mitochondrial protein synthetic system.     

Predictors of Introduction Success in the South Florida Avifauna

Biological invasions are an increasing global challenge, for which single-species studies and analyses focused on testing single hypotheses of causation in isolation are unlikely to provide much additional insight. Species interact with other species to create communities, which derive from species interactions and from the interactions of species with the scale specific elements of the landscape that provide suitable habitat and exploitable resources. I used logistic regression analysis to sort among potential intrinsic, community and landscape variables that theoretically influence introduction success. I utilized the avian fauna of the Everglades of South Florida, and the variables body mass, distance to nearest neighbor (in terms of body mass), year of introduction, presence of congeners, guild membership, continent of origin, distribution in a body mass aggregation or gap, and distance to body-mass aggregation edge (in terms of body mass). Two variables were significant predictors of introduction success. Introduced avian species whose body mass placed them nearer to a body-mass aggregation edge and further from their neighbor were more likely to become successfully established. This suggests that community interactions, and community level phenomena, may be better understood by explicitly incorporating scale.     

Normalized cDNA libraries from a porcine model of orthopedic implant-associated infection

Staphylococcal infections that result from an alteration in a patient's immune response at the surgical site are a major problem in procedures that incorporate biomaterials in trauma surgery and joint replacement. Diagnosis of infection based on pathogen detection is difficult and exacerbated by increasing numbers of partially or totally resistant strains of nosocomial pathogens, particularly Staphylococcus aureus. Expression profiling of a host's cellular immune response could facilitate the identification of the pathways involved in pathogen recognition and eradication and could lead to more rational design of drugs and therapies. To this end, we constructed and characterized ten individually tagged and directionally cloned cDNA libraries from peripheral blood cells (PBC), spleen (Sp), thymus (Th), lymph node (LN), and bone marrow (BM) from immunologically naive and challenged pigs as part of an implant-associated orthopedic model of deep infection. Three of these libraries were normalized at C _{0 t} values 5, 10, 20, and 30. The libraries comprise more than 20 million primary transformants with an average insert length >1.4 kb. Cluster analysis of 7620 ESTs revealed 1029 clusters containing an average of 3.6 sequences and 3846 singletons. Gene discovery is estimated to be ∼64%. Searches of public databases resulted in 49.3% annotated porcine sequences, of which 22.2% had significant homologies to ESTs from a variety of species, and 28.5% were without a significant match in any public database. We also identified 9.1% ESTs as involved in host cell and organism defense and 11.5% related to cell signaling and communication. These sequences, together with the 28.5% appearing as novel, are of specific interest to the infectious disease process.