Entamoeba histolytica and Giardia lamblia: Growth responses to reducing agents

The growth responses of Entamoeba histolytica strains HM-1:IMSS and HK-9 to a variety of reducing agents were tested for one subculture in TYI-S-33 medium, prepared with no cysteine or ascorbic acid. Amoebae did not grow in this medium. Addition of l-ascorbic acid, d- or l-cysteine, or l-cystine each permitted the maximum growth observed. Dithiothreitol supported 68% maximum growth of HK-9 amoebae, but only 12% of HM-1. In contrast, growth of both strains was greatly diminished (0–13% growth) with 11 other compounds tested including glutathione, thiomalic acid, thioglycolic acid, and methionine. The growth responses of Giardia lamblia were similarly tested in TYI-S-33, as well as in TP-S-1 media. If l-cysteine was omitted from either medium, trophozoites did not grow, and eventually lysed. In TYI-S-33 medium, the requirement for l-cysteine was specific, whereas in TP-S-1 medium, other sulfhydryl compounds were partially effective and lower concentrations of l-cysteine satisfied the requirement. Ascorbic acid or l-cystine alone was totally ineffective; however, in combination, 30 to 60% of maximum growth was achieved. Once added to either medium, cysteine was rapidly oxidized. Amino acid analysis of the growth media revealed that the broth components of TP-S-1 medium contained 2.8 mM and TYI-S-33 broth 2.1 mM endogenous levels of cysteine (or half-cystine), with an additional 3 mM contributed by 10% serum.     

Stuessya (Asteraceae: Heliantheae), a new genus from southcentral Mexico

Stuessya, a new genus from the Pacific slopes of southcentral Mexico is described. It is comprised of three species:S. apiculata, previously assigned to the genusViguiera;S. perennans, the generotype; andS. michoacana. The latter two taxa are previously undescribed. The genus is characterized by its urceolate, sclerified (at maturity) involucre. Chromosome counts of2n = 34 are reported forS. perennans. Relationships are problematical, but are reckoned to be somewhere betweenAldama andViguiera.     

A model for ganglioside behaviour in cell membranes

Gangliosides from beef brain have been spin-labeled using two different attaching groups and employed to investigate the physical nature of ganglioside behaviour in membranes. Results obtained using EPR spectroscopy indicate that, in phosphatidylcholine bilayers at physiological pH, ganglioside oligosaccharide chains are quite mobile and show a measurable tendency towards cooperative interaction amongst themselves. We suggest that the source of this interaction is the formation of H-bonds between sugar residues in adjacent ganglioside molecules. We present evidence that physiological (extracellular fluid) levels of Ca²⁺ and Mg²⁺ lead to cross-linking and condensing of ganglioside headgroups by complexing sialic acid carboxyl residues. Ganglioside headgroup interactions are not very sensitive to changes in the buffer ionic strength, suggesting that ionic interactions are of minor importance. We have found no measurable tendency for headgroup carbohydrate to penetrate hydrophobic regions of lipid bilayers. EPR spectroscopy was also used to follow the interaction of spin-labeled gangliosides with the glycoprotein, glycophorin, and with intact BHK cells.We suggest that these carbohydrate-based interactions should contribute significantly to the properties of the eucaryotic cell glycocalyx. We predict that laterally mobile carbohydrate-bearing components of cell surfaces will show a tendency to cluster about complex glycoprotein arrays, especially if the species involved bear accessible carboxylic acid functions.     

Localization of Drosophila nasutoides satellite DNAs in metaphase chromosomes

Metaphase chromosomes of D. nasutoides were hybridized situ with ³H-cRNA synthesized from the four satellites which make up 50–60% of the total DNA of this species. All four satellites were localized in the large, metacentric, heterochromatic chromosome four. They did not, however, appear to hybridize to centromeric or other constitutive heterochromatin, nor did they, with the exception of satellite I, seem to hybridize in the specific regions of chromosome four which, on the basis of C, Q, and H banding and AT contents, were predicted to contain some of these satellites. —Comparison of grain patterns with the results of fluorescent staining indicated that satellite-bearing heterochromatin was not always associated with other fractions of constitutive heterochromatin in interphase nuclei and was, at least partially, decondensed in some larger nuclei.     

A comparative study of the temporal bone in three populations of man

A comparative study was made to determine race and sex differences in the temporal bone, to investigate growth relationships, and to establish a basis for phylogenetic studies of the temporal bone and the temporal lobe of the brain. Data on Eskimo, Indian, and white crania were collected from radiographs and directly from the skulls. Of the 25 variables studied, only the minimum diameter of porus failed to demonstrate some difference among the races. Variation between sexes was found for all measurements except the cranial base angle (of deflection) and three angles related to the petrous pyramids. Correlation coefficients indicated that none of the angles are related in any consistent manner to the other variables studied. This is interpreted as further evidence of cranial base stability. The Indians have the lowest, longest squamae, differing most from the whites. The position of squama is more anterior in the Eskimos. Females of each race possess more anteriorly positioned squamae than males. When the squama is more anteriorly located, the porus is in a more posterior position within the squama itself. Strong race variation exists in the shape of porus. In order to establish a basis for phylogenetic studies of the temporal lobe of the brain better reference points for reflecting its size and shape must be found.     

HL-A antigens in North American black families

The polymorphic HL-A histocompatibility system has been studied in North American black families. The family studies show that haplotype frequencies differ between black and white populations. Seven haplotypes (W28,W5; W28,W17; W28, undefined four; W23,W5; W19,W5; undefined LA,W5; and undefined LA, undefined four) were significantly more frequent in blacks than whites, while haplotypes 1,8 and 3,7 were significantly less frequent. Some of these differences may be accounted for by differences in gene frequencies between the two groups; other differences may be explained by linkage disequilibrium in the white population. No significant linkage disequilibrium between the LA and FOUR loci was found in the black population.     

Studies on normal human bone marrow cultures in controlled environment thin-film culture systems

Summary Two thin film culture systems, the controlled environment steady state system (SS) and the rocker tube configuration of that system (RT), were used to identify some of the conditions that appear to maintain morphologic and functional characteristics of cells of human bone marrow explants in vitro. The systems configuration assured continual gassing, control and easy monitoring of the cultures. Cytocentrifuge preparations of media of specimens cultured in RT disclosed, though in decreasing numbers, various hematopoietic cells for periods exceeding one month. Hematopoietic cells shed from specimens cultured in the SS system were retained in the culture tubes; cells of the myelocytic series predominated for the first 2 weeks while an increasing number of monocytes and macrophages appeared in the media of older cultures. Histologic examination of cultured explants disclosed preservation of the marrow architecture and the persistence of hematopoietic cells. Specimens cultured in RT tubes tended to be less cellular than similar cultures placed in dialysis bags or as cultured in the SS system. Immunoglobulins (Ig) were released into the culture media at a constant rate throughout the period of culture. Specimens that were cultured at a controlled pH of 7.4 released 2 to more than 4 times as much Ig as similar specimens maintained at a pH level of 7.1. There were no definitive differences in Ig levels in the cultures maintained at comparable pH levels and overlaid with various CO₂ concentrations, i.e. 2%, 5%, 10%; similarly, no differences in Ig levels were found in specimens cultured in media containing fetal bovine sera as opposed to horse sera. Supported by U.S.P.H.S. Grant CA-5834 from the National Cancer Institute. Department of Medicine A. Department of Cell Physiology Department of Immunology and Immunochemistry.     

Reactive oxygen species play a role in P2X7 receptor-mediated IL-6 production in spinal astrocytes

Purinergic Signalling - Astrocytes mediate a remarkable variety of cellular functions, including gliotransmitter release. Under pathological conditions, high concentrations of the purinergic...