Ribosomal DNA and ITS-2 sequence comparisons as a tool for predicting genetic relatedness

The determination of the secondary structure of the internal transcribed spacer (ITS) regions separating nuclear ribosomal RNA genes of Chlorophytes has improved the fidelity of alignment of nuclear ribosomal ITS sequences from related organisms. Application of this information to sequences from green algae and plants suggested that a subset of the ITS-2 positions is relatively conserved. Organisms that can mate are identical at all of these 116 positions, or differ by at most, one nucleotide change. Here we sequenced and compared the ITS-1 and ITS-2 of 40 green flagellates in search of the nearest relative to Chlamydomonas reinhardtii. The analysis clearly revealed one unique candidate, C. incerta. Several ancillary benefits of the analysis included the identification of mislabelled cultures, the resolution of confusion concerning C. smithii, the discovery of misidentified sequences in GenBank derived from a green algal contaminant, and an overview of evolutionary relationships among the Volvocales, which is congruent with that derived from rDNA gene sequence comparisons but improves upon its resolution. The study further delineates the taxonomic level at which ITS sequences, in comparison to ribosomal gene sequences, are most useful in systematic and other studies. Received: 14 February 1997 / Accepted: 28 March 1997     

Epidemiologic features of Lyme disease in New York

During 1982, surveillance identified 207 cases of Lyme disease in New York State. Cases were clustered in two geographic areas, eastern Long Island and northern Westchester counties. Symptoms and signs of Lyme disease in cases were consistent with previous reports, with erythema chronicum migrans (ECM) being the most frequently (77 percent) reported sign of disease. Facial palsy was reported in a surprisingly high 18 percent of cases. Of 160 cases whose sera were submitted for Lyme spirochete specific IgG antibody testing, 112 (70 percent) had titers greater than or equal to 64, while 88 (55 percent) had titers greater than or equal to 128. Positive titers were not associated with any single sign or symptom of disease, but were significantly associated with symptom onset or tick bite occurring during the three-month period of June, July, and August. We conclude that the incidence of Lyme disease in New York is much higher than previously recognized. In addition, our data suggest that a serologic test for Lyme-spirochete IgG antibody lacks sensitivity, but can be useful in confirming the diagnosis of Lyme disease when antibody titers are high.     

Microsomal and lysosomal enzymes of triacylglycerol metabolism in rat placenta.

The placenta plays a major role in transporting lipid to the developing foetus. Since previous studies have suggested that placental lipid transport involves intermediate esterification steps, we investigated selected microsomal and lysosomal enzymes of triacylglycerol metabolism in rat placenta. Between gestational days 10 and 14, microsomal phosphatidic acid phosphatase specific activity was 6-fold greater than the activity in adult rat liver. Phosphatidic acid phosphatase activity decreased 50% on day 15. Studies employing several different phosphorylated substrates indicated a high degree of substrate specificity. Lysosomal triacylglycerol lipase and cholesterol esterase activities decreased about 50% between days 15 and 18, then rose late in gestation. No changes were observed in the specific activities of fatty acid: CoA ligase, glycerolphosphate acyltransferase, lysophosphatidate acyltransferase, diacylglycerol acyltransferase or diacylglycerol cholinephosphotransferase during the final 12 days of gestation. Kinetic observations (competitive inhibition by alternative substrates, pH-dependence and thermal inactivation) were consistent with the hypothesis that glycerol phosphate and dihydroxyacetone phosphate can be acylated by a single microsomal enzyme in placenta. Except for fatty acid: CoA ligase, the activities of microsomal and lysosomal enzymes of triacylglycerol metabolism were comparable with those in adult rat liver. These observations are consistent with physiological studies suggesting that triacylglycerol synthetic and degradative pathways are very active in rat placenta.     

Identification of Extracellular Carbonic Anhydrase of Chlamydomonas reinhardtii

We have examined the induction of carbonic anhydrase activity in Chlamydomonas reinhardtii and have identified the polypeptide responsible for this activity. This polypeptide was not synthesized when the alga was grown photoautotrophically on 5% CO₂, but its synthesis was induced under low concentrations of CO₂ (air levels of CO₂). In CW-15, a mutant of C. reinhardtii which lacks a cell wall, between 80 and 90% of the carbonic anhydrase activity of air-adapted cells was present in the growth medium. Furthermore, between 80 and 90% of the carbonic anhydrase is released if wild type cells are treated with autolysin, a hydrolytic enzyme responsible for cell wall degradation during mating of C. reinhardtii. These data extend the work of Kimpel, Togasaki, Miyachi (1983 Plant Cell Physiol 24: 255-259) and indicate that the bulk of the carbonic anhydrase is located either in the periplasmic space or is loosely bound to the algal cell wall. The polypeptide associated with carbonic anhydrase activity has a molecular weight of approximately 37,000. Several lines of evidence indicate that this polypeptide is responsible for carbonic anhydrase activity: (a) it appears following the transfer of C. reinhardtii from growth on 5% CO₂ to growth on air levels of CO₂, (b) it is located in the periplasmic space or associated with the cell wall, like the bulk of the carbonic anhydrase activity, (c) it binds dansylamide, an inhibitor of the enzyme which fluoresces upon illumination with ultraviolet light, (d) antibodies which inhibit carbonic anhydrase activity only cross-react with this 37,000 dalton species.     

Ethylene-Induced Chlorosis in the Pathogenesis of Bipolaris sorokiniana Leaf Spot of Poa pratensis

Endogenous ethylene of Poa pratensis leaves infected by Bipolaris sorokiniana was evaluated as a factor in leaf chlorosis during pathogenesis. Detectable increases in endogenous ethylene of leaves of intact plants under normal ambient pressure occurred 12 hours after inoculation and was maximum at 48 hours; from 48 to 96 hours the ethylene progressively decreased. Necrotic lesions surrounded by chlorotic halos occurred on infected leaves between 24 and 48 hours. Midvein chlorosis interconnecting individual lesions and complete chlorosis of all tissues not directly affected by the lesions occurred between 72 and 96 hours, after maximum production of ethylene at 48 hours. The chlorophyll loss in infected leaves by 96 hours was 44% compared with controls.

Subjecting inoculated leaves of intact plants to a controlled atmospheric-environmental system with an atmospheric pressure of 233 millibars and O₂ and CO₂ partial pressures adjusted to approximately that of normal ambient pressure during infection and disease development prevented most midvein chlorosis and complete chlorosis, but did not prevent necrotic lesion or chlorotic halo development. Under the hypobaric conditions, chlorophyll loss during disease development was reduced to 22% compared with controls at 96 hours. The observations suggest that ethylene may function late in pathogenesis of this host-pathogen interaction and is responsible for much of the chlorophyll loss after its maximum production at 48 hours.

     

Mineralization dynamics in fallow dryland wheat plots,Colorado

Summary There was a flush of mineralization in fallow wheat plots in the wet and warm summer of 1982 at Akron, Colorado. Peak mineralization rates and concentrations of N and P coincided with a 2.5-fold increase in protozoan biomass. No-till contained considerably more activity than stubble mulch plots, especially in the surface 2.5 cm and there was more water storage in no-till on all dates. Differential management of agricultural residues and the resultant effects upon the microbial community significantly altered patterns of nutrient cycling.     

The metabolism of starch, glucose, amino acids, purines, pyrimidines and bacteria by the rumen ciliate Polyplastron multivesiculatum.

The large rumen ciliate protozoon Polyplastron multivesiculatum grown in vitro engulfed a wide range of bacteria (from a population density of 10(9) bacteria ml(-1)) at a rate of 1500 to 137000 bacteria h(-1) protozoon(-1). No evidence was found for the preferential engulfment of bacteria of rumen origin. Except for Proteus mirabilis none of the bacteria were digested with the liberation of soluble materials into the medium. Glucose and amino acids were taken up rapidly by P. multivesiculatum compared with the rate of uptake by Entodinium caudatam. Glucose was incorporated into protozoal polysaccharide and into bacteria associated with the protozoa and was used for the synthesis of a wide range of amino acids. Evidence showed that bacteria and free amino acids at the concentrations found in the rumen could supply the protein requirements of the protozoa for division at least once each day.     

ANATOMICALLY PRESERVED SEED CONES OF THE PINACEAE FROM THE EARLY CRETACEOUS OF VIRGINIA

A collection of anatomically preserved conifer cones from the Early Cretaceous of Virginia contains two new species of the extinct pinaceous genus Pityostrobus. Superficially, the fossil cones resemble those of modern species of Picea. However, the fossils reveal such a peculiar mixture of anatomical features that they cannot be assigned to any extant genus of the Pinaceae. One of the new species, Pityostrobus hueberi, is most comparable with Pityostrobus corneti Alvin from the Early Cretaceous of Belgium. Pityostrobus virginiana, the other new species, differs from all other members of the genus in only slight—but nonetheless significant—attributes. Pityostrobus hueberi and P. virginiana are the first species of this genus to be reported from Early Cretaceous sediments of the North American Atlantic Coastal Plain. As such, they increase our knowledge of the structural variation exhibited by ancient members of the Pinaceae.     

Immunoglobulin E decapeptide-induced 5-hydroxytryptamine release from rat peritoneal mast cells. Comparison with corticotropin-(1-24)-peptide, polyarginine, polylysine and antigen.

A synthetic basic decapeptide from the C4 domain of human immunoglobulin E, corticotropin-(1-24)-peptide, polyarginine and polylysine stimulated up to 90% net release of 5-hydroxytryptamine from mast cells in rat peritoneal-cell suspensions. Concentration-response curves to all four polypeptides were parallel. Polyarginine and polylysine (EC50 congruent to 0.05 microM) were approximately 100-fold more potent than immunoglobulin E decapeptide and corticotropin-(1-24)-peptide (EC50 congruent to 5 microM). Polypeptide-induced release was complete within 5-10s. Immunoglobulin-E-decapeptide-induced 5-hydroxytryptamine release was additive to that induced by low concentrations of polyarginine, but non-additive to that induced by high concentrations of polyarginine. In contrast, release induced by antigen was additive along the whole length of the concentration-response curve to polyarginine. Benzalkonium chloride inhibited immunoglobulin-E-decapeptide- and polyarginine-induced 5-hydroxytryptamine release but enhanced release induced by immunological stimulation.