The effects of ultraviolet-B radiation on plant competition in terrestrial ecosystems

Evidence regarding the interaction of ultraviolet-B (UV-B, 280-320 nm) radiation and plant competition in terrestrial ecosystems is examined. The competitive interactions of some species pairs were affected even by ambient solar UV-B radiation (as exists without ozone depletion), when compared to control pairs grown without UV-B. Also, the total shoot biomass of these species pairs was depressed under ambient UV-B. Relatively large increases in UV-B radiation (approximating a 40% ozone layer reduction when weighted with the generalized plant action spectrum) altered the competitive interactions of some species pairs grown in pots under field conditions, but did not affect the total shoot biomass production of those pairs. Recent field experiments have examined the competitive interactions of wheat ( Triticum aestivum L. cv. Bannock) and wild oat ( Avena fatua L.) under a simulated increased UV-B regime resulting from a 16% ozone layer reduction when weighted with the generalized plant action spectrum. This increase in UV-B altered the competitive interactions of these two species without affecting the total shoot biomass production of the species pair. The manner in which increased UV-B affected the relative competitive abilities of the two species was highly dependent upon the environmental conditions during the early life stages of the plants. The implications of these results for both agricultural and natural plant communities are discussed.     

Species identity of insect cell lines

Summary Three mosquito cell cultures designated as Suitor's clone ofAedes aegypti, Culiseta inornata andAedes vexans were shown to be moth by immunological, karyological, and isozyme analyses. The cells reacted with rabbit antimoth serum but not rabbit antimosquito serum. Chromosome analyses indicated Lepidopteran rather than Dipteran morphology, and three isozyme systems were confirmative. Any one of these assays would be sufficient to indicate that contamination had occurred and could be used as a periodic check for identity of cell cultures. Morphology and growth characteristics are also valid criteria to distinguish between these particular orders of insect cells. These studies were supported by Grant CA-04953-12 from the National Cancer Institute; General Research Support Grant FR-5582 from the National Institues of Health; and Grant-in-Aid Contract M-43 from the State of New Jersey. Recipient of Research Career Award 5-K3-16,749. from the National Institutes of Health.     

Species identity of insect cell lines

Summary Three mosquito cell cultures designated as Suitor's clone ofAedes aegypti, Culiseta inornata, andAedes vexans were shown to be moth by immunological, karyological, and isozyme analyses. The cells reacted with rabbit antimoth serum but not rabbit antimosquito serum. Chromosome analyses indicated Lepidopteran rather than Dipteran morphology, and three isozyme systems were confirmative. Any one of these assays would be sufficient to indicate that contamination had occurred and could be used as a periodic check for identity of cell cultures. Morphology and growth characteristics are also valid criteria to distinguish between these particular orders of insect cells. These studies were supported by Grant CA-04953-12 from the National Cancer Institute; General Research Support Grant FR-5582 from the National Institutes of Health; and Grant-in-Aid Contract M-43 from the State of New Jersey. Recipient of Research Career Award 5-K3-16,749 from the National Institutes of Health.     

Deoxyribonucleic Acid Polymerase of Rous Sarcoma Virus: Studies on the Mechanism of Double-Stranded Deoxyribonucleic Acid Synthesis

The deoxyribonucleic acid (DNA) polymerase of Rous sarcoma virus synthesizes both single- and double-stranded DNA, utilizing the ribonucleic acid (RNA) of the viral genome as the initial template. Results of pulse-chase experiments indicate that the single-stranded DNA serves as unconserved template and precursor for the synthesis of double-stranded DNA. The latter reaction is apparently initiated in association with the viral RNA and may involve a partially double-stranded intermediate form.     

Pig liver pyruvate carboxylase. Purification, properties and cation specificity

1. Pyruvate carboxylase was purified to apparent homogeneity from pig liver mitochondria and shown to be free of all kinetically contaminating enzymes. 2. The enzyme has a mol. wt. of 520000 and is composed of four subunits, each with a mol. wt. of 130000. 3. The enzyme can exist as the active tetramer, dimer and monomer, although the tetramer appears to be the form in which the enzyme is normally assayed. 4. For every 520000g of the enzyme there are 4mol of biotin, 3mol of zinc and 1mol of magnesium. No significant concentrations of manganese were detected. 5. Analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis indicates three polypeptide chains per monomer unit, each with a mol. wt. of 47000. 6. The amino acid analysis, stoicheiometry of the reaction and the activity of the enzyme as a function of pH are also presented. 7. The enzyme is activated by a variety of univalent cations but not by Tris(+) or triethanolamine(+). 8. The activity of the enzyme is dependent on the presence of acetyl-CoA; the low rate in the absence of added acetyl-CoA is not due to an enzyme-bound acyl-CoA. The dissociation constant for enzyme-bound acetyl-CoA is a marked function of pH.     

Cultivation and Survival Studies of Neisseria gonorrhoeae in a Human Diploid Cell Strain

Neisseria gonorrhoeae was cultivated in a human diploid cell strain (WI-38). Eighty percent of the cultures contained viable gonococci for at least 4 m at 36°C, as evidenced by subculture to brain heart infusion broth. Monthly subcultures of bacteria could be made to fresh WI-38 cultures for at least 11 monthly passages with a 69% survival rate. The identity of gonococci was confirmed by morphology, gram staining, oxidase testing and fermentation reactions. Viability in brain heart infusion broth, minimum essential medium (Eagle), and WI-38 spent fluid was of much shorter duration. The organisms grown in WI-38 cultures appeared to orient largely in the vicinity of the WI-38 cells as well as within the cytoplasm of the cells.     

Gallium-67 Scans in the Diagnosis of Pyelonephritis

Gallium-67 (⁶⁷Ga) citrate was administered intravenously (50 microcuries per kg of body weight) to patients in whom acute and chronic urinary tract infections were suspected. Scanning was done, using both the Anger-type scintillation camera and the rectilinear scanner, 24 to 78 hours after injection of the isotope.The preliminary results imply that ⁶⁷Ga renal uptake is present in patients with pyelonephritis whether overt or silent, as well as in patients with uretero-sigmoidostomies. However, ⁶⁷Ga renal uptake is not present in patients with radiographic evidence of chronic pyelonephritis without active infection and in patients without renal disease.     

Pig liver pyruvate carboxylase. The reaction pathway for the carboxylation of pyruvate

1. The reaction pathway for the carboxylation of pyruvate, catalysed by pig liver pyruvate carboxylase, was studied in the presence of saturating concentrations of K(+) and acetyl-CoA. 2. Free Mg(2+) binds to the enzyme in an equilibrium fashion and remains bound during all further catalytic cycles. MgATP(2-) binds next, followed by HCO(3) (-) and then pyruvate. Oxaloacetate is released before the random release, at equilibrium, of P(i) and MgADP(-). 3. This reaction pathway is compared with the double displacement (Ping Pong) mechanisms that have previously been described for pyruvate carboxylases from other sources. The reaction pathway proposed for the pig liver enzyme is superior in that it shows no kinetic inconsistencies and satisfactorily explains the low rate of the ATP[unk][(32)P]P(i) equilibrium exchange reaction. 4. Values are presented for the stability constants of the magnesium complexes of ATP, ADP, acetyl-CoA, P(i), pyruvate and oxaloacetate.