In situ estimation of net CO2 assimilation, photosynthetic electron flow and photorespiration in Turkey oak (Q. cerris L.) leaves: diurnal cycles under different levels of water supply

Diurnal time courses of net CO₂ assimilation rates, stomatal conductance and light-driven electron fluxes were measured in situ on attached leaves of 30-year-old Turkey oak trees (Quercus cerris L.) under natural summer conditions in central Italy. Combined measurements of gas exchange and chlorophyll a fluorescence under low O₂ concentrations allowed the demonstration of a linear relationship between the photochemical efficiency of PSII (fluorescence measurements) and the apparent quantum yield of gross photosynthesis (gas exchange). This relationship was used under normal O₂ to compute total light-driven electron fluxes, and to partition them into fractions used for RuBP carboxylation or RuBP oxygenation. This procedure also yielded an indirect estimate of the rate of photorespiration in vivo. The time courses of light-driven electron flow, net CO₂ assimilation and photorespiration paralleled that of photosynthetic photon flux density, with important afternoon deviations as soon as a severe drought stress occurred, whereas photochemical efficiency and maximal fluorescence underwent large but reversible diurnal decreases. The latter observation indicated the occurrence of a large non-photochemical energy dissipation at PSII. We estimated that less than 60% of the total photosynthetic electron flow was used for carbon assimilation at midday, while about 40% was devoted to photorespiration. The rate of carbon loss by photorespiration (R₁) reached mean levels of 56% of net assimilation rates. The potential application of this technique to analysis of the relative contributions of thermal de-excitation at PSII and photorespiratory carbon recycling in the protection of photosynthesis against stress effects is discussed.     

Evaluation of PAPNET-assisted cervical rescreening

Evaluation of PAPNET-assisted cervical rescreening
We have compared the results of targeted manual rescreening of 1211 randomly selected smears with the results of PAPNET-assisted rescreening of 1613 cervical smears, containing at least 6.3% low-grade squamous intraepithelial lesion (SIL). PAPNET diagnosis and the targeted rescreening diagnosis were compared with the initial report, issued on the corresponding smear. Reproducibility scores for inadequacy, presence of endocervical and endometrial cells, specific infections and squamous cell abnormalities were determined. The reproducibility scores for the diagnosis of inadequate smears and specific infections were lower with the PAPNET-assisted rescreening. The detection of squamous cell abnormalities was excellent for both methods (>0.95), with a higher detection rate for false-negative smears with the PAPNET testing system.     

Genetic and physiologic analysis of a formyl-tetrahydrofolate synthetase mutant of Streptococcus mutans.

Previously we reported that transposon Tn917 mutagenesis of Streptococcus mutans JH1005 yielded an isolate detective in its normal ability to produce a mutacin (P. J. Crowley, J. D. Hillman, and A. S. Bleiweis, abstr. D55, p. 258 in Abstracts of the 95th General Meeting of the American Society for Microbiology 1995, 1995). In this report we describe the recovery of the mutated gene by shotgun cloning. Sequence analysis of insert DNA adjacent to Tn917 revealed homology to the gene encoding formyl-tetrahydrofolate synthetase (Fhs) from both prokaryotic and eukaryotic sources. In many bacteria, Fhs catalyzes the formation of 10-formyl-tetrahydrofolate, which is used directly in purine biosynthesis and formylation of Met-tRNA and indirectly in the biosynthesis of methionine, serine, glycine, and thymine. Analysis of the fhs mutant grown anaerobically in a minimal medium demonstrated that the mutant had an absolute dependency only for adenine, although addition of methionine was necessary for normal growth. Coincidently it was discovered that the mutant was sensitive to acidic pH; it grew more slowly than the parent strain on complex medium at pH 5. Complementation of the mutant with an integration vector harboring a copy of fhs restored its ability to grow in minimal medium and at acidic pH as well as to produce mutacin. This represents the first characterization of Fhs in Streptococcus.     

Role of the extracellular domain of human herpesvirus 7 glycoprotein B in virus binding to cell surface heparan sulfate proteoglycans.

In an attempt to identify the human herpesvirus 7 (HHV-7) envelope protein(s) involved in cell surface binding, the extracellular domain of the HHV-7 glycoprotein B (gB) homolog protein was cloned and expressed as a fusion product with the Fc domain of human immunoglobulin G heavy chain gamma1 (gB-Fc) in an eukaryotic cell system. Indirect immunofluorescence followed by flow cytometric analysis revealed specific binding of gB-Fc to the membrane of SupT1 cells but not to other CD4+ T-lymphoblastoid cell lines, such as Jurkat or PM1, clearly indicating that gB-Fc did not bind to the CD4 molecule. This was also suggested by the ability of gB-Fc to bind to CD4-negative fibroblastoid Chinese hamster ovary (CHO) cells. The binding was abrogated by enzymatic removal of cell surface heparan sulfate proteoglycans by heparinase and heparitinase but not by treatment with condroitinase ABC. In addition, binding of the gB-Fc fusion protein to CHO cells was severely impaired in the presence of soluble heparin, as well as when heparan sulfate-deficient mutant CHO cells were used. Consistent with these findings, soluble heparin was found to block HHV-7 infection and syncytium formation in the SupT1 cell line. Although the CD4 antigen is a critical component of the receptor for the T-lymphotropic HHV-7, these findings suggest that heparin-like molecules also play an important role in HHV-7-cell surface interactions required for infection and that gB represents one of the HHV-7 envelope proteins involved in the adsorption of virus-to-cell surface proteoglycans.     

The effects of inbreeding on the parental values of potato dihaploids

Dihaploids obtained from a somatically chromosome-doubled dihaploid potato were crossed with Solanum phureja clones. To test the effect of inbreeding, measurements were made of their seed production and the tuber yield, tuber number and mean tuber weight of their offspring. On average, seed production of the second generation dihaploids was higher than that of the original dihaploid progenitor. Progeny tuber yield and its components were little different from those of the original dihaploid's progeny. Tuber flesh quality, as measured lack of blemishes, was better in the offspring of second generation dihaploids.
It is suggested that the negative effects of producing second generation dihaploids are minor compared with producing the first generation dihaploid from a tetraploid, because most deleterious recessives have already been unmasked. The results indicated residual variation within the original dihaploid which could be exploited for plant breeding purposes.
An indicator of inbred status, alternative to the inbreeding coefficient, is suggested which could be applied to both diploids and tetraploids.     

bel-2 protein in breast cancer cells obtained by fine needle aspiration (FNA): a preliminary report

The bcl-2 protein plays a role in the regulation of programmed cell death (PCD), overriding apoptosis. Its expression has been reported in breast ductal cells, where it is believed to be involved in the hormonal regulation of hyperplasia and involution. to date, bcl-2 gene product has not been investigated on breast cancer FNA. the expression of bcl-2 protein was evaluated using an immunoalkaline phosphatase technique in 54 pre-operative breast cancer aspirates and in paraffin-embedded sections from 20 matched surgical specimens. A high rate of bcl-2 protein expression was found on FNA samples (65%) and on the corresponding tissue sections (60%); there was a nearly absolute concordance in the two specimens, with 19/20 (95%) cases showing a concordant staining. These findings concur with the view that bcl-2 gene is frequently expressed in breast cancer, possibly through a hormonal-dependent pathway.     

A trans-acting regulatory product necessary for expression of the Drosophila melanogaster 68C glue gene cluster

The mutation I(1)npr-1 is located at cytological location 2B5 on the X chromosome in Drosophila melanogaster. We have found that this mutation causes absence of the normal product of the 2B5 locus and that it has the following phenotypes: the 68C glue puff on the third chromosome does not regress when mutant salivary glands are cultured in the presence of ecdysterone; the three 68C glue protein mRNAs are not synthesized; and a transformed Drosophila strain carrying both a normal resident 68C Sgs-3 gene and an introduced functional Sgs-3 gene with only a few kb of flanking sequences expresses neither Sgs-3 RNA if the I(1)npr-1 mutation is crossed into the stock. Thus the normal product of the I(1)npr11 gene is required for regression of the 68C puff, and the I(1)npr-1 gene product allows expression of the Sgs-3 gene by interacting, either directly or indirectly, with DNA sequences near this glue protein gene.     

Entamoeba histolytica: Collagenolytic Activity and Virulence1

Several axenic strains of pathogenic and nonpathogenic Entamoeba histolytica were tested for their capacity to digest native radioactive type I collagen gels and to produce liver abscesses when injected into the liver of newborn hamsters. The results demonstrate that the pathogenic strains of amebas (HM1:IMSS, HM3:IMSS, HM38:IMSS, and HK9) have a collagenolytic activity that closely correlates with their in vivo capacity to produce liver lesions. The nonpathogenic isolate (Laredo) did not show collagenolytic activity and failed to produce lesions in the liver of newborn hamsters. The results also demonstrate that type I collagen obtained from rodents and cats is degraded less by amebic collagenase than is bovine collagen, which is similar to human collagen. These findings suggest that species susceptibility to invasive infection may depend, among other factors, on the characteristics of the extracellular components of host tissues.     

Analogs of arachidonic acid methylated at C-7 and C-10 as inhibitors of leukotriene biosynthesis

The syntheses and biological activity of (all )-7,7-dimethyl-5-8,- 11,14-eicosatetraenoic acid, (all )-7,7,-dimethyl-5,8,11-eicosatrienoic acid, ( , -7,7-dimethyl-5,8-eicosadienoic acid, (all )-10,10-dimetyl- 5,8,11,14-eicosatetraenoic acid, (all -10,10-dimethyl-5,8,11-eicosatrienoic acid, and .-( , -15-hydroxy-7,7-dimethyl-5,8-eicosadienoic acid are described. These arachidonic acid analogs are all inhibitors of ionophore-induced SRS-A biosynthesis in rat peritoneal cells. Their mode of action may involve inhibition of phospholipase A₂ rather than Δ⁵-lipoxygenase. These compounds failed to exhibit significant activity in an model designed to detect inhibitors of antigen-induced, leukotriene-mediated bronchoconstriction is sensitized guinea pigs.