Photoacoustic and fluorescence measurements of the chilling response and their relationship to carbon dioxide uptake in tomato plants

The response of tomato plants to various chilling treatments was studied using two approaches for the measurement of photosynthetic activity. One involved the use of a portable fluorometer for the measurement of in-vivo chlorophyll fluorescence, while the other employed a newly introduced photoacoustic system which allowed changes in oxygen evolution to be followed in a leaf disc. A strong correlation was found between results obtained by each system and those obtained by a conventional open gas-exchange system for the determination of CO₂ uptake. Both systems of measurements could readily distinguish between the effects of chilling in the dark (at 3° C for 18 h) and chilling at high photon flux density (2000 mol m^-2 s^-1 for 5h at 5° C). Chilling in the dark had practically no effect on the quantum yield of oxygen evolution, chlorophyll fluorescence or CO₂ uptake, while chilling at excessively high photon flux density resulted in a sharp reduction (50–70%) in the quantum yields obtained. The results support the view that photosystem II cannot be the primary site of damage by chilling in the dark, although it is significantly affected by chilling at high light intensity.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - PA photoacoustic - PFD photon flux density - PSII photosystem II     

Duration of hormonal deprivation: influences on physiological and behavioral responsiveness to estradiol

A total of 54 ovariectomized female guinea pigs were divided into three groups and tested six times at 2-week intervals for their responsiveness to exogenous ovarian hormones (3 days of 4 micrograms/kg estradiol benzoate plus 1 day of 0.4 mg/kg progesterone) or control injections (0.2 ml oil vehicle). Two weeks after ovariectomy, treatment with estradiol significantly reduced food intake and body weight, and also produced vaginal membrane rupture in 98.1% of the females. When tested for sexual behavior at 4, 6, and 8 hr after the progesterone injection, 29 of the subjects (53.7%) displayed lordosis in response to manual stimulation. Twelve weeks after ovariectomy, the effects of estradiol on food intake, body weight, and vaginal membrane condition had not diminished. However, the overall proportion of females from which lordosis could be elicited declined to 27.8%. Biweekly injections of estradiol benzoate plus progesterone to one of the groups of females did not prevent this decline in the sexual response. Based on these results, it was concluded that the observed reduction in behavioral lordosis does not represent a general decline in the responsiveness of ovariectomized guinea pigs to estrogenic stimulation, but may involve changes in their responsiveness to progesterone or in other mechanisms more specifically associated with sexual behavior.     

Stability enhancement and circular dichroism spectral anomaly as an indication of non-covalent interactions in histidine- and tyrosine-containing ternary copper(II)—amino acid systems

Visible absorption and CD spectral and potentiometric studies on the His- and Tyr-containing ternary copper(II) complexes Cu(A)(L-B), where A refers to L-His, D-His, or L-Tyr and B to Lys, Tyr, Trp, Phe, Ala, Val, Arg, Glu, Asn, Gln, Ser, or Thr, were made to study ligand-ligand interactions in the complexes. While the CD spectral magnitudes in the d—d region are additive in the absence of side chain interactions and can be estimated from the magnitudes for the ternary systems involving DL-A or DL-B, deviation from the additivity was observed for Cu(L-His)(L-B) (B = LysH, Tyr, Trp, or Phe) and Cu(L-Tyr)(L-Trp). From the stability constants determined at 25 °C and I = 0.1 M (KNO₃), the equilibrium constants, K, for the following hypothetical equilibria were calculated to be large (0.14–0.60) for formation of Cu(L-/D-His)(L-B)(B = Tyr or Trp) and Cu(D-His)(L-Phe) with Cu(en)(L-Ala) as standard: $Cu(A)(L?Ala)+Cu(en)(L?b)\stackrel{K}{?}Cu(A)(L?B)+Cu(en)(L?Ala)$ The positive values indicate the stabilization due to the stacking between the imidazole ring of His and the aromatic side chain of L-B. Solvent dependence of the CD spectra for Cu(L-His)(L-LysH) and Cu(L-His) L-Trp) further supported the existence of the intramolecular electrostatic and hydrophobic interactions.     

An Immunoblot Study of Neurofilament Degradation In Situ and During Calcium-Activated Proteolysis

The degradation of neurofilament (NF) proteins was examined by immunoblot methods to identify, characterize, and monitor the appearance of immunoreactive breakdown products during the loss of NF triplet proteins. Individual NF proteins and their breakdown products were identified using polyclonal and monoclonal antibodies to NF proteins. NF degradation was compared during calcium-activated proteolysis of isolated rat NF, during an experimental influx of calcium into excised rat spinal nerve roots, and during NF breakdown in transected rat peripheral nerve. These different experimental conditions produced similar patterns of NF fragmentation, including the transient appearance of NF immunobands between Mr 150,000-200,000 and 110,000-120,000 as well as the appearance and accumulation of NF immunobands between Mr 45,000 and 65,000. Most immunoreactive NF fragments remained Triton-insoluble. Low levels of the same immunoreactive fragments were present in control neural tissues, suggesting that calcium-activated proteolysis may be operative in the turnover and/or processing of NF proteins in vivo. Very similar patterns of NF degradation during experimental calcium influxes into different CNS and PNS tissues are indicative of the widespread distribution of calcium-activated NF protease in neural tissues.     

Line and crossing effects in a diallel mating system with highly inbred lines of White Leghorn chickens

Summary Seven highly inbred lines of White Leghorn chickens were used in a near complete diallel mating plan during eight years. The lines originated from three different base populations selected for egg weight. Average inbreeding coefficients of parents of chicks hatching in successive years were 0.75, 0.80, 0.84, 0.86, 0.89, 0.91, 0.93 and 0.94. The composition of line, specific combining ability and reciprocal effects and their estimated values are given. These effects were estimated for age at first egg (AFE), average weight of all eggs laid to 40 weeks (EW40), body weight at 40 weeks (BW40), number of eggs to 40 weeks (EP40) and number of eggs between 41 and 60 weeks (EP60). Records of 3247 hens surviving to 40 weeks and of 3133 birds to 60 weeks could be used. Large differences between line effects could be found in all traits. They were only partly due to the preceding selection in the base populations. All specific combining effects were in the expected direction, negative for AFE and positive for EW40, BW40, EP40 and EP60. Recovery of inbreeding depression inflated these effects rather substancially. Average heterosis, defined as the relative superiority of a line combination over the mid parent value, was –11.3%, 5.8%, 7.8%, 45.1% and 35.8% for AFE, EW40, BW40, EP40 and EP60 respectively. One line showed a relative superiority in AFE of -19.3% compared to about –7.9% for all other combinations. Reciprocal or sex-linked effects were generally smaller in all traits than specific combining effects, they were considerably smaller in AFE, EP40 and EP60. General reciprocal effects could be found for several lines in one or more traits. Offspring of two lines, when used as sire lines, showed a negative correlation between reciprocal effects of egg weight and body weight.     

The colon of Leucophaea maderae: fine structure and physiological features

The colon of L. maderae consists of a single columnar epithelium covered with a cuticle and of a musculo-connective sheath. The apical plasma membranes form a system of leaflets with numerous mitochondria inserted in association with microfilaments. Lateral plasma membranes are linked together by junctional complexes consisting of a zonula adherens and a long convoluted septate junction of the pleated type. In the basal region of the cell, numerous membrane infolds and scattered scalariform junctions with associated mitochondria are present. These cell specializations are typical of arthropod transporting organs, being distinctive features of ion and fluid transporting epithelia. The isolated colon exhibited a transepithelial electrical potential difference (PD) of about 100 mV, lumen side positive with respect to the haemolymph side. The PD was almost abolished by metabolic inhibitors, it was reduced by acetazolamide and SITS, and it was unaffected by ouabain. These effects suggest that HCO3- and Cl- are involved in the genesis of the PD, whereas Na+ is not directly responsible of the PD. Measurements of Na+ and Cl- fluxes across the colon wall confirm that Na+ moves following the PD across the tissue, while Cl- movement occurs against an electrochemical potential difference. The electrical profile of the epithelial cells is of the well type and it suggests that the primary or secondary active step for Cl- transport across the epithelium should be located at the mucosal border of the cell.     

Activity expressed from cloned Anacystis nidulans large and small subunit ribulose bisphosphate carboxylase genes

Summary The ribulose bisphosphate carboxylase/oxygenase (EC4.1.1.39) (RubisCO) large and small subunit genes from Anacystis nidulans have been cloned as a single fragment into M 13mp10 and pEMBL8 and expressed in Escherichia coli. From M 13mp10 a low yield of enzyme with high specific activity was obtained. The molecular weight of the active enzyme was 260 000 Da and of the inactive enzyme approximately 730 000 Da. The small and large subunits cloned separately did not express activity. The RubisCO gene cloned into pEMBL8 expressed activity up to 22 times that from the M 13 cloned RubisCO DNA. The RubisCO protein produced by the pEMBL cloned gene had a normal MW (550 000). Immunoprecipitation and polyacrylamide gel electrophoresis showed the presence of both large and small subunits.     

Thiols and pancreatic beta-cell function: a review

In pancreatic islets insulin secretion in response to a variety of stimulators is sensitive to the redox state of extracellular and intracellular thiols. In this connection variations of plasma glutathione (GSH) may also be of importance. In the process of stimulus-secretion coupling, membrane thiols play an important role. One major localization of critical thiols appears to be related to the influx of calcium through the voltage-dependent channel. Other transmembranal ion movements and the cAMP system seem to be less sensitive to thiol oxidation than calcium influx via voltage-dependent Ca channels.     

Restriction endonuclease EcoO109 from Escherichia coli H709c with heptanucleotide recognition site 5'-PuG/GNCCPy

A new restriction endonuclease, EcoO109, has been isolated from Escherichia coli H709c by polyethyleneimine (PEI) precipitation, DEAE-cellulose chromatography and heparin agarose chromatography. The yield was high, more than 3000 units/g of wet cells. The EcoO109 endonuclease recognizes and cleaves a nucleotide sequence of (formula: see text), in the presence of 10 mM Mg2+. The enzyme will be useful for structural analysis and molecular cloning of DNA because of the stability, high yield and easy handling of the producer strain.