Tissue water relations of four co-occurring chaparral shrubs

Summary Chaparral shrubs of California have a suite of morphological and physiological adaptations to withstand the prolonged summer droughts of a mediterranean climate. Not all species of chaparral have the same rooting depth and there is some evidence that those with shallow roots have tissue that is most tolerant to water stress. We tested this notion by comparing the tissue water relations of four co-occurring chaparral shrubs: Quercus durata, Heteromeles arbutifolia, Adenostoma fasciculatum, and Rhamnus californica. We used a pressure-volume technique and a dew-point hygrometer to metsure seasonal changes in osmotic potential when plant tissue was fully hydrated and osmotic potential at predawn, midday, and the turgor loss point. We also calculated seasonal changes in the minimum daily turgor potential, saturated weight/dry weight ratio of leaf tissue, and the bulk modulus of elasticity. We had information on the seasonal water use patterns and apparent rooting depths of these same four shrubs from a previous study (Davis and Mooney 1986). All evidence indicated that Rhamnus had shallow roots and Quercus deep roots. Our results indicated that the tissue water relations of our four co-occurring chaparral shrubs were not alike. Even though Rhamnus had shallow roots, it had the least xerophytic tissue. Seasonal osmotic potential and saturated weight/dry weight ratios were relatively high and bulk modulus of elasticity and minimum daily turgor potentials were low. Furthermore, even though Quercus had deep roots and experienced no seasonal water stress at our study site, its tissue water relations indicated relatively high tolerance to water stress. We conclude that seasonal drought tolerance of stem and leaf tissue of co-occurring chaparral shrubs does not necessarily correspond to rooting depth, to soil moisture resources available to the shrub, or to the degree of seasonal water stress experienced by the shrub.     

Purification of nuclear cAMP-independent protein kinases from rat ventral prostate

Two nuclear cAMP-independent protein kinases (designated PK-N1 and PK-N2) were purified from rat ventral-prostate and liver. The yield of enzyme units was 4-5% and 7-9% for each enzyme from the prostatic nuclei and liver nuclei, respectively. The average fold purification for prostatic nuclear protein kinase N1 and N2 was 1360 and 1833, respectively. The respective average specific activity of the two enzymes towards casein was 81,585 and 110,000 nmol 32P incorporated/hr/mg of enzyme. Protein kinase N1 comprised one polypeptide of Mr 35,000 which underwent phosphorylation in the presence of Mg2+ + ATP. Protein kinase N2 comprised two polypeptides Mr 40,000 and 30,000 of which only the Mr 30,000 polypeptide was autophosphorylated. Both enzymes were active towards casein, phosvitin, dephosphophosvitin, spermine-binding protein, and non-histone proteins in vitro. Little activity was detected towards histones. Both enzymes were stimulated by 150-200 mM NaCl. MgCl2 requirement varied with the protein substrate but was between 2-4 mM for both enzymes. With dephosphophosvitin as substrate, the apparent Km for ATP for N1 protein kinase was 0.01 mM. GTP did not replace ATP in this reaction. Protein kinase N2 was active in the presence of ATP or GTP. The apparent Km was 0.01 mM for ATP, but 0.1 mM for GTP.     

Cytochalasin D and cationized ferritin as probes for the morphological investigation of blebbing in two human cell lines

Summary The potent fungal metabolite cytochalasin D (CD) and cationized ferritin (CF) are used in combination to test for negative charge distribution on blebs (knobs). Two established human epithelial cell lines, WISH and HeLa, that display blebs in various phases of the cell cycle or under certain culture conditions (37,46) are investigated. CD alone, applied at a low concentration (1.0 μg/ml) and for a short time period (3 min), causes blebs to appear as the prevalent surface feature. These are filled mainly with free ribosomes. Additionally, feltlike mats, presumed to be disorganized, compacted microfilaments, are formed directly beneath the cell membrane. These are especially evident in the cortical cytoplasm below the blebs or bleb clusters. CF (0.345 mg/ml), applied for a 5-min period after CD administration (1.0 μg/ml) for 3 min, appears along the surface of microvilli, at the base of blebs, and in vesicles beneath the bleb clusters. In some cases, microfilaments (6 nm in diameter) are closely related to the vesicles. CF does not preferentially bind to the apical cell membrane of blebs. Above areas of the subplasmalemmal microfilaments, CF membrane binding is apparent, even under circumstances where the filaments are disorganized by cytochalasin treatment. These results seem to show the following: (a) bleb membranes are different from the remainder of the cell and do exhibit a loss of negative charge and (b) surface charge may be dependent on the presence or structural integrity of membrane-related 6-nm microfilaments. The support of this research by a grant from the Baylor College of Dentistry and The Oklahoma College of Osteopathic Medicine and Surgery is gratefully acknowledged. The assistance of Dr. J. H. Martin, Department of Pathology, Baylor University Medical Center, is also greatly appreciated.     

Microwave-field-driven acoustic modes in DNA.

The direct coupling of a microwave field to selected DNA molecules is demonstrated using standard dielectrometry. The absorption is resonant with a typical lifetime of 300 ps. Such a long lifetime is unexpected for DNA in aqueous solution at room temperature. Resonant absorption at fundamental and harmonic frequencies for both supercoiled circular and linear DNA agrees with an acoustic mode model. Our associated acoustic velocities for linear DNA are very close to the acoustic velocity of the longitudinal acoustic mode independently observed on DNA fibers using Brillouin spectroscopy. The difference in acoustic velocities for supercoiled circular and linear DNA is discussed in terms of solvent shielding of the nonbonded potentials in DNA.     

Genetic Variation for the Sex Ratio in NASONIA VITRIPENNIS

We detected genetic variation for the sex ratio in the parasitoid wasp Nasonia vitripennis by analysis of inbred lines and with an artificial selection experiment. Sex ratios differed significantly among five independently isolated lines. Furthermore, sex ratio in broods produced by single females in single hosts shifted from 80-90% female to 50-55% female in 13 to 15 generations in each of two replicate selection lines. The final sex ratios of both selection lines were significantly lower than any of the inbred line sex ratios. Backcrosses revealed that the selection response was due to nuclear genes acting through the female parent. In light of known facultative sex ratio behavior and major genes affecting sex ratio in Nasonia, our results suggest that population and individual sex ratios in this species are molded by processes at both genetic and behavioral levels.     

Systemic and renal hemodynamic responses to vascular blockade of vasopressin in conscious dogs with ascites

A role for arginine vasopressin has been implicated in the compensatory control of arterial blood pressure in several animal models with reported increases in plasma levels of arginine vasopressin. A threefold elevation in plasma vasopressin has been reported in conscious dogs following constriction of the inferior vena cava. In the present study, infusion of the arginine vasopressin antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-O-methyltyrosine] Arg8-vasopressin into conscious dogs with chronic caval constriction did not decrease mean arterial blood pressure. However, the dose of infused antagonist completely blocked the pressor response to 2 micrograms of exogenous vasopressin. Also the antagonist produced no effect on heart rate, plasma renin activity, or urinary volume and electrolyte excretions. A slight, transient increase (P less than or equal to 0.05) was observed in creatinine clearance and in PAH clearance following antagonist infusion, suggesting a possible decrease in renal vascular resistance. These data suggest that the direct vasoconstrictor actions of vasopressin contribute minimally, if at all, to blood pressure maintenance following chronic caval constriction. Alternatively, blockade of endogenous vasopressin receptors at the level of peripheral arterioles may have resulted in no depressor response due to a masking of this response by other compensatory hormonal and neural pressor systems.     

Experimental dissociation of food intake and plasma beta-endorphin following 2-deoxy-D-glucose in rats

The present studies were undertaken to further assess the role of plasma beta-endorphin (beta-EP) in the hyperphagia induced by the glucose antimetabolite, 2-deoxy-D-glucose (2-DG). Plasma concentrations of immunoreactive beta-EP (ir-beta-EP) were measured at the end of the first hour of feeding in all animals treated with 400 mg/kg 2-DG. Previous studies had shown a consistent, positive association between 2-DG hyperphagia and plasma ir-beta-EP concentrations, but the present data revealed dissociations between hyperphagia and plasma ir-beta-EP. Dexamethasone administration blocked the 2-DG-induced rise in plasma ir-beta-EP, but had no effect on the 2-DG hyperphagia measured at 1 hour. Forced drinking of a 2% NaCl solution decreased 2-DG hyperphagia, but not the 2-DG induced rise in plasma ir-beta-EP. Thus, elevations in plasma ir-beta-EP are not necessary for the full expression of 2-DG-induced hyperphagia in dexamethasone-treated rats. Furthermore, decreased feeding responses to 2-DG could coexist with increased levels of plasma ir-beta-EP in NaCl-treated normal rats. Elevations in plasma ir-beta-EP do not appear to be the critical opiate link in 2-DG induced hyperphagia.     

Analysis of a continuous, aerobic, fixed-film bioreactor. I. Steady-state behavior

The analysis of a continuous, aerobic, fixed-film bioreactor is performed by simulating the behavior of penicillin production in a three-phase fluidized bed. Rigorous mathematical models are developed for a fluidized-bed fermentor in which bioparticles are fluidized by the liquid medium and air. The steady-state performance of the fluidized-bed reactor is appraised in terms of penicillin productivity and outlet concentration by considering the two extremes in contacting patterns, complete back-mix and plug flow, in the absence of a growing biofilm. The results show that the complete back-mix contacting pattern is preferred over that of plug flow due to the nature of the penicillin kinetic relationships. It is also shown that for the dual-nutrient (glucose and oxygen) penicillin reaction system the optimum biofilm thickness does not equal the penetration depth of a limiting nutrient, but depends upon the total reactor configuration.     

Bovine conglutinin is a collagen-like protein

Conglutinin is a bovine plasma protein which is relatively large and asymmetric with elevated contents of glycine and, to some extent, proline. Although its physiologic function is unknown, conglutinin is known to bind, in the presence of calcium, to yeast cell walls and to the solid-phase-inactivated third component of complement. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions, isolated conglutinin appeared to consist of a single polypeptide chain (Mr 48 000). Unreduced conglutinin consisted of a single stained band with an apparent molecular weight of approximately 300 000. Cross-linking experiments with glutaraldehyde and dimethyl suberimidate suggested that this Mr 300 000 molecule consists of six of the disulfide-linked polypeptide chains. Amino acid composition revealed hydroxylysine and hydroxyproline together with elevated glycine and proline contents. Digestion of reduced, alkylated conglutinin with bacterial collagenase resulted in formation of a precipitate which consisted of an Mr 24 000 peptide which was digested to Mr 21 000 with large quantities of collagenase. These peptides contained less glycine, proline, hydroxylysine, and hydroxyproline than did the intact protein. The supernatant from this digestion mixture was, however, enriched in these four amino acids, with glycine making up nearly one-third of the total. Prolonged digestion with pepsin at 37 degrees C resulted in an Mr 20 000 peptide which was enriched in glycine, proline, hydroxyproline, and hydroxylysine. Amino-terminal sequence analysis showed that the glycine-X-Y repeating sequence begins at residue 26.(ABSTRACT TRUNCATED AT 250 WORDS)