Correlation of pulmonary ACE activity and capillary surface area during postnatal development

Although a considerable amount of information is available regarding the remodeling and growth of the pulmonary arterial circulation, relatively little is known regarding postnatal development of the pulmonary microcirculation. We hypothesized that the maximal velocity (Vmax) of pulmonary angiotensin-converting enzyme (ACE) activity, measured from indicator-dilution outflow curves using a synthetic substrate, 3H-labeled benzoyl-phenylalanyl-alanyl-proline (BPAP), is directly related to the capillary endothelial cell surface area in the lungs of developing lambs. Accordingly we measured apparent kinetics of pulmonary ACE activity in 22 anesthetized ventilated lambs (2-171 days old) and compared our functional assessment to simultaneous in vivo determinations of CO diffusing capacity (DLCO) and postmortem structural assessment of alveolar septal dimensions using stereology and electron microscopy. There was a progressive increase in Vmax of ACE in this age group, with little change in apparent affinity for BPAP. Similar functional manifestation of growth was noted by an age-dependent increase in DLCO. Neither Vmax nor DLCO was significantly affected by an increase in left atrial pressure to 19 Torr (via inflation of a balloon in the left atrium), suggesting little recruitment of vessels under conditions of the present protocol. A close correlation was observed when either Vmax for ACE activity or DLCO was plotted vs. capillary endothelial cell surface area. Double logarithmic transformation of capillary endothelial cell surface area, Vmax-ACE and DLCO vs. lung volume revealed power functions with slopes all greater than that predicted from isotropic growth, suggesting selective differential postnatal development of the endothelium of the alveolar septum in lambs from 2-171 days of age.     

Bidirectional effect of met-enkephalin on macrophage effector functions

Summary Met-enkephalin (ME) exerts a bimodal effect on functional activities of rat peritoneal macrophages (PM); in a range of low concentration (10^-9-10^-7 M) antibody dependent cellular cytotoxicity (ADCC)was markedly stimulated with a simultaneous decrease of Fc receptor (FcR) mediated phagocytosis while the opposite was observed at 10^-6-10^-5 M concentrations.Studying the possible underlying mechanism(s) the followings were recorded: (1) ME in all applied concentrations induced an early Na⁺ influx which was followed by a Ca²⁺ efflux in the range of low concentrations. In the range of high concentrations Na⁺ influx was accompanied by a Ca²⁺ influx. (2) ME at 10^-8 M concentration induced a rise in cGMP level with a plateau in the 60–120th min of incubation. This effect was prevented by 10^-5 M of naloxone. At 10^-6 M concentration a transient rise of cAMP level was recorded which was not affected by naloxone. (3) Verapamil in 10^-6 M abolished both the Ca²⁺ influx and the rise in cAMP level induced by 10^-6-10^-5 M ME but not the rise in cGMP level induced by lower ME concentrations. (4) cAMP elevation by high ME concentrations was abolished by enkephalinase inhibitory puromycin. (5) PM-enkephalinase as assessed by the cleavage of fluorogenic substrate L-alanine beta naphthylamide (ABNA), was inhibited by 10^-6-10^-5 M of ME. This inhibition was abolished by verapamil, but not affected by naloxone. In the range of low concentrations ME appears to act on specific delta opioid receptors and its action is positively coupled to guanylate cyclase. In relatively higher concentrations ME-action is not mediated by specific delta opioid receptors and it appears to involve Ca²⁺ influx, adenylate cyclase activation as well as the processing of hormone by PM-enkephalinase.     

p140mDia, a mammalian homolog of Drosophila diaphanous, is a target protein for Rho small GTPase and is a ligand for profilin.

Rho small GTPase regulates cell morphology, adhesion and cytokinesis through the actin cytoskeleton. We have identified a protein, p140mDia, as a downstream effector of Rho. It is a mammalian homolog of Drosophila diaphanous, a protein required for cytokinesis, and belongs to a family of formin-related proteins containing repetitive polyproline stretches. p140mDia binds selectively to the GTP-bound form of Rho and also binds to profilin. p140mDia, profilin and RhoA are co-localized in the spreading lamellae of cultured fibroblasts. They are also co-localized in membrane ruffles of phorbol ester-stimulated sMDCK2 cells, which extend these structures in a Rho-dependent manner. The three proteins are recruited around phagocytic cups induced by fibronectin-coated beads. Their recruitment is not induced after Rho is inactivated by microinjection of botulinum C3 exoenzyme. Overexpression of p140mDia in COS-7 cells induced homogeneous actin filament formation. These results suggest that Rho regulates actin polymerization by targeting profilin via p140mDia beneath the specific plasma membranes.     

Phytohormone mutants in plant research

The techniques used for the production and identification of plant hormone mutants are described. The properties used to classify these mutants into the broad synthesis and sensitivity categories are discussed, and the genetic considerations needed to allow their effective use in plant hormone research examined. A brief outline of significant recent work on the gibberellin (GA), abscisic acid (ABA), auxin, ethylene, cytokinin and phytochrome mutants is provided. Suggestions for future emphasis are made, particularly relating to an examination of the tissue and ontogenetic specificity of the plant hormone genes.     

Derivation of the sequence of the signal peptide in human C4b-binding protein and interspecies cross-hybridisation of the C4bp cDNA sequence

A 5' cDNA clone coding for human C4b-binding protein (C4bp) was isolated, characterised and sequenced to complete the cDNA sequence coding for residues 1-32 thus confirming the protein sequence data of Chung et al. [(1985) Biochem. J. 230, 133-141]. The sequence extended to allow derivation of the putative leader peptide sequence which was 32 residues in length and showed a high of hydrophobicity typical of other documented leader sequences. Cross hybridisation was detected between the human C4bp cDNA probes and genomic DNA isolated from various species on Southern blots suggesting that genomic sequence homologous to that coding for C4bp has been conserved during evolution.     

Interaction between PGPR and PGR for water conservation and plant growth attributes under drought condition

Drought is one of the key restraints to agricultural productivity worldwide and is expected to increase further. Drought stress accompanied by reduction in precipitation pose major challenges to future food safety. Strategies should be develop to enhance drought tolerance in crops like chickpea and wheat, in order to enhance their growth and yield. Drought tolerance strategies are costly and time consuming however, recent studies specify that plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGRs) can help plants to withstand under harsh environmental condition and enable plants to cope with drought stress. PGPR can act as biofertilizer and bioenhancer for different legumes and non-legumes. The use of PGPR and symbiotic microorganisms, may be valuable in developing strategies to assist water conservation in plants. The use of PGPR has been confirmed to be an ecologically sound way of enhancing crop yields by facilitating plant growth through direct or indirect mechanism. The mechanisms of PGPR for water conservation include secretion of exopolysaccharides, biofilm formation, alternation in phytohormone content, improvement in sugar concentration, enhancing availability of micro- and macronutrients and changes in plant functional traits. Similarly, plant growth regulators (PGRs) are specially noticed in actively growing tissues under stress conditions and have been associated in the control of cell division, embryogenesis, root formation, fruit development and ripening, and reactions to biotic and abiotic stresses and upholding water conservation status in plants. Previous studies also suggest that plant metabolites interact with plant physiology under stress condition and impart drought tolerance. Metabolites like, sugars, amino acids, organic acid and polyols play a key role in drought tolerance of crop plants grown under stress condition. It is concluded from the present study that PGRs in combination with PGPR consortium can be an effective formulation to promote plant growth and maintenance of plant turgidity under drought stress. This review is a compilation of the effect of drought stress on crop plants and described interactions between PGPR/PGRs and plant development, knowledge of water conservation and stress release strategies of PGPR and PGRs and the role of plant metabolites in drought tolerance of crop plants. This review also bridges the gaps that summarizes the mechanism of action of PGPR for drought tolerance of crop plants and sustainability of agriculture and applicability of these beneficial rhizobacteria in different agro-ecosystems under drought stress.