Synthesis and biological activity of analogs of dynorphin-A(1-13) substituted in positions 2 and 4: design of [Ala2,Trp4]-Dyn-A(1-13) as a putative selective opioid antagonist

Mono- and di-substituted analogs of dynorphin-A(1-13) (Dyn-A(1-13)) were synthesized by the solid-phase procedure. The products were purified and analyzed for their ability to inhibit the electrically evoked contractions of the guinea pig ileum (GPI) and mouse vas deferens (MVD) and to compete with the binding of [3H]etorphine ([3H]ET) and [3H]ethylketocyclazocine ([3H]EKC) to homogenates of rat brain (mu-, delta-, kappa 2-receptors) and guinea pig cerebellum (kappa-receptor), respectively. Introduction of Ala in position 2 caused a drastic decrease in the activity of the peptide on the smooth muscle preparations (IC50 of 104 and 2.250 nM in the GPI and the MVD as compared with 0.7 and 21 nM for the parent peptide, respectively). Conversely, this analog retained much of the opioid binding activity of Dyn-A(1-13) (relative binding potencies of 15 and 72% for the displacement of [3H]ET and [3H]EKC, respectively). The replacement of Phe4 by Trp also caused drastic decreases in the activity of the peptide in the smooth muscle preparations (relative potencies of 0.8 and 8.8% on the GPI and MVD) while much of the binding potency to the opioid receptors was retained (31 and 67% for the displacement of [3H]ET and [3H]EKC, respectively). [Ala2,Trp4]-Dyn-A(1-13) was the least potent peptide tested in the smooth muscle assays (relative potencies: 0.1 and 0.6%). However, this latter analog still retained some opioid binding activity in the displacement of [3H]ET to rat brain homogenates (3%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inheritance of stomatal conductance in cotton (Gossypium barbadense)

Stomatal conductance in improved Pima cotton cultivars (Gossypium barbadense) has been previously shown to be positively associated with heat resistance and yield potential. In the present study we determined the mode of inheritance of stomatal conductance in crosses of six G. barbadense parents varying in origin, degree of agronomic development and stomatal conductance. Parents included a primitive tropical cotton (B368), two obsolete cultivars (St Vincent V135, Pima 32), one modern commercial line (Pima S-6) and two elite genotypes of the Pima germplasm (P70, P73). These lines showed distinct differences in stomatal conductance, under greenhouse and field conditions. The primitive B368 had the lowest conductance, and the elite lines the highest. Generation means analysis was used to quantify genetic effects in the crosses P70 × St Vincent V135, Pima S-6 × B368, Pima S-6 × Pima 32, P73 × Pima 32 and P73 × Pima S-6. Best-fit models of the inheritance of stomatal conductance varied in complexity from a simple additive-dominance model in the cross P70 × St. Vincent V135 to models displaying digenic epistatic interactions in the remaining crosses. Significant additive mean effects for stomatal conductance were detected in all crosses. Dominance mean effects were significant in the crosses P73 × Pima 32 and P73 × Pima S-6. Broadsense heritability estimates of stomatal conductance were relatively low (0.16–0.44) in all crosses except Pima S-6 × B368 (0.74). Results also show that the mode of inheritance of stomatal conductance is multigenic, and may have maternal as well as nuclear components. Recouping higher stomatal conductance levels from genetically wider crosses appears feasible and could proceed at a moderate rate. Fixing higher levels of stomatal conductance in populations from crosses of elite germplasm may be more difficult because of the presence of dominant mean effects and digenic epistatic interactions.     

Increasing the effectiveness of clinical supervision.

Effective use of preceptors in the clinical training and supervision of residents involves four essential steps: careful screening of the preceptor''s practice to ensure it reflects the goals of the residency program and teaching the preceptor about the goals; setting a realistic contract for learning between resident and preceptor; teaching the preceptor to use constructive feedback techniques in the day-to-day supervision of residents; and developing the preceptor''s skills in the reliable and valid evaluation of the resident''s performance. Clinical preceptors must be trained to become effective teachers and evaluators in residency programs.     

Chemical synthesis and surface activity of lung surfactant phospholipid analogs. III. Chiral N-substituted ether-amide phosphonolipids

A homologous series of chiral (R) ether-amide phosphonolipid analogs of naturally occurring (R) glycerophospholipids were synthesized and characterized for their interfacial behaviors. The phosphonolipids possess isoteric ether, amide, and phosphonate functions at positions corresponding to the sn-1, sn-2, and sn-3 ester functions, respectively, of naturally occurring glycerophospholipids. All compounds were synthesized with disaturated C16:0 alkyl/acyl moieties to give structural analogy with dipalmitoyl phosphatidylcholine (DPPC), the major glycerophospholipid component of lung surfactant. Further substitutions at the headgroup nitrogen were also used to generate differences in headgroup size and polarity in the synthetic compounds. The surface activity of the ether-amide phospholipids was investigated in terms of adsorption to the air-water interface, together with studies of dynamic respreading after monolayer collapse and surface tension lowering in dynamically compressed spread films and dispersions. Results showed that several ether-amide phosphonolipids had more rapid adsorption and improved dynamic respreading behavior compared to DPPC, plus the ability to lower surface tension into the range of less than 1 to 4 mN/m in spread films and in dispersions under dynamic conditions. In combination with a series of diether phosphonolipids synthetized in a companion study [1], these ether-amide compounds are useful in the development of molecular structure-surface activity correlates for lung surfactant-related materials, and should assist in investigating the specificity of interactions between phospholipids and other pulmonary biological molecules.     

Biochemical adaptation of cardiac and skeletal muscle to physical activity.

1. Female Wistar rats were randomly assigned to control (C) or exercising (T) groups and subsequently portioned into 1, 3, 5 and 10 day T and C groups. The T groups completed a progressive endurance running program. Biochemical indices of adaptation were measured in cardiac muscle and in plantaris and soleus muscles of C and T animals after their last exercise bout. 2. In cardiac muscle, myofibrillar ATPase activity was significantly elevated in the 3T (0.241 +/- 0.031) and 5T (0.242 +/- 0.013) groups (P less than or equal to 0.05) compared to their respective controls (3C = 0.187 +/- 0.015 and 5C = 0.190 +/- 0.007). 3. After 10 days of training cardiac myofibrillar ATPase activity was elevated by 17% but this was not significant (P greater than or equal to 0.05). 4. No changes in myofibrillar ATPase activity were seen in skeletal muscle (P greater than or equal to 0.05), however, hexokinase activity progressively increased and was significantly elevated in the 3T, 5T and 10T soleus and plantaris muscles of rats over controls (P less than or equal to 0.05). 5. Minimal nonsignificant changes were noted in the hexokinase activity of the hearts of all T groups (P greater than or equal to 0.05). 6. These results indicate that metabolic adaptation of the heart and skeletal muscles takes place after as little as three training sessions. 7. Although the adaptation of the skeletal muscles continually progresses, the adaptation of the heart appears to be transitory.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lipid conjugates of antiretroviral agents. II. Disodium palmityl phosphonoformate: anti-HIV activity, physical properties, and interaction with plasma proteins

Disodium palmityl phosphonoformate, a novel lipid phosphoester of the anti HIV agent phosphonoformate (foscarnet), inhibits HIV replication in H9 cells and syncytia formation in MOLT-3 cells as effectively as foscarnet itself, as shown by dose-response data from assays for expression of p17 and p24 viral antigens and syncytia formation. Protein binding studies indicate that in serum, the derivative exists bound to albumin and the lipoproteins, and would therefore be likely to exhibit improved serum lifetime in vivo.     

Repression of the alpha-fetoprotein gene promoter by progesterone and chimeric receptors in the presence of hormones and antihormones.

Using transient transfection assays, we showed that repression of the alpha-fetoprotein promoter by intact and deletion mutants of the progesterone receptor and by chimeric progesterone/glucocorticoid-estrogen receptors in the presence of their cognate hormones was closely correlated with their ability to bind to a progesterone/glucocorticoid-responsive element. This negative regulation was also observed in the presence of antihormones, providing evidence that receptor-antihormone complexes can bind to their responsive elements in vivo.     

Physical properties of arabinofuranosylcytosine diphosphate diacylglycerol,an antitumor liponucleotide

Dispersed from a dry film into buffer (5 mM phosphate, 0.15 M NaCl, pH 7.4), the liponucleotide 1-β-d-arabinofuranosylcytosine 5′-diphosphate l-1,2-diacylglycerol (ara-CDPdiacylglycerol) spontaneously forms vesicles which are several microns in diameter and probably unilamellar. Their average size immediately begins to decrease, and after 2 h none can be seen in the light microscope. During 1–2 days in unstirred solutions at 25°C, the vesicles are transformed to spherical or nearly spherical micelles having an apparent partial specific volume of 0.835 ml·g^?1, a maximum possible aggregation number of about 150, and an anhydrous radius of about 37 Å. The critical micelle concentration (CMC) is about 10 μM in buffer and 20 μM in distilled water, but micelle-monomer equilibration requires at least 1 week at a total concentration of 66 μM. This exceedingly slow equilibration is unique among reported detergents. The standard enthalpy and entropy of micellization are ?13 kJ·mol^?1 and 87 J·mol^?1·K^?1, respectively. These values are within the range reported for other detergents. Sonication accelerates the vesicle-micelle transformation to 30 min.