Domain exchanges between KNAT3 and KNAT1 suggest specificity of the kn1-like homeodomains requires sequences outside of the third helix and N-terminal arm of the homeodomain

Domain exchange constructs that traded regions surrounding the homeodomain were constructed for two kn1 -like genes, KNAT1 and KNAT3, and introduced into Arabidopsis thaliana under the control of the 35S CaMV promoter. The kn1-like homeodomain proteins all have the homeodomain located near the C-terminus of the protein, and also share a second conserved domain (the ELK domain) immediately N-terminal to the homeodomain. Progeny were scored for the appearance of the KNAT1 overexpression phenotype. A construct containing the KNAT3 N-terminus and the KNAT1 ELK- and homeodomain resulted in a KNAT1 overexpression phenotype, indicating that specificity mainly resides within the ELK- and homeodomain region. Further exchanges demonstrated that specificity probably does not arise from a single region within the ELK and/or homeodomain but rather requires sequences both N-terminal and C-terminal to residue 23 of the homeodomain. Further, in contrast to some animal homeodomains, KNAT1 does not utilize the residues of the N-terminal arm of the homeodomain for specificity.     

Mapping of a Gene for Long QT Syndrome to Chromosome 4q25-27

Long QT syndrome (LQTS) is a heterogeneous inherited disorder causing syncope and sudden death from ventricular arrhythmias. A first locus for this disorder was mapped to chromosome 11p15.5. However, locus heterogeneity has been demonstrated in several families, and two other loci have recently been located on chromosomes 7q35-36 and 3p21-24. We used linkage analysis to map the locus in a 65-member family in which LQTS was associated with more marked sinus bradycardia than usual, leading to sinus node dysfunction. Linkage to chromosome 11p15.5, 7q35-36, or 3p21-24 was excluded. Positive linkage was obtained for markers located on chromosome 4q25-27. A maximal LOD score of 7.05 was found for marker D4S402. The identification of a fourth locus for LQTS confirms its genetic heterogeneity. Locus 4q25-27 is associated with a peculiar phenotype within the LQTS entity.     

Ecomorphological correlates in ten species of subtropical seagrass fishes: diet and microhabitat utilization

Synopsis Ecomorphological correlates were sought among ten species of distantly related subtropical seagrass fishes. Morphometric data associated with feeding and microhabitat utilization were compared by principal components analysis, cluster analysis, and canonical correspondence analysis to dietary data. Morphology was generally a poor predictor of diet except for a group of mid-water planktotrophic filter feeders. Separation of the species along morphological axes appears to be related more to microhabitat utilization resulting in three major groups: (1) a group of planktotrophic, mid-water fishes specialized for cruising and seeking out evasive prey characterized by a compressed fusiform body, forked caudal fin, long, closely spaced gill rakers, short to intermediate! length pectoral fin, pointed pectoral fin, large lateral eye, short head, and a terminal or subterminal mouth; (2) slow swimming, less maneuverable epibenthic fishes that pick or suck their prey off the substrate. They are united by more rounded caudal and pectoral fins, and short or no gill rakers; and (3) a group of more mobile and maneuverable epibenthic foragers characterized by a more compressed, sub-gibbose body, long, pointed pectoral fins, forked caudal fins, large lateral eyes, subterminal mouth, and greater jaw protrusibility. Cases of convergence in trophic and microhabitat utilization characters were apparent in some of the groups.     

Somatostatin analogues containing o-aminomethylphenylacetic acid as a bridge unit

Summary A new cis-peptide bond mimetic, -benzyl-o-aminomethylphenylacetic acid, was synthesized and incorporated in a homodetic somatostatin analogue. Biological binding tests and 2D NMR conformational analysis indicate that the configuration of the bridge-unit asymmetric center and the orientation of the benzyl side chain play a key role in the biological activity of this type of somatostatin analogues.     

Leukotriene B4 binding to human neutrophils

[³H] Leukotriene B₄ (LTB₄) binds concentration dependency to intact human polymorophonuclear leukocytes (PMN's). The binding is saturable, reaches equilibrium in 10 min at 4°C, and is readily reversible. Mathematical modeling analysis reveals biphasic binding of [³H] LTB₄ indicating two discrete populations of binding sites. The high affinity binding sites have a dissociation constant of 0.46 × 10⁻⁹M and B_max of 1.96 × 10⁴ sites per neutrophil; the low affinity binding sites have a dissociation constant of 541 × 10⁻⁹M and a B_max of 45.6 × 10⁴ sites per neutrophil. Competitive binding experiments with structural analogues of LTB₄ demonstrate that the interaction between LTB₄ and the binding site is stereospecific, and correlates with the relative biological activity of the analogs. At 25°C[³H] LTB₄ is rapidly dissociated from the binding site and metabolized to 20-OH and 20-COOH-LTB₄. Purification of neutrophils in the presence of 5-lipoxygenase inhibitors significantly increases specific [³H] LTB₄ binding, suggesting that LTB₄ is biosynthesized during the purification procedure. These data suggest that stereospecific binding and metabolism of LTB₄ in neutrophils are tightly coupled processes.     

The effect of membrane preparation and cellular maturation on human erythrocyte adenylate cyclase

We found that adenylate cyclase activity of human erythrocytes is potentially labile during isolation of their plasmalemma. Addition of 1 mM EGTA to solution used to remove hemoglobin from lysed cells protected activity. Human erythrocyte adenylate cyclase is minimally activated by catecholamines, in the absence or presence of exogenous guanyl nucleotide, but substantially by 5′-guanylyl imidodiphosphate or sodium fluoride and concentration-dependently by Mg²⁺ or Mn²⁺. Basal catalytic activity is an age-dependent component of the human erythrocyte; 5′-guanylyl imidodiphosphate- or fluoride-activated activities decline with cellular maturation proportionally to the decrease in basal activity.