NEIL3-Dependent Regulation of Cardiac Fibroblast Proliferation Prevents Myocardial Rupture

1. Download high-res image (135KB)
2. Download full-size image

     

Periodic breathing in the crocodile, Crocodylus niloticus: consequences for the gas exchange ratio and control of breathing.

The ventilatory pattern in the Nile crocodile consists of episodes of breathing, interrupted by periods of breath-holding, the latter occupying 80% of total time during normal breathing at 25 degrees C. End-tidal gas composition varied with the periodic breathing but PO2 was always high (PO2 less than 110 torr) and PCO2 low (PCO2 less than 25 torr). The alveolar gas exchange ratio, RE, was very low during the non-ventilatory periods (RE congruent to 0.5), but increased markedly during ventilation. Breathing of hypoxic and hpercapnic gases caused a pronounced decrease in the duration of breath-holds. Hypercapnia decreased breathing frequency during ventilatory periods, but increased tidal volume. The results are discussed in relation to the practice of prolonged breath-holding associated with diving in crocodiles.     

Die Vogelfauna Westsibiriens

Ohne Zusammenfassung     

Die Vogelfauna Westsibiriens

Ohne Zusammenfassung10. Fortsetzung: J. f. Orn. 101, p. 472–495.     

Designing synthetic superagonists of C3a anaphylatoxin

An extensive structure-activity study of synthetic analogues of the C3a anaphylatoxin was conducted. Our goal was to map C3a-C3a receptor interactions by designing synthetic analogue molecules having maximal biologic potency. Nonspecific binding of the polycationic C3a to polyanionic molecules on cellular surfaces often obscures specific binding to the receptor. Less cationic synthetic C3a analogues would be useful tools in identifying and characterizing the various cell types having C3a receptors. These factors should also be useful as pharmacologic probes for mechanism studies, as high-affinity ligands for target cell identification, and for receptor isolation. Attachment of amino-terminal hydrophobic groups such as Fmoc to C3a analogues [as orginally introduced by Gerardy-Schahn et al. (1988) Biochem. J. 255, 209] markedly enhanced the potency of synthetic C3a peptides. The enhancement effect on potency from introducing hydrophobic groups to C3a analogues was interpreted as possibly being nonspecific. Our systematic search for an optimal peptide length, composition, and N-terminal hydrophobic unit resulted in several superpotent C3a analogues having 200-1500% the potency of natural C3a. One particularly potent C3a peptide was designed by incorporating two tryptophanyl residues at the N-terminal end of a 15-residue C3a analogue. The superpotent peptide W-W-G-K-K-Y-R-A-S-K-L-G-L-A-R has several residues differing (underlined) from the sequence corresponding to positions 63-77 in human C3a, a region that contains the essential functional site of the molecule. This 15-residue model peptide exhibited the greatest biological potency of all peptides tested, being 12-15 times more active than natural C3a. Since an optimal distance was found to exist between the N-terminal hydrophobic unit (W-W) and the C-terminal primary binding site (LGLAR), we concluded that the hydrophobic unit interacts specifically with a secondary binding site on the C3a receptor. The presence of both a primary (effector) and secondary (hydrophobic) binding site on these linear synthetic ligands, which can interact cooperatively with the C3a receptor, presumably accounts for the high relative potency of the analogues. Our design of superpotent analogues of C3a demonstrates the feasibility for constructing small synthetic peptides to mimic natural biologic factors that depend on secondary or tertiary structure for their activity. These synthetic peptide studies demonstrate that a linear array of amino acids (e.g., W-W) can successfully substitute for a conformation-dependent binding site on a bioactive factor.     

PCR-based identification of individuals of Schistosoma japonicum representing different subpopulations using a genetic marker in mitochondrial DNA.

A mitochondrial NADH dehydrogenase I gene fragment (NDI) was sequenced for three laboratory maintained isolates of Schistosoma japonicum. Comparison of sequences representing the isolates (originally obtained from the Anhui and Zhejiang provinces of the People's Republic of China, and from the Philippines) revealed inter-isolate sequence variations of 0.2-0.6% and no intra-isolate variation was found. The sequences also indicated that while the amplification products of the Zhejiang and Philippine isolates contained a recognition site for the endonuclease RsaI, there was no such site in the Anhui isolate. This was tested by digesting amplification products from a number of individual worms with RsaI. Then an infection experiment was designed to test the value of this genetic marker for studies of the population biology of S. japonicum in the final host. For this, the two Chinese isolates were used. Three groups of mice (A-C) were exposed firstly to a primary infection and then challenge-infected at weeks 4 and 7 of the experiment. In group A the first infection was done with the Anhui isolate, and the two others with the Zhejiang isolate, thereby providing a specific, detectable cohort. In groups B and C the Anhui isolate was used for the second and third infection. All mice were perfused 5 weeks after the last challenge infection, and the NDI was subsequently amplified from DNA of the perfused worms and digested with RsaI. The digestion revealed that while infection groups A and B contained mixed populations of the Anhui and Zhejiang isolates, only Zhejiang worms were present in group C. We concluded that the absence/presence of the RsaI site in the NDI provides a useful marker for the delineation of cohorts of S. japonicum.     

Tryptophan Hydroxylase Is Phosphorylated by Protein Kinase A

Abstract: The effect of protein kinase A on the catalytic activity and phosphorylation of brain tryptophan hydroxylase was examined. Stimulation of endogenous protein kinase A by cyclic AMP or its analogues, dibutyryl-cyclic AMP and 8-thiomethyl-cyclic AMP, failed to activate tryptophan hydroxylase. The activation of tryptophan hydroxylase by calcium/calmodulin-phosphorylating conditions was not modified by cyclic AMP. Endogenous protein kinase A phosphorylated a large number of proteins and tryptophan hydroxylase could be identified as one substrate by sucrose gradient centrifugation, immunoprecipitation, and immunoblotting. These results indicate that tryptophan hydroxylase is phosphorylated by protein kinase A in brain and question whether this protein kinase exerts direct regulatory influence over tryptophan hydroxylase activity via phosphorylation.