Similarities in Structure and Expression between Mouse P-Cadherin,Chicken B-Cadherin and Frog XB/U-Cadherin

By immunological methods, we show that the monoclonal antibody 6D5 which reacts specifically with Xenopus laevis XB/U-cadherin, also binds to mouse P-cadherin and to chicken B-cadherin but not to the respective E-cadherins (L-CAM) or other “classical” cadherins in these species. In the first extracellular domain, three amino acid residues are identified that are shared by frog XB/U-cadherin, chicken B-cadherin and mammalian P-cadherins but not by the other “classical” cadherins. With few exceptions, the other cadherins possess residues at these positions that are also characteristic of each type of cadherin. Moreover, the expression patterns of P-, B-, and XB/U-cadherin in mouse, chicken and frog are more similar to each other than they are to those of the E-cadherins, L-CAM or other classical cadherins. Taken together, our results suggest that mammalian P-cadherins, chicken B-cadherin and frog XB/U-cadherin are closely related, if not homologous, molecules. A number of differences in the expression patterns between P-, B-, and XB/U-cadherin indicate that these molecules assume differential morphogenetic roles in different species.     

A possible role of cyclic 3′,5′-adenosine monophosphate in the germination of Cicer arietinum seeds

Changes in the activities of adenyl cyclase, cyclic AMP phosphodiesterase, protein phosphokinase, RNase, protease, DNA, RNA and protein synthesis during the initial imbibition phase of the germination cycle of Cicer arietinum (chick pea, Bengal gram) are reported. Activation of adenyl cyclase and phosphorylation of cellular proteins appears to precede RNA and protein synthesis in the imbibed seeds.     

Endogenous substrates for cyclic AMP-dependent and calcium-dependent protein phosphorylation in rabbit peritoneal neutrophils

As in other cells, cAMP-dependent (protein kinase A) and calcium-dependent protein kinases are present in the rabbit peritoneal neutrophil. The major substrates for protein kinase A in the cytosol of rabbit peritoneal neutrophil is a 43 kDa protein which appears to be actin (pI 5.7). The other substrates for protein kinase A in the cytosol are very acidic proteins with molecular weights of 135 000 (pI 4.6) and 130 000 (pI 4.8). Two classes of calcium-dependent protein kinases are present in the rabbit peritoneal neutrophil: one is calcium, calmodulin-dependent, the other is calcium, phosphatidylserine-dependent. Phosphatidylserine appears to be much more effective than calmodulin in stimulting calcium-dependent protein kinase activity. The phospolipid-sensitive, calcium-dependent protein kinase (protein kinase C), present only in the cytosol fraction, exhibits much higher activity than the cAMP-dependent protein kinase from the same source. At least four substrates (M_r 130 000 (pI 4.6) 43 000 (pI 4.8), 41 000 (pI 6.3) and 34 000) of the protein kinase C in the cytosol were identified. Trifluoperazine, a compound which inhibits the degranulation, aggregation and stimulated oxygen consumption of rabbit peritoneal neutrophils. (Alobaidi, T., Naccache, P.H. and Sha'afi, R.I. (1981) Biochim. Biophys. Acta 675, 316–321), also inhibits the activity of protein kinase C. The possible role of cAMP-dependent and calcium-dependent phosphorylation system in neutrophil function is discussed.     

Studies of exposure of rabbits to electromagnetic pulsed fields

Dutch rabbits were acutely exposed to electromagnetic pulsed (EMP) fields (pulse duration 0.4μs, field strengths of 1–2 kV/cm and pulse repetition rates in the range of 10 to 38 Hz) for periods of up to two hours. The dependent variables investigated were pentobarbital-induced sleeping time and serum chemistry (including serum triglycerides, creatine phosphokinase (CPK) isoenzymes, and sodium and potassium). Core temperature measured immediately pre-exposure and postexposure revealed no exposure-related alterations. Over the range of field strengths and pulse durations investigated no consistent, statistically significant alterations were found in the end-points investigated.     

Expression of three members of the calcium-dependent protein kinase gene family in Arabidopsis thaliana

Calcium-dependent protein kinases (CDPKs) belong to a unique family of enzymes containing a single polypeptide chain with a kinase domain at the amino terminus and a putative calcium-binding EF hands structure at the carboxyl terminus. From Arabidopsis thaliana, we have cloned three distinct cDNA sequences encoding CDPKs, which were designated as atcdpk6, atcdpk9 and atcdpk19. The full-length cDNA sequences for atcdpk6, atcdpk9 and atcdpk19 encode proteins with a molecular weight of 59343, 55376 and 59947, respectively. Recombinant atCDPK6 and atCDPK9 proteins were fully active as kinases whose activities were induced by Ca²⁺. Biochemical studies suggested the presence of an autoinhibitory domain in the junction between the kinase domain and the EF hands structure. Serial deletion of the four EF hands of atCDPK6 demonstrated that the integrity of the four EF hands was crucial to the Ca²⁺ response. All the three atcdpk genes were ubiquitously expressed in the plant as demonstrated by RNA gel blot experiments. Comparison of the genomic sequences suggested that the three cdpk genes have evolved differently. Using antibodies against atCDPK6 and atCDPK9 for immunohistochemical experiments, CDPKs were found to be expressed in specific cell types in a temporally and developmentally regulated manner.