Mating system ofTokunagayusurika akamusi (Diptera: Chironomidae): I. Copulation in the air by swarming and on the ground by searching

Observations on the mating system of the midge,Tokunagayusurika akamusi, revealed mating to occur both in the air by swarming and on the ground by searching. At the shores of Lake Biwa, midges appeared from November to early December. Newly emerged adults arrived at the resting place, lakeside vegetation, in the morning, during which time a number of males also walked about in search of mates. Many copulating pairs were observed at the resting place. Huge swarms occurred chiefly before sunset but the frequency of copulation observed in the swarm was extremely low. It is likely that, in the Lake Biwa population, the proportion of females inseminated by searching males at the resting place was much larger than that by swarming males in the air. Furthermore, by searching, males copulated with younger females than by swarming. The differences between the searching and swarming tactics are discussed.     

Phosphorylation of smooth muscle heavy meromyosin by calcium-activated, phospholipid-dependent protein kinase. The effect on actin-activated MgATPase activity

Smooth muscle heavy meromyosin (HMM) can serve as a substrate for the Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C) as well as for the Ca2+/calmodulin-dependent kinase, myosin light chain kinase. When turkey gizzard HMM is incubated with protein kinase C, 1.7-2.2 mol of phosphate are incorporated per mol of HMM, all of it into the 20,000-Da light chain of HMM. Two-dimensional peptide mapping following tryptic hydrolysis revealed that protein kinase C phosphorylated a different site on the 20,000-Da HMM light chain than did myosin light chain kinase. Moreover, sequential phosphorylation of HMM by myosin light chain kinase and protein kinase C resulted in the incorporation of 4 mol of phosphate/mol of HMM, i.e. 2 mol of phosphate into each 20,000-Da light chain. When unphosphorylated HMM was phosphorylated by myosin light chain kinase, its actin-activated MgATPase activity increased from 4 nmol to 156 nmol of phosphate released/mg of HMM/min. Subsequent phosphorylation of this phosphorylated HMM by protein kinase C decreased the actin-activated MgATPase activity of HMM to 75 nmol of phosphate released/mg of HMM/min.     

Complex effects of inhibitors on cyclic GMP-stimulated cyclic nucleotide phosphodiesterase

We have investigated the effects of several phosphodiesterase inhibitors on the activity of a cGMP-stimulated cyclic nucleotide phosphodiesterase purified from calf liver supernatant. Theophylline, RO 20-1724, and MY 5445 were not effective inhibitors. With 0.5 microM [3H]cGMP as substrate or with 0.5 microM [3H]cAMP in the presence of 1 microM cGMP, activity was inhibited by papaverine, dipyridamole, isobutylmethylxanthine (IBMX), and cilostamide. With 0.5 microM [3H]cAMP as substrate, however, only cilostamide was inhibitory; papaverine, dipyridamole, and IBMX increased activity. The increase was dependent on both drug and substrate concentration with maximal stimulation (150-180%) at concentrations of cAMP between 0.5 and 2.5 microM. At higher cAMP concentrations, the three drugs were inhibitory; inhibition was maximal at approximately 40 microM and decreased at higher cAMP concentrations. Inhibition of cGMP hydrolysis was maximal at approximately 3 microM and decreased at higher concentrations. Papaverine, IBMX, dipyridamole, and cilostamide inhibited [3H] cGMP hydrolysis competitively with Ki values of 3, 6.5, 7, and 11.5 microM, respectively. Papaverine, IBMX, or dipyridamole reduced the Hill coefficient for cAMP hydrolysis from 1.8 to 1.1-1.2, and Lineweaver-Burk plots were linear or nearly linear. With cilostamide, however, Lineweaver-Burk plots remained curvilinear. Thus, three competitive inhibitors, papaverine, dipyridamole, and IBMX, can mimic substrate and effect allosteric transitions that increase catalytic activity, whereas another, cilostamide, apparently cannot. Differences in the actions of these inhibitors presumably reflect differences in the molecular requirements for effective interaction at catalytic and allosteric sites on phosphodiesterase, i.e. differences in the structure of these sites.     

Isolation and characterization of a calcium-binding protein derived from mRNA termed p9Ka, pEL-98, 18A2, or 42A by the newly synthesized vasorelaxant W-66 affinity chromatography.

W-66 (N-(2-aminoethyl)-N-[2-(4-chlorocinnamylamino) ethyl]-5-isoquinolinesulfonamide), a newly synthesized isoquinolinesulfonamide, was shown to have a potent vasodilatory action and calmodulin (CaM)-antagonizing action. Using the W-66 affinity chromatographic technique, we purified two Ca(2+)-binding proteins from the EGTA-soluble fraction of bovine aorta. One was CaM and the other was an acidic protein with a molecular mass of 11 kDa. It was tentatively named "calvasculin." Calvasculin was a dimeric protein. Equilibrium dialysis showed that 1 mol of calvasculin (dimer) bound to 1.98 +/- 0.30 mol of Ca2+ in the presence of 10(-3) M Ca2+. Calvasculin failed to activate Ca2+/CaM-dependent enzymes such as myosin light chain kinase, Ca2+/CaM-dependent phosphodiesterase, or Ca2+/CaM-dependent protein kinase II and to inhibit the CaM stimulation of these enzymes. The partial amino acid sequence of calvasculin revealed a high homology to the predicted protein derived from mRNA, named pEL-98, 18A2, 42A, or p9Ka. We also examined the physicochemical and biochemical properties of calvasculin. Using the antibody specific for calvasculin, we obtained evidence that calvasculin is present in abundance in bovine aorta but not in brain, lung, heart, or testis.     

Characterization of a calcium/calmodulin-dependent protein kinase homolog from maize roots showing light-regulated gravitropism

Roots of many species respond to gravity (gravitropism) and grow downward only if illuminated. This light-regulated root gravitropism is phytochrome-dependent, mediated by calcium, and inhibited by KN-93, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMK II). A cDNA encoding MCK1, a maize homolog of mammalian CaMK, has been isolated from roots of maize (Zea mays L.). The MCK1 gene is expressed in root tips, the site of perception for both light and gravity. Using the [³⁵S]CaM gel-overlay assay we showed that calmodulin-binding activity of the MCK1 is abolished by 50 M KN-93, but binding is not affected by 5 M KN-93, paralleling physiological findings that light-regulated root gravitropism is inhibited by 50 M KN-93, but not by 5 M KN-93. KN-93 inhibits light-regulated gravitropism by interrupting transduction of the light signal, not light perception, suggesting that MCK1 may play a role in transducing light. This is the first report suggesting a physiological function for a CaMK homolog in light signal transduction.Abbreviations CaM calmodulin - CaMK (II) Ca²⁺/calmodulin-dependent protein kinase (II) - CBP CaM-binding protein - CDPK Ca²⁺-dependent protein kinase - MCK1 maize homolog of mamalian CaMK This work is supported by the National Aeronautics and Space Administration grant No: NAGW 238.     

Immunocytochemical detection of Ca2+-dependent subspecies of protein kinase C in mouse embryos before and during compaction

Summary To confirm the possibility that protein kinase C is involved in compaction of mouse embryos, the presence and distribution pattern of Ca²⁺-dependent subspecies of this enzyme in mouse embryos, before and during compaction, were examined immunocytochemically with three different monoclonal antibodies. These were MC-1a, MC-2a and MC-3a, which selectively interact with the subspecies of the enzyme known as types I, II and III, respectively. Only when embryos were incubated with MC-3a, was immunofluorescence clearly detected in all cells of embryos before and during compaction. This result demonstrates the presence of type III protein kinase C in embryos before and during compaction and suggests the possibility that the type III enzyme may be involved in compaction. No marked differences were found in the distribution pattern of the type III enzyme between embryos examined before and during compaction.