Normal cells of patients with high cancer risk syndromes lack transforming activity in the NIH/3T3 transfection assay

Oncogenes capable of transforming NIH/3T3 cells are often present in human tumors and tumor cell lines. Such oncogenes were not detected in normal fibroblast lines derived from patients with several clinical syndromes associated with greatly increased cancer risk. Thus, germ-line transmission of these oncogenes does not appear to be the predisposing factor responsible for these high cancer risk syndromes.

Cyclic AMP and its receptor protein are required for expression of transfer genes of conjugative plasmid F in Escherichia coli

A number of cya and crp mutants of Escherichia coli HfrH were analyzed for several Tra functions of the F plasmid. The mutants were observed to be deficient in conjugal donor ability, absorption of phages MS2 and Q beta and surface exclusion. These defects were suppressed in cya mutants grown with cAMP supplementation. A cAMP concentration of 3 X 10(-4) M produced maximal suppression of donor ability defect in a cya strain. cAMP did not suppress the Tra- phenotype of crp mutants. Latent periods of MS2 were shorter in cya and crp bacteria. Phage T7 development appeared similar in wild type, cya, and crp cells. It is concluded that tra genes of F plasmid are expressed only to a small extent in cya and crp mutants and that cAMP and its receptor protein are required for the normal expression of tra genes.

Labeling of platelet surface proteins with 125I by the iodogen method

A procedure for the 125I-iodination of platelet suspensions is described. The procedure utilizes Iodogen, a solid-phase oxidizing agent similar to chloramine-T. Platelets were labeled under a variety of conditions, including in the presence of 0.1% albumin, and showed between 7 and 28% incorporation of 125I. Best labeling results were obtained at low platelet concentrations (3-5 x 10(8) platelets/ml), short reaction times (15 min), and with 2-ml glass vials coated with 100 micrograms of Iodogen. Analysis of the labeled platelet proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by autoradiography revealed that the same major protein bands were labeled by this procedure as were labeled by the lactoperoxidase procedure. At low platelet concentrations, the Iodogen procedure gives twice the amount of iodine incorporation.

Conversion of a Ca2+-dependent myosin light chain kinase from skeletal muscle to a Ca2+-independent form

The Ca2+- and calmodulin-dependent myosin light chain kinase of rabbit skeletal muscle was converted to a Ca2+-independent form by limited proteolysis with alpha-chymotrypsin. The conditions prevailing during proteolysis are important and the loss of Ca2+-dependence was achieved best by hydrolysis of the Ca2+-calmodulin-kinase complex. The lack of Ca2+- and calmodulin-dependence was found using both myosin and isolated light chains as substrates. The specific activity of the Ca2+-independent form (Mr approximately 65,000) was similar to that of the native enzyme, i.e., 2 to 5 mumol phosphate transferred min-1 mg-1 kinase. The 65,000-dalton fragment was phosphorylated by the catalytic subunit of the cAMP-dependent protein kinase and approximately 0.8 moles phosphate were incorporated per fragment.

Mutagenesis of Alcaligenes eutrophus by insertion of the drug-resistance transposon Tn5

Drug-resistance element Tn5 coding for kanamycin resistance was used for mutagenesis of Alcaligenes eutrophus strain H16. The vehicle for introducing Tn5 into A. eutrophus was plasmid pJB4JI harboured by Escherichia coli. Kanamycin-resistant transconjugants occurred at a frequency of approximately 5 x 10(-8). One third of the transconjugants exhibited other plasmid-coded resistances such as gentamycin and spectinomycin. However, the latter markers were not stably maintained in the new host. Among the kanamycin-resistant transconjugants three classes of mutants were found: (i) Auxotrophic mutants occurred at a frequency of 0.8% and showed requirements for histidine, methionine, aspartate or isoleucine. Out of eleven auxotrophic mutants examined eight reverted to prototrophy. However, none of the revertants was kanamycin-sensitive. (ii) Mutants unable to grow with fructose as the carbon source occurred at a frequency of almost 10%. (iii) Mutants which had lost the ability to grow autotrophically with hydrogen and carbon dioxide were found at a frequency of 1%. Further analyses revealed that this class of mutants was either defective in carbon dioxide fixation or impaired in hydrogen metabolism.

Modification of the rapidly reacting thiols of atrial and ventricular myosins. Evidence for structural variances around the SH-1 thiol of the two isozymes

Environmental variances were noted around the rapidly reacting SH-1 thiol of ventricular versus atrial myosin, based on electron paramagnetic resonance studies. Further studies, in which either SH-1 or SH-1 + SH-2 thiols were modified with N-ethylmaleimide, indicated the importance of the SH-2 moiety of both isozymes for generation of tension, when analyzed as synthetic actomyosin threads. Comparative EPR studies showed that the spin label was more strongly immobilized when complexed to ventricular SH-1 thiol as compared to when it was complexed to atrial myosin. Likewise, addition of PPi, ATP or ADP created a greater mobility in the spin label when added to ventricular spin-labeled myosin as compared to that of atrial myosin. comparative studies of spin-labeled actomyosin versus myosin analyzed at different EPR power settings also demonstrated disparaties surrounding the SH-1 thiol between the two myosin isozymes.

Characterization of the beta-adrenoceptors in coronary vasculature of the dog heart

In the present study an attempt has been made to characterize the beta-adrenoceptors of coronary vasculature in dog. Blockade of beta 1-adrenoceptors with ICI 50172 or beta 2-adrenoceptors with RB2 showed only partial antagonism of isoprenaline-induced decrease in coronary resistance. However, combined treatment with ICI 50172 and RB2 completely blocked the isoprenaline-induced fall in coronary resistance. Essentially similar results were observed in controlled heart rate experiments where the drugs were administered locally into the coronary circulation. These results demonstrate the involvement of both beta 1 and beta 2 adrenoceptors in isoprenaline-induced coronary vasodilation.

Influence of myosin heavy chains on the Ca2+-binding properties of light chain, LC2

The association of myosin light chains with heavy chains, i.e. the intact oligomeric structure, profoundly affects the Ca(2+)-binding properties of the light chains. The Ca(2+)-binding affinity of the light chains is more than two magnitudes higher in the presence of heavy chains than in its absence. Modification of the reactive SH(2) thiol of myosin results in an alteration in the conformation of heavy chains of the molecule that influences the Ca(2+)-binding properties of light chains and generation of tension. When the SH(2) moiety is blocked with N-ethylmaleimide the influence of the heavy chains on the Ca(2+)-binding properties of light chain LC(2) is lost; under these conditions the Ca(2+)-binding affinity value of SH(2)-N-ethylmaleimide-blocked myosin (3.3x10(4)m(-1)) decreases to near that expressed with the dissociated light chain LC(2) (0.7x10(4)m(-1)). Conversely, the presence of actin, nucleotides or modification of either the reactive lysyl residue or SH(2) thiol does not affect Ca(2+) binding. The native secondary and tertiary structure of myosin seem to be required for Ca(2+) binding; binding does not occur in the presence of 6m-urea with either native myosin or the dissociated light chains. With SH(2)-N-ethylmaleimide-blocked myosin normal Ca(2+)- and (Mg(2+)+actin)-stimulated ATPase activities are expressed; however, there is a loss in K(+)-stimulated ATPase activity and the synthetic actomyosin threads of such myosin express no isometric tension. There are also variances in the binding of Ca(2+) with alterations in pH values. In the absence of Ca(2+)/EGTA buffer the biphasic Ca(2+)-binding affinity of myosin is twice as high at pH7.4 (site one: 1.2x10(6)m(-1) and site two: 0.4x10(6)m(-1)) as compared with values obtained at pH6.5 (site one: 0.64x10(6)m(-1) and site two: 0.2x10(6)m(-1)). The Ca(2+)-binding affinity of light chain LC(2) and S(1), where the (S-1)-(S-2) junction was absent, were not influenced by changes in pH values. Both expressed a low Ca(2+)-binding affinity, approx. 0.7x10(4)m(-1), whereas heavy meromyosin, where both (S-1) and (S-2) myosin subfragments were present, expressed a Ca(2+)-binding affinity value similar to that of native myosin, but was not biphasic. However, it is important to point out than in preparation of S(1) myosin subfragment light chain LC(2) was lost and thus was added back to the purified S(1) fraction. Light chain LC(2) was not, however, added to the heavy meromyosin fraction because it was not lost during preparation of the heavy meromyosin subfragment. In conclusion, it appears that the (S-1)-(S-2) junction is needed for the positioning of light chain LC(2) and thus influences its essential conformation for Ca(2+) binding.

Dissociation and reassociation of rabbit skeletal muscle myosin

Whereas dissociation of rabbit skeletal muscle myosin light chains occurs at an increased temperature (25 degrees) and in the absence of divalent cations, reassociation of the myosin oligomer requires a low temperature (4 degrees C) and the presence of divalent cations, thus resulting in the original light to heavy chain stoichiometry. With a 5-10 per cent release of alkali light chains, LC1 and LC3, and a 50 per cent dissociation of the Ca2+ binding light chain, LC2, there is no significant decrease in myosin ATPase activity irrespective of the cation activator, however, there is an approximate 15-20 per cent decrease in actomyosin ATPase activity. With reassociation of the myosin oligomer, actomyosin ATPase activity is partially restored as well as the original number of Ca2+ binding sites.

Effectiveness of combined preventive methods on erupting teeth in children in a fluoridated community

Several preventive methods were used in combination to reduce dental caries in children residing in a fluoridated area. The method included dental health education, prophylaxis, pit and fissure sealants, topical fluoride and restorative care. Prophylaxis, sealant and fluoride procedures were repeated every 6 months. Sealant was applied to all fully erupted caries free posterior teeth in the mouth. This report compares results obtained for teeth that erupted after the study began with those teeth that were already present at the time treatment procedures were applied. Percent reductions in caries increment for newly erupted teeth at the end of 3 years for treated 6th graders was 77.5% in DMFT and 79.2% DMFS as compared to 71% and 58.3% for previously erupted teeth. Results for children in 1st grade did not how such beneficial results. Permanent first molars in younger children appear to be highly susceptible to caries. Sealant retention for newly erupted teeth follows the same pattern as for teeth previously erupted.