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.

Studies on Ca2+-Mg2+ binding sites of frog skeletal muscle myosin

From skeletal muscle myosin light chains readily dissociate from the myosin oligomer in the absence of divalent cations, and unlike rabbit skeletal muscle myosin light chains, the released light chains of frog skeletal muscle myosin have a high Ca2+ binding affinity. Whereas each Ca2+ binding light chain of frog skeletal muscle myosin, when in association with the heavy chains bound 1 mol of Ca2+, when in the dissociated state bound 0.5 mol of Ca2+; the latter were readily displaced with low Mg2+ concentrations. Whereas 10(-5) M Mg2+ displaced all of the Ca2+ binding sites on the released light chains at Ca2+ concentration ranges of 10(-7) to 10(-4) M, there was negligible displacement of the Ca2+ binding sites with native frog skeletal muscle myosin under these same conditions.

Indomethacin fails to alter basal or phenothiazine-induced prolactin concentrations in man

In order to evaluate the possible role of prostaglandins in pituitary prolactin (PRL) secretion, PRL was serially measured following perphenazine (Trilafon) ingestion in 8 men before and after 5 days of indomethacin administration. Since estrogens have been shown to modulate prolactin secretion in man, serum steroids including estrone (E1), estradiol (E2), progesterone (P) and testosterone (T) were measured before and after indomethacin ingestion. Serum E1, P and T levels were similar during the pre- and post-indomethacin study periods: 56 +/- 4 (1 SEM) vs 48 +/- 5 pg/ml, 298 +/- 28 vs 315 +/- 32 pg/ml, and 8.1 +/- 0.7 vs 8.6 +/- 0.7 ng/ml, respectively. Serum E2 levels were slightly, but significantly, lower following indomethacin treatment at 30 +/- 3 vs 37 +/- 3 pg/ml (p less than .01). Basal serum PRL concentrations were unaffected by indomethacin administration (9 +/- 3 pre- vs 8 +/- 2 ng/ml post-drug treatment). Integrated perphenazine-induced PRL responses were likewise similar during the 2 study periods: 101 +/- 16 ng . hr/ml during the control period and 104 +/- 14 ng . hr/ml following indomethacin. Thus, short-term indomethacin treatment had no effect on basal or perphenazine-stimulated PRL secretion in men.

Pattern of sealant retention in children receiving a combination of caries-preventive methods: three-year results

Sealant retention varied according to site of the tooth. Figures for intact sealant were particularly low for permanent first molars among first graders and for permanent second molars among sixth graders at the end of three years. Although a large percentage of these teeth needed sealant reapplications, the percentages of teeth that were lost to caries were as low as 12.2% and 12.8%, respectively. Deciduous molars had the best rate (60.9%) of complete retention and also the highest percentage (20.2%) of loss caused by caries. However, in sixth graders, the premolars had the highest percentage (46.7%) of complete retention and, at the same time, the lowest caries rate (5.6%). The sealant retention pattern has remained the same during the three-year period.

A combined approach to preventing dental caries in schoolchildren : caries reductions after 3 years

A combination of preventive methods have been used to reduce dental caries in children residing in a fluoridated area of Southeastern Michigan. These children had very low restorative treatment levels. The methods used include dental health education, prophylaxis, pit and fissure sealants, topical application of fluoride and restorative care. Prophylaxis, sealant and fluoride procedures were repeated every 6 months. Sealant was applied to all caries-free posterior teeth in the mouth. Three-year results show reduction of occlusal caries increments of nearly 73% for both 1st and 6th school grades. Although at baseline examination there was no statistically significant difference between the two groups in mean DMF teeth and surface scores, the difference in mean increments at the end of 3 years was statistically significant (P less than 0.01). Percent reductions in caries increment for permanent first molars in 1st graders were 65.6 for DMF teeth and 66.7 for DMF surfaces. Corresponding figures for permanent teeth among 6th graders were 71% and 58.3%.

Ocular penetration of hydrocortisone and dexamethasone into the aqueous humour after subconjunctival injection

The concentration of steroids in the aqueous humour was measured at various intervals after subconjunctival injection in a series of 130 patients of both sexes who came to cataract extraction. Both hydrocortisone acetate (0.5 ml of 2.5 per cent solution) and dexamethasone sodium phosphate (0.5 ml of 0.4 per cent solution) attained a peak concentration in the aqueous of 214.4 and 268.0 micrograms/ml respectively within 10 minutes. Dexamethasone was from 30 to 47 times more effective than hydrocortisone for up to 24 hrs, but the latter provided a reasonably high concentration for up to 7 days.

Sealant effectiveness for children receiving a combination of preventive methods in a fluoridated community: two-year results

A series of preventive methods in combination have been used to reduce dental caries in children including dental health education, prophylaxes, pit and fissure sealants, topical application of fluoride and restorative care. Prophylaxes, sealant, and fluoride procedures are repeated every six months. Two-year results show reductions of occlusal caries increments of 74.3% for first graders and 77.1% for sixth graders. Sealant loss, as defined in this study, varied from 33% to 90% with the highest loss occurring in the newly erupted permanent molars during the first six months of the project. These high sealant loss rates are thought to be related to the age of the population which was designed to include children at the ages of peak eruption of permanent molar teeth (ages six and twelve). These teeth were often only minimally erupted and maintaining the dry field required for sealant retention was extremely difficult. However, in spite of these high rates of sealant loss, caries reduction on occlusal surfaces was highly significant in comparision to that of children who did not receive sealants.

A phospholipid derivative of cytosine arabinoside and its conversion to phosphatidylinositol by animal tissue

We have synthesized an analog (ara-CDP-DL-dipalmitin) of cytidine diphosphate diglyceride (CDP-diglyceride) in which the antitumor drug, cytosine arabinoside, is substituted for the cytidine moiety. Enzymes in rat and human liver convert this analog to phosphatidylinositol, thereby releasing cytosine arabinoside-5'-monophosphate, an obligatory intermediate in the activation of cytosine arabinoside. Unlike cytidine diphosphate diglyceride, however, ara-CDP-DL-diapalmitin is not an efficient substrate for phosphatidylglycerophosphate synthesis in liver or phosphatidylserine in Escherichia coli. The antitumor activity of ara-CDP-DL-dipalmitin in mice bearing L5178Y leukemia is described.

The role of nerves in the production of cardiac arrest during surgical anaesthesia

The role of cardiac nerves in the production of cardiac arrest during surgical anaesthesia on coronary ligated hypoxic heart has been studied. When atropinished coronary ligated dogs were exposed to hypoxia the terminal event was a cardiac asystole in 88% of the dogs. In propranolol treated dogs, or in dogs where sympathetic ganglia upto T6 were bilaterally removed earlier, coronary ligation and hypoxia produced ventricular extrasystoles, ventricular tachycardia and repeated sinus arrest followed by ventricular fibrillation. The possibility of the origin of arrythmia from the damaged myocardium, and the presence of an intact vagus in the production of ventricular fibrillation has been discussed.

Nonenzymatic conversion of human hexosaminidase A

Incubation of purified hexosaminidase A with merthiolate, parahydroxymercuribenzoic acid, or silver ions resulted in the formation of an enzyme which was identical, in all respects tested, with hexosaminidase B. Its electrophoretic mobility was identical to hexasaminidase B at three different pH levels. Its chromatographic properties, thermostability, and immunologic reactivity with specific anti-hexosaminidase A and anti-hexosaminidase B antisera were indistinguishable from hexosaminidase B. Conversion could be prevented by GSH but was not reversed by GSH once it had occurred. Conversion of hexosaminidase A to hexosaminindase B was accompanied by the appearance of an electrophoretically rapid, catalytically inactive protein. Hexosaminidase B, itself, was unaltered by incubation with merthiolate. These findings support a previously proposed model of hexosaminidase structure in which hexosaminidase A is (alphabeta)3 and hexosamindase B is (betabeta)2. On treatment of hexosaminidase A with merthiolate and other converting agents alpha and beta subunits are presumably dissociated and they reassociate as (betabeta)3, that is, hexosaminidase B. The expected free or polymerized catalytically inactive, alpha chains are detected on acrylamide gel electrophoresis. We suggest that the catalytic site of human hexosaminidase may be present only on the beta subunit and that the alpha subunit influences the substrate specificity of the enzyme, particularly as directed toward GM2.