Ultrastructural localization of alkaline phosphatase in the hypertrophic chondrocyte of the frog

Summary The ultrastructural localization of alkaline phosphatase was studied in the hypertrophic chondrocyte of the frog (Rana temporaria) by incubating sections of glutaraldehyde fixed tissue in a medium containing sodium glycerophosphate and calcium chloride. Control specimens were incubated in substrate free medium.Alkaline phosphatase (orthophosphoric monoester phosphohydrolase) is a hight molecular weight glycoprotein that hydrolyses phosphorylated metabolites much as acid phosphatase does except that its action is optimal at an alkaline pH.The results of this investigation showed that alkaline phosphatase activity was present within the cytoplasm and around the plasma membrane of frog hypertrophic chondrocytes. Although only a small proportion of frog hypertrophic chondrocytes demonstrated enzyme activity, there was evidence that this was concentrated within Golgi lamellae and vesicles leaving other organelles unreactive. The finding of alkaline phosphatase activity within Golgi lamellae of hypertrophic chondrocytes is regarded as unusual although positive reactions within chondrocyte lysosomes have previously been reported (Doty and Schofield, 1976).     

Responsiveness of the lamb ductus arteriosus to prostaglandins and their metabolites

The relative potencies of the prostaglandins A₁, A₂, E₁, E₂, F_2α and their 15-keto-, 15-keto-13,14-dihydro-, and 13,14-dihydro-metabolites were investigated on isolated lamb ductus arteriosus preparations contracted by exposure to elevated PO₂. All the prostaglandins (except PGF_2α and its 15-keto-metabolites) relaxed the tissue. However, only PGE₁, E₂, and their 13,14-dihydro-metabolites, were effective at concentrations below 10⁻⁸ M. Therefore, events that alter metabolism of circulating PGs in the perinatal period may have significant effects on the relative patency or closure of the ductus arteriosus.     

Increased Spontaneous Mitotic Segregation in Mms-Sensitive Mutants of SACCHAROMYCES CEREVISIAE

Methyl methanesulfonate (MMS)-sensitive mutants of Saccharomyces cerevisiae belonging to four different complementation groups, when homozygous, increase the rate of spontaneous mitotic segregation to canavanine resistance from heterozygous sensitive (canr/+) diploids by 13-to 170-fold. The mms8-1 mutant is MMS and X-ray sensitive and increases the rate of spontaneous mitotic segregation 170-fold. The mms9-1 and mms13-1 mutants are sensitive to X rays and UV, respectively, in addition of MMS, and increase the rate of spontaneous mitotic segregation by 13-fold and 85-fold, respectively. The mutant mms21-1 is sensitive to MMS, X rays and UV and increases the rate of spontaneous mitotic segregation 23-fold.     

Fixation and distribution of 14C in Populus deltoides during dormancy induction

Photosynthetically fixed ¹⁴C was analyzed in various chemical fractions from leaves and stems of cottonwood (Populus deltoides Bartr. ex. Marsh.) during dormancy induction. Dormancy was induced by 8-h photoperiods and 20/14°C temperature regimes. Within 4 weeks under short days, terminal buds were set and leaf expansion and stem elongation had stopped. ¹⁴C₂ was fed to a leaf at Leaf Plastochron Index 7 for 30 min. Either after this 30 min feeding period or after a 48-h translocation period the plants were sampled, freeze-dried, extracted and analyzed for¹⁴C. ¹⁴C-fixation decreased during dormancy induction from 60% to 17% of the 3.7 MBq ¹⁴C applied at 0 week and 8 weeks, respectively. Percentage distribution of ¹⁴C in chemical fractions of source leaves reflected leaf age and translocation inhibition. In rapidly growing plants, considerable ¹⁴C was incorporated into leaf protein while most of the soluble¹⁴C-sugars were either metabolized or translocated out of the leaf. After terminal bud set, the percentage of ¹⁴C in the protein and residue fractions decreased rapidly and that in the sugar fraction increased. Percent distribution in stems closely reflected changing metabolic pathways of carbon flow as influenced by dormancy induction. For example, the ¹⁴C in structural carbohydrates decreased in 5 weeks under short days from 65 to less than 10% of the ¹⁴C recovered in the chemical fractions, thus indicating cambium inhibition. At the same time the percentage of ¹⁴C in starch and sugar increased indicating storage. Short term (after 30 min) incorporation of ¹⁴C into the protein and starch fractions of leaves changed relatively little throughout the 8-week induction period. In contrast the turnover rates of these fractions (¹⁴C present after 48 h) increased considerably after active growth of the whole plant stopped.     

Steady state osmotic adaptation inUlva lactuca

The effects of hyper- and hypo-saline stresses on the levels of various inorganic and organic solutes inUlva lactuca have been recorded. Hypoosmotic stress decreased the tissue concentration of K⁺, Na⁺ and Cl^- while hyper-osmotic stress caused a transient increase in Na⁺ and a stable accumulation of K⁺ and Cl^-. The tissue content of -dimethylsulphoniopropionate (-dimethylpropiothetin) responded to changes in salinity. The time course of hypersaline stress showed the -dimethylsulophoniopropionate concentration rose as the Na⁺ level fell. The levels of free sugars and amino acids, including proline, were relatively low in this alga and did not appear to be important in osmotic adjustment. The possibility that tertiary sulphonium dipolar ions have an analogous role in some algae to glycinebetaine and possibly other quaternary nitrogen compounds in higher plants as cytoplasmic osmotica is discussed briefly.Abbreviations DMSP -dimenthylsulphomiopropionate - AFT apparent free space - TLE thin layer electrophoresis - NPS ninhydrin positive substances - TLC thin layer chromatography     

Influence of free fatty acid anion on the binding of warfarin to cytoplasmic proteins from rat liver

In vitro binding studies have shown that warfarin binds strongly to both ligandins (Y) and Z protein obtained from rat liver cytosol with dissociation constants of 11.7 and 10.1 μM respectively. Increasing concentrations of oleate ion significantly increased the dissociation constant of warfarin with either protein, whereas laurate ion showed the same behavior only with Z protein. On the other hand, the binding of warfarin to liver cytoplasmic proteins in vivo was decreased in 72-h-pre-fasted rats, although such fasting failed to produce any increase in the in vivo levels of the cytoplasmic free fatty acids (FFA). However, based on the results of the in vitro binding study, it is suggested that changes in the composition of hepatic cytoplasmic free fatty acids as a result of fasting could reduce the in vivo binding of warfarin to Y and Z proteins and hence could lead to an increase of unbound warfarin in liver cytosol.     

Proposed replicative role of the NS polypeptide of vesicular stomatitis virus: structural analysis of an electrophoretic variant.

The structural lesion in the temperature-sensitive mutant E1 of the New Jersey serotype of vesicular stomatitis virus has been assigned to the NS protein. Although the packaged wild-type and mutant NS proteins were similarly phosphorylated, the mutant NS protein migrated faster than the wild-type NS protein in polyacrylamide slab gels electrophoresed in the presence of sodium dodecyl sulfate. The resolution appears to be the result of conformational rather than size differences since the two proteins comigrated in polyacrylamide gels which contained 4 M urea in addition to sodium dodecyl sulfate. Peptide maps, obtained by limited proteolysis of 32P-labeled wild-type and mutant NS proteins with Staphylococcus aureus V8 protease and papain, revealed striking differences which suggested that the mutant alteration could involve an aspartic or glutamic acid residue. Since NS proteins obtained from naturally occurring revertants of E1 were indistinguishable from the wild-type protein in all of these analyses, the structural alteration in the mutant NS protein correlates with the functional lesion. Because E1 is defective in the RNA replication pathway at the restrictive temperature, a replicative role is proposed for the NS protein.     

Cytological effects of urecholine stimulation on the rat pancreas

Summary Stimulation of the exocrine pancreas by the secretagogue urecholine causes degranulation of the acinar cells. Under in vivo conditions, this degranulation is not uniform throughout the tissue. Indeed some of the acini are almost completely depleted of their granules while others display the appearance of resting acini. A noticeable feature is that all the cells of the same acinus display a comparable degree of degranulation. Moreover, groups of neighbouring acini seem to respond simultaneously suggesting that the secretory stimulus is propagated from one acinus to the other. In vitro stimulation of dispersed acini also showed that some of the acini are more responsive than others indicating that this phenomenon can not be attributed to accessibility of the secretagogue to its receptor. These observations lead us to the concept that the response of the pancreatic acinar cell is controlled at the level of the acinus.