Levels of endogenous ethylene, carbon dioxide, and soluble pectin, and activities of pectin methylesterase and polygalacturonase in ripening tomato fruits

In 4 cultivars of tomato (Lycopersicon esculentum Mill.), theearly detachment of fruits advanced ripening and considerablyreduced the threshold value of endogenous C₂H₄. This indicatesa supply from the vegetative parts of (a) labile ripening-inhibitingsubstance(s) antagonizing the action of C₂H₄. The endogenous level of CO₂ increased shortly after the risein C₂H₄, and maximum levels of C₂H₄ and CO₂ occurred almostsimultaneously. The activity of PE showed no connection with ripening, but PGactivity did not occur until the onset of ripening. However,this activity increased at considerably higher C₂H₄ concentrationsthan the rise in WSP, and was independent of the possible presenceof ripening inhibitor(s). Hence PG is considered not to be involvedin the primary events leading to fruit ripening. Exposure of fruits to different C₂H₄ concentrations in the ambientatmosphere also showed PG activity to increase only after therise in WSP had started. Other pectin degrading or synthesizingenzymes may be involved. In the non-ripening Rin mutant of cv. Rutgers, no rise occurredin C₂H₄, CO₂, WSP, and PG activity. ¹ Present address: Department of Agricultural Chemistry, Facultyof Agriculture, Kochi University, Otsu 200 Monobe, Nangoku City,Kochi Prefecture 783, Japan. (Received February 16, 1978; )     

Cartilage proteoglycan aggregates. Electronmicroscopic studies of native and fragmented molecules

1. Proteoglycan aggregates from bovine nasal cartilage were studied by using electron microscopy of proteoglycan/cytochrome c monolayers. 2. The aggregates contained a variably long central filament of hyaluronic acid with an average length of 1037nm. The proteoglycan monomers attached to the hyaluronic acid appeared as side chain filaments varying in length (averaging 249nm). They were distributed along the central filament at an average distance of about 36nm. 3. Chondroitin sulphate side chains were removed from the proteoglycan monomers of the aggregates by partial chondroitinase digestion. The molecules obtained had the same general appearance as intact aggregates. 4. Proteoglycan aggregates were treated with trypsin and the largest fragment, which contains the hyaluronic acid, link protein and hyaluronic acid-binding region, was recovered and studied with electron microscopy. Filaments that lacked the side chain extensions and had the same length as the central filament in the intact aggregate were observed. 5. Hyaluronic acid isolated after papain digestion of cartilage extracts gave filaments with similar length and size distribution as observed for the central filament both in the intact aggregate and in the trypsin digests. 6. Umbilical-cord hyaluronic acid was also studied and gave electron micrographs similar to those described for hyaluronic acid from cartilage. However, the length of the filament was somewhat shorter. 7. The electron micrographs of both intact and selectively degraded proteoglycans corroborate the current model of cartilage proteoglycan structure.     

Distribution and some properties of NADPH and NADH oxidase in parenchymal and nonparenchymal liver cells

The activities of NADPH and NADH oxidase were determined in homogenates of isolated pure parenchymal and nonparenchymal rat liver cells at neutral (7.4) and acid (5.5) pH. The NADPH oxidase at pH 7.4 is about equally active in parenchymal and nonparenchymal cells and in both cell types is rather insensitive to KCN (1 mm) inhibition. By lowering the pH to 5.5, the NADPH oxidase of the nonparenchymal cells is stimulated (twofold) while the activity in parenchymal cells is decreased. The NADH consumption at neutral pH in parenchymal cells is 75% inhibited by KCN, while this activity in nonparenchymal cells is relatively insensitive to KCN. The NADH oxidase in both parenchymal and nonparenchymal liver cells is less active when the pH is lowered from 7.4 to 5.5. The distribution of NAD(P)H oxidases between parenchymal and nonparenchymal liver cells and the effect of pH on their activities suggest that in the nonparenchymal cells, the NADPH oxidase might play a role in the synthesis of H₂O₂ within the phagocytic vacuole. A scheme is proposed which describes the metabolic events involved in H₂O₂ formation and catabolism of endo(phago)cytosed particles in nonparenchymal liver cells.     

Influence of Diet on Experimental Swine Dysentery. 1. Effects of A Vitamin E and Selenium Deficient Diet Supplemented with 6.8 % Cod Liver Oil

Sixteen growing pigs were fed a vitamin E and selenium deficient diet; half of the animals (Group 2) were given a daily supply of vitamin E and selenium. After having been fed these diets for 53 days, the pigs were infected orally with minced colonic material from cases with typical swine dysentery. This exposure resulted in outbreaks of swine dysentery in both groups. The incubation times were, however, distinctly shorter and the clinical symptoms much more pronounced in Group 1 than in Group 2. The patho^morphological lesions in the colon also differed between the 2 groups. In the pigs of Group 1 evident pseudomembraneous lesions were observed in the spiral colon. In Group 2, the colonic alterations consisted predominantly of a catarrhal enteritis; pseudomembranes occurred in a minor part of colon in only 4 pigs. Both the clinical and the chemical observations and the pathological findings indicated a much better vitamin E and selenium balance in the pigs of Group 2. It is concluded that the treatment with vitamin E and selenium in Group 2 greatly increased resistance to swine dysentery.     

Cloning of the locus encoding synthesis of an outer membrane protein (Omp2) of the calcium dependence plasmid of Yersinia pestis (Lehmann, Neumann)

The genetic locus of Yersinia pestis encoding synthesis of a 46-kDa heat-inducible outer membrane protein (Omp2) was cloned into pBR322 plasmid. The Omp2 was shown to be analogous to previously described YopH and Yop2b proteins. The fifth HindIII fragment of 48-MDa calcium dependence plasmid pCad358 mediates production of 31- and 28-kDa proteins, irrespective of orientation of the insertion. A 31-kDa polypeptide seems to correspond to the YopJ described elsewhere. The maps of BamHI and HindIII of pCad358 region studied differed from those described for pCD1 plasmid of Y. pestis KIM. The products encoded by genes from the fragment cloned in the Pgm+ background give rise to considerable growth of Y. pestis within mouse peritoneal macrophages but were not sufficient to cause lethal infectious process.     

Elevation of Taurine in Hippocampal Extracellular Fluid and Cerebrospinal Fluid of Acutely Hypoosmotic Rats: Contribution by Influx from Blood?

Previous work has demonstrated that there is a selective increase in extracellular taurine in the brain during acute water intoxication. One aim of the present study was to investigate whether plasma taurine contributes to this increase. To this end, the concentrations of taurine, other amino acids, and ethanolamine (EA) were measured in plasma and CSF of urethane-anesthetized rats injected with 150 ml/kg body weight of distilled water. Blood pressure, blood gases, and pH, as well as plasma and CSF osmolality, were also measured. The CSF level of albumin was quantitated to study the function of the blood-CSF barrier. In separate experiments, hippocampal microdialysis was performed to determine the effects of acute plasma hypoosmolality on extracellular amino acids. Finally, the effect of water injection on hippocampal specific gravity and tissue amino acids was assessed. Blood gases and pH were essentially unchanged after water administration. Mean arterial blood pressure increased to peak levels approximately 50 mm Hg above control. Plasma osmolality decreased rapidly, whereas the depression of CSF osmolality was slower and less pronounced. The average volume of the hippocampus increased by 8%. Water injection was accompanied by a 25-fold elevation of taurine in plasma, whereas phosphoethanolamine (PEA) and EA increased moderately. A small fraction of the increase in plasma taurine might derive from blood cells because dilution of blood in vitro led to doubled plasma levels of the amino acid. Taurine, PEA, and EA increased consistently in CSF and hippocampal microdialysates. Plasma hypoosmolality transiently opened the blood-CSF barrier is reflected by augmented CSF concentrations of albumin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rapid high-performance liquid chromatographic assay for total homocysteine levels in human serum

A rapid, isocratic high-performance liquid chromatographic (HPLC) method is described for the determination of total homocysteine levels in human serum. Prior to reversed-phase HPLC analysis, the serum thiols were derivatized with SBD-F (ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate), a thiol-specific fluorogenic probe which is commercially available. Retention of SBD-homocysteine was sensitive to pH, and a mobile phase pH of 2.1 ensured baseline separation of serum thiols within 6 min. The method is simple, sensitive, reproducible (between-run coefficient of variation of 6.6%) and very suitable for routine determination of serum homocysteine levels in a clinical pathology laboratory.     

Selenium in the central nervous system of rats exposed to 75-Sel-selenomethionine and sodium selenite

The aim of the present study is to investigate the accumulation and retention of organic and inorganic selenium in the central nervous system (CNS) of the rat. Selenium accumulation was investigated after oral treatment (3.0 mg Se/L drinking water) or ip injection (1.7 mg Se/kg body wt) of rats exposed to 75-Se L-selenomethionine (SeMeth) or sodium selenite (NaSe). Significant higher concentrations were observed after exposure to organic compared to inorganic selenium after oral as well as ip administration. Highest concentrations in both experiments were observed in cerebellum followed by the nearly identical levels in the cerebral hemisphere and spinal cord independent of the chemical form of selenium or the route of administration. The difference in concentrations observed between the different parts of the CNS investigated in each group were, however, not significant. Retention of selenium in the CNS was investigated after a single ip injection (1.7 mg Se/kg body wt) of 75-Se SeMeth or NaSe. In both groups, we observed an initial fast excretion phase followed by a slower excretion phase resembling a first-order reaction. Organic selenium disappeared much slower from all parts of the central nervous system compared to NaSe after a single injection.