Postmortem Changes in Rat Brain: Studies on Membrane-Bound Enzymes and Receptors

The relationship between the stability of potential neurochemical markers and autolysis time was studied at 4 degrees C and 25 degrees C using postmortem brain samples from two rat strains. In general, qualitatively similar results were obtained with either N/Nih or Sprague-Dawley rats; however, quantitative differences were often observed, particularly in regard to benzodiazepine receptor changes. For every enzyme activity or binding property examined, no significant change was found when brains were kept at 4 degrees C for up to 72 h prior to freezing at -70 degrees C. Na,K-ATPase and low-affinity Ca-ATPase activities were also stable in brains kept at 25 degrees C for up to 72 h. Mg-ATPase activity was reduced in brains kept at 25 degrees C for 24 and 48 h. [3H]Guanidinoethylmercaptosuccinic acid [( 3H]GEMSA) binding to enkephalin convertase in the cytosol was not significantly changed in brains kept at 25 degrees C; however, a small increase was seen for [3H]GEMSA binding to the membrane fraction at 24, but not 48 and 72 h postmortem. [3H]Quinuclidinyl benzilate [( 3H]QNB) binding to muscarinic cholinergic receptors decreased in brains kept at 25 degrees C for 72 h. Opioid receptor binding also decreased in brains kept at 25 degrees C. Using [3H]2-D-alanine-5-D-leucine enkephalin to label delta opioid receptors, a statistically significant decrease in binding was observed as early as 6 h postmortem, and was completely abolished after 72 h at 25 degrees C. In contrast, [3H]naloxone binding was unchanged after 24 h at 25 degrees C, but was decreased after 48 and 72 h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Issues in analysis of data on paternal age and 47,+21: implications for genetic counseling for Down syndrome

Summary Data and analyses on paternal age and 47,+21 are reviewed. It is concluded that there are few, if any, grounds to justify the inference of a paternal age effect independent of maternal age for those paternal age-maternal age combinations on which there are prenatal diagnostic data. It is suggested that genetic counseling as to increased (or decreased) risk of Down syndrome associated with various paternal ages is not justified at present.     

Plasmalemma- and tonoplast-ATPase activity in mesophyll protoplasts,vacuoles and microsomes of the Crassulacean-acid-metabolism plant Kalanchoe daigremontiana

Adenosine-triphosphatase activity on the plasmalemma and tonoplast of isolated mesophyll protoplasts, isolated vacuoles and tonoplast-derived microsomes of the Crassulacean-acid-metabolism plant Kalanchoe daigremontiana Hamet et Perr., was localized by a cytochemical procedure using lead citrate. Enzyme activity was detected on the cytoplasmic surfaces of the plasmalemma and tonoplast. The identity of the enzymes was confirmed by various treatments differentiating the enzymes by their sensitivity to inhibitors of plasmalemma and tonoplast H⁺-ATPase. Isolated vacuoles and microsomes prepared from isolated vacuoles clearly exhibited single-sided deposition on membrane surfaces.Abbveviations CAM Crassulacean acid metabolism - H⁺-ATPase proton-translocating ATPase     

Olfactory adaptation as an aspect of odor similarity

Two experiments examined self-adaptation within and cross-adaptationbetween two structurally different substances with almost identicalbitter chocolate odors, trimethyl pyrazine (TMP) and 2-propionyl-3-methylfuran (PMF). The first experiment charted psychophysical functionsfor odor intensity under steady-state self- and cross-adaptationwith adapting concentrations matched in perceived intensityat two different levels. Participants breathed an adapting concentrationcontinuously for 2 min and then rated test concentrations everyminute during momentary respites from the adapting stimulus.Both self-adaptation and cross-adaptation weakened the intensityof low test concentrations proportionally more than higher onesand thereby steepened the psychophysical functions. Adaptingstimuli at matched levels caused equivalent self-adaptation(i.e. altered the functions equivalently) and equivalent, thoughweaker, cross-adaptation (i.e. exhibited symmetry of cross-adaptation).The second experiment examined whether cross-adaptation to TMPand PMF would prove relatively specific. At a matched perceivedintensity of adapting stimulus, adaptation to TPM and PMF againproduced equal amounts of self-adaptation and of cross-adaptationto each other, though not on three other test stimuli: anethole,ethyl butyrate and 2,3 pentanedione. Both TMP and PMF showedsome generality as cross-adapting stimuli, with PMF showinga bit more than TMP. The present protocols and others discussedherein offer opportunities to consider functional criteria forthe relatedness of similar-smelling substances.     

Rat heart gap junctions as disulfide-bonded connexon multimers: Their depolymerization and solubilization in deoxycholate

Summary Unproteolyzed gap junctions isolated from rat heart and liver were analyzed for the presence of inter-subunit disulfide bonds by sodium dodecylsulfate polyacrylamide gel electrophoresis. Rat cardiac junctions contained multiple disulfide bonds connecting theM _r 47,000 subunits of the same connexon and of different connexons. Inter-subunit disulfide bonds were absent in liver junctions. Unproteolyzed rat heart gap junctions were resistant to deoxycholate in their oxidized state, but dissolved readily in the detergent when the disulfide bonds were cleaved with -mercaptoethanol. Disulfide bonding in proteolyzed cardiac junctions was limited to pairs ofM _r 29,500 subunits. These junctions were not soluble in deoxycholate even in the presence of -mercaptoethanol. These results show that heart and liver junctions differ in their quarternary organization.     

The effects of crude oil on the growth of Spartinaalterniflora Loisel. and Spartina cynosuroides (L.) Roth

Greenhouse studies were conducted to examine the effects of crude oil on the growth of Spartinaalterniflora Loisel. and S. cynosuroides (L.) Roth from North Carolina. The way in which crude oil came into contact with the plant tissue and/or substratum was an important factor in determining the responses of both species to oil pollution. Plants recovered from a single application of oil to aerial tissue with relatively little impact on productivity. The presence of an oil layer on the surface of an overlying layer of water had little impact on existing aerial portions of S. alterniflora plants; however, regrowth following harvest was completely inhibited. Incorporation of oil into the substratum significantly reduced aerial productivity and regrowth of S. alternflora and S. cynosuroides. Observations suggest that decreased productivity and regrowth may have been caused by decreased root and rhizome growth. Regrowth potential of S. alterniflora grown in oiled substratum was greater in fine-textured marsh substratum than in sand substratum.     

The relevance of imidazole tautomerism for the hormonal activity of histidine-containing peptides

Substitution of 5-nitro- -histidine for -histidine is proposed as a useful tool to study the relationships among tautomerism, acid-base properties, and biological activity of peptide hormones. This approach is illustrated by an analog of the tripeptide thyroliberin, [5-nitro- -histidine]²-thyroliberin, which has been prepared by solid-phase peptide synthesis. The acid-base properties of the hormone analog and the position of the imidazole ring tautomeric equilibrium have been investigated by spectroscopic methods. Correlation of these properties with the biological activity of the nitrated tripeptide strongly supports the idea that imidazole ring tautomerism is a key factor for hormonal activity and that the N^τ-H tautomer must be considered the biologically active form of thyroliberin.     

Column cellulose hydrolysis reactor: Cellulase adsorption profile

Summary A column cellulose hydrolysis reactor was set up using a single passage of cellulase enzyme which was followed with a continuous percolation of buffer. Hydrolysis rates were found to decline precipitously upon the removal of the non-adsorbed cellulase components. By comparing specific activities of the cellulase before and after adsorption on the cellulose column, it was concluded that the adsorption efficiencies for the cellulase components decreased from exoglucanase (1,4--d-glucan cellobiohydrolase EC 3.2.1.91) to endoglucanase [1,4-(1,3;1,4)--d-glucan 4-glucanohydrolase, EC 3.2.1.4] to -glucosidase (-d-glucoside glucohydrolase, EC 3.2.1.21). Of the adsorbed cellulase components, the rate of endoglucanase leaching from the cellulose column was 20 times that for the exoglucanase despite the greater adsorption efficiency of the latter. By analysing the cellulase components which were bound and not bound by the cellulose column and comparing them with a purified exoglucanase enzyme on sodium dodecyl sulfate polyacrylamide gels, it was confirmed that the major cellulase component adsorbed to the cellulose column was an exoglucanase component. The resultant loss of other cellulase components from the reactor was probably the cause for the much reduced rate of cellulose hydrolysis when these components were flushed out of the column.     

Column cellulose hydrolysis reactor: An efficient cellulose hydrolysis reactor with continuous cellulase recycling

Summary The use of a column cellulose hydrolysis reactor with continuous enzyme recycling was demonstrated by incorporating a continuous ultrafiltration apparatus at the effluent end of the column reactor. Using this setup, over 90% (w/v) cellulose hydrolysis was achieved, resulting in an average sugar concentration of 6.8% (w/v) in the effluent stream. The output of the system was 1.98 g of reducing sugar/l/h with a ratio of 87% (w/v) of the reducing sugars being monomeric sugars. Batch hydrolysis reactors were less effective, resulting in 57% (w/v) of the cellulose being hydrolyzed. The output of the batch reactor was 1.33 g of reducing sugar/l/h with similar product concentrations and percentage of monomeric sugars. The ratio of reducing sugar/filter paper unit of cellulase activity for the column method was 69.1 mg/U as compared to only 21.2 mg/U for the batch reactor.