The myocardium and its vasculature: a histochemical comparison of the normal and chronically sympathectomized dog heart

Summary Using histochemical techniques, the reactivities of selected enzymes and other metabolic components were examined in the myocardium, coronary arteries, and coronary arterioles of normal, two-week-sympathectomized, and sham-operated canine hearts. There were no differences in the histochemistry of coronary arteries in any of the hearts, but important differences were noted in the myocardium and especially in the arterioles. The reactivities of the enzyme glucose-6-phosphate dehydrogenase and the nucleic acids were increased in arterioles of the sympathectomized heart, possibly indicating an increased protein synthesis. The reactivities of succinate dehydrogenase, NAD-isocitrate dehydrogenase, and cytochrome oxidase were reduced in myocardium and arterioles of sympathectomized hearts as well as in arterioles of sham-operated hearts; the changes were greater in the sympathectomized arterioles where there was also observed an increase in reactivity of lactate dehydrogenase. These findings suggest a depression in aerobic metabolic capacity and, in the case of the sympathectomized arteriole, imply a possible shift in adaptation from aerobic to anaerobic metabolism.     

Gylcerol-3-phosphate shuttle and its function in intermediary metabolism of hamster brown-adipose tissue.

1. Brown adipose tissue of the hamster possesses high specific activities of soluble, cytoplasmic NAD-linked, as well as mitochondrial flavin-coupled, glycerol-3-phosphate dehydrogenases. The ratio of the two enzyme activities is high (close to 1), when compared with other tissues of the hamster. 2. In the presence of rotenone, NADH is oxidised very poorly by homogenates of brown adipose tissue. A high rate of oxidation is obtained upon further addition of dihydroxyacetone phosphate, which itself is negligible oxidised. When followed fluorimetrically glycerol 3-phosphate can also be observed to induce NADH oxidation, but only after a significant lag time. Similar results are obtained with isolated mitochondria plus high-speed supernatant. With high-speed supernatant alone, only dihydroxyacetone phosphate has any effect, whereas with isolated mitochondria neither dihydroxyacetone phosphate nor glycerol 3-phosphate induce any NADH disappearance. 3. Respiration induced by NADH plus dihydroxyacetone phosphate in homogenates equals 56% of the respiration induced by glycerol 3-phosphate alone. 4. Respiration induced by NADH plus dihydroxyacetone phosphate, as well as that induced by glycerol 3-phosphate, is inhibited by the same concentrations of inhibitors as are required for inhibition of the mitochondrial dehydrogenase i.e. EDTA, long-chain unsaturated fatty acids, long-chain fatty acyl CoA esters. 5. In isolated brown adipocytes in the presence of rotenone, norepinephrine significantly inhibits respiration induced by glycerol 3-phosphate. 6. The results obtained are discussed with respect to the role of glycerol 3-phosphate as an electron sink for cytosolic reducing equivalents to maintain a low level of extramitochondrial NADH. A means of maintaining a level of glycerol 3-phosphate adequate for triglyceride synthesis is also considered.     

Which Factors Affect the Success or Failure of Eradication Campaigns against Alien Species?

Although issues related to the management of invasive alien species are receiving increasing attention, little is known about which factors affect the likelihood of success of management measures. We applied two data mining techniques, classification trees and boosted trees, to identify factors that relate to the success of management campaigns aimed at eradicating invasive alien invertebrates, plants and plant pathogens. We assembled a dataset of 173 different eradication campaigns against 94 species worldwide, about a half of which (50.9%) were successful. Eradications in man-made habitats, greenhouses in particular, were more likely to succeed than those in (semi-)natural habitats. In man-made habitats the probability of success was generally high in Australasia, while in Europe and the Americas it was higher for local infestations that are easier to deal with, and for international campaigns that are likely to profit from cross-border cooperation. In (semi-) natural habitats, eradication campaigns were more likely to succeed for plants introduced as an ornamental and escaped from cultivation prior to invasion. Averaging out all other factors in boosted trees, pathogens, bacteria and viruses were most, and fungi the least likely to be eradicated; for plants and invertebrates the probability was intermediate. Our analysis indicates that initiating the campaign before the extent of infestation reaches the critical threshold, starting to eradicate within the first four years since the problem has been noticed, paying special attention to species introduced by the cultivation pathway, and applying sanitary measures can substantially increase the probability of eradication success. Our investigations also revealed that information on socioeconomic factors, which are often considered to be crucial for eradication success, is rarely available, and thus their relative importance cannot be evaluated. Future campaigns should carefully document socioeconomic factors to enable tests of their importance.     

Use of thionitrobenzoic acid to characterize the stability of nitric oxide in aqueous solutions and in porcine aortic endothelial cell suspensions

Nitric oxide is an important vasodilator which can be biologically produced from leukocytes and endothelial cells. However, it is highly unstable, which is an obstacle to detection and quantitation. We have exploited the reactivity of nitric oxide with thiols to establish an assay based on oxidation of thionitrobenzoic acid (TNB). The oxidation of thionitrobenzoic acid and the reaction with oxygen, which was measured by employing an oxygen electrode, were examined after the addition of nitric oxide solutions. The inhibition of aggregation of human platelets after challenge with 2.5 microM adenosine diphosphate was also investigated. These studies show the following properties of nitric oxide in aqueous solutions. (i) Nitric oxide is highly reactive to oxygen. (ii) Thiols react with a labile, highly reactive nitric oxide-oxygen product. (iii) Medium with very low oxygen content increases the life span of nitric oxide in aqueous solution. We also used the nitric oxide quantitation using TNB to study the metabolism of nitric oxide by porcine aortic endothelial cells and the results show that nitric oxide added to these cells in low oxygen content solution is stable. From these studies, we conclude that deoxygenated solutions stabilize nitric oxide. An important consequence of low oxygen content at localized tissue sites may be to augment biological effects mediated by nitric oxide.     

Light chain variable region sequence of rabbit antipneumococcal type III polysaccharide antibody 3368.

The amino acid sequence of the amino-terminal 111 residues (variable region) for the light chain of the homogeneous rabbit antipneumococcal type III polysaccharide antibody 3368 was determined. This sequence was obtained principally through automated Edmann degradations of the intact light chain and of peptides generated by tryptic digestion of the citraconylated light chain. With these methods only 2 mumol of purified light chain was required to determine the reported sequence. When compared with the light chains of four other antipneumococcal type III polysaccharide antibodies, the 3368 light chain exhibits a unique sequence in those segments of the variable region that contribute to formation of the antigen binding site (complementarity-determining regions) (10 or 11 residue differences in 12 positions). The 3368 light chain also demonstrates an insertion of three residues relative to the other four light chains in the complementarity-determining region at positions 89 to 98. These five light chains have greater than 80% sequence homology for the portion of the variable region which is not involved in antigen binding (framework).     

Carboxyatractyloside effects on brown-fat mitochondria imply that the adenine nucleotide translocator isoforms ANT1 and ANT2 may be responsible for basal and fatty-acid-induced uncoupling respectively

In brown-fat mitochondria, fatty acids induce thermogenic uncoupling through activation of UCP1 (uncoupling protein 1). However, even in brown-fat mitochondria from UCP1-/- mice, fatty-acid-induced uncoupling exists. In the present investigation, we used the inhibitor CAtr (carboxyatractyloside) to examine the involvement of the ANT (adenine nucleotide translocator) in the mediation of this UCP1-independent fatty-acid-induced uncoupling in brown-fat mitochondria. We found that the contribution of ANT to fatty-acid-induced uncoupling in UCP1-/- brown-fat mitochondria was minimal (whereas it was responsible for nearly half the fatty-acid-induced uncoupling in liver mitochondria). As compared with liver mitochondria, brown-fat mitochondria exhibit a relatively high (UCP1-independent) basal respiration ('proton leak'). Unexpectedly, a large fraction of this high basal respiration was sensitive to CAtr, whereas in liver mitochondria, basal respiration was CAtr-insensitive. Total ANT protein levels were similar in brown-fat mitochondria from wild-type mice and in liver mitochondria, but the level was increased in brown-fat mitochondria from UCP1-/- mice. However, in liver, only Ant2 mRNA was found, whereas in brown adipose tissue, Ant1 and Ant2 mRNA levels were equal. The data are therefore compatible with a tentative model in which the ANT2 isoform mediates fatty-acid-induced uncoupling, whereas the ANT1 isoform may mediate a significant part of the high basal proton leak in brown-fat mitochondria.     

Adrenergic receptor density in brown adipose tissue of active and hibernating hamsters and ground squirrels

The ligand-binding characteristics (B(max) and K(D)) of alpha(1)- and beta(1)/beta(2)-adrenoceptors were investigated in membranes prepared from brown adipose tissue (BAT) of warm-acclimated, cold-acclimated, hibernating and arousing ground squirrels (Spermophillus undulatus) and hamsters (Mesocricetus auratus) by specific binding of [(3)H]prazosin and [(3)H]CGP-12177, respectively. The physiological state did not change the affinity for the adrenoceptors in the BAT of ground squirrels and hamsters. There was a significant decrease in alpha(1)-receptor density in arousing ground squirrels and a significant decrease in beta(1)/beta(2) density in hibernating ground squirrels. The level of alpha(1)-receptors was in all conditions higher than that of beta(1)/beta(2) receptors. The results indicate a possible change in balance of adrenoceptor density in the processes of cold acclimation, hibernation and arousal. The balance between the various adrenoceptor subtypes may be important for the final effect of catecholamines in BAT in different physiological states.