Fine Structural Alterations in Cell Particles During Chemical Carcinogenesis : II. Further Evidence for Their Involvement in the Mechanism of Carcinogenesis. The Swelling of Rat Liver Mitochondria During Feeding of Amino Azo Dyes

Swelling under carefully controlled conditions has been used to study alterations in the structure of rat liver mitochondria as a result of feeding azo dyes. The changes of the swelling properties of the mitochondria during feeding of the hepatocarcinogenic 3'-methyl-4-dimethylaminoazobenzene are essentially comparable to those observed previously with the microsomes, under the same dietary conditions. These alterations in mitochondrial swelling are not related to changes in the amount of these cell particulates per unit weight of tissue, during feeding of this azo dye. As with the microsomes, feeding of the isomeric but relatively noncarcinogenic 2-methyl-4-dimethylaminoazobenzene does not affect swelling. The structural differences between liver and hepatoma mitochondria show up not only in the rate and extent of swelling but also in the form of the curves of pH dependence. The influence of ketones and sulfhydryl compounds on the swelling of normal liver mitochondria were studied, with particular emphasis to the role of sulfhydryl groups in membrane permeability. The sudden steep rise in the tumor incidence in groups of rats fed 3'-methyl-4-dimethylaminoazobenzene for increasing intervals of time occurs at about 4 weeks. This time correlates with the point of the minimum swelling of microsomes and mitochondria isolated from the livers of rats fed this same dye. Thus, a correlation is established between the alterations of the swelling properties of these particulates and the carcinogenic process.     

THE AMINASE OXIDASE INHIBITORS—Their Current Place in Clinical Medicine

Development of the MAO-inhibitors has been an important advance in the treatment of tuberculosis, mental depression, several of the collagen diseases, hypertension and angina pectoris. Treatment must be carefully controlled and individualized. A sufficient number of MAO-inhibitors is available at present to afford ready and correct selection of the proper one for a given patient and disease. Provided such care is observed, treatment is most successful and side effects are few and, as a rule, readily corrected.     

Respiratory sinus arrhythmia in the denervated human heart

We performed this study to test whether the denervated human heart has the ability to manifest respiratory sinus arrhythmia (RSA). With the use of a highly sensitive spectral analysis technique (cross correlation) to define beat-to-beat coupling between respiratory frequency and heart rate period (R-R) and hence RSA, we compared the effects of patterned breathing at defined respiratory frequency and tidal volumes (VT), Valsalva and Mueller maneuvers, single deep breaths, and unpatterned spontaneous breathing on RSA in 12 normal volunteers and 8 cardiac allograft transplant recipients. In normal subjects R-R changes closely followed changes in respiratory frequency (P less than 0.001) but were little affected by changes in VT. On the R-R spectrum, an oscillation peak synchronous with respiration was found in heart transplant patients. However, the average magnitude of the respiration-related oscillations was 1.7-7.9% that seen in normal subjects and was proportionally more influenced by changes in VT. Changes in R-R induced by Valsalva and Mueller maneuvers were 3.8 and 4.9% of those seen in normal subjects, respectively, whereas changes in R-R induced by single deep breaths were 14.3% of those seen in normal subjects. The magnitude of RSA was not related to time since the heart transplantation, neither was it related to patient age or sex. Thus the heart has the intrinsic ability to vary heart rate in synchrony with ventilation, consistent with the hypothesis that changes, or rate of changes, in myocardial wall stretch might alter intrinsic heart rate independent of autonomic tone.     

31P NMR studies on the effect of phosphite on Phytophthora palmivora

31P NMR spectra were obtained from perchloric acid (PCA) and KOH extracts of Phytophthora palmivora mycelium. Signals indicating the presence of large amounts of short-chain polyphosphate were observed in the spectra of PCA extracts of mycelia grown under both low (0.1 mM) and high (10 mM) phosphate conditions. The mean chain length of polyphosphate was calculated from the relative areas of signals arising from terminal and internal P nuclei in the polyphosphate chain. The small amount of polyphosphate evident in the KOH extract had an average chain length similar to PCA-soluble polyphosphate. 32P tracer studies indicated that phosphorus in the PCA fraction accounted for between 50 and 60% of total phosphorus, the bulk of the remainder being divided between the lipid and KOH extracts. The presence of the fungicide phosphorous acid markedly reduced the average chain length of acid-soluble polyphosphate. This reduction occurred both under low-phosphate conditions, in which treatment with phosphorous acid retards growth, and under high-phosphate conditions, in which no significant growth retardation is observed. Treatment with phosphorous acid perturbed phosphorus distribution and lipid composition under low-phosphate conditions.     

Carbon metabolism in Bradyrhizobium japonicum bacteroids

Abstract Carbon metabolism in Bradyrhizobium japonicum bacteroids is reviewed. Additionally, the bacteroid tricarboxylic acid (TCA) cycle and its regulation under oxygen-limited conditions is considered, with emphasis on possible sites of TCA cycle rate-limiting reactions. Furthermore, we consider other adaptive pathways that may be employed by these organisms while in symbiosis. These pathways include: (1) a poly-β-hydroxy-butyrate shunt, (2) a malate-aspartate shuttle, (3) an α-ketoglutarate-glutamate shunt, (4) a modified dicarboxylic acid cycle, and (5) fermentation pathways leading to lactate, acetaldehyde and ethanol. The effects of oxygen limitation on host carbon metabolism are also considered briefly.     

Chromosome damage in rat pulmonary alveolar macrophages following ozone inhalation

To determine whether ozone is clastogenic at environmentally relevant exposure levels, rats were exposed for 6 h to 0.0, 0.12, 0.27, or 0.80 ppm ozone. The alveolar macrophages were isolated from animals sacrificed 28 h after the end of the exposure. The mitotic index and frequency of chromosome aberrations were determined. No change in the mitotic index was detected following 0.12 ppm ozone exposure. A significant decrease in mitotic index was observed after exposure to 0.27 ppm ozone; a significant (4-fold) increase in the frequency of dividing macrophages was detected following exposure to 0.8 ppm ozone. Only chromatid-type aberrations were observed. There was a significant increase in the frequency of cells with chromatid gaps and in the frequency of cells with chromatid deletions. Animals exposed to 0.27 ppm ozone had the highest proportion of cells with chromatid deletions (0.172) relative to background level (0.028). No exchanges or chromosome-type aberrations were detected in any of the animals. These data suggest that ozone, at relatively low levels, is clastogenic in macrophages from exposed rats.     

Substrate stereospecificity of phosphatidylinositol-specific phospholipase C from Bacillus cereus examined using the resolved enantiomers of synthetic myo-inositol 1-(4-nitrophenyl phosphate).

The substrate stereospecificity of phosphatidylinositol-specific phospholipase C from Bacillus cereus is examined using the resolved optical isomers of synthetic myo-inositol 1-(4-nitrophenyl phosphate), a chromogenic substrate for the phospholipase. The synthetic route employs mild acid-labile protecting groups and separation of the substituted myo-inositol enantiomers as the (-)-camphanyl ester diastereomers. Measurements of the initial rates of cleavage of the D and L enantiomers of the nitrophenyl substrate by phosphatidylinositol-specific phospholipase C from B. cereus show that this enzyme is essentially stereospecific for the D enantiomer. Under identical conditions, the rate of cleavage of the L isomer is less than 0.2% of that observed for the D isomer. The same is observed for the highly homologous enzyme from Bacillus thuringiensis. There is no measurable inhibition by the L enantiomer of the B. cereus enzyme acting on the D enantiomer, even when the molar ratio of L:D is 5, indicating that binding of the L enantiomer to the phospholipase is negligible. Thus, the enzyme active site is exquisitely sensitive to the stereochemistry of the myo-inositol group of the substrate.     

The tyrosine-based lysosomal targeting signal in lamp-1 mediates sorting into Golgi-derived clathrin-coated vesicles.

Diversion of membrane proteins from the trans-Golgi network (TGN) or the plasma membrane into the endosomal system occurs via clathrin-coated vesicles (CCVs). These sorting events may require the interaction of cytosolic domain signals with clathrin adaptor proteins (APs) at the TGN (AP-1) or the plasma membrane (AP-2). While tyrosine- and di-leucine-based signals in several proteins mediate endocytosis via cell surface CCVs, segregation into Golgi-derived CCVs has so far only been documented for the mannose 6-phosphate receptors, where it is thought to require a casein kinase II phosphorylation site adjacent to a di-leucine motif. Although recently tyrosine-based signals have also been shown to interact with the mu chain of AP-1 in vitro, it is not clear if these signals also bind intact AP-1 adaptors, nor if they can mediate sorting of proteins into AP-1 CCVs. Here we show that the cytosolic domain of the lysosomal membrane glycoprotein lamp-1 binds AP-1 and AP-2. Furthermore, lamp-1 is present in AP-1-positive vesicles and tubules in the trans-region on the Golgi complex. AP-1 binding as well as localization to AP-1 CCVs require the presence of the functional tyrosine-based lysosomal targeting signal of lamp-1. These results indicate that lamp-1 can exit the TGN in CCVs and that tyrosine signals can mediate these sorting events.