Arginase,an s-phase enzyme in a human cell line

Suspension cultures of ‘Chang liver’ cells were synchronized by preincubation in a glutamine-deficient medium or by thymidine blockade. Specific arginase activity varied in the synchronized cultures, being high when the number of S-phase cells was maximal. A relationship between high arginase activity and a high percentage of (S+G₂) cells was also found when unsynchronized cells were separated by velocity sedimentation. The increase in arginase activity near the G₁/S border was totally inhibited in the presence of cycloheximide. The rate of decrease in activity after addition of the drug indicated that the variations in the rate of synthesis of the enzyme, while the rate of degradation was more or less constant, corresponding to 4–6% per h. The role of arginase in cells lacking a urea cycle and the regulation of arginase activity in ‘Chang liver’ cells is discussed.     

Mice Lacking Platelet-Derived Growth Factor D Display a Mild Vascular Phenotype

Platelet-derived growth factor D (PDGF-D) is the most recently discovered member of the PDGF family. PDGF-D signals through PDGF receptor β, but its biological role remains largely unknown. In contrast to other members of the PDGF family of growth factors, which have been extensively investigated using different knockout approaches in mice, PDGF-D has until now not been characterized by gene inactivation in mice. Here, we present the phenotype of a constitutive Pdgfd knockout mouse model (Pdgfd^-/-), carrying a LacZ reporter used to visualize Pdgfd promoter activity. Inactivation of the Pdgfd gene resulted in a mild phenotype in C57BL/6 mice, and the offspring was viable, fertile and generally in good health. We show that Pdgfd reporter gene activity was consistently localized to vascular structures in both postnatal and adult tissues. The expression was predominantly arterial, often localizing to vascular bifurcations. Endothelial cells appeared to be the dominating source for Pdgfd, but reporter gene activity was occasionally also found in subpopulations of mural cells. Tissue-specific analyses of vascular structures revealed that NG2-expressing pericytes of the cardiac vasculature were disorganized in Pdgfd^-/- mice. Furthermore, Pdgfd^-/- mice also had a slightly elevated blood pressure. In summary, the vascular expression pattern together with morphological changes in NG2-expressing cells, and the increase in blood pressure, support a function for PDGF-D in regulating systemic arterial blood pressure, and suggests a role in maintaining vascular homeostasis.     

Mercury in blood cells—Altered elemental profiles

The study was composed of 27 persons that displayed vague symptoms similar to those of the victims of Minamata and Iraq. Skew distributions of mercury were observed in individual erythrocytes and neutrophil granulocytes when measured by PIXE. Mercury could not be detected in the platelets. The erythrocytes also displayed lowered concentrations of magnesium and zinc, together with increased concentrations of calcium and strontium. The neutrophils displayed decreased concentrations of magnesium and zinc and increased concentrations of calcium, strontium, and iron. The presence of mercury and the altered elemental profiles in the erythrocytes and the neutrophil granulocytes are suggested as early signs of exposure.     

Transformation of Penicillium chrysogenum by a vector containing a mitochondrial origin of replication

Summary In order to establish a transformation system for P. chrysogenum autonomously replicating vectors were constructed using mitochondrial DNA sequences from the fungus. A physical map of the mt DNA of a production strain was established using ten different restriction enzymes. Unexpectedly, the mt DNA of this strain proved to be significantly smaller than that of a second strain from a culture collection (27 kb versus 49 kb). Various fragments representing about 71% of the 27 kb mt DNA were cloned and, at first, preselected for replicating activity in an intermediate host (Saccharomyces cerevisiae). Two of these fragments also promoted autonomous replication in P. chrysogenum, which was confirmed by isolation of bulk DNA and transfer into E. coli. For selection of transformants in P. chrysogenum the prokaryotic kanamycin resistance gene was used which increased about twofold the resistance against G418. Present address: Institut für Biotechnologie, Fachgebiet Mikrobiologie, Techn. Universität Berlin, Seestr. 13, D-1000 Berlin 65     

International Commission for Protection against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 15/3. Human acetaldehyde levels: aspects of current interest

The determination of acetaldehyde levels in blood and other tissues is a difficult task, and depends on the method used. Different methods and their pros and cons are discussed in detail. Quantitative results are shown for endogenous acetaldehyde levels and for acetaldehyde levels during alcohol intoxication. One article pertains to acetaldehyde bound to blood and tissue proteins.     

Effect of arteriovenous flow reversal on blood flow and metabolism in a skin flap

Twelve pig buttock island flaps (10 X 10 cm) were studied for 6 hours after arteriovenous flow reversal at the level of the pedicle. Follow-up was 48 hours. Blood pressure, Po2, pH, and lactate were measured in flap arteries and veins. Oxygen consumption was calculated. Data indicated true flow reversal. Blood pressure and Po2 in flap veins increased to systemic arterial levels. Outflow was provided by the arterial system, demonstrating venous pressure and Po2 values. Lactate increased significantly (1.8 +/- 0.5 to 4.0 +/- 2.3 mmol/liter), while pH dropped from 7.43 +/- 0.03 to 7.11 +/- 0.02. Oxygen consumption remained below baseline. In four flaps thrombosis occurred within 6 hours; no flap survived 48 hours. The results of this study do not encourage clinical application of the concept of flow reversal.     

N-Deacetylation of 2-acetamido-2-deoxy-hexosecontaining oligosaccharides and polysaccharides by calcium in liquid ammonia

N-Deacetylation of 2-acetamido-2-deoxy-hexose residues is accomplished in liquid ammonia containing calcium. Oligosaccharides, lacto-N-fucopentaose II and lacto-N-difucohexaose I, containing 3,4-disubstitutedN-acetylhexosamine residues are quantitativelyN-deacetylated. When applied to polysaccharides, however, only partialN-deacetylation was achieved.Author for correspondence. AXRD     

Characterization of the proteolytic compartment in rat hepatocyte nodules

Persistent liver nodules (hepatocyte nodules, neoplastic nodules) were produced in rat liver by intermittent feeding with 2-acetylaminofluorene. Dense bodies (secondary lysosomes) were purified and characterized from the nodules. The purity of the dense body fraction was 90%. The levels of various lysosomal enzyme activities were lower in these dense bodies in comparison with dense bodies from control liver. Similarly, protein degradation was 50% lower in dense bodies from liver nodules than in control liver. The number of autophagic vacuoles (AVs) in the nodular tissue increased considerably after 3 h vinblastine treatment. We have taken advantage of this expansion in an effort to isolate these organelles from liver nodules. Autophagic vacuoles have been isolated recently from liver and kidney but not from putatively premalignant liver nodules. Fraction purity of AVs from liver nodules was 95%. As with dense bodies, AVs from nodular tissue displayed lower activities of proteinases and lower rates of protein degradation when compared with their counterparts from normal liver tissue. Accordingly, the lower rate of overall protein degradation in liver nodules can be ascribed to a decrease in lysosomal activity. A diminished autophagic sequestration capacity is the most plausible explanation for the decreased rate of proteolysis in cells. This could conceivably give these nodular cells a growth advantage and assist in their selective outgrowth as well as in their transformation from neoplastic into true cancer cells.