Protein kinase C activity and reactivity to phorbol ester in vascular smooth muscle from spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY)

Protein kinase C (PKC) activity in aortic and renal arterial smooth muscle from SHR (20-23 wk male; mean arterial pressure = 178 mm Hg) and WKY (age/sex matched; mean arterial pressure = 126 mm Hg) was quantitated. Activity was greatest in the particulate fractions relative to the soluble fractions in all sources. The only difference between SHR and WKY was in the soluble fraction from SHR renal arteries, which had 2 fold more activity (255 pmol/mg/min) when compared with WKY (136 pmol/mg/min). This difference was not apparently related to force modulation, since the magnitude of isometric force development in renal arteries in response to phorbol 12,13-dibutyrate was not different between SHR and WKY. The magnitude of force developed in response to phorbol 12,13-dibutyrate and PKC activity in the particulate fraction was greatest in aorta vs. renal arteries in both WKY and SHR. These results suggest that regional vascular differences in the amount of PKC activity may exist which are not apparently related to a disease state (i.e., hypertension). These differences may be related to differential sensitivity to phorbol ester-mediated contractions in isolated smooth muscle.     

Inactivation of the ribonucleoside triphosphate reductase from Lactobacillus leichmannii by 2'-chloro-2'-deoxyuridine 5'-triphosphate: a 3'-2' hydrogen transfer during the formation of 3'-keto-2'-deoxyuridine 5'-triphosphate

The ribonucleoside triphosphate reductase of Lactobacillus leichmannii converts the substrate analogue 2'-chloro-2'-deoxyuridine 5'-triphosphate (ClUTP) into a mixture of 2'-deoxyuridine triphosphate (dUTP) and the unstable product 3'-keto-2'-deoxyuridine triphosphate (3'-keto-dUTP). This ketone can be trapped by reduction with NaBH4, producing a 4:1 mixture of xylo-dUTP and dUTP. When [3'-3H]ClUTP is treated with enzyme in the presence of NaBH4, the isomeric deoxyuridines isolated after alkaline phosphatase treatment retained 15% of the 3H in ClUTP. Degradation of these isomeric nucleosides has established the location of the 3H in 3'-keto-dUTP as predominantly 2'(S). The xylo-dU had 98.6% of its label at the 2'(S) position and 1.5% at 2'(R). The isolated dU had 89.6% of its label at 2'(S) and 1.4% at 2'(R), with the remaining 9% label inferred to be at the 3'-carbon, this resulting from the direct enzymic production of dUTP. These results are consistent with enzymic production of a 1:1000 mixture of dUTP and 3'-keto-dUTP, where the 3'-hydrogen of ClUTP is retained at 3' during production of dUTP and is transferred to 2'(S) during production of 3'-keto-dUTP. The implications of these results and the unique role of the cofactor adenosylcobalamin (Ashley et al., 1986) are discussed in terms of reductase being a model for the B12-dependent rearrangement reactions.     

Protonation mechanism and location of rate-determining steps for the Ascaris suum nicotinamide adenine dinucleotide-malic enzyme reaction from isotope effects and pH studies

The pH dependence of the kinetic parameters and the primary deuterium isotope effects with nicotinamide adenine dinucleotide (NAD) and also thionicotinamide adenine dinucleotide (thio-NAD) as the nucleotide substrates were determined in order to obtain information about the chemical mechanism and location of rate-determining steps for the Ascaris suum NAD-malic enzyme reaction. The maximum velocity with thio-NAD as the nucleotide is pH-independent from pH 4.2 to 9.6, while with NAD, V decreases below a pK of 4.8. V/K for both nucleotides decreases below a pK of 5.6 and above a pK of 8.9. Both the tartronate pKi and V/Kmalate decrease below a pK of 4.8 and above a pK of 8.9. Oxalate is competitive vs. malate above pH 7 and noncompetitive below pH 7 with NAD as the nucleotide. The oxalate Kis increases from a constant value above a pK of 4.9 to another constant value above a pK of 6.7. The oxalate Kii also increases above a pK of 4.9, and this inhibition is enhanced by NADH. In the presence of thio-NAD the inhibition by oxalate is competitive vs. malate below pH 7. For thio-NAD, both DV and D(V/K) are pH-independent and equal to 1.7. With NAD as the nucleotide, DV decreases to 1.0 below a pK of 4.9, while D(V/KNAD) and D(V/Kmalate) are pH-independent. Above pH 7 the isotope effects on V and the V/K values for NAD and malate are equal to 1.45, the pH-independent value of DV above pH 7. From the above data, the following conclusions can be made concerning the mechanism for this enzyme. Substrates bind to only the correctly protonated form of the enzyme. Two enzyme groups are necessary for binding of substrates and catalysis. Both NAD and malate are released from the Michaelis complex at equal rates which are equal to the rate of NADH release from E-NADH above pH 7. Below pH 7 NADH release becomes more rate-determining as the pH decreases until at pH 4.0 it completely limits the overall rate of the reaction.     

Phosphorylation sites and inactivation of branched-chain alpha-ketoacid dehydrogenase isolated from rat heart, bovine kidney, and rabbit liver, kidney, heart, brain, and skeletal muscle

Branched-chain alpha-ketoacid dehydrogenase complex was isolated from rat heart, bovine kidney, and rabbit liver, heart, kidney, brain, and skeletal muscle. Phosphorylation to approximately 1 mol Pi/mol alpha-subunit of the alpha-ketoacid decarboxylase component was linearly associated with 90-95% inactivation. The complex from some tissues (i.e., from rabbit kidney and heart, and rat heart) showed 30-40% more phosphate incorporation for an additional 5-10% inactivation. Reverse-phase HPLC analysis of tryptic digests of 32P-labeled complexes from all of the above tissues revealed two major (peaks 1 and 2) and one minor (peak 3) phosphopeptide which represent phosphorylation sites 1, 2, and a combination of 1 and 2, respectively. These phosphopeptides, numbered according to the order of elution from reverse-phase HPLC, had the same elution time regardless of the tissue or animal source of the complex. The amino acid sequence of site 1 from rabbit heart branched-chain alpha-ketoacid dehydrogenase was Ile-Gly-His-His-Ser(P)-Thr-Ser-Asp-Asp-Ser-Ser-Ala-Tyr-Arg. Regardless of the source of the complex, both sites were almost equally phosphorylated until total phosphorylation was approximately 1 mol Pi/mol of alpha-subunit and the rate of inactivation was correlated with the rate of total, site 1, or site 2 phosphorylation. Phosphorylation beyond this amount was associated with greater site 2 than site 1 phosphorylation. alpha-Chloroisocaproate, a potent inhibitor of branched-chain alpha-ketoacid dehydrogenase kinase activity, greatly reduced total phosphorylation and inactivation; however, phosphorylation of site 2 was almost abolished and inactivation was directly correlated with phosphorylation of site 1. Thus, the complex isolated from different tissues and mammals had an apparent conservation of amino acid sequence adjacent to the phosphorylation sites. Both sites were phosphorylated to a similar extent temporally although site 1 phosphorylation was directly responsible for inactivation.     

Characterization of human platelet basic protein, a precursor form of low-affinity platelet factor 4 and beta-thromboglobulin

Platelet basic protein (PBP) was purified from the supernatant of thrombin-stimulated, washed human platelets by ion-exchange, affinity, molecular sieve, and high-performance liquid chromatography (HPLC). The NH2-terminal amino acid sequence was determined by automated Edman degradation, revealing 9 unique residues followed by 10 residues of the established low-affinity platelet factor 4/beta-thromboglobulin (LA-PF4/beta TG) sequence. Among the nine were three basic residues, accounting for the high isoelectric point of PBP. Additional evidence for precursor status includes the immunological cross-reactivity of all three species and the ability of plasmin and trypsin to produce from PBP a species resembling beta TG in charge, hydrophobicity, and size. Tryptic peptide maps of PBP and LA-PF4 obtained by reverse-phase HPLC were very similar, and from each protein, a peptide was isolated which showed the amino acid composition predicted for the COOH-terminal tryptic peptide of beta TG. Normal platelets contained predominantly LA-PF4, with PBP ranging from 10% to 30% of total beta TG antigen. This was true even when fresh platelets were lysed with trichloroacetic acid in order to provide the most complete and rapid inhibition of proteolytic activity. beta TG itself was never detected in this situation or in the release supernatant of stimulated platelets, and only rarely in unprotected lysates. In agreement with earlier results, crude preparations of PBP were mitogenic for 3T3 cells, but highly purified preparations of PBP and LA-PF4 were free of this activity.     

Sensitivity to X-irradiation of peripheral blood lymphocytes from ageing donors

The proliferation of human blood lymphocytes from ageing donors, responding to concanavalin A, showed greater sensitivity to inhibition by X-rays than similar cells from younger donors. This increased sensitivity was associated with deficiency in repair of X-ray-induced damage to nuclear material, as measured by density in sucrose gradients, and with increased incidence of chromosomal damage following exposure of freshly isolated lymphocytes. There was also an increased frequency of spontaneous chromosomal aberrations in ageing subjects whose lymphocytes were deficient in repair of DNA damage.     

Craniofacial and mucopolysaccharide abnormalities in Kniest dysplasia

Serial roentgencephalograms of a male patient with Kniest dysplasia were obtained between 1 7/12 and 11 3/12 years of age and were analyzed and compared to cephalometric normative data. The patient displayed macrocephaly with increased size of the neurocranium in all three dimensions. The cranial base angle was significantly flattened, partly as a result of anterior displacement of the sella turcica. The odontoid process was short and wide. At 11 years of age there was bony fusion between the anterior arch of the atlas and the odontoid process as well as between the posterior arch of the atlas and the cranial base. The facial skeleton, including the nasal bones, infra-orbital rims, maxilla and mandible, was retropositioned relative to the anterior cranial base. The mandibular retrognathia was pronounced at an early age but improved with growth. At age 11 years the patient had a straight facial skeletal profile. Examination of the patient's 24-hour urinary excretion of keratan sulfate revealed values markedly elevated for his age. Three additional patients with Kniest dysplasia demonstrated similarly increased excretion of this glycosaminoglycan. The diagnosis of Kniest dysplasia can usually be made from roentgenograms of the extremities, the spine, and the pelvis. However, the morphologic characteristics of the head, as shown by cephalometric analysis, and the increased urinary excretion of keratan sulfate add confirmatory evidence useful in differential diagnosis.     

Distribution of calcium during interphase and mitosis as observed by ion microscopy

The ion microscope, based on secondary ion mass spectrometry, has been used to demonstrate the distribution of calcium in the root tip cells of two plant species, Allium cepa and Vicia faba. Interphase nuclei showed higher intensities of calcium than cytoplasm, while nucleoli exhibited higher calcium intensities than the rest of the nucleoplasm. The chromosomes showed high intensities of calcium at all stages of mitosis. Calcium was also detected in the cell plate and phragmoplast region of dividing cells. It appears that during prophase calcium concentrates in the condensing chromosomes, and during telophase it is transferred to nucleoli. These observations suggest that chromosomes may serve as a reservoir of calcium during mitosis.     

Gastro-intestinal helminths of donkeys in Burkina Faso

Thirty adult donkeys from Burkina Faso were necropsied and their gastro-intestinal worm burdens counted and determined. The strongylids were the most abundant species with a prevalence of 100% for Strongylus vulgaris. Four species of Strongylus, two of Triodontophorus and six of the Cyathostominae were recovered. All of the animals were also infested with habronematid nematodes, but oxyurid and ascaridid nematodes were found in low numbers. In addition to the nematodes, the paramphistomid trematode Gastrodiscus aegyptiacus and the anoplocephalid cestode Anoplocephala magna occurred in varying numbers. Faecal egg-counts from 131 donkeys ranged between 100 and 9,200 for strongylid eggs.     

Ethics of predictive testing for Huntington's chorea: the need for more information.

The finding of a genetically linked polymorphic DNA marker has made possible a predictive test for Huntington''s chorea. This DNA probe has so far been used only for research and has technical limitations, but some workers now wish to apply it to clinical predictions. Those identified by the probe as being probable carriers of the Huntington''s chorea gene would be exposed to uncertain psychological risks and social pressures. Ethical guidelines should be established, but these require greater knowledge of the potential benefits and hazards of this powerful new procedure. Controlled clinical trials are urgently needed.