Shivering in patients recovering from CABG

Thirty-eight patients diagnosed as having continuous schizophrenia progrediens, 35 patients with shift-like schizophrenia and six patients with hypertoxic (feverish) schizophrenia were studied. The examinees displayed a marked increase in the blood content of lipid peroxidation products, such as malonic dialdehyde and conjugated dienes, together with an enhancement of the degree of erytrocytolysis, which events are particularly noticeable in hypertoxic- and continuous schizophrenia. Blood catalase activity gets higher, that of superoxide dismutase is on the decrease, which facts suggest to us some faults in the system of antioxidant defence.     

A new metal-binding site in photosynthetic bacterial reaction centers that modulates QA to QB electron transfer

Isolated reaction centers (RCs) from Rhodobacter sphaeroides were found to bind Zn(II) stoichiometrically and reversibly in addition to the 1 equiv of non-heme Fe(II). Metal and EPR analyses confirm that Zn(II) is ligated to a binding site that is distinct from the Fe site. When Zn(II) is bound to this site, electron transfer between the quinones QA and QB (QA-QB --> QAQB-) is slowed and the room-temperature kinetics become distributed across the microsecond to millisecond time domain. This effect of metal binding on the kinetics is similar to the more global effect of cooling RCs to 2 degreesC in the absence of Zn(II). This suggests that Zn(II) binding alters localized protein motions that are necessary for rapid QA-QB --> QAQB- electron transfer. Inspection of the RC crystal structure suggests a cluster of histidine ligands located beneath the QB binding pocket as a potential binding site.     

Structure-based design of cathepsin K inhibitors containing a benzyloxy-substituted benzoyl peptidomimetic

Peptidomimetic cathepsin K inhibitors have been designed using binding models which were based on the X-ray crystal structure of an amino acid-based, active site-spanning inhibitor complexed with cathepsin K. These inhibitors, which contain a benzyloxybenzoyl group in place of a Cbz-leucine moiety, maintained good inhibitory potency relative to the amino acid-based inhibitor, and the binding models were found to be very predictive of relative inhibitor potency. The binding mode of one of the inhibitors was confirmed by X-ray crystallography, and the crystallographically determined structure is in close qualitative agreement with the initial binding model. These results strengthen the validity of a strategy involving iterative cycles of structure-based design, inhibitor synthesis and evaluation, and crystallographic structure determination for the discovery of peptidomimetic inhibitors.     

LGMD 2E in Tunisia is caused by a homozygous missense mutation in beta-sarcoglycan exon 3

Four of the currently recognized autosomal recessive limb-girdle muscular dystrophies (LGMD type 2C-F) are caused by mutations in the genes encoding components of the sarcoglycan complex. LGMD 2C, caused by mutations in gamma-sarcoglycan, is prevalent in northern Africa, especially in Tunisia, where this type of muscular dystrophy was originally described. Although the disease initially was assumed to be genetically homogeneous in this region, linkage to the alpha-sarcoglycan locus (LGMD 2D) has also been found. We have now identified the first Tunisian family with beta-sarcoglycanopathy (LGMD 2E), further adding to the genetic heterogeneity of autosomal recessive LGMD in this population. Direct sequencing of the beta-sarcoglycan gene revealed a homozygous mutation (G272-->T, Arg91Leu) in exon 3. This change affects the same arginine residue in the immediate extracellular domain of the protein that was mutated to a proline (G272-->C, Arg91Pro) in a Brazilian family with a severe form of the disease. Immunohistochemical analysis for the sarcoglycan complex demonstrates absence of the known components of the complex in both of these families. We postulate that the immediate extracellular domain of beta-sarcoglycan may be important for the assembly and/or maintenance of this complex, potentially mediated by disulfide-bond formation to another sarcoglycan via the single cysteine residue in that domain.     

Synthesis and two-dimensional electrophoretic analysis of mixed populations of circular and linear RNAs

Spontaneous cleavage of the less abundant form of tobacco ringspot virus satellite RNA is readily reversible. Capitalizing on earlier observations by Feldstein and Bruening that small 'mini-monomer' RNAs derived from this molecule and containing little more than covalently attached ribozyme and substrate cleavage products are able to efficiently circularize, we have constructed a series of self-circularizing RNAs of precisely known size. Mixtures of linear and circular RNAs synthesized in vitro and containing 225-1132 nt could be completely resolved using a novel two-dimensional denaturing polyacrylamide gel electrophoresis system. Similar analyses of a complex mixture of coconut cadang-cadang viroid RNAs revealed the presence of relatively large amounts of a previously undescribed 'fast-slow' heterodimeric RNA species in infected palms. Only a single DNA template is required to prepare each pair of circular and linear RNA markers.     

Ricin A chain can be chemically cross-linked to the mammalian ribosomal proteins L9 and L10e

Indirect immunofluorescence studies revealed that when fixed, permeabilized cultured human cells were incubated with ricin A chain, the toxin molecule localized in a staining pattern indicative of binding to the endoplasmic reticulum and to nucleoli. Chemical cross-linking experiments were performed to identify the cellular components that mediated the binding of ricin A chain. Conjugates were formed between 125I-labeled ricin A chain and two proteins present in preparations of total cell membranes and in samples of purified mammalian ribosomes. Specificity of the ricin A chain-ribosome interaction was demonstrated by inhibition of formation of the complexes by excess unlabeled ricin A chain, but not by excess unlabeled gelonin, another ribosome-inactivating protein. Complexes of ricin A chain cross-linked to the ribosomal proteins were purified and subjected to proteolytic digestion with trypsin. Amino acid sequencing of internal tryptic peptides enabled identification of the ricin A chain-binding proteins as L9 and L10e of the mammalian large ribosomal subunit.     

Effect of catecholamine depletion on myocardial infarct size in dogs: role of catecholamines in ischemic preconditioning

OBJECTIVES: Cardioprotective adaptation to brief periods of ischemia and reperfusion is termed ischemic preconditioning (PC). Limitation of infarct size by preconditioning is associated with marked slowing of ischemic metabolism. The cause of metabolic slowing has not been determined but may involve either pro- or anti-adrenergic mechanisms. Hypothetically, adrenergic stimulation could signal the adaptive response. Alternatively, metabolic slowing during the sustained ischemic challenge could occur through a reduction in beta-adrenergic stimulation. This study was designed to test the role of cardiac norepinephrine (NE) in PC. METHODS: The effect of PC on myocardial infarct size was studied in control dogs and dogs depleted of catecholamines by pretreatment with reserpine (RES; 0.25 mg/kg i.v.). PC was induced by four cycles of 5 min of ischemia and 5 min of reperfusion. Infarcts were produced by 60 min of ischemia and 3 h of reperfusion. Cardiac NE depletion was verified by radioimmunoassay of tissue samples and by absence of hemodynamic response to a tyramine bolus (1.4 mg/kg) administered at the end of each experiment. Infarct size, expressed as percent of area at risk, was controlled for variation in collateral blood flow using analysis of covariance (ANCOVA). RESULTS: Adjusted mean infarct size was 25.5 +/- 3.2% in untreated controls vs. 19.1 +/- 3.3% in RES-treated controls (P = NS). PC limited infarct size in untreated dogs (7.4 +/- 1.8 vs. 25.5 +/- 3.2%; PC vs. control; P < 0.01) but not in RES-treated dogs (15.7 +/- 3.0% vs. 19.1 +/- 3.3%; RES + PC vs. RES; P = NS). Infarct size was larger in dogs with RES + PC than with PC alone, even though there was a trend toward a slight beneficial effect with RES alone. CONCLUSION: The cardioprotective effect of ischemic preconditioning cannot be explained entirely as an anti-adrenergic effect. On the contrary, adrenergic receptor stimulation may be required for the full expression of ischemic preconditioning in canine myocardium.     

Use of lectins to characterize plasma membrane preparations from boar spermatozoa: a novel technique for monitoring membrane purity and quantity

The object of this study was to develop a method to quantify the amount of outer acrosomal membrane material in isolated plasma membranes from boar sperm cells. The cells were fractionated by nitrogen cavitation, and plasma membranes were isolated by subsequent differential centrifugation steps. Marker enzyme measurement showed that the plasma membrane isolates were enriched in plasma membrane markers and did not contain nuclei, inner acrosomal membranes, or mitochondria. Since there is no marker enzyme known for the outer acrosomal membrane, lectins were used for the detection of this membrane. The membrane specificity of a number of lectin conjugates was tested with fluorescence microscopy and transmission electron microscopy. Membrane binding of these lectin conjugates was quantified with flow-cytometry and an enzyme-linked lectin binding assay. Wheat germ agglutinin was specific for the plasma membrane while peanut agglutinin was specific for the outer acrosomal membrane. The use of these lectins made it possible for the first time to discriminate between these two membranes. The isolated plasma membrane fraction was enriched more than 10-fold (17-fold after further purification by a sucrose gradient) in plasma membrane material compared to outer acrosomal membrane material. Highly purified sperm plasma membranes should prove to be useful for research on primary sperm-zona interactions.