An information-retrieval system for classifying work in the field of cerebral asymmetry

A hierarchically-branching system is recommended for classifying published work in the field of cerebral asymmetry, and its rapid retrieval. It can readily accommodate partically everything published since 1965.     

Metal ion-mediated substrate-assisted catalysis in type II restriction endonucleases

The 2.15-A resolution cocrystal structure of EcoRV endonuclease mutant T93A complexed with DNA and Ca2+ ions reveals two divalent metals bound in one of the active sites. One of these metals is ligated through an inner-sphere water molecule to the phosphate group located 3' to the scissile phosphate. A second inner-sphere water on this metal is positioned approximately in-line for attack on the scissile phosphate. This structure corroborates the observation that the pro-SP phosphoryl oxygen on the adjacent 3' phosphate cannot be modified without severe loss of catalytic efficiency. The structural equivalence of key groups, conserved in the active sites of EcoRV, EcoRI, PvuII, and BamHI endonucleases, suggests that ligation of a catalytic divalent metal ion to this phosphate may occur in many type II restriction enzymes. Together with previous cocrystal structures, these data allow construction of a detailed model for the pretransition state configuration in EcoRV. This model features three divalent metal ions per active site and invokes assistance in the bond-making step by a conserved lysine, which stabilizes the attacking hydroxide ion nucleophile.     

Endomorphin-1 and endomorphin-2 activate mu-opioid receptors in myenteric neurons of the guinea-pig small intestine

An association between hyperhomocysteinemia and premature atherosclerosis in patients with non-insulin-dependent diabetes mellitus (NIDDM) has recently been described. Little is known about the role of insulin in homocysteine [H(e)] metabolism. We measured plasma H(e) concentrations in the fasting state and during a hyperinsulinemic-euglycemic clamp in normal subjects and patients with NIDDM. Plasma H(e) decreased significantly from 7.2 +/- 2.6 to 6.0 +/- 2.7 mmol/L (P < .01) in normal subjects, but did not change in patients with NIDDM (6.0 +/- 2.7 to 5.9 +/- 2.5 mmol/L, respectively). These data suggest that plasma H(e) concentrations are regulated by acute hyperinsulinemia in normal subjects, but not in insulin-resistant NIDDM subjects. These abnormalities may have implications for the pathogenesis of premature vascular disease associated with NIDDM.     

Calcific phacolysis

BACKGROUND AND METHODS: The authors report the clinical and ocular histopathologic findings in three patients with longstanding unilateral post-traumatic blindness. After one or more decades, acute pain associated with conjunctival hyperemia and apparent keratoprecipitates or a hypopyon developed in the affected eye of each individual. Phacoanaphylaxis was diagnosed preoperatively in two patients. RESULTS: Calcified granular lens fragments were dispersed throughout all three eyes. The anterior chamber in all patients contained extracellular calcified lens particles, but only one eye contained conspicuous macrophages. Two eyes showed elevated intraocular pressure (IOP), and in one patient calcified particles extended into a glaucomatous optic nerve head. CONCLUSION: To the authors' knowledge, this is the first report describing a rare condition involving the intraocular dispersal of calcified lens particles after disruption of the lens capsule. The authors have designated this entity as calcific phacolysis.     

Contact eczema caused by pine wood

A 34 year-old woman, working with pine wood treated with sodium hydroxide and pyrogallol, developed dermatitis on arms, face and neck. Patch testing showed allergic reaction to colophony and pine wood, but not to sodium hydroxide or pyrogallol. Pine wood contains colophony. Since avoiding pine wood, she has had no further attack of dermatitis.     

Interaction of the major epitope region of HIV protein gp41 with membrane model systems. A fluorescence spectroscopy study

Fluorescence spectroscopy (both steady-state and time-resolved) was used to study the fragment 579-601 of gp41 ectodomain (HIV-1), a highly conserved sequence and major epitope, regarding (1) structural information, (2) interaction with membrane model systems, and (3) location in the phospholipid bilayer. The peptide was characterized both in its monomeric (after reduction of the disulfide bond between cysteine residues) and in the dimeric forms. The change of the fluorescence anisotropy between monomer and dimer was rationalized on the basis of energy migration, and a distance between the two tryptophan (Trp) residues of approximately 6 A was obtained. Using different fluorescence spectroscopy approaches, it was demonstrated that, despite the fact that monomeric gp41 fragment incorporates in the membrane model systems studied, the dimeric form does not interact with these vesicles. A methodology based on the increase of the mean fluorescence lifetime averaged by the preexponentials was derived, to obtain the partition coefficient of the peptide in the different lipid systems. Fluorescence quenching using lipophilic probes and red edge excitation shift (REES) were used to study the location of the gp41 fragment in the membrane. It was concluded that the Trp residue is located in a shallow position, near the interface. The REES results show an uncommonly large wavelength shift (18 nm) for the gp41 fragment incorporated in the membrane. Our results are consistent with a "two steps" model for the gp41 fusion mechanism similar to the one proposed for influenza virus hemagglutinin.     

Solubilization of hydrophobic peptides by reversible cysteine PEGylation

"PEG-a-Cys" reagent, synthesized by the esterification of monomethoxy-poly(ethylene glycol) (avg. MW = 5 kDa) to Ellman's reagent [5,5'-dithiobis(2-nitrobenzoic acid)], is shown to "PEGylate" reversibly the cysteine residue of a 25-residue synthetic hydrophobic peptide (H2N-REAAALAAAAALAAWAALCPARRRR-CO2H) designed to model a transmembrane segment of a membrane protein. A mixed disulfide bond was formed between the reagent and the peptide that was readily cleaved with the mild reducing agent tricarboxyethylphosphine hydrochloride (TCEP.HCl). Carboxypeptidase B digestion of the charged carboxyl terminus of the peptide through to the Ala residue--which mimics the enzymatic cleavage of a TM segment from a fusion protein--releases a highly hydrophobic peptide. A time-dependent decrease in the amplitude of the digested peptide circular dichroism (CD) spectra was attributed to the aggregation and/or precipitation of the peptide. While PEGylation of the peptide with PEG-a-Cys had a negligible effect on conformation, it inhibited the loss of CD amplitude in both intact and digested peptides, suggesting that it was effective in solubilization of hydrophobic peptides.     

A naturally occurring hPMS2 mutation can confer a dominant negative mutator phenotype

Defects in mismatch repair (MMR) genes result in a mutator phenotype by inducing microsatellite instability (MI), a characteristic of hereditary nonpolyposis colorectal cancers (HNPCC) and a subset of sporadic colon tumors. Present models describing the mechanism by which germ line mutations in MMR genes predispose kindreds to HNPCC suggest a "two-hit" inactivation of both alleles of a particular MMR gene. Here we present experimental evidence that a nonsense mutation at codon 134 of the hPMS2 gene is sufficient to reduce MMR and induce MI in cells containing a wild-type hPMS2 allele. These results have significant implications for understanding the relationship between mutagenesis and carcinogenesis and the ability to generate mammalian cells with mutator phenotypes.     

Effect of dry fibrin sealant dressings versus gauze packing on blood loss in grade V liver injuries in resuscitated swine

In mammalian fertilization, inositol 1,4,5-trisphosphate receptor (IP3R)-dependent Ca2+ release is a crucial signaling event that originates from the vicinity of sperm-egg interaction and spreads as a wave throughout the egg cytoplasm. While it is known that Ca2+ is released by the type 1 IP3R in the egg cortex, the potential involvement of other isoform types responsible for the Ca2+ rise in the mouse egg (interior) and their spatial distribution are not known. In addition, the biochemical basis has not been definitively established for the development of increased sensitivity to inositol 1,4,5-trisphosphate (IP3) during meiotic maturation. Using specific antibodies to the type 1, 2, and 3 IP3R, we tested the hypotheses that different IP3R isoforms are responsible for the internal Ca2+ elevation and that they contribute to the maturation-associated acquisition of IP3 sensitivity. In both preovulatory oocytes and ovulated eggs of CF-1 mice, immunofluorescence revealed that types 1 and 2 isoforms were present in the cell cortex and interior. Type 1 was observed throughout the cytoplasm, and Western analysis indicated a 1.9-fold maturation-associated increase. In contrast, the signals detected for the type 2 (high-affinity) isoform and type 3 were present to a lesser extent, with type 2 restricted to isolated islands (similar to aggregates of vesicles detected by electron microscopy), which, in the cortex, may amplify early sperm-egg signaling events. The cortical-to-perinuclear localization of the receptor and cortical vesicle aggregates imply an efficient mechanism for propagating Ca2+ release from the cortex into the interior of the egg to activate development, and the isoform localization analysis indicates a clear spatial and biochemical heterogeneity. Types 1 and 2 isoforms were also present in granulosa cells.