Increased striatal acetylcholine after 14 months cis-flupenthixol treatment in rats suggests functional supersensitivity of dopamine receptors

Rats received continuous administration of cis-flupenthixol (0.8-1.2 mg/kg/day) or trans-flupenthixol (0.9-1.2 mg/kg/day) in drinking water for 14 months. The administration of cis-flupenthixol, but not trans-flupenthixol, caused apparent cerebral dopamine receptor supersensitivity. Thus, animals receiving cis-flupenthixol, but not trans-flupenthixol, showed enhanced apo-morphine-induced stereotyped behaviour. Dopamine concentration in striatum was not altered by drug treatment but striatal HVA and DOPAC concentrations were reduced in animals receiving cis-flupenthixol, but not trans-flupenthixol. No consistent change in Bmax of KD for specific striatal 3H-spiperone binding was observed after 14 months drug intake. However, in cis-flupenthixol treated animals a 40% increase in Bmax was observed following 2 weeks drug withdrawal. Continuous cis-flupenthixol intake increased striatal acetylcholine concentrations; trans-flupenthixol was without effect. This suggests the apparent increase in cerebral dopamine receptor supersensitivity caused by continuous long-term cis-flupenthixol administration is of functional importance in the intact animal.     

Chirality of electrons from beta-decay and the left-handed asymmetry of proteins

A simplified mathematical model of the origin of the left-handed asymmetry of proteins in living matter is presented. The model is based on the hypothesis of Vester and Ulbricht that the chirality of (lefthanded) electrons from naturally beta-active elements, e.g.,¹⁴C,⁴⁰K, etc., was the specific source of the asymmetry; it requires for its application data on the interaction of electrons having non-zero chirality with racemic mixtures of amino acids. This interaction is here treated theoretically in an order-of-magnitude calculation. Our analysis yields a very approximate value of the induced steady-state asymmetry in the amino acids at the beginning of protein synthesis and indicates that this asymmetry, though small, may have been suffcient to account for the dominant left-handedness of proteins now observed.     

Destruction of kelp-beds by sea-urchins: A cyclical phenomenon or irreversible degradation?

A stable kelp bed ecosystem in St. Margaret's Bay, Nova Scotia (Canada), had as its main producersLaminaria longicruris andL. digita. Most algal production was exported as detritus, but there was a moderate population of herbivores, mainly the sea urchinsStrongylocentrotus droebachiensis. These were eaten by crabs,Cancer irroratus and by lobsters,Homarus americanus. Lobsters also preyed on crabs. Beginning in 1968, sea urchins became locally abundant and overgrazed the kelp beds, converting large areas to urchindominated barren grounds. Almost all kelp beds in St. Margaret's Bay (140 km²) have now been destroyed. During the same period, lobster biomass decreased, and the hypothesis was put forward that reduction in lobster predation led to increased urchin abundance and kelp bed destruction. Evidence is presented for the hypothesis that urchin-dominated barren grounds are a new, stable configuration of the ecosystem, and that a long-term decrease in primary and secondary productivity of these coastal waters can be expected.     

Neuronal metabolism and DOPA decarboxylase immunoreactivity in terminal noradrenergic sympathetic axons of rat.

This study was undertaken to determine whether immuno-histochemical staining for DOPA decarboxylase (DDC) is present in axons of rat noradrenergic sympathetic neurons. A sparse plexus of varicose axons exhibiting DDC-like immunoreactivity (DDC-IR) was associated with blood vessels and acini in the submandibular gland, but this was much less extensive than the population that exhibited tyrosine hydroxylase-like immunoreactivity (TH-IR). The varicose terminal TH-IR axons in atrium, spleen, and vas deferens were devoid of DDC-IR both in grown rats and during the post-natal period of axon growth, although weak DDC-IR was seen in large pre-terminal nerve bundles. Similar patterns of staining were seen with paraffin-embedded and with frozen, formaldehyde-fixed material. No enhancement of DDC-IR was seen in any tissue after chronic alteration of catecholamine turnover with reserpine or alpha-methyl-para-tyrosine, and the numbers of submandibular DDC-IR axons were not increased by disruption of axonal transport with colchicine or by decentralization of the superior cervical ganglion. We conclude that terminal noradrenergic axons contain insufficient DDC-IR for microscopic visualization, regardless of their metabolic state, reinforcing previous evidence that DDC-IR can be used as a histochemical marker for dopaminergic axons. By this criterion, the rat submandibular gland may receive a sparse dopaminergic innervation.     

Class pi glutathione S-transferase from pig lung. Purification, biochemical characterization, primary structure and crystallization

A cytosolic glutathione S-transferase from pig lung was purified 210-fold to apparent homogeneity. The enzyme was classified as a class pi isoenzyme on the basis of its physical and chemical properties. It is homodimeric with a subunit Mr of 23,500, has a pI of 7.2, and shows a high specific activity towards ethacrynic acid. The glutathione analogues, S-hexylglutathione and glutathione sulfonate, were strong reversible inhibitors. The enzyme's primary structure, established entirely by protein chemical methods, consists of 203 amino acids and is highly similar (82-84% residue identity) to the rat and human class pi isoenzymes. Furthermore, there was no evidence of microheterogeneity or post-translational modifications. Each subunit contains a highly reactive cysteine residue, the modification of which leads to enzyme inactivation. None of the cysteine residues in the pig enzyme appear to form intramolecular disulfide bonds. Singel crystals of the glutathione-S-transferase-glutathione-sulfonate complex were obtained by the hanging-drop method of vapour diffusion from poly(ethylene glycol) 4000 solutions. The crystals belong to the orthorhombic space group P212121 with unit cell dimensions of a = 10.125 nm, b = 8.253 nm and c = 5.428 nm and diffract to better than 0.22 nm.     

Influence of site-directed modifications on the formation of iron cores in ferritin

The structure and crystal chemical properties of iron cores of reconstituted recombinant human ferritins and their site-directed variants have been studied by transmission electron microscopy and electron diffraction. The kinetics of Fe uptake have been compared spectrophotometrically. Recombinant L and H-chain ferritins, and recombinant H-chain variants incorporating modifications in the threefold (Asp131----His or Glu134----Ala) and fourfold (Leu169----Arg) channels, at the partially buried ferroxidase sites (Glu62,His65----Lys,Gly), a putative nucleation site on the inner surface (Glu61,Glu64,Glu67----Ala), and both the ferroxidase and nucleation sites (Glu62,His65----Lys,Gly and Glu61,Glu64,Glu67----Ala), were investigated. An additional H-chain variant, incorporating substitution of the last ten C-terminal residues for those of the L-chain protein, was also studied. Most of the proteins assimilated iron to give discrete electron-dense cores of the Fe(III) hydrated oxide, ferrihydrite (Fe2O3.nH2O). No differences were observed for variants modified in the three- or fourfold channels compared with the unmodified H-chain ferritin. The recombinant L-chain ferritin and H-chain variant depleted of the ferroxidase site, however, showed markedly reduced uptake kinetics and comprised cores of increased diameter and regularity. Depletion of the inner surface Glu residues, whilst maintaining the ferroxidase site, resulted in a partially reduced rate of Fe uptake and iron cores of wider particle size distribution. Modification of both ferroxidase and inner surface Glu residues resulted in complete inhibition of iron uptake and deposition. No cores were observed by electron microscopy although negative staining showed that the protein shell was intact. The general requirement of an appropriate spatial charge density across the cavity surface rather than specific amino acid residues could explain how, in spite of an almost complete lack of identity between the amino acid sequences of bacterioferritin and mammalian ferritins, ferrihydrite is deposited within the cavity of both proteins under similar reconstitution conditions.     

Quantitation of a mitochondrial DNA deletion in Parkinson's disease.

A 5 kilobase deletion in mitochondrial DNA (mtDNA) has been reported to be responsible for the specific complex I deficiency in the substantia nigra (SN) of the Parkinson's disease (PD) brain. We have studied mitochondrial respiratory chain function in the SN from control and PD subjects, and analysed mtDNA, extracted from the same tissues, by Southern blot and the polymerase chain reaction (PCR). Quantitation of the levels of the deletion indicate that it does not contribute to the pathogenesis of PD nor to a complex I deficiency but seems likely to be an age-related observation.     

The disulfide bridge pattern of snake venom disintegrins, flavoridin and echistatin.

Flavoridin and echistatin, isolated from the venom of Trimeresurus flavoviridis and Echis carinatus, respectively, belong to the disintegrin family of integrin beta 1 and beta 3 inhibitors of low molecular weight RGD-containing, cysteine-rich peptides. Since disulfide bonds are critical for expression of biological activity, we sought to determine their location in these two proteins. In flavoridin, direct evidence for the existence of linkage between Cys4-Cys19 and between Cys45 and Cys64 was obtained by analysis of proteolytic products, and indirect evidence suggests links between Cys6-Cys14 and Cys13-Cys36. In echistatin, links between Cys8-Cys37 and Cys20-Cys39 were identified by direct chemical analysis.