The localization of calcium by X-ray microanalysis in myopathic muscle fibers

An electron histochemical study was undertaken to localize calcium with ammonium oxalate precipitation technique in soleus muscle of rat in normal cases and in myopathy induced experimentally by a prolonged treatment of 2,4-dichlorophenoxyacetate (2,4-D). The calcium content of precipitates was detected by energy-dispersive X-ray microanalysis. In normal cases, the electron dense precipitates containing calcium were mainly found in the vesicles of sarcoplasmic reticulum, whereas in 2,4-D induced myopathy the deposits were shifted near the Z line into the myofibrils. Calcium, because the uptake into sarcoplasmic vesicles was inhibited by 2,4-D, could attach to other binding sites, such as to the troponin-C.A long-lasting binding of calcium might lead to a prolonged activation of the actin-myosin system.     

Affi-gel blue treatment simplifies the protein composition of sarcoplasmic reticulum vesicles

Sarcoplasmic reticulum vesicles isolated by conventional techniques usually contain, in addition to the recognized sarcoplasmic reticulum components, several other proteins (phosphorylase, myosin, glyceraldehyde-3-phosphate dehydrogenase, etc.) in variable amounts; these proteins complicate the interpretation of chemical modification data. Incubation of sarcoplasmic reticulum vesicles with Affi-Gel blue particles for 1-4 h at 2 degrees C, followed by sedimentation of the Affi-Gel in a clinical centrifuge, simplifies the protein composition by selective adsorption of the accessory proteins, and improves the consistency of the preparations. The Affi-Gel blue treatment is recommended as part of the standard procedure for the isolation of sarcoplasmic reticulum vesicles.     

Effects of acute hypoxia on the adenylate cyclase and evans blue transport of brain microvessels

Kinetic parameters of the albumin transport were measured during and after an acute hypoxic insult evoked in newborn piglets by experimental bilateral pneumothorax. Adenylate cyclase activity was determined in the cerebral microvessels isolated by ultracentrifugation from different stages of brain damage. A decrease of the adenylate cyclase activity was observed in the cerebral microvessels of animals with acute hypoxic condition. However, the adenylate cyclase activity was found to be increased significantly in the microvessels during recirculation.

The activation of adenylate cyclase in the microvessel wall may be of pathogenetic importance in the development of vasogenic brain oedema.     

Effects of disuse on the function of fragmented sarcoplasmic reticulum of rabbit M. gastrocnemius

A preparation method has been described to obtain a relatively pure and functionally intact fragmented sarcoplasmic reticulum (SR) vesicles fraction from normal and atrophied muscles. Purified SR preparations from rabbit gastrocnemius muscle atrophied by disuse showed similar protein composition (gel electrophoresis; Laemmli 1970) and similar vanadate induced crystallization (Dux and Martonosi 1983) properties of Ca2+-ATPase as those of control preparations. In the early period of atrophy (1-2 weeks) both the Ca2+-ATPase activity and Ca2+ uptake showed a 2-3-fold increase (from 3.42 +/- 0.24 to 7.34 +/- 0.25 mumol Pi X mg-1 prot X min-1 and from 1.26 +/- 0.10 to 3.36 +/- 0.22 mumol/l Ca2+ X min-1 X mg-1 prot. respectively).     

Calcium in hippocampus following lidocaine induced seizures: an electron cytochemical study

The effect of lidocaine seizures on cellular accumulation of calcium was studied in hippocampal subfields CA1 and CA3 and the dentate gyrus of rats, using the combined oxalate-pyroantimonate method. The specificity of the reaction was ascertained by EGTA treatment and X-ray microanalysis. In control rats, calcium was visualized between myelin lamellae of axons, in synaptic vesicles and in some lysosomes. Two hours after onset of lidocaine seizures selective neuronal degenerations appeared in hippocampal subfields CA1 and CA3 but not in the dentate gyrus. Calcium deposits were present in numerous mitochondria of pyramidal cells and, occasionally, also of neuroglial cells. Many of these mitochondria exhibited ultrastructural alterations. Calcium uptake was most prominent in the CA3 sector but was also present in the CA1 subfield as well as the dentate gyrus. Intracellular calcium uptake, in consequence, is not the unique attribute of selectively vulnerable hippocampal neurons.     

Structure of the vanadate-induced crystals of sarcoplasmic reticulum Ca2+-ATPase

The projected structure of the vanadate-induced crystalline aggregates of Ca2+-ATPase molecules in isolated sarcoplasmic reticulum membranes has been determined. The molecules form tubular crystals with an oblique surface lattice having cell dimensions a = 65.9 A, b = 114.4 A and gamma = 77.9 degrees. The space group is P2. The crystalline tubules are formed through lateral aggregation of chains made up of dimers of Ca2+-ATPase molecules.     

Studies on a Capillary-Rich Fraction Isolated from Brain: Histaminic Components and Characterization of the Histamine Receptors Linked to Adenylate Cyclase

Abstract: A fraction enriched in capillaries has been prepared from the guinea pig cerebral cortex. The purity of this fraction was checked by light- and electron-microscopic examination and by its high enrichment in alkaline phosphatase and γ-glutamyl transpeptidase. In the capillary-rich fraction, the endogenous level of histamine was 1.9%'of that measured in the initial hornogenate. The histamine-synthesizing enzyme, I-histidine decarboxylase, and the metabolizing enzyme, histamine-N-methyltransferase, were barely detectable. In addition, histamine elicits a twofold stimulation in the accumulation of cyclic AMP in this capillary fraction with an EC₅₀ of 5 γM. Agonists and antagonists of the two types of histamine receptors (H₁ and H₂) were used for the characterization of the receptors mediating this action: H₂-receptor agonists were able to activate the adenylate cyclase with "relative potencies" similar to that found on typical H₂-receptors, and cimetidine, a specific H₂-receptor antagonist, competitively inhibited the response to histamine with a K₁ value reflecting its interaction with a single population of H₂-receptors. On the contrary, data obtained with H₁-receptor agonists and antagonists reflect their interaction with H₂-receptors rather than H₁-receptors. Thus H₂-receptors are involved in the activation of adenylate cyclase of the capillary fraction.     

Rapid pacing-induced preconditioning is recaptured by farnesol treatment in hearts of cholesterol-fed rats: Role of polyprenyl derivatives and nitric oxide

Sodium selenate, administered intraperitoneally (i.p.), resulted in an improvement in glucose tolerance in treated diabetic rats. Fed rat plasma glucose levels were reduced by selenate treatment in streptozotocin diabetic rats. The lowest values of blood glucose were reached within 3 weeks of beginning the treatment. Food and fluid consumption was reduced in treated compared to untreated diabetic rats. Diabetic treated rats did not release insulin in response to a glucose challenge and insulin release in response to a challenge was markedly reduced in control treated rats. Assessment of heart function using a working heart apparatus showed that treated diabetic rats with improved blood glucose levels had normal heart function at 8 weeks of diabetes in contrast to hearts from non-treated diabetics. This study extends previous observations on the in vivo insulin-like effects of sodium selenate.     

Synthesis of chicken galanin and its N- and C-terminal segments,and preparation of their antisera

Summary We describe the synthesis of the first avian galanin (GAL), chicken GAL, and its N-terminal and C-terminal segments by solid-phase synthesis, using Boc/Bzl amino acid protection groups and MBHA resin. The three peptides were prepared with purities of over 97%, as determined by RP-HPLC, HPCE, FAB-MS or ESI-MS and amino acid analysis. Antibodies against these synthetic peptides were raised in rabbits and used for immunohistochemical localization of GAL-immunoreactive neurons in chicken brain.