Calcium Uptake and Release through Sarcoplasmic Reticulum in the Inferior Oblique Muscles of Patients with Inferior Oblique Overaction

We characterized and compared the characteristics of Ca2+ movements through the sarcoplasmic reticulum of inferior oblique muscles in the various conditions including primary inferior oblique overaction (IOOA), secondary IOOA, and controls, so as to further understand the pathogenesis of primary IOOA. Of 15 specimens obtained through inferior oblique myectomy, six were from primary IOOA, 6 from secondary IOOA, and the remaining 3 were controls from enucleated eyes. Ryanodine binding assays were performed, and Ca2+ uptake rates, calsequestrins and SERCA levels were determined. Ryanodine bindings and sarcoplasmic reticulum Ca2+ uptake rates were significantly decreased in primary IOOA (p < 0.05). Western blot analysis conducted to quantify calsequestrins and SERCA, found no significant difference between primary IOOA, secondary IOOA, and the controls. Increased intracellular Ca2+ concentration due to reduced sarcoplasmic reticulum Ca2+ uptake may play a role in primary IOOA.

Oxalate binding protein from the kidney of rat and human mitochondria: studies on properties.

The oxalate binding protein of rat and human kidney mitochondria were extracted by Triton X-100 and purified on Sephadex G-200 column followed by HPLC. Their molecular masses were found to be 62 kD and 58 kD respectively, rich with arginine and acidic amino acids, 7% of carbohydrates and 1% of inorganic ions. Antibodies raised to the rat protein inhibited the oxalate binding and cross-reacted to the human protein as well as rat liver protein. The binding of oxalate to the protein was rapid, reversible, dependent on concentration of oxalate, temperature sensitive and inhibited by oxalate analogues. The saturation reached at 175 nM oxalate for rat protein with a Kd of 33.3 nM and Bmax of 21 nmoles while for human protein the saturation reached at 183 nM oxalate and had a Kd of 41 nM and Bmax of 14 n moles. The half-saturation concentration of inhibitor (IC50) of oxalate was 0.25 microM for rat protein and 0.225 microM for human protein while the structural analogues of oxalate had higher IC50 values. Proteoliposomes showed accumulation of oxalate confirming transport function of the protein. The rat protein promoted calcium oxalate crystallization in vitro better than that of human protein and antibody inhibited the crystal growth in vitro.

Investigation with chitosan-oxalate oxidase-catalase conjugate for degrading oxalate from hyperoxaluric rat chyme.

Enteric hyperoxaluria manifests due to hyperabsorption of dietary oxalate, secondary to a variety of chronic gastrointestinal disorders. The potential use of chitosan immobilized oxalate oxidase-catalase conjugate to deplete the oxalate content of food materials, while they are in the digestive tract has been evaluated by treating rat stomach chyme with such an enzyme preparation. Oxalate oxidase, obtained from beet stem, was adsorbed on chitosan along with catalase and then cross linked with glutaraldehyde to stabilize the derivative. This chemical modification of oxalate oxidase brought about a shift in its optimal pH from 4.2 to 3.8 with a marginal increase in its K(m). Compared to native enzyme, the modified oxalate oxidase exhibited increased storage stability, higher thermal stability and enhanced resistance to proteolytic digestion and heavy metal inactivation. These improved properties of the immobilized oxalate oxidase possibly render it suitable for oral administration under hyperoxaluric conditions.

Oxalate binding to rat kidney mitochondria: induction by oxidized glutathione.

Increased oxalate binding with negative correlation with reduced glutathione content was observed during lipid peroxidation in rat kidney mitochondria. In presence of oxidized glutathione (GSSG), peroxidized mitochondria lost 48% of protein-SH with concomitant 3-fold increase in oxalate binding activity while control mitochondria lost only 20% protein-SH with only 0.8 fold increase in oxalate binding activity. The GSSG-induced oxalate binding was apparently due to two-fold increased affinity of oxalate to the protein. Reduced glutathione (GSH) inhibited oxalate binding competitively with Ki, 1.4 x 10(-3) M. Urolithic rat kidney mitochondria showed 30-50% increase in oxalate binding activity along with depletion of GSH and protein-SH. These studies suggest that oxalate binding is regulated by thiol status of mitochondria.

Electrokinetic energy conversion studies of aqueous solutions of oxalic acid and urea across urinary bladder membranes.

Electrokinetic studies namely hydrodynamic permeability, electroosmotic permeability and streaming potential measurements of aqueous solutions of oxalic acid and urea have been made across urinary bladder membranes of goat. Energy conversion maxima and degree of coupling for these permeants have computed. It has been found that these values increase with increases in concentration of the permeants. Since electro-osmotic flux tendency is quite opposite for oxalic acid in comparison to that of urea, energy conversion values increase with increase in concentration but in opposite directions. Such studies are expected to be of use in understanding electrophysiology of the bladder as inefficient functioning of the bladder leads to formation of urinary calculi and many other types of disorders. Methodology of non-equilibrium thermodynamics have been used to explain the data.

Fisiopatologia do intestino curto: a propósito de dois casos / Physiopathology of the short intestine: apropos of 2 cases

Os autores apresentam dois casos de intestino curto. O primeiro deles refere-se a uma paciente de cor branca, com 54 anos de idade, correspondendo o segundo caso a um indivíduo do sexo masculino, de cor branca. Ambos apresentaram acentuada desnutriçäo e esteatorréia, tendo sido submetidos a alimentaçäo parenteral. Nos dois casos esteve presente calculose das vias urinárias por oxalato de cálcio; também litíase vesicular e pancreatite aguda. Baseados nos elementos clínicos e laboratoriais, os autores discutem a fisiopatologia do intestino curto, dando realce ao papel dos sais biliares e ao relativo esvaziamento do "pool" desses sais, bem como a açäo dos mesmos sobre os cólons e na gênese da bile litogênica. Ao nível dos cólons, as investigaçöes até o momento desenvolvidas, indicam certa "liberaçäo" na absorçäo de oxalato, ao mesmo tempo em que a água tem sua absorçäo colônica diminuida. A conduta clínica é comentada, com ênfase particular ao papel da terapêutica pelo cálcio, emprego da colestiramina e de dieta suplementar