Regulation of tubulin by triiodothyronine in hypothyroid rat brain

The effect of T3 (triiodothyronine) on the induction of tubulin in hypothyroid developing rat brain has been examined using organ cultures of brains from late fetal, neonatal and postnatal rats. The neonatal brain displayed maximum sensitivity to T3. Hypothyroidism resulted in a 26% decline in the level of tubulin in the neonatal brain as opposed to a 5-15% decline in the fetal or postnatal brain. Exposure of the hypothyroid neonatal brain to T3 for 2 h in culture led to a 61% rise in the level of tubulin in contrast to a 41% increase seen in the case of normal brain. Total protein synthesis was not significantly affected. The preferential decline of tubulin in the neonatal hypothyroid brain, its enhanced sensitivity to T3 compared to normal brain, and the coincidence of the period of sensitivity to that of brain maturation indicate that the regulation of the level of tubulin by T3 in the developing brain is a natural ontogenic phenomenon.

Influence of retinoid nutritional status on cellular retinol- and cellular retinoic acid-binding protein concentrations in various rat tissues

Studies were conducted to explore the effects of differences in retinoid nutritional status and of sex on the tissue distribution and levels of cellular retinol-binding protein (CRBP) and of cellular retinoic acid-binding protein (CRABP) in the rat. Sensitive and specific radioimmunoassays were developed and employed to measure the levels of both CRBP and CRABP. Four groups of six male rats each were fed experimental diets that differed greatly in the amount and kind of retinoids provided, but were otherwise identical. These groups were comprised of rats that were normal controls, retinoid-deficient, retinoic acid-fed, and excess retinol-fed. A fifth group of six female rats was fed the control diet. Immunogens identical with rat testis CRBP and CRABP, as assessed by radioimmunoassay displacement curves, were found in every rat tissue examined (21 tissues in males, 18 in females). The highest levels of CRBP were found in the proximal portion of the epididymis, the liver, and kidney. The highest levels of CRABP were found in the seminal vesicles, vas deferens, and skin. A significant (p less than 0.01) inverse relationship was found between CRBP and CRABP levels in the different tissues of the male reproductive tract. In both males and females, CRBP levels were highest in the gonads and proximal portion of the reproductive tract and decreased distally, whereas the opposite was true for CRABP. Retinoid-deficient rats showed reduced tissue levels of CRBP; thus, tissue CRBP levels are influenced by diet and retinoid availability. No differences in tissue CRBP levels were found in the rats fed the control, the retinoic acid, or the excess retinol diets. Female control rats had higher CRBP levels than male controls in 4 of 15 tissues compared (liver, lung, thymus, and fat). In contrast, tissue CRABP levels showed no diet- or sex-dependent differences. Only in one tissue, the skin, were differences observed (lower CRABP in retinoid-deficient and in female rats). Thus, CRABP metabolism and levels appear to be minimally influenced by the amount or kind of retinoid ligand available or by sex.

Demonstration of an internal pancreatic fistula by computed tomography

The computed tomographic demonstration of a mediastinal pseudocyst communicating with the pancreatic duct in a patient with severe acute pancreatitis is reported. An awareness of this communication was essential in planning the appropriate surgical management.

Cellular retinol-binding protein. Quantitation and distribution

The distribution of cellular retinol-binding protein was localized in three tissues involved in the transport of vitamin A using the peroxidase-antiperoxidase technique. In addition, a sensitive radioimmunoassay was developed to quantitate cellular retinol-binding protein in various tissues. In liver, the protein was found in the hepatocytes and in the perisinusoidal fat-storing cells. The columnar epithelial cells of the jejunum and the cells of the proximal tubuli also exhibit high concentrations of cellular retinol-binding protein. Estimations of the content of the protein in various tissues from normal and retinol-deficient rats showed that the retinol status did not affect the tissue levels or the subcellular distribution. The appearance of high amounts of this protein in cells involved in the dietary uptake, storage, mobilization, and resorption of vitamin A suggest that one function of the cellular retinol-binding protein is to act as a vehicle in the intracellular transport of retinol through these organs.

Structure and tissue distribution of some retinoid-binding proteins

Vitamin A has, apart from its function in the visual pigments, general effects on several organs. Early signs of vitamin A deficiency include keratinization of epithelia and hyperkeratosis of the skin. To elucidate a generalized function for vitamin A, we have taken the approach of tracing the vitamin from its storage site in the liver via its blood transport by the retinol-binding protein (RBP) to its uptake by susceptible cells. We have also examined the intracellular occurrence of vitamin A as regards its binding to specific receptor proteins. Here we summarize data on the amino acid sequences of several vitamin A-binding proteins. The finding that CRBP and CRABP, the two intracellular proteins, are homologous to each other, to a myelin protein, and to a fatty acid-binding protein may shed light on the functions of these proteins. Retinoic acid, which binds to CRABP but not CRBP, induces differentiation of teratocarcinoma cells. This is accompanied by a lowering of the CRABP concentration, an increase of the CRBP level, and an increase in the uptake of retinol from RBP. The epidermis contains both CRBP and CRABP, and their distributions are rather similar. However, in contrast to CRBP, CRABP is most abundant in cells lining the hair follicles. CRBP occurs in greatest relative amounts in the outer layers of the epidermis. Since techniques have been developed to measure CRBP and CRABP, normal and disease-affected skin may now be explored as to quantity and cellular distribution of the retinoid-binding proteins.

Effect of age and short-term cold stress on SDH activity and oxygen consumption of lizard brain

The SDH (EC 1.3.99.1) activity of both whole brain and mid-brain homogenates and the specific oxygen consumption of mid-brain homogenate are significantly lower in old than in young lizards. Short-term cold stress (1 h at 0--4 degrees C) did not induce a significant change in the enzyme activity of the whole brain homogenate, but the activity was depressed in the mid-brain homogenate of lizards of both age groups, not showing appreciable age-dependency of the response. The respiratory rates of mid-brain homogenates of both young and old lizards were depressed following cold stress. Lizards of both age groups showed almost complete reversal of depressed respiratory rate during the same time, i.e. between 30 and 45 min of rewarming at room temperature (30 +/- 2 degrees C). Though statistically insignificant the old lizards showed a trend of slower rate of recovery as compared to the young lizards, suggesting further detailed studies on the problem in question.

Effect of short-term cold stress on the respiratory metabolism of brain tissue homogenates of male garden lizards of two different age-groups

The endogenous oxygen uptake and the uptake with added substrate of whole-brain and mid-brain homogenates were significantly lower in older lizards as compared to younger. Both whole brain and mid-brain showed responses to cold stress for different lengths of time but the decline in oxygen uptake was more pronounced in the younger age-group. Respiratory rate and response to cold stress were more marked in the mid-brain than in the whole brain. Basing on earlier reports on mammals and on the present findings, it is suggested that the decline in physiological adaptation in older animals may be a general feature in vertebrates.

Affinity chromatography of enzyme cofactors: the separation of NAD on immobilised dehydrogenase colums

1. Alcohol dehydrogenase (EC 1.1.1.1.) has been immobilised to aminoethyl-cellulose by glutaraldehyde, to DEAE-cellulose by an s-triazine derivative and to agarose using CNBr. Lactate dehydrogenase has been immobilised to the latter two supports. 2. Their use for affinity chromatography of NAD was compared and alcohol dehydrogenase immobilised to CNBr-activated agarose chosen for detailed study due to the efficient coupling of applied enzyme and the specific nature of binding. 3. The efficiency of coupling of alcohol dehydrogenase dropped from 94.5 to 72.2% when the applied load was increased from 18 to 54 mg/g activated agarose. Activity relative to free enzyme fell from 21 to 11%. The binding of NAD was maximal between pH 5.5 and 6. With the lowest loading of enzyme, NAD binding fell from 450 to 320 mug/g support when the linear flow rate was increased from 0.84 to 3.95 cm/min. 4. NAD was completely separated from a mixture with ATP, ADP and AMP. Separation from NMN and hydrolysed RNA and DNA was evidently possible. Immobilised alcohol dehydrogenase used for 34 binding experiments over a period of weeks maintained 60% of its original enzyme activity. 5. The method was applied to yeast NAD following mechanical disruption of yeast, clarification and either ultrafiltration or hollow-fibre dialysis to permit separate purification of macromolecules and nucleotides.