Extraction Of Slices Research Articles

Aneurysm of the main stem of the left coronary artery associated with aortic insufficiency and aneurysm of the ascending aorta. Report of a case with successful surgical repair.

A case of aneurysm of the main stem of the left coronary artery associated with aortic insufficiency and an aneurysm of the ascending aorta is reported. The importance of coronary angiography in diagnosing this condition is illustrated. Surgical repair included isolation of the coronary aneurysm and replacement of the ascending aorta and aortic valve, combined with triple aortocoronary saphenous vein bypass grafts. A review of the aetiology, clinical features, and surgical management of coronary artery aneurysms is presented.

Effects of Calcium Ionophores on the Synthesis and Release of Parathyroid Hormone

The parathyroid gland is unusual among endocrine and other secretory tissues in that increased concentrations of calcium in the extracellular fluid inhibit rather than facilitate or stimulate hormone secretion. To determine whether translocation of calcium ions across the plasma membrane might be involved in the secretory processes of the parathyroid gland, we studied the effects of the calcium ionophores A23187 and X537A on the secretion and biosynthesis of parathyroid hormone (PTH) in vitro. Slices of bovine parathyroid glands were incubated for 3–4 h with radioactive leucine. Secretion of radioactive and immunoreactive parathyroid hormone by the gland slices was evaluated by measurements of acid-insoluble radioactivity and radiolabeled PTH by polyacrylamide-gel electrophoresis and by radioimmunoassay, respectively. Biosynthesis of parathyroid hormone was evaluated by electrophoretic analysis of radiolabeled proparathyroid hormone (ProPTH) and PTH in extracts of gland slices that had been pulse-labeled ...

State of stress in rocks when ore bodies are worked by the longwall slicing system

To investigate roof behavior and the state of stress of the rocks around a working of complex shape a finite-element numerical analysis has been performed. The effect exerted by different orders of extraction of the ore body on the stress distribution around the working was investigated. Different sequences of working the ore lead to markedly different stress distributions in the solid rock. The highest stress concentration is observed for the descending order of slice extraction where the upper slice is considerably in advance. As a consequence, a considerable mass of the roof sags over the more yielding stowage. Table 2 gives the comparative maximal values of the stress components for the ore body, the stowing, and the surrounding rock. Analysis of the stressed state of the rock shows that the yielding stowing promotes removal of dangerous stresses in the sagging rocks. But in the stress concentration zones they reach the strength of the rocks. These calculations are applicable during mining, in the planning stage, and in the construction of analogous mines.

Factors affecting morphine uptake into kidney slices

The uptake of [ n-methyl 14C]morphine by mouse kidney slices was saturable, reversible, temperature- and pH-dependent, and was inhibited by strong metabolic poisons and by structural analogs, thereby satisfying criteria for mediation by active transport processes. There were species differences: rat kidney cortex slices took morphine up at rates similar to those of mouse kidney, but guinea pig kidney cortex had lower uptake. Thin-layer chromatography (t.l.c.) of slice extracts after incubation with [ 14C]morphine did not indicate significant metabolism of morphine. Morphine efflux after equilibrium uptake from 30 nM or 10 μM initial medium levels required 20 min for 50 per cent of the [ 14C]morphine to exit. The uptake at 5 min was proportional to the equilibrium level at 30 min from 5 nM to 10 μM. No evidence for counter-transport was observed. Tissue/medium levels of 10–12 at 39–90 nM morphine (after 30 min at 37°) were reduced 50 per cent at pH 6.5 or at 20°, or by mitochondrial enzyme inhibitors, e.g. rotenone. Narcotic antagonists and analogs (methadone, nalorphine and levorphanol) and quinine also reduced the uptake of morphine from medium levels of 0.01 to 0.1 μM. However, at morphine concentrations above 10 μM, narcotic analogs or antagonists up to 50 μM did not inhibit uptake. Transport system inhibitors, quarternary bases, reducing agents and SH-oxidants also inhibited morphine uptake from 30 nM to 0.5 mM. Phloretin, phloridzin and atractyloside did not block uptake, while glucose, ouabain and NaF were very weak inhibitors. The results suggest that uptake of morphine in kidney slices involves SH groups and mitochondrial activity rather than glycolytic or ion-pump mechanisms. With a few exceptions, the characteristics and inhibitor sensitivity of morphine uptake by kidney slices and of amino acid uptake by brain slices appear similar.

Endogenous proteolytic activity and constituent polypeptide chains of sheep and pig 19 s thyroglobulin

Porcine and ovine 19-S thyroglobulins prepared from frozen glands in several buffers using slice extraction or homogenization, ammonium sulfate precipitation and DEAE-cellulose chromatography or Sepharose 6B gel filtration were contaminated with protease activity of pH optima 4.5 and 8.6, as shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Optimum temperatures of autodigestion were 37°C at pH 4.5 and 25°C at pH 8.6. Thyroglobulins prepared from unfrozen glands pH 7.2 in 0.1 M sodium phosphate using slice extraction, ammonium sulfate precipitation and Sepharose 6B gel filtration were devoid of acid proteolytic activity but still underwent autodigestion at pH 8.6. Diisopropylfluorophosphate was a potent inhibitor of the alkaline protease activity of ovine thyroglobulin preparations. In contrast to thyroglobulin obtained from frozen glands the proteins purified from fresh unfrozen glands at pH 7.2 only showed the 19-S and the 12-S species by electrophoresis in sodium dodecyl sulfate polyacrylamide gels. Very few bands migrating faster than 12-S were visible. After full reduction and S-alkylation of porcine and ovine thyroglobulins, no qualitative changes were observed in the gel electrophoresis pattern as compared to the unmodified proteins. Species of apparent mol.wt. corresponding to the native 12 S were the major component, strongly suggesting a mol.wt. of about 330 000 for the elementary peptide chains of pig and sheep thyroglobulins.

Compartmentation and exchangeability of brain amino acids: Evidence from studies of transport into tissue slices

Compartmentation of the free amino acid pool of brain slices was investigated by measuring the approach to isotopic equilibrium between tissue and medium when slices were incubated with traces of radioactive amino acids. Trace quantities were used to minimize the effects of uptake, which could make the detection of slowly equilibrating pools difficult by greatly increasing tissue amino acid levels. Small, sequestered compartments were found. After 2 h in 20 vol of glucose-containing, oxygenated medium, the nonequilibrating compartments for lysine, leucine, tyrosine, histidine, valine, and threonine were 41, 20, 17, 16, 11, and 6% of their final tissue concentrations, respectively. The data for rapidly metabolized, nonessential, amino acids were more difficult to interpret. Considerable mixing of incoming glutamic and aspartic acids with their endogenous pools was observed and tissue glycine reached isotopic equilibrium within 1 h. With higher concentrations of amino acids, equilibration was complete in 30 min with 2 m m glycine in the medium; 83% in 30 min with 2 m m glutamic acid, and 95% in 60 min with 5 m m glutamic acid in the medium. The amino acid composition of protein free extracts of slices and medium was determined. During incubation, despite a large efflux of amino acids into the medium, most tissue amino acids remained close to their initial concentrations. Net increases in essential amino acids were accounted for by the breakdown of 0.7% of total tissue protein during the first hour and 0.3% during the second hour of incubation.

Proton and malate fluxes in cells of Bryophyllum daigremontianum leaf slices in relation to potential osmotic pressure of the medium

Summary Leaf slices obtained from the CAM plant Bryophyllum daigremontianum at the end of the dark phase were used to study proton und malate fluxes. Increasing potential osmotic pressure (π*) of the medium decreases loss of H + and malate from the leaf cells to the medium and increases the amounts of H+ and malate retained in the cells. As compared to the initial H + and malic acid levels, after the efflux experiments a certain amount of H+ and malate is not accounted for by efflux and retainment in the tissue. This amount is thought to be due to metabolic utilization of malic acid, it is smaller in the dark than in the light, and it is not clearly correlated to π * of the medium. Changes in potential osmotic pressure of extracts (Δπ * ) of the leaf slices are highly correlated to changes in malate content of the extracts. Malic acid accounts for about 55% of Δπ * of the extracts. It is suggested that net efflux of malic acid from the vacuoles of B. daigremontianum depends on turgor of the cells and that this mechanism plays a role in regulation of crassulacean acid metabolism (CAM) in vivo .

The effect of L-epinephrine and triamcinolone on the incorporation of acetate-2-14C and 32Pi into phospholipids and neutral lipids in liver slices from adrenalectomized rats, in vitro.

In liver slices from adrenalectomized rats, L-epinephrine (3×10−6M) and triamcinolone (1×10−6M) stimulated gluconeogenesis from L-alanine, but neither treatment significantly changed the concentration of tissue neutral lipids or phospholipids. Phosphatidylinositol was not found in the lipid extracts of liver slices from rats 3–5 days after adrenalectomy. L-Epinephrine decreased the incorporation of acetate-2-14C into phosphatidylcholine, phosphatidylethanolamine and triglycerides, but did not affect incorporation into tissue free fatty acids, phosphatidylserine, cholesterol, or cholesterol esters. L-Epinephrine caused a 3.4-fold increase in 32Pi incorporation into phosphatidylserine, but caused much smaller per cent increases in the incorporation of 32Pi into phosphatidylcholine and phosphatidylethanolamine. Triamcinolone had no effect on the tissue levels or on the incorporation of acetate-2-14C into tissue neutral lipids and phospholipids. Incubation of liver slices in vitro for 3 hr decreased the conce...

Medullary Sodium and Urea Gradient of the Dog Kidney in Hypothermia

SummaryThe kidneys were removed from 11 euthermic and 8 hypothermic (average rectal temp. 25°C) dogs and four slices of the tissue from papilla to cortex were taken from each kidney. The Na, K, and urea concentrations of the slice were then determined in slice extracts. Although urine osmolality was significantly reduced in hypothermia, the papillary Na and urea concentrations at a given urine osmolality were markedly higher in hypothermic kidneys than in euthermic, suggesting that the impairment of renal concentrating ability in hypothermia is partly attributable to a failure of the collecting duct urine to osmotically equilibrate with the surrounding media. On the basis of the latter finding, it is postulated that the action of ADH is less effective in hypothermia.

The problem of halting enzyme action when extracting plant tissues

In studies on plant extracts, tissues have often been killed in boiling 80% methanol. This method takes minutes to inactivate phosphatase completely, and allows measurable enzyme action to occur in plant tissue slices and cell suspensions. In Chlorella extracts, the amount of ADP and UDP can be doubled by post mortem phosphatase action. Much larger changes are caused in tissue slice extracts. A model tissue disk system was used to show that, in slices, phosphatase action during killing in boiling methanol was equivalent to that obtained with the fully active enzyme in 60 sec at 25°C. The use of acid killing media at low temperature was studied. There was much less enzyme action during killing and in the extracts; and in the model tissue disk system, post mortem action was equivalent to less than 2 sec at 25°. Plant acid phosphatase functions at −28°C in the frozen state and in 40% methanol solution. Tissues or extracts taken for studies on phosphate metabolism should not be stored undried in the cold without first inactivating the phosphatase. Plant ribonuclease may show a similar behavior.

Conditions de formation d'une combinaison rotéique iodée et tritiée au cours de la désiodation des hormones thyroidiennes doublement marquées (131I et 3H)

1.1. Thyroid hormones doubly labeled in α-β position with 3H and in 3′,5′ or 3′ with 131I ([131I, 3H]dl-thyroxine and [131,3H]3,5,3′-triiodo-dl-thyronine) can be deiodinated by mitochondria and several acellular preparations: salt extracts of slices and mitochondria, purified preparations of thyroxine deiodinase. The only labelled compounds produced under the adopted experimental conditions are 131I- and a protein complex, PX, which contains both 3H and 131I. No trittium-labelled thyronine or tyrosine is formed. Since no 3H loss occurs during the incubation there is no exchange between the tritium atoms of the iodothyronine and the hydrogen atoms of the medium, neither do any metabolic modifications occur in the alanine side chain during the process.2.2. The ratio of the specific activities of the two isotopes in the chromatographic zones where residual dl-thyroxine or 3,5,3′-triiodo-dl-thyronine are located is identical to the blank after incubation with thyroxine deiodinase. However, this is not so in the other cases where a disagreement is observed in the rate of deiodination calculated from the measurements of 131I and 3H.PX does always, at the end of the reaction, contain a fraction of the 131I and the total 3H provided for by the disappeared iodothyronine. The 131I concentration of PX is not constant during the incubation period, but decreases when considered as a total and even in relationship to the concentration of 3H. The 131I deiodination of PX takes place in two steps which seems to indicate that the 131I is present in the protein in two different forms.3.3. All the used preparations lead to the same reaction products. Also, it seems that the mechanism of the deiodination is the same in the different cases. The deiodination of the thyroid hormones proceeds in two steps: (a) the fixation of the hormone to the protein, probably the enzyme, (b) the iodine is partially liberated from the complex which retains completely the organic skeleton of the iodothyronine. The formation of PX thus appears as a necessary step in the deiodination of the thyroid hormones.