Decrease in adenylate cyclase activity in dog livers during endotoxic shock

The effects of endotoxin administration on adenylate cyclase in dog liver plasma membranes were studied. The basal, fluoride-, guanine nucleotide-, isoproterenol-, and glucagon-stimulated adenylate cyclase activities were decreased by 61, 62, 69, 83, and 63%, respectively, 2 h after in vivo administration of endotoxin. Endotoxin (100 micrograms/ml) in vitro decreased the guanine nucleotide-, isoproterenol-, and glucagon-stimulated adenylate cyclase activities by 24, 25, and 21%, respectively. These data demonstrate that endotoxin administered in vivo or in vitro had an inhibitory effect on the adenylate cyclase enzyme system in dog liver plasma membranes. Because of the involvement of the adenylate cyclase-adenosine 3',5'-cyclic monophosphate (cAMP) system in the regulation of hepatic carbohydrate metabolism, the finding that endotoxin administration decreased adenylate cyclase activity in the liver should contribute to the understanding of the pathophysiology of altered hepatic glucose homeostasis during shock.

Changes in beta-adrenergic receptors in dog livers during endotoxic shock

The effects of endotoxin administration on beta-adrenergic receptors in dog liver plasma membranes were studied using [3H]dihydroalprenolol as a radioactive ligand. The Scatchard analysis revealed a one-component binding characteristic both in control and endotoxin-injected dogs. The Kd (dissociation constant) value was increased by 60% (4.2 +/- 0.5 nM for control vs. 6.7 +/- 0.5 nM for endotoxic; P less than 0.01) and the Bmax (maximum binding capacity) was decreased by 38% (600 +/- 60 and 370 +/- 70 fmol/mg protein for control and endotoxic, respectively; P less than 0.01) 2 h following endotoxin administration. The competitive inhibition studies show that the apparent Kd values for (-)-isoproterenol, (-)-epinephrine, and (-)-norepinephrine were increased by 14, 51, and 5 times, respectively, 2 h postendotoxin. In addition, endotoxin in vitro had a dose-dependent inhibitory effect on the specific binding of [3H]dihydroalprenolol, and it also reduced the number of beta-receptors. These data demonstrate that endotoxin, both in vivo and in vitro, decreased the binding affinity and the number of beta-adrenergic receptors in dog liver plasma membranes. A modification of the beta-adrenergic receptors in dog livers induced by endotoxin administration may play an important role in the development of hepatic glucose dyshomeostasis during shock.

Changes in alpha-adrenergic receptors in dog livers during endotoxic shock

The effects of endotoxin administration on alpha-adrenergic receptors in dog liver plasma membranes were studied using [3H]dihydroergocryptine as a radioactive ligand. The Scatchard analysis revealed a two-component binding characteristic both in control and endotoxin-injected dogs. The Kd (dissociation constant) of the high-affinity component was increased by 32.5% (0.4 +/- 0.04 nM for control vs 0.53 +/- 0.06 nM for endotoxic; P less than 0.05) with no significant change in the Kd for the low-affinity component (3.0 +/- 0.44 nM for control vs 3.4 +/- 0.44 nM for endotoxic) 2 hr following endotoxin administration. The maximum binding capacity of the high-affinity component was decreased by 38.1% (460 +/- 19.3 and 285 +/- 14.8 fmole/mg protein for control and endotoxic, respectively; P less than 0.01) and that of the low-affinity component was decreased by 34.2% (1050 +/- 66.4 and 690 +/- 44.6 fmole/mg protein for control and endotoxic, respectively; P less than 0.05) 2 hr after endotoxin injection. The competitive inhibition studies show that the apparent Kd values for (-)-epinephrine, (-)-norepinephrine, and prazosin were increased 15, 13, and 25 times, respectively, with no significant change in the apparent Kd values for yohimbine or phentolamine 2 hr postendotoxin. These data demonstrate that the binding affinity of the high-affinity component and the number of alpha-adrenergic receptor binding sites were decreased in endotoxic shock. A modification of the alpha-adrenergic receptors in dog livers induced by endotoxin administration may play an important role in the development of hepatic glucose dyshomeostasis during shock.

Changes in phase transition temperature of phospholipids induced by endotoxin

The effects of endotoxin (lipopolysaccharide from Salmonella minnesota Re 595) on the phase transition temperature (Tm) of various phospholipids were studied. Endotoxin had no effect on the Tm and the width of the phase transition of dipalmitoyl-sn-3-phosphatidylcholine. Endotoxin at 100 micrograms/ml increased the Tm of dipalmitoyl-sn-3-phosphatidylethanolamine by 1.1 degrees C (P less than 0.01) and narrowed the range of transition from 4.5 to 2.6 degrees C; the endotoxin-induced changes in the Tm and the transition range were abolished by the presence of 0.25 mM CaCl2. Endotoxin increased the Tm of dipalmitoyl-sn-3-phosphatidic acid by 1.1 (P less than 0.01), 1.2 (P less than 0.01), and 3.1 (P less than 0.01) degrees C at 25, 50 and 100 micrograms/ml, respectively. Furthermore, the width of phase transition of phosphatidic acid was narrowed from 6.5 to 4.0 degrees C by endotoxin at 100 micrograms/ml. The endotoxin-induced changes in the Tm and the transition range of phosphatidic acid were not affected by the presence of EDTA (1 mM) or CaCl2 (0.05-0.1 mM). These results suggest that endotoxin decreases the fluidity of negatively charged phospholipids such as phosphatidic acid and phosphatidylethanolamine. A change in the physical properties of membrane lipid bilayers induced by endotoxin may have an adverse effect on the function of biological membranes.

Changes in surface charge density on liposomes induced by Escherichia coli endotoxin

Changes in surface charge density of liposomes induced by E. coli endotoxin were studied by microelectrophoresis. Endotoxin altered the surface charge of phosphatidylcholine liposomes from neutral to negative. The negative charge of the endotoxin-phosphatidylcholine complex was neutralized electrostatically by binding with Ca2+ (2 mM). Phosphatidylcholine liposomes were made positive by addition of the positively charged detergent, hexadecyltrimethylammonium chloride. Endotoxin made the positively charged liposomes less charged. On the other hand, phosphatidylserine liposomes which were negatively charged became less charged in the presence of high concentration of endotoxin (8 mg/ml). The endotoxin effect on phosphatidylserine liposomes was abolished by EDTA (1 mM) but potentiated by CaCl2 (0.1--2 mM). These results indicate that endotoxin interacts with liposomes both hydrophobically and electrostatically.

Comparison of radiopaque perfluorocarbon and Ethiodol in lymphography

Lymphangiography was performed on 40 adult cats, 39 dogs, 20 rabbits, and 12 rats of mixed sex using Ethiodol or radiopaque perfluorocarbon (BPC). Ethiodol was more radiodense than RPC, but imaging of lymph channels and nodes was satisfactory with the latter. RPC could be infused rapidly, while Ethiodol infusion was time consuming. RPC was biologically inert; Ethiodol produced both local and systemic inflammatory reactions. The lymph node distribution with RPC was more uniform and persisted for longer periods. It was concluded that RPC was an improvement over Ethiodol for lymphangiography.

Fatty acid and lactate metabolism by heart homogenates from alloxan-diabetic dogs

Myocardial homogenates from control of alloxan-diabetic dogs were incubated in the presence of lactate or palmitate as the sole substrate. The rate of lactate oxidation of the homogenates from diabetic dogs was less than half of the oxidation rate of homogenates from control animals. The incorporation of labelled palmitate into triglyceride was greatly enhanced in the heart taken from diabetic animals. The tissue concentration of l-carnitine was twice and that of triglyceride was three times as high in the diabetic animals as in their control counterparts. Thus the myocardium of diabetic animals exhibited both altered substrate utilization and increased rate of triglyceride synthesis.

Perfluoroctylbromide as a diagnostic contrast medium in gastroenterography

The efficacy and safety of perfluoroctylbromide as a diagnostic contrast medium for gastroenterography was studied in laboratory animals. It was found that perfluoroctylbromide possesses excellent coating properties and a short transit time in the gastrointestinal tract. The conscious animals tolerated 64 ml/kg without any toxic manifestations. Thorough hematologic, serologic and histologic examinations showed no evidence of any adverse effects. Perfluoroctylbromide may be especially useful in patients with advanced inflammatory lesions of the gastrointestinal tract or in those with risk of aspiration of contrast medium into the lungs during gastroenterographic examinations.

Biological disposition of perfluoroctylbromide: tracheal administration in alveolography and bronchography

Perfluoroctylbromide, given tracheally either as neat liquid in alveolography or as 10:1 emulsion in bronchography, was cleared roentgenologically from the lungs within 24 hours. Quantitative analysis was performed on a gas chromatograph. The rats were given either 2 ml/kg of neat liquid or 0.4 ml/kg emulsion. One per cent of the neat liquid and 8% of the emulsion were recovered from the tissues respectively 24 hours later. The lungs had the largest amount followed by the intestine, adipose tissue and lymph nodes. Dogs were sacrificed at various intervals following 4 ml/kg of neat liquid or 2 ml/kg of emulsion. Less than 1% of the dose was found in the tissues at 24 hours. A similar pattern of perfluoroctylbromide distribution was observed as in the rats. The tissue contents of perfluoroctylbromide at three months were below the limit of detection. The perfluoroctylbromide levels in the blood and urine of dogs and human volunteers were either non-detectable or barely detectable over a 48-hour period.

Myelography wiht perfluoroctylbromide. Comparison with Pantopaque

The efficacy and toxicity of perfluoroctylbromide in myelography were studied in dogs. Perfluoroctylbromide moves freely in intrathecal space and provides satisfactory radiopacity for diagnosis of subarachnoid structures. The outstanding feature of this substance is its low toxicity. The dog tolerates 0.5-1.0 ml/kg intrathecally without toxic manifestation. Histological studies and CSF analyses show that it is much less irriating than Pantopaque. Because of the long retention of the perfluorocarbon removal may be necessary. Perfluoroctylbromide shows promise as a diagnostic contrast medium, particularly in cases where the currently available contrast media are not suitable.

Uptake of amino acids by the marine centric diatom Cyclotella cryptica

The transport systems for all of the amino acids studied, with the exception of isoleucine, obey saturation kinetics. The strong inhibition of the process by cyanide and dinitrophenol provides evidence that energy is required. Additional evidence for the requirement of energy for amino acid transport is the strong temperature dependence (Q10 about 2) and the high concentration ratios measured for transported amino acids.Transport parameters (Ks and Vmax) for several amino acids were determined from data for two different concentration ranges. The results of the kinetic studies indicate the presence of two or more transport systems that become saturated at different substrate concentrations for each of the amino acids. The presence of a high affinity – high capacity transport system for arginine indicates that this amino acid may be utilized efficiently by the diatom when present at low concentrations in the natural environment.Interactions between pairs of amino acids suggest that several transport systems are available. There appears to be one system for ornithine and arginine, one for glutamate and aspartate, and several for neutral amino acids.Restriction of nitrogen in the growth medium produces a marked increase in the rate of amino acid uptake, indicating that amino acids are acquired more rapidly from the medium by nitrogen-limited cells.

Utilization of amino acids as nitrogen sources, and their effects on nitrate reductase in the marine diatom Cyclotella cryptica

Several amino acids supplied at 0.1 mM allow good growth of Cyclotella cryptica. The cells can grow as well on arginine and glutamine as on nitrate. Glutamate, proline, ornithine, and asparagine also allow good growth, while glycine, alanine, and aspartate support relatively low initial growth rates. Isoleucine appears not be utilized at all. Ammonium and urea are excellent nitrogen sources for growth.There is good correlation between chlorophyll and protein content in cells grown on different nitrogen sources. Cells grown in nitrate, arginine, and glutamine media contain the highest amount of protein and the best pigmentation. Although both glutamate and proline allowed good growth, cells grown in these media have low levels of protein and chlorophyll, indicating nitrogen limitation. No growth inhibition was observed for any of the amino acids tested at 0.1 mM in the presence of nitrate. It is estimated that amino acids at naturally occurring concentrations may contribute significantly to the nitrogen economy of this diatom when more common nitrogen supplies such as nitrate and ammonia are scarce.Nitrate reductase in C. cryptica appears to be found only in the presence of nitrate, and is repressed by other nitrogen compounds. The extent of repression by amino acids, urea, and ammonium is related to their ability to promote growth when supplied as sole sources of nitrogen.

Characteristics of mitochondrial and microsonal monoacyl- and diacylglycerol 3-phosphate biosynthesis in rabbit heart

Acylation of sn-glycerol 3-phosphate by heart subcellular fractions was characterized. The enzyme kinetics revealed that the rate of reaction of acylation by mitochondria was slower, but constant for a longer period (up to 20min), than that by the microsomal fraction. The range of palmitate, oleate and linoleate concentrations yielding optimal sn-glycerol 3-phosphate acylation was broader for mitochondria than for the microsomal fraction, the latter showing a preference for linoleate. The mitochondrial fraction synthesized a relatively large quantity of monoacyl-sn-glycerol 3-phosphate, reaching 135% of the microsomal biosynthesis during an assay period of 15min. By contrast, the microsomal fraction formed considerably more diacyl- than monoacyl-sn-glycerol 3-phosphate, except with linoleate as the acyl donor, in which case approximately equal quantities of the two products were produced. The biosynthesis of monoacyl-sn-glycerol 3-phosphate was also observed in experiments in which hepatic subcellular fractions were used to provide supporting evidence. Cardiac mitochondrial diacyl-sn-glycerol 3-phosphate formation was less than 17% of the microsomal formation. However, evidence is presented to exclude the possibility that monoacyl-sn-glycerol 3-phosphate in the mitochondrial fraction is formed by deacylation of the contaminating microsomal diacyl-sn-glycerol 3-phosphate. The participation of the dihydroxyacetone phosphate pathway in the biosynthesis of these substances was minimal. The addition of CTP and the fatty acid specificity of the reaction both provided results that reinforced the postulate that mitochondrial differs from microsomal acylation. Thus our findings demonstrate that the characteristics of acyl-CoA-sn-glycerol 3-phosphate O-acyltransferase (EC 2.3.1.15) in rabbit heart mitochondria are distinct from those of cardiac microsomal enzyme and hepatic enzymes.

High-Pressure Polymorph of Thulium: An X-ray Diffraction Study

An x-ray diffractiotn study of thulium at room temperature and high pressure by means of a diamond-anvil press has shown that thulium transforms from a hexagonal close-packed structure to the samarium type, as other rareearth elements (gadolinium, terbium, dysprosium, and holmium) do. Unlike the other rare-earth elements, thulium (hexagonal close-packed) has an axial ratio (c/a) that is independent of pressure within experimental error and the transition is reversible. The transition occurs with increasing pressure in the range of 60 to 116 kilobars. The lattice paralieters of the samarium-type phase of thulium at about 116 kilobars are a = 3.327 +/- 0.005 angstroms and c = 23.48 +/- 0.04 angstroms, and the volume change at the transition is estimated to be - 0.5 percent of the volume of the hexagonal close-packed phase at the transition.