Morphine effects on the cardiovascular system of awake, freely behaving rats

The effects of small, i.v. infusion of morphine on the heart rate was studied in unanesthetized rats. A dose-response study indicated that all values of morphine between 5 and 1000 mug/kg resulted in a transient bradycardia. In addition, morphine doses above 20 mug/kg induced cardiac irregularities including atrial fibrillation, atrioventricular block and temporary cardiac arrest. When morphine was delivered daily over a period of eight weeks, cardiac responding (first arrhythmias and then the bradycardia) became tolerant at a time when catatonia was still present. These results indicate that in an unanesthetized rat, profound cardiovascular effects are seen to very small, mug range, doses of morphine.

An analysis of 70 years of morphine classical conditioning: implications for clinical treatment of narcotic addition

A review of all morphine classical conditioning studies performed since Pavlov reveals significant shifts in methodological and conceptual thinking during the past 7 decades. These shifts have tended to obscure the fact that a great deal of basic data are still needed before morphine classical conditioning can be understood. These data are needed to help clarify the relationship between drug conditioning and drug addiction. Recent evidence, for example, suggests that once morphine autonomic conditional reactions are established, they are highly resistant to extinction. The inclusion of these types of data in any conceptualization of drug dependency would appear to be of help in the formulation of new clinical approaches to this problem.

Isolation and properties of a sarcoplasmic calcium-binding protein from crayfish

The sarcoplasmic calcium-binding protein from crayfish muscle has been purified to homogeneity. The protein has a molecular weight of 44000, as determined by sedimentation equilibrium and Sephadex chromatography. It dissociates in the presence of sodium dodecyl sulfate, 8 M urea, or, after succinylation, into two subunits of 22000 molecular weight. The protein is free of carbohydrate and phosphorus but contains 4 g-atoms of calcium/44000 at a free calcium concentration of 0.1 muM. Approximately 45% of the polypeptide backbone appears to be alpha-helical. The amino acid composition reveals a high proportion of alanine and acidic amino acids, a normal content of aromatic amino acids, and the absence of histidine. The isoelectric point, as determined by isoelectric focusing, is 5.1. The protein contains a free threonyl NH2 terminal. Two thiols react rapidly in the native protein, six in the calcium-free form. Immunochemically, there is no difference between the protein from tail, claw, and heart muscle. In these three crayfish tissues, the concentrations of calcium-binding protein, as determined by rocket immunoelectrophoresis, are markedly different: 2.73 g/kg in tail, 0.72 in claw, and 0.073 in heart muscle. A functional analogy with the parvalbumins of vertebrates can be postulated.

On the subunit structure of particulate aminopeptidase from pig kidney

Solubilization of particulate aminopeptidase (EC 3.4.11.2) from pig kidney with Triton X-100 yields an aggregate (mol. wt. approx. 10(6)) that decomposes into "free" aminopeptidase (mol. wt. 280 000) either upon autolysis at pH 5 or after exposure to trypsin. Both procedures yield free enzymes that are identical with respect to electrophoretic mobility, enzymatic activity and zinc content. After dissociation, the enzyme resulting from autolysis yields a single subunit of 140 000 molecular weight while the trypsin-treated enzyme produces three fragments (140 000, 95 000 and 48 000 mol. wt.). As the aggregate is formed by subunits 10 000 daltons heavier than those of the free enzyme, the existence of a hydrophobic portion anchoring the enzyme to the membrane might be postulated. Reactivation experiments carried out on the three purified fragments of urea-denatured aminopeptidase show that the 140 000 molecular weight subunit is the only one able to yield an active enzyme (after spontaneous dimerization). It can be concluded that the smaller fragments are artefacts resulting from trypsin degradation during purification.

Lowering of plasma cholesterol levels in free-living adolescent males; use of natural and synthetic polyunsaturated foods to provide balanced fat diets

Two hundred and twenty-nine adolescent male pupils, attending two boarding schools, participated in a study, under free-living dietary conditions, designed to assess the effects on plasma lipids of altering only the type and not the amount of dietary fat. The students were monitored for 6 weeks on three different diets. During the first study period, dietary changes comprised substituting a polyunsaturated dried "filled" milk and products derived therefrom for conventional dairy products (diet A). The second dietary phase involved replacing all meat and dairy products with equivalent polyunsaturated ruminant fat products (diet B). The third period consisted of a control diet of conventional dairy and meat products. During both polyunsaturated diets a 14% reduction in plasma cholesterol was achieved compared with control levels. Low-density lipoprotein cholesterol was similarly suppressed. A greater decrease in plasma cholesterol of 19-21% was recorded in those pupils with initial cholesterol levels greater than 230 mg/dl. There was no significant difference in plasma triglycerides between diet A and the control diet whereas the triglyceride levels were 16.5% lower during diet B. The fall in plasma cholesterol coincided with an increase in plasma triglyceride linoleate from 8% to 19% of total triglyceride fatty acids. Dietary analysis of the pupils' diet indicated an increase in the ratio of polyunsaturates to saturates from 0.27 during the control period to 1.08 on the dried filled milk and 0.90 on the polyunsaturated ruminant fat products. A palatability survey showed that both the dried filled milk and the polyunsaturated ruminant fat products were as well accepted by the pupils as the conventional products. The results suggest that such products could, if introduced to the general population, play an important part in plasma cholesterol suppression in the hope that this would significantly reduce the incidence of coronary artery disease.

Colestipol, clofibrate, cholestyramine and combination therapy in the treatment of familial hyperbetalipoproteinaemia

Fifty-seven patients, mean age 26 years, suffering from familial hyperbetalipoproteinaemia (Fredrickson type lla and llb), were treated on a low cholesterol, modified polyunsaturated fat diet for a period of 6-12 weeks prior to the introduction of drug therapy. No significant reduction in the serum levels of total cholesterol, low density lipoprotein (LDL) cholesterol or triglyceride was found. Fifty patients were then treated with colestipol for 6 weeks; total and LDL cholesterol decreased by 23%, but triglyceride levels were unaffected. During the following 6 weeks, placebo was administered, and total and LDL cholesterol returned to pretreatment levels. The patients were then randomly allocated into two groups of 16. The first group continued with clofibrate therapy, while the second group received cholestyramine. In the clofibrate group a reduction in total and LDL cholesterol of the order of 17% was noted, similar to cholestethat achieved in this group on colestipol. Triglyceride levels were 15% lower on clofibrate therapy than on colestipol. In the cholestyramine group, there was a 25% decrease in total and LDL cholesterol, compared with pretreatment levels. This reduction was similar to that found when colestipol was administered. Triglyceride values were significantly raised during cholestyramine therapy. Thirteen patients were then subjected to a 6-week period of combination therapy, either clofibrate or colestipol, or clofibrate and cholestyramine. Total and LDL cholesterol were reduced by 32% on combination therapy compared with 18% on colestipol and 23% on either clofibrate or cholestyramine alone. Furthermore, on combined therapy, triglyceride concentrations fell by 20% when compared with the levels found when colestipol, clofibrate or cholestyramine were administered on their own.

Portacaval shunt in four patients with homozygous hypercholesterolaemia

Four patients with homozygous hyperbetalipoproteinaemia who had proved resistant to intensive medical therapy have undergone portacaval shunt. During 3 weeks of total parenteral alimentation before the operation, the serum-cholesterol decreased significantly in each of the four patients. During the fat-emulsion phase of hyperalimentation, one patient experienced a rise in cholesterol. Postoperatively, the size of xanthomas decreased in all cases; serum-cholesterol levels rose above those achieved during hyperalimentation, and this rise continued for as long as 3 months before a further reduction was recorded. In patients with angina, this improved considerably; and in most cases bruits decreased in itensity. The results at this stage do not, however, suggest portacaval shunt for all patients with homozygous hypercholesterolaemia.