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D D Lund

Publications and source records attributed to D D Lund.

64 records · Page 4Linked to original sources
PubMed1979

Humoral regulation of vascular resistance after 30 days of pulmonary artery constriction.

In an earlier study of guinea pigs with constriction of the pulmonary artery (PA) for 30 days, hindquarters' vascular resistance was maintained primarily by humoral mechanisms. In the present study, we investigated the contribution of circulating catecholamines, angiotensin II, and other constrictor stimuli to hindquarters' vascular resistance by observing vasodilator responses to specific competitive antagonists. Pressure-flow curves indicated vascular resistances in isolated, perfused, sympathectomized hindquarters of anesthetized guinea pigs. Phentolamine produced significantly greater (P less than 0.05) vasodilatation in animals with constriction of pulmonary artery than in sham animals [Sar1-Ala8]angiotensin II produced no vasodilation in either group. After alpha-adrenergic blockade, papaverine produced similar vasodilatation and similar final perfusion pressures in both groups. It appears that circulating catecholamines and augmented vasoconstrictor responsiveness to norepinephrine are totally responsible for the increased humoral regulation of vascular resistance in this experimental model of right ventricular hypertrophy.

Angiotensin II↗
PubMed1978

Choline acetyltransferase activity in rat heart after transplantation.

Choline acetyltransferase (CAT) catalyzes the biosynthesis of acetylcholine according to the chemical equation: Acetyl-CoA + Choline in equilibrium Acetylcholine + CoA. To demonstrate the neuronal relationship of this enzyme, CAT activity was measured in hearts to which the extrinsic innervation was completely interrupted by extirpation of the heart from a donor animal and transplantation in a heterotopic position into the recipient's abdominal cavity. After the animals were killed at 8 days, enzyme activity in the transplanted hearts was measured and compared with that of the recipient. Choline acetyltransferase activity decreased 98% in the right atrium of the transplanted denervated hearts, 94% in the SA node, 87% in the left atrium, 80% in the right ventricle, and about 50% in the interventricular septum and left ventricle. These data show that sectioning the extrinsic parasympathetic innervation to the heart results in variable decreases in CAT activity, a finding which confirms that CAT activity is related to the extrinsic cholinergic innervation. The extrinsic (preganglionic) component of the parasympathetic system is nonuniform and supplies predominantly the specialized regions of the heart with conduction tissue. The residual enzyme activity is related to intrinsic (postganglionic) parasympathetic neurons. The intrinsic component is uniformly distributed to both specialized and contractile regions of the heart.

Animals↗
PubMed1978

Regional choline acetyltransferase activity in the guinea pig heart.

Choline acetyltransferase is the enzyme that catalyzes the biosynthesis of acetylcholine, the neurotransmitter of the pre- and postganglionic parasympathetic system. To assess the extent of parasympathetic innervation, enzyme activity was measured in specialized and contractile regions throughout the guinea pig heart. Enzyme activity in the right atrial appendage was 137 nmol g(-1) hr(-1). Activity was greatest in the region of the sinoatrial node (187 nmol g(-1) hr(-1). Also, enzyme activity was high in the regions of the atrioventricular node (153 nmol g(-1) hr(-1), the proximal conduction bundles (133 nmol g(-1) hr(-1), and the base of the anterior papillary muscle of the right ventricle (179 nmol g(-1) hr(-1), which contains the moderator band and Purkinje fibers. In contrast, the enzyme activity in the inferior interventricular septum and the free walls of the right and left ventricles, which are more predominantly contractile tissue, was 67 +/- 6,108 +/- 14, and 56 +/- 11 nmol g(-1) hr(-1), respectively. This activity is significantly lower than in the right atrial appendage. These results suggest that the density of parasympathetic innervation is similar in all the components of the conduction system, from the sinoatrial node to Purkinje tissues. Furthermore, the parasympathetic innervation of regions specialized for conduction is up to four times more dense than that of contractile regions.

Animals↗
PubMedDate not supplied

Effect of fidarestat and alpha-lipoic acid on diabetes-induced epineurial arteriole vascular dysfunction.

In the present study, the authors examined whether treating streptozotocin-induced diabetic rats with the combination of alpha-lipoic acid and fidarestat, an aldose reductase inhibitor, can promote the formation of dihydrolipoic acid in diabetic animals and thereby enhance the efficacy of alpha-lipoic acid as monotherapy toward preventing diabetic vascular and neural dysfunction. Treating diabetic rats with the combination of 0.25% alpha-lipoic acid (in the diet) and fidarestat (3 mg/kg body weight) prevented the diabetes-induced slowing of motor nerve conduction velocity and endoneurial blood flow. This therapy also significantly improved acetylcholine-mediated vasodilation in epineurial arterioles of the sciatic nerve compared to nontreated diabetic rats. Treating diabetic rats with 0.25% alpha-lipoic acid and fidarestat (3 mg/kg body weight) was equally or more effective in preventing vascular and neural dysfunction than was monotherapy of diabetic rats with higher doses of alpha-lipoic acid or fidarestat. Treating diabetic rats with the combination of 0.25% alpha-lipoic acid and fidarestat (3 mg/kg body weight) significantly improved several markers of oxidative stress and increased the serum levels of both alpha-lipoic acid and dihydrolipoic acid. These studies suggest that combination therapy consisting of alpha-lipoic acid and fidarestat may be more efficacious in preventing diabetes-induced vascular and neural dysfunction in peripheral tissue compared to monotherapy, which requires higher doses to be equally effective. The effect of this combination therapy may in part be due to the increased production and/or level of dihydrolipoic acid.

Acetylcholine↗