Reconstituted Elastin
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P-8 The Significance of Plasma Calcium Concentrations on the Thrombotic Effect of Platelet Aggregators. Pylia Penglis and F. Michal (Smith, Kline and French Research Institute, Department of Pharmacology, University of Sydney, Sydney, N.S.W. 2006). The present investigation attempts to correlate the effect of varying the concentrations of plasma calcium with the aggregating and thrombus promoting action of adenosine diphosphate (ADP), 2-chloroadenosine diphosphate (2-Cl- ADP) and 5-hydroxytryptamine (5-HT). Platelet aggregation was carried out by measuring turbidity changes in sheep platelet-rich plasma during clumping; thrombus formation was assessed in the Chandler's apparatus by the angular shift of the platelet-rich plasma flowing through a circular, rotating plastic tube. ADP (5 X 10-^M), 2-Cl-ADP (1 x lO-^^M) and 5-HT (1 x 10-»M) produced aggregation which was potentiated by adding Ca^+ in the range of 5 x 10~'*M to 1 X 10"-M to citrated platelet-rich plasma. In the Chandler tube the time for the formation of a thrombus was reduced in the presence of the aggregating agents while 2-chloroadenosine delayed the thrombus formation time. With the Ca-+ concentration of 2mM all aggregating or inhibitory actions were optimal; increasing or lowering this concentration decreased the drug effects. These experiments confirm that the normal physiological Ca-+ concentration (approx. 2mM) has to be closely approximated in the study of haemostasis and experimental thrombosis. Reconstituted Elastin. W. J. Cliff and E. G. Cleary (Department of Experimental Pathology, John Curtin School of Medical Research, Australian National University, Canberra, A.C.T. 2600). Electron microscopic observations to date have been inconclusive in elucidat- ing the fundamental structural organisation of the protein elastin. When highly- purified insoluble elastin is partially hydrolyzed by prolonged boiling in weak oxalic acid, a soluble product is obtained. By gel filtration this material can be shown to consist of fragments which vary in apparent molecular weights from greater than two million down to several thousand. These fragments exhibit the property of coacervation or reversible precipitation on warming or the addition of phosphate ions. The fractions obtained have been examined in the electron microscope both with negative staining and metal shadowing and appear as collections of globular subunits with an average diameter of about lOOA. When the elastin fractions are precipitated by phosphate in each instance a rubbery mass was obtained. This was fixed, ultrasonically disrupted and examined by negative staining, metal shadowing as well as in thin sections. It was found that the elastin was now in fibrous form regardless of the apparent size of the parent polypeptides in solution. The basic fibres observed in all samples had a diameter of approximately 15A and were of indefinite length. In places there was a suggestion of a substructure of finer filaments. Lathyrism in Swine. E. G. Cleary (Department of Experimental Pathology, John Curtin School of Medical Research, Australian National University, Canberra, A.C.T. 2600). Vascular aneurysms are common to lathyrism in young rats and to copper deficiency in swine. Aortic elastin isolated from copper-deficient animals shows defective formation of the cross-linking amino acids peculiar to elastin—isodes- mosine and desmosine. Experiments were undertaken to examine the eflects
Transcript of Reconstituted Elastin
P-8
The Significance of Plasma Calcium Concentrations on theThrombotic Effect of Platelet Aggregators.Pylia Penglis and F. Michal (Smith, Kline and French Research Institute,Department of Pharmacology, University of Sydney, Sydney, N.S.W. 2006).
The present investigation attempts to correlate the effect of varying theconcentrations of plasma calcium with the aggregating and thrombus promotingaction of adenosine diphosphate (ADP), 2-chloroadenosine diphosphate (2-Cl-ADP) and 5-hydroxytryptamine ( 5 - H T ) . Platelet aggregation was carried outby measuring turbidity changes in sheep platelet-rich plasma during clumping;thrombus formation was assessed in the Chandler's apparatus by the angularshift of the platelet-rich plasma flowing through a circular, rotating plastic tube.ADP (5 X 10-^M), 2-Cl-ADP (1 x lO-̂ ^M) and 5-HT (1 x 10-»M) producedaggregation which was potentiated by adding Ca^+ in the range of 5 x 10~'*Mto 1 X 10"-M to citrated platelet-rich plasma. In the Chandler tube the time forthe formation of a thrombus was reduced in the presence of the aggregatingagents while 2-chloroadenosine delayed the thrombus formation time. Withthe Ca-+ concentration of 2mM all aggregating or inhibitory actions wereoptimal; increasing or lowering this concentration decreased the drug effects.These experiments confirm that the normal physiological Ca-+ concentration(approx. 2mM) has to be closely approximated in the study of haemostasisand experimental thrombosis.
Reconstituted Elastin.W. J. Cliff and E. G. Cleary (Department of Experimental Pathology,John Curtin School of Medical Research, Australian National University,Canberra, A.C.T. 2600).
Electron microscopic observations to date have been inconclusive in elucidat-ing the fundamental structural organisation of the protein elastin. When highly-purified insoluble elastin is partially hydrolyzed by prolonged boiling in weakoxalic acid, a soluble product is obtained. By gel filtration this material canbe shown to consist of fragments which vary in apparent molecular weightsfrom greater than two million down to several thousand. These fragmentsexhibit the property of coacervation or reversible precipitation on warming orthe addition of phosphate ions. The fractions obtained have been examined inthe electron microscope both with negative staining and metal shadowing andappear as collections of globular subunits with an average diameter of aboutlOOA. When the elastin fractions are precipitated by phosphate in each instancea rubbery mass was obtained. This was fixed, ultrasonically disrupted andexamined by negative staining, metal shadowing as well as in thin sections. Itwas found that the elastin was now in fibrous form regardless of the apparentsize of the parent polypeptides in solution. The basic fibres observed in allsamples had a diameter of approximately 15A and were of indefinite length.In places there was a suggestion of a substructure of finer filaments.
Lathyrism in Swine.E. G. Cleary (Department of Experimental Pathology, John Curtin Schoolof Medical Research, Australian National University, Canberra, A.C.T. 2600).
Vascular aneurysms are common to lathyrism in young rats and to copperdeficiency in swine. Aortic elastin isolated from copper-deficient animals showsdefective formation of the cross-linking amino acids peculiar to elastin—isodes-mosine and desmosine. Experiments were undertaken to examine the eflects
