Effects of timolol on blood flow distribution in the feline myocardium with acute regional ischaemia during controlled haemodynamic conditions

The beta-adrenergic blocking agent timolol was given to cats with acute coronary artery ligation under controlled haemodynamic conditions. Regional myocardial tissue flow was measured by the distribution of labelled microspheres. Timolol reduced cardiac contractility and left ventricular end-diastolic pressure rose, whereas heart rate and ventricular systolic pressure were kept constant by atrial pacing and aortic clamping. The systolic period increased following timolol administration under these conditions. Myocardial blood flow remained unchanged in central ischaemic and border areas, whereas flow increased both endocardially and epicardially in normally perfused area following timolol administration. Without pacing there was a significant flow reduction in the epicardium of the normally perfused area, compared with the situation where heart rate was constant. Under controlled haemodynamic conditions, therefore, timolol appears to improve coronary perfusion in normal myocardium, whereas blood flow to ischaemic myocardium remains essentially unchanged.

Effect of timolol on blood flow distribution in the myocardium during acute regional ischaemia in cats

The beta-adrenergic blocking agent timolol was given to cats with acute coronary artery ligation. Regional myocardial tissue flow was measured by the distribution of 15 micrometers labelled microspheres. Timolol reduced heart rate, cardiac contractility and left ventricular systolic pressure, but end-diastolic pressure rose. Ischaemic tissue blood flow remained unchanged following timolol, thus improving the marked imbalance between oxygen demands and delivery. In normal areas of the myocardial tissue flow was reduced, indicating the beta 2-adrenergic blocking effect of timolol. This was also the case for the border area between ischaemic and non-ischaemic tissue, but significantly less flow reduction was found on the endocardial side than on the epicardial side in the border area. Except for this latter observation, timolol does not appear to improve coronary perfusion. The present study, therefore, indicates that beneficial effects of timolol on ischaemic myocardium are mainly related to a reduction of myocardial oxygen demand.

Pulmonary circulation and loss of microspheres from the lung following acute pulmonary venous occlusion

The pulmonary vein from right upper lobe was ligated in 15 rats while 15 others served as controls. Prior to occlusion, 15 mum microspheres were injected into the superior caval vein. Another population of 15 mum microspheres was similarly given 1 min, 10 min or 30 min after ligation. All rats were killed 5 min after the second microsphere injection. The weight of the ligated lobe was 63% higher than that of the controls. This was probably due to acute vascular congestion since no significant oedema developed. Increased weight caused a reduction in the number of preocclusion microspheres per gram of tissue in the ligated lobe. In addition a gradual loss of preocclusion microspheres took place following pulmonary venous ligation. After 35 min of ligation, 30% of the preocclusion spheres had disappeared from the ligated lobe. Postocclusion flow through the pulmonary artery into right upper lobe was estimated by microspheres from the second injection, and averaged 5% of normal flow. Following acute venous occlusion, a rapid dilatation of the bronchopulmonary communicating system probably takes place. By reversal of the flow in this system, blood and microspheres can be drained into the bronchial venous circulation. In spite of methodological problems caused by acute congestion and loss of microspheres after pulmonary venous occlusion, we consider the microsphere method to be useful for further studies of collateral lung circulation.

Migration of 15 micron microspheres from infarcted myocardium

The fate of 15 micrometers microspheres in ischaemic myocardial tissue was investigated. The spheres were delivered to the left atrium before acute coronary artery ligation. 10 h later the myocardium was examined for its contents of preocclusion spheres, as well as spheres delivered immediately before sacrifice. The ischaemic tissue contained 11 to 60% less preocclusion spheres, compared with nonischaemic tissue in the same hearts. On average, 26% of preocclusion spheres were lost during the 10 h period. Negligible amounts of the lost spheres could be retrieved from cardiac lymph nodes in the mediastinum. Most likely, the spheres migrated through venous pathways; a substantial number of preocclusion spheres were present in the lungs after 10 h, the bulk of which had originated from other organs than the infarct. These results quantify an important limitation to the use of microsphere distribution as a method for tissue blood flow measurements in infarcted myocardium when the period of coronary artery occlusion exceeds a few hours.

Congenital pseudarthrosis of the leg. Late results

Forty-six patients with congenital pseudarthrosis of the leg were followed for twelve years or more. Forty of these patients were examined, interviewed, or both from 1974 to 1975. Congenital pseudarthrosis is a condition most often combined with neurofibromatosis. In neurofibromatosis the prognosis of the pseudarthrosis is dependent on the roentgenographic type. Of the procedures used, insertion of intramedullary rods and grafting gave the highest rate of union. Atrophy, shortening, valgus deformity, and limited range of motion complicated the functional results.

Congenital pseudarthrosis of the tibia and neurofibromatosis

On the basis of 21 cases of congenital pseudarthrosis of the tibia, which were radiologically typed and later personally examined, it was found that all cases of the dysplastic type also showed evidence of neurofibromatosis. No evidence of neurofibromatosis was found among the cystic and the clubfoot type of pseudarthroses.

pH Dependence and Cofactor Requirements of Photochemical Reactions in Maize Chloroplasts

The pH dependence of the photoreduction of ferricyanide and the photoreduction of NADP from water and photosystem I activity have been compared in isolated chloroplasts from mesophyll and bundle sheath cells of Zea mays. The maximum activity of photoreduction of ferricyanide occurs at pH 8.5 in isolated mesophyll chloroplasts. The addition of methylamine does not cause a marked shift in the pH maximum, but brief sonication lowers the pH maximum to 7.0. In contrast, isolated bundle sheath chloroplasts have a pH maximum at 7.0 and the shape of the pH versus activity curve is similar to that of sonicated mesophyll chloroplasts. When photoreduction of ferricyanide by the isolated chloroplasts is measured at their pH maxima, the values for bundle sheath chloroplasts are about half those of methylamine-treated mesophyll chloroplasts on a chlorophyll basis.The pH maxima for the photoreduction of NADP from water and photosystem I activity are similar in both mesophyll and bundle sheath chloroplasts with maximum activity occurring at pH 7.0 in both cases. In the presence of added plastocyanin and ferredoxin NADP-reductase, the photosystem I activities of both sonicated mesophyll and sonicated bundle sheath chloroplasts are significantly higher than those of the unsonicated preparations. On a chlorophyll basis, photosystem I activity of bundle sheath chloroplasts is at least twice that of mesophyll chloroplasts.

Photosystem II Activity in Agranal Bundle Sheath Chloroplasts from Zea mays

The photochemical activities of chloroplasts isolated from bundle sheath and mesophyll cells of maize (Zea mays var. DS606A) have been measured. Bundle sheath chloroplasts are almost devoid of grana, except in very young leaves, while mesophyll chloroplasts contain grana at all stages of leaf development.Chloroplast fragments isolated from bundle sheath cells showed a light-dependent reduction of potassium ferricyanide, 2, 6-dichlorophenolindophenol, mammalian cytochrome c, plastocyanin, and Euglena cytochrome c(552). These activities were inhibited by 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea at 1.25 micromolar. However, the photoreduction of NADP from water was extremely low or absent, except in chloroplasts from very young leaves, and the capacity for NADP reduction appeared to be related to the degree of grana formation.Photosystem I activity was present in bundle sheath chloroplast preparations at all stages of leaf growth and senescence examined. However, the activity was lower than in isolated mesophyll chloroplasts. NADPH diaphorase activity was comparable in both types of chloroplast.Chloroplasts isolated from bundle sheath cells of plants grown under a variety of conditions, including continuous and intermittent light, high and low light intensities, and high temperature, exhibited photosystem II activity.

Nicotinamide adenine dinucleotide phosphate photoreduction from water by agranal chloroplasts isolated from bundle sheath cells of maize

Photoreduction of NADP from water in agranal chloroplasts isolated from the leaf bundle sheath cells of Zea mays (var. DS 606A) or Sorghum bicolor (var. Texas 610) was dependent upon addition of plastocyanin as well as ferredoxin. Activity was further increased by the addition of ferredoxin NADP-reductase. Saturation for plastocyanin was reached at about 6 micromolar. In contrast, grana-containing chloroplasts isolated from leaf mesophyll cells of these plants or from pea (Pisum sativum L.) leaves did not require either plastocyanin or ferredoxin NADP-reductase for NADP photoreduction from water, although with some preparations plastocyanin stimulated the activity.Photosystem I activity, which was low in washed preparations of bundle sheath chloroplasts, was also stimulated by plastocyanin. The effect of plastocyanin on photosystem I activity in the grana-containing chloroplasts was similar to that on NADP photoreduction from water.In the presence of plastocyanin, the rates of NADP photoreduction from water were about the same in the agranal and granal chloroplasts, but photosystem I activity was considerably higher in bundle sheath chloroplasts. In these chloroplasts photosystem II appeared to limit the rate of NADP photoreduction.The results indicated that the agranal bundle sheath chloroplasts reduced plastocyanin via photosystem II and oxidized it via photosystem I. Both types of maize chloroplast photoreduced oxidized plastocyanin, but in the presence of methyl viologen, reduced plastocyanin was photo-oxidized only by the bundle sheath chloroplasts.

Photoreduction and Oxidation of Cytochrome f in Bundle Sheath Cells of Maize

The photo-oxidation of cytochrome f (cytochrome c(554)) in bundle sheath cells isolated from leaves of maize (Zea mays var. DS 606A) has been compared with that in intact maize leaf and in isolated pea leaf cells (Pisum sativum L.). In all cases, illumination with red light caused a negative absorbance change at 554 nm which was attributed to the oxidation of cytochrome f. The extent of this change was greater using monochromatic red light at wavelengths above 700 nm compared with wavelengths below 700 nm. 3-(3,4-Dichlorophenyl)-1, 1-dimethylurea abolished this difference in bundle sheath cells. After illumination for 1 minute or longer in bundle sheath cells, reduction of cytochrome f in the dark was rapid only if the wavelength of the illuminating light was below 700 nm. In the presence of 3-(3,4-dichlorophenyl)-1, 1-dimethlyurea, reduction was slow after illumination at all wavelengths.Cytochrome f photo-oxidation was also followed in cells of a mutant of Chlamydomonas reinhardi, ac-21, which has isolated chloroplasts that exhibit photochemical reactions similar to those shown by isolated bundle sheath chloroplasts. No evidence was obtained for photoreduction of cytochrome f in the mutant.It was concluded that in the chloroplast of the intact bundle sheath cell of maize there is electron flow between photosystem II and cytochrome f resulting in photoreduction of the cytochrome.