Adrenergic receptors in the forehead microcirculation

The presence of - and -adrenoceptors in the forehead microcirculation was investigated in 49 healthy subjects. Local vascular responses to noradrenaline, isoprenaline and adrenergic antagonists, administered transcutaneously by iontophoresis, were monitored via laser Doppler flowmetry. Iontophoresis of the -adrenergic antagonist phentolamine induced a persistent increase in skin blood flow, whereas iontophoresis of saline induced a minor increase in skin blood flow which subsided rapidly. Skin blood flow increased moderately after the iontophoresis of the -adrenergic antagonist propranolol. Pretreatment of the experimental site with phentolamine blocked the normal vasoconstrictor response to noradrenaline, and unmasked a minor vasodilator component of response in some subjects. Iontophoresis of the -adrenergic agonist isoprenaline induced dose-dependent vasodilatation which was antagonised by propranolol. These findings indicate that -adrenoceptors in the forehead microcirculation normally mediate a vasoconstrictor response to iontophoretically-applied noradrenaline. In addition, -adrenoceptors appear to mediate a minor vasodilator component of response.     

Detection of drug-induced apoptosis by flow cytometry after alkaline extraction of ethanol fixed cells

A new flow cytometric method was developed to detect apoptotic cells with fragmented DNA and to determine cell cycle distribution of viable cells, in the same sample, by propidium iodide staining. Apoptosis, in HT58 human B lymphoma cells, was induced by etoposide and/or by staurosporine. Using appropriate alkaline solutions (between 1-10 mN NaOH in 150 mM saline) followed by neutralization with buffer solution, the fragmented DNA can be extracted quantitatively from ethanol fixed cells. Further, good resolution of the cell cycle distribution can be obtained in unimpaired cells without RNase treatment. Furthermore, unlike the widely used hypotonic-detergent extraction of unfixed cells, the suggested extraction method can prevent drug-induced disintegration of dead cells when karyorrhexis occurs. This work was supported by Hungarian National Research Foundation (OTKA I/352 and OTKA II/2622).     

CO2 and indomethacin vasoreactivity in patients with head injury

Summary The purpose of this study was to compare the effect of hyper-ventilation and indomethacin on cerebral circulation, metabolism and pressures in patients with acute severe head injury in order to see if indomethacin may act supplementary to hyperventilation. Fourteen severely head injured patients entered the study. Intracranial pressure (ICP), mean arterial blood pressure (MABP) and cerebral perfusion pressure (CPP) were monitored continuously. Within the first four days after the trauma the CO₂ and indomethacin vasoreactivities were studied by measurements of cerebral blood flow (CBF) (Cerebrograph 10a, intravenous¹³³Xe technique) and arterio-venous difference of oxygen (AVdO₂). Ischaemia was evaluated from changes in CBF, saturation of oxygen in the jugular bulb (SvjO₂), lactate and lactate/oxygen index (LOI). Data are presented as medians and ranges, results are significant unless otherwise indicated. Before intervention ICP was well controlled (14.8 (9–24) mmHg) and basic CBF level was 39.1 (21.6–75.0) ml/100 g/min). The arterio-venous oxygen differences were generally decreased (AVdO₂ = 4.3 (1.8–8.1) ml/100 ml) indicating moderate luxury perfusion. Levels of CMRO₂ were decreased (1.54 (0.7–3.2) ml/100 g/min) as well.Duringhyperventilation (APaCO₂ = 0.88 (0.62–1.55) kPa) CBF decreased with 11.8 (–33.4–29.7) %/kPa and ICP decreased with 3.8 (0–10) mmHg. AVdO₂ increased 34.0 (4.0–139.2) %/kPa, MABP was unchanged, CMRO₂ and CPP increased (CPP = 3.9 (–10–20) mmHg). AVD (lactate) and LOI were unchanged. No correlations between CBF responses to hypocapnia and outcomes were observed.An i.v. bolus dose ofindomethacin (30 mg) decreased CBF 14.7 (–16.7–57.4) % and ICP decreased 4.3 (–1–17) mmHg. AVdO₂ increased 27.8 (–40.0–66.7)%, MABP (MABP = 4.9 (–2–21) mmHg) and CPP (CPP = 8.7 (3–29) mmHg) increased while CMRO₂ was unchanged. No changes in AVd (lactate) and LOI indicating cerebral ischaemia were found.Compared to hyperventilation (changes per 1 kPa, at PaCO₂ level = 4.05 kPa) the changes in MABP, CPP and CBF were significantly greater after indomethacin, while the changes in AVdO₂, ICP, SvjO₂, and LOI were of the same order of magnitude.Nocorrelation between relative reactivities to indomethacin and CO₂, evaluated from changes in CBF and AVdO₂, or between the decrease in ICP after the two procedures were found. Thus, some patients reacted to indomethacin but not to hyperventilation, and vice versa.These results suggest that indomethacin and hyperventilation might act independently, or in a complementary fashion in the treatment of patients with severe head injury.     

Intraoperative internal mammary artery transit-time flow measurements: comparative evaluation of two surgical pedicle preparation techniques

Objects.

Myocardial revascularization is performed preferentially with internal mammary artery grafts. Pedicle preparation and pharmacologic vasodilatory treatment vary greatly. Objective measurements are difficult since peripheral and later coronary vascular resistance and possible competitive flow of the native bypassed coronary artery will influence the results significantly. Our objectives were: (1) measurement of internal mammary artery graft flow with the transit-time flow technique; (2) comparison of two surgical take-down techniques (skeletonizing vs standard pedicle preparation); (3) quantitation of transit-time flow compared to the free pedicle flow and (4) the vasodilatory effect of papaverine on internal mammary artery flow.

Method.

Consecutive elective cases of coronary artery bypass grafting, performed by two surgeons using routinely either skeletonizing of the internal mammary artery (group A, n=10) or classical pedicle preparation technique (group B, n=10), were studied prospectively. Anesthesia, cardiopulmonary bypass and operative data were otherwise comparable; likewise, hemodynamic parameters showed no statistical differences between the two groups. Transit-time flow (CardioMed, Medi-Stim, Norway) was measured at the following time points: beginning (1) and end of take-down (2); after papaverine soaking: before (3) and on cardiopulmonary bypass (4); free flow into a beaker (5); after anastomosis; on (6) and off cardiopulmonary bypass (7).

Results.

Measurement of mean flow showed the following results: (1) severe vasoconstruction of the internal mammary artery was detected in both groups regardless of the preparation technique (occurring earlier in group A); (2) papaverine soaking caused a moderate flow increase (up to 40%); (3) with corresponding cardiopulmonary bypass flow (4.4 vs 4.1 l/min in group B) a higher free flow in group A was evident (67.7 vs 50.7 ml/min); (4) after coronary grafting, transit-time flow showed no significant differences between the two groups and (5) using a 3 mm probe, a linear correlation was demonstrated between transit-time flow and simultaneously measured free flow (r=0.89).

Conclusion.

Intraoperative transit-time flow measurement is a reliable method for assessing internal mammary artery and coronary artery bypass flow; considering the simple technical application, the procedure may be regarded as a valuable instrument of quality control.     

Vascular and electromyographic responses evoked in forearm muscle by isometric contraction of the contralateral forearm

There is controversy over whether isometric contraction of the forearm evokes vasoconstriction or vasodilatation in the muscles of the contralateral forearm. In the present study we have investigated in normal man, the effects of isometric contraction of one arm at 75, 50 and 25% maximum voluntary contraction (MVC) on arterial pressure, heart rate, blood flow and vascular resistance of the contralateral forearm and on electromyographic (EMG) activity recorded from that same arm with sensitive, surface electrodes.When EMG activity was not being recorded from the resting arm, isometric contraction of the contralateral arm for 2 min evoked increases in arterial pressure and heart rate whose magnitudes were graded with % MVC and an increase in forearm blood flow and a decrease in forearm vascular resistance at 75, 50 and 25% MVC, indicating vasodilatation. Further experiments in which EMG activity was recorded from the resting arm demonstrated that the decrease in forearm vascular resistance evoked by 75% MVC was associated with a substantial increase in EMG activity of the extensor and flexor muscles of that arm. By contrast, when forearm contraction was performed at 75% MVC whilst subjects viewed the EMG activity in the resting arm on an oscilloscope and kept EMG activity minimal, vascular resistance increased in that arm, indicating vasoconstriction. Further, when subjects performed contraction at 25% MVC whilst showing minimal EMG activity in the contralateral arm, vascular resistance in that same arm increased (from 78 ± 16 to 124 ± 29 mmHg/ml/min/100 ml tissue). These results are discussed in relation to those of previous studies. We propose, that in normal man, isometric contraction of the forearm evokes primary vasoconstriction in the muscles of the contralateral forearm, but that this response may be overcome by muscle vasodilatation occurring secondary to unintended muscle contraction or as part of the alerting response to acute stress.     

Neuropathological and neurophysiological effects of interstitial white matter autologous and non-autologous protein containing solutions: Further evidence for a glioma derived permeability factor

Summary The feline infusion model of brain edema was used to evaluate the pathophysiological effects of 0.6ml infusions of autologous serum protein (66%), human serum protein (66%), human glioma cyst fluid and a tissue culture medium (TCM) on the structure and function of the forebrain white matter. These infusions increased local white matter water content by between 10.8 and 12.5 ml/100 g brain and were associated with moderate increases in ICP and CSF outflow resistance and a significant decrease in lumped craniospinal compliance. Cortical somatosensory potentials, motor evoked potentials, EEG and local cerebral blood flow (rCBF) at normocapnia were generally unchanged by the various infusions. All infusates except the 66% autologous serum protein infusion impaired rCBF CO₂ reactivity. Histologically all infusates caused marked extracellular edema. The autologous serum protein infusion caused no additional histological changes whereas the glioma cyst infusates caused profound endothelial and astrocytic swelling, focal endothelial necrosis, basement membrane disruption, perivascular microglial reaction and pavementation and perivascular migration of polymor-phonuclear leukocytes. Similar but less marked changes were seen after infusion of human serum protein whilst the TCM produced only minimal changes. The intensity and extent of Evans Blue extravasation into the forebrain white matter was greatest with glioma cyst infusates and with all infusions reflected the extent to microvascular changes.These studies show that products derived from gliomas cause additional damage to the blood-brain-barrier than that caused by non-autologous serum proteins. These results add further support for the existence of glioma derived permeability factors (GDPF), but suggest neither serum proteins nor glioma derived compounds in the white matter interstitium significantly influence local electrophysiological function. Some limitations of the infusion edema model when using non-autologous infusions and difficulties quantitating brain dysfunction are emphasised.Preliminary results had been presented at the symposium on Brain Edema VIII, which took place at Bern, Switzerland, in June 1990 and have been published in: Reulenet al (eds) 1990. Brain Edema VIII, Acta Neurochirurgica (Wien) [Suppl] 51: 71–73     

Doppler flow velocity measurements in patients with intracranial hypertension

Summary In patients with severe brain lesions monitoring of the intracranial pressure as well as monitoring of cerebral blood flow can be of clinical value. While at the moment there is no atraumatic method for measuring cerebral blood flow in man, it is recommended to measure blood flow velocity with the ultrasound Doppler technic in the common carotid artery. On theoretical grounds a positive correlation between cerebral blood flow and blood flow velocity can be expected and the observations presented show that such a correlation exists in normal controls and in neurological patients. In many neurological patients the flow velocity in the common carotid artery decreases with increasing intracranial pressure. This suggests that the autoregulation is disturbed. The demonstration of such a disturbance can have clinical implications.

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Zusammenfassung Bei Patienten mit ernsten Läsionen im Gehirn kann Monitoring von sowohl intercraniellem Druck als auch der zerebralen Blutdurchströmung für die Klinik von Bedeutung sein. Da im Moment keine atraumatische Methode für die Messung der zerebralen Blutdurchströmung besteht, wird anempfohlen, die Durchströmungsgeschwindigkeit mit der Ultraschall-Doppler-Technik in der Arteria carotis communis zu messen. Theoretisch kann eine positive Korrelation zwischen der zerebralen Blutdurchströmung und der Strömungsgeschwindigkeit erwartet werden.Die beschriebenen Ergebnisse zeigen, daß tatsächlich ein solcher Zusammenhang besteht, sowohl bei gesunden Versuchspersonen als auch bei neurologischen Patienten.Bei vielen dieser Patienten nimmt die Durchströmungsgeschwindigkeit in der Arteria carotis communis ab bei einer Zunahme des intracraniellen Druckes. Dies suggeriert eine gestörte Autoregulation. Das Aufzeigen einer solchen Störung kann klinische Bedeutung haben.

     

Study of a new oral beta-adrenergic drug,clenbuterol, in patients with chronic bronchitis

Summary In a double-blind, placebo-controlled, incomplete cross-over study the bronchodilator, cardiovascular, respiratory and metabolic effects of 3 different oral doses of clenbuterol were studied in 12 patients suffering from partly reversible airways obstruction due to chronic bronchitis. The ventilatory response to oral clenbuterol or placebo was assessed by measurement of specific airway resistance (sRaw) to detect changes in central airways, and of flow at 85% of vital capacity ( _{85% VC}) to detect change in peripheral airways. Clenbuterol 20, 30 and 40 µg produced a significant decrease in sRaw between 15 and 480 min after administration. Its effect on the large airways was not related to the dose. Clenbuterol 30 and 40 µg caused a significant increase in _{85% VC} between 60 and 480 min after administration. After 20 µg a significant improvement in _{85% VC} was found between 120 and 240 min. The over-all effect of 30 µg on the small airways was significantly more pronounced than that of 20 µg and was more sustained than that of 40 µg 120 min after administration. No significant changes in heart rate, ECG or blood pressure were noted. Decreases in PaO₂ and O₂-saturation after clenbuterol were not related to dose. Slight falls in PaO₂ and O₂-saturation were also observed after placebo. These observations are briefly discussed. There was negligible lipid mobilization after either the placebo or bronchodilator. A slight but insignificant rise in blood glucose was observed after both 30 and 40 µg of clenbuterol.     

Ultracytochemical studies of the blood-meningeal barrier (BMB) in rat spinal cord

Summary Alkaline phosphatase(AP),5-nucleotidase(5N) and nucleoside diphosphatase (NDPase) activities were studied by cytochemical methods applied to light and electron microscopy in the microvasculature of spinal cord leptomeningeal strips of normal and protamine sulfate (PS) treated rats. The increased permeability to intravenously injected horseradish peroxidase was observed in some segments of microvessels of PS treated rats. Enhanced formation of plasmalemmal pits and deep invaginations, formation of numerous pinocytic vesicles and the appearance of channel-like structures in the cytoplasm of endothelial cells were the most striking ultrastructural evidence of increased permeability of the affected microvessels. All of these structures also showed activity of AP, and to lesser extent, of NDPase; 5N activity was mainly associated with the delimiting membranes of pinocytic vesicles. Our data present evidence that a shift of enzymatic activity from luminal to abluminal surface of affected endothelial cells results from membrane flow accompanying increased transport activity via formation of pinocytic vesicles and channel-like structures.Supported in part by a grant from NINCDS No. 17271-01Visiting scientist from the Neurological Institute of the University of Vienna, Vienna, Austria     

Value of a radionuclide limb blood flow technique in the assessment of percutaneous balloon and dynamic angioplasty

In a prospective study, a radionuclide technique was used to evaluate the limb blood flow (LBF) changes in 30 patients undergoing dynamic (n=15) or balloon (n=15) angioplasty for arterial occlusions or stenoses, respectively. The results were compared with Doppler Ankle Brachial Index (DABI) and treadmill exercise tests. Whilst LBF values (ml of blood flow per 100 ml of limb volume per min) were significantly lower in limbs with arterial occlusion than stenosis (4.5±0.46 and 6.4±0.74, respectively; P<0.05), DABI provided no discrimination. Immediately after balloon angioplasty, there was a fall in DABI, from 0.60±0.05 to 0.47±0.04 (P<0.05), which rose 24 h later to 0.73±0.02 (P<0.01). Following dynamic angioplasty, DABI improved from 0.60±0.05 to 0.66±0.02 (P<0.05). At 3 weeks, the LBF improved from 4.6±0.66 to 11.1±0.53 (P<0.001) following dynamic angioplasty and from 6.2±0.68 to 8.53±0.81 (P<0.001) following balloon angioplasty. Normal LBF (> 10 ml/100 ml per min) was achieved in 80% of patients who underwent successful dynamic angioplasty but in only 36% of the balloon group (P<0.05, ²-test). Reproducibility of repeated LBF measurements in control limbs was superior to that of DABI. This was indicated by a lower coefficient of variation, 13.8% compared with 25.2%, and a higher correlation coefficient, r=0.79 compared with 0.27. Treadmill exercise tests were invalid or impossible in 30% of all occasions. There was a good correlation between the improvement in maximum walking distance on the treadmill and that in LBF (r=0.84, P<0.05). In conclusion, measurement of LBF using radionuclide technique is a potentially valuable method for the assessment of patients undergoing percutaneous angioplasty. LBF results are reproducible and correlate well with the improvement in walking ability, which cannot always be assessed objectively. Offprint requests to: A.A. Gehani