Regeneratively initiated self-mode-locked Ti:sapphire laser

It is demonstrated that the incorporation of an acousto-optic modulator within the cavity of a self-mode-locked Ti:sapphire laser can lead to self-starting and stable generation of pulses that have durations of 60 fs when the acousto-optic device is driven regeneratively from the laser output. Data are also presented that show that the application of cavity-frequency locking techniques dramatically improves the phase noise characteristics of the mode-locked laser.

Synthesis and antihypertensive activity of pyran oxygen and amide nitrogen replacement analogues of the potassium channel activator cromakalim

The synthesis and oral antihypertensive activity in conscious spontaneously hypertensive rats of two new series of compounds related to the prototype potassium channel activator cromakalim (1) are described. In the first series, replacement of the benzopyran oxygen atom by nitrogen or methylene led to the 1,2,3,4-tetrahydroquinoline 12 and 1,2,3,4-tetrahydronaphthalene 13, which were both less active than 1. However, in contrast to the equivalent activity found previously for 1 and its dehydrated analogue 28, the dihydronaphthalene 27 was found to be more active than 13. In the second series, replacement of the C(4) amide nitrogen atom in acyclic amides related to cromakalim by methylene gave ketone 16 that was less active than the corresponding amide 15. However, replacement of the 4-acetonyl substituent in 16 by N,N-dimethylacetamido as in compound 22 resulted in a marked enhancement in activity. The compounds described in this paper thus illustrate the importance of the benzopyran oxygen and C(4) substituent on antihypertensive activity in the cromakalim series of potassium channel activators.

Angiotensin II does not contribute to rapid reflex control of arterial pressure

Pharmacological blockade of the renin-angiotensin converting enzyme reportedly alters the heart rate (HR) power spectrum in conscious dogs, suggesting that these hormones contribute to the short-term regulation of arterial blood pressure. We tested this possibility using four independent procedures. First, HR power spectrum was determined in seven awake dogs before and after administration of enalaprilat (300 ng/kg), a converting-enzyme inhibitor. There were no significant changes in the average amplitude for the spectral peak between 0.003 and 0.1 Hz (i.e., the "low-frequency peak"). Second, the HR power spectrum was measured in 11 awake rabbits before and after treatment with deoxycorticosterone acetate (1 mg.kg-1.day-1) and salt (0.9% saline ad libitum) for 7 days to depress plasma renin levels. There were no significant changes in the amplitude of the HR power spectrum, although mean HR decreased from 206 +/- 3 to 184 +/- 4 beats/min after treatment. In the third experiment, another group of rabbits (n = 8) was tested after 2 wk on a low-salt diet to elevate plasma angiotensin levels and then after 2 wk on a normal salt diet. Once again there were no significant effects on the HR power spectrum. Finally, tranquilized dogs (n = 9) were subjected to sinusoidally varying lower body negative pressure at selected frequencies of 0.008-0.12 Hz. Tests were conducted in the control state and after administration of an angiotensin receptor antagonist (saralasin, 1 microgram.kg-1.min-1). Lower body negative pressure-induced fluctuations in arterial blood pressure were similar in both states. We find no evidence for the role of the renin-angiotensin system in the moment-to-moment regulation of arterial pressure and HR.

Participation of the cysteinyl leukotrienes in the acute bronchoconstrictor response to inhaled platelet activating factor in man

To determine whether the effects of platelet activating factor on the airways may be due to the production of leukotrienes we studied the effects of pretreatment with the selective cysteinyl leukotriene antagonist SK&F 104353-Z2 on the airway and cellular responses to inhaled platelet activating factor. Eight healthy men were studied in a randomised, double blind placebo controlled cross-over study. A single dose of platelet activating factor that caused a fall of at least 35% in specific airways conductance (sGaw) was determined initially for each subject. Challenge with this dose of platelet activating factor was then carried out on two further occasions after pretreatment with a single nebulised dose of SK&F 104353-Z2 or placebo. The % reductions in specific airways conductance and of partial flow at 30% of vital capacity (PVmax30) were less after SK&F 104353-Z2 than after placebo (22 versus 34 for sGaw, 19 versus 31 for PVmax30). The mean (95% confidence limits (CL] differences in the maximum % fall from control values for SK&F 104353-Z2 and placebo were -12.6 (-23.8, -1.4) for sGaw and -12.5, (-20.8 -4.2) for PVmax30. The mean % fall in neutrophil count was similar after SK&F 104353-Z2 (46%) and after placebo (50%) (95% CL of difference 13.6, 6.6). Bronchial responsiveness to methacholine did not increase above baseline values in any subject when measured two weeks after challenge by platelet activating factor. This study suggests that leukotrienes play a part in the response to platelet activating factor in man.

Variation in the aromatic ring of cromakalim: antihypertensive activity of pyranopyridines and 6-alkyl-2H-1-benzopyrans

The synthesis and antihypertensive activity in the spontaneously hypertensive rat of two new series of analogues related to cromakalim (1) are described. In the first series, where the benzopyran nucleus has been replaced by a pyranopyridine nucleus, the position of the nitrogen atom has been found to be critical for activity, and the most potent compounds are the pyrano[3,2-c]pyridines. In the second series, where the powerful electron-withdrawing cyano group of compound 1 has been replaced by alkyl and phenyl groups, the order of antihypertensive potency is ethyl, isopropyl, tert-butyl greater than propyl, cyclopentyl greater than methyl greater than phenyl.

Synthesis and antihypertensive activity of 4-(substituted-carbonylamino)-2H-1-benzopyrans

The synthesis and antihypertensive activity of a series of novel 4-(substituted-carbonylamino)-2H-1-benzopyran-3-ols, administered orally to conscious spontaneously hypertensive rats, are described. Optimum activity was observed for compounds with alkyl, amino, or aryl groups flanking the carbonyl group. Of the alkyl and amino series the most potent compounds contained the methyl and methylamino groups, respectively. Several analogues have been compared with cromakalim (1) for their effects on potassium ion efflux in the rabbit mesenteric artery using rubidium-86 as a marker. The ability of each compound to enhance rubidium-86 efflux is approximately parallelled by its blood pressure lowering activity, and thus these analogues, like compound (1), belong to the series of drugs which have been classified as potassium-channel activators.

Platelet activating factor does not cause a reproducible increase in bronchial responsiveness in normal man

The reproducibility of acute effects of inhaled PAF on airway calibre, circulating neutrophil count and any subsequent increase in bronchial responsiveness has been studied in six normal subjects and compared to the effects of inhaled lyso-PAF, the inactive precursor and metabolite of PAF. PAF caused acute bronchoconstriction and a transient fall in neutrophil count on two separate occasions in five out of six subjects (minimum percentage of baseline values (mean): first PAF challenge; sGaw 69%, Vmax30 72%; neutrophil count 70%; second PAF challenge; sGaw 61%, Vmax30 74%, neutrophil count 63%). In one subject inhaled PAF caused bronchoconstriction and a transient fall in neutrophil count once, but a second challenge resulted in no detectable changes. There was no significant increase in bronchial responsiveness to methacholine in any subject studied on five occasions over a 2-week period following each PAF challenge. Challenge with lyso-PAF did not cause acute effects or any subsequent changes in bronchial responsiveness. These findings demonstrate that any effects of inhaled PAF on bronchial responsiveness in normal man are small and probably not of clinical significance. It would also be inappropriate to use this human model to study the mechanisms of bronchial hyperresponsiveness or for the preliminary assessment of potential new anti-asthma drugs.

Influence of cardiac innervation on intrinsic heart rate in dogs

Intrinsic heart rate is defined as the rate at which the heart beats when all cardiac neural and hormonal inputs are removed. We determined the effect of prevailing autonomic innervation of the heart on the intrinsic heart rate in chronically maintained, sedated, normally innervated dogs (n = 14), and in 14 other dogs that had previously (greater than 12 day) undergone complete surgical cardiac denervation. Intrinsic rate was determined in both groups using the following two procedures: 1) pharmacological effector blockade; and 2) pharmacological ganglionic blockade. The intrinsic rate determined by effector blockade was 142.9 +/- 7.2 (SE) beats/min in the dogs with intact cardiac innervation. When the same treatment was given after total surgical cardiac denervation, intrinsic rate was 97.9 +/- 4.8 beats/min. Intrinsic heart rate was significantly (P less than 0.05) lower in surgically denervated dogs. Ganglionic blockade in surgically denervated animals yielded an intrinsic rate of 90.0 +/- 8.5 beats/min, which was again significantly lower than the corresponding value of 128.4 +/- 5.5 beats/min in normal dogs. There was no difference in the intrinsic heart rate as determined by effector vs. ganglionic blockade in either group of dogs. An additional six dogs were subjected to selective surgical sinoatrial nodal parasympathectomy; their intrinsic rate (effector blockade) in the conscious state was 115.8 +/- 4.3 beats/min; this was significantly lower than the corresponding value for normal dogs and significantly greater than in dogs subject to total surgical cardiac denervation. The lower rate observed in the totally denervated and selectively denervated dogs after effector and/or ganglionic blockades implies that intrinsic heart rate depends on the level or nature of prevailing autonomic activity.

The generation and metabolism of leukotrienes in the ionophore-stimulated blood of normal and asthmatic subjects

The generation and metabolism of leukotrienes (LTs) B4, C4, D4, and E4 were studied in vitro in the A23187-stimulated whole blood of normal (N) and atopic asthmatic (AA) human subjects. Using a combination of reversed-phase high performance liquid chromatography and radioimmunoassay, we have demonstrated that the blood cells of atopic asthmatic patients have an enhanced ability to release LTB4 and LTC4 when compared to those of normal subjects. The release of LTB4 and LTC4 in response to ionophore is dose- and time-dependent. Half-maximal doses of ionophore caused the generation of high, sustained levels of LTB4, which are significantly higher in the AA blood than in N blood. Incubations of 3H-LTB4 in ionophore-stimulated N and AA blood revealed a slow metabolism to 20-OH-LTB4 and 20-COOH-LTB4. LTC4 is generated in smaller amounts than LTB4, with an early peak after 10 min which is significantly higher (p less than 0.01) in the AA blood compared to the N blood. Subsequent metabolism of LTC4 elicits significantly greater amounts of LTD4, and consistently higher levels of LTE4, in the AA blood. Parallel incubations of 3H-LTC4 in ionophore-stimulated N and AA blood demonstrated rapid metabolism of LTC4 by the glutathione detoxification pathway. The elevated production of LTB4 and LTC4 in AA blood was not accounted for by differences in leukocyte sub-type counts in the two groups, nor by differences in their rates of catabolism. The novel, selective 5-lipoxygenase inhibitor BW A4C [N-(3-phenoxycinnamyl) acetohydroxamic acid] caused dose-dependent inhibition of LTB4 and LTC4 generation and was equipotent in N and AA blood.

Lower oesophageal contractility monitoring during anaesthesia for cardiac surgery: preliminary observations

Lower oesophageal contractility (LOC), a means of assessing anaesthesia 'depth', has been measured during anaesthesia for cardiac surgery. Appropriate changes in LOC were observed in association with anaesthetic and surgical events.

L-648,051, a novel cysteinyl-leukotriene antagonist is active by the inhaled route in man

1. We have studied some of the pharmacological properties of inhaled L-648,051 which has been shown to be a selective cysteinyl-leukotriene (LT) antagonist in vitro and in vivo in various animal models. 2. The effects of three different doses (1.6, 6.0 and 12.0 mg) on the bronchoconstriction induced by inhaled LTD4 have been investigated in normal male subjects in a series of double-blind, placebo controlled studies. Furthermore, the specificity of the drug has been investigated by challenging subjects with histamine after pre-inhalation of 12.0 mg L-648,051. 3. At all doses L-648,051 partially blocked the bronchoconstriction induced by LTD4 inhalation in a dose related manner. At a dose of 12.0 mg, L-648,051 decreased the maximum fall in specific airways conductance (sGaw) (placebo, 49% vs L-648,051, 21%, P less than 0.01) and shortened the time to recovery from LTD4-induced bronchoconstriction (placebo, 41 min vs L-648,051, 19 min, P less than 0.01). 4. There was no evidence of partial agonist activity, and no effect on histamine-induced bronchospasm. Inhaled L-648,051 at all doses was well tolerated. 5. We conclude that LT antagonism is possible by the inhaled route in man. Inhaled L-648,051 is an active and selective LT-antagonist in man which is well tolerated and may prove to be a useful drug for assessing the role of leukotrienes in asthma and other lung diseases.

A dynamic analysis of cardiovascular regulation using sinusoidal acceleration in dogs

Control of cardiovascular function during time-dependent pooling of blood in the upper and lower body was studied in intact dogs (n = 5) and in dogs in which hearts had been surgically denervated (n = 5). The animal was positioned horizontally on a platform mounted on the arm of a centrifuge; rotation of the platform at one of nine rates with a period ranging from 3.3 min to 4 s exposed the subject to a sinusoidally varying force (+/- 2 g) that periodically translocated blood from the chest to the lower quarters and back again. The resulting oscillatory changes in arterial blood pressure (BP), cardiac output, stroke volume, heart rate (HR), and peripheral resistance (PR) were analyzed using a fast Fourier transform. Normal dogs were superior to cardiac-denervated dogs in minimizing arterial BP fluctuations, especially in the midfrequency range (i.e., approximately 0.032 Hz); after pharmacological alpha-, beta-, and muscarinic-receptor blockade, the BP oscillations were similar in the two groups. The unblocked denervated dogs regulated BP poorly primarily because of their inability to 1) make appropriately timed changes in HR and 2) minimize inappropriate oscillations in SV. Both groups of dogs in the unblocked state showed large appropriately timed PR fluctuations at the lower frequencies, which minimized BP oscillations; these became less optimally timed as acceleration frequency increased, thereby potentiating the natural disposition for BP to oscillate at the acceleration frequency. Afferent information from cardiac receptors did not appear to be essential for controlling this aspect of vascular function.

Studies on the formation of 6-hydroxydopamine in mouse brain after administration of 2,4,5-trihydroxyphenylalanine (6-hydroxyDOPA)

2,4,5-Trihydroxyphenylalanine (6-OH-DOPA) destroys central and peripheral noradrenergic neurons, while sparing dopaminergic neurons. Previous studies indicate that 6-OH-DOPA toxicity is mediated by the formation of 6-hydroxydopamine. However, levels of 6-hydroxydopamine in brain following peripheral administration of 6-OH-DOPA have not been documented. In the current study, 6-OH-DOPA and 6-hydroxydopamine were measured in brain by HPLC with electrochemical detection after intraperitoneal injection of 6-OH-DOPA. When mice were injected with 100 mg 6-OH-DOPA/kg, 6-hydroxydopamine levels in the striatum were highest (1.9 microgram/g) at 15 min and fell slowly to 24% of the peak value at 4 h. Experiments with reserpine indicated that the relatively stability of 6-hydroxydopamine was largely dependent upon storage in synaptic vesicles. Reserpine (10 mg/kg) lowered striatal 6-hydroxydopamine levels to 21.6% of control (non-reserpine-treated) values at 1 h, and to 8.9% of control values at 4 h. Levels of 6-hydroxydopamine in the striatum at 1 h were increased 113% by pargyline (100 mg/kg), 145% by alpha-methyldopahydrazine (carbidopa; 25 mg/kg), and 261% by pargyline and carbidopa together. Levels of dopamine in the striatum were unchanged at 2.5 h after 200 mg 6-OH-DOPA/kg (with pargyline and 50 mg carbidopa/kg), whereas levels of norepinephrine in the frontal cortex fell by 77%. At the same time, 6-hydroxydopamine levels were 8.8-fold higher in the striatum (5.54 micrograms/g) than in the cortex (0.63 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)

The biotransformation in vitro of cysteinyl leukotrienes in blood of normal and asthmatic subjects

The metabolism of exogenous leukotriene C4 (LTC4), LTD4 and LTE4 (10(-8) M) was studied in vitro in blood of normal and asthmatic subjects for up to 2 hr by reverse-phase high performance liquid chromatography. In whole blood, incubation of LTC4 (T1/2 = 11.5 min) resulted in the formation of LTD4 and LTE4 whose biosynthesis was inhibited by serine borate (30 mM). Similar experiments performed with LTD4 (T1/2 = 5 min) produced a single metabolite (LTE4) which was inhibited by L-cysteine (10 mM). On the other hand, LTE4 represented a highly stable product in our in vitro system. The bioconversion of LTC4 or LTD4 was slower in plasma but this effect appeared more pronounced for the cysteinylglycinyl derivative. The bioconversion of LTD4 in whole blood or plasma was almost twice as rapid as LTC4. Experiments performed with asthmatic blood showed no significant difference in the survival of LTC4. These results suggest that blood may play a role in regulating the bioavailability of cysteinyl-containing LTs which could be of relevance to their excretion in man.

Measurement of normal portal venous blood flow by Doppler ultrasound

The volume flow rate of blood in the portal vein was measured using a duplex ultrasound system. The many errors inherent in the duplex method were assessed with particular reference to the portal vein and appropriate correction factors were obtained by in vitro calibration. The effect of posture on flow was investigated by examining 45 healthy volunteers in three different positions; standing, supine and tilted head down at 20 degrees from the horizontal. The mean volume blood flow in the supine position was 864 (188)ml/min (mean 1SD). When standing, the mean volume blood flow was significantly reduced by 26% to 662 (169)ml/min. There was, however, no significant difference between flow when supine and when tilted head down at 20 degrees from the horizontal.

Hospital anaesthesia and general practice

Images

Response of lower esophageal contractility to changing concentrations of halothane or isoflurane: a multicenter study

A multiple-center study was performed to determine the relationship between lower esophageal contractility, clinical signs, and anesthetic concentration as expressed by minimum alveolar concentration (MAC). One hundred four American Society of Anesthesiologists Class I through III patients were exposed to isoflurane (with and without nitrous oxide) or halothane in concentrations of 0.5, 1.0, and 1.5 MAC. Heart rate and systolic blood pressure were continuously monitored. Both the amplitude and frequency of spontaneous and provoked lower esophageal contractions were measured in situ by using a 24-F probe equipped with provoking and measuring balloons. Combined results demonstrated statistically significant correlations (P less than 0.001) between lower esophageal contractility and MAC. Spontaneous lower esophageal contractions decreased from 1.10 +/- 0.12 (SEM) contractions per minute (0.5 MAC) to 0.42 +/- 0.05 (1 MAC) to 0.18 +/- 0.05 (1.5 MAC). Provoked lower esophageal contractility values decreased from 45 +/- 4 mm Hg (0.5 MAC) to 29 +/- 3 (1 MAC) to 19 +/- 2 (1.5 MAC). Heart rate changes did not correlate with MAC, and systolic blood pressure correlated in only one of three centers. Intracenter and intercenter analyses failed to demonstrate a significant relationship between lower esophageal contractility and heart rate or systolic blood pressure. No intracenter differences in either amplitude or frequency of lower esophageal contractions were observed, despite differences in volatile agents, induction techniques and agents, patient populations, and durations of anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

The metabolism "in vitro" of leukotriene B4 in blood of normal subjects and asthmatic patients

The metabolism of exogenous leukotriene B4 (LTB4) was investigated in venous blood obtained from normal and asthmatic subjects. Using specific radioimmunoassay (RIA) and reverse-phase high performance liquid chromatography (RP-HPLC) techniques we have demonstrated that LTB4 is relatively stable during a 2 hr incubation period at 37 degrees C in our system in vitro. Nevertheless, chromatographic analysis revealed the presence of two products which had retention times identical to 20-hydroxy LTB4 (20-0H LTB4) and 20-carboxy LTB4 (20-C00H LTB4) in which the dicarboxylic derivative was the main metabolite present after 15 min incubation. The amount of LTB4 and its w-oxidation products observed after a 2 hr incubation period was 73% and 24% respectively. There was no basal release of LTB4 from blood. The appearance of these oxidative products was totally suppressed at 4 degrees C and with incubations performed with either venous plasma or Hartmann's control. No significant difference was observed in substrate metabolism between normal and asthmatic subjects. Our results demonstrate that LTB4 is slowly degraded in human whole blood through a cellular dependent process of w-oxidation which may be an important pathway for regulating the availability of this potent biologically active substance.

Control of left ventricular function during acceleration-induced blood volume shifts

Peripheral pooling of blood was produced in chronically instrumented, sedated dogs (n = 7) by subjecting them to a +2 Gz force (along their spinal axis) for 3 min. The acceleratory force was then quickly removed, thereby mobilizing blood toward the thoracic cavity. Left ventricular volume, calculated from ultrasound measurements of major and minor axes and wall thickness, increased (p less than 0.05) from 21.7 +/- 3.6 ml (diastolic, mean +/- S.E.M.) and 14.1 +/- 3.3 ml (systolic) during the peripheral pooling of blood to 28.2 +/- 4.1 ml (diastolic) and 16.0 +/- 2.9 ml (systolic) as measured at 2 min after release of the acceleratory force. The d(LVP)/dt was essentially unchanged (i.e., from 3415 +/- 482 mm Hg.s-1 to 3536 +/- 249 mm Hg.s-1). The experiment was repeated after total pharmacologic autonomic blockade (propranolol, atropine, phenoxybenzamine). Left ventricular volumes during +2 Gz after blockade were 27.7 +/- 2.5 ml (diastolic) and 21.2 +/- 2.9 (systolic). The acceleration-induced changes in cardiovascular function, including the changes in ventricular volume, were not significantly different from those of the reflexive state. These results, therefore, do not reveal a substantial role for the autonomic nervous system in the regulation of left ventricular volume responses to the sudden cessation of G-induced peripheral blood pooling. Since the cessation of the G force induced essentially identical increases in left ventricular volumes and stroke volumes both before and after the autonomic blockade, it is concluded that the heart relied mainly upon the Frank-Starling mechanism to adapt to the changes in load.

Pulse-generated runoff: a new method of determining calf vessel patency

A non-invasive method of determining calf vessel patency before femorodistal bypass has been developed. This pulse-generated runoff (PGR) system generates blood flow in patent calf arteries by means of a pulsatile cuff even if the existing Doppler signal is inaudible. PGR was compared with pre-operative arteriography in 95 ischaemic limbs and both were compared with the peripheral resistance measured at operation in 62 limbs. There was a highly significant correlation between the PGR and arteriogram scores (rs = 0.74, P less than 0.001) but PGR tended to detect more patent vessels than arteriography. The peripheral resistance correlated better with PGR than arteriography (rs = -0.71 and -0.54 respectively, P less than 0.001). PGR is a simple, non-invasive method of determining calf and foot vessel patency pre-operatively.

Haemodynamic changes in man during immersion in water at different temperatures

1. Stroke volume and cardiac output were measured using the Doppler ultrasound technique in 16 normal subjects immersed to the neck in water at 33 degrees C, 35 degrees C, 37 degrees C and 39 degrees C. A standard aortic diameter was assumed and results were expressed as percentage changes from pre-immersion resting values. 2. Cardiac output rose progressively at higher temperatures, increasing by 30% at 33 degrees C and by 121% at 39 degrees C. At thermoneutral temperatures (33 degrees C and 35 degrees C) this was achieved by an increase in stroke volume of 50% despite a significant decrease in heart rate. There was a further rise in stroke volume and pulse rate at higher temperatures and a mean tachycardia of 109 +/- 4 beats/min was noted at 39 degrees C. Calculated peripheral resistance reduced progressively with increasing temperature of immersion. 3. This non-invasive and simple technique may provide a non-exercise-related cardiovascular stress test to study cardiovascular responses in a variety of pathophysiological states.

Relationship between lower oesophageal contractility, clinical signs and halothane concentration during general anaesthesia and surgery in man

The effects of a range of concentrations of halothane upon lower oesophageal contractility (LOC) and on defined clinical signs has been studied in patients undergoing surgery. Changes in clinical signs were assigned a numerical value by means of a scoring system. One hundred and eighty-one sets of measurements were made in 46 patients exposed to concentrations of halothane between 2.0 and 0.5 minimum alveolar concentration (MAC). The results were examined to identify relationships between (i) the clinical signs and alveolar halothane concentration, (ii) the clinical signs and LOC and (iii) the changes in LOC and alveolar concentration; significant correlations were found between these variables. Decreasing alveolar halothane concentration was associated with an increase in LOC and these increases in LOC were also associated with increases in the clinical score.

A data collection system for gathering electrical impedance measurements from the human breast

A data collection system for gathering electrical impedance measurements from the human breast is described. The system consists of 16 electrodes which are held in a ring that encompasses the breast. The system, which is battery operated, is controlled by a microprocessor enabling computer control of electrode selection and storage of data.

An analogue mean frequency estimator for the quantitative measurement of blood flow by Doppler ultrasound

Ultrasonic Doppler-shifted signals from blood can be displayed in various forms using either analogue or digital processing techniques. One of the most commonly extracted parameters from the Doppler spectrum is the mean frequency envelope. This waveform can be used for the interpretation of physiological changes within man and can also be used for the estimation of volume flow rate within a vessel. This paper describes a practical implementation of an analogue, instantaneous mean frequency estimator and its use in the measurement of blood flow volume. The circuit is linear to within two per cent and operates over a frequency range of 200 Hz to 10 kHz. It can extract a velocity-time envelope from a Doppler signal within noise and performs well in a clinical environment. It is relatively inexpensive compared with digital signal processing techniques and requires minimal setting up. Simple connection to a Doppler velocimeter using phase quadrature demodulation will produce a directional output.

Synthesis and antihypertensive activity of 4-(cyclic amido)-2H-1-benzopyrans

The synthesis and antihypertensive activity of a series of novel 4-(cyclic amido)-2H-1-benzopyran-3-ols, administered orally to conscious spontaneously hypertensive rats, are described. The effects of lactam ring size, the presence of heteroatoms in the lactam ring, substitution at C(2) and C(3), relative stereochemistry at C(3) and C(4), and aromatic substitution pattern on the blood pressure lowering activity of this series have been determined. The key compound 2 from this work [BRL 34915; (+/-)-6-cyano-3,4-dihydro-2,2-dimethyl-trans-4-(2-oxopyrrolidin-1- yl)-2H-1-benzopyran-3-ol] has been resolved, and antihypertensive activity was found to reside primarily in the (-) enantiomer. The key step in the preparation of this class of compounds is the action of a cyclo amidic anion on an appropriate epoxide. Another approach, involving a cyclization step to the lactam was found to be more convenient in certain cases, particularly in forming the cis analogue of compound 2. Compound 2 has been shown to possess a novel mechanism of action, and it has been selected for progression to the clinic.

Transcutaneous Doppler ultrasound measurement of superior mesenteric artery blood flow in man

A duplex scanner which consists of a real time two dimensional scanner and a pulsed Doppler flowmeter was used to measure superior mesenteric blood flow in 70 healthy subjects. By processing the Doppler shift signals, the instantaneous average Doppler shift frequency and then the instantaneous average velocity of the flow rate were calculated. Both diameter of the vessel and angle between vessel and beam were measured from real time imaging. The mean (+/- standard error of the mean) of the superior mesenteric blood flow was 517 +/- 19 ml/min. There was neither significant difference in flow between sexes, nor correlation between flow and age (r = 0.042). The mean of coefficients of variability were 6.8% over the short term, and 8.2% in long term studies.

Observations on the effect of immersion in Bath spa water

Immersion in water in spas has been practised for centuries and has many proponents. Despite fierce debate about its efficacy there has been little scientific evaluation of the effect of immersion in mineral waters. Eight normal subjects were immersed in Bath spa water for two hours and the renal, haematological, and cardiovascular responses were compared with those in the control periods before and after immersion. Significant, twofold diuresis and natriuresis, 5% haemodilution, and a 50% increase in cardiac index were observed in subjects immersed, sitting, in Bath spa water at 35 degrees C. These changes may constitute part of the scientific rationale for spa treatment in many states of disease.

Cost effectiveness of home health care as an alternative to inpatient care

This study of a sample of patients discharged from the Visiting Nurse Association of Greater St. Louis (VNA) focused on the extent to which VNA services were used as an alternative to institutional care. Based on physician estimates, patients averaged 18 fewer days in the hospital due to home care, saving more than $3,300 per patient. Utilization patterns are discussed for patients grouped by age, diagnosis, payment source and disposition upon discharge. Variations observed suggest valuable avenues for additional investigation into the types of patients for whom home care is most likely to be an appropriate alternative to hospital care.

Transcutaneous Doppler ultrasound measurement of coeliac axis blood flow in man

Transcutaneous Doppler ultrasound was used to measure coeliac axis blood flow in 42 normal subjects in the fasting state and in 10 subjects following a liquid meal. A Duplex scanner was used and coeliac axis blood flow was estimated by calculating the instantaneous average velocity of blood flow over the cardiac cycle. Both the diameter of the vessel and the angle between the vessel and the beam were measured from real time imaging. The mean (+/- s.e.m.) of coeliac axis blood flow was 703 +/- 24 ml/min. There was no difference in the results between the sexes nor any correlation between flow and age. The mean coefficient of variability was 7.8 per cent in a 1 day test and 9.2 per cent in a 2 day test. Coeliac axis blood flow increased by 38 per cent immediately after the end of ingestion of the meal and declined to 29 per cent 5 min and 24 per cent 10 min later.

Electrocardiographical changes in the peri-operative period. A pilot study

The value of continuous electrocardiogram recording in the peri-operative period has been examined. In a group of 15 patients, 14 developed changes two of which persisted into the postoperative period. Dysrhythmias, ST segment and T-wave changes occurred frequently. Continuous recording is of potential benefit in the study of cardiovascular disease and therapy in the peri-operative period.

Synthesis and antihypertensive activity of 6,7-disubstituted trans-4-amino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-3-ols

A series of novel 6,7-disubstituted trans-3,4-dihydro-2, 2-dimethyl-4-pyrrolidino-(or piperidino)-2H-1-benzopyran-3-ols was prepared and tested for antihypertensive activity in the conscious spontaneously hypertensive rat (SHR) and compared with certain of their monosubstituted analogues. The potent blood pressure lowering activity of the 6-monosubstituted compounds was enhanced by incorporation of an acetylamino or amino group at C(7) and that of the 7-nitro-substituted compound by incorporation of an amino (but not an acetylamino group) at C(6). The combination of 6-nitro or 6-cyano with 7-(acetylamino) or 7-amino groups and 6-amino with 7-nitro groups in trans-4-pyrrolidino- or -4-piperidino-2,2-dimethyl-2H-1-benzopyranols conferred superior antihypertensive activity to hydralazine and to the calcium antagonist, nifedipine, in SHR. The synthetic route to these compounds involves the conversion of 2H-1-benzopyrans to bromohydrins that were treated with pyrrolidine or piperidine. Preparation of the 6-cyano-7-amino analogue was accomplished when 6-cyano-7-[(trifluoroacetyl)amino]-2,2-dimethylbenzopyran was used as starting material.