Influence of the marine feeding area on the muscle and egg fatty-acid composition of Atlantic salmon Salmo salar spawners estimated from the scale stable isotopes.

Fatty acids in muscle tissue and eggs of female Atlantic salmon Salmo salar spawners were analysed to evaluate the dietary quality of their final feeding areas in the Baltic Sea. The final likely feeding area was identified by comparing stable carbon and nitrogen isotope composition of the outermost growth region (final annulus) of scales of returned S. salar with that of reference S. salar caught from different feeding areas. Some overlap of stable-isotope reference values among the three areas, in addition to prespawning fasting, decreased the ability of muscle tri-acylglycerols to discriminate the final likely feeding area and the area's dietary quality. Among three long-chained polyunsaturated fatty acids, docosahexaenoic acid (DHA; 22:6n-3), eicosapentaenoic acid (EPA; 20:5n-3) and arachidonic acid (ARA; 20:4n-6), the proportions of ARA in total lipids of spawning S. salar muscle and eggs showed a significant negative correlation with increasing probability of S. salar having returned from the Baltic Sea main basin (i.e. the Baltic Sea proper). The results suggest that ARA in muscle and eggs is the best dietary indicator for dietary characteristics of final marine feeding area dietary characteristics among S. salar in the Baltic Sea.

Bacterial community response to changes in a tri-trophic cascade during a whole-lake fish manipulation.

Microbial communities play a key role in biogeochemical processes by degrading organic material and recycling nutrients, but can also be important food sources for upper trophic levels. Trophic cascades might modify microbial communities either directly via grazing or indirectly by inducing changes.in other biotic or in abiotic factors (e.g., nutrients). We studied the effects of a tri-trophic cascade on microbial communities during a whole-lake manipulation in which European perch (Perca fluviatilis) were added to a naturally fishless lake divided experimentally into two basins. We measured environmental parameters (oxygen, temperature, and nutrients) and zooplankton biomass and studied the changes in the bacterial community using next generation sequencing of 16S rRNA genes and cell counting. Introduction of fish reduced the biomass of zooplankton, mainly Daphnia, which partly altered the bacterial community composition and affected the bacterial cell abundances. However, the microbial community composition was mainly governed by stratification patterns and associated vertical oxygen concentration. Slowly growing green sulfur bacteria (Chlorobium) dominated the anoxic water layers together with bacteria of the candidate division ODI. We conclude that alterations in trophic interactions can affect microbial abundance, but that abiotic factors seem to be more significant controls of microbial community composition in sheltered boreal lakes.

Seasonal and ontogenetic shifts in the diet of Arctic charr Salvelinus alpinus in a subarctic lake.

Seasonal and ontogenetic shifts in the diet of Arctic charr Salvelinus alpinus were studied in a deep, ultra-oligotrophic lake in subarctic Finland from both stomach contents and the stable carbon (delta(13)C) and nitrogen (delta(15)N) isotope compositions of muscle and liver tissues. Both diet and isotope results indicated that the S. alpinus population relied mainly on littoral benthic energy sources. The strong littoral reliance appeared largely independent of season or fish size, although the data lacked small (total length, L(T), <130 mm) and young (<3 years) S. alpinus. Liver isotope values of intermediate-sized S. alpinus (200-350 mm), however, suggested exploitation of the increase in the abundance of pelagic zooplankton in the late open-water season. The results suggest that, in general, a strong littoral reliance of fishes can be a feature in subarctic lakes throughout the year. Due to its faster isotopic turnover rate and thus higher resolution for temporal diet changes, liver could be more commonly used in stable-isotope studies of fish trophic niche shifts instead of using only the less responsive muscle tissue.

Stable isotope analysis of the origins of zooplankton carbon in lakes of differing trophic state.

Carbon stable isotope analysis was carried out on zooplankton from 24 United Kingdom lakes to examine the hypothesis that zooplankton dependence on allochthonous sources of organic carbon declines with increasing lake trophy. Stable isotope analysis was also carried out on particulate and dissolved organic matter (POM and DOM) and, in 11 of the lakes, of phytoplankton isolates. In 21 of the 24 lakes, the zooplankton were depleted in 13C relative to bulk POM, consistent with previous reports. δ13C for POM showed relatively little variation between lakes compared to high variation in values for DOM and phytoplankton. δ13C values for phytoplankton and POM converged with increasing lake trophy, consistent with the expected greater contribution of autochthonous production to the total organic matter pool in eutrophic lakes. The difference between δ13C for zooplankton and that for POM was also greatest in oligotrophic lakes and reduced in mesotrophic lakes, in accordance with the hypothesis that increasing lake trophic state leads to greater dependence of zooplankton on phytoplankton production. However, the difference increased again in hypertrophic lakes, where higher δ13C values for POM may have been due to greater inputs of 13C-enriched organic matter from the littoral zone. The very wide variation in phytoplankton δ13C between lakes of all trophic categories made it difficult to detect robust patterns in the variation in δ13C for zooplankton.

Pneumosinus dilatans: a discussion of four cases and the possible aetiology.

Pneumosinus dilatans is an abnormal dilatation of the paranasal sinuses, which contains only air and is lined by normal mucosa. It is a rare condition, the aetiology of which is unclear. We describe four patients who presented to our department with pneumosinus dilatans. The aetiology was either developmental hydrocephalus (n = 1), post-traumatic (n = 1) or idiopathic (n = 2). Two patients underwent surgery, and follow-up is at least 12 months to date. The radiological aspects of this rare condition and the possible aetiologies are discussed.

Simultaneous measurement of left ventricular function and myocardial perfusion during a single exercise test: dual isotope imaging with gold-195 m and thallium-201.

The state of left ventricular function and myocardial perfusion are important determinants of prognosis in patients with coronary artery disease and information on both can be valuable for planning individual patient management. We have studied the feasibility of simultaneous measurement of left ventricular ejection fraction with ultra short-lived gold-195 m (half life 30.5 seconds) and myocardial perfusion with thallium-201, at rest and after exercise with a single-crystal gamma camera. The results with first-pass radionuclide angiocardiography (RNA) using gold-195 m at rest were reproducible and agreed closely with the results obtained using technetium-99 m equilibrium radionuclide angiocardiography (r = 0.93). Ejection fraction by first-pass gold-195 m RNA during semi-supine ergometric exercise decreased by greater than 5% in 13 out of 18 patients with coronary artery disease and stable angina. Simultaneous myocardial imaging with thallium-201 was abnormal in all patients. The change in regional wall motion abnormality score during exercise correlated with the change in myocardial perfusion (r = 0.71, P less than 0.01) and with the change in global left ventricular ejection fraction (r = 0.77, P less than 0.001). The widely differing energy levels and half-lives of gold-195 m and thallium-201 made it possible to separate clearly the images due to each radionuclide. This study has demonstrated the feasibility of simultaneous or sequential assessment of left ventricular function and myocardial perfusion during a single exercise test, a technique which can offer advantages in clinical evaluation of patients with coronary artery disease.

Ambulatory blood pressure and assessment of pacemaker function.

Ten patients in sinus rhythm with ventricular demand (VVI) pacemakers implanted for the sick sinus syndrome underwent 24 hour ambulatory blood pressure and electrocardiographic recording by a modified version of the Oxford system. Five patients had symptoms of dizziness or presyncope at the time of study and five were symptom free. The onset of pacing was associated with a fall in arterial blood pressure in both groups which was larger in the patients with symptoms, and in these patients the blood pressure recovery consequent on baroreflex activation was delayed by up to fifteen beats. In three of the patients with symptoms the original pacemaker was replaced by an atrioventricular pacing (DVI) device. This abolished symptoms and the initial fall and delayed recovery of blood pressure. Thus it appears that the development of symptoms of hypotension after the onset of ventricular pacing is determined by the rate of the baroreflex response. These symptoms and the haemodynamic consequences may be alleviated by dual chamber pacing.

Left ventricular function during isometric hand grip and cold stress in normal subjects.

Both isometric exercise and cold stress have been suggested as alternatives to dynamic exercise for the detection of obstructive coronary artery disease. A non-imaging nuclear probe was used to measure left ventricular ejection fraction and relative left ventricular volumes continuously during both of these stress tests in 24 normal subjects. There was a significant fall in left ventricular ejection fraction within 15 seconds of subjects starting a two minute isometric hand grip test at 50% maximal voluntary contraction, with a mean (SE) maximal fall of 10% (1.8) after 90 seconds. During two minutes immersion of the hand and wrist in iced water left ventricular ejection fraction fell significantly within 30 seconds with a mean maximal fall of 7% (1.7) after one minute. Nine subjects underwent repeat tests under identical conditions approximately two weeks later. The standard error of the change in ejection fraction on two occasions was 5.4% at rest, 7.0% at the peak of isometric exercise, and 4.8% at peak cold stress. These results indicate that the reproducibility of both of these stress tests is acceptable when they are performed under carefully controlled conditions. The resulting changes in ejection fraction are transient, however, and moreover depend upon the choice of stress protocol. The discrepancies between published reports of such studies in coronary artery disease may be mainly due to methodological differences, and neither test is likely to be of sufficient discriminative ability to distinguish between individuals with obstructive coronary artery disease and normal subjects.

Twice-daily verapamil for hypertension: a comparison with propranolol.

Recent reports have confirmed that some slow calcium channel inhibitors have useful antihypertensive properties because they produce dilatation of the peripheral arterioles without reflex tachycardia. Verapamil is such a drug, but its clinical role in the management of hypertension is not clear. An open crossover trial was performed to compare the 24-hour profiles of blood pressure reduction after long-term therapy with a standard beta-adrenoceptor blocker, propranolol, and verapamil. Nineteen patients were studied by continuous ambulatory intraarterial recording and the order of drug administration was determined by random allocation. The drugs were administered 2 times a day and titrated according to casual clinic pressures (propranolol, 40 to 240 mg 2 times a day; verapamil, 120 to 240 mg 2 times a day). Mean hourly blood pressure and heart rate values were obtained over a 24-hour cycle and the responses to isometric and dynamic exercise were also examined. The drugs produced a uniform and comparable reduction in blood pressure throughout the day, together with a reduction in heart rate, which was greater with propranolol. Comparable effects were also seen on the pressor responses to exercise. Both drugs were equally well tolerated and caused no patient withdrawals. Thus, oral verapamil given 2 times a day shows a degree of efficacy similar to that of propranolol and provides 24-hour blood pressure control. This slow calcium channel inhibitor was well tolerated and may be used as initial therapy for hypertension.

Changes in left ventricular function during exercise and their relation to ST segment changes in patients with angina.

The high count sensitivity of the non-imaging nuclear probe affords the possibility of measuring left ventricular ejection fraction continuously during short term interventions. The nuclear probe was used to examine the pattern of change of left ventricular function during dynamic exercise and its temporal relation to ST segment depression in 12 patients with stable exertional angina. After in vivo blood pool labelling with technetium-99m the left ventricular time-activity waveform was detected by the nuclear probe and was continuously recorded on a strip chart. The 15 beat mean ejection fraction and the ST segment level 80 ms after the J point were measured at rest and every 30 seconds during maximal ergometric exercise and during recovery. The mean ejection fraction was 54.3% (range 46-64%) at rest and fell during exercise in all subjects by a mean of 16.8% (range 6-25%). In contrast, in a control group of 16 healthy male volunteers the mean ejection fraction was 55.9% (range 47-64%) at rest and increased in all by a mean of 10.2% (range 3-19%) during exercise. The difference of ejection fraction response to exercise between the patients and controls was due to pronounced increases in relative end diastolic and especially end systolic volumes in the patients. Relative stroke volume differed between patients and controls only at peak exercise. ST segment depression greater than 1 mm developed in 11 of the 12 patients. A decrease of greater than 5% in ejection fraction occurred within 1 minute of starting exercise in nine of the 12, and in 11 patients it preceded the beginning of ST depression. In most of this selected group of patients the ejection fraction had fallen during exercise before the appearance of ischaemic electrocardiographic changes.

Effect of enalapril at rest, during tilt, static and dynamic exercise in systemic hypertension.

Using the "Oxford system" for ambulatory monitoring of direct arterial blood pressure (BP), the hypotensive effect of enalapril (20 to 40 mg/day), was assessed in 15 patients with essential hypertension. BP was reduced by enalapril throughout the 24 hours of study. A within-patient comparison of corresponding mean hourly systolic and diastolic BP values showed a reduction from (p less than 0.05 to p less than 0.001) for 18 of the 24 hours. Four patients had an increase in BP during treatment with enalapril. There was a significant decrease in systolic BP in response to 60 degrees head-up tilt. During isometric and dynamic exercise there was a smaller increase in systolic BP but a less marked effect on diastolic BP. Heart rate was unaffected either during free ambulation or during physiologic testing. The incidence of side effects was low. These results indicate that enalapril administered once daily may be an effective form of antihypertensive therapy. However, there is a group of patients who are unresponsive to treatment with converting enzyme inhibitors.

Assessment of left ventricular function in coronary artery disease with the nuclear probe during intervention studies.

The nuclear probe was used for measuring left ventricular function in 11 normal subjects and the results compared with those using a digital gammacamera. The probe was then used to measure left ventricular function in patients with coronary artery disease during dynamic exercise and stress atrial pacing. The ability of the probe to detect changes induced by glyceryl trinitrate was also evaluated in separate parallel studies. In the 11 normal subjects there was a good correlation between the left ventricular ejection fraction measured by the gammacamera and the nuclear probe both at rest and during exercise. Exercise increased this value by at least 5% in all normal subjects during measurements with both the gammacamera and the nuclear probe. The mean (SD) difference was -0.3% (2.60) at rest and 2.3% (5.02) at peak exercise. Both exercise and pacing produced angina in the patient group and the mean (SEM) value fell from 52% (3.5) to 28% (2.6) and from 46% (5.1) to 34% (3.2) respectively. Glyceryl trinitrate prolonged the exercise and pacing times, and the corresponding falls in ejection fraction were significantly reduced. The non-imaging nuclear probe is a cheap and portable instrument capable of assessing left ventricular function in patients with cardiac disease. It is designed for high count rate acquisition over a short period of time and can thus provide both beat to beat and summated left ventricular time activity curves suitable for quantitative analysis. It therefore has important advantages in the clinical setting and during controlled interventions compared with the gammacameras.

Propranolol versus verapamil for the treatment of essential hypertension.

Recent reports have confirmed that slow calcium channel inhibitors have useful antihypertensive properties because they produce dilatation of the peripheral arterioles without reflex tachycardia. Their clinical place in the management of hypertension has yet to be clearly defined, and thus we have performed an open crossover trial to compare the 24-hour profiles of blood pressure reduction after chronic therapy with propranolol and verapamil. Nineteen patients were studied by continuous ambulatory intraarterial recording and the order of drug administration was decided by random allocation. Drug dosage was twice daily and titrated according to casual clinic pressures (propranolol, 40 to 240 mg twice a day; verapamil, 120 to 240 mg twice a day). Mean hourly blood pressure and heart rate values were obtained over a 24-hour cycle, and the responses to isometric and dynamic exercise were also examined. Both drugs were shown to produce a uniform and comparable reduction in blood pressure throughout the whole day, together with a reduction in heart rate, which was greater with propranolol. Comparable effects were also seen on the pressor responses to exercise. Both drugs were equally well tolerated and caused no patient withdrawals. We conclude that oral verapamil given twice daily showed a similar degree of efficacy to propranolol and provided 24-hour blood pressure control. This slow calcium channel inhibitor may be useful as initial therapy for hypertension, particularly for those patients in whom beta-adrenoreceptor blockers are contraindicated.

The safety of ambulatory intra-arterial pressure monitoring: a clinical audit of 1000 studies.

Between 1973 and 1981 1000 successful studies involving ambulatory monitoring of intra-arterial blood pressure were performed using percutaneous cannulation of the brachial artery. We have reviewed the clinical effects of these studies and 35 other cases where attempted cannulation was unsuccessful. One major complication occurred, when an infected haematoma arising at the cannulation site led to the formation of a false aneurysm. In only one other case was distal pulsation diminished following the study. There were 157 reported "minor" complications in 122 studies, including haematoma, haemorrhage, transient paraesthesiae in median nerve territory, and evidence of micro-emboli. A limited study using pulsed wave Doppler ultrasound revealed no significant alteration in arterial lumen size or flow in 20 subjects. The procedure was therefore associated with a much smaller incidence of clinical problems than has been reported with other investigations involving cannulation of the brachial artery.

A non-invasive technique for continuous monitoring of left ventricular function using a new solid state mercuric iodide radiation detector.

A miniature solid-state mercuric iodide (HgI2) nuclear probe detector has been developed in conjunction with a computerized nuclear probe (Nuclear Stethoscope) to enable continuous non-invasive monitoring of left ventricular function using 99Tc-labelled equilibrium blood pool techniques. Left ventricular ejection fraction was measured in 54 patients undergoing radionuclide angiography with a gamma-camera and with the Nuclear Stethoscope and a good correlation was obtained between both techniques (r = 0.94, n = 54, P less than 0.001). The prototype mercuric iodide detector was compared with the sodium iodide detector of the Nuclear Stethoscope and a study in 41 consecutive patients demonstrated a good correlation for the measurement of ejection fraction, ejection rate, peak filling rate and time to peak filling rate (r = 0.94, 0.89, 0.90 and 0.78 respectively). It may be possible to adapt the mercuric iodide detector for continuous non-invasive monitoring of left ventricular performance in critically ill patients and during physiological or pharmacological interventions.

The effect of a new calcium channel blocker nicardipine on 24-hour ambulatory blood pressure and the pressor response to isometric and dynamic exercise.

We have assessed the potential antihypertensive effect of a new slow channel blocker, nicardipine, in a group of patients with essential hypertension. Fourteen patients completed a study using the 'Oxford' system for recording blood pressure during free ambulation and physiological testing. An initial 24-h recording was performed on no treatment and repeated following chronic therapy with 40 mg b.d. of nicardipine. During each recording, the patients performed isometric and dynamic exercise according to a standardized protocol. Within-patient comparisons of consecutive mean hourly systolic and diastolic blood pressures showed a reduction throughout the 24 h during nicardipine therapy. The reduction in blood pressure was also maintained at the peaks of isometric and dynamic exercise. Side-effects were encountered frequently and led to four patient withdrawals. Nicardipine appears to be effective in reducing blood pressure although the frequency of encountered side-effects may limit its usefulness as a first-line antihypertensive agent.

Nifedipine tablets for systemic hypertension: a study using continuous ambulatory intraarterial recording.

The action of nifedipine tablets was examined in 17 patients with essential hypertension focusing particularly on the profile of blood pressure (BP) reduction over 24 hours resulting from both twice-daily and once-daily therapy (dose range 40 to 120 mg daily). This new formulation of nifedipine has a more prolonged and lower peak plasma level than an equivalent dose of nifedipine capsules. Our patients were fully ambulant and studied by continuous intraarterial recording techniques. BP responses during isometric and dynamic exercise testing were also observed. Within-patient comparisons of consecutive mean hourly systolic and diastolic BP showed a highly significant effect from twice-daily therapy (p less than 0.001) for nearly the entire day. Also, significantly lower BP was maintained during isometric and dynamic exercise. Mean hourly heart rates were not significantly altered. The profile of action of the single morning dose was initially similar, but its efficacy diminished from 6 P.M. to 8 A.M. on the following day. Side effects were not unduly troublesome and did not cause any patient withdrawals. Four patients developed mild ankle edema. Two others had facial flushing. Nifedipine given twice daily in tablet form, therefore, is an effective antihypertensive drug capable of lowering BP consistently over 24 hours in ambulant patients and during formal exercise testing. We suggest that this agent may be useful as initial therapy for systemic hypertension, although the tablets are not as yet widely available.

Nifedipine tablets for hypertension: a study using continuous ambulatory intra-arterial recording.

A study using continuous ambulatory intra-arterial blood pressure recording has shown that nifedipine tablets given twice daily can provide 24 hour control of blood pressure and maintain lower absolute blood pressure levels during isometric and dynamic exercise.