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In the denervated mammalian heart a change in right atrial pressure will still alter heart rate (intrinsic rate response, IRR). We have examined the IRR in isolated right atria of the guinea-pig maintained in oxygenated Krebs-Henseleit solution at 37 degrees C, to compare with and extend studies in other species, and to determine whether the guinea-pig is a suitable model for electrophysiological studies of the IRR. Baseline diastolic transmural pressure was set at 2 mmHg. A 6-mmHg increase in right atrial pressure (RAP) caused an increase in atrial rate that reached a steady value of 15 min(-1) after 1-2 min. This response was enhanced by carbamylcholine and attenuated by isoprenaline. The influence of RAP on the rate response to vagal stimulation was examined. With RAP set at 8 mmHg, the reduction in atrial rate following vagal stimulation was 72+/-5% of that at 2 mmHg (n=6, mean+/-S.E., P<0.005). Continuous vagal stimulation produced a sustained bradycardia, and the effect of this bradycardia on the IRR was examined. When atrial rate was reduced 6% by vagal stimulation, the IRR was augmented to 202+/-21% of the control (n=6, P<0.005). This augmentation was larger (P<0.05) than that seen when atrial rate was reduced 8% by carbamylcholine (130+/-8% of control; n=7, P<0.05). Overall, the IRR in the guinea-pig is similar to that in the rabbit, and shows similar interactions with the autonomic nervous system.

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The aim of the study was to evaluate which ionic currents are modified in the sinoatrial node of guinea pigs when the vagus is stimulated. Responses of isolated atrial preparations to bilateral vagus nerve stimulation were examined. In bath-mounted preparations, 10-s trains of vagal stimulation (1-50 Hz) slowed the rate at which atrial contractions occurred. After the trains of stimuli, the force generated by each contraction was reduced. Both vago-inhibitory responses persisted in the presence of caesium (2 mM) and barium ions (1 mM). Vagal stimulation evoked a similar bradycardia in superperfused preparations in which intracellular recordings were made from pacemaker cells in the sinoatrial node. When pacemaking activity was abolished by adding the organic calcium channel antagonist nifedipine (1 microM) to the perfusate, vagal stimulation generated an inhibitory junction potential (IJP). Both the bradycardia and the amplitude of the inhibitory junction potential increased as the frequency of vagal stimulation was increased. The ability of vagal stimulation to produce inhibitory junction potentials was unaffected by the addition of caesium and barium ions to the perfusate. These observations suggest that the negative chronotropic and inotropic responses to vagal stimulation only minimally involve a muscarinically activated potassium current (I(KACh)) or changes in the hyperpolarization-activated pacemaker current Ih.

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We have examined the expression of the ovine clusterin gene in the sheep pituitary gland, with the aim of determining its site of synthesis in this tissue. Northern blotting analysis of extracted polyadenylated RNA, using a (32)P-labelled rat clusterin cDNA probe, detected the greatest amounts of clusterin mRNA in the anterior part of dissected pituitary glands. In situ hybridisation studies showed clusterin mRNA in anterior and intermediate pituitary cells, with lower amounts in vascular endothelium and posterior pituicytes. Clusterin protein, detected by immunohistochemistry, was observed in some single secretory cells, within the capillary lumen and in cells around capillaries in the anterior and intermediate lobes, but no immunoreactivity was observed in posterior pituitary tissue. The pattern of clusterin expression in anterior and intermediate pituitary cells suggests possible roles for the protein in secretory cell turnover and/or hormone secretion or lipid uptake. Clusterin does not appear to be involved in ovine posterior pituitary hormone neurosecretion.

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We have recently shown that the intrinsic rate response to an increase in right atrial pressure is augmented when cardiac muscarinic receptors are activated. This present study examines the cardiac pacemaker response to vagal stimulation at different values of right atrial pressure in isolated rat right atrium and in the rabbit heart in situ. In the rat atrium, when pressure was raised in steps from 2 to 10 mmHg, there was a progressive reduction in the response to vagal stimulation [40.5 +/- 7.2% reduction (mean +/- SE) at 8 mmHg, P < 0.01], which was independent of the level of vagal bradycardia, that persisted in the presence of the beta-adrenergic agonist isoproterenol. In barbiturate-anesthetized rabbits with cervical vagi cut and beta-adrenergic blockade, raising right atrial pressure approximately 2.5 mmHg by blood volume expansion reduced the bradycardia elicited by electrical stimulation of the peripheral end of the right vagus nerve (9.1 +/- 1.1% reduction, P < 0.0001). These results demonstrate that vagal bradycardia is modulated by the level of right atrial pressure and suggest that normally right atrial pressure may interact with cardiac vagal activity in the control of heart rate.

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Experiments were performed on rat right atria maintained at 37 degrees C in oxygenated Krebs-Henseleit solution, at a baseline diastolic transmural pressure of 2 mmHg. A step increment in right atrial pressure caused an increase in atrial rate which reached a steady value after 2-3 min (rate response). An 8-mmHg increase in atrial pressure caused an 8% increase in atrial rate (n = 9, P < 0.01). When the atrial rate was reduced by carbamylcholine, the rate response was augmented. After a 34% reduction in atrial rate, an 8-mmHg increase in atrial pressure increased atrial rate by 51% (n = 7, P < 0.01). When atrial rate was elevated 71% by isoprenaline, the rate response was reversed (atrial rate decreased 3% following an 8-mmHg increase in atrial pressure; n = 7, P < 0.01). In another series of experiments, atrial rate was adjusted to a wide range of values by exposure to carbamylcholine and isoprenaline, first applied singly, and then in combination. At any given atrial rate, the rate response was always larger when both agonists were present; this difference was greatest when atrial rate was near the control untreated value.

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Previous reports have suggested that a peripheral pressure-modulated reflex operates at the level of the superior cervical ganglion to alter evoked activity in the postganglionic nerves of the ganglion in both the cat and rabbit. In the present study we have examined if spontaneous activity of the external and internal carotid nerves of the rabbit superior cervical ganglion can be modulated during changes of the carotid bifurcation pressure (CBP), independent of central nervous system (CNS) integration. For external carotid nerve recordings increases in CBP resulted in a reduction in spontaneous activity while decreases in CBP were associated with an increase in spontaneous activity. For internal carotid nerve recordings similar effects were observed in the majority of recordings although a subset of recordings showed opposite effects or were not responsive to changes in pressure. To determine if vagus nerve afferents contribute to the observed pressure-modulated spontaneous activity effects, the influence of CBP on external carotid nerve recordings was examined before and after section of the vagus nerve rostral to the nodose ganglion. We found that even following section of the vagus nerve the external carotid nerve response to an increase in pressure remained intact. These results demonstrate that, after section of centrally-projecting afferent pathways from the carotid bifurcation to the CNS, changes in CBP can still modify spontaneous sympathetic activity of the rabbit superior cervical ganglion. The data reinforce previous findings related to evoked responses in the postganglionic nerves and also suggest that a pressure-modulated reflex, integrated at the level of the superior cervical ganglion, can influence ongoing sympathetic nervous outflow from the superior cervical ganglion in the rabbit.

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The influence of angiotensin II (ANG II) on sympathetic ganglionic transmission was examined in the in situ, normally perfused, superior cervical ganglion in pentobarbitone-anaesthetized rabbits. Compound action potentials were evoked in the external carotid nerve by repetitive electrical stimulation of the decentralized preganglionic cervical sympathetic nerve (supramaximal intensity, 1 ms, 0.5 Hz). A continuous partial nicotinic block was maintained by intravenous infusion of hexamethonium. The converting enzyme inhibitor captopril was infused to prevent the endogenous generation of ANG II. Graduated intravenous infusion of ANG II brought about graduated increases in the height of the S2 potential; the threshold rate of infusion for this effect was 40 ng min-1. At this infusion rate, the plasma concentration of ANG II was estimated to lie between 80 and 600 pg ml-1. While ANG II can modify sympathetic ganglionic transmission, it is unlikely that it has any effect at physiological plasma concentrations of circulating ANG II reported for the rabbit (2-80 pg ml-1).

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Plants and herbivores have been co-evolving for thousands of years, and as a result, plants have defence mechanisms that offer protection against many herbivores such as nematodes, insects, birds and mammals. Only when a herbivore has managed to adapt to these defence mechanisms does it have the potential to become a pest. One such method of plant defence involves the production of protease inhibitors (PIs). These inhibitors are proteins that may be found constitutively in various parts of the plant, or may be induced in response to herbivore attack. PIs work at the gut level, by inhibiting the digestion of plant protein. This review focuses on insect herbivores and looks at the mechanisms involved in the role and function of PIs in plant defense against insects, as well as at the ability of well adapted species to overcome the effects of these plant PIs.

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We investigated the effect of alterations in carotid bifurcation pressure on transmission in the superior cervical ganglion of pentobarbital-anaesthetized rabbits. Compound action potentials were evoked in the internal and external carotid nerves (post-ganglionic fibres) by electrical stimulation of the decentralized cervical sympathetic trunk. Pressure in the ipsilateral isolated carotid bifurcation (CBP) was maintained at a control value of 100 mmHg. Increases of CBP to between 125 and 200 mmHg caused graded reductions in the height and increases in the time to peak (TTP) of the S2 wave of the compound action potential recorded from the external carotid nerve (mean +/- SEM: -5.8 +/- 0.9% and +3.0 +/- 0.5%, respectively, at 200 mmHg, P < 0.05). In the same nerve, reductions in CBP to between 25 and 75 mmHg caused graduated increases in the height and decreases in TTP of the S2 wave (+6.3 +/- 0.8% and -2.8 +/- 0.4% at 25 mmHg, P < 0.05). Similar responses were obtained from the internal carotid nerve. The response of the S2 wave in the external carotid nerve to a step increase of CBP from 100 to 175 mmHg was examined before and after section of either the ganglioglomerular or carotid sinus nerve. Section of the ganglioglomerular nerve abolished the response (height and TTP of the S2 wave: before -10.7 +/- 0.8% and +5.9 +/- 0.9%; after -0.6 +/- 0.6% and +0.2 +/- 0.5%, P < 0.05). Section of the carotid sinus nerve had no effect on the S2 wave response. It appears that a population of ganglioglomerular nerve fibres, with pressure-sensitive endings located in the wall of the carotid bifurcation, form the afferent limb of a reflex integrated in the superior cervical ganglion of the rabbit. The efferent limb includes postganglionic fibres in the internal and external carotid nerves.

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Experiments were made on preparations of the rabbit right atrium maintained at 37 degrees C in oxygenated Krebs-Henseleit solution. Baseline diastolic transmural pressure was held at 2 mmHg. A step increase in diastolic pressure was accompanied by an immediate and rapid increase in atrial rate (fast response), followed by a slower increase (t1/2 approximately 0.5 min) (slow response). The slow response to pressure steps was graded, approaching a maximum increase after a 12 mmHg step (44 +/- 4 min-1 from a baseline of 196 +/- 5 min-1; mean +/- SEM; n = 7; P < 0.01). In preparations where baseline atrial rate had been reduced 50% by application of carbamylcholine, the slow response to an increase in pressure was augmented (n = 7; P < 0.01); an increase of 55 +/- 9 min-1 for a 12 mmHg step in atrial pressure. In preparations where baseline rate had been increased 63% by the application of isoprenaline, the slow response was attenuated (n = 5, P < 0.01), an increase of 22 +/- 7 min-1 for a 12 mmHg step. During sinusoidal pressure forcing (0.002-1.0 Hz), rate responses of control and carbamylcholine-treated preparations had a high gain at frequencies < or = 0.02 Hz. Carbamylcholine-treated preparations also showed a high gain at frequencies > or = 0.2 Hz. There appear to be two distinct intrinsic responses to changes in right atrial pressure; a rapid response which is augmented by cholinergic stimulation, and a slower response which is augmented by cholinergic stimulation and reduced by beta-adrenergic stimulation.

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Intrinsic cardiac regulation, the direct effect of changes in right atrial pressure on heart rate, was examined in rabbits under chloralose/urethane anaesthesia. Autonomic influences on the cardiac pacemaker were eliminated by cervical vagotomy and intravenous propranolol. Right atrial transmural pressure was monitored as the difference between right atrial and pleural pressures. Blood volume expansion (5-15%) increased right atrial transmural pressure and heart rate and produced a sinus arrhythmia associated with respiration-linked fluctuations in right atrial transmural pressure. The gain of intrinsic cardiac rate regulation was calculated as 0.96 +/- 0.24 beats min-1 mmHg-1 at a heart rate of 218 +/- 6 beats min-1 (values as the mean +/- SEM, n = 12). When heart rate was reduced by electrical stimulation of the peripheral end of the right vagus nerve, gain increased to 2.25 +/- 0.57 and 4.61 +/- 1.6 beats min-1 mmHg-1 at heart rates of 180 +/- 4 and 130 +/- 4 beats min-1, respectively (n = 6 and n = 10; P < 0.05 compared with pre-stimulation values). During vagally-induced bradycardia, rapid infusion of blood into the left superior vena cava produced a brief marked cardiac acceleration. We conclude that right atrial pressure has a small direct influence on heart rate, and this is enhanced by background cardiac parasympathetic stimulation.

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Leaves of 18- to 24-d-old tomato (Lycopersicon esculentum) plants exposed to gaseous methyl jasmonate (MJ) for 24 h at 30[deg]C in continuous light contained high levels of soluble protein that inhibited papain. Chromatographic analysis demonstrated that the active protein had a molecular mass of 80 to 90 kD. Induction of papain inhibitor was directly related to the concentration of air-borne MJ up to a maximum of 0.1 [mu]L MJ per treatment and depended on the duration of exposure up to 18 h. Inhibitor activity in plants treated for less than 18 h increased with time after treatment. Levels remained constant for up to 4 d after treatment, after which time activity decreased. The youngest leaf, leaf 5, consistently lost activity at a faster rate than older, lower leaves. Inhibitor concentration in all leaves was reduced to minimum levels by 11 d after MJ treatment, but did not return to control levels. Treatment with MJ in the dark did induce inhibitor activity, but at a significantly lower rate. Polyclonal antibodies raised to purified potato tuber skin cysteine proteinase inhibitors (CPI) cross-reacted with the tomato inhibitor, suggesting that the tomato papain inhibitor and the potato CPI are closely related. No papain inhibitor activity was observed in extracts from wounded tomato leaves, nor was there any immunoreactivity with antibodies raised to potato tuber skin CPI.

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The distribution of neurones innervating the carotid sinus of the rabbit was determined by inserting chips of horseradish peroxidase (HRP) into the adventitial layer of the carotid sinus. Labelled neurones were found in the superior cervical ganglion, along the cervical sympathetic trunk and in the nodose ganglion (mean counts of 1876, 139 and 232, respectively). No labelled neurones were located in the middle cervical ganglion or the stellate ganglion. Within the superior cervical ganglion, the fraction of labelled neurones found in equal longitudinal quadrants of the ganglion were, from rostral to caudal, 2%, 12%, 42% and 44%. Thus the majority of neurones were located in the caudal region of the superior cervical ganglion. The primary pathway for sympathetic fibres innervating the carotid sinus was shown to be in branches of the external carotid nerve. The greatest number of labelled neurones in the nodose ganglion were located in the most rostral quadrants of the ganglion.

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In 16 patients with unstable angina pectoris haemodynamic and clinical effects of diltiazem were investigated. In a second group patients (n = 11) with unstable or therapy-refractory course the long-term effect was tested. The acute intervention with injected and infused diltiazem via an improved oxygen balance due to decreased minute work and reduced product of cardiac frequency and pressure stabilized the clinical picture from the haemodynamic aspect. The decreases of the ST segment were significantly lower. In the long-term use a significant influence on the frequency of angina pectoris with increase of the range of efficacy by one NYHA-state was the result. Diltiazem can be regarded as alternative medicament in unstable phases and in therapy-refractory courses of the chronic coronary heart disease.

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One of the most precise methods of determining hydrogen peroxide (H2O2) formation by biological systems is based on measuring the rate of enzyme-substrate complex formation between H2O2 and cytochrome c peroxidase (CCP). The main problem with this method is that CCP is not commercially available and has to be prepared in the laboratory. We have modified some currently available methods for purifying a highly active preparation of CCP in about 4 d. It includes a batch extraction of protein using DEAE-sepharose followed by concentration either by lyophilization or by passing the extract through a small DEAE-sepharose column instead of by ultrafiltration. The concentrated preparation is passed through a Sephadex G-75 column and the final CCP crystallized against water. The final preparations had a purity index (PI, ratio of absorbance at 408 nm/280 nm, equivalent to heme/protein ratio) above 1.2. These changes make the overall procedure very simple, preserving enzyme activity and spectral properties. In addition, we point out that special care has to be taken to eliminate cytochrome c from crude CCP extracts. Cytochrome c not only introduces an artifact when determining PI, but is also may act as a hydrogen donor for CCP when monitoring H2O2 formation, thus decreasing the sensitivity of this method.

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The fumigant insecticide phosphine (PH3) is known to inhibit cytochrome c oxidase in vitro. Inhibition of the respiratory chain at this site has been shown to stimulate the generation of superoxide radicals (O2-), which dismutate to form hydrogen peroxide (H2O2). This study was performed in order to investigate the production of H2O2 by mitochondria isolated from granary weevil (Sitophilus granarius) and mouse liver on exposure to PH3. Other respiratory inhibitors, antimycin, myxothiazol, and rotenone were used with insect mitochondria. Hydrogen peroxide was measured spectrophotometrically using yeast cytochrome c peroxidase as an indicator. Insect and mouse liver mitochondria, utilizing endogenous substrate, both produced H2O2 after inhibition by PH3. Insect organelles released threefold more H2O2 than did mouse organelles, when exposed to PH3. Production of H2O2 by PH3-treated insect mitochondria was increased significantly on addition of the substrate alpha-glycerophosphate. Succinate did not enhance H2O2 production, however, indicating that the H2O2 did not result from the autoxidation of ubiquinone. NAD(+)-linked substrates, malate and pyruvate also had no effect on H2O2 production, suggesting that NADH-dehydrogenase was not the source of H2O2. Data obtained using antimycin and myxothiazol, both of which stimulated the release of H2O2 from insect mitochondria, lead to the conclusion that glycerophosphate dehydrogenase is a source of H2O2. The effect of combining PH3, antimycin, and myxothiazol on cytochrome spectra in insect mitochondria was also recorded. It was observed that PH3 reduces cytochrome c oxidase but none of the other cytochromes in the electron transport chain. There was no movement of electrons to cytochrome b when insect mitochondria are inhibited with PH3. The spectral data show that the inhibitors interact with the respiratory chain in a way that would allow the production of H2O2 from the sites proposed previously.

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As a result of hormonal changes processes of adaptation of the cardio-vascular system occur during pregnancy. These regulative changes are the basis for the present echo-cardiographic study which was made under standardized conditions with healthy primigravidae (n = 20) compared to nulligravidae (n = 24). Besides blood pressure and heart frequency dimension and volume sizes of the left ventricle (LV) as well as the LV-weight of muscle and the peripheral vascular resistance were analysed. As result significant increases from the 15th to the 35th week of pregnancy (SSW) could be found for the following parameters: heart frequency, arterial blood pressure, endosystolic volume of the left ventricle, cardiac output, left ventricular weight of muscle (p less than 0.01) endosystolic diameter of the left ventricle, enddiastolic volume of the left ventricle and heart index (p less than 0.05). The peripheral resistance was continuously decreased in the course of pregnancy (p less than 0.01). Compared to non-pregnant women the following parameters showed significantly higher values: heart frequency, cardiac output and heart index (p less than 0.01). The peripheral resistance was significantly lower in pregnant women compared to non-pregnant women (p less than 0.01). From the results the conclusion can be drawn that with statistic certainty echocardiography records adaptive processes of the circulation regulation relative to pregnancy and enables a separation in the groups of pregnant and non-pregnant women.

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The temperature sensitivity of the human cardiac pacemaker was investigated during exhaustive exercise. From graded runs to exhaustion, we established the relationship between maximum exercise heart rate (HRmax) and rectal temperature (Tr). After warm-up periods of varying intensity and duration, four male subjects completed 4 to 6 runs each, each run performed on a separate day. For every subject there was a strong linear correlation between HRmax and Tr (r = 0.79 to 0.96). Various measures of the temperature sensitivity were: linear sensitivity, 8.8 +/- 4.3 beats min-1.degrees C-1; Q10, 1.6 +/- 0.4 and the Arrhenius constant, mu, 35.9 +/- 16.6 kJ.mol-1. At HRmax the value for linear temperature sensitivity was similar to, but the values for Q10 and mu lower than, those observed previously for intrinsic heart rate. Sympathetic influence on the cardiac pacemaker during exercise may cause this reduction, by shifting the pacemaker location to cells with a lower temperature sensitivity, or by altering a rate-limiting step determining the diastolic pacemaker potential.

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Cardiac dysfunction and neurohumoral dysregulation show that the administration of vasodilators is reasonable in a cardiac insufficiency which is therapy-refractory against glycosides and saluretics. The alpha 1-blocker prazosin is a potent substance. On the basis of haemodynamic investigations of 55 patients the acute effects are demonstrated. Depending upon the degree of the cardiac insufficiency and the sympathetic dysregulation--measured at the behaviour of the resistance--the acute effects are convincing in more than 60% of the patients. For the long-term course patients with unequivocal initial improvement are suitable. This group can undergo a satisfactory therapy for a longer time by means of a carefully increased dosage, by corrections of the application of saluretics and by short interruptions of therapy and by the change of the dilator, respectively, or by an additional administration of another vasodilator. In the total spectre of the vasodilators which are administered in cardiac insufficiency prazosin occupies one of the first places.

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