Signal-averaged ECG abnormalities in haemodialysis patients. Role of dialysis

BACKGROUND

Late potentials (LP) on the signal-averaged electrocardiogram (SAECG) are predictive of malignant ventricular arrhythmias and sudden cardiac death in patients with ischaemic and non-ischaemic cardiomyopathy. Cardiac dysfunction, both regional and global, as well as supraventricular and ventricular arrhythmias are reported in a high percentage of patients with end-stage renal failure (ESRF). The aim of the study was to assess the prevalence of LP and the effects of haemodialysis on the SAECG of ESRF patients.

METHODS

SAECG was recorded immediately before and within 30 min after the end of dialysis in 48 patients in sinus rhythm, free of conduction disturbances on ECG and of signs of congestive heart failure. Serum electrolytes were sampled together with the SAECG recordings. An echo-Doppler exam was performed within 2 weeks of the study. SAECGs were adequate for analysis in 45/48 patients. LP were present when at least two of the following criteria were fulfilled: QRS duration < or = 115 ms, LAS40 < or = 38 ms, RMS40 > or = 38 microV at 40 Hz high pass bidirectional filter, and noise <0.7 microV.

RESULTS

LP were detected in 12/45 patients (25%) on the SAECG before dialysis; of these 12 patients, seven had a history of a previous myocardial infarction and two had documented coronary artery disease (CAD). A significant greater wall motion score index--calculated on a 16 segment model--was reported in patients with LP (1.20+/-0.20 vs 1.01+/-0.03, P<0.01), while left ventricular mass was comparable in the two groups of patients. At the end of dialysis, a significant prolongation of fQRS duration was found both at 25 and 40 Hz filters (from 98+/-11 to 106+/-16 ms and from 97+/-12 s to 102+/-13 ms, respectively, P<0.001). A significant inverse relationship was seen between the percentage of dialysis-induced serum potassium reduction and fQRS changes at 40 Hz (r=-0.68, P<0.001).

CONCLUSIONS

LP were detected in a significant proportion of dialysis patients, probably related to underlying CAD with left ventricular dysfunction. Prolongation of fQRS after dialysis could be explained by the acute reduction in serum potassium levels.

Immunoreactive prolactin forms colocalize with vasopressin in neurons of the hypothalamic paraventricular and supraoptic nuclei

The prolactin (PRL) gene is expressed in the hypothalamo-neurohypophyseal system as revealed by the detection of the PRL mRNA and of PRL-like immunoreactive and biologically active proteins in hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei and in the neurohypophysis. We have investigated the distribution of cells containing PRL-like molecules in the PVN and SON by immunocytochemistry with a specific antiserum directed against the 16-kD N-terminal fragment of PRL. PRL-positive cells were found to be concentrated throughout the ventral SON and in the lateroposterior region of the PVN. The cellular distribution of PRL-immunoreactive cells resembled more closely that of vasopressin (VP) than that of oxytocin magnocellular neurons. Moreover, double immunofluorescence labelling, followed by confocal microscopy, indicated the coexistence of PRL- and VP-related antigens within the same neurons of the PVN and SON. Pre-embedding immunoperoxidase on the ultrastructural level showed a PRL-like product in granular-type particles within the neural soma and projections in the SON and PVN. These findings are consistent with the expression and secretion of PRL-like molecules by vasopressinergic neurons of the hypothalamo-neurohypophyseal system.

Infectious bronchitis: effect of viral doses and routes on specific lacrimal and serum antibody responses in chickens

An enzyme-linked immunosorbent assay was used to measure the effect of various infectious bronchitis virus (IBV) (strain H-120) vaccine doses and routes of immunization on specific lacrimal and serum antibody responses. The results of the first trial showed that the maximum dose, 10(6) median embryo infective doses (EID50s), delivered by the ocular route elicited both a systemic and a local antibody response in the vaccinated chickens. Lower doses of vaccinal virus, 10(4) (median dose) and 10(2) (minimum dose) EID50 delivered by the same route did not induce a detectable systemic antibody response. A significant increase of IBV-specific lacrimal IgA was elicited by both the maximum and the median vaccine doses. The low vaccine dose (10(2) EID50) did not induce a detectable increase of lacrimal IgA. In a second trial approximately the same vaccine dose was administered to different chicken groups by ocular instillation, drinking water, spray, and cloaca. The results showed that all routes of vaccination tested, including the cloacal route, resulted in an increase of specific serum antibodies. Higher IgG levels were detected throughout the experimental period after vaccination by the ocular route as compared with vaccination via the drinking water. All routes of vaccination tested resulted in an increase of specific IgA in lacrimal fluid. The vaccine application methods spray, ocular instillation, and drinking water induced similar lacrimal IgA responses.

Topographic relationship of neurotensin-containing axon terminals with cardiac and noncardiac principal ganglion cells in the stellate ganglia of the cat

The pattern of association between neurotensin (NT)-immunoreactive (NTIR) preganglionic nerve terminals and cardiac and noncardiac neurons in the stellate ganglion of the cat is analyzed, based on the finding of an excitatory modulation effect of exogenous NT on cardiac functions. For this purpose, NT-containing terminals were labeled by immunohistochemistry, and ganglion cells were detected by retrograde labeling of cardiac and vertebral nerves to identify cardiac and noncardiac neurons. To determine a possible regional localization of NTIR terminals and ganglion cells, the ganglia were divided into four areas: caudal, dorsomedial, cranial, and ventromedial, related to the two major afferent nerves (thoracic white rami 3 [T3WR] and 2 [T2WR]) and the two efferent nerves (vertebral and cardiac). NTIR terminals were widespread in the complete ganglion tissue; they covered practically all the regions explored, although two clusters of high concentration of NTIR terminals were detected in the cranial and caudal areas. By retrograde labelling it was found that cardiac cells were arranged around the exit of the cardiac nerve and that the vertebral neurons were extended from the exit of the vertebral nerve to the entrance of T3WR. The finding of association of NTIR terminals with cardiac neurons may account for the cardioregulatory effect of NT; however, since the presence of NTIR terminals close to the noncardiac neurons is notorious, other regulatory functions of NT must be considered.

Prognostic value of dobutamine-atropine stress echocardiography early after acute myocardial infarction. Echo Dobutamine International Cooperative (EDIC) Study

OBJECTIVES

The aim of this multicenter, multinational, prospective, observational study was to assess the relative value of myocardial viability and induced ischemia early after uncomplicated myocardial infarction.

BACKGROUND

Dobutamine-atropine stress echocardiography allows evaluation of rest function (at baseline), myocardial viability (at low dose) and residual ischemia (peak dose, up to 40 micrograms with atropine up to 1 mg) in one test.

METHODS

Dobutamine-atropine stress echocardiography was performed 12 +/- 5 days (mean +/- SD) after a first uncomplicated acute myocardial infarction in 778 patients (677 men; mean age 58 +/- 10 years) with technically satisfactory rest echocardiographic study results. Patients were followed-up for 9 +/- 7 months.

RESULTS

Dobutamine-atropine stress echocardiographic findings were positive for myocardial ischemia in 436 of patients (56%) and negative in 342 (44%). During follow-up, there were 14 cardiac-related deaths (1.8% of the total cohort), 24 (2.9%) nonfatal myocardial infarctions and 63 (8%) hospital readmissions for unstable angina. One hundred seventy-four patients (22%) underwent coronary revascularization (bypass surgery or coronary angioplasty). Spontaneous events occurred in 61 of 436 patients with positive and 40 of 342 patients with negative findings on dobutamine-atropine stress echocardiography (14% vs. 12%, p = 0.3). When only spontaneously occurring events were considered, the most important predictor was myocardial viability (chi-square 9.7). Using the Cox proportional hazards model, only the presence of myocardial viability (hazard ratio [HR] 2.0, p < 0.002) and age (HR 1.03, p < 0.001) were predictive of spontaneously occurring events. When only hard cardiac events were considered, age was the strongest predictor (chi-square 3.6, p = 0.056), followed by wall motion score index (WMSI) at peak dose (chi-square 3.3, p = 0.06) and remote ischemia (chi-square 2.25, p = 0.1). When cardiac death was considered, WMSI at peak dose was the best predictor (HR 9.2, p < 0.0001).

CONCLUSIONS

During dobutamine stress, echocardiographic recognition of myocardial viability is more prognostically important than echocardiographic recognition of myocardial ischemia for predicting unstable angina, whereas WMSI at peak stress was the best predictor of cardiac-related death. Different events can be recognized with different efficiency by various stress echocardiographic variables.

Plasma HIV-1 RNA as a predictor of the efficacy of adding zalcitabine to a previous regimen with zidovudine

The objective of this study was to determine whether or not plasma HIV-1 RNA levels, the syncytium-inducing phenotype assay or mutations at codon 215 of the gene encoding HIV-1 reverse transcriptase could have prognostic value in patients already undergoing therapy with zidovudine who were started on combination therapy with zidovudine and zalcitabine. A prospective study was performed in 37 HIV-1-infected individuals who had received at least 6 months (mean: 9 months; range: 6-24 months) of zidovudine to which zalcitabine was added. The mean initial CD4 cell count was 330 cells/mm3 (range: 20-520 cells/mm3). At baseline and at the end of the study (12 months), we analysed CD4 and CD8 cell counts, plasma HIV-1 RNA levels, the syncytium-inducing phenotype of virus isolated from peripheral blood mononuclear cells and mutations at codon 215 of the gene encoding reverse transcriptase. These variables were studied by Fisher's exact and U Mann-Whitney tests. There were statistically significant differences between progressor and non-progressor groups at baseline and after a 12-month period in the following parameters: CD4 and CD8 cell counts and HIV-1 RNA level (P < 0.05). Clinical progression occurred significantly more often in patients with CD4 cell counts < or = 300 cells/mm3 and HIV-1 RNA > 30000 copies/ml at baseline (P = 0.003). Moreover, we found that progression to AIDS only occurred in those patients whose viral load increased during the follow-up period and who had a CD4 cell count < 300 cells/mm3. Our results show the usefulness of HIV-1 RNA level as a surrogate marker for clinical outcome.

Characterization of myocardial tissue in patients undergoing maintenance hemodialysis by quantitative echocardiography

The uremic state affects myocardial structure, bringing about, among other things, interstitial calcium deposition. Abnormalities of myocardial structure can be assessed quantitatively and noninvasively during life by the analysis of the gray-level distribution of conventional two-dimensional echocardiograms. The aim of this study was to evaluate the role of quantitative echocardiography in providing information on myocardial structure in patients under maintenance hemodialysis and to relate the ultrasonic findings with abnormalities in calcium-phosphate metabolism. Forty patients undergoing dialysis without abnormalities in left ventricular regional and global function and 17 hypertensive patients with comparable left ventricular hypertrophy were studied. The distribution of the gray levels within a region of interest in the interventricular septum was analyzed off-line by an array processor-based computer. Compared with hypertensive patients, patients undergoing dialysis showed a greater myocardial echogenicity (mean 92 +/- 20 versus 72 +/- 15; p = 0.004) and a reduced homogeneity of distribution of gray levels (entropy 4.5 +/- 0.2 versus 4.2 +/- 0.2, p < 0.01; uniformity 0.010 +/- 0.003 versus 0.020 +/- 0.004, p < 0.005). In the same patients, a significant negative linear relation was found between entropy and calcium-phosphate product (r = -0.66; p = 0.001). Quantitative analysis of conventional two-dimensional echocardiograms allows the detection of a pathologic myocardial structure in patients under maintenance hemodialysis with normal left ventricular function. These abnormalities are related to disorders of calcium-phosphate metabolism and bear no relationship to the degree of left ventricular hypertrophy.

Role of endothelium in the vasodilating effect of progestins and androgens on the rat thoracic aorta

1. In the rat thoracic aorta, contractions induced by noradrenaline were inhibited by the steroids progesterone, pregnanolone, testosterone and 5 alpha- and 5 beta-dihydrotestosterone. 2. Removal of endothelium did not prevent relaxation to the steroids, suggesting that the vasodilating effect of steroids occurred on the smooth muscle cells. 3. gamma-Aminobutyric acid (GABA) did not modify noradrenaline-induced contraction. Thus, the vasodilation elicited by steroids is not apparently mediated by GABA receptors. 4. On the basis that noradrenaline opens receptor-operated calcium channels to induce contraction, we suggest that relaxation by steroids involves a blockade of this type of channels.

Localization of choline acetyltransferase in rat peripheral sympathetic neurons and its coexistence with nitric oxide synthase and neuropeptides

Indirect immunofluorescence methods using a mouse monoclonal antibody raised to rat choline acetyltransferase (ChAT) revealed dense networks of ChAT-immunoreactive fibers in the superior cervical ganglion, the stellate ganglion, and the celiac superior mesenteric ganglion of the rat. Numerous and single ChAT-immunoreactive cell bodies were observed in the stellate and superior cervical ganglia, respectively. The majority of ChAT-immunoreactive fibers in the stellate and superior cervical ganglia were nitric oxide synthase (NOS) positive. Some ChAT-immunoreactive fibers contained enkephalin-like immunoreactivity. Virtually all ChAT-positive cell bodies in the stellate ganglion were vasoactive intestinal polypeptide (VIP)-positive, and some were calcitonin gene-related peptide (CGRP)-positive. After transection of the cervical sympathetic trunk almost all ChAT- and NOS-positive fibers and most enkephalin- and CGRP-positive fibers disappeared in the superior cervical ganglion. The results suggest that most preganglionic fibers are cholinergic and that the majority of these in addition can release nitric oxide, some enkephalin, and a few CGRP. Acetylcholine, VIP, and CGRP are coexisting messenger molecules in some postganglionic sympathetic neurons.

Ergonovine-echo test to assess the significance of chest pain at rest without ECG changes

The aim of this study was to assess the feasibility and diagnostic role of ergonovine maleate infusion under continuous two-dimensional echocardiographic monitoring for the identification of vasospastic myocardial ischaemia in patients with chest pain at rest not associated with diagnostic ECG changes. One hundred and twenty-eight consecutive patients, selected on the basis of absence of ischaemic ECG changes during angina at rest before or during hospitalization, were enrolled in the study. Ergonovine maleate was i.v. administered in scaled doses (from 0.025 to 0.2 mg at 10 min intervals) under echocardiographic, electrocardiographic and systemic blood pressure monitoring. Wall motion asynergies were observed in 33 patients, accompanied by typical chest pain in 24 patients and by ECG changes in 25 (ST elevation in 13 patients, ST depression in seven, T wave changes in five). All patients were able to complete the test. Non life-threatening ventricular arrhythmias were observed in four patients exclusively in association with ischaemia. In seven patients with a positive test, coronary artery spasm was documented at angiography. In 16 patients with a positive test, the vasospastic event was reproduced by a hyperventilation-echo test or a second ergonovine maleate-echo test performed within 3 days of the first examination. In none of the patients with a negative test was documentation of myocardial ischaemia due to a primary reduction in coronary blood flow. Thus, in patients who do not show ECG changes during chest pain at rest, the ergonovine maleate-echo test is feasible and safe; it permits the recognition of ischaemic episodes on the basis of wall motion abnormalities when conventional 12-lead ECG-recorded chest pain is non-diagnostic.

Non-invasive monitoring of hemodynamic parameters during hemodialysis

We studied in 13 hemodialysis patients intradialytic variations of blood volume (BV) and cardiac output, by means of non-invasive methods. We found a weak correlation, r 0.2 or less, between BV variations and intradialysis blood pressure variations. The sensitivity of the former in describing the variations of the latter was only 32%. During the 30 min preceeding the hypothensive crisis the percent BV variations did not show any predictive trend. On the contrary, refilling increased as blood pressure dropped and a weak inverse relation (r -0.35) was found between these two parameters. Unstable patients had predialytic blood volume values significantly lower than stable ones and comparable to healthy subjects. On the contrary, the correlation between percent variations of cardiac output index and MAP was 0.68 with a sensitivity and specificity of 90% and 59%, respectively. Unfortunately these promising results were obtained only with an estimate of cardiac output obtained by echocardiography and not by transthoracic impedance cardiography, which is much more feasible than the former as on-line monitoring of cardiac output. On-line monitoring of hemodynamic parameters is an appealing but still unsolved task.

Thermal balance and dialysis hypotension

Many studies have confirmed our original observation that dialysate T set at about 35 degrees C affords a better hemodynamic protection than the standard dialysate T of 37-38 degrees C. In this review we present some new data on the hemodynamic mechanism of the protective effect of cold dialysis on blood pressure. The study was based on serial assessment of the percent changes occurring during dialysis treatment in estimated stroke volume (aortic blood flow determined by Doppler echocardiography), blood volume (hemoglobinometry), arterial pressure (Dynamap), and heart rate (ECG), from which cardiac output (CO) indexes and total peripheral vascular resistances (TPVR) were derived. Of the 14 pts studied, 7 showed a drop in mean arterial pressure (MAP) of 25% or greater during standard dialysis (unstable patients). Compared with the 7 patients having more stable intradialysis MAP, unstable pts showed greater reduction in CO which was disproportionately greater than the reduction in blood volume, and a paradoxical decrease in TPVR, the difference being highly significant (p < 0.01 for both changes). When crossed-over to cold dialysis, along with a significantly lower reduction in MAP (p < 0.01) the unstable pts showed a lower decrease in CO which paralleled the reduction in blood volume, and an increase in TPVR. These changes were highly significant (p < 0.01). Data suggest that dialysis hypotension is characterized by an impaired venous return, probably due to the peripheral blood pooling (increased ratio between the 'unstressed' and 'stressed' blood volume) associated with the decrease in TPVR. Exposure of extracorporeal blood to cold dialysate favours the venous return to the heart by increasing TPVR and the 'stressed' blood volume.

Vasorelaxant effect of the analgesic clonixin on rat aorta

1. A novel vasorelaxant effect of clonixinate of L-lysine (Clx), analgesic and anti-inflammatory, was studied in rat aortic rings. 2. Clx completely relaxed aortic rings contracted by KCl 70 mM and together with its analog flunixin exhibited lesser potency but equal efficacy than verapamil. In comparison, indomethacin, which is a more potent cyclo-oxygenase inhibitor relaxed only about 40% of the maximal contraction of aortic rings. 3. Furthermore, Clx antagonized Ca2+ dependent aortic contraction and BAY K-8644 induced aortic contraction suggesting its calcium antagonist character. 4. From these results it can be concluded that the hypotensive effect seen in rats in vivo after Clx i.v. injection arises because of vasodilatory effect of Clx and gives further support to the proposal that the pharmacological mechanism of action of Clx should be calcium antagonism.

The prolactin gene is expressed in the hypothalamic-neurohypophyseal system and the protein is processed into a 14-kDa fragment with activity like 16-kDa prolactin

The 23-kDa form of prolactin (PRL) has been proposed to function as both a mature hormone and a prohormone precursor for different uniquely bioactive forms of the molecule. We have shown that the 16-kDa N-terminal fragment of PRL (16K PRL) inhibits angiogenesis via a specific receptor. In addition, 16K PRL stimulates natriuresis and diuresis in the rat, and kidney membranes contain high-affinity specific binding sites for this PRL fragment. 16K PRL can be derived from an enzymatically cleaved form of PRL (cleaved PRL). With the use of a specific 16K PRL antiserum, we have localized a 14-kDa immunoreactive protein in the paraventricular and supraoptic nuclei of the hypothalamus and in the neurohypophysis. Reverse transcription-polymerase chain reaction of RNA from isolated paraventricular nuclei showed the expression of the full-length PRL mRNA. The neurohypophysis was found to contain the enzymes that produce cleaved PRL, small amounts of PRL, and cleaved PRL. Medium conditioned by neurohypophyseal cultures, enriched with the 14-kDa immunoreactive protein, has antiangiogenic effects that are blocked by the 16K PRL antiserum. These results are consistent with the expression of PRL in the hypothalamic-neurohypophyseal system, and the preferential processing of the protein into a 14-kDa fragment with biological and immunological properties of 16K PRL.

Pre- and postsynaptic components of nicotinic long-term potentiation in the superior cervical ganglion of the cat

1. In anesthetized, atropine-treated cats we measured the acetylcholine (ACh) release into the venous effluent of the superior cervical ganglion (SCG) and the nictitating membrane (NM) contraction evoked by a 2-Hz, 20-s test train to the ipsilateral cervical sympathetic trunk (CST). We also measured NM contraction produced by injection of ACh (50 micrograms) or 1,1-dimethyl-4-phenylpiperazinium (DMPP, 5 micrograms) into the arterial supply of the ipsilateral SCG. 2. After a 10- to 30-s, 40-Hz conditioning train to CST these responses were all potentiated. The potentiation of the NM response evoked by the test train or by the exogenous agonists was long lasting (90% decay in 64 +/- 10 min, mean +/- SE, for the train-evoked response; 42 +/- 9 min for the response to injected ACh; 61 +/- 18 min for the response to injected DMPP), whereas the potentiation of the ACh release lasted only for 9 min. 3. On the assumption that ACh and DMPP injected into the ganglionic arterial supply acted postsynaptically, these data suggest that the main mechanism of the long-term potentiation (LTP) of nicotinic transmission in SCG is an increase in postsynaptic responsiveness. Because the response to KCl (250 micrograms) injected into the ganglionic arterial supply was not potentiated after the conditioning train, a posttrain increase in excitability of the postsynaptic membrane is not likely to be the cause of the postsynaptic increased responsiveness to ACh and DMPP.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-antagonist effects of quercetin on aortic smooth muscle

Relaxation induced by quercetin was studied on aortic rings depolarized with KCl and on Ca2+ dependent aortic contraction. Quercetin's actions as a cyclooxygenase inhibitor were compared with those of indomethacin. To determine the possible effects of quercetin on internal Ca2+ mobilization, it was assayed on aortic muscle contracted with caffeine. Quercetin relaxes aortic smooth muscle contracted with KCl (RC50 = 1.8 x 10(-4) M) and induces a rightward displacement of Ca2+ curves. The relaxation induced by quercetin is higher than that produced by indomethacin, suggesting that its action is independent of cyclooxygenase inhibition. Caffeine-induced aortic contraction was not modified by quercetin, suggesting that its effect should not involve internal calcium modulation. Our results further support the thesis that the spasmolytic action of quercetin arises from its negative modulation of calcium entry to the smooth muscle.

Ultrastructural localization of neurotensin immunoreactivity in the stellate ganglion of the cat

The morphological features and cellular relationships of neurotensin-containing axon terminals were studied at light and electron microscopic levels in the cat stellate ganglion using peroxidase and immunogold immunocytochemistry. By light microscopy, neurotensin immunoreactivity was detected within thin varicose fibres distributed throughout the ganglion. Immunoreactive fibres were no longer apparent following chronic deafferentation of the ganglion indicating that they were of extrinsic origin. Ultrastructural analysis of peroxidase immunostained material confirmed the presence of neurotensin immunoreactivity within a subpopulation of axonal varicosities which made synaptic contacts with the dendrites of ganglion cells. Within labelled varicosities neurotensin immunoreactivity was found by both immunoperoxidase and immunogold methods to be concentrated within large dense core vesicles 80-120 nm in diameter. These large dense core vesicles were characteristically distant from the active zone, in keeping with a possible extrasynaptic release of the peptide.

Dynamics of large dense-cored vesicles in synaptic boutons of the cat superior cervical ganglion

We have shown previously that stimulation of the cat cervical sympathetic trunk for 2 h at 40 Hz depletes the large dense-cored vesicle store in synaptic boutons of the superior cervical ganglion and that post-depletion recovery of the store takes several days. In the present study, we examine the properties of the depletion and recovery mechanisms. Invaginations of the plasmalemma suggestive of the exocytosis of dense cores were seen frequently in boutons from stimulated ganglia. The depletion process is calcium dependent: in ganglia perfused with calcium-free Krebs solution no depletion was produced by 40 Hz preganglionic stimulation. The depletion process is rapid: during continuous stimulation of the cervical sympathetic trunk with 40 Hz, depletion observed by the end of 2 h was similar to depletion by the end of the initial 5 min of stimulation. The depletion process is frequently dependent: when the cervical sympathetic trunk was stimulated with a constant number of stimuli, no depletion occurred at the frequency of 2 or 10 Hz, while the frequencies of 20 and 40 Hz produced depletion, which was greater at 40 Hz. Recovery of the large dense-cored vesicle store during the initial 24 h after 10 min of 40 Hz stimulation was faster, and of approximately the same magnitude, than during the succeeding five days. Recovery of the store after stimulus-evoked depletion was prevented by application of colchicine to the cervical sympathetic trunk, which suggests dependence of recovery on fast axonal transport. Large dense-cored vesicles accumulated in the colchicine-treated segment of cervical sympathetic trunk axons. In conclusion, these observations suggest that the stimulus-evoked depletion of large dense-cored vesicle stores in synaptic boutons of the cat superior cervical ganglion is the result of calcium-dependent exocytosis of the large dense-cored vesicle core and that the post-stimulus recovery is critically dependent on microtubule-mediated axonal transport.

Hyperventilation-echocardiography test for the diagnosis of myocardial ischaemia at rest

The purpose of this study was to assess the feasibility, safety, specificity and sensitivity of the hyperventilation test performed under echocardiographic monitoring for the provocation of vasospastic ischaemia. Hyperventilation (approximately 30 cycles.min-1 for 5 min) was performed in 104 hospitalized patients, referred for pain typical of angina at rest, under 2-D echocardiographic and 12-lead electrocardiographic monitoring. All the tests were completed and no significant side effect was observed. In-hospital documentation of spontaneous myocardial ischaemia and/or ergonovine-induced ischaemia was achieved in 38 patients (group I). A positive hyperventilation-echocardiography test (occurrence of new transient asynergies or worsening of basal ones) was obtained in 32/38 patients. Among the group I patients, only 23 had diagnostic ST-T changes and only 16 experienced chest pain during the hyperventilation-echo test. Of the 66 patients without evidence of myocardial ischaemia at rest (negative ECG monitoring during hospitalization and/or negative ergonovine maleate-echo test)--Group II, none showed echocardiographic changes, seven presented ST-T changes and six complained of typical chest pain during the test. Thus, in relation to in-hospital documentation of myocardial ischaemia at rest, both spontaneous and/or ergonovine-induced episodes, the hyperventilation-echo test showed a specificity of 100%, a sensitivity of 84%, a positive predictive value of 100% and a negative predictive value of 92%. In conclusion, hyperventilation performed under echocardiographic monitoring is feasible and safe; it can be proposed as a screening test to unmask vasospastic myocardial ischaemia in patients with angina at rest, in whom documentation of spontaneous episodes is not available.

Efficacy of isosorbide-5-mononitrate versus nifedipine in preventing spontaneous and ergonovine-induced myocardial ischaemia. A double-blind, placebo-controlled study

This study was designed to assess the efficacy of oral nifedipine as compared to oral isosorbide-5-mononitrate in the prevention of spontaneous and induced vasospastic myocardial ischaemia. Twenty-one patients admitted to the Coronary Care Unit as a result of angina at rest underwent both Holter monitoring and an echo-ergonovine test during placebo and following either isosorbide-5-mononitrate or nifedipine according to a double-blind randomized trial. Both drugs caused a statistically significant reduction in spontaneous (87% and 95%, respectively) and induced ischaemic attacks (66% and 75%, respectively). No significant difference was found between the two drugs.

Characterization and immunolocalization of a Cryptosporidium protein containing repeated amino acid motifs

The oocyst wall is one of the components that permits cryptosporidia both to survive in the environment and to retain infectivity. With the aim of identifying Cryptosporidium proteins specifically expressed at the oocyst stage, we screened lambda gt11 genomic libraries of Cryptosporidium parvum with both an oocyst antiserum and a specific genetic probe. We isolated, from distinct libraries, two overlapping clones containing an open reading frame encoding a 1,252-amino-acid polypeptide. The analysis of the deduced amino acid sequence revealed unusually high contents of cysteine, proline, and histidine. The sequence was also characterized by two distinct amino acid motifs, each repeated several times. The DNA sequences coding for the amino acid repeats showed a high frequency of synonymous mutations, a result suggesting that the repeated motifs may be functionally and/or structurally important to the parasite. Antisera and monoclonal antibodies developed against a recombinant polypeptide encompassing the first 786 amino acids revealed that the corresponding protein in C. parvum had an apparent molecular weight of 190,000. Moreover, confocal microscopy analysis with immunofluorescence indicated that the protein was localized on the oocyst wall as a uniform stain and within the oocyst itself as bright granules in close association with the residual body.

Effects of flunixin and mefenamic acid on cardiac pacemaker cells. Structure-activity relationship and comparison with clonixin

1. The electrophysiological effects of flunixin and mefenamic acid, non-steroidal analgesics, on frog cardiac pacemaker cells, were studied by intracellular action potential recording. 2. Results show that flunixin (Flx) between 2 x 10(-6) and 1 x 10(-4) M, exerts a frequency, OS, APA and Vmax concentration-dependent decrease, similar to the effects of clonixin (Clx) reported elsewhere (Morales et al., Gen. Pharmac. 23, 515-521, 1992). 3. At 2.5 x 10(-4) M, Flx induces a complete cessation of the electrical activity of subsidiary pacemaker cells. 4. Mefenamic acid (Mef), in spite of its structural similarity with Clx and Flx, induces no appreciable electrophysiological changes. 5. Flx effects were partially reversed by increasing external calcium concentration and fully antagonized by BAY K-8644, a calcium L-type channel agonist. 6. By comparing the structures of the three fenamates studied, it is suggested that the nitrogen of the heterocycle and the electron-donor capacity of the bencenic ring are essential features for the calcium-antagonist activity of Clx and Flx.

Comparison of human trichinellosis caused by Trichinella spiralis and by Trichinella britovi

The first documented report of an outbreak of human trichinellosis caused by Trichinella spiralis in Italy is described. Two family groups were involved. The source was wild boar meat products. The principal clinical features were fever (60%), myalgia (50%), and diarrhea (40%). The most useful laboratory indicators were eosinophilia (100%), elevated levels of creatine phosphokinase (CPK) (90%) and other muscle enzymes, parasite-specific IgG titers (100%), and anti-newborn larvae antibodies (30%). The levels of these responses correlated with the number of infective muscle larvae ingested, which was influenced by the length of time the ingested meat was cured. The clinical and biological features observed during human infection with T. spiralis appear to have been different from those reported during two outbreaks due to T. britovi, which occurred in southern Italy. The main distinctions between the two types of infections were a longer duration of parasite-specific IgG, increased CPK levels, and a more severe intestinal symptomatology in T. spiralis-infected patients than in those infected with T. britovi.

[Prevalence of antibodies against hepatitis C virus in a sample of homosexual males]

BACKGROUND

The finding of an important proportion of cases of hepatitis C without previous contact with blood or hemoderivates has led to suspect that there may be other routes of transmission among which sexual transmission may be found.

METHODS

The presence of antibodies against the hepatitis C virus (anti-HCV) and the association of this infection with certain epidemiologic parameters and sexual practice was determined in 184 homosexual males with no other risk factors for virasis of intravenous transmission. Moreover, the prevalence of anti-HCV was evaluated in 210 voluntary blood donors. Every homosexual was surveyed on sexual practice and the first serum sample available of each of these patients was analyzed for anti-HVC and anti-HIV-1.

RESULTS

Twenty-two homosexual (12%) were anti-HCV positive while only one (0.5%) of the control was positive for this marker (p < 0.0001). Thirty-six cases (19%) were anti-HIV positive (none of the controls). No statistical association was found between both serologic markers or between the presence of anti-HCV and the epidemiologic parameters evaluated.

CONCLUSIONS

Homosexuals constitute a risk group for hepatitis C virus infection although the sexual route is probably not effective for transmission of this entity.

Modulated intra-train spike responses in the cat superior cervical ganglion in vivo

The known two-stage facilitation/depression pattern of postganglionic responses was found at high (24 Hz) frequency stimulation of the preganglionic nerves. We found that the depression stage was exaggerated under partial hexamethonium blockade but it was not affected by partial transection of the preganglionic trunk. At low frequency (8 Hz) normal recruitment turned into the familiar two-stage pattern under moderated hexamethonium doses. The depression course under the competitive nicotinic antagonist dihydro-beta-erythroidine was markedly slower than under hexamethonium. These observations are accountable to the known use-dependence effect of hexamethonium.