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Biomedical subjects

C Falcone

Publications and source records attributed to C Falcone.

At least 73 records · Page 4Linked to original sources
PubMed1986

Sequence organization of the circular plasmid pKD1 from the yeast Kluyveromyces drosophilarum.

pKD1 is the only circular plasmid known in the genus Kluyveromyces. Nucleotide sequence analysis has revealed that this 4757 base-pairs long plasmid contained three major open reading frames, A, B, and C, and a pair of inverted repeats of 346 base-pairs. The molecule exists in two isomeric forms generated by internal recombination at these repeats. The functional organization of pKD1 genome appears to be quite analogous to that of the 2u plasmid of Saccharomyces cerevisiae. There is however little homology of sequences between these plasmids, except that the gene A has a dispersed but significant homology with the FLP recombinase gene of the 2u plasmid. S.cerevisiae cells can be transformed by derivatives of pKD1 carrying URA3 gene as a selection marker.

Base Sequence↗
PubMed1986

Analysis of a 1.6-micron circular plasmid from the yeast Kluyveromyces drosophilarum: structure and molecular dimorphism.

A new plasmid has been found in the yeast Kluyveromyces drosophilarum. It is a double-stranded circular DNA, 1.6 micron in length (4.8 kilobase pairs). As in the case of Saccharomyces 2 mu circles, this plasmid occurs in two isomeric forms corresponding to the inversion of a segment between two 346-bp-long inverted repeats within the molecule. Each form has been separately cloned into bacterial plasmids. The new yeast plasmid, called pKD1, contains sequences that allow its replication in Saccharomyces cerevisiae.

Base Sequence↗
PubMed1986

Significance of the walk-through angina phenomenon during exercise testing.

Out of 3,900 patients who performed an exercise test at our clinic, 3 patients demonstrated a walk-through phenomenon (WTP), defined as the occurrence of mild angina during the first stages of exercise with disappearance of chest pain at higher workloads despite a greater pressure-rate product. 2 patients had variant angina, one with normal coronary arteries and the other with single vessel disease, while the third patient had stable exertional angina and a severe coronary artery disease with occlusion of two major vessels retrogradely filled by collateral channels. Repeat exercise tests failed to reproduce constantly the WTP in the 2 patients with variant angina, while in the third patient the phenomenon was repeatedly induced by exercise testing. Thus the WTP, although rarely found during exercise testing, can be observed in two subsets of patients. In variant angina the WTP is not reproducible and is probably due to coronary spasm, spontaneously subsiding during exercise. In patients with exertional angina and severe coronary artery disease, the WTP can be repeatedly observed during exercise and is likely to be secondary to a delayed vasodilation of collateral vessels. The clinical characteristics of the patients and the response to repeat exercise tests may be useful in identifying the different pathogenetic mechanisms.

Adult↗
PubMed1986

Cardiac arrhythmias during exercise-induced myocardial ischaemia in patients with coronary artery disease.

Exercise may induce ventricular arrhythmias (VA) in patients with coronary artery disease. Exercise-induced VA can identify a subset of patients at higher risk of cardiac sudden death. The role of myocardial ischaemia and/or left ventricular disease in the appearance of VA during exercise is not completely understood. The incidence of VA during exercise-induced myocardial ischaemia was investigated in patients with suspected CAD or those undergoing a stress exercise test after a previous myocardial infarction (MI). Patients were divided in four groups. Group A, 836 patients without a previous MI showing exercise-induced myocardial ischaemia associated with ST-segment depression--group B, 72 patients without a previous MI and exercise-induced ST-segment elevation--group C, 50 patients survivors of a recent (1 month) MI and exercise-induced ST-segment depression--group D, 580 patients with an old MI (greater than 3 months) and a positive exercise test associated with ST-segment depression. Exercise-induced VA were found to be significantly more frequent in patients of groups C (40.0%) and B (23.6%) as compared with groups A (5.1%) and D (7.06%) (P less than 0.001). Furthermore VA in groups B and C were more frequently complex (couplets, triplets, ventricular tachycardia and fibrillation). In all groups the appearance of VA during exercise-induced myocardial ischaemia did not appear to be related to exercise duration, maximal heart rate, maximal work capacity, left ventricular end diastolic pressure, ejection fraction or extent of coronary artery lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1986

Ventricular arrhythmias during acute myocardial ischaemia in man. The role and significance of R-ST-T alternans and the prevention of ischaemic sudden death by medical treatment.

Malignant ventricular arrhythmias appearing during acute myocardial ischaemia, are the most frequent mechanism of sudden death. ST-T alternans is the result of an intraischaemic conduction delay and is frequently associated with those potentially lethal arrhythmias. In fact, such a phenomenon was seen in 35% of 46/86 patients with Prinzmetal's variant angina who showed ventricular arrhythmias during ischaemia, while it was never observed in the remaining 40 patients without arrhythmias during ischaemia. Therefore ST-segment alternans should be considered a reliable marker of the possible occurrence of ventricular arrhythmias during myocardial ischaemia. ST-T-segment alternans is associated with R alternans, as clearly demonstrated by thoracic maps, and this phenomenon is due to a 2:1 intraischaemic block. The patients with Prinzmetal's variant angina who present ventricular arrhythmias during ischaemia, show a more prominent increase of the positive area of the QRS (411.75 +/- 102.5 vs 294.05 +/- 80.3 mu volts ms), that is, a more relevant intraischaemic conduction delay. The effects of different pretreatments (lidocaine, propranolol and diltiazem) on arrhythmias related to vasospastic myocardial ischaemia induced by ergonovine maleate, were evaluated in four patients with Prinzmetal's variant angina. As in experimental observations, neither a 'pure' antiarrhythmic agent like lidocaine, nor a betablocking agent like propranolol, prevented acute ischaemic ventricular arrhythmias. Only the calcium antagonist, diltiazem, seemed to prevent such arrhythmias. However, these findings necessitate further confirmation.

Angina Pectoris, Variant↗
PubMed1985

Exercise-induced coronary artery spasm. A regional coronary blood flow study.

Regional myocardial blood flow during exercise was determined using the thermodilution technique in 2 patients suffering from both spontaneous and exertional chest pain. In both cases we observed that effort-related anginal attacks were due to coronary spasm with sudden reduction of regional left ventricular blood flow. In 1 patient the exercise-induced ST-segment elevation in the anterior leads was accompanied by a reduction of flow in the great cardiac vein. In the second patient the exercise-induced ST-segment depression in the lateral leads was accompanied by a reduction of coronary flow in the area supplied by the circumflex artery. In 1 patient, nifedipine was effective in prolonging exercise tolerance by preventing the occurrence of coronary spasm and by increasing blood supply to the ischemic region during exercise.

Angina Pectoris↗
PubMed1985

[Myocardial ischemia during exertion. Correlations between blood levels of thromboxane B2 and changes in coronary flow and resistance].

Platelet activation, with the subsequent generation of Thromboxane (Tx) A2, has been implied as a possible cause of resting as well as exercise induced myocardial ischemia. To verify the latter hypothesis, we measured the exercise release of TxB2, the stable metabolite of TxA2, in 9 patients with exertional angina and left anterior descending coronary artery disease. Three of the patients also suffered from angina at rest, due to coronary vasospasm. The great cardiac vein flow, venous efflux from the myocardial territory supplied by the left anterior descending, was determined by the thermodilution technique in the basal conditions, at peak exercise when angina and/or significant ST changes occurred, and 20 min after exercise. Simultaneous blood samples were drawn from the great cardiac vein and a peripheral artery for TxB2 measurements. Regional coronary resistances were calculated as the ratio of mean arterial pressure and coronary flow. At peak exercise the great cardiac vein flow increased and regional coronary resistances decreased in all patients, except in one who showed exercise induced coronary spasm. An increase in TxB2 release was found in 3 patients, a decrease in 3, while the remaining 3 patients did not show significant changes. After exercise the great cardiac vein flow and regional coronary resistances returned to control values in all, whereas both great cardiac vein and arterial TxB2 levels were increased in 6 patients. Our data show that no apparent relation exists between exercise-induced changes in coronary resistances and generation of TxB2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

[Plasma profile of free amino acids in children with chronic renal insufficiency undergoing hemodialysis therapy].

Some Authors found changes in plasma aminoacids concentration in patients with chronic renal failure treated with conservative therapy or with dialysis. Particularly they observed a reduction in the concentration of essential aminoacids (EAA) and an increase of the non essential (NEAA), with increase in their ratio. In our study we analyzed the plasma aminoacids pools in 12 children with chronic renal failure treated with hemodialysis. We have measured the plasma aminoacids concentrations before and after hemodialysis to evaluate their variations and their role in the pathogenesis of some symptoms of uremia. A decreased concentration of EAA and an increased concentration of NEAA, before hemodialysis, were observed. These findings were not modified by this therapy, but turned out to be related to protein intake.

Adolescent↗
PubMed1984

Mental arithmetic stress testing in patients with coronary artery disease.

A mental arithmetic stress test was performed by 122 consecutive patients undergoing diagnostic coronary arteriography. Twenty-two patients showed significant ST segment abnormalities during the test (group 1). Of these patients, 20 performed a bicycle exercise test, which was positive in all of them. Seventy patients had a negative mental stress but a positive exercise test (group 2), whereas in 30 patients both tests were negative (group 3). There were no patients with a positive mental stress test and a negative exercise test. Mental stress induced a significant increase in heart rate and systolic blood pressure in the three groups of patients. Group 1 patients, however, achieved higher values of double product during mental stress and had a shorter exercise duration than group 2 and group 3 patients. The extent of coronary artery disease (CAD) was similar in groups 1 and 2, while group 3 patients had a significantly lower prevalence of two or more vessel disease. To investigate the pathogenetic mechanism of mental stress-induced myocardial ischemia, great cardiac vein flow was measured by means of the thermodilution technique in four patients with isolated left anterior descending artery disease, who showed ST segment depression in anterior leads in response to mental stress. In three patients without vasospastic angina the calculated coronary resistance decreased during mental stress, as a result of a normal vasodilatory response to the increased myocardial oxygen consumption induced by the test. By contrast, in one patient with variant angina, coronary resistance increased suggesting coronary vasoconstriction. Our findings demonstrate that mental arithmetic stress testing may induce significant ST segment abnormalities in patients with CAD.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Variable threshold exertional angina in patients with transient vasospastic myocardial ischemia. Repeat exercise test results and therapeutic implications.

Thirty-five of 70 patients with vasospastic angina at rest complained of chest pain during exercise or during usual daily activity. In 22, the angina threshold was described as variable during exercise: that is, the amount of exertion that induced angina was not always the same. In 12 patients with variable threshold exertional angina, 3 exercise tests performed in the morning on different days yielded different results, because chest pain and ischemic electrocardiographic changes occurred at different work loads with a wide range in heart rate-systolic pressure product. Two patients, in whom great cardiac vein flow was measured during exercise before and after taking nifedipine, tolerated heavier work loads after receiving the drug, with a more marked increase in flow during exercise. It is concluded that variable threshold exertional angina can be objectively demonstrated by repeat exercise tests in patients with vasospastic angina. Variability of the angina threshold may be due to a functional mechanism that causes myocardial ischemia in addition to the increased myocardial metabolic requirements provoked by exercise. Because in such patients fluctuations in coronary arterial tone play an important role in determining the response to exercise, calcium antagonistic drugs, which lower coronary tone and prevent the occurrence of coronary spasm, are effective in increasing exercise capacity.

Adult↗
PubMed1983

Mitochondrial translation products during release from glucose repression in Saccharomyces cerevisiae.

Mitochondrial protein synthesis was studied during release from glucose repression in Saccharomyces cerevisiae cells bearing different mitochondrial genomes. The increase in the rate of the synthesis of mitochondrial translation products was analyzed during respiratory induction. Different kinetic patterns were found for strains having a different structure of mitochondrial mosaic genes, even when the nuclear background was the same. A very limited response of the synthesis of the var1 ribosomal protein to inducing conditions was observed.

Cycloheximide↗
PubMed1983

Effects of nifedipine on coronary hemodynamic findings during exercise in patients with stable exertional angina.

To investigate the mechanism by which nifedipine improves exercise tolerance in patients with coronary artery disease, we studied 14 patients with stable exertional angina and left anterior descending artery disease by measuring great cardiac vein flow (GCVF) and calculating anterior regional coronary resistance (ARCR) during exercise before and after sublingual administration of 20 mg of nifedipine. After nifedipine seven patients (group I) had no increase in exercise capacity and showed a similar magnitude of ST segment depression at peak exercise, while another seven patients (group II) had prolonged exercise duration (p less than .001) with less ST segment depression at peak exercise (p less than .01). Such effects were achieved despite a significant increase in double product, an indirect index of myocardial oxygen consumption. In group I patients no significant change was induced by nifedipine in GCVF or in ARCR either at rest or at peak exercise. In contrast, in group II patients nifedipine significantly increased GCVF at rest (p less than .05) and at peak exercise (p less than .001). Moreover, resting ARCR was decreased (p less than .01) and remained significantly lower at peak exercise (p less than .01) compared with the prenifedipine values. These data show that nifedipine may increase GCVF and decrease ARCR at rest and at peak exercise in patients with left anterior descending artery disease. Such increase in myocardial oxygen supply seems the most likely mechanism by which nifedipine may improve exercise capacity in patients with stable exertional angina.

Adult↗
PubMed1981

Variable threshold of angina during exercise: a clinical manifestation of some patients with vasospastic angina.

Two patients complained of chest pain while at rest and during physical activities. However there seemed to be no direct relation between exertional angina and an increasing level of work performed, indicating that these patients had a variable threshold of angina during exercise. In one patient spontaneous chest pain was associated with transient S-T segment changes in precordial leads, and during coronary arteriography the administration of ergonovine induced spasm of the left anterior descending coronary artery. The other patient showed S-T segment elevation in inferior leads during an ergonovine-induced anginal attack and coronary arteriography revealed a spontaneous spasm of the right coronary artery. In both patients repeated exercise tests yielded different results, because the chest pain and S-T segment depression occurred at different work loads with large differences in heart rate-systolic blood pressure product. It is concluded that a variable threshold of angina during exercise is a clinical manifestation in some patients with vasospastic angina and is probably due to the difference in coronary arterial tone at the onset of exercise.

Angina Pectoris↗
PubMed1981

Significance of exercise-induced ST-segment elevation in patients without myocardial infarction.

Sixteen patients with exercise-induced ST-segment elevation and without a history of myocardial infarction or left ventricular aneurysm were studied. Fourteen complained of angina at rest, which was associated with ST-segment elevation in the same leads where it was recorded during exercise, and two patients had only exertional angina. Exercise-induced ST-segment elevation was generally reproducible in subsequent exercise tests performed in different hours of the day, but exercise tests repeated a mean of 15 months later did not induce this electrocardiographic abnormality. All patients had a marked susceptibility to coronary spasm, as shown by the response to the ergonovine test (12 positive tests in 12 patients) and by the occurrence of spontaneous spasm during coronary arteriography in two patients. In addition, coronary arteriography, performed in seven patients at the time of exercise-induced ST-segment elevation, revealed spasm of a major coronary vessel in all. In two patients we documented that exercise-induced ST-segment elevation was accompanied by a decreased coronary blood flow and increased coronary vascular resistance. We conclude that exercise-induced ST-segment elevation in patients without a history of myocardial infarction or left ventricular aneurysm is caused by coronary spasm of a major coronary vessel.

Adult↗
PubMed1981

The exercise test in variant angina: results in 114 patients.

One hundred fourteen patients with variant angina performed bicycle exercise stress tests, and were divided into three groups. Group 1 included 37 patients with a normal exercise test. Coronary arteriography revealed absence of significant coronary stenoses in 18 patients, one-vessel disease in 17 and involvement of two or more vessels in two. Group 2 consisted of 40 patients who had ST-segment elevation during or just after exercise. Coronary arteriography in these cases revealed absence of significant coronary stenoses in nine patients, one-vessel disease in 18 and disease of two or more vessels in 13. Group 3 included 37 patients who had ST-segment depression during exercise. Absence of coronary artery disease was found in only two patients, one-vessel disease was found in 19 and disease of two or more vessels was found in 16. Sixty-one patients repeated the exercise test after a mean of 18 months after hospital discharge. Exercise-induced ST-segment elevation was no longer present in surgically or medically treated patients; ST-segment depression was still evident in all the medically treated patients, but was absent in eight of 13 patients who underwent aortocoronary bypass surgery. Exercise testing can be useful in the follow-up of patients with variant angina and in selecting patients most likely to be helped by bypass surgery.

Adult↗
PubMed1980

Angiographic demonstration of different pathogenetic mechanisms in patients with spontaneous and exertional angina associated with S-T segment depression.

Three patients complained of spontaneous and exertional chest pain, both associated with S-T segment depression in anterior electrocardiographic leads. In each, coronary spasm was demonstrated on coronary arteriography during a spontaneous attack of pain. Coronary arteriograms taken during exercise-induced angina did not show evidence of spastic obstruction; this suggests that exercise-induced chest pain and S-T segment depression were secondary to the increase in oxygen requirements rather than to a sudden decrease in coronary blood flow. Thus, two pathogenetic mechanisms coexisting in the same patient may cause chest pain associated with subendocardial ischemia.

Angina Pectoris↗