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Biomedical subjects

E Rapaport

Publications and source records attributed to E Rapaport.

At least 109 records · Page 6Linked to original sources
PubMed1980

Compartmentalized ATP pools produced from adenosine are nuclear pools.

Incubation of African green monkey kidney (BS-C-1) cells and mouse fibroblasts (3T6) in the presence of adenosine for 4 hours resulted in increases in the nuclear compartment pools of adenosine 5'-triphosphate (ATP) and nuclear ATP/adenosine 5'-diphosphate (ADP) ratios. Adenine and inosine, which yield increases in total cellular ATP pools and ATP/ADP ratios similar to those promoted by adenosine, do not produce similar increases in the nuclear compartment. Adenosine-promoted increases in nuclear ATP pools were higher in the untransformed, serially propagated, BS-C-1 cells than in the spontaneously transformed 3T6 cells. Adenosine-promoted compartmentalized ATP pools in primary chick embryo fibroblasts were reduced upon transformation of these cells with Rous sarcoma virus, resulting in free mixing of all of the ATP pools synthesized from various salvage precursors. The growth regulatory properties of the nuclear compartment pools of adenine nucleotides is suggested by the big increases in nuclear ATPase and adenosine 5'-monophosphate (AMP) deaminase activities upon the entry of 3T6 cells into the S phase of their cycle. These enzymatic activities would tend to lower the nuclear ATP/ADP ratios and reduce the total adenine nucleotide pools in these nuclei respectively--conditions which were shown by earlier in vitro studies to be favorable to DNA replication.

Adenosine↗
PubMed1980

A new method for quantification of aortic regurgitation during cardiac catheterization.

Clinical methods of estimating aortic insufficiency are unsatisfactory. We developed a radioisotope method of quantitating aortic regurgitant volume. The method is easily performed, convenient, and can be carried out repetitively. The mathematical derivation of the method is presented and a mechanical model is used to verify assumptions. The potential utility and possible difficulties of applying the method clinically are discussed.

Aortic Valve Insufficiency↗
PubMed1980

Renal effects of nitroprusside and hydralazine in patients with congestive heart failure.

The acute effects of nitroprusside infusion and intravenous hydralazine on renal hemodynamics and function were evaluated in nine male patients with severe, low cardiac output, congestive heart failure (CHF). Both drugs resulted in marked systemic hemodynamic improvement. Nitroprusside had a more profound effect on pulmonary artery pressure, while hydralazine produced a greater elevation in cardiac output. Significant decreases in both systemic and pulmonary vascular resistance and pulmonary capillary wedge pressure with increases in stroke volume and stroke work index were noted with both drugs. Total renal resistance decreased and renal blood flow (RBF) significantly increased with both drugs, while the distribution of cardiac output to the kidney remained depressed. Glomerular filtration rate (GFR) did not change significantly with either drug, although increases in GFR were seen in selected patients in whom RBF increased by more than 10% from control. The fraction of plasma filtered decreased toward normal with both drugs and excretion of total cations was significantly increased. These changes all represent improvements in systemic and renal hemodynamic abnormalities occurring in patients with CHF; their maintenance during long-term therapy would facilitate patient management.

Adult↗
PubMed1980

Continuous positive-pressure ventilation decreases right and left ventricular end-diastolic volumes in the dog.

We investigated the mechanism(s) responsible for the decreased cardiac output during continuous positive-pressure ventilation (CPPV). Seven dogs were anesthetized with chloralose-urethane, intubated, and ventilated using a volume ventilator. We measured heart rate, stroke volume, and the determinants of stroke volume: left and right ventricular end-diastolic volumes, isovolumic and ejection phase indices of myocardial contractility, and pulmonary and systemic arterial pressures. Myocardial blood flow was estimated using radioactive microspheres. Variables were measured during a control period of intermittent positive-pressure ventilation (IPPV), 8-20 minutes after the initiation of CPPV using 12 cm H2O positive end-expiratory pressure (PEEP), and 8-20 minutes after the removal of PEEP. CPPV decreased cardiac output but did not affect total or regional myocardial blood flow or the ratio of subendocardial to subepicardial blood flow. Isovolumic and ejection phase indices of myocardial cointractility, heart rate, and systemic arterial pressure did not change during CPPV. Right and left ventricular end-diastolic and end-systolic volumes decreased markedly during CPPV. We conclude that CPPV decreases cardiac output in accordance with Starling's law by decreasing preload.

Animals↗
PubMed1979

Selective high metabolic lability of uridine, guanosine and cytosine triphosphates in response to glucose deprivation and refeeding of untransformed and polyoma virus-transformed hamster fibroblasts.

Sugar deprivation of hamster fibroblasts (NIL) affected the steady state levels (pool sizes) of cellular acid soluble nucleotides in the folloing fashion: the pools of UTP, GTP and CTP decreased to a much greater extent than the cellular ATP pools, with the UTP pools undergoing the most dramatic reduction. Sugar deprivation of polyoma-transformed NIL cells (PyNIL) yielded even sharper decreases in the nucleoside triphosphate pools with relative changes similar to those of the untransformed cells. Inhibition of protein synthesis by cycloheximide, initiated at the onset of (and continued during) sugar deprivation, prevented the reduction in pool sizes and yielded values slightly higher than those observed for pool sizes in cells cultured in sugar-supplemented medium. Refeeding glucose to sugar-depleted hamster fibroblasts led to rapid increases (within 1 hour) in the UTP and CTP pools to levels well above the pool sizes observed in cells which were continuously cultured (16 hours) in sugar supplemented medium. Feeding NIL or PyNIL cells with fructose instead of glucose as the only hexose source did not appreciably affect any of the ribonucleoside triphosphate pool sizes. Measurements of hexose uptake by NIL and PyNIL cells under a variety of conditions suggest that hexose transport is not regulated by the total cellular pools of ATP or any of the other ribonucleoside triphosphates.

Animals↗
PubMed1979

Regulation of DNA replication in S phase nuclei by ATP and ADP pools.

Synchronized 3T6 (mouse fibroblast) ghost monolayers (isolated nuclei) were utilized to study the effects of ATP and ADP levels on DNA replication in vitro. A system yielding discontinuous semiconservative DNA replication (without any detectable repair) in synchronized S phase nuclei has been developed. Lack of initiation of new sites has been observed in isolated S phase 3T6 nuclei without the presence of cytoplasmic material; DNA synthesis is comprised only of elongation at sites where initiation had previously taken place. DNA synthesis in S phase nuclei proceeded optimally at an ATP concentration of 4-5 mM. High ATP levels as well as high ATP/ADP ratios (produced by an ATP-regenerating system at a variety of ATP concentrations) yielded marked inhibition of [(3)H]dTTP incorporation. The cellular and nuclear pools of ATP and ADP in intact synchronized 3T6 cells were accurately determined by high-pressure liquid chromatography. A good correlation with the studies on isolated nuclei has been observed. Whereas total cellular ATP pools increase during the progression of 3T6 cells from G(1) to S phase of the cell cycle, nuclear ATP pools do not increase, and the nuclear ATP/ADP ratios decrease once the cells enter the S phase of their cycle. These experiments suggest that nuclear ATP pools and ATP/ADP ratios act as S phase controls, regulating DNA elongation at sites where its synthesis has previously been initiated by cytoplasmic factors.

Adenosine Diphosphate↗
PubMed1978

Creatine phosphokinase MB isoenzyme in hypothermia: case reports and experimental studies.

Six patients with severe medical disorders and profound hypothermia are presented who had elevated total serum creatine phosphokinase (CPK) and CPK-MB isoenzyme activity without clinical or postmortem evidence of acute myocardial infarction. Experiments in dogs indicate that hypothermia reduces total CPK activity in both striated and myocardial muscle resulting in increased serum enzyme activity. These data suggest that profound hypothermia may result in diffuse striated and cardiac muscle cellular injury without evidence of discrete infarction with consequent release of CPK-MB isoenzyme into serum.

Adult↗
PubMed1978

Increased incorporation of adenosine into adenine nucleotide pools in serum-deprived mammalian cells.

The effects of serum deprivation on the incorporation of adenosine into the intracellular adenine nucleotide pools by several mamalian cell lines were studied. Cells arrested in the G1 phase of the cell cycle showed increased incorporation of exogenous adenosine into their adenine nucleotide pools as compared with growing cells. This phenomenon is unexpected because salvage pathways from all other preformed nucleosides and bases as well as the de novo synthesis of adenine nucleotides is decreased after arrest of growth by serum deprivation. The incorporation of adenosine into adenine nucleotides may serve as an intracellular signal in the regulation of growth in mammalian cells.

Adenine Nucleotides↗
PubMed1978

Echocardiography of left ventricular masses.

The M-mode and two-dimensinal real-time echocardiographic findings in 10 patients with left ventricular masses are discussed. Two patients had left ventricular tumors and eight had left ventricular thrombi. In all cases the diagnosis was confirmed by angiography or surgery. The intracavitary and intramural left ventricular tumors were detected both by M-mode and two-dimensional echocardiography . M-mode echocardiography, however, did not detect the left ventricular thrombus in all instances. Two-dimensional echocardiography was able to identify the four large and inhomogeneous left ventricular thrombi but did not clearly identify four cases of smaller mural thrombi. Echocardiography techniques useful in detection of left ventricular masses are discussed.

Adult↗
PubMed1977

The role of adrenergic receptor blockade in serotonin-induced changes in the pulmonary circulation.

1. In dogs i.v. injection of serotonin caused a rise in pulmonary artery pressure and pulmonary arteriocapillary resistance that persisted even after alpha- and beta-adrenergic receptor blockade; pulmonary venous resistance also increased, but this was abolished by pretreatment with either propranolol or phenoxybenzamine. 2. The injection of serotonin into the ascending aorta produced an immediate rise in systemic, pulmonary arterial and pulmonary venous pressures and pulmonary venous resistance. After phenoxybenzmine, the rise in systemic and pulmonary arterial pressures remained unchanged, but previously observed increases in pulmonary venous pressure and resistance were blocked. In contrast, propranolol failed to abolish the rise in pulmonary venous resistance after serotonin injection into the ascending aorta. 3. These results confirm the observation that the vasoconstrictor effect attributed to intravenously injected serotonin on the arterial side of the pulmonary circulation is independent of the known sympathetic pathways. The data suggest that the pulmonary venoconstriction induced by intravenous serotonin is of reflex origin, abolished by alpha and beta receptor blockade, whereas the efferent arm of the reflex pulmonary venoconstriction following injection of serotonin into the ascending aorta is mediated via alpha-adrenergic receptors.

Animals↗
PubMed1977

Improved signal processor for the ultrasonic dimension gauge.

Inexpensive modifications and additions to improve the performance of a widely used ultrasonic dimension gauge are presented in detail. These include a pulse width demodulator, averaging peak detector, and improved signal processing circuits. Benefits of the modifications are improved frequency response (to 1 kHz), lowered drift, increased sensitivity (to 128 mV/mm), rational gain calibration, calibrated zero suppression, and improved recovery from signal dropout. The modifications result in the ability to take the derivatives of ventricular wall motion with greater reliability.

Echocardiography↗
PubMed1977

Should valvular replacement be reserved for symptomatic valvular heart disease?

Valvular replacement should generally be reserved for patients with valvular heart disease who are symptomatic. With the exception of an occasional case of tight aortic stenosis, morbidity and mortality are less in the asymptomatic patient managed medically versus surgically with prosthetic valve replacement. Therefore, patients with valvular lesions are best managed without prosthetic valve surgery until less than ordinary exertion makes the patient clearly symptomatic. At this point, significant hemodynamic impairment at rest is present, and the prognosis is worse if the patient is managed medically rather than surgically. Until then, however, one should not operate on an asymptomatic or minimally symptomatic patient with valvular heart disease, particularly when the surgical procedure can be expected to require valve replacement.

Aortic Valve Insufficiency↗