Search PubMed⌕ Search

Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 703 records · Page 39Linked to original sources
PubMed1978

Control of globin gene expression by steroid hormones in differentiating Friend leukemia cells.

Low levels of dexamethasone and related glucocorticoid hormones suppress the expression of globin genes during the DMSO-induced differentiation of Friend leukemia cells. In this response, the glucocorticoids appear to act at both the transcriptional and post-transcriptional levels in that 10(-8) M dexamethasone prevents the accumulation of both globin mRNA and globin protein, whereas 10(-9) M dexamethasone allows the accumulation of normal levels of hybridizable globin mRNA but prevents the accumulation of globin protein. This suppressive action of dexamethasone is more effective with DMSO as the inducer of globin gene expression than with hemin as the inducer. In contrast to the situation with glucocorticoids, certain sex steroids (etiocholanolone, testosterone and estradiol) facilitate the expression of globin genes in DMSO-treated Friend leukemia cells. The modulation of globin gene expression by steroid hormones is achieved in DMSO-treated cells without altering the growth and morphological changes which characteristically attend the differentiation of these cells.

Cell Differentiation↗
PubMed1978

The precursor of mouse beta-globin messenger RNA contains two intervening RNA sequences.

We have investigated the locations of the poly(A), the mRNA-specific sequences and the RNA sequences that are eventually cleaved from the 1860 nucleotide precursor of mouse beta-globin mRNA. Biochemical and electron microscopic data demonstrate that there are two intervening RNA moieties in the precursor which separate the beta-globin mRNA sequences into three portions containing 480, 205 and 155 nucleotides. One of the two intervening RNA moieties contains 780 nucleotides. The size of the smaller intervening RNA has not been determined precisely, but it is 125 nucleotides or less. The largest mRNA-specific fragment is derived from the 3' terminus of the precursor, and contains the 3' terminal poly (A) and 330 mRNA-specific transcribed nucleotides. At least one, and probably both, intervening RNAs occur within the coding portion of the mRNA sequences. The larger of the intervening RNAs is located next to the 480 nucleotide mRNA-specific fragment, and the smaller intervening RNA is located between the 205 and 155 nucleotide mRNA-specific fragments. These experiments are consistent with the notion that the intervening sequences in the DNA of mouse beta-globin genes are transcribed into the mRNA precursor and are excised from the RNA by post-transcriptional events.

Animals↗
PubMed1978

A survey of the haematological, nutritional and biochemical state of the rural elderly with particular reference to vitamin C.

A survey of the rural elderly has been carried out to determine basic haematological and biochemical data, and to establish a pattern of living for this 'well' population. The blood parameters related to diet, such as haemoglobin, folate, cholesterol, vitamin C etc., show considerable changes with increasing age in the male but little significant change in the female. The vitamin C status for both sexes compares favourably with that reported by other workers studying the urban elderly. The biochemical and haematological data derived provide a normal range with which the 'sick' elderly can be compared. The subjects were generally active and independent in spite of (or because of) a somewhat Spartan existence.

Adolescent↗
PubMed1978

Myocardial infarction in the baboon: regional function and the collateral circulation.

Occlusion of the anterior descending coronary artery was produced in sedated baboons 7-15 days after implantation of a micromanometer and ultrasonic crystals for measurement of regional left ventricular dimensions in ischemic, marginal, and control segments. One minute after coronary occlusion (CO), ischemic segments exhibited a marked systolic bulge with wall thinning, and percent systolic shortening of marginal segments decreased. Over the ensuing weeks, there was a progressive increase of end-diastolic lengths in marginal and ischemic segments, whereas systolic shortening in these segments did not improve significantly. Control segments did not change. In control baboons, the coronary collateral index was 55 +/-25 (SE) compared to 560 +/- 74 in normal dogs. One month after CO, the collateral index was 543 +/- 144 in baboons compared to 6,685 +/- 716 in dogs, regions of normal tissue were seen in the infarct (14.2 +/- 2% of left ventricular mass). Minimal coronary collateral development in the baboon provides a likely explanation for differences from the dog in regional functional responses and in the character of the infarct.

Animals↗
PubMed1978

Variability, reproducibility, and applications of precordial ST-segment mapping following acute myocardial infarction.

In 58 patients with uncomplicated acute anterior myocardial infarction, a mean decline in the sum of ST segments (sigmaST) of 34% was observed when comparing sigmaST values recorded at 3-6 hours with those recorded at 6-9 hours after the onset of symptoms (P less than 0.05). The mean absolute difference between 19 paired readings 1-2 hours apart was 2.9 +/- 3.0 mm and between 29 readings 2-4 hours apart 3.0 +/- 3.0 mm. However, the mean absolute difference between 38 paired readings 4-8 hours apart was 12.2 +/- 11.8 mm with a wide range of differences. Left ventricular failure and pericarditis were also associated with significantly higher sigmaST values. We conclude that there is a complex relationship between ST-segment elevation and a number of clinical factors during the first 48 hours after infarction. Nevertheless, precordial mapping remains a useful method for the evaluation of short-term (less than 4 hours) therapeutic interventions, if other relevant variables are unaltered and if carefully matched control groups are employed.

Acute Disease↗
PubMed1978

Alteration of the left ventricular diastolic pressure-segment length relation produced by the pericardium. Effects of cardiac distension and afterload reduction in conscious dogs.

Left ventricular pressure and segment length were measured in seven conscious chronically instrumented dogs with the pericardium intact and 3-9 days after pericardiectomy. Diastolic pressure-length plots were obtained under control conditions and after acute volume loading followed by sodium nitroprusside infusion. In all dogs with intact pericardium, volume loading displaced the entire diastolic pressure-length curve upwards and sodium nitroprusside shifted it toward control. After pericardiectomy the pressure-segment length data during control, volume loading and sodium nitroprusside fell on a single curve (intercepts and slopes not statistically different); After dextran infusion, intrapericardial pressure rose from control 1.5 +/- 0.7 mm Hg to 8.2 +/- 0.5 mm Hg, and it fell to 4.8 +/- 0.1 mm Hg after nitroprusside. Therefore, in acute cardiac dilatation the pericardium contributed significantly to the increased left ventricular diastolic pressure and to the fall during sodium nitroprusside infusion and appeared responsible for shifts in the diastolic pressure-segment length relation.

Animals↗
PubMed1978

Evaluation of chamber and myocardial compliance in pressure overload hypertrophy.

The effect of pressure overload hypertrophy on isolated myocardial muscle preparations remains controversial. Moreover, the ultimate effect on the diastolic function of the left ventricle in the pressure overload states of man and the relative changes in chamber and myocardial stiffness remain incompletely studied. We review here the methods as well as results of dynamic diastolic stiffness analysis in 18 patients with valvular aortic stenosis and 5 normal subjects based upon the pressure-volume and circumferential stress-strain relations obtained by simultaneous left ventricular micromanometry and high-speed cineangiography. In addition, complementary analysis of dynamic diastolic stiffness findings in chronically instrumented animals, before and after the induction of hypertrophy, are reviewed. Increased diastolic intracavitary pressures during concentric hypertrophy were found to be attributable to both increased muscle mass as well as enhanced myocardial stiffness. However, both chamber and myocardial stiffness changes during hypertrophy were quite variable with some patients (and 2 of 6 dogs) showing no enhancement of stiffness parameters. In the chronically instrumented animals where dynamic, instantaneous stiffness changes and strain rates are more readily studied than in man, viscous (velocity dependent) effects were noted to be enhanced during hypertrophy. It is postulated that variable increases in diastolic stiffness during concentric hypertrophy in the intact heart results from varying degrees of myofiber architectural distortion and/or inconstant collagen content, and further correlative studies of morphology and mechanical function are needed.

Animals↗
PubMed1978

[Nitroglycerin in experimental myocardial infarction in the baboon. The effect of reducing the pre-charge and post-charge on regional myocardial function].

A left anterior descending coronary artery occlusion was produced in the sedated state in baboons previously instrumented with a left ventricular micromanometer and ultrasonic crystals measuring segmental myocardial lengths of control, marginal and ischemic regions. 3-8 days after the onset of the ischemia, nitroglycerin (0.4 mg IV) was injected. Following the injection (NG), heart rate increased significantly compared to the control ischemic state (CIS); end diastolic pressure and systolic pressure decreased significantly. In control segments, VCF increased from 0.99 +/- 0.11 circ/s to 1.26 +- 0.11 circ/s (p less than 0.01); in marginal segments VCF increased (CIS: 0.32 +/- 0.07 circ/s; NG: 0.42 +/- 0.09/s; p less than 0.01); in ischemic segments, the bulge observed before the injection persisted after nitroglycerin. Increased performances of control and marginal regions were attributed mainly to afterload reduction although preload reduction tended to decrease this response. The contribution of improved marginal function was small indicating that improvement of active hemodynamic function was largely due to changes in control segments function.

Animals↗
PubMed1977

[The perioperative myocardial infarct after aortocoronary bypass].

Two sets of criteria are developed for the diagnosis of perioperative myocardial infarction: 1) new, persistent Q waves and either an elevated 48-hour MB-CPK area or a positive pyrophosphate scan, 2) severe ischemic ST-T wave changes and both elevated MB-CPK area and a positive scan.

Coronary Artery Bypass↗
PubMed1977

Usefulness of preoperative and postoperative Tc-99m (Sn)-pyrophosphate scans in patients with ischemic and valvular heart disease.

To assess the usefulness of myocardial imaging with technetium-99m-stannous pyrophosphate for detecting acute myocardial necrosis in patients undergoind cardiac surgery, 66 such patients were stldied. Tc-99m (Sn)-pyrophosphate scans were obtained in all patients 3 to 6 days postoperatively and in 45 preoperatively. Electrocardiograms and serum samples for measuring myocardial isoenzyme of creatine kinase (MB CK) levels were obtained before and serially after cardiac surgery. Seven of the 46 patients undergoing myocardial revascularization had a definite new myocardial infarction as indicated by electrocardiogram and MB CK isoenzyme concentrations, and postoperative pyrophosphate scans were abnormal in all but one. In addition, six of the eight patients with possible myocardial infarction (elevated MB CK levels and persistent ST-T wave depressions) had an abnormal scan postoperatively. Seven of the 20 patients undergoing aortic or mitral valve replacement, or both, had a possible postoperative myocardial infarction by electrocardiogram and MB CK criteria and the myocardial scan was positive in two. All the patients with a normal electrocardiogram and normal MB CK levels had a normal pyrophosphate scan. Preoperative scans were obtained in 22 patients wit; valvular heart disease and were positive in two with a heavy calcified mitral valve on fluoroscopy and in one with a calcified aortic valve. After valve replacement, the pyrophosphate scan became normal in two patients and remained abnormal in the third patient with electrocardiograms and MB CK levels suggesting acute myocardial infarction. We conclude that the Tc-99m (Sn)-pyrophosphate scan is useful for analyzing the occurrence of acute myocardial infarction in patients undergoing cardiac surgery and that, in conjunction with the electrocardiogram, it permits confirmation or exclusion of that diagnosis. Furthermore, false positive pyrophosphate scans may occur in patients with heavy valve calcifications.

Adult↗
PubMed1977

Interventricular septal motion and left ventricular function after coronary bypass surgery: evaluation with echocardiography and radionuclide angiography.

To evaluate interventricular septal motion and left ventricular function after coronary bypass graft surgery, 40 patients were studied early postoperatively and serially for up to 16 months with echocardiography and radionuclide angiography. Early after operation mean left septal excursion decreased significantly from 4.6 +/- 0.4 (standard error) to 0.8 +/- 0.6 mm (P less than 0.001), and left septal motion was abnormal in 23 of the 40 patients. Mean right septal excursion reversed from 2.1 +/- 0.5 to -2.1 +/- 0.5 mm early after operation in the 22 patients in whom these measurements could be made, and 15 patients showed paradoxical right septal excursion. At a mean of 4 months after operation, only 7 of 35 patients followed up had abnormal left septal motion, and mean left septal excursion had returned toward normal (3.6 +/- 0.7 mm); mean right septal excursion remained reversed (--1.1 +/- 0.7 mm), and 6 of the 14 patients followed up had paradoxical motion. In the 22 patients whose wall thickness could be measured, mean septal thickening during systole decreased significantly from 35 +/- 4 to 21 +/- 3 percent early after operation (P less than 0.01). During late follow-up septal thickening returned toward normal (32 +/- 4 percent). Mean normalized posterior wall velocity increased significantly after operation from 0.76 +/- 0.03 to 1.01 +/- 0.05 sec-1 (P less than 0.001), but posterior wall thickening remained unchanged. Left ventricular end-diastolic dimension and the radionuclide-determined left ventricular ejection fraction were unchanged postoperatively. It is concluded that (1) echocardiographically detected abnormal septal movement is frequent early after coronary bypass graft operation; (2) both decreased myocardial contraction in the septum and increased anterior movement of the whole heart contribute to this abnormality; (3) the abnormalities in septal movement decrease during late follow-up in many patients but persist in some patients; and (4) posterior wall function tends to increase early after operation and therefore overall left ventricular function remains normal.

Adult↗