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Biomedical subjects

A Pines

Publications and source records attributed to A Pines.

At least 91 records · Page 5Linked to original sources
PubMed1993

Persistent activation of thrombocytes in neurosurgical patients operated for primary brain tumours.

A prospective study was designed to investigate whether platelet hyperactivity exists following neurosurgical removal of primary brain tumours. The level of beta-thromboglobulin (beta TG), a protein released by platelets during the activation process, was measured in the plasma of 13 consecutive patients prior to surgery (T 1) and on the first (T 2) and seventh (T 3) post-operative days. A significant and sustained increase in beta TG levels from a baseline of 20.7 +/- 1.7 ng/ml (mean +/- sem) at T 1 to 37.0 +/- 5.2 ng/ml (p < 0.005) at T 2 and 35.9 +/- 3.7 at T 3 (p < 0.005) occurred. When patients were grouped according to tumour malignancy, significantly higher beta TG levels were found in the malignant group at T 2 (51.8 +/- 6.3 ng/ml) when compared to the benign group (30.6 +/- 6.0 ng/ml) (p = 0.025). Postoperative T 3 levels were linearly correlated to T 1 levels (r = 0.58, p = 0.04). This significant and sustained platelet activation that occurs following brain surgery may be part of the biochemical sequel leading to a hypercoagulable state and thrombo-embolic phenomena (TEP) in these patients.

Adolescent↗
PubMed1993

Left ventricular dynamics during strenuous isometric exercise in marathon runners, weight lifters and healthy sedentary men: comparative echocardiographic study.

Global and segmental left ventricular dynamics during strenuous large-muscle isometric exercise were compared between endurance and static type professional athletes and sedentary men. Using a trunk dynamometer and supine echocardiography, only the weight lifters manifested increased (p < 0.01) wall thickness during both diastole and systole, resulting in decreased left ventricular volume at end systole. These group-related differences would suggest a causal relationship between chronic intensive weight-lifting training and efficient myocardial dynamics at the time of strenuous isometric exercise.

Adult↗
PubMed1993

Onset of intolerance symptoms during exercise testing is a reproducible threshold for evaluation of cardiac function.

Twenty-one male patients with a history of myocardial infarction underwent bicycle cardiopulmonary exercise testing. The onset of leg pain or dyspnea, which reflects anaerobic metabolism, was termed anaerobic exercise symptom threshold (AEST). Our aims were (1) to evaluate the temporal relationship between AEST and the ventilatory anaerobic threshold (VAT) and (2) to determine whether heart rate, rate-pressure product, exercise time, and the ventilatory parameters at AEST are reproducible and correlate with the same parameters at VAT. AEST overlapped VAT in 4 patients and lagged behind VAT in 15. AEST never preceded VAT. The mean exercise time at VAT was 4.1 +/- 1.2 min and at AEST 5.6 +/- 1.6 min (p < 0.0001); the mean heart rate was 97 +/- 10 and 107 +/- 12, respectively (p < 0.001). The mean values of the rate-pressure product and the oxygen consumption at AEST were significantly higher than at VAT. The correlation coefficient ranged from r = 0.74 to r = 0.93. Fifteen patients were examined twice within 1 month; the above parameters were reproducible at AEST, VAT, and peak exercise. In conclusion, AEST, which is easily recorded during bicycle exercise testing, is useful as a reference point for evaluation and follow-up of the cardiac aerobic function.

Anaerobic Threshold↗
PubMed1993

The effect of the hypoestrogenic state, induced by gonadotropin-releasing hormone agonist, on Doppler-derived parameters of aortic flow.

The effect of the hypoestrogenic state, induced by a GnRH agonist (GnRH-a), on cardiac function in healthy young women, was evaluated by Doppler echocardiography performed before treatment and when serum 17 beta-estradiol levels were suppressed by GnRH-a to 36.7 pmol/L. The following parameters of aortic flow were measured: peak flow velocity, ejection time, and acceleration time. Additional parameters calculated were flow velocity integral, cardiac index, and mean acceleration. The study group included 15 menstruating women, aged 25-42 yr (mean, 33 yr), with symptomatic fibroids, endometriosis, or scheduled for in vitro fertilization, who were treated with a GnRH-a. There were significant decreases in peak flow velocity (99 +/- 11 vs. 86 +/- 11 cm/s; P = 0.0004) and cardiac index (3.0 +/- 0.7 vs. 2.5 +/- 0.5 L/min.m2; P = 0.002). A decrease that did not reach statistical significance was noted in flow velocity integral (18.9 +/- 2.7 vs. 16.5 +/- 3.4 cm; P = 0.07). Mean acceleration was decreased significantly (12.6 +/- 2.6 vs. 10.8 +/- 1.8 m/s.s; P = 0.01), but no significant changes in acceleration time (81 +/- 16 vs. 83 +/- 10 ms; P = 0.7) or ejection time (296 +/- 25 vs. 295 +/- 27 ms; P = 0.8) were observed. These results indicate that estrogen deprivation is associated with smaller stroke volume and flow acceleration and might suggest that hypoestrogenism has a direct effect on cardiovascular performance.

Adult↗
PubMed1993

Correlates of military tank simulator sickness.

A military tank driving simulator is currently widely used as a training aid for tank drivers. The purpose of this study was to investigate the relationship between possible correlates of simulator sickness and the occurrence of sickness and performance test results among simulator drivers. The average number of motion sickness-like symptoms reported after driving the simulator among subjects with a history of susceptibility to motion sickness was 3.4, significantly higher than the average of 1.6 reported among subjects who did not report previous susceptibility to motion sickness (p < 0.05). Subjects driving the simulator while screen image quality was disturbed had a longer reaction time (42.0 s) than when driving the simulator without screen interferences (18.4 s, p = 0.001). Subjects driving the simulator for a short period had the same number of symptoms as did those driving for a longer period, but had better digit symbol test results. There was no statistically significant association between the development of sickness and tank driving experience. Suggested countermeasures are expected to prevent simulator sickness among some of the simulator trainees and to make simulator training more effective.

Adolescent↗
PubMed1992

Usefulness of heavy isometric exercise echocardiography for assessing left ventricular wall motion patterns late (> or = 6 months) after acute myocardial infarction.

The aim of this prospective study was to determine the effects of heavy isometric exercise on left ventricular (LV) wall motion patterns in patients who have had myocardial infarction, and to compare heavy isometric exercise with dynamic exercise for competence in eliciting LV wall motion abnormalities at equivalent rate-pressure products. Echocardiography was performed in 42 patients during supine bicycle ergometry and during heavy dynamometer stretching at 50% of maximal voluntary contraction. Systemic vascular resistance increased from 1,484 to 1,649 dynes s cm-5 (p < 0.05) during isometric exercise, and decreased significantly during dynamic exercise. Wall motion abnormalities or new asynergy were induced by isometric exercise in 120 segments, 107 of which (89%) showed significant stenosis of the perfusing coronary artery. Hypokinesia was the dominant pattern in the range of 76 to 90% narrowing; akinesia was dominant at 91 to 100% narrowing. Wall motion abnormalities were also documented in 13 segments (11%) assumed to be supplied by vessels with nonsignificant stenosis. Dyskinesia, seen in 7% of the segments, was equally distributed between both groups with significant stenosis. Sensitivity and positive predictive value in identifying specific coronary vessel disease was similar for both isometric and dynamic exercise. In conclusion, heavy isometric exercise in patients who have had myocardial infarction induces wall motion abnormalities of a severity proportional to the degree of coronary narrowing. This exercise method is similar to dynamic exercise for ability in identifying obstructions in a specific vessel. Furthermore, when compared at near-equal rate-pressure products, heavy isometric exercise is far superior in sensitivity to dynamic exercise.

Adult↗
PubMed1992

Quantification of the disorder in network-modified silicate glasses.

Local order in silicate glasses has been observed by many experimental techniques to be similar to that in crystalline materials. Details of the intermediate-range order are more elusive, but essential for understanding the lack of long-range symmetry in glasses and the effect of composition on glass structure. Two-dimensional 17O dynamic-angle-spinning nuclear magnetic resonance experiments reveal intermediate-range order in the distribution of inter-tetrahedral (Si-O-Si) bond angles and a high degree of order in the disposition of oxygen atoms around the network-modifying cations.

Glass↗
PubMed1992

Sidebands in dynamic angle spinning (DAS) and double rotation (DOR) NMR.

A theory of dynamic angle spinning (DAS) and double rotation (DOR) NMR is described using average Hamiltonian and irreducible tensor methods. Sideband intensities in DAS and DOR spectra are analyzed by both the moment and Bessel function methods, and general formulae are derived. Results show that the DAS moments depend on the relative rotor phase between the first and the second evolution periods, whereas the second and third DOR moments are independent of the relative phase between the inner and outer rotors. Sideband intensities in DAS spectra also depend on the relative rotor phases between evolution at the first and second angles, as well as on the ratio of time spent at each angle. Sideband intensities and phases in DOR spectra are related to the relative rotor phases between the inner and outer rotors, and the sideband pattern is determined by the ratio of the inner and outer rotor spinning speeds. An inversion symmetry of the odd numbered DOR sidebands at the relative rotor phase gamma r = 0 degree, 180 degrees permits the elimination of these sidebands. Finally, numerical simulations are implemented and shown to agree with experimental results. Quadrupolar parameters can therefore be recovered either by calculating the second and third moments or by simulating the sideband intensities and phases.

Magnetic Resonance Spectroscopy↗
PubMed1992

Solid-state 27Al NMR studies of aluminophosphate molecular sieves. Enhanced resolution by quadrupole nutation and double-rotation.

Solid-state 27Al NMR spectra of several aluminophosphate molecular sieves have been recorded with conventional magic-angle spinning (MAS), double-rotation (DOR) and quadrupole nutation with fast MAS. Enhanced resolution was obtained in the quadrupole nutation experiment at certain radiofrequency pulse strengths. This extra resolution can be comparable to that attainable using DOR, and does not introduce spinning sidebands.

Aluminum↗
PubMed1992

Are tiny polyps important when found on sigmoidoscopy in asymptomatic people?

To determine the occurrence of synchronous large bowel polyps located proximal to the sigmoid, in persons undergoing screening flexible sigmoidoscopy, we examined those who had diminutive polyps (less than or equal to 0.5 cm) as the only finding in the distal colon by further colonoscopy. One hundred one asymptomatic persons (mean age 61 +/- 13 years) had 143 diminutive polyps; a single polyp was found in 76%, and 64% of all polyps were located in the rectum. Thirty (21%) were hyperplastic and 86 (60%) were neoplastic, including 14 with moderate and one with severe dysplasia. The others were inflammatory (five) or unclassified (hot biopsy changes or normal mucosa, 14 polyps), and eight were lost before processing. Colonoscopy revealed that 16 (16%) of the 101 patients had 21 additional polyps proximally, mostly less than 1 cm in diameter. These included one hyperplastic and 18 neoplastic polyps, and two specimens showed hot biopsy changes. Age, histological type, number or location of the index diminutive polyps, were not associated with proximal lesions. We question whether immediate colonoscopy is justified in asymptomatic patients with only diminutive polyps at flexible sigmoidoscopy.

Adult↗
PubMed1992

Neurocirculatory asthenia revisited: elevated arterial pressure at presentation is a marker for subsequent hypertension.

Neurocirculatory asthenia (NCA) is a fairly common functional disorder often encountered among military recruits. Symptoms in NCA tend to appear in waves, and are believed to disappear completely with the passage of time. Elevated arterial pressure is known to occur as part of the various haemodynamic manifestations of NCA. However, the exact prevalence of hypertension, as well as its long-term prognosis, is still unknown. The present case-control study was designed to address these two issues. The target population consisted of 370 patients with NCA representing two separate cohorts: patients diagnosed in 1979, 10 years prior to this study, and patients diagnosed in 1983-84, 5 years prior to the study. An overall 20% prevalence rate of mild hypertension at diagnosis was calculated for the entire study population. In total, 100 patients representing equal numbers of hypertensive and matched normotensive subjects from each cohort were re-evaluated. At follow-up, hypertension was present in 27% (1979 cohort) and 30% (1983-84 cohort) of patients originally considered to be hypertensive. Hypertension was either non-existent (1979 cohort) or limited to a single case (1983-84 cohort) among originally normotensive individuals. In parallel, resting heart rate was higher in the hypertensive subjects of the 1979 cohort both at presentation (85.5 +/- 3.2 vs. 73.7 +/- 2.4 beats min-1; P less than 0.005) and at follow-up (79.6 +/- 3.2 vs. 70.0 +/- 2.5 beats min-1; P less than 0.01). These results indicate that hypertension complicates the diagnosis of NCA in 20% of patients and that, contrary to common belief, it cannot be regarded as another transient manifestation of this condition. Thus hypertension in this context is, as in the younger members of the population in general, a major risk factor for lifelong hypertension, rather than an inconsequential phenomenon.

Adolescent↗
PubMed1992

Disseminated intravascular coagulation with renal and liver damage as the predominant manifestations of recurrent relapses in systemic juvenile rheumatoid arthritis.

Relapses of systemic juvenile rheumatoid arthritis associated with intravascular coagulation are rare. This paper describes a patient who, over a two year period, had two relapses, each accompanied by evidence of liver and renal damage and disseminated intravascular coagulation. The patient was not receiving non-steroidal anti-inflammatory drugs, and all laboratory and clinical manifestations of her disease rapidly resolved after treatment with prednisone. It is therefore believed that the hepatocellular damage, in addition to the disseminated intravascular coagulation, was a direct manifestation of disease activity. A possible pathogenic role for tumour necrosis factor is suggested.

Adult↗
PubMed1992

Colonoscopy in patients aged 80 years or older and its contribution to the evaluation of rectal bleeding.

Colonoscopies performed in patients aged 80 years or older at the Sheba Medical Center were analysed according to the primary indication for the procedure: 101 colonoscopies were performed because of rectal bleeding of at least 2 months duration, and 335 for all other indications. Carcinoma of the large bowel was found in 29 (28.7%) bleeders, with the rectum being the most frequently involved site (12 patients). Among the non-bleeders, the prevalence of cancer was significantly lower (33 cases, 9.8%; P less than 0.001), and rectal carcinoma was less common (five patients, P = 0.04), but proximal tumours were more frequent. Of patients with cancer who had operations, the majority (72%) had a tumour confined to the bowel wall (Dukes A or B). The rate of adenomas was similar for both groups (34% vs 29%). The non-bleeders complained more frequently of abdominal pain or a change in bowel habits as compared to the bleeders, but both groups had similar rates for anaemia and weight loss. In all, 47% of these octogenarians with cancer, and 26% with adenomas were referred for colonoscopy because of rectal bleeding. This procedure was found to be safe in old age, as we recorded only four (0.9%) non-fatal complications among our series, a similar figure to the overall incidence of complications at our Institute. In conclusion, our data indicate that rectal bleeding in octogenarians warrants a complete colonic investigation, preferably by total colonoscopy.

Aged↗