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At least 343 records · Page 19Linked to original sources
PubMed1993

Effect of red blood cell shape on oxygen transport in capillaries.

A mathematical model of oxygen (O2) transport within a capillary utilizes axisymmetric red blood cell (RBC) shapes that were predicted theoretically by Zarda et al. in 1977. Chemical kinetics and both free and facilitated diffusion of O2 are accounted for in this time-dependent model. The finite-element method is used to solve the governing partial differential equations. It is found that the shape of RBCs, characterized by the shape parameter theta adapted from Zarda et al., affects such important O2 transport characteristics as capillary wall O2 flux and hemoglobin (Hb) saturation. At an RBC residence time (time for an RBC to travel from the capillary inlet to a given point) of 0.22 s, a change in the shape parameter theta from 0 (undeformed cell) to 26 (parachute-shaped cell) decreases the spatially averaged O2 flux by 26%. The dependence of O2 flux on RBC shape diminishes as the RBC residence time increases. The difference in Hb saturation at the RBC residence time of 0.22 s can be as large as 10% for different values of theta. The mass transfer Nusselt number, which is inversely proportional to transport resistance, decreases with increases in theta. The fractional transport resistance in the plasma region accounts for approximately 65-80% of the total intracapillary resistance. Calculations show that local chemical equilibrium in the O2-Hb chemical reaction is attained everywhere except within a thin boundary layer adjacent to the erythrocyte membrane, where significant deviation from chemical equilibrium occurs.

Animals↗
PubMed1996

NGF regulatory role in stress and coping of rodents and humans.

Nerve growth factor (NGF) is a polypeptide growth factor which exerts trophic and differentiative effects on specific peripheral and central populations of neurons. Recent data showing that various cellular types of the endocrine and immune systems are able to synthesize and release NGF have suggested that this neurotrophic factor may also play an important role in vertebrate physiologic homeostasis. Previous studies using a mouse model of aggressive behavior have shown that NGF levels increase in both plasma and the CNS following intermale agonistic encounters. More recently, we have extended this research area to include other species: in particular, humans. The data now available indicate that labour and lactation, or the occurrence of a stressful event such as the very first jump with a parachute causes in NGF plasma levels as well as changes in the distribution of NGF receptors on lymphocytes. This review aimed to outline the current understanding of NGF role in vertebrates in stress-related events.

Adaptation, Psychological↗
PubMed1983

Some effects of emotion on the normal and abnormal heart.

Increased heart rate and catecholamine secretion are induced by certain emotions. Automobile driving in busy city traffic, racing driving, speaking before an audience, and parachute jumping are associated with sinus tachycardia 120-180 per minute, and increase in the plasma levels of adrenaline and/or noradrenaline. Electrocardiographic changes, chiefly ST depression, may occur in a small proportion of persons without ischemic symptoms and with normal resting tracings. Patients with clinical coronary disease, angina, and ischemic ST changes and arrhythmias may be induced by the emotional stimuli associated with car driving and public speaking; plasma catecholamine levels are increased in proportion to the intensity of the stimulus. beta-blockade reduces the tachycardia, and prevents in whole or in part the ST changes, arrhythmia and symptoms associated with emotional challenge to the heart. We would like to leave the reader with a final morsel of food for thought. Emotion may parallel exercise in its ability to accelerate the heart rate up to 180 per minute in healthy subjects, comparable to the maximum reached during physical exertion. Thus, there are good grounds to advise persons at risk not only against violent exercise but also against exposing themselves to intense emotion. At the same time, we would not advocate emotional overprotection, and we believe our ideas would be misinterpreted if healthy persons were to be deterred on the grounds of apprehension or nervousness from facing up to reasonable everyday professional or social challenges.

Adult↗
PubMed1990

Cross-sectional echocardiography in the diagnosis of atrioventricular septal defect.

Between 1983-1988 cross-sectional echocardiography was performed in 63 patients having an atrioventricular septal defect with common atrioventricular orifice. We excluded from this study all those patients with separate right and left orifices ("ostium primum" defects), those with isomerism of the right and left atrial appendages, those with univentricular atrioventricular connexions and those with discordant atrioventricular and ventriculo-arterial connexions. Parasternal long- and short-axis views, apical 4-chamber views and subcostal long-axis views were employed in all patients. In the last 26 cases, we also obtained the subcostal short-axis view. Nineteen patients showed ventricular dominance, with the right ventricle being dominant in 15. Ten patients had an associated defect in the oval fossa, while the atrial septum was partially or completely absent in the other 53. A ventricular septal defect was observed in all, but it was small in 10 and multiple in 2. Attachments of the superior and inferior bridging leaflets to the crest or the right side of the ventricular septum were seen in 32 cases. The inferior leaflet was hypoplastic in 19 patients. There was narrowing of the left ventricular outflow tract in 8 patients, and obstruction of the right ventricular outflow tract in 3. Abnormal attachment of the right portion of the common valvar orifice was present in 2 cases. A solitary papillary muscle supporting the left ventricular component of the common valve was seen in 6 cases producing a parachute-like arrangement. Our study shows that cross-sectional echocardiography is an excellent technique for the analysis of this anomaly.

Child, Preschool↗
PubMed1984

Self-report and heart rate responses to a stressful task.

Data were obtained from a risk task, the zipwire, in order to examine self-report and heart rate responses of males and females. Using this task, heart rate data demonstrated similar patterns to those found in earlier parachuting studies. ANOVAs demonstrated significant differences between sexes in self-report measures, but no significant differences in heart rate. In addition, examination of the relationships between heart rate and self-report showed a positive correlation for the women, while there was a negative correlation for the men.

Adolescent↗
PubMed1995

Beta-endorphin, but not substance-P, is increased by acute stress in humans.

The role of neuropeptides in the psychoneuroendocrinological stress response is largely unknown. In this study the effect of acute psychological stress on beta-endorphin and substance-P plasma concentrations was investigated and further the effect of different anxiety levels or control attributions on beta-endorphin or substance-P levels were determined. Blood samples were obtained from 47 inexperienced tandem-parachutists 2 h before, immediately after, and 1 h after a parachute jump and plasma concentrations of beta-endorphin and substance-P were analysed. Anxiety levels and control attributions were assessed by psychometric scales. Whereas substance-P concentrations seemed to be unaffected by the jump stress, there was a transient but significant increase in beta-endorphin levels immediately after jumping. However, subjects higher in state-anxiety at the point of jumping (exit) displayed higher substance-P values at all three time points compared to the "low-anxiety" jumpers. In addition, stress-induced beta-endorphin secretion was dependent on subjective control attributions.

Adult↗
PubMed2006

[Urethrovesical anastomosis in retropubic radical prostatectomy].

Urethrovesical anastomosis is the most codified step in radical prostatectomy. Most of the time, the bladder neck diameter makes it possible to carry out a congruent anastomosis. Otherwise one has to resort either to the tennis racket closure or the parachute technique. Stenosis will remain an exceptional complication if the technique is applied with strictness and precision.

Anastomosis, Surgical↗
PubMed2005

Operative results and outcomes in children with Shone's anomaly.

BACKGROUND: The outcome of children with multilevel left heart obstructions with mitral valve involvement (Shone's anomaly) is generally poor. This study reviews our results and outcomes in patients with staged repair for left ventricular outflow tract obstruction (LVOTO) and mitral valve reconstruction. METHODS: A total of 27 children underwent staged repair for Shone's anomaly between 1978 and 2003. The mean age at the first operation was 9.0 months (range, 2 days to 3 years). Mitral stenosis was present in all; with supravalvular mitral ring (n = 11), mitral valve abnormalities including parachute mitral valve, fused chordae, single papillary muscle (n = 10), and "typical" (Ruckman & Van Praagh) congenital mitral stenosis (n = 14). The LVOT obstruction features included subaortic stenosis (n = 16), valvar aortic stenosis (n = 7), bicuspid aortic valve (n = 24), and coarctation (n = 18). All 27 patients underwent 94 surgical procedures, including 22 mitral operations and 48 LVOT operations. RESULTS: There were no operative deaths at the first operation. Mean follow-up was 4.7 +/- 4.4 years (range, 6 months to 15 years). There were three late deaths (11%). All late deaths were secondary to severe mitral valve disease. Overall 15-year actuarial survival was 89%. All surviving patients are in New York Heart Association functional class I or II. CONCLUSIONS: Patients with Shone's anomaly are seen with a wide spectrum of major anatomic and hemodynamic abnormalities. A favorable outcome is possible for most. Operative mortality is adversely affected by the severity of mitral valve disease, the degree of left ventricular hypoplasia, and the need for multiple operative procedures.

Adolescent↗
PubMed2006

Neonatal surgical aortic commissurotomy: predictors of outcome and long-term results.

BACKGROUND: The objective of this study was to review our institutional experience concerning neonatal aortic commissurotomy and to identify predictors of outcome. METHODS: From January 1, 1990, to January 1, 2005, 65 neonates were referred for critical aortic stenosis. Among these 36 consecutive patients underwent surgical valvotomy by the same surgeon and 16 patients had balloon valvotomy. We examined clinical records to establish determinants of outcome and illustrate long-term results. RESULTS: In the surgical group 6 patients had nonstenotic parachute mitral valve, 6 had aortic coarctation, 13 had endocardial fibroelastosis; and 15 had depressed fractional shortening. In the balloon valvotomy group most infants had associated mitral stenosis (n = 7), small aortic annulus (n = 5), multiple anomalies (n = 2), endocardial fibroelastosis (n = 9), and depressed fractional shortening (n = 13). In the surgical group global mortality was 19%; 47% in infants with depressed fractional shortening and 0% in infants with normal fractional shortening. Mortality in the balloon valvotomy group was 56%. Low fractional shortening, low mean aortic gradient, endocardial fibroelastosis, and small aortic annulus were associated with fatal outcome. In the surgical group 6 patients needed Ross operation at a median interval of 4 years from commissurotomy. In the balloon valvotomy group 3 patients needed early mitral replacement and 5 aortic valve surgery. At a median follow-up of 6 years, all children are in New York Heart Association class I, all have a normal ventricular function, 2 have aortic restenosis, and 5 have at least moderate aortic incompetence. CONCLUSIONS: In a selected population of neonates with isolated aortic stenosis, surgical valvotomy offers an excellent long-term outcome to patients with a normokinetic left ventricle, while patients with a hypokinetic left ventricle have a poor outcome. Balloon valvotomy offers poor results when performed in patients with complex anomalies.

Aortic Valve Stenosis↗
PubMed2006

Particle method for computer simulation of red blood cell motion in blood flow.

A particle method for the computer simulation of blood flow was proposed to analyze the motion of a deformable red blood cell (RBC) in flowing blood plasma. The RBC and plasma were discretized by particles that have the characteristics of an elastic membrane and a viscous fluid, respectively. The membrane particles were connected to their neighboring membrane particles by springs, and the motion of the particles was determined on the basis of the minimum energy principle. The incompressible flow of plasma that was expressed by the motion of the fluid particles was determined by the moving-particle semi-implicit (MPS) method. The RBC motion and plasma flow were weakly coupled. The two-dimensional simulation of blood flow between parallel plates demonstrated the capability of the proposed method to express the blood flow phenomena observed in experiments, such as the downstream motion of the RBC and the deformation of the RBC into a parachute shape.

Blood Circulation↗
PubMed2005

Singular case of shooting a football fan with a signal rocket.

The authors present a very rare case of fatal injuries resulting from shooting a parachute signal rocket with a hand operated launcher of signal pistol kind by pseudo-football fans. A 16-year-old football fan sustained extensive thermal burn of his lower extremities and abdomen, lacerated wound of his left thigh with a deep signal rocket-shot canal which caused injuries in subcutaneous tissue, fascia and both medial and posterior muscles of the thigh as well as injured both femoral vein and artery with subsequent hemorrhagic, burn and traumatic shocks. In spite of specialistic surgical treatment, the victim was not rescued. Analysis of medical documentation and our autopsy results were supplemented with an expert's opinion on physicochemical examinations supported by photographic documentation.

Abdominal Injuries↗
PubMed2004

A systematic genome-wide screen for mutations affecting organogenesis in Medaka, Oryzias latipes.

A large-scale mutagenesis screen was performed in Medaka to identify genes acting in diverse developmental processes. Mutations were identified in homozygous F3 progeny derived from ENU-treated founder males. In addition to the morphological inspection of live embryos, other approaches were used to detect abnormalities in organogenesis and in specific cellular processes, including germ cell migration, nerve tract formation, sensory organ differentiation and DNA repair. Among 2031 embryonic lethal mutations identified, 312 causing defects in organogenesis were selected for further analyses. From these, 126 mutations were characterized genetically and assigned to 105 genes. The similarity of the development of Medaka and zebrafish facilitated the comparison of mutant phenotypes, which indicated that many mutations in Medaka cause unique phenotypes so far unrecorded in zebrafish. Even when mutations of the two fish species cause a similar phenotype such as one-eyed-pinhead or parachute, more genes were found in Medaka than in zebrafish that produced the same phenotype when mutated. These observations suggest that many Medaka mutants represent new genes and, therefore, are important complements to the collection of zebrafish mutants that have proven so valuable for exploring genomic function in development.

Animals↗
PubMed2006

Nerve growth factor serum concentrations rise after successful cognitive-behavioural therapy of generalized anxiety disorder.

Generalized anxiety disorder (GAD) is a chronic stress disease with permanent physical tension and cognitive strain. Raised nerve growth factor (NGF) serum levels were reported as an acute stress reaction in soldiers before their first parachute jump even before the rise in cortisol. Taking GAD as a clinical model of chronic stress, we measured NGF in the serum of 22 patients with GAD before and after cognitive-behavioural therapy (CBT) and compared them to those of healthy normal controls. Treatment response was tested by the values of the State and Trait of Anxiety Inventory (STAI) and the Hamilton Anxiety Scale (HAM-A) as treatment outcome variables. The NGF values of patients and controls were similar at baseline (p=0.8941); however, with successful treatment, corresponding to a mean reduction in the HAM-A by more than 50% and a reduction in the clinical global impression scale (CGI) median from 4 to 1, the patients' NGF serum concentrations rose significantly (p=0.0006) which might correspond to an altered stress reaction, possibly contributing to good therapeutic response with CBT. There were 3 patients with a HAM-A decrease of less than 15%. In those patients NGF rose only marginally. Hence, the increase in serum NGF seems to indicate good treatment response.

Adolescent↗
PubMed2004

Systematic evaluation of stone basket dimensions.

OBJECTIVES: To evaluate 17 commercial stone baskets for characteristics we believe are favorable for stone extraction. METHODS: The ACMI (Sur-Catch 3.0), Bard (Dimension 3.0), Boston Scientific (Zero-tip 2.4/3.0, Segura 2.4/3.0, Gemini 3.0, Parachute 3.1), Cook (N-Circle 2.2/3.0/3.2, N-Force 3.2, Flatwire 2.0), and Sacred Heart (Halo 1.9, Vantage 2.4, Summit 3.0, Hercules 3.0) were tested in triplicate. The maximal basket width was measured with a digital caliper as the basket length was opened in 0.5 to 2-mm increments using a mechanical caliper under optical light microscope visualization. Baskets were rated for the linearity of opening and length at which the target basket width (5 mm) was reached. RESULTS: The only basket to exhibit linear opening was the N-Circle. All other baskets opened in an exponential fashion, with the initial excursion in length corresponding to little change in basket width, followed by a rapid increase in basket width as the basket extended further. The N-Circle 2.2F, 3.0F, and 3.2F baskets reached the target basket width at a basket length of 9.4, 9.7, and 9.6 mm, respectively. As a group, the tipless baskets opened more rapidly to the target basket width (9.4 to 14.8 mm) than did the flat-wire baskets (17.5 to 22.7 mm) or helical baskets (18.6 to 24.8 mm). CONCLUSIONS: A basket that requires a shorter basket excursion to reach a 5-mm width will be easier to maintain in the field of view. Linear basket opening provides the operator with greater control to engage a stone. After closure of a basket on a 5-mm stone, the larger the basket length dimension, the greater the likelihood the calculus may escape.

Equipment Design↗
PubMed1996

Occlusion of large atrial septal defects with a centering buttoned device: early clinical experience.

A feasibility clinical study was conducted for the transcatheter occlusion of large ostium secundum atrial septal defects with the centering buttoned device. The centering buttoned device is a modification of the regular buttoned device in which a centering counter-occluder is sutured at the central 40% portion of the occluder. During centering it is stretched, forming a parachute-shaped structure and pulling the occluder over the center of the defect. During buttoning, the counter-occluder forms a double figure eight, opposing the right atrial side of the atrial septum. Occlusion was performed in 12 patients aged 6 to 56 years. All had been rejected for transcatheter occlusion by the regular buttoned device, because of either their defect size or the lack of adequate septal rim. The defect size varied between 23 and 31 mm, and the device size varied between 45 and 60 mm. Nine had immediate effective occlusions of their defects and three residual shunts. One patient with unbuttoning had hemolysis at 2 weeks and underwent surgery. Early results of the transcatheter occlusion of large atrial septal defects are promising, and larger clinical trials are justified.

Adolescent↗
PubMed2004

Accessory mitral valve tissue causing severe left ventricular outflow tract obstruction in an adult.

Accessory mitral valve (AMV) is a rare cause of left ventricular outflow tract (LVOT) obstruction and is extremely rare in adults. We report a case of an older adult with an AMV that caused severe LVOT obstruction. A parachute-like piece of tissue (the AMV) protruding into the LVOT during systole was first detected in a 45-year-old woman by echocardiography. Because the pressure gradient and dyspnea gradually progressed, she finally underwent a successful operation for removal when she was 48 years old.

Adult↗
PubMed1997

Multiple left heart obstructions (Shone's anomaly) with mitral valve involvement: long-term surgical outcome.

BACKGROUND: The outcome of children with multilevel left heart obstructions (Shone's anomaly) is generally poor. Literature is scarce, consisting mainly of case reports. The mitral disease may be the predominant factor affecting outcome. METHODS: Surgical results in 19 consecutive patients are presented, with a median follow-up of 8 years. Mitral stenosis was present in all, with parachute deformity in 12 patients. Supramitral rings were found in 9 patients. Other features included subaortic stenosis (15 patients), valvar aortic stenosis (9), bicuspid aortic valve (16), and coarctation (13 patients). The patients underwent 46 surgical procedures, including 18 mitral operations (9 replacements, 9 repairs). RESULTS: There were three in-hospital (16%) and two late (10.5%) deaths. Of the 5 nonsurvivors, 4 patients (80%) had predominant mitral disease and moderate to severe pulmonary hypertension, versus 4 (28.5%) and 5 (36%) survivors, respectively (p = not significant). Valve repair was the final procedure in 9 survivors. The other 5 patients had repeated valve replacements (1), aortoventriculoplasty with valve replacements (2), or no mitral operation (2). Freedom from mitral reoperation was 78% (7 of 9 patients) after repair procedures and 43% (3 of 7 patients) after replacement. At follow-up, 10 patients (71.4%) are in New York Heart Association functional class I and the other 4 in class II and III. Six (43%) await reoperation due to recurrent aortic (4) or subaortic (1) stenosis and recoarctation (2). Echocardiography reveals mild mitral stenosis or regurgitation in 3 patients after repair (33%). Four are considered free of residual disease (21% of all). CONCLUSIONS: Late outcome in Shone's anomaly seems to correlate with the predominance of mitral valve involvement and the degree of pulmonary hypertension. Valve repair is indicated whenever feasible and should be considered before the occurrence of pulmonary hypertension.

Aortic Coarctation↗
PubMed1998

Surgical repair of the congenitally malformed mitral valve in infants and children.

BACKGROUND: Mitral valve remodeling techniques were applied to 26 infants and children (mean age, 6.0 years, range, 0.4 to 15.9 years) with various forms of congenital mitral valve disease over a 7-year period. Patients with atrioventricular canal, L-transposition and single ventricle were excluded. Intraoperative transesophageal echocardiography (TEE) was utilized to assess the repair and guide the need for immediate intervention. METHODS: Twenty-one patients had mitral regurgitation: 10 with cleft anterior mitral leaflet, 7 with annular dilatation, 1 with normal leaflets with an obstructing cord, 2 with prolapsed leaflets and elongated cords, and 1 with restricted leaflet motion, normal papillary muscles, and shortened cords. Of the 5 mitral stenosis patients, 3 had supravalvular mitral ring, 1 had midvalvular mitral ring, and 1 had a parachute valve. Three of the mitral stenosis patients had additional stenotic lesions. Concurrent repair of associated lesions was performed in 21 patients (78%). RESULTS: Operative mortality was 3.8% (n = 1). There were no late deaths. Immediate rerepair in 4 patients resulted in improved function. All mitral stenosis patients improved. A total of 20 mitral regurgitation patients (95%) improved; 1 required mitral valve replacement. Mean follow-up is 31 months (range, 2 to 81 months). All patients are in New York Heart Association functional class I or II. CONCLUSIONS: Mitral valve repair can be successfully performed in infants and children with excellent short- and midterm results. Assessment using transesophageal echocardiography can guide the necessity for immediate rerepair to achieve improved function.

Adolescent↗