Dynamics and transport in mean-field coupled, many degrees-of-freedom, area-preserving nontwist maps.

Area-preserving nontwist maps, i.e., maps that violate the twist condition, arise in the study of degenerate Hamiltonian systems for which the standard version of the Kolmogorov-Arnold-Moser (KAM) theorem fails to apply. These maps have found applications in several areas including plasma physics, fluid mechanics, and condensed matter physics. Previous work has limited attention to maps in 2-dimensional phase space. Going beyond these studies, in this paper, we study nontwist maps with many-degrees-of-freedom. We propose a model in which the different degrees of freedom are coupled through a mean-field that evolves self-consistently. Based on the linear stability of period-one and period-two orbits of the coupled maps, we construct coherent states in which the degrees of freedom are synchronized and the mean-field stays nearly fixed. Nontwist systems exhibit global bifurcations in phase space known as separatrix reconnection. Here, we show that the mean-field coupling leads to dynamic, self-consistent reconnection in which transport across invariant curves can take place in the absence of chaos due to changes in the topology of the separatrices. In the context of self-consistent chaotic transport, we study two novel problems: suppression of diffusion and breakup of the shearless curve. For both problems, we construct a macroscopic effective diffusion model with time-dependent diffusivity. Self-consistent transport near criticality is also studied, and it is shown that the threshold for global transport as function of time is a fat-fractal Cantor-type set.

Prosthetic valve endocarditis caused by Brucella melitensis. A report of four cases successfully treated with tetracycline, streptomycin, and sulfamethoxazole and trimethoprim plus valve replacement.

Optimal treatment of prosthetic valve endocarditis due to Brucella melitensis is unknown. The presence of ring abscess makes extensive surgical débridement and valve replacement essential steps of management. Antimicrobial therapy with tetracycline hydrochloride plus streptomycin sulfate or sulfamethoxazole and trimethoprim can achieve the sterilization of infected cardiac tissue. Late bland periprosthetic leaks occur frequently. Reoperation can be safely performed after a period of antimicrobial therapy. Prolonged treatment with doxycycline hyclate seems advisable.

Potentiation of glucagon secretion by serotonin antagonists in man.

To study the possible implication of endogenous serotonin in the control of glucagon secretion in man, normal volunteers were subjected to alpha-cell stimulation before and after oral treatment with serotonin antagonists (cyproheptadine and methysergide) and with an inhibitor of serotonin synthesis (para-chlorophenylalanine, PCPA). After administration of cyproheptadine (16 mg daily, for two days) the glucagon responses to arginine (N=12) and to insulin-induced hypoglycemia (N=9) were more marked than in the control experiments (differences between maximal elevations: +165 pg/ml, P less than 0.0001, and +197 pg/ml, P less than 0.02, respectively). After methysergide treatment (9 mg daily, for two days), a potentiation of arginine-provoked glucagon secretion was also observed (+260 pg/ml, P less than 0.002; N=7). Similarly, after PCPA administration (2 g daily, for four days) the alpha-cell responsiveness to both aminogenic (N=12) and hypoglycemic (N=7) stimuli was enhanced (+108 pg/ml, P less than 0.05, and +164 pg/ml, P less than 0.05, respectively). Since glucagon secretion is potentiated by treatment with drugs which either antagonize serotonin action or inhibit its synthesis, the suggestion can be made that endogenous serotonin modulates alpha-cell function in man by acting as an inhibitor.

Long-term comparative analysis of the Björk-Shiley and Hancock valves implanted in 1975.

The long-term results in all patients undergoing isolated mitral, aortic, or double mitral-aortic heart valve replacement operated upon in 1975 has been retrospectively analyzed. A total of 153 patients received the standard Björk-Shiley (flat pyrolytic disc) mechanical prostheses and 150 patients received the noncomposite Hancock porcine xenograft. Overall operative mortality was not significantly different between groups. All patients receiving a Björk-Shiley prosthesis, but none in the Hancock group, received long-term anticoagulant therapy. Medium and long-term actuarial survival rates (5 and 10 years postoperatively) were comparable for the two groups (88% for Björk-Shiley and 84% for Hancock [NS] at 5 years; 86% for Björk-Shiley and 80% for Hancock at 10 years [NS]). The incidence of systemic embolism was similar in the two groups (1.6% +/- 0.4% per patient-year for the Björk-Shiley group and 1.3% +/- 0.3% per patient-year for the Hancock group [NS]). Also the incidence of endocarditis was similar (0.6% +/- 0.2% per patient-year for the Björk-Shiley group and 0.8% +/- 0.3% per patient-year for the Hancock group [NS]). In the Hancock group the overall incidence of reoperations was significantly higher than in the Björk-Shiley group (4.2% +/- 0.6% per patient-year versus 0.9% +/- 0.3% per patient-year (p = 0.001). The major cause for reoperation in the Hancock group was primary tissue failure (3% +/- 0.5% per patient-year). In the Björk-Shiley group the major cause of reoperation was valve thrombosis (0.5% +/- 0.2% per patient-year). Therefore, accepting the fact that other bioprostheses may behave differently from the Hancock noncomposite xenograft, we currently restrict our indications for valve replacement with bioprostheses.

Comparative clinical results with Omniscience (STM1), Medtronic-Hall, and Björk-Shiley convexo-concave (70 degrees) prostheses in mitral valve replacement.

The intermediate clinical results of 289 patients undergoing isolated mitral valve replacement with three different low-profile mechanical prostheses have been retrospectively analyzed and compared. Between June, 1980, and September, 1983, 70 patients received the Omniscience prosthesis, 159 patients the Medtronic-Hall valve, and 60 patients the convexo-concave 70 degree Björk-Shiley prosthesis. Hospital mortality was 15% for the Björk-Shiley group, 4.4% for the Medtronic-Hall group, and 7.1% for the Omniscience group. Cumulative follow-up was 88 years (mean 1.7 years) for the Björk-Shiley, 229 years (mean 1.5 years) for the Medtronic-Hall, and 223 years (mean 3.3 years) for the Omniscience group. All patients were placed on a program of anticoagulant therapy (dicumarol) postoperatively. Actuarial survival rates (+/-SE) 2 years postoperatively were comparable for the three groups: Björk-Shiley, 90% +/- 4.7%; Medtronic-Hall, 93% +/- 2.2%; and Omniscience, 88% +/- 4.1% (p = NS). Late mortality, expressed at linearized rates (percent patient-year +/-SE), was 3.4% +/- 1.9% for the Björk-Shiley group, 1.7% +/- 0.8% for the Medtronic-Hall group, and 3.6% +/- 1.2% for the Omniscience group (p = NS). Actuarially determined rates of freedom from thromboembolic complications (systemic embolism and valvular thrombosis) 2 years postoperatively were 97% +/- 2.2% for the Björk-Shiley group, 94% +/- 2.1% for the Medtronic-Hall, and 84% +/- 4.7% for the Omniscience group (p = 0.05, Omniscience versus Medtronic-Hall; p = 0.02, Omniscience versus Björk-Shiley) The actuarial probability of being free from reoperation 2 years postoperatively was 92 +/- 3.5 for the Björk-Shiley group, 92 +/- 2.9 for the Medtronic-Hall group, and 82 +/- 3.9 for the Omniscience group (p = 0.04). The major cause for reoperation in the Omniscience group was valve thrombosis (seven patients), yielding a linearized incidence (+/-SE) of 3.1 +/- 1.1 (p = 0.01). No statistically significant differences were obtained regarding the incidence of prosthetic infective endocarditis or perivalvular leak. Overall rates of anticoagulant-related hemorrhage were comparable for the three groups.

Results and complications with the Omniscience prosthesis.

A clinical trial with the Omniscience heart valve was conducted from June, 1980, until May, 1981. In this period 166 patients underwent heart valve replacement: mitral valve replacement (MVR) 70 patients, aortic valve replacement (AVR) 37, and combined mitral-aortic valve replacement (M/AVR) 59 patients. There were 20 hospital deaths, for a mortality of 12%. Total follow-up was 226 patient-years (range 6 to 28 months, mean 18 months). There were eight late deaths (MVR 4.6%, AVR 3.1%, and M/AVR 8.1%). All patients were taking oral anticoagulants. The incidence of valve-related complications (expressed as events per 100 patient-years) was as follows: Systemic embolism--MVR 2, AVR 4.7, and M/AVR 2.5; and anticoagulant complications--MVR 1.9, AVR 2.3, and M/AVR 0. The incidence of valvular dysfunction (expressed as events per 100 patient-years) was as follows: valvular thrombosis--MVR 4.8, AVR 0, and M/AVR 1.2; perivalvular leakage--MVR 1.9, AVR 2.3, and M/AVR 2.5; and infective endocarditis--MVR 0.96, AVR 0, and M/AVR 1.2. The actuarial probability of being free of valvular dysfunction 30 months postoperatively is 73% for the MVR group, 90% for the AVR group, and 71% for the M/AVR group. Despite a short follow-up, the incidence of valvular dysfunction has been significant. For this reason, we have discontinued using these prostheses for heart valve replacement.

The natural history of bacteriuria in childhood.

Urinary tract infections are common during infancy and childhood but are easily overlooked because of the unspecific symptoms. Prevention of renal scarring and its potential long-term consequences is possible but requires an increased awareness of the diagnosis, the imaging revealing anomalies within the urinary tract, and the long-term supervision. This should include any possibility of the child having pyelonephritic recurrences, which should be treated without delay; however, asymptomatic bacteriuria in infants and children is an innocent condition and screening is not recommended.

Reoperations for left-sided low-profile mechanical prosthetic obstructions.

A series of 2,474 hospital survivors of primary mitral, aortic, and double mitral-aortic valve replacement were observed for a cumulative period of 11.945 years (mean, 4.2 years; range, 0.6-14 years). The linearized incidences of reoperations for thrombotic obstructions were 0.33 +/- 0.08% for mitral valve replacement, 0.36 +/- 0.1% for aortic valve replacement, and 0.42 +/- 0.1% for double valve replacement (p = not significant). Forty-one patients (16 mitral, 12 aortic, and 13 double valve replacements) underwent a total of 44 reoperations with a mean interval of 36 +/- 29 months (range, 0.25-85 months) between operations. Diagnosis was established invasively only in 13 patients (30%). Hospital mortality at reoperation was 18% (8 patients); 28 patients (63%) required emergency surgery. The choice surgical procedures were thrombectomy for clotted aortic prostheses (18 of 24) and valve replacement for obstructed mitral valves (22 of 25; p less than .001). Rethrombosis occurred in 3 patients (1 aortic and 2 double valve replacements). At hospital admission 17 patients (38%) had prothrombin times outside therapeutic ranges (between 20 to 30% of the normal value). The incidence of reoperations for thrombosis in low-profile mechanical prostheses was unaffected by valvar position and number of prostheses implanted. Rethrombosis occurred only in previously cleaned valves, although its occurrence was not significant. The present results indicate that, as experience is gained in the diagnosis and surgical management of this complication, hospital mortality can be reduced significantly (from 37% to 4%).

The Swedish version of the Childhood Health Assessment Questionnaire (CHAQ) and the Child Health Questionnaire (CHQ).

We report herein the results of the cross-cultural adaptation and validation into the Swedish language of the parent's version of two health related quality of life instruments. The Childhood Health Assessment Questionnaire (CHAQ) is a disease specific health instrument that measures functional ability in daily living activities in children with juvenile idiopathic arthritis (JIA). The Child Health Questionnaire (CHQ) is a generic health instrument designed to capture the physical and psychosocial well-being of children independently from the underlying disease. The Swedish CHAQ CHQ were already published and therefore were revalidated in this study. A total of 129 subjects were enrolled: 69 patients with JIA (13% systemic onset, 39% polyarticular onset, 25% extended oligoarticular subtype, and 23% persistent oligoarticular subtype) and 60 healthy children. The CHAQ clinically discriminated between healthy subjects and JIA patients, with the systemic, polyarticular and extended oligoarticular subtypes having a higher degree of disability, pain, and a lower overall well-being when compared to their healthy peers. Also the CHQ clinically discriminated between healthy subjects and JIA patients, with the systemic onset, polyarticular onset and extended oligoarticular subtypes having a lower physical and psychosocial well-being when compared to their healthy peers. In conclusion the Swedish version of the CHAQ-CHQ are reliable, and valid tools for the functional, physical and psychosocial assessment of children with JIA.

[Cardiovascular surgery in Spain in 1991. Registry of operations of the Spanish Society of Cardiovascular Surgery (SECCV)]. / Cirugía cardiovascular en España en el año 1991. Registro de operaciones de la Sociedad Española de Cirugía Cardiovascular (SECCV).

The Spanish Society of Cardiovascular Surgery has sent a questionnaire to all 37 cardiovascular surgical groups to know the number and type of cardiovascular operations carried out in our country during 1991. The questionnaire was answered by 36 out of 37. In the year 1991, 21,771 cardiovascular patients have been operated upon and 10,913 interventions with extracorporeal circulation have been carried out: 42.4% in valvular disease, 37.2% in coronary and 11.2% in congenital. The number of operations was 5,415 for vascular disease, 4,627 for valvular, 3,168 for coronary, 1,896 for congenital and 3,741 for pacemaker implantation. The total number of operations in 1991 comparing to those performed during 1988 is similar; but the number of open heart operation and the number of these per cardiac unit and per million population during 1991 have increased 20.5, 13.9 and 24.3% respectively. Coronary and valvular operations have also increased 11 and 27% respectively, as well as the number of pacemaker implanted (30%). The number of congenital cases remains the same and the number of vascular operations has decreased by 7.9%.

[Cardiovascular surgery in Spain in 1992. The Registry of Operations of the Spanish Society of Cardiovascular Surgery (SECCV)]. / Cirugía cardiovascular en España en el año 1992. Registro de operaciones de la Sociedad Española de Cirugía Cardiovascular (SECCV).

The Spanish Society of Cardiovascular Surgery Registry of 1992 includes data from 41 centers. Within this year a total of 24,127 patients were operated on, with an average of 588 operations/center. Twelve thousand twenty-two of these were cardiac operations under extracorporeal circulation, with an average of 300 cases/hospital. The average of cardiac surgeons/hospital was 5.9 and the average of open heart operations/surgeon was 50. For the first time, the number of coronary bypass surgeries was superior to that of valvular procedures (5,049 vs 4,951). In the coronary bypass patients the average of grafts/patient was 2.43. The number of valvular prostheses implanted was 5,526 and 81% of these were mechanical. The number of patients operated on for congenital cardiac defects was 2,251 (1,278 open heart surgeries and 973 closed). The global mortality in the patients operated on under extracorporeal circulation was 7.6% (7.0% in valvular, 7.9% in congenital and 5.4% in coronary bypass). There were 6,054 patients subjected to surgery for peripheral vascular disease.

Pregnancies in women with and without renal scarring after urinary infections in childhood.

OBJECTIVE: To compare the outcome of pregnancy in women with and without renal scarring after childhood urinary infections with that in unmatched controls. DESIGN: Retrospective study of pregnancies in women prospectively followed up from their first recognised urinary infection. SETTING: Tertiary referral centre in Gothenburg. SUBJECTS: 111 Women attending an outpatient clinic for women with urinary infection during 1975-83, of whom 41 (65 pregnancies) were studied (19 women with renal scarring (32), 22 without scarring (33)), and 65 controls (65) randomly selected and matched for parity, age, smoking habits, and date of delivery. MAIN OUTCOME MEASURES: Urinary infections and complications in pregnancy. RESULTS: The incidence of bacteriuria during first pregnancies was significantly greater in women with (9, 47%) and without (6, 27%) renal scarring after childhood urinary infection than in controls (1, 2%) (p less than 0.001, 0.01 respectively). Symptomatic infections were seen only among women with a history of urinary infection: four women with renal scarring (three of whom had vesicoureteric reflux) developed pyelonephritis and three cystitis, and one woman without scarring developed pyelonephritis. Mean blood pressure was higher among women with severe renal scarring than controls (4/11 v 3/44; p less than 0.05) before and during pregnancy. There was no significant difference in the incidence of pre-eclampsia, operative delivery, prematurity, or birth weight. CONCLUSIONS: Women with a history of previous urinary infections had a high incidence of bacteriuria during pregnancy, and those with renal scarring and persistent reflux were prone to develop acute pyelonephritis. The risk of serious complications in pregnancy, however, was not increased in women with severe renal scarring, possibly owing to their continuous clinical supervision.

[Gene amplification in viral CNS infections. Rapid diagnostic identification of herpesviruses]. / Genamplifiering vid virala CNS-infektioner. Snabb diagnostik av herpesgruppens virus.

DNA amplification with the polymerase chain reaction (PCR) technique was used as a diagnostic test on cerebrospinal fluid samples in cases where herpesvirus infection of the central nervous system (CNS) was suspected. During the period, 1992-93, 47 (8.9%) of 528 patients tested were positive for one or another of the following herpesviruses: herpes simplex virus type 1 (n = 16) or type 2 (n = 9), cytomegalovirus (n = 16), varicella-zoster virus (n = 4), or Epstein-Barr virus (n = 2). The study showed PCR to be a rapid and useful diagnostic method in clinical routine, enabling early antiviral intervention in several cases with an atypical clinical picture. Moreover, cytomegalovirus was found to be an important CNS pathogen in addition to herpes simplex virus, especially during childhood.

Liver function during treatment with cefuroxime.

The liver function was studied in 15 patients before and during treatment with cefuroxime. Four elderly patients had a prolonged half-life of galactose at admission but they all showed declining values during the cefuroxime treatment. Only in one patient did the galactose half-life increase during treatment (from 14 to 25 min.). This patient was an old diabetic who also had prostatic cancer. Cefuroxime treatment seems to be well tolerated also in patients with signs of impaired metabolic liver function at start of treatment.

Urinary infection, reflux and renal scarring in females continuously followed for 13-38 years.

This study describes the pattern of urinary tract infections (UTI) in 87 females prospectively followed for a median of 23 years from their first recognized symptomatic infection in childhood. At 16 years of age they were selected for follow-up into adulthood because of renal scarring (reflux nephropathy) in 45 and recurrent UTI in 42. The attack rate (number of urinary tract infections per individual per observation year) was highest during the 1st year of life (1.9), with a gradual decrease to the lowest rate (0.2) at age 11-15 years. A moderately increased attack rate (0.4), was seen in the late teens, extending through to the mid twenties. The proportion of infections having a pyelonephritic character decreased with age and number of infection episodes, but not in females with severe renal scarring. Pyelonephritic infections were correlated with vesicoureteric reflux, and renal scarring to low age at the index infection, total number of pyelonephritic episodes and reflux. Females with renal scarring continued to have a high proportion of pyelonephritic recurrences after 10 years of age, implying that they risk progressive renal disease and should be closely followed into adulthood.

Mechanical cardiac valve thrombosis. Is thrombectomy justified?

To determine the incidence and results of the treatment offered to acute thrombotic obstructions of mechanical valvular prostheses, we have reviewed a series of 3,637 consecutive hospital survivors who, between January 1970 and September 1990, underwent single mitral or aortic and double mitroaortic valve replacements (MVR, AVR, and DVR, respectively). The cumulative follow-up in these patients was 22,783 years (mean, 7.2 years; range, 0.6-19 years). Sixty-five patients (24 MVR, 13 AVR, and 28 DVR) experienced 72 thrombotic prosthetic obstructions (42 mitral and 41 aortic prostheses) at a mean interval of 3.4 years (range, 0.6-14 years) after the operation. The actuarial prosthetic thrombosis free estimates were 96 +/- 0.9% for MVR, 97 +/- 0.9% for AVR, and 96 +/- 0.8% for DVR (all NS). Mortality associated with prosthetic thrombosis was 25% (four in the MVR group, five in the AVR group, and seven in the DVR group). Fifty-seven patients (22 MVR, 12 AVR, and 23 DVR) underwent a total of 62 reoperations, with a hospital mortality of 17% (two MVR, four AVR, and four DVR). In 37 of the latter patients (20 MVR, three AVR, and 14 DVR), we performed valve replacement (31 mitral prostheses and 14 aortic prostheses), with a hospital mortality of 16% (six of 37) and only one case of subsequent rethrombosis (actuarial rethrombosis free estimate, 96 +/- 3.6%). Conversely, five of the 27 patients (actuarial rethrombosis free estimate, 41 +/- 20%) (two MVR, 11 AVR, and 14 DVR) (seven mitral prostheses and 21 aortic prostheses) whose prosthetic valves were debrided developed rethrombosis during follow-up (p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)