Biochemical basis of partial nephrogenic diabetes insipidus phenotypes

Biochemical properties of mutant type 2 vasopressin receptors (V2Rs) causing a partial phenotype of nephrogenic diabetes insipidus were investigated in transiently transfected HEK 293 cells. Cell surface expression of the V2R was not altered by substituting Asp85 in the second transmembrane region by Asn as determined by saturation binding assays. Although the affinity of the mutant V2R for arginine vasopressin (AVP) was reduced only 6-fold, the response of adenylyl cyclase activity to AVP revealed a 50-fold right shift in EC50 and a decreased maximum response for the mutant V2R. These data indicated that replacement of Asp85 by Asn affected coupling of the receptor to Gs, a conclusion substantiated by a 20-fold decrease in the calculated coupling efficiency of this receptor. The Gly201Asp mutation in the second extracellular loop, also found associated with an NDI partial phenotype, decreased cell surface expression of the V2R with minor reduction in ligand-binding affinity and coupling efficiency to Gs. A pronounced difference was observed for this mutant V2R between the stimulation of adenylyl cyclase activity promoted by AVP and the V2 vasopressin receptor agonist deamino[Cys1,D-Arg8]-vasopressin, suggesting an involvement of Gly201 in the selectivity of the receptor for different ligands. These data demonstrated that while decreased ligand-binding affinity and decreased coupling to Gs are responsible for the attenuation of response to ligand in the Asp85Asn mutant V2R, cell surface expression of the V2R is the major factor reducing cellular responses to ligand for the Gly201Asp mutant V2R.

Tranexamic acid reduces blood loss and transfusion in reoperative cardiac surgery

PURPOSE

The objective of this study was to assess the effect of tranexamic acid (TA), a synthetic antifibrinolytic, on blood loss and the need for transfusion of blood products following repeat cardiac valve surgery.

METHODS

After ethics committee approval, 41 patients scheduled for reoperative valve replacement were enrolled in this randomized, double blind, placebo controlled study. Patients were randomized to receive TA (10 g in 500 ml NSaline) or placebo (NSaline) as an iv bolus over 30 min, after anaesthesia induction and prior to skin incision. Intraoperative blood loss was assessed by estimating blood volume on drapes, weighing surgical sponges, and measuring suction bottle returns. Postoperative blood loss was measured from mediastinal chest tube drainage following surgery. Blood products were transfused according to a standardized protocol.

RESULTS

Patient demographics were similar for age, sex, cardiopulmonary bypass pump time, cross clamp time, surgical time, preoperative haemoglobin, coagulation profile, and the number of valves replaced during surgery. Tranexamic acid administration reduced intraoperative blood loss [median (range)] from 1656 (575-6270) to 720 ml (355-5616) (P < 0.01) and postoperative blood loss from 1170 (180-4025) to 538 ml (135-1465) (Intent to Treat n = 41, P < 0.01). The total red blood cells transfused (median, range) was reduced from 1500 (0-9300) ml to 480 (0-2850) ml (P < 0.01) in the TA group. In hospital complications and mortality rates were not reduced in the TA group.

CONCLUSION

Tranexamic acid reduced blood loss and the need for blood product transfusion and appears to be an effective treatment for patients undergoing reoperative cardiac valvular surgery.

[Follow-up after heart transplantation]

The prognosis of patients with end-stage cardiac disease has dramatically changed with transplantation. The incidence of complications remains relatively high and needs a very careful follow-up to have good long term results.

Phosphorylation of the V2 vasopressin receptor

The V2 vasopressin receptor undergoes ligand-induced sequestration and desensitization (Birnbaumer, M., Antaramian, A., Themmen, A. P. N., and Gilbert, S. (1992) J. Biol. Chem. 267, 11783-11788). The V2 receptor expressed in transfected cells labeled with [32P] orthophosphate was phosphorylated following the addition of 100 nM arginine vasopressin (AVP). Phosphorylation was complete 5 min after addition of AVP, and was not stimulated by increased levels of Ca2+ or cAMP. The half-maximal dose of AVP that stimulated phosphorylation was 2.4 +/- 0.4 nM, similar to the receptor KD of 4. 5 +/- 0.4 nM. The role of phosphorylation on receptor desensitization was investigated by studying two vasopressin receptors 14 and 27 amino acids shorter than the wild type receptor. The missing segments were not needed for normal ligand binding or coupling to Gs, but the last 14 amino acids were required for phosphorylation. The truncated receptors exposed to 100 nM AVP were sequestered and desensitized. The R137H V2R mutant receptor that binds vasopressin with wild type-like affinity and does not couple to Gs (Rosenthal, W., Antaramian, A., Gilbert, S., and Birnbaumer, M. (1993) J. Biol. Chem. 268, 13030-13033) was phosphorylated and subjected to ligand-induced sequestration. These results established that phosphorylation is not essential for sequestration and desensitization of the V2 vasopressin receptor. Furthermore, they revealed that the conformation acquired after ligand occupancy is necessary for receptor phosphorylation and sequestration, while coupling to Gs is not.

St. Jude Medical valve prosthesis: an analysis of long-term outcome and prognostic factors

Between 1979 and 1984, 321 patients received 354 St. Jude Medical prostheses (194 aortic, 94 mitral, 1 tricuspid, and 32 multiple valve replacements). Follow-up was 96% complete (2967 patient-years; mean 9.5 years per patient). Actuarial event-free rates at 10 years and linearized rates (in parentheses) of late complications were as follows: embolism, 85.0% +/- 2.3% (2.3% per patient-year); anticoagulant-related hemorrhage, 74.8% +/- 2.7% (3.3% per patient-year); cerebrovascular accident, 81.8% +/- 2.5% (2.6% per patient-year); prosthesis thrombosis, 98.5% +/- 0.7% (0.1% per patient-year); endocarditis, 97.2% +/- 1.1% (0.4% per patient-year); prosthesis dysfunction, 97.1% +/- 1.0% (0.4% per patient-year); hemolytic anemia, 98.5% +/- 0.7% (0.1% per patient-year); reoperation, 97.4% +/- 1.0% (0.4% per patient-year); overall mortality, 63.3% +/- 2.7% (4.2% per patient-year); and valve-related death (including sudden death), 84.7% +/- 2.2% (1.4% per patient-year). Independent preoperative risk factors were as follows: (1) for embolism, cardiac failure as indication for operation and history of prior systemic embolism; (2) for cerebrovascular accidents, the same two factors and age; (3) for endocarditis, diabetes, chronic alcoholism, and aortic valve replacement; (4) for overall mortality, age, ejection fraction (or cardiac index or cardiothoracic index), chronic alcoholism, and history of systemic embolism; and (5) for valve-related death, chronic alcoholism, degenerative cause of valve disease, and prosthetic diameter 23 mm or smaller. Ninety percent of survivors were in New York Heart Association functional class I or II at the end of follow-up. In conclusion, this study confirms the excellent durability of the St. Jude Medical valve and the remarkable functional benefit for the majority of the patients. However, prosthesis-related complications are still common, particularly for small-diameter prostheses. Outcome is strongly related to the patient's preoperative cardiac condition and to the adequacy of anticoagulation control.

On the molecular basis and regulation of cellular capacitative calcium entry: roles for Trp proteins

During the last 2 years, our laboratory has worked on the elucidation of the molecular basis of capacitative calcium entry (CCE) into cells. Specifically, we tested the hypothesis that CCE channels are formed of subunits encoded in genes related to the Drosophila trp gene. The first step in this pursuit was to search for mammalian trp genes. We found not one but six mammalian genes and cloned several of their cDNAs, some in their full length. As assayed in mammalian cells, overexpression of some mammalian Trps increases CCE, while expression of partial trp cDNAs in antisense orientation can interfere with endogenous CCE. These findings provided a firm connection between CCE and mammalian Trps. This article reviews the known forms of CCE and highlights unanswered questions in our understanding of intracellular Ca2+ homeostasis and the physiological roles of CCE.

[Heart-kidney transplantation of the same donor following failure of a first renal transplantation due to chronic rejection]

Combined heart and renal transplantation from the same donor is an uncommon procedure. We describe the case of a patient with prior kidney transplantation whose renal graft had to be removed a few years later because of chronic rejection. The patient then developed severe hypertensive and ischemic left ventricular dysfunction. Combined heart and kidney transplantation was performed several years after the first renal transplantation. This observation is the first description of a combined heart and kidney transplantation after removal of a former renal graft whose failure was due to chronic rejection. Great care was taken to avoid identical MHC antigens (HLA-A; -B; -DR) between the two donors, to prevent recurrent rejection of the grafted organs. After 18 months, no rejection was detected in either organ. This case report confirms the feasibility of this complex procedure, provided care is taken to avoid identical HLA groups between the two donors so as to reduce immunological complications.

Prognosis after stroke followed by surgical closure of patent foramen ovale: a prospective follow-up study with brain MRI and simultaneous transesophageal and transcranial Doppler ultrasound

BACKGROUND

The risk of stroke and the long-term prognosis of recurrent strokes in young patients with patent foramen ovale (PFO) are not well known. For this reason, the treatment of these patients remains empirical. An alternative treatment to prolonged antithrombotic therapy may be surgical closure of the PFO.

METHODS

Thirty patients (20 men and 10 women) with stroke and PFO were prospectively selected among 138 patients with stroke and PFO for a study of surgical closure of PFO at our center. Eligible patients were < 60 years old, had negative results of a systematic search for another cause of stroke (first criterion), and met two of the four following criteria: (1) recurrent clinical cerebrovascular events or multiple ischemic lesions on brain MR, (2) PFO associated with an atrial septal aneurysm, (3) > 50 microbubbles counted in the left atrium on contrast transesophageal echocardiography (TEE), and (4) Valsalva maneuver or cough preceding the stroke. Patients selected in this manner for surgery were considered to be a subgroup with a higher risk of stroke recurrence.

RESULTS

All patients had a direct suture of PFO while under cardiopulmonary bypass without recorded early or delayed significant complication. All patients underwent a new brain MRI and TEE simultaneous with transcranial Doppler ultrasonography after contrast injection at 8 +/- 3 months after surgery. After a mean follow-up of 2 years without antithrombotic treatment, no recurrent cerebrovascular event (stroke or transient ischemic attack [TIA]) and no new lesion on MRI had developed. Postoperative contrast TEE and transcranial Doppler ultrasonography showed that two patients had residual interatrial right-to-left shunting, although much smaller than before surgery, associated with single versus double continuous suture.

CONCLUSIONS

Our study of 30 selected stroke patients with surgical suture of PFO showed a stroke recurrence rate of 0% and no significant complication. Residual right-to-left shunting may be avoided by double continuous suture of the PFO. In the absence of controlled studies to guide individual therapeutic decisions, our findings show that PFO closure can be done safely and may be considered to avoid recurrence in selected patients with long life expectancy and presumed paradoxic embolism.

Doppler echocardiographic assessment of the new ATS medical prosthetic valve in the aortic position

Advancing The Standard (ATS) Medical (ATS Medical Inc., Minneapolis, MN) is a new mechanical bileaflet valve, composed of pyrolitic carbon. The aim of this study was to define in a blinded manner the Doppler echocardiographic characteristics of normally functioning ATS Medical prostheses with respect to their size. Forty consecutive patients (29 men, mean age 58 +/- 13 years), clinically stable, and without evidence of valve dysfunction, were studied from 1993 to 1995. Doppler echocardiography was performed at least 3 months after valve replacement with ATS Medical valves (5 n degrees 21, 8 n degrees 23, 12 n degrees 25, 10 n degrees 27, 5 n degrees 29). Maximum and mean transprosthetic pressure gradients were calculated by the simplified Bernoulli equation. Functional valve surface area was assessed by the continuity equation using the external diameter of the prostheses to calculate the subaortic surface area. The Doppler velocity index was obtained by the ratio of subaortic and transaortic velocities and the performance index was calculated dividing the effective orifice area by the actual orifice area. For the most commonly used aortic valve (25 mm), the maximum pressure gradient was 17 +/- 8 mmHg, the mean gradient 11 +/- 4 mmHg, the functional surface area 2.2 +/- 0.4 cm2, the Doppler velocity index 0.44 +/- 0.07, and the performance index 0.68 +/- 0.11. This study provides the normal range for Doppler hemodynamic characteristics of the various sizes of the ATS valve.

A fully active nonglycosylated V2 vasopressin receptor

The human V2 vasopressin receptor belongs to the superfamily of G protein-coupled receptors believed to be anchored to the plasma membrane by seven transmembrane regions. The extracellular portion of the human V2 vasopressin receptor contains one site susceptible to N-linked glycosylation. Metabolic labeling and immunoprecipitation of the receptor expressed in transfected cells were applied to examine whether the protein was indeed glycosylated. The V2 vasopressin receptor expressed transiently was glycosylated, but glycosidase treatment to test the complexity of the sugar moiety linked to asparagine revealed that the majority of the receptor protein lacked complex carbohydrates, an indication of an improperly processed protein. This immature protein displayed a tendency to form aggregates. In contrast with these data, testing of the sugar complexity of the receptor protein synthesized in stably transfected cells identified the predominant form as an appropriately processed receptor protein. Mutagenesis of asparagine 22 to glutamine produced on expression in transfected cells a nonglycosylated receptor with ligand binding affinity and coupling characteristics almost identical to those of the wild-type form. After exposure to elevated concentrations of AVP (100 nM), the nonglycosylated form desensitized to the same extent as the wild-type receptor.

Surgical prophylaxis of recurrent stroke in patients with patent foramen ovale: a pilot study

Prevention of recurrent stroke in adults with patent foramen ovale represents a therapeutic challenge. Antiplatelet or anticoagulant treatment is widely introduced, but its exact indication is not known. In this pilot study, eight men and three women with previous ischemic cerebral events underwent direct surgical closure of the patent foramen ovale. Mean age was 39.4 (from 30 to 58) years. No coexisting cause of stroke was found after extensive investigations, including blood and coagulation tests, echocardiography, 24-hour three-lead electrocardiographic monitoring, extracranial and transcranial Doppler ultrasonography, and cerebral angiography. Criteria for operation also included at least two of the following: atrial septal aneurysm, multiple cerebral infarcts, a history of multiple cerebral events, and Valsalva strain before stroke. Before operation, one patient had two shunts (1 patent foramen ovale, 1 intrapulmonary shunt). No intraoperative or postoperative complications occurred, but a few hours after operation transient arrhythmias developed in two patients without atrial fibrillation, hemodynamic instability, or embolism. During a median follow-up of 12.2 months, no patient had recurrent stroke. All patients prospectively underwent brain magnetic resonance imaging and contrast echocardiography with simultaneous transcranial Doppler ultrasonography. A residual right-to-left interatrial shunt, smaller than the preoperative one, was observed in only one patient, whereas no lesion was seen on magnetic resonance imaging. Our study suggests that surgical closure of patent foramen ovale in patients with presumed paradoxic embolism is safe, with no recurrent stroke in the first year of follow-up. Further studies are needed to evaluate the long-term prognosis of patients with versus without operation and to define the role of operation as an alternative to prolonged antithrombotic treatment.

Coronary stenting for coronary artery narrowing in a heart transplant recipient

Transplant atherosclerotic coronary disease remains the leading cause of death in heart transplant recipients. We report the first case of coronary stent implantation in a heart graft for epicardial focal stenosis. Due to the lower rate of restenosis after stenting in the native coronary artery, we suggest that coronary stenting be considered an acceptable, first intention therapeutic option instead of angioplasty alone whenever possible.

[Cardiac surgery in octogenarians]

37 patients aged 80 or over underwent cardiac surgery during an 11-year period. Operative indications included angina, dyspnea and syncope. The majority of patients (n = 32) had a left ventricular ejection fraction greater than 0.5. There were 28 aortic valve procedures, of which seven were combined with coronary artery bypass grafts (CABG), and 2 with mitral valve repair; in addition, 7 isolated CABG procedures and one isolated mitral valve repair were performed. 36-day mortality was 5.4% (2 patients); 9 patients died at a later date (2.5 to 118 months after surgery). The most frequent postoperative complications were atrial fibrillation, pulmonary infection or atelectasis, transient delirium and atrioventricular conduction disturbances. Mean hospital stay was 14.5 days. 1- and 5-year actuarial survival rates were 83% and 57%. In a control group of patients aged 60-69 matched for preoperative characteristics, there were no in-hospital fatalities and 1- and 5-year survival were, respectively, 100% and 82%. Among complications, only conduction disturbances and transient delirium were significantly more frequent in the octogenarian group. At follow-up, the proportion of severely symptomatic octogenarians had diminished to 24% from 84%. In conclusion, cardiac surgery can be performed on octagenarians with adequate myocardial reserve, exposing them to a perioperative mortality that is in the range of younger age groups while offering an equivalent prospect for functional improvement.

[Patient management following cardiac transplantation]

Prognosis of heart transplant patients has dramatically improved in the last decade thanks to the use of cyclosporine as immunosuppressive treatment. Optimal follow-up and early recognition of complications and side effects of treatment lead to longer survival and marked improvement of these patients' quality of life. However, the incidence of complications remains high and their management calls for particular care. We review our experience of heart transplantation in Lausanne and describe in detail the results and complications such as rejection, transplant coronary artery disease, hypertension, renal failure, metabolic disorders, cancer and conduction problems. Cooperation of the medical team (cardiologist, surgeon, anesthetist, general practitioner) is essential to long term success of the transplant program.

Cardiac perforation after surgical repair of pectus excavatum

Five days after surgical repair of pectus excavatum, this 7-year-old boy had a right-sided Kirschner wire protruding beneath the skin. The wire was repositioned blindly. Severe congestive heart failure developed. Surgical exploration showed a pierced right atrium, a torn septal leaflet of the tricuspid valve and noncoronary aortic cusp, and a large traumatic ventricular septal defect. The outcome and the indications and possible complications of surgery are discussed.

Selective induction of interleukin-1 receptor antagonist and interleukin-8 in human monocytes by normal polyspecific IgG (intravenous immunoglobulin)

We have investigated the effects of intravenous immunoglobulin (IVIg), a therapeutic preparation of normal human polyspecific IgG, on the synthesis and release of cytokines by peripheral blood monocytes. IVIg was found to selectively induce gene transcription and secretion of interleukin-1 receptor antagonist (IL-1ra) and IL-8 in cultures of normal human monocytes. The addition of IVIg to cultures of purified monocytes induced a dose-dependent secretion of IL-1ra and IL-8 without stimulating the production of IL-1 alpha, IL-1 beta, tumor necrosis factor-alpha or IL-6. The effects of IVIg required both the Fc and F(ab')2 portions of IgG. IVIg-induced production of IL-8 by monocytes was enhanced by lipopolysaccharide (LPS), although LPS inhibited the secretion of IL-1ra, suggesting that IVIg and LPS stimulate distinct intracellular pathways in monocytes. Induction of IL-1ra and IL-8 by IVIg was enhanced in the presence of autologous T lymphocytes. Our observations document the selectivity of the effects of IVIg on the synthesis of cytokines and cytokine antagonists by human monocytes. Induction of IL-1ra and IL-8 by IVIg may contribute to the anti-inflammatory effects of immunoglobulin therapy in patients with autoimmune and systemic inflammatory disorders.

Augmentation of the effectiveness of porcine GH with swine antibodies induced by a synthetic GH peptide

An effort was made to evaluate the potential usefulness of a peptide vaccine in improving the growth performance of farm animals. It was previously reported that a murine PS-7.6 monoclonal antibody (mAb) which was specific to porcine GH (pGH) enhanced the growth-promoting activity of pGH in an experimental hypophysectomized rat model. Additional data from a epitope mapping study suggested that PS-7.6 mAb recognized a pGH fragment corresponding to an amino acid sequence 54-95. In this report, therefore, a peptide pGH(54-95) was synthesized in an attempt to induce PS-7.6-like antibodies in swine. It was demonstrated that the peptide pGH(54-95) competed with PS-7.6 mAb for the binding to radioactive pGH in a competition radioimmunoassay and also caused pigs to elicit polyclonal antibodies immunoreactive to pGH protein. The association and dissociation rate constants of the swine antibody to pGH were 1.9 x 10(2) M-1 s-1 and 3.2 x 10(-4)s-1 respectively, thus producing an overall binding affinity of Kd = 1.6 x 10(-6) M. The swine antibody partially competed with murine PS-7.6 mAb for the binding to pGH, suggesting that the pGH-recognizing sites for both antibodies might be closely related. The biological effect of the swine antibody was examined in hypophysectomized rats and shown to significantly augment pGH activity in promoting the growth of these GH-deficient animals. The present findings suggest that a synthetic peptide may be developed as a potential growth vaccine for swine to generate antibodies capable of enhancing the effectiveness of endogenous pGH.

Surgery in native valve endocarditis: indications, results and risk factors

Seventy-nine patients (mean age 49 years) underwent valve replacement or repair for active (58.2%) or healed (41.8%) native valve endocarditis between 1976 and 1992. The most common indication for surgery was congestive heart failure (73.4%), followed by multiple systemic emboli (21.5%). Emergency operation was necessary in 27.8% of the cases. Operative mortality was 3.8% (3 patients) and late mortality 15.1% (12 patients). Streptococci were the most common infecting agents (41.8%), followed by Staphylococcus aureus (11.4%). No organisms were isolated in 27 cases (34.2%). Follow-up spanned 379.8 patient-years with a maximum of 15.8 years. Fifteen late valve-related events (periprosthetic leak, recurrent endocarditis, thrombo-embolic events and hemolysis) and 20 other late complications (anticoagulant-related hemorrhage, arrhythmias or congestive heart failure) occurred in 22 patients. The linearized rate for all late complications is 5.8% per patient-year. The influence of eight preoperative variables on overall mortality and late valve-related complications was assessed: age, valve(s) affected, active or healed infection, bacteriology, annular abscess, emergency or elective surgery, preoperative renal function and NYHA class. Only Staphylococcus aureus (P = 0.0012) was a significant predictor of late valve-related complications. Furthermore, no difference in survival or in valve-related complications was found between the active and healed infections.

Incidence of deep and superficial sternal infection after open heart surgery. A ten years retrospective study from 1981 to 1991

Between January 1981 and December 1991, 4137 adult patients underwent various cardiac procedures via a median sternotomy under cardiopulmonary bypass. The overall infection rate was 1.33%, including superficial wound infections (SWI) (1.18%) and deep sternal infection (DSI) (0.145%). Pericardial and retrosternal suction drains with a vent allowed a better drainage of blood and serosities and probably contributed to our low DSI rate. Eleven factors predisposing to infection were evaluated by Fisher's exact test. Only the operative urgency (P = 0.006), reexploration for bleeding (P = 0.00001) and preoperative renal failure (P = 0.0005) were statistically significant. Twenty of our infected patients had no risk factors for infection. When the risk factors described in the literature were applied to our infected patients, only one had no risk factor.

[Infectious complications in cardiac transplantation: Lausanne experience]

Infectious complications, a major cause of morbidity and mortality after heart transplantation, were reviewed in 49 heart transplant patients at Lausanne. The follow-up lasted 32 months on average. 43 patients (88%) presented 108 infections (2.20 episodes of infection/patient). 38 severe infections (0.78 episodes/patient) were diagnosed in 27 patients (55%). 2 of the 9 deaths which occurred were due to infection. The viruses, principally of the herpes group, were responsible for 37% of all the infections, and bacteria for 28%. About a third of the viral and bacterial infections were severe. The other documented infections were caused by fungi (13%), which were most often responsible for superficial infections, and rarely by protozoa (5%). Finally, in 17% of infectious episodes, the pathogen could not be identified. Cytomegalovirus was the pathogen the most frequently responsible in severe infections. The highest incidence of infections occurred during the first 2-3 months after transplantation and was reduced considerably after the 6th month. The distribution of different pathogens was related to specific periods after the transplant. Our results confirm that infection is a major complication of heart transplantation. Clinical and prophylactic aspects of some infections are reviewed.