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Biomedical subjects

R M Langer

Publications and source records attributed to R M Langer.

17 recordsLinked to original sources
PubMed2006

Bourneville-Pringle disease for kidney transplantation: a single-center experience.

The Bourneville-Pringle disease is an autosomal-dominant disease affecting the kidneys in about 60%, causing end-stage renal disease in about 10% of the cases. Among more than 2800 renal transplant recipients during the last 33 years, we had two patients with this original disease. A third patient who underwent bilateral nephrectomy is currently awaiting a graft. The first patient was diagnosed at the age of 20 years after a few episodes of retroperitoneal bleeding. At the age of 26 years her left kidney was removed after a rupture; it measured 7500 g, and the histology described angiomyolipomatosis. A year later she underwent a cadaveric kidney transplantation. Subsequently her right kidney was removed due to bleeding. She is currently 5 years posttransplant with stable kidney function and good health. Our second patient was nephrectomized at the age of 35 years and 38 years because of angiomyolipomatosis. She underwent a cadaveric kidney transplantation 7 years later. After 5 years of excellent kidney function and a year after her arteriovenous fistula was ligated her upperarm had to be amputated because of uncontrollable bleeding. After another 6 months, she displayed rapid progression of a jejunal tumor and during operation received 54 U of blood transfusion but died at the age of 49 years with a well-functioning graft. Our third patient consecutively underwent two nephrectomies because of angiomyolipomatosis of her kidneys at the ages of 25 and 28 years. She has two children with the same disease. In addition she carries Leyden mutation, which has caused deep venous thromboses and pulmonary emboli. She is currently on our waiting list for kidney transplantation. The Bourneville-Pringle disease is a rare indication for kidney transplantation; the prognosis of the patient is dependent on the original disease.

Adult↗
PubMed2005

Significant differences in the efficacy of kidney transplantation between Hungarian Caucasians and Gypsies.

In a retrospective study we examined the differences between Caucasian (Group A) and Gypsy (Group B) renal allograft recipients transplanted in Hungary. From 1983 to 2001, 1918 transplants were performed in Budapest (1825 Caucasian and 93 Gypsy recipients). Group B patients were younger (34 +/- 12 vs 42 +/- 14 years of age; P < .01) and Group A had more polycystic kidney disease (12% vs 3%; P < .025). Blood group B was more common in Group B (27% vs 19%; P = NS) than in Group A patients, and Group A had seemingly more diabetes (5% vs 1%; P = NS) than did Group B. There were no differences in HLA mismatches or panel reactive antibodies (PRA). No differences were seen in Group A vs Group B patient survivals at 1, 3, 5, or 10 years' posttransplant (98% vs 95%; 90% vs 93%; 85% vs 88%; and 74% vs 82%, respectively). However, Group A graft survivals were significantly better than Group B at 1, 3, 5, and 10 years' posttransplant (89% vs 77%; 82% vs 66%; 76% vs 54%; and 57% vs 34%; each comparison P < .01). Group B recipients experienced a greater number of acute rejection episodes (66% vs 49%; P < .01), irreversible acute rejections (15% vs 6%; P < .001), chronic rejections (34% vs 18%; P < .001), and graft loss due to immunosuppression noncompliance (5% vs 1%; P < .05) than did Group A recipients. As has been previously described for other non-Caucasian ethnic groups (eg, African-Americans), Hungarian Gypsies appear to be at a greater immunological risk for rejection and poorer long-term graft survival.

Adult↗
PubMed2005

Laurence-Moon-Bardet-Biedl syndrome for kidney transplantation at the age of 57 years.

Laurence-Moon-Bardet-Biedl syndrome represents a very rare indication for kidney transplantation. Previous reports mention only pediatric organ recipients with this diagnosis. We present the case of a Caucasian male patient who underwent a cadaveric renal transplantation at the age of 57 years. Our patient had an uneventful immediate postoperative course; however, 4 months after the operation he suffered pneumonia and cytomegalovirus infection. He recovered fully and had an episode of acute cholecystitis. At the time of the laparoscopic cholecystectomy we also laparoscopically removed his Tenckhoff catheter, a procedure he could not undergo for more than a year because of a chronic scabies infection. Now, 18 months after his transplantation he is fully rehabilitated with a serum creatinine of 90 micromol/L. In selected cases even in older age kidney transplantation could offer a higher quality of life for this mentally retarded, blind population.

Bardet-Biedl Syndrome↗
PubMed2005

Improving results of renal transplantation with the use of elderly donors: the Budapest experience.

The use of elderly donors has become a necessity with the increasing demand for deceased donor organs resulting in transplant centers worldwide expanding their donor criteria. We, therefore, thought it appropriate to review our experience using elderly (>60 years) brain-dead donors for kidney transplantation. We investigated the influence of donor parameters on early graft function and survival. A retrospective comparative analysis of three periods was performed: 1994 to 1998 (P1) n = 40; 1999 to 2000 (P2) n = 28; and 2001 to 2002 (P3) with n = 31 donors. Mean donor age in each period was 63.4 +/- 3.3, 64.5 +/- 3.4, and 63.8 +/- 2.7 years; mean diuresis was 473 +/- 450, 307 +/- 316, and 276 +/- 185 mL/hour; and the need for vasopressors during donor management was 81%, 85%, and 70% respectively. The number of kidney recipients was 59, 30, and 37, mean age was 49 +/- 13, 53 +/- 11 and 54 +/- 8 years, the recipient ratio of patients >60 years was 17%, 33%, and 27% respectively, and no differences among the groups in the HLA mismatch. Primary nonfunction occurred in 8.5%, 0%, and 2.8%; acute rejection ratio at 1 year was 35%, 36%, and 32%, the mean serum creatinine at 12 months was 183.7 +/- 66.0, 157.8 +/- 41.2 and 160.7 +/- 46.5 mumol/L. The 1-year graft survival was 71.2%, 91.0% and 92.0% and the 1-year patient survival 88.2%, 96.6%, and 97.2%, respectively, for periods 1, 2, and 3. There has been a considerable improvement in the 1-year graft and patient survivals. With careful donor and recipient evaluation, individualized immunosuppression, and age matching the results of renal transplantation from elderly deceased donors can be comparable to the results of the "optimal" deceased donor kidney transplantation.

Adolescent↗
PubMed2004

Successful islet after kidney transplantations in a distance over 1000 kilometres: Preliminary results of the Budapest-Geneva collaboration.

To overcome critical islet processing and to ensure patient safety and quality care, we have established an international collaboration between two geographically distant transplant centers for islet transplantation. Four pancreata were harvested and immediately preserved by the two-layer method (oxygenated perfluorocarbon+University of Wisconsin) and subsequently transported for the automated method isolation to Geneva. After purification, the islets were cultured overnight and transported the next day back to Budapest. Three consecutive kidney transplant patients with type 1 diabetes mellitus underwent islet transplantation via percutaneous transhepatic portal embolization using the bag-method. The immunosuppression consisted of daclizumab, sirolimus, and low-dose tacrolimus. Mean donor age was 43.7 years, mean body mass index: 26.5. The islet isolation process began within 8 hours from the donor aorta cross-clamp in all cases. The isolation success rate was 80% (4 of 5). In Budapest, the islets were assessed for viability. No complications occurred during the transplantation, and the portal pressure remained within the normal range. The first patient received 12,000 IU/BW from two donors and the insulin requirement decreased from 40 U/d to 10 U/d. The second patient received 7200 IU/BW from a single donor and became immediately insulin free. The third patient was given 7100 IU/BW; the insulin requirement decreased from 39 U/d to 14 U/d. Posttransplant follow-up for the three patients are 7 months, 4 months, and 2 weeks, respectively. All patients achieved metabolic stability. These preliminary results demonstrate the feasibility of an international collaborative islet transplantation program at a distance over 1000 km.

Adult↗
PubMed2003

De novo tumors after kidney transplantation: the Budapest experience.

In a retrospective study we analyzed the incidence and characteristics of de novo tumors developing in renal transplant recipients treated in our center. The 5% incidence de novo tumors developing among patients treated with azathioprine and prednisolone (n = 241) was similar to the 5.4% incidence of de novo tumors developing among patients treated with calcineurin-based immunosuppression (n = 1918). The most common malignancies among our patients were basal cell (21.7%) and squamous cell (13.9%) carcinomas of the skin, followed by urogenital (10.4%) and lung malformations (9.6%). A high incidence of Kaposi's sarcoma (9.6%; half cutaneous and half visceral) and a lower than expected incidence of posttransplant lymphoproliferative disorder (PTLD; 3.5%) was found. Among patients developing de novo tumors, the incidence of death with a functioning graft was higher than among recipients without tumors. Moreover, the incidence of tumor-related death was high among the de novo tumor recipients. Among our recipients, the most aggressive tumors were Kaposi's sarcoma, lung tumors, lymphomas, and gastrointestinal tumors, which occurred relatively early after transplantation and were the cause of death in most cases. Compared to tumor registry data, we found an inverse basal-to-squamous cell carcinoma ratio, a lower incidence of PTLD, and a higher incidence of Kaposi's sarcoma.

Azathioprine↗
PubMed1988

Transmembrane flux and receptor desensitization measured with membrane vesicles. Homogeneity of vesicles investigated by computer simulation.

The use of membrane vesicles to make quantitative studies of transmembrane transport and exchange processes involves an assumption of homogeneity of the membrane vesicles. In studies of 86Rb+ exchange mediated by acetylcholine receptor from the electric organ of Electrophorus electricus and of 36Cl- exchange mediated by GABA receptor from rat brain, measurements of ion exchange and receptor desensitization precisely followed first order kinetics in support of this assumption. In other measurements a biphasic decay of receptor activity was seen. To elucidate the molecular properties of receptors from such measurements it is important to appreciate what the requirements of vesicle monodispersity are for meaningful results and what the effect of vesicle heterogeneity would be. The experiments were simulated with single vesicle populations with variable defined size distributions as well as with mixtures of different populations of vesicles. The properties of the receptors and their density in the membrane could be varied. Different receptors could be present on the same or different membrane vesicles. The simulated measurements were not very sensitive to size dispersity. A very broad size distribution of a single vesicle population was necessary to give rise to detectable deviations from first order kinetics or errors in the determined kinetic constants. Errors could become significant with mixtures of different vesicle populations, where the dispersity in initial ion exchange rate constant, proportional to the receptor concentration per internal volume, became large. In this case the apparent rate of receptor desensitization would diverge in opposite directions from the input value when measured by two different methods, suggesting an experimental test for such kinetic heterogeneity. A biphasic decrease of receptor activity could not be attributed to vesicle heterogeneity and must be due to desensitization processes with different rates. Significant errors would not arise from the size dispersity apparent in subpopulations of vesicles seen by imaging techniques in membrane preparations.

Animals↗
PubMed1970

Glycogenesis and glyconeogenesis in human platelets. Incorporation of glucose, pyruvate, and citrate into platelet glycogen; glycogen synthetase and fructose-1,6-diphosphatase activity.

Washed human platelets are capable of depositing 1-4 as well as probable 1-6 glucosyl linkages onto preexistent glycogen primer. They are also capable of degrading (glycogenolysis) newly synthesized 1-4 as well as probable 1-6 glucosyl linkages. A higher rate of glycogen synthesis was found in platelet suspensions containing lower concentrations of platelets. This was shown to result from decreased glycogen degradation and consequent increased residual glycogen primer in low platelet suspensions. The increased glycogen content of low platelet suspensions was not a result of platelet washing, removal of platelets from plasma, or release of platelet metabolites into the media. The enzyme glycogen synthetase was found to be present at a rate of 5.2 mumoles of uridine diphosphate (UDP) glucose incorporated into glycogen per gram platelets per hour at 37 degrees C. The K(m) for UDP glucose was 6.6 mmoles/liter. At optimum concentration of glucose 6-phosphate, the K(m) was reduced 4.6 fold and V(max) was increased 4.3-fold. Human platelets contain the glyconeogenic pathway. They incorporate pyruvate-(14)C and citrate-(14)C into platelet glycogen and contain an apparent fructose-1,6-diphosphatase. The apparent fructose-1,6-diphosphatase was activated by adenosine monophosphate (AMP) and adenosine diphosphate (ADP), inhibited by adenosine triphosphate (ATP), and shown to be rate limiting for glyconeogenesis at physiologic concentration of adenine nucleotide.

Adenosine Triphosphate↗
PubMed1968

Biochemical energetics of simulated platelet plug formation. Effect of thrombin, adenosine diphosphate, and epinephrine on intra- and extracellular adenine nucleotide kinetics.

Washed human platelets were incubated in a modified Ringer's solution, pH 7.1, at 37 degrees C for 1 hr. Intracellular basal levels for glycogen, adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and orthophosphate were 31.1, 2.52, 1.39, 0.36, and 1.2 mumoles/ml of platelets, respectively. Extracellular ATP, ADP, and AMP remained fairly constant and represented 4, 2, and 4% of total adenine nucleotide content. Total adenine nucleotide content remained unchanged during the period of control incubation. Glycogen depletion was 17.8 mumoles/ml at the end of 1 hr; lactate production was 20.7 mumoles/ml per hr. In the presence of glucose, lactate production increased 100%, and glycogen depletion was spared 13%. Approximately 55% of glucose or glycogen fuel was converted to lactate. The agglutinating agents, thrombin, ADP, and epinephrine, resulted in increased glycogen depletion and lactate production both in the presence and absence of glucose. The effect of thrombin was greater than epinephrine. The effect of epinephrine was greater than ADP. All three agglutinating agents resulted in loss of high energy phosphates (net decline in adenine nucleotides) with release of adenine nucleotides into the extracellular environment. The effect of thrombin was greater than ADP. The effect of ADP was greater than epinephrine. In experiments with ADP addition, significant quantities of ADP were converted to AMP extracellularly. In experiments with thrombin and epinephrine appreciable quantities of extracellular orthophosphate were taken up by plateletes and could not be accounted for by changes in intracellular orthophosphate or adenine nucleotide. Sufficient ADP was released during exposure to thrombin and epinephrine to account for platelet agglutination. Changes in intracellular adenine nucleotides and orthophosphate could be correlated with the activation of regulator glycogenolytic and glycolytic enzymes.

Adenine Nucleotides↗