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Biomedical subjects

L B Melton

Publications and source records attributed to L B Melton.

13 recordsLinked to original sources
PubMed2001

End-stage renal disease (ESRD) after orthotopic liver transplantation (OLTX) using calcineurin-based immunotherapy: risk of development and treatment.

BACKGROUND: The calcineurin inhibitors cyclosporine and tacrolimus are both known to be nephrotoxic. Their use in orthotopic liver transplantation (OLTX) has dramatically improved success rates. Recently, however, we have had an increase of patients who are presenting after OLTX with end-stage renal disease (ESRD). This retrospective study examines the incidence and treatment of ESRD and chronic renal failure (CRF) in OLTX patients. METHODS: Patients receiving an OLTX only from June 1985 through December of 1994 who survived 6 months postoperatively were studied (n=834). Our prospectively collected database was the source of information. Patients were divided into three groups: Controls, no CRF or ESRD, n=748; CRF, sustained serum creatinine >2.5 mg/dl, n=41; and ESRD, n=45. Groups were compared for preoperative laboratory variables, diagnosis, postoperative variables, survival, type of ESRD therapy, and survival from onset of ESRD. RESULTS: At 13 years after OLTX, the incidence of severe renal dysfunction was 18.1% (CRF 8.6% and ESRD 9.5%). Compared with control patients, CRF and ESRD patients had higher preoperative serum creatinine levels, a greater percentage of patients with hepatorenal syndrome, higher percentage requirement for dialysis in the first 3 months postoperatively, and a higher 1-year serum creatinine. Multivariate stepwise logistic regression analysis using preoperative and postoperative variables identified that an increase of serum creatinine compared with average at 1 year, 3 months, and 4 weeks postoperatively were independent risk factors for the development of CRF or ESRD with odds ratios of 2.6, 2.2, and 1.6, respectively. Overall survival from the time of OLTX was not significantly different among groups, but by year 13, the survival of the patients who had ESRD was only 28.2% compared with 54.6% in the control group. Patients developing ESRD had a 6-year survival after onset of ESRD of 27% for the patients receiving hemodialysis versus 71.4% for the patients developing ESRD who subsequently received kidney transplants. CONCLUSIONS: Patients who are more than 10 years post-OLTX have CRF and ESRD at a high rate. The development of ESRD decreases survival, particularly in those patients treated with dialysis only. Patients who develop ESRD have a higher preoperative and 1-year serum creatinine and are more likely to have hepatorenal syndrome. However, an increase of serum creatinine at various times postoperatively is more predictive of the development of CRF or ESRD. New strategies for long-term immunosuppression may be needed to decrease this complication.

Adult↗
PubMed2001

Renal replacement therapy and orthotopic liver transplantation: the role of continuous veno-venous hemodialysis.

BACKGROUND: The need for renal replacement therapy (RRT) either before or after orthotopic liver transplant (OLTX) has been reported to be a poor prognostic indicator for survival. Use of continuous veno-venous hemodialysis (CVVHD) for RRT has been reported in three series of OLTX patients with high 90-day mortality rates of 57-60%. We have examined our patient population to determine the effect of necessity and type of RRT on patient survival after OLTX. METHODS: We analyzed 1535 OLTX that were performed at our institution from 1985 through 1999, 1037 from 1985 to 1995 (period I) and 498 from 1996 to 1999 (period II). Combined liver-kidney transplants were excluded from analysis. Hospital dialysis unit records and a prospectively maintained database on all OLTX patients served as the source of data. Patients were classified into groups defined on whether or not they received RRT, when they received RRT, and the type of RRT. Groups were compared for preoperative intensive care unit status, time on the waiting list, laboratory variables, 90-day postoperative mortality, 1-year patient survival, and absolute survival. RESULTS: Use of RRT increased from 8.29% in period I to 12.45% in period II, along with increased median waiting times. In period I, patients receiving preoperative RRT had a 90-day mortality (0%) and a 1-year survival (89.5%) almost identical to those patients who never required RRT (1.7% and 90.6%). Patients who developed acute renal failure postoperatively requiring RRT, however, had a 90-day mortality of 28.6% and a 1-year survival of 55%. In period II, patients requiring RRT had a 90-day mortality of 39.7% and a 1-year actuarial survival of 54.5% compared with 6.9% and 88.6% in patients never requiring RRT. Patients treated with CVVHD had a 90-day mortality of 42% compared with 25% in patients treated with hemodialysis alone. However, patients receiving CVVHD both pre- and postoperatively had a 90-day mortality of 27.7% vs. 50% in those patients who only received CVVHD postoperatively. Patients who developed acute renal failure postoperatively, which required RRT, regardless of therapy, had a 1-year survival of only 41.0% compared with a 1-year survival of 73.6% in those patients started on RRT preoperatively, P=0.03. CONCLUSIONS: The need for RRT has increased along with waiting time in OLTX patients. Patients developing the need for RRT postoperatively have an increased 90-day mortality and lower 1-year survival with the highest being present in patients receiving CVVHD, which was started postoperatively. These findings may reflect a trend toward a sicker population awaiting OLTX and emphasize the negative impact of renal failure on survival after OLTX.

Acute Kidney Injury↗
PubMed1996

Ammonia transport by the urinary bladder of Bufo marinus.

All experiments were performed in vitro on toad bladders. Bladder sacs from acidotic toads produced a concentration gradient across the bladder with both [NH3] and [NH4] higher in the mucosal media. By varying the pH of the serosal media, paired sacs from normal toads were incubated with similar [NH3] in the serosal media but a 75 fold difference in [NH4] of the serosal media of the pairs. The hemibladders with the higher [NH4] had a 2.4 fold greater excretory flux than the paired sac. Both serosal to mucosal and mucosal to serosal fluxes were determined in normal bladders between chambers at various ammonium concentration gradients. The plot of mucosal to serosal flux against concentration produced a curve compatible with both carrier mediated and diffusion transport; the plot of serosal to mucosal flux produced a straight line with flux increasing when the ammonium concentration was increased. The serosal to mucosal transepithelial flux was augmented by making the serosal side of the bladder 50 mV positive. Although NH3 diffusion may occur, it cannot be the primary method of ammonia transport in the toad bladder.

Ammonia↗
PubMed1996

Pancreas transplantation for diabetes mellitus.

Pancreas transplantation has become a viable option for the patient wi th insulin-dependent diabetes mellitus with progressive renal failure. The most common type of pancreas transplantation is a simultaneous pancreas and kidney transplantation performed from a single cadaver donor (SPK). The next most common is pancreas transplantation after successful kidney transplantation (PAK). A few centers are performing pancreas transplantation alone (PTA) in diabetic recipients without renal disease but who have significant complications from their diabetes. Pancreas transplantation is associated with a higher morbidity than kidney transplantation alone. Most pancreas transplantation centers report a significant increase in acute rejection, which can lead to increased hospitalization and risk of opportunistic infection. In addition, the early era of pancreas transplantation was associated with significant surgical complications. However, with bladder drainage of the pancreas exocrine secretions, the surgical complication rate has decreased significantly. Despite medical and surgical complications, the overall results for pancreas transplantation are excellent, with 1 -year graft survival of 75% for SPK transplantations and 48% for PAK and PTA transplant recipients. The effects of a pancreas transplantation on the secondary complications of diabetes have been studied extensively. Most studies have shown a modest improvement in secondary complications with the exception of diabetic retinopathy. The major benefit of pancreas transplantation appears to be enhanced quality of life for patients successfully transplanted. For these reasons, the Kidney-Pancreas Committee of the American Society of Transplant Physicians believes the current results of pancreas-kidney transplantation justify its use as a valid option for insulin-dependent diabetic transplant recipients.

Costs and Cost Analysis↗
PubMed1991

The role of interleukin-6 in mitogenic T-cell activation: detection of interleukin-2 heteronuclear RNA by polymerase chain reaction.

It has been documented that interleukin-6 (IL-6) supports the proliferation of purified, anti-CD3-stimulated murine T cells. We found that stimulation of human peripheral blood mononuclear cells (PBMCs) with anti-CD3 induced a significant accumulation of IL-6 mRNA, indicating that antigen-mediated T-cell activation may involve IL-6 release from accessory cells. Phytohemagglutinin (PHA) had little effect upon IL-6 gene expression. In keeping with these findings, anti-IL-6 reduced but did not abolish anti-CD3-mediated proliferation of PBMCs, but had no significant effect upon PHA-stimulated proliferation. The addition of recombinant (r) IL-6 enhanced the proliferation of anti-CD3-stimulated PBMCs and increased the accumulation of IL-2 mRNA in PHA-stimulated PBMCs during the first 5 hr of culture. Nuclear run-off experiments did not reveal significant changes in IL-2 transcription in PHA plus rIL-6-treated PBMCs attempting to assume that IL-6 mediates stabilization of IL-2 mRNA. However, monitoring of partially spliced IL-2 mRNA by polymerase chain reaction revealed a clear increase in IL-2 heteronuclear RNA. Thus IL-6 increases the rate of IL-2 transcription which was not detectable by conventional in vitro transcription assays. We conclude that anti-CD3 triggers T-cell proliferation through a process that is partially but not entirely dependent upon release of IL-6. IL-6, in turn, supports IL-2 transcription. Insofar as anti-CD3 mimics antigen-triggered activation of the T-cell receptor complex, IL-6 appears to support the early immune response by augmenting antigen-triggered IL-2 gene expression.

Antibodies, Monoclonal↗
PubMed1990

Possible association of the immunosuppressive and B cell lymphoma-promoting properties of cyclosporine.

Central to the immunosuppressive properties of cyclosporine is a drug imposed blockade of the interleukin-2 gene activation. As IL-6 stimulates antigen-activated T cells to release IL-2, we examined the influence of CsA on IL-6 gene expression and IL-6-supported T cell proliferation. Northern blot analysis revealed that CsA failed to abolish IL-6 gene expression in mitogen-activated peripheral blood mononuclear cells. In fact, increased IL-6 gene transcription and increased release of IL-6 bioactivity were detected using mitogen-activated PBMCs cultured with CsA doses (200-800 ng/ml) only slightly in excess of the minimal antiproliferative dose. CsA completely abrogated the IL-6-stimulated proliferative responses of macrophage-depleted T cells stimulated with polyvalent anti-CD3 monoclonal antibodies. It is interesting that CsA-treated patients evidence an increased incidence of polyclonal lymphoproliferative disorders and B cell lymphomas. As IL-6 fosters B cell activation and growth of EBV-transformed B cells, excessive CsA doses may support development of EBV-transformed B cell lymphomas via superinduction of the IL-6 gene.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Antibody valence and induced signal transduction: the role of antibody valence in anti-CD3-induced signal transduction in isolated normal T cells.

This report provides direct evidence that protein kinase C (PKC) is activated in isolated, rigorously accessory cell (AC)-depleted T cells when the T cell antigen recognition complex is stimulated by divalent anti-CD3 monoclonal antibody. Anti-CD3 monoclonal antibody-stimulated PKC activation alone does not, however, directly stimulate T cell proliferation in the absence of AC. A rise in cytosolic calcium is the second signal believed to be of paramount importance in T cell activation. While mitogenic concentrations of some divalent anti-CD3 antibodies do not cause a rise in cytosolic calcium, polyvalent anti-CD3 does evoke increased intracellular Ca2+ in rigorously AC-depleted resting human T cells.

Antibodies, Monoclonal↗
PubMed1988

Endotoxin-associated protein: interleukin-1-like activity on serum amyloid A synthesis and T-lymphocyte activation.

Bacterial endotoxins or lipopolysaccharides (LPS) elicit a variety of biologic activities in intact animals and various in vitro systems. LPS from most gram-negative bacteria have appeared to have similar biologic activities regardless of the species of origin or method of preparation of the LPS. More recent studies have suggested differences in the effects of protein-rich as opposed to protein-free LPS in inducing mitogenesis of lymphocytes from endotoxin-resistant C3H/HeJ mice. These studies examine other activities of endotoxin-associated protein (EAP), purified to less than 0.007% contamination with LPS, and demonstrate that this material has activity mimicking some of the effects of interleukin-1 (IL-1). EAP proved to be as potent as LPS in eliciting rises in concentrations of serum amyloid A (SAA) and was active in both endotoxin-sensitive (CF1) and endotoxin-resistant (C3H/HeJ) mice. In contrast to LPS, which mediates its SAA-inducing activity by release of an inducer (IL-1) from LPS-stimulated macrophages, EAP appeared to act directly to induce SAA production, in that incubation with macrophages failed to increase its activity. EAP also exhibited IL-1-like activity in the lymphocyte-activating factor assay when both CF1 and C3H/HeJ thymocytes and macrophages were tested. The lymphocyte-activating factor activity of EAP was not blocked by addition of polymyxin B. In addition, EAP exerted stimulatory activity on resting human T lymphocytes, costimulated with Sepharose-bound anti-CD3 monoclonal antibody 64.1, comparable to that observed with purified human monocyte IL-1. These studies indicate that proteins from procaryotic cells may act as cytokines for some eucaryotic cells.

Animals↗
PubMed1979

Stimulation of ammonium ion excretion in the toad urinary bladder by an extract of human urine.

It is well known that ammonium ion excretion is increased during metabolic acidosis in mammals. The purpose of this study was to determine whether we could isolate from human urine during metabolic acidosis a factor that would stimulate NH+4 and/or H+ excretion in toad urinary bladder. Extracts of urine from six human subjects collected during NH4Cl-induced acidosis were prepared. These extracts were tested for their effect on NH+4 excretion in hemibladders mounted between plastic chambers. The extracts significantly increased NH+4 excretion in the toad urinary bladder. We found no effect on H+ excretion by these extracts. This ammoniuretic activity was not present in the urine when the same individuals were in metabolic alkalosis. We conclude that during metabolic acidosis a humoral factor is present which stimulates the excretion of NH+4. The factor could act as a permease in the bladder cell or as a stimulator of an NH+4 transport system.

Acid-Base Equilibrium↗
PubMed1976

The effect of angiotensin II on electrolyte excretion by the renal tubules.

In vivo studies were done on mongrel dogs to determine the effect of angiotensin II on renal electrolyte excretion. Angiotensin II was infused directly into the left renal artery at a rate of 1 ng/kg/min. Angiotensin produced consistent reductions in the excretion of Na+, K+, and Cl- in the left kidney. These reductions could not be attributed to decreases in GFR or RPF. Electrolyte excretion by the right kidney was constant. These data are consistent with the hypothesis that angiotensin II may function as an intrarenal, antinatriuretic hormone.

Angiotensin II↗