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Biomedical subjects

L A Fernandez

Publications and source records attributed to L A Fernandez.

At least 19 recordsLinked to original sources
PubMed2007

Quantification of basal and stimulated ROS levels as predictors of islet potency and function.

We have developed a luminol-based assay using intact islets, which allows for quantification of reactive oxygen species (ROS). In addition, an index capable of characterizing metabolic and mitochondrial integrity prior to transplantation was created based on the capacity of islets to respond to high glucose and rotenone (mitochondrial respiratory chain complex I inhibitor) by production of ROS. To validate this assay, lipid peroxidation and antioxidative defense capacity were evaluated by detection of malondialdehyde (MDA) levels and glutathione peroxidase activity (GPx), respectively. Also, flow cytometric analyses of ROS (dihydroethidine), apoptosis (Annexin V, active caspases), necrosis (Topro3), and mitochondrial membrane potential (JC-1) were done in parallel to correlate with changes in luminol-measured ROS. ATP/ADP ratios were quantified by HPLC and the predictive value of ROS measurement on islet functional potency was correlated with capacity to reverse diabetes in a streptozotocin-induced diabetic NOD.scid mouse model as well as in human transplant recipients. Our data demonstrate that levels of ROS in islets correlate with the percentage of apoptotic cells and their functional potency in vivo. The ROS indices following glucose and rotenone exposure are indicative of metabolic potency and mitochondrial integrity and can be used as surrogate markers to evaluate the quality of islets prior to transplantation.

Animals↗
PubMed2006

Outcomes of pancreas transplantation in the United States using cardiac-death donors.

Organs donated after cardiac death (DCD) are used to expand the donor pool. We analyzed the outcomes in the United States of pancreatic transplantation of organs from DCD donors performed between 1993 and 2003. We used the OPTN/UNOS Registry to compare outcomes of primary pancreas allografts from DCD donors and donors after brain death (DBD). The primary endpoints were graft failure and patient death. A national survey regarding the use of DCD donors in pancreas transplantation was conducted among the directors of pancreas transplant centers. Data were obtained on 47 simultaneous pancreas-kidney transplants (SPK) and 10 solitary pancreas transplants from DCD donors and on 2431 SPK and 1607 solitary pancreas transplants from DBD donors. Recipients of a SPK transplants from DCD and DBD donors had equivalent patient and graft survival rates at 1, 3 and 5 years. For recipients of SPK transplants, the wait for organs from DCD donors was significantly shorter than that for organs from DBD donors. SPK recipients of organs from DCD donors had longer hospital stays than did recipients of organs from DBD donors. With renal allografts, the incidence of delayed graft function was almost four times higher with organs from DCD donors than with organs from DBD donors. Selective use of organs from DCD donors is safe for pancreas transplantation.

Adult↗
PubMed2001

Protection against ischemia: a physiological function of the renin-angiotensin system.

The renin-angiotensin system (RAS) is involved in a complex mechanism that serves to preserve the blood supply to organs so that they can maintain cellular function. Angiotensin II exerts this effect, independently of the blood pressure generated, through two time-related events: a fast opening of the reserve collateral circulation and a much slower response of new vessel formation or angiogenesis. This effect is observed in rats with ligation of the abdominal aorta and in gerbils with abrupt or progressive unilateral carotid artery ligation. Inhibition of the angiotensin-converting enzyme (ACE) or the angiotensin II receptor represses this effect, and it appears that it is mediated through a non-AT1 receptor site of angiotensin II. Many tumors, both benign and malignant, express renin and angiotensin. It seems that the stimulating action of angiotensin II on angiogenesis could also be involved in preserving the blood supply to tumor cells. Administration of converting enzyme inhibitors increases survival and decreases tumor size in tumor-bearing rats. These observations support the hypothesis that the RAS, directly or indirectly, is involved in situations in which the restoration of blood supply is critical for the viability of cells and that it is present not only in normal but also in pathological conditions such as tumors. In view of the ubiquitous presence of renins and angiotensins, it is also likely to be involved in other conditions, such as inflammation, arthritis, diabetic retinopathy, and retrolental fibroplasia, among others in which angiogenesis is prominent. In addition, angiotensin II could be involved, through the counterbalance of the AT1 and AT2 receptors, in the rarefaction of blood vessels as an etiologic component of essential hypertension.

Angiogenesis Inducing Agents↗
PubMed2001

An unusual presentation of extramedullary plasmacytoma occurring sequentially in the testis, subcutaneous tissue, and heart.

Extramedullary plasmacytoma (EMP) is a rare neoplasm of soft tissue that usually arises in the respiratory tract, nasal cavity, sinuses, and nasopharynx. It is even more uncommon for it to arise either in the testis or heart. We report the presentation of a case where plasmacytomas were found sequentially in the testis, subcutaneous tissue, and heart. EMP usually has a good prognosis except when it involves the heart. Our patient survived for only 15 months post autologous hematopoietic stem cell transplantation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Combined carotid artery injury and laryngeal fracture secondary to dog bite: case report.

Approximately 914 new dog bite injuries requiring emergency department visits occur daily in the United States. Attacks by dogs with training and strength to attack should be triaged cautiously because of the possibility of serious internal injury. A high index of suspicion is needed when treating patients with neck injuries secondary to dog bites. We report a case of successfully treated combined carotid artery and laryngeal injury produced by a dog bite.

Adult↗
PubMed1999

The effects of maintenance doses of FK506 versus cyclosporin A on glucose and lipid metabolism after orthotopic liver transplantation.

BACKGROUND: Posttransplant diabetes mellitus (PTDM) has gained widespread attention due to the micro and macro-vascular complications that increase the morbidity and mortality of patients receiving solid organs. The higher incidence of PTDM has been mainly attributed to the immunosuppressive therapy. Therefore, this study compares the metabolic side effects of low dose maintenance therapy of FK-506 and Cyclosporin A (CsA) in 14 patients 1 year after orthotopic liver transplant and analyzes possible factors that contribute to the development of PTDM. METHODS: Two groups (n=7) differing in their immunosuppressive regimen (FK506 or CsA) were matched to eight control subjects and compared to each other. The effects of in vivo insulin action were assessed by means of the euglycemic hyperinsulinemic clamp technique. Arginine stimulation tests at normo- (5.5 mM) and hyperglycemic (15 mM) levels were performed and the acute insulin, C-peptide, and glucagon response (2-5 min) to arginine were determined. RESULTS: Insulin sensitivity (total glucose disposal) was statistically lower in patients treated with FK-506 and CsA (5.05+/-0.47 and 5.05+/-0.42 mg/kg/min) as compared to controls (6.62+/-0.38 mg/kg/min) (P<0.02), with a significantly higher nonoxidative glucose disposal for the control group (P<0.01), and lower free fatty acid levels (P<0.05). Absolute values for acute insulin response were higher but not significantly different for the transplanted groups. The lower percentage of increase of insulin release after arginine stimulation observed in the FK-506 and CsA groups as compared with controls (754%+/-100, 644%+/-102 vs. 1191%+/-174) (P<0.03 and 0.02, respectively), suggests a reduced beta cell secretory reserve in both treated groups. Also, the acute glucagon response to arginine during hyperglycemia declined less in the FK-506 (28%) and CsA groups (29%) compared with controls (48%) (P<0.05) indicating a defect in the pancreatic beta cell-alpha cell axis. CONCLUSIONS: There are no major metabolic differences on low maintenance doses between FK-506 and CsA. Both immunosuppressant agents contribute to the development of PTDM at different levels.

Blood Glucose↗
PubMed1999

Long-term survival and function of intrahepatic islet allografts in baboons treated with humanized anti-CD154.

Clinical islet cell transplantation has resulted in insulin independence in a limited number of cases. Rejection, recurrence of autoimmunity, and impairment of normal islet function by conventional immunosuppressive drugs, e.g., steroids, tacrolimus, and cyclosporin A, may all contribute to islet allograft loss. Furthermore, intraportal infusion of allogeneic islets results in the activation of intrahepatic macrophages and endothelial cells, followed by production of proinflammatory mediators that can contribute to islet primary nonfunction. We reasoned that the beneficial effects of anti-CD154 treatment on autoimmunity, alloreactivity, and proinflammatory events mediated by macrophages and endothelial cells made it an ideal agent for the prevention of islet allograft failure. In this study, a nonhuman primate model (Papio hamadryas) was used to assess the effect of humanized anti-CD154 (hu5c8) on allogeneic islet engraftment and function. Nonimmunosuppressed and tacrolimus-treated recipients were insulin independent posttransplant, but rejected their islet allografts in 8 days. Engraftment and insulin independence were achieved in seven of seven baboon recipients of anti-CD154 induction therapy administered on days -1, 3, and 10 relative to the islet transplant. Three of three baboons treated with 20 mg/kg anti-CD154 induction therapy experienced delayed rejection episodes, first detected by elevations in postprandial blood glucose levels, on postoperative day (POD) 31 for one and on POD 58 for the other two. Re-treatment with three doses of anti-CD154 resulted in reversal of rejection in all three animals and in a return to normoglycemia and insulin independence in two of three baboons. It was possible to reverse multiple episodes of rejection with this approach. A loss of functional islet mass, as detected by reduced first-phase insulin release in response to intravenous glucose tolerance testing, was observed after each episode of rejection. One of two baboons treated with 10 mg/kg induction therapy became insulin independent post-transplant but rejected the islet graft on POD 10; the other animal experienced a reversible rejection episode on POD 58 and remained insulin independent and normoglycemic until POD 264. Two additional baboon recipients of allogeneic islets and donor bone marrow (infused on PODs 5 and 11) were treated with induction therapy (PODs -1, 3, 10), followed by initiation of monthly maintenance therapy (for a period of 6 months) on POD 28. Rejection-free graft survival and insulin independence was maintained for 114 and 238 days, with preservation of functional islet mass observed in the absence of rejection. Prevention and reversal of rejection, in the absence of the deleterious effects associated with the use of conventional immunosuppressive drugs, make anti-CD154 a unique agent for further study in islet cell transplantation.

Animals↗
PubMed1998

Transplantation of allogeneic islets of Langerhans in the rat liver: effects of macrophage depletion on graft survival and microenvironment activation.

Early impairment of islet function and graft loss limit the success of allogeneic islet transplantation. Nonspecific inflammatory events occurring at the transplant site immediately after grafting, involving the production of cytokines and free radicals and sinusoidal endothelial cell (SEC) activation, may contribute to islet cell damage. To evaluate whether Kupffer cell inactivation would result in prolonged allograft survival in a model system of intrahepatic islet transplantation in rats, we systemically administered either gadolinium chloride (GdCl3) or dichloromethylene diphosphonate (Cl2MDP) to assess the effects of macrophage inactivation on rejection and on the release of proinflammatory molecules, as well as to assess the functional profile of SEC. The results obtained were compared with those observed in untreated, sham-injected animals and in rats receiving intraportal infusions of microbeads. Transient macrophage inhibition, particularly in hepatic Kupffer cells, is associated with significant prolongation of graft survival after intraportal islet allotransplantation (ITx) in rats: 7.2 days in the control group versus 11.9 days in the GdCl3 group (P < 0.01) and 15.6 days in the Cl2MDP group (P < 0.0006), respectively. Although systemic release of inflammatory mediators was observed only when islet transplantations were performed and it could be inhibited by macrophage-targeting treatments, perturbation of the functional profile of endothelial cells was also observed when microembolization was induced by the use of microbeads and could not be prevented by macrophage inhibition. These experiments provide evidence to support the concept that macrophages play a key role in early inflammatory events known to adversely affect islet engraftment and suggest that manipulation of nonspecific immune activation by inhibition of macrophage function may facilitate hepatic engraftment of islet allografts. The mechanisms mediating this effect are likely to include prevention of release of tumor necrosis factor-alpha, interleukin-1beta, and NO and interference with the rate of immune response to the islets.

Animals↗
PubMed1997

Human islet allografts in patients with type 2 diabetes undergoing liver transplantation.

BACKGROUND: Most patients with cirrhosis have insulin resistance and impaired glucose tolerance, and 20% eventually develop diabetes. Although diabetes in this setting may be reversible after orthotopic liver transplantation (OLTx), immunosuppressive agents administered after transplantation could exacerbate this disease. We report the results of the first pilot trial of islet cell transplantation (ICTx) in patients with diabetes undergoing OLTx. METHODS: Five patients with diabetes and liver cirrhosis underwent OLTx and ICTx. Donor bone marrow cells were also infused to enhance the acceptance of the graft. We identified seven patients who received only OLTx and donor bone marrow cells as historical controls. RESULTS: Preliminary results suggest that ICTx in conjunction with OLTx may improve glucose metabolism (insulin requirement, hemoglobin A1c) in patients with liver cirrhosis. However, there was virtually no change in pre- and posttransplant basal C-peptide levels in the recipients of OLTx + ICTx. CONCLUSIONS: We are planning to further evaluate the effect of OLTx with or without ICTx in a randomized prospective trial, using euglycemic insulin clamp studies.

Adolescent↗
PubMed1997

Normal CD5+ B lymphocytes are poor stimulators in the autologous mixed lymphocyte reaction (AMLR).

The AMLR is decreased in chronic lymphocytic leukaemia (CLL), which is characterized by a monoclonal expansion of CD5+ B lymphocytes. Since B cells are used to stimulate the AMLR, we investigated the capacity of normal CD5+ B cells to function as stimulators in the AMLR. We isolated B cells from the peripheral blood of normal individuals and fractionated them into subpopulations enriched for CD5+ and CD5- cells, which were used as stimulators in the AMLR. We found that the CD5- B cells were excellent stimulators, whereas stimulation of AMLR by B cells enriched for CD5+ cells resulted in significantly reduced proliferative responses (P < 0.005). This suggests that the reduced AMLR in CLL is due to the predominance of CD5+ B lymphocytes in the stimulating cell population.

B-Lymphocytes↗
PubMed1997

Effects of ketamine sedation on glucose clearance, insulin secretion and counterregulatory hormone production in baboons (Papio hamadryas).

Since the effects of ketamine sedation seem to differ between subspecies of baboons, we assessed the endocrine response to an intravenous glucose tolerance test (IVGTT) in 12 hamadryas baboons. The first phase insulin secretion, basal insulin, and glucose levels, as well as the glucose clearance, were significantly lower in sedated baboons as compared to fully awake animals. Glucagon and cortisol were significantly higher, while growth hormone was lower during ketamine sedation. Papio hamadryas appears to be a promising pre-clinical model for the study of endocrine replacement therapy in insulin-dependent diabetes. However, the data obtained must be interpreted with the knowledge that the anesthetic employed to allow for testing of the animals does have an effect on the parameters described in this report.

Anesthetics, Dissociative↗
PubMed1996

Direct evidence of cavitation in vivo from diagnostic ultrasound.

Recent increases in the pressure output of diagnostic ultrasound scanners have led to an interest in establishing thresholds for bioeffects in many organs including the lungs of mammals. Damage may be mediated by inertial cavitation, yet there have been no such direct observations in vivo. To explore the hypothesis of cavitation-based bioeffects from diagnostic ultrasound, research has been performed on the thresholds of damage in rat lungs exposed to 4.0-MHz pulsed Doppler and color Doppler ultrasound. A 30-MHz active cavitation detection scheme complementing these studies provides the first direct evidence of cavitation in vivo from diagnostic ultrasound pulses.

Animals↗
PubMed1996

Prevalence of abnormal levels of serum tumour markers in elderly people.

The study was conducted to evaluate the prevalence of abnormal levels of several serum tumour markers in an institutionalized elderly population. Serum tumour markers assay of carcinoembryonic antigen (CEA), the carbohydrate antigens CA 19-9, CA 72-4 and CA 15-3 (Enzymun-test, Boehringer Mannheim GmbH Diagnostic), alpha-fetoprotein (AFP) and prostate specific antigen (PSA) (Abbot Diagnostic Division) were performed in 228 unselected, institutionalized elderly subjects, whose mean age (SD) was 82.4 (5. 79) range (66-99 years). Patients with acute or neoplastic diseases were excluded from the study. The serum markers were also measured in 52 healthy young adults (controls). Using the established threshold values, 92 subjects (40%) were found to have at least one elevated marker. PSA was elevated in 33%, CA 19-9 in 16%, CEA in 11. 5%, CA 15-3 in 11%, CA 72-4 in 8% and AFP in 3%. We found a significant difference in the serum levels between the two groups for CEA, CA 19-9. CA 15-3, and PSA (p < 0.0001). Healthy aged people appear to have an elevated prevalence of elevated levels of serum tumour markers. The results suggest that apart from PSA, elevated antigen levels in elderly subjects are related to the ageing process itself rather than to occult pathology.

Aged↗
PubMed1995

Feedback suppression of B cell colony formation by supernatants of B colony cells: role of immunoglobulin.

We have reported previously that CD5+ B cells from mature B cell colonies provide a negative feedback signal to the growth of autologous B cell colonies. Now we have observed that supernatants from mature B cell colonies also provide a negative feedback signal to the growth of autologous B cell colonies. We investigated the mechanism of this effect by growing B cell colonies physically separated by a 0.45 micron filter from T cells in millicell-CM chambers. Addition of colony supernatants to the T cell compartment reduced the number of B cell colonies by 28 +/- 6%. Colony numbers were reduced by 11 +/- 2 and 17 +/- 5% when the supernatants were added to the B cell or to both compartments, respectively. Pulsing T cells with the B cell colony supernatants before adding them to the colonies also decreased colony numbers by 33 +/- 13%. The addition of exogenous Ig classes and IgG subclasses to B cells decreased B cell colony numbers, although the effect was variable. In the presence of T cells, IgG had the greatest suppressive activity and the subclass IgG4 was most suppressive. In the absence of T cells, high concentrations of IgG almost abolished B cell colony formation. We conclude that these supernatants provide a negative feedback signal either directly to B cells, or via T cells which may be mediated at least in part by Ig.

Antigens, CD↗