Effect of hypothermia on renal sodium reabsorption

Summary The relationship between sodium reabsorption and oxygen consumption was studied in an isolated rabbit kidney preparation perfused with blood at 37, 28 and 19° C. When the temperature was lowered from 37° C to 28° C and to 19°C the rate of oxygen consumption and of the maximal P.A.H. excretion (Tm P.A.H.) decreased more than that of sodium reabsorption.TheQ ₁₀ for sodium reabsorption is about 1.8, while that for maximal P.A.H. excretion is 2.5. Some hypothesis on the possible mechanisms of the lowQ ₁₀ of the Na⁺ reabsorption are forwarded.Preliminary reports have been published [Boll. Soc. Ital. Biol. Sper.43, 1019–1023 (1966) and44, 1784–1787 (1967);45, 860–862 (1969) and45, 863–865 (1969)].     

In situ characterization of human cytomegalovirus infection of bronchiolar cells in human transplanted lung

Distal airway cell infection by human cytomegalovirus (HCMV) in transplanted lung has been occasionally reported but not systematically investigated. The present study aimed at testing the prevalence of HCMV bronchiolar infection in human transplanted lung. We identified and immunophenotyped, with double labeling, infected lung cells in 31 transbronchial biopsies with HCMV infection, containing distal airways (7 HCMV pneumonias, 7 HCMV infection without inflammation, and 17 morphologically occult, non-cytopathic HCMV infection). HCMV-infected cells in pneumonias, localizations, and occult infections were alveolar epithelia (32.8%, 42.8%, and 53.5%, respectively), endothelia (22.9%, 24.7%, and 26.4%, respectively), macrophages (0.006%, none, and none, respectively), airway epithelia (0.01%, 8.9%, and none, respectively), and bronchiolar smooth muscle cells (0.011%, 14.6%, and 16.1%, respectively). Ciliated and bronchiolar smooth muscle cells in transplanted lung only occasionally harbored viral infection and never showed viral cytopathy. On the basis of our morphological observations, HCMV infection of bronchiolar wall cells is rare, while alveolar epithelia and capillary endothelial cells are the major targets of lung infection.     

Histopathologic and molecular profile of human cytomegalovirus infections in patients with heart transplants.

From November 1985 to December 1990, 2,552 endomyocardial biopsy specimens from 209 heart transplant patients were studied. Forty-four (21%) patients developed 45 episodes of major human cytomegalovirus infection (HCMV). Human cytomegalovirus infection was primary in 13 of 44 patients. Thirty-one patients developed episodes of recurrent major infection. One patient had both primary and recurrent infections. Conventional histopathologic and immunohistochemical study, in situ hybridization, and polymerase chain reaction were used to diagnose HCMV myocardial involvement on corresponding endomyocardial biopsy specimens performed during infection. Conventional morphologic study showed typical viral inclusion bodies in four biopsy specimens. Two cases had myocyte HCMV localization with necrotizing myocarditis, whereas two had endothelial cell involvement without any inflammatory reaction. In these four biopsy specimens, immunohistochemistry showed a higher number of infected cells than that recognized by conventional histopathologic study. In situ hybridization detected infected cells with no evidence of cytopathic effect. Polymerase chain reaction gave HCMV amplification products in two additional biopsy specimens otherwise interpreted as moderate and mild rejection, respectively. Therefore, 6 biopsies showed HCMV myocardial involvement (6 of 45; 13.3%): all were from patients with primary HCMV infection (6 of 13; 46%). None of 32 major recurrent infections showed any myocardial involvement. In conclusion, our study is the first to demonstrate that myocardial HCMV involvement preferentially occurs in primary infection and HCMV endothelial localization can be free from inflammatory reaction, whereas HCMV myocyte localization leads to necrotizing myocarditis. Polymerase chain reaction has a higher diagnostic sensitivity than in situ hybridization. However, polymerase chain reaction findings of HCMV DNA on otherwise negative endomyocardial biopsy specimens remains of questionable significance because polymerase chain reaction-positive biopsy samples do not necessarily indicate tissue infection. It is impossible to determine whether amplified sequences derive from circulating leukocytes or from tissue cells.     

Loss of lamin A/C expression revealed by immuno-electron microscopy in dilated cardiomyopathy with atrioventricular block caused by<Emphasis Type="Italic"> LMNA</Emphasis> gene defects

Mutations of the LMNA gene encoding the lamin A and C nuclear envelope proteins cause an autosomal dominant form of dilated cardiomyopathy (DCM) with atrioventricular block (AVB). The aim of this study was to investigate ultrastructural nuclear membrane changes by conventional electron microscopy and protein expression by immuno-electron microscopy in the heart of patients with DCM and AVB due to LMNA gene mutations. Four immunohistochemical techniques were used: pre-embedding and post-embedding in Epon-Araldite resin and London Resin White (LRW), with and without silver enhancement. Parallel light microscopy immunohistochemistry studies were performed. Conventional electron microscopy showed a loss of integrity of the myocyte nuclei with blebs of the nuclear membrane, herniations and delamination of the nuclear lamina and nuclear pore clustering. Post-embedding LRW was the most informative technique for morphology and immuno-labelling. Immuno-labelling was almost absent in the nuclear envelope of patients with LMNA gene mutations, but intensely present in controls. The loss of labelling selectively affected myocyte nuclei; the endothelial cell nuclei were immunostained in patients and controls. Light immunohistochemistry confirmed the results. These findings confirm the hypothesis that LMNA gene defects are associated with a loss of protein expression in the selective compartment of non-cycling myocyte nuclei.     

Post bending of the polypropylene flexible stent in mitral Hancock bioprostheses

The occurrence of stent post deformity was investigated in 38 consecutive, polypropylene flexible-stented Hancock porcine bioprostheses (PB) recovered from the mitral position because of early postoperative death or late tissue failure. The degree of deformity was assessed for each explant by calculating the triangular area obtained by projecting the apex of the stent posts on a plane and comparing it with the same area calculated for unimplanted PBs of comparable size. A significant stent deformity (reduction of the triangular area greater than 40%) was observed only in 6 PBs explanted because of tissue failure after a mean function time of 69.6 +/- 28 months. In these PBs, scanning electron microscopy of the bare surface of the stent at the point of maximal flexion showed cracks 0.7-1 microns large, which represent the morphological substrate of the so-called "creep" of polypropylene. Inward stent post bending may occur after implantation in mitral PBs and when severe, it corresponds to a definite ultrastructural plastic deformity of polypropylene.     

Hydrophobic Bombyx mori Silk Fibroin: Routes to Functionalization with Alkyl Chains

Bombyx mori silk fibroin (SF) is a very versatile biopolymer due to its biocompatibility and exceptional mechanical properties which make possible its use as a functional material in several applications. SF can be modified with a large variety of chemical approaches which endow the material with tailored chemical–physical properties. Here, a systematic investigation of different routes is reported to graft long alkyl chains on SF based on both liquid- and solid-phase, aiming to modulate its hydrophobic behavior. The liquid phase method involves direct activation of SF tyrosine residues via diazo coupling and cycloaddition reactions, generating hydrophobic materials insoluble in any common solvent. The solid phase approach consists of the chemical modification of drop-casted SF films by esterification of hydroxyl groups of serine, threonine, and tyrosine SF residues with acyl chlorides of fatty acids. For the solid-state functionalization, a new class of hydrophobic pendant groups is synthesized, based on triple esters of gallic acid anhydrides, that are reacted with the biopolymer to further enhance its resulting hydrophobic features.     

Clinical pharmacokinetics of tacrolimus in heart transplant recipients

We report pharmacokinetic data on tacrolimus in 14 heart transplant patients (2 women, 12 men). The median age and the median body weight were 55.5 years (range, 23-61 years) and 67.0 kg (55-79 kg), respectively. All patients were maintained on a triple-drug protocol (tacrolimus, azathioprine, and prednisone), with a 7-day antithymocyte globuline induction. The first tacrolimus dose, administered orally 1 to 5 days posttransplant, ranged from 0.03 to 0.4 mg/kg (median = 0.052 mg/kg). The maintenance dose ranged from 0.03 to 0.13 mg/kg/day (administered in two equal doses) to achieve blood levels of 5 of 20 ng/ml, as determined by a microparticle enzyme immunoassay (MEIA). Whole blood samples were drawn just before, at 0.5 hour, and at 1, 2, 3, 4, 6, 8, 10, and 12 hours after the administration of the first dose; trough levels were measured thereafter.The mean oral clearance (CL/F) and apparent volume of distribution (Vd/F) averaged 0.21+/-0.08 L/hour/kg and 2.4+/-0.8 L/kg while the half-life averaged 8.7+/-3.5 hours. Tacrolimus accumulation index during chronic therapy (Rac = Cmin(steady state)/Cmin(first dose) normalized to the same dose) averaged 1.3. Eighty-eight percent of the trough blood levels measured in our patients were within 5 and 20 ng/ml. The incidence of rejection in the study population was extremely low: a prevalence of grade 2 rejection or more, of 0.4+/-0.8 episodes/ patient was observed after a follow-up period of 8.8+/-2.2 months. Only one patient experienced severe renal toxicity, probably because of his preoperative precarious hemodynamic status. Pharmacokinetic data suggest that maintenance tacrolimus daily dose should be equal to 0.1 mg/kg/day to obtain trough blood concentrations of approximately 10 ng/ml. Inter- and intra-patient variability of tacrolimus blood concentration should be expected and justify careful monitoring.     

Immunohistochemical characterization of coronary thrombi in allograft vascular disease

BACKGROUND: Coronary thrombosis is a frequent complication of allograft vascular disease (AVD) in cardiac transplant recipients. No data are available on thrombus composition in these hearts. METHODS: The present study aimed at characterizing thrombus components in coronary arteries from transplanted hearts with AVD, using single and double immunostain with anti-gpIIb-IIIa, anti-fibrin, and anti-endothelial antibodies. The pathologic series consists of 55 grafts survived longer than 2 months, and obtained from 55 patients deceased (n=44) or undergone repeat transplantation (n=11). RESULTS: Mural thrombi were found in multiple segments of 75 of 440 total coronary vessels (17%) (recent in 33, organizing in 28, and organized in 14), whereas occlusive thrombi were found in 19 vessels (8 recent and 11 with multichannel pattern of organization). Recent and thin mural thrombi were mostly constituted of CD41a- and CD61-positive platelets; the amount of fibrin progressively increased with the increase of thrombus size. In organizing mural thrombi, gpIIb-IIIa immunostain was still present. Fibrin was the only identifiable thrombus component in old mural thrombi embedded within the intimal lesions. Recent occlusive thrombi immunoreacted both with anti-CD41a and anti-CD61 and with anti-fibrin antibodies, whereas organized occlusive thrombi with multichannel pattern exclusively immunoreacted with anti-fibrin antibodies. Double immunostain showed that mural thrombi were stratified on de-endothelized arterial segments. CONCLUSIONS: Thrombus composition is related to both type and "age" of thrombus, with platelets as the early and major components of mural microthrombi at one end of the spectrum, and fibrin as the dominant component of occlusive thrombi at the other end.     

Efficacy of tacrolimus rescue therapy in refractory acute rejection after lung transplantation.

BACKGROUND: Encouraging results in transplantation of other solid organs led to investigation of the use of tacrolimus in lung transplantation as a salvage immunosuppressant in persistent acute rejection. METHODS: The incidence and severity of acute rejection and the number of steroid pulses were analyzed in 20 lung recipients who were converted from a cyclosporine- to a tacrolimus-based immunosuppressive regimen because of refractory biopsy-proven acute rejection. RESULTS: Tacrolimus was started 12.0 +/- 13.0 months after transplantation, and the mean follow-up was 25.0 +/- 13.7 months. After shifting to tacrolimus, a significant decline was observed in both the number of acute rejections per patient (3.0 +/- 1.56 to 0.85 +/- 1.14, p < 0.0001), and the incidence of acute rejection per 100 patient-days (1.52 +/- 0.99 to 0.14 +/- 0.21, p < 0.0001). Furthermore, the average histologic grade of rejection decreased from 1.9 +/- 0.8 to 0.4 +/- 0.5 (p < 0.0001). Methylprednisolone pulses similarly decreased from 1.9 +/- 1.3/patient to 0.3 +/- 0.7/patient (p < 0.0001). During cyclosporine immunosuppression, the mean forced expiratory volume in 1 second decreased to 84.4% +/- 13.3% of individual best value. The average lung function parameters were stable 3 months after the change of medication, and then began to improve. After an average follow-up of 36.5 +/- 19.2 months, 2 patients have developed bronchiolitis obliterans syndrome (one has Stage 1 and one has Stage 3). CONCLUSION: Conversion to a tacrolimus-based immunosuppressive regimen for refractory acute lung rejection is associated with reduced incidence and severity of acute rejection episodes, steroid sparing, and stabilization or improvement of pulmonary function.