Carlos Silva López

Association of Renal Allograft Rejection with Virus Infections

Abstract Sixty-one immunosuppressed renal transplant recipients were systematically screened for virus infections and the findings correlated with their clinical course. Only herpesvirus (cytomegalovirus, herpes simplex and herpes zoster) were consistently isolated. The onset of virus infections could usually be associated with clinical syndromes. Patients without virus infections were usually asymptomatic. The clinical syndrome associated with virus infection consisted of fever, leukopenia and renal allograft rejection. Renal biopsy, performed at the time serum creatinine levels were elevated, revealed classic rejection; most rejections were reversed by increasing the dose of steroids. Patients continued to excrete virus even after antibody response and clinical recovery. Virus infections do not appear to be incidental findings in transplant patients except after recovery when the virus persists in the immune patient. The clear-cut association between virus infection and rejection episodes suggests a pathogenic relationship. The two mechanisms which seem to best explain the relationship are (1) the virus infection acting as an adjuvant and triggering the rejection of the allograft or (2) the allograft rejection activating a latent virus infection.

Effects of the PPARγ agonist pioglitazone on lipoprotein metabolism in patients with type 2 diabetes mellitus

Elevated plasma levels of VLDL triglycerides (TGs) are characteristic of patients with type 2 diabetes mellitus (T2DM) and are associated with increased production rates (PRs) of VLDL TGs and apoB. Lipoprotein lipase–mediated (LPL-mediated) lipolysis of VLDL TGs may also be reduced in T2DM if the level of LPL is decreased and/or the level of plasma apoC-III, an inhibitor of LPL-mediated lipolysis, is increased. We studied the effects of pioglitazone (Pio), a PPARγ agonist that improves insulin sensitivity, on lipoprotein metabolism in patients with T2DM. Pio treatment reduced TG levels by increasing the fractional clearance rate (FCR) of VLDL TGs from the circulation, without changing direct removal of VLDL particles. This indicated increased lipolysis of VLDL TGs during Pio treatment, a mechanism supported by our finding of increased plasma LPL mass and decreased levels of plasma apoC-III. Lower apoC-III levels were due to reduced apoC-III PRs. We saw no effects of Pio on the PR of either VLDL TG or VLDL apoB. Thus, Pio, a PPARγ agonist, reduced VLDL TG levels by increasing LPL mass and inhibiting apoC-III PR. These 2 changes were associated with an increased FCR of VLDL TGs, almost certainly due to increased LPL-mediated lipolysis.

Cytomegalovirus: Clinical Virological Correlations in Renal Transplant Recipients

One-hundred thirty-two renal transplant recipients were systematically screened for viral infections and the findings correlated with the clinical course. One-hundred ten patients showed evidence of infection with herpesviruses and 89 patients showed laboratory evidence of infection with cytomegalovirus (CMV) uncomplicated by bacterial infections or technical complications. Patients without viral infections were usually asymptomatic. After recovery and development of anti-viral antibodies, most patients were asymptomatic despite the persistence of viral excretion in the urine. In contrast, the onset of viral infections were almost always accompanied by a significant clinical illness characterized by fever, leukopenia, and renal malfunction. Of 89 patients with cytomegalovirus infections, 83 survived at least three months. In these patients, the fever appeared to be self-limited and resolution of the fever was accompanied by increases in anti-CMV antibody. Renal biopsies demonstrated typical rejection reactions in all the biopsied patients and renal malfunction usually responded to anti-rejection treatment. Six of the 89 patients with CMV infections died within a month of viral isolation. These patients could be distinguished from those who recovered by a decreased or absent antibody response to the virus, suppressed lymphocyte responses to mitogen in autochthonous blood, and absent histologic evidence of rejection in the renal allografts. Thus, two paradoxical responses to CMV infections are seen in transplant patients: In the relatively immunocompetent patient, the infection is associated with renal allograft rejection, a prompt antibody response to the virus, and recovery. The severely immunosuppressed patient cannot make an antibody response, does not exhibit allograft rejection as a cause of renal malfunction, he may be further immunosuppressed by the viral infection, and is susceptible to sequential opportunistic infections leading to death.

Marrow transplantation for juvenile osteopetrosis

Two children with the juvenile form of osteopetrosis were treated with marrow transplants from their HLA identical siblings. Following transplantation each child exhibited extensive bone reabsorption with a marked augmentation of osteoclastic function attributable to donor osteoclasts, including remodeling of bone with expansion of intramedullary hematopoiesis and correction of associated abnormalities of thymic factor and natural killer cells. Osteopetrosis ultimately recurred in one patient in whom engraftment of donor hematopoietic elements was not achieved. Our studies indicate that marrow transplantation will correct osteopetrosis but that permanent reconstitution necessitates sustained engraftment of marrow precursors of cells with osteoclastic activity.

Site-Specific Hydration Dynamics in the Nonpolar Core of a Molten Globule by Dynamic Nuclear Polarization of Water

Water-protein interactions play a direct role in protein folding. The chain collapse that accompanies protein folding involves extrusion of water from the nonpolar core. For many proteins, including apomyoglobin (apoMb), hydrophobic interactions drive an initial collapse to an intermediate state before folding to the final structure. However, the debate continues as to whether the core of the collapsed intermediate state is hydrated and, if so, what the dynamic nature of this water is. A key challenge is that protein hydration dynamics is significantly heterogeneous, yet suitable experimental techniques for measuring hydration dynamics with site-specificity are lacking. Here, we introduce Overhauser dynamic nuclear polarization at 0.35 T via site-specific nitroxide spin labels as a unique tool to probe internal and surface protein hydration dynamics with site-specific resolution in the molten globular, native, and unfolded protein states. The (1)H NMR signal enhancement of water carries information about the local dynamics of the solvent within ∼10 Å of a spin label. EPR is used synergistically to gain insights on local polarity and mobility of the spin-labeled protein. Several buried and solvent-exposed sites of apoMb are examined, each bearing a covalently bound nitroxide spin label. We find that the nonpoloar core of the apoMb molten globule is hydrated with water bearing significant translational dynamics, only 4-6-fold slower than that of bulk water. The hydration dynamics of the native state is heterogeneous, while the acid-unfolded state bears fast-diffusing hydration water. This study provides a high-resolution glimpse at the folding-dependent nature of protein hydration dynamics.

Defective recognitive immunity in family aggregates of colon carcinoma.

Cancer-free individuals from family agregates of seemingly hereditary colon carcinoma were studied to determine the nature of their cell-mediated immune capacities in miexed leukocyte culture. Members of families who demonstrated no evidence of a precancerous condition such as polyposis coli did demonstrate substantial cellular immunopathology. Of these, 44% showed a decreased responsiveness of their peripheral mononuclear cells to allogeneic stimuli, and in a number of these individuals this deficiency clearly manifested itself as an inappropriate suppression of potentially normal lymphocyte blastogenic capacities by an adherent population of mononuclear leukocytes. This in vitro defect of recognitive immunity appears to be the same type of defect that has already been described for individuals with established maligancies. The pattern of phenotypic expression of this immunopathology within these families is not inconsistent with an hereditary disorder. Individuals from families with a known hereditary somatic precancerous condition usually did not demonstrate this immunopathology. It is appropriate to speculate that the defect of recognitive immunity in the former families could be contributory to the genesis of the colon carcinoma.

Mechanism of the Gold-Catalyzed Rearrangement of (3-Acyloxyprop-1-ynyl)oxiranes : A Dual Role of the Catalyst

The three competing paths for the rearrangement of 1 (involving 1,2- and 1,3-ester migration with alkyne or oxirane activation) evidence the multifaceted character of gold as a catalyst. The most favorable mechanism for this useful synthetic transformation involves a cascade of more than eight steps. All the functional groups in the substrate play a crucial and synergistic role, and sequential gold coordination to both the pi-system and the lone pairs of oxygen is needed. Exploration of these three paths suggests the use of a nonalkynophilic Lewis acid (BF(3)) as a possible synthetic alternative for this transformation.

Noyori hydrogenation: aromaticity, synchronicity, and activation strain analysis.

By means of density functional theory calculations, we have computationally explored the intimacies of the crucial step of Noyori hydrogrogenation reactions of multiple bonds. This process can be considered analogous to the so-called double group transfer reactions. Both kinds of transformations proceed concertedly via the simultaneous migration of two hydrogen atoms/groups in a pericyclic [σ2s + σ2s + π2s] reaction through six-membered transition structures. Despite the structural resemblances of both types of saddle points, significant differences are found in terms of synchronicity and in-plane aromaticity. In addition, the activation strain model has been used to get quantitative insight into the factors which control the corresponding barrier heights. It is found that the presence of a heteroatom in the acceptor moiety is responsible for a remarkable increase of the interaction energy between the reactants which can compensate the destabilizing effect of the strain energy associated with the deformation of the initial reagents leading to low reaction barriers.

On the memory of chirality in gold(I)-catalyzed intramolecular carboalkoxylation of alkynes.

A computational study of the mechanism of the intramolecular carboalkoxylation of alkynes reported by Toste et al. allows the characterization of the chirality transfer process that makes this reaction enantioselective. Memory of chirality is preserved up until the stereocenter-generating iso-Nazarov cyclization through the synergy between the helicity of a pentadienyl cation intermediate and the control in the conformation of the allyl group, both elements defined upon alkoxy migration. The high barriers to conformational scrambling relative to those corresponding to chemical steps ensure the robustness of the chirality transfer mechanism and result in an unusual importance of conformational changes in reactivity that seems to be common in gold-catalyzed transformations.

Allenyl Azide Cycloaddition Chemistry. Photochemical Initiation and CuI Mediation Leads to Improved Regioselectivity

Irradiation of 2-(3-alkenyl)allenylphenyl azides in the presence of excess CuI furnished functionalized 2,3-cyclopentenylindoles in good yield with only trace amounts of competitive C-N-bonded regioisomeric products. These results represent a significant departure from the modest-to-nonexistent regioselectivity that attended thermal cyclization of these allenyl azide substrates.