Aggregation states of mitochondrial malate dehydrogenase

The oligomeric state of fluorescein-labeled mitochondrial malate dehydrogenase (L-malate NAD+ oxidoreductase; mMDH; EC 1.1.1.37), as a function of protein concentration, has been examined using steady-state and dynamic polarization methodologies. A "global" rotational relaxation time of 103 +/- 7 ns was found for micromolar concentrations of mMDH-fluorescein, which is consistent with the reported size and shape of mMDH. Dilution of the mMDH-fluorescein conjugates, prepared using a phosphate buffer protocol, to nanomolar concentrations had no significant effect on the rotational relaxation time of the adduct, indicating that the dimer-monomer dissociation constant for mMDH is below 10(-9) M. In contrast to reports in the literature suggesting a pH-dependent dissociation of mMDH, the oligomeric state of this mMDH-fluorescein preparation remained unchanged between pH 5.0 and 8.0. Application of hydrostatic pressure up to 2.5 kilobars was ineffective in dissociating the mMDH dimer. However, the mMDH dimer was completely dissociated in 1.5 M guanidinium hydrochloride. Dilution of a mMDH-fluorescein conjugate, prepared using a Tris buffer protocol, did show dissociation, which can be attributed to aggregates present in these preparations. These results are considered in light of the disparities in the literature concerning the properties of the mMDH dimer-monomer equilibrium.

Correlated flickering of erythrocytes membrane observed with dual time resolved membrane fluctuation spectroscopy under different D-glucose concentrations

A correlated human red blood cell membrane fluctuation dependent on D-glucose concentration was found with dual time resolved membrane fluctuation spectroscopy (D-TRMFS). This new technique is a modified version of the dual optical tweezers method that has been adapted to measure the mechanical properties of red blood cells (RBCs) at distant membrane points simultaneously, enabling correlation analysis. Mechanical parameters under different D-glucose concentrations were obtained from direct membrane flickering measurements, complemented with membrane fluidity measurements using Laurdan Generalized Polarization (GP) Microscopy. Our results show an increase in the fluctuation amplitude of the lipid bilayer, and a decline in tension value, bending modulus and fluidity as D-glucose concentration increases. Metabolic mechanisms are proposed as explanations for the results.

Grading the strength and certainty of the scientific evidence of the bidirectional association between periodontitis and noncommunicable diseases: an umbrella review

OBJECTIVE

Periodontitis and various noncommunicable diseases (NCDs) have been proposed to have a bidirectional relationship. The purpose of this umbrella review is (1) to synthesize the evidence and (2) to grade the strength and certainty of the scientific evidence regarding the bidirectional association between periodontitis and NCDs.

DATA SOURCES

Electronic databases were systematically searched from January 2021 and July 2024; MEDLINE (via PubMed), Embase and SciELO.

DATA SELECTION AND EXTRACTION

Potential epidemiologic systematic reviews with meta-analysis that studied the bidirectional association between periodontitis and NCDs were identified by two independent reviewers and filtered by title and abstract according to the selection criteria. The strength and the quality and certainty of the evidence was assessed according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) guide. 561,554 potential results were identified. After removing duplicates and excluding records deemed ineligible by automated filters, 450 results were screened by title and abstract. This process led to 41 records being appraised in full-text. Of these, 17 were further excluded leaving a total of 24 systematic reviews that met the inclusion criteria.

DATA SYNTHESIS

24 systematic reviews with a total of 32 NCDs were appraised and consolidated. Risk of bias assessment indicated that 21 systematic reviews (87.5%) demonstrated low bias (high quality), 2 had medium bias, and 1 exhibited high bias (low quality). Key issues identified included the formulation of explicit research questions, critical appraisal, data extraction, and publication bias. The association between periodontitis and NCDs was strong in 1 systematic review, moderate in 8, weak in 10 and absent in 7 systematic reviews. The strength of the association between NCDs and periodontitis was moderate in 6 systematic reviews and weak in 3 systematic reviews. The size of the reported effect (odds ratio/risk ratio/hazard ratio) was broader with increasing strength. Although data supports the association between periodontitis and some NCDs, and to a lesser extent between some NCDs and periodontitis, the certainty of the evidence was classified as low to very low.

CONCLUSIONS

There is some data that, with varying degrees of association and low to very low certainty, provide evidence that periodontitis may be a potential risk factor for some NCDs and vice versa.

[Laparoscopic splenectomy in autoimmune thrombocytopenic purpura]

OBJECTIVE

To describe the perioperative characteristics, complications and outcome of the first 22 patients who underwent laparoscopic splenectomy for refractary/recurrent ITP in our institution.

MATERIAL AND METHODS

Clinical and biochemical characteristics, spleen size, indication for surgery, operative time, blood requirements, complications and outcome of 22 patients who underwent laparoscopic splenectomy between 1994 and 1997 were prospectively recorded. Their mean age was 40 +/- 15 (+/- SD), 15 females and 7 males.

RESULTS

The preoperative platelet count was 56 thousand +/- 58.7/uL, average spleen size 10.5 +/- 2 cm. The surgical time averaged 4.5 +/- 1 hours; accessory spleens were removed from two patients. Conversion to the open procedure was necessary in two cases. Complete response was achieved in 59%, partial response in 27%, and no response in 14% (none of these due to missed accessory spleens). Six patients developed complications. One of them died two days after surgery. The mean postoperative stay was 4.7 +/- 2.6 days.

CONCLUSIONS

The results of laparoscopic splenectomy were similar to our previous results with the open approach. The laparoscopic technique took longer in our hands but the postoperative stay was shorter.

The role and impact of viruses on cancer development

This review focuses on three major aspects of oncoviruses' role in cancer development. To begin, we discuss their geographic distribution, revealing that seven oncoviruses cause 20% of all human cancers worldwide. Second, we investigate the primary carcinogenic mechanisms, looking at how these oncogenic viruses can induce cellular transformation, angiogenesis, and local and systemic inflammation. Finally, we investigate the possibility of SARS-CoV-2 infection reactivating latent oncoviruses, which could increase the risk of further disease. The development of oncovirus vaccines holds great promise for reducing cancer burden. Many unanswered questions about the host and environmental cofactors that contribute to cancer development and prevention remain, which ongoing research is attempting to address.

Retrospective observational study of the persistence of SARS-CoV-2 infection in patients previously treated with rituximab

Introducción

La inmunodepresión inducida por rituximab podría ser un factor de riesgo de mortalidad por COVID-19. El objetivo del estudio fue describir la prevalencia de infección por SARS-CoV-2 en pacientes que habían recibido rituximab y conocer si conduce a una mayor persistencia del virus.

Material y métodos

Estudio observacional retrospectivo de pacientes que recibieron rituximab en los 6 meses previos al inicio de la pandemia, analizándose la presencia de infección. Se recogieron las siguientes variables: edad, sexo, enfermedades previas, factores de riesgo para COVID-19, dosis recibidas de rituximab, resultados de los test diagnósticos, hospitalización, tipo de soporte ventilatorio, desarrollo de eventos tromboembólicos y tratamiento recibido. Se realizó un análisis descriptivo de todas las variables y se compararon pacientes que se habían infectado (C+) y los que no (C-).

Resultados

68 pacientes habían recibido rituximab (me-diana de dosis acumulada: 4.161mg (2.611–8.187,5)), 54,4% hombres con edad media de 60,8 años (15,7; 25-87). Se confirmó C+ en 22 pacientes, entre los cuales existían los siguientes antecedentes: 45,5% hipertensión arterial, 36,4% Diabetes Mellitus, 31,8% tabaquismo/exfumador, 22,7% neumopatía, 13,6% cardiopatía y 4,5% obesidad. No se apreciaron diferencias estadísticamente significativas entre C+ y C-. Sólo 2 pacientes C+ desarrollaron inmunidad y 10 de ellos (45,5%) no negativizaron PCR a la finalización del seguimiento. No se encontró asociación con la dosis acumulada de rituximab. La tasa de mortalidad en la C+ fue de 22,7%.

Conclusiones

En nuestros pacientes tratados con rituximab y con infección por SARS-CoV2 se observó una peor evolución y una mayor persistencia de la infección, por lo que debería valorarse el uso de otras alternativas durante la pandemia, ya que la disminución de la función de células B podría producir un mayor riesgo de evolución fatal por COVID-19.