Amidolytic assay of human factor XI in plasma: comparison with a coagulant assay and a new rapid radioimmunoassay

The traditional coagulant assay for plasma factor XI suffers from a relatively high coefficient of variation, the need for rare congenitally deficient plasma, and a poor correlation between precision and sensitivity. We have developed a simple functional amidolytic assay for factor XI in plasma using the chromogenic substrate PyrGlu-Pro-Arg- p-nitroanilide (S-2366). After inactivation of alpha 1-antitrypsin, CI inhibitor, and other plasma protease inhibitors with CHCI3, plasma was incubated with kaolin, in the absence of added calcium, which limited the enzymes formed to those dependent on contact activation. Soybean trypsin inhibitor was used to minimize the action of kallikrein on the substrate. Once the reaction was complete, corn trypsin inhibitor was used to inactive factor XIIa, the enzyme generated by exposure of plasma to negatively charged surfaces, which had activated the factor XI. The assay is highly specific for factor XI, since plasma totally deficient in that zymogen yielded only 1%-3% of the enzymatic activity in normal plasma under identical conditions. The requirements for complete conversion of factor XI to XIa in plasma within 60 min were, respectively, factor XII, 0.6 U/ml, and high molecular weight kininogen, 0.2 U/ml. Prekallikrein was not an absolute requirement for complete activation but did accelerate the reaction. The intraassay coefficient of variation was 3.4%, and the mean of 35 normal plasmas was 1.00 U +/- 0.24 SD. In addition, a new rapid radioimmunoassay was devised using staphylococcal protein A as the precipitating agent for a complex of factor XI antigen with monospecific rabbit antibody. The mean was 1.01 U +/- 0.30 SD. The correlation coefficients for amidolytic versus coagulant and amidolytic versus radioimmunoassay were r = 0.95 for the former and 0.96 for the latter. Thus, a simple, accurate amidolytic assay and a radioimmunoassay have been devised for measuring factor XI in plasma that correlate well with the coagulant activity of factor XI, as determined in our laboratory.     

Seasonal reproduction in the mongoose, Herpestes auropunctatus. II. Testicular responsiveness to luteinizing hormone

The male mongoose is a seasonal breeder and displays a distinct seasonal pattern in serum androgen levels. In this series of experiments testicular responsiveness to luteinizing hormone (LH) was evaluated during the breeding (active) and inactive seasons. The responsiveness of testes to LH was assessed by measuring [¹²⁵I]hCG (human chorionic gonadotropin) binding to dispersed interstitial cells and by measuring in vitro LH-stimulated androgen release by dispersed interstitial cells. The binding data indicated that there was a significantly greater concentration of $\text{LH}\text{hCG}$ binding sites/Leydig cell during the active season than during the inactive season. In contrast, dispersed interstitial cells prepared from animals trapped during the active and inactive seasons were equally responsive to small doses (“physiological”) of ovine LH (oLH); however, higher doses of oLH produced a significant depression in the interstitial cell output of androgen during the inactive season but not during the active season. These results indicate that there are seasonal differences in the responses of the testis to LH. Whether the seasonal pattern of serum androgen levels in the male mongoose is directed by seasonal changes in serum gonadotropin levels or changes in testicular responsiveness to LH is discussed.     

Fibroblasts as maestros orchestrating tissue regeneration

Fibroblasts constitute a dynamic and versatile population of cells of mesenchymal origin, implicated in both regenerative strategies and pathological conditions. Despite being frequently associated to disease development, particularly through the establishment of fibrotic tissue, fibroblasts hold great potential for tissue engineering and regenerative medicine applications. They are responsible for synthesizing and depositing extracellular matrix components, allowing other cells to settle and migrate along a three‐dimensional support and thereby generating an organ‐specific architecture. Additionally, they produce bioactive molecules that are involved in several physiological processes, including angiogenesis and tissue repair. Although there seems to be much still to unveil about these fascinating cells they have been attracting increasing interest and are now being intensively explored as a cell source to develop bioengineered tissue constructs or to improve stem cell‐based technologies. This review intends to highlight the potential of fibroblasts in orchestrating tissue regeneration, as well as to contribute to uncover uncharted prospective applications of these cells. Copyright © 2017 John Wiley & Sons, Ltd.     

Can demographic and anthropometric characteristics predict clinical improvement in patients with chronic non-specific low back pain?

Objective

To identify potential prognostic factors that may predict clinical improvement of patients treated with different physical therapy interventions in the short-term.

Association of frailty with short-term outcomes,organ support and resource use in critically ill patients

Purpose

Frail patients are known to experience poor outcomes. Nevertheless, we know less about how frailty manifests itself in patients’ physiology during critical illness and how it affects resource use in intensive care units (ICU). We aimed to assess the association of frailty with short-term outcomes and organ support used by critically ill patients.

Methods

Retrospective analysis of prospective collected data from 93 ICUs in Brazil from 2014 to 2015. We assessed frailty using the modified frailty index (MFI). The primary outcome was in-hospital mortality. Secondary outcomes were discharge home without need for nursing care, ICU and hospital length of stay (LOS), and utilization of ICU organ support and transfusion. We used mixed logistic regression and competing risk models accounting for relevant confounders in outcome analyses.

Results

The analysis consisted of 129,680 eligible patients. There were 40,779 (31.4%) non-frail (MFI?=?0), 64,407 (49.7%) pre-frail (MFI?=?1–2) and 24,494 (18.9%) frail (MFI?≥?3) patients. After adjusted analysis, frailty was associated with higher in-hospital mortality (OR 2.42, 95% CI 1.89–3.08), particularly in patients admitted with lower SOFA scores. Frail patients were less likely to be discharged home (OR 0.36, 95% CI 0.54–0.79) and had higher hospital and ICU LOS than non-frail patients. Use of all forms of organ support (mechanical ventilation, non-invasive ventilation, vasopressors, dialysis and transfusions) were more common in frail patients and increased as MFI increased.

Conclusions

Frailty, as assessed by MFI, was associated with several patient-centered endpoints including not only survival, but also ICU LOS and organ support.

     

A review of potential pharmacogenetic effects on catecholamine responses

Considerably, variability in the clinical response to inotropic agents is observed and could be explained partially by the genetic variants, such as single-nucleotide polymorphism (SNP) in genes encoding for enzymes implicated in catecholamines synthesis, metabolism, storage and release or in the signaling pathway. This review highlights the potential effect of pharmacogenetics studies in hemodynamic response and identified 11 SNPs that could be relevant to explain the high variability drug response for a same dose. Cardiovascular instability, such as hypotension, is one of the premature birth complications. The pharmacogenetics studies evaluating these SNP may be useful to better understand the clinical outcome, particularly in this population.     

Enzymatic characterization of Vibrio alginolyticus strains isolated from bivalves harvested at Venice Lagoon (Italy) and Guanabara Bay (Brazil)

The aquatic ecosystem is the natural habitat of microorganisms including Vibrio and Aeromonas genus which are pathogenic to human and animals. In the present investigation the frequency of these bacteria and the enzymatic characteristics of 34 Vibrio alginolyticus strains isolated from bivalves harvested in Venice Lagoon (Italy) and Guanabara Bay (Brazil) were carried out from November 2003 to February 2004. The mussels' samples were submitted to enrichment in Alkaline Peptone Water (APW) added with 1% of sodium chloride (NaCl) and APW plus 3% NaCl incubated at 37 degrees C for 18-24 h. Following the samples were streaked onto TCBS Agar (Thiossulfate Citrate Bile Sucrose Agar) and the suspected colonies were submitted to biochemical characterization. Also, the Vibrio alginolyticus strains were evaluated to collagenase, elastase and chondroitinase production. The results showed the isolation of 127 microorganisms distributed as follows: 105 Vibrio strains such as V. alginolyticus (32.4%), V. harveyi (19%) and V. parahaemolyticus (7.6%), 20 Aeromonas strains and two Plesiomonas shigelloides were the main pathogens isolated. We observed the production of the three enzymes from V. alginolyticus strains considered as the main virulence factors of the bacteria, especially in cases of human dermatological infection.