Post-PKS Tailoring Steps of the Spiramycin Macrolactone Ring in Streptomyces ambofaciens

Spiramycins are clinically important 16-member macrolide antibiotics produced by Streptomyces ambofaciens. Biosynthetic studies have established that the earliest lactonic intermediate in spiramycin biosynthesis, the macrolactone platenolide I, is synthesized by a type I modular polyketide synthase (PKS). Platenolide I then undergoes a series of post-PKS tailoring reactions yielding the final products, spiramycins I, II, and III. We recently characterized the post-PKS glycosylation steps of spiramycin biosynthesis in S. ambofaciens. We showed that three glycosyltransferases, Srm5, Srm29, and Srm38, catalyze the successive attachment of the three carbohydrates mycaminose, forosamine, and mycarose, respectively, with the help of two auxiliary proteins, Srm6 and Srm28. However, the enzymes responsible for the other tailoring steps, namely, the C-19 methyl group oxidation, the C-9 keto group reduction, and the C-3 hydroxyl group acylation, as well as the timing of the post-PKS tailoring reactions, remained to be established. In this study, we show that Srm13, a cytochrome P450, catalyzes the oxidation of the C-19 methyl group into a formyl group and that Srm26 catalyzes the reduction of the C-9 keto group, and we propose a timeline for spiramycin-biosynthetic post-PKS tailoring reactions.     

The effect of cooling on muscle co-ordination in spasticity: assessment with the repetitive movement test

Purpose: Cooling muscles might produce a temporary reduction of spasticity. This study investigated muscle coordination in spasticity under the influence of cooling. Methods: A repetitive movement (RM-) test of the ankle was used, while measuring the angle and surface-electromyography (EMG) of the m. tibialis anterior and m. triceps surae. Ensemble averaging provided quantified measures of muscle activation. Sixteen patients with spasticity in their lower extremity due to stroke or spinal cord injury participated in the study. Physical examination and the RM-test was done before and after cooling the m. triceps surae for 20 minutes by coldpacks. Results: The results show that Achilles hyperreflexia and clonus were abolished in all, and all but one patient, respectively. The EMG of the m. triceps surae, acting as a prime mover, was increased (p 0.028). However, this improved muscle coordination resulted in just a slightly increased active range of motion (less than 2 degrees at p 0.049). Conclusion: Apparently, the increase in excitability of the alpha motoneuron pool in voluntary movements of patients with spasticity is not followed by an improvement in the ability to move.     

Aging-related Decrease of Human ASC Angiogenic Potential Is Reversed by Hypoxia Preconditioning Through ROS Production

Adipose stroma/stem cells (ASC) represent an ideal source of autologous cells for cell-based therapy. Their transplantation enhances neovascularization after experimental ischemic injury. Aging is associated with a progressive decrease in the regenerative potential of mesenchymal stem cells (MSCs) from bone marrow. This work aims to determine the aging effect on human ASC capacities. First, we show that aging impairs angiogenic capacities of human ASC (hASC) in a mouse ischemic hindlimb model. Although no change in hASC number, phenotype, and proliferation was observed with aging, several mechanisms involved in the adverse effects of aging have been identified in vitro combining a concomitant decrease in (i) ASC ability to differentiate towards endothelial cells, (ii) secretion of proangiogenic and pro-survival factors, and (iii) oxidative stress. These effects were counteracted by a hypoxic preconditioning that improved in vivo angiogenic capacities of hASC from older donors, while hASC from young donors that have a strong ability to manage hypoxic stress were not. Finally, we identified reactive oxygen species (ROS) generation as a key signal of hypoxia on hASC angiogenic capacities. This study demonstrates for the first time that age of donor impaired angiogenic capacities of hASC in ischemic muscle and change in ROS generation by hypoxic preconditioning reverse the adverse effect of aging.     

Daily variation in gastric emptying when using the double sampling technique.

The purpose of this study was to establish the intra-individual variation in the rate of gastric emptying (GE) by using the double sampling technique of George. Eight healthy male volunteers, all familiar with gastric intubation and testing, participated in four GE tests, using an isotonic fluid as a test meal. Conditions were kept constant during all four tests, and each test was separated by at least 48 h. The within-subjects coefficient of variation proved to be 29%. The findings demonstrate that, given standard conditions, GE is reproducible from day to day.     

Contraction-Relaxation Coupling and Impaired Left Ventricular Performance in Coronary Surgery Patients

Background: Dependence of left ventricular (LV) relaxation on cardiac systolic load is a function of myocardial contractility. The authors hypothesized that, if a tight coupling would exist between LV contraction and relaxation, the changes in relaxation rate with an increase in cardiac systolic load would be related to the changes in LV contraction.

Methods: Coronary surgery patients (n = 120) with preoperative ejection fraction > 40% were included. High-fidelity LV pressure tracings (n = 120) and transgastric transesophageal echocardiographic data (n = 40) were obtained. Hearts were paced at a fixed rate of 90 beats/min. Effects on contraction were evaluated by analysis of changes in dP/dtmax and stroke area. Effects on relaxation were assessed by analysis of R (slope of the relation between [small tau, Greek] and end-systolic pressure). Correlations were calculated with linear regression analysis using Pearson's coefficient r.

Results: Baseline LV end-diastolic pressure was 10 +/- 3 mmHg (mean +/- SD). During leg raising, systolic LV pressure increased from 93 +/- 9 to 107 +/- 11 mmHg. The change in dP/dtmax was variable and ranged from -181 to +254 mmHg/s. A similar variability was observed with the changes in stroke area, which ranged from -2.0 to +5.5 cm2. Changes in dP/dtmax and in stroke area were closely related to individual R values (r = 0.87, P < 0.001; and r = 0.81, P < 0.001, respectively) and to corresponding changes in LV end-diastolic pressure (r = 0.81, P < 0.001; and r = 0.74, P < 0.001, respectively).     

Length-dependent regulation of left ventricular function in coronary surgery patients.

BACKGROUND: Load-dependent impairment of left ventricular (LV) function was observed after leg elevation in a subgroup of coronary surgery patients. The present study investigated underlying mechanisms by comparing hemodynamic effects of an increase in LV systolic pressures with leg elevation to effects of a similar increase in systolic pressures with phenylephrine. METHODS: The study was performed in patients undergoing elective coronary surgery prior to cardiopulmonary bypass. High-fidelity LV pressure tracings (n = 25) and conductance LV volume data (n = 10) were obtained consecutively during leg elevation and after phenylephrine administration (5 microg/kg). RESULTS: Leg elevation resulted in a homogeneous increase in end-diastolic volume. The change in stroke volume (SV), stroke work (SW) and dP/dtmax was variable, with an increase in some patients but no change or a decrease in other patients. For a matched increase in systolic pressures, phenylephrine increased SW and dP/dtmax in all patients with no change in SV. Load dependence of relaxation (slope R of the tau-end-systolic pressure relation) was inversely related for changes in SV, SW, and dP/dtmax with leg elevation but not with phenylephrine. CONCLUSIONS: The different effects of leg elevation and phenylephrine suggest that the observed decrease in SV, SW, and dP/dtmax with leg elevation in some patients could not be attributed to an impaired contractile response to increased systolic LV pressures. Instead, load-dependent impairment of LV function after leg elevation appeared related to a deficient length-dependent regulation of myocardial function.     

Pure Progressive Ataxia and Palatal Tremor (PAPT) Associated with a New Polymerase Gamma (<Emphasis Type="Italic">POLG</Emphasis>) Mutation

Progressive ataxia with palatal tremor (PAPT) is a syndrome caused by cerebellar and brainstem lesions involving the dentato-rubro-olivary tract and associated with hypertrophic olivary degeneration. Etiologies include acquired posterior fossa lesions (e.g. tumors, superficial siderosis, and inflammatory diseases) and genetic disorders, such as glial fibrillary acidic protein (GFAP) and polymerase gamma (POLG) mutations. We describe the case of a 52-year-old man who developed pure progressive ataxia and palatal tremor. Genetic analysis has shown that he is compound heterozygote for a known pathogenic (W748S) and a novel POLG variant (I1185N). Patients with POLG recessive mutations usually manifest a more complex clinical picture, including polyneuropathy and epilepsy; our case emphasizes the need to consider a genetic origin in a seemingly sporadic and pure PAPT.     

Aspects éthiques de la transplantation rénale (donneurs et receveurs)

One of the most significant advances in medicine during the last 50 years is the development of organ transplantation. In the context of chronic kidney diseases, renal transplantation offers patients a better clinical outcome than other treatment options. However, the benefits of organ transplantation have not been maximized due to an inadequate supply of organs for transplantation. Despite the establishment of elaborate legal rules for organs procurement, both on deceased and living donors in numerous countries, ethical concerns remain. Most of them are consequences of the strategies implemented or proposed to address the so-called organ shortage. The involvement of society in these complex problems is crucial as numerous questions emerge: could actual state of organ procurement change? Is it possible and/or realistic to increase the number of organs, with respects to living donors or deceased persons? Is the shortage an indicator to limit the use of kidney transplantation? How do we maintain efficiency and justice, in this context.     

Bisphosphonates for preventing bone disease in kidney transplant recipients: a meta‐analysis of randomized controlled trials

An estimated 60% of kidney transplant recipients have mineral bone disease and about 0.5% break their hip within the first year after transplantation. We conducted a systematic review of benefits and harms of bisphosphonates in kidney transplant recipients. We searched CENTRAL (Issue 5, 2015) for randomized controlled trials in all languages and screened the reference list of an earlier Cochrane review. One reviewer identified the trials, extracted all data, and assessed risk of bias. Meta‐analysis used a random effects model, with results expressed as risk ratios (RR) or mean differences (MD) with 95% confidence intervals (CI). Bisphosphonates have uncertain effects on death (RR 0.45, CI 0.04–4.69) and vertebral fractures (RR 0.58, CI 0.24–1.43, I² 0%). Bisphosphonates moderately to importantly reduce the loss of vertebral bone mineral density (MD 5.98%, CI 3.77–8.18% change from baseline in g calcium/cm² at 12 months, I² 91%) and femoral bone mineral density (MD 5.57%, 3.12–8.01% change from baseline in g calcium/cm² at 12 months, I² 69%). At this stage, insufficient evidence exists to support routine use of bisphosphonates to reduce fracture risk after kidney transplantation. Data on important health outcomes are lacking, surrogate outcomes poorly reflect bone quality in kidney transplant recipients, and serious adverse events are not studied and reported systematically.     

Extended transthoracic resection compared with limited transhiatal resection for adenocarcinoma of the mid/distal esophagus: five-year survival of a randomized clinical trial

OBJECTIVE: To determine whether extended transthoracic esophagectomy for adenocarcinoma of the mid/distal esophagus improves long-term survival. BACKGROUND: A randomized trial was performed to compare surgical techniques. Complete 5-year survival data are now available. METHODS: A total of 220 patients with adenocarcinoma of the distal esophagus (type I) or gastric cardia involving the distal esophagus (type II) were randomly assigned to limited transhiatal esophagectomy or to extended transthoracic esophagectomy with en bloc lymphadenectomy. Patients with peroperatively irresectable/incurable cancer were excluded from this analysis (n = 15). A total of 95 patients underwent transhiatal esophagectomy and 110 patients underwent transthoracic esophagectomy. RESULTS: After transhiatal and transthoracic resection, 5-year survival was 34% and 36%, respectively (P = 0.71, per protocol analysis). In a subgroup analysis, based on the location of the primary tumor according to the resection specimen, no overall survival benefit for either surgical approach was seen in 115 patients with a type II tumor (P = 0.81). In 90 patients with a type I tumor, a survival benefit of 14% was seen with the transthoracic approach (51% vs. 37%, P = 0.33). There was evidence that the treatment effect differed depending on the number of positive lymph nodes in the resection specimen (test for interaction P = 0.06). In patients (n = 55) without positive nodes locoregional disease-free survival after transhiatal esophagectomy was comparable to that after transthoracic esophagectomy (86% and 89%, respectively). The same was true for patients (n = 46) with more than 8 positive nodes (0% in both groups). Patients (n = 104) with 1 to 8 positive lymph nodes in the resection specimen showed a 5-year locoregional disease-free survival advantage if operated via the transthoracic route (23% vs. 64%, P = 0.02). CONCLUSION: There is no significant overall survival benefit for either approach. However, compared with limited transhiatal resection extended transthoracic esophagectomy for type I esophageal adenocarcinoma shows an ongoing trend towards better 5-year survival. Moreover, patients with a limited number of positive lymph nodes in the resection specimen seem to benefit from an extended transthoracic esophagectomy.