Structural and Functional Analysis of Validoxylamine A 7′-phosphate Synthase ValL Involved in Validamycin A Biosynthesis

Validamycin A (Val-A) is an effective antifungal agent widely used in Asian countries as crop protectant. Validoxylamine A, the core structure and intermediate of Val-A, consists of two C7-cyclitol units connected by a rare C-N bond. In the Val-A biosynthetic gene cluster in Streptomyces hygroscopicus 5008, the ORF valL was initially annotated as a validoxylamine A 7′-phosphate(V7P) synthase, whose encoded 497-aa protein shows high similarity with trehalose 6-phosphate(T6P) synthase. Gene inactivation of valL abolished both validoxylamine A and validamycin A productivity, and complementation with a cloned valL recovered 10% production of the wild-type in the mutant, indicating the involvement of ValL in validoxylamine A biosynthesis. Also we determined the structures of ValL and ValL/trehalose complex. The structural data indicates that ValL adopts the typical fold of GT-B protein family, featuring two Rossmann-fold domains and an active site at domain junction. The residues in the active site are arranged in a manner homologous to that of Escherichia coli (E.coli) T6P synthase OtsA. However, a significant discrepancy is found in the active-site loop region. Also noticeable structural variance is found around the active site entrance in the apo ValL structure while the region takes an ordered configuration upon binding of product analog trehalose. Furthermore, the modeling of V7P in the active site of ValL suggests that ValL might have a similar SNi-like mechanism as OtsA

Non-randomness of the anatomical distribution of tumors

Background: Why does a tumor start where it does within an organ? Location is traditionally viewed as a random event, yet the statistics of the location of tumors argues against this being a random occurrence. There are numerous examples including that of breast cancer. More than half of invasive breast cancer tumors start in the upper outer quadrant of the breast near the armpit, even though it is estimated that only 35 to 40% of breast tissue is in this quadrant. This suggests that there is an unknown microenvironmental factor that significantly increases the risk of cancer in a spatial manner and that is not solely due to genes or toxins. We hypothesize that tumors are more prone to form in healthy tissue at microvascular ‘hot spots’ where there is a high local concentration of microvessels providing an increased blood flow that ensures an ample supply of oxygen, nutrients, and receptors for growth factors that promote the generation of new blood vessels. Results: To show the plausibility of our hypothesis, we calculated the fractional probability that there is at least one microvascular hot spot in each region of the breast assuming a Poisson distribution of microvessels in two-dimensional cross sections of breast tissue. We modulated the microvessel density in various regions of the breast according to the total hemoglobin concentration measured by near infrared diffuse optical spectroscopy in different regions of the breast. Defining a hot spot to be a circle of radius 200 μm with at least 5 microvessels, and using a previously measured mean microvessel density of 1 microvessel/mm2, we find good agreement of the fractional probability of at least one hot spot in different regions of the breast with the observed invasive tumor occurrence. However, there is no reason to believe that the microvascular distribution obeys a Poisson distribution. Conclusions: The spatial location of a tumor in an organ is not entirely random, indicating an unknown risk factor. Much work needs to be done to understand why a tumor occurs where it does. Electronic supplementary material The online version of this article (10.1186/s41236-017-0006-7) contains supplementary material, which is available to authorized users

Laparoscopic free omental lymphatic flap for the treatment of lymphedema

Advances in microsurgery have displayed promising results for the treatment of lymphedema. The use of vascularized lymph node transfers has increased in popularity but incurs the potential risk for donor-site lymphedema. The omentum has been previously described for the treatment of lymphedema but has been overlooked because of presumed high morbidity, including the need for celiotomy and pedicled complications. The authors present a novel technique and early results of the laparoscopic free omental lymphatic flap for the management of lymphedema. The minimally invasive harvest successfully avoids both the previously associated morbidity of this flap and the risk of iatrogenic lymphedema to the donor site.5 page(s

1H-NMR study of 2,3,4,6,3',4'-hexa-O-acetyl-1',6'-diacetamido-1',6'-dideoxy sucrose at 300 MHz

The 1H-NMR parameters of the title compound (1) have been obtained for D2O and benzene/acetone solutions. The conformations of the rings and around the C(5′)-C(6′) fragment of the β-D-fructofuranosyl part are discussed. The furanose moiety behaves differently from that in sucrose octaacetate itself

An Algorithmic approach to simultaneous vascularized lymph node transfer with microvascular breast reconstruction

Background: Lymphedema is a common, progressive, and often debilitating condition that can occur after breast cancer treatment. Preliminary reports on vascularized lymph node transfer (VLNT) have been promising. We propose an algorithmic approach to simultaneous VLNT with microvascular breast reconstruction (MBR) and provide early results. Methods: All patients who underwent simultaneous VLNT with MBR were included. Postoperative evaluation was performed at standardized time points and included qualitative assessment and quantitative volumetric analysis. Results: Between 2011 and 2013, 29 consecutive patients with refractory lymphedema secondary to breast cancer treatment underwent simultaneous VLNT with MBR. Mean follow-up was 11 months. On average, patients had experienced 3.3 years of lymphedema symptoms with 21 % increased volume in the affected arm compared with the unaffected arm. Using our algorithmic approach, all patients underwent successful breast reconstruction. There were no flap losses, and no patients developed donor site lymphedema. Six patients (21 %) experienced donor site wound complications that resolved with conservative measures; 23 patients (79 %) reported sustained symptomatic improvement after reconstruction. The mean volume differential volumes improved to 20, 19, 14, and 10 % at 1, 3, 6, and 12 months after reconstruction, respectively. Conclusions: Our algorithm provides a reliable approach to optimizing simultaneous abdominal free flap breast reconstruction and VLNT and demonstrates promising results. Long-term studies are warranted to further delineate and improve the safety and efficacy of lymph node transfers.6 page(s