Selvamicin, an atypical antifungal polyene from two alternative genomic contexts

The bacteria harbored by fungus-growing ants produce a variety of small molecules that help maintain a complex multilateral symbiosis. In a survey of antifungal compounds from these bacteria, we discovered selvamicin, an unusual antifungal polyene macrolide, in bacterial isolates from two neighboring ant nests. Selvamicin resembles the clinically important antifungals nystatin A1 and amphotericin B, but it has several distinctive structural features: a noncationic 6-deoxymannose sugar at the canonical glycosylation site and a second sugar, an unusual 4-O-methyldigitoxose, at the opposite end of selvamicin’s shortened polyene macrolide. It also lacks some of the pharmacokinetic liabilities of the clinical agents and appears to have a different target. Whole genome sequencing revealed the putative type I polyketide gene cluster responsible for selvamicin’s biosynthesis including a subcluster of genes consistent with selvamicin’s 4-O-methyldigitoxose sugar. Although the selvamicin biosynthetic cluster is virtually identical in both bacterial producers, in one it is on the chromosome, in the other it is on a plasmid. These alternative genomic contexts illustrate the biosynthetic gene cluster mobility that underlies the diversity and distribution of chemical defenses by the specialized bacteria in this multilateral symbiosis.National Institutes of Health/[R01 GM086258]/NIH/Estados UnidosNational Institutes of Health/[U19 AI09673]/NIH/Estados UnidosUniversidad de Costa Rica//UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM

Pyrazines from bacteria and ants: convergent chemistry within an ecological niche

Ants use pheromones to coordinate their communal activity. Volatile pyrazines, for instance, mediate food resource gathering and alarm behaviors in different ant species. Here we report that leaf-cutter ant-associated bacteria produce a family of pyrazines that includes members previously identified as ant trail and alarm pheromones. We found that L-threonine induces the bacterial production of the trail pheromone pyrazines, which are common for the host leaf-cutter ants. Isotope feeding experiments revealed that L-threonine along with sodium acetate were the biosynthetic precursors of these natural products and a biosynthetic pathway was proposed

Simultaneous arthroscopic implantation of autologous chondrocytes and high tibial osteotomy for tibial chondral defects in the varus knee.

There is no consensus on the ideal management of patients with chondral defects of the medial tibial plateau and varus malalignment of the knee. We performed a cohort study to evaluate the outcome of patients affected by these conditions, who underwent arthroscopic implantation of autologous chondrocytes and a medial opening wedge high tibial osteotomy. Eight patients (four men and four women; mean age, 50 years, range: 42 to 58) with chondral defects of the medial tibial plateau in a varus knee underwent arthroscopic implantations of autologous chondrocytes in conjunction with a medial opening wedge osteotomy. At final post-operative follow up of 28 months following the index procedure, the post-operative scores were improved for the IKDC score (four patients abnormal and four patients severely abnormal to four patients normal, three patients nearly normal and one patient abnormal), Lysholm score (65.7 range 49-88 to 94.6 range 89-100), Tegner score (3.7 range 3-5 to 7 range 5-8) and VAS score (7.2 to 2.0). In conclusion, the association of arthroscopic implantation of autologous chondrocytes with a medial opening wedge osteotomy of the proximal tibia is a viable option for the management of chondral defects in varus knees

Effect of pulsed electromagnetic fields on human osteoblast cultures.

BACKGROUND AND PURPOSE: Exogenous electromagnetic fields (EMFs) affect bone metabolism, but the mechanisms responsible for this phenomenon are unclear. Pulsed EMFs (PEMFs) can be effective in the management of congenital pseudarthrosis or delayed union or non-union of fractures. We investigated the effects of PEMFs used in clinical practice on human osteoblast cultures. METHODS: Primary osteoblastic cells were isolated from a human femoral head. Cultures were exposed to the PEMF stimulation for 72 hours, 7 and 10 days and compared with a control group of primary osteoblastic cells non-exposed to PEMF. Cell growth and alkaline phosphatase activity were evaluated in the osteoblast cell cultures at each observation time. RESULTS: At each observation time, the differences in cell numbers between PEMF-exposed cells and control group were statistically significant (p < 0.05). The alkaline phosphatase-specific activity of PEMF-exposed osteoblast cultures showed a statistically significant (p < 0.05) increase when compared with the control group after 7 and 10 days of exposure. CONCLUSIONS: The application of PEMF stimulation on human osteoblasts accelerates cellular proliferation when compared with a control group of non-PEMF-exposed cells

Adhesion and collagen production of human tenocytes seeded on degradable poly(urethane urea).

PURPOSE: The aim of this study was to investigate whether human tenocytes taken from ruptured quadriceps tendon could be seeded on a biodegradable polycaprolactone-based polyurethanes (PU) urea scaffold. Scaffold colonization and collagen production after different culture periods were analyzed to understand whether tenocytes from ruptured tendons are able to colonize these biodegradable scaffolds. METHODS: Human primary tenocyte cultures of ruptured quadriceps tendons were seeded on PU scaffolds. After 3, 10 and 15 days of incubation, the samples were stained with haematoxylin and eosin and were examined under white light microscopy. After 15 and 30 days of incubation, samples were examined under transmission electron microscope. Total collagen accumulation was also evaluated after 15, 30 and 45 days of culture. RESULTS: After 15 and 30 days of culture, tenocyte-seeded scaffolds showed cell colonization and cell accumulation around interconnecting micropores. Tenocyte phenotype was variable. Collagen accumulation in seeded scaffolds demonstrated a progressive increase after 15, 30 and 45 days of culture, while control non-seeded scaffolds show no collagen accumulation. CONCLUSION: These results showed that human tenocytes from ruptured quadriceps tendon can be seeded on polycaprolactone-based PU urea scaffolds and cultured for a long time period (45 days). This study also showed that human tenocytes from ruptured tendons seeded on PU scaffolds are able to penetrate the scaffold showing a progressively higher collagen accumulation after 15, 30 and 45 days of incubation. This study provides the basis to use this PU biodegradable scaffold in vivo as an augmentation for chronic tendon ruptures and in vitro as a scaffold for tissue engineering construct

Effect of pulsed electromagnetic fields on human tenocyte cultures from supraspinatus and quadriceps tendons.

OBJECTIVE: : To investigate the effects of pulsed electromagnetic fields (PEMFs) on human tenocyte cultures and to assess whether PEMFs could represent a viable therapeutic option in tendon pathologies. DESIGN: : Controlled laboratory study in which primary human tenocytes were isolated from healthy supraspinatus and quadriceps tendons and were exposed to the electromagnetic field stimulation. Cell growth and cell cycle were evaluated after 72 hrs, 5 days, and 7 days of continuous PEMF exposure. In quiescent confluent tenocyte culture, an in vitro cut was mechanically produced, and the width of the cell-free zone was measured 12, 24, and 36 hrs after the injury in the presence of PEMF stimulation. Total collagen accumulation was also evaluated after 5, 7, and 14 days of PEMF exposure. RESULTS: : Tenocyte growth analysis, cell cycle analysis, and total collagen accumulation did not show statistically significant differences between exposed and control groups. Exposure to PEMF significantly accelerated cut closure 12 and 24 hrs after the injury. CONCLUSIONS: : PEMFs comparable with the ones used for the management of pseudoarthrosis stimulate closure of an in vitro laceration of a tenocyte monolayer. Our results provide the preliminary in vitro work and the basis to support the study of the in vivo effects of PEMFs on tendinopathies

Effect of dihydrotestosterone on cultured human tenocytes from intact supraspinatus tendon.

The role of hormones in the pathogenesis of tendinopathy is not well recognised, even though the use of anabolic steroids is correlated with a higher incidence of spontaneous tendon ruptures. The aim of this study was to investigate the effects of dihydrotestosterone (DHT) on human tenocyte cultures from the intact supraspinatus tendon of male subjects. Cultured human tenocytes were seeded into culture plates at a density of 5 x 10(4) cells per well and incubated for 24 h. Then, 10(-9) M-10(-7) M DHT or Dulbecco's modified Eagle's medium (DMEM) only (control) was added to the culture plate wells. Cell morphology assessment and cell proliferation tests were performed 48, 72 and 96 h after DHT treatment. DHT-treated tenocytes showed an increased proliferation rate at DHT concentration higher than 10(-8) M. Differences in cell numbers between control and DHT-treated cells were statistically significant (P < 0.05) after 48 and 72 h of treatment with DHT concentrations of 10(-8) and 10(-7) M. The tenocytes treated with DHT (10(-8) and 10(-7) M) became more flattened and polygonal compared to control cells that maintained their fibroblast-like appearance during the experiment at each observation time. In conclusion, in vitro, progressive increasing concentration of DHT at doses greater than 10(-8) M had direct effects on male human tenocytes, increasing cell number after 48 and 72 h of treatment, and leading to a dedifferentiated phenotype after 48 h of treatment. This effect can be important during tendon-healing and repair, when active proliferation is required. Our results represent preliminary evidence for a possible correlation between testosterone abuse and shoulder tendinopathy