A locking mechanism preventing radical damage in the absence of substrate, as revealed by the x-ray structure of lysine 5,6-aminomutase

Lysine 5,6-aminomutase is an adenosylcobalamin and pyridoxal-5'-phosphate-dependent enzyme that catalyzes a 1,2 rearrangement of the terminal amino group of dl-lysine and of l-beta-lysine. We have solved the x-ray structure of a substrate-free form of lysine-5,6-aminomutase from Clostridium sticklandii. In this structure, a Rossmann domain covalently binds pyridoxal-5'-phosphate by means of lysine 144 and positions it into the putative active site of a neighboring triosephosphate isomerase barrel domain, while simultaneously positioning the other cofactor, adenosylcobalamin, approximately 25 A from the active site. In this mode of pyridoxal-5'-phosphate binding, the cofactor acts as an anchor, tethering the separate polypeptide chain of the Rossmann domain to the triosephosphate isomerase barrel domain. Upon substrate binding and transaldimination of the lysine-144 linkage, the Rossmann domain would be free to rotate and bring adenosylcobalamin, pyridoxal-5'-phosphate, and substrate into proximity. Thus, the structure embodies a locking mechanism to keep the adenosylcobalamin out of the active site and prevent radical generation in the absence of substrate.     

Enhanced Functions of Human Embryonic Stem Cell-derived Hepatocyte-like Cells on Three-dimensional Nanofibrillar Surfaces

Human embryonic stem cell (hESC)-derived hepatocytes provide a promising unlimited resource for the treatment of liver disease. However, current protocols for the generation of mature and functional hepatocytes are inefficient. Therefore, in order to better differentiate and maintain the function of differentiating hESCs, we have hypothesized that hESCs undergo better differentiation into hepatocyte-like cells (HLCs) when induced on three-dimensional nanofibrillar surfaces. We have demonstrated that, during stepwise differentiation of induction, the markers of hepatic lineage expressed and finally lead to the generation of functional mature cells. In the presence of an ultraweb nanofiber, HLCs produced lower AFP, greater urea, glycogen storage, metabolic PROD activity, uptake of LDL and organic anion ICG, all of which are indicative of the differentiation of HLCs. These results show that topographically treated hESCs at the nano level have a distinct hepatic functionality profile which has implications for cell therapies.     

Glasses: Hiding or causing skin cancer?

This article evaluates malignant transformation of lesions presenting in the periocular skin under the eye spectacle nose pad. A non-comparative retrospective chart review of clinical features and pathological findings of patients presenting with periocular malignancies in the exact vicinity where the nose pads of their eye spectacles rested was completed. The study took place in one tertiary oculoplastic referral center between 2007–2013. Ten patients were included, six of whom were male. All subjects wore eye spectacles while awake for at least 15 years, and had an evident suspicious lesion in the exact area that coincided with the resting place of the nose pad. The mean age was 73.5 years (range 65-85 years) and all patients had the lesion present for at least one year. Most cases were squamous skin malignancies (five squamous cell carcinomas [SCC], 2 intra-epidermal carcinomas [IEC], while 3 basal cell carcinomas [BCC]). Treatment involved surgical excision of the lesion with frozen section for margin control and reconstruction with a myocutaneous flap. Periocular malignancies of the inferior medial canthal area, where the nose pad of eye spectacle places pressure, can be easily missed or misdiagnosed. Marjolin ulcers (MU) classically present as an aggressive SCC in area of chronic inflammation, which has been previously correlated to constant pressure, repetitive trauma, or non-healing wounds in other areas of the body. We propose that the traumatic chronic pressure in the infero-medial canthal region from long-term eye spectacle nose pad use, may induce poor lymphatic regeneration leading to an immune system deficiency that predisposes this skin to a malignant transformation. The presence of chronic eye spectacle nose pads also prevents proper and timely detection of such malignancies. Complete excision of these lesions with margin control, adequate follow-up for possible recurrence, and surveillance for new lesions on the patient’s contralateral side, is crucial for adequate management.     

The assessment of lead pollution in milk collected from all dairy farms in Lorestan province,Iran

Milk has been regarded as a unique source of food for all ages but when it is exposed to various contaminants including lead, it is considered as a risk to humans. Therefore, it is important to monitor lead pollution in foods. In this study, 85 samples of raw cow milk were obtained from 85 dairy farms of Lorestan province in Iran. After the digestion process, the atomic absorption method with graphite furnace was applied. The mean level of lead content was 3.24?±?1.31?ppb, ranging from?<?0.7 to 23.73?ppb. Except two farms in Boroujerd and Aligodarz, lead content in other farms were less than the authorized limit by Codex (20?ppb). With respect to the results obtained, it seems that the concentrations of Pb in raw milk produced in Lorestan did not present any major risk to human health (infants and adults).     

Systemic treatment of locally advanced nonmetastatic cutaneous squamous cell carcinoma: a review of the literature

Summary Background There is a small subset of locally advanced nonmetastatic cutaneous squamous cell carcinoma (cSCC) for which local therapy is not curative or feasible, making systemic therapy a possible treatment option. Objectives To calculate overall response rates (ORR), median time to response (TTR) and median duration of response (DOR) of locally advanced nonmetastatic cSCC to systemic therapy [targeted agents, biological response modifiers (BRM) and chemotherapy]. Patients and methods Medline and PubMed were searched for reports of nonmetastatic locally advanced cSCC treated with systemic therapy from 1970 to 2011. No limits were placed on study design. ORR, TTR and DOR were calculated for systemic therapy overall and for each treatment category. Results Twenty‐eight observational studies yielded 119 patients for analysis. The ORR for systemic therapy was 72% (TTR 9 weeks, DOR 42 weeks). Targeted therapy and BRM achieved ORR of 100% (TTR 12 weeks, DOR 20 weeks) and 86% (TTR 10 weeks, DOR 20 weeks), respectively, and oral chemotherapy, intravenous chemotherapy and intra‐arterial chemotherapy achieved ORR of 20% (TTR 10 weeks, DOR 24 weeks), 68% (TTR 3 weeks, DOR 44 weeks) and 100% (TTR 15 weeks, DOR 112 weeks), respectively. A limitation of this study was that no controlled data were identified and sample sizes were small. Conclusions Systemic treatment leads to objective responses in locally advanced cutaneous SCC that are not amenable to local cure.     

Concise review: alchemy of biology: generating desired cell types from abundant and accessible cells

A major goal of regenerative medicine is to produce cells to participate in the generation, maintenance, and repair of tissues that are damaged by disease, aging, or trauma, such that function is restored. The establishment of induced pluripotent stem cells, followed by directed differentiation, offers a powerful strategy for producing patient-specific therapies. Given how laborious and lengthy this process can be, the conversion of somatic cells into lineage-specific stem/progenitor cells in one step, without going back to, or through, a pluripotent stage, has opened up tremendous opportunities for regenerative medicine. However, there are a number of obstacles to overcome before these cells can be widely considered for clinical applications. Here, we focus on induced transdifferentiation strategies to convert mature somatic cells to other mature cell types or progenitors, and we summarize the challenges that need to be met if the potential applications of transdifferentiation technology are to be achieved.     

A high prevalence of mupirocin and macrolide resistance determinant among Staphylococcus aureus strains isolated from burnt patients

Infections due to Staphylococcus aureus have become increasingly common among burn patients. The antibiotic resistance profile of S. aureus isolates and inducible resistance against clindamycin were investigated in this study. The presence of mecA gene, mupA gene and macrolide resistance genes were detected using PCR and multiplex-PCR. The resistance rate to methicillin, erythromycin and mupirocin were 58.5%, 58% and 40%, respectively. The prevalence of constitutive and inducible resistance among macrolide resistant isolates was 75% and 25%, respectively. Ninety five percent of the isolates were positive for one or more erm genes. The most common genes were ermA (75%), ermC (72%) and ermB (69%), respectively. The ermA gene predominated in the strains with the inducible phenotype, while ermC was more common in the isolates with the constitutive phenotype. The msrA gene was only found in one MRSA isolate with the constitutive phenotype. A total of 27 isolates (25%) carried the mupA gene. All the mupirocin resistant isolates and almost all the erythromycin resistant isolates were also resistant against methicillin which may indicate an outbreak of MRSA isolates with high-level mupirocin and erythromycin resistance in the burn unit assessed.     

A male infant with anhidrotic ectodermal dysplasia/immunodeficiency accompanied by incontinentia pigmenti and a mutation in the NEMO pathway

Patients with anhidrotic ectodermal dysplasia and immunodeficiency (EDA-ID) have mutations in the gene on the X chromosome encoding nuclear factor kappaB (NF-kappaB) essential modulator (NEMO), resulting in conical teeth, sparse hair, anhidrosis or hypohydrosis, and recurrent bacterial infections. The same gene is mutated in incontinentia pigmenti (IP), and mutations that do not completely abolish NF-kappaB activity allow survival of male fetuses. We present a case of a 1-year-old boy with a history of EDA-ID who was evaluated for an eruption that intermittently affected his scalp, upper back, cheeks, legs, and arms. A biopsy specimen taken from the back showed the presence of compact dyskeratotic cells with fragmented nuclei and numerous apoptotic keratinocytes scattered throughout the spinous and granular layer. The diagnosis of EDA-ID with IP was made. This case illustrates the complexity and overlapping features of the genodermatoses involving signaling pathways of the cell.