Hyaluronic acid production in Bacillus subtilis

The hasA gene from Streptococcus equisimilis, which encodes the enzyme hyaluronan synthase, has been expressed in Bacillus subtilis, resulting in the production of hyaluronic acid (HA) in the 1-MDa range. Artificial operons were assembled and tested, all of which contain the hasA gene along with one or more genes encoding enzymes involved in the synthesis of the UDP-precursor sugars that are required for HA synthesis. It was determined that the production of UDP-glucuronic acid is limiting in B. subtilis and that overexpressing the hasA gene along with the endogenous tuaD gene is sufficient for high-level production of HA. In addition, the B. subtilis-derived material was shown to be secreted and of high quality, comparable to commercially available sources of HA.     

Shape optimization in steady blood flow: a numerical study of non-Newtonian effects

We investigate the influence of the fluid constitutive model on the outcome of shape optimization tasks, motivated by optimal design problems in biomedical engineering. Our computations are based on the Navier-Stokes equations generalized to non-Newtonian fluid, with the modified Cross model employed to account for the shear-thinning behavior of blood. The generalized Newtonian treatment exhibits striking differences in the velocity field for smaller shear rates. We apply sensitivity-based optimization procedure to a flow through an idealized arterial graft. For this problem we study the influence of the inflow velocity, and thus the shear rate. Furthermore, we introduce an additional factor in the form of a geometric parameter, and study its effect on the optimal shape obtained.     

Identification of the novel evolutionary conserved obstructor multigene family in invertebrates

Insects have evolved chitin-containing structures such as the cuticle or peritrophic membranes that serve to protect their bodies against the hostile environment. The specific mechanisms by which these structures are produced, are mostly unknown. We have identified a novel multigene family, the obstructor family, which encodes ten putatively secreted chitin-binding proteins that are characterized by a stereotype arrangement of a N-terminal signaling peptide and 3 chitin-binding-domains. Gene expression studies in Drosophila melanogaster embryos demonstrate that obstructor family members are expressed in cuticle forming tissues. Using computational and phylogenetic analysis, we show that obstructor genes represent an evolutionary conserved multigene family in invertebrates.     

Tonic finite element model of the lower limb

It is widely admitted that muscle bracing influences the result of an impact, facilitating fractures by enhancing load transmission and reducing energy dissipation. However, human numerical models used to identify injury mechanisms involved in car crashes hardly take into account this particular mechanical behavior of muscles. In this context, in this work we aim to develop a numerical model, including muscle architecture and bracing capability, focusing on lower limbs. The three-dimensional (3-D) geometry of the musculoskeletal system was extracted from MRI images, where muscular heads were separated into individual entities. Muscle mechanical behavior is based on a phenomenological approach, and depends on a reduced number of input parameters, i.e., the muscle optimal length and its corresponding maximal force. In terms of geometry, muscles are modeled with 3-D viscoelastic solids, guided in the direction of fibers with a set of contractile springs. Validation was first achieved on an isolated bundle and then by comparing emergency braking forces resulting from both numerical simulations and experimental tests on volunteers. Frontal impact simulation showed that the inclusion of muscle bracing in modeling dynamic impact situations can alter bone stresses to potentially injury-inducing levels.     

Increased cerebral oxidative damage and decreased antioxidant defenses in ovariectomized and sham-operated rats supplemented with vitamin A

Previous studies have linked oxidative stress with aging and aging-related processes, including menopause. Abnormalities in the redox state similar to those observed in menopausal women can be modeled experimentally with rat ovariectomy. The aim of the present study was to investigate the effects of vitamin A (retinol palmitate) supplementation (500 or 1,500?IU?kg(-1)?day(-1) for 30?days) on behavioral parameters and brain redox profile in ovariectomized (OVX) and sham-operated rats. Ovariectomy caused pronounced uterine atrophy and decreased locomotor/exploratory activity. Moreover, we found increased hypothalamic and frontal cortex superoxide dismutase/catalase (SOD/CAT) ratio and decreased hippocampal thiol content, accompanied by increased frontal cortex lipid oxidative damage (TBARS) in OVX rats. Vitamin A at 1,500?IUkg(-1)?day(-1) decreased exploratory behavior and decreased total hippocampal thiol content in sham-operated rats, increased hippocampal SOD/CAT ratio and decreased total antioxidant potential in the hippocampus of both sham and OVX groups, and increased cortical TBARS levels in OVX rats. Thus, vitamin A may induce a pro-oxidant state in discrete brain regions of sham-operated and OVX rats. These results suggest some caution regarding the use of high doses of vitamin A supplementation during menopause.     

The Claudin Megatrachea Protein Complex

Claudins are integral transmembrane components of the tight junctions forming trans-epithelial barriers in many organs, such as the nervous system, lung, and epidermis. In Drosophila three claudins have been identified that are required for forming the tight junctions analogous structure, the septate junctions (SJs). The lack of claudins results in a disruption of SJ integrity leading to a breakdown of the trans-epithelial barrier and to disturbed epithelial morphogenesis. However, little is known about claudin partners for transport mechanisms and membrane organization. Here we present a comprehensive analysis of the claudin proteome in Drosophila by combining biochemical and physiological approaches. Using specific antibodies against the claudin Megatrachea for immunoprecipitation and mass spectrometry, we identified 142 proteins associated with Megatrachea in embryos. The Megatrachea interacting proteins were analyzed in vivo by tissue-specific knockdown of the corresponding genes using RNA interference. We identified known and novel putative SJ components, such as the gene product of CG3921. Furthermore, our data suggest that the control of secretion processes specific to SJs and dependent on Sec61p may involve Megatrachea interaction with Sec61 subunits. Also, our findings suggest that clathrin-coated vesicles may regulate Megatrachea turnover at the plasma membrane similar to human claudins. As claudins are conserved both in structure and function, our findings offer novel candidate proteins involved in the claudin interactome of vertebrates and invertebrates.     

Combined influence of fermentation and drying conditions on survival and metabolic activity of starter and probiotic cultures after low-temperature vacuum drying

The influence of low temperature vacuum drying process parameters on the survival, metabolic activity and residual water content of three different bacterial strains (Lactobacillus paracasei ssp. paracasei, Lactobacillus delbrueckii ssp. bulgaricus and Bifidobacterium lactis) was investigated. Shelf temperature and chamber pressure were varied and optimized by response surface methodology with regard to survival and residual water content. It is shown that the survival rate after low temperature vacuum drying is comparable to that of freeze drying. Based on the optimization experiments the combined influence of fermentation pH and drying process parameters was studied for the most detrimental and the best process condition, respectively. The results show that interactions between process and fermentation conditions have to be taken in account and that these influences are highly strain specific.     

Minimally invasive transabdominal collection of preimplantation embryos from the common marmoset monkey (Callithrix jacchus)

A novel, minimally invasive, transabdominal embryo collection method (transabdominal method) was developed as an alternative to a standard abdominal incision for embryo collection in the common marmoset. The abdominal incision method was used for 304 flushes using 36 female animals, whereas the transabdominal method was used for 488 flushes using 48 females; successful embryo collection rates were 48.0% and 48.4% (P > 0.05), respectively. These techniques were successfully duplicated at another institute (German Primate Center, DPZ). At that institution, successful embryo collection rates were 88.9% and 77.8% for the abdominal incision and transabdominal methods, respectively (P > 0.05), whereas the average numbers of preimplantation embryos obtained per flush were (mean ± SD) 1.91 ± 0.35 and 1.71 ± 0.14 (P > 0.05). The transabdominal method reduced animal stress, did not require incisional wound healing, and enabled successive embryo recoveries to be done much sooner. More embryos in early developmental stages (zygotes/morulae) were recovered using the transabdominal method (76.1%) than the abdominal incision method (52.6%, P < 0.01). In contrast, recovery of arrested or abnormal embryos was not significantly different between these two methods (9.8% and 8.3%). To verify developmental ability of embryos recovered by the transabdominal method, transfer of 28 normal embryos to 14 surrogate mothers yielded a nidation rate of 57%. Five females sustained term pregnancies and eight neonates were born. This novel transabdominal method will facilitate progress in marmoset developmental biology and embryology.