A multiscale synthesis: characterizing acute cartilage failure under an aggregate tibiofemoral joint loading

Biomechanics and Modeling in Mechanobiology - Knee articular cartilage is characterized by a complex mechanical behavior, posing a challenge to develop an efficient and precise model. We argue that...     

Evidence of sibling species between two host-associated populations of brown planthopper, N. lugens (stål) (Homoptera: Delphacidea) complex based on morphology and host–plant relationship studies

Morphological and host–plant relationship studies were conducted to differentiate two sympatric populations of brown planthopper (BPH), Nilaparvata lugens, one from rice (Oryza sativa) and the other from Leersia hexandra, a weed grass. In morphometric studies based on esterase activities, an UPGMA dendrogram using 17 quantitative morphological characters, including stridulatory organs (courtship signal-producing organs) between two sympatric populations of N. lugens, one from rice and the other from L. hexandra, a weed grass revealed that both populations were separated from each other. An out-group, N. bakeri, was found to be completely different from the two sympatric populations of N. lugens. Rice plants were best suited for the establishment of the rice-infesting population, and L. hexandra was a favourable host for the Leersia-infesting population. The individuals derived from one host did not thrive on the other host, as shown by a significant reduction in survival and nymphal development, ovipositional preferences, ovipositional response, and egg hatchability. Therefore, morphological and host–plant relationship studies indicate that rice-associated population with high esterase activities and L. heaxandra-associated population with low esterase activities are two closely related sibling species.     

Anchorage-independent growth of murine melanoma in serum-less media is dependent on insulin or melanocyte-stimulating hormone

α-Melanocyte-stimulating hormone (MSH) is known to stimulate melanogenesis in murine melanoma, particularly in Cloudman S-91 melanoma cells. The effects of MSH and insulin on the proliferation of S91 murine melanoma cells have aroused controversy; in various reports, both hormones have been reported to either stimulate or inhibit murine melanoma growth. In our studies both MSH and insulin stimulated the colony-forming ability and the proliferative capacity of S-91 murine melanoma cells grown in soft agar with either serum-supplemented or serum-less medium. Unless insulin and/or MSH were present, Cloudman S-91 melanoma cells failed to clone in soft agar. The insulin effect was greater than that of MSH, and was more pronounced in serum-less than in serum-supplemented medium. The concurrent treatment of S91 melanoma cells with both MSH and insulin resulted in a greater increase in the total number of colonies formed than caused by treatment with either hormone alone. The combined MSH-insulin stimulation of anchorage-independent growth was specific, since the effect could not be mimicked by epidermal growth factor (EGF), gonadotropin-releasing hormone (GRH), luteinizing hormone (LH), nerve growth factor (NGF) or platelet-derived growth factor (PDGF). Therefore, MSH and insulin may be specific growth factors for murine melanoma cells.     

Interleukin 2 receptor dysfunction in mice undergoing a graft-vs-host reaction

Mice of the (C57BL/10 X B10.A)F1 combination were given a single i.v. inoculation of 3 to 4 X 10(7) B10.A spleen cells, which induces a graft-vs-host (GVH)-associated immune deficiency in F1 mice. Between 1 and 4 wk later, spleen cells from the F1 mice were tested for the expression of IL 2 receptors by flow microfluorometry, using the 7D4 rat monoclonal antibody directed against an epitope murine IL 2 receptor. A reduction in intensity of spleen cell staining with 7D4 was detected as early as 8 days after parental cell inoculation, and no IL 2 receptors were detected by 28 days after initiation of GVH. Furthermore, the loss of IL 2 receptors was correlated with abrogation of proliferative responses to concanavalin A and lipopolysaccharide, of IL 2 production, and of cytotoxic T lymphocyte responses. These observations may be relevant for our understanding of GVH reactions, of immune disorders associated with GVH, and possibly of primary and acquired immunodeficiencies in general.     

Novel Covellite CuS Single-Crystal Thin Films for Optoelectronic Applications

Copper sulfide (CuS) thin films have been used in many applications such as solar cells, photo-thermal, electro-conductive, and microwave shielding. In this work, copper sulfide thin films were deposited on glass and silicon substrates by thermal evaporation of in situ synthesized CuS powder. XRD analysis of these films revealed a single-crystal structure, AFM measurements indicated the films have a surface roughness (14.1 nm) and agglomerates of multiple monocrystalline particles with average size (66 nm), and the optical properties were investigated by UV-Vis spectrophotometer showing the films have high transmission (>80%) in the visible region and low absorbance with wide energy gap (3.813 eV). This novel structure with outstanding optical properties makes it very promising optical materials in optoelectronics.

     

Isolation and characterization of two genes encoding proteases associated with the mycelium of Streptomyces lividans 66.

A strain of Streptomyces lividans 66 deleted for a major tripeptidyl aminopeptidase (Tap) was used as a host to screen an S. lividans genomic library for clones overexpressing activity against the chromogenic substrate Ala-Pro-Ala-beta-naphthylamide. In addition to reisolation of the tap gene, clones representing another locus, slpD, were uncovered. slpD was analyzed by deletion subcloning to localize its functional sequence. Nucleotide sequence determination revealed an open reading frame encoding a 55-kDa protein exhibiting significant amino acid sequence homology to Tap, particularly around the putative active-site serine residue. No secreted protein was observed for strains harboring the slpD clone, but inspection of the predicted protein sequence revealed a putative lipoprotein signal peptide (signal peptidase II type), suggesting a mycelial location for the SlpD proteinase. In an attempt to isolate an endoprotease known to be active against some heterologous proteins, a second clone was isolated by using a longer substrate (t-butyloxycarbonyl [Boc]-APARSPA-beta-naphthylamide) containing a chemical blocking group at the amino terminus to prevent aminopeptidase cleavage. This locus, slpE, appeared to also encode a 55-kDa mycelium-associated (lipoprotein) proteinase, whose predicted protein sequences showed significant amino acid homology to Tap and SlpD, particularly around the putative active-site serine residues. Chromosomal integration and deletion analysis in both the wild-type and Tap-deficient backgrounds appeared to indicate that SlpD was essential for viability and SlpE was required for growth on minimal media.     

The effects of interelectrode distance on electromyographic amplitude and mean power frequency during isokinetic and isometric muscle actions of the biceps brachii.

The purpose of this study was to examine the effects of interelectrode distance (IED) on the absolute and normalized electromyographic (EMG) amplitude and mean power frequency (MPF) versus isokinetic and isometric torque relationships for the biceps brachii muscle. Ten adults [mean+/-SD age=22.0+/-3.4 years] performed submaximal to maximal, isokinetic and isometric muscle actions of the dominant forearm flexors. Following determination of isokinetic peak torque (PT) and the isometric maximum voluntary contraction (MVC), the subjects performed randomly ordered, submaximal step muscle actions in 10% increments from 10% to 90% PT and MVC. Surface EMG signals were recorded simultaneously from bipolar electrode arrangements placed over the biceps brachii muscle with IEDs of 20, 40, and 60mm. Absolute and normalized EMG amplitude (muVrms and %max) increased linearly with torque during the isokinetic and isometric muscle actions (r(2) range=0.988-0.998), but there were no significant changes for absolute or normalized EMG MPF (Hz or %max) from 10% to 100% PT and MVC. In some cases, there were significant (p<0.05) differences among the three IED arrangements for absolute EMG amplitude and MPF values, but not for the normalized values. These findings suggested that for the biceps brachii muscle, IEDs between 20 and 60mm resulted in similar patterns for the EMG amplitude or MPF versus dynamic and isometric torque relationships. Furthermore, unlike the absolute EMG amplitude and MPF values, the normalized EMG data were not influenced by changes in IED between 20 and 60mm. Thus, normalized EMG data can be compared among previous studies that have utilized different IED arrangements.