The Effect of Leaf Age on Gas Exchange and Malate Accumulation in C3-CAM Plant Marrubium Frivaldszkyanum (Lamiaceae)

For the first time the expression of C₃ and CAM in the leaves of different age of Marrubium frivaldszkyanum Boiss, is reported. With increasing leaf age a typical C₃ photosynthesis pattern and high transpiration rate were found. In older leaves a shift to CAM occurred and the 24-h transpiration water loss decreased. A correlation was established between leaf area and accumulation of malate. Water loss at early stages of leaf expansion may be connected with the shift to CAM and the water economy of the whole plant.     

Architectural specialization of the intrinsic thoracic limb musculature of the American badger (Taxidea taxus)

Evaluation of the relationships between muscle structure and digging function in fossorial species is limited. Badgers and other fossorial specialists are expected to have massive forelimb muscles with long fascicles capable of substantial shortening for high power and applying high out‐force to the substrate. To explore this hypothesis, we quantified muscle architecture in the thoracic limb of the American badger (Taxidea taxus) and estimated the force, power, and joint torque of its intrinsic musculature in relation to the use of scratch‐digging behavior. Architectural properties measured were muscle mass, belly length, fascicle length, pennation angle, and physiological cross‐sectional area. Badgers possess hypertrophied shoulder flexors/humeral retractors, elbow extensors, and digital flexors. The triceps brachii is particularly massive and has long fascicles with little pennation, muscle architecture consistent with substantial shortening capability, and high power. A unique feature of badgers is that, in addition to elbow joint extension, two biarticular heads (long and medial) of the triceps are capable of applying high torques to the shoulder joint to facilitate retraction of the forelimb throughout the power stroke. The massive and complex digital flexors show relatively greater pennation and shorter fascicle lengths than the triceps brachii, as well as compartmentalization of muscle heads to accentuate both force production and range of shortening during flexion of the carpus and digits. Muscles of most functional groups exhibit some degree of specialization for high force production and are important for stabilizing the shoulder, elbow, and carpal joints against high limb forces generated during powerful digging motions. Overall, our findings support the hypothesis and indicate that forelimb muscle architecture is consistent with specializations for scratch‐digging. Quantified muscle properties in the American badger serve as a comparator to evaluate the range of diversity in muscle structure and contractile function that exists in mammals specialized for fossorial habits. J. Morphol. 2013. © 2012 Wiley Periodicals, Inc.     

Paclitaxel enhances macrophage IL-12 production in tumor-bearing hosts through nitric oxide.

Tumor-induced macrophages (Mphis) mediate immunosuppression, in part, through increased production of factors that suppress T cell responsiveness and underproduction of positive regulatory cytokines. Pretreatment of tumor-bearing host (TBH) Mphis with the anticancer agent paclitaxel (Taxol) partially reverses tumor-induced Mphi suppressor activity, suggesting that paclitaxel may restore TBH Mphi production of proimmune factors. Because paclitaxel demonstrates LPS-mimetic capabilities and increased production of the LPS-induced immunostimulatory cytokine IL-12 could account for enhanced T cell responsiveness, we investigated whether paclitaxel induces Mphi IL-12 production. Tumor growth significantly down-regulated Mphi IL-12 p70 production through selective dysregulation of IL-12 p40 expression. LPS stimulation failed to overcome tumor-induced dysregulation of p40 expression. In contrast, paclitaxel significantly enhanced both normal host and TBH Mphi IL-12 p70 production in vitro, although TBH Mphi IL-12 production was lower than that of similarly treated normal host Mphis. Paclitaxel enhanced p40 expression in a dose-dependent manner. Through reconstituted Mphi IL-12 expression, paclitaxel pretreatment relieved tumor-induced Mphi suppression of T cell alloreactivity. Blocking Mphi NO suppressed paclitaxel's ability to induce IL-12 production. This suggests that paclitaxel-induced activities may involve a NO-mediated autocrine induction pathway. Collectively, these data demonstrate that paclitaxel restores IL-12 production in the TBH and ascribe a novel immunotherapeutic component to the pleiotropic activities of NO. Through its capacity to induce IL-12 production, paclitaxel may contribute to the correction of tumor-induced immune dysfunction.     

Chromatid damage induced by fluorescent light during G2 phase in normal and Gardner syndrome fibroblasts. Interpretation in terms of deficient DNA repair

Skin fibroblasts from Gardner syndrome (GS) compared with those from normal donors showed a significantly higher incidence of chromatid gaps and breaks following exposure to low-intensity, cool-white fluorescent light during G2 phase of the cell cycle. Considerable evidence supports the concept that chromatid gaps and breaks seen directly after exposure to DNA-damaging agents represent unrepaired DNA single- and double-strand breaks respectively. The changes in incidence of chromatid aberrations with time after light exposure are consistent with the sequence of events known to follow DNA damage and repair. Initially, the incidence of light-induced chromatid gaps was equivalent in GS and normal fibroblasts. In the normal cells, the chromatid gaps disappeared by 1 h post-exposure, presumably as a result of efficient repair of DNA single-strand breaks. In contrast, the incidence of gaps increased in GS cells by 0.5 h followed by a decrease at 1 h and concomitant increase in chromatid breaks. It appears from these findings that the increased incidence of chromatid damage in GS fibroblasts results from deficient repair of DNA single-strand breaks which arise from incomplete nucleotide excision of DNA damage during G2 phase.     

Separation of precultured pollen from Nicotiana tabacum by aqueous polymer two-phase partition

Pollen isolated from cold treated and precultivated anthers of tobacco (Nicotiana tabacum L. var. Wisconsin 38) were separated into different fractions with counter-current distribution using an aqueous Dextran-polyethylene glycol two-phase system. It was possible to distinguish among eight pollen classes differing in developmental stage and in partitioning. A part of each fraction was cultivated for analysis of embryo formation. This was highest in a fraction with an intermediate to high partition in the phase system. Enriched in this fraction were also pollen that were fairly well stained with acetocarmine, contained several nuclei and had a relatively low mitochondrial activity. The enrichment of embryogenic pollen offers several advantages especially to physiological studies on embryogenesis.     

Characterization of transducin from bovine retinal rod outer segments. Participation of the amino-terminal region of T alpha in subunit interaction

The GTP-induced dissociation of T alpha from T beta gamma initiates the release of transducin from photolyzed rhodopsin and the subsequent activation of the cGMP phosphodiesterase. In this study, site-specific proteolysis and immunoprecipitation were used to map the domain of T alpha that interacts with T beta gamma. We found that Staphylococcus aureus V8 protease rapidly removes a small fragment from T alpha under native conditions, resulting in the formation of a single 38-kDa polypeptide (T alpha'). Under the same conditions, T beta gamma remains intact. A 4.5-fold decrease in the rate of T alpha cleavage by S. aureus protease was observed in the presence of T beta gamma, suggesting T beta gamma binding blocks the protease-sensitive site on T alpha. Amino acid sequence analysis indicated that T alpha' is derived from the cleavage of T alpha at Glu-21. The ability of T alpha' to interact with and activate the retinal phosphodiesterase is not diminished. However, T alpha' is unable to participate in T beta gamma-dependent activities such as the light-stimulated binding of guanine nucleotides, binding to photoexcited rhodopsin, and ADP-ribosylation catalyzed by pertussis toxin. Moreover, the anti-T alpha monoclonal antibody TF16 was able to precipitate T beta gamma in the presence of T alpha, but not with either T alpha' or T alpha-guanosine 5'-O-(3-thiotriphosphate). We conclude that the amino-terminal region of T alpha participates in T beta gamma interaction and discuss our results with respect to the known structure and function of transducin.