Effect of murine tumors upon delayed hypersensitivity to dinitrochlorobenzene. III. In vivo activity of the nonspecific suppressor cell

Tumor-induced immunosuppression was investigated in an in vivo model of delayed hypersensitivity (DH) to the chemical sensitizer, dinitrochlorobenzene (DNCB). DH to DNCB as measured in a footpad assay was decreased in C3H/HeJ mice bearing MCA-F, a 3-methylcholanthrene-induced syngeneic fibrosarcoma. Suppressor cells from the spleens of tumor-bearing mice inhibited the induction of DH to DNCB in otherwise normal syngeneic C3H/HeJ recipients. Ten million spleen cells (SpC) harvested from mice bearing MCA-F for 10 days and adoptively transferred to tumor-free mice at the time of sensitization with DNCB suppressed the response to the sensitizer. The suppressor cells were macrophages, since they were adherent to plastic, removed by treatment with a magnet after phagocytosis of carbonyl iron, resistant to exposure to gamma radiation and to treatment with anti-Thy 1.2 serum and complement. Further, the nonspecific suppressor cells were activated by progressive tumor growth rather than by induction of tumor-specific immunity using irradiated tumor cells. Titration studies revealed that suppression of DH occurred with the transfer of as few as 10(6) SpC. Thus, nonspecific suppressor cells are effective at inhibiting in vivo DH to DNCB and suggest that nonspecific suppression in the intact host occurs through mechanisms different from those involved in suppression in vitro.     

Inactivation and reactivation of proteins (enzymes)

The molecular mechanisms of protein inactivation, i.e. aggregation, thiol-disulphide exchange, alteration of the primary structure, dissociation of cofactor molecules from the active centre, dissociation of the oligomeric proteins into subunits and conformational changes have been analysed. All these mechanisms are closely interrelated during inactivation of proteins. However, in many cases, the conformational changes accompany and trigger other inactivation processes. Reactivation of irreversibly inactivated proteins is·discussed. Reactivation can be successful when inactivation has been caused by aggregation, modification of SH-groups (or S-S bonds) or as a consequence of irreversible conformational changes.     

Systematic studies of Pinus balfouriana based on volatile terpenoids from wood and needles and on seed morphology

Essential oil from wood and from needles of Pinus balfouriana, growing in six geographically well-separated locations in California, was analysed by GLC. Several monoterpenoid components, in particular -pinene from needles, were found to be usable for distinguishing between trees from the northern and southern parts of the geographic range. Similarity coefficients were calculated and dendrograms constructed. These demonstrated the distinct separation of the northern from the southern populations, and thus substantiated the proposal by Mastrogiuseppe to regard the southern populations as a subspecies. While the northern populations exhibited a tendency to produce larger seeds with longer wings, the difference was of only moderate diagnostic value.     

Modulatory multiplicity in the feeding mechanism in cichlid fishes, as exemplified by the invertebrate pickers of Lake Tanganyika

Electromyography, motion analysis, osteology, myology and feeding behaviour of a morphologically specialized monophyletic lineage of cichlids in Lake Tanganyika have revealed that Eretmodus, Spathodus and Tanganicodus possess a feeding apparatus with a more extensive functional repertoire than that of any other teleost studied to date. When collecting a wide range of foods by inertial suction this trophic group can employ two strategies, a preprogrammed cyclical, energy saving pattern, or a modulated mode effected by extensive overlap of the firing patterns of multiple muscles resulting in a precise control of the magnitude and direction of suction. When dislodging sessile prey from the substrate the complexity of electromyographic and kinematic patterns increases. Because upper jaw protrusion can be effected and controlled independently from the complex couplings causing mouth opening and movements of the suspensory apparatus, a new decoupled model of upper jaw protrusion is proposed. The decoupled model predicts that upper jaw protrusion can be effected directly by contraction of epaxial muscles that raise the neurocranium, causing the premaxillae to slide anteroventrally. Upper jaw protrusion can be modulated continuously and directly by balanced cocontractions of antagonistic muscle sets giving the decoupled model an improved function over a very extensive range. The morphologically symmetrical muscular apparatus can function asymmetrically. Very pronounced asymmetrical firings of multiple muscles produce a continuously modulated jaw mechanism with an extensive repertoire.     

Purification and characterization of a nitrilase from Fusarium solani O1

An intracellular nitrilase was purified from a Fusarium solani O1 culture, in which the enzyme (up to 3000 U L⁻¹) was induced by 2-cyanopyridine. SDS-PAGE revealed one major band corresponding to a molecular weight of approximately 40 kDa. Peptide mass fingerprinting suggested a high similarity of the protein with the putative nitrilase from Gibberella moniliformis. Electron microscopy revealed that the enzyme molecules associated into extended rods. The enzyme showed high specific activities towards benzonitrile (156 U mg⁻¹) and 4-cyanopyridine (203 U mg⁻¹). Other aromatic nitriles (3-chlorobenzonitrile, 3-hydroxybenzonitrile) also served as good substrates for the enzyme. The rates of hydrolysis of aliphatic nitriles (methacrylonitrile, propionitrile, butyronitrile, valeronitrile) were 14–26% of that of benzonitrile. The nitrilase was active within pH 5–10 and at up to 50 °C with optima at pH 8.0 and 40–45 °C. Its activity was strongly inhibited by Hg²⁺ and Ag⁺ ions. More than half of the enzyme activity was preserved at up to 50% of n-hexane or n-heptane or at up to 15% of xylene or ethanol. Operational stability of the enzyme was examined by the conversion of 45 mM 4-cyanopyridine in a continuous and stirred ultrafiltration-membrane reactor. The nitrilase half-life was 277 and 10.5 h at 35 and 45 °C, respectively.     

On testing predictions of species relative abundance from maximum entropy optimisation

A randomisation test is described for assessing relative abundance predictions from the maximum entropy approach to biodiversity. The null model underlying the test randomly allocates observed abundances to species, but retains key aspects of the structure of the observed communities; site richness, species composition, and trait covariance. Three test statistics are used to explore different characteristics of the predictions. Two are based on pairwise comparisons between observed and predicted species abundances (RMSE, RMSE_Sqrt). The third statistic is novel and is based on community‐level abundance patterns, using an index calculated from the observed and predicted community entropies (E_Diff). Validation of the test to quantify type I and type II error rates showed no evidence of bias or circularity, confirming the dependencies quantified by Roxburgh and Mokany (2007) and Shipley (2007) have been fully accounted for within the null model. Application of the test to the vineyard data of Shipley et al. (2006) and to an Australian grassland dataset indicated significant departures from the null model, suggesting the integration of species trait information within the maximum entropy framework can successfully predict species abundance patterns. The paper concludes with some general comments on the use of maximum entropy in ecology, including a discussion of the mathematics underlying the Maxent optimisation algorithm and its implementation, the role of absent species in generating biased predictions, and some comments on determining the most appropriate level of data aggregation for Maxent analysis.