Number of adult female mites Varroa jacobsoni Oud. on hive debris from honey bee colonies artificially infested to monitor mite population increase (Mesostigmata: Varroidae)

Six honey bee colonies hived in Langstroth nuclei were each artificially infested with 100 phoretic Varroa mites. Hive debris on bottom inserts was inspected every 3–4 days. The adult Varroa mites were compared with mounted specimens and catalogued into lightly pigmented and darkly pigmented females. After 4 months, an acaricide treatment was used to estimate the final mite population. Based on light and dark adult counts, we propose a balancing equation that follows the Varroa population increase at 7 day intervals and allows the calculation of experimental population growth rates. The calculated Varroa finite rate of increase is =1.021. Exponential and logistic growth models fitted to the balancing equation data gave R ²=0.986 and R ²=0.991, respectively. To develop a more precise model it would be necessary to follow the population growth beyond our experimental data.     

Toxicology of vanadium compounds in diabetic rats: The action of chelating agents on vanadium accumulation

The possible use of vanadium compounds in the treatment of diabetic patients is now being evaluated. However, previously to establish the optimal maximum dose for diabetes therapy, it should be taken into account that vanadium is a highly toxic element to man and animals. The toxic effects of vanadium are here reviewed. The tissue vanadium accumulation, which would mean an additional risk of toxicity following prolonged vanadium administration is also discussed. Recently, it has been shown that coadministration of vanadate and TIRON, an effective chelator in the treatment of vanadium intoxication, reduced the tissue accumulation of this element, decreasing the possibility of toxic side effects derived from chronic vanadium administration without diminishing the hypoglycemic effect of vanadium. However, previously to assess the effectiveness of this treatment in diabetic patients, a critical reevaluation of the antidiabetic action of vanadium and its potential toxicity is clearly needed.     

Characterization of SKM1, a Saccharomyces cerevisiae gene encoding a novel Ste20/PAK-like protein kinase

Ste20/PAK serine/threonine protein kinases have been suggested as playing essential roles in cell signalling and morphogenesis as potential targets of Cdc42 and Rac GTPases. We have isolated and characterized the Saccharomyces cerevisiae SKM1 gene, which codes for a novel member of this family of protein kinases. The amino acid sequence analysis of Skm1p revealed the presence of a PH domain and a putative p21-binding domain near its amino terminus, suggesting its involvement in cellular signalling or cytoskeletal functions. However, deletion of SKM1 produced no detectable phenotype under standard laboratory conditions. Moreover, disruption of each of the two other S. cerevisiae Ste20/PAK-like kinase-encoding genes, STE20 and CLA4 , in skm1 backgrounds, showed that Skm1p is not redundant with Ste20p or Cla4p. Interestingly, overexpression of SKM1 led to morphological alterations, indicating a possible role for this protein in morphogenetic control. Furthermore, overproduction of Skm1p lacking its N-terminus caused growth arrest. This effect was also seen when similarly truncated versions of Ste20p or Cla4p were overexpressed. We further observed that overproduction of this C-terminal fragment of Skm1p complements the mating defect of a ste20 mutant strain. These results suggest that the N-terminal domains of S. cerevisiae Ste20/PAK-like protein kinases share a negative regulatory function and play a role in substrate specificity.     

Functional properties of FC-2.15, a monoclonal antibody that mediates human complement cytotoxicity against breast cancer cells

FC-2.15 is a murine IgM monoclonal antibody (mAb) that recognizes a cell-surface antigen (Ag2.15) expressed in most tumor-proliferating cells of human breast carcinomas and other neoplasias. In this study the cytotoxic ability of mAb FC-2.15, its cell-surface binding properties and endocytosis in Ag2.15-expressing (Ag2.15⁺) cells were investigated. A⁵¹Cr-release assay was used to test the FC-2.15-mediated cytotoxicity. When human serum was used as source of complement, FC-2.15 exerted a strong cytotoxic effect against human Ag2.15⁺ cells such as MCF-7 (breast cancer cell line), primary breast carcinoma cells, polymorphonuclear leukocytes and chronic myeloid leukemia cells. The mAb concentration range was 1–50 g/ml. Cytotoxicity was completely abolished when complement was inactivated. Only 3.8±2.9% of MCF-7 cells survived the treatment with FC-2.15 in the presence of human serum. A flow-cytometry assay was performed to study the Ag2.15 expression of the surviving cells and they were found to be Ag2.15^–. FC-2.15 did not mediate antibody-dependent cell cytotoxicity when different effector cells were used. Scatchard analysis with¹²⁵I-FC-2.15 on MCF-7 cells demonstrated an affinity constant of 6.9×10⁷ M^–1 and 2.8×10⁶ antigenic sites/cell.¹²⁵I-FC-2.15 was internalized to cytoplasmic vesicles reaching a maximum of 27% after 6 h incubation, followed by the release of labeled degradation products to the supernatant. FC-2.15 appears to exert its cytotoxic effect mainly in the presence of human complement, it reacts with intermediate affinity with a high-density surface antigen, and it is slowly internalized by Ag2.15⁺ cells.     

Combined use of 13C chemical shift and 1Hα−13Cα heteronuclear NOE data in monitoring a protein NMR structure refinement

Summary A large portion of the ¹³C resonance assignments for murine epidermal growth factor (mEGF) at pH 3.1 and 28°C has been determined at natural isotope abundance. Sequence-specific ¹³C assignments are reported for 100% of the assignable C, 96% of the C, 86% of the aromatic and 70% of the remaining peripheral aliphatic resonances of mEGF. A good correlation was observed between experimental and back-calculated C chemical shifts for regions of regular -sheet structure. These assignments also provide the basis for interpreting ¹H–¹³C heteronuclear NOE (HNOE) values in mEGF at natural isotope abundance. Some of the backbone polypeptide segments with high internal mobility, indicated by these ¹H–¹³C HNOE measurements, correlate with locations of residues involved in the putative mEGF-receptor binding site. Using four families of mEGF structures obtained over the last few years, we demonstrate that standard deviations between experimental and back-calculated C values can be used to monitor the refinement of this protein's structure, particularly for -sheet regions. Improved agreement between calculated and observed values of C is correlated with other measures of structure quality, including lowered values of residual constraint violations and more negative values of conformational energy. These results support the view that experimental conformation-dependent chemical shifts, C, can provide a reliable source of information for monitoring the process of protein structure refinement and are potentially useful restraints for driving the refinement.Abbreviations HSQC heteronuclear single-quantum coherence spectroscopy - PFG pulsed-field gradient - TOCSY ¹H-¹H total correlation spectroscopy - EGF epidermal growth factor - mEGF murine EGF - hEGF human EGF - hTGF human type- transforming growth factor - DIPSI spm-locking pulse sequence - NOE nuclear Overhauser effect - HNOE heteronuclear Overhauser effect     

Gibberellin-induced ethylene production and its effect on cowpea epicotyl elongation

The effect of gibberellin A₁ (GA₁) on production of ethylene by cowpea (Vigna sinensis cv Blackeye pea no. 5) epicotyl explants and its relationship to epicotyl elongation was investigated. The explants were placed upright in water and incubated in sealed culture tubes or in large jars. GA, and IAA in ethanol solution were injected into the subapical tissues of the decapitated epicotyls. Cowpea epicotyl explants elongated after GA but not after IAA treatment, and they were very sensitive to exogenous ethylene. As little as 0.14 1/1 ethylene reduced significantly GA₁-induced epicotyl elongation.Treatment with GA₁ induced the production of ethylene which began 10 h after GA application, showed a peak at about 22 h and then declined. The yield of ethylene was proportional to the amount of GA, injected. The inhibition of epicotyl elongation in closed tubes was avoided by absorbing ethylene released with Hg(Cl0₄)₂ , or by adding AVG to the incubation solution to inhibit ethylene production. Treatment with IAA elicited a rapid production of ethylene which ceased about 10 h after application. The effects of IAA and GA₁ on ethylene production were additive.Abbreviations AVG aminoethoxyvinylglycine 2-amino-4-(2-aminoethoxy)-trans-3butenoic acid - ACC 1-aminocyclopropane-1-carboxylic acid - GA gibberellin - IAA indole-3-acetic acid     

Copper distribution in the normal human brain

Copper concentration was determined in samples from 38 areas of 7 normal human brains. The grey matter contained higher concentrations of copper than the white matter. Identical areas of the grey and white matter of the cerebral cortex showed significant differences between individuals. In the caudate nucleus the highest concentrations of copper were found in the tail followed by the body and the head, respectively. A negative linear regression between age and brain copper levels was demonstrated.