Bigenic Cre/loxP, puΔtk conditional genetic ablation

Genetic ablation experiments are used to resolve problems regarding cell lineages and the in vivo function of certain groups of cells. We describe a two-component conditional ablation technology using a mouse carrying an X-linked puΔtk transgene, which is only activated in cells expressing Cre. Ablation of the Cre-expressing cells can be temporally regulated by the time of ganciclovir (GCV) administration. This strategy was demonstrated using a Col2Cre transgenic line. Differentiating chondrocytes in bigenic animals could be ablated at different developmental stages resulting in disorganized growth plates and dwarfism. Macrocephaly, macroglossia and umbilical hernia were also observed in ablated 18.5 dpc embryos. Crosses between the puΔtk selector transgenic line and existing cre lines will facilitate numerous temporally regulated tissue-specific ablation experiments.     

Natural products for cancer chemotherapy

For over 40 years, natural products have served us well in combating cancer. The main sources of these successful compounds are microbes and plants from the terrestrial and marine environments. The microbes serve as a major source of natural products with anti‐tumour activity. A number of these products were first discovered as antibiotics. Another major contribution comes from plant alkaloids, taxoids and podophyllotoxins. A vast array of biological metabolites can be obtained from the marine world, which can be used for effective cancer treatment. The search for novel drugs is still a priority goal for cancer therapy, due to the rapid development of resistance to chemotherapeutic drugs. In addition, the high toxicity usually associated with some cancer chemotherapy drugs and their undesirable side‐effects increase the demand for novel anti‐tumour drugs active against untreatable tumours, with fewer side‐effects and/or with greater therapeutic efficiency. This review points out those technologies needed to produce the anti‐tumour compounds of the future.     

Nonlinear Anisotropic Elastic Properties of the Canine Aorta

A nonlinear theory of large elastic deformations of the aortic tissue has been developed. The wall tissue has been considered to be incompressible and curvilinearly orthotropic. The strain energy density function for the tissue is expressed as a polynomial in the circumferential and longitudinal Green-St. Venant strains. Limiting application to states of strains wherein the geometric axes are the principal axes and truncating the energy expression to include terms with highest degrees 2, 3, and 4, three expressions with 3, 7, and 12 constitutive constants are obtained. Results of application of these expressions to data from three series of in vitro and in vivo experiments involving 31 dogs have been presented. Whereas all the three expressions are found to be applicable to various degrees, the third-degree expression for the strain energy density function with seven constitutive constants is particularly recommended for general use.     

Geographic variations and their impact on bioefficacy amongst <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> Nuclear Polyhedrosis Virus isolates from India

Helicoverpa armigera Nuclear Polyhedrosis Virus (HearNPV) was isolated from the larva, obtained from four different geographic locations in India. All the HearNPV isolates appeared clear, irregular, six sided in outline with rounded edges; phase bright under phase contrast microscope; but varied in size, bioefficacy and restriction profiles. Anand isolate had largest mean diameter, highest frequency of large polyhedral inclusion bodies and gave highest total percent mortality with lowest LC₅₀ and LT₅₀ followed by Surat, Patancheru and Junagadh isolates. Mortality rate of Anand and Surat isolates projected two peaks at two different time intervals pointing at the presence of more than one genotype in the same host origin. Restriction digestion analysis produced many unique fragments for each isolates proving that variation existed between the four isolates. These studies have clearly demonstrated that baculoviruses are very diverse, and that this diversity occurs at a range of scales from between isolates collected from the same host species, to between caterpillars collected at the same site and, from the current study, within variants collected from within an individual larva. The efficacy of such geographic isolates can be greatly improved by a deeper knowledge of their physical, chemical and biological properties. The knowledge can be applied for strain selection of the viruses from wild populations which would prove useful to develop NPVs desirable for biopesticides.     

Role of peroxidase and esterase activities during cotton fiber development

Cytoplasmic and salt-extracted wall peroxidase and nonspecific esterase activities along with growth analysis were investigated during the entire period of cotton fiber development. Both the peroxidase fractions, when assayed with chlorogenic and ferulic acids as substrates, recorded low levels during the fiber elongation phase, and a close relationship between cessation of elongation growth and increase in peroxidase activity was discernible. Nonspecific esterase activity in both cytoplasmic and salt-extracted fractions, on the other hand, showed higher activity during the elongation phase, whereas during the secondary thickening phase it decreased. The role of cytoplasmic peroxidase in IAA oxidation is discussed. It is suggested that esterases and peroxidases associated with wall fractions may well be involved in turnover of phenolic acids that are cross-linked to wall polysaccharides.