Immobilization of tomato (Lycopersicon esculentum) pectinmethylesterase in calcium alginate beads and its application in fruit juice clarification

Clarity of fruit juices is desirable to maintain an aesthetically pleasing quality and international standards. The most commonly used enzymes in juice industries are pectinases. A partially-purified pectinmethylesterase from tomato was entrapped in calcium alginate beads and used for juice clarification. The activity yield was maximum at 1 % (w/v) CaCl₂ and 2.5 % (w/v) alginate. The immobilized enzyme retained ~55 % of its initial activity (5.7 × 10^?2 units) after more than ten successive batch reactions. The K_m, pH and temperature optima were increased after immobilization. The most effective clarification of fruit juice (%T₆₂₀ ~60 %) by the immobilized enzyme was at 4 °C with a holding time of 20 min. The viscosity dropped by 56 % and the filterability increased by 260 %. The juice remains clear after 2 months of storage at 4 °C.     

Biodiversity associated with an irrigated rice agro-ecosystem in Sri Lanka

Irrigated rice fields are temporary wetland agro-ecosystems, managed with a variable degree of intensity. A survey was carried out in Sri Lanka to document the overall biodiversity associated with this unique agro-ecosystem, using a combination of sampling techniques to document different groups of fauna and flora. The total number of biota recorded and identified from the rice field ecosystem during the entire study period consisted of 494 species of invertebrates belonging to 10 phyla and 103 species of vertebrates, while the flora included 89 species of macrophytes, 39 genera of microphytes and 3 species of macrofungi. Of the total species documented, 15 species of invertebrates and one weed species are new records to Sri Lanka. Arthropods were the dominant group of invertebrates (405 species), of which 55 species were rice pest insects, and 200 species were natural enemies of pest insects. The fauna and flora recorded from the rice field were observed to follow a uniform pattern of seasonal colonization and succession during successive rice cultivation cycles. The biodiversity of the irrigated rice agro-ecosystem interests both agroecologists and conservation biologists. Therefore, the integrated efforts of these two groups can result in the formulation of strategies based on biodiversity as an organizing principal in the sustainable management of the rice field agro-ecosystem.     

The role of cell membrane in the regulation of cell division and malignant transformation

An earlier model in which uptake of essential nutrients for which the cell is auxotrophic, regulates cell division, is discussed in the light of new experimental findings, specifically the purification of a new type of transport-inhibitory protein from rat liver and the properties of the protein. The possible role of such proteins in malignant transformation is also discussed.     

AAV-mediated leptin receptor installation improves energy balance and the reproductive status of obese female Koletsky rats

Leptin is a hormone secreted primarily by white adipocytes that regulates energy homeostasis and reproduction via CNS receptors. Koletsky (f/f) rats with a leptin receptor (OB-Rb) gene mutation are obese, diabetic and infertile. We employed recombinant adeno-associated viral (rAAV) vectors to transfer the human OB-Rb gene into the brains of female Koletsky rats to identify sites of leptin action in the brain. rAAV-OB-Rb was microinjected into the medial preoptic area (MPOA), the paraventricular nucleus (PVN), the ventromedial hypothalamus, the arcuate nucleus (ARC), or the dorsal vagal complex in the brainstem. Food intake and body weight were monitored bi-weekly for 55 days. Vaginal cytology was examined daily to assess estrous cyclicity. After sacrifice, uncoupling protein-1 (UCP-1) mRNA in brown adipose tissue and serum concentrations of leptin, insulin, glucose, estradiol and progesterone were measured. Expression of OB-Rb was documented by RT-PCR and site specificity of microinjection was verified by immunohistochemical detection of green fluorescent protein following a control microinjection of rAAV-GFP. OB-Rb installation in the ARC reduced food intake, however, energy expenditure, assessed by UCP-1 mRNA expression, was increased by OB-Rb installation in all sites except the PVN. When injected into the MPOA and ARC, rAAV-OB-Rb stimulated the reproductive axis as evidenced by normalization of estrous cycle length and increased luteinizing hormone releasing hormone concentrations in the hypothalamus. These studies show that long-term installation of a functional leptin receptor in the CNS is achievable using rAAV vectors and further show that leptin acts on specific sites in the brain to produce differential effects on food intake, energy expenditure and reproduction.     

Th17 Inflammation Model of Oropharyngeal Candidiasis in Immunodeficient Mice

Oropharyngeal Candidiasis (OPC) disease is caused not only due to the lack of host immune resistance, but also the absence of appropriate regulation of infection-induced immunopathology. Although Th17 cells are implicated in antifungal defense, their role in immunopathology is unclear. This study presents a method for establishing oral Th17 immunopathology associated with oral candidal infection in immunodeficient mice. The method is based on reconstituting lymphopenic mice with in vitro cultured Th17 cells, followed by oral infection with Candida albicans (C. albicans). Results show that unrestrained Th17 cells result in inflammation and pathology, and is associated with several measurable read-outs including weight loss, pro-inflammatory cytokine production, tongue histopathology and mortality, showing that this model may be valuable in studying OPC immunopathology. Adoptive transfer of regulatory cells (T_regs) controls and reduces the inflammatory response, showing that this model can be used to test new strategies to counteract oral inflammation. This model may also be applicable in studying oral Th17 immunopathology in general in the context of other oral diseases.