A role for sialic acid containing substrates in the exocytosis-like in vitro interaction between adrenal medullary plasma membranes and chromaffin granules

The “in vitro” interaction between bovine adrenal medullary plasma membranes and chromaffin granules has recently been proposed as a putative cell-free model for exocytosis because calcium ions specifically control the plasma membrane-induced release of 10^?7 and 10^?5 M. Addition of ruthenium red or pretreatment with neuraminidase gradually blocks this interaction indicating that sialic acid containing substrates may be of major importance. These observations and similar results obtained by other authors working on different systems suggest a role for sialic acid containing moieties in exocytosis.     

Plant cell-made protein antigens for induction of Oral tolerance

The gut associated lymphoid tissue has effective mechanisms in place to maintain tolerance to food antigens. These can be exploited to induce antigen-specific tolerance for the prevention and treatment of autoimmune diseases and severe allergies and to prevent serious immune responses in protein replacement therapies for genetic diseases. An oral tolerance approach for the prevention of peanut allergy in infants proved highly efficacious and advances in treatment of peanut allergy have brought forth an oral immunotherapy drug that is currently awaiting FDA approval. Several other protein antigens made in plant cells are in clinical development. Plant cell-made proteins are protected in the stomach from acids and enzymes after their oral delivery because of bioencapsulation within plant cell wall, but are released to the immune system upon digestion by gut microbes. Utilization of fusion protein technologies facilitates their delivery to the immune system, oral tolerance induction at low antigen doses, resulting in efficient induction of FoxP3⁺ and latency-associated peptide (LAP)⁺ regulatory T cells that express immune suppressive cytokines such as IL-10. LAP and IL-10 expression represent potential biomarkers for plant-based oral tolerance. Efficacy studies in hemophilia dogs support clinical development of oral delivery of bioencapsulated antigens to prevent anti-drug antibody formation. Production of clinical grade materials in cGMP facilities, stability of antigens in lyophilized plant cells for several years when stored at ambient temperature, efficacy of oral delivery of human doses in large animal models and lack of toxicity augur well for clinical advancement of this novel drug delivery concept.     

Is direct spectrophotometric determination of chlorophyll in pigment extracts of tissues under different physiological conditions valid?

Direct spectrophotometric determination of chlorophyll content from methanol extracts of young and senescent leaves of $\text{Thunbergia}\text{grandiflora}$ showed 29 and 16%, respectively, of mature leaves. Spectrophotometric estimation in the same extracts after separation of chlorophyll by thin layer chromatography or by direct fluorometric determination showed only 15 and 0.5% of mature leaves, indicating an error of 4 to 40 fold. In the above wide range of absorbance (0.5 to 100%) the lack of linearity between absorption and concentration resulted in additional error. Bound chlorophyll remaining in the pellet, not extractable by any solvent system, was also reported to vary depending on the physiological conditions of the tissue (Plant Physiol. 51, 660–666). Therefore, it is pointed out that the aforementioned errors observed in direct spectrophotometric determinations could be checked by monitoring simultaneously the cell or plastid suspensions $\text{in}\text{vivo}$ by fluorometry without any extraction.