Milking gene therapy

Lactose Intolerance - Single Nucleotide Polymorphisms and Treatment

The majority (about 70%) of the world's population suffers from lactose intolerance. Lactose intolerance leads to long-term discomfort when consuming milk and dairy products, and hence, to their avoidance. Consequently, the intake of important nutrients is reduced, which potentially has a negative impact on the overall health. Knowing the condition - lactose intolerance - will prevent people from unnecessarily restricting dairy products in their diets. In this study, lactose synthesis and catabolism in the human body are presented, also the types of lactose intolerance, as well as the methods of diagnosing this condition, are discussed. Special attention is paid to the genetic causes of this discomfort and to the tests that can be performed. Solutions for the treatment of lactose intolerance have also been proposed, both up-to-date and easily applicable, as well as future developments.

Membrane topology modulates beta-galactosidase activity against soluble substrates

The effect of bio-surfaces of contrasting curvature, on the kinetic parameters of ortho-nitrophenyl-beta-D-galactopiranoside hydrolysis catalyzed by E. coli beta-galactosidase, was investigated. The self-aggregating state and structure of the amphiphiles (Phosphatidylcholine, Lubrol-PX, Triton X-100, DocNa, SDS and CTAB) were inferred from their c.m.c. values and light-scattering measurements. Low curvature phosphatidylcholine or mixed phosphatidylcholine-detergent vesicles increased V(max) without affecting K(M). High curvature micellar structures containing ionic detergents modulated negatively the enzyme activity (decreased or abolished V(max) and increased K(M)). Neither micelles containing non-ionic detergents nor the amphiphiles in a monomeric form, affected enzyme activity. CTAB at a concentration below its c.m.c but incorporated into a bilayer, became an activator (K(M) decreased respect to the control). Non-enzymatic interfacial hydrolysis of the substrate was discarded. Enzyme-membrane interaction and membrane elasticity, were evaluated using monomolecular layers at the air-water interface. Beyond particular molecular structures, topology affected the direction of the modulatory effects exerted by these amphiphiles on beta-galactosidase activity.

Lactose intolerance: diagnosis and management

Lactose intolerance affects hundreds of millions of people worldwide. Although the presentation is frequently atypical, it should be part of the differential diagnosis when evaluating nonspecific gastrointestinal symptoms. We review the terminology, types of lactase deficiencies, diagnostic procedures, and management.

Transgenic animal bioreactors

The production of recombinant proteins is one of the major successes of biotechnology. Animal cells are required to synthesize proteins with the appropriate post-translational modifications. Transgenic animals are being used for this purpose. Milk, egg white, blood, urine, seminal plasma and silk worm cocoon from transgenic animals are candidates to be the source of recombinant proteins at an industrial scale. Although the first recombinant protein produced by transgenic animals is expected to be in the market in 2000, a certain number of technical problems remain to be solved before the various systems are optimized. Although the generation of transgenic farm animals has become recently easier mainly with the technique of animal cloning using transfected somatic cells as nuclear donor, this point remains a limitation as far as cost is concerned. Numerous experiments carried out for the last 15 years have shown that the expression of the transgene is predictable only to a limited extent. This is clearly due to the fact that the expression vectors are not constructed in an appropriate manner. This undoubtedly comes from the fact that all the signals contained in genes have not yet been identified. Gene constructions thus result sometime in poorly functional expression vectors. One possibility consists in using long genomic DNA fragments contained in YAC or BAC vectors. The other relies on the identification of the major important elements required to obtain a satisfactory transgene expression. These elements include essentially gene insulators, chromatin openers, matrix attached regions, enhancers and introns. A certain number of proteins having complex structures (formed by several subunits, being glycosylated, cleaved, carboxylated...) have been obtained at levels sufficient for an industrial exploitation. In other cases, the mammary cellular machinery seems insufficient to promote all the post-translational modifications. The addition of genes coding for enzymes involved in protein maturation has been envisaged and successfully performed in one case. Furin gene expressed specifically in the mammary gland proved to able to cleave native human protein C with good efficiency. In a certain number of cases, the recombinant proteins produced in milk have deleterious effects on the mammary gland function or in the animals themselves. This comes independently from ectopic expression of the transgenes and from the transfer of the recombinant proteins from milk to blood. One possibility to eliminate or reduce these side-effects may be to use systems inducible by an exogenous molecule such as tetracycline allowing the transgene to be expressed only during lactation and strictly in the mammary gland. The purification of recombinant proteins from milk is generally not particularly difficult. This may not be the case, however, when the endogenous proteins such as serum albumin or antibodies are abundantly present in milk. This problem may be still more crucial if proteins are produced in blood. Among the biological contaminants potentially present in the recombinant proteins prepared from transgenic animals, prions are certainly those raising the major concern. The selection of animals chosen to generate transgenics on one hand and the elimination of the potentially contaminated animals, thanks to recently defined quite sensitive tests may reduce the risk to an extremely low level. The available techniques to produce pharmaceutical proteins in milk can be used as well to optimize milk composition of farm animals, to add nutriceuticals in milk and potentially to reduce or even eliminate some mammary infectious diseases.