Characterization of the promastigote surface protease of Leishmania as a membrane-bound zinc endopeptidase

The effects of a variety of inhibitors suggested that the promastigote surface protease (PSP) of Leishmania might be a zinc metalloprotease. To investigate this possibility, we conducted atomic emission and absorption spectroscopic analyses, which show that PSP contains 1 atom of zinc per 63-kDa monomer. Further studies showed that the enzyme can be biosynthetically labeled with 65ZnCl2. The comparison of the amino acid sequence of Leishmania major PSP with nine other zinc metalloproteinases revealed significant similarity in the area of their zinc-binding sites. These data show clearly that the promastigote surface protease of Leishmania is a zinc metalloproteinase. Secondary structure analysis by circular dichroism spectroscopy indicates that PSP contains over 40% beta-strand and less than 20% alpha-helical structure. The molecular masses of amphiphilic PSP (152 kDa) and of hydrophilic PSP (142 kDa), determined by quantitative electron scattering, suggest that the purified enzyme occurs in solution, and presumably at the cell surface, as a non-covalent homodimer.     

Clinical consequences of heterozygosity for autosomal-recessive diseases*,**

Heterozygotes of autosomal-recessive diseases can often be recognized by special heterozygote tests, since enzyme activities are normally reduced in comparison with the normal homozygote state. In Drosophila, the majority of recessive lethal mutations shows a reduction of fitness in heterozygotes, whereas in a strong minority fitness of heterozygotes is increased. This review will be devoted to a consideration of the extent to which heterozygotes for a wide variety of nominally recessive diseases are subject either to an increased liability for common diseases or slight shifts of behavioral characteristics. The available evidence has been collected and will be discussed in three steps: Most studies are available for phenylketonuria. For this group of diseases, a slight reduction of average--especially verbal--I.Q. in heterozygotes has been reported together with signs of a slightly increased cerebral irritability, a possible slight increase of risk for mental disease, and an increase of blood phenylalanine levels in stress situations. The PKU example is used to discuss methodological problems involved in such studies. Other conditions for which relevant deviations in heterozygotes are possible or even likely include among others lipid storage diseases, microcephaly, myoclonus epilepsy, Wilson's disease, galaktokinase deficiency, homocystinuria, recessive myotonia and ataxia- teleangiectasia (increased cancer risk). Since heterozygotes for autosomal recessive diseases are common, it is possible that an appreciable fraction of "multifactorial" genetic liabilities for common, "constitutional" or mental disease might simply be due to heterozygosity for genes whose homozygous affects are already well known. By the same token, much of the "normal" genetic variability influencing cognitive performance (I.Q.)--especially in the lower range--and personality characteristics could also be caused by recessive genes in the heterozygous state.     

European vestibular experiments on the Spacelab-1 mission: 7. Ocular counterrolling measurements pre- and post-flight

Summary The static ocular counterrolling (OCR) of the four scientific crew members in the first Spacelab mission was measured during baseline-data-collection before and after the flight of SL-1. It was presumed that the modification of otolithic responses during spaceflight will be reflected in specific changes of the OCR-gain on the first days after recovery. The magnitude of OCR was determined analysing colour-transparencies of subjects right eyes that were produced in different positions of lateral body tilt. In general, one subject did not show any changes at all; three subjects exhibited a significant decrease of OCR-gain after exposure to weightlessness, whereby differences could be found between the responses for small and large angles of lateral body tilt. Moreover, asymmetrical effects of OCR-gain were found between body tilt to the left and tilt to the right side. Two subjects already demonstrated such an asymmetry before the flight with the higher gain on left-tilt (or right eye up), and three subjects exhibited left-right asymmetries after the spaceflight with the higher gain tilting to the right (or right eye down). A possible correlation between these vestibular asymmetries and space-sickness susceptibility is discussed.     

Effects of transforming growth factor beta1 on bonelike tissue formation in three-dimensional cell culture. I. Culture conditions and tissue formation

Bone tissue engineering based on growing bone marrow stromal cells on poly(L-lactic-co-glycolic acid) fiber meshes suffers from limited matrix production and mineralization when the cells are cultured with the standard differentiation supplements (dexamethasone, beta-glycerophosphate, and ascorbic acid). To overcome this problem we included transforming growth factor beta1 (TGF-beta1), which is described as playing a key role in collagen type I formation, although its effect on mineralization is controversially discussed. The investigations focused on establishing culture conditions for the application of TGF-beta1 in three-dimensional cell culture and on the effects of different doses of TGF-beta1 (1-20 ng/mL) on bonelike extracellular matrix formation. Immunohistochemical staining showed that TGF-beta1 enhanced the formation of procollagen type I, collagen type I, and collagen type V, especially under dynamic culture conditions (orbital shaker). A long-term study confirmed positive effects on the formation of extracellular matrix, which penetrated the scaffold to a depth of 250 to 300 microm. Mineralization, qualified by scanning electron microscopy in combination with energy-dispersive X-ray analysis and evaluated by determination of the Ca2+ content per scaffold, was up to 1.7-fold increased by TGF-beta1 compared with the control. In conclusion, the growth factor TGF-beta1 seems to be effective in improving extracellular bonelike matrix formation in vitro.     

Delta9-tetrahydrocannabinol increases C6 glioma cell death produced by oxidative stress

(-)Delta9-tetrahydrocannabinol is a scavenger of free radicals. However, the activation of the CB1 receptor in cultured C6 glioma cells by (-)delta9-tetrahydrocannabinol in the presence of reagents generating reactive oxygen species leads to amplification of the cellular damage from oxidative stress. This was evident by increased loss of cell wall integrity, impaired mitochondrial function and reduction of glucose uptake. In addition, (-)delta9-tetrahydrocannabinol treatment was also found to be deleterious to the cells under conditions of glucose starvation. Free radicals have been implicated in various conditions leading to cell death and, as a routine, the Fenton reaction is utilized for modeling reactive oxygen species production. Our study was performed using a cell permeating Fe(III) chelating quinone that provides more physiological conditions for mimicking the naturally occurring oxidative stress within the cell and thus serves as a better model for natural reactive oxygen species formation.     

Mimotope and anti-idiotypic vaccines to induce an anti-IgE response

We have defined epitopes on human IgE by screening different phage display random peptide libraries with a monoclonal anti-IgE antibody termed BSW17. The selected mimotopes and epitopes within the Cepsilon3 and Cepsilon4 region of IgE induced antibodies that were nonanaphylactogenic and had biological activity similar to BSW17. The chemically synthesized and KLH-coupled IgE epitopes or mimotopes were used to induce an anti-IgE response in rhesus monkeys. The immunized rhesus monkeys were subsequently protected in a PCA test when sensitized with human IgE and triggered with the corresponding allergen. Furthermore, using the same monoclonal anti-IgE antibody, we also generated an anti-idiotypic antibody that showed sequence homology with the IgE epitope in the Cepsilon3 domain. This anti-idiotypic antibody as well as the mimotopes were then used in a mouse model to induce orally an anti-IgE immune response. For this purpose mice were fed by intragastric gavages with bacteriophages displaying the small IgE-homologous structures. Orally immunized mice produced serum anti-IgE antibodies that were inhibited by BSW17 suggesting that it may be possible to induce a systemic anti-IgE response orally.