Versuch einer Kausalanalyse der geotropischen Reaktionskette im Chara-Rhizoid

Summary In the initial phase of the geotropical reaction of the Chara rhizoid the growth difference postulated by Sievers (1967c) between the physically upper, slightly subapical flank and the lower one is demonstrated. In horizontal exposure the growth of the extreme cell apex is continued, while the growth of the lower flank is inhibited and that of the upper one is promoted. In the end phase the cell apex shows a damped oscillation until it finally reaches the vertical growth direction. The statoliths follow the oscillating growth of the cell tip from one flank to the opposite one until they are statistically equally redistributed in their normal position.—In vertical exposure under reduced turgor pressure the statoliths fall down into the extreme cell apex, where they inhibit the growth of this part of the cell wall, while the subapical wall grows transversally.—It is concluded that the statoliths inhibit the growth of the cell wall area which they cover.—The physical phase of the reaction chain, the susception, is the gravity-induced downward displacement of the statoliths. The physiological phase starts with the diversion of the acropetal transport of the Golgi vesicles to the upper part of the cell, which is caused by the block of statoliths (perception). The greater rate of vesicle incorporation into the upper flank in comparison to the lower one causes the subapical growth difference which results in the curvature (reaction).—In the case of the Chara rhizoid Golgi- and statolith-apparatus function as a self-regulating cellular system.

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Herrn Prof. Dr. Dr. h. c. Kurt Mothes zum 70. Geburtstag.     

Characterisation of Trypanosoma cruzi populations by dna polymorphism of the cruzipain gene detected by single-stranded dna conformation polymorphism (SSCP) and direct sequencing

Fifty fresh isolates of Trypanosoma cruzi from Triatoma dimidiata vectors and 31 from patients with Chagas disease were analysed for DNA polymorphisms within the 432-bp core region of the cruzipain gene which encodes the active site of cathepsin L-like cystein proteinase. The cruzipain gene showed signs of polymorphism consisting of four different DNA sequences in Central and South American isolates of T. cruzi. The PCR fragments of Guatemalan isolates could be divided into three groups, Groups 1, 2 and 3, based on different patterns of single-stranded DNA conformation polymorphism. All of the strains isolated from Brazil, Chile, and Paraguay, except for the CL strain, showed a Group 4 pattern. Two to four isolates from each group were analysed by cloning and sequencing. A silent mutation occurred between Groups 1 and 2, and five nucleotides and two aa substitutions were detected between Groups 1 and 3. The DNA sequence of Group 4 contained five nucleotides and one aa substitution from Group 1. All of the DNA sequences corresponded well with the single-stranded DNA conformation polymorphism. The Group 1 isolates, the majority in the Guatemalan population (70/81, 86.4%), were isolated from both triatomines and humans, but Group 3 were isolated only from humans. Moreover, the Group 2 isolates were detected only in triatomine vectors (9/50; 18%), but never in humans (0/32, P<0.05) suggesting that this group has an independent life-cycle in sylvatic animals and is maintained by reservoir hosts other than humans.     

Luminescence immunoassay of pollen allergens on air sampling polytetrafluoroethylene filters.

A new method for quantification of airborne birch and grass pollen allergens collected on porous polytetrafluoroethylene filters has been developed. In this method, the allergens firmly adsorbed to the sampling filter of 25 mm in diameter are reacted with specific antibodies conjugated to alkaline phosphatase, generating a matrix-bound allergen-antibody-phosphatase complex. The filter is then floated on a chemiluminescent enzyme substrate solution. The light intensity of the product is linearly related to the amount of allergen over a large mass range, 0-1000 SQ (1 SQ is about 250 pg of protein). This direct on sampling filter in solution (DOSIS) technique demonstrated intra-assay precisions between 6-16% and 11-15% for the levels of 1-100 SQ units of grass allergen Phl p 5 and 4-400 SQ units of birch allergen Bet v 1, respectively. The limits of quantification for the corresponding allergens were estimated to 0.5 and 2 SQ units. Application of DOSIS to analysis of the grass pollen allergen concentrations of outdoor air for 12 days in July 1998 revealed a correlation coefficient of 0.69 between pollen grain and allergen concentrations for the dry weather period. After rainy days large amounts of grass allergens were present even in the absence of pollen grains.     

Elementary steps in protein folding.

The mechanism of protein folding is under intense theoretical and experimental investigation. From stopped-flow mixing experiments we have detailed knowledge of processes slower than about 1 ms, but until recently little was known about folding and unfolding reactions on the microsecond to nanosecond time scale. The use of novel techniques allowed to explore the elementary steps in protein folding, such as intrachain diffusion and formation of alpha-helices, beta-hairpins and loop structures. This brief review discusses the time scales of these early elementary events which are crucial for the understanding of how proteins fold.     

Direct microsensor measurement of nitric oxide production by the osteoclast.

Nitric oxide (NO) triggers marked osteoclast retraction which closely resembles that due to Ca2+. The effect of Ca2+ has been attributed to a stimulated release of NO. Here, we show for the first time, by direct measurement with a microsensor, that osteoclasts do indeed produce NO and that this production is enhanced by a high Ca2+. We also show that the Ca2+ ionophore, A23187, mimics the latter. Furthermore, osteoclasts on dentine produce more NO than osteoclasts on glass and NO release from dentine-plated osteoclasts is much less sensitive to stimulation by Ca2+. Finally, the microsomal Ca2+ store-depleting agent, thapsigargin, attenuates NO release only from osteoclasts on glass, suggesting that stored Ca2+ has the dominant effect in modulating NO release from non-resorbing cells. NO is a powerful inhibitor of bone resorption: a direct demonstration of its production is therefore strong evidence for a role in modulating osteoclast function.     

Effect of a low-frequency magnetic field on systemic arterial pressure in spontaneously hypertensive rats

The effect of low-frequency magnetic field (MF) on systemic blood pressure has been studied in chronic experiments on 21 spontaneously hypertensive rats. The animals' kidney area was exposed to MF (induction value 30T). Direct blood pressure measurements have revealed an antihypertensive effect.     

Recognition of influenza virus hemagglutinin by subtype-specific and cross-reactive proliferative T cells: contribution of HA1 and HA2 polypeptide chains

The recognition of influenza virus hemagglutinin (HA) by T lymphocytes was examined by assaying the T cell proliferative response of influenza virus-primed T cells to purified HA of different influenza A subtypes or to isolated heavy (HA1) or light (HA2) polypeptide chains of the HA molecule. The proliferative response to HA was dependent on the activation of an Ly-1+2- subset of T cells and required the presence of nylon wool-adherent, radiation-resistant accessory cells. T cells from mice primed by infection with one strain of type A influenza virus cross-reacted with other purified HA not only of the same subtype as the priming virus but also of serologically distinct subtypes of influenza A (but not B) virus. The response of virus-primed T cells to the homologous HA or to HA of the same subtype was shown to involve recognition of determinants on both the HA1 and the HA2 chains. The recognition of HA of different subtype by cross-reactive T cells appeared to be directed predominantly to determinants on HA2. Because the antibody response to influenza virus HA is not cross-reactive between subtypes and is directed predominantly to determinants on HA1, the present results indicate that at least some of the determinants on HA recognized by T cells are different from those recognized by B cells and that the HA2 chain may be involved primarily in stimulation of T cell rather than B cell immunity.     

Screening method for microorganisms producing L-aminoacids from D,L-5-monosubstituted hydantoins

Summary The ability of microorganisms to produce hydantoinase and L-N-carbamoylase could be established by an overlay assay. Enzyme producing strains form clear areas around their colonies caused by the cleavage of D,L-indolylmethylhydantoin. A second overlayer with a tryptophan-auxotroph yeast enables us to detect microorganisms which are able to produce L-tryptophan from D,L-indolylmethylhydantoin.