Laser-diffraction analysis (LDA) is a rapid automated method achieving highly resolved frequency distributions of particle sizes. Recently, LDA has come into use in environmental sciences. However, in the size range of silt and clay deviations from the particle-size analysis with the standard pipette method, which is regarded as the reference method for soil-texture classification, have been reported. Therefore, this study concentrates (1) on the verification of systematic relations between both methods using a series of soils of Lower Saxony (Germany) and (2) on the general applicability of the laser-diffraction method to soil-texture classification as well as (3) texture-based estimates of air capacity, available field capacity, and permanent wilting point. The comparison of LDA with the pipette method demonstrated highly significant linear correlations in each of the particle-size fractions from clay to coarse silt. The slope of regressions ranged from 0.4 with fine silt to 3.1 with clay. If the clay content derived from LDA was applied to texture classification, the resulting textural classes differed from the standard textural classes, except for purely sandy samples with a clay content of <5%. However, the linear-regression model enabled an approach of the LDA-based clay content to values produced with the standard pipette method. Using this transformation, a texture classification became practicable in many cases, but, despite of a high significance level between LDA and pipette method, still led to wrong textural classes in several cases. A comparison with regression models from other regions in Europe showed both similarities and discrepancies, even for similar substrates. Hence, the laser-diffraction analysis cannot be used for the texture classification of soil samples without verification by the standard pipette method.

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The development of cochlear receptor cells and their supporting elements was studied by means of semi-thin and ultra-thin sections during the first postnatal weeks in the rat. The temporal and spatial patterns of the receptor cell development were investigated between the 4th and 24th days after birth. At approx. ten equidistant positions along the entire cochlear duct length of inner and outer hair cells, width of outer hair cell triad and stereocilia-length of the outer hair cells were quantitatively analyzed. Striking maturational changes take place before the 12th day after birth, that is, when the onset of hearing occurs. These changes are the formation of the tunnel of Corti, of the Nuel spaces, the appearance of filaments within the supporting elements and the change in cell shape of the hair cells. Between 4 days and 20 days after birth the maturation of outer hair cells is characterized by a decrease of organelles in the cytoplasm and establishment of the subsurface cistern. The quantitative analysis revealed a unique developmental pattern of the length of the outer hair cells, the width of the outer hair cell triad and the stereocilia length of the outer hair cells. Shortly after birth these structures have an almost constant size along the whole cochlear duct, but with increasing age the structures shorten at the cochlear base and enlarge at the apex. This pattern results in the establishment of a baso-apical gradient of the above mentioned structures. We assume that this baso-apical gradient is of central importance for the frequency representation.

Insulin-like growth factor I1 (IGF 11) and four structural analogs, constructed by site-directed mutagenesis, were expressed as protein A fusion proteins in Escherichia coli BL2lpLysS cells, cleaved with cyanogen bromide and purified by affinity chromatography and HPLC. Two mutants (Ser29 substituted by Arg-Leu-Pro-Gly, and Ser33 substituted by Cys-Gly-Asp) represent two naturally occurring variants of IGF 11. The other two mutants, (7 -67)IGF I1 and (9 -67)IGF 11, are truncated at the amino-terminus in analogy to the naturally occurring des(1-3)IGF I ('truncated LGF 1').Thcse mutants were tested for their binding affinities to type-I and type-2 IGF receptors, to IGF binding protein-3 (IGFBP-3) and for their stimulation of thymidine incorporation into DNA. The affinities of the Ser29 and Ser33 mutants to the type-1 IGF receptor were 85% and 39%, respectively, compared to wild-type IGF 11, those of (7 -67)lGF 11 and (9 -67)IGF 11 96% and 15%, respectively.The potencies of the Ser33 and the (9-67) mutant to stimulate thymidine incorporation into DNA correlated closely with the affinities to the type-1 IGF receptor, whereas the bioavailability of the Ser29 mutant was lower and that of the (7-67) mutant higher than the type-1 receptor binding, possibly due to interferences with endogenously secreted IGFBPs. The affinities of the Ser29 and Scr33 mutants to the type-2 IGF receptor were 110% and 73o/u, respectively, those of the two truncated mutants 25% and 23%, respectively. The affinity of the Ser29 mutant to IGFBP-3 was increased to 171Y0, whereas those of the Ser33 mutant and the two truncated mutants were reduced (34'/0, 10% and 19%, respectively).Insulin-like growth factors (IGFs) are single-chain polypeptides found in blood and body fluids of vertebrates (for a review see [I]). In chicken and mammals, two homologous polypeptides, IGF I and 11, are present, which are in turn homologous to proinsulin. IGF I, identical with somatomedin C, is a growth-hormone-dependent growth factor with well established biological effects in vztro and in vivo [I, 21. IGF I1 shows the same in virro effects as IGF I [2]; it seems to act as a fetal growth factor in some species [3,4], but its role in man has remained elusive so far. IGF I and I1 are ligands for the insulin receptor (with low affinities [5]), for the type-1 IGF receptor (homologous to the insulin receptor [6]), to the type-2 IGF receptor (identical wit the cation-independent mannose-6-phosphate receptor [7]), and to several types of IGF binding proteins (IGFBPs) [S]. Probably most of the growthenhancing effects of the IGFs are mediated via the type-I IGF receptor [9]. The biological significance of the type-2 IGF receptor is as yet not clear [lo].The bulk of IGF I and I1 in human plasma and body fluids consists of the two 7.5-kDa peptides originally isolated and sequenced [11 -131. Besides these two 'classical' IGFs with 70 and 67 residues, respectively, several variants of different length have been described. A variant of IGF 11 with an insert of the tetrapeptidc A...

The development of the rat organ of Corti was studied during the first postnatal weeks. The temporal and the spatial patterns of cochlear development were investigated between 4 and 24 days after birth by means of semi-thin sections at approx. ten equidistant positions along the entire cochlear duct. At all examined positions width, thickness and cross sectional area of basilar membrane, cross-sectional area of tectorial membrane, of cells of Hensen, Claudius and Boettcher and of the organ of Corti were quantitatively analyzed. The most conspicuous maturational changes occur between 8 and 12 days after birth. These are the detachment of the tectorial membrane, the first appearance of filaments within the basilar membrane, the formation of the tunnel of Corti and the opening of the inner spiral sulcus. Quantitative analysis revealed that structures of a given position along the cochlear duct do not develop synchronously. Width of the basilar membrane and cross-sectional area of the tectorial membrane are already mature at the onset of hearing (10-12 days after birth). Length, thickness and cross-sectional area of the basilar membrane as well as cross-sectional area of the organ of Corti and of the cells of Hensen, Claudius and Boettcher still develop after the onset of hearing (up to 20-24 days after birth). We suggest that basic cochlear function is established by structures which are mature before the onset of hearing. Cochlear structures which develop after the onset of hearing might be involved in this improvement during this period.