ALBERT

Notes: Zusammenfassung Die Molekulargewichtsverteilung eines in Gegenwart von Thymochinon durch thermische Polymerisation erhaltenen Polystyrols wird untersucht. Es handelt sich um eine “wahrscheinlichste Verteilung”Schulz-Verteilung mit dem Kopplungsgrad 1). Die Verteilung stimmt mit der schon früher aus kinetischen Messungen postulierten zusätzlichen Übertragungswirkung des Thymochinons überein.

Notes: Summary 1. In populations of the dipteran Phryne cincta (2n = 6+XX♀, XY♂) several X-chromosomes of different structure are present. These are allocyclic in contrast to the (eucyclic) autosomes, as seen in their behaviour in mitosis and meiosis and in their varied appearance in polytene nuclei (comp. Wolf 1950, 1957). 2. The polytene autosomes (2–4 s. Pig. 7) differ from each other in easily recognizable characters and form no chromocenter. The polytene X-chromosome is always relatively much shorter than the autosomes and more or less β-heterochromatic (granular or indistinctly banded) in larvae, raised at room temperature. In larvae raised at low temperature (0–4° C) it passes through a morphogenesis, growing to normal or nearly normal length and assuming the aspect of an euchromatic element (comp. X a in Figs. 3 and 4). 3. Two stocks, characterized by different X-chromosomes, symbolized by X a and X b or a and b respectively, were chosen for the experiments. In mitosis both these X-chromosomes are rod-like, a is as long as autosome 4, b has only half its length (Figs. 1, 2a–d). 4. Just before pupation, in polytene nuclei of larvae raised at low temperature a and b are of almost equal length. They differ from each other in several inversions and in the appearance of two large α-heterochromatic bands in a (α2 and α3, Fig. 5; “α-quantum-difference”). 5. The α-bands, especially the large block α2, show a considerable intercellular variation in their relative DNA-content (measured as length of the α-element). The mean DNA-content is negatively correlated with the degree of stretching of the chromosome (Table 1). 6. In polytene nuclei of female hybrids from the crosses aaxbY or bbxaY, a and b are unpaired or incompletely paired in variable degrees (Figs. 7, 8a–e). The heterozygotic chromosome pair can be devided into 5 segments (I–V, Fig. 6), three of which are marked by clearly defined structural differences (I, III, V). 7. The pairing-segments II and IV, exhibiting an identical and parallel sequence of discs in a and b, allow six crossing-over recombinations (cb, db, eb, fb, gb, hb; comp. Figs. 9, 10). These new types of X-chromosomes occur in very different frequencies in the progeny of the hybrid ♀♀ when backcrossed to standard ♂♂ bY. The types eb and fb occur relatively rarely, while gb and hb are extremely rare (Figs. 9, 10, Table 2); in 70% of the progenies they are not present. The recombination-process is mainly restricted to pairing segment IV. 8. In a and in the crossover-chromosomes c, e, g very often a threadlike constriction appears in the region of α 2, resulting mostly in a pseudofragmentation with more or less independent location of the two chromosome parts (Figs. 3d, 8f-i, 11a). A variety of kinds of fusion between the parts and the autosomes, especially in their α-heterochromatin, is possible (Figs. 3e, 8g–i). 9. Lowering the breeding-temperature increases the duration of development, the size of the larvae, and the lengthening and euchromatization of the β-heterochromatic parts of the X-chromosomes. In the hybrids it also results in increasing the recombination rate (Table 3 and 4). 10. In the main experiments, hybrid offspring from the same parental pair, were raised at different temperatures: some individuals at high (20–26° C), others at low temperatures (2–8° C). The resulting two series of imagos were kept in optimal or room temperatures (14–22° C). The female progeny of 23 hybrids raised at elevated temperature and of 27 hybrids raised at low temperature, i.e. 1766 and 2102 X-chromosomes respectively, have been tested (Table 5, Fig. 12). No or only little recombination occurred in hybrids raised at 20–26° C (mean = 2.4%) in contrast to their sisters raised at 2–8° C, which gave a relative high frequency (mean = 18,2%). 11. In these cases only the first egg batches of each hybrid ♀ have been evaluated. Later progeny exhibits a reduction in crossing-over frequency in cold-raised hybrids with growing age. The mean rate of recombination of 14 hybrids is lowered from 16,6% in the first to 7,1% in the following progeny (n=1813; Table 6, Fig. 15) presumably as a consequence of keeping the imago in higher temperature. 12. The results from several larger groups of cold-raised sister hybrids more or less clearly demonstrate a bimodal distribution of recombination values (Fig. 13) suggesting a difference in recombination potentiality between the two X-chromosomes in the mother of the hybrids. Some data indicate the recombination rate in the X-chromosome as negatively correlated with the rate of development (Table 7). 13. The Mendelian ratio, 1∶1, of the non-recombinant types, ab and bb, is found in the progeny of the warm-raised hybrids (1769∶1778). This ratio is shifted considerably in favour of type ab in the case of low temperature hybrids (1996∶1626). In the recombinant types, cb and db, the ratio is always markedly shifted in favour of cb, irrespective of temperature (712:343). There must exist a causal relation between the Mendelian anomaly and the recombination process the nature of which is yet unknown. 14. The temperature at which a larva is raised effects both the frequency of crossing over and the stretching and euchromatization of β-heterochromatin in the polytene X-chromosome. This parallele suggests that structural changes comparable to those in the polytene chromosomes are induced by low temperature in meiotic chromosomes as well, and that these changes are responsible for the effect on the crossing-over frequency. These changes, which are reversible by age or temperature, are supposed to cause the extention of the “effective pairing” (as in euchromatic segments) on β-heterochromatic elements, which normally are unpaired. 15. The so-called “α-quantum-difference”, i.e. the difference in the amount of α-heterochromatin (or in the “relative DNA-content”) between the X-chromosomes is considered to be causally related to the crossing-over process (“α-differential-effect”). By way of a potential function it effects crossing over not only within the “α-differential” tetrad but also crossing over in non-homologous and unrelated pairs of chromosomes in the same meiotic cell. 16. This hypothesis was ascertained by two independent inversions in autosome 2 (In 2a and In 2b, Fig. 16) which permitted to test the influence of the “α-quantum-difference” in the X-chromosomes on crossing over in the autosome. In preliminary studies the progenies of 8 females (ab, bb, cb) and 3 males (aY, cY) of the heterozygous F1 backcrossed to homozygous b-stock have been investigated. In the progeny of the males only the parental combinations in autosome 2 were found. In the test cross progeny of the females the two expected types of recombination appeared (with only one inversion, In 2a or In 2b), but there existed a very high difference in linkage between bb- ♀♀ on the one side (3.6% crossing over) and ba- and bc-♀♀ on the other (40.2% crossing over).

Notes: Abstract We observed near-Main-Sequence B-stars in the Magellanic Clouds with the 3.6 m telescope and CASPEC at La Silla. We obtained spectra of high resolution and high S/N-ratio. The stars are members of the blue globular clusters NGC 1818 (LMC) and NGC 330 (SMC). The spectra are used for differential abundance analyses using ι HER as galactic reference star. Apart from CNO the metals are underabundant by about a factor of three and four for the LMC and SMC star, respectively. The CNO pattern is interesting since in both stars oxygen is considerably more abundant than carbon.

Notes: Summary Streptozotocin treatment at birth induces, in the pancreas of rats, first depletion of insulin and thyrotropin-releasing hormone and then early regeneration ofβ cells and insulin, but not TRH. This study was undertaken to investigate whether the reduction in pancreatic TRH content can be associated with changes in the intensity and the distribution of TRH-immunoreactivity, and to follow the pattern of regeneration ofβ cells through insulin- and TRH-immunoreactivity. In control animals, strong TRH-immunoreactivity was seen in insulin-containing cells on days 1–4 after birth. At day 7, the TRH-immunoreactivity was already decreased. In contrast, insulin-immunoreactivity was present throughout the neonatal period. A sparse population of cells near ducts also contained both TRH- and insulin-immunoreactivity at 1–2 days age. In streptozotocin-treated animals, TRH-immunoreactivity is found only in a few scattered insulin-containing cells in altered islets on days 1–4. Near the ducts, there were new insulin-containing cells which did not contain TRH. From day 7 regeneration of endocrine cells was characterized by new, typical islets, but these contained insulin-, but not TRH-immunoreactivity. These findings suggest a differential control of the biosynthesis of insulin and TRH within the pancreas.

Notes: Summary The chromatin structure of the 5′-upstream region of the Shrunken (Sh) gene in Zea mays has been examined. We have identified a region of DNase I hypersensitivity extending at least from the 3′-end of exon 1 for 2 kb into the 5′-flanking region. This region is composed of a set of closely spaced hypersensitive sites separated by small regions that are less accessible to DNase I. The most sensitive sites are located within 300 bp upstream of the transcription start site. Hypersensitive sites are found essentially at the same positions in kernels, roots and leaves, although the latter display different relative intensities. No changes are found in roots within the tested region upon anaerobic induction. Testing protein-free plasmid DNA containing the 5′ upstream region of the Sh gene, we found a site sensitive to the single strand specific nuclease S1 located very close to a DNase I hypersensitive site identified in chromatin. Several hypersensitive sites are flanking in vitro binding sites of nuclear proteins as determined by Werr et al. (1988; accompanying paper).

Notes: Summary A new member of the patatin gene family belonging to the class II subfamily was isolated and characterized by DNA sequencing. In order to study the expression profile of this gene, the promoter was fused to the β-glucuronidase gene and transferred to potato and tobacco. Histochemical analysis revealed high expression in a few defined cells in potato tubers and in a specific layer of both potato and tobacco root tips. In contrast to the developmentally and metabolically regulated class I patatin gene B33 this gene was not inducible by elevated levels of sucrose. Expression of this chimaeric gene was also found in callus and suspension cultures of potato.