Desynaptische Mutanten mit Unterschieden im Univalentenverhalten

After application of neutrons on dry seeds ofPisum sativum three recessive mutants were isolated showing irregularities in the course of meiosis. A cytogenetical analysis showed that at metaphase I, a varying number of univalents are formed, most likely as a result of reduced chiasma frequencies. At anaphase I, some univalents divide precociously in mutant 2982 but none do so in mutants 2989 and 2552. As a consequence, most cells of 2989 and 2552 built up more than two spindles at anaphase II, whereas the majority of cells in 2982 form two spindles. This situation is reflected in the frequency distribution of gones per PMC at tetrad stage. The discussion deals with the possible causes of univalent formation at meiotic prophase and the variability of univalent behaviour at anaphase I.     

A test of distributive pairing in Zea mays utilizing doubly monosomic plants

Summary The v _x1 deficiency in Zea mays induces chromosomal nondisjunction during the megagametophyte divisions after meiosis producing large numbers of monosomes, trisomes, double monosomes, double trisomes, and even triple monosomes. In this study, microsporogenesis in six doubly monosomic combinations was analyzed. Double monosomes in a diploid organism provide the ideal material to determine if there is an interaction between two nonhomologous univalent chromosomes because two nonhomologous chromosomes lacking partners are present in each meiotic cell.At diakinesis and metaphase I, the two nonhomologous monosomic chromosomes were infrequently paired (3.76% and 2.18% respectively). These estimates are the upper estimates of pairing of nonhomologous monosomic chromosomes and probably represent an overestimate of these values because cells with any connections between the monosomic chromosomes were scored as having nine pairs and similar connections are not infrequently observed between two bivalents.The transmission of two nonhomologous unpaired chromosomes was deduced by studying the progeny of maize plants hyperploid for two chromosomes (a B⁴ and Wd ring). The two nonhomologous univalents disjoined randomly.Since no evidence for an interaction between nonhomologous univalent chromosomes which leads to their non-random disjunction to opposite poles was found in this study, these data confirm my earlier conclusion (Weber, 1966, 1969) that distributive pairing does not occur in maize (and probably most other plants) or that it occurs with a much lower efficiency than in Drosophila females. The frequent pairing between nonhomologous chromosomes at diakinesis and metaphase I and the non-random distribution at anaphase I in doubly trisomic maize plants reported by Michel and Burnham (1969) was found neither in my earlier studies (Weber, 1966, 1969) nor in the present study. The current study is far more sensitive than any of the previous studies because two nonhomologous chromosomes lacking pairing partners are found in every cell of a doubly monosomic plant.Research supported in part by U.S. Atomic Energy Commission Contract AT(11-1)-2121. Tech. Report No. COO-2121-10. This paper is dedicated to Professor Marcus M. Rhoades on the occasion of his 70th birthday. His guidance and help will be cherished throughout my lifetime.     

A test of distributive pairing in Zea mays

Zea mays plants containing two extra chromosomes were analyzed to determine if distributive pairing takes place in maize. No interaction between two univalent chromosomes generated in such plants could be detected at diakinesis or metaphase I. The chromosome disjunction in such plants was random at anaphase I. Furthermore, it was found that two chromosomes which are found as univalents in essentially 100 percent of the meiotic cells assorted randomly to the progeny. These experiments duplicated as closely as possible certain of Grell's (1962) experiments on distributive pairing. The author could detect no evidence for distributive pairing in maize. It was concluded that distributive pairing either does not occur in maize or that it occurs with a far lower efficiency than it does in Drosophila melanogaster females. Speculations on the reasons for these differences are included.Research supported in part by a grant (GM82-08) from the National Institutes of Health, U. S. Public Health Service.     

Further studies on polyploid amphibians

The manner in which centromere regions of mitotic chromosomes are distributed with respect to the age of their DNA was studied. Cells of the Indian deer, Muntiacus muntjak, were grown in the presence of bromodeoxyuridine (BrdU) for two generations and stained with the fluorescent dye Hoechst 33258. Chromatids containing granddaughter DNA appear dim when compared with those containing grandparental DNA. The frequencies of the various anaphase patterns of bright and dim centromere regions were binomially distributed, indicating random distribution of chromatids with respect to the age of their DNA templates.     

Experimental hybridization within the genus Triturus (Urodela: Salamandridae)

The spermatogenesis of 9 F₁ hybrids of Triturus cristatus carnifex × T. vulgaris meridionalis was studied in squash preparations of testicular fragments, treated by the C-staining method. The chromosome number of these hybrids was examined in spermatogonial metaphases and found to be diploid. The two parental sets were always recognized, which means that a regular, although heterospecific, amphimixis occurred (2n=n+n). Meiotic prophase I is greatly altered owing to a failure of typical chromosome pairing and chiasma formation. At metaphase I and/or meta-anaphase I, the effects of the hybrid combination of the 2 specific parental sets are clearly visible. Most primary spermatocytes contain only univalents. A few show chromosome associations (bivalents, trivalents and, more rarely, quadrivalent chains) besides univalents. Such associations are of 2 types: (a) intragenomal associations = associations of 2 chromosomes by a terminal (a¹) or subterminal chiasma (a²); (b) intergenomal associations = associations of 2 chromosomes by a terminal (b¹) or subterminal chiasma (b²). Univalents segregate at random while the associations often lag on the equatorial plane or migrate entire to a spindle pole. Primary spermatocytes with chromosome multivalents can encounter greater difficulties in accomplishing the first cytokinesis. Secondary spermatocytes are numerically and qualitatively unbalanced; however, some of them undergo spermiogenesis and can give rise to a small number of sperms, generally abnormal and never united in bundles. — Problems related to the occurrence of anomalous chiasmata and of intra- and inter-genomal homologies are discussed.     

Further examination of the production-line hypothesis in mouse foetal oocytes

Pachytene oocytes from foetal mice heterozygous for the translocation T(14; 15)6Ca were screened for evidence of a production-line effect on chromosome pairing. Metaphase I oocytes from adult heterozygotes were also examined to determine whether any such effect on pahytene chromosome pairing is subsequently repeated during adult reproductive life as anticipated by the production-line hypothesis. It was found that as gestation proceeded the proportion of pachytene oocytes with a translocation quadrivalent declined and that with a trivalent and univalent correspondingly increased. That is, there was evidence of variation in pairing behaviour of the translocation at different times of gestation. In contrast, the proportions of metaphase I cells with either a quadrivalent or a trivalent plus univalent did not vary between adult females of different ages. Thus if the variation observed at pachytene was the result of a production-line effect, clearly this was not reflected in the behaviour of the translocation at metaphase I. Our observations therefore do not support the production line hypothesis for the maternal age effect on nondisjunction.     

Cytological evidence of constant tetraploidy in the bisexual South American frog Odontophrynus americanus

Odontophrynus americanus has 2n=44 chromosomes in somatic and gonad cells which can be ordered in 11 groups of homologues. In spermatocytes I they form mostly ring quadrivalents. In metaphase II 22 dyads are present. There is no indication of abnormalities in and gonad development.     

The transformation of the synaptonemal complex into the “elimination chromatin” in Bombyx mori oocytes

In Bombyx mori oocytes the synaptonemal complexes are retained in modified form from pachytene to metaphase I. At the end of pachytene the length and width of the lateral components of the complex increase, whereafter the complexes become compacted during later stages of the meiotic prophase. Ultimately, at metaphase I the modified synaptonemal complexes of individual bivalents fuse to form a more or less continuous sheet between the homologous chromosomes. This sheet corresponds to the structure historically known as the elimination chromatin. It is concluded that in the absence of crossing over and chiasma formation in Bombyx mori females the retainment and subsequent modification of the synaptonemal complex has evolved as a substitute mechanism to ensure regular disjunction of the bivalents.     

Microtubule organization in cultured soybean and black spruce cells: Interphase —mitosis transition and spindle morphology

Summary Microtubule (MT) distribution during the cell cycle, especially spindle organization, has been investigated using immunofluorescence light microscopy in cultured cells of two higher plant species, soybean (angiosperm) and black spruce (gymnosperm). In soybean, the prophase and metaphase spindles were different in morphology and structure. The prophase spindle covering the nucleus was barrel-shaped and MTs extended between poles. The metaphase spindle consisted mainly of short MT bundles on either side of the chromosome mass. During prometaphase, the polarity and shape of the prophase spindle disappeared, suggesting that the metaphase spindle is newly formed in prometaphase and not derived from the prophase spindle. A striking feature of MT organization in black spruce was sharply defined poles during prometaphase and anaphase. They were located close to the cell edge, suggesting that a structure in the cytoplasm or associated with the plasma membrane is responsible for their formation. In black spruce the metaphase spindle was long with pointed poles and MT fir tree structures. In contrast, the metaphase spindle of soybean was short with very broad poles and lacked MT fir trees. These results suggest that MT fir tree structure may not be necessary for a functional spindle.     

Taxol affects meiotic spindle function in locust spermatocytes

Summary Addition of 0.1 to 10 M taxol to meiotic spindles in locust spermatocytes leads to a concentration dependent promotion of MT assembly at the centrosomes and depletion of MTs at the kinetochores, leading to the formation of prominent asters. In anaphase spindles, the equatorial region of the interzone becomes partly depleted of MTs, too. Microcinematographically, cytostatic effects are highly concentration/time dependent, being most rapid and nearly complete at 10 M taxol, but even in 0.1 M and 1 M taxol anaphase A movement is clearly affected. The drug strongly reduces the rate of chromosome-to-pole movement (anaphase A), leading to an insufficient separation of the chromosomes which indirectly hampers cytokinesis. Obviously, the chromosomal movement seems to be ratelimited by the compactness of the centrosomal asters reaching the equatorial plane in meta- and anaphase. Although the interzonal MT-number has become strongly reduced, anaphase B is not seriously affected but appears even slightly accelerated. Together with an occasional broadening of the cell equator (transverse elongation) instead of normal elongation, these results could be taken as an indication of the previously suggested active role of the cell's cortex in spindle pole separation during anaphase B (Daub andHauser 1986).Prof. Dr. K.-E.Wohlfarth-Bottermann on the occasion of his 65th birthday.     

Secondary structural effects on protein NMR chemical shifts

For an amino acid in protein, its chemical shift, (, )_s, is expressed as a function of its backbone torsion angles ( and ) and secondary state (s): (, )_{s=, )_coil+(, )_s}, where (, )_coil represents its chemical shift at coil state (s=coil); (, )_s (s=sheet or helix) is herein defined as secondary structural effect correction factor, which are quantitatively determined from Residue-specific Secondary Structure Shielding Surface (RSS) for ¹³CO, ¹³C, ¹³C,¹H, ¹⁵N, and ¹HN nuclei. The secondary structural effect correction factors defined in this study differ from those in earlier investigations by separating out the backbone conformational effects. As a consequence, their magnitudes are significantly smaller than those earlier reported. The present (, )_sheet and (, )_helix were found varying little with backbone conformation and the 20 amino acids, specifically for ¹³CO, ¹³C, and ¹H nuclei. This study also carries out some useful investigations on other chemical shift prediction approaches – the traditional shielding surfaces, SHIFTS, SHIFTX, PROSHIFT, and identifies some unexpected shortcomings with these methods. It provides some useful insights into understanding protein chemical shifts and suggests a new route to improving chemical shifts prediction. The RSS surfaces were incorporated into the program PRSI [Wang and Jardetzky, J. Biomol. NMR, 28: 327–340 (2004)], which is available for academic users at http://www.pronmr.com or by sending email to the author (yunjunwang@yahoo.com).     

The association of the human ε-globin gene with the nuclear matrix: a reconsideration

The association of the human -globin gene with the nuclear matrix was studied in erythroid and non-erythroid cell lines. Using a high salt method to prepare histone depleted nuclei we studied the association of variety of fragments covering a 7.8 kb region which contains the human -globin gene. We furthermore studied the association of a set of DNA fragments covering the 13 kb human G/A-globin gene domain, the 16 kb /-globin gene domain and the 10 kb -globin gene domain with the nuclear matrix of K562 and Raji cells. The results show that all fragments studied are easily released from the nuclear matrix, indicating no specific association.Summarizing our results we could say that a region starting 5.7 kb 5 to the human -globin gene and ending 4 kb 3 to the human -globin gene seems to contain no attachment sites with the nuclear matrix of both erythroid and non-erythroid cells.     

Differences in N-acetyllactosamine synthesis between β-1,4-galactosyltransferases I and V

Unlike classical -1,4-galactosyltransferase (-1,4-GalT I), -1,4-GalT V (formerly IV*) has little activity towards 1 mM N-acetylglucosamine [Sato et al. (1998) Proc Natl Acad Sci USA 95: 472-477]. The human -1,4-GalTs I and V were expressed individually in Sf-9 cells by transfection of the full coding sequences, and their N-acetyllactosamine synthetase activities were determined towards different N-acetylglucosamine concentrations. Kinetic studies using the cell homogenates as an enzyme source revealed that -1,4-GalTs I and V possess Km values of 0.6 mM and 33 mM towards N-acetylglucosamine, and of 48 µM and 41 µM towards UDPGal, respectively. No significant inhibition of N-acetyllactosamine synthesis with -lactalbumin was observed for -1,4-GalT V but the significant inhibition with -lactalbumin was observed for -1,4-GalT I.     

Acclimation of the Sea Cucumber Apostichopus japonicus to Decreased Salinity at the Blastula and Gastrula Stages: Its Effect on the Desalination Resistance of Larvae at Subsequent Stages of Development

Apostichopus (= Stichopus) japonicus blastulae and gastrulae were acclimated for 18 h to salinities of 32 (control), 24 and 22 (the lower limit of the range of tolerance), and 20 (below the range of tolerance). Acclimation to 20 resulted in the appearance of teratic larvae, most of which subsequently died. Acclimation to 24, 22, and 20 led to a shift in the range of tolerance of the larvae at further stages of development. With a decrease in salinity, acclimated larvae developed more successfully than unacclimated larvae. Acclimated larvae attained the pentactula stage and settled at a salinity range of 32–20; unacclimated larvae, at 32–22. At different stages of development, acclimated larvae survived greater decreases in salinity than unacclimated larvae. The acclimation effects could be traced up to metamorphosis and settling, i.e., two weeks after the end of the acclimation process.     

Inhibition of D-amino Acid Oxidase by α-Keto-γ-Methiolbutyric Acid,product of the reaction with D-Methionine

Summary The inhibition of D-Amino Acid Oxidase by -Keto Acid, product of the reaction with D-Amino Acid is described for the first time. Inhibition of the enzyme by -Keto--Methiolbutyric Acid (4-methylthio-2-oxobutanoic acid), product of the reaction with D-Methionine, was studied. From the results obtained it is deduced that inhibition is competitive with the substrate, the value of the inhibition constant being 1.85 10^–3 M.     

Heterogeneity of the hemoglobin of the Ohrid trout (Salmo L. typicus)

We have analyzed the hemoglobins of five individual trout from the Ohrid Lake (Salmo L. typicus) by electrophoretic methods, by reversed-phase high-performance liquid chromatography, and by limited structural analyses. The two major classes of hemoglobin are type I (35% of total) and type IV (65%). Type IV is the major oxygen-transporting hemoglobin; it consists of three types of chain (in about equal quantities) and three types of chain (one major and two minor types). Several structural differences have been observed between these three (IV) chains and between the three (IV) chains, suggesting a complex genetic system governing the synthesis of these proteins. Moreover, a few amino acid substitutions occur at positions involved in contacts between chains, which suggests that differences in oxygen affinity may exist between these various type IV hemoglobins. Type I hemoglobin is less complex because it contains one type of chain and two chains; the latter two differ in numerous positions, suggesting duplications of the (I)-globin gene. The and chains of type I hemoglobin differ considerably from the and chains of type IV hemoglobin, indicating the existence of (I)- and (I)-globin genes separate from the (IV)- and (IV)- globin genes.This study was supported in part by the Yugoslav-American Joint Funds, pp 812 (to G.D.E.), and by United States Public Health Service Research Grant HLB-05168 (to T.H.J.H.).     

The Expression of Mutation sy2 Causing Nonhomologous Synapsis in Meiosis of Diploid Rye Secale cereale L.

The cytological expression of spontaneous mutation sy2 isolated from a population of weedy rye was examined. It was demonstrated that the primary defect of meiosis in the mutant plants is nonhomologous synapsis, which occurs simultaneously with the homologous one. An electron microscope study of the synaptonemal complex (SC) at prophase I showed synaptic abnormalities that were manifested as switches of synapting axial elements to the nonhomologous partner and the formation of foldbacks of lateral SC elements. The sy2 mutants are characterized by one to two such events per meiocyte. Nonhomologous synapsis leads to the appearance of univalents at metaphase I (on average 4.16 ± 0.002 per meiocyte) and multivalents (on average 0.12 ± 0.007 per meiocyte). The presence of multivalents in 12% of meiocytes at metaphase I may result from recombination in ectopic regions of homology. It is suggested that the sy2 mutation impairs a component of the system that limits synapsis in meiocytes to only homologous chromosome pairs.     

Cytochalasin D blocks chromosomal attachment to the spindle in the green algaOedogonium

Summary Mitosis in living cells ofOedogonium observed by time-lapse, was blocked by cytochalasin D (CD; 25–100 g/ml). Normal prometaphase to anaphase takes 10–15 min; blockage of entry into anaphase by CD was reversible up to 2–2.5 h in CD and washout was followed within 10–20 min by normal anaphase and cytokinesis. After 3–6 h in CD, unseparated chromatids segregated randomly into two groups as the spindle slowly elongated considerably, becoming distorted and twisted. During this pseudoanaphase, chromatids sometimes split irregularly and this was stimulated by late washout of CD. CD affected chromosomal attachment to the spindle. If applied at prophase and prometaphase, spindle fibres entered the nucleus; chromosomes moved vigorously and irregularly. A few achieved metaphase only briefly. Treatment at metaphase caused chromosomes to irregularly release and after random movement, all slowly gathered at either pole. Upon removal of CD, chromosomes rapidly achieved metaphase and anaphase A and B soon followed. If CD took effect during anaphase, chromatids detaching from the spindle oscillated rapidly along it; anaphase and cytokinesis (phycoplast formation) were delayed as the cell attempted to correct for abnormal chromosomal behaviour. Thus, CD prevents normal kinetochore attachment to the spindle and actin may be the target for this response.Abbreviations A-LP anaphase-like prometaphase - CD cytochalasin D - MT microtubule     

Meiosis in Mesostoma ehrenbergii ehrenbergii (Turbellaria,Rhabdocoela)

At metaphase I during spermatogenesis in Mesostoma ehrenbergii ehrenbergii (2 × = 10), 3 bivalents and 4 univalents form. The bivalents each have a single distally localised chiasma. Electron microscope serial section reconstructions have shown that 3 short pieces of synaptonemal complex (SC) are present in pachytene nuclei in the testis. All the SC is contained in a lobe which is separated by an invagination from the main body of the nucleus. The SC pieces vary in length from approximately 2 m to 5 m, and the greatest amount found in one nucleus was approximately 13 m. It is proposed that the pieces of SC correspond to the paired regions of the 3 bivalents present at metaphase I. This system is therefore an example of localised pairing leading to localised chiasmata. Later prophase stage nuclei have also been reconstructed, in which stacks of polycomplex are present but no SC has been found. The polycomplex is thought to be an association of discarded SC sub-units.     

Harzkonservierte fossile Vogelfedern aus der untersten Kreide

Zusammenfassung Harzkonservierte Fossilien ermöglichen bei Anwendung adäquater Methoden die morphologische Analyse der Feinmerkmale bis zur Auflösungsgrenze des Lichtmikroskops, Beobachtung in verschiedenen Ebenen und Richtungen, und somit konkrete Rückschlüsse auf die Wirkung und Bedeutung der Einzelelemente und des Gesamtgefüges.Eine so eingehende funktionsmorphologische Analyse mit Berücksichtigung der Positionsvariation (graduell verschiedene Gestaltung in gesetzmäßiger Abhängigkeit von der Lage innerhalb der Gesamtfeder) der Einzelelemente wie Abzweigungs-, Knick-, Neigungswinkel, Krümmung, Länge, Dicke, Querschnitt, Dichte, Differenzierungsgrad der verschiedenen Abschnitte von Rhachis, Rami, Radii inklusive Häkchen und Cirren wird erstmals für fossile Vogelfedern geliefert (hier als Abriß zu einer dokumentarisch und thematisch ausführlicheren Darstellung in Stuttgarter Beiträge zur Naturkunde).Diese Federn entstammen der untersten Unterkreide und sind damit nur relativ wenig jünger alsArchaeopteryx. Sie weisen extrem differenzierten Aufbau auf, der auf hohe flugtechnische und wärmeisolierende Leistungsfähigkeit schließen läßt.Die hier vorgelegten funktionsmorphologischen Ermittlungen an fossilen Körperkonturfedern mögen auch zu einer intensiveren Analyse der bis jetzt stark vernachlässigten Untersuchung ganz normaler Körperfedern rezenter Vögel anregen. Erst dann, nach umfassender Kenntnis ihrer Ausgestaltung innerhalb der verschiedensten rezenten Vogelgruppen, läßt sich überzeugend begründen, ob und wieweit die hier vorgelegten Federn dieses Unterkreide-Vogels noch ursprüngliche Elemente (Plesiomorphien) oder ihnen eigene Sonderbildungen (Autapomorphien) aufweisen; das gilt sowohl für morphologische wie für funktionelle Elemente der Gesamtstruktur.

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Resin-preserved fossil bird's feathers from the Lowermost Cretaceous

Summary Parts of some feathers, originating from a single bird, were discovered in our collections of Lower Cretaceous amber from the Lebanon mountains — which, in general, contains the oldest terrestrial microfossils preserved with all morphological details.These contour feathers of the trunk, which are nearly as old as Archaeopteryx (Lowermost Cretaceous: Neocomian/Uppermost Jurassic: Kimmeridigian) were studied with magnifications of 500–900 in several levels by a special technique. (In normal fossils, i.e., impressions, the granulation of the sediment and the fossil's bulky carbon remainders cause a blurred image even at a magnification of merely 100).Special emphasis was laid on the study of the individual elements' gradual variation, depending on the respective position within the total feather (position variation). Where appropriate, an analysis of lengths, quantity, degree of differentiation, angle of inclination, break, and branching, cross-sectional view, curvature, etc. of the rhachis, rami, distal and proximal radii, barbicles, hooklets, etc. were undertaken. [Through measurements of the depth of details the effects caused by a sloping position (apparent variation) may be precisely separated from the real variation.]On the basis of such a detailed knowledge of structure and relative position a thorough functional analysis of the single elements as well as the total system is given.Principal features: The production of plain stability in the feather's center, and of flexibility in its apical and lateral rims; dispersion of forces in case of pressure or a pulling load; function of the hooklets (which donot serve as an interlocking mechanism while the feather is in the normal resting position, but function with increasing braking action only when a neighboring ramus diverges to a precisely defined extent from its resting position) including the mechanism of their unhooking; devices for the avoidance of harmful hooking into contacted parts of other feathers; production of maximal stability by minimal air resistance, and of minute chambers (<0,00001 mm³) with still air for optimal heat isolation.Apart from this abstract, further information, accompanied by numerous figures, will be given in a later paper in Stuttgarter Beiträge zur Naturkunde.

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Veränderte Fassung eines am 11. 10. 1971 gehaltenen Vortrages auf der 83. Jahresversammlung der Deutschen Ornithologengesellschaft in Bonn.