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PubMed2002

Adsorption of heavy metal ions to floc-type biosorbents.

Adsorption of cadmium and lead ions to floc-type biosorbents was reported in this work. Two types of biosorbents containing a marine microalga, Heterosigma akashiwo (Hada) Hada, or a purple non-sulfur bacterium, Rhodobacter sphaeroides, were prepared. The micro-organisms inactivated by steam sterilization were immobilized in casein floc and cross-linked with glutaraldehyde. In the present immobilizing method, we obtained the biosorbents comprising as much as 67% of micro-organism on a dry-weight basis. Simple metal-binding models were applied to explain the adsorption mechanism of bivalent metal ions to the biosorbents. The results showed that casein acted as both the immobilizing material and the adsorbent material. The adsorption of bivalent metal ions to the biosorbents was due to bidentate binding to the acidic sites on casein and monodentate binding to the acidic sites on micro-organisms. The metal-binding constants and the binding capacities of micro-organisms were scarcely influenced by immobilization.

Adsorption↗
PubMed1998

Probability distributions of thermodynamic affinities for heterogeneous receptor populations.

A statistical approach to characterize the thermodynamic affinity distributions of heterogeneous receptor populations in terms of stoichiometric binding constants is presented. The use of stoichiometric density distributions provides a novel description of ligand binding systems. The distributions of stoichiometric constants, Ti(Ki)'s, are obtained assuming that the distribution of site constants N(k) is known. It is found that in the case of heterogeneous systems with multivalent receptors, N(k) is an average over all the Ti(Ki)'s even when there are positive or negative site-site interactions. It is seen that in the absence or in the presence of site-site interactions the mean and the variance of the Ki's can be derived from a Scatchard plot. Some of these results are particularly applicable to bivalent heterogeneous antibody populations and other results are applicable to bivalent heterogeneous systems with different binding sites.

Antigen-Antibody Reactions↗
PubMed1999

Cytological, genetic and evolutionary functions of chiasmata based on chiasma graph analysis.

The nature of the chiasma as a cytological parameter for analysing cross-over was reexamined quantitatively by an improved chiasma graph method. It was reconfirmed in Mus platythrix (n =13) that interstitial chiasmata at diakinesis are distributed randomly and almost uniformly along bivalents except for the centromere and telomere regions. The size of these chiasma blank regions was consistently 0.8% of the total length of haploid autosomes in all chromosomes. There was a minimum value of chiasma interference distance between two adjacent chiasmata, which was constantly 1.8% in all chromosomes. The chiasma frequency at diakinesis was 20.1+/-2. 0 by the conventional method including terminal chiasmata. However, the primed in situ labeling technique revealed that terminal chiasmata were mostly telomere-telomere associations. From these data and also from recent molecular data we concluded that the terminal chiasma is cytologically functional for ensuring the normal disjunction of bivalents at anaphase I, but genetically non-functional for shuffling genes. The chiasma frequency excluding terminal chiasmata was 14.6+/-1.8. Reexamination of the chiasma frequency of 106 animal species revealed that the chiasma frequency increased linearly in proportion to the haploid chromosome number in spite of remarkable difference in their genome size. The increase in chiasma frequency would be evolution-adaptive, because gene shuffling is expected to be accelerated in species with high chromosome numbers.

Animals↗
PubMedDate not supplied

Attack on neoplastic cell membranes by therapeutic antibody.

Mouse monoclonal antibody is not well fitted to destroying tumour cell targets. Complement and cellular effectors are inefficiently recruited, the cells can undergo antigenic modulation, antigen-negative mutants can arise, and the tumour-bearing subject can amount an immune response against the therapeutic antibody. This paper describes the preparation of two chimeric antibody derivatives designed to cirvumvent some of these problems. The first derivative is FabFc, prepared by linking Fab' gamma from monoclonal antibody to Fc gamma from human IgG. The bismaleimide linking agent forms a thioether bond with an SH group released by reduction of SS bonds in the hinge of each constituent. The second derivative is bisFabFc, formed by a bismaleimide in this case joining two FabFc molecules via a free SH in the Fc hinge of each. As regards antibody activity against target cells bisFabFc can be univalent (one active, one inactive Fab arm), bivalent, or bispecific (with each Fab arm directed against a different cell surface antigen). Its juxtaposed dual Fc regions are designed to promote cooperative binding of effectors. Some preliminary characterization in vitro has employed antibodies of anti-idiotypic specificity directed against guinea-pig L2C leukaemic B lymphocytes. The parent mouse IgG1 antibody failed to invoke complement cytotoxicity or antibody-dependent cellular cytotoxicity, while the chimeric derivatives yielded good killing in both systems. In complement lysis bivalent bicFabFc outperformed univalent, which in turn outperformed the FabFc monomer.

Animals↗
PubMed1979

Nucleolar organizers in human oocytes at meiotic prophase I, studied by the silver-NOR method and electron microscopy.

Use of the silver-NOR method to study the nucleolar organizers in human oocytes demonstrates that topographic and quantitative variations occur during meiotic prophase. In the oogonia nucleolus the nucleolar organizers are dispersed, whereas beginning at leptotene and throughout the remaining stages of meiotic prophase they occupy a marginal position in the nucleolus. At leptotene, a modal number of seven nucleolar organizers can be observed, whereas this number falls to 2.5 at pachytene and rises to ten at diplotene, thus showing that there is intense rRNA synthesis during the latter stage of meiosis. During pachytene, one end of the bivalents containing the ribosomal cistrons is always associated with the Ag-positive zone of the nucleolus. Observation of pachytene in the electron microscope shows that the secondary constriction region of D and G bivalents is constantly associated with the fibrillar center of the nucleolus. Comparison of these two methods of investigation reveals that the silver-stained regions of the nucleolus correspond to the fibrillar centers. The latter are surrounded by a layer of electron-dense fibrils corresponding to the zone of rDNA transcription. This electron-dense layer is absent during pachytene when the nucleolus displays spontaneous segregation of its components; this absence is related to temporary arrest of rDNA transcription. The affinity of the fibrillar centers for silver-NOR staining confirms that these structures contain ribosomal cistrons. During the diplotene stage, numerous micronucleoli are formed outside the nucleolar organizers of D and G chromosomes. Most of these micronucleoli present an Ag-positive granule on one of their margins, thus indicating that they contain an actively transcribed sequence of rDNA. This observation confirms the existence of amplification of ribosomal genes in the human oocyte.

Cell Nucleolus↗
PubMed1981

Fanconi's anemia: anomaly of enzyme passage through the nuclear membrane? Anomalous intracellular distribution of topoisomerase activity in placental extracts in a case of Fanconi's anemia.

In cells of Fanconi's anemia (FA) spontaneous breakage of chromosomes was first recognized by Schroeder et al. (1964). Sensitivity to bivalent alkylants has been found to be a constant feature, whereas low levels of several repair-related enzymes have been described in different FA cell lines. In a family with known FA, during a further pregnancy the prenatal diagnosis of the disease was made by cytogenetic analysis of amniotic cells. After birth the fresh placenta was extracted for further enzymologic analysis. An unusual distribution of DNA topoisomerase activity was noted: high in the cytoplasm and only a little activity in the nuclear sap. This contrasts with findings in normal placentae. Since amniotic cells, lymphocytes, and fibroblasts of this child exhibited both high spontaneous breakage of chromosomes and sensitivity to the bivalent alkylant, diepoxybutane, a correlation between the findings on cytogenetic and enzymologic levels is assumed. Whereas in other published cases, a true reduction of activities of enzymes involved in DNA replication and repair has been found, the present results suggest the interpretation that in our patient the genetic anomaly does not affect the level of synthesis of the enzyme itself, but the passage of the enzyme from the place of synthesis (the cytoplasm) to the substrate (inside the nucleus). A genetic anomaly of the nuclear membrane might be a possible explanation, or alternatively, a structural mutation of the enzyme at a site not affecting the catalytic activity, but affecting the membrane passage or intranuclear accumulation. Meanwhile, placentae of two other cases gave similar results, thus supporting our findings.

Adult↗
PubMed1980

Chromosome polymorphism in the Italian newt, Triturus italicus.

A chromosomal variation, changing shape and C-banding pattern of chromosome XII of Triturus italicus was detected among the offspring of two F1 hybrid families of T. italicus female x T. vulgaris meridionalis male. In both families a number of individuals appeared to have a metacentric instead of the expected subtelocentric chromosome XII of T. italicus.--Investigations in three well separated localities in the range of the species showed the polymorphism to have a wide distribution and to be part of a complex pattern involving at least two inversions and (presumably) deficiencies of large C-bands. At meiosis, the shape of bivalent XII, and the location and frequency of chiasmata in the bivalent varied with the karyomorph involved. It is suggested that large rearrangements may still play an important role in the karyological evolution of Triturus.

Animals↗
PubMed1984

Meiotic configurations in female trisomy 21 foetuses.

Analysis of the meiotic configurations formed by the three No 21 chromosomes in oocytes from two trisomy 21 foetuses was undertaken using a spreading technique. Light microscope analysis of the first gave limited resolving power, such that over half the oocytes could not be classified as to presence or absence of trivalent or bivalent plus univalent. In the second, investigated at the electron microscope level, all 65 cells analysed were informative and precise detail of meiotic pairing in trivalents could be obtained. Two principal forms of trivalent occurred, one in which pairing was initiated at opposite ends of the three No 21's, each initiation point involving only two of the three homologous lateral elements; the other in which pairing was initiated by all three elements at the same end, a triple synaptonemal complex being formed. Only in one oocyte out of the 65 analysed at EM level, however, did triple pairing occur along the entire length of the No 21 trivalent. All others showed splitting into bivalent and univalent at some point along the structure. Unpaired regions within trivalents and all univalents were consistently seen to be thickened and dark staining with silver over the whole period from pachytene to diplotene. This contrasted with the desynapsing lateral elements of previously paired synaptonemal complexes which appeared thin by comparison at diplotene. The significance of the thickening remains, as yet, obscure.

Amniocentesis↗
PubMed1980

[Preliminary study of stages of human meiosis in spermatocytes and ovocytes (author's transl)].

Human meiotic chromosomes, from spermatocytes and ovocytes, are described after observations of whole mount preparations under E.M. Small testicular and ovarian fragments are put in distillated water, then macerated; the cell suspension is spread on the surface of sheet copper grids covered with formvar plus collodion films. After dehydratation interesting stages are selected under L.M. before observations under E.M. Zygotene and pachytene are the most common stages. During pachytene the chromomeres are well individualized; the synaptonemal complex may be observed; chromatin fibers connect the chromosomes to nuclear pores, interchromosomal fibers joint the bivalents. Zygotene and pachytene bivalents are very similar in the male and the feminine germ cells.

Chromatin↗
PubMed1982

The structure of partly decondensed metaphase chromosomes.

The technique of freeze-drying was applied to examine the submicroscopic organisation of metaphase chromosomes from Chinese hamster after removal of bivalent cations with EDTA and removal of histone HI with 0,6 M NaCl. Treated chromosomes increased in size, and nucleosomal filaments appeared at the periphery of the chromosomes. Removal of bivalent cations is accompanied with the appearance of regularly organized structures of the "beads-on-a-string" type. The regular organization of the fibers is damaged as soon as histone H1 is removed. After decondensation in a 0.6 M NaCl solution the metaphase chromosomes were treated with staphylococcal nuclease in situ on EM grids nd the residual structures analysed using electron microscopy. Nucleohistone fibers wer visible at the periphery of the chromosomes at the beginning of digestion. After complete elimination of the nucleohistone fibers in the course of digestion the remaining proteinaceous material was represented by aggregates of irregular shape and of varying size. These were either concentrated along the central axis of the chromatids or, at the final step of digestion, scattered evenly over the entire area that had been occupied by the chromosome. Presumably, in the chromosome prior to digestion, the material did not form an integral protein structure similar to a scaffold in dehistonised and spread chromosomes. An alternative interpretation for the fragmentation of protein material in the chromosome considers possible degradation of the protein scaffold in the course of digestion.

Animals↗
PubMed1984

A calcium-rich intraspindle membrane system in spermatocytes of wolf spiders.

The meiotic spindle of spermatocytes of two wolf spiders contains a highly organized system of ER-like membranes. In cells observed ultrastructurally at early prometaphase, these membranes completely invest each bivalent and are present in the periphery of the spindle in association with the centrosomes. By metaphase each bivalent and its kinetochore fibers are completely encased in a tube of this membrane. We have treated living spermatocytes with the permeant, fluorescent-chelate probe, chlorotetracycline (CTC) to determine whether or not the intraspindle membrane system is rich in associated Ca2+. Spider testes were dissected into PIPES-buffered saline containing 200 microM CTC and were kept in this solution for 10 min. Autofluorescence controls were prepared by incubation in saline without CTC, and nonspecific effects of CTC were assessed by incubation for 10 min in 200 microM oxytetracycline (OTC). Neither unstained nor OTC-treated spermatocytes emit significant fluorescence. In contrast, CTC treatment yields bright, punctate fluorescence, which coincides with the distribution of the mitochondria. The plasma membrane is only weakly fluorescent, while the nuclear envelope exhibits prominent fluorescence. The chromosomes are not fluorescent during prophase, but after nuclear envelope breakdown, they become outlined by dim, but distinct fluorescence. As spindle formation commences, the CTC signal from the intraspindle membrane system becomes strong. In some cells, thin lines of CTC fluorescence are apparent in the metaphase half spindle; this fluorescence pattern mimics the distribution of the intraspindle membrane system and suggests that it is rich in associated Ca2+. We suggest that the intraspindle membrane system functions in the regulation of cytosolic Ca2+ during meiosis through sequestration of the cation.

Animals↗
PubMed1986

Abnormal RNA synthesis in sex vesicles of tertiary trisomic male mice.

The XY bivalent contained within the sex vesicle of chromosomally normal male mice shows virtually no RNA transcriptional activity as measured by autoradiography during the prophase of meiosis. Tertiary trisomic males, derived from the T 70 H and T 31 H reciprocal translocations, include the extra small marker chromosome to varying degrees within the sex vesicle. It has been found that RNA transcription occurs within the sex vesicles of such trisomics. An attempt has been made to correlate such activity either to the extra marker chromosome itself or to a possible reactivation of the normally quiescent sex bivalent. The relationship of the abnormal RNA synthesis to the breakdown of meiosis in tertiary trisomics and to their subsequent reduced fertility is discussed.

Animals↗
PubMed1986

Heterosynapsis and suppression of chiasmata within heterozygous pericentric inversions of the Sitka deer mouse.

The patterns of chromosomal pairing and chiasma distribution were analyzed in male Sitka deer mice (Peromyscus sitkensis) polymorphic for terminally positioned pericentric inversions of chromosomes 6 and 7. G- and C-banding of somatic metaphases indicated that the inversions involved 30% and 40% of chromosomes 6 and 7, respectively. Analysis of silver-stained synaptonemal complexes in surface-spread zygotene and pachytene nuclei from heterozygous individuals revealed that inversion loops were not formed. The inverted segments proceeded directly to heterosynapsis without an intervening homosynaptic phase, and the heteromorphic bivalents remained straight-paired throughout pachynema. C-banded pachytene nuclei corroborated the occurrence of heterosynapsis, as the heteromorphic bivalents exhibited nonaligned centromeres. Analysis of diplonema and diakinesis indicated that crossing over had not occurred within the heterosynapsed inverted segments. The observation of chiasma suppression within the inversions indicates that pericentric inversion heterozygosity does not lead to the production of unbalanced gametes. Heterosynapsis of the inverted segments during zygonema and pachynema and the resulting chiasma suppression therefore represent a meiotic mechanism for the maintenance of pericentric inversion polymorphisms in this population of P. sitkensis.

Animals↗
PubMed1982

The synaptonemal complexes of caenorhabditis elegans: comparison of wild-type and mutant strains and pachytene karyotype analysis of wild-type.

Normal synaptonemal complexes (SCs), consisting of two lateral elements and a central element, are present in wild-type, him-4 and him-8 mutant strains in both hermaphrodites and males of caenorhabditis elegans. Thus, the increase in rate of nondisjunction in the him mutants is not related to aberrant SC morphology. The wild-type hermaphrodite has six SCs, as determined from 3-D reconstruction analysis of serial section from electron microscopy. Thus, n=6 and this confirms early reports based on cytological studies with the light microscope. Only one end of the SC is attached to the nuclear envelope while the other end is free in the nucleoplasm and there is no apparent bouquet formation. Either end of the SC can attach to the nuclear envelope. The pairing behavior of the XX bivalent is normal and occurs synchronously with the autosomes. Electron dense bodies, or knobs, are associated with the SC via the central element and displace the chromatin for a distance of 200 nm. Each pachytene nucleus of the wild-type hermaphrodite has six such structures that are randomly dispersed along the bivalents such that some SCs have one or two knobs while others have none. Their function is unknown.

Animals↗
PubMed1976

The meotic prophase in Bombyx mori females analyzed by three dimensional reconstructions of synaptonemal complexes.

Serial sectioning followed by three dimensional reconstruction of lateral componenets of the synaptoemal complex have been used to follow chromosome pairing during theprophase of the achiasmatic meiotic division in the silkworm. Bombyx mori. During leptotene and early zygotene, the lateral components become attached to the nuclear envelope at a specific region, thus forming a chromosome bouquet. The attachment of lateral componenets to the nuclear envelope precedes the completion of the components between their attachment points. Synapsis and synaptonemal complex formation start during the period of lateral component organization in the individual nucleus. Telomeric movements on the nuclear envelope occur at two stages of the prophase: the chromosome pairing appears to be initiated by an association of unpaired ends of homologus chromosomes, the nature of this primary attraction and recognition being unknown. Secondly, the paired chromosomes become dispersed in the nucleus by shifting of attachment sites of completed synaptonemal complexes at the end of zygotene. This movement is possible related to a membranes flow occuring during this stage. Membrane material is synthesized at the region of synaptonemal complex attachment. Later, the excess membrane material is shifted to the opposite pole where it protudes into the lumen of the nuclei thus forming vacuoles. Two previously undescribed features of chromosomes paring were revealed. In late zygotene, chromosome pairing and synaptonmal complex formation were frequently observed to be delayed or even prevented over s short distance by interlocking two bivalents, both being attached to the nuclear envelope. Such interlocking of bivalents was not found in pachytene...

Animals↗
PubMed1985

Synaptonemal complexes of normal and mutant yeast chromosomes (Saccharomyces cerevisiae).

Synaptonemal complex (SC) analysis of six laboratory yeast strains showed the SC karyotypes to be repeatable within strains. Chromosomal differences were found between strains. In five of the strains, two SCs insert into the nucleolus. This represents a single bivalent with a nucleolar organizer in a medial position as is suggested by genetic data or two bivalents each with a terminal nucleolar organizer. In the first interpretation, n = 16; in the second, n = 17. Strain Tris has a single nucleolar SC and n = 17. In strains DCx374, DCx416 and x8366a the genetically determined rearrangements of linkage group III could not be identified. Presumably the short SC (0.33 micron) associated with linkage group III cannot accommodate an inversion loop or a translocation configuration. The strains however were found to harbour a reciprocal translocation involving the nucleolar chromosome. Trisomy for one of the longer chromosomes was observed in Tris and spo10. It is concluded that rearrangements of the medium and long but not short yeast chromosomes can be detected cytologically. Measurements of nuclear volumes show SC length to vary with artifactually induced swelling of the nucleus. Linear regression of SC length over nuclear radius indicates that actual SC length is only about one-half the observed length. As a result the DNA packing per SC unit length is higher than previously estimated.

Aneuploidy↗
PubMed1987

Chromosome banding in amphibia. XI. Constitutive heterochromatin, nucleolus organizers, 18S + 28S and 5S ribosomal RNA genes in Ascaphidae, Pipidae, Discoglossidae and Pelobatidae.

The karyotypes of 14 species of Anura from 9 genera of the suborders Amphicoela, Aglossa, Opisthocoela and Anomocoela were analysed with various banding techniques and conventional cytogenetic methods. The 18S + 28S and 5S ribosomal RNA genes were localized by means of in situ hybridization. No Q-, R- and G-banding patterns in the euchromatic segments of the metaphase chromosomes could be demonstrated in any of the species; this does not seem to be caused by a higher degree of spiralization of the amphibian chromosomes, but by the special DNA organization in these organisms. In most karyotypes, constitutive heterochromatin is present at centromeres, telomeres and nucleolus organizer regions (NORs), but rarely in interstitial positions. The heterochromatic regions are either quinacrine positive and mithramycin negative or vice versa. All species examined possess only one homologous pair of NORs: these display the brightest mithramycin fluorescence in the karyotypes. Many specimens exhibited unequal labelling of the two NORs both after silver and mithramycin staining as well as after in situ hybridization with 3H-18S + 28S rRNA. In four species, between one and six chromosome pairs with homologous 5S rRNA sites could be identified. The 5S rRNA genes and the 18S + 28S rRNA genes are closely linked in two species. In the male meiosis of the Amphicoela and Opisthocoela, there are intersitial, subterminal and terminal chiasmata in the bivalents, whereas only terminal chiasmata are observed in the bivalents of the Aglossa and Anomocoela. No heteromorphic sex-specific chromosomes could be demonstrated in any of the species. The differential staining techniques revealed that the chromosomal structure in these four suborders is largely the same as in the highly evolved anuran suborders Procoela and Diplasiocoela.

Amphibians↗
PubMed1989

Chromosomally derived sterile mice have a 'fertile' active XY chromatin conformation but no XY body.

We have previously shown that the sex chromosome bivalent of normal, fertile male mice possesses extensive regions of potentially active chromatin, even though, as has been shown by others, certain X-linked genes, and perhaps most of the X chromosome, become inactivated during pachytene. The male meiosis of a fertile (2;11) translocation carrier mouse, a chromosomally derived sterile (11; 19) translocation carrier and that of normal mice is compared. In situ nick translation shows a similar DNase I sensitivity pattern in the sex chromosomes of all examined mice. The X chromosome has four regions of potentially active chromatin conformation, two at the ends of the chromosome and two interstitial ones, coinciding with flexures which become prominent towards late pachytene. The Y chromosome is almost uniformly sensitive to DNase I. The similarity of chromatin conformation patterns in fertile and sterile mice is compatible with the hypothesis that unscheduled transcription of particular genes, possibly included in the active conformation regions, occurs in mice which become sterile. In the sterile (11;19) translocation carrier, a vast majority of all pachytenes are "associated": usually one unpaired segment of chromosome 19 is in end-to-end contact with the X chromosome. The tips of both unpaired segments of chromosome 19 have a thickened axis and display a peculiar chromatin appearance, similar to the modification of the centromeric tip of the X chromosome. Telomeric unpairedness of certain chromosome segments seems to be conducive to autosome-X chromosome association. We suggest that compartmentalization of the nucleus into an autosome mass and a fully developed, protruding, metabolically quiescent XY body, is a precondition for the normal progressing of meiosis. In the associated cells, the autosomal quadrivalent anchors the XY bivalent among the autosomes; as a consequence no XY body is formed. This interference with the course of compartmentalization leads to the abolishment of inactivation of part or all of the potentially active genes and results in meiotic arrest, and hence in sterility.

Animals↗