Breeding ecology of the Aquatic Warbler Acrocephalus paludicola on the Biebrza marshes, northeast Poland

Aquatic Warblers Acrocephalus paludicola were studied in a natural fen mire in the Biebrza River valley, the main breeding ground of the species in its entire distribution range. The number of males present and singing at the sample plot changed considerably during the breeding season. Individual identified colour-ringed males sang with unchanged intensity throughout the breeding season. The period of daily singing activity differed from other species of Acrocephalus ; males sang at dusk rather than at dawn. Males took no part in rearing nestlings but remained on territory and showed vigilance behaviour. The density of males in the breeding season ranged from 1.0 to 10.9 per 10 ha. The density of nesting females ranged from 1.3 to 15.7 per 10 ha. In the most suitable habitat females were more numerous than males. The distribution of females (nests) was clumped where potential food resources were higher. Nests were well hidden in places with deeper water between sedge tufts and an abundance of old dry sedge. Females feeding nestlings collected most food within a 5–60-m radius (mean 31.7 m). The return rate of males was higher than that of females. The results suggest a mating system that is intermediate between facultative polygyny and promiscuity.     

Induction of Blocks in Nuclear Divisions and Overcondensation of Meiotic Chromosomes with Cycloheximide During Conjugation of Tetrahymena thermophila

During conjugation, the micronucleus of Tetrahymena thermophila undergoes five consecutive nuclear divisions: meiosis, third prezygotic division (pregamic mitosis) and two postzygotic mitoses of the synkaryon. The four products of the synkaryon differentiate into macronuclear anlagen and new micronuclei and the old macronucleus is resorbed. The protein synthesis inhibitor cycloheximide, applied during conjugation, induced several developmental blocks. Pairs shifted to the drug during early meiotic prophase (stages I–III) were arrested at prophase. Cycloheximide applied to cells at pachytene (stages IV-VI) to metaphase arrested the conjugants at the stage of modified prometaphase/metaphase with overcondensed, swollen bivalents. In contrast to other systems, in the presence of cycloheximide, separation of chromatids, decondensation of chromosomes and exit from metaphase I were inhibited in both diploid and haploid cells. Pairs shifted to the drug after metaphase I were arrested at postmeiotic interphase after completing one nuclear cycle. The same rule applied to the subsequent cycle; then cells were arrested at the stage of pronuclei, and those pairs with functional pronuclei and synkarya were arrested at the stage of two products of the first postzygotic division (pronuclei were not arrested in nuclear transfer and karyogamy). Only pairs with two products of the first postzygotic division were arrested at the same stage after the cycloheximide treatment. Pairs shifted to cycloheximide during the second postzygotic division were arrested in development of macronuclear anlagen and resorption of old macronuclei. The postmeiotic conjugants pulse-treated with cycloheximide (2 h) yielded heterokaryons retaining parental macronuclei (i.e. they exhibited macronuclear retention).     

Structure of Trichomonads as Revealed by Scanning Electron Microscopy*†

SYNOPSIS.
A scanning electron microscope (SEM) study of Hypotrichomonas acosta (Moskowitz), Trichomonas vaginalis Donné. Pentatrichomonas hominis (Davaine), and Tritrichomonas foetus (Riedmüller) provided new information about the structure of the periflagellar canal: emergence of the flagella from the cell body; structure of the undulating membrane; and position, shape, and size of the pelta. Of special interest were the spatial relationships of the attached part of the recurrent flagellum and the accessory filament in Hypotrichomonas and in the members of Trichomonadinae, i.e. Trichomonas and Pentatrichomonas.     

L-DOPA Inhibits In Vitro Phosphorylation of Melanoma Glycoproteins

L-DOPA had no effect on the endogenous phosphorylation of proteins after extraction with 1% Triton X-100 from hamster melanoma. When proteins were purified further by wheat germ-agglutinin chromatography, however, a dramatic and dose-dependent inhibitory effect of DOPA on glycoprotein phosphorylation was observed in the presence of Mn ⁺².     

Joint Report of the Third International Bovine Lymphocyte Antigen (BoLA) Workshop, Helsinki, Finland, 27 July 1986

Summary. Two hundred and eighty-two alloantisera were submitted by 20 participating laboratories from 13 countries and tested against lymphocytes of 1298 cattle. The cell panel consisted of samples from 38 Bos taurus breeds, 11 Bos taurus crossbreeds, 4 Bos indicus breeds, 6 Bos taurus X Bos indicus , and a variety of other crossbred populations. Using a standardized lymphocytotoxicity test, all 17 previously identified BoLA specificities were confirmed. The workshop produced agreement on 16 new lymphocyte alloantigenic specificities. Three of the new specificities behaved as splits of previously identified BoLA specificities. Four of the new specificities behaved as alleles at the agreed BoLA-A locus. Seven new specificities are tentatively assigned to the BoLA-A locus but require further definition. Two new specificities may represent products of a second closely-linked BoLA locus.     

To be or not to be a valid genus: the systematic position of Ophyra R.‐D. revised (Diptera: Muscidae)

Ophyra Robineau‐Desvoidy is one of the better‐studied genera of the family Muscidae (Diptera). The larvae of species of this genus feed on highly decomposed organic matter of various origins, and may reveal predatory behaviour as they mature. These feeding habits, combined with the widespread distribution and close association with human dwellings of some species, give the genus commercial and medico‐legal importance. However, the systematic position of Ophyra has been a matter of debate for many years. Ophyra has been considered by muscid workers to be either a valid genus or a junior synonym of Hydrotaea Robineau‐Desvoidy. A lack of agreement about the systematic position of Ophyra has led to serious errors, particularly in the applied literature. Recent molecular and morphological studies provided contradictory information on the validity of the genus and its subfamilial classification. We revise the systematic position of Ophyra herein by means of molecular phylogenetic reconstruction. Our results are incongruent with opinions on the systematic position of Ophyra based on previously published molecular phylogenies, although they correspond with the concept of the genus based on adult morphology. All analyses of the concatenated dataset revealed Ophyra as monophyletic and placed within a paraphyletic Azeliini. Depending on the phylogenetic approach, Ophyra was placed within either a monophyletic, paraphyletic or polyphyletic Hydrotaea, yet always closely related to a certain group of species. We conclude that Ophyra, as currently defined, should not be considered a valid name, yet a detailed reconstruction of the genus Hydrotaea awaits future studies with greater increases in both taxon sampling and the number of molecular markers.     

Production and characterization of alloantisera specific for bovine class II major histocompatibility complex antigens

Ten alloantisera defining five major histocompatibility complex (MHC) class II specificities of the bovine lymphocyte antigen (BoLA) complex were produced and characterized. Eight antisera defining four of the specificities were generated by immunizing cattle with class I compatible-class II incompatible lymphocytes. The alloantiserum defining the fifth class II specificity was produced by skin implant immunization. A pregnancy serum specific for one of the class II specificities was also identified. The class II antigens recognized by these antisera were designated 'Dx' antigens to indicate that they are BoLA-D region antigens encoded by one or more undetermined class II loci. The molecules identified by the alloantisera are heterodimers composed of a 34-kd alpha and a 26- to 28-kd beta chain, and are expressed on B-lymphocytes but not on resting T-lymphocytes. In family studies the BoLA-Dx antigens segregated in linkage with the BoLA-A locus alleles. Most of the BoLA-A alleles present in the Cornell Holstein herd at a high frequency were found to exist in gametic association with two or more serologically defined class II haplotypes. On the basis of a population study it was determined that three pairs of class I and class II alleles (w10-Dx4, w31-Dx5, and c3-Dx2) were present in the Cornell herd at significantly increased frequencies.     

Effect of past and present behavioural specialization on brain levels of biogenic amines in workers of the red wood ant Formica polyctena

Social insect workers usually participate first in intranidal tasks (i.e. act as nurses within the nest) and then switch to extranidal tasks and become foragers. However, foragers sometimes switch back again to brood care and become reverted nurses. Behavioural and physiological correlates of the transition nurse–forager (behavioural maturation) and forager–reverted nurse (behavioural reversion) are relatively well known in the honeybee, although they are less explored in ants. To understand better the role of biogenic amines in ant behavioural maturation and behavioural reversion, the levels of octopamine (OA), dopamine (DA) and serotonin (5‐HT) are examined in the brains of nurses, foragers and reverted nurses of the red wood ant Formica polyctena Först. (Hymenoptera: Formicidae). Brain OA levels and the ratios OA : DA and OA : 5‐HT are higher in nurses than in foragers and reverted nurses. Reverted nurses and foragers do not differ significantly with respect to brain biogenic amine levels and amine ratios. Biogenic amine levels in brains of workers of F. polyctena are thus maturation‐related rather than task‐related. This is one of the first studies of neurochemical correlates of ant behavioural maturation and the first attempt to identify neurobiological correlates of ant behavioural reversion. The data obtained provide further evidence that neurobiological processes underlying honeybee and ant behavioural maturation and behavioural reversion reveal important differences.     

At least two loci encode polymorphic class I MHC antigens in the horse

Summary. Six monoclonal antibodies and ten alloantisera were used to precipitate cell surface molecules of approximately 44kDa (class I MHC antigens) from radiolabelled equine peripheral blood lymphocytes. All ten antisera were raised against antigens of a single donor horse (horse 0834, ELA-A2,-A2). Four methods of producing antisera were compared: one or two pregnancies, skin allografting, and skin grafting followed by pregnancy. Immunization by pregnancy appeared to produce antibodies against class I products only, while skin grafting raised antibodies to class II antigens as well. Nine of the antisera were raised across an entire MHC haplotype barrier, while one recipient carried the ELA-A2 antigen of the donor. The pregnancy antiserum raised across this barrier probably identifies a second polymorphic class I locus in the horse. Sequential immunoprecipitation using this antiserum in the first stage and an anti-MHC haplotype antiserum or monoclonal antibody reagent in the second stage supported this hypothesis. Gene products of this second ELA class I locus are immunogenic in pregnancy.     

Ultrastructural Organization of Leaves of Transgenic Tobacco Overexpressing Histone H1 from Arabidopsis thaliana

We investigated the anatomical and ultrastructural featuresof transgenic tobacco plants that overexpressed a gene of histoneH1 from Arabidopsis thaliana. The overexpression of the heterologousgene resulted in more than a 2.5-fold increase over the physiologicallevel of the histone H1:DNA ratio in chromatin. H1-overexpressingplants had a distinct mutant phenotype characterized by dwarfappearance and severely hampered flowering. These changes wereaccompanied by extensive and unusual heterochromatinizationof nuclei occurring in all leaf parenchymal cells but not inleaf epidermal cells. The observed anomalies in the growth rateand size of the cells and in nuclei/chloroplast proportionsin histone H1-overexpressing plants suggest that the H1:DNAratio can influence some specialized cellular functions involvingthe cytoskeleton, and nuclear/organellar interactions whichare of importance for the normal development of a plant. Copyright1999 Annals of Botany Company Transgenic tobacco plant, histone H1 overexpression, heterochromatinization.