Immunofluorescent analysis of meiotic recombination in the domestic cat

The paper presents the analysis of the frequency, density, and distribution of recombination sites in the male meiosis of the domestic cat (Felis silvestris catus). The study was carried out using immunofluorescent staining of synaptonemal complex (SC) proteins, centromeric proteins and mismatch repair protein MLH1, a reliable marker of crossingover sites. We mapped 2633 sites of crossing over in 1098 individual autosomes. Based on these data, we estimated the total length of the genetic map of the domestic cat to be 2176 centimorgans. Positive correlation between the length of SC and the number of recombination sites common for mammalians was also found in the domestic cat. It was shown that this species was characterized by the highest density of recombination and the lowest interference in mammals.     

From oocyte maturation to the in vitro cell cycle: the history of discoveries of Maturation-Promoting Factor (MPF) and Cytostatic Factor (CSF)

This article briefly reviews the classical cell cycle studies using oocytes and zygotes of mainly amphibians in the past century. The discussions are focused on the investigations into the cytoplasmic factors that regulate meiosis during oocyte maturation and the initiation of mitosis during fertilisation, which were carried out in the author's lab between 1967 and 1987. This chronicle traces the development of the problems and the direction in which their solutions were attempted in the course of these investigations. The author tries to answer the following questions: why he decided to study oocyte maturation, how he discovered progesterone as a maturation-inducing hormone, how he discovered and characterised the cytoplasmic regulators of the cell cycle, Maturation-Promoting Factor (MPF) and Cyto-Static Factor (CSF), and how he invented the method of observing cell cycle processes in a cytoplasmic extract in vitro.     

Genome relationship betweenPsathyrostachys huashanica andP. fragilis (Poaceae)

Hybrids between the Chinese endemic speciesPsathyrostachys huashanica Keng and the SW. Asian speciesP. fragilis (Boiss.)Nevski (all 2n = 14) developed normally but were completely sterile. Meiotic analyses revealed a high chiasma frequency indicating that the two species as well asP. juncea (Fisch.)Nevski share the same basic genome (called N). The hybrid nature of the plants was established through karyotype analysis and Giemsa C-banding.     

Effect of demecolcine (colcemid) on goldfish oocyte meiosis in Vitro

Germinal vesicle migration (GVM) and dissolution (GVD) were studied in goldfish oocytes treated with 17-α,20–β-dihydroxyprogesterone (DHP) and/or demecolcine (DE; a colchicine derivative also known as colcemid) in vitro. DE (100 μg/ml) in the presence of DHP, enhanced steroid-induced GVM, after both 24 and 48 hr of incubation and significantly reduced the DHP ED₅₀ value for GVM. Similarly, administration of DE alone elicited a significant, dose-related increase in GVM after 24 or 48 hr of incubation. The presence of DE, either alone or in combination with DHP, was without effect on GVD. The effect of DE was also tested on ooplasmic viscoelasticity in goldfish follicles subjected to a centrifugal force (160g for 1 min). Preincubation (24 hr) of goldfish follicles in DE significantly influenced the direction and the extent of the centrifugally induced GV movement along the axis of centrifugal force in a dose-related fashion. The present results provide support for the hypothesis that cytoskeletal components, such as microtubules that are sensitive to DE, are involved in the mechanism of GVM in goldfish oocytes.     

Tachyarrhythmia in a baboon: a case report

An adult baboon with multiple organ symptomatology and tachycardia was successfully treated with one-time electrical cardioversion. The case is presented to demonstrate the need to include ECG monitoring in diagnostic assessment of primate animals with nonspecific symptoms.     

Cytogenetic studies of cultivatedCrocus sativus (Iridaceae)

Meiosis and mitosis are described in cultivatedCrocus sativus of Iran. This indicates that this species is an autotriploid and sterile. Karyotype analysis, rare inversions, laggard chromosomes and distribution of chromosomes in the first anaphase are described, and the reasons for its sterility are given.     

Cytogenetic study of mentally retarded children in Taipei

560 blood samples collected from mentally retarded children in Taipei were karyotypically analyzed for the incidence of fragile X and other chromosome abnormalities. The fragile site at Xq27.3 was observed in 18 patients (3.21%), 11 males and 7 females, out of the 560 blood cultures using M medium. Down syndrome (6.25%), 24 males and 11 females, was the other major category of abnormality. Other abnormalities, including inversion, translocation, deletion, duplication, ring as well as an extra marker chromosome were observed. The overall incidence of chromosomal abnormalities in these children was 14.82%.     

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).     

Repetitive Micronuclear Divisions in the Absence of the Macronucleus During Conjugation of Paramecium caudatum

ABSTRACT. The germinal micronucleus divides six times during conjugation of Paramecium caudatum : this includes two meiotic divisions and one mitosis of haploid nuclei during mating, and three mitoses of a fertilization nucleus (synkaryon). Microsurgical removal of the macronucleus showed that micronuclei were able to divide repeatedly in the absence of the macronucleus, after metaphase of meiosis I of the micronucleus and also after synkaryon formation. When the macronucleus was removed after the first division of synkaryon, in an extreme case the synkaryon divided five times and produced 32 nuclei, compared to three divisions and eight nuclei produced in the presence of the macronucleus. Treatment with actinomycin D (100 μ /ml) inhibited the morphological changes of the macronucleus during conjugation and induced a multimicronucleate state in exconjugants. However, in other cells, it induced production of a few giant micronuclei. We conclude that the micronucleus is able to undergo repeated divisions at any stage of conjugation in the absence of the macronucleus once the factor(s) for induction of the micronuclear division has been produced by the macronucleus. The macronucleus may also produce a regulatory factor required to stop micronucler division.     

The modifying effect of gibberellic acid and kinetin on the growth abnormalities induced by 2,4-D in marrow seedlings and the possible involvement of endogenous ethylene

Swelling of the hypocotyl base induced by 2,4-D in seedlings of marrow was much reduced if GA₃ was also present in the incubation medium. At appropriate concentrations kinetin also counteracted this 2,4-D effect, although at higher concentrations appeared to be ineffective. GA₃ was also able to overcome the inhibitory effects of 2,4-D on extension growth in the hypocotyl but kinetin was much less effective in this case. None of the treatments employed was able to alleviate the inhibition of radicle extension induced by 2,4-D.Ethephon induced similar responses in the seedlings to those resulting from 2,4-D treatment, while treatment with a mixture of 2,4-D and CoCl₂ removed many of these growth abnormalities. These observations are interpreted as indicating that 2,4-D operates at least partly by stimulating the production of ethylene in the tissues. 2,4-D strongly inhibited the accumulation of endogenous gibberellin during the period of seedling development examined, but enhanced cytokinin levels during the later stages of the same period. The possibility of interactions at the biosynthetic level between gibberellins, cytokinins and ethylene and their involvement in the regulation of seedling development are discussed.