Free and conjugated gibberellins in dormancy and germination of apple seeds

Halińska, A. and Lewak, St. 1987. Free and conjugated gibberellins in dormancy and germination of apple seeds.
The presence of gibberellin A₄ (GA₄) was confirmed in partly stratified seeds of apple ( Malus domestica Borb., cv. Antonówka) by mass spectrometry of the methyl ester. Levels of free and conjugated gibberellins A₄₊₇ and A₉ changed during drying of mature seeds, during cold and warm stratification, as well as during germination of dormant and non-dormant embryos. The temporary rise in GA₄₊₇ during cold stratification and during the culture of dormant embryos as well as the lack of it under conditions of warm stratification, allowed us to postulate a role for GA₄₊₇ in the removal of dormancy. In addition, GA₉ was absent in dormant embryos and increased during cold stratification and during the culture of non-dormant embryos. This suggests the involvement of GA₉, in induction of normal development of the seedling. The equivalence between changes in free and conjugated GAs suggests that formation and hydrolysis of conjugates are involved in the control of the physiologically active levels of free GA₄₊₇ and GA₉.     

Comparative study of embryonic thermoresistance of two inbred strains of the medaka (Oryzias latipes)

Summary By using inbred strains (HO4C and HB32C) of the medaka,Oryzias latipes, the involvement of genetic factor(s) in the determination of thermoresistance of fish was investigated. The thermoresistance of embryos of the medaka was quantitated by the fraction of the embryos surviving 1 day after heat treatment. At early stages of development (st. 13 and st. 20–21), the HO4C strain was more resistant than the HB32C strain. At st. 20–21, the HO4C strain was more resistant than the HB32C strain at all temperatures used (42, 43, and 44°C). At later stages of development (st. 27 and st. 32), however, the HB32C strain was more resistant than the HO4C strain.The results of genetic cross experiments raised the following possibilities; the thermoresistance of embryos at early developmental stages can be lowered by some factor(s) inherited in the HO4C strain and/or increased by those in the HB32C strain. By contrast, the sensitivity of embryos at later stages of development was not affected by factor(s) of their parents, but by their own genetic constitution.     

Effect of dexamethasone and hydrocortisone on the course of superovulation in cattle

The effect of hydrocortisone and dexamethasone on superovulation was examined in 12 cows. On the day PMSG was given, each animal received either the first of five daily doses of 250 mg succinate hydrocortisone or one injection of 30 mg dexamethasone. In the 48-hr interval between the injection of PMSG and PGF(2)alpha, the concentration of progesterone rose from 6.97 to 10.22 ng/ml in the experimental groups and only to about 2.8 ng/ml in the control group. In the following days progesterone increased even more, from 15.7 to 26.0 ng/ml seven days after estrus in the experimental group and to 19.25 ng/ml in the control group. The group which received dexamethasone had an average of 4.7 corpora lutea and one embryo flushed per animal. The hydrocortisone group had an average of 2.5 corpora lutea and one cow had two embryos. The control group had 6.2 corpora lutea and 5.2 embryos per animal.     

The early ontogeny of the southern mouthbrooder,Pseudocrenilabrus philander (Pisces,Cichlidae)

Synopsis The early development of the southern mouthbrooder,Pseudocrenilabrus philander, is documented from activation until the early stages of the juvenile period. The duration of the embryonic period is about 14 days at 25°C. Development is direct and there is accelerated exogenous feeding into the embryonic period. The pattern of development and the timing of ontogenetic events and structure formation are a reflection of both internal and external environmental conditions. During mouthbrooding, oxygen uptake is facilitated by embryonic respiratory plexuses and flapping of the pectoral fins. At the time of first release from the buccal cavity, the embryos are in an advanced state of development. The switch-over from the temporary embryonic respiratory system to the adult branchial system has occurred. The yolksac serves as a supplemental source of nutrition as the embryos develop their external food-gathering abilities. The skeletal and sensory systems are sufficiently developed to allow the young to return to the safety of the female's buccal cavity. Pigmentation may provide disruptive colouration. The rate and pattern of development of another mouthbrooding cichlid,Oreochromis mossambicus, is similar to that ofP. philander despite their phylogenetic differences, and may be a consequence of similar life-history styles.     

Gene introduction into mouse blastocysts via “pricking”

It is a well-known phenomenon that cultured mammalian cells that have been pricked in the presence of foreign DNA can be transformed. This micromanipulation ‘pricking’ technique was applied to mouse blastocysts to determine whether uptake of exogenous DNA would occur in the embryos. The middle region of the inner cell mass (ICM) was pricked three times in each blastocyst in a medium containing a linearized plasmid DNA. When the 60 treated blastocysts were transferred to the uterine horns of pseudopregnant females, 30 developing fetuses (50%) at the mid-gestation stage were obtained. Twenty-two of the 30 fetuses (73%) had less than 1 copy of the foreign DNA per diploid cell, as revealed by polymerase chain reaction (PCR)-Southern analysis, a sensitive technique combined with Southern blot processing of the PCR products. The 8 other fetuses were negative for the foreign DNA. When blastocysts were pricked in the presence of vector DNA coupling E. coli β-galactosidase (β-gal) gene to a mouse metallothionein-I (MT-I) promoter and assessed for β-gal activity histochemically after 1 and 5 days of culture in the presence of 1 μM CdCI₂, at least 65% of the embryos exhibited β-gal activity mainly in the ICM region. These results indicate that mouse blastocysts can be transfected with a relatively high efficiency after pricking, and that the introduced gene expression occurs. This approach provides a means of mapping the regulatory elements of genes that are active in the mouse blastocyst ICM, and may be useful in investigating the fate of the ICM cells in an intact blastocyst by labeling them via pricking technique. © 1993 Wiley-Liss, Inc.     

Accumulation of multiacetylated forms of histones by trichostatin A and its developmental consequences in early starfish embryos

Summary External application of 10 rig/ml (R)-trichostatin A (TSA), a potent and specific inhibitor of mammalian histone deacetylase, to the embryo of the starfish Asterina pectinifera inhibited development during the early gastrula stage before formation of mesenchyme cells. The TSA-sensitive period was limited to the mid-blastula stage before hatching. The pulse-chase experiment clearly demonstrated that TSA induced an accumulation of acetylated histone species in blastulae through inhibition of historic deacetylation. Similar blockage of development at the early gastrula stage was observed with n-butyrate, which has been known as a weak inhibitor of historic deacetylase. These results suggest an intimate role for historic acetylation-deacetylation equilibria in starfish development. Correspondence to: S. Ikegami     

Culture of bovine embryos after invitro exposure to Brucellaabortus

Fifty-four day-6 through day-10 (estrus=day 0) embryos were collected nonsurgically from 13 superovulated, brucellosis-free mixed breed cows. Forty-eight excellent and good zona pellucida-intact (ZP-I), three zona pellucida-defective (ZP-D), and three zona pellucida-free (ZP-F) embryos were incubated in media containing $\text{Brucella}$$\text{abortus}$. Subsequently, embryos were washed ten times in groups of one, two, three, or four. Embryos and serial washes were cultured for $\text{B}$. $\text{abortus}$.Brucellae were not isolated from any ZP-I embryo or from any washing beyond the sixth serial wash. Brucellae were not isolated from the three ZP-F embryos but were detected in the eighth wash for one and in the tenth wash for the others. Brucellae were isolated from one of three ZP-D embryos. Results show that ZP-I embryos can be effectively washed free of $\text{B}$. $\text{abortus}$.     

Membrene turnover in imbibed and dormant embryos of the wild oat (Avena fatua L.)

A comparative study of protein synthesis has been carried out with embryos excised from dormant (D) and non-dormant (ND) caryopses of the wild oat. Although D embryos imbibed in water or ND embryos imbibed in abscisic acid do not germinate, they incorporate [¹⁴C]leucine into TCA-insoluble material for the first 48 h as readily as embryos that do germinate (ND embryos imbibed in water, or D embryos imbibed in gibberellic acid). Pulsechase experiments with [¹⁴]leucine show that in both D and ND embryos the proteins associated with the membranes undergo turnover. The rates of decay of incorporated radioactivity are similar in both dormant and germinating embryos up to 98 h following embryo excision. Fractionation of the membrane proteins in SDS-polyacrylamide gels indicates that the different polypeptides have different rates of turnover. It is concluded that membrane proteins in imbibed D embryos are in a state of constant turnover, and that this is a part of the replacement processes necessary to maintain the integrity of hydrated cells. The continuation of such synthetic events could account for long term survival of dormant Avena fatua in the imbibed state.Abbreviations CCRSE cytochrome relative stain equivalents - D dormant - ND nondormant - ABA abscisic acid - GA gibberellic acid GA₃     

Effect of the “zero” Magnetic Field on Early Embryogenesis in Mice

It was shown that the 250-fold screening of the geomagnetic field (GMF) (“zero” magnetic field with an induction of 0.2?μT) affects early embryogenesis and the reproduction capacity of mice in vivo. Pregnant NMRI mice at the zygote stage placed in this “zero” magnetic field (MF) lost the ability to bear offspring babies although their embryos developed up to the blastocyst stage without any visible deviations from the norm. The abortion of development in the “zero” MF occurred after the exit of the blastocysts from the zona pellicida and invasion into the uterus during implantation. Histological analysis indicates that possible reasons of the abnormalities of postimplantation development are a decrease in the proliferative activity of embryonic cells and the impairment of the interaction between the trophoblast and endometrium, which finally results in the resorption of embryos in the uterus.     

Positioning of the mouse Hox gene clusters in the nuclei of developing embryos and differentiating embryoid bodies

Expression of Hox genes located on different chromosomes is precisely regulated and synchronized during development. In order to test the hypothesis that the Hox loci might cluster in nuclear space in order to share regulatory components, we performed 3D FISH on cryosections of developing mouse embryos and differentiating embryoid bodies. We did not observe any instances of co-localization of 4 different Hox alleles. Instances of 2 different alleles touching each other were found in 20-47% of nuclei depending on the tissue. The frequency of such “kissing” events was not significantly different in cells expressing a high proportion of the Hox clusters when compared to cells expressing none or only a few Hox genes. We found that the HoxB and HoxC clusters, which are located in gene-rich regions, were involved more frequently in gene kissing in embryonic nuclei. In the case of HoxB, this observation correlated with the positioning of the corresponding chromosome towards the interior of the nucleus. Our results indicate that co-regulation of the different Hox clusters is not associated with co-localization of the loci at a single regulatory compartment and that the chromosomal context may influence the extent to which they contact each other in the nucleus.