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PubMed2003

Latitudinal and temperature-dependent variation in embryonic development and growth in Rana temporaria.

Variation in seasonal time constraints and temperature along latitudinal gradients are expected to select for life history trait differentiation, but information about the relative importance of these factors in shaping patterns of divergence in embryonic traits remains sparse. We studied embryonic survival, growth and development rates in the common frog (Rana temporaria) along a 1,400-km latitudinal gradient across Sweden by raising embryos from four populations in the laboratory at seven temperatures (9 degrees C, 12 degrees C, 15 degrees C, 18 degrees C, 21 degrees C, 24 degrees C, 27 degrees C). We found significant differences in mean values of all traits between the populations and temperature treatments, but this variation was not latitudinally ordered. In general, embryonic survival decreased at the two highest temperatures in all populations, but less so in the southernmost as compared to the other populations. The northernmost population developed slowest at the lowest temperature, while the two mid-latitude populations were slowest at the other temperatures. Hatchling size increased with increasing temperature especially in the two northern populations, whereas the two southern populations showed peak hatchling size at 15 degrees C. Analyses of within-population genetic variation with a half-sib design revealed that there was significant additive genetic variation in all traits, and egg size-related maternal effects were important in the case of hatchling size. Overall, our results indicate that unlike larval growth and development, variation in embryonic development and growth in R. temporaria cannot be explained in terms of a latitudinal gradient in season length. While adaptation to a latitudinal variation in temperature might have contributed to the observed differentiation in embryonic performance, the effects of other, perhaps more local environmental factors, seem to have overridden them in importance.

Analysis of Variance↗
PubMed2002

Nitric oxide level regulates the embryonic development of the pond snail Lymnaea stagnalis: pharmacological, behavioral, and ultrastructural studies.

On the basis of the distribution of NADPH-diaphorase (NADPH-d) activity, we have previously suggested a role for nitric oxide (NO) in the development of Lymnaea stagnalis. In the present study, the long-term effects of NO donors (sodium nitroprusside, S-nitroso-N-acetyl-penicillamine) and nitric oxide synthase (NOS) inhibitors (nitro-L-arginine methyl-ester [L-NAME], N(G)-nitro-L-arginine [L-NOARG]) were tested on the survival, length of embryonic (intracapsular) life, locomotion (gliding), heartbeat activity and feeding behavior, as well as on the ultrastructure of the developing ganglia in the embryonic Lymnaea. No effect of any of the substances applied can be observed under 10(-5) M concentration, whereas at 10(-3) M concentration both kinds of treatment proved to be toxic. Between 10(-5) M and 10(-3) M concentrations the effects are reversible. At 10(-4) M concentration, NO donors slightly increase the frequency of gliding and heartbeat of E70% embryos, and evoke a more than twofold enhancement of the feeding activity, i.e., the frequency of radula protrusions in the E90% embryonic stage. In contrast, NOS inhibitors at 10(-4) M concentration strongly inhibit the locomotion and heartbeat of E70% embryos, and the feeding of E90% embryos. Under 10(-3) M concentration, L-arginine diminishes the effect of NOARG, whereas the D-isomer of NAME has little or no significant effect. Neither type of treatment alters the course of gangliogenesis, and the light-microscopic appearance of neurons also remains unaffected. Ultrastructural analysis of the central nervous system of E90% embryos treated with 10(-4) M NOS inhibitors revealed a significant reduction of the glycogen granule content and accumulation of lipid droplets in a number of the neuronal perikarya, as well as the occurrence of disintegrated mitochondria in axonal profiles. The effect of 10(-4) M NO donors is mainly characterized by the increased number of lysosomes, disintegrated mitochondria and degenerating axonal profiles. The present findings suggest that NO is involved in the regulation of different behaviors and physiological functions, such as feeding activity, locomotion and heartbeat, during the embryonic development of Lymnaea. Changes observed in neuronal ultrastructure in ganglia seem to indicate NOergic regulatory processes at the central level.

Animals↗
PubMed1993

Estrogen receptors, estradiol, and diethylstilbestrol in early development: the mouse as a model for the study of estrogen receptors and estrogen sensitivity in embryonic development of male and female reproductive tracts.

To date, there is no conclusive evidence that ERs are present in preimplantation embryos. There are reports that estrogen is made by the rabbit blastocyst (61), and estrogens have been used to induce implantation in mice (62), but whether estrogens act through ERs in the embryo or in the maternal uterus is not known. ERs may be present in early embryos, but if so, levels are below the methods of detection used thus far. Perhaps with more sensitive immunodetection methods, it may be possible to detect ERs in embryos if they are present. Using PCR, messenger RNA for ER has been detected as early as the oocyte stage in mouse embryos (Q. Hou and J. Gorski, unpublished results). This was confirmed recently by Wu et al. (83a). Figure 7 shows a model for the pattern of ER expression in the developing mouse fetus based on the various reports discussed in this review. ERs are present in the 10-day mouse fetus, possibly in the developing ambisexual reproductive tract. Analysis of seven individual 10-day-old fetuses taken from the same litter showed similar levels of an immunostained protein the size of the ER in each fetus (57). The pattern of expression of ER between implantation and the development of the reproductive tract may be the same in male and female mice. Estrogen, acting through ERs, may be one factor (of many) that determines which cells are destined to be part of the indifferent reproductive tract. We were not able to isolate fetal mouse reproductive tracts at an indifferent stage (day 10) due to their very small size. One way to study ER in the indifferent reproductive tract would be to examine these tissues in a larger animal, such as the bovine, using similar immunodetection methods. The distribution of ER in the fetal mouse reproductive tract on fetal days 13 (before sexual differentiation) and 15 (initiation of sexual differentiation) is similar in males and females (71, 72). Thus, estrogen does not appear to be responsible for the initiation of sexual differentiation. Early experiments by Jost (41) showed that removal of the gonad from male or female rabbit fetuses resulted in the female phenotype, which lent weight to the hypothesis that ovarian hormones are not critical in the development of the female phenotype, whereas testicular hormones are essential for the development of the male phenotype.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Differentiation of fiber types in wing muscles during embryonic development: effect of neural tube removal.

The embryonic precursors of the avian slow (type I and III) and fast (type II) fibers can be distinguished from each other early in muscle formation (stage 28, V. Hamburger and H. L. Hamilton, J. Morphol, 88, 49-92, 1951) on the basis of the differential sensitivity of their myosin ATPases. To test the neural dependence of fiber type differentiation, the source of motor innervation was eliminated by excision of the brachial neural tube at stages 16-18 before muscles are innervated. Removal of the brachial neural tube did not affect the number of primary myotubes in a sample muscle of the forelimb (ulnimetacarpalis dorsalis, UMD) up until stage 36. Myosin ATPase staining at a variety of pHs revealed the typical patterns of fiber types in muscles of neural-tube free embryos in stages 35-37. These muscles included the anterior latissimus dorsi, brachialis, and UMD which showed presumptive type III staining (type IIIEMB), the pronator superficialis and flexor carpi ulnaris which showed embryonic type II staining (type IIEMB), and the triceps brachii muscles which showed characteristic arrangements of both type IEMB and type IIEMB fibers. The normal patterns of type IEMB and type IIEMB myotubes were also seen in muscles containing a heterogeneous mixture of fiber types such as the biceps brachii, extensor metacarpi radialis, and adductor indicis muscles, although the intensity of acid-stable ATPase staining of the type IEMB myotubes in these muscles was lower than in innervated muscles. It is concluded that the earliest differentiation of muscle fiber types is independent of the nervous system.

Adenosine Triphosphatases↗