Embryonic and larval hemoglobins during the early development of the bullfrog, Rana catesbeiana

The main hemoglobin (Hb) found in Shumway (embryonic) stage 25 bullfrogs is that which we have designated Td-4. The other major tadpole Hbs (Td-1, 2, and 3) predominate during Taylor and Kollros (larval) stages I-XVIII. We propose that Td-4 is an embryonic Hb, whereas Td-1, 2, and 3 are larval (fetal-like) Hbs. Embryonic Hb Td-4 continues to be synthesized during the larval stages. During the larval period, the average peripheral blood Hb profile changes very little with morphological stage or general growth. However, there is great heterogeneity in the embryonic:larval Hb ratio among individual tadpoles of a given stage or weight, apparently due to differential Hb and red cell production by the two active erythropoietic sites, mesonephric kidneys (Td-4), and liver (Td-1, 2, 3).     

Follicular development during early pregnancy and the estrous cycle of the sow

The objective of this study was to monitor and compare follicle populations and follicular development in pregnant and nonpregnant sows from Day 3 to Day 20 after breeding. Twenty-four sows were paired within parity on the day of artificial insemination and were randomly allocated within pair for insemination with either killed (n=12) or live spermatozoa (n=12). All the sows were artificially inseminated with the pooled ejaculate of the same boar. From Day 3 through Day 20 post estrus, ovarian follicles were scanned daily by ultrasonography. Ultrasound images were recorded on videotape and were retrospectively analyzed. Follicles were mapped to indentify the existence of follicular waves. The follicles were then classified as small (< 3 mm), medium (3-5 mm), or large (>/=5 mm). Pregnancy diagnosis was performed on Day 21 by ultrasonography. Pregnant sows maintained a constant proportion of the follicle population in the small, medium and large follicle categories. However, in the nonpregnant sows, the proportion of follicles in the various size categories remained constant until Day 15. Thereafter, the proportion of small follicles decreased (P < 0.05) from Day 15 to 20, and the proportions of medium and large follicles increased (P < 0.05). The predictability of pregnancy status on Day 20 based on follicle populations in any of the 3 follicle categories was low. Moreover, there was no evidence of follicular waves during the estrous cycle or early pregnancy. In conclusion, the proportion of small follicles decreased while medium and large follicle increased from Day 15 through Day 20 of the estrous cycle, but not during a similar stage of pregnancy. This latter finding concurs with follicle recruitment from the pool of small follicles for ovulation following PGF2alpha secretion to induce luteolysis, which reduces progesterone concentrations and thereby allows for the stimulation of the pool of small follicles by gonadotropins.     

The development of the region between the preexisting and nascent membranes during the first cleavage of Rana amurensis eggs

The region between the preexisting and nascentmembranes of a cleaving Rana egg is a dense protrusionregion of nearly 40μm wide at 180°stage.Later,thisregion differentiate,into an upper part,a strip withlong, branched and randomly distributed protrusionswhich are derived largely from the preexistingmembrane,and a lower part,a band with microvilli.During 4-and 8-cel1 stages,the strip is almost vanishedand microvilli in the band is shortened.The nascentmembrane is smooth at the 180°stage,then a rough areaappears below the smooth region and quickly expands.Wheat germ agglutinin which can bind to preexistingmembrane interrupts the development of the regionbetween the preexisting and nascent membranes.Detergent,Brij,having the property to increase the areaof nascent membrane,does not interrupt the developmentof the region between the preexisting and nascentmembranes.     

Long duration of mitosis and consequences for the cell cycle concept, as seen in the isthmal cells of the mouse pyloric antrum. II. Duration of mitotic phases and cycle stages, and their relation to one another

Abstract. The kinetics of isthmal cells in mouse antrum were examined in three ways: (a) the duration of cell cycle and DNA-synthesizing (S) stage was measured by the 'fraction of labelled mitoses' method; (b) the duration of interphase and mitotic phases was determined from how frequently they occurred; and (c) mice were killed at various intervals after an intravenous injection of ³H-thymidine to time the acquisition of label by the various phases of mitosis.
The duration of the isthmal cell cycle was found to be 13.8 hr and that of the DNA-synthesizing (S) stage, 5.8 h. Estimates for the duration of the G₁ and G₂ stages were 6.8 and 1.0 hr, respectively.
From the frequency of mitotic phases, defined as indicated in the preceding article (El-Alfy & Leblond, 1987) and corrected for the probability of their occurence, it was estimated that prophase lasted 4.8 hr; metaphase, 0.2 hr; anaphase, 0.06 hr and telophase, 3.3 hr, while the interphase lasted 5.4 hr. In accordance with this, the duration of the whole mitotic process was 8.4 hr.
Ten minutes after an intravenous injection of ³H-thymidine, 38% of labelled isthmal cells were in interphase and 62% in early or mid prophase, while cells in late prophase and other mitotic phases were unlabelled. After 60 min, label was in late prophase, after 120 min, in mid telophase and after 180 min, in late telophase.
We conclude that there is overlap between some mitotic phases and cycle stages. Thus, while nuclei are at interphase during the early third of S, they are in prophase during the late two-thirds as well as during G₂. Also, nuclei are in telophase during the early half of G₁ but at interphase during the late half. Differences in nuclear diameter show that subdivision of both S and G₁ into early and late periods is practical.     

Expression of ISWI and its binding to chromatin during the cell cycle and early development

We have characterized Xenopus ISWI, a catalytic subunit of a family of chromatin-remodeling complexes. We show that ISWI is expressed constitutively during development but poorly expressed in adult tissues except oocytes which contain a large store of maternal protein. We further analyzed its localization both in vivo and in vitro in Xenopus cell cycle extracts and identified that ISWI binds to chromatin at the G1-S period. However, its association to chromatin does not require ongoing DNA replication. Immunodepletion of ISWI has no effect on either sperm chromatin decondensation or the kinetics and efficiency of DNA replication. Nucleosome assembly also occurs in ISWI-depleted extracts, but nucleosome spacing is disturbed. From these results, we conclude that ISWI is not necessary for sperm chromatin decondensation and the accelerated rates of DNA replication that characterize early development.     

Gap genes define the limits of antennapedia and bithorax gene expression during early development in Drosophila.

The maintenance of selective patterns of homeotic gene expression within the Drosophila CNS involves cross-regulatory interactions among the genes of the antennapedia and bithorax complexes (ANT-C and BX-C). Such a mechanism does not appear to be responsible for the establishment of these selective expression patterns during early development. Here we show that mutations in several of the gap genes strongly alter the early patterns of Antp and Abd-B expression. The altered patterns that are observed do not always correlate with simple expectations based on cuticular pattern defects observed in advanced-stage mutants. It appears that the initial patterns of Antp and Abd-B expression involve their differential regulation by a common set of gap genes. We propose that the gap genes are largely responsible for integrating the processes of segmentation and homeosis.     

Distribution of aromatase and sex steroid receptors in the baculum during the rat life cycle: effects of estrogen during the early development of the baculum

The baculum, also called os penis, plays an important role during copulation. However, the hormonal regulation of its development remains to be elucidated. To determine the direct involvement of sex steroids in the development of the baculum of rats, the distributions of androgen receptors (ARs), aromatase, and estrogen receptor alpha (ESR1) were observed immunohistochemically. On Postnatal Day 1, the rudiment of the baculum expressed ARs, aromatase, and ESR1. In the proximal segment of the baculum of neonatal rats, ARs were expressed in the parosteal layer but not in the periosteum or osteoblasts. Aromatase was expressed from the parosteal layer to the endosteum, particularly in the inner osteogenic layer. ESR1 was also abundantly expressed in almost all cells from the parosteal layer to the endosteum. ARs, aromatase, and ESR1 were all abundantly expressed during the neonatal period in the hyaline cartilage of the proximal segment and in fibrocartilage of the distal segment of the baculum. Expression in all the tissues was attenuated in an age-dependent manner and became quite weak at puberty. To determine the effect of estrogen on the growth of the baculum, the aromatase inhibitor 1,4,6-androstatrien-3,17-dione (ATD) was subcutaneously injected daily into pregnant rats from Days 19 to 23 of gestation and into pups on postnatal Days 1, 3, 5, 7, and 9. On Day 10, the length of the baculum in the ATD-treated rats was significantly shorter than that in the controls, although the body weight did not change. These findings suggest that not only androgen but also locally aromatized estrogen is involved in the early growth and development of the baculum.     

Correlation between the cell cycle in the neurectoderm and differentiation during the early development of Xenopus laevis. 2 Inhibition of DNA synthesis and mitosis during gastrulation

The hypothesis that cell differentiation during primary induction may be coupled with a 'quantal' cell cycle in the presumptive neurectoderm is considered. Embryos of Xenopus laevis were incubated with fluorodeoxyuridine or mitomycin C during gastrulation or neurulation. Embryos treated during the gastrula stage developed abnormalities of the brain but not of other tissues. This is seen as lending support to the idea that the wave of DNA synthesis and mitosis in the presumptive neurectoderm during gastrulation is an important event in the process of primary induction.     

The distribution of cytoplasmic microtubules throughout the cell cycle of the centric diatom Stephanopyxis turris: their role in nuclear migration and positioning the mitotic spindle during cytokinesis

The cell cycle of the marine centric diatom Stephanopyxis turris consists of a series of spatially and temporally well-ordered events. We have used immunofluorescence microscopy to examine the role of cytoplasmic microtubules in these events. At interphase, microtubules radiate out from the microtubule-organizing center, forming a network around the nucleus and extending much of the length and breadth of the cell. As the cell enters mitosis, this network breaks down and a highly ordered mitotic spindle is formed. Peripheral microtubule bundles radiate out from each spindle pole and swing out and away from the central spindle during anaphase. Treatment of synchronized cells with 2.5 X 10(-8) M Nocodazole reversibly inhibited nuclear migration concurrent with the disappearance of the extensive cytoplasmic microtubule arrays associated with migrating nuclei. Microtubule arrays and mitotic spindles that reformed after the drug was washed out appeared normal. In contrast, cells treated with 5.0 X 10(-8) M Nocodazole were not able to complete nuclear migration after the drug was washed out and the mitotic spindles that formed were multipolar. Normal and multipolar spindles that were displaced toward one end of the cell by the drug treatment had no effect on the plane of division during cytokinesis. The cleavage furrow always bisected the cell regardless of the position of the mitotic spindle, resulting in binucleate/anucleate daughter cells. This suggests that in S. turris, unlike animal cells, the location of the plane of division is cortically determined before mitosis.     

光周期对内蒙古三种草原蝗虫高龄若虫发育、存活、羽化、生殖的影响

研究不同光周期(L8∶D16、L12∶D12及L16∶D8)对毛足棒角蝗Dasyhippus barbipes(F.-W.),亚洲小车蝗Oedaleus decorus asiaticus B.-Bidenko,小翅雏蝗Chorthippus fallax(Zub.)3种草原蝗虫高龄若虫的发育、存活、羽化、生殖的影响。结果表明:在白天温度(28±1)℃,黑夜温度(23±1)℃的恒定温度下,不同光周期对毛足棒角蝗和亚洲小车蝗高龄若虫的发育、羽化、产卵影响不大,但是对其存活率有极显著的影响:毛足棒角蝗和亚洲小车蝗高龄若虫到成虫的发育速度在中光照下(L12∶D12)最快。而在短光照(L8∶D16)下更有利于小翅雏蝗若虫发育,其次是中光照;毛足棒角蝗的羽化在中光照条件下最适宜,而长光照时数(L16∶D8)更有利于亚洲小车蝗和小翅雏蝗的羽化;光周期对亚洲小车蝗产卵影响最为明显,毛足棒角蝗和亚洲小车蝗在中光照和长光照时数条件下有利于它们产卵,而小翅雏蝗在短光照和中光照时数下有利于产卵。     

The effect of low temperatures on the photosynthetic apparatus of Quercus ilex subsp. ballota at its lower and upper altitudinal limits in the Iberian peninsula and during a single freezing-thawing cycle

We investigated the response of the photosynthetic apparatus during an episode of extreme low winter temperature in Quercus ilex subsp. ballota (Desf.) Samp., a typical Mediterranean evergreen species in the Iberian peninsula. Both plants in a woodland located at high altitude (1,177 m. a.s.l.) and potted plants obtained from acorns of the same populations grown at low altitude (225 m. a.s.l.) were analyzed. Net CO₂ assimilation rate was negative and there was a marked decrease in photosystem II (PSII) efficiency during winter in leaves of the woodland population (high altitude individuals). These processes were accompanied by increases in non-photochemical quenching (NPQ) and in the de-epoxidated carotenoids within the xanthophyll cycle, mechanisms aimed to dissipate excess energy. In addition, these de-epoxidated carotenoids were largely preserved during the night. There was no chlorophyll bleaching during the winter, which suggests that leaves were not experiencing photoinhibitory damage. In fact, the net photosynthetic rate and the PSII efficiency recovered in spring. These changes were not observed, or were much more reduced, in individuals located at lower altitude after a few frosts. When the response to rapid temperature changes (from 20°C to –5°C and from –5°C to 20°C) was studied, it was found that the maximum potential PSII efficiency was fairly stable, ranging from 0.70 to 0.75. The rest of the photosynthetic parameters measured, actual and intrinsic PSII efficiency, photochemical and NPQ, responded immediately to the changes in temperature and, also, the recovery after cold events was practically immediate.     

Cellular titers and subcellular distributions of abundant polyadenylate-containing ribonucleic acid species during early development in the frog Xenopus laevis.

The distribution of cytoplasmic messenger ribonucleic acids (RNAs) in translationally active polysomes and inactive ribonucleoprotein particles changes during early development. Cellular levels and subcellular distributions have been determined for most messenger RNAs, but little is known about how individual sequences change. In this study, we used hybridization techniques with cloned sequences to measure the titers of 23 mitochondrial and non-mitochondrial polyadenylate-containing [poly(A)+]RNA species during early development in the frog Xenopus laevis. These RNA species were some of the most abundant cellular poly(A)+ RNA species in early embryos. The concentrations of most of the non-mitochondrial (cytoplasmic) RNAs remained constant in embryos during the first 10 h of development, although the concentrations of a few species increased. During neurulation, we detected several new poly(A)+ RNA sequences in polysomes, and with one possible exception the accumulation of these sequences was largely the result of new synthesis or de novo polyadenylation and not due to the recruitment of nonpolysomal (free ribonucleoprotein) poly(A)+ RNA. We measured the subcellular distributions of these RNA species in polysomes and free ribonucleoproteins during early development. In gastrulae, non-mitochondrial RNAs were distributed differentially between the two cell fractions; some RNA species were represented more in free ribonucleoproteins, and others were represented less. By the neurula stage this differential distribution in polysomes and free ribonucleoproteins was less pronounced, and we found species almost entirely in polysomes. Some poly(A)+ RNA species transcribed from the mitochondrial genome were localized within the mitochondria and were mapped to discrete fragments of the mitochondrial genome. Much of this poly(A)+ RNA was transcribed from the ribosomal locus. Nonribosomal mitochondrial poly(A)+ RNA species became enriched in polysome-like structures after fertilization, with time courses similar to the time course of mobilization of cytoplasmic poly(A)+ RNA.