The uptake of macromolecular materials in the hindgut of viviparous rockfish embryos

Regions of the gut of near-term embryos and new-born larvae of the viviparous rockfish Sebastes taczanowskii were examined histologically and immunohistochemically in order to ascertain whether they possessed the potential to absorb intact macromolecules. Compared with the hindgut of larvae 24 h after parturition, that of near-term embryos (stage 31) was found to be markedly hypertrophied and to react positively when tested for the presence of eosinophilic materials and with antibodies raised against extracts of the rockfish yolk (ab.a-E). In addition, near-term embryos incubated in Ringer solution containing 1% bovine serum albumin appeared to accumulate the protein within the epithelium of the hindgut. Furthermore, as confirmed by immunodiffusion analysis, the ovarian fluid contained materials which reacted positively to ab.a-E. These results suggest that ingestion of intact macromolecules occurs during the late embryonic stages and that the yolk-like substances detected within the hindgut epithelium of such embryos may be derived from the bathing ovarian fluid.     

乌骨鸡胚胎发育过程中卵内蛋白质脂肪的变化研究

对乌骨鸡胚胎发育过程中卵内各组成成分(蛋清、蛋黄、胚胎)在不同胚龄(即入孵的第0、3、6、9、12、15、18d和出壳)时蛋白质、脂肪含量变化进行测定与分析．结果表明：在不同胚龄时,蛋清中蛋白质含量显著高于蛋黄,蛋黄中脂肪含量始终高于蛋清;而胚胎中的蛋白质、脂肪逐渐增加。另外,胚胎发育过程中胚胎蛋白质的主要来源是蛋黄中的蛋白质,说明蛋黄是禽类胚胎发育过程中营养需要的主要来源。     

Influence of egg size on embryos and larvae of Fundulus heteroclitus (L.)

Egg size for Fundulus heteroclitus (L.) populations is concordant with the distribution of the two F . heteroclitus subspecies, i.e. F. h. heteroclitus eggs are considerably larger than F. h. macrolepidotus eggs. The influence of egg size on survival of embryos during incubation and survival and growth of newly-hatched larvae was estimated for four populations representing both subspecies along the Atlantic coast of the United States and in Delaware Bay. Survival of embryos was determined for incubation periods of 14, 21 and 28 days. Greatest differences in survival were detected following the longest incubation period where less than 50 per cent of the smaller F. h. macrolepidotus eggs survived while little or no mortality was detected among the larger F. h. heteroclitus eggs . Influence of egg size on larval survival was also greatest among those larvae hatched after 28 days where F. h. macrolepidotus larvae survived without food, for an average of 6 days, while F. h. heteroclitus larvae survived 11–12 days. F. h. heteroclitus larvae were significantly larger at hatching than F. h. macrolepidotus larvae. Larval growth rates were the same (0.4 mm day⁻¹) in both subspecies. As a result, size differences at hatching were still maintained after 42 days of growth. The differences in egg size along with other morphological and reproductive characteristics of F. heteroclitus populations probably represent genetically based adaptations to environmental conditions, of which the length of the spawning season is one of the major components stimulating the coevolution of these traits.     

Persistence of the developmental block of in vitro fertilized domestic cat embryos to temporal variations in culture conditions

A series of studies examined the influence and temporal interaction of energy substrate, media complexity, and tissue co-culture on the development of in vitro fertilized cat embryos and the persistence of the morula-to-blastocyst developmental block. In Study I, oocytes were fertilized and cultured for 144 hr in a simple culture medium (modified Krebs Ringer bicarbonate; mKrb), containing either glucose or glutamine, or cultured in mKrb w/ glutamine for the initial 72 hr with transfer to mKrb w/ glucose for the final 72 hr. Fertilization rate, percent development to morulae, and cell number per embryo were similar (P > 0.05) between treatments and blastocyst formation was universally low (<10%). In Study II, oocytes were fertilized and cultured in either mKrb (w/ glucose or glutamine) or in a complex medium, Ham's F10 (w/ 10% fetal bovine serum [FBS]). After 72 hr of initial culture, embryos in mKrb were transferred into Ham's F10. Fertilization rate was lower (P < 0.01) in Ham's F10 but embryo development to the morulae stage and cell number per embryo were comparable (P > 0.05) for all treatments. A higher percentage of blastocysts and morulae becoming blastocysts were observed after initial culture in mKrb w/ glutamine than after initial culture in mKrb w/ glucose. In Study III, oocytes were fertilized and cultured initially in mKrb (w/ glutamine), and then switched to either Ham's F10 or cat oviductal cell monolayers (in Ham's F10). Additional embryos were cultured exclusively in Ham's F10 or on cat oviductal cell monolayers. Fertilization rates were lower (P < 0.05) on oviductal cells but cell number per embryo was similar (P > 0.05) in all treatments. Blastocyst formation was lower (P < 0.05) on oviductal cells than in mKrb-Ham's F10 treatment and was <20% in all treatments. In summary, while in vitro fertilization-derived cat embryos develop to morulae under a variety of culture conditions, the morula-to-blastocyst developmental block was minimally responsive to alterations in energy substrate and medium complexity or fluctuations in their temporal availability. In addition, oviductal cell culture, alone or in combination with other culture variations, was ineffective in overcoming the developmental block. © 1996 Wiley-Liss, Inc.     

Heat production during early development of frog egg

The production of heat in the fertilized eggs, during the early development of the Japanese pond frog, Rana brevipoda porosa, was measured using a pyroelectric detector constructed with a polyvinylidene fluoride film. One and 2 μW of heat production was detected during the cleavage periods in the embryogenesis of the 2-cell embryo and the 4-cell embryo, respectively. The heat production increased stepwise with the cleavage in the embryogenesis of each stage. In comparison with the heat production during the inter-cleavage periods, a larger amount was noted at the cleavage periods in the two embryonic stages.     

The effect of constant and changing temperatures on the development rates of the eggs and larvae of Ostertagia ostertagi

The duration of the egg stage at constant temperature showed a decrease with increasing constant temperature up to 30°; above this, there was a slight increase in the duration and a decrease in survival. Regularly changing temperature had a slight but significant retarding effect on egg duration in one experiment but in the second, there was no significant effect. In two experiments in which there were two sudden changes of temperature in the same direction, there was no significant effect. The duration of the larval stages from hatching up to the third stage showed a decline with increasing constant temperature up to 25°. Survival was poor at 30°. The larvae were fed on E. coli cultures. In the regularly changing experiments on the larvae one showed a slight retardation and the second an acceleration in development. Both were significant (P < .05). In the experiments in which temperature changed in two sudden jumps in the same direction, one showed a slight acceleration and the other showed no effect. It is concluded that the effects of changing temperature while significant are probably not large enought to be of significance in nature. Newly hatched and third stage larvae grown at constant temperatures showed a tendency to be longer at higher temperatures.     

Lipids in yolks and neonates of the viviparous lizard Niveoscincus metallicus

Niveoscincus metallicus is a small viviparous skink which provides a substantial amount of yolk to each of its developing embryos although some organic nutrients are also transferred across the placentae. The total amount of lipid present in the yolk of N. metallicus (37% of dry weight) is very much higher than that in the newborns (19% of dry weight), confirming that the yolk is utilised as an energy source during gestation. Triacylglycerols (TAG), which are storage compounds, are the major lipid resource available to the embryos and are present in relatively large amounts in the yolk of N. metallicus. Polar lipids (PL), which form the structural components of membranes, and sterols (ST), which are involved in the synthesis of hormones and vitamins, are also present in the yolk. The proportions of each of these lipid classes differs markedly between yolks and newborns. This may reflect variations in the role played by each lipid class in the provision of nutrients to, and development of, embryos.     

Effect of incubation temperature on green sturgeon embryos, <Emphasis Type="Italic">Acipenser medirostris</Emphasis>

Regulation of river flow and the amount of winter rainfall are the major factors affecting the water temperature of the spawning grounds, for green sturgeon in the Klamath River. During the primary spawning period of green sturgeon, mid-April to June, the water temperature may vary from 8 to 21°C. To estimate the potential implications of this modified thermal regime, we examined the survival and development in three progeny groups of green sturgeon embryos from zygote to hatch, at constant incubation temperatures (11–26°C). Temperatures 23–26°C affected cleavage and gastrulation and all died before hatch. Temperatures 17.5–22°C were suboptimal as an increasing number of embryos developed abnormally and hatching success decreased at 20.5–22°C, although the tolerance to these temperatures varied between progenies. The lower temperature limit was not evident from this study, although hatching rate decreased at 11°C and hatched embryos were shorter, compared to 14°C. The mean total length of hatched embryos decreased with increasing temperature, although their wet and dry weight remained relatively constant. We concluded that temperatures 17–18°C may be the upper limit of the thermal optima for green sturgeon embryos, and that the river thermal regime during dry years may affect green sturgeon reproduction.     

能源植物的资源开发与应用

随着矿石能源储量的减少,应大力开发和应用以能源植物为主的生物质能。针对在开发和利用能源植物资源过程中遇到的问题,从生物质能角度出发,对能源植物进行了归类,介绍了能源植物的开发历史和国内外利用现状,总结了能源植物的利用方式,分析了我国开发、利用能源植物资源应采取的措施和步骤。