The effect of vitamin A on limb regeneration in Rana temporaria

Previous experiments in which vitamin A has been administered to developing or regenerating limbs have shown that different limb axes are affected. In regenerating axolotl limbs, serial reduplications in the proximodistal axis are produced. In the developing chick limb bud, mirror-imaged reduplications in the anteroposterior axis are produced. Results reported here on Rana temporaria limb buds reveal that vitamin A causes both effects to occur. That is, limbs are both serially reduplicated in the proximodistal axis and mirror imaged in the anteroposterior axis. Time and concentration effects are explored and the significance of these results for our current understanding of axial organisation in limbs is discussed.     

Isolation of ouabain-resistant human diploid fibroblasts

Seventeen clones resistant to the cytotoxic action of ouabain were isolated in culture by direct selection from 5 independent strains of diploid human fibroblasts. Resistant clones were recovered at frequencies on the order of 10^?7 per wild type cell selected from populations treated with the mutagen EMS, but no resistant cells were detected among 10⁸ unmutagenized cells. Most selected clones remained ouabain-resistant following further propagation in the absence of drug. The growth of wild type cells was inhibited by 50% at ouabain concentrations of 2–5 × 10^?8 M, while resistant clones required 15–180 fold higher drug concentrations to cause equivalent inhibition. Ouabain-resistant clones showed increased resistance of K+ transport function to ouabain inhibition that paralleled their increased resistance to growth inhibition. Initial experiments suggest that under selective conditions the resistant diploid fibroblasts differ significantly from wild type in binding of ³H-ouabain per unit surface area. The ouabain-resistant cells were similar to wild type in transport properties unrelated to ouabain inhibition. Resistant cells had normal karyotypes and senesced with a lifespan similar to control clones. The ouabain-resistant phenotypes of these diploid human fibroblast isolates apparently reflect point mutations that specifically affect the Na+/K+ transport ATPase with respect to ouabain-binding and/or response to bound ouabain.     

The reproductive biology of female Père David's deer (Elaphurus davidianus)

Data for this study came from breeding records of 27 Père David's (Elaphurus davidianus) hinds maintained in large pastures and from estrous records of four hand-reared nulliparous hinds. The mean estrous cycle length ranged from 17.5 to 19.6 days. Standing estrus resembled that of other cervids, except that a low, moaning vocalization was given in response to contact, and activity (as measured by pedometers) did not increase. Mean gestation length was 183.38 ± SD 6.11 days (n = 21), and nearly all females conceived in the second and third years. The median interbirth interval was 362 days. The median birth date was April 8, and 80% of the births occurred over a 9.5-week period. Multiparous hinds gave birth an average of 20.5 days earlier in the season than primiparous hinds. There was no dimorphism in birth weight. The results are discussed in light of comparative data for other species.     

A stereological method for estimating fish fecundity

This paper describes the application and evaluation of a stereological method for counting fish oocytes. The method has been applied to herring, Clupea harengus L., Dover sole, Solea solea L., and mackerel, Scomber scombrus L., and compared with existing volumetric and/or automated particle counter methods. The stereological method has been shown to given similar results and to have a number of distinct advantages over the other methods.     

皖南、赣北奥陶纪笔石立体标本形成环境的初步研究*

皖南、赣东北和赣西北地区奥陶纪笔石地层发育良好,笔石化石丰富。宁国组和胡乐组均为笔石相地层,但笔石的保存特点并不相同。立体保存的黄铁矿化笔石标本主要见于宁国组,而胡乐组的笔石几乎均为薄膜标本。在比较宁国组和胡乐组在岩性、颜色、化石、矿物和元素等方面的特点后发现,两者有较明显的差异。这表明宁国组和胡乐组形成时的环境是不同的,前者为弱还原环境,后者为较强的还原环境,而在研究区内影响笔石体立体保存的主要因素为还原环境和较高的铁含量。在还原环境下,铁可呈Fe~(2+)存在,笔石体内含有硫,死亡后经降解作用可生成H_2S;H_2S和Fe~(2+)结合可使笔石体黄铁矿化,从而使笔石体硬化而呈立体保存下来。宁国组的铁含量明显高于胡乐组,这似可以解释宁国组产有较多笔石立体标本的原因。     

THERMAL EVOLUTION OF EGG SIZE IN DROSOPHILA MELANOGASTER

We measured the size of eggs produced by populations of Drosophila melanogaster that had been collected along latitudinal gradients in different continents or that had undergone several years of culture at different temperatures in the laboratory. Australian and South American populations from higher latitudes produced larger eggs when all were compared at a standard temperature. Laboratory populations that had been evolving at 16.5°C produced larger eggs than populations that had evolved at 25°C or 29°C, suggesting that temperature may be an important selective agent in producing the latitudinal clines. Flies from laboratory populations produced larger eggs at an experimental temperature of 16.5°C than at 25°C, and there was no indication of genotype-environment interaction for egg size. Evolution of egg size in response to temperature cannot be accounted for by differences in adult body size between populations. It is not clear which life-history traits are direct targets of thermal selection and which are showing correlated responses, and disentangling these is a task for the future.     

蓝氏贾第虫核被膜缺口的电镜观寨

双滴虫类是迄今所知的现存最原始的真核生物类群。以蓝氏贾第虫作为双滴虫类的代表,对其细胞核进行了电镜观察。除了未见有核仁外,还发现其核被膜的横切面上存在有缺口。在缺口的边缘处,核内膜与校外膜是相互连接着的,表明并非切片时所造成的假象。核被膜缺口处常有一核纤层样的薄层分隔核质与细胞质。用高锰酸钾固定细胞以求只保存膜结构时,核被膜缺口仍然可见,上述的薄层即未见到。核被膜缺口的发现证实了李靖炎（１９７９）的核被膜起源假说所作出的推断。     

Genetically stable cell lines of cucumber for the large-scale production of diploid somatic embryos

For the initiation of embryogenic cucumber ( Cucumis sativus L.) cell lines, from excised radicles, directly in liquid medium, the culture regime, explant density and type and concentration of hormones were adjusted so that pro-embryogenic masses (PEMs) were formed within about 8 weeks. The established cucumber cell lines were maintained tor several years without loss of embryogenic and genetic stability. The ploidy level of somatic embryos from different cucumber eell lines was either diploid or tetraploid and depended on the ploidy level of Ihe cell line. Cucumber cell lines that produced only diploid embryos were obtained by selecting completely diploid explant material and growing it in the dark during the initiation phase. Mixoploid explains could lead to tetraploid or mixoploid ceil lines. Isolation and additional selection and subculturing of single PEMs resulted in either completely diploid or tetraploid cell lines, indicating that all cells of individual PEMs are either diploid or tetraploid. The ernbryogenic cucumber cell Imes, differing only in ploidy level, were indistinguishable in growth rate and embryogetiic potential and were genetically stable over several years.     

Alternating bolus and continuous infusion 5-fluorouracil: a strategy to overcome resistance to this fluoropyrimidine in advanced colorectal cancer patients

Focusing our effort on the importance of FUra scheduling we have tested the hypothesis that pulse and continuous infusion (CI) of the fluoropyrimidine have different mechanisms of cytotoxicity. Our initial approach was to compare the mechanism of resistance of a cell line resistant to a short term exposure to FUra (HCT-8/FU4hR) to that of a cell line resistant to a prolonged exposure to the fluoropyrimidine (HCT-8/FU7dR). Cytotoxicity studies showed that HCT-8/FU4hR cells were still sensitive to FUra given as a 7-d exposure, suggesting different mechanisms of resistance. Indeed, rapid recovery of TS activity after drug removal was evident in the HTC-8/FU7dR cell line while HCT-8/FU4hR cells were similar to the parental cell line with regard to both the degree of in situ TS inhibition by FUra and duration of inhibition after FUra removal. In contrast, labelling studies with [³H-6] FUra (4 h exposure, 100 M) showed that the incorporation of the fluoropyrimidine into RNA is significantly decreased in HCT-8/FU4hR cells as compared to parental HCT-8 cells.Given the lack of cross resistance between the two schedulesin vitro, a pilot trial was done on patients with colorectal cancer refractory to bolus FUra. On 15 patients failing after FUra+LV or FUra alone 1 PR, 3 MR, 3 SD and 8 P were observed, confirmng a certain degree of activity of CI FUra in patients clinically resistant to bolus FUra.Based on this rationale, a phase II trial of schedule-oriented biochemical modulation of FUra in advanced colorectal cancer patients was conducted, employing a hybrid regimen of 2 biweekly cycles of FUra bolus (600 mg/sqm), preceeded by (24 h interval) methotrexate, 200 mg/sqm (in order to maximize the RNA effect of the drug) alternating with FUra continuous infusion, 200 mg/sqm daily for 3 weeks, modulated by leucovorin, 20 mg/sqm weekly bolus (in order to maximize the DNA effect).Thirty-three consecutive patients (median ECOG PS 1) with advanced measurable colorectal cancer and no prior therapy for metastatic disease entered the study, from February 1992 to August 1993. Three complete and 13 partial responses were obtained among these 33 patients (RR=48%, 95% confidence limis, 31–66%). After a median follow-up time of 23 months, 16 patients are still alive. The median progression free survival and overall survival were 9.6 and 20.8 months, respectively. No toxic deaths or grade 4 toxicity occurred. The incidence of grade 3 toxicity per patient in any cycle was: mucositis 6%, diarrhea 3% and vomiting 3% for the bolus part and 21%, 3% and 6% respectively, for the continuous infusion part of the regimen. Hand-foot syndrome occurred in 27% of the patients treated with the continuous infusion regimen.In conclusion, this experimental and clinical project has generated a novel regimen of schedule oriented biochemical modulation that is twice as active and half as toxic compared to bolus FU+LV given with either the daily x 5 or the weekly schedule. This high clinical activity is very encouraging, especially considering that 1) consecutive patients were entered, 2) the responses were independently reviewed, 3) the progression free survival and survival were much longer than those actually reported for this disease, 4) the toxicity of the program, in particular the bolus regimen, was relatively low allowing further intensification.