Hymenolepis diminuta: Worm loss and worm weight loss in long-term infections of the rat

Infections of one and two Hymenolepis diminuta established in newly weaned rats continued to grow for the duration of the experiment (238 days), whereas infections of 5 worms per rat became asymptotic around Day 55 postinfection and remained at or below this level thereafter as shown by biomass and mean weight per worm measurements. Infections of 50 worms established in newly weaned rats became asymptotic around Day 28 postinfection and thereafter worms were lost from the rats. Initially the biomass fell with the loss of worms, but by Day 56 a new lower biomass persisted for the remainder of the infection period. This level was maintained, despite diminishing numbers of worms, due to the growth of surviving individuals to a weight exceeding the original weight at maturity by a factor of more than 2. Experiments using rats that were mature at the time of infection demonstrated that the same response occurred, but approximately 3 weeks earlier.     

Sex determination of fetal and neonate skeletons by means of discriminant analysis

Facing the requirements of refined paleodemographical analyses, the access to the early ontogenetic sex ratio of skeletal populations is an important feature. Using raw data provided byFazekas & Kosa (1978) for a sample of known sex, discriminant functions are derived from hip and thigh bone dimensions that allow an almost unbiased classification of more than 70% of fetal and neonate individuals.     

Use of tissue culture to bypass wheat hybrid necrosis

Summary Hybrid necrosis in wheat is a barrier to gene transfer in wheat breeding practice. It is based on two complementary genes, Ne1 and Ne2. Recovery mutants (Re1, Re2 and Re3) which can grow to maturity were recovered from immature embryo cultures of necrotic hybrids between T. aestivum and T. durum. Cytological observation demonstrated that Re1 had 34 chromosomes instead of 35. This indicated that one of the chromosomes carrying the Ne genes was lost. Genetic study suggested that for Re1, the lost chromosome was chromosome 5B of the durum parental line. Re mutants are male sterile but can be maintained through a young ear culture method. Re mutants could be successfully pollinated by either parental line and the BC1 progeny is partially fertile. Re mutants were repeatedly induced in about 1% of the regenerated plants from immature embryo culture. This technique provides a practical way to bypass hybrid necrosis.     

Evidence for the Neurotrophic Regulation of Collagen-Tailed Acetylcholinesterase in Immature Skeletal Muscle by β-Endorphin

Abstract: Acetylcholinesterase (AChE) was extracted in a high-saline medium from gastrocnemius muscles of rat embryos and young rats aged 14 days'gestation to 40 days post partum. The molecular forms of the enzyme were separated by low-salt precipitation, followed by velocity sedimentation. During gestation, all molecular forms increased in activity, particularly the 16 S (A₁₂) form. During the first 2 weeks of life, there was a large increase in the activity of soluble AChE (G forms), whilst the activity of insoluble AChE (A forms) was reduced. Denervation of the muscle reversed the change in the relative proportions of the molecular forms. The embryonic pattern of activities of AChE forms persisted in cultures of myotubes obtained at 20 days'gestation and maintained in the absence of spinal cord. When myotubes were maintained in medium previously conditioned by developing spinal cord explants, 16 S AChE declined while the soluble (4 and 6 S) forms increased in activity in a manner resembling that seen in early postnatal muscles in vivo . β-Endorphin (β-EP) immunoreactivity was detected in the spinal cord-conditioned medium and was identified by HPLC and ion-exchange chromatography as β-EP-(l–31) plus its shortened and N -acetylated forms. Cultivation of myotubes in the presence of synthetic camel β-EP resulted in a reversible change in the pattern of AChE forms which was similar to that seen with spinal cord-conditioned medium. These studies provide evidence for the neuroregulation of AChE A and G forms in immature skeletal muscle. A major candidate for this role is β-EP, produced and released by developing spinal cord.     

Formation and function of cytoplasmic annulate lamellae in the eggs ofPomatoceros triqueter L.

Summary During an ultrastructural study of the eggs of the serpulid wormPomatoceros triqueter L., annulate lamellae were frequently encountered in the cytoplasm. In particular, some observations indicated that they originate by successive outfoldings of the nuclear envelope. Consequently, annulate lamellae must consist of alternating layers of nuclear and cytoplasmic material, each layer being separated by part of the nuclear envelope. It was observed that there was a similarity between nuclear and inter-annulate lamellar material. Moreover tritiated thymidine was shown to be present in the stacks. It is inferred that this system might well function as an efficient means of transporting nuclear material into the cytoplasm. The authors wish to thank Messrs. P. C. Lloyd, P. Henley and D. Williams for technical assistance.     

A statistical model of the reproduction of aphids

1. The logistic function has been generally used to describe the reproductive process of a “population” of animal. However, this model can not give us any information about the reproductive process of “individuals” in the population. In this study a statistical model on the basis of the reproduction of individuals of barley aphid is presented to find the proportion of the mature individuals, the heterogeneity in reproductive ability of the aphids, etc.
2. The model is constructed as follows:
3. The probability that j insects are found on a plant at time t₀ is represented as Q(j).
4. The probability that h individuals of j have reproductive ability, say, mature individuals, in the period t₀ to t₁ is represented as B(h/j)=_jC_hw^h(1−w)^j−h, where w is the proportion of mature individuals.
5. In a population with a homogeneous reproductive ability, the probability that each parent lays i offspring in the period t₀ to t₁ is represented as P(i/m)=e^−mmⁱ/i!, where m is mean. And, in a population, m changes according to the gamma distribution. Hence the probability that a parent lays i offspring between t₀ and t₁ is represented as , where p and k are parameters of negative binomial distribution. The probability that h parents on a plant lays s offspring is represented as .
6. From the assumptions mentioned above, the probability that s offspring are to be found at time t₁ on a plant with the original j individuals at time t₀ is represented by
7. The experimental populations were demonstrated to fit well to the model.

     

基因型和胚龄对小麦未成熟胚离体培养反应的影响

本文对34种基因型的小麦未成熟胚在离体培养中的反应进行了比较。结果表明,94％的供试基因型愈伤组织诱导率都可达到80％以上,若排除供体植株环境条件的不同和接种过程中的人为因素可能造成的影响,不同基因型的愈伤组织诱导率看来没有根本的差异。愈伤组织分化率因基因型的不同变动在0—60％之间,平均为32.7％。虽然同一基因型的盾片愈伤组织分化率在不同年份中有所不同,但是愈伤组织是否具有再生能力?看来是个稳定的遗传性状。因此小麦未成熟胚对愈伤组织诱导的反应和愈伤组织的再生能力可能具有不同的遗传基础。本文的结果还表明,虽然最适于培养的未成熟胚的大小为1毫米左右,伹小至0.3毫米的未成熱胚仍能以几乎100％的频率形成愈伤组织,60％左右的愈伤组织能分化出再生檀株,只是所需的时间比1毫米左右的胚较长。     

我国微茎类吸虫研究:ⅩⅢ.微茎类吸虫成虫结构特征排序

对我国52种微茎类吸虫的18项成虫形态学特征进行主成分分析,结果表明:卵巢位置、子宫延伸位置等7项性状对第一主成分贡献较大,提示描述器官位置的指标是重要的分类依据。52个虫种在前三个主成分上的排序图显示应将其划分成4个亚科。     

可育的抗除草剂溴苯腈转基因小麦

报道了采用微粒轰击（Ｍｉｃｒｏｐｒｏｊｅｃｔｉｌｅ ｂｏｍ ｂａｒｄｍ ｅｎｔ） 幼胚将除草剂抗性基因导入小麦（Ｔｒｉｔｉｃｕｍａｅｓｔｉｖｕｍ Ｌ．）的转化研究。实验共使用了１３ 个小麦品种, 从开花后１４～１８ ｄ 的籽粒中剥取幼胚, 植物表达质粒含有ＣａＭＶ ３５Ｓ启动子控制的除草剂溴苯腈抗性基因ｂｘｎ 以及筛选标记基因ＮＴＰⅡ。采用高压放电基因枪,用质粒ＤＮＡ 包被的钨粒轰击预培养３ ｄ 的幼胚。在含有卡那霉素类似物ｇｅｎｅｔｉｃｉｎ Ｇ４１８ｓｕｌｐｈａｔｅ 的ＭＳ培养基上, 经过多步骤筛选和分化, 从８００ 多个幼胚中获得了１６ 株转化苗。除草剂抗性鉴定和Ｓｏｕｔｈｅｒｎ 杂交分析证明, 其中４ 株为转基因植物,具有溴苯腈抗性, 并且自交可育。转化工作从分离幼胚到转化苗鉴定完毕, 最短时间为６ 个月, 因此, 该方法是一项快速有效的基因导入技术