The significance of the leaf epidermis in the taxonomy of the combretaceae III. The genus combretum in America

The value of the leaf epidermis, particularly the glandular trichomes, in the identification and classification of the 37 species of Combretum recognized in America is assessed. The wide range of trichome types found, in general, differentiates groups of species corresponding closely with the 11 sections recognized by Exell, rather than distinguishing individual species. The taxonomic value of these trichomes is demonstrated to be at least as great as that of any other organ in the genus, and in a number of cases valuable criteria have been obtained for the first time.     

The role of the methylation in the detoxication of arsenate in the rabbit

The biotransformation, tissue retention, intracellular binding and biokinetics of arsenic were studied in rabbits exposed to [74As]arsenate (0.4 mg As/kg body wt., i.v.). Inhibition of the methyltransferase activity by injection of periodate-oxidized adenosine (PAD) caused a marked decrease of the formation of [74As]dimethylarsinic acid (DMA), which gave rise to 1.5-4 times increased tissue levels of 74As. This is almost the same as reported for rabbits given arsenite in combination with PAD and was due to a rapid reduction of the arsenate to arsenite which bound to the tissues. Only about 30% of the arsenate given was excreted unchanged in the urine, indicating that a large part was reduced to AsIII. Thus the methylation to DMA seems to be almost as important for the detoxication following exposure to arsenate as that following exposure to arsenite. In the rabbits with normal methylating capacity 50-70% of the produced AsIII was methylated to DMA. The liver was the only organ in which DMA was present 1 h after the administration, indicating that this is the main site of the methylation. The DMA was rapidly cleared from all tissues except the thyroid.     

转pGH基因猪血清pGH含量的分析

用ELISA方法分别测定了 3头F0 代成年阳性猪和 8头F1代幼年阳性猪血清pGH的水平 ,发现阳性个体间在激素含量及变化趋势上有很大差别 ,其中F1代个体pGH变化趋势与阴性对照较为一致。研究结果表明阳性个体本身性别及生理状况与外源基因表达有关 ,同时也反映出外源pGH基因的表达状况与该基因在宿主基因组中的插入位点不同有着密切的联系。     

The state of the chromosomes in the interphase nucleus

In the living interphase nucleus no chromosomal structures are visible. Yet in the injured cell and after treatment with most histological fixatives chromatin structures become apparent. Under certain conditions this appearance of structure in the living interphase nucleus is reversible. We have found that this change in the interphase nucleus is the result of a change in the state of the chromosomes. In the living nucleus the chromosomes are in a greatly extended state, filling the entire nucleus. Upon injury the chromosomes condense and therefore become visible. At the same time the nuclear volume decreases. This behavior of the chromosomes is connected with their content of desoxyribonucleic acid (DNA). This view is based on the following observations: (a) Distribution of DNA in the Nucleus.-(1) The living interphase nucleus of uninjured cells absorbs diffusely at 2537 A. No chromosomal structures are visible in ultraviolet photographs unless they are also distinct in ordinary light. If the chromosomes are made to condense they become visible and the absorption at 2537 A is now localized in these structures. (2) After fixation with formalin and osmic acid interphase nuclei stain diffusely with Feulgen. These fixatives preserve the extended state of the chromosomes. (3) If nuclei are teased out in non-electrolytes (sucrose, glycerin) the chromosomes are extended. Such nuclei stain homogeneously with methyl green. On adding salts the chromosomes condense and the methyl green is now restricted to the visible structures. (b) Extension and Condensation of Isolated Chromosomes.-When chromosomes isolated from interphase nuclei of calf thymus are suspended in sucrose, their volume is four to five times larger than in saline, but they retain their characteristic shapes. Chromosomes from which DNA and histone have been removed do not show this reversible extension and condensation, neither do lampbrush chromosomes of frog oocytes which contain very little DNA. During mitosis a partial condensation of the DNA occurs in prophase, so that the mitotic chromosomes now occupy a much smaller volume of the nucleus. At telophase the chromosomes swell again to fill the entire nucleus.     

肠道病毒71型实验室诊断研究进展

肠道病毒71型(Enterovirus 71,EV71)为手足口病(Handf,oot and mouth disease,HFMD)和相关疾病的主要病原体,多感染婴幼儿,少数病例可以并发呼吸道感染和心肌炎、无菌性脑膜炎、脑炎、急性弛缓性麻痹等严重疾病,可致残、致死。因此EV71实验室诊断对EV71引起疾病的治疗和防控具有重要意义。本文将从核酸检测、抗体检测及其他检测等三部分对EV71的实验室诊断方法研究进展进行了综述。     

The normal development of the anorectum in the pig

The development of the anorectum was studied in forty-four embryos and foetuses of pig varying in length from 9 mm total length to 210 mm crownrump length and in three newborn pigs. The presence of some features during critical stages in the development of the cloaca in the pig such as an epithelial mass protruding into the dorsal cloaca near its intestinal orifice and distinct differences in the type of epithelium in different regions of the cloacal system greatly facilitated the study of the developmental process. Thus it could be established that a change in position of the dorsal cloaca and adjacent structures such as the distal part of the gut and the urorectal septum via the dorsal part of the cloacal plate towards the tailgroove is of major importance for the partition of the cloaca into a separate intestinal and urogenital division. A subsequent disintegration of the dorsal part of the cloacal plate results in two separate openings for both the systems at the same time. Disintegration of the ventral part of the cloacal plate leads only to a further widening of the external opening of the urogenital system. In the cloacal system three distinct zones were discerned, a dorsal and ventral cloacal and a cloacal plate region. From the dorsal cloacal epithelium the whole anorectal segment between the intestinal mucosa and the anal epidermis develops. The epithelium of ventral cloacal origin seems to disappear completely . Cloacal plate epithelium forms the epithelial lining of distal parts of the urogenital system. The penile urethra in the male is formed by a ventralward movement of the urogenital opening by the growing perineum and not by fusion of genital folds.     

The myelination of the cerebellar cortex in the cat

Summary The myelination of the cerebellar cortex of the cat was investigated in 61 cats aged from 3 hrs post partum to two and a half years. The first myelinated fibers appear at the time of birth in the central medullary ray. Before the onset of myelination, all fibers reach a critical diameter of about 1 m. About the 14th day of life the number of oligodendrocytes in the prospective white matter increases markedly. Thereafter, the oligodendrocytes invade the inner granular layer. It therefore seems that the myelination of the cerebellar cortex proceeds from the central medullary ray towards the granular layer. At the 60th day of postnatal life, most of the afferent and efferent fiber systems are myelinated. These findings are discussed in relation to the development of function and the maturation of the electrical activity of the cerebellar circuit.Dedicated to Prof. Dr. H. Leonhardt in honour of his 60th birthdaySupported by the Deutsche Forschungsgemeinschaft (La 184/3)     

The status of the Chough in the British Isles

This review of our current knowledge of the movements of Fulmars to and from their breeding colonies, and of the relationship of this phenomenon with such questions as the annual moult and the first return of immature birds, shows how incomplete is our understanding of this expanding species.