Dynamics of water usage in Haloxylon ammodendron in the southern edge of the Gurbantünggüt Desert

植物的水分来源是荒漠地区植物水分关系研究的重要方面, 有助于理解荒漠植物对干旱环境的适应。为了研究古尔班通古特沙漠主要建群种梭梭(Haloxylon ammodendron)生长季的水分利用动态, 以及其对发生在不同时期相似量级降水脉冲的响应, 利用稳定性同位素技术测量了梭梭小枝木质部水、降水、0-300 cm不同土层的土壤水和地下水的δ ¹⁸O值。水源依据深度划分为4个: 浅层土壤水(0-40 cm), 中层土壤水(40-100 cm), 深层土壤水(100-300 cm)和地下水。然后, 应用IsoSource模型计算了梭梭对潜在水源的利用比例。结果表明: 4月份, 梭梭主要利用浅层土壤水, 利用比例为62%-95%; 5-9月份梭梭主要利用地下水, 利用比例为68%-100%。梭梭对不同时期发生的两场相似量级的降水具有不同程度的响应。5月22日, 6.7 mm降水后第1天, 梭梭对土壤水的吸收达到最大值, 由降水前的9.8%增长为降水后的40.4%, 同时降低了对地下水的吸收, 由降水前的83%-98%下降为42%-81%。8月31日7 mm降水后, 梭梭对土壤水的吸收没有增加, 仍然保持对地下水的高比例利用, 达71%-98%。低的土壤含水量可能抑制了表层根系的活性, 导致梭梭对降水不敏感。由冬季融雪和春季降水补给的浅层土壤水和地下水是梭梭种群可利用的两个重要水源。梭梭的水分利用动态反映了其对干旱环境的适应。     

Vaccination-induced syphilis and the Hübner malpractice litigation

This article examines smallpox vaccination in the 19th century as background for a notorious medical malpractice case that occupied Bavarian courts from April 1853 until May 1854. Dr. Georg Hübner, the defendant, was accused of having initiated a small epidemic of syphilis by using the lymph of a syphilitic infant to vaccinate 13 infants. The litigation and its published contemporaneous discussion demonstrate conflicts in the understanding of syphilis, the hazards of having to make a purely clinical diagnosis, the effect of obsolete legal wording in medical litigation, and the attitude of leading physicians to a guilty colleague. This case ultimately led to efforts to make arm-to-arm smallpox vaccination safer, and by 1898 to abandon the technique in favor of bovine sources that were sterilized and stabilized by various methods.     

Carl Düsing (1884) on the regulation of the sex-ratio

In three publications in 1883 and 1884 Carl Düsing of Jena gave a mathematical account of the influence of natural selection on the sex ratio based on the same argument that Darwin had advanced in The Descent of Man (1871). The argument thus became quite well known, being included in the principal books on the subject around the turn of the century, as well as in the Encyclopaedia Britannica, references to Düsing being given. By 1930, when Fisher gave a verbal account of the argument in The Genetical Theory of Natural Selection, he saw no need to give references, and no other book of the period treated the subject, as a result of which Düsing's contribution became lost to view. We here give the important paragraphs of Düsing's mathematical account, translated into English.     

Contacts between Wolffian and Müllerian cells at the tip of the outgrowing Müllerian duct in rat embryos

The developing Müllerian duct was studied at the light microscopic as well as the electron microscopic level in rat embryos, especially in the section of the terminal bud and its tip, where Wolffian and Müllerian duct are enclosed by a common basal membrane. In this zone desmosomes can be found among Wolffian cells and also among Müllerian cells. In addition, we found cell contacts between Müllerian and Wolffian cells, namely short electron-dense segments on adjacent surfaces or disc-shaped thickenings within opposite plasma membranes, as well as fusions of the plasmalemmata over short distances. Until now, these cell contacts have not been described in rat embryos.     

Hypothermia and hypoxia inhibit the Hering-Breüer reflex in the marsupial newborn

The effects of lowering body temperature (T(b)) on metabolic rate, ventilation, and the strength of the Hering-Breüer expiratory promoting reflex (HB reflex; determined from an inhibitory ratio calculated from volumetric measurements of the respiratory rhythm) were examined in 18-day-old ectothermic pouch young of the tammar wallaby during normoxia or hypoxia (10% O(2)). Hypoxia and hypothermia, either singularly or combined, depressed metabolic rate. At all T(b), the hypoxic hyperventilation was associated with a significant hyperpnea. At pouch T(b) (36.5 degrees C) during normoxia, inflation of the lungs with -5 or -10 cmH(2)O extrathoracic pressure induced a significant HB reflex. Exposure to cold reduced the strength of the reflex, almost abolishing it at 28 degrees C. For T(b) above 28 degrees C, the reflex in hypoxia was always less than the corresponding normoxic value. Taken in context with the changes in metabolic state that occurred, these data in the ectothermic marsupial newborn suggest that the decline in the HB reflex during moderate hypothermia is the result of a direct effect of T(b) on vagal mechanisms rather than a temperature-driven decline in metabolic rate that should have acted to strengthen the HB reflex. Therefore, it seems that inputs inhibitory to breathing are more negatively affected during cold than those inputs that are excitatory.     

The arthropodCheloniellon from the devonian hunsrück shale

Cheloniellon calmani Broili 1932, is restudied with the aid of the radio-graphic technique applied to the two well known specimens (CI and CII), and also two other specimens (CIII and B).Bundenbachiellus giganteus (B) (Broili 1929) is probably a synonym, but the incomplete and distorted condition makes it appear expedient to consider this name as a nomen nudum. New radiographs of CI, CII and CIII allow a better reconstruction of C.calmani than the one based on the distorted specimen CI. The new picture shows a head with two tergite plates on the dorsal side and one pair of antennae, a second preoral pair of appendages and four pairs of probably uniramous legs with gnathobases on the ventral side. Only the last pair is situated beneath the second tergite. The body has eight tergites with wide pleura corresponding to eight pairs of biramous appendages. The outer branch carries very stout lamellar spines. The ninth tergite is small and cylindrical and corresponds to long furcal rami. The posterior end is probably formed by a conical piece, possibly a telson, without appendages.Cheloniellon was a benthic carnivore. The second preoral appendages and postoral gnathobases make it unexpectedly similar to eurypterids and xiphosurids, and it may be a late representative of a group of trilobitomorphs that gave rise to the Chelicerata.     

Occurrence of the Ciliate Protozoa Bütschlia parva Schuberg in the Rumen of the Ovine

The holotrich ciliate protozoa, Bütschlia parva Schuberg, has been observed in the rumen of the ovine. Limited data suggest that the concentration of B. parva in the rumen follows a diurnal cycle similar to that of the other holotrichs.     

Variation in the cell cycle time in the crypts of lieberkühn of the mouse

The durations of the phases of the cell cycle were measured at different levels in the jejunal crypts of male Balb/c mice. A mean cell cycle time of 12.3 h was found for the whole crypt. In cell positions 1 and 2, the cell cycle time was 16.7 h, and this time steadily decreased to a value of between 10 and 11 h for cell positions above 11. It is concluded that basally situated crypt cells in the mouse are cycling relatively slowly, and that they form the functional stem cell pool for the crypt. These cells may also compose the potential stem cell pool which repopulates the crypt after death of proliferative cells.     

Progress of a half century in the study of the Luria-Delbrück distribution

The Luria-Delbrück mutation model has been mathematically formulated in a number of ways. This review article examines four most important formulations, focusing on important practical issues closely linked with the distribution of the number of mutants. These issues include the probability generating functions, moments (cumulants), computational methods and asymptotics. This review emphasizes basic principles which not only help to unify existing results but also allow for a few useful extensions. In addition, the review offers a historical perspective and some new explanations of divergent moments.     

Short-term feeding of Temora longicornis Müller in the laboratory and the field

Short-term feeding (min to h) of the copepod Temora longicomis (Müller) was investigated in the laboratory and in the field by monitoring the increase in gut fluorescence of adult females. Laboratory feeding studies using the diatoms Thalassiosira pseudonana (Hust.), T. weissflogii (Hust.) and Ditylumbrightwellii (West) showed that ingestion rates increased with increased food concentration and cell size. The maximum ingestion rate was 9.5 ng chl. equiv. female ⁻¹. h ⁻¹ on a diet D. brightwellii. Clearance rates decreased with increased food concentration and decreased cell size. Maximum clearance rate was 1.9 ml. female⁻¹·h⁻¹ also on a diet of D. brightwellii. On two of three occasions, ingestion and clearance rates in the field were twice as high at night as during the day. Night rates were similar to laboratory rates in the chlorophyll range found in the field. Diel differences in feeding activity in the field appeared to have been behaviorally induced rather than being related to vertical migration of individuals into food rich layers.     

Studies on the ovotestis of the slug Agriolimax reticulatus (Müller)

Summary The follicle cells, nurse cells and germinal epithelia, which are closely associated with the oocyte of Agriolimax reticulatus (Müller) during its development in the ovotestis, have been studied using light and electron microscopy. The various secretory, digestive and phagocytic activities of these cells have also been investigated using electron cytochemical tests for oxidisable polysaccharide, acid phosphatase and electron-opaque tracer molecules. The oocyte lies initially between the germinal epithelia and a layer of nurse cells but, as oocyte vitellogenesis proceeds, it becomes encapsulated by a layer of follicle cells. Both the follicle and the nurse cells are active in secretion and digestion and contain Golgi apparatus, granular endoplasmic reticulum and acid phosphatase-rich digestive vacuoles. The significance of these activities is discussed in relation to oocyte vitellogenesis, secondary envelope formation and the digestion and recycling of cellular material.