Trypanosoma brucei: A rapid “matching” method for estimating the host's parasitemia

A new technique for estimating the absolute level of parasitemias in trypanosome infections is described. At higher levels of infection this is achieved by matching microscopic fields of a wet blood film against charts and, where fewer organisms are present, by counting the number of trypanosomes in 5, 10, or 20 such microscope fields. Good estimates of the number of organisms per milliliter of blood can be made rapidly over the whole range of microscopically patent parasitemia, i.e., above antilog 5.4 (250,000) organisms/ml.     

Bacterial periphyton of the Vltava River

Bacterial periphyton formed during 48 hours was studied by glass slide method and direct counting in Vltava River in Praha, Czechoslovakia. At water temperatures 8–11°C the numbers of rods ranged between 24,000 and 336,000 per 1 cm² and those of cocci between 30,000 and 228,000. The relation rods: cocci ranged between 0,9 and 2,4 with an average value of 1,7, whereas in a fishpond this average was 0,5. Among the periphyton 81,3% bacterial cells were active. The rods: cocci relation seems to be a good indicator of water pollution by organic matter, but numbers distinguishing the individual saprobic levels cannot be given yet.

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Zusammenfassung Es wurde der bakterielle Bewuchs von Glassplatten im Vltava-Fluss in Praha untersucht. Zweitägige Exposition erwies sich als am meisten geeignet, um den Bewuchs mikroskopisch durch direkte Zählung quantitativ zu erfassen. In Abhängigkeit von der Tiefe, Wassertemperatur, Verunreinigungsgrad, Sonnenstrahlung u.a. entwickelte sich der Bewuchs quantitativ unterschiedlich und zeigte auch eine unterschiedliche Relation von Stäbchen zu Kokken. Im beta-mesosaproben Bereich wurden im Herbst (Wassertemperaturen 8–11 °C) 24.000 bis 336.000 Stäbchen und 30.000 bis 228.000 Kokken per 1 cm² gefunden, mit den Mittelwerten 163.100 Stäbchen und 104.100 Kokken. Die Vergleichswerte von einem Fischteich in Motol lagen für Stäbchen im gleichen Bereich, während die Kokken, bis 254.000 erreichten.Die Relation Stäbchen: Kokken variierte im Vltava-Fluss zwischen 0,9 (nur einmal) und 2,4 mit dem Mittelwert 1,7, im Fischteich zwischen 0,4 ufnd 0,7 mit dem Mittelwert 0,5. Es hat sich erwiesen, dass diese Relation brauchbare Angaben über die organische Verunreinigung gibt. Leider liegen bisher zu wenige Ergebnisse vor, um eine Skale gegenüber den Saprobitätsstufen zu errichten.Unter den Bewuchsbakterien gab es in der Vltava durchschnittlich 81,3% aktive Zellen, wie durch Fluoreszenzanalyse festgestellt wurde.Fast alle Daten indizieren eine schwächere Verunreinigung des Wassers am linken Ufer als am rechten.

     

INHIBITION OF CHLORELLA (CHLOROPHYCEAE) GROWTH BY FATTY ACIDS, USING THE PAPER DISC METHOD1,2

Using the paper disc-agar plate method, a number of fatty and related acids have been tested for tested activity for inhibiting the growth of Chlorella pyrenoidosa Chick. Of the saturated acids, a peak in growth inhibiting activity wax observed in the C₇–C₁₂ range, where inhibition wax observed when solutions down to 0.02 M were applied to the discs. Most of the unsaturated acids tested showed greater inhibition than did the corresponding saturated acids. Acrylic acid showed detectable inhibition at 0.001 M concentration.     

Pericytes and perivascular microglial cells in the basal forebrain of the neonatal rabbit

Summary Three types of pericytes outline the vascular bed in Golgi preparations of the newborn rabbit brain. Elongate cells (Type I) are restricted to capillaries, elements resembling smooth muscle cells (Type II) surround vessels of intermediate size, and large flat forms (Type III) cover the surface of arterioles and venules. Electron microscopy shows all types to be located within a well defined perivascular basement membrane. It also reveals the presence of filaments in the cytoplasm of some pericytes resembling the myofilaments of smooth muscle cells. It suggests the possibility that some pericytes are capable of contraction and may participate in regulating blood flow in small vessels.Microglia cells bear no resemblance to pericytes in terms of their shape, distribution or staining characteristics. Microglia cells are located outside the vascular basement membrane (external basal lamina) in the brain parenchyma, and they vary in form according to their location and the character of the surrounding extracellular space. This study does not support the hypothesis that microglia cells arise from pericytes but indicates that they originate either by in situ division or from hematogenous elements that enter the brain by crossing the vessel wall.Support provided by N.I.H. Grants No. NS 10864 and NS 07938 from the U.S. Public Health Service.     

A three-step method for isolating a few to several hundred milligrams of protein

An operationally simple general protein isolation method was devised from three previously available separation tools, and was tested by application to two demanding fractionation problems and for yield. One test system was the isolation by gel electrofocusing of two model proteins with pI values of 4.6 and 4.8, bovine serum albumin and ovalbumin, with a load of 220 mg each. The other test was the isolation of 10 mg of human growth hormone isohormone B from a mixture of closely migrating other isohormones. The three-step procedure comprises of: (1) separation into zones of homogeneous protein by gel electrofocusing; (2) excision of the zones of homogeneous protein from the gel followed by concentration of the protein to a small volume of solution by means of Steady-State Stacking; (3) purification from polyacrylamide-like contaminants and non-volatile buffers by gel filtration followed by lyophilization. The average overall recovery was 70--80%.     

Positive indirect effect of aquatic insects on terrestrial prey is not offset by increased predator density

1. Changes in one prey species' density can indirectly affect the abundance of another prey species if a shared predator eats both species. Sometimes, indirect effects occur when prey straddle habitats, including when riparian predator populations grow in response to emergent aquatic insects and increase predation on terrestrial prey. However, predators may largely switch to aquatic insects or become satiated, reducing predation on terrestrial prey. 2. To determine the net indirect effect of aquatic insects on terrestrial arthropods via generalist spider predators, a field experiment was conducted mimicking midge influx and a wolf spider numerical response inside enclosures near an Icelandic lake. Lab mesocosms were also used to assess per capita rates of spider predation u nder differing levels of midge abundance. 3. Midges always decreased sentinel prey predation, but this effect increased with predator density. When midges were absent, predation increased 30% at a high spider density, but predation was equal between spider treatments when midges were present. In situ arthropods showed no effect of midge or spider treatments, although non‐significant abundance patterns were observed congruent with sentinel prey results. 4. In lab mesocosms, prey survivorship increased ≥50% where midges were present and rapidly saturated; the addition of 5, 20, 50, and 100 midges equivalently reduced spider predation, supporting predator distraction rather than satiation as the root cause. 5. The present results demonstrate a strong positive indirect effect of midges and broadly support the concept that predator responses to alternative prey are a major influence on the magnitude and direction of predator‐mediated indirect effects.     

Reputation,a universal currency for human social interactions

Decision rules of reciprocity include ‘I help those who helped me’ (direct reciprocity) and ‘I help those who have helped others’ (indirect reciprocity), i.e. I help those who have a reputation to care for others. A person''s reputation is a score that members of a social group update whenever they see the person interacting or hear at best multiple gossip about the person''s social interactions. Reputation is the current standing the person has gained from previous investments or refusal of investments in helping others. Is he a good guy, can I trust him or should I better avoid him as a social partner? A good reputation pays off by attracting help from others, even from strangers or members from another group, if the recipient''s reputation is known. Any costly investment in others, i.e. direct help, donations to charity, investment in averting climate change, etc. increases a person''s reputation. I shall argue and illustrate with examples that a person''s known reputation functions like money that can be used whenever the person needs help. Whenever possible I will present tests of predictions of evolutionary theory, i.e. fitness maximizing strategies, mostly by economic experiments with humans.     

Testing parameter sensitivities and uncertainty analysis of Biome-BGC model in simulating carbon and water fluxes in broadleaved-Korean pine forests

生态过程模型的发展为研究者在长时间序列和区域尺度的研究提供了便利, 但模型模拟的准确性受到模型自身结构、模型参数估计合理性的影响。敏感性分析能够定量或定性筛选出对模型模拟结果影响较大的敏感参数, 是模型参数校准过程中的重要工具, 也是建模和应用的先决条件。该文以阔叶红松林为研究对象, 采用全局敏感性分析方法——傅里叶幅度灵敏度检验扩展法(EFAST)对Biome-BGC模型的生理生态参数进行了敏感性分析, 分别分析了红松(Pinus koraiensis)和阔叶树的净初级生产力(NPP)、蒸散(ET)对参数变化的敏感性。结果表明: (1)模拟红松NPP的不确定性高于阔叶树, 但二者的模拟ET的不确定性均较小。阔叶树的NPP和ET对生理生态参数的敏感性总体上都小于红松。(2)无论是红松、阔叶或其他植被类型, 模拟NPP均表现出对叶片碳氮比、细根碳氮比、比叶面积(SLA)和冠层截留系数的敏感性, 这4个参数的高敏感性主要是由模型自身结构所决定的, 与植被类型和研究地区的关系较小。对模拟ET而言, 细根与叶片碳分配比、新茎与新叶碳分配比和SLA均是影响红松和阔叶树ET的敏感参数, 但红松ET主要受参数与参数间的二阶或多阶交互作用的间接影响, 而阔叶树ET则主要是受到敏感参数直接效应的影响。(3)除了上述影响红松和阔叶树碳水通量的共性参数外, 诸如核酮糖-1,5-二磷酸羧化酶中叶氮含量、叶片与细根周转率、所有叶面积与投影叶面积之比等也是对模拟结果有影响的重要参数, 但是其敏感程度随物种不同和研究区不同而不同, 所以这类参数可以根据具体情况进行参数本地化, 对于其他不敏感参数则可以采用模型缺省值。     

The Exact Distribution of the Anderson-Kannemann Statistic

The Anderson-Kannemann test is a rank test for treatment effects in a randomized block design with K treatments and N blocks. In this paper, an algorithm for computing the exact distribution of the Anderson-Kannemann test statistic under the null hypothesis is deduced. Then, the exact distribution is compared with the asymptotic χ²-distribution, and it is shown that the exact distribution is approximated fairly well by the asymptotic distribution. Tables of the exact distribution are given for K = 3, N = 3(1)15; K = 4, N = 3(1)11; K = 5, N = 3(1)7; and K = 6, N = 3(1)5.