Evolution of the secondary haustoria to a primary haustorium in the parasiticScrophulariaceae/Orobanchaceae

In the parasiticScrophulariaceae andOrobanchaceae, two types of contact organs exist: secondary and primary haustoria. Secondary haustoria are lateral organs, developing in large numbers and only when the seedling is fully established. In contrast, a primary haustorium represents the first developmental stage of the seedling itself. In the root system of the parasiticLesquereuxia syriaca (=Siphonostegia syriaca) there are only secondary haustoria, but a few of them apparently develop in a terminal position. This is achieved by transferring the haustorial initiation region closer to the root apex. One can interpret this as a transformation of the apical meristem into a meristematic haustorial tissue. On the condition that an extreme shortening (abbrevation) of the primary root could happen, we discuss the transformation of the terminal secondary into a primary haustorium.     

Mutations in the E1a gene of type 5 adenovirus result in oncogenic transformation of Fischer rat embryo cells

Transformation of a specific clone of Fischer rat embryo (CREF) cells with wild-type 5 adenovirus (Ad5) or the E1a plus E1b transforming gene regions of Ad5 results in epithelioid transformants that grow efficiently in agar but that do not induce tumors when inoculated into nude mice or syngeneic Fischer rats. In contrast, CREF cells transformed by a host-range Ad5 mutant, H5hrl, which contains a single base-pair deletion of nucleotide 1055 in E1a resulting in a 28-kd protein (calculated) in place of the wild-type 51-kd acidic protein, display a cold-sensitive transformation phenotype and an incomplete fibroblastic morphology but surprisingly do induce tumors in nude mice and syngeneic rats. Tumors develop in both types of animals following injection of CREF cells transformed by other cold-sensitive Ad5 E1a mutants (H5dl101 and H5in106), which contain alterations in their 13S mRNA and consequently truncated 289AA proteins. CREF cells transformed with only the E1a gene (0-4.5 m.u.) from H5hrl or H5dl101 also produce tumors in these animals. To directly determine the role of the 13S E1a encoded 289AA protein and the 12S E1a encoded 243AA protein in initiating an oncogenic phenotype in adenovirus-transformed CREF cells, we generated transformed cell lines following infection with the Ad2 mutant pm975, which synthesizes the 289AA E1a protein but not the 243AA protein, and the Ad5 mutant H5dl520 and the Ad2 mutant H2dl1500, which do not produce the 289AA E1a protein but synthesize the normal 243AA E1a protein. All three types of mutant adenovirus-transformed CREF cells induced tumors in nude mice and syngeneic rats. Tumor formation by these mutant adenovirus-transformed CREF cells was not associated with changes in the arrangement of integrated adenovirus DNA or in the expression of adenovirus early genes. These results indicate, therefore, that oncogenic transformation of CREF cells can occur in the presence of a wild-type 13S E1a protein or a wild-type 12S E1a protein when either protein is present alone, but does not occur when both wild-type E1a proteins are present.     

Acute phase response to recombinant interleukin-6 and macrophage- and fibroblast-derived crude cytokine preparations in primary cultures of mouse hepatocytes

A number of acute phase proteins were determined by electroimmunoassay in media from CBA mouse hepatocytes cultured for 2 days with human recombinant IFN beta 2/IL-6, as well as with conditioned media from LPS-stimulated rat macrophages, and of murine L fibroblasts. It was found that human recombinant IL-6 caused three-fold increase in secretion of fibrinogen, while haptoglobin, complement C3 and transferrin were increased respectively, to 168 per cent, 151 per cent, and 145 per cent of the control. DEX(10(-7) M) in DMEM supplemented with 5 per cent FCS, enhanced the IL-6 effect on the three positive acute phase proteins. IL-6 elevated haptoglobin mRNA in mouse hepatocytes to a degree comparable with the concentration of the protein in the culture medium. The effect of conditioned media from murine fibroblasts and peritoneal rat macrophages was generally similar to that of recombinant IL-6. However, both natural preparations of the cytokines caused decrease in albumin and alpha-1-proteinase inhibitor secretion.     

Benthic algal biomass and productivity in high subarctic streams,Alaska

Year-round measurements of the standing crop of epilithic algae (as chlorophyll a concentration) in two streams — one second and one fourth order (map scale 1:63 360) — in interior Alaska (64°–65° N) were only about one tenth that reported from streams of temperate North America. Cell densities in these streams, however, were similar to those in comparable temperate streams. Year-round domination of the benthic flora by very tiny diatoms (Achnanthes spp.) may explain the apparent disparity between low chlorophyll a content and nearly average cell densities. Chlorophyll a standing crop in a more alkaline groundwater-fed stream, however, was higher and within the range of similarly sized temperate streams. Maximum chlorophyll a standing crop varied positively with alkalinity in 5 clear-water streams where standing crop was measured on natural or artificial substrates. Seasonal mean concentrations of sestonic chlorophyll a (used as estimates of benthic algal chlorophyll a standing crop) varied directly and significantly with alkalinity among ten clear-water streams; and, with total phosphorus among 8 of 10 clear-water and 5 brown-water streams studied. During the summer, when there is little darkness, gross primary productivity (as estimated by the diurnal dissolved-oxygen method) was similar to that of northern temperate streams. Gross primary productivity was also seen to vary directly with alkalinity in 5 clear-water streams of this region.U.S. Fish and Wildlife Service     

Distinction between light-mediated and light-independent variations in phytoplankton production rates

An array of factors simultaneously controls phytoplankton photosynthesis and hence the primary production process. Because their relative importance shifts both with depth and with season, the significance of individual factors cannot be resolved by in situ incubations, even if all relevant environmental and biotic variables are measured.Here a procedure is described by which in addition to in situ measurements, photosynthesis is simultaneously assessed in identical subsamples under constant temperature (10 °C) and light (0.66 mol m^–2 h^–1 PAR conditions, in vitro). By calculating photosynthesis per unit of chlorophyll, effects of shifting biomass on photosynthesis can be eliminated but seasonal variations of light-saturated photosynthesis generated by temperature, and vertical changes of light-requirements (e.g. by light-shade adaptation) remain obscure. Quotients of in situ photosynthetic rates divided by in vitro rates allow the quantification of light-mediated changes. Provided that photosynthesis measured in vitro is light-saturated, quotients in situ: in vitro rates should never exceed unity. They are a measure for the degree of light-limitation. In vitro rates normalized to chlorophyll give information on temporal changes caused by variations in photosynthetic capacity. In Lake Constance, mean cell size appears to control light-saturated assimilation numbers.     

Functional response of Fucus vesiculosus communities to tributyltin measured in an in situ continuous flow-through system

The effects of antifouling paint leachate containing tributyltin on community metabolism and nutrient dynamics were measured in situ on natural communities dominated by Fucus vesiculosus. The measurements were made in two areas with different salinities and at various TBT concentrations up to about 5 µg 1^–1. A portable continuous flow-through system was used in which the communities were incubated for a week. Continual measurements of oxygen, temperature, light and flow rate of water were made. A Perturbation Index (PI) and an Absolute Disturbance Index (ADI) were used to describe the changes due to treatment relative to the control, and to obtain a total picture of disturbance using all measured parameters. Photosynthesis was particularly strongly affected and changes were obvious in oxygen production and nutrient uptake at TBT levels as low as 0.6 µg 1–1.     

δ and κ Opiate receptors in primary astroglial cultures from rat cerebral cortex

The effects of , , and receptor-agonists on forskolin stimulated cyclic adenosine-3, 5-monophosphate (cAMP) formation were examined in astroglial enriched primary cultures from the cerebral cortex of newborn rats. Intracellular cAMP accumulation was quantified by radioimmunoassay. Morphine was used as a -receptor agonist, D-Ala-D-Leu-Enkephalin (DADLE) as a -receptor agonist and dynorphine 1–13 (Dyn) as a -receptor agonist. Basal cAMP levels were unaffected by either the opiate agonists or the antagonists used. In the presence of the cAMP stimulator forskolin, morphine had no significant effect on the cytoplasmic cAMP levels. DADLE caused a dose related inhibition of the forskolin stimulated cAMP accumulation. The effects of this receptor stimulation was blocked with the selective antagonist ICI 174.864. In the presence of Dyn, the forskolin stimulated cAMP accumulation was inhibited in a dose related manner. This receptor stimulation was blocked with the selective antagonist MR 2266. Co-administration of DADLE and Dyn resulted in a non additive inhibition of the forskolin stimulated accumulation of cAMP. These findings indicate that astroglial enriched cultures from the cerebral cortex of rats express and -receptors co-localized ont he same population of cells, and that these receptors are inhibitory coupled to adenylate cyclase.     

在原代培养的大鼠肝细胞观察消炎痛的细胞保护作用

我们曾观察到消炎痛预处理能明显减轻四氯化碳和半乳糖胺对大鼠的肝损伤作用,本工作采用原代培养的大鼠肝细胞进一步观察了这一现象。结果表明,经消炎痛整体处理后分离的大鼠肝细胞,在原代培养的条件下,对四氯化碳的损伤仍然具有明显的抵抗作用,表现为细胞内酶的漏出少于对照组。正常大鼠离体肝细胞在原代培养条件下用消炎痛处理,在相当大的剂量和相当长的时间范围内未出现明显的抗损伤作用。结果提示:消炎痛整体处理可使肝细胞本身获得抗损伤的能力,而这种抗损伤能力的产生可能有赖于肝细胞外其它因素的参与。     

Analysis of nuclear proteins from silk glands ofBombyx mori

A gentle method for the isolation of nuclei from developing silk glands ofBombyx mori has been standardized. The nuclei, whether isolated or directly visualizedin situ within the silk glands, exhibit complex morphology. The nuclei occupy almost the entire volume of the gigantic silk gland cells. Although the isolated nuclei still retain their ramified morphology, being polyploid they are fragile and often become fragmented. The histone and low-salt-extractable proteins from nuclei isolated from the middle and posterior silk glands on different days of the fourth and fifth instars of larval development have been analysed. The histones did not show any stage- or tissue-specific variations whereas the low-salt-extractable proteins showed some developmental stage specific variation. Using the antibody raised against one such protein, its absence in the early stage of development has been confirmed by Western blotting techniques. This developmental stage specific protein may be functionally linked to some activities responsible for boosting up the production of silk or silk-related proteins during the fifth instar of larval development.     

An in vitro test for measuring cytotoxicity of mercuric chloride to human kidney epithelial cells by specific enzyme release

Mercuric compound toxicity is well documented in animals and man for practically all organs. The recent development of cell culture techniques appeared as a novel fruitful tool in toxicology, especially in renal toxicology. Heavy metal induced renal cell alterations can be evaluated by membrane permeability damages.The present study evaluates mercuric chloride nephrotoxic effect in human kidney epithelial cells by measuring the release of two specific nephrotoxicity marker enzymes, Gamma Glutamyl Transferase (GGT) and Alkaline Phosphatase (ALP) in the culture medium. Cultured kidney epithelial cells were exposed to different HgCl₂ concentrations (5, 10, 20, and 50 g). Cultures were examined after 6 and 24 hours exposure. A good correlation between mercury dose and toxic effect, and exposure time and toxic effect was found. Enzymes were significantly released into the culture medium for 5 g and 10 g HgCl₂/ml after 6 hours exposure; and after 24 hours exposure, enzymes were released for 5 g/ml only.It appears that the specific tubular enzyme release in the culture medium is a good in vitro test for quantification of specific tubular damage.