缺氧对右心室最大心肌血流量的影响

为了探讨缺氧对冠状血管贮备力的影响,我们观察了缺氧时大鼠血流动力学及右心室最大心肌血流量的变化。结果表明,急性缺氧引起ＰａＯ２、心输出量及氧运送量降低,但右心室心肌血流量增加,右心室最大与安静血流量比值降低。慢性缺氧时ＰａＯ２降低,血球比积和右心室重量指数增加,氧运送量和右心室血流量正常,但最大血流量降低,小动脉增厚、外膜胶元增加。以上结果提示,慢性缺氧对冠状血管贮备减少可能是小动脉壁增厚、外膜胶元增加和血液粘滞性增加及右心室肥大的结果。     

Quantification of the presence and activity of specific microorganisms in nature

Traditional techniques for assessment of microbial numbers and activity generally lack the specificity required for risk assessment following environmental release of genetically engineered microbial inocula. Immunological and molecular-based techniques, such as DNA probing and genetic tagging, were initially used to determine the presence or absence of microorganisms in environmental samples. Increasingly they are being developed for quantification of populations of specific organisms, either indigenous or introduced, in the environment. In addition, they are being used to quantify the activity of particular organisms or groups of organisms, greatly extending the range of techniques available to the microbial ecologist. This article reviews the use of traditional techniques for the quantification of microbial population size and activity and the application of molecular techniques, including DNA probing, genetic marking, use of fluorescent probes, and quantitative PCR, in combination with advanced cell detection techniques such as confocal laser scanning microscopy and flow cytometry.     

The Life Cycle of Chlorine, Part II: Conversion Processes and Use in the European Chemical Industry

The major purpose of this article is to construct a plausible emissions profile for the European chemical industry from process data and mass balance considerations.' In it we describe this industry and its major conversion processes and emissions. Four major process chains, beginning with methane, ethylene, propylene, and benzene are analyzed, along with five important stand-alone processes. A self-consistent version of the industry is constructed for 1992, based on data from a variety of sources.
In 1992 Europe consumed 9,297 metric kilotons as measured by weight of chlorine (kMT[CI]) of salt and 2 I I kMT(CI) of recycled hydrochloric acid (HCI) to produce 86 I0 kMT of virgin elemental chlorine, plus 278 kMT(CI) of virgin by-product HCI. Total chlorine input to the industry was 8,689 kMT including I2 kMT(CI) of recycled chlorinated hydrocarbons (CHCs) and (net) 79 kMT(CI) of HCI. Shipments of chlorine and HCI to other sectors was 1,367 kMT(CI), while 7,322 kMT(CI) was embodied in products or lost within the sector: Of this subtotal, 350 kMT(CI) was used to manufacture identified inorganic chemicals, 5,694 kMT(CI) for identified organic chemicals, and 1,278 kMT(CI) for "other unspecified" chemicals.
We estimate that products account for 41.6% of inputs (measured at the "fence"), while wastes account for 24.7%     

DIEL PHASING OF THE CELL-CYCLE IN THE FLORIDA RED TIDE DINOFLAGELLATE, GYMNODINIUM BREVE

The diel cycle is a key regulator of the cell-cycle in many dinoflagellates, but the mechanisms by which the diel cycle entrains the cell-cycle remain poorly understood. In this study, we describe diel phasing of the cell-cycle in the Florida red tide dinoflagellate Gymnodinium breve Davis, determine the diel cue which serves to entrain the cell-cycle, and provide evidence for the presence of cyclin-dependent kinase (CDK), a cell-cycle regulator which may be responsive to this cue. Four laboratory isolates from the West Coast of Florida were compared. When grown on a 16:8 h LD cycle, all isolates displayed phased cell division, with the S-phase beginning 6–8 h into the light phase, and mitosis following 12–14 h later, as determined by flow cytometry. A naturally occurring bloom of G. breve, studied over one diel cycle, displayed diel cell-cycle phasing similar to that in the laboratory cultures, with the S-phase beginning during daylight and the peak of mitosis occurring approximately 4 h after sunset. In the laboratory cultures, the dark/light "dawn" transition was found to provide the diel cue which serves to entrain the G. breve cell-cycle, whereas the light/ dark "dusk" transition did not appear to be involved. Evidence for the presence of CDK in G. breve was obtained using two approaches: (1) identification of a 34-kDa protein, immunoreactive to an antibody against a conserved amino acid sequence (α-PSTAIR) unique to the CDK protein family and (2) inhibition of the cell-cycle by olomoucine, a selective CDK inhibitor. Together, these results provide the basis from which one can begin addressing mechanisms by which the diel cycle regulates the cell-cycle in G. breve.     

Spatial distribution of genetic relatedness in a moorland population of red grouse (Lagopus lagopus scoticus)

Several aspects of the ecology and biology of red grouse (Lagopus lagopus scoticus) could prevent the complete admixture of genes within and between populations. Male red grouse display a high degree of natal philopatry, are territorial, and show less aggression to kin man to non-kin. Such factors acting in combination predict limited male-mediated gene flow, which will promote social structure within a population by the formation of stable kin clusters, and facilitate a rapid rise in allelic coancestry and/or inbreeding. In this study we utilize hypervariable microsatellite polymorphisms to examine the extent of social affiliation between relatives in a moorland population of grouse from NE Scodand. Levels of genetic relatedness between individual male red grouse occupying territories at Glas Choille in die spring and autumn of 1995 were examined, and kin clusters delimited. Nine kin groups (mean size = 2.4 individuals) were identified prior to breeding in the spring, which increased to 11 kin groups (mean size =4.0 individuals) when territories were reformed in the autumn. The majority of tiiose individuals that were recruited into the adult population during the autumn already had a first-order male relative established, supporting the hypothesis that recruitment is facilitated by behavioural interactions among relatives. The demographic and population genetic consequences of philopatric recruitment and kin clustering are examined and discussed.     

HYDROTHERMAL-VENT ALVINELLID POLYCHAETE DISPERSAL IN THE EASTERN PACIFIC. 2. A METAPOPULATION MODEL BASED ON HABITAT SHIFTS

Marine organisms typically fall into two main categories: those with a high level of population structuring and those with a low one. The first are often found to be poor dispersers, following isolation by distance or stepping-stone theoretical predictions. The second are commonly associated with high-dispersal taxa and are best described by the island model. Deep-sea hydrothermal vent systems represent a good model for studying one-dimensional metapopulations. Whereas isolation by distance might be expected to be the rule in such a system for species with limited dispersal capabilities, a biological paradox can be observed: an apparent genetic homogeneity in some vent species with short-scale dispersal potential, in a one-dimensional fragmented habitat. This can be explained if one key assumption of the existing models is not met: gene flow between populations and genetic drift may not have the time to equilibrate. Geophysical models revealed that hydrothermal convection is intrinsically unstable, inducing processes of coalescence or splitting of venting areas in a chaotic manner. This is likely to generate frequent extinctions and recolonizations. Theoretical genetic predictions derived from extinctions/recolonizations cannot satisfactorily model a situation where habitat shifts are frequent and constantly affect the metapopulation equilibrium. Because neither the island and the stepping-stone models nor the classical metapopulation models resemble the hydrothermal vent reality, we present here a realistic model developed to provide a compromise between existing conceptual models and what is currently known of the biology and ecology of one of the most peculiar and best-studied vent species, the polychaete Alvinella pompejana. This model allows us to define the boundaries between which the metapopulation is evolutionary stable in an unstable context. Simulations show different patterns in which metapopulation size and recolonization vary but reach an equilibrium despite chaotic vent extinctions. In contrast, the model also shows that displacing habitat continuously affects the equilibrium between gene flow and drift. As a consequence, the time required to balance these evolutionary forces can never be attained, leading to chaotic fluctuations in F-statistics. Those fluctuations are mainly due to stochastic changes of the interpatch distance which affect migration rates. The shifting of active zones of venting can episodically counterbalance differentiation and allow a long-term genetic homogenization at the ridge scale. These findings lead to a new concept in which the exchanges between populations would mainly depend on the habitat's movements along the ridge axis rather than the organim's dispersal. We therefore propose a new model based on patch-network displacements in which transient contact zones allow low levels of gene flow throughout the metapopulation.     

Population subdivision in marine environments: the contributions of biogeography, geographical distance and discontinuous habitat to genetic differentiation in a blennioid fish, Axoclinus nigricaudus

The relative importance of factors that may promote genetic differentiation in marine organisms is largely unknown. Here, contributions to population structure from a biogeographic boundary, geographical distance and the distribution of suitable habitat were investigated in Axoclinus nigricaudus, a small subtidal rock-reef fish, throughout its range in the Gulf of California. A 408-bp fragment of the mitochondrial control region was sequenced from 105 individuals. Variation was significantly partitioned between 28 of 36 possible combinations of population pairs. Phylogenetic analyses, hierarchical analyses of variance and a modified Mantel test substantiated a major break between two putative biogeographic regions. This genetic discontinuity coincides with an abrupt change in ecological characteristics, including temperature and salinity, but does not coincide with known oceanographic circulation patterns or any known historic barriers. There was an overall relationship of increasing genetic distance with increasing geographical distance between population pairs, in a manner consistent with isolation-by-distance. A significant habitat-by-geographical-distance interaction term indicated that, for a given geographical distance, populations separated by discontinuous habitat (sand) are more distinct genetically than are populations separated by continuous habitat (rock). In addition, populations separated by deep open waters were more genetically distinct than populations separated by continuous habitat (rock). These results indicate that levels of genetic differentiation among populations of A. nigricaudus cannot be explained by a single factor, but are due to the combined influences of biogeography, geographical distance and availability of suitable habitat.     

Historical interdrainage dispersal of eastern rainbowfish from the Atherton Tableand, north-eastern Australia

The widespread distribution of the eastern rainbow fish Melanotaenia splendida splendida throughout the isolated headwaters of the rivers on the Atherton Tableland, north-eastern Australia, suggests multiple colonization events from the eastern lowlands via each respective river channel, or a single colonization event on to the tableland with subsequent dispersal between the headwaters. To explore the likely processes that resulted in the current distribution on the tableland, two models of gene flow were tested: (a) the hierarchical gene flow model that tests the hypothesis for contemporary gene flow via stream channels and (b) the stepping stone model that tests for dispersal between streams. Neither of these models explained the observed genetic structure, adequately. However, there is support for extensive historical dispersal across the headwaters of the isolated drainages. If this dispersal followed a single colonization event, the subsequent range expansion could have facilitated a rapid rise in population size due to an increase in suitable habitat. The genetic data indicates an eight-fold increase in population size c. 100 thousand years ago.     

Decomposition Analysis of Finnish Material Flows: 1960–1996

To the extent that environmental impacts are the consequence of the magnitude of total material input into production in an economy, they can be lessened by reducing the use of materials—by concentrating on what has been called qualitative growth. This article presents a summary of Finnish resource use over the period 1960–1996 as a means of evaluating the trends in material use and providing a basis for assessments of sustainability. It adapts the technique of decomposition analysis developed in the field of energy studies to distinguish the effects of changes in aggregate economic activity ("activity effect"), composition of industrial activity ("structural effect") and materials intensity of use ("intensity effect") on a sectoral basis.p
According to the analysis presented here, materials consumption in Finland has grown substantially between 1960 and 1996 in the electricity, gas and water supply, pulp and paper production, civil engineering, and mining and quarrying sectors. In the same period, the ratio of GDP/mass of material mobilized has improved by 175 percent. Economic growth has caused the largest increases in materials use in the building of infrastructures; for example roads, waterways, means of supplying electricity, gas, and water, and in the production of paper and paper products. The least growth took place in the transport, basic metals production, and mining and quarrying sectors.     

Materials Flow Accounting in Sweden Material Use for National Consumption and for Export

This article presents Swedish economy‐wide material flow accounts for the period 1987‐1998. It also shows possibilities for enhancing the international comparability of aggregated data on material use, by distinguishing between materials used for consumption and export purposes. The direct material input (DMI) is used as an aggregate measure to estimate the amounts of natural resources (except water and air) that are taken from nature into the economy within a year, including imports to and production within the region in question. The division of materials used for consumption and export purposes avoids double counting trade flows when DMI is applied to a group of countries. The annual DMI in Sweden for 1997‐1998, including production and imports, amounts to 24 to 27 metric tons per capita (t/c). The fossil fuel input varies only slightly over the period, from 3.2 t/c in 1991 to 3.6 t/c in 1996, a level deemed unsustainable by the Swedish Environmental Protection Agency. The input of renewable raw materials varies between 8 and 9 t/c. Ores and minerals vary between 11 and 15 t/c. The DMI puts Sweden above estimates made for Germany, the United States, and Japan and in the same range as the Netherlands. The differences in these values can mainly be explained by the relative importance of exports as compared to the size of the economy and by the variation in system boundaries for the data on natural resources. The system boundaries and data sources for natural resources need to be further defined to make the measures fully comparable. Around 5 t/c is exported, whereas the rest, around 20 t/c, is national consumption. The aggregate direct material consumption (DMC), which is the DMI minus exports, communicates the magnitude of resource use. Comparisons of the input with solid waste statistics indicate that quantity of waste (excluding mining waste) in Sweden is equal to about 10% relative of the total resource use. Material collected for recycling by the waste management system is equal to about 5% of the amount of virgin resources brought into society each year.