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1.
The following scheme lists the problems which have been and will continue to be encountered in grazing experiments on natural particle assemblages. In some cases there are solutions, but many of the problems listed below remain intractable. To solve them will require innovative approaches, most probably combining the use of particle counters with other techniques to approach the problem to be solved from several angles at once. Variance between samples due to - statistical causes (especially caused by large particles) and - differences between experimental bottles and between experimentals and controls at start of experiment. Shifts in particle distribution during experiment due to - increase in small particles - growth of bacteria and other organisms due to excretion of grazers and - breakage during handling by grazers into fragments. Processes, independent of grazing, leading to changes in particle size distribution due to - primary production - grazing by additional components and - bacterial growth on detrital particles and the formation of detrital flocs. 相似文献
2.
G. Peres 《Andrologie》1995,5(3):326-331
Androgenic hormones seem to be of beneficial effects on sports performance: - they increase motivation, will, aggressiveness, resistance to the stress and to the fatigue, leading to an increase of the training quantity, - they increase bone mineralization and probably mechanical resistance, - they stimulate the bone marrow and so, with the erythropoietin, the erythropoiesis, - they increase the tendancy to hyperglycemia, but with a decrease of the tolerance to the glucose, - they stimulate the fatty acids mobilization from the adipose tissue, for their utilization in the muscle during the exercise, - they participate, for the trained sportmen, to a better gestion of the muscle glycogen storage: their utilization during exercise is decreased, - they increase the lean body mass, with an increase of the protein synthesis and a decrease of the protein catabolism, leading also to an increase of the muscle force under training. There is no beneficial effect upon the tendons, - they have an immunomodulation action. 相似文献
3.
D. Bruce Campbell 《Molecular neurobiology》1995,11(1-3):193-216
Pharmacological and toxicological studies undertaken on drugs that affect the brain are frequently performed in disparate species under various experimental conditions, at doses often greatly in excess of those expected to be administered to humans, and the findings are extrapolated implicitly or explicitly with scant regard to differences in the biodisposition of the drugs. Such considerations are necessary since:
- Species;
- Strain;
- Gender;
- Route;
- Dose;
- Frequency and time of administration;
- Temperature;
- Coadministration of drugs; and
- Surgical manipulation
4.
U. H. Mane 《Hydrobiologia》1975,47(3-4):439-451
- The neutral red technique was employed to study the rate of filtration in Katelysia opima.
- The weight specific water filtration was found to be greater for younger clams compared to the older ones.
- The rate of water filtration increased with decreasing salinity.
- Water filtration was found to increase as temperature increased, reaching a maximum at 35°C. but then sharply decreasing at 39°C.
- Light had no significant effect on the rate of filtration.
- Suspended matter was found to affect the rate of water filtration.
- The rate of filtration was low at high pH and high in low pH.
- The rate of water filtration was found to be faster during high tide than during low tide.
- The presence of the parasitic crab, Pennotheris sp., in the mantle cavity of clams had a marked effect on the particle filtration.
- Accidental cut of the siphon tips had no effect on the rate of filtration.
5.
J. B. Messenger 《Invertebrate neuroscience : IN》1996,2(2):95-114
- ACh, dopamine, noradrenaline, 5-HT,l-glutamate, and GABA are widely distributed in cephalopods and probably all function as neurotransmitters; octopamine also occurs and at one site is known to act as a neuromodulator.
- Several peptides are also present, as well as nitric oxide synthase.
- In the brain and sense organs cholinergic, aminergic, serotonergic and glutamatergic systems seem to be the most important.
- ACh is also active in the gut, vascular system and some body muscles: it is generally inhibitory. The ACh receptors are similar to the vertebrate nicotinic type.
- The catecholamines are important in the gut and vascular system: they are generally excitatory. The NA receptors are like the α-adrenergic subtype of vertebrates, but the nature of the DA and OA receptors is less certain.
- 5-HT is important in the gut but is endogenous in some chromatophore nerves and acts on receptors that seem like the vertebrate 5-HT1 type.
- l-glutamate is an excitatory transmitter at the chromatophore (and probably at other) nerve-muscle junctions and is an extremely strong candidate for being the excitatory transmitter at the squid giant synapse. There are NMDA receptors on Schwann-cells but the receptors on neurons and muscles are like the vertebrate kainate type.
- Little is known about the mode of action of cephalopod peptides; nor has it ever been shown that they co-exist with conventional transmitters in these animals.
- The structure of one (FMRFamide) receptor has been elucidated, but apart from this nothing is known of the molecular biology of receptors in cephalopods.
6.
Mike Ainsworth 《Acta biotheoretica》1993,41(1-2):43-51
Computer analysis of biological systems, using approaches such as metabolic control analysis is common. A typical example is a language like Herbert Sauro's SCAMP (Sauro & Fell, 1991), which allows simulations of enzyme systems, and calculation of control coefficients and elasticities. However such systems are motivated by the underlying biochemical theory and often have limitations as programming languages which mean that they can only be applied to particular classes of problems. ABPL (a biochemical programming language) extends these ideas by adding all the facilities of a fully-fledged programming language, together with some of the capabilities of a modern computer algebra system. Syntactically it derives from the programming language LISP, while the underlying functionality is that of iMAP, the successor to SCAMP. This provides us with a computer system capable of performing most of the tasks undertaken by existing packages, but more importantly, a system which can be easily extended into new areas. Key features of the work are: - Ability to use the language both interactively and as a batch programming language - Ability to work both symbolically and numerically - Ability to handle matrices and vectors - Ability to define and manipulate reaction schemes - Common techniques are built in to the language - Ability to add new operations to the language The implementation is in ANSI standard C for portability. 相似文献
7.
Purpose
to determine diagnosis and prognosis value of MRI in Peyronie’s disease.Material and Methods
thirty one penile MR examinations have been performed in 28 patients aged between 21 and 73. (1 tesla; surface coil; sagittal SET1, axial SET2 weighted, T1 before and after Gadolinium)Results
Conclusion
MRI can be helpfull in the pretreatment assessment and int he follow-up of Peyronie’s disease. 相似文献8.
Chi-Ken Chen Jinn-Ming Liaw Jih-Guang Juang Te-Hsien Lin 《Biological trace element research》1997,58(1-2):149-157
Antioxidant enzymes together with trace elements in 26 patients with chronic renal failure treated with hemodialysis and 25 healthy subjects were investigated. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSHPx) in plasma and erythrocytes were examined immediately before and after hemodialysis. The results are summarized as follows:
- A significant decrease in plasma SOD, CAT, and GSHPx and erythrocyte GSHPx were found in patients before hemodialysis.
- Erythrocyte CAT and GSHPx were significantly lower in the patients after hemodialysis than in the controls.
- Plasma GSHPx was significantly higher after a single hemodialysis than before hemodialysis.
- A good correlation between erythrocyte SOD and copper (Cu) in patients before hemodialysis was found.
- A good correlation of GSHPx in erythrocytes and plasma was found before hemodialysis, whereas an even better correlation was found after hemodialysis.
- Abnormalities of trace elements were found in hamodialyzed patients.
- There is indirect evidence for increased oxidizing stress in uremic patients with hemodialysis. Dialysis treatment may improve some abnormalities (e.g., Hb, P), but may also induce some deleterious effects of free radicals or lipid peroxidation.
9.
10.
From the Avocado Rooting Promoter (ARP) 4 compounds were isolated and identified as:
- 1 acetoxy - 2,4 dihydroxy-n-heptadeca-16-en;
- 1 acetoxy - 2,4 dihydroxy-n-heptadeca-16-yn;
- 1,2,4 trihydroxy-n-heptadeca-16-en;
- 1,2,4 trihydroxy-n-heptadeca-16-yn.
11.
D. V. Subba Rao 《Hydrobiologia》1973,43(1-2):77-91
- The phytoplankton cycle off Lawson's Bay, Waltair follows a bimodal pattern with a major peak during March–May; a minor peak during October–November months and with a low production during the summer months i.e., June–August.
- During the summer months of 1957, 1958, 1960 and 1962 dumping of dredged spoil from the entrance channel of the harbour into the sea resulted in a natural enrichment of waters.
- Following this enrichment, there was a qualitative and quantitative increase in the phytoplankters thus leading to the development of a bloom.
- Only Thalassiosira subtilis and Chaetoceros curvisetus commonly bloomed during the four years.
- The increase in gross production which varied from 3–13 fold and the high photosynthesis-respiration ratios 5.1 to 10.5 indicated that the bloom populations were in a healthy state.
- The decrease of the populations to the initial levels suggests that some unknown factor, other than those investigated must have been operating.
- Consequences of eutrophication of different origins on stimulation of phytoplankton production are briefly discussed.
12.
- A method for the direct recording of the PEP efflux from isolated mitochondria is described.
- This method has been used to show the stimulation of PEP efflux by externally added Mn++ ions.
- Valinomycin, uncoupler and oleate were also shown to stimulate PEP efflux.
- Valinomycin caused an increase in the internal concentration of both PEP and citrate.
- The results indicate that the major pathway of PEP synthesis in isolated mitochondria is via PEP carboxykinase and the results do not call for an unknown pathway of metabolism.
- Two interactions between PEP and citrate are described; competition for the mitochondrial interior and the stimulation of PEP production by citrate.
13.
EPR spectroscopy is a powerful tool to identify at a molecular level, the different steps of catalyst preparation, and of catalytic reactions: - the distribution among the different sites in zeolites can be determined; - the dispersion of the active phase may be appreciated; - the unsaturation degree of the active site may be evaluated using probe molecules such as water or13C enriched carbon monoxide.
- Deposition of paramagnetic transition metal ions onto a support is monitored, and the coordination sphere of the metallic center is characterized by EPR.
- The catalyst is also characterized after activation (thermal oxidation or reduction):
- The catalytic mechanisms can be investigated by studying the elementary steps of the catalytic reaction, as illustrated for methanol oxidation over Mo/SiO2 catalysts whose EPR results have extended the reaction mechanism proposed on the basis of kinetic data. In addition, reaction intermediates may be isolated inquasi-in situ conditions as in the case of olefin oligomerization catalyzed by Ni/SiO2 systems.
14.
- A diurnal study of inland fresh water lake has been made with respect to physical and chemical properties and the plankton.
- Chlorides have followed the total carbonates while dissolved oxygen and pH have shown no relation.
- Microcystis has followed no definite pattern of diurnal movement.
- All crustaceans, some of the rotifers andTrachelomonas perform considerable diurnal movement in the course of a twenty four hour period.
15.
E. Schürg-Pfeiffer C. Spreckelsen J. -P. Ewert 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,173(3):363-376
In freely moving toads, the temporal discharge patterns of tectal and medullary neurons were observed during prey-catching.
- Tectal T5.2 and T8.1 neurons displayed a premotor warming up firing that in the former was addressed specifically to prey orienting or snapping and in the latter generally to almost any kind of body movement.
- The temporal discharge patterns of T5.2 neurons during snapping were different from those during orienting toward prey. Snapping started in the peak phase of warming up; firing was immediately terminated during the snap; thereafter some rebound activity was observed. Orienting started after the premotor warming up in the declining phase whilst the neuron kept on firing during orienting and then settled when the orienting movement was completed.
- In toads which were not motivated to catch prey — comparabl to immobilized ones — the discharge frequency of T5.2 neurons toward a prey stimulus revealed no such warming up.
- Because it is known that prey-selective T5.2 neurons are controlled by pretectal inhibitory influences, the following experiment was conducted: during recording a T5.2 neuron a pretectal lesion was applied ipsilaterally to the recording site. After a few seconds, the neuron showed a strong premotor wanning up in response to any kind of moving object, followed by prey-catching.
- In the medulla oblongata, different H-type neurons of the hypoglossal nucleus displayed specific discharge patterns which resembled the tongue protractor and retractor muscle activities; a third type resembled the activity of the genio/sterno-hyoid muscle, which are suggested to stabilize the hyoid bone during snapping.
- There were medullary M8-type neurons with properties similar to T8.1.
- Snapping could be triggered by electrical stimulation of the optic tectum in the representation of the frontal visual field, but not by stimulation in the hypoglossal nucleus or the adjacent medial reticular formation.
- A concept of a neuronal circuit for the coordination of tongue muscle contractions in response to prey is proposed.
16.
Hilmar Brunn Rolf Bretz Peter Fankhauser Thomas Spengler Otto Rentz 《The International Journal of Life Cycle Assessment》1996,1(4):221-225
Synthetic sulfuric acid is used in a wide range of applications in fine chemical industry. Despite an already performed optimization of input amounts, used sulfuric acid is still a quantitatively important waste by-product. As a result, different utilization technologies for used sulfuric acid exist: ? the starting point for a comparative LCA of the above mentioned utilization technologies at a concrete situation is explained, in a work of Ciba-Geigy Corp. ? a short summary of the comparative LCA is presented ? lessons learned from performing the LCA and using it in a decision process are described. 相似文献
- production of gypsum
- thermal reductive cracking
- thermal cracking and oxidation
17.
Robert B. Hespell Michael F. Thomashow Sydney C. Rittenberg 《Archives of microbiology》1974,97(1):313-327
- Washed cell suspensions of Bdellovibrio bacteriovorus harvested shortly after lysis of their substrate organisms and shaken in buffer have a constant and high endogenous respiration rate for a bout 6 h which then declines sharply to a rate approximately 10% of the original. Viability of cell suspensions shows little change over the first 4–6 h and then decreases by some 50% in 10 h.
- Over the first 5–6 h of starvation there is a loss of about 50% of total cell carbon. This loss is distributed about equally between CO2 and small molecules released into the suspending buffer. The protein and nucleic acid contents of the cells decrease concomitantly from time zero during starvation while DNA content remains constant. Ribosomal profiles show a rapid degradation of ribosomes.
- In the presence of glutamate or glutamate plus a balanced amino acid mixture, loss of cell material and loss of viability is partially or completely prevented. There is extensive protein turnover when glutamate and an amino acid mixture are available to the bdellovibrio.
- The pattern of changes observed in B. bacteriovorus during starvation is compared to reported changes in other species of bacteria, and the significances of its high endogenous respiration and sensitivity to starvation are discussed.
18.
- All methods used to analyze amino acid composition of different enzymes agree well with each other.
- They lead to a relationship between amino acid composition and function of proteins.
- Cytochrome oxidase is in a class by itself; copper-containing oxidases are closely related as expected.
19.
D. Delavierre 《Andrologie》1999,9(1):53-59
The vacuum erection device (VED) is a nonsurgical alternative for the treatment of erectile dysfunction. This method is based on 2 phenomena:
- an erection-like state occurs when the penis is placed in a vacuum
- this state can be maintained by a constricting band placed around the base of the penis
- blood flow into the penis decreases
- penile skin temperature falls
- congestion of extra-corporeal penile tissues occurs
- the penis pivots at its base
- the ejaculate is trapped in the proximal urethra
20.
N. Nicholls 《Plant Ecology》1991,91(1-2):23-36
The El Niño-Southern Oscillation (ENSO) phenomenon has a marked effect on Australia's rainfall. The tendency for major Australian droughts to coincide with ENSO “events” (i.e. anomalously warm sea surface temperatures in the east equatorial Pacific), and for extensive wet periods to accompany “anti-ENSO” events, is well documented. Also well-known is the partial predictability of Australian rainfall anomalies provided by ENSO. Some other ENSO-related characteristics of interannual fluctuations of Australian rainfall are lesswidely recognised, viz: - rainfall variability is very large - droughts and wet periods have time scales of about one year - they exhibit very large (continental) spatial scales - they tend to be phase-locked with the annual cycle - they are often followed/preceded by the opposite rainfall anomaly. The character of Australian rainfall fluctuations is thus very different from that of areas where the influence of ENSO is weak, Europe for instance. Rainfall in some other areas, notably southern Africa and India and parts of the Americas, is also strongly affected by ENSO and shares some of the above characteristics. The relevance of these ENSO-related characteristics of Australian rainfall to its vegetation will be discussed. Australian native vegetation is adapted to these characteristics, especially in the semi-arid inland where ENSO's influence is strong. Most introduced plants are not adapted to ENSO and this has sometimes complicated their use here. The combination of ENSO-related rainfall fluctuations and European land-use strategies has resulted in some very rapid, unpredicted and undesirable changes in vegetation in the past two centuries. It has also increased the risk of soil erosion. Recognition of the real character of Australian rainfall fluctuations may help avoid further degradation of soil and vegetation. 相似文献