Showing papers by "Ghent University published in 1977"
01 Jan 1977
TL;DR: In terms of the global fluxes between aerial and terrestrial-aquatic systems, the simplified nitrogen cycle can be envisioned as a triangle where the only biologically reversible reaction occurs between ammonium and nitrate.
Abstract: The transformations of nitrogenous compounds by soil bacteria have beenstudied for over a century. In terms of the global fluxes between aerial and terrestrial-aquatic systems, the simplified nitrogen cycle can be envisioned as a triangle where the only biologically reversible reaction occurs between ammonium and nitrate. The reverse reactions of dinitrogen fixation or denitrification by biological means do not occur in nature. Hence, the reductive process of denitrification, defined as the reduction of nitrate or nitrite to gaseous nitrogen (usually N2), is intimately associated with the oxidative process of nitrification.
870 citations
TL;DR: The technology developed by the authors for the routine decapsulation of Artemia cysts is described and the advantages which result from the use of decapsulated cysts in aquacultural hatcheries are discussed.
168 citations
TL;DR: This method, which allows direct identification of even the longer Ap tracts in a double digest of an oligonucleotide or an RNA chain, is very rapid and highly sensitive and can be applied to the simultaneous analysis of a large number of samples in a single run.
106 citations
TL;DR: In this paper, the basic integral equations for the electrostatic and magnestostatic problems are reviewed and the results of the calculations are compared with Cohn's experimental values for four typical aperture shapes.
Abstract: The basic integral equations for the electrostatic and magnestostatic problems are reviewed. These equations are solved with a digital computer for four typical aperture shapes. The results of the calculations are compared with Cohn's experimental values. Some data are given concerning the corresponding acoustic problems.
93 citations
TL;DR: In this paper, the surface treatment, deactivation and coating of glass capillaries is discussed and several techniques described in the literature are compared and for some critical points, new improved methods are advanced.
Abstract: The surface treatment, deactivation and coating of glass capillaries is discussed. Several techniques described in the literature are compared and for some critical points, new improved methods are advanced. Full details are given of optimised procedures yielding good results with every possible stationary phase. As an example, Table II mentions efficiencies of 3800 plates m−1 for OV-17 and of 1850 plates m−1 for OF-1, which hitherto was an “impossible” phase in (GC)2 (proposed abbreviation for glass capillary gas chromatography).
70 citations
TL;DR: 32P-Labeled RNA or an oligonucleotide is hydrolyzed to 3′-mononucleotides by means of a crude preparation containing ribonucleases T1 and T2 by a very fast and simple method that requires less than 50 dpm per analysis.
67 citations
TL;DR: In this article, two experimental fields were studied in terms of their soil microbial and biochemical characteristics in relation to soil management practice and crop yields, and it was shown that the yields of winter wheat were related positively to phosphatase activity while the sugarbeet yields were related negatively to soil urease activity.
Abstract: From 1969 to 1974, two experimental fields were studied in terms of their soil microbial and biochemical characteristics in relation to soil management practice and crop yields. Of the various microbial and biochemical properties measured soil phosphatase, saccharase, β-glucosidase and urease activities, N mineralization and soil respiration were found valuable to characterize the soils. These characteristics increased with increasing soil organic matter, clay and CaCO 3 content. They also revealed a strong effect of organic fertilization. Multiple regression analyses indicated that the alkalinity and the humus content of the soil largely determined the magnitude of these characteristics. The regression analyses also showed that the yields of winter wheat were related positively to phosphatase activity while the sugarbeet yields were related negatively to soil urease activity.
67 citations
TL;DR: By ‘H and 13C NMR the preferential conformation of Met-enkephalin in DMSOd6 solution is studied, in favour of a folded conformation bearing a structural analogy between morphine and the N-terminal part of the peptide.
59 citations
TL;DR: Seven patients with postfacial palsy contracture and mass contractions were investigated electrophysiologically and in 3 patients the early blink reflex showed an unusually high amplitude, which can be attributed to enhanced excitability of facial motor neurons.
Abstract: Seven patients with postfacial palsy contracture and mass contractions were investigated electrophysiologically. In 3 patients the early blink reflex showed an unusually high amplitude, which can be attributed to enhanced excitability of facial motor neurons. In 5 patients the early blink reflex had acquired a crossed character. It is assumed that changes in organization of the facial nucleus contribute to the altered function of reinnervated facial muscles.
56 citations
TL;DR: Since in nature spawning occurs at temperatures inferior to 20°C, lead will probably not drastically decrease the potential recruitment of mussel spat in the littoral populations of the northern Adriatic Sea, where the salinity of the water is relatively stable.
Abstract: Combined effects of lead, salinity and temperature on the embryonic development of the mussel Mytilus galloprovincialis Lmk. were studied under laboratory conditions. The basic experimental design was a 4x6 factorial experiment using 4 lead concentrations (100, 250, 500 and 1000 ppb Pb2+) and 6 salinity levels (from 25 to 37.5‰ with 2.5‰ intervals). These factorial designs were carried out at three constant temperatures (150, 17.50 and 20°C). The statistical analysis indicated that salinity changes have more effect on the embryonic development than temperature. Optimal development was observed at 34.8‰ and 15.6°C, which is in accordance with observations in the field. The effect of lead was mininal in optimal salinity and temperature conditions. The deleterious effect of lead on the embryonic development was especially conspicuous at 20°C. Since in nature spawning occurs at temperatures inferior to 20°C, lead will probably not drastically decrease the potential recruitment of mussel spat in the littoral populations of the northern Adriatic Sea, where the salinity of the water is relatively stable. Under experimental conditions, lead caused a delay or inhibition of the embryonic development with the occurrence of a large number of abnormal larvae.
53 citations
TL;DR: The elemental composition of aerosol particles collected at 5220 meters altitude from Chacaltaya Mountain, Bolivia, in the eastern cordillera of the altiplano, has been determined by X-ray, neutron activation and atomic absorption techniques as discussed by the authors.
TL;DR: 22 species of Cladocera and 14 species of Copepoda are reported, mainly from Kathmandu valley, Central Nepal and some from high-altitude lakes in the Khumbu area, East Nepal, and neither can, however, be named due to inadequate material.
Abstract: 22 species of Cladocera and 14 species of Copepoda are reported, mainly from Kathmandu valley, Central Nepal and some from high-altitude lakes in the Khumbu area, East Nepal. Two species are new to science; neither can, however, be named due to inadequate material. The relation between Macrothrix laticornis (Jurine, 1820), M. spinosa King, 1853 and M. goeldii Richard, 1897 is discussed; M. goeldii is set as synonym to M. spinosa; new morphological criteria, permetting a separation to M. laticornis and M. spinosa, are given. Some biogeographical aspects of the fauna encountered are: 1) among Copepoda two calanoids of oriental origin and one of supposed palaearctic origin reach Kathmandu valley; all other Copepoda are circumtropical or cosmopolite species; no oriental Cyclopoida were found; 2) at higher altitudes, no Cyclopoida were found, and the Calanoida were endemic species of the palaearctic genus Arctodiaptomus; 3) no oriental Cladocera were found in Kathmandu valley; the majority of species were cosmopolitan, the remainder circumtropical; 4) at high altitudes, endemic species of palaearctic genera exist next to a set of cosmopolitans.
TL;DR: A balance sheet has been drawn up which suggests that membrane-bound dopamine β-hydroxylase lost from the large noradrenergic vesicles upon stimulation is almost quantitatively recovered in the small norad Renaline storage particles.
TL;DR: Serum protein binding of phenylbutazone has been measured in the rat, guinea pig, cat, rabbit and dog, and the influence on it of renal failure induced by uranyl nitrate injection has been studied; in all species a clearcut decrease was observed after the occurrence of kidneys failure.
Abstract: Serum protein binding of phenylbutazone has been measured in the rat, guinea pig, cat, rabbit and dog, and the influence on it of renal failure induced by uranyl nitrate injection has been studied. In all species a clearcut decrease in binding was observed after the occurrence of renal failure; the time course of the fall in binding correlated well with development of renal failure. In further experiments, serum protein binding of two acidic drugs (phenylbutazone, warfarin), two basic drugs (papaverine, quinidine) and one neutral drug (digitoxin) was studied in rabbits with experimental renal failure, and the results compared with those obtained in patients with acute renal failure. In the rabbits, a decrease in the binding of phenylbutazone, warfarin, papaverine and quinidine was found, whereas protein binding of digitoxin was unchanged. In man, there was a definite fall in protein binding of phenylbutazone and digitoxin, a small decrease for warfarin and papaverine, and a slight increase for quinidine.
TL;DR: In this article, the plasma levels of thioridazine and four of its metabolites were determined in a series of fifteen young acute schizophrenics and the apparent volume of distribution and half life were calculated.
Abstract: Plasma levels of thioridazine and four of its metabolites were determined in a series of fifteen young acute schizophrenics. Consistent individually different metabolic patterns were detected in a group of patients who had the same value for the sum of thioridazine plus metabolites. The apparent volume of distribution and half life were calculated. Clinical evolution tended to correlate best with the level of mesoridazine.
TL;DR: In this paper, the analysis of proton nmr spectra at 300 MHz in C 6 D 6 and in CDCl 3 of the divalent cation ionophore A23187 and its magnesium salt is reported and discussed in terms of configurational and conformational behaviour.
TL;DR: In vivo experiments with KS14CN-treated rats gave good agreement between the analytical results and the amount of thiocyanate determined by isotope dilution, which was +/-5%; the recoveries were over 90%.
TL;DR: The effect of intramammary infusion of Escherichia coli endotoxin upon mammary blood flow was studied in lactating goats and cows, accompanied by a significant increase in mammaryBlood flow, characterized by 2 conspicuous peaks.
Abstract: The effect of intramammary infusion of Escherichia coli endotoxin upon mammary blood flow was studied in lactating goats and cows. Blood flow was recorded by means of an electromagnetic flow probe chronically implanted around one mammary artery. Endotoxin mastatis was always accompanied by a significant increase in mammary blood flow, characterized by 2 conspicuous peaks. The flow returned to control values by the thirteenth hour after infusion. Other symptoms of acute mastitis were: fever, increased heart rate, swelling, heat and pain of the gland, increased chloride and total cell count in milk.
TL;DR: Dopamine was administered intravenously and/or intra‐aortically, either as a bolus injection of 4 or 16 μg/kg, or as a continuous infusion of 4, 8, 16 or 32 μg kg−1 min−1.
Abstract: 1 The dopamine-induced neurogenic vasodilation, previously described in the isolated perfused hindleg of the dog, has been studied in anaesthetized dogs with intact circulation in the hindleg. Dopamine was administered intravenously and/or intra-aortically, either as a bolus injection of 4 or 1l mug/kg, or as a continuous infusion of 4, 8, 16 or 32 mug kg-1 min-1. 2 Dopamine, given as a bolus injection or by infusion reversibly inhibited synaptic transmission in the paravertebral lumbar ganglia, studied with preganglionic stimulation at 1Hz. The inhibitory effect decreased gradually when the frequency of stimulation was increased to 16 Hz. The inhibition by dopamine was also present when spontaneous postganglionic activity was recorded. These effects were more pronounced on intra-aortic than on intravenous administration of dopamine. 3 In about half of the animals studied, injection or infusion of dopamine elicited a decrease of vascular resistance in the innervated femoral artery, whereas systemic blood pressure either did not change or decreased. In the denervated femoral artery, an increase in vascular resistance was alway observed. 4 The decrease in femoral vascular resistance was considered to correspond with neurogenic vasodilation caused by paravertebral ganglionic inhibition since (i) it only occurred in the innervated hindleg, (ii) blood pressure did not rise, (iii) this decrease was insensitive to atropine or propranolol and (iv) it was blocked by small doses of haloperidol. When hypovolemic shock was produced, the incidence of the neurogenic decrease of vascular resistance was smaller. 5 Dopamine also increased renal blood flow. This increase was not reduced by the occurrence of the neurogenic vasodilation in the inervated femoral artery. 6 These results are consistent with the idea that the dopamine-induced neurogenic vasodilation, originally described in the isolated perfused hindleg of the dog, also occurs when the circulation to the hindleg is intact. This suggests that, in the dog, also occurs when the circulation to the hindleg is intact. This suggests that, in the dog. the inhibitory effect of dopamine on sympathetic ganglia modulates its peripheral vasoconstrictor effects. In hypovolemic shock, where sympathetic nervous activity is high, the inhibitory effect of dopamine on sympathetic ganglia disappears and its direct vasoconstrictor effect on the vessels dominates.
TL;DR: The spectral sensitivity curves of the affected retinal areas were found to be unevenly lowered in juvenile macular degeneration and in progressive cone dystrophies, in central serous retinopathy, in some cases of peripheral pigmentary Retinopathy and in some Cases of optic nerve disease.
Abstract: Energetical achromatic increment thresholds on a white background of 10 cd.m−2 were determined at 5 eccentricities by means of 8 interference filters in corporated to a calibrated Tubingen perimeter.
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01 Jan 1977TL;DR: Sulfur-containing polymers vary from highly reactive to chemically inert substances; they can have high softening points or be viscous oils, be thermally stable or not.
Abstract: Owing to the fact that sulfur can exist in different oxidation states and that in each oxidation state it can form different functions, there exist many different sulfur-containing chemical functions with a widespread array of chemical and physical properties. Consequently, sulfur-containing polymers vary from highly reactive to chemically inert substances; they can have high softening points or be viscous oils, be thermally stable or not. Some of these polymers have found commercial applications, others are of academic interest.
TL;DR: The segregation along the horizontal space dimension of the niche has been investigated in six copepod species occurring together in a brackish water habitat and all but one species show an aggregated pattern which may be described by a negative binomial distribution.
TL;DR: The results suggest that apomorphine dilates the femoral vasculature by an action on a "dopamine receptor," and the possibility that the receptor is located on sympathetic nerve endings is discussed.
Abstract: Apomorphine, injected into the dog femoral artery in doses of 0.6 microng or higher, produced a marked increase in femoral blood flow, without a change in blood pressure. No increase in flow was produced by comparable doses of dopamine or morphine. After sympathetic denervation or administration of phenoxybenzamine, the apomorphine vasodilatation was either abolished or greatly reduced. When the vascular tone in the denervated hindleg was restored by sympathetic nerve stimulation, the vasodilatory effect of apomorphine often re-established itself; this was not the cases when the vascular tone was restored by an infusion of noradrenaline. The apomorphine vasodilatation was not antagonized by propranolol or atropine. Mepyramine, in doses that antagonize histamine, often inhibited the apomorphine vasodilatation. Haloperidol, injected i.a., antagonized the apomorphine effect without changing the responses to isopropylnoradrenaline, acetylcholine, histamine and and nitroglycerin. Haloperidol blockade was overcome by increasing the dose of apomorphine. These results suggest that apomorphine dilates the femoral vasculature by an action on a "dopamine receptor." The possibility that the receptor is located on sympathetic nerve endings is discussed.
TL;DR: It was concluded that the victim died of a combined endosulfan-alcohol poisoning.
Abstract: Stomach, small intestine contents, “blood, liver, kidney and urine of a 28-years old man, were analyzed for residues of Endosulfan (6, 7, 8, 9, 10, 10-hexachloro-1, 5, 5a, 6, 9, 9a-hexahydro-6, 9-methano-2, 4, 3-benzo(e)dioxathiepin 3-oxide). The analysis results showed the presence of high concentrations of the two endosulfan isomers in all samples. Since also alcohol was present in all the tissues analyzed, it was concluded that the victim died of a combined endosulfan-alcohol poisoning. No other drugs were found.
TL;DR: In this article, the chemical ionization mass spectra of the trimethylsilyl and methylboronate derivatives of some isomeric 2,3-dimethyl-1,4-cyclopentanediols have been determinded using methane and isobutane as reagent gases.
Abstract: The chemical ionization mass spectra of the trimethylsilyl and methylboronate derivatives of some isomeric 2,3-dimethyl-1,4-cyclopentanediols have been determinded using methane and isobutane as reagent gases. The degree of loss of TMSOH or CH3B(OH)2 appears to be strongly dependent upon the stereochemistry of the 2,3-dimethyl-1,4-cyclopentanediol moiety and permits differentiation between the structural isomers. The results obtained from the chemical ionization (isobutane) spectra of the methylboronates are in excellent agreement with those derived from infrared data.
TL;DR: One of the most probable functions of the “reflected layer” is to protect the larva from being damaged by the acid gastric juice during its passage through the host.
Abstract: In Hymenolepis microstoma the formation of calcareous corpuscles involves three different processes: (1) primarily petrification of nucleus of some of the cortical cells, this is being followed by the continuous deposition of minerals in concentric layers in a granular fashion or irregularly by agglomeration of calcareous salts and finally obscuring the protoplasm of the harbouring cells, (2) deposition of calcium in the cytoplasmic “vacuoles” or “vesicles” in a liquid state and later layering of minerals either in concentric rings or in whorls and (3) by regularly or irregularly mineralization in the vesiculated cells which are connected to the excretory canals
TL;DR: Experiments with broken-cell systems, especially with protoplasts and their lysates have been encouraging with respect to the elucidation of β-lactam antibiotic biosynthesis, and nonantibiotic-producing mutants of Penicillium, Cephalosporium, and Streptomyces mutants are gaining importance as potential tools for the elucidated of intermediates and enzymes involved in β- lactam antibiotics synthesis.
Abstract: Publisher Summary This chapter discusses the enzymes involved in β-lactam antibiotic biosynthesis. Experiments with broken-cell systems, especially with protoplasts and their lysates have been encouraging with respect to the elucidation of β-lactam antibiotic biosynthesis. Such systems eliminate permeability barriers, but still give rise, as do all experiments with cell extracts, to modified enzyme activities caused by loss of membrane supports or conformational changes. The availability of cell lysates derived from high-producing strains of Penicillium, Cephalosporium, and Streptomyces used in the fermentation industries would certainly help throw more intense light on this complex problem. Specific mutations that influence the availability of the building blocks influence β-lactam biosynthesis, and can resolve the relationships between primary metabolism and antibiotic synthesis. Nonantibiotic-producing mutants of Penicillium, Cephalosporium, and Streptomyces mutants are gaining importance as potential tools for the elucidation of intermediates and enzymes involved in β-lactam antibiotic synthesis.