Showing papers by "Ghent University published in 1984"

Leydig Cell Function in Normal Men: Effect of Age, Life-Style, Residence, Diet, and Activity*

Abstract: The decrease of plasma testosterone (T) in old age may be inherent to the aging process or secondary to environmental factors such as stress, minor illness, physical inactivity, etc. We determined plasma T, apparent free T, and gonadotropin levels in healthy men (n = 71), aged 26–90 yr living under identical conditions, i.e. as monks in a monastery. We found a highly significant age-dependent decrease in morning and mean 24-h T and apparent free T levels and a moderate increase in gonadotropin levels; the nycthemeral variation in plasma levels was, however, decreased in the elderly. In a larger group of healthy normal men (n = 302), smokers had higher T levels than nonsmokers in all age groups; values were similar whether older men lived in a geriatric institution or in their home. Diet had no discernable effect on T levels, whereas in young men plasma T levels decreased more in response to stress such as hypoglycemia or myocardial infarction than in elderly subjects. Moderate physical training i...

Activation of a NADPH oxidase from horse polymorphonuclear leukocytes in a cell-free system.

Abstract: A postnuclear cell fraction from resting horse polymorphonuclear (PMN) leukocytes incubated with fatty acid-salt ions such as oleate or linoleate generated a NADPH-dependent oxygen consumption and superoxide production. Oxidative activity was negligible or absent in the postnuclear fraction from mononuclear leukocytes, p-chloromercuribenzene sulfonic acid-treated granulocytes, and granulocytes from a patient with chronic granulomatous disease. Although consistently associated with the membrane fraction from resting PMN leukocytes, the superoxide-generating activity was shown to be dependent on a thus far unknown cytosolic constituent. The apparent Km's for NADPH and NADH (66 and 1,600 microM, respectively), the pH optimum for the reaction (7.0), the cyanide insensitivity, and transient nature of the reaction together with the stoichiometric relationship between oxygen uptake and NADPH oxidation led to the conclusion that in the presence of cytosol a cell-free latent respiratory burst oxidase can be converted into an active enzyme by interaction with oleate micelles.

A simplified system for biotyping Staphylococcus aureus strains isolated from different animal species

Abstract: A biotyping system for Staphylococcus aureus strains is proposed which is a simplified version of biotyping procedures described in the literature It differentiates Staph aureus strains from man and animals into host-specific ecovars and biotypes which are not host-specific With the help of tests for beta-haemolysin, staphylokinase , coagulation of bovine plasma and the crystal-violet reaction, the origin of many but not all Staph aureus strains can be determined: 604 of 809 strains from man, poultry, cattle, pigs, goats, rabbits and foods could be alloted to four ecovars which are typically associated with man, poultry, sheep and goats and cattle The other strains belonged to five non-host specific biotypes

The complete nucleotide sequence of the TL-DNA of the Agrobacterium tumefaciens plasmid pTiAch5

Abstract: We have determined the complete primary structure (13 637 bp) of the TL-region of Agrobacterium tumefaciens octopine plasmid pTiAch5 . This sequence comprises two small direct repeats which flank the TL-region at each extremity and are involved in the transfer and/or integration of this DNA segment in plants. TL-DNA specifies eight open-reading frames corresponding to experimentally identified transcripts in crown gall tumor tissue. The eight coding regions are not interrupted by intervening sequences and are separated from each other by AT-rich regions. Potential transcriptional control signals upstream of the 5' and 3' ends of all the transcribed regions resemble typical eukaryotic signals: (i) transcriptional initiation signals ('TATA' or Goldberg- Hogness box) are present upstream to the presumed translational start codons; (ii) ' CCAAT ' sequences are present upstream of the proposed 'TATA' box; (iii) polyadenylation signals are present in the 3'-untranslated regions. Furthermore, no Shine-Dalgarno sequences are present upstream of the presumed translational start codons.

Long-term clinical study of porcelain-fused-to-gold restorations

Abstract: S everal years ago porcelain-fused-to-gold (PFG) restorations were introduced to fixed partial denture prosthodontics. The new materials and related clinical techniques represent an important step toward an optimal solution to many problems in fixed prosthodontics, especially in the anterior region. The method combines the esthetic qualities of porcelain with the strength, accuracy, and marginal adaptation of the metal. Several studies have been published on the clinical and material aspects of PFG restorations.‘-6 The chemical characteristics of the porcelain-to-gold bonding and the possible defects caused by inadequate laboratory procedures also have been reported.‘-‘” Much attention has been paid to the strength of the bonding between gold and porcelain.“.?’ Hobo and Shillingburg2r described the specific preparation techniques and the coping design. In histologic studies others showed the positive clinical tolerance of the marginal periodontium to the porcelain.?“‘“’ As far as we know, only one long-term clinical study of PFG restorations has been published.3’ The purposes of this clinical long-term survey were to examine the frequency of mechanical failures of PFG restorations and to provide some suggestions for their possible prevention. -

Nitrite: a key compound in N loss processes under acid conditions?

Abstract: Nitrite is very important in N transformation processes because it is an intermediate product in the aerobic nitrification as well as in the anaerobic denitrification process. Under soil conditions whereby aerobic and anaerobic zones are close to each other, the mobile nitrite can be a link between both N transformation processes. Because of its low stability in acid conditions, nitrite can be a key compound in N loss processes.

A brief summary of the bounds on the solution of the algebraic matrix equations in control theory

Abstract: In recent years, several bounds have been reported for different measures of the ‘ extent’ or ‘ size ’ of the solution of the algebraic matrix equations arising in control theory, such as the Riccati equation and the Lyapunov equation. This paper collects the bounds that have been presented up to now and summarizes them in an unified form. This will prove particularly convenient for those wishing to get a ready estimate of the solution while solving the equations numerically or to develop theoretical results that rely on these bounds.

Mass culture of microalgae in aquaculture systems: Progress and constraints

Abstract: For several decades considerable efforts have been made to promote the production and use of microalgae as direct food for man. However, the high costs of production and harvesting, and the potential rejection of algal food by consumers for toxicological reasons or concerns, have so far been major obstacles to a real breakthrough (Soeder, 1980). As a result, human consumption of microalgae is limited at present to expensive ‘health’ foods. Hope is rising, however, that in the near future inexpensive Spirulina grown on wastes will be successfully used in human nutrition (Fox, 1980; Olguin & Vigueras, 1981; Becker & Venkataraman, 1982).

Androgen plasma levels in male diabetics

Abstract: Plasma level of androgens were studied in 47 normal male controls (20-50 yr-old; mean age 38 yr) and in a group of forty-one male diabetics (23-55 yr-old; mean age: 37.5 yr). Of these 36 showed type II and 5 type I diabetes. The results showed that while the mean basal plasma LH was unchanged, there was a decrease in testosterone levels in the diabetics. Moreover, testosterone binding globulin (TeBG) capacity appeared to be augmented and, as a consequence, the apparent free testosterone concentration (AFTC) was markedly decreased. It is interesting to note that the anomalies in androgen secretion observed are rather similar to those found in elderly man and could play some role (with other factors) in the onset of the frequent sexual disturbances in male diabetics.

Recursive cyclotomic factorization--A new algorithm for calculating the discrete Fourier transform

Abstract: In this paper, a new recursive algorithm for calculating the discrete Fourier transformation is presented. This new, so-called recursive cyclotomic factorization algorithm (RCFA) is more efficient than the fast Fourier transformation (FFT) algorithm. Moreover, due to its recursive nature, the RCFA can also be easily implemented, using only a limited number of different computation cells.

The evaluation of “reversed phase” high-performance liquid chromatography packing materials

Abstract: For the evaluation of reversed phase packing materials a mixture of acetylacetone, I-nitronaphthalene and naphthalene is proposed. This will reveal the usual optimum kinetic chromatographic parameters (the naphthalene peak), the degree of activity or endcapping status of the column (the ratio of the I-nitronaphthalene and naphthalene retention times) and trace metal activity (the shape and intensity of the acetylacetone peak).

The Estimation of Ultrametric and Path Length Trees from Rectangular Proximity Data

Abstract: A least-squares algorithm for fitting ultrametric and path length or additive trees to two-way, two-mode proximity data is presented. The algorithm utilizes a penalty function to enforce the ultrametric inequality generalized for asymmetric, and generally rectangular (rather than square) proximity matrices in estimating an ultrametric tree. This stage is used in an alternating leastsquares fashion with closed-form formulas for estimating path length constants for deriving path length trees. The algorithm is evaluated via two Monte Carlo studies. Examples of fitting ultrametric and path length trees are presented.

The estimation of ultrametric and path length trees from rectangular proximity data

Abstract: A least-squares algorithm for fitting ultrametric and path length or additive trees to two-way, two-mode proximity data is presented. The algorithm utilizes a penalty function to enforce the ultrametric inequality generalized for asymmetric, and generally rectangular (rather than square) proximity matrices in estimating an ultrametric tree. This stage is used in an alternating least-squares fashion with closed-form formulas for estimating path length constants for deriving path length trees. The algorithm is evaluated via two Monte Carlo studies. Examples of fitting ultrametric and path length trees are presented.

Dielectric properties of softwood species at microwave frequencies

Abstract: Dielectric measurements at 3 GHz were made for three softwoods, European pine, spruce and hemlock. The longitudinal, radial and tangential grain directions of the wood were considered as well as moisture contents ranging from 6% to 35%. The positive effect of the moisture content on the loss factor e″ illustrates the selectivity of microwave drying techniques, while the observations also show that the longitudinal dielectric properties are substantially higher than the transverse ones. The specific effect of the wood species on the dielectric behaviour has to be ascribed mainly to those intrinsic characteristics of the species which influence the sorptive capacity of the wood.

Influence of MgO addition on mineralogy of iron ore sinter

Abstract: The influence of MgO addition on sinter mineralogy was studied on sinters produced in a laboratory installation, with a wide range of MgO/CaO ratios at several basicity indices [B = (CaO + MgO)/ (SiO2 + A12O3)] between 0.7 to 1.9. The most striking influence of MgO is the suppression of hematite and Ca-ferrite phases and the increase in magnetite phase. In general, MgO favors the formation of glass and suppresses the precipitation of dicalcium silicates in favor of Ca-Fe-Mg olivines and pyroxenes. Microprobe studies revealed that most of the Mg was picked up by the magnetite phase to form mixed spinels of type (Fe, Mg)O · Fe2O3. At a constant basicity index, increased replacement of CaO by MgO also led to increased participation of FeO in the slag formation process, thus increasing the overall FeO content of sinter. A mechanism for the formation of mixed spinels has been proposed. The effect on various sinter properties resulting due to change in sinter mineralogy has been outlined.

A Fundamental Lower Bound on the Performance of Practical Joint Carrier and Bit Synchronizers

Abstract: In this paper we derive a fundamental lower bound on the linearized mean-square phase and time delay errors resulting from a practical synchronizer operating on a carrier-modulated PAM waveform which is corrupted by stationary Gaussian noise. Our bound applies to a large class of synchronizers and, unlike the linearized performance itself, it is easily evaluated from the modulation format, the baseband PAM pulse shape, the additive noise spectrum, and the synchronizer's closedloop transfer function matrix.

Observations on the in vitro sensitivity and resistance of Gram positive intestinal bacteria of farm animals to growth promoting antimicrobial agents

Abstract: Dutta, G.N. Devriese, L.A. 1984. Observations on the in vitro sensitivity and resistance of Gram positive intestinal bacteria of farm animals to growth promoting antimicrobial agents. Journal of Applied Bacteriology56, 117–123. Results of qualitative in vitro sensitivity tests made with growth promoting antimicrobial agents on clostridia, lactobacilli and enteric streptococci, isolated from caeca of pigs, cattle and poultry, are summarized. The compounds were active in vitro against most of the 19 bacterial species studied. However, their activity spectra differed markedly. Only four bacterial species were naturally sensitive to all agents. The natural resistances, typical for many species and compounds, could be differentiated from the acquired resistances found with all growth promotors except avoparcin. High resistance and complex patterns of cross-resistance involving one or more of the macrolide, lincosamide and streptogramin antibiotics were detected.