Search PubMed⌕ Search

Biomedical subjects

W M Janssen

Publications and source records attributed to W M Janssen.

28 records · Page 2Linked to original sources
PubMed1991

Short TI short TR inversion recovery imaging using reduced flip angles.

In this paper the effects of reducing the flip angle of the 90-degree observation pulse in inversion recovery imaging are described and analyzed. When incorporated in an IR sequence with a short inversion time (STIR), reduction to the 90-degree pulse allows a significant shortening of the repetition time without loss in contrast, although at the expense of some signal/noise. The generalized STIR sequence thus combines the previously reported advantages of a conventional STIR sequence--suppression of ghost artifacts from abdominal wall movement, suppression of chemical shift and boundary artifacts, additive effects of N(H), T1 and T2 on image contrast--with reduced power deposition and the advantages resulting from shorter repetition times, viz, single heart-beat triggering, increased number of signal averages for suppression of motion artifacts, acquisition of interleaved contiguous slices without cross-talk or considerable time savings when the number of required slices is limited. The proposed method is demonstrated and experimentally verified by imaging experiments on phantoms and human subjects. In principle the method is applicable to all cases where STIR imaging has been proven to be successful.

Brain↗
PubMed1991

Limiting amino acids in low protein maize-soyabean meal diets fed to broiler chicks from 3 to 7 weeks of age.

1. An experiment with separately housed male and female broiler chicks was carried out during the period of 3 to 7 weeks of age to determine the limiting amino acids (AA) in a low protein maize-soyabean meal diet. Chicks were fed on diets containing 170, 180, 190 and 200 g crude protein (CP)/kg with or without combined additions of L-threonine (Thr), L-tryptophan (Trp) and L-arginine (Arg) to those in the 180, 190 or 200 g CP/kg diets and a 170 g CP/kg diet with or without combined additions of Thr, Trp, Arg, L-isoleucine (Ile), L-leucine (Leu) and L-valine (Val) to those in the 190 g CP/kg diet. The diets were iso-energetic and contained the same concentrations of lysine (Lys) and sulphur-containing amino acids. 2. Decreasing the dietary CP had a significantly negative effect on performance. 3. No significant effects on performance were found when diets with 180 and 190 g CP/kg were supplemented with Thr, Trp and Arg to those in the 200 g CP/kg diet. 4. There were no significant differences in performance between the groups fed on the diets with 170, 180 and 190 g CP/kg when the 170 and 180 g CP/kg diets were supplemented with Thr, Trp and Arg to those in the 190 g CP/kg diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1990

European reference method of in vivo determination of metabolisable energy in poultry: reproducibility, effect of age, comparison with predicted values.

1. Apparent metabolisable energy corrected to zero-nitrogen retention (AMEn) was measured using the European reference procedure in 9 European laboratories. Seven pelleted diets were evaluated. AMEn was measured with adult cockerels and young birds. 2. Between-laboratory standard deviations were for dry matter (DM) 12.5 g/kg, gross energy 0.085 MJ/kg DM, Kjeldahl nitrogen 0.768 g/kg DM, AMEn (adults) 0.256 MJ/kg DM, and AMEn (young) 0.337 MJ/kg DM. Corresponding coefficients of variation between laboratories were 1.42, 0.45, 2.15, 1.88 and 2.60% respectively. 3. AMEn values of experimental diets were always significantly lower when measured with young birds. This effect was more pronounced when diets contained added fat. 4. Tallow or soyabean oil were incorporated into two basal diets at 40 g/kg inclusion rate. No significant differences were observed between AMEn values of either diet with adults or young birds, suggesting that AMEn energy values of these fats are indistinguishable at this inclusion rate. 5. Similar AMEn values were obtained in young birds by estimating nitrogen accretion, either by the difference between intake and excreta nitrogen or by measuring body weight gain. Determined AMEn values were very similar to those predicted using three different regression equations.

Age Factors↗
PubMed1989

Atrial natriuretic peptide-induced decreases in renal blood flow in man: implications for the natriuretic mechanism.

1. We studied the effect of a low-dose infusion of atrial natriuretic peptide (ANP) on renal blood flow in healthy volunteers. We additionally investigated the effect of ANP on renal haemodynamic function and on urinary sodium excretion. 2. ANP induced a rise in packed cell volume and a slight increase (but no decrease) in the renal extraction of hippuran. These changes did not offset the observed fall in effective renal plasma flow. Renal blood flow thus truly decreased and renal vascular resistance increased. 3. ANP induced an increase in glomerular filtration rate and a decrease in urinary osmolality in the first hour of ANP infusion, whereas absolute and fractional sodium excretion increased significantly only in the second hour of ANP infusion. The decrease in urinary osmolality in the first hour of ANP infusion correlated with the induced natriuresis. The changes in urinary osmolality and sodium excretion both correlated with the changes in plasma ANP levels. 4. These data indicate that ANP may cause a decrease in renal blood flow and an increase of renal vascular resistance in man. Our results suggest a role for ANP-induced (intra)renal haemodynamic changes in ANP-induced natriuresis, possibly through an increase in the filtered load of sodium into a washed-out medullary interstitium.

Adult↗
PubMed1989

Antihypertensive effect of a 5-day infusion of atrial natriuretic factor in humans.

Atrial natriuretic factor was infused in a low dose (0.2 microgram/min) during 5 days in six patients with essential hypertension. Atrial natriuretic factor infusion caused plasma levels of atrial natriuretic factor to increase from 49 +/- 10 to 106 +/- 19 pg/ml. Within 4 hours after the start of the atrial natriuretic factor infusion, urinary sodium excretion increased in all subjects. Sodium balance was regained after 24 hours with a net loss of 72.3 +/- 14.6 mmol. However, systolic as well as diastolic blood pressure started to decrease gradually in all subjects only after 12 hours of atrial natriuretic factor infusion, reaching a stable level after 36 hours with a decrease of 11.5 +/- 1.5% and 10.3 +/- 0.8%, respectively. Heart rate increased in parallel by 12.6 +/- 3.1%. Hematocrit rose 7.1 +/- 2.3%. After cessation of atrial natriuretic factor infusion, plasma atrial natriuretic factor levels, sodium balance, and hematocrit returned to baseline within 24 hours, whereas blood pressure slowly returned toward baseline values over 3 days. These data show that chronic atrial natriuretic factor infusion in patients with essential hypertension causes a negative sodium balance and a rise in hematocrit, followed by a smooth decrease in blood pressure with a rise in heart rate until a new equilibrium is reached after approximately 2 days. Thus, atrial natriuretic factor in low doses appears intimately involved in the regulation of sodium balance and blood pressure in humans. Moreover, these data suggest that atrial natriuretic factor-like substances will eventually become useful antihypertensive drugs.

Antihypertensive Agents↗
PubMed1986

[The use of flocculation sludge in poultry feed. Chemical and microbiological composition].

For the purpose of making inventories, the chemical and microbiological composition of samples of flocculated sludge of poultry, pig and cattle-stock slaughter-houses were examined. This was required to study the possibilities of using flocculated sludge as raw material in animal feed. Chemical studies showed that the dry matter (dm) levels of the various specimens of sludge varied markedly. (Broiler sludge 7.1% of dm, pig sludge 7.5%, cattle-stock sludge 5.5% and laying-hen sludge 13.3%). Broiler- and laying-hen sludge contained more crude fat than did the other samples of sludge. Measured by the concentrations of lysine, methionine and cystine, the sludge product was most similar to the protein of meal-and-bone meal and soy-bean meal. The iron content of almost all samples examined was very high. In view of the current standards for concentrations of metal in complete animal feeds, the concentrations of iron and lead will have to be taken into account in using this sludge product. The proportion of total polymers in the fat fractions of samples of sludge varied from 2.4% to 39.2%, less than 10% only being observed in two samples. The microbiological composition of broiler and pig sludge did not differ. Both the total aerobic bacterial count and the number of Enterobacteriaceae, Escherichia coli and Salmonella were found to be high. Species of Campylobacter were not isolated; however, a number of samples were found to be positive for adenovirus. Prior to deciding to use flocculated sludge in livestock feeding, the product will have to undergo thorough decontamination.

Animal Feed↗
PubMed1986

Effect of human atrial natriuretic peptide on blood pressure after sodium depletion in essential hypertension.

Human atrial natriuretic peptide was infused over four hours in three patients with essential hypertension. When the patients had a sodium intake of 200 mmol (mEq) daily an infusion of 0.5 micrograms atrial natriuretic peptide/min caused no significant change in blood pressure, whereas an infusion of 1.0 micrograms/min caused a gradual decrease in blood pressure and an increase in heart rate. After two to three hours of infusion with the higher dose two patients showed a sudden decrease in heart rate, with symptomatic hypotension. When the same patients had an intake of 50 mmol sodium daily their blood pressure was more sensitive to infusion of atrial natriuretic peptide; one patient again developed symptomatic hypotension, this time during an infusion of 0.5 micrograms/min. During all infusions distinct natriuresis occurred irrespective of whether blood pressure was affected. Prolonged, relatively low dose infusions of atrial natriuretic peptide can cause unwanted symptomatic hypotension. The effect on blood pressure is enhanced after sodium depletion, and blood pressure should be monitored carefully during longer infusions of atrial natriuretic peptide in patients with essential hypertension.

Adult↗
PubMedDate not supplied

Bioresorption of ceramic strontium-85-labeled calcium phosphate implants in dog femora. A pilot study to quantitate bioresorption of ceramic implants of hydroxyapatite and tricalcium orthophosphate in vivo.

Ceramic hydroxyapatite and tricalcium orthophosphate were radioactively labeled with their strontium-85 analogs. Porous blocks of these materials (dimensions 2.5 X 1.25 X 0.5 cm) were implanted into surgically created defects in dog femora. The fate of the implants was studied by roentgenography, radioactivity measurements, histology, and microradiography. The radioactivity over the implant site was followed for 22 weeks. Implants were retrieved after 20-25 and 50-55 weeks. Hydroxyapatite implants were not affected by biodegradation processes, while tricalcium orthophosphate implants were subject to extensive bioresorption (25%-30% in 22 weeks). Resorption debris from tricalcium orthophosphate implants was found in mononuclear phagocytes and multinuclear osteoclastlike cells. The supposition is that tricalcium orthophosphate is transformed into hydroxyapatite in a physiologic environment. Labeling of ceramic calcium phosphate implants with strontium-85 analogs offers an adequate technique to quantitate bioresorption in vivo.

Animals↗