Studies on the absorption of sodium and chloride from the rumen of sheep

The net absorption of Na and Cl from the temporarily isolated rumen of sheep was studied using an artificial ruminal fluid with different Na and K and constant Cl concentrations. The net absorption of Na and Cl was linearly correlated. The net absorption of Cl was abolished and a small net secretion was observed when no sodium was in the artificial rumen fluid. The net absorption of Na was significantly reduced under chloride free conditions. It is concluded that the active transport of Na and Cl is coupled. The mechanism of an Na-Cl cotransport can not be deduced from these studies.

Effect of intraruminal sodium and potassium concentrations and of the transmural potential difference on magnesium absorption from the temporarily isolated rumen of sheep

The net absorption of magnesium from the temporarily isolated and washed reticulo-rumen of sheep has been studied using buffer solutions with different sodium, potassium and chloride concentrations. An increased potassium concentration led to an increased potential difference (p.d.) and a decreased magnesium absorption. The exchange of chloride in the buffer solutions with sulphate (at constant sodium and potassium concentrations) caused a significant increase of the p.d. and again a reduced net magnesium absorption indicating that the p.d. is an important factor associated with decreased net magnesium absorption. The replacement of sodium with lithium (at constant potassium concentrations) did not influence the net magnesium absorption. It is concluded that the low apparent availability of magnesium after an oral load of potassium is mainly caused by the high transmural potential difference across the rumen wall under such feeding conditions. However, the presented data cannot rule out an effect of potassium per se independent of the effect of the p.d.

The effect of dinitrophenol on magnesium transport across an isolated preparation of sheep rumen epithelium

Mg transport across an isolated preparation of sheep rumen epithelium was studied in vitro. The efflux (flux from the mucosal side to serosal side) and the influx (flux with serosal to mucosal side) were estimated with 28Mg. Under physiological conditions a significant net efflux of Mg was observed, in which the unidirectional efflux was seven to eight times that of the influx. In experiments where ATP synthesis was blocked by the addition of dinitrophenol, Mg efflux was reduced to that of the influx. These observations support the conclusion that Mg absorption across the rumen wall of the sheep is an active process.

Saturation kinetics of magnesium efflux across the rumen wall in heifers

1. Absorption of magnesium from the temporarily-isolated, emptied and washed rumen of four 10-12-month-old heifers was measured at five different Mg concentrations (2.5, 5.0, 7.5, 12.5 and 20 mmol/l). 2. Net absorption of Mg was observed at all concentrations. Saturation occurred at a concentration of 12.5 mmol Mg/l. 3. Using an Eadie-Hofstee plot, the Michaelis-Menten constant (Km; 11.43 mmol/l) and maximal efflux (Vmax; 120.3 mumol/min) were estimated. 4. The phenomenon of saturation supports the assumption that Mg transport across the rumen wall of heifers is an active process.

[Postoperative moving field therapy of the thoracic wall with high energy electrons]

With regard to the moving field irradiation of the thoracic wall with electrons, the dependence of the surface dose from the depth of the rotation axis, which had been determined theoretically and under simplifying hypotheses, is checked by phantom measurements. There is conformity between measurement and calculation if the moving field irradiation extends over an angular dimension which contains also fully the contribution of the electrons scattered in the collimated region. The consequences for the shielding of the environment of the irradiated region are discussed. The admissible deviations of the thorax from a circular cylindric form for given maximum dose differences can be taken from the calculations. A nearly constant surface dose can be reached despite differences of the thorax form, if the scattering of electrons perpendicular to the rotation axis comes from divergency centres whose distance from the rotation axis corresponds to the double length of the average thorax radius.

Cytotoxic estrogens in hormone receptive tumors

A high proportion of human mammary cancers contain a measurable amount of estrogen receptors. The presence of estrogen receptors correlates well with the response of patients to endocrine therapy, but not with their response to chemotherapy. However, receptor-mediated chemotherapy should result in more selective and efficient treatment of receptor-positive tumors. Several agents containing an estrogenic and a cytotoxic moiety have been synthesized in the past. It is not surprising that the affinity of these compounds for the estradiol receptor is very low, since most of them were synthesized before our knowledge of hormone receptor mechanisms. An international workshop on cytotoxic estrogens was held on September 27-28, 1979, in Diepenbeek, Belgium, to celebrate the opening of the Dr. L. Willems-Instituut. The purpose of the workshop was to determine the structural requirements for binding to the estrogen receptor and to obtain a consensus on screening techniques for selecting potential drugs of this type.

Thiamin balance in the gastrointestinal tract of sheep

Six 5- to 6-month-old sheep fitted with rumen fistulas and reentrant cannulas in the duodenum and in the ileum were adapted to two dies low in thiamin and containing different percentages of urea nitrogen. The sheep were subjected to seven thiamin balance experiments, with continuous feeding and total collection of duodenal and ideal contents and feces for periods of 6 day each. Thiamin and dry matter were determined in aliquots of collected digesta and feces. Daily thiamin intake was always less than .3 mg, but average daily flow of thiamin into the duodenum was between 1.53 and 3.46 milligrams. Microbial net synthesis of thiamin in the forestomach system was between 1.44 and 3.23 mg/day, so 90 to 96% of thiamin entering the duodenum was of microbial origin. Disappearance of thiamin from the small intestines approximately equaled thiamin net synthesis in the forestomachs, indicating high absorption of microbially produced thiamin. In five experiments, thiamin balance in the large intestines was positive, but no measurements were made of thiamin breakdown within, and absorption from, the large intestines.

Aspects of urea metabolism in ruminants with reference to the goat

In goats and other ruminants, urea functions as a source of nitrogen for protein biosynthesis in the digestive tract. Ammonia can be absorbed in the digestive system when formed in excessive quantitites and enhance formation of urea, or it can be derived from urea of blood plasma when its formation from feed sources is small. Entry rates of urea into plasma may vary from 4 to 80 mumol/min per kg.75 body weight depending on dietary conditions. Urea formation is related to nitrogen intake of which approximately 70% passes into the urea pool of plasma. Irreversible losses of urea of plasma into the digestive tract vary between 10 and 90% depending on the protein to energy ratios of the diet. Entry of urea from plasma into the rumen appears to be a passive process which is sensitive to short-term changes of urea concentrations in plasma. Permeability of ruminal epithelium to urea may be altered by fermentation products of rumen (ammonia, carbon dioxide, volatile fatty acids). The influx of nitrogen into the rumen is related to needs for nitrogen of microbial populations and is associated with changes of renal excretion and tubular reabsorption of urea. Combined gastrointestinal and renal responses exert a synergistic effect on improved utilization of urea of plasma when uptake of dietary nitrogen is limited in goats and other ruminants.

Thermal stability of fatty acid-serum albumin complexes studied by differential scanning calorimetry

Differential scanning calorimetry has been used to study the thermal stability of bovine serum albumin as affected by binding of fatty acids (lauric acid and stearic acid) and sodium dodecyl sulfate (SDS). All the ligands stabilized the protein molecules in a similar manner, but to different levels. A maximum increase in denaturation temperature of 30 degrees C was obtained with lauric acid. The thermograms indicate the presence of several ligand-albumin complexes having different heat stabilities. Variations in pH in 0.9% NaCl affected the heat stability of both ligand-poor and ligand-rich albumin, the former being more sensitive to variations in pH within the physiological range. Variations in NaCl concentration affected the thermal stabilities at neutral pH, expecially at low salt concentrations. While ligand-rich albumin was somewhat destabilized by increasing NaCl concentrations, ligand-poor albumin was strongly stabilized. The potential use of differential scanning calorimetry in ligand-albumin research is discussed.

Magnesium transport by isolated rumen epithelium of sheep

The mechanism of transfer of magnesium across isolated rumen epithelium was studied in vitro using 28Mg. Isolated pieces of rumen epithelium developed a transmural potential difference of 8.2 +/- 2.3 mV, lumen side negative, during the first hour of incubation when mounted between the two halves of an incubation chamber. A significant net transport of magnesium from lumen to blood was measured when the initial concentration of magnesium in the solutions bathing both surfaces of the epithelium was 2.5 mM. Net flux of magnesium took place against an electrical gradient and was dependent on the presence of the transmural potential difference. The process was saturable at magnesium concentrations of about 5 mM and was markedly reduced by lowering the temperature of the bathing solution, by addition of 10(-4) M ouabain and by extending the time of incubation. The findings strongly support the view that magnesium absorption from the rumen is mediated by an active transport process.

[Clinical double-blind study with two different dosages of maprotiline (150 and 225 mg per day) (author's transl)]

Effects and side-effects of 150 mg and 225 mg maprotiline per day were compared by means of a double-blind trial in 20 depressed inpatients. The first 2 days patients received a high initial dosage of 300 mg per day. Patients were examined on days 0, 2, 5, 10, 15, 20, and 30. Symptoms were evaluated by the AMP system and the Hamilton scale for depressions. Laboratory examinations were carried out on days 0, 10, 20, and 30. Exanthemas developed in five patients, three of whom were on the higher dosage. Moreover, the lower dosage caused less fine hand tremor. Coinciding with the beginning of treatment a linear decrease of depressive symptoms was noted. This demonstrates the rapid onset of the antidepressant effect. Moreover, contrary to what has been stated for antidepressants generally, the onset of action was frequently noted well before 10-20 days of treatment. Some patients improved within a few days while others needed more time. The time lag until antidepressants influence depressive symptoms shows pronounced individual differences. No significant difference between the two dosages was found. The profiles show a better antidepressant effect for the higher dosage; however, because of a higher incidence of side-effects on the higher dosage of maprotiline, it cannot be recommended as routine. On the other hand, depressive inpatients should receive a daily dosage of at least 150 mg. Our findings suggest a dose-effect relationship for maprotiline.

Synthesis of ruminal microbial protein and volatile fatty acid production in vitro

Growth of a mixed ruminal population taken from a sheep on a protein-free (all urea) purified diet was estimated by an in vitro fermentation technique including precipitation of microbial protein by trichloracetic acid. Volatile fatty acid production in vitro was determined, and the associated a denosine triphosphate was estimated as moles volatile fatty acids X 2.4. On this basis, the quantity of microbial protein synthesized per mole of adenosine triphosphate increased at higher microbial growth rates.

Comparison of a new antidepressive, lofepramine, with imipramine in a double-blind multicentre trial

Lofepramine, an imipramine derivative, shows lower acute toxicity in animals when compared with desipramine and imipramine. Its anticholinergic effect is less pronounced than that of desipramine. In an open clinical trial lofepramine showed a marked antidepressive action. A double-blind multicenter trial of lofepramine v. imipramine, evaluated by means of the AMP system, showed a remarkable degree of concurrence with regards to the effects of those two products.