Biomedical subjects

K Schümann

Publications and source records attributed to K Schümann.

51 records · Page 3Linked to original sources

PubMed1989

In-vivo inhibition by polycations of small intestinal absorption of methyl alpha-D-glucoside and leucine in the rat.

Polycations are able to inhibit active transport processes in rat small intestine in vitro. Whether this effect can also be confirmed in vivo is the concern of this study. Therefore, the effect of various polycations, e.g., protamine and polylysine, on the absorption of methyl alpha-D-glucoside and leucine was investigated in vivo by single-pass perfusion of rat jejunum. The inhibition of absorption of methyl alpha-D-glucoside and leucine by the polycations was strongly dose dependent. At a substrate concentration of 1 mmol/l a 50% inhibition was achieved with a protamine concentration of 3.2 mg/ml. The inhibition increased as the chain length of the polycation increased. In the presence of protamine the concentration-dependent leucine absorption was reduced at leucine concentrations below 60 mmol/l, but was increased at 100 mmol/l. Absorption of mannitol and 2-deoxy-D-glucose was significantly enhanced by the polycations. These results demonstrate that polycations inhibit active transport and increase passive diffusion processes in the rat small intestine in vivo. In addition, pretreatment of rats with a polycation added to the drinking water impaired the small intestinal absorption of methyl alpha-D-glucoside as subsequently measured by the tissue accumulation technique in vitro. Since polycations are hardly absorbed in the intestine, but do attach to negatively charged groups at the mucosal surface, polycations may be useful to study the influence of these negative groups on the absorption of nutrients and drugs.

Animals↗

PubMed1989

[The role of iron as a deficient element].

Iron is an essential trace element. In its heme-form as well as in its non heme-form it is a part of enzymes and hemoproteins. For a safe and adequate dietary intake 10-18 mg of iron are recommended daily. Frequently, this quantity is not available: approximately 20% of the world population is iron-deficient. In this state the enteral transfer capacity for toxic metals, e.g., Cd and Pb, is increased and the adaptation to physical strain as well as the immunological responses are depressed. Alterations of body iron-stores are almost exclusively balanced by adequate adaptation of the enteral iron-transfer capacity. The mechanism of this adaptation process can neither be satisfactorily explained by the "mucosal block hypothesis", nor by the "mucosal transferrin hypothesis". When the time-course of iron storage and its relation to intestinal iron transfer was investigated after i.v. iron administration to iron-deficient rats, the results indicated that the process of adaptation is located in the intestinal mucosa. Intestinal iron loading is decreased in iron deficiency, whereas the iron transfer into the organism is increased. Further investigation is necessary to find out by which mechanism the iron manages to bypass existing mucosal storage capacity in this situation. The geographical distribution of iron deficiency is influenced by a variety of local factors. Still, the paramount causes of iron-deficiency are unbalanced iron losses and the lack of bioavailable iron in the diet. The bioavailability of non heme iron is influenced by the composition of the diet. The effect of promotors of iron absorption, such as meat, amino acids, polycarbonic acids and ascorbate is opposed by the influence of inhibitors, such as bran, soya products, vegetables and egg-dishes. Iron losses are mainly due to blood losses. Thus, the wide distribution of hookworm diseases in tropical areas contributes significantly to the endemic iron-deficiency in these regions. A more physiological loss of iron is caused by menstruation and pregnancy. In small infants the iron-demand of the organism is increased by rapid growth, which in turn increases the intestinal iron transfer. An increased iron-demand can be balanced by an iron-supplemented diet or by pharmaceutical iron compounds. Acute intoxications can be caused by an overdose of such preparations. The pathophysiology and symptoms of acute iron intoxication are summarized. Their frequency has markedly decreased since "childproof" packaging has been introduced for iron-preparations. To meet the increased iron demand of young children, commercial infant formulas are frequently fortified with iron, preferentially with heme-iron.(ABSTRACT TRUNCATED AT 400 WORDS)

Absorption↗

PubMed1989

Determination of residual erythrocytes in rat tissue homogenates using commercially available anti-red blood cell sera.

A method to determine the residual erythrocyte content in rat tissue homogenates by means of radial immunodiffusion (Mancini et al., 1965) is described. The method makes use of commercially available antisera against rat erythrocytes. Tissues were homogenized after addition of digitonin and applied on Mancini plates. To measure within the linear part of the calibration curve, the tissue homogenates were diluted to concentrations between 0.062% and 2.5% wet weight content, depending on the type of tissue and on the degree of bleeding before the death of the animal. Recovery data of added blood as well as a comparison with results from organ distribution studies with 59Fe-labeled erythrocytes demonstrated that this simple method is sufficiently reliable and sensitive. The present procedure is to control experiments in which drug tissue levels (e.g., antibiotics) are to be determined and in which the drug content of residual blood is likely to bias the results to an unknown extent. It can be used as well in organ distribution studies of substances with a high affinity for erythrocytes (e.g., Pb; As in rats). It is possible to individually control the success of procedures without the use of isotopes--such as exsanguination or vascular perfusion--that are performed in order to reduce the blood content in the organs under consideration.

Animals↗

PubMed1989

Increase of the intestinal iron absorption in growing rats and mice after 8 days of iron-deficient feeding.

In investigations of intestinal iron absorption the combination of repetitive bleeding and iron-deficient feeding is frequently used. It induces iron deficiency which, in turn, stimulates iron absorption. When this combined procedure was compared with the effect of an 8 d iron-deficient feeding schedule in growing rats, no significant differences were found regarding the stimulating effect on intestinal iron transfer. Body iron stores, however, as represented by the hepatic ferritin and iron content are remarkably less depleted. Contrary to the effect of the combined procedure the animals growth was only marginally retarded and anaemia did not develop. This was also demonstrated in mice. The stimulation of intestinal iron absorption by iron-deficient feeding of growing animals thus seems preferable, as this procedure largely avoids the disturbing side effects observed with repetitive blood sampling.

Anemia, Hypochromic↗

PubMed1988

On the origin of intestinal transferrin.

The incorporation of 35S-L-methionine (35S-Met) into TCA-precipitable protein is used to measure protein synthesis in isolated non-vascular perfused jejunal segments and in isolated liver cells under steady-state conditions in rats. 10(5) X g supernatants of homogenates from jejunal segments and from liver cells as well as the jejunal absorbate were processed immuno-electrophoretically. Incorporation of 35S-Met radioactivity into precipitin lines with sera against transferrin, IgG and plasma proteins were autoradiographed and compared semiquantitatively with each other. Calculated on a wet-weight basis this system is sensitive enough to detect transferrin synthesis down to a level of 1% of that in the liver. Still, no transferrin synthesis was found in the jejunal mucosa, while 35S-Met incorporation into TCA precipitates and into IgG continued in isolated jejunal segments for over 2 h. A good correlation was found (r = 0.88, P less than 0.01) between mucosal and plasma transferrin in normal as well as in iron deficient rats. A complete immunologic cross-reactivity could be demonstrated between different plasma transferrins and the transferrin in three different preparations of the intestinal mucosa. Immunoblots of electropherograms after isoelectric focussing showed no distinct differences between transferrin in the plasma, bile, and in the mucosal epithelium.

Animals↗

PubMed1988

Influence of food intake on the 24-hr variations of plasma iron concentration in the rabbit.

Circadian variations in plasma iron levels were first reported in humans in 1937. Influences of the sleeping pattern and of plasma cortisol and adrenaline levels on these variations as well as the reproducibility of the phenomenon itself are discussed controversially in the literature. The influence of food intake, however, was not considered in most of the studies and is therefore subject of this investigation. Circadian plasma iron and plasma transferrin variations were determined in rabbits and compared under free access to food and under starvation (caecotrophy was not prevented). Population-mean-cosinor analysis of circadian plasma iron concentrations showed similar variations in the fed and starved condition (mesor: 116.6 micrograms/dl vs 118.1 micrograms/dl, acrophase 0752 hr vs 0728) except for a significant increase of the circadian amplitude under free access to food (30.9 micrograms/dl vs 22.3 micrograms/dl, P less than 0.05). There was no variation in plasma transferrin, which shows that 24 hr variations in plasma iron are not caused by modulation of plasma transferrin. These findings demonstrate a circadian rhythm for plasma iron, the amplitude of which is increased by food intake.

Animals↗

PubMed1986

Independence of in vitro iron absorption from mucosal transferrin content in rat jejunal and ileal segments.

Isolated non blood-perfused intestinal segments from normal and iron-deficient rats were used in vitro. A modification of the luminal perfusion method according to Fisher and Parsons allowed the comparison of iron and transferrin quantities in the serosal fluid at 15 min intervals. Iron transfer in jejunal and ileal segments was directly proportional to the luminal iron concentration within a dose range of 1 to 100 mumol/l, did not show saturation characteristics and was linear over time. Jejunal segments from iron-deficient rats transferred about twice as much iron as the jejunal controls. In ileal segments there was no difference in iron transfer between iron-deficient and control rats; in both cases transfer amounted to approx. 10% of jejunal controls. An exponential correlation was found, when the decreasing transferrin content of the tissue was plotted against the cumulative water transport. Transferrin and albumin release from jejunal and ileal segments into the absorbate cumulated asymptotically, which is typical for wash-out phenomena. As iron transfer cumulated linearly while transferrin release cumulated in an asymptotic manner, the capacity of transferrin to bind iron ions is exceeded roughly 100 times by molar equivalents of iron in the last absorbate fractions. Independence of iron transfer from mucosal transferrin quantities is concluded. As the molar transferrin/albumin ratios do not show significant differences between plasma and the sequence of absorbate samples, a wash-out from the gut's interstitial space is assumed, which makes plasma the most likely origin of transferrin in the mucosa.

Absorption↗

PubMed1986

Iron absorption and biliary excretion of transferrin in rats.

The content of transferrin, albumin, and iron was determined in plasma and bile from normal and iron-deficient rats. In the plasma as well as in the bile there is a decrease of iron and an increase of transferrin due to iron depletion, whereas the albumin level remains constant. No significant difference of iron contents in plasma and bile was found, but the content of transferrin and albumin in bile was markedly lower than in the plasma. Thus, in the bile the iron content substantially exceeded the binding capacity of transferrin. The ratio between transferrin and albumin was the same in bile as in blood which argues for a bulk transfer of plasma proteins into the bile.

Absorption↗

PubMed1985

Transferrin in isolated cells from rat duodenum and jejunum.

Mucosal transferrin was determined as transferrin-like immunoreactivity (TLIR) by means of a 2-site immunoradiometric assay (IRMA). Scraped-off mucosal tissue as well as isolated mucosal cells from the duodenum and jejunum of normal and iron-deficient rats before and after a washing procedure were examined. In iron-deficient rats there was about twice as much TLIR in scraped-off mucosal tissue as in the untreated animals. In the duodenum and jejunum of normal and iron-deficient rats, TLIR contents of the isolated cells in the magnitude of 320-510 ng/mg dry weight were found. Washing isolated cells three times in ice-cold Hank's solution resulted in a nearly tenfold decrease of TLIR content in all groups. In contrast the cells' RNA content remained unchanged.

Animals↗

PubMed1984

[Significance of iliac crest biopsy in the diagnosis of immunovasculitis in neurologic disease pictures].

In the present study we evaluated and analysed 81 patients with mainly neurological symptoms in whom iliac crest biopsy was performed because of a suspected immunovasculitis. In 20 of these patients, an immunopathy could be verified via the iliac crest biopsy. The relevance, reliability and accuracy of iliac crest biopsy is compared with the corresponding properties of other conventional methods of biopsy and neurological examination. The clinical syndromes of patients with immunovasculitis are analysed and compared with those of a group without detectable immunovasculitis in the iliac crest biopsy sample. For immunovasculitides with neurological symptomatology, no typical complex of symptoms was seen compared with the control group which would support a suspected diagnosis of immunovasculitis. Four selected case histories are described in keyword style. It follows from the result of this study that iliac crest biopsy is a low-risk examination method which the patient can be expected to tolerate, which is far more accurate in respect of the specific question of an immunodisease such as immunovasculitis with a strongly predominant neurological syndrome, compared with all other conventional neurological examination methods including other biopsy methods.

Adult↗

PubMed1984

Microvascular permeability and blood flow in atrial homografts in the hamster cheek pouch.

Atrial heart tissue grafts from newborn golden hamsters were transplanted into cheek pouches and were studied using intravital microscopic techniques. The smallest microvessels in the homografts showed a mean diameter of 13.3 +/- 1.1 micron (mean +/- S.E.M.) thus being in the dimensional range of terminal arterioles of the fourth branching order (A4, 14.0 +/- 2.1 micron) in normal cheek pouch tissue. Arteriolar red cell velocity was measured using a modified dual slit method. Volumetric blood flow was calculated and seen to be similar in terminal cheek pouch arterioles (116 +/- 34 pl/s) and in the graft vessels (119 +/- 26 pl/s). The responsiveness to topically applied norepinephrine of the graft vessels was found to be significantly lower than in cheek pouch arterioles. Microvascular permeability studied with FITC-dextrans (intravenous application) revealed significantly higher intensity values in the homografts as compared with the surrounding cheek pouch tissue. The difference was most pronounced for the largest tracer molecules used (Mw 150 000). This phenomenon is most probably due to an increased macromolecular permeability of the microvessels in the graft. The present findings point towards functional differences between the transplant vessels and cheek pouch capillaries.

Animals↗

PubMed1984

Morphological and functional aspects of heart homograft adaptation to hamster cheek pouch. Spontaneous pulsatile activity and ultrastructure.

Atrial homografts from newborn hamsters, transplanted into cheek pouches of adult Syrian golden hamsters, were studied using intravital and electron microscopy. Half of the transplants survived up to 1 year, performing spontaneous pulsatile activity. The transplants could be influenced by beta-receptor activating or blocking substances applied intravenously to the host animal. For morphological analysis homografts were taken 3, 6, and 12 months after transplantation. Irregular arrangement of the myofibers occurred, and the T system was seen to be replaced by plasmalemmal and sub-plasmalemmal vesiculations. There was some evidence for hypoxia in the grafts. Dedifferentiation of atrial cardiocytes, somehow resembling smooth muscle cells, is discussed. Despite these morphological changes the specific contractile function of the grafts was preserved.

Animals↗

PubMed1977

[Experiments on disinfection of vaccinia virus embedded in scabs and/or at the hand].

Vaccinia viruses embedded in rabbit dermal scabs were subjected to physical and chemical disinfection procedures. Scabs were suspended in vitro without saline or in physiological saline, and left for 1 hour at 70 to 90 degrees C. A complete inactivation was achived only in those scab samples which had been incubated at 90 degrees C for 1 hour and suspended in physiological saline. Scabs which had been placed in a disinfecting apparatus (Vacudes 4000) filled with mattrasses consistently proved to be free of infectious vaccinia viruses in each of the chosen programs. In addition scabs were subjected to disinfection by means of chemical disinfecting agents. The scabs had been placed in a chemical disinfecting suspension and left there for 90 minutes. Complete disinfection was obtained with glutaraldehyde 2%, formaldehyde 2%, Lysoformin 2% or 3%, phenol 5% and chloramine T 2%. Complete disinfection was likewise achieved after 3 hours treatment with some alchohols (ethylalcohol 80%, isopropylalcohol 7%, n-propylalcohol 60%), Amocid 5% and formaldehyde 1%.0.5% formaldehyde caused complete disinfection when applied for 6 hours. The only exception was a Quat which did not disinfect fully even after 18 hours application. Concerning the tests to disinfect the hands complete disinfection occurs when using chloramine T (1.5%) or isopropylalcohol (70%) in 2 to 5 minutes. Further tests were performed with scabs which were placed in sick rooms that were terminally disinfected with formaline vapor. It could be confirmed that the usual terminal disinfection with formaldehyde vapor was unable to completely disinfect the scabs. It is necessary to double the amount of formaldehyde (10 g formaldehyde per cubic metre of space) and prolong the period of treatment to 24 hours to achieve a greater degree of disinfection rate.

Animals↗

PubMedDate not supplied

The longitudinal distribution of cadmium, zinc, copper, iron, and metallothionein in the small-intestinal mucosa of rats after administration of cadmium chloride.

Different routes of Cd intake may influence the intestinal distribution of Cd, metallothionein (MT), and trace metals differently. Therefore, we compared the effects of parenteral and enteral administration of Cd on the distribution of trace metals and MT along the small intestine. In a first experiment three groups of rats were employed: a control, one receiving CdCl2 within the drinking water, and another receiving sc injections of CdCl2. In a second experiment, rats were fed three different diets with either 0, 0.3, or 1 mmol CdCl2/kg for one and two weeks to study the time- and dose-dependent effects of orally administered Cd. Metal concentrations (Cd, Zn, Cu, Fe) were measured by atomic emission spectrometry and MT was determined by radioimmunoassay. Intestinal MT levels did not show proximodistal gradients in controls or after sc administration of Cd, but orally administered Cd increased mucosal MT levels longitudinally from the duodenum to the ileum. Cd levels paralleled those of MT. Compared with the metal concentrations in the controls, sc administration of Cd did not change intestinal Zn, Cu, and Fe levels. Oral administration of Cd, however, increased Cu and decreased Fe levels in the intestinal mucosa significantly. The second experiment revealed that only high dietary concentrations of Cd increase intestinal Cd and MT levels longitudinally toward the distal parts, whereas at lower dietary concentration the longitudinal distribution was reversed. This shows that different routes and doses of Cd intake lead to a different trace metal and MT distribution and emphasizes the role of dietary Cd in the local induction of small-intestinal MT.

Administration, Oral↗

PubMedDate not supplied

Lipid peroxidation and morphology of rat testis in magnesium deficiency.

Male Wistar rats were fed diets with different Mg content, ranging from 70 to 850 ppm Mg, for 30 days. After 0, 10, 20 and 30 days, some of the rats were sacrificed for measuring weight, lipid peroxidation, Fe, vitamin E, Na+, K+, Mg2+ and Ca2+ content of testes. After 30 days, the morphology of the testes was investigated by electron microscopy. Mg deficiency induced an increase in weight, Na+, Ca2+ and Fe content and a reduction of K+ and Mg2+ content. Vitamin E content was reduced and the content of malondialdehyde as an indicator of lipid peroxidation was increased. Mg deficiency induced morphological alterations in up to 40% of the spermatids in the 70 ppm Mg group, which consisted: 1) in injured stretching of spermatids; 2) in an irregular arrangement of coarse fibres with missing microtubulus complex (axoneme) and microtubulus sheath; 3) in the development of up to 4 bundles of outer fibrils in one spermatid. The increase of Fe content, lipid peroxidation and the onset of morphological alterations occurred already at a mild degree of Mg deficiency.

Animals↗