Shock metamorphism in lunar samples.

Indications of shock metamorphism produced by pressures up to the megabar region have been observed in the fine material and the breccias, but very rarely in the coarser fragments of crystalline rocks. These indications are deformation structures in plagioclase and pyroxene, diaplectic plagioclase glasses, and glasses formed by shock-induced melting of lunar rocks. Two sources of shock waves have been distinguished: primary impact of meteorites and secondary impact of crater ejecta. There are two major chemical types of shock-induced melts. The differences in chemistry may be related to impact sites in mare and highland areas.

[Large intestinal epithelium and short-chain fatty acids. Expected, unexpected, unexplained findings]. / Dickdarmepithel und kurzkettige Fettsäuren Erwartetes, Unerwartetes, Ungeklärtes.

Short-chain fatty acids (SCFA) are present in hindgut contents in high concentrations. SCFA are generated and also absorbed rapidly in the large intestine. Absorption results from diffusion of the undissociated and lipid soluble form or in exchange for bicarbonate. The controversial concepts concerning the extent of diffusion or the exchange for bicarbonate are partly due to contradictory findings and unequal mechanisms in different species and in different segments of the large intestine as well as in the different methods used. An almost neutral pH microclimate at the luminal surface is of importance for absorption of SCFA. The apical membranes of the epithelial cells in caecum and in proximal colon of guinea pigs are an substantial barrier for the diffusion of SCFA. After withdrawal of butyrate for only one hour from the perfusion or incubation solutions a massive apoptosis had been observed during the in situ perfusion of segments of guinea pig large intestine and also in in vitro studies with isolated epithelia in Ussing-chambers. In vitro apoptotic bodies and cells are emitted at the epithelial surface. However, in vivo induced by butyrate deprivation resident macrophages were tightly clustered below the surface epithelium. Aided by cytoplasmatic projections these macrophages phagocytose and transport apoptotic material from the epithelial intercellular spaces into their bodies. Obviously macrophages can be overloaded by this massive apoptosis, and some of the undigested apoptotic fragments are emitted into the lamina propria. Formation of a colitis ulcerosa may originate from these released undigested apoptotic bodies. Furthermore hints indicate aetiological interrelations between deprivation of butyrate and colon cancer. Butyrate-paradox denotes the contrarian effects on apoptosis and cell proliferation after addition or deprivation of butyrate in cultures of large intestinal tumour-cell-lines in comparison with the healthy, intact epithelium.

Metabolism of the macrolide immunosuppressant, tacrolimus, by the pig gut mucosa in the Ussing chamber.

1. The macrolide tacrolimus (FK506), used as an immunosuppressant, is a cytochrome P450 (CYP) 3A substrate in the liver. The metabolism of tacrolimus and the transport of its metabolites in the pig gut was studied in the Ussing chamber. Tacrolimus and its metabolites were quantified by h.p.l.c./mass spectrometry. 2. In the Ussing chamber, demethyl, didemethyl, hydroxy and hydroxy-demethyl tacrolimus were generated. Their formation was concentration- and time-dependent. The metabolite pattern was not different from that after incubation of tacrolimus with human small intestinal microsomes. 3. The metabolite formation was highest in the duodenum and declined in the order duodenum > jejunum > ileum > colon > stomach. 4. Since tacrolimus metabolism was inhibited by the specific CYP3A inhibitors, troleandomycin and ketoconazole, we concluded that these enzymes are involved in intestinal metabolism of tacrolimus. 5. Tacrolimus metabolites re-entered the mucosa chamber (> 90%) and passed through the small intestinal preparation into the serosa chamber. 6. It is concluded that tacrolimus is metabolized in the intestine, that the metabolites are able to re-enter the gut lumen and also enter into the portal vein and that small intestinal metabolism and transport is at least in part responsible for the low oral bioavailability of tacrolimus.

Role of short-chain fatty acids in the hind gut.

Short-chain fatty acids (SCFA) are produced by microbial fermentation in the hindgut in considerable amounts. Most of the anions in hindgut contents are SCFA, mainly acetate, propionate and butyrate. SCFA are rapidly absorbed. Mechanisms involved in the transepithelial transport are discussed. Besides the contribution to the overall energy metabolism of animals or men, SCFA have a number of further important effects on the colonic mucosa. Factors affecting the pH of compartments in the mucosa, cell swelling, stimulation of mucin release and of mucosal blood flow are mentioned. Controversial reports are known on the role of SCFA in the metabolism of colonocytes. In spite of the conflicting opinions on the interaction between SCFA metabolism and the development of colitis ulcerosa, diverticulosis and colorectal cancer seems to exist. The obscure differences between the effects of SCFA on cell proliferation, differentiation and apoptosis of colonocytes in vivo and in vitro indicate that besides direct effects of SCFA systemic effects such as neural and humoral factors are of crucial importance. The opposing effects of SCFA on proliferation and apoptosis in normal colonocytes and in colonic cancer cells may open possibilities for prevention and/or therapy of patients with colonic diseases.

[Physical performance--a comparison between horses and men]. / Körperliche Leistungsfähigkeit--ein Vergleich zwischen Pferden und Menschen.

During heavy exercise horses can increase oxygen uptake compared to resting conditions considerably more than man. Processes involved like respiration, heart size, cardiac output, oxygen transport capacity of the blood and oxygen release in the capillaries are discussed. Besides these advantages in the aerobic metabolism conditions for the anaerobic metabolism are also more advantageous in horses than in man. The portion of fast contracting muscle fibers with little fatigue-resistance and also some of the enzymes required for the anaerobic metabolism are higher in horses.

Forestomach motility in llamas and camels.

Major aspects of forestomach anatomy in llamas and camels are described. The pattern of forestomach motility is a succession of motoric cycles, consisting of A- and B-contraction sequences and a pause. Respective differences between llamas and camels are discussed. Observations on regulation of motility are mentioned. Occurrences and courses of rumination and eructation within the motility cycles are emphasized. Motility of the forestomach achieves a selective retention of feed particles in the forestomach; a long retention time is a prerequisite for an effective microbial digestion, especially of poor quality feed.

Comparative views of electrophysiological parameters of large intestinal segments in pig, sheep, pony, guinea pig and rat.

Short circuit current (ISC) and transepithelial conductance (gt) across sheets of epithelia were measured in the caecum, the proximal and the distal colon of pig, sheep, pony, rat and guinea pig. The electrical parameters underline the basic segmental and species differences. The diversity of ISC demonstrates the different nature of electrogenic transport mechanisms, and data clearly show the heterogeneity with respect to transport mechanisms along the large intestine in the various species. The great differences in amiloride sensitive ISC indicate the variabilities in the electrogenic Na transport. Whereas in the pig, sheep and pony caecum, in the guinea pig proximal colon and in all segments of the rat hindgut no indications for a major electrogenic Na transport was seen, in all other segments amiloride caused a marked decrease in ISC. Electrogenic Na transport seems to be highest in sheep distal colon and in pig proximal and distal colon, somewhat less in guinea pig and in pony distal colon. The epithelium with the lowest Powest transepithelial conductance clearly is that of the pony caecum. Except in sheep, gt-values are not much different from those in pony and also pig and guinea pig. By far the epithelium with the highest conductance is that of the rat proximal colon. gt was similar in the proximal and the distal colon of pig, sheep and pony; in guinea pig values were slightly, in rat much lower.

Regulation of intracellular pH in the colonic epithelial cell line HT29 clone 19A.

Intracellular pH (pHi) of the colonic tumor cell line HT29 cl. 19A was studied by microspectrofluorometry using the pH-sensitive dye BCECF. Single cells within a confluent monolayer grown in a polarized manner on permeable supports were examined. An amiloride-sensitive Na(+)-H+ exchange and a stilbene-insensitive Cl(-)-HCO3- exchange mechanism have been identified in the basolateral membrane. This Na(+)-H+ exchange mechanism in the basolateral membrane is an acid extruder, whereas the Cl(-)-HCO3- exchanger is an acid loader. Both of these in the basolateral membrane located mechanisms are important for the maintenance of intracellular pH in HT29 cl. 19A cells.

[Skeletal muscle samples from slaughtered bodies of swine in student laboratories for the study of muscle physiology]. / Skelettmuskelproben aus Schlachtkörpern von Schweinen im Praktikum zur Muskelphysiologie.

Viable, excitable and contractile samples from gracilis muscle of pig carcasses were used in our student laboratory of muscle physiology. Samples were taken about 20 minutes after stunning. Sampling, transport of the samples and equipment are described. Some examples of registered isometric contractions are shown.

Absorption of short-chain fatty acids, sodium and water from the forestomach of camels.

In camelids the ventral parts of compartments 1 and 2 (C1/C2) and the total surface of compartment 3 of the forestomach are lined with tubular glands, whereas in ruminants the surface of the forestomach is composed entirely of stratified, squamous epithelium. Thus, differences in absorption rates between these foregut fermenters can be expected. In five camels C1/C2 was temporarily isolated, washed and filled with buffer solutions. Absorption of short-chain fatty acids (SCFA) and net absorption of sodium and water were estimated relative to Cr-ethylenediaminetetraacetic acid as a fluid marker. SCFA were extensively absorbed in the forestomach; clearance rates of SCFA with different chain lengths were equal. After lowering the pH of solutions SCFA absorption rates increased, but much less than the increase of the non-ionized fraction. Absorption of propionate was lower when acetate had been added. Findings suggest that most of the SCFA in camels are transported in the ionized form, most likely via an anion exchange mechanism. Net water absorption is closely related to net sodium absorption. Apparently water absorption results from an iso-osmotic process. Differences between absorption mechanisms of SCFA from the forestomach of camelids and ruminants are discussed.

Distribution patterns of the glucose transporters GLUT4 and GLUT1 in skeletal muscles of rats (Rattus norvegicus), pigs (Sus scrofa), cows (Bos taurus), adult goats, goat kids (Capra hircus), and camels (Camelus dromedarius).

Earlier studies demonstrated that forestomach herbivores are less insulin sensitive than monogastric omnivores. The present study was carried out to determine if different distribution patterns of the glucose transporters GLUT1 and GLUT4 may contribute to these different insulin sensitivities. Western blotting was used to measure GLUT1 and GLUT4 protein contents in oxidative (masseter, diaphragm) and glycolytic (longissimus lumborum, semitendinosus) skeletal muscle membranes of monogastric omnivores (rats and pigs), and of forestomach herbivores (cows, adult goats, goat kids, and camels). Muscles were characterized biochemically. Comparing red and white muscles, the isocitrate dehydrogenase (ICDH) activity was 1.5-15-times higher in oxidative muscles of all species, whereas lactate dehydrogenase (LDH) activity was 1.4-4.4-times higher in glycolytic muscles except in adult goats. GLUT4 levels were 1.5-6.3-times higher in oxidative muscles. GLUT1 levels were 2.2-8.3-times higher in glycolytic muscles in forestomach herbivores but not in monogastric animals. We conclude that GLUT1 may be the predominant glucose transporter in glycolytic muscles of ruminating animals. The GLUT1 distribution patterns were identical in adult and pre-ruminant goats, indicating that GLUT1 expression among these muscles is determined genetically. The high blood glucose levels of camels cited in literature may be due to an "NIDDM-like" impaired GLUT4 activity in skeletal muscle.

Feed intake, forestomach fluid volume, dilution rate and mean retention of fluid in the forestomach during water deprivation and rehydration in camels (Camelus sp.).

Camels were deprived of water for 11 days. Before and during water deprivation and during rehydration changes in body weight, feed and water intake were measured. Using the liquid marker Cr-EDTA forestomach fluid volume, mean fluid retention and fluid dilution in the forestomach were estimated. At the eleventh day of water deprivation hay intake had decreased to only 9.6% of controls, dilution rates had decreased to 31%, mean retention time of fluid in the forestomach had increased to 189%. At the end of dehydration flow of saliva of 2 l/h mainly contributed to the still rather high dilution rates. Thereby buffering capacity and flow of fluid into the forestomach for microbial digestion as well as the outflow from the forestomach were maintained. At the beginning of rehydration camels drank 97 l within a few minutes, and animals thereby replaced all the water lost. Following this first huge water intake water is rapidly absorbed from the forestomach, and forestomach volume decreased again to dehydration values. At the third day of rehydration control values were reached again. Although feed intake decreased dramatically during water deprivation, functions of the forestomach can be maintained sufficiently mainly due to saliva inflow. This explains the mostly rapid recovery of camels when water is available again.

Chewing activities and oesophageal motility during feed intake, rumination and eructation in camels.

It was the aim of this study to characterize rumination behaviour, eructation and oesophageal motility in camels to identify similarities and differences between camels and domestic ruminants. Recordings were carried out in five camels fed on a hay-based diet. On an average, the duration of rumination, feeding and resting was 8.3, 5.6 and 10.1 h per 24 h, respectively. Rumination activity peaked in the morning between 9:00 and 11:00 and in the night between 02:00 and 04:00 a.m. During rumination periods, on an average 67 boluses were regurgitated per hour. Each bolus was chewed for an average of 45 s with 68 chews per min. The pause between two rumination cycles lasted on an average 9 s. Hay intake took 61 min/kg dry matter (DM), rumination lasted 71 min/kg DM of hay consumed. The regurgitation of a bolus started with a contraction of cranial compartment 1 (C 1) during a B-sequence, followed by a deep inspiration with closed glottis. Digesta enters the oesophagus, and an antiperistaltic wave transported the bolus orally. Eructation starts with a contraction of the caudal C1 during a B-sequence when the cranial C1 is relaxed. After entering the oesophagus, a rapid antiperistaltic wave transports the gas orally. Results revealed that the parameter values obtained in the camels were remarkably similar to those in domestic ruminants despite profound morphological differences and different patterns of forestomach motility.

Concentration- and pH-dependence of short-chain fatty acid absorption in the proximal and distal colon of guinea pig (Cavia porcellus).

1. Absorption of short-chain fatty acids (SCFA), acetate, propionate, and butyrate was studied in simultaneously perfused proximal and distal segments of the colon in anaesthetized guinea pigs. 2. Acetate absorption rates increased linearly with concentration in both segments, indicating passive transport. 3. SCFA-clearance was independent of bulk luminal pH between pH 6.2 and 8.1 in the proximal and distal colon. SCFA-clearance was slightly higher in both segments at pH values less than 6. 4. The unexpected pH-independence of SCFA-absorption is attributed to the existence of a constant pH-microclimate at the surface of the colonic epithelium. 5. Relative permeabilities to acetate:propionate:butyrate were estimated as 1:1.19 +/- 0.03:1.27 +/- 0.05 in the proximal colon and 1:2.31 +/- 0.39:3.50 +/- 0.61 in the distal colon. The significance of these findings with respect to the pH-partition hypothesis are discussed.

Is gastro-intestinal mucus an ion-selective barrier?

The mucus layer at the epithelial surface seems to be responsible for the formation of a microclimate in which the concentrations of H+, K+, Na+, and Cl- are rather constant. It is possible that this is not due simply to an unstirred layer effect, but also to a higher diffusion resistance of mucus. Flux measurements revealed that sodium and potassium permeabilities in mucus are 50% lower than those in saline. Dilution and biionic diffusion potentials indicated a higher relative permeability of mucus for sodium and potassium than for chloride. Thus mucus represents a diffusion barrier, slightly more permeable for cations than for anions.