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.     

Water and NaCl absorption by the intestine of the tilapiaSarotherodon mossambicus adapted to fresh water or seawater and the possible role of prolactin and cortisol

Summary Rates of intestinal water, sodium and chloride absorption in tilapia, adapted to fresh water (FW) and seawater (SW), were measured in vitro, using noneverted sacs made from the anterior, middle and posterior intestinal regions. The anterior intestine from SW fish showed considerably less water, sodium and chloride absorption compared with that seen in FW fish. The middle intestine showed either minimal absorption or some secretion in both FW and SW. In the posterior intestine, water absorption was only limitedly affected by SW-adaptation, but sodium and chloride absorption rates were significantly lower in SW fish. Reductions in water absorption were already evident in the anterior intestine 24 h after transfer to 1/3 SW but reached lower levels 3 to 5 days following transfer to 100% SW. Thus, the anterior intestine of tilapia responds to increased environmental salinity by decreasing uptake of ions, whereas the posterior intestine maintains similar water absorption in both FW and SW, although ion absorption is lower in SW.Prolactin administration to SW fish augmented sodium and water absorption in the anterior intestine but had no effect on chloride absorption. In contrast, cortisol administration to FW fish decreased absorption of sodium, chloride and water to levels usually seen in SW fish. The observed effects of these hormones in tilapia intestinal absorption may be confined to the specialized anterior intestinal region in this species; hormonal effects on the rest of the intestine were not examined.     

Handling of water and dietary monovalent ions by the young turkey

Sodium and water turnover rates were measured in young turkeys fed diets with three concentrations of NaCl and kept at 12, 18 or 30 degrees C. Sodium absorption averaged approximately 60% and was unaffected by temperature. Water and sodium pools were affected by temperature and sodium intake. Water turnover was linear to sodium turnover at the lower two temperatures. No significant relationship was apparent in birds kept at 30 degrees C. The reciprocal of the slope of the function of water turnover on sodium turnover was 125-170 mM, suggesting an increase in isotonic urine excretion with sodium intake and a corresponding increase in water intake. Dietary sodium and potassium stimulated water turnover similarly. Dietary chloride concentration did not affect water turnover. In the turkey plasma pH and pCO2 were unaffected by a wide range of the anion-cation balance. It is concluded that excess sodium or potassium intakes is handled effectively in the turkey by increased water intake and excretion.     

The influence of urea feeding on the bacterial and archaeal community in the forestomach of collared peccary (Artiodactyla, Tayassuidae)

Aims:  This study was carried out to test whether bacterial and archaeal populations, and products of fermentation in each compartment of collared peccary stomach, vary significantly with urea feeding. Bacteria and archaeal population variation among the four stomach compartments were also compared.
Methods and Results:  Archaeal and bacterial communities in the forestomach of four individuals per treatment – peccaries fed diets with and without urea – were analysed at molecular level using PCR followed by denaturing gradient gel electrophoresis. Volatile fatty acids profiles in the three different compartments of the forestomach were also compared. The bacterial community composition varied considerably among each compartment and with urea provision, but no variation was observed between archaeal populations. Differences in bacterial communities between treatments – with and without urea – were greater than amongst stomach compartments. The acetate: propionate proportion decreased with urea provision in diet. Some differences in bacterial but not archaeal community composition were observed in each compartment of the collared peccary forestomach.
Conclusions:  There are some differences in bacterial but not archaeal populations in each compartment of collared peccary stomach. Use of urea in the diet of peccary can substantially modify the profile of volatile fatty acids released in its forestomach, but does not influence the archaeal community composition. Urea has an important effect on bacterial population DGGE profile present in the peccary's forestomach.
Significance and Impact of the Study:  These results demonstrate the ability of the collared peccary to use urea as source of nonprotein nitrogen, and confirm a hypothesis that the collared peccary has a digestive physiology more similar to ruminant than nonruminant animals.     

Possible involvement of NO-mediated oxidative stress in induction of rat forestomach damage and cell proliferation by combined treatment with catechol and sodium nitrite

To clarify the mechanisms underlying forestomach carcinogenesis in rats by co-treatment with catechol and sodium nitrite (NaNO2), we investigated the involvement of oxidative stress resulting from reaction of the two compounds. Since generation of semiquinone radical, hydroxyl radical (*OH), and peroxynitrite (ONOO-) arose through the reaction of catechol with NO, we proposed that superoxide resulting from catechol oxidation reacted with excess NO, consequently yielding *OH via ONOO-. Male F344 rats were co-treated with 0.2% catechol in the diet and 0.8% NaNO2 in the drinking water for 2 weeks. Prior to occurrence of histological evidence indicating epithelial injury and hyperplasia, 8-hydroxydeoxyguanosine levels in forestomach epithelium significantly increased from 12 h together with appearance of immunohistochemically nitrotyrosine-positive epithelial cells. There were no remarkable changes in rats given each chemical alone. We conclude that oxidative stress due to NO plays an important role in induction of forestomach epithelial damage, cell proliferation, and thus presumably forestomach carcinogenesis.     

Fate of peritoneal progesterone in the rabbit

The efficiency of peritoneal absorption of progesterone was investigated by following the appearance of 3H-progesterone and its metabolites in the circulation after intravenous or intraperitoneal administration. Tritium rapidly entered the peripheral circulation when given by either route. The percentage of tritium appearing as modified progesterone was substantially lower following intraperitoneal administration. This difference can be largely attributed to splanchnic absorption and hepatic metabolism of intraperitoneal steroids. The potentially large amount of progesterone secreted into the peritoneal compartment may not contribute significantly to the peripheral circulating pool of progesterone.     

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.     

Changes in plasma volume during hypohydration and rehydration in subjects from the tropics

Plasma volume (PV) at different levels of hypohydration was determined using radio-iodinated serum albumin-125 in 28 heat acclimated male volunteers in hot dry condition in a climatic chamber. The heat acclimated subjects were hypohydrated to varying degrees i.e. 1%, 2%, 3% and 4% body mass deficit by moderate work in hot conditions in a climatic chamber maintained at 45 degrees C dry bulb temperature and 30% relative humidity. A rehydration study was carried out in only those subjects who were hypohydrated to 3% and 4% body mass and they were brought back to a 2% level of hypohydration by giving a calculated amount of water. A significant decrease in PV was observed at 3% and 4% hypohydration only. The magnitude of the decrease was the same in both the groups and not related to the level of hypohydration. With partial rehydration in the 3% hypohydrated group PV was restored fully, while in the 4% hypohydrated group restoration was incomplete, indicating that at this hypohydration level some of the replenished water that entered in plasma may have moved to the intracellular compartment which may have contributed more at 4% hypohydration. It is suggested that with higher levels of thermal hypohydration significant reduction in the intracellular compartment may result in accentuated physiological strain during work in the heat.     

Mechanisms of transport of Na+ and Cl- in the lizard colon

1. Ionic fluxes of sodium and chloride across lizard colon mucosa were measured and compared with the electrical characteristics of the tissue under voltage-clamped conditions. 2. In a Ringer-bicarbonate solution there was both a net sodium flux (JNanet) and a net chloride flux (JClnet) from mucosa to serosa. The net flux residual (JR) was near zero, indicating that net sodium and chloride transport is the result of an electrically neutral transport mechanism. 3. In the presence of sodium, the net chloride flux was abolished and the short-circuit current (Isc) and the electrical potential difference (PD) were unchanged. In the absence of chloride the net sodium flux was abolished and the short-circuit current and electrical potential difference were not modified. 4. From an analysis of the effects of the inhibitors, furosemide, amiloride and disulfonic stilbene (DIDS), a plausible model was developed to explain the characteristics of sodium and chloride absorption.     

Forestomach motility in the camel (Camelus dromedarius)

There is a cyclical pattern of motility in compartments 1 and 2 of the forestomach of the camel which can be categorized into A- and B-contractions. An average motility cycle is composed of 7 A- and 5 B-contractions and lasts 5 min, including a pause of 2.3 min. The glandular sacs within the caudal sac of compartment 1 contract 1.7 sec earlier than the caudal sac. The proximal part of the canal between compartment 2 and 3 contracts 1.2 sec prior to the distal part. Forestomach motility is stimulated by distention of the cranial sac of compartment 1 and inhibited by distention of the tubiform portion of compartment 3.     

Correction of Chloride Transport and Mislocalization of CFTR Protein by Vardenafil in the Gastrointestinal Tract of Cystic Fibrosis Mice

Although lung disease is the major cause of mortality in cystic fibrosis (CF), gastrointestinal (GI) manifestations are the first hallmarks in 15–20% of affected newborns presenting with meconium ileus, and remain major causes of morbidity throughout life. We have previously shown that cGMP-dependent phosphodiesterase type 5 (PDE5) inhibitors rescue defective CF Transmembrane conductance Regulator (CFTR)-dependent chloride transport across the mouse CF nasal mucosa. Using F508del-CF mice, we examined the transrectal potential difference 1 hour after intraperitoneal injection of the PDE5 inhibitor vardenafil or saline to assess the amiloride-sensitive sodium transport and the chloride gradient and forskolin-dependent chloride transport across the GI tract. In the same conditions, we performed immunohistostaining studies in distal colon to investigate CFTR expression and localization. F508del-CF mice displayed increased sodium transport and reduced chloride transport compared to their wild-type littermates. Vardenafil, applied at a human therapeutic dose (0.14 mg/kg) used to treat erectile dysfunction, increased chloride transport in F508del-CF mice. No effect on sodium transport was detected. In crypt colonocytes of wild-type mice, the immunofluorescence CFTR signal was mostly detected in the apical cell compartment. In F508del-CF mice, a 25% reduced signal was observed, located mostly in the subapical region. Vardenafil increased the peak of intensity of the fluorescence CFTR signal in F508del-CF mice and displaced it towards the apical cell compartment. Our findings point out the intestinal mucosa as a valuable tissue to study CFTR transport function and localization and to evaluate efficacy of therapeutic strategies in CF. From our data we conclude that vardenafil mediates potentiation of the CFTR chloride channel and corrects mislocalization of the mutant protein. The study provides compelling support for targeting the cGMP signaling pathway in CF pharmacotherapy.     

Gelatinisation of sago starch in the presence of sucrose and sodium chloride as assessed by differential scanning calorimetry

The inhibitory effect of sucrose and sodium chloride on sago starch gelatinisation was investigated by differential scanning calorimetry (DSC). The temperature of gelatinisation of starch in the presence of low levels of water and high levels of sucrose was found to increase in the presence of sucrose, whereas the gelatinisation enthalpy was unaffected. The gelatinisation temperature range was not as broad in the presence of sucrose as without sucrose. Furthermore, the shape of the gelatinisation endotherm was changed by the addition of sucrose. The double endotherm obtained in limited water:starch systems was changed into a single endotherm, similar to the endotherm obtained in excess water:starch systems at a higher temperature. DSC was also used to examine the effects of water and sodium chloride content on the phase transitions of sago starch. Samples were adjusted to starch:water ratios of 2:3 and 3:2 in sodium chloride concentrations of 0.0, 1.0, 2.0, 3.0, 4.0, 5.0 M. The gelatinisation temperatures of sago starch increased and then decreased as the sodium chloride concentration increased. Sodium chloride created similar effects on the endotherms in excess water content and on the first endotherm with limited water content. In the presence of sucrose and sodium chloride, gelatinisation shifted to higher temperatures, and enthalpy associated with the endothermic process decreased. The extent of temperature shift and enthalpy change was dependent on the water to starch to solutes ratios.     

Effect of acetazolamide on sodium transport through the isolated frog skin at low and high external sodium concentrations.

The action of acetazolamine on sodium transport in $\text{Rana esculenta}$ skin was studied with the external face bathed in dilute (2mMM) or concentrated (Ringer) solutions of sodium chloride.The absorption of Na⁺ from a dilute solution is inhibited at an acetazolamide concentration of 10⁻⁵M. This is due to an inhibition of the influx: the efflux remains unchanged. Acetazolamide has no effect, however, on transport from Ringer solution.The graphic determination of the Na⁺ transport pool at the 2 mM NaCl concentration showed that acetazolamide diminished the pool without affecting the $\text{t}\text{1}\text{2}$. The inhibitor had no effect on the pool at the higher (Ringer) concentration.These results indicate that acetazolamide acts on the external barrier of the sodium transport compartment without affecting the active pump of this ion when it is being transported from a dilute sodium chloride solution.     

Expression,localization and possible functions of aquaporins 3 and 8 in rat digestive system

Although aquaporins (AQPs) play important roles in transcellular water movement, their precise quantification and localization remains controversial. We investigated expression levels and localizations of AQP3 and AQP8 and their possible functions in the rat digestive system using real-time polymerase chain reactions, western blot analysis and immunohistochemistry. We investigated the expression levels and localizations of AQP3 and AQP8 in esophagus, forestomach, glandular stomach, duodenum, jejunum, ileum, proximal and distal colon, and liver. AQP3 was expressed in the basolateral membranes of stratified epithelia (esophagus and forestomach) and simple columnar epithelia (glandular stomach, ileum, and proximal and distal colon). Expression was particularly abundant in the esophagus, and proximal and distal colon. AQP8 was found in the subapical compartment of columnar epithelial cells of the jejunum, ileum, proximal colon and liver; the most intense staining occurred in the jejunum. Our results suggest that AQP3 and AQP8 play significant roles in intestinal function and/or fluid homeostasis and may be an important subject for future investigation of disorders that involve disruption of intestinal fluid homeostasis, such as inflammatory bowel disease and irritable bowel syndrome.     

Salt excretion by the perfused head of trout adapted to sea water and its inhibition by adrenaline

Summary Isolated heads of trout (Salmo gairdneri) were used to study the unidirectional flux of sodium and chloride across the gills in salt water.Two perfusion techniques were employed. Under constant pressure perfusion, the addition of adrenaline during the perfusion causes an increase in the flow-rate. Under constant flow-rate conditions, adrenaline provokes a decrease in pressure. A comparison of influx determination made with these two techniques of perfusion shows that variations in flow-rate of perfusion do not affect the assessment of these fluxes.A net efflux of sodium, but not of chloride, is demonstrated in sea water. The effluxes of sodium and chloride observed in sea water are decreasedd about 50% during a rapid transfer to fresh water. The addition of potassium to this medium stimulates the effluxes of sodium and chloride, suggesting a Na/K exchange participating in the chloride excretion.Adrenaline causes an inhibition of sodium and chloride efflux in sea water which persists after transfer to fresh water and the addition of potassium. Only the influx of chloride is inhibited at a concentration of 10^–5 M whereas the sodium influx is unaffected. The presence of adrenaline results in a net influx of both sodium and chloride.The differential action of adrenaline on the influxes of sodium and chloride suggests that the hemodynamic modifications provoked by this catecholamine occur independently of its aforementioned ion exchange effects.     

Functional activities of the colon of the desert gerbil (Gerbillus cheesmani)

The effects of starvation and undernourishment on the potential differences (pd in mV), basal short-circuit current (Isc in microA/cm(2)), resistance (R in omega) and glucose-dependent short-circuit current (Isc in microA/cm(2)) across stripped sheets of proximal, mid and distal colon of the gerbil (Gerbillus cheesmani) were investigated. The effects of replacing sodium chloride by lithium chloride, replacing chloride in Krebs buffer by gluconate and removing bicarbonate from bathing buffers were also investigated. Starvation (4 days, water ad lib) and undernourishment (50% control food intake for 21 days) had no significant changes on pd and R of the three regions of stripped colon. Starvation increased the basal Isc in the proximal and the mid-colon only while undernourishment increased the basal Isc of three regions of the colon. In addition, starvation and undernourishment increased the glucose-dependent Isc in the three regions. Replacing sodium chloride by lithium chloride caused a slight decrease in the basal Isc of proximal and mid colon taken from starved animals. In undernourished gerbils, although there was a slight decrease in basal Isc of proximal and mid colon the big decrease was observed in Isc of the distal colon. Replacing chloride by gluconate had no effect on the Isc of the different regions of colon taken from fed and starved animals but decreased the Isc of the three regions of undernourished animals. The absence of bicarbonate reduced the Isc of proximal and mid colon taken from starved gerbils and those of three regions taken from undernourished animals. The results of the present study suggest that the Isc of proximal and mid colon from starved gerbils could result from active sodium transport together with bicarbonate secretion while the Isc of the three regions taken from undernourished gerbils results from active sodium absorption together with both chloride and bicarbonate secretion.     

Effects of impermeant medium ions on the composition of rabbit renal cortical slices

When incubated in isosmotic oxygenated medium in which chloride was completely replaced by gluconate, rabbit renal cortical slices lost chloride with sodium, potassium and water before reaching a new steady-state composition after 15-30 min. When corrected for extracellular space, there was an electroneutral loss of alkali metal cations (Na + K) with chloride, accompanied by isosmotic loss of water from the cells. The losses of chloride and water were independent of medium pH over the range of 6.4-8.2, and were the same with potassium rather than sodium as the dominant medium cation. Incubation in isosmotic sodium chloride medium restored tissue composition of slices transferred from gluconate medium. This recovery was not dependent specifically upon medium chloride, for slice water content also recovered when nitrate rather than chloride was substituted for medium gluconate. With sodium completely replaced by n-methyl d-glucamine (nmdG+), cells in slices lost far more sodium and potassium than chloride before reaching a new steady-state composition after some 30 min. However, the loss of water was as predicted from the total losses of measured inorganic ions. With sodium and chloride completely replaced by nmdG+ and gluconate, there was a greater loss of water than found with unilateral substitutions. Again, the combined loss of diffusible inorganic cations exceeded the loss of chloride but the water loss was that expected for isosmotic loss accompanying the measured losses of ions. These results reveal that both gluconate and nmdG+ behave as impermeant ions in this tissue preparation. It is suggested that, in the absence of medium sodium, sodium-hydrogen exchange is inhibited. Retained hydrogen ions are buffered on charged cellular non-diffusible solutes and the associated hydroxyl (or bicarbonate) ions are lost from the cells accompanied by the inorganic univalent cations lost in excess of chloride in nmdG+ medium.     

Transport of a fluorescent macromolecule via endosomes to the vacuole in Saccharomyces cerevisiae

Fluorescein isothiocyanate-conjugated dextran (FITC-dextran) is internalized by endocytosis into the lysosome-like vacuoles of Saccharomyces cerevisiae (Makarow, M., 1985, EMBO (Eur. Mol. Biol. Organ.) J. 4:1861-1866). Here we show that under energy depletion conditions FITC-dextran accumulated in a cytoplasmic compartment, from which it could be chased to the vacuole when the energy block was removed. The internal pH of the intermediate compartment under energy depletion was determined by fluorometry to be 5.8. The pH could be raised by the lysosomotropic agent ammonium chloride, the protonophore carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (CCCP) and the ATPase inhibitors dicyclohexylcarbodiimide (DCCD) and sodium vanadate. The pH of the vacuole was found to be 6.5. It was raised by ammonium chloride, CCCP, and DCCD, but not with sodium vanadate. Efrapeptin had no effect on the internal pH of either compartment. By dissecting the endocytic pathway, two portions of the route leading to the vacuole could be studied separately. The internalization of FITC-dextran from the extracellular fluid to the intermediate compartment followed linear kinetics, was independent of energy, and occurred at temperatures of between 15 degrees and 37 degrees C. Transfer of the marker from the intermediate compartment to the vacuole required energy, took place at temperatures between 19 degrees and 37 degrees C, and had a half-time of 7 min at 37 degrees C. Transport of the marker from the exterior of the cell to the vacuole did not require acidic pH values in the intermediate compartment or the vacuole. We suggest that the cytoplasmic compartment revealed by FITC-dextran, under energy depletion, represents the equivalent of the endosomes of mammalian cells.     

Rheological Properties of Succinoglucan 10C3 from Alcaligenes faecalis var. myxogenes

The H-, Na- and Ca-forms of succinoglucan 10C3 form homogenous dispersions in water. The viscosities of 1% aqueous dispersion of the H- and Ca-forms were 1560 and 2500 centipoises respectively at 30°C. The viscosity of the Na-form, which is extremely low, was increased greatly by an addition of many inorganic salts and especially the Fe³⁺ and Al³⁺ iones. The viscosity of the Ca-form did not change by the presence of sodium chloride or calcium chloride.

The viscosities of Ca-form, and Na-form in the presence of 1% sodium chloride became near zero at 65.5 °C and 69.5°C, respectively. When the dispersions were kept at 70°C or 90°C for ten minutes, the viscosities of the H-form, the Na-form, and the Ca-form in the presence of sodium chloride increased greatly. The viscosity of the Ca-form and that of the Na-form in the presence of 1% sodium chloride were essentially independent of pH.