A major histocompatibility complex class I-related Fc receptor for IgG on rat hepatocytes.

Intestinal epithelial cells of the neonatal rat and mouse have been shown to express a major histocompatibility complex (MHC) class I-like Fc receptor, or FcRn, which transports IgG in an apical to basolateral direction. Previous studies have suggested the possible expression of this receptor beyond the neonatal period within the liver. Since bile contains high levels of IgG, we sought to determine whether the FcRn was functionally expressed by adult rat hepatocytes. Using primers specific for FcRn, which did not cross hybridize with MHC class I transcripts, FcRn DNA was amplified by reverse transcriptase polymerase chain reaction from RNA of adult rat hepatocytes. This RNA contained functional FcRn transcripts as it encoded a beta 2-microglobulin-associated cell surface protein as determined by immunoprecipitation of biotinylated cell surface proteins with a polyclonal anti-FcRn specific antiserum. Western blotting of hepatocyte canalicular (apical) and sinusoidal (basolateral) plasma membranes with an FcRn-specific monoclonal antibody further confirmed the protein expression and suggested that FcRn was enriched on the canalicular surface membranes. FcRn, on the surface of hepatocytes, was biologically functional as it bound Fc fragments of IgG at pH 6.0 but not 8.0, which is the same pH dependence observed for FcRn in rat neonatal enterocytes. Thus, FcRn is functionally expressed outside of the neonatal period on the canalicular cell surface of adult hepatocytes. This suggests that hepatocyte FcRn may bind luminal IgG, providing a potential functional communication between parenchymal immune cells and bile.

[Longterm study of the effectiveness of different dental care programs in school children]. / Langzeitstudien zur Effektivität von unterschiedlichen Betreuungsstrategien bei Schulkindern.

The caries prevalence was examined in children from the first to the tenth grade in Rostock and Krakow between 1974 and 1988. In Krakow, a town with a preventive orientated dental care program, a significance caries reduction was found. Therefore there is an increase of health and an improvement of oral situation for the children on the way to the goals of WHO for oral health by the year 2000.

Plasma and red cell ionic composition in rainbow trout exposed to progressive temperature increases.

Yearling rainbow trout, Salmo gairdneri Richardson, were exposed to progressive increases in temperature from 10 to 26.1 degrees C, and variations in haemoglobin, haematocrit and plasma and erythrocytic concentrations of Na+, K+, Ca2+, Mg2+ and Cl- were compared with those of animals maintained at 10 degrees C. Despite the effects which increases in temperature are known to have on branchial ventilation, perfusion and effective exchange area, and consequently upon passive water and electrolyte fluxes, plasma ion concentrations were little affected at other than acutely stressful temperatures. Presumably this reflects the consequences of previously demonstrated changes in branchial, renal and erythrocytic (Na+/K+)- and (HCO3-)-activated ATPase and carbonic anhydrase activities. Haemoglobin and haematocrit were also little influenced by increases in temperature between 10 degrees C and about 25 degrees C. It is unclear whether the decreases seen at higher temperatures reflected accelerated ageing and breakdown of circulating red cells or were a consequence of changes in tissue water content and distribution with resulting haemodilution. Red cell levels of Cl- and K+ increased more or less steadily at temperatures exceeding 16-18 degrees C. So also did [Cl-]: [Hb] and [K+]: [Hb]. Sodium and [Na+]: [Hb] were essentially constant up to about 25 degrees C but thereafter increased sharply. Much the same was true of Ca2+. However, red cell Ca2+ concentrations were normally less than 0.15 mmol l-1 cell water, and may be physiologically insignificant in the context of the present study. A more complex pattern of change was encountered in the case of Mg2+. Concentrations of this ion and the [Mg2+]: [Hb] ratio declined between 10 degrees C and 20-22 degrees C and thereafter increased. A significant positive correlation existed between red cell levels of Cl- and K+; significant negative correlations between Cl- and Mg2+ and K+ and Na+. Negative, but insignificant correlations were also seen between Ca2+ and both Cl- and K+. Given the known direct and indirect effects of inorganic ions upon haemoglobin-oxygen affinity, the reductions in intraerythrocytic pH which accompany increases in temperature and the effects of temperature per se on affinity, the compositional changes observed in this study would be expected to prompt reductions in haemoglobin-oxygen affinity and increases in P50 values. Previous studies have, however, revealed little thermo-acclimatory variation in the P50 of this species. Thus, some as yet unidentified factor or factors may operate in opposition to these influences.

Water-electrolyte balance in goldfish Carassius auratus, under constant and diurnally cycling temperature conditions.

1. The effects of acclimation to constant and diurnally cycling temperatures upon water-electrolyte regulation were examined in goldfish held at 20, 25, 30 and 25 +/- 5 degrees C, and sampled at 03.00, 09.00 15.00 and 21.00 h. Plasma and epaxial muscle levels of Na, K, Ca, Mg, Cl and water were determined. Using Cl space as an indicator of extracellular phase volume, mean cellular cation concentrations were estimated. 2. Fish held at constant temperature exhibited significant diurnal variations in all ions except plasma magnesium and muscle potassium. With the exception of muscle choride, however, the occurrence of peak and/or minimum concentrations tended to be inconsistent in relation to specific sampling times. Somewhat more regularity was apparent in terms of dark or light periods. 3. Under constant temperature conditions plasma Cl increased with increasing temperature, while Na declined. Plasma magnesium was consistently higher at 25 degrees C than at either 20 or 30 degrees C. This was true of muscle Mg as well and, generally, also of Na, K and Cl. Water content tended to rise at higher temperatures in these animals, as did cellular phase volume, while extracellular phase volume was reduced. 4. Exposure to cycling temperatures was associated with a number of significant departures from the pattern seen at constant temperature. Ionic concentrations tended to be lower. By comparison with animals sampled at constant temperature and comparable times, diurnal stability was greater. In several instances (e.g. muscle Cl- and K+, cellular and extracellular phase volumes) variations with temperature were significantly different. This was also the case with ion pairs such as K and Na, and Ca and Mg. 5. These observations raise obvious questions regarding the validity of earlier descriptions of water-electrolyte status in species normally exposed to fluctuating temperatures. The variations seen under cycling temperature conditions, however, appeared to be adaptively appropriate. Reductions in plasma ion levels, for example, would tend to reduce costs of ionic regulation. The stability of plasma: cellular K concentrations should desensitize muscular excitability in relation to changing temperature conditions. This was also true of cellular levels of generally stimulating (Mg, K) and generally inhibitory ions (Ca, Na) known to influence metabolic processes.