Caractérisation de quelques activités enzymatiques digestives chez Mugil capito en relation avec la taille

The activities of esterase 2C, esterase 14C, L-leucine aminopeptidase, α-glucosidase, alkaline and acid phosphatases of the stomach, the caeca and the gut of Mugil capito were examined by polyacrylamide gradient gel electrophoresis. Fishes of three sizes were compared: the smallest only showed esterase 2C and phosphatases activities. Zymograms for each size and each organ were examined and the molecular weights of the isozymes evaluated with an accuracy of 10,000 daltons. It was found that (a) the existence of some isozymes is dependent to the size and the organ; (b) some enzymes are found only in some parts of the digestive tract; (c) for any given organ, enzymatic activity differs from one isozyme to another; and (d) the digestive enzymatic activities differ for each organ considered and in different ways dependent on the size of the fish.     

Thermal acclimation,mitochondrial capacities and organ metabolic profiles in a reptile (<Emphasis Type="Italic">Alligator mississippiensis</Emphasis>)

Reptiles thermoregulate behaviourally, but change their preferred temperature and the optimal temperature for performance seasonally. We evaluated whether the digestive and locomotor systems of the alligator show parallel metabolic adjustments during thermal acclimation. To this end, we allowed juvenile alligators to grow under thermal conditions typical of winter and summer, providing them with seasonally appropriate basking opportunities. Although mean body temperatures of alligators in these groups differed by approximately 10°C, their growth and final anatomic status was equivalent. While hepatic mitochondria isolated from cold-acclimated alligators had higher oxidative capacities at 30°C than those from warm-acclimated alligators, the capacities did not differ at 20°C. Cold acclimation decreased maximal oxidative capacities of muscle mitochondria. For mitochondria from both organs and acclimation groups, palmitate increased oligomycin-inhibited respiration. GDP addition reduced palmitate-uncoupled rates more in liver mitochondria from warm- than cold-acclimated alligators. In muscle mitochondria, carboxyatractyloside significantly reduced palmitate-uncoupled rates. This effect was not changed by thermal acclimation. The aerobic capacity of liver, skeletal muscle and duodenum, as estimated by activities of cytochrome c oxidase (COX), increased with cold acclimation. At acclimation temperatures, the activities of COX and citrate synthase (CS) in these organs were equivalent. By measuring COX and CS in isolated mitochondria and tissue extracts, we estimated that cold acclimation did not change the mitochondrial content in liver, but increased that of muscle. The thermal compensation of growth rates and of the aerobic capacity of the locomotor and digestive systems suggests that alligators optimised metabolic processes for the seasonally altered, preferred body temperature. The precision of this compensatory response exceeds that typically shown by aquatic ectotherms whose body temperatures are at the mercy of their habitat.     

Effects of temperature acclimation on cardiorespiratory performance of the Antarctic notothenioid Trematomus bernacchii

Notothenioid fishes of the Southern Ocean have evolved under cold and stable temperatures for millions of years. Due to rising temperatures in the Southern Ocean, investigating thermal limits and the capacities for inducing a temperature acclimation response in notothenioids has become of increasing interest. Here, we investigated effects of temperature acclimation on cardiorespiratory responses and cardiac and skeletal muscle energy metabolism in a benthic Antarctic notothenioid, Trematomus bernacchii. We acclimated specimens to ?1, 2 and 4.5 °C for 14 days and quantified heart rates and ventilation rates during an acute increase in temperature. Ventilation rates showed an effect of acclimation both at initial steady-state acclimation conditions and during an acute temperature increase, suggesting a partial thermal compensatory response. However, acclimation did not affect heart rates at steady-state acclimation conditions and the temperatures at which onset of cardiac arrhythmia occurred, suggesting lack of inducible thermal tolerance in cardiac performance. Citrate synthase (CS), lactate dehydrogenase (LDH) and 3-hydroxyacyl dehydrogenase activities in skeletal muscle tissues suggested acclimation-induced shifts in metabolic fuel preferences, and a marked increase in LDH activity with acclimation to 4.5 °C showed an increase in anaerobic metabolism. In heart tissue, CS and LDH activities decreased with acclimation to 4.5 °C, suggesting reduced cardiac ATP production. Overall, the data suggest a partial acclimatory response to temperature by T. bernacchii and support the hypothesis that reduced cardiac acclimatory capacity may play a role in limiting the thermal plasticity of T. bernacchii.     

Influence de la température sur quelques activités enzymatiques chez Palaemon serratus

Variation in Esterase 2 C activities, involving the hydrolysis of 2-carboxylic esters, α-glucosidase acetyl-glucosaminidase and alkaline and acid phosphotases, in the hepatopancreas and the abdominal muscle of Palaemon serratus was examined by polyacrylamide gradient gel electrophoresis. Soluble proteins were measured in the hepatopancreas and the abdominal muscle, and trypsin and chymotrypsin activities in the hepatopancreas. The activities and the isoenzymatic variations in shrimps acclimated at 5 different temperatures (between 14 and 30°) were compared and the molecular weight of each isozyme evaluated. It was found that: (a) the concentrations of soluble proteins decrease in the hepatopancreas between 18 and 30°, but remain unchanged in the abdominal muscle; (b) esterase and phosphatase activities increase with temperature but in a more or less random manner, according to the isozyme under consideration; (c) glycosidase activities increase with temperature; and (d) trypsin activity varies in an inverse relation to chymotrypsin activity.     

The effect of temperature and body size on digestive efficiency in Fundulus heteroclitus (L.)

The digestive efficiency of temperature acclimated mummichogs, Fundulus heteroclitus (L.), was determined using the amphipod Orchestia grillus Bosc as prey. Experiments were conducted on three size groups of mummichogs (<1 g, 1–3 g, > 3 g) at 5, 13, 21, and 29 °C. No difference was found in digestive efficiency by different sizes of mummichogs. There was, however, a statistically significant difference in efficiency over the range of acclimation temperatures, with the efficiencies being temperature independent from 13 to 29 °C and dropping slightly at 5 °C. From 13 to 29 °C, digestive efficiencies were the maximum possible. Temperatures in this range are normal late spring, summer, and early fall habitat temperatures in Maine estuaries. The ability to maintain a maximum efficiency of digestion over this 16°C temperature range allows mummichogs to get the maximum amount of energy from their prey during the time of year when they are utilizing substantial energy for growth (somatic and gonadal, and for activity (foraging and mating). The digestive efficiency at 5 °C was only about 13.5% less than at 21 and 29 °C. This drop is probably of little ecological or energetic significance, so that mummichogs are actually able to absorb food energy across their alimentary tract relatively independent of acclimation temperature over a 24 °C range.     

Electrophoretic study of heating in situ on proteins and enzymes in germinated Arachis hypogaea cotyledons: Comparison with dormant seed

-Cotyledons from 5-day germinated seed of Arachis hypogaea were heated in a moisturized chamber at temperatures from 25 to 121°. Proteins were extracted in phosphate buffer and analyzed with horizontal starch gel electrophoresis to determine the effect of heat on migration patterns of soluble proteins, malate dehydrogenase, glutamate dehydrogenase, leucine aminopeptidase, peroxidases and nonspecific esterases. The intensity of staining of soluble proteins from 5-day cotyledons began decreasing at 80–90°; very little staining occurred at 100° with the exception of a distinct band at R_f 1·0. Glutamate dehydrogenase and benzidine peroxidase retained some activity at 80° but other enzymes were inactivated at temperatures near 65°. Differential heat sensitivities of isoenzymes were obvious. Heat did not alter the R_f values of the bands of soluble proteins or enzymes but influenced the intensity of staining. Two-year storage at 4° of viable seed and 33-month storage at -10° of frozen extracts from dormant seed had no influence upon migration patterns of soluble proteins and enzymes assayed.     

Temperature acclimation in respiratory and cytochrome c oxidase activity in common carp (Cyprinus carpio)

• 1.1. Common carp (Cyprinus carpio) exposed to experimental temperatures of 12, 18, 24, 30 or 36°C for a 4-week period were used to investigate the effect of temperature acclimation on the frequency of opercular movement (FOM), growth and cytochrome c oxidase (CCO) activity in heart, liver and muscle.
• 2.2. An exponential relationship between FOM and temperature after the first week (10₁₀ =1.76) disappeared after the second week.
• 3.3. The initially high FOM at temperatures of 30 or 36°C and the low FOM at 18 or 12°C changed over 4 weeks to approach the FOM of fish at 24°C.
• 4.4. This change in the relationship of FOM to temperature from highly dependent to independent appeared to be thermal compensation.
• 5.5. Heart and liver CCO activities were significantly affected by temperature, with the lowest activity at the approximate optimum temperature for growth, 24°C.
• 6.6. Highest CCO activities for heart and liver occurred at both the highest and lowest temperatures.
• 7.7. Among the three tissues, heart CCO activity was generally the highest and most affected by acclimation temperature.
• 8.8. Muscle tissue had the lowest CCO activity and was unaffected by temperature.
• 9.9. The high CCO activity at a cold acclimation of temperature 12°C was probably due to thermal compensation and the high activity at 36°C may have been a result of thermal stress.

     

The glutathione-dependent system of antioxidant defense is not modulated by temperature acclimation in muscle tissues from striped bass,Morone saxatilis

Cold temperature generally induces an enhancement of oxidative capacities, a greater content of intracellular lipids, and a remodeling of lipids in biological membranes. These physiological responses may pose a heightened risk of lipid peroxidation (LPO), while warm temperature could result in greater risk of LPO since rates involving reactive oxygen species and LPO will be elevated. The current study examines responses of the glutathione system of antioxidant defense after temperature acclimation. We measured total glutathione (tGSH), and protein levels of GPx1, GPx4, and GST (cardiac and skeletal muscles), and enzymatic activity (skeletal muscle) of glutathione-dependent antioxidants (GPx, GPx4, and GST) in tissues from striped bass (Morone saxatilis) acclimated for six weeks to 7 °C or 25 °C. tGSH of cardiac muscle from cold-acclimated animals was 1.2-times higher than in warm-bodied counterparts, but unchanged with temperature acclimation in skeletal muscle. A second low molecular weight antioxidant, ascorbate was 1.4- and 1.5-times higher in cardiac and skeletal muscle, respectively in warm- than cold-acclimated animals. Despite 1.2-times higher oxidative capacities (as indicated by citrate synthase activity), in skeletal muscle from cold- versus warm-acclimated fish, levels and activities of antioxidant enzymes were similar between acclimation groups. Lipid peroxidation products (as indicated by TBARS), normalized to tissue wet weight, were more than 2-times higher in skeletal muscle from cold- than warm-acclimated animals, however, when normalized to phospholipid content there was no statistical difference between acclimation groups. Our results demonstrate that the physiological changes, associated with acclimation to low temperature in the eurythermal striped bass, are not accompanied by an enhanced antioxidant defense in the glutathione-dependent system.     

Enzyme cytochemistry of rat organs after uremia with special reference to proteases

Wistar rat organs and tissues were investigated after acute and chronic uremia using enzyme cytochemical means whereby special attention was paid to plasma membrane and lysosomal proteases. Heart muscle, pancreas, spleen, stomach, duodenum, jejunum, colon and skeletal muscle did not show any clear-cut indications of alterations. After acute uremia activities of dipeptidyl peptidase IV, glutamyl aminopeptidase and microsomal alanyl aminopeptidase were decreased in the extraorbital gland and that of dipeptidyl peptidase IV in the submandibular gland. The thymus showed an increased staining for glutamyl aminopeptidase and lysosomal proteases. An activity increase of dipeptidyl peptidase IV, acid phosphatase and beta-N-acetyl-D-glucosaminidase occurred in bronchial lavage cells among which the alveolar macrophages predominated. In addition, their number was comparatively higher. Non-specific esterase activity was lowered in these cells. Alkaline phosphatase activity was drastically enhanced at the biliary pole of hepatocytes. Following chronic uremia all effects were less pronounced except for the lavage cells which were positive for glutamyl aminopeptidase, microsomal alanyl aminopeptidase and gamma-glutamyl transpeptidase and showed increased staining for lysosomal proteases, glycosidases and nonspecific phosphatases.     

Characterization of an aminopeptidase from Pseudozyma hubeiensis 31-B and potential applications

Yeast strain 31-B was isolated from the digestive juices of Nepenthes alata as an aminopeptidase producer and identified as Pseudozyma hubeiensis via morphological testing and comparative 26S ribosomal DNA-D1/D2 gene sequence analysis. Strain 31-B produced aminopeptidase as extracellular peptidase, but proteinase activity was not detected in the culture filtrate. The aminopeptidase from strain 31-B was purified from filtered culture medium by (NH₄)₂SO₄ precipitation and four column chromatography steps: Diethylaminoethyl (DEAE)-Toyopearl 650 M, Butyl-Toyopearl 650 M, hydroxylapatite, and Toyopearl HW-55. Sodium dodecyl sulfate polyacrylamide gel electrophoresis yielded the purified enzyme as a single band with molecular mass 75.3 kDa. The optimum temperature and pH were approximately 40 °C and 8.0, respectively. The purified aminopeptidase preferentially hydrolyzed Leu-p-NA and its activity was inhibited by ethylenediaminetetraacetic acid. The isolated aminopeptidase reduced the bitterness of peptides generated from milk casein using a bacterial proteinase. These results show that the aminopeptidase produced by P. hubeiensis 31-B has potential application as a food additive in the dairy industry.     

Is digestive capacity limiting growth at low temperatures in roach?

In roach Rutilus rutilus growth ceases below a temperature threshold of 12° C. This cessation of growth is accompanied by a reduction in feeding. Do roach decrease feeding in the cold because of reduced energy demand, caused by the decelerating effect of low temperature on metabolism and growth, or is feeding directly limited by low temperatures, leading to reduced growth rates? It was found that at low temperatures the intake and digestion of food may be limited by reduced activities of digestive enzymes. Trypsin, amylase and γ‐glutamyl transferase showed a negative compensation with respect to temperature, resulting in very low activities at acclimation temperatures of ≤12° C. Trypsin activity, falling from 400·5 ± 131·2 U g^?1 fresh mass of the gut at 27° C to 12·5 U g^?1 fresh mass at 4° C, displayed the strongest linear correlation with growth rates, suggesting that trypsin activities may set a limit to growth in the low temperature range. If protein digestion is limiting at low temperatures, this should be reflected in reduced concentrations of amino acid in the white muscle. The size of the total amino acid pool was not affected by temperature acclimation and ranged between 19·2 ± 6·2 and 25·2 ± 3·6 µmol g^?1 fresh mass of the white muscle. A decrease, however, was found of several amino acids, mainly of threonine and glutamine, in the low temperature range. Low concentrations of the essential amino acid threonine (0·14 ± 0·03 µmol g^?1 fresh mass at 12° C and 0·12 ± 0·05 µmol g^?1 fresh mass at 4° C) were probably due to nutritional or digestional limitations and may therefore have resulted from reduced trypsin activity in the cold. The non‐essential amino acid glutamine, however, can be endogenously synthesized and its low level observed at 4° C (0·16 ± 0·09 µmol g^?1 fresh mass) was not necessarily a result of low trypsin activities. It is more likely that low temperatures impair glutamine synthesis. The possibility that glutamine concentrations may be down regulated under conditions when anabolic processes are not advantageous is discussed.     

Temperature-dependent physiological and biochemical responses of the marine medaka Oryzias melastigma with consideration of both low and high thermal extremes

This study aimed to investigate temperature effect on physiological and biochemical responses of the marine medaka Oryzias melastigma larvae. The fish were subjected to a stepwise temperature change at a rate of 1 °C/h increasing or decreasing from 25 °C (the control) to six target temperatures (12, 13, 15, 20, 28 and 32 °C) respectively, followed by a 7-day thermal acclimation at each target temperature. The fish were fed ad libitum during the experiment. The results showed that cumulative mortalities were significantly increased at low temperatures (12 and 13 °C) and at the highest temperature (32 °C). For the survivors, their growth profile closely followed the left-skewed ‘thermal performance curve’. Routine oxygen consumption rates of fish larvae were significantly elevated at 32 °C but suppressed at 13 and 15 °C (due to a high mortality, larvae from 12 °C were not examined). Levels of heat shock proteins and activities of malate dehydrogenase and lactate dehydrogenase were also measured in fish larvae exposed at 15, 25 and 32 °C. The activities of both enzymes were significantly increased at both 15 and 32 °C, where the fish larvae probably suffered from thermal discomfort and increased anaerobic components so as to compensate the mismatch of energy demand and supply at these thermal extremes. Coincidently, heat shock proteins were also up-regulated at both 15 and 32 °C, enabling cellular protection. Moreover, the critical thermal maxima and minima of fish larvae increased significantly with increasing acclimation temperature, implying that the fish could develop some degrees of thermal tolerance through temperature acclimation.     

Salivary digestive enzymes of the wheat bug, Eurygaster integriceps (Insecta: Hemiptera: Scutelleridae)

The digestive enzymes from salivary gland complexes (SGC) of Eurygaster integriceps, and their response to starvation and feeding were studied. Moreover, digestive amylases were partially purified and characterized by ammonium sulfate precipitation and gel filtration chromatography. The SGC are composed of two sections, the principal glands and accessory glands. The principal glands are further divided into the anterior lobes and posterior lobes. The SGC main enzyme was α-amylase, which hydrolyzed starch better than glycogen. The other carbohydrases were also present in the SGC complexes. Enzymatic activities toward mannose (α/β-mannosidases) were little in comparison to activities against glucose (α/β-glucosidases) and galactose (α/β-galactosidases), the latter being the greatest. Acid phosphatase showed higher activity than alkaline phosphatase. There was no measurable activity for lipase and aminopeptidase. Proteolytic activity was detected against general and specific protease substrates. Activities of all enzymes were increased in response to feeding in comparison to starved insects, revealing their induction and secretion in response to feeding pulse. The SGC amylases eluted in four major peaks and post-electrophoretic detection of the α-amylases demonstrated the existence of at least five isoamylases in the SGC. The physiological implication of these findings in pre-oral digestion of E. integriceps is discussed.     

Experimental evidence for interactions between bacterial peptidase and alkaline phosphatase activity in the Baltic Sea

From the observed pattern of aminopeptidase and alkaline phosphatase activities in the Baltic Sea, the question arose whether there is an interaction between the activities of both enzymes. In experiments with 0.8 m filtered seawater, the effects of commercial alkaline phosphatase on bacterial aminopeptidase, the effects of commercial peptidase on bacterial alkaline phosphatase activity (APA), and the effects of proteins, carbohydrates and inorganic nutrients on the activities of both enzymes were investigated.Addition of commercial alkaline phosphatase stimulated bacterial aminopeptidase activity and, similarly, the addition of commercial peptidase increased the APA in bacteria. The proteins, albumin and casein, stimulated aminopeptidase activity and APA simultaneously. Experiments using ammonium and glucose suggested that stimulation of APA by peptidase could be mediated by nitrogen and carbon availability. There were also some indications that stimulation of aminopeptidase activity by alkaline phosphatase functioned by catalysing phosphate release from organic phosphorus compounds.     

Differential temperature dependencies of antioxidative enzymes in two contrasting species: Fagus sylvatica and Coleus blumei

In order to characterise the sensitivity of antioxidative systems to temperature-induced oxidative stress, two species (Coleus blumei and Fagus sylvatica, L.) representative of environments with contrasting temperature characteristics have been exposed to low or high temperatures of 10 or 35 °C, respectively. Beech leaves were harvested in light and darkness. Coleus leaves were separated into green and white leaf tissue. The thermal dependencies of the activities of protective enzymes and chlorophyll fluorescence over a temperature range from 10 to 35 °C were determined. Ascorbate peroxidase activities were activated at low temperatures in vitro and, thereby, may provide an instantaneous protection against H₂O₂ accumulation which is faster than de novo synthesis. Monodehydroascorbate radical reductase was apparently not involved in short-term acclimation to low or high temperature. After short-term acclimation to low temperature, glutathione reductase and glutathione were more diminished in Coleus than in beech. Both species contained higher concentrations of ascorbate and glutathione at high temperatures than at low temperatures whereas glutathione reductase activity increased. Ascorbate peroxidase activity from Coleus leaves, though detectable under standard assay conditions (25 °C), failed at 35 °C in vitro. The results suggest that the higher temperature susceptibility of Coleus than that of beech was associated with a differential loss in glutathione reductase/glutathione at low temperature and an inhibition of ascorbate peroxidase at high temperature. Since the thermal dependencies of antioxidative enzymes were significantly affected by the preceding environmental conditions, the relative enzymatic activities determined under standard assay conditions may not be representative of enzymatic activities in foliage exposed to varying environmental temperatures.     

White muscle 20S proteasome activity is negatively correlated to growth rate at low temperature in the spotted wolffish Anarhichas minor

The effect of temperature and mass on specific growth rate (G) was examined in spotted wolffish Anarhichas minor of different size classes (ranging from 60 to 1500 g) acclimated at different temperatures (4, 8 and 12° C). The relationship between G and 20S proteasome activity in heart ventricle, liver and white muscle tissue was then assessed in fish acclimated at 4 and 12° C to determine if protein degradation via the proteasome pathway could be imposing a limitation on somatic growth. Cardiac 20S proteasome activity was not affected by acclimation temperature nor fish mass and had no correlation with G. Hepatic 20S proteasome activity was higher at 12° C but did not show any relationship with G. Partial correlation analysis showed that white muscle 20S proteasome activity was negatively correlated to G (partial Pearson's r = ?0·609) but only at cold acclimation temperature (4° C). It is suggested that acclimation to cold temperature involves compensation of the mitochondrial oxidative capacity which would in turn lead to increased production of oxidatively damaged proteins that are degraded by the proteasome pathway and ultimately negatively affects G at cold temperature.     

Synthesis and secretion of alkaline phosphatase in vitro from first-trimester and term human placentas.

The synthesis and secretion of alkaline phosphatases in vitro by human placental tissue incubated in organ culture were studied. First-trimester placenta synthesizes and secretes two different alkaline phosphatase isoenzymes (heat-labile and heat-stable), whereas in term placenta nearly all the alkaline phosphatase synthesized and secreted is heat-stable. The specific activities of alkaline phosphatases in first-trimester and term placental tissue remain constant throughout the time course of incubation. In the media, specific activities increase with time. Hence, alkaline phosphatase synthesis seems to be the driving force for its own secretion. The rates of synthesis de novo and of alkaline phosphatases were measured. The specific radioactivities of the secreted alkaline phosphatases were higher than the corresponding specific radioactivities in the tissue throughout the entire incubation period. The intracellular distribution of the alkaline phosphatase isoenzymes was compared.     

Effect of thermal acclimation on subunit cooperativity in Palaemon serratus glutamate dehydrogenase

Glutamate dehydrogenase (GDH) from the abdominal muscle of the shrimp Palaemon serratus displays a complex cooperatively pattern with respect to the cofactor (NAD) and substrate (glutamate) concentrations: at low concentrations negative cooperativitiy is predominant whereas positive cooperativity prevails at high concentrations. GDH is sensitive to thermal variations of the environment and to conditions of thermal acclimation. The maximum cooperativity indexes (positive and negative) are obtained at 13° for NAD irrespective of the acclimation temperature (13 or 18°). In contrast, for glutamate, positive cooperativity is only observed at temperatures near the acclimation temperature. At 13° for animals adapted at 18° and at 27° for animals adapted at 13° a complete loss of subunit cooperativity and a Michaelian kinetic pattern are observed.     

TEMPERATURE ACCLIMATION AND THE NERVOUS SYSTEM

1. The conduction velocity of the compound action potential of peripheral nerves shows compensatory acclimation to temperature in a fish, a snail, a crab, and probably also in the frog. The heat and cold tolerances of peripheral conduction are probably both increased by cold acclimation in the frog. 2. The properties of compound action potentials are not suitable for temperature acclimation studies, since different neuronal populations in the same nerve have been found to exhibit different temperature characteristics. 3. Single but septate giant nerve fibres of earthworms show compensatory temperature acclimation of the conduction properties, the form of the action potential and of the axonal cable properties, especially below 13–19 °C. 4. The fatty acids and the plasmalogen aldehydes of the phospholipids of the goldfish brain are more unsaturated at lower acclimation temperatures. 5. The Na⁺-K⁺ ATPase activity of the earthworm nerve cord shows compensatory acclimation at low temperatures. 6. The spontaneous activity of the central nervous system of insects is altered in a compensatory manner by temperature acclimation. In fish, the cold tolerance of simple and complex reflexes and of conditioning is adaptively altered by temperature acclimation. The role of the central nervous system, especially of the thermoregulatory centre, in the temperature acclimation of homeotherms is established. 7. There are adaptive isoenzymes of acetylcholinesterase in the brain of the rainbow trout. These isoenzymes differ from each other in respect of the temperature dependence of their enzyme-substrate affinity. The synthesis of acetylcholine receptor molecules may also be affected by temperature acclimation. 8. The metabolism of putative synaptic neurotransmitters (5-hydroxytryptamine, adrenaline, noradrenaline) is altered in the frog and mouse brains during the early phases of temperature acclimation. These changes may initiate the physiological processes connected with temperature acclimation. 9. The neuromuscular transmission in the frog shows after acclimation to cold, increased resistance to it and some indications of temperature compensation. 10. Changes in neurosecretion seem to be involved in temperature acclimation both in poikilotherms and homeotherms. The fast axonal transport of proteins shows compensatory acclimation to cold in the frog.     

Enzyme cytochemistry of rat organs after uremia with special reference to proteases

Summary Wistar rat organs and tissues were investigated after acute and chronic uremia using enzyme cytochemical means whereby special attention was paid to plasma membrane and lysosomal proteases. Heart muscle, pancreas, spleen, stomach, duodenum, jejunum, colon and skeletal muscle did not show any clear-cut indications of alterations. After acute uremia activities of dipeptidyl peptidase IV, glutamyl aminopeptidase and microsomal alanyl aminopeptidase were decreased in the extraorbital gland and that of dipeptidyl peptidase IV in the submandibular gland. The thymus showed and increased staining for glutamyl aminopeptidase and lysosomal proteases. An activity increase of dipeptidyl peptidase IV, acid phosphatase and -N-acetyl-d-glucosaminidase occurred in bronchial lavage cells among which the alveolar macrophages predominated. In addition, their number was comparatively higher. Non-specific esterase activity was lowered in these cells. Alkaline phosphatase activity was drastically enhanced at the biliary pole of hepatocytes. Following chronic uremia all effects were less pronounced except for the lavage cells which were positive for glutamyl aminopeptidase, microsomal alanyl aminopeptidase and -glutamyl transpeptidase and showed increased staining for lysosomal proteases, glycosidases and nonspecific phosphatases.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthdaySupported by the German Research Foundation (Sfb 174)