J. Planas

Changes in plasma glucagon, insulin and tissue metabolites associated with prolonged fasting in brown trout (Salmo trutta fario) during two different seasons of the year

1. Pyrenean brown trout juveniles (Salmo trutta fario) were fasted for 50 days in late winter (experiment 1) and summer (experiment 2). Plasma insulin, glucagon and glucose and some metabolites in plasma and in tissues were analysed. 2. Glucagon increased significantly on the 3rd day of fasting in the winter experiment (controls 653.7 +/- 92.4 pg/ml, fasted 912.7 +/- 135.2 pg/ml), and the same tendency was observed on the 5th day in the summer experiment (controls 430.5 +/- 56.2 pg/ml, fasted 555.5 +/- 95.3 pg/ml). During this initial period of fasting, plasma glucose was maintained in both experiments (75.5 +/- 4.7-67.6 +/- 4.1 mg/100 ml), but from day 8, glucose and glucagon decreased simultaneously. 3. Insulin decreased from the beginning of fasting, reaching lowest values after 50 days of fasting (winter experiment: controls 6.4 +/- 0.3 ng/ml, fasted 1.6 +/- 0.1 ng/ml; summer experiment: controls 4.8 +/- 0.1 ng/ml, fasted 1.2 +/- 0.2 ng/ml). Glucagon/insulin molar ratio (G/I) increased after 3 days in the winter experiment (controls 0.21 +/- 0.02, fasted 0.39 +/- 0.05), while in the summer experiment, the ratio rose from day 5 and reached a peak at day 30 (controls 0.16 +/- 0.02, fasted 0.48 +/- 0.07). 4. Muscle proteins were significantly mobilized after 50 days of fasting. Visceral index decreased significantly after day 15 while liver glycogen was already significantly lower at day 8. However, in the summer experiment, a transitory increase of liver glycogen was observed at day 30, coinciding with the peak of G/I.

Comparative respiratory functions of blood in some passeriform birds

Abstract 1. 1. Classical hematological parameters, hemoglobin oxygen affinity and Bohr effect have been determined in 16 species of 9 families (Fringilidae, Sylvidae, Turdidae, Prunellidae, Ploceidae, Certhidae, Emberizidae. Paridae and Troglodytidae) of the order Passeriform. 2. 2. The average values of the hematological parameters show a tendency to be high due to the greater metabolic rate of the passeriform group. 3. 3. The P50 of the different species was between 43 and 53 torr, and the Bohr effect ranged from −0.403 to −0.532. 4. 4. A parallel may be made between altitude adaptation for hypoxia and high oxygen requirements for activity.

Muscle myoglobin and flying habits in birds

Abstract 1. 1. The myoglobin (Mb) content of different muscles (heart, pectoral, wing, thigh and gastrocnemius) in chickens (New Hampshire strain), quail (Wild quail, Coturnix coturnix coturnix; and farm quail, Coturnix c. japonica), urban pigeons (Columbia livia), starling (Sturnus vulgaris) and seagulls (Larus argentatus and L ridibundus) have been analyzed. 2. 2. Differences in Mb in the same muscle from different species, have been statistically demonstrated. The Mb concentration data (0.59–6.8 mg Hb/g wet muscle) from these species, fits in well with the range in birds, compiled from the literature. 3. 3. Differences in Mb content in the same muscle, from different species, have been statistically shown. However, it is difficult to establish a relationship with flight habits. 4. 4. After only a 2 week captivity in pigeons, the myoglobin content was already significantly reduced in heart, pectoral and wing muscles, but not in the leg muscle.

Hexose transport across the apical and basolateral membrane of enterocytes from different regions of the chicken intestine

The properties of hexose transport across the apical and basolateral membranes of chicken enterocytes have been studied in the small and large intestine. Results show that (a) isolated epithelial cells from all segments except the coprodeum can accumulate 3-O-methylglucose (Glc3Me) against a concentration gradient, by a Na+-dependent and phloridzin-sensitive mechanism, (b) The cell cumulative capacity for Glc3Me (control/phloridzin-incubated cells) is lower in the small intestine than in the large intestine (rectum = proximal caecum = ileum > jejunum > duodenum). (c) Theophylline enhances the cell Glc3Me cumulative capacity 2.9-fold in the duodenum and 2.4-fold in the jejunum but has no effect in the other segments studied. (d) Analysis of sugar uptake indicates that net hexose influx rates decrease from proximal to distal regions: jejunum > duodenum > ileum = proximal caecum = rectum for the apical transport system (α-methyl glucoside as substrate and phloridzin as inhibitor) and duodenum > jejunum > ileum = proximal caecum = rectum for the basolateral system (2-deoxyglucose; theophylline). (e) The duodenum and the jejunum show high apical and basolateral hexose transport rates, which confer a significant capacity for sugar absorption on the proximal intestine. More distal regions, including the ileum, the proximal caecum and the rectum, have transport systems analogous to those of the proximal intestine that keep a considerable potential capability to recover hexoses from the lumen.

Characterization of D-fructose transport by rat kidney brush-border membrane vesicles: changes in hypertensive rats.

Abstract: D-fructose transport was characterized in renal brush-border membrane vesicles (BBMVs) from both spontaneously hypertensive rats (SHR) and normotensive genetic control Wistar-Kyoto (WKY) rats. Kinetic studies indicated that the maximal rate (Vmax) of D-fructose transport was significantly lower in SHR compared with WKY rats. No differences were observed in the Michaelis constant (Km) or the diffusion constant (Kd) between the two groups of animals. D-fructose inhibited its own transport, whereas the presence of D-glucose, D-galactose, phlorizin, and cytochalasin B did not inhibit the transport of D-fructose in either animal group. To explain the reduction in D-fructose transport in SHR, the density of the D-fructose transporter, GLUT5, was analyzed by Western blot. GLUT5 levels were lower in SHR, a reduction similar to that of the Vmax. Thus, there appears to be a high-affinity, low-capacity, GLUT5-type fructose carrier in the apical membranes of rat kidney cortex, and the decrease in the Vmax of D-fructose transport in renal BBMVs from hypertensive rats correlates well with a reduction in the expression of GLUT5 protein.

Characteristics of the chicken proximal cecum hexose transport system

The properties of the sugar transport system present in chicken proximal cecum have been studied and compared to the jejunal transport system. Experiments were carried out in isolated enterocytes from 5- to 7-weak-old birds. Results show that: (1) Cecal cells are capable of high sugar transport rates by a phloridzin-sensitive mechanism. After 60 min incubation, the accumulation ratio (control/phloridzin-incubated cells) for 0.1 mmol/l α-methyl-d-glucoside (α-MG) was 43 and that of 3-oxy-methyl-d-glucose (3-OMG) was 25. In jejunal cells, ratios were 37 for α-MG and 13 for 3-OMG. The differences found in cumulative capacity of 3-OMG between cecal and jejunal cells suggest that the sodium-independent pathway offers a very small contribution to sugar efflux in the steady-state in the former cells. (2) Lowering external Na+ concentration reduces the steady-state α-MG accumulation in cecal cells (as in jejunal cells), indicating that the transport system is Na+-dependent. (3) The process depends on the electrochemical Na+ gradient across the cell membrane since both 2,4-dinitrophenol (0.2 mmol/l) and ouabain (0.25 mmol/l) abolish sugar accumulation. (4) Addition of 10 mmol/l 3-OMG to the incubation medium markedly reduces the uptake of α-MG (concentration: 0.1 mmol/l), indicating that the cecal transport system can be inhibited by analogues of the transported substrate. (5) The specific sugar transport process is a saturable function of α-MG concentration, the apparentKm being 1.02 mmol/l andVm 10.7 nmol/mg cell protein · min. Kinetic constants in jejunal enterocytes were 1.58 mmol/l (Km) and 24.7 nmol/mg cell protein · min (Vm), respectively. In brief, the proximal cecal epithelium has a sugar transport system with properties similar to those of the jejunum which suggests a role of this epithelium in the absorption of hexoses of either ileal or cecal origin.

Hexose transport by chicken cecum during development

Hexose accumulation during development has been studied in tissue slices from chicken cecum. The age of birds ranged from 0 to 7 weeks after hatch. Ceca were divided into six portions according to their situation either proximal (PC), medial (MC) or distal (DC) to the ileocecal junction. In 0-day-old chicks all segments can accumulate 3-O-methyl-d-glucose (0.5 mmol/l) against a concentration gradient through a phloridzin-sensitive mechanism.Cumulative capacity is lower in DC than in PC and declines with development. Distal segments lose sugar transport ability 1–2 days after hatch whereas the medial region retains some concentrative ability in older birds. In 7-week chickens, PC slices have a similar cumulative ability to that of jejunum (yolk sac region). Kinetic studies showed that in PC the apparentKm for phloridzin-sensitive transport was half that in 1-day- than in 7-week-old birds; apparentVm increased by 50% in this time range. The ability to transport sugars by the cecum was further confirmed in isolated enterocytes from 5- to 7-week-old chickens using α-methyl-d-glucoside (0.1 mmol/l) as substrate. Cell sugar concentration was greater in PC than in jejunal cells and jejunal greater than MC enterocytes. Sugar present in cells from DC was the same as in phloridzin-treated cells. It is concluded that cecal epithelium may play a significant role in the absorption of sugars during development.

Blood respiratory properties of swifts

Abstract 1. 1. The mean hematological values obtained in Apus apus, A. melba and A. pallidus were, respectively; Hematocrit: 50, 51 and 54%; Hemoglobin concentration: 17.8, 18.8 and 18.3 g%; RBC count: 4.66, 4.02 and 5.27 mill/cc; Oxygen affinity (P50): 39, 35 and 35 mm Hg; Bohr effect: −0.48, −0.46 and −0.36; Oxygen capacity: 15.8 and 14.7 ml O2%. 2. 2. The breast and heart relative to body weight were 18.9, 15.6 and 19.7%; and 1.26, 0.93 and 1.25% in Apus apus, A. melba and A. pallidus respectively. 3. 3. The hematological and anatomical values are discussed in relation to the peculiar flight habits of this apodiform group.

Annual cycle of plasma lipids in sea bass, Dicentrarchus labrax L.: Effects of environmental conditions and reproductive cycle

Abstract 1. 1. Plasma lipid concentrations in sea bass were very high compared to reported levels in other fish (mean value: 32.1 g/1 total lipids; range of values: 11.1–107.0 g/1, of which 35.2% were phospholipids and 15.5% were cholesterol). Plasma acetoacetate levels were low and plasma free-glycerol high. No appreciable levels of 3-hydroxybutyrate were detected. 2. 2. Definite seasonal fluctuations occurred in the plasma levels of all parameters studied. Lipid phosphorus (LP), free glycerol (FGly) and acetoacetate (AcAc) presented the greatest variations throughout the year, whereas cholesterol showed more regular values. 3. 3. In summer, plasma levels of the lipidic fractions were low, but during the gonadal maturation period (September-December) transient increases in all lipid parameters were observed. At spawning, when temperature and photoperiod were the lowest of the year, total lipids (TL) and fractions as well as AcAc reached minimal levels. 4. 4. Plasma lipid variations observed in the fish adapted to 3.5%.S are more directly related to the alterations in the reproductive cycle caused by the different environmental conditions, than to the salinity change per se.

Seasonal variations of insulin and some metabolites in dogfish plasma, Scyliorhinus canicula, L

Plasma levels in insulin, glucose, ketone bodies, and lactate were analyzed during a 1-year period in the lesser spotted dogfish (Scyliorhinus canicula) in captivity. Plasma insulin levels fluctuated similarly for both sexes. The highest insulin levels were found during late prespawning (from January to March) and another increase was observed during the active feeding period (September and October). During the spawning period, insulin decreased and in the postspawning period the lowest values were reached. Glucose, however, showed a different trend. It was at a minimum in late prespawning and it reached its highest values in postspawning. It decreased again in September and October. Plasma ketone body levels were highest in late prespawning and could be considered as an alternative energy source for this hypoglycemic period. In the summer months plasma lactate levels rose, with maximum levels occurring in July.