Cholecystokinin and serotonin receptors in the regulation of fat-induced satiety in rats

The present study investigated the relationship between endogenous CCK and serotonin (5-HT) in fat-induced satiety. Male Wistar rats with duodenal cannulas were adapted to eating 6 h/day along with receiving an infusion of saline or one of two isocaloric solutions (10 ml, 1 kcal/ml, 0.45 ml/min) varying in fat and carbohydrate content (20 or 80% energy from fat). Rats were infused 10 min after food presentation. The satiation/satiety response was determined from measures of meal size (MS), intermeal interval (IMI), and total food intake (TFI). Infusion with either fat solution reduced MS compared with saline; however, the 80% fat infusate reduced TFI and lengthened the IMI compared with saline and the 20% fat infusate. CCK and 5-HT involvement in fat-induced satiety was investigated by preceding the 80% fat infusate with CCK and/or 5-HT3 receptor antagonists Devazepide (Dev) and Tropisetron (Trop). A CCK releaser, trypsin inhibitor (TI), was added to the 20% fat infusate to enhance satiety. Pretreatment with Dev or Trop alone attenuated the inhibitory effects of the 80% solution on IMI, whereas reversal of the inhibitory effects on MS and TFI were sensitive only to Dev at the doses provided. Both antagonists together completely blocked the satiating effects of the 80% fat infusate on all feeding variables measured. Addition of TI to the 20% fat infusate lengthened the IMI but did not affect MS or TFI. These results provide evidence for the participation of both endogenous CCK and 5-HT in the satiety response to fat in the intestine.

The Effect of GDL-induced pH Decrease on the Formation of Biogenic Amines in Meat

The effect of pH on the formation of biogenic amines has mainly been studied in broths in which pH has been fixed before incubation. However, in the fermentation of dry sausage, pH quite rapidly decreases from the initial value to a certain level. In this study glucono-delta-lactone (GDL) was used to decrease pH in meat, Six minced meat samples were each divided into three portions (A–C): 0% (A), 0.5% (B), or 1.0% (C) of GDL was added and the samples were incubated at 20–22°C for 7 d. The amounts of biogenic amines (histamine, tyramine, putrescine, cadaverine, phenylethylamine, tryptamine, spermine, and spermidine) as well as pH, water activity, and the bacterial counts of lactic acid bacteria, fecal streptococci, coliforms, and total plate count were measured. Addition of GDL resulted in a significant decrease in pH and in the levels of histamine and putrescine as well as in the levels of fecal streptococci, coliforms, and total plate counts. Of 87 fecal streptococci, seven Enterococcus faecalis strains produced tyramine. All the coliforms and related strains isolated from violet red bile agar produced tyramine, putrescine, and cadaverine on agar plates. However, the proportion of histamine-positive strains of these strains, especially Hafnia alvei, increased from 0 to 57% during the incubation. The rate and level of pH decrease clearly affected amine formation in meat, indicating that the levels of, e.g., histamine produced could be decreased by optimizing the pH decrease during fermentation. Addition of GDL facilitates study of the effect of pH decrease without interactions between the starter culture and contaminant flora.

Inhibition of rat follicular androgen synthesis by dibutyryl cyclic AMP

LH exerts a biphasic effect on rat follicular steroidogenesis: an initial general stimulation of steroidogenesis later followed by an inhibition of androgen and oestrogen synthesis. It is known that the stimulation by LH of steroidogenesis is mediated by cAMP. The present paper examines the role of cAMP in the late inhibitory phase of steroidogenesis. Pre-ovulatory follicles were isolated from PMSG treated immature rats and incubated in modified bicarbonate buffer for different time periods. The accumulation of progesterone (P), androstenedione (A), testosterone (T) and oestradiol-17β (E2) in the medium was measured. Addition of dibutyryl cAMP (dbcAMP, 1 mm) to the medium caused a prolonged increase in P accumulation for 10 h while A and E2 accumulation was stimulated only for 4–6 h whereafter the levels were sustained. The pattern was identical to that produced by LH (10 μg/ml) in vitro. In a second type of experiments follicles were pre-incubated for 6 h with or without LH or dbcAMP and then transferred for a second 2 h incubation, in the presence or absence of unlabelled 17-hydroxyprogesterone (17-OHP) or T (1 μg/ml). Follicles pre-incubated in plain medium increased their formation of A and T in the presence of 17-OHP, while follicles exposed to LH or dbcAMP did not. Addition of T caused a similar increase in E2 formation in all groups (control, LH and dbcAMP). It is concluded that since dbcAMP mimicked the entire response of follicular steroidogenesis normally elicited by LH, cAMP seems to be the physiologic mediator of LH, both on the early stimulatory and on the late inhibitory phase of pre-ovulatory follicular steroidogenesis.

Staphylococcal Enterotoxin A and C Production with Various Sugars as Energy Source1

One percent added sugar (sucrose, maltose, lactose, glucose and glucose plus fructose) to casein hydrolysate (NAK) medium with or without starch or low methoxyl pectin did not significantly affect enterotoxin C production but did significantly decrease the pH at 12 and 24 h. The increased viscosity of colloidally thickened media resulted in decreased aeration in shaken cultures and decreased quantities of enterotoxin C. Sugars tested did not differ practically in their effects on the parameters of multiplying Staphylococcus aureus 361 and 265-1 which were measured. Addition of 1% of glucose, sucrose, or maltose prevented the decreased growth rate observed when strain 265-1 was grown in 20% O2 + 80% N2 instead of air.

Ion Selective Method for the Determination of Nitrite in Smoked Fish

In a direct ion selective electrode method for determining nitrite in smoked fish, the nitrite extracted from the sample is converted to nitrous acid with a measured addition of an acid buffer. The released nitrous acid is measured by a nitrogen oxide electrode. A known addition procedure is used to accurately measure the amount of nitrite in solution and the nitrite concentration is determined directly from Gran’s plot paper. Recoveries of nitrite from spiked smoked chub samples ranged from 94.0 to 100.0% with an average of 96.7 and a relative standard deviation of ±1.9% at the 100 ppm level. Results from the ion selective method were comparable with those from the official first action AOAC method 24.037–24.038.

Effect of glucose on lipolysis and on release of lipolytic products in isolated adipocytes

Isolated adipocytes were prepared from epididymal adipose tissues removed from rats which had been fed or starved for 48 h (fed adipocytes or fasted adipocytes). These cells were incubated at 37 degrees C for 90 min in media containing 0, 3, or 30 mM glucose, with or without norepinephrine (1.0 mug/ml). Then the concentrations of free fatty acids (FFA) and free glycerol (FG) in the total mixture (medium plus cells) and in the medium alone were measured. Addition of glucose to the medium increased the total PG, presumably by increasing the basal lipolysis, and it decreased the intracellular retention ratio of FG (the ratio of intracellular FG to total FG). Addition of glucose did not change the total FFA, but decreased the FFA/FG ratio, presumably by increasing reesterification. The increase in FG and decrease in the FFA/FG ratio on addition of glucose were greater in fed than in fasted adipocytes. The intracellular retention ratio of FFA also decreased on addition of glucose. Glucose enhanced norepinephrine-induced lipolysis (release of free glycerol), and this effect of glucose was greater in fasted adipocytes. However, the increase in FFA in fasted adipocytes induced by norepinephrine was not altered by addition of glucose. In fed adipocytes norepinephrine decreased the total FFA in the presence of glucose. Reesterification of FFA following norepinephrine was increased by addition of glucose. Norepinephrine decreased the intracellular retention ratios of FG and FFA in the presence of glucose. These results suggest that the passage of the lipolytic products, FFA and FG, through the cell membranes may not occur by simple diffusion, but may require energy.

Oxygen uptake by motile and germinating zoospores of Pythium aphanidermatum

Oxygen uptake by Pythium aphanidermatum zoospores during motility, encystment, and germination was measured. Addition of glucose or fructose had no appreciable effect on motile zoospore respiration. The effects of various substrates on the respiratory rate of germinating cysts were as follows: glucose, glucose-6-phosphate, xylose, acetate, citrate, glutamate, and 6-phosphogluconate did not increase the respiratory rate; whereas fructose, fructose-6-phosphate, iructose-l,6-diphosphate, sucrose, alphaketoglutarate, pyruvate, and dilute pea root exudate all significantly increased cyst respiration.