Effects of taste stimulation on the behavior of serum amino acid concentrations and amylase and trypsin activities in fasting rats.

The effect of taste stimulation on serum free-amino acid concentrations and amylase and trypsin activities in fasting rats was studied. Following an acclimation period of 5 d, male Sprague-Dawley rats were fasted for 4 d and sacrificed after taste stimulation with a palatable sodium saccharin or unpalatable quinine sulfate flavored diet. Blood was collected from the portal vein and inferior vena cava at 0, 5, 10, 20 and 30 min after taste stimulation. Intestinal contents were also collected at the same time intervals as the blood collections. Total amino acid concentrations in the saccharin stimulated group increased significantly at 5 and 20 min following taste stimulation in comparison with the control of 0 time in the portal vein, and a significant difference between the saccharin and quinine stimulated groups was also observed at 5 min. No difference was found in the inferior vena cava. A high level of alanine and low level of glutamine were depicted in the portal vein as compared to that of the inferior vena cava. The elevation of alanine that is gluconeogenic amino acid was remarkable in the saccharin group at 20 min in the portal vein. Moreover, amylase and trypsin activities in the saccharin group reached peak values promptly and kept constant throughout the experiment as compared to the quinine group. The results suggest that taste stimulation originates changes in the cephalic phase amino acid concentrations in the portal vein and that taste information, overcoming a hunger, plays an important role in amino acid metabolism and digestive enzyme activities. Therefore, eating with gusto is significant for the maintenance of body functions even under starvation conditions.

The timing of protein feeding and dietary protein levels affect taste preference, serum zinc concentration and glossal epithelial morphology in growing rats.

OBJECTIVE: The present study investigated the effect of timing of protein feeding on taste preference, serum zinc concentration and morphological changes of tongue epithelia. METHODS: Weanling rats were fed one of three diets: protein-free and 2.5 or 8% purified egg protein (PEP) diets for 14 days (first feeding period). Rats in each group were further subdivided into three dietary treatments, totaling nine groups and fed one of the same three diets for 14 days (second feeding period). Preference tests between 3 or 6 mmol/L NaCl vs. deionized water were conducted in both feeding periods. At the end of each period, blood and tongue were collected for the measurement of serum zinc concentrations and morphological observations. RESULTS: The rats fed the protein-free diet in the first feeding period did not discriminate 3 mmol/L NaCl from deionized water in both feeding periods, even though adequate protein was administered in the second feeding period. The rats fed the 2.5 or 8% PEP diet in the first feeding period discriminated 3 mmol/L NaCl from deionized water regardless of the protein levels in the diet during the second feeding period. Serum zinc concentration was proportionate to protein content in the diet at the end of each feeding period (p < 0.001), and low serum zinc concentration was restored by protein feeding. Abnormal changes of tongue epithelia were observed only in the rats fed the protein-free diet throughout the two feeding periods. CONCLUSIONS: The results suggest that protein nutrition immediately after weaning is important to maintain normal taste function.

Influence of zinc supplementation to diets at graded levels of protein on taste sensitivity, morphological changes of tongue epithelia and serum zinc concentration in growing rats.

OBJECTIVE: We previously reported dietary protein was needed to maintain normal taste function and low serum zinc concentration led due to protein insufficiency [1], but generally zinc has been known to improve taste dysfunction. The present study was designed to determine whether zinc supplementation is effective in maintaining normal taste function at different levels of dietary protein. METHODS: Sixty weanling rats were given free access to one of six diets: protein-free, 2.5% and 8% purified egg protein (PEP), and 10 ppm zinc supplementation at each protein level for 28 days. Preference tests between aqueous solution of 1, 2, 5 or 10 mmol/L NaCl vs. deionized water were conducted on days 14, 17, 20 and 23, respectively. Blood was collected for the measurements of serum zinc concentration, and the tongue of each rat was excised for observation by electron microscopic scanning. The number of fungiform papillae with normal taste pores and also the number of rats with abnormal morphological changes on tongue epithelia were recorded. RESULTS: In basal diet groups, the rats fed 8% and 2.5% PEP diets discriminated 2 mmol/L NaCl liquid, while those fed the protein-free diet discriminated only the highest concentration of 10 mmol/L in this experiment. Serum zinc concentration and the ratio of fungiform papillae with normal taste pores increased with increasing dietary protein level. Abnormal morphological changes of tongue epithelia were observed in the protein-free diet group whether or not it contained additional zinc. No significant differences were observed between the basal and zinc supplemented diets at the other protein levels in the other parameters. CONCLUSION: These results suggest that adequate dietary protein is more important in maintaining normal taste function and zinc supplementation did not improve taste function when dietary protein was suboptimal.

The effect of palatability and feeding conditions on digestive functions in rats.

OBJECTIVE: Information concerning various post prandial gastrointestinal functions modulated by taste stimulation is rather limited. Thus, effects of different types of palatability and feeding condition on digestive functions were studied. METHODS: Male Sprague-Dawley rats were divided into two different feeding groups, meal feeding and ad libitum. In meal feeding, the daily feeding period was shortened gradually and was restricted eventually only 3 hours. In ad libitum feeding, food was freely available for 24 hours until experiment. After each rat in both feeding groups was fed 8.29 mM saccharin or 1.28 mM quinine flavored diet as a taste stimulant for 15 minutes, changes of gastric and intestinal nitrogen and pH and pancreatic amylase activities were compared with meal feeding vs ad libitum feeding. RESULTS: In meal feeding, no difference was observed between before and after taste stimulation or between saccharin and quinine flavored diets on gastric and intestinal nitrogen contents, pH in the stomach and in the small intestine, and amylase activity. On the other hand, in ad libitum feeding, intestinal nitrogen contents tended to stagnate until 60 minutes after tasting quinine, although there was little difference between saccharin and quinine diets on gastric nitrogen contents. Gastric juice was hardly secreted before tasting (pH 6.2) and then pH in the stomach changed to become more acid following taste stimulation. Although amylase secreted in small intestine was hardly secreted before tasting, activities after tasting saccharin were increased immediately and lasted until 120 minutes. Amylase activity in rats fed the quinine diet, however, showed slower increase and faster recovery than that in rats fed the saccharin diet. CONCLUSIONS: The results confirmed that various postingestive functions after taste stimulation depend on feeding conditions and it suggests that the ad libitum feeding condition is more appropriate than meal feeding on the experiment related to gustatory response.

Decline of taste sensitivity in protein deficient adult rats.

The influence of dietary protein levels on taste sensitivity was studied in adult rats. Low protein diets of 0.0, 2.5, or 5.0% purified egg protein (PEP) were fed to animals for 28 days. Two bottle choice preference tests between aqueous solutions of either 2, 9, 17, or 86 mM sodium chloride and deionized water were conducted in an ascending order on days 14, 16, 18, and 20. Urine samples were collected for zinc and creatinine analysis. Blood samples were also collected for measuring serum zinc and creatinine concentrations. Scanning electron microscopy was performed to observe rats' tongue epithelia. Protein free diet group showed significantly lower taste sensitivity and renal reabsorption rate than other protein containing diet groups, while serum zinc and creatinine concentrations, and creatinine clearance were not affected by dietary protein level. Degeneration of filiform papillae and imperforation of taste pore of fungiform papillae were observed in protein free diet group. This experiment implies at least 2.5% dietary protein is required to manifest normal taste function in the adult.

Preference for sodium chloride is reduced in protein-deprived juvenile rats.

The influence of dietary protein levels on the preference for sodium chloride was studied in juvenile rats fed diets containing 0, 25 or 50 g purified egg protein/kg and 20.0 mg zinc/kg diet. Preference tests between aqueous solution of NaCl (2-51 mmol/L) or deionized water were conducted. Blood samples were collected for measuring the serum zinc concentration. Scanning electron microscopy was performed to observe the rats' tongue epithelia. Only the rats fed 50 g purified egg protein/kg diet preferred the lowest concentration of 2 mmol/L NaCl solution to deionized water, whereas the rats fed protein-free diet did not discriminate diluted NaCl solution until the concentration was 9 mmol/L. The filiform papillae of the protein-free diet fed group showed significantly less development than the 25 g purified egg protein/kg and the 50 g purified egg protein/kg diet-fed groups. The more protein the diets contained, the higher was the serum concentration of zinc. Significant correlations were observed between protein intake and discriminated NaCl concentration (r = -0.93, P < 0.001), serum zinc (r = 0.90, P < 0.001) or length of filiform papillae (r = 0.93, P < 0.001). The present study suggests that taste preference is impaired by protein malnutrition and this may be related to zinc status.

Induction of avascular yolk sac due to reduction of basic fibroblast growth factor by retinoic acid in mice.

Vasculogenesis depends on autocrine secretion of basic fibroblast growth factor (bFGF) from capillary endothelial cells. Retinoic acid (RA) induced avascular yolk sac (AVY) of mouse embryos of dams given 60 mg/kg of RA orally on Day 8 of gestation and sacrificed 3 days later. We studied the localization and transcriptional expression of bFGF and FGF-receptor (flg), heparin-binding growth factor (HBGF) activity, localization of lysosomal enzymes and alpha 1-antitrypsin (AAT), and electron microscopy of the normal mouse visceral yolk sac (VYS) and AVY. bFGF, which is normally present in the endoderm of the VYS of 8-day-old embryos and in all components of the VYS by Day 11 of gestation, was reduced in the AVY. However, in the presence of bFGF in vitro capillary nets were restored in the AVY. The mRNA for bFGF was not detectable in either VYS or AVY, while flg mRNA was detected equally in both organs in Northern blotting. The characteristic distribution pattern of lysosomal enzymes, acid phosphatase, lysozyme, and cathepsin D, and AAT was altered in the AVY. The level of acid phosphatase and AAT was reduced to 10% in the AVY. Electron microscopy revealed a partial or total loss of lysosomal membranes where the contents of lysosomes fused with adjacent lysosomes and the external organelles. These results suggest that vitelline blood vessels are not developed by endogenous autocrine bFGF but by exogenous transcellular bFGF from absorptive endodermal cells. Retinoic acid does not affect the angiogenic capacity of the VYS mesenchyme but destroys lysosomes, which release hydrolytic enzymes, leading to degradation of AAT in the endodermal cells and then digestion of endocytosed bFGF.

Interaction of MSG taste with nutrition: perspectives in consummatory behavior and digestion.

Studies in the taste system of mammals indicate that monosodium glutamate (MSG) produces a unique taste sensation termed umami. As a derivative of glutamic acid, MSG is a naturally occurring nutrient in many foods; its commercial use to improve food palatability for humans is well documented. Behavioral studies with experimental animals have revealed that preference for MSG in solutions and selection of MSG-flavored diets can be explained by sensory means with no appreciable effects on preference by postingestive consequences. However, preference for umami-flavored fluids is reduced by feeding rats low-protein diets or low quality protein. MSG-flavored diets, initially unpreferred, were subsequently highly selected. However, the adulteration of diets by MSG either did not or only slightly increased food intake. In light of the significant contribution of MSG to diet taste, apparently as a signal coupled to dietary proteins, physiological studies have been initiated to reveal its role as a stimulator of the cephalic phase of pancreatic exocrine secretion. Modified sham-feeding experiments with dogs have shown that oral stimulation by MSG produced significant stimulation of both pancreatic flow and protein output in conscious dogs.

Diurnal variations of cephalic exocrine pancreatic response in dogs.

The purpose of this study was to determine effects of oral stimulation of sucrose on the diurnal output of pancreatic secretion in conscious dogs. Male beagle dogs weighing 9-11 kg were prepared with gastric and duodenal fistulae. Once a day at 14:00 the animals were trained to eat a sufficient amount of a commercial stock diet to maintain their body weight. Gustatory receptors were stimulated at 9:00, 13:00, 15:00, and 18:00 for 5 min with 100 ml of 0.5% agar solutions containing 0.3 M sucrose. Pancreatic juice was collected every 5 min before and after stimulation, and volume flow and protein output were measured. As a result, we demonstrated daily fluctuations timed by feeding not only in the pancreatic basal secretions but also in pancreatic responses to the gustatory stimulation. These results suggest the significant role of taste stimuli in the nutrition of, at least digestion in, animals.

[Surgical application of low-power laser: experimental study, development of equipments and clinical application].

We carried out experimental and clinical studies with low-power laser to perform the surgical application. The developed device for microvascular anastomosis with semiconductor laser diode made of In-Ga-As-P was used to perform 15 end-to-end laser assisted microvascular anastomoses of carotid arteries in rabbits. In four of 7 cases which were irradiated with power output 50mW showed patency immediately after surgery with no wound disruption. A new medical device with Ga-A1-As semiconductor laser diode was developed for pain relief. A double-blind evaluation of the test was initiated in 124 patients suffering from chronic inflammatory pain. Result is that of 63 patients irradiated laser, 45(71%) were effective and of 61 cases not irradiated laser, 8(13%) were relieved pain. The data were analyzed statistically by chi square, and criterion for statistical significance was the 0.01 level. The spectral properties of laser-excited fluorescence of three photosensitizers, namely tetracycline, hematoporphyrin free base and chlorin e6Na, taken up in human arterial intima were detected. Photosensitizers were administrated to resected human arteries for 2 hours in vitro. The main results are following: 1) Photosensitizers are confirmed to be taken up in arterial intima and the fluorescence intensity decreases as the time goes on. 2) The fluorescence intensity from atheromatous plaque is usually stronger than that from normal region.

Long-term effects on male reproductive organs of prenatal exposure to ethinyl estradiol.

The effects of oral contraceptives on human offspring have not been established. This study shows the long-term effects of prenatal exposure to ethinyl estradiol, a common estrogenic component of oral contraceptives, on the testes and epididymides of aged mice. Five (83%) of the six aged male mice examined showed atrophy of seminiferous tubules, four (67%) had Leydig's cell hyperplasia, and one (17%) had precancerous changes in the epididymis. These phenomena may be results of decreases in testosterone content and its drastic conversion into estradiol-17 beta in the fetal testes at critical periods induced by ethinyl estradiol.

Cephalic phase response of pancreatic exocrine secretion in conscious dogs.

The effects of three taste solutions on the cephalic phase of pancreatic secretion were studied in conscious dogs. Male beagle dogs weighing 9-11 kg were prepared with gastric and duodenal fistulas. Gustatory receptors were stimulated for 5 min with 100 ml of 0.5% agar solutions containing 0.05, 0.12, and 0.3 M of either sodium chloride, sucrose, or monosodium glutamate (MSG). Pancreatic juice was collected every 5 min before and after stimulation, and volume flow and protein output were measured. Pancreatic secretory responses were found to vary with the type of taste stimulus. Sucrose was a better stimulus than MSG for both protein output and volume flow. Taste stimulation with sodium chloride produced a lower pancreatic response than those with sucrose or MSG.

The effect of hematocrit on photoelectric plethysmogram.

In order to study the effect of hematocrit (Ht) on the photoelectric plethysmograms of fingers and toes, an experimental model study and a clinical study were carried out. Experimentally, it was found that the height of the plethysmograms increased when the values of Ht were lowered. In the clinical study, 3 groups of patients with different HT values ranging from 27 to 55% were examined. A reverse relationship was found between the Ht value and pulse height of the plethysmogram. The physical effects of the blood flow and contents upon the plethysmograms were discussed.

Comparison of the nutritive values of L-, DL- and D-tryptophan in the rat and chick.

Experiments were designed to compare the nutritive values of L-, DL- and D-tryptophan in rats and chicks. Growing rats and chicks were fed for 19 and 21 days, respectively, diets containing amino acid mixtures with graded levels of either L-, DL- or D-tryptophan so that the regression of weight gain or protein retention on tryptophan intake could be established. After the end of the experiments, plasma free L-tryptophan was estimated by a microbiological method. The nutritive values of DL- and D-tryptophan relative to the L-isomer were 47 and 21%, respectively in chicks and close to 100% in rats. In chicks, plasma free L-tryptophan concentration increased with the increase of L- and DL-tryptophan levels in the diet, but remained at a low level regardless of the D-tryptophan level in the diet. In rats, however, a good correlation was observed between plasma free L-tryptophan and tryptophan level in the diet.

Inversion of D-tryptophan to L-tryptophan and excretory patterns in the rat and chick.

The behavior of D-tryptophan in the blood plasma and the pattern of tryptophan excretion in the urine were studied in the rat and the chick. When D-tryptophan was administered orally to rats and chicks, both showed D-tryptophan in the plasma. Conversion of D-tryptophan to the L-isomer in the rat was found by an examination of plasma from the posterior vena cava and the portal vein, following stomach intubation of 100 micromoles D-tryptophan/100 g of body weight. The peak in the increase of L-tryptophan was approximately 150 nmoles/ml plasma when measured at 30 minutes after administration and the peak was 200 nmoles when measured 2 hours after administration. No conversion of D-tryptophan to the L-isomer was found in chicks. Under similar conditions, D-tryptophan was measured in the urine of rats and chicks. In rats the D-tryptophan excreted was at most 1% of the amount administered; while in chicks most of the D-tryptophan was excreted.

The influence of carrier of gustatory stimulation on the cephalic phase of canine pancreatic secretion.

The pancreatic secretory responses of dogs to various taste stimuli were examined in this study. Additionally, taste preferences were examined in 24-hour exposure tests to taste stimulus solutions as well as in short exposure tests to taste solutions mixed with commercial stock diet. The liquid and solid food preference tests produced quite different results. In dogs with cannulated gastric and duodenal fistulas, gustatory receptors were stimulated orally with 100 ml of taste stimulus solution (water 0.05 M monosodium glutamate (MSG), 0.05 M citric acid or 0.3 M sucrose) mixed with 25 g of a carrier (commercial stock diet, purified diet or cellulose). Pancreatic secretory responses to the taste stimuli varied with the type of carrier. Stock diet carrier was a better stimulant than the purified diet for both protein output and volume flow. Taste stimuli with a cellulose carrier did not produce any pancreatic response at all. The differences in responses to the different carriers were greater than the differences between taste stimuli when the same carrier was used. This experiment indicates that gustatory stimulation does influence the function of pancreatic secretion depending on the carriers used.

The circulatory effect of drug on lymphedema.

Various kinds of drugs are used to improve the lymphedema of the extemities. In this report, a dye transducer was applied on the site of edema of the leg, foot, or hand and indocyanine green was injected intravenously. The change of circulating dye was recorded by means of dye densitometer. The edematous tissue showed higher dye concentration with lapse of time, while drugs, i.e., Esberiven, urokinase, kallikrein, etc., accelerated the dye dilution. These drugs have the effect to correct the stagnant microcirculation to a more steady flow in the region of edema.