Diminished taste reactivity to saccharin following chronic administration of theophylline in rats

Under a successive increase in the concentration of saccharin adulteration, a dual effect of facilitation and inhibition on food intake was observed in normal rats. At low concentrations (0.25 to 1.5%), saccharin adulterated diets were more acceptable than the normal one with a peak at 1.0% concentration. Food intake was conversely suppressed at a high concentration (3.0%). On exposure to either 1.0 or 3.0% saccharin diet, this facilitatory or inhibitory effect disappeared with chronic administration of theophylline. This diminution of acceptance or rejection response to saccharin was interpreted to be an impairment of taste discrimination induced by theophylline.     

Ascorbic acid metabolism in rats and guinea pigs after the administration of ethanol

Ascorbic acid metabolism was studied in guinea pigs and rats after the administration of ethanol and a high dose of ascorbic acid (AA). Male guinea pigs were maintained for 30 days as follows: (1) controls (1 mg AA/100 g body wt.); (2) ethanol (1 mg AA/100 g body wt. + 900 mg ethanol/100 g body wt); (3) ascorbic acid (25 mg AA/100 g body wt.); (4) ascorbic acid + ethanol (25 mg AA/100 g body wt. + 900 mg ethanol/100 g body wt.). Rats were also grouped into four groups as in the case of guinea pigs, but the dose of AA was 200 mg/100 g body weight. Rats adjusted to ethanol intoxication by enhancing the biosynthesis of ascorbate as evidenced by elevated activity of L-gulono lactone oxidase (GLO). Hence ascorbate levels were not lowered in rats after administration of alcohol. However, alcohol administration lowered tissue levels of ascorbate in guinea pigs. But the supplementation of ascorbate along with alcohol raised the tissue level of this vitamin. Guinea pigs responded to the ascorbate deficiency during alcohol administration by lowering the degradation of ascorbate, as seen by the lower activity of the degrading enzyme gulono lactone hydrolase. It is concluded that on the administration of alcohol, guinea pigs are dependent upon additional exogenous supplies of ascorbic acid, whereas rats are not.     

Mesenteric lymph as a major source of serum IgA in guinea pigs and rats

The mean concentration of IgA in the mesenteric lymph of guinea pigs and rats was 4.5 and 13.4-fold higher, respectively, than that in their serum. For IgG, IgM, albumin, transferrin and α-macroglobulin, the mesenteric lymph-versus-serum concentration ratios were lower than unity and inversely related to their molecular size, indicating that their presence in mesenteric lymph was essentially due to filtration through the walls of the mesenteric blood capillaries. In contrast, it was calculated that 90–97 % of IgA in mesenteric lymph was derived from local synthesis by the intestinal immunocytes. Considering mesenteric lymph flow and plasma volume, it was concluded that the intestinal mucosa is a major source of serum IgA in guinea pigs and rats.     

Relationship between intracellular calcium and airway reactivity in guinea pigs.

The present study was carried out to examine the relationship between intracellular free calcium ion concentrations and its regulatory enzymes, sodium potassium adenosine triphosphatase (Na(+),K(+)-ATPase) and calcium adenosine triphosphatase (Ca(2+)-ATPase), with airway reactivity to inhaled histamine in guinea pigs. Forty-nine guinea pigs were included in this study. Of these, 34 animals responded to histamine bronchoprovocation challenge in vivo with a greater than 35% fall in specific airways conductance and were labeled as "reactive," and the remaining 15 were "nonreactive." The dose of histamine producing a 35% fall in specific airways conductance was labeled as ED(35) SGaw. The animals were then sacrificed, and the following biochemical measurements were carried out: intracellular free calcium ion concentrations [Ca(2+)](i) in leukocytes and isolated tracheal smooth muscle cells, activities of Na(+),K(+)-ATPase and Ca(2+)-ATPase in tracheal homogenate, and plasma levels of lysophosphatidylcholine (LPC). Reactive guinea pigs showed significantly higher [Ca(2+)](i) and Na(+),K(+)-ATPase and Ca(2+)-ATPase activities. Airway reactivity (ED(35) SGaw) had significant negative correlation with [Ca(2+)](i), with activities of each of the ATPases and with plasma lysophosphatidylcholine. It is concluded that the level of [Ca(2+)](i) is an important determinant of airway reactivity. Intracellular calcium levels modulate airway response to histamine with higher levels being associated with greater reactivity.     

Total serum copper and ceruloplasmin levels following administration of copper aspirinate to rats and guinea-pigs

Total serum copper and ceruloplasmin oxidase activities have been measured over a 24-h period in rats and guinea-pigs treated with 100 mg/kg body weight of copper (II) aspirinate. In the rat, administration s.c. produced higher total serum copper levels than oral administration at all time intervals studied, whereas in the guinea-pig, oral administration produced the higher level after 1 h and s.c. administration the higher level after 5 h. In both species, the rate of elimination of the additional copper was faster following oral administration. Ceruloplasmin oxidase activity appeared to be inhibited in certain cases but rose in all cases except for orally treated rats after 24 h. The initial rise in serum copper was due mainly to copper present on albumin. The increased albumin copper was detected directly by electrophoresis of serum samples and subsequent determination of the copper level in the portions of the strip which contained proteins. After s.c. administration to the rat, the amount of ultrafilterable copper was raised by a detectable amount. 7 h after s.c. or oral administration of copper aspirinate, the thiol concentration of the serum was reduced in both rats and guinea-pigs. The relationship of these levels to the anti-inflammatory action of copper(II) aspirinate in rats and guinea-pigs is discussed.Present address: Wyeth Laboratories Inc. P.O. Box 8299, Philadelphia, Pa. 19101, USA.     

Total and specific IgE in serum and cerebrospinal fluid of rats and guinea pigs infected withAngiostrongylus cantonensis

The total and specific IgE response toAngiostrongylus cantonensis infection was evaluated according to host permissiveness. Total IgE levels measured by a double antibody radioimmunoassay (RIA) increased slowly in the permissive host (the rat), reaching a maximum between 4 and 8 weeks after infection. This maximum was earlier but significantly lower in the non-permissive host (the guinea pig). IgE antibodies specific for adult worms or L1 or L3 larvae ofA. cantonensis were measured by a radioallergosorbent test (RAST). In the case of adult worms and L1 antigens, specific IgE antibody levels showed large variations in relation to the duration of infection in rats. In contrast to total IgE levels, the specific IgE response to L3 larvae was lower in rats than in guinea pigs in both the serum and cerebrospinal fluid (CSF). These results suggest variations in the total vs specific IgE response according to host permissiveness or non-permissiveness toA. cantonensis infection. These results are discussed in the context of the possible participation of IgE antibodies in immune defence.     

Bronchial sensitization in guinea pigs following ingestion of ovalbumin

Local bronchial mucosal hypersensitivity following antigen feeding was studied in the guinea pig. Groups of 6 animals were fed 1% ovalbumin (OA) in tap water or tap water without antigen (control group) for different feeding periods (14, 28, 42, and 56 days). Inhalative provocations with increasing concentrations of OA (0.5-8% OA) were performed at the end of each feeding period followed by body plethysmographic measurement of airway obstruction. Specific bronchial hypersensitivity to inhaled OA was not found in the control group, whereas specific bronchial reactivity to OA, described as reactivity index, was significantly different from the control group after 14 (p less than 0.05), 28 (p less than 0.001) and 42 days (p less than 0.01) of feeding. No difference to the control group was found after 56 days of feeding. Anti-OA IgG total and IgG1 in serum and bronchoalveolar lavage fluid were increased in OA-fed animals reaching maximal concentrations at day 28 of the feeding period. We conclude that oral feeding of a 1% solution of OA can induce a transient state of local hypersensitivity to inhaled antigen in the guinea pig as manifested by bronchoconstriction on OA inhalation and increased concentrations of local and systemic specific antibodies. This period of local hypersensitivity is followed by tolerance.     

Bronchial hyperresponsiveness to histamine following antigen challenges in actively sensitized guinea pigs

Guinea pigs were actively sensitized by intraperitoneally administered ovalbumin and challenged by intravenous injections of ovalbumin. Respiratory resistance and dynamic compliance were measured by pulmonary mechanics analyzer Buxco Model 6. Changes in resistance (delta R) and compliance (delta C) induced by intravenously administered histamine were investigated before and after the challenge. Responses to the histamine in sensitized guinea pigs were also compared with those in naive guinea pigs. The following results were obtained. 1) A significant increase in delta R by histamine administration was observed following the antigen challenge. delta C by histamine administration showed a tendency to increase after the challenge. 2) A significant increase of delta R by 7.2 micrograms/kg histamine administration was observed in actively sensitized guinea pigs. However, delta C by the histamine administration did not change in the sensitized animals.     

Prostaglandin synthesis of the trachea in rats and guinea pigs

The synthesis of 5 prostaglandins in the trachea of rats and guinea pigs is studied by means of radio-thin-layer chromatography. The role of PGs in physiological and pathophysiological processes is discussed.     

Increased NADPH-diaphorase reactivity in the hypothalamic paraventricular nucleus and tanycytes following systemic administration of leptin in rats

Leptin, a hormone mainly produced by adipocytes in proportion to fat mass, is a key component in the regulation of energy homeostasis and reproductive, neuroendocrine, immune, and metabolic functions. Leptin binds to the leptin receptor, which is expressed throughout the central nervous system but particularly in neurons of several nuclei of the hypothalamus, such as the arcuate nucleus (ARC) and paraventricular nucleus (PVN). It has been found that nitric oxide (NO) plays an important role in mediating effects of leptin. Since PVN and ARC neurons are known to express leptin receptors, we investigated the effects of leptin on nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) reactivity in the PVN and ARC of male Wistar rats. Our results have shown that systemic administration of leptin resulted in increased NADPH-d positive cell number in the PVN and ARC, suggesting that both the PVN and ARC may be important centers in the hypothalamus for the leptin action, mediated by increased NO production. In addition, we have also observed that hypothalamic tanycytes in the ventral portion of the third ventricle were NADPH-d positive. We speculate that leptin may affect the release of neurohormones and hypothalamic neurogenesis by activating nitric oxide synthase in hypothalamic tanycytes.     

Device for nonstressful restraining of rats and guinea pigs

An atraumatic restraining device—a high, unsteady platform, which allows the recording of auditory, somatosensory and visual evoked potentials of conscious rats and guinea pigs, during long-lasting experiments. These animals are fully conscious, and to avoid falling, they remain quietly on the platform. Thus, animals are reproducibly stimulated and average evoke responses are not affected by excessive muscular activity or by depression of potentials caused by sleep induced animals.