The effect of estradiol on carbohydrate utilization during prolonged exercise in rats

Female--castrated and male-sham operated rats were subjected to five hours of swimming. It was found that estradiol administered to female rats promotes a supercompensatory pattern of glycogen recovery in the myocardium at the end of the fifth hour of exercise. The hormone markedly delayed the glycogen mobilization from the liver during the first hour of swimming. Glycogen level in m. biceps femoris was essentially unchanged by estradiol both at rest and during exercise. Estradiol signifcantly increased glycogen level in m. masseter of resting rats. Hypoglycaemia developing at the end of the fifth hour of exercise was less pronounced in the estradiol--treated female rats than in the animals from other groups. It may be concluded that estradiol exerts a "sparing" effect on carbohydrate reserves during exercise in rats.     

Evaluation of treatment for the prevention of acute gastric lesions in stress, in rats

Since portal hypertension affects the gastric mucosa, leading to congestive gastropathy and thus to increased incidence of bleeding, it is one of the possible causes of increased permeability of gastric mucosal capillaries. The aim of this study was the quantitative assessment of the permeability of the gastric mucosal endothelial cells. Eight CCl4-induced cirrhotic rats and eight matched controls were subjected to i.v. injection of FITC-albumin, and a morphometric evaluation of fluorescence in serial histological sections of the gastric mucosa was performed by a video image analysis system. Fluorescence was found to be 0.351 +/- 0.01% of the area scanned in experimental animals versus 0.073 +/- 0.005% in controls, i.e. it was significantly increased by the treatment, which implies a significant endothelial leakage into the extravascular space.     

Kinetics of intraocular cytokines in the suppression of experimental autoimmune uveoretinitis by type I IFN

The systemic administration of IFN-alpha/beta was previously found to suppress inflammation in rats with experimental autoimmune uveoretinitis (EAU); however, an effect on the systemic immune response was not identified. In order to investigate an immunological basis for suppression at the intraocular level, rats immunized with interphotoreceptor retinoid-binding protein (IRBP) were administered daily intramuscular injections of 10(5) IU IFN-alpha/beta and cytokines were measured by ELISA in intraocular extracts prepared by ultrasonification at various timepoints throughout the course of EAU. In control EAU, intraocular concentrations of IFN-gamma were found to be non-detectable on day 8 before the onset of inflammation, significantly elevated on day 12 at peak inflammation (182+/-106 pg/ml), then non-detectable again on day 16 after inflammation had begun to subside. In contrast, intraocular IFN-gamma in IFN-alpha/beta-treated rats remained non-detectable or low at all timepoints. Measurement of intraocular IL-2 revealed no difference between the two groups of rats. Intraocular IL-4 concentrations were elevated in rats treated with IFN-alpha/beta, although this cytokine was also detected in the same range in controls as well as normal rats. Finally, intraocular IL-10 was non-detectable on day 8, significantly elevated at peak inflammation on day 12 (588+/-139 pg/ml), then decreased to low levels on day 16 in control EAU rats, while remaining non-detectable or low in IFN-alpha/beta-treated rats. These results suggest that acute inflammation in IRBP-induced EAU in rats involves both IFN-gamma and IL-10 at the local intraocular level, and that systemic administration of IFN-alpha/beta inhibits EAU via a mechanism that involves suppression of both cytokines.     

The ethical problem of the health-environment relationship]

The effects of sustained stress on response rate and temporal patterning (quarter-life) of rats performing either a previously learned fixed-interval schedule (FI 60) or learning an FI 60 simultaneously with stress onset were determined. Rats lived 24 h/day in operant cages, where they earned all of their food via lever-pressing. During the stress portion of each experiment, one group of rats was able to avoid or escape signalled intermittent footshock (Avoidance/ Escape Group), a second group (Yoked) did not have control over shock termination, a third group never received shock (Control). Shock trials were presented around the clock at approximately 5-min intervals and the stress portion of each study lasted 1-2 weeks. We have previously reported that rats tolerate this paradigm well and avoid/escape 99% of the shock trials. In rats previously trained on the FI task, both rate of responding and quarter-life values were significantly decreased on the first day of stress for both the Avoidance/Escape and Yoked Groups. Food intakes and quarter-life values were not significantly different from the controls by stress Days 3 and 2, respectively. In the acquisition study, controls learned the F1 task by Day 4 as judged by quarter-life of responding. FI task acquisition was significantly impaired in stressed rats compared to controls, not reaching asymptotic performance until Day 9 of stress. There were no major differences between the 2 stress groups in either study. These data demonstrate that stress may impair both the rate and patterning of behavior, and suggest that this rodent paradigm may usefully model some aspects of the effects of stress in humans.     

Total peptic activity in gastric juice and peptic cell mass (chief fundic cells and mucopeptic fundic-antral cells): cellular-secretory correlations in normal subjects

BACKGROUND: This study aimed at determining the turnover rate of parietal cells after inhibition of acid secretion. METHODS: Rats were given omeprazole (80 mumol/kg) by gavage once daily or ranitidine (1200 mumol/kg) by osmotic minipump for 5 days. Control rats received saline only. All rats were also given 3H-thymidine by osmotic minipumps. The animals were killed, 5, 14, 28, or 56 days after the start of the 3H-thymidine infusion. After formaldehyde fixation by perfusion through the aorta, light microscopic autoradiography was carried out on plastic sections of the oxyntic mucosa to determine the labeling index of the parietal cells. RESULTS: The average turnover rate in the control rats was calculated to be 0.61% per day, corresponding to a mean turnover time of 164 days. In the rats given inhibitors of acid secretion, the turnover rates did not differ significantly from those of the control group. CONCLUSION: Inhibition of gastric acid secretion did not significantly change the turnover rate of the parietal cells.     

No differences in mucosal adaptive growth one week after intestinal resection in rats given enteral glutamine supplementation or deprived of glutamine

OBJECTIVE: To evaluate the effects of intraluminal glutamine on the adaptation of intestinal mucosa after resection compared with transsection and un-operated on control animals. DESIGN: Open, controlled, experimental study. SETTING: University hospital, Sweden. SUBJECTS: 123 Sprague-Dawley rats. INTERVENTION: Daily isonitrogenous oral diet was given either free of glutamine or supplemented with 4% glutamine for 2 or 7 days to rats subjected to intestinal resection, transection or no operation. MAIN OUTCOME MEASURES: Body weight and protein content, DNA content, and thymidine incorporation in jejunal and ileal mucosa. RESULTS: Resection resulted in a significant growth stimulation evaluated by weight/body weight, protein, and DNA content (p < 0.05-0.001). Glutamine supplementation did not significantly influence this growth response. Thymidine incorporation in jejunum was stimulated by glutamine on day 3 (p < 0.05-0.001). CONCLUSION: The glutamine fortified diet had no growth stimulating effects compared with a glutamine free diet one week after 60% intestinal resection. An early increase in thymidine incorporation indicated that glutamine had a transient proliferative effect.     

Protective effect of 21-aminosteroid pretreatment in peripheral nerve low-load crush injury in mature and immature rats

The effects of U-74006F (tirilazad mesylate), a 21-aminosteroid antioxidant, on injured peripheral nerve were studied. Twenty-two immature and 44 mature rats were divided equally into two groups. The experimental group received two injections of 3 mg/kg of U-74006F at a 2 hour interval. The control group received the same volumes of a citrate buffer. A 5 mm segment of the sciatic nerve was subjected to a crush load of 100 g for 2 hours. Motor function (sciatic functional index) was assessed to day 48 postoperatively. There was total paralysis of the crushed limb in all rats the first week after crushing. The experimental group had a statistically significant improvement in motor function compared with the controls on days 14, 21, 25, and 28 for the mature rats and on days 11 and 14 for the immature rats. The mature controls attained complete recovery on day 42 and had a significantly slower recovery rate than the immature controls, which had recovered fully by day 25. The recovery rates were almost similar among mature and immature groups pretreated with U-74006F, both of which had fully recovered motor function by day 28. The results indicate that pretreatment with U-74006F can significantly promote peripheral nerve function after low-load crush injury and that the age of the animal influences the rate of peripheral nerve recovery.     

Application of solid-phase microextraction and gas chromatography-mass spectrometry for the determination of chlorophenols in urine

Previously, we have demonstrated that chronic exposure to immobilization (IMO) did not modify the influence of catecholamines on active behaviour of rats in the holeboard, but clearly increased the role of these amines in the forced swimming test (FST). In the present experiment, it was studied whether or not chronic IMO altered the role of dopamine in the two tests. Adult male Sprague-Dawley rats were left either undisturbed or subjected daily to 2 h of IMO stress for 12 days. On the following day, half of the rats were administered saline and the others the dopamine antagonist haloperidol (0.5 mg/kg). Then the rats remained undisturbed in the animal room (controls) or were subjected to acute IMO for 2 h. Finally, all animals were exposed consecutively to the holeboard (4 min) and the FST (5 min). In non-chronically stressed rats, acute IMO depressed behaviour in the holeboard but not in the FST. In chronic IMO rats the inhibitory effect of acute IMO on holeboard activity was slightly reduced as compared to controls. Acute IMO increased struggling in rats previously exposed to chronic IMO but did not alter struggling in non-chronically stressed rats. Whereas the inhibition caused by haloperidol treatment in the active behaviour of rats in the holeboard was not altered by chronic IMO, the inhibitory effect of haloperidol in the active behaviour of rats in the FST was greater after chronic IMO, particularly in rats also subjected to acute IMO. These data suggest that chronic IMO stress potentiates the role of dopamine in a specific behavioural task such as the FST and adds support to the previously published data demonstrating enhanced behavioural and neurochemical responses to dopamine-related drugs after chronic stress.     

Restoration of Leydig cells after repeated administration of ethane dimethanesulfonate in adult rats

Adult male rats were repeatedly treated with ethane dimethanesulfonate (EDS), an agent known to destroy Leydig cells selectively. Following a second injection, changes in serum testosterone levels and histological and morphometric changes of Leydig cells showed the time course to be similar to those after the first treatment. The number and volume of Leydig cells markedly decreased at day 2, began to increase from day 7, and recovered to the values of the control rats at day 30, concomitant with the changes of serum testosterone levels. Cells in the interstitial tissue labeled with bromodeoxyuridine markedly increased in number at day 2, gradually decreased thereafter, and returned to the values of the controls at day 14. During this period, cells undergoing mitosis were seen, their type unable to be determined, but were presumed to be regenerating Leydig cells. Even 30 days following four treatments with intervals of 30 days each, serum testosterone levels were the same as those in the controls. Also the numerical and volume densities of Leydig cells and the volume of an average Leydig cell were the same as those of the controls. Mitosis was observed in mature Leydig cells at this period, if any. It appears that new Leydig cells began to proliferate by division earlier than 14 days after EDS, allowing that there were several stages of proliferation, and that the source of reappearing Leydig cells may not be a limited number of precursor cells, implying the presence of stem cells for Leydig cells.     

Septal ablation in the rat and bar pressing under appetitive and aversive control.

Assigned 6 male hooded rats with bilateral septal lesions and 3 Ss with bilateral cortical control lesions to bar-press in a successive discrimination (go, no-go) task. Over successive experimental conditions, responding was maintained by the following reinforcers: food, shock escape, shock avoidance, concurrent food reinforcement and shock avoidance, and, once again, food. Ss with septal lesions responded to the no-go stimulus at higher rates than did controls only under the simple food-reinforcement conditions. Results suggest that disinhibition of bar pressing following septal ablation in rats may occur with appetitive and not with aversive schedules of reinforcement. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Regulatory mechanism of non-shivering thermogenesis in cold acclimation--with special reference to in vitro thermogenic activity and lipolysis of brown adipose tissue

In vitro brown adipose tissue (BAT) thermogenesis from cold-acclimated (CA) rats has been shown to exhibit the decreased responses to noradrenaline (NA) and glucagon (G), although an enhanced biochemical machinery for thermogenesis develops in the tissue. The present study was undertaken to clarify the inhibitory mechanism of in vitro thermogenic responses of BAT in CA rats. NA-treated rats were injected NA (40 micrograms/100g BW) twice a day for 2 or 4 weeks. The other rats were kept at 25 +/- 1 degree C (warm controls: WC), 5 +/- 1 degree C (CA), or 5 +/- 1 degree C/6h/day (intermittent cold exposure: ICE) for 5-6 weeks. The oxygen consumption, and glycerol as well as free fatty acids (FFA) release were measured on finely minced tissue blocks in Krebs-Ringer phosphate buffer at 37 degrees C. In vitro BAT thermogenic responses to NA and G in NA-treated rats did not differ from those in vehicle-injected controls. NA as well as G increased-oxygen consumption was greatest in WC, followed by ICE and CA. NA as well as G increased glycerol and FFA releases in WC and ICE, but the degree of increment was greater in WC than that in ICE, while NA or G did not increase glycerol and FFA releases in CA. FFA/glycerol ratio in WC was decreased by NA as well as G, but it was not changed in ICE, and increased in CA. Mitochondrial GDP binding as an index of BAT thermogenic capacity did not differ between CA and WC under resting state (CA rats were transferred in warm condition before 18h at the beginning of the experiment), but it was significantly greater in ICE. GDP binding was significantly greater in CA sacrificed at 5 degrees C compared with WC and CA resting. Acute cold exposure (5 degrees C/1h) enhanced GDP binding in WC, resting CA and ICE resting, but the degree of increment was greater in CA and ICE than in WC. These findings suggest that cold exposure inhibits BAT thermogenic responses according to the duration NA action during cold exposure, by means of suppressing fatty acid utilization and/or masking uncoupling protein.     

Application of infrared spectroscopy to development of stable lyophilized protein formulations

Global cerebral ischemia selectively damages neurons, but its contribution to glial cell death is uncertain. Accordingly, adult male rats were sacrificed by perfusion fixation at 1, 2, 3, 5, and 14 days following 10 minutes of global ischemia. This insult produces CA1 hippocampal neuronal death at post-ischemic (PI) day 3, but minor or no damage to neurons in other regions. In situ end labeling (ISEL) and immunohistochemistry identified fragmented DNA of dead or dying glia and distinguished glial subtypes. Rare ISEL-positive oligodendroglia, astrocytes, and microglia were present in control brain. Apoptotic bodies and ISEL-positive glia significantly increased at PI day 1 in cortex and thalamus (p < 0.05), but were similar to controls in other regions and at other PI intervals. Most were oligodendroglia, although ISEL-positive microglia and astrocytes were also observed. These results show that oligodendroglia die rapidly after brief global ischemia and are more sensitive than neurons in certain brain regions. Their selective vulnerability to ischemia may be responsible for the delayed white matter damage following anoxia or CO poisoning or that associated with white matter arteriopathies. Glial apoptosis could contribute to the DNA ladders of apoptotic oligonucleosomes that have been found in post-ischemic brain.     

Respiratory potentials recorded from the human hindbrain

OBJECTIVES: An experimental study has been conducted to investigate testicular blood flow alterations through acute biochemical changes during unilateral testicular torsion and detorsion. METHODS: One hundred twenty male albino rats were divided into 12 groups, each containing 10 rats. One group served to determine basal values of biochemical parameters, 4 groups were subjected to varying periods of unilateral testicular torsion (3, 6, 12, and 24 hours, respectively), 3 groups were subjected to detorsion following varying periods of torsion (6, 12, and 24 hours, respectively), and 4 groups underwent sham operations as controls. Levels of lactic acid, hypoxanthine, and lipid peroxidation products were determined in testicular tissues. RESULTS: Values of these 3 parameters obtained from sham operation control groups did not differ significantly from basal values (p > 0.05). All 3 parameters were increased significantly in both ipsilateral torted and contralateral nontorted testes after unilateral testicular torsion when compared with basal values (p < 0.05). Detorsion did not cause significant changes in levels of lipid peroxidation products in both ipsilateral torted and contralateral nontorted testes when compared with values obtained after torsion (p > 0.05). CONCLUSIONS: Ipsilateral testicular torsion causes a decrease not only in the ipsilateral torted but also in the contralateral nontorted testicular perfusion. The clues of reperfusion injury do not become evident following detorsion of testicular torsion lasting more than 6 hours.     

Correlation between esophageal motility and 24-hour pH recording in patients with gastroesophageal reflux

The relationship between manometric and pH-metric data was studied in a group of 50 patients with symptoms of gastroesophageal reflux. Using a multiple regression analysis, we found that the total percentage of reflux was significantly correlated to the infradiaphragmatic length and resting pressure of the lower esophageal sphincter and also to the mean amplitude of the contractile waves of the distal esophagus, thus revealing the important role of these factors in the antireflux mechanism. When the patients were divided into groups according to their manometric characteristics and the values of the various pH-metric parameters between these groups compared using a one-way analysis of variance, we found that the amplitude of the contractile waves and the percentage of deglutitions without response were related not only to the total percentage of reflux but also to the number of reflux episodes of greater than 5 min duration and to the duration of the longest episode. This shows that prolonged exposure of the esophageal mucosa to the refluxed material may be due, in part, to an alteration in the capacity for esophageal clearing.     

The anatomy of a consultation: a teaching method

Two dosages of Smokeless Tobacco (ST) extract were given to gravid Sprague-Dawley rats by oral gavage on gestational days (GD) 6-20. The low dosage contained ST extract equivalent to 1.33 mg/kg nicotine (STD-1), and the high dosage contained ST extract equivalent to 4.0 mg/kg nicotine (STD-2). Dams were dosed three times daily at 8 a.m., 11 a.m., and 2 p.m., thus providing total daily nicotine equivalent dosages of 4 mg/kg/day and 12 mg/kg/day. Controls received equivalent amounts of distilled water by gavage. Dams were allowed to deliver and all experimental pups were fostered to control mothers. On postnatal day 1 (PND 1) litters were culled to 4 +/- 1 females and 4 +/- 1 males. Weights, physical landmark development, and behavioral performance of pups were monitored during pre- and post-weaning periods. Behavioral tests included: surface righting, negative geotaxis, swimming development, open-field activity, active avoidance in shuttle box, and Cincinnati swimming maze. Our results show that the STD-2 dose resulted in reduced maternal weight gain. Offspring weights were reduced in a dose-related manner, with the most consistent weight deficits seen in the STD-2 group until PND29. Consistent STD-1 weight deficits were seen up to PND 8. The incidence of deaths was increased in the STD-2 dosage group. No significant treatment-related differences were observed in development of physical landmarks. Male STD-2 pups righted faster than controls, and significant differences were noted in swimming development with the STD-1 group of pups performing less effectively than controls. Activity levels, assessed during both pre- and post-weaning periods were not affected. No treatment-related differences were seen in the active avoidance shuttle box or Cincinnati swimming maze tests, which assessed learning. Female brain weights were reduced in the STD-1 treatment group.     

Dual-earner families: the importance of work stress and family stress for psychological well-being

The effect of neonatal hippocampal lesions on behavioral sensitivity to amphetamine (AMPH) and dopamine (DA) release in the nucleus accumbens (NAc) were examined. The ventral hippocampus was damaged bilaterally by ibotenic acid on postnatal day 7 (PD7). Spontaneous exploration and AMPH-stimulated locomotor activity were examined on postnatal day 35 (PD35) and day 56 (PD56). Extracellular DA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were sampled using in vivo microdialysis while simultaneously AMPH-stimulated locomotion was examined in freely moving rats on PD56. Spontaneous exploration increased in rats with hippocampal lesions relative to controls on PD56 but not PD35. AMPH (0, 0.187, 0.375, 0.75, 1.5, and 3 mg/kg) enhanced locomotion dose-dependently in both control and lesioned groups. Locomotor activity was higher in lesioned rats than controls following AMPH at the dose of 0.75 mg/kg on PD35 and at the doses of 1.5 and 3.0 mg/kg on PD56. The basal level of DA in the NAc was not different between the hippocampal and control groups. AMPH (1.5 mg/kg) induced hyperlocomotion in lesioned rats relative to controls. DA release in the NAc for both groups was enhanced following injections of AMPH. However, neonatal hippocampal lesions had no further enhancement on AMPH-stimulated release of DA as compared to the control group. The levels of DOPAC and HVA in the NAc were altered by AMPH but not lesions. The level of 5-HIAA was not influenced by either lesions or AMPH. The results of neonatal lesion-induced hyperlocomotion suggest that an emergence of behavioral hyperresponsiveness to AMPH was dependent on an interaction of lesions, age of examination, and dose of the drug. A dissociation between the effect of AMPH on lesion-enhanced hyperlocomotion and a lack of a lesion-enhanced DA release in the NAc suggest that presynaptic release of DA had no major contribution to lesion-enhanced DA transmission in the mesolimbic DA system.     

Esophagitis in Sprague-Dawley rats is mediated by free radicals

Free radical-mediated esophagitis was studied during duodenogastroesophageal reflux (mixed reflux) or acid reflux in rats. The influence of reflux on esophageal glutathione levels was also examined. Mixed reflux caused more gross mucosal injury than acid reflux. Gross mucosal injury occurred in the mid-esophagus. Total glutathione (GSH) in the esophageal mucosa of control rats was highest in the distal esophagus. The time course of esophageal GSH in rats treated by mixed reflux showed a significant decrease 4 hr after initiation of reflux, followed by a significant increase from the 12th hour on. Mucosal GSH was increased in both reflux groups after 24 hr but significantly more so in the mixed than in the acid reflux group. The free radical scavenger superoxide dismutase (SOD) prevented esophagitis and was associated with decreased GSH levels. GSH depletion by buthionine sulfoximine (BSO) prevented esophagitis and stimulated SOD production in the esophageal mucosa. It is concluded that gastroesophageal reflux is associated with oxidative stress in the esophageal mucosa. The lower GSH levels in the mid-esophagus may predispose to damage in this area. Duodenogastroesophageal reflux causes more damage than pure acid reflux. Oxidative stress leads to GSH depletion of the esophageal mucosa in the first few hours following damage but then stimulates GSH production. GSH depletion by BSO does not worsen esophagitis since it increases the esophageal SOD concentration.     

Tumor promotion in a breast cancer model by exposure to a weak alternating magnetic field

In view of the methodological problems of epidemiological studies on associations between exposures to 50/60 Hz magnetic fields (MF) and increased incidence of cancers, laboratory studies are necessary to determine if 50/60 Hz MF are cancer promoters or can progress cancers. The objective of the present study was to determine if an alternating MF of low flux density exerts tumor-promoting or co-promoting effects in a model of breast cancer in female rats. Mammary tumors were induced by the chemical carcinogen 7,12-dimethylbenz(a)anthracene (DMBA). A group of 99 rats was exposed to a homogeneous MF of 50 Hz, 100 microT (microtesla), for 24 h/day 7 day/week for a period of 91 days; another group of 99 rats was sham-exposed under the same environmental conditions as the MF-exposed rats. The exposure chambers were identical for MF-exposed and sham-exposed animals. DMBA was administered orally at a dose of 5 mg/kg at the first day of exposure and at weekly intervals thereafter up to a total dose of 20 mg per rat. The animals were palpated once weekly to assess the development of mammary tumors. In controls, DMBA induced tumors in about 40% of the animals within three months of first application. Eight weeks after DMBA application the MF-exposed rats exhibited significantly more tumors than sham-exposed animals. This difference in the rate of tumor development was observed throughout the period of exposure. At the end of the three-month period of MF exposure the tumor incidence in MF-exposed rats was 50% higher than in sham-exposed rats, the difference being statistically significant. Furthermore, the size of tumors as estimated by palpation was significantly larger in the MF-exposed compared to sham-exposed rats. The data demonstrates that long-term exposure of DMBA-treated female rats to an alternating MF of low flux density promotes the growth and increases the incidence of mammary tumors, thus strongly indicating that MF exposure exerts tumor-promoting and/or copromoting effects.     

Observations on the pharmacology of cholinoceptive neurones in the rat brain stem

Fasted rats were injected six times over a 48-hr period with G-17 I, G-17 II, G-34 II in doses doubling from 3.38 nmoles per kg to 54 nmoles per kg. Twelve rats were studied at each dose. NaCl-injected animals were used as controls. The rats were killed and the in vitro incorporation of [3H]thymidine into DNA as well as the total DNA content of the mucosa of the duodenum and oxyntic gland area of the stomach were determined. All gastrins, as well as pentagastrin, stimulated DNA synthesis. Peak stimulation occurred at 13.5 nmoles per kg for G-17 I and G-17 II and at 6.75 nmoles per kg for G-34 II. Pentagastrin's peak trophic effect was produced by 325 nmoles per kg. In order to compare the efficacies of the various types of gastrins, 60 rats were divided into groups of 12. One group received saline and the other four groups received the maximally effective dose of one of the four types of gastrins. The responses to each of the gastrins were not significantly different, and DNA synthesis was doubled in each tissue. Total DNA content increased slightly, but significantly, in response to each gastrin. Several conclusions can be drawn from these data: (1) G-17 and G-34 possess trophic activity; (2) the efficacies of pentagastrin, G-17 I, G-17 II, and G-34 II for the stimulation of DNA synthesis are not significantly different; (3) sulfation of G-17 has no significant effect on its trophic activity; (4) based on the effects of exogenous molar doses and their respective half-lives, both G-17 and G-34 would be expected to contribute to the trophic effect of endogenous gastrin; and (5) G-17 and G-34 are at least as effective in stimulating DNA synthesis as they are in stimulating gastric acid secretion.     

Rats alternate on a dry-land but not swimming-pool (Morris task) place task: Implications for spatial processing.

Groups of rats were rewarded with food for traveling from a start point to 2 different locations while their alternations in choice between those locations on 2 daily trials were recorded. In one experimental condition, the rats swam and received food once they climbed upon a platform that was hidden just below the surface of the water at the food location. In the other condition, the rats walked to reach the food. It was found that the rats did not alternate their choices between target locations when swimming but that they did alternate target choices when walking. Even experience in alternating when walking did not produce reliable alternation when swimming. It is proposed that rats treat escape (swimming) and search (walking) tasks in different ways, and this difference is discussed with respect to the possibility that different central processes may be used in the task solutions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)