Physiology and Pharmacology
Year:2001 | Volume:5 | Issue:1|Papers Count:11

Visual object recognition can be largely invariant to the viewing angle of objects. Previous studies have shown that most inferotemporal neurons respond selectively to moderately complex features of object images. The projected image of an object can be represented as a combination of several inferotemporal cells that respond to different features in the image. Changes in the viewing angle cause changes in the aspect ratio of the features. In the present study, the features critical to the activation of individual inferotemporal cells were determined and the effects of changes in the aspect ratio of the optimal shapes on the responses were examined. The results showed that the responses of a majority of inferotemporal cells were not sharply tuned to the aspect ratio of their optimal shapes, instead, the tunings were broad. We suggest that responses of these inferotemporal cells are not tuned to a shape defined in twodimensional pictorial space, but their selectivity is defined by combination of primitives representing projection-invariant features. It is also suggested that the limitation in view-angle invariance of object recognition is not necessarily determined by the selectivity to the representation of individual features, but by the selectivity to the combination of features.

Previous investigations have shown that cimetidine has radioprotective effect against gamma radiation. Since famotidine like cimetidine is a H2-receptorantagonist, therefore in this study the radioprotective effect of cimetidine and famotidine against gamma rays-induced micronuclei was tested in bone marrow cells of 8 weeks-old male Balb/c mouse. Cimetidine at doses of 7.5, 15 and 30 mg/Kg and famotidine at doses of 0.75, 1.5 and 3 mg/Kg was injected (i.p.) alone or 2 hours before gamma rays exposure. For both groups frequency of MNPCE and MNNCE and the ratio of PCE/PCE+NCE were determined 24 hours after the drug treatments and/or gamma irradiation of mice. After exposure of mice to 2 Gy gamma rays, the frequency of MNPCE increased significantly (P<0.0001) and the ratio of PCE/PCE+NCE was decreased (P<0.0001) compared to control group. Results showed that the drugs given alone with no subsequent gamma irradiation had no effect on the frequency of MNPCE and the ratio of PCE/PCE+NCE in comparison to control group (P<0.05). In addition, cimetidine and famotidine administered prior to gamma irradiation resulted in a reduction of frequency of MNPCE (P<0.001) in comparison to gamma-irradiated group, but famotidine produced a stronger effect than cimetidine (P<0.05). Furthermore, cimetidine increased the ratio of PCE/PCE+NCE (P<0.05), but famotidine had no effect in this respect. It is also concluded that the radioprotective effect of the drugs was also dose-dependent.

Human beings and animals that have undergone stressful conditions during the embryonic period show some disturbances in social behavior and regulation of hypothalamic-hypophyseal axis. In this study, the female adult and pregnant rats were divided into one control and two experimental groups. The experimental groups I and II were exposed to immobility stress every morning from the days 14 to 21 for a period of 2 and 3 h respectively, the parameters, weight and consumption rate of food and water were measured in born pups 2 months old. The results showed that the difference between these parameters was significant (P<0.001). The control group and experimental group I were similar regarding weight, but there existed a significant difference for group II (P<0.05). Therefore, consumption rate of food and weight was less in stress-tolerated group compared to control group and there was a positive association between the period of stress and reduction in weight, food and water consumption. It is also concluded that in rats with prenatal stress there is a greater reduction in weight than food and water consumption and possibly different mechanisms are involved in this phenomenon and it can not be recovered as observed in food-deprived rats.

It has been shown that enhanced acid secretion can be suppressed in the rat by systemic administration of glucose. We have recently reported that enhancement of acid secretion as a result of pentagastrin was diminished by intragastric administration of D-glucose.Present study was designed to investigate whether intragastric D-glucose influences gastric acid secretion associated with carbachol and histamine in rat, and then we compared these results with our previous results obtained by pentagastrin-induced hyperacidity.Intravenous infusion of carbachol (1 mg/100 g/h) and histamine (0.5 mg/100 g/h) caused an immediate increase in acid secretion with a peak starting after 40 and 60 min and then reached to a steady state respectively. lntragastric administration of D-glucose significantly reduced the hyperacidity induced by histamine and carbachol (P<0.01). The effect of intragastric D-glucose On hyperacidity induced by pentagastrin or histamine when compared with carbachol-induced hyperacidity was significantly greater than carbachol group.In conclusion, it is suggested that the inhibitory effect of intragastric D-glucose observed in hyperacidity may be the result of glucose-induced modification of intragastric pathways in parietal cells that control gastric acid secretion.

The role of prostaglandins in control of joint blood flow was investigated in chronically inflamed knee of rat. Joint inflammation was induced by intraarticular injection of Freund's Complete Adjuvant (FCA) into right knee joint and experiments were performed on the ipsilateral (right) and contralateral. (left) joints for 28 days post- treatment. Blood flow measurements of the exposed joints were made using Laser Doppler Flowmeter (LDF).Injection of FCA caused a significant increase in diameter of both ipsilateral and contralateral knees as compared with pre-injection diameter. Indomethacin (3 mg/kg, i.p.) can restore the diameter of inflamed knee to control value. Topical application of phenylephrine (10-7 to 10-3 M) in normal rats produced a dose-dependent vasoconstriction of the articular microvasculature. This constrictor response was attenuated in the ipsilateral and contralateral knee joints of inflamed animals for 21 days, but this reduction was more obvious in contralateral knee than in ipsilateral knee and was significant as compared with control group at days 3-14. After treatment with indomethacin at days 3 and 7, vasoconstrictor response to phenylephrine increased and returned to control value in contralateral knee but had no significant effect on ipsilateral knee. At day 14, indomethacin decreased or didn't change this response in contralateral knee. These data suggest that prostaglandins increase knee diameter in chronic inflammation and these substances appear to involve in modulation of vasoconstrictor response to phenylephrine.

Morphine can induce psychological dependence by blocking inhibitory GABAergic interneuron's in the mesolimbic dopaminergic pathway. Since the involvement of GABAergic receptor subtypes in this respect is not clear, therefore in this research study the possible role of GABAAand GABABreceptor subtypes on the expression of conditioned place preference (CPP) in male Swiss-Webster mice were investigated. The results showed that GABAA receptor agonist muscimol, (0.15-1.2 mg/kg, i.p.) had no effect on morphine action, while GABAA receptor competitive antagonist bicuculline, (0.75-1 mg/kg, i.p.) and GABAA receptor noncompetitive antagonist picrotoxin (2 mg/kg, i.p.) potentiated the expression of morphine induced CPP. Baclofen, a GABAB receptor agonist (5 mg/kg, i.p.) reduced the expression of CPP induced by morphine, while CGP 35348, a GABA Breceptor antagonist (2.5-400 mg/kg, i.p.) had no effect on morphine action. Moreover, pretreatment with bicuculline (1 mg/kg, i.p.) or picrotoxin (2 mg/kg, i.p.) or CGP 35348 (400 mg/kg, i.p.) reverses the baclofen (5 mg/kg, p.) effect on the expression of morphine-induced CPP. Pretreatment with both bicuculline (0.5 mg/kg, p.) and CGP 35348 (200 mg/kg, i.p.) compensated reducing effect of baclofen (5 mg/kg, i.p.) on the expression of orphine-induced CPP.In conclusion, it can be suggested that blockade of GABAA receptors might potentate the rewarding effect of morphine, while activation of these receptors could attenuate the rewarding effect of morphine. On the other hand, GABAc receptors might also strengthen the action of morphine.

The nucleus reticularis paragigantocellularis (PGi) covers a large region in the rostral ventral medulla and shows a cytological and functional heterogeneity. In this study we evaluated responsiveness of the PGi neurons to the formalin in hyperthermic condition by extracellular single-unit recording. The experiments were carried out on male anaesthetized NMRl rats. Baseline activity of 50 neurons in 36 animals was recorded for 60-180 min. Their firing rates was 1.37 spikes/sec. In 25 animals (25 neurons) temperature was raised from 35.5±0.1 to 38.5±0.1°c In this hyperthermic condition neuronal recording was carried out for 30 min, and then after 60 min, 50? I of diluted formalin (5.2%) was injected into the plantar region of hindpaw. Our previous observation indicated three types of responsiveness of PGi neurons to the formalin, that is, inhibited (48.4%), excited (19.3%) and unchanged (32.3%). However, statistical analysis showed only two neuronal types in hyperthermic condition, that is, excited (44%) and unchanged (56%).It is concluded that responses of the PGi neurons to the formalin are affected by hyperthermia. In addition, inhibited neurons may be disinherited by fever-induced mediators.

To investigate the effects of slow freezing and vitrification using ethylene glycol and 1, 2 propandiol as cryoprotectants on the survival, fertilization and developmental rate of Mil oocyte of female N-Mari mice. The animals were 6-10 weeks old, which were superovulated using IP injection of 10 IU human menopausal gonadotropin (hMG) and 10 IU human Chorionic Gonadotropin (hCG). Ovulated oocytes were then collected from the ampullary portion of the oviducts at 12-13 hours after hCG injection. Cumulus cell mass was separated by 0.1% hyaluronidase. Mature oocytes were slow frozen or vitrified by ethylene glycol or 1,2 propandiol, which were used as cryoprotectans. Then, they were stored in liquid nitrogen. After thawing, frozen and non-frozen oocytes were inseminated with epididymal sperm, cultured in T6 medium. The survival rates of the oocytes using slow frozen method with ethylene glycol and 1, 2-propandiaol were 0.56% and 85% respectively. On the other hand, this rates were were 80% and 6.7% in vitrified groups respectively. Accordingly, the fertilization rates of slow frozen and vitrified groups using both cryoprotectants and control group were 50%, 91%, 94%, 7% and 96.2% respectively. Moreover, the rate of embryos reaching to the hatching blastocyst stage were 0%, 0%, 29.7%, 0% and 28.6% respectively, which were significantly higher than that of the control group using X2-test (P<0.0001). Thus, vitrification method using ethylene glycol could be more effective and useful for cryopreservation of oocytes.

Acetaminophen, a well-known antipyretic and analgesic substitue for salicylate has been increasingly used in recent years. However, the potential for hepatotoxicity and renal failure accompanying its chronic and excessive use or its overdose in suicidal attempt necessitates a reliable, interference-free procedure for determination of acetaminophen in serum.Various spectrophotometric methods have been established for acetaminophen determination.Two of the common methods are Chafetz & Walberg and Indophenol. For evaluation of the two methods, different concentrations of acetaminophen, ranging between 20 and 200 mg/L were put in the presence or absence of urea and creatinine and in addition, in normal and uremic sera. The average retrieval of acetaminophen was 79% for sample without urea and creatinine and 86% for sample containing urea and creatinine. The difference between two retrievals was7% that indicates the interference of the materials used in the Chafetz & Walberg method. This difference was significant statistically (p=0.005, t=3.24).The retrieval of acetaminophen in normal and uremic sera by this method were 72% and 86% respectively. Also, in this case the present difference (14%) was highly significant (p=0.0001, t=5.67), which indicates the interference of urea and creatinine and phenolic substances. The rate of acetaminophen retrieval in the presence of mentioned compounds and in normal and uremic sera was about 89% which is not significant. Thus, urea, creatinine and uremia have no effects on acetaminophen determination by Indophenol method. Analysis of variation coefficient of the two methods in 40mg/L and 100mg/L of acetaminophen showed that taken together, Indophenol method is more appropriate than the Chafetz & Walberg method for acetaminophen determination.

There have been many reports on the involvement of oxygen-derived free radicals (OFR) in the pathogenesis of reperfusion injury (RI). To determine the role of OFR in RI, the first evidence was based on the indirect methods obtained from the beneficial effects of antioxidants during post-ischemic reperfusion In some studies, OFR are detected locally and chemical production of OFR reproduces cellular dysfunction similar to that observed during ischaemia-reperfusion injury. Using of new techniques for direct detection and quantitation of these radicals showed their burst generation during first seconds of reperfusion.Several factors are implicated in the pathogenesis of RI including endothelial cells, endothelin, nitric oxide, cytokines, and neutrophils. The interaction of OFR with these factors makes RI more complicated. Therefore, knowledge of the mechanisms involved in the pathophysiology of reperfusion injury is clinically very significant to prevent the occurrence of RI.In this review, the cellular changes during ischemia and reperfusion and the possible role of OFR in these changes are to be discussed. It is worth mentioning that the involvement of OFR in tissue injury is still under intensive investigation.