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Biomedical subjects

W Cao

Publications and source records attributed to W Cao.

At least 199 records · Page 11Linked to original sources
PubMed1989

[Antagonism of morphine analgesia and electroacupuncture analgesia by cholecystokinin octapeptide (CCK-8) administered in periaqueductal gray (PAG) of the rabbits].

We have reported that intracerebroventricular (i. c. v.) injection of 1-4 ng of CCK-8 to the rat produced a remarkable antagonistic effect on morphine analgesia. In order to study the species specificity and the site of action, CCK-8 was microinjected into the PAG of the rabbit, and its influence on morphine analgesia and electroacupuncture analgesia was observed. The latency of the escape response (ERL) to radiant heat focused on the snout was measured as an index of the pain threshold. Microinjections were made via cannulae chronically implanted into the PAG. The drug solutions were delivered in a volume of 1 microliter, at a speed of 0.125 microliter/min. The ERL was measured for a period of 60 or 70 minutes at 10 min intervals. 1. CCK-8 administered unilaterally to the PAG of the rabbit at a dose of 3 ng antagonized the analgesia induced by morphine (4 mg/kg, i. v.) by 73% (P less than 0.001), and reduced the analgesic effect of electroacupuncture by 67% (P less than 0.001). These effects were dose-dependent within the range from 1.5 ng to 6.0 ng. The effect of CCK-8 was reversed by CCK receptor blocker proglumide (4 microliters, intra-PAG injection). Unsulfated CCK-8 (CCK-us) had no effect in this regard. These results indicate that in the PAG of the rabbit, exogenously administered CCK-8 was capable of antagonizing opioid analgesia by the activation of CCK receptors. 2. Two groups of rabbits were given with morphine (2 mg/kg, i. v.) and simultaneous injection of CCK-8 antiserum (CCK-AS, 1 microliter) or normal rabbit serum (NRS) into the PAG.(ABSTRACT TRUNCATED AT 250 WORDS)

Acupuncture Analgesia↗
PubMed1988

Oxygen free radical involvement in ischemia and reperfusion injury to brain.

Evidence is presented which implicates increased oxygen free radicals during ischemia reperfusion of gerbil brain. Salicylate, which reacts with hydroxyl free radicals to yield dihydroxybenzoic acid (DHBA), was used as an in vivo trap. Brain ischemia for at least 5 min followed by reperfusion yielded significantly increased brain DHBA. Without reperfusion or with only 2 min of ischemia and then reperfusion, the production of DHBA was not increased. Increased levels of DHBA in brain correlated with ischemia reperfusion-mediated behavioral modification of gerbils, but salicylate administration did not protect against the behavior changes.

Animals↗
PubMed1988

Effects of chronic amphetamine in BALB/cBy mice, a strain that is not stimulated by acute administration of amphetamine.

The effects of d-amphetamine and methylphenidate on locomotor activity of BALB/cByJ mice were evaluated. d-Amphetamine had no effect or inhibited locomotor activity at acute doses of up to 10 mg/kg while methylphenidate stimulated locomotor activity at acute doses between 10 and 32 mg/kg. The dose-response curves for methylphenidate and d-amphetamine appeared to be quantal in nature. During a 21-day chronic treatment with 10 mg/kg d-amphetamine no evidence of tolerance to the depressant effects of relatively high doses of d-amphetamine was observed. However, a 3.2 mg/kg dose of d-amphetamine, which acutely inhibited locomotor activity, was found to stimulate locomotor activity following chronic amphetamine treatment. Doses of methylphenidate which acutely stimulated activity were without effect in mice chronically receiving amphetamine. Although the mechanism underlying these behavioral effects has yet to be established, our results indicate that inherent alterations can differentially affect both acute and chronic susceptibility to the behavioral effects of amphetamine and methylphenidate. Use of such altered strains of mice can be especially revealing of subtle behavioral effects brought about by chronic drug treatment which are not readily demonstrated following acute administration of amphetamine.

Animals↗
PubMed1986

Inherent hyporesponsiveness to methylxanthine-induced behavioral changes associated with supersensitivity to 5'-N-ethylcarboxamidoadenosine (NECA).

Two inbred mouse strains, SWR and CBA, differed significantly in their susceptibility to acute dose dependent theophylline- and caffeine-induced stimulation of locomotor activity. The efficacy of both methylxanthines was reduced in the SWR strain compared to the CBA strain. When brain levels of theophylline were determined at a dose (32 mg/kg IP) which gave maximal behavioral separation of the two strains, no significant differences were found between them (SWR levels 12.5 +/- 1.9, CBA levels 14.3 +/- 1.7 micrograms/g wet weight brain). The dose dependent ability of several adenosine agonists (N6-cyclohexyladenosine, (-)-N6-phenylisopropyladenosine, 5'-N-ethylcarboxamidoadenosine) to depress locomotor activity was investigated. SWR mice were found to be significantly more sensitive to NECA-induced depression of locomotor activity and the NECA-induced hypothermia than were CBA mice (respective ED50 values for inhibition of activity, 11.6 and 30.5 nmoles/kg IP). No differences were found in brain [3H]-NECA levels at doses which produced marked differences in behavioral effects between the two strains. The differences in adenosine agonist sensitivity between the strains were both agonist- and behavior-specific. These data indicate that an inherited alteration in behavioral responsiveness to methylxanthine administration can be inversely associated with inherent alterations in susceptibility to the action of specific adenosine analogs. An adenosine A-2 receptor sub-class may be involved in these changes in in vivo pharmacological susceptibility to the action of both methylxanthines and adenosine agonists on locomotor activity.

Adenosine↗
PubMed1986

Differential antagonism of the behavioral depressant and hypothermic effects of 5'-(N-ethylcarboxamide) adenosine by theobromine.

The methylxanthine, theobromine (3,7-dimethylxanthine), was tested in mice, to determine whether theobromine could function in vivo as an adenosine receptor antagonist, in keeping with its reported in vitro effects as a blocker of agonist binding to the adenosine A-1 receptor. Theobromine doses, which themselves had no direct effects on spontaneous locomotor activity, completely blocked N6-cyclohexyladenosine-induced suppression of locomotor activity but were without effect on 5'-N-ethylcarboxamide adenosine (NECA)-induced decreases in motor activity. In contrast to the specific antagonism, theobromine blocked the hypothermia induced by both of these adenosine analogs. These results demonstrate that theobromine is an active in vivo adenosine receptor antagonist and that the antagonism of N6-cyclohexyladenosine sensitive systems occurs even though theobromine does not stimulate spontaneous locomotor activity. Thus, the behavioral stimulant effects of methylxanthines may be more related to effects on NECA-sensitive systems, which are not blocked by theobromine. The use of in vivo differences in the effects xanthine may provide a useful tool in the development of compounds to probe the mechanisms of caffeine induced CNS effects.

Adenosine↗
PubMed1982

Study of lung flukes from Philippines: --a preliminary report.

In this paper taxonomic study on paragonimus including their metacercariae obtained from the crabs collected from Sorsogon, Luzon, Philippines and adult worms and ova obtained through animal feeding, with light microscopy and scanning electron microscopy revealed that there may exist two or more species of lung flukes in Philippines. The occurrence of Semisulcospira libertina in addition to Antemelania dactylus (Lea) as an additional snail host is mentioned for the first time. The chromosome Karyotyping of the adult worms revealed that they belong to the diploid pattern. Electronic scanning showed that the cuticular spines of the Paragonimus from Sorsogon look like "pineapple ears" both in distribution and in appearance, a new finding that has not been recorded before. In the lungs of a white rat killed 290 days after infection, two adult worms were obtained within the solitary cyst. These 2 adult worms measured 4.5 x 2.5 mm and 4.5 x 3.0 mm respectively. Their unusually small size and somewhat round shape suggest that they may be of a different species from those hitherto reported in the Philippines. Clearcut evidence is presented for the first time, demonstrating the occurrence of the phenomenon of cross fertilization (allogamy) of lung flukes.

Animals↗
PubMedDate not supplied

Ethanol effects on 2-deoxyglucose uptake into tissues obtained from LS and SS mice.

The uptake of 2-deoxy-D-[14C]glucose (2-DG) has been used with some success to identify neuronal sites of drug action, and has also been useful in identifying brain regions that are differentially sensitive to ethanol in selectively bred rat lines, the alcohol tolerant (AT) and alcohol nontolerant (ANT) lines. The studies reported here utilized the 2-DG method in an attempt to ascertain whether the LS and SS mouse lines, which were selectively bred for differences in sensitivity to high dose, anesthetic effects of ethanol, do so because of disruption of specific neuronal sites. LS and SS mice were injected with saline or a 4.0-g/kg dose of ethanol 15 min before injection with 2-deoxy-D-[14C]glucose, and uptakes into blood, eight brain regions, the liver, and adrenal tissues were measured 2-60 min afterwards. Ethanol produced statistically significant decreases in 2-DG uptake into every region of the LS mouse brain, but only three brain regions showed significant decreases in uptake in the SS brain. Other SS brain regions showed a trend towards decreased uptake, but these trends were not significant. A comparison of percent decrease in 2-DG uptake across all brain regions showed that ethanol decreased 2-DG uptake approximately twice as much in LS brain regions as in SS brain regions. Since 2-DG uptake into adrenal and hepatic tissue was not affected by ethanol injection in either mouse line, it seems likely that the decreased 2-DG uptake, seen more readily in the LS brain, is due to ethanol-induced central nervous system (CNS) depression.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMedDate not supplied

Chronic intragastric infusion produces tolerance to ethanol in LS and SS mice.

Tolerance to ethanol's effects is seen after chronic injections and after chronic treatment with ethanol-containing liquid diets. However, tolerance associated with injections is often associated with environmental cuing (learned tolerance) and liquid diets do not allow for careful control of dose. The studies reported here demonstrate that chronic (3 g/kg every 6 h for 7 days) intragastric infusion of ethanol produces tolerance to ethanol in both LS and SS mice, as measured by sleep time and effects on open field activity and body temperature. LS mice developed more tolerance for all measures than the SS. The rate of ethanol elimination was increased slightly in both the LS and SS mouse lines following chronic ethanol infusion, which suggests that both lines developed a modest metabolic tolerance to ethanol. In contrast, the waking blood ethanol levels were altered only in the LS mice, which argues that some of the tolerance to ethanol seen in the LS mice is pharmacodynamic tolerance. Thus, chronic intragastric infusion of ethanol is a reliable method for treating animals chronically with ethanol that allows for the precise control of dose and dose interval, oral administration of ethanol, and minimal animal handling that can be associated with drug delivery, thereby reducing the risk of developing learned tolerance to ethanol.

Animals↗
PubMedDate not supplied

The interaction of surface plasmon polaritons with a silver film edge.

A prism coupling arrangement is used to excite surface plasmons at the surface of a thin silver film and a photon scanning tunnelling microscope is used to detect the evanescent field above the silver surface. Excitation of the silver/air mode of interest is performed at lambda1 = 632.8 nm using a tightly focused beam, while the control of the tip is effected by exciting a counter-propagating surface plasmon field at a different wavelength, lambda2 = 543.5 nm, using an unfocused beam covering a macroscopic area. Propagation of the red surface plasmon is evidenced by an exponential tail extending away from the launch site, but this feature is abruptly truncated if the surface plasmon encounters the edge of the silver film--there is no specularly reflected 'beam'. Importantly, the radiative decay of the surface mode at the film edge is observable only at larger tip-sample separations, emphasizing the importance of accessing the mesoscopic regime.

Journal Article↗
PubMedDate not supplied

Starch concentration and impact on specific leaf weight and element concentrations in potato leaves under varied carbon dioxide and temperature.

Foliar concentrations of starch and major elements, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg), along with specific leaf weight (SLW) were determined in the potato (Solanum tuberosum L.) cvs 'Denali', 'Norland', and 'Russet Burbank' grown for 35 days under CO2 concentrations of 500, 1,000, 1,500 and 2,000 micromoles mol-1 at both 16 degrees C and 20 degrees C air temperature. The starch concentration, pooled from the three cultivars, increased with increasing CO2 concentration at both 16 degrees C and 20 degrees C and was consistently higher at 16 degrees C than at 20 degrees C. The SLW (g m-2) was positively related to the foliar starch concentration on the basis of leaf area or dry weight. The concentrations of N, P, Ca, and Mg in leaves were negatively related to starch concentration under approximately 14% starch on a dry weight basis. Above 14% starch, there was no significant relationship between element and starch concentrations. Similar patterns were seen when the SLW and element concentrations were expressed on a starch-free basis. In contrast, the leaf concentration of K was not closely related to the starch concentration because the K concentration was similar at varied CO2 levels. The results of this study indicate that the changes in SLW and concentrations of N, P, Ca, and Mg in potato leaves only partially resulted from the changed starch concentration.

Biomass↗