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Biomedical subjects

M Davis

Publications and source records attributed to M Davis.

At least 613 records · Page 34Linked to original sources
PubMed1978

Effects of N,N-dimethyltryptamine (DMT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) on shock elicited fighting in rats.

Rats were tested for shock elicited fighting under various doses of N,N-dimethyltryptamine (0.12, 0.25, 0.50, 1.0, 4.0, 8.0 mg/kg) and 5-methoxy-N,N-dimethyltryptamine (0.06, 0.12, 0.5, 2.0 mg/kg). Both drugs produced an inhibition of fighting at higher doses but no significant effects at lower doses. The effects of these drugs on shock elicited fighting, as well as on other behaviors, thus differ from those of another indole hallucinogen, d-lysergic acid diethylamide, and are discussed in relation to their effects on single unit activity of the raphe-serotonin system and their interaction with other neurotransmitter systems.

Aggression↗
PubMed1978

Conditioned fear and startle magnitude: effects of different footshock or backshock intensities used in training.

In Experiment 1 four groups of rats received 30 light-shock pairings using footshock intensities of either .2, .4, .8, or 1.6 mA. One day later all rats were tested for startle by presenting tones in the presence or absence of the light CS. Potentiated startle (the difference between startle on light-tone vs tone-alone trials) was nonmonotonically related to the shock intensity used in training, with the greatest potentiation at intermediate shock levels. Experiment 3 demonstrated a similar relationship when backshocks instead of footshocks were used. In Experiment 2 rats were trained with either a moderate or high shock and then given an extended extinction-test session 1 day later. The moderate-shock group showed a gradual decline in potentiated startle over extinction. The high-shock group showed a nonmonotonic extinction curve where potentiation progressively increased toward the middle of extinction and dissipated thereafter. The results suggest that acoustic startle bears an inverted U-shaped relationship to fear and are discussed in relation to other studies concerned with this issue.

Acoustic Stimulation↗
PubMed1978

Prednisone or prednisolone for the treatment of chronic active hepatitis? A comparison of plasma availability.

1 The plasma availability of prednisolone after oral doses of prednisolone and its precursor, prednisone, were compared in ten normal controls and twenty-five patients with chronic active hepatitis by estimation of the area under the plasma concentration--time curve for the drug (AUC). 2 In controls, values for AUC were significantly more variable after prednisone than prednisolone, and two subjects showed markedly inefficient conversion of prednisone to prednisolone. In patients, variability was similarly wide after both preparations, but overall bioavailability after both prednisone and prednisolone was similar to that found in controls, although three patients showed subnormal values after both preparations, possibly as a result of impaired intestinal absorption. 3 Patients with biochemical and histological evidence of active hepatocellular necrosis showed evidence of impaired activation of prednisone, but this was compensated for by a decreased rate of elimination of prednisolone from the plasma. 4 It is concluded that plasma prednisolone levels will be more predictable after prednisolone than after prednisone in subjects without hepatic dysfunction. In the presence of liver disease, because of the marked variability in plasma prednisolone levels after either drug, estimation of these could be of value in those patients whose disease cannot be controlled by normal maintenance doses.

Adult↗
PubMed1978

Red blood cell transketolase activity and the effect of thiamine supplementation in patients with chronic liver disease.

Biochemical evidence of thiamine deficiency was found in 58% of patients with chronic liver disease, the incidence being higher in alcoholic than in non-alcoholic patients. Daily supplementation with high doses of thiamine hydrochloride (200 mg/day) for one week restored levels of thiamine pyrophosphate (TPP), the active co-enzyme form of thiamine, to normal in all cases. Such supplementation also stimulated synthesis of the TPP dependent enzyme transketolase. Because of the essential role of TPP as a co-factor in intermediary metabolism, it is concluded that high doses of thiamine should be included in the routine nutritional management of patients with severe chronic liver disease.

Ascorbic Acid↗
PubMed1978

The degradation of tryptophan in severe liver disease.

Patients with severe acute or chronic liver disease were found to have a high mean plasma free tryptophan, an abnormal urinary excretion pattern of tryptophan-kynurenine metabolites and low circulating levels of the vitamins required for tryptophan degradation, i.e. pyridoxine, thiamine and ascorbic acid. In patients with decompensated chronic liver disease (DCLD), ineffective vitamin B6(pyridoxine hydrochloride) supplementation with effective thiamine and ascorbic acid supplementation increased urinary 3-hydroxykynurenine, 3-hydroxyanthranilic acid and xanthurenic acid excretion. Effective B6(pyridoxal phosphate) supplementation did not cause a similar change. It is postulated that the combination of increased input into the pathway together with vitamin B6 deficiency may explain the abnormal tryptophan-kynurenine pathway in severe liver disease. Imbalanced or ineffective vitamin supplementation may aggravate the disturbance of tryptophan degradation.

Acute Disease↗
PubMed1977

Changing pattern of alcoholic liver disease in Great Britain: relation to sex and signs of autoimmunity.

A survey of 293 patients with alcoholic liver disease showed that women, particularly those aged under 45, had a significantly higher incidence of alcoholic hepatitis, with or without superimposed cirrhosis, than men. The long-term prognosis for both women who continued to drink and those who stopped drinking was worse than that for men. Autoantibodies were more common in women, which suggested that immune mechanisms may play a part in the pathogenesis and progression of alcoholic liver disease in women.

Adult↗
PubMed1977

Effects of clonidine on habituation and sensitization of acoustic startle in normal, decerebrate and locus coeruleus lesioned rats.

Rats were presented with startle-eliciting tones after injection of clonidine (0.01, 0.02, 0.04, 0.08, 0.5, 1.0 or 2.0 mg/kg) or saline. Clonidine potently depressed startle amplitude and the effect was monotonically related todose. Pretreatment with piperoxane (10 mg/kg) antagonized this effect but pretreatment with phentolamine (10 mg/kg) did not. Clonidine still depressed startle in acutely decerebrate rats and in rats with bilateral ablation of the locus coeruleus. Clonidine did not interfere with sensitization to background noise and did not interfere with the ability to startle but instead improved within-session habituation. The results represent one of the few instances in the literature where a drug appears to improve habituation without directly interfering with the ability to respond. The possibility that clonidine might affect startle by stimulating central epinephrine rather than norepinephrine receptors is discussed.

Acoustic Stimulation↗
PubMed1977

Psilocybin: biphasic dose-response effects on the acoustic startle reflex in the rat.

The startle reflex was measured in 7 groups of 10 rats each after intraperitoneal injection of saline or 0.25, 0.50, 0.75, 1.0, 2.0, 4.0 or 8.0 mg/kg psilocybin. Low doses (0.75-2.0 mg/kg) increased startle amplitude whereas high doses (4.0-8.0 mg/kg) depressed startle. Selected low (0.71 mg/kg) or high (5.70 mg/kg) doses of psilocin also had a biphasic dose-response effect on startle comparable in magnitude to equimolar doses of psilocybin. This biphasic dose-response relationship of the indole hallucinogen, psilocybin, on startle is consistent with the hypothesis that startle is increased when the firing rates of midbrain raphe neurons are selectively inhibited but is depressed when neurons postsynaptic to raphe cells are also inhibited.

Acoustic Stimulation↗
PubMed1977

Detection and grading of oesophageal varices by fibre-optic endoscopy and barium swallow with and without Buscopan.

Detection of oesophageal varices is important in the diagnosis of portal hypertension. We have, therefore, compared the results of fibre-optic endoscopy and barium swallow in 56 patients with chronic liver disease. Oesophageal varices were graded as small, moderate or gross by independent observers for each technique. In 12 patients varices were not detected by either method, and in six cases varices were detected by endoscopy when the barium swallow was negative. In 15 of the remaining 38 patients varices were found to be one grade larger at endoscopy than on barium swallow. Since it is possible that varices appear larger at endoscopy because of the Buscopan (hyoscine N-butyl bromide) used as a relaxant, we carried out barium examinations after Buscopan 20 mg i.v. in 23 of the patients. In eight cases varices were one grade larger after Buscopan than on the standard barium swallow, and in two were only detected after Buscopan had been given. Eight cases negative after Buscopan were also negative at endoscopy. Although emergency endoscopy has particular value in locating the site of bleeding in patients with portal hypertension and acute gastrointestinal haemorrhage, the results of the present study suggest that a barium meal with Buscopan is as accurate as endoscopy in the detection of oesophageal varices.

Butylscopolammonium Bromide↗
PubMed1977

Plasticity of the acoustic startle response in the acutely decerebrate rat.

Plasticity of the acoustic startle reflex was measured in rats in which a complete transection between the forebrain and midbrain was made. During a period from 60 to 100 min after surgery, startle amplitude in the transected rats was relatively stable and comparable with that of the controls (which had been anesthetized with halothane and placed in a stereotaxic instrument). During this period the transection did not alter the temporal recovery process (with intervals of 2, 4, 8, or 16 sec) or auditory prepulse inhibition (with intervals of 25, 50, 100, 500, or 1,000 msec) or the normal reduction in startle caused by high levels of background noise. The transection did prevent the normal increase in startle caused by moderate levels of background noise and eliminated within-session habituation. The effect on habituation was particularly convincing since the curves of the transected and nontransected rats actually crossed. The results are discussed in terms of how the transection procedure can be used to evaluate various hypotheses about underlying mechanisms of startle plasticity.

Acoustic Stimulation↗