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Biomedical subjects

M Davis

Publications and source records attributed to M Davis.

At least 649 records · Page 36Linked to original sources
PubMed1976

Effects of apomorphine and haloperidol on the acoustic startle response in rats.

A series of 3 experiments tested the effects of 0.01, 0.04, 0.19, 0.75, 3.00, and 6.00 mg/kg apomorphine and 0.13, 0.25, and 0.50 haloperidol on the acoustic startle response in rats. Apomorphine markedly facilitated startle amplitude for about 40 min after injection and then depressed startle over the next 40 min. Both the early facilitory and later inhibitory effects were directly related to the dose. Haloperidol (0.5 mg/kg--given 30 min before) completely blocked both the early facilitory and the later depressant effect of apomorphine (3 mg/kg). Haloperidol alone had only a slight depressant effect on startle. The data support the conclusion that DA receptor stimulation enhances acoustic startle amplitude and indicate that a previous report failed to find an effect of apomorphine on startle because startle was only measured 40 min after injection.

Acoustic Stimulation↗
PubMed1976

Why do people use paracetamol for suicide?

A questionnaire to assess motives for choosing paracetamol as a suicidal agent was completed by 107 patients admitted after an overdose of the drug. None of the 48 patients interviewed would have chosen paracetamol had they known that there would be an interval of two to three days before the onset of serious symptoms. Only five of the patients had obtained the drug on prescription, but the remainder had obtained it easily from a retail pharmacy. There was no apparent reason for the preference for paracetamol. It would be difficult to restrict the availability of paracetamol, and educating the public about the effects of an overdose would be more appropriate.

Acetaminophen↗
PubMed1976

Clinicopathologic correlations in diabetic retinopathy. I. Histology and fluorescein angiography of microaneurysms.

A patient with adult-onset diabetes mellitus was referred with a diagnosis of malignant melanoma of the choroid of the left eye. A nonproliferative type of diabetic retinopathy was present, which was studied and documented by stereoscopic fundus photographs and fluorescein angiograms. Following enucleation, the microangiopathies were correlated histologically, using the retinal trypsin digest technique. Four types of microaneurysms were seen histologically that were believed to represent stages in the development of this lesion. Most thin-walled aneurysms tightly packed with erythrocytes did not fluoresce. Aneurysms that were hypercellular and those with thick walls showed early and late fluorescence. Intraretinal microvascular abnormalities were hypercellular dilated channels. Those that take origin from terminal arterioles are believed to represent attempts at neovascularization.

Aneurysm↗
PubMed1976

p-Chloroamphetamine: short and long term effects upon shock-elicited aggression.

In a series of experiments the effects of p-chloroamphetamine (PCA) on shock-elicited aggression in rats were investigated. 15 min after 5 mg/kg PCA, shock elicited aggression was inhibited. 2 h to 4 weeks after PCA, fighting was facilitated. Both the inhibitory and the excitatory effects of PCA were directly related to the dose of PCA (1.5, 2.5 OR 5 mg/kg) and were blocked by pretreatment with p-chlorophenylalanine but not by alpha-methyl-p-tyrosine. PCA-increased pain thresholds 15 min after injection and then decreased pain thresholds over the next 24 h but not thereafter, even though shock-elicited aggression continued to be facilitated. The results are consistent with the idea that inhibition of shock-elicited aggression is associated with enhanced release of serotonin whereas enhancement of shock-elicited aggression is associated with serotonin depletion.

Aggression↗
PubMed1976

p-Chloroamphetamine (PCA): acute and chronic effects on habituation and sensitization of the acoustic startle response in rats.

In a series of 6 experiments the effects of p-chloroamphetamine (PCA) on the acoustic startle response in rats were investigated. 15 min after 5 mg/kg PCA startle amplitude was inhibited, 2-15 hr after PCA startle was facilitated. Rate of habituation however was not altered. Both the inhibitory and excitatory effects of PCA were blocked by pretreatment with p-chlorophenylalanine but not by alpha-methyl-p-tyrosine. 24 hr, 1 week and 4 weeks after PCA, initial startle amplitude was unchanged but PCA increased rate of sensitization over successive tone blocks. Increased sensitization was most pronounced at 10 mg/kg and absent at 2.5 mg/kg. The early inhibitory effect of PCA but not the later facilitatory effect was eliminated by reducing the level of background noise. The results suggest that inhibition of startle sensitization is associated with enhanced release of serotonin (5-HT) whereas enhancement of startle sensitization is associated with 5-HT depletion.

Acoustic Stimulation↗
PubMed1976

Acute intravenous infusion in freely moving rats through the sagittal and transverse sinuses.

A technique is described which allows drugs to be injected intravenously using the junction of the sagittal and transverse sinuses as the point of entry into the venous system. The procedure is rapid and uses conventional stereotaxic techniques. Subsequent restraint of movement during drug infusion is minimal. Using this method, 15 mug/kg d-lysergic acid diethylamide produced an increase in acoustic startle amplitide within about 1-2 min which lasted for about 25 min.

Acoustic Stimulation↗
PubMed1976

Automated system for acquisition and reduction of startle response data.

A system specifically designed for the acquisition and reduction of startle data is described. It is able to (1) sample startle responses from 5 animals simultaneously during a specific time band after the eliciting stimulus; (2) convert the analogue startle amplitudes into 2-digit numbers; (3) print the digital results of each startle in each animal; (4) add up the startle amplitudes for each rat over a preset number of stimuli and print the totals; (5) print the interstimulus interval and (6) code for up to six diferent types of trials. A non-technical description and complete wiring diagrams are provided.

Animals↗
PubMed1976

Occult gastrointestinal bleeding due to aspirin: comparison of two compounds.

Occult gastrointestinal bleeding as measured by the faecal 51Cr-labelled red-cell loss was compared in eight healthy volunteers while on therapeutic doses of soluble aspirin and a new slow-release formulation of aspirin (Deskoval). While both preparations led to increased faecal blood loss, this was significantly less during administration of Deskoval than when soluble aspirin was taken.

Aspirin↗
PubMed1976

Why paracetamol?

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Acetaminophen↗
PubMed1976

Paracetamol metabolism in the rat: relationship to covalent binding and hepatic damage.

1. The degree of liver damage observed 48 h after administration of 14C ring-labelled paracetamol (3-23 mmol/kg) to rats was proportional to the amount of a highly reactive metabolite retained in the liver, bound covalently to hepatocellular proteins. 2. With increasing doses of paracetamol, urinary excretion of the glucuronide and sulphate conjugates reached a plateau, whereas the output of cysteine and mercapturic acid conjugates increased markedly. 3. The degree of covalent binding at 48 h was proportional to the rate of urinary elimination of these two latter conjugates in the first 24 h after dosing.

Acetaminophen↗
PubMed1976

Paracetamol overdose in man: relationship between pattern of urinary metabolites and severity of liver damage.

The urinary excretion of paracetamol and its conjugates was studied, using a two dimensional thin layer chromatography system, in three volunteers after therapeutic (6-5-26-6 mmoles) doses of the drug, and in 30 patients admitted early after overdoses taken in suicidal attempts. In both volunteers and patients 85-100 per cent of the drug was excreted into the urine--almost entirely as conjugates--in the first 24 hours, which was before biochemical signs of liver damage had appeared. Higher quantities of paracetamol conjugates were recovered from patients who developed moderate of severe liver damage than those less severely affected, although correlations in individuals between quantity excreted and clinical outcome was poor. The pattern of individual paracetamol conjugates changed markedly the higher the ingested dose of the drug. Thus, the excretion of paracetamol sulphate reached a plateau as the administered dose was increased from 20-26-5 mmoles in the volunteers, whilst in patients who developed liver damage after overdose there was also a plateau in the excretion of the glucuronide conjugate. In the latter group, there was a greatly increased production of the cysteine and mercapturic acid conjugates of the drug. These are formed via a highly chemically reactive metabolite of the drug, which binds to glutathione, and if hepatic stores of the latter become depleted, binding will occur instead to hepatocyte macromolecules with ensuing liver damage.

Acetaminophen↗
PubMed1975

Histological evidence of carcinoma in a hepatic tumour associated with oral contraceptives.

A primary hepatic tumour occurred in a 21-year-old woman who had been taking oral contraceptives for two years; she was treated by partial hepatectomy. Part of the neoplasm showed features suggestive of focal nodular hyperplasia, while the remainder had the histological characteristics of a well-differentiated hepatocellular carcinoma. This is the first report of malignant transformation of a tumour in a patient taking oral contraceptives.

Adult↗