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Biomedical subjects

M F Morris

Publications and source records attributed to M F Morris.

5 recordsLinked to original sources
PubMed2000

Amphetamine-induced activation of forebrain EEG is prevented by noradrenergic beta-receptor blockade in the halothane-anesthetized rat.

RATIONALE: Amphetamine (AMPH)-like stimulants represent an intensively studied class of psychoactive drugs. Despite the well-known and potent arousal-enhancing effects of these drugs, the neurobiological substrates of AMPH-induced arousal have rarely been examined explicitly. Activity of the locus coeruleus-noradrenergic system is causally and positively related to behavioral and electroencephalographic (EEG) indices of arousal. For example, activation of locus coeruleus neurons or stimulation of medial basal forebrain noradrenergic beta-receptors elicits activation of forebrain EEG in the anesthetized rat. Further, stimulation of noradrenergic beta-receptors within the medial basal forebrain elicits a substantial increase in alert, active waking. These and other observations suggest that at least some of the arousal-enhancing actions of AMPH-like stimulants derive from AMPH-induced increases in noradrenergic neurotransmission at beta-receptors. The current study examines the extent to which AMPH-induced activation of cortical EEG is dependent on actions of central beta-receptors. METHODS: The effects of intracerebroventricular (ICV; 2 microl) pretreatment with either vehicle (artificial extracellular fluid) or the beta-antagonist, timolol (25, 50 or 100 microg), on the cortical EEG activating effects of intravenous AMPH (0.15 mg/kg) were examined in the halothane-anesthetized rat. EEG was recorded on polygraph and video recording tape and later analyzed using power spectral analyses (PSA). AMPH-induced alteration in cortical EEG activity was measured using PSA in vehicle- and timolol-pretreated animals. RESULTS: Neither vehicle nor timolol ICV infusions altered cortical EEG activity patterns. In vehicle-pretreated animals, AMPH elicited a robust activation of cortical EEG, characterized by the substantial decrease in large-amplitude, slow-wave activity. Timolol pretreatment dose-dependently prevented AMPH-induced cortical EEG activation. This effect of timolol was statistically significant at the 50 microg and 100 microg dose. CONCLUSIONS: These observations indicate that, under these experimental conditions, AMPH-induced activation of the forebrain is dependent on actions of noradrenergic beta-receptors. Combined with previous observations, these observations support the hypothesis that AMPH-induced increases in arousal involve noradrenergic neurotransmission at beta-receptors.

Amphetamine↗
PubMed1999

Psychological and physiological characteristics of sweet food "addiction".

OBJECTIVE: Drug addicts in general can be distinguished from nonaddicts by their affective and physiological and craving responses to drug-related cues. The purpose of this study was to examine similar affective, physiological, and behavioral variables in chocolate "addicts" and control subjects. METHODS: Sixteen addicts and 15 control subjects took part in two laboratory experiments in which their heart rate, salivation, and self-reported responses were measured. RESULTS: In the presence of external chocolate cues, chocolate addicts were more aroused, reported greater cravings, experienced more negative affect, and also ate more chocolate than control subjects. Self-report measures on eating attitudes and behavior, body image, and depression confirmed that a relationship exists between "chocolate addiction" and problem eating. Chocolate addicts showed more aberrant eating behaviors and attitudes than controls, and were also significantly more depressed. DISCUSSION: Chocolate addicts may be considered to be a parallel with addicts generally, because they differ from controls in craving for chocolate, eating behavior, and psychopathology (in respect of eating and affect).

Adult↗
PubMed1999

Clinical efficacy of two dentin desensitizing agents.

PURPOSE: To compare the clinical effect over 3 months of two commercially available desensitizing agents on the level of discomfort of patients with complaints of dentin sensitivity. MATERIALS AND METHODS: An oxalate-containing pre-polymerized resin suspension (Pain-Free), a 0.7% fluoride solution (DentinBloc), and a distilled water placebo were compared in a clinical setting. Ten volunteer patients exhibiting three or more teeth that were sensitive to touch and to a stream of forced air were enrolled in the study (52 teeth total). Each patient's level of sensitivity to tactile stimuli and to a forced air stream was recorded using a visual analog scale (VAS). The tactile stimulus was a metal probe rubbed across the exposed dentin with a constant pressure of 40 grams. A 1-second blast of air from a dental unit air syringe was used to generate the air stream. The desensitizing agents were applied according to manufacturers' guidelines. Sensitivity measurements were recorded at baseline, immediately after treatment, at 1 week, 1 month, and at 3 months. VAS pain scores were analyzed using a repeated measures ANOVA (alpha = 0.05). RESULTS: The pre-polymerized resin suspension (Pain-Free), the fluoride-containing solution (DentinBloc), and the placebo all decreased dentin sensitivity. No significant difference was found among the desensitizing agents at any time period (P > 0.05).

Adult↗
PubMed1989

Carbohydrate removal fails to eliminate the heterogeneity of human prostatic acid phosphatase.

Human prostatic acid phosphatase is known to display considerable charge heterogeneity upon isoelectric focusing. The structural basis of this heterogeneity is not known, although it has been widely attributed to variations in the nature of the carbohydrate chains or to substituents on the carbohydrate chains of the glycoprotein. In this study, the role of the carbohydrate chains in the charge heterogeneity of the protein was examined. First, sialic acid residues were removed by treatment of the acid phosphatase with neuraminidase. The desialo enzyme was fractionated and purified by L-tartramic acid affinity chromatography. Then, after the protein oligosaccharide linkages were made accessible by the presence of NP-40 or by denaturing the protein, the protein was completely deglycosylated by endo-beta-N-acetylglucosaminidase F at pH 4.5 and 9.3. Two discrete intermediates were clearly resolved by SDS gel electrophoresis during the deglycosylation of the denatured protein at pH 9.3, indicating the existence of three sites of glycosylation on the protein. Peptide mixtures were obtained by digestion of carboxymethylated and citraconylated derivatives of the enzyme with trypsin and the glycopeptides were isolated. The amino acid compositions of the glycopeptides were consistent with the interpretation that there are a minimum of two sites of glycosylation on each peptide subunit of the enzyme. Isoelectric focusing experiments on the native, desialo, and denatured, deglycoso acid phosphatase showed that the heterogeneity of the protein is not eliminated either by desialylation or by deglycosylation. Thus, the electrophoretic heterogeneity of human prostatic acid phosphatase does not lie primarily in the oligosaccharide part of the glycoprotein or in altered conformational states of the protein, but in structural variations of the polypeptide itself. The heterogeneity may be due to variations at the C-terminus, partial deamidation, phosphorylation, sulfation or other posttranslational modifications of the protein chain.

Acetylglucosamine↗