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Biomedical subjects

M A Morrison

Publications and source records attributed to M A Morrison.

At least 19 recordsLinked to original sources
PubMed2002

Seasonal and dose-dependent effects of intracerebroventricular leptin on lh secretion and appetite in sheep.

The role of leptin in neuroendocrine appetite and reproductive regulation remains to be fully resolved. A series of three experiments was conducted using adequately nourished oestradiol-implanted castrated male sheep. In a cross-over design (n=6), responses to a single i.c.v. (third ventricle) injection of leptin (0.5, 1.0 and 1.5 mg ovine leptin (oLEP) and 1.0 mg murine leptin (mLEP)), N-methyl-D-aspartate (NMDA, 20 micro g) or 0.9% saline (control) were measured in terms of LH secretion (4 h post-injection compared with 4 h pre-injection) and appetite (during 2 h post-injection) in autumn (Experiment 1). NMDA and 1.0 mg oLEP treatments were repeated in the same sheep in the following spring (Experiment 2). With an additional 12 sheep (n=18 in cross-over design), responses to low-dose 'physiological' i.c.v. infusion of leptin (8 ng/h for 12 h daily for 4 days), insulin (0.7 ng/h) and artificial cerebrospinal fluid were measured in the next spring (Experiment 3). LH was studied over 8 h and appetite over 1 h on days 1 and 4 of infusion. In Experiment 1 (autumn), oLEP overall increased LH pulse frequency by up to 110% (P<0.05), decreased LH pulse amplitude (P<0.05) and decreased appetite (P<0.05). mLEP reduced LH pulse amplitude (P<0.05) without significant effect on appetite, while NMDA reduced appetite (P<0.05) but had no effect on LH. In Experiment 2 (spring), LH responses were 'surge-like' with highly significant increases in the moving average LH concentration after 1.0 mg oLEP (P<0.001) and after NMDA (P<0.001). Compared with similar analysis of experiment 1 results, the LH response in spring was greater than that in autumn for both 1.0 mg oLEP (P<0.05) and NMDA (P<0.005). Conversely, unlike in autumn (Experiment 1), there was no effect of 1.0 mg oLEP or NMDA on appetite in the spring (Experiment 2). In Experiment 3 (spring), 'physiological' i.c.v. infusion of oLEP or insulin increased LH pulse frequency by up to 100% (P<0.001) compared with the control infusion on both days 1 and 4, but there were no effects on appetite. These results indicate that intracerebral leptin both stimulates reproductive neuroendocrine output and decreases appetite in adequately nourished sheep. However, the responses of these two axes were dose-dependent and differentially affected by the time of year, suggesting dissociation of the neural pathways involved.

Animals↗
PubMed2001

Filtration artifacts caused by overloading membrane filters.

The conventional practice of using 0.45 or 0.40 microm membranes to distinguish between the particulate and dissolved phases in natural waters neglects the importance of colloids. Many of the colloids in natural waters pass through 0.45 or 0.40 microm membranes, but a significant fraction at the upper end of the colloidal particle size range is retained. Membrane clogging during filtration decreases the effective pore size and can cause the retention of increasing amounts of colloids. This filtration artifact can cause serious errors in sampling and in assigning trace metals to various particle size classes. We evaluated the effect of membrane loading for two common membrane types (0.45 microm Millipore Durapore and 0.40 microm Nuclepore) on the retention of colloidal Fe, Al, Mn, and OM in three Connecticut rivers. In addition, we used a 1.0 microm Nuclepore membrane to estimate the amount of colloids in the 0.40-1.0 microm size fraction that are retained by membranes during conventional filtration. All samples were collected with clean techniques, and all filtrations were carried out in a class 100 clean room. A peristaltic pump, set at an initial flow rate of 120 mL/min, was used to pump samples through 47 mm diameter inline Teflon filter holders. Back pressure and flow rate were monitored during filtration, and both are good indicators for the onset of membrane clogging. The results show a consistent correlation between increasing back pressure and decreasing concentration of colloidal Fe and sometimes Al, Mn, and OM in the filtrate for all membrane types. Although the shape of the loading-retention curves varied dramatically by site and by membrane type, the essential relationship between back pressure, flow rate, and filtration artifacts during membrane clogging remained the same.

Artifacts↗
PubMed2000

Pyruvate ingestion for 7 days does not improve aerobic performance in well-trained individuals.

The purposes of the present studies were to test the hypotheses that lower dosages of oral pyruvate ingestion would increase blood pyruvate concentration and that the ingestion of a commonly recommended dosage of pyruvate (7 g) for 7 days would enhance performance during intense aerobic exercise in well-trained individuals. Nine recreationally active subjects (8 women, 1 man) consumed 7, 15, and 25 g of pyruvate and were monitored for a 4-h period to determine whether blood metabolites were altered. Pyruvate consumption failed to significantly elevate blood pyruvate, and it had no effect on indexes of carbohydrate (blood glucose, lactate) or lipid metabolism (blood glycerol, plasma free fatty acids). As a follow-up, we administered 7 g/day of either placebo or pyruvate, for a 1-wk period to seven, well-trained male cyclists (maximal oxygen consumption, 62.3 +/- 3.0 ml. kg(-1). min(-1)) in a randomized, double-blind, crossover trial. Subjects cycled at 74-80% of their maximal oxygen consumption until exhaustion. There was no difference in performance times between the two trials (placebo, 91 +/- 9 min; pyruvate, 88 +/- 8 min). Measured blood parameters (insulin, peptide C, glucose, lactate, glycerol, free fatty acids) were also unaffected. Our results indicate that oral pyruvate supplementation does not increase blood pyruvate content and does not enhance performance during intense exercise in well-trained cyclists.

Adult↗
PubMed1999

The psychometric properties of the Homonegativity Scale.

This research details the psychometric properties of an instrument designed to measure negative attitudes toward gay men and lesbians (the Homonegativity Scale-HS). Four studies were conducted using adolescents (N = 1078), university students (N = 343), and members of the general population (N = 146). Results suggest that the HS possesses a unidimensional factor structure and a high degree of internal consistency for both male and female participants. As predicted, scores on the HS were positively correlated with machismo, authoritarianism, political conservatism, religiosity, and modern sexism. In addition, responses on the HS did not appear to be contaminated by social desirability bias. The usefulness of this measure in survey research is discussed.

Adolescent↗
PubMed1990

Addiction in adolescents.

Some symptoms seen in adolescents with the disease of chemical dependence are similar to those seen in adults. Because of their age, lack of personality development, dependent family role, immaturity, and acting out of age-related behavioral tendencies, however, symptoms specific to this population occur. These may become exacerbated and telescope--intensify and shorten--the progression of the disease. A plan to solve the problem of adolescent chemical dependence must focus on education, demonstration, cooperation, prevention, intervention, habilitation, treatment, and recovery. The phenomenon of denial in a chemically dependent adolescent yields a more complex delusional system that dictates age-specific intervention approaches. Habilitation is necessary for successful adolescent treatment and recovery because what is needed is an initial process of learning, not relearning or rehabilitation. If specific adolescent issues are addressed through comprehensive, multimodality treatment approaches, then treatment and recovery outcomes for chemically dependent adolescents and their families are substantially improved. Primary care physicians must be alert to the possibility of drug use in their young patients and aware of treatment options.

Adolescent↗
PubMed1987

Identification of ninhydrin-positive caprolactam metabolites in the rat.

Caprolactam (2-oxohexamethylenimine) is metabolized in the rat partly to 4-hydroxycaprolactam or the corresponding free acid. The 4-hydroxy metabolite rearranges spontaneously in acidic aqueous medium to an equilibrium mixture of which 6-amino-gamma-caprolactone is the major component and 6-amino-4-hydroxyhexanoic acid is a minor component. Approximately 16% of the caprolactam ingested daily by rats fed a diet containing 3% caprolactam was excreted as the 4-hydroxy metabolite and a small amount was excreted as the non-hydroxylated acid, 6-aminohexanoic acid. The metabolites were isolated by ion-exchange chromatography and identified by gas chromatography-mass spectroscopy and infra-red and nuclear magnetic resonance spectroscopy.

Amino Acids↗
PubMed1987

Psychiatric issues of adolescent chemical dependence.

Pediatricians, as well as other health care professionals, must always consider psychoactive drug use by adolescents as possible causes of general health or emotional problems, such as poor appetite, insomnia, problem behavior, academic underachievement, and loss of energy and motivation. Early diagnosis and intervention with youth can result in enormous benefits for the lives of the youth, families, and society. The physician must be alert to the adolescent who manifests such signs of abuse. This article details the recognition and management of these problems.

Adolescent↗
PubMed1983

Effects of proton release from adenine nucleotide degradation during ischemic necrosis of myocardium in vitro.

The effects of the progressive production of hydrogen ions and inorganic phosphate from adenine nucleotides on the lowering of pH in heart muscle has been investigated in dog myocardium maintained under anoxic conditions in vitro at 37 degrees C. Tissue samples were taken at 15-min intervals for up to 105 min and the following biochemical parameters determined: pH, lactate, Pi, ATP, ADP, AMP, G6P, and PC in selected instances. From these data the net proton changes during prolonged anoxia were calculated, assuming homogeneity of the tissue milieu. Net proton change was negative after 15 min and became increasingly more so throughout the remainder of the experimental period, indicating that adenine nucleotide catabolism in fact has a protective effect against fall in pH. When tissue pH falls to ca. 6.2 (45-60 min anoxia), proton production due to lactic acid is reduced by approximately 16% because of absorption of protons by phosphate and ammonia liberated from the nucleotides.

Adenine Nucleotides↗
PubMed1983

Supervised versus independent student laboratories.

The purpose of this study was to determine if classroom laboratory time could be reduced in a basic physical agents course. Fifty-seven junior physical therapy students were randomly assigned to three laboratory sections. All students received identical lectures, demonstrations, course materials, and laboratory manuals. The control group, Section 1, received supervision and assistance during laboratory practice. Students in Section 2 and Section 3 worked independent of instructor supervision but could receive assistance from the instructor in an adjacent room. Students in Section 2 were provided with feedback following periodic assessment by the instructor. Attitudinal questionnaire responses indicated that the students preferred the supervised laboratory section. The presence of the instructor during classroom laboratory practice of basic physical agents did not affect student performance. Comparison of written and practical examination results indicated no significant differences in student performance. Classroom laboratory time for faculty and students was reduced when students worked independently.

Curriculum↗
PubMed1983

The potassium/sodium ratio in the demonstration of sudden ischemic cardiac death: a critical appraisal.

The practical value of measuring the ratio of potassium ion (K+) to sodium ion (Na+) in myocardium as an indicator of early inapparent infarction in sudden cardiac death was assessed using a series of 29 human hearts from selected coroner's autopsies together with experimental material from dogs, including infarcts of 5 min to 4 h duration. Samples for electrolyte analysis were derived from a transverse slice of each heart, taken through both ventricles midway between base and apex, all slices being completely subdivided into a numbered sequence of blocks. Ratios were mapped and compared with macroscopic enzyme staining and histological stains for injured muscle. Detailed examination of coronary arteries was performed on all human cases. Measurement of the K+/Na+ ratio did not detect all human cases of proven acute coronary occlusion and did not unequivocally demonstrate experimental infarcts less than 2 h old. Moreover, all ratios fell with increasing duration of autolysis, emphasizing the need for multiple sampling so that each heart may serve as its own control. As a routine test, therefore, the method is both impracticable and unreliable and as previously used has been subject to misinterpretation.

Adolescent↗
PubMed1982

Follow-up of the graduates of one curriculum. 1956-1980.

A questionnaire was developed to obtain information from the graduates of the Marquette University Program in Physical Therapy from 1956, the year the program was established, to 1980. The response rate was 65 percent, with 433 graduates from 25 classes returning the questionnaire. The profile derived from the responses is of a graduate who remains employed in physical therapy full time or part-time, is satisfied with the undergraduate preparation received, and is a member of the American Physical Therapy Association. Compared with other studies, this survey reveals that lower percentages of physical therapy graduates are employed in hospital settings, higher percentages are earning graduate credits, and the dropout rate from the profession has decreased significantly. Other information obtained from the questionnaire is presented relating ti demographics, continuing education, and participation in professional organizations.

Adult↗
PubMed1980

Comparison of textbook and self-instructional learning methods.

Physical therapists have voiced their concern that independent study units, self-assessment tools, and refresher courses be made available. In response, we developed a series of self-instructional units in radiology, gross anatomy, and applied anatomy. To evaluate two of the units (hip and knee), we compared the self-instructional method with a traditional method using assigned textbook readings. We found no significant differences in performance levels between physical therapists and physical therapy students using self-instruction and those using textbook methods of reviewing anatomy. It took less time for the participants to do self-instruction reviews than textbook reviews, and the six-month retention rate was higher for those using self-instruction. Results of an attitude questionnaire, however, indicated approval of the self-instructional method of review as being more acceptable and enjoyable than the textbook method.

Anatomy↗