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Biomedical subjects

C B Campbell

Publications and source records attributed to C B Campbell.

At least 19 recordsLinked to original sources
PubMed2000

A conceptual framework to guide the development of self-directed, lifelong learning in problem-based medical curricula.

CONTEXT: The information explosion and continual changes in the means of accessing information have reinforced the importance of preparing graduates to direct their own learning throughout their careers. Increasingly, medical schools are turning to problem-based curricula to develop in graduates the capacity to 'self-direct' further learning. PROBLEM: Experience shows that, to achieve this goal, there needs to be consistency in interpretation of the goal and faculty-wide agreement about the way the problem-based curriculum fosters self-direction. SUGGESTED SOLUTION: This paper describes the conceptual framework developed by the Graduate School of Medicine, The University of Queensland, to guide the achievement of self-directed, lifelong learning in a graduate entry, problem-based curriculum. IMPLICATIONS: It may be useful for others who are experiencing difficulties with implementing problem-based curricula, and for those who are contemplating changing to problem-based models.

Clinical Competence↗
PubMed1999

A lesson from the introduction of a problem-based, graduate entry course: the effects of different views of self-direction.

OBJECTIVES: Difficulties in the early years of a new curriculum are to be expected as staff and students come to terms with new structures, and with different approaches to teaching and learning. During the first year of implementation of the Graduate Medical Course at the Graduate School of Medicine, The University of Queensland, we experienced our share of 'teething troubles'. One source of difficulty was different interpretations of the concept of 'self-directed learning' as it was to be applied in the new course. This paper presents an analysis of the effects of these differences on the development of the curriculum. DESIGN: An orientation programme was designed to introduce students to staff, facilities and the PBL process. SETTING: The University of Queensland. SUBJECTS: Problem-based learning (PBL) tutors, medical students. RESULTS: The overall effect was to place in jeopardy the achievement of student self-direction and commitment to lifelong learning as a goal of the course. To counter the undesirable effects of different interpretations, we have developed a conceptual framework to promote an agreed understanding of the meaning of self-direction, and to guide review and further development of the curriculum. A further paper describes the framework. CONCLUSIONS: Consistency in interpretation of key concepts is an important factor in the success of problem-based curricula.

Adult↗
PubMed1997

Search for frequency-specific effects of millimeter-wave radiation on isolated nerve function.

Effects of a short-term exposure to millimeter waves (CW, 40-52 GHz, 0.24-3.0 mW/cm2) on the compound action potential (CAP) conduction were studied in an isolated frog sciatic nerve preparation. CAPs were evoked by either a low-rate or a high-rate electrical stimulation of the nerve (4 and 20 paired pulses/s, respectively). The low-rate stimulation did not alter the functional state of the nerve, and the amplitude, latency, and peak latency of CAPs could stay virtually stable for hours. Microwave irradiation for 10-60 min at 0.24-1.5 mW/cm2, either at various constant frequencies or with a stepwise frequency change (0.1 or 0.01 GHz/min), did not cause any detectable changes in CAP conduction or nerve refractoriness. The effect observed under irradiation at a higher field intensity of 2-3 mW/cm2 was a subtle and transient reduction of CAP latency and peak latency along with a rise of the test CAP amplitude. These changes could be evoked by any tested frequency of the radiation; they reversed shortly after cessation of exposure and were both qualitatively and quantitatively similar to the effect of conventional heating of 0.3-0.4 degree C. The high-rate electrical stimulation caused gradual and reversible decrease of the amplitude of conditioning and test CAPs and increased their latencies and peak latencies. These changes were essentially the same with and without irradiation (2.0-2.7 or 0.24-0.28 mW/cm2), except for attenuation of the decrease of the test CAP amplitude. This effect was observed at both field intensities, but was statistically significant only for certain frequencies of the radiation. Within the studied limits, this effect appeared to be dependent on the frequency rather than on the intensity of the radiation, but this observation requires additional experimental confirmation.

Absorption↗
PubMed1992

Effect of hindlimb unweighting on anaerobic metabolism in rat skeletal muscle.

Female Sprague-Dawley rats (250 g) were hindlimb suspended for 14 days, and the effects of hindlimb unweighting (HU) on skeletal muscle anaerobic metabolism were investigated and compared with nonsuspended controls (C). Soleus (SOL), plantaris (PL), and red and white portions of the gastrocnemius (RG, WG) were sampled from resting and stimulated limbs. Muscle atrophy after HU was 46% in SOL, 22% in PL, and 24% in the gastrocnemius compared with nonsuspended C animals. The muscles innervated by the sciatic nerve were stimulated to contract with an occluded circulation for 60 s with trains of supramaximal impulses (100 ms, 80 Hz) at a train rate of 1.0 Hz. Peak tension development by the gastrocnemius-PL-SOL muscle group was similar in HU and C animals (13.0 +/- 1.2, 12.2 +/- 0.8 N/g wet muscle). Occlusion of the circulation before stimulation created a predominantly anaerobic environment, and in situ glycogenolysis and glycolysis were estimated from accumulations of glycolytic intermediates. Total glycogenolysis and glycolysis were higher in the RG muscle of HU animals (74.6 +/- 3.3, 58.1 +/- 1.1) relative to C (57.1 +/- 4.6, 46.1 +/- 2.9 mumol glucosyl units/g dry muscle). Consequently, total anaerobic ATP production was also increased (HU, 251.3 +/- 1.1; C, 204.6 +/- 8.9 mumol ATP/g dry muscle). Total ATP production, glycogenolysis, and glycolysis were unaffected by HU in SOL, PL, and WG muscles. The enhanced glycolytic activity in RG after HU may be attributed to a shift in the metabolic profile from oxidative to glycolytic in the fast oxidative-glycolytic fiber population.

Adenosine Triphosphate↗
PubMed1991

Effect of aging on the buffering capacity of fast-twitch skeletal muscle.

The effects of aging on the in situ buffering capacity of fast-twitch muscle fibers was examined in the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles of specific pathogen free Fischer 344 rats. Muscles were electrically stimulated with trains of impulses lasting 100 ms at a frequency of 80 Hz. Trains were delivered at a rate of 1 Hz for 1 min with the hindlimb circulation occluded. Muscle hydrogen ion (H+) release during stimulation was estimated from the accumulation of metabolites. The free [H+] was measured using an homogenate technique. Muscle buffering capacity (Slykes) was estimated as delta mmol H+/l muscle water/delta pH unit. Muscle pH was unaffected by age both at rest and following stimulation in the TA and EDL. H+ release and buffering capacity were significantly reduced in aged TA muscle but unaffected by age in the EDL. Reduced buffering through metabolic processes accounted for only a small portion of the lower buffering capacity in aged TA. Most of the decrease in buffering capacity appeared to be due to reduced protein buffering. Therefore, aged TA muscle was less able to buffer a given H+ load when compared to adult controls. A more rapid accumulation of H+ during intense stimulation may lead to a earlier onset of fatigue in the aged muscle. It is not clear why the EDL buffering capacity was unaffected by age when the fiber mass profiles of the EDL and TA muscles appear similar (approximately 80% fast glycolytic fibers). It is possible that alterations in activity patterns with aging could have differential effects on the two muscles. Detailed activity pattern and fiber mass analyses are required in adult and aged EDL and TA muscles of Fischer 344 rats to answer this question.

Aging↗
PubMed1991

The Scala naturae revisited: evolutionary scales and anagenesis in comparative psychology.

Recent suggestions that evolutionary scales have a place in theorization about the evolution of behavior have been based on the concept of anagenesis, formerly associated with notions of biological progress. An associated concept is that of grades, often used as units of anagenetic advance. Advocates of anagenetic analysis in comparative psychology cite the writings of biologists Bernard Rensch, Julian Huxley, George Gaylord Simpson, and Stephen Jay Gould to support the usefulness of anagenesis but treat the positions of each of these theorists as if they were the same. In fact, they differ considerably in their definition of anagenesis and in its application to specific issues in evolution. The anagenetic approach is criticized as axiological and frequently anthropocentric. Although the formation of grades can be useful, a sequence of grades must not be assumed to represent historical stages in the evolution of specific structures or behaviors.

Adaptation, Physiological↗
PubMed1991

Anaerobic energy provision in aged skeletal muscle during tetanic stimulation.

The effect of age on skeletal muscle anaerobic energy metabolism was investigated in adult (11 mo) and aged (25 mo) Fischer 344 rats. Hindlimb skeletal muscles innervated by the sciatic nerve were stimulated to contract with trains of supramaximal impulses (100 ms, 80 Hz) at a train rate of 1 Hz for 60 s, with an occluded circulation. Soleus, plantaris, and red and white gastrocnemius (WG) were sampled from control and stimulated limbs. All muscle masses were reduced with age (9-13%). Peak isometric tensions, normalized per gram of wet muscle, were lower throughout the stimulation in the aged animals (28%). The potential for anaerobic ATP provision was unaltered with age in all muscles, because resting high-energy phosphates and glycogen contents were similar to adult values. Anaerobic ATP provision during stimulation was unaltered by aging in soleus, plantaris, and red gastrocnemius muscles. In the WG, containing mainly fast glycolytic (FG) fibers, ATP and phosphocreatine contents were depleted less in aged muscle. In situ glycogenolysis and glycolysis were 90.0 +/- 4.8 and 69.3 +/- 2.6 mumol/g dry muscle (dm) in adult WG and reduced to 62.3 +/- 6.9 and 51.5 +/- 5.5 mumol/g dm, respectively, in aged WG. Consequently, total anaerobic ATP provision was lower in aged WG (224.5 +/- 20.9 mumol/g dm) vs. adult (292.6 +/- 7.6 mumol/g dm) WG muscle. In summary, the decreased tetanic tension production in aged animals was associated with a decreased anaerobic energy production in FG fibers. Reduced high-energy phosphate use and a greater energy charge potential after stimulation suggested that the energy demand was reduced in aged FG fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1990

Glycogen content has no effect on skeletal muscle glycogenolysis during short-term tetanic stimulation.

The effect of skeletal muscle glycogen content on in situ glycogenolysis during short-term tetanic electrical stimulation was examined. Rats were randomly assigned to one of three conditions: normal (N, stimulated only), supercompensated (S, stimulated 21 h after a 3-h swim), and fasted (F, stimulated after a 20-h fast). Before stimulation, glycogen contents in the white (WG) and red gastrocnemius (RG) and soleus (SOL) muscles were increased by 13-25% in S and decreased by 15-27% in F compared with N. Hindlimb blood flow was occluded 60 s before stimulation to produce a predominantly anaerobic environment. Muscles were stimulated with trains of supramaximal impulses (100 ms at 80 Hz) at a rate of 1 Hz for 60 s. Muscle glycogenolysis was measured from the decrease in glycogen content and estimated from the accumulation of glycolytic intermediates in the closed system. The resting glycogen content had no effect on measured or estimated glycogenolysis in all muscles studied. Average glycogenolysis in the WG, RG, and SOL muscles was 98.4 +/- 4.3, 60.9 +/- 4.0, and 11.2 +/- 3.6 mumol glucosyl U/g dry muscle, respectively. Hindlimb tension production was similar across conditions. The results suggest that in vivo glycogen phosphorylase activity in skeletal muscle is not regulated by the content of its substrate glycogen (range 80-165 mumol/g) during short-term tetanic stimulation in an anaerobic environment.

Adenosine Triphosphate↗
PubMed1985

The effects of lead on the renin-angiotensin system.

Acute lead treatment of rabbits resulted in significant increases in both plasma renin activity and aldosterone concentration. No significant changes were observed in blood pressure, heart rate and plasma angiotensin-converting enzyme activity. The calcium channel-blocking drug verapamil attenuated the renin and aldosterone response in vivo. Lead increased renin release in a dose-dependent manner in a renal cortex slice preparation. Both verapamil and diltiazem attenuated the lead-induced renin release in vitro, but only with diltiazem did this attain statistical significance.

Aldosterone↗
PubMed1983

Conjunctivodacryocystorhinostomy with mucous membrane graft.

Eleven patients with obstructed lacrimal canaliculi underwent conjunctivodacryocystorhinostomy modified by lining the fistula with buccal mucosa at the time of surgery. Four patients had the tube removed after six months. All four have parent mucous membrane lined fistulas with follow-up ranging from ten to 13 months. One patient removed his tube on the second post-operative day. His fistula closed immediately. For comparison, the remaining six patients retain their tubes. They are free from epiphora but suffer from some of the complications of the tube itself, namely tube extrusion, tube migration, and chronic conjunctival irritation and discharge. The surgical technique is described, histopathologic material is presented, and the initial results are discussed.

Adolescent↗
PubMed1981

Comparison of three methods to estimate steatorrhoea.

Faecal fat excretion was estimated in 24 patients using three methods. Quantitative estimations of fat excretion were calculated from both a three day faecal fat collection and a twenty-four hour faecal collection corrected for excretion of a cuprous thiocyanate marker. Breath 14CO2 excretion was measured after ingestion of a liquid meal containing 2.5 microCi of 14C-triolein in an arachis oil emulsion. Peak concentrations of 14CO2 in breath were used as an estimate of the degree of fat absorption. Correlation between the two quantitative measures of faecal fat was good (r = 0.87), 17 patients having steatorrhoea of more than 7 g fat per day by both estimations. Results of the breath test were disappointing. With the standard meal containing 20 g arachis oil the lowest peak 14CO2 excretion rate seen in subjects without steatorrhoea, 3 percent of the dose per hour, was taken as the lower limit of normal. Seven subjects with steatorrhoea as shown by faecal collections excreted normal amounts of 14CO2. When the size of the fat meal was increased to 1.0 g arachis oil per kg body weight in 16 of the subjects previously studied, all patients with proven steatorrhoea excreted less than 3 percent of the dose per hour but three of the subjects without steatorrhoea gave abnormal breath excretion results. It is concluded that the collection of a 24 hour faecal specimen using a cuprous thiocyanate marker provides a more reliable estimate of faecal fat excretion than the 14C-triolein breath test.

Breath Tests↗
PubMed1981

The extent of reflux of unconjugated 14C-cholic acid from the liver in subjects with normal liver function.

An improved understanding of bile acid physiology is a prerequisite for the construction of an acceptable model for describing plasma clearance of bile acids. The aim of this study was to determine the extent of reflux unconjugated cholic acid from the liver to the plasma in subjects with normal liver function. The clearance of a bolus injection of unconjugated 14C-cholic acid was studied in four subjects using samples collected simultaneously from a peripheral and a hepatic vein. Hepatic extraction ratios calculated directly from the data were found to be essentially constant during the 20 min following injection, with average values of 0.60-0.72. This indicates that reflux did not occur significantly in the subjects investigated. These results are interpreted as favouring a model in which exchange of unconjugated 14C-cholic acid occurs between the plasma and a peripheral compartment with final removal from the plasma to the liver.

Carbon Radioisotopes↗
PubMed1981

Bile acid metabolism in mild arteriohepatic dysplasia.

Arteriohepatic dysplasia is a rare congenital syndrome in which attenuated peripheral pulmonary arteries are associated with liver impairment. The earliest indication is usually persistent cholestatic jaundice in the first few months after birth. Although this is invariably associated with pruritus, bile acid kinetic studies have not been reported in such patients. This report describes a girl with a particularly mild form of the syndrome who was never observed to be clinically or biochemically jaundiced. Bile acid studies indicated that there was a defect in bile acid excretion but not in uptake or conjugation.

Bile Acids and Salts↗
PubMed1981

The use of autogenous fascia lata to correct lid and orbital deformities.

Autogenous and homologous fascia lata have been used to correct many problems in ophthalmic surgery. This paper has described the use of autogenous fascia late to correct lid retraction secondary to thyroid ophthalmopathy, cicatricial entropion and extruding orbital implants. The surgical procedures have been briefly discussed, as well as the presentation of one clinical example of each procedure the pathologic and immunologic aspects of fascia lata grafts will be reported at a later date.

Adult↗
PubMed1980

Serum bile acids and other liver function tests in hepatocellular damage from carbon tetrachloride ingestion.

The deliberate ingestion of carbon tetrachloride by a 48-year-old woman provided an opportunity to study the sequential biochemical changes of a severe but self-limited event of hepatocellular damage. The initial phase of cellular injury characterised by high levels of serum aspartate aminotransferase, ferritin and bile acids was followed by a period of partial cholestasis. This was indicated by a marked decrease in secondary bile acids and small rises in alkaline phosphatase and 5' nucleotidase. Improving liver function and regeneration became evident during this period and was associated with abnormal levels of gamma glutamyl transpeptidase. A late rise in serum ferritin and alphafetoprotein may represent a non-specific inflammatory reaction.

Alkaline Phosphatase↗
PubMed1980

Evaluation of enzymic and radioimmunoassay methods for measuring serum bile acids.

Serum bile acids were measured in control subjects and in 23 patients with cirrhosis or cholestasis using an enzymic method which measures total non-sulphated bile acids and 2 commercially available radioimmunoassay methods which measure cholylglycine (CG) and sulpholithocholylglycine (SLCG) respectively. All 3 methods gave abnormal values in patients with cholestasis. In cirrhosis the CG method gave abnormal values more often than the enzymic method. The SLCG method was much less sensitive. Measurement of CG in 2 postprandial samples per patient detected only one patient with normal fasting but abnormal postprandial levels. Analysis of samples by gas liquid chromatography (GLC) showed that the enzymic and CG methods gave a good estimation of total non-sulphated bile acids and cholic acid respectively. Values determined by the SLCG method were much higher than the equivalent GLC values. The CG method is faster than the enzymic method and is less expensive provided sample are analysed in sufficiently large batches.

Bile Acids and Salts↗