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Biomedical subjects

S Ferguson

Publications and source records attributed to S Ferguson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Exercise cardiac function in endurance-trained males versus females.

OBJECTIVE: To examine and compare the exercise cardiac function of endurance-trained (ET) women and men. PARTICIPANTS: Six ET women aged 20 to 29 years (mean VO2max = 64 ml.kg-1.min-1) and 9 ET men aged 20 to 29 years (mean VO2max = 69 ml.kg-1.min-1) were included in the study. MAIN OUTCOME MEASURES: Cardiac output (Q), stroke volume (SV), diastolic filling rate (DFR), and left ventricular ejection rate (LVER) were compared at rest and during exercise at heart rates (HRs) of 110, 130, 150, 170 bpm, and max. Resting blood volume (BV) and hemoglobin concentration ([Hb]) were also compared. RESULTS: Compared to women, men had a higher BV and [Hb]. At HRmax, men had a higher Q (31.0 +/- 0.6 versus 24.1 +/- 0.9 l.min-1), SV, DFR, and LVER than women. When expressed relative to body mass (kg), there were no gender differences in SVmax, and women had a significantly higher a-v DO2max (approximately 19%) than men. The SV of the men and women did not plateau at a submaximal level but continued to increase progressively to HRmax. During maximal exercise, the DFR was significantly faster than the LVER in the men and the women. CONCLUSIONS: When ET men and women are matched for body mass, the gender difference in SVmax is reduced so that it is no longer statistically significant. However, there are still significant gender differences in Q, DFR, LVER, BV, and [Hb] that contribute to a higher VO2max (ml.kg-1.min-1) in ET men compared to women. To augment SVmax, women and men rely to a greater extent on diastolic filling than on left ventricular emptying.

Adult↗
PubMed1998

The expression of interleukin-6 in the pregnant rat corpus luteum and its regulation by progesterone and glucocorticoid.

Interleukin (IL)-6, a multifunctional cytokine originally described as a T cell-derived factor, is also produced by different cell types, and it influences a wide variety of physiological and pathophysiological processes. Recent studies further suggest that IL-6 has a role in down-regulating hormone production by endocrine organs and can negatively affect the steroidogenic capacity of both ovaries and testes. Thus, the aims of this investigation were to examine whether IL-6 plays a role in luteolysis and, more specifically, to determine whether luteal cells express the IL-6 gene, whether this expression is developmentally and hormonally regulated in pregnancy, and whether the corpus luteum could be a target for IL-6 action. Using semiquantitative RT-PCR, messenger RNA (mRNA) encoding both components of the IL-6 receptor [the ligand-binding subunit (IL-6 R) and the IL-6 R-associated signal transducer (gp130)] were found to be highly expressed in corpora lutea throughout pregnancy. In contrast, IL-6 mRNA expression was barely detectable from day 4 through the end of pregnancy, whereas a sharp and abrupt expression of IL-6 mRNA occurred immediately after parturition. Although the corpus luteum does not express IL-6 mRNA during most of pregnancy, it could be induced to express this gene with an in vivo injection of the bacterial endotoxin, lipopolysaccharide. In addition, when corpora lutea from day-15 pregnant rats were isolated and maintained in culture, IL-6 mRNA that was undetectable at 0 h increased in a time-related manner and reached significant levels after 4 h of incubation, followed by a similar increase in IL-6 protein secreted in the culture media. Isolation of the small and large luteal cells by elutriation indicated that both cell populations can secrete IL-6 in culture. The apparent ability of luteal cells to spontaneously express IL-6 in vitro, together with the lack of IL-6 expression during most of pregnancy, led us to examine whether the IL-6 gene is silenced throughout pregnancy by luteotropic hormones. Corpora lutea from day-15 pregnant rats were cultured in the presence of different doses of progesterone; the synthetic glucocorticoid, dexamethasone; 17beta-estradiol; and PRL. Progesterone and dexamethasone markedly inhibited IL-6 mRNA expression, whereas 17beta-estradiol had a minimal inhibitory effect, and PRL did not affect IL-6 mRNA expression. In summary, results of this investigation have revealed that the rat corpus luteum expresses the IL-6 receptor system and that luteal cells are able to secrete IL-6. However, IL-6 gene expression is silenced during most of pregnancy, probably by the high levels of progesterone locally produced in the corpus luteum. The salient finding that progesterone and glucocorticoid strongly inhibit the expression of IL-6 in the corpus luteum suggests that one important luteotropic role of progesterone and glucocorticoids could be to prevent the expression of IL-6, which might have a deleterious effect on luteal function.

Animals↗
PubMed1997

A prospective study of the effect of fundoplication on primary and secondary peristalsis in the esophagus.

We studied 13 patients before and after Nissen fundoplication and compared them with 11 healthy volunteers and 12 other patients with dysphagia after fundoplication. Esophageal manometry was performed to assess primary and secondary peristalsis induced by esophageal distention with air and water boluses. In patients with reflux disease, secondary peristalsis was initiated at a median rate of 60% of distending episodes, propagation of the secondary peristaltic wave occurred in 40% and lower oesophageal sphincter relaxation occurred with 70% of secondary peristaltic waves. Fundoplication did not alter the initiation or propagation rate of secondary peristalsis but it decreased the median lower esophageal sphincter relaxation rate to 45% (P < 0.03). Fundoplication was not associated with a change in the amplitude of primary peristaltic waves even in patients complaining of dysphagia. In post-fundoplication patients, successful secondary peristaltic waves had significantly lower (P < 0.005) proximal and distal amplitude than primary peristaltic waves. We conclude that there is no improvement in primary or secondary peristalsis after fundoplication and dysphagia after fundoplication is not due to altered peristalsis.

Adult↗
PubMed1997

Lasers in pediatric surgery.

Lasers, once a laboratory curiosity, have quickly become a viable and valuable surgical instrument. They have been found useful in almost every surgical specialty. This chapter will discuss how laser light is produced and its effects on tissue. The various laser types are discussed, and their clinical implications are reviewed. Most important, we also review the hazards associated with these systems and the ramifications of their use. The perioperative nurse must be familiar with the various protocols used in treating patients with lasers, applications of the lasers, and specific safety requirements.

Child↗
PubMed1996

Enhancement of the mechanical properties of polylactides by solid-state extrusion. II. Poly(L-lactide), poly(L/D-lactide), and poly(L/DL-lactide.

Polylactides with various degrees of chain regularity-crystalline poly(L-lactide); amorphous poly(L/D-lactide), and amorphous poly(L/DL-lactide)-were processed into high-strength, high-modulus resorable rods using solid-state extrusion through a conical die. The rods with a highly fibrillated structure had flexural strengths at a yield of up to 215 MPa and flexural modulus of up to 13.7 GPa. The initially amorphous poly(L/DL-lactide) developed approximately 25% of crystallinity after solid-state extrusion. Poly(L/D-lactide) remained amorphous independently of the treatment procedure applied. The shear strengths, flexural strengths, and flexural moduli of the solid-state extruded rods increased with increasing draw ratio. For the semicrystalline materials, solid-state extrusion enhanced the crystallinity. The achievable draw ratios during solid-state extrusion, and in consequence the final mechanical properties, were lower for poly(L/D-lactide) and poly(L/DL-lactide) than for poly(L-lactide).

Calorimetry, Differential Scanning↗
PubMed1996

The rectus sheath block in paediatric anaesthesia: new indications for an old technique?

The rectus sheath block has been used with success for postoperative analgesia in adults. This paper reviews the anatomy of the rectus sheath, and presents our initial experience of using the block to provide intra- and postoperative analgesia in children having repair of umbilical and paraumbilical hernia. The rectus sheath block appears to be a useful technique in children, particularly for paediatric day-cases surgery.

Abdominal Muscles↗
PubMed1996

Moebius syndrome: a review of the anaesthetic implications.

Moebius syndrome is a rare congenital anomaly characterized by multiple cranial nerve palsies, orofacial malformations and limb anomalies. This study retrospectively reviewed the anaesthetic records of 19 children with Moebius syndrome who had anaesthesia at the Royal Alexandra Hospital for Children over a 15 year period and analysed the complications which occurred. Affected children most commonly present for anaesthesia for correction of strabismus, or for orthopaedic procedures to improve limb function. Despite the abnormal facies and drooling of saliva, these children are almost always of normal intelligence. Problems can arise during anaesthesia, with a high incidence of difficult or failed intubation. The use of a facemask and spontaneous breathing technique, where appropriate, seems to present no problems and maintaining an airway in this way appears to be safe. However, the potential for problems with aspiration of oral secretions should be remembered and the use of antisialogogue premedication is recommended. Affected children have a high incidence of other anomalies, including congenital cardiac disease, spinal anomalies, corneal abrasions and peripheral neuropathies and a careful preoperative assessment is essential.

Adolescent↗
PubMed1996

Porosity reduction in bone cement at the cement-stem interface.

The fatigue failure of bone cement, leading to loosening of the stem, is likely to be one mode of failure of cemented total hip replacements. There is strong evidence that cracks in the cement are initiated at voids which act as stress risers, particularly at the cement-stem interface. The preferential formation of voids at this site results from shrinkage during polymerisation and the initiation of this process at the warmer cement-bone interface, which causes bone cement to shrink away from the stem. A reversal of the direction of polymerisation would shrink the cement on to the stem and reduce or eliminate the formation of voids at this interface. We have investigated this by implanting hip prostheses, at room temperature or preheated to 44 degrees C, into human cadaver femora kept at 37 degrees C. Two types of bone cement were either hand-mixed or vacuum-mixed before implantation. We found that the area of porosity at the cement-stem interface was dramatically reduced by preheating the stem and that the preheating temperature of 44 degrees C determined by computer analysis of transient heat transfer was the minimum required to induce initial polymerisation at the cement-stem interface. Temperature measurements taken during these experiments in vitro showed that preheating of the stem caused a negligible increase in the temperature of the bone. Reduction of porosity at the cement-stem interface could significantly increase the life of hip arthroplasties.

Bone Cements↗
PubMed1995

Verification of surface dose on patients undergoing low to medium energy X-ray therapy.

About 5% of patients still undergo cancer treatment with superficial (peak energy < or = 120 kVp) X-ray radiation. Dosimetry of these beams is difficult since the maximum dose is delivered at the surface and backscatter contributes significantly to the dose. This is particularly a problem in the difficult geometries encountered in superficial treatments in the head and neck area. It has recently been shown that surface dose measurements in mega-voltage X-ray beams can be performed using TLD (Thermoluminescence Dosimetry) extrapolation. In this technique, LiF TLD chips with a surface area of 3.15 x 3.15 cm2 and three different thicknesses (0.230, 0.099, and 0.038 g/cm2) are used together in the same radiation beam which allows the extrapolation of the measured dose back to the true surface. The energy response curve of the three thicknesses of LiF chips was measured for the energy range of 60kVp, HVL 1.6 mm Al to 300kVp, 4 mm Cu. LiF was found to over respond by a factor of 1.7 at 60kVp HVL 1.6 mm Al with respect to a 6MV photon beam. A feasibility study was carried out on three patients undergoing treatment at 120kVp. Because of the small field sizes involved it was necessary to limit irradiation to one or two chips at a time. The dose fall off in the first millimetre of tissue could be clearly detected. TLD extrapolation, in low to medium energy beams, was found to be useful to assess the dose of patients undergoing treatment for superficial lesions.

Feasibility Studies↗
PubMed1995

Evaluating clinical educators: an employer's perspective.

An Australian school of nursing's attempt to introduce an evaluation process required by management for clinical educators involved in undergraduate preregistration education is discussed. Reliance on student feedback and clinical agencies' perceptions of the quality of teaching were seen as inadequate mechanisms for evaluation. The evaluation process adopted incorporated observation of the educators together with self-reflection on their performance. We conclude that post-briefings were poorly used and generally not reflective. Educators relied heavily on their clinical skills and used a limited range of teaching strategies. Whilst evaluation of clinical educators was time consuming and therefore costly, it is argued that it is essential to the integrity of the course. The evaluation process has provided direction for support and development of clinical educators within the context of the curriculum.

Education, Nursing, Diploma Programs↗
PubMed1995

Self-regulation of smoking intensity. Smoke yields of the low-nicotine, low-'tar' cigarettes.

It has been assumed for some time that the 'tar' and nicotine data for individual cigarette brands, as reported by the Federal Trade Commission (FTC), do not adequately reflect the levels of exposure to toxic and carcinogenic agents in the smoke. The trend of decreasing 'tar' and nicotine yields of the sales-weighted average US cigarettes was not followed by a proportionate decline of lung cancer incidence and mortality rates. Utilizing a 'tobacco smoke inhalation testing system', we determined smoking profiles for four men and four women who smoked low-nicotine cigarettes ( < or = 0.8 mg/cigarette according to FTC), and for two men and two women who smoked cigarettes with medium-nicotine (0.9-1.2 mg) yields. The recorded smoking profiles were programmed into a smoking machine to establish mainstream smoke yields for 'tar', nicotine, benzo[a]pyrene and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. The analytical data obtained for each smoker's cigarette were compared with corresponding measurements in the smoke from the same cigarette brand that was generated by machine-smoking under the standardized FTC conditions (1 puff of 2 s duration and 35 ml volume drawn once/min). Significant increases in terms of total volume of smoke inhaled and exposures to 'tar', nicotine, and lung carcinogens were measured (2- to 4-fold) and, because of smokers' compensation for low nicotine delivery, much greater overall exposure resulted from smoking low-nicotine cigarettes. Although these measurements were obtained for a limited number of smokers, they strongly indicate that both low- and medium-nicotine cigarettes are being smoked much more intensely than would be implied from the FTC-data. Therefore, there is an urgent need to accurately quantify the exposure of consumers of the various types of cigarettes to toxic and carcinogenic agents.

Adult↗
PubMed1995

A perspex flattening filter for a 300k Vp orthovoltage X-ray beam.

For economic reasons modern equipment which produces low to medium energy X-rays covers the whole range of beam qualities from traditional superficial to orthovoltage radiation qualities. A recent trend shows an increasing number of installations of orthovoltage units in the cancer therapy community in the last five years. The use of a single anode for accelerating voltages between 60 and 300 kVp leads to compromises with regards to beam flatness and symmetry in the anode/cathode direction of the Siemens Stabilipan II radiation beam. A perspex flattening filter was designed to improve these beam parameters of the 300 kVp radiation beam (HVT 4mm Cu) at 50 cm and 60 cm FSD using a diaphragm-mounted field defining device. The filter design correlates with focal spot characteristics of the beam. The use of the filter improves flatness and symmetry for all measured field sizes from 6 x 6 cm2 to 18 x 18 cm2 by up to 8% (flatness) and 7% (symmetry) respectively. No significant difference in the depth dose characteristic of the 300 kVp beam was found with and without the filter. The only modification in the planning procedures required is the use of an attenuation factor of 0.89 for the filter. The use of the filter improves the dose distribution in treatment of patients undergoing orthovoltage radiotherapy--in particular treatments with large field sizes such as for metastases in the spinal column.

Radiographic Image Enhancement↗
PubMed1994

Automating the generation and collection of rate-frequency functions in a curve-shift brain stimulation reward paradigm.

The electrical self-stimulation paradigm has proven to be very useful in research aimed at delineating the neural substrates involved in reward-related learning. Of the procedures currently employed the curve-shift method is among the more useful since it distinguishes between treatment effects on reward and performance. This method involves generating and plotting rate-frequency functions and quantifying the effects of experimental manipulations on reward by measuring the degree of lateral shift in these functions. We have designed a computerized system that automatically generates and collects descending rate-frequency functions from self-stimulating rats. The 3 main units of this system consisted of a 6809 micro-controller, a programmable timer logic board and a constant current source. The micro-controller and programmable timer operated on custom written software that monitored lever pressing in the operant chambers and controlled stimulation parameters to generate and record rate-frequency functions. The present report describes this system and presents some typical data collected from rats self-stimulating on ventral tegmental electrodes before and after the administration of intra-accumbens vehicle (0.5 microliter distilled H2O), (+)-amphetamine (20.0 micrograms/0.5 microliter), quinpirole (10.0 micrograms/0.5 microliter) and systemic quinpirole (1.0 mg/kg), all dopamine agonists. Stimulation consisting of 300-ms trains of cathodal rectangular pulses (0.1 ms) was available in 50-s trials. The number of pulses per train was decreased logarithmically from a value that sustained maximal responding to one that would not sustain responding. Self-stimulation thresholds were obtained by fitting the Gompertz growth model to the data and calculating the point of maximal acceleration of the sigmoidal curve. It was found that the present system generated and collected rate-frequency functions similar to those that have been obtained manually in previous experiments. The data showed that the system was sensitive to both central and systemic pharmacological manipulations by producing lateral and vertical shifts of the rate-frequency functions, indications of reward and motor effects, respectively. It was concluded that the present design was useful in conducting entire self-stimulation sessions that required minimal monitoring by the experimenter.

Amplifiers, Electronic↗