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Biomedical subjects

A MacDonald

Publications and source records attributed to A MacDonald.

At least 109 records · Page 6Linked to original sources
PubMed1994

Emigrant etherist: the medical and scientific influence of John Henry Hill Lewellin (1818-86), pioneer anaesthetist and surgeon and patron of botany in Australia.

The pioneer anaesthetists in Australia came from varying professional backgrounds. To the influence of Belisario in Sydney. Pugh in Launceston and Buchanan in Stroud, can be added the role of John Henry Hill Lewellin (1818-86). Lewellin immigrated from Scotland to become a pioneer Melbourne etherist and surgeon from 1852. Born in India, he studied surgery at Bart's Hospital in London (1842) and as a Member of the Royal College of Surgeons from that year, practised as a surgeon and dentist in Glasgow. On 19 December 1746 he was the first to use the newly discovered ether in anesthetic practice in Glasgow, and one of the first to do so in the United Kingdom. He emigrated to Melbourne in 1852, where he achieved considerable success in the management of tetanus with ether. He was an active member of the Medical Society of Victoria and a vigorous participant in its clinical discussions. As a surgeon, Lewellin pursued a significant community role in the broader Melbourne society of the day. He served as a Magistrate, became Vaccination Officer in Victoria and, as an active doctor-soldier, served with sequential promotions finally to the rank of Surgeon-Major in the Volunteer Force (Rifles) of the Colony. He became a patron of science and a supporter of the Melbourne botanist, Ferdinand von Mueller. Of all his prodigious scientific writing, von Mueller dedicated Volume 8 of his Fragmenta to his surgical colleague, as one 'who is a most skillful physician' and later as 'a most generous promoter of my investigations'. Lewellin's legacy, in his pioneering contributions as an early anaesthetist in two continents, lives on in the scientific names of two floral species which perpetuate his name.

Anesthesiology↗
PubMed1994

Adrenoceptors mediating relaxation to catecholamines in rat isolated jejunum.

1. The characteristics of adrenoceptors mediating relaxation to catecholamines in rat isolated jejunum were investigated. 2. Catecholamines and BRL 37344 produced relaxation of the KCl-contracted strips with an order of potency of isoprenaline (1.0) > BRL 37344 (0.63) > noradrenaline (0.1) > adrenaline (0.04). 3. In the presence of both prazosin (1 microM) and propranolol (1 microM) only small dextral shifts of the concentration-response curves to agonists were observed and an order of potency of BRL 37344 (2.5) > isoprenaline (1.0) > noradrenaline (0.2) > adrenaline (0.1) was obtained. 4. In the presence of prazosin (1 microM) and propranolol (1 microM), cyanopindolol (0.1-10 microM) produced a concentration-dependent rightward shift of the concentration-response curve to adrenaline with a Schild slope not significantly different from unity and a mean pA2 value of 7.01. 5. The resistance of relaxant responses to propranolol, the relatively high potency of BRL 37344 compared to catecholamines and the competitive antagonism of relaxant responses to adrenaline by cyanopindolol suggest that beta-adrenoceptors in rat small intestine are mainly atypical in nature.

Adrenergic Antagonists↗
PubMed1994

Feeding problems in young PKU children.

Behavioural feeding problems were found to be more prevalent in a group of 15 PKU children aged 1-5 years when compared to non-PKU controls. The parents of PKU children identified poorer apatites (p < 0.01), a more limited range of foods consumed (p < 0.03) and more gastrointestinal symptoms such as vomiting and constipation (p < 0.03) than control children. The children were slower to feed (p < 0.03), were more likely to dislike sweet foods and some ate separately from the rest of the family at mealtime (p < 0.03). The effects on normal feeding behaviour should be considered when advocating strict diet therapy for young PKU children.

Case-Control Studies↗
PubMed1994

Bacterial contamination of enteral feeds.

Enteral nutrition is increasingly used to provide nutritional support for children in hospital and at home. No suitable formula is available for preschool children, however, and until recently a modular feed has been prepared. The hypotheses were examined that the use of a modular feed is associated with increased bacterial contamination, and that contamination is more common in the home than in hospital. Thirty five children receiving enteral nutrition initially in hospital and subsequently at home were allocated randomly to receive either a modular feed or a newly available sterile ready to use paediatric feed. Samples of feed were taken from the nutrient container immediately after filling and at the end of feeding. The results show that feed contamination is common in hospital and at home, but significantly more so at home. The data indicate the importance of hygiene training for parents and the desirability of a ready to use formula.

Bacteria↗
PubMed1994

Cloning and expression of a new member of the melanocyte-stimulating hormone receptor family.

A new member of the G protein-coupled receptor superfamily has been isolated from an ovine genomic library with a probe generated by the application of the PCR technique, using cDNA synthesized on a mRNA template isolated from the ovine pars tuberalis. This genomic clone encodes a novel receptor of 325 amino acids with seven transmembrane domains. These domains share homology with other members of this family, but the best homology is with the recently cloned human MC-1 (50% in the transmembrane domains) and MC-3 (69% in the transmembrane domains) MSH receptors and the human ACTH (42% in the transmembrane domains) receptor. When this receptor was expressed in Cos7 cells, it was able to bind a potent analogue of alpha-MSH, [Nle4,D-Phe7]-alpha-MSH (NDP-MSH), with high affinity. This binding could be displaced by pro-opiomelanocortin-derived and related peptides, with the order of potency NDP-MSH > alpha-MSH = ACTH > beta-MSH and with no effect of gamma-MSH, delta-MSH or beta-endorphin. The expressed receptor was demonstrated to be functionally coupled to the adenylate cyclase second messenger pathway, with alpha-MSH, beta-MSH and ACTH stimulating cyclic AMP production. The amount of the mRNA for this receptor was found to be very low. The tissue distribution of this receptor could only be observed using the reverse transcription-PCR technique and the receptor was found to be present in a number of somatic tissues. These data indicate that this is a new and distinct member of the melanocortin receptor family.

Amino Acid Sequence↗
PubMed1993

Relationship between intra-abdominal and intrarectal pressure in the proctometrogram.

During normal defaecation the intrarectal pressure increases but, in the absence of a reference catheter in the pelvis, the contribution of abdominal straining and rectal contraction to this rise is unclear. Anorectal manometry was performed in ten consecutive women with no gastrointestinal symptoms in an attempt to measure intrapelvic pressure using a catheter in the bladder. During filling the mean (s.e.m.) rectal pressure increased from 2(1) to 18(4) cmH2O. The mean(s.e.m.) intravesical pressure remained unchanged at 2(1) cmH2O. Evacuation of the rectal balloon produced an increase in mean (s.e.m.) intrarectal pressure from 18(4) (end-filling pressure) to 68(15) cmH2O. The mean (s.e.m.) intravesical pressure increased from 2(1) to 51(18) cmH2O. The true intrarectal pressure (intrarectal minus intravesical) did not rise during defaecation. The rise in intrarectal pressure during rectal evacuation occurs by increased intrapelvic pressure alone.

Abdominal Muscles↗
PubMed1993

Idiopathic slow-transit constipation.

Until recently, the surgical management of idiopathic slow-transit constipation had remained unchanged since the condition was first described by Arbuthnot Lane in 1908. Although colectomy and ileorectal anastomosis is a successful treatment for the majority of patients, symptoms persist or are worse in some cases following such surgery. The previously inaccessible colon is now an area of interest in both health and disease; recent observations on aetiology, clinical investigation, neuropathology and surgical outcome lead us to question the rationale of colectomy for all patients with severe constipation.

Anastomosis, Surgical↗
PubMed1993

Pseudocyst of the maxillary sinus.

A case report is presented involving the endodontic retreatment of a maxillary second molar associated with a sinus radiopacity. Disappearance of sinus pathosis occurred within 6 days after root canal debridement. A direct relationship between apical pathosis and a pseudocyst of the maxillary sinus is suggested. Thirteen-month recall shows no recurrence.

Adult↗
PubMed1993

Effects of selective antagonism of beta-adrenoceptor sub-types on responses to isoprenaline in rat distal colon in vitro.

1. The effects of the beta 1- and beta 2-adrenoceptor selective antagonists, CGP 20712A and ICI 118551 respectively, on responses to isoprenaline-induced relaxation of rat distal colon were investigated in order to determine the contributions of these subtypes to relaxation. In addition, the properties of ICI D7114, a novel putative stimulant of atypical beta-adrenoceptors, were investigated. Our preliminary experiments with ICI D7114 showed that this compound lacked agonist activity in rat distal colon and in fact antagonized responses to isoprenaline. We therefore studied the antagonism of isoprenaline by ICI D7114 in more detail. 2. Longitudinal segments of rat distal colon were suspended in Krebs solution at 37 degrees C for isometric recording. The Krebs solution contained EDTA (23 microM) and prazosin (0.1 microM) and was gassed with 95/5% O2/CO2. After an initial equilibration period, reproducible contractions to a submaximal concentration of methacholine (1 microM) were obtained before carrying out a concentration-response curve (CRC) to isoprenaline in a non-cumulative manner. Four consecutive CRCs to isoprenaline were carried out in each tissue with a 1 h interval between each curve. Antagonists were present in increasing concentrations during the intervals between CRCs. Control tissues received no antagonists to allow estimation of the magnitude of time-dependent changes. 3. Isoprenaline produced a concentration-dependent inhibition of methacholine-induced contractions. CRCs to isoprenaline were reproducible with no significant time-dependent changes. Propranolol produced no shift of the isoprenaline CRC at 0.01 microM and a 5 fold shift at 0.1 microM. No further shift was observed with 1 microM. CGP 20712A had no effect on the CRC to isoprenaline at 0.1, 1 and 3 microM. ICI118551 produced little or no shift at 0.1 microM and a six fold shift with 1 microM. No further shift was observed with 3 microM. ICI D7114 produced a concentration-dependent parallel rightward shift of the CRC to isoprenaline. Schild analysis gave a slope close to unity and a mean pA2 value of 7.29 for ICI D7114.4. The results with propranolol and ,l- and 132-adrenoceptor antagonists confirm the mainly atypical nature of beta-adrenoceptors in rat distal colon. There may also be a small contribution from beta2-adrenoceptors in the response to isoprenaline but beta1-adrenoceptors are absent. ICI D7114 has no agonist activity and behaves as a relatively high affinity reversible competitive antagonist of atypical beta-adrenoceptors in this preparation.

Animals↗
PubMed1993

Scores on field independence and performance in snooker.

The purpose of this study was to compare the scores on the Group Embedded Figures Test, a measure of field dependence, for 25 male intermediate-level snooker players with scores of 25 intermediate-level sportsmen engaged in soccer, rugby, field hockey, and tennis and to examine the relation between scores on field dependence and performance on a snooker decision-making test. All the snooker players also took a test of decision making in snooker. The snooker players scored significantly more field independent than the sports-science majors on the Group Embedded Figures Test. A Pearson correlation of 0.78 was obtained between scores on the Group Embedded Figures Test and the decision-making test. As there may be an association between scores on field dependence and decision making in snooker, further research should examine sports like lawn bowls and pool where decisions are made in a static environment.

Attention↗
PubMed1993

Excretion of catecholamines and metabolites in response to increased dietary phosphate intake.

The urinary excretion of free dopamine, norepinephrine, and epinephrine could reflect the contribution of the neural release and filtration of these catecholamines as well as the intrarenal tubular synthesis and metabolism of dopamine. Because these catecholamines are rapidly metabolized, the excretion of the free amines represents only a fraction of the total release and synthesis by the kidney. The present study determined the effect of increasing dietary phosphate intake on the excretion of free dopamine, norepinephrine, and epinephrine and their primary stable metabolites. Seven male rats were placed in metabolic balance cages and fed 12 gm/day of normal phosphate diet (NPD) (0.7% inorganic phosphorus [Pi]) for 4 days and then fed a high phosphate diet (HPD) (1.8% Pi) for 4 days. Twenty-four-hour urine samples were collected for determination of free catecholamines, their major stable metabolites, and electrolyte excretions. The urinary excretion data for the seven rats was combined for all 4 days of each dietary regimen. Increasing phosphate intake from 0.7% to 1.8% significantly increased free dopamine excretion by 23%, from 5.6 +/- 0.2 to 6.8 +/- 0.1 micrograms/day (n = 7, p < 0.05). This increase in free dopamine excretion was associated with similar increases in urinary excretion of dopamine glucuronide, 21.6 +/- 1.3 to 27.9 +/- 1.8 micrograms/day (32%) and the dopamine metabolite DOPAC, 9.4 +/- 0.5 to 12.1 +/- 0.6 micrograms/day (30%) and total dopamine excretion from 32.9 +/- 1.7 to 41.0 +/- 1.9 micrograms/day (27%). Plasma DOPA levels were unchanged by increased dietary phosphate intake; however, plasma norepinephrine levels decreased significantly. Excretion of free or sulfated norepinephrine was not changed by increased phosphate intake. However, excretion of MHPG, a metabolite of norepinephrine and epinephrine, decreased significantly, from 33.7 +/- 2.1 to 23.9 +/- 0.8 micrograms/day, n = 7, p < 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Manual dilatation of the anus.

A group of 100 consecutive patients undergoing manual dilatation of the anus between 1980 and 1983 were reviewed retrospectively by examining the clinical presentation, diagnosis, treatment and outcome. Anal fissure was diagnosed in 46 patients, 22 had either first- or second-degree haemorrhoids, and stenosis of the anal canal was identified in seven. Manual dilatation of the anus was performed on 25 patients in the absence of a diagnosis. Dilatation failed to treat 26 anal fissures successfully. Where it was employed alone in ten cases of haemorrhoids and seven of anal stenosis, manual dilatation failed to cure seven and five patients respectively. Of the patients with no diagnosis, 23 were relieved of their symptoms following dilatation. Episodes of incontinence occurred in 27 patients, 21 of whom were female. There should be a reduced role for manual anal dilatation in the treatment of common anorectal disorders.

Adolescent↗
PubMed1992

A clinical and pharmacological study of high-dose mitozolomide given in conjunction with autologous bone marrow rescue.

In conjunction with autologous bone marrow rescue, high-dose mitozolomide was given i.v. to 16 patients with refractory malignancies at doses ranging from 100 to 400 mg/m2 over 1 h. Neutropaenia occurred consistently at 300 mg/m2, and three trivial infective episodes were recorded. Thrombocytopaenia occurred consistently at 150 mg/m2, and three patients experienced episodes of minor bleeding. The death of one subject was attributable to pulmonary thromboembolism during the bone marrow reinfusion. Transient emesis and mild alopecia were the only other toxicities. Three of six evaluable patients receiving greater than or equal to 300 mg/m2 exhibited measurable reductions in tumour dimensions, although these failed to fulfil the criteria for a partial response. Mitozolomide was undetectable in plasma at 12 h after drug administration. The plasma pharmacokinetic data fitted mono- or biexponential models in all patients. Model-independent pharmacokinetic parameters were: peak plasma drug concentration, 3.4-46 mg/l; AUC, 8-82 mg h l-1; clearance, 7.6-45 l/h; steady-state volume of distribution, 11-85 l; and plasma elimination half-life, 1.4-2.8 h. Dose-dependent pharmacokinetics were not observed, and only a small percentage of the delivered dose was eliminated unchanged in the urine. The maximally tolerated dose of mitozolomide given with autologous bone marrow rescue was greater than 400 mg/m2. At this dose myelosuppression was the only major toxicity, and the plasma drug levels and AUC values were comparable to those obtained after therapeutic doses in experimental models.

Adult↗
PubMed1992

A new oesophageal tube: assessment of collagen/vicryl composite membrane.

Collagen/vicryl composite membrane has been previously shown to be of use in an experimental model as a patch graft in the bladder and oesophagus. Attempts to use it as a circumferential tube graft have been unsuccessful due to the development of strictures at the site of anastomosis. We inserted a polytetrafluoroethylene (PTFE) stented collagen/vicryl bioprosthetic tube into rat omentum, which served as a vascular pedicle. Subsequent histology of the graft showed serial replacement of the bioprosthesis with host collagen and the development of a blood supply. In a second stage procedure, the bioprosthesis was anastomosed to the distal ileum and brought out on the skin to form a fistula. Squamous epithelium was subsequently identified growing the full length of the graft. Therefore, we have developed a vascularised bioprosthetic tube graft which will support the growth of unspecialised epithelium. This model could be of use in bridging congenital atresias or pathological strictures.

Anastomosis, Surgical↗
PubMed1992

Characterisation of ovine mast cells derived from in vitro culture of haemopoietic tissue.

Ovine mast cells generated in vitro from bone marrow (BMMC) were compared with mucosal mast cells (MMC) isolated from parasitised abomasum. Ultrastructurally, the granules of BMMC were partially developed and immature. Both cells types contained beta-hexosaminidase, arylsulfatase, histamine, dopamine and sheep mast cell proteinase (SMCP). Greater amounts of beta-hexosaminidase, but less SMCP, histamine and arylsulfatase were present in BMMC. Stimulation with calcium ionophore A23187 caused the secretion of granule constituents and generation of leukotriene C4 by BMMC in a dose-dependent manner. An additional [3H]diisopropylfluorophosphate-binding 31,500 mol. wt. serine esterase, antigenically related to SMCP (27,000 mol. wt.) was present in cultures of BMMC but was not detected in isolated MMC. Both enzymes were detected in BMMC by Day 7 of culture and were secreted concomitantly following stimulation of BMMC with ionophore.

Abomasum↗