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Biomedical subjects

A Mackay

Publications and source records attributed to A Mackay.

At least 37 records · Page 2Linked to original sources
PubMed1999

Is the 'tunnel of death' a suitable modality for investigating the severely traumatized child?

BACKGROUND: The child who has suffered severe physical trauma and is physiologically unstable can often present a diagnostic dilemma to the clinician in the emergency room. METHODS: In an attempt to clarify the situation there is often a decision made to perform computed tomographic scanning in such children. RESULTS: This is an extremely dangerous investigation in this situation given that the child has to have a GA as well as being unstable from the injuries. CONCLUSION: Ultrasound is easier, less expensive, can be performed in the emergency room and can be performed by relatively inexperienced operators with good diagnostic accuracy.

Child↗
PubMed1999

Ultrasonographic diagnosis of a laryngeal cyst in a cat.

The ultrasonographic appearance, surgical treatment and pathological classification of a laryngeal cyst in a four-year-old cat is described. This is the first description of such a cyst diagnosed with the help of ultrasonography. The cat presented with dyspnoea and respiratory noise. An intraluminal fluid-filled cyst attached to the vocal cord was identified by ultrasonography and drained under ultrasound guidance. The cyst recurred three weeks later and ultrasonography showed an increase in size compared to the previous examination. There was no evidence of recurrence of the lesion 18 months after surgical removal.

Animals↗
PubMed1997

Interleukin-18 (interferon-gamma-inducing factor) is produced by osteoblasts and acts via granulocyte/macrophage colony-stimulating factor and not via interferon-gamma to inhibit osteoclast formation.

We have established by differential display polymerase chain reaction of mRNA that interleukin (IL)-18 is expressed by osteoblastic stromal cells. The stromal cell populations used for comparison differed in their ability to promote osteoclast-like multinucleated cell (OCL) formation. mRNA for IL-18 was found to be expressed in greater abundance in lines that were unable to support OCL formation than in supportive cells. Recombinant IL-18 was found to inhibit OCL formation in cocultures of osteoblasts and hemopoietic cells of spleen or bone marrow origin. IL-18 inhibited OCL formation in the presence of osteoclastogenic agents including 1alpha,25-dihydroxyvitamin D3, prostaglandin E2, parathyroid hormone, IL-1, and IL-11. The inhibitory effect of IL-18 was limited to the early phase of the cocultures, which coincides with proliferation of hemopoietic precursors. IL-18 has been reported to induce interferon-gamma (IFN-gamma) and granulocyte/macrophage colony-stimulating factor (GM-CSF) production in T cells, and both agents also inhibit OCL formation in vitro. Neutralizing antibodies to GM-CSF were able to rescue IL-18 inhibition of OCL formation, whereas neutralizing antibodies to IFN-gamma did not. In cocultures with osteoblasts and spleen cells from IFN-gamma receptor type II-deficient mice, IL-18 was found to inhibit OCL formation, indicating that IL-18 acted independently of IFN-gamma production: IFN-gamma had no effect in these cocultures. Additionally, in cocultures in which spleen cells were derived from receptor-deficient mice and osteoblasts were from wild-type mice and vice versa, we identified that the target cells for IFN-gamma inhibition of OCL formation were the hemopoietic cells. The work provides evidence that IL-18 is expressed by osteoblasts and inhibits OCL formation via GM-CSF production and not via IFN-gamma production.

Animals↗
PubMed1997

Distribution and activity of male harbour seals during the mating season

Little is known about male reproductive strategies in aquatically mating pinnipeds. To study the mating patterns of harbour seals, Phoca vitulinaVHF telemetry was used to relate the distribution and behaviour of adult males to the distribution of females during the summer pupping and mating season. Prior to July males occupied large and variable ranges. At the beginning of July, males decreased their mean range size, but continued to spend much of their time in the water where they made characteristic short dives. Acoustic recordings in the presence of several radiotagged males suggested that these short dives were associated with underwater vocal displays. Throughout July, males varied in the geographical areas which they used to perform these displays. Some individuals were found in the water around haul-out sites; others were located on foraging grounds, up to 50 km from pupping sites, and some were consistently located displaying on transit routes between these two areas. This study supports previous suggestions that vocalizations and diving displays may be associated with male mating behaviour, but suggests that males may display over a much wider geographical area than was previously recognized. This system of dispersed but small display territories is suggestive of lekking. However, further research on the distribution of the clumping of displaying males is required to confirm this.

Journal Article↗
PubMed1995

Sequential analysis of gene expression after an osteogenic stimulus: c-fos expression is induced in osteocytes.

We have recently developed an experimental model whereby mechanical stimulation induces osteogenesis in the caudal vertebrae of rats. We used this model to assess expression of genes induced by mechanical loading. Bulk preparations of mRNA extracted after loading did not show > 2-fold increases in expression of mRNA for matrix proteins or growth factors in Northern blotting analysis. c-jun was undectable. However, c-fos showed a 4-fold increase in expression within 60 mins of loading, before returning to control levels by 4 hrs. This increase was associated with intense signals in in situ hybridization, not seen in any nonloaded vertebrae, for c-fos over cortical osteocytes: thus osteocytes respond to mechanical loading with c-fos expression so strongly as to be visible even in the bulk RNA preparations. The results represent persuasive evidence for a role for osteocytes, and for c-fos, in the osteogenic response of bone to mechanical stimulation.

Animals↗
PubMed1995

Diagnostic criteria for neoplastic myoepithelial cells in pleomorphic adenomas and myoepitheliomas. Immunocytochemical detection of muscle-specific actin, cytokeratin 14, vimentin, and glial fibrillary acidic protein.

OBJECTIVE: Markers for normal salivary gland myoepithelium were used to determine the extent of their expression in the neoplastic myoepithelial (nonluminal) cells of pleomorphic adenomas and then in the tumor cells in myoepitheliomas and to gather information necessary to establish diagnostic criteria, especially muscle actin expression, for myoepitheliomas. STUDY DESIGN: Methanol/acetic acid-fixed and paraffin-embedded tissue was used to immunohistochemically study expression of intermediate and smooth-muscle actin filaments in nonluminal cells in 14 pleomorphic adenomas and to compare this to their expression in five myoepitheliomas. RESULTS: In routine histologic sections, the morphologic variants of nonluminal tumor cells--spindle, stellate, polygonal, angular, and plasmacytoid--in pleomorphic adenoma mirror the spectrum of tumor cells in myoepitheliomas. Immunocytochemical similarities are also apparent. Two specific markers for myoepithelial cells in the normal salivary gland, muscle-specific actin and cytokeratin 14, were both variably, independently, and never uniformly expressed in nonluminal cells of pleomorphic adenoma and tumor cells in myoepitheliomas regardless of their morphology. Cytokeratin 14 in addition labels basal cells of excretory ducts. Both muscle-specific actin and cytokeratin 14 preferentially localized to single layers of periductal cells in pleomorphic adenomas, angular, polygonal, and plasmacytoid cells preferentially expressed cytokeratin 14. Similar patterns were noted in the three myoepitheliomas with reasonable expression of the two markers. Only isolated single cells or small groups of plasmacytoid cells in four pleomorphic adenomas with a significant component of these cells and the two plasmacytoid myoepitheliomas immunostained for muscle-specific actin and cytokeratin 14. In both tumor types, vimentin was nearly uniformly expressed in nonluminal tumor cells of all morphologic types, including plasmacytoid cells. CONCLUSIONS: The range and transition of morphology of nonluminal cells in pleomorphic adenomas is reflected in myoepitheliomas. Incomplete or absent expression of the myoepithelial/basal cell markers, muscle-specific actin, and cytokeratin 14, and the general expression of vimentin is common to both tumors. Because these findings apply to the majority of plasmacytoid cells in pleomorphic adenomas, tumor cells with a similar morphology and immunoprofile are to be expected in myoepitheliomas; the term plasmacytoid myoepitheliomas is thus appropriate regardless of the presence or absence of muscle-specific actin.

Actins↗
PubMed1994

The pathobiology of salivary gland. III. PCNA-localization of cycling cells induced in rat submandibular gland by low-dose x-radiation.

Application of ionizing radiation to adult rat major salivary glands tested tenets of the bicellular reserve cell hypothesis for the induction of salivary gland tumors, namely, that stem cells preferentially located to luminal cells of the intercalated duct and basal cells of the excretory duct in normal salivary glands. The effect of a single, low dose (3000 cGy) of x-radiation administered to the parotid and submandibular glands was followed with the use of immunocytochemistry and an antibody to the cell cycle-related protein proliferating cell nuclear antigen to detect the kinetics and localization of cycling cells up to 15 days postirradiation. Maximal responses occurred in acinar cells (12.6-fold increase) of submandibular glands on day 7 postirradiation. Similar but less dramatic concurrent increases in proliferating cells were evident in intercalated (3.4-fold) and striated (2.2-fold) duct cells, but little response was seen in basal or luminal cells of submandibular gland excretory ducts. A limited but maximal proliferative response again occurred on day 7 in the parotid gland. Neither in the steady state nor irradiated submandibular gland was there evidence of specific stem ("reserve") cells associated with the intercalated or excretory ducts. It appears unnecessary to invoke stem cells in a model of cellular proliferation in salivary glands. Therefore current concepts of salivary gland tumorigenesis require modification because all cell types, including acinar cells, are at risk in the carcinogenic process.

Animals↗
PubMed1993

Evolution of structural proteins of feline immunodeficiency virus: molecular epidemiology and evidence of selection for change.

The DNA sequences of structural genes of several U.K. and European isolates of feline immunodeficiency virus (FIV) were determined and compared with those of other worldwide isolates. Phylogenetic analyses of both gag and env sequences demonstrate that a Japanese isolate represents a distinct sequence subgroup, with corrected amino acid distances to the other isolates averaging 23% in env and 8% in gag. Analysis also reveals that an evolutionary radiation of FIV occurred with many isolates diverging at approximately the same time, and that although isolates from similar geographical sources often cluster together, there is evidence of more than one origin for FIV in the U.K., The Netherlands and Italy. Estimation of the numbers of silent and replacement nucleotide substitutions indicates the presence of constraints against amino acid changes in gag and conserved regions of env but suggests that positive selection for protein sequence changes operates in variable regions of env. The possible immunological forces underlying these changes are discussed.

Amino Acid Sequence↗
PubMed1985

Preoperative prediction of prosthesis size using cross sectional echocardiography in patients requiring aortic valve replacement.

In 43 patients who underwent aortic valve replacement for aortic stenosis with or without regurgitation the accuracy of preoperative left ventricular angiography, parasternal long axis cross sectional echocardiography of left ventricular outflow tract and proximal ascending aorta, and M mode echocardiography of aortic root in predicting aortic root size and thereby prosthesis size was compared. Cross sectional echocardiographic measurements and angiographic measurements of aortic root correlated well with prosthesis size, with over two thirds of the indirect measurements being within 2 mm of prosthesis diameter. M mode echocardiography did not yield useful predictive information. Non-invasive preoperative evaluation of patients likely to require aortic valve replacement may be usefully extended to include aortic root dimensions measured by cross sectional echocardiography.

Adult↗
PubMed1983

Inverse relation of exchangeable sodium and blood pressure in hypertensive patients with renal artery stenosis.

Measurements of exchangeable sodium, arterial pressure and plasma concentrations of active renin, angiotensin II, aldosterone, sodium and potassium were made in 35 hypertensive patients with renal artery stenosis, 30 having unilateral renal arterial lesions. Plasma urea was below 7 mmol/l in 24 of the patients with unilateral lesions. In these and in the whole group of 35 patients there were significant inverse correlations between exchangeable sodium and diastolic blood pressure and between plasma sodium concentration and diastolic pressure. Six patients had hyponatraemia with a plasma sodium concentration less than 135 mmol/l. All were sodium-deplete with secondary hyperaldosteronism, three also having malignant-phase hypertension. Twelve of the patients with unilateral renal artery stenosis underwent bilateral ureteric catheterization. Sodium excretion was greater from the contralateral kidney than from the affected kidney and the rate of sodium excretion from the former, but not from the latter, was significantly related to arterial pressure. The relation of diastolic blood pressure and exchangeable sodium is the opposite of the positive correlation found in essential hypertension and Conn's syndrome. In renal artery stenosis the inverse correlation could result from a natriuretic effect of increased arterial pressure occurring mainly in the contralateral kidney.

Adult↗
PubMed1983

Hypospadias repair under the age of 1 year.

Hypospadias repair is a complex and challenging problem. Psychological, physiological, technical, and logistic problems all play a part. A retrospective survey of 108 infants, aged between 6 and 12 months, operated upon at the two Brisbane children's hospitals between 1977 and 1982, by a one stage total repair procedure, produced results comparable technically, functionally and aesthetically with other reported series. There were minimal psychological effects on the infant, and coincidentally reduced financial cost of the repair and hospitalization to the parents and society.

Age Factors↗
PubMed1983

The decision on surgery in renal artery stenosis.

Eighty-six hypertensive patients with arteriographic evidence of renal artery stenosis presented between 1968 and 1979. Thirty-nine subsequently underwent surgery and were followed thereafter for at least one year. In 54 per cent blood pressure was reduced to within one standard deviation of the mean for a normal individual of the same sex and age. A further thirty-one per cent of patients were 'improved', but needed hypotensive drugs to maintain blood pressure within this range. In the remaining 15 per cent of patients the operation did not reduce blood pressure. The purpose of the study was to assess our ability to predict this varies surgical outcome using clinical observations and special tests. The latter included measurement of plasma renin concentration in both peripheral vein and renal vein plasma, catheterization of both ureters and studies of the response of blood pressure to brief infusion of saralasin. No single observation or test, no combination of observations or tests and no discriminant function clearly separated patients in whom surgery would succeed from those in whom it would fail. Renal vein renin ratio was the best test; all patients with a ratio greater than 2.0 underwent successful surgery, but so too did some patients with a lower ratio. We also analysed the factors which had influenced our decision to undertake special investigations in 65 of the 86 patients and, having done these investigations, to recommend surgery in 39. No single factor seemed to have had overriding importance in making these decisions.

Adolescent↗