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Biomedical subjects

M MacKenzie

Publications and source records attributed to M MacKenzie.

At least 19 recordsLinked to original sources
PubMed2003

Structure and composition of silicon-stabilized tricalcium phosphate.

Silicon stabilized tricalcium phosphate [Si-TCP] is formed within the calcium hydroxyapatite (HA)-tricalcium phosphate (TCP) system when a stoichiometric precipitate of hydroxyapatite is fired at 1,000 degrees in the presence of SiO(2). This paper proposes a composition range and crystallographic structure for Si-TCP. Reitveld XRD powder diffraction, transmission electron microscopy, infrared and proton nuclear magnetic resonance measurements show that crystalline Si-TCP is associated with the displacement of OH from an initial hydroxyapatite structure. The resulting calcium phosphate is modified by the incorporation of silicon into its structure with excess silica contributing to an amorphous component. Si-TCP has a monoclinic structure with a space group P2(1)/a akin to alpha-TCP with estimated lattice constants of a=12.863+/-0.004 A, b=9.119 +/-0.003 A, c=15.232+/-0.004 A, beta=126.3+/-0.1 degrees. It is proposed that Si(4+) substitutes for P(5+)in the TCP lattice with the average chemical composition of Si-TCP set primarily by the mechanisms available for charge compensation. While the formation of OH vacancies in HA initiates the transformation to Si-TCP, two mechanisms of charge compensation in the Si-TCP structure are plausible. If O(2-) vacancies provide charge compensation, the composition of Si-TCP is Ca(3)(P(0.9)Si(0.1)O(3.95))(2) derived for the addition of 0.33 mol SiO(2):mol HA. If excess Ca(2+) compensates, the composition is Ca(3.08)(P(0.92)Si(0.08)O(4))(2) derived for the addition of 0.25 mol SiO(2):mol HA. The reaction occurs most effectively when SiO(2) is added as a colloidal suspension rather than by the in-situ thermal decomposition of a silicon metallorganic compound. The material is a bioceramic of major biological interest because of its osteoconductivity and unique influence on skeletal tissue repair and remodeling.

Absorption↗
PubMed1997

A novel limb-support system to reduce postural load in theaters.

Theatre nurses regularly stress their body when they support patients' limbs for prepping. This makes nurses vulnerable to back or upper limb pain. The Victoria Infirmary in Glasgow and the West of Scotland Department of Clinical Physics and Bio-Engineering, have developed an electrically braked limb support system to take the weight from the nurse.

Arm↗
PubMed1995

Recent isolates of Newcastle disease virus in Australia.

Forty-five recently isolated strains of Newcastle disease virus and the V4 vaccine strain of Newcastle disease virus were used to infect experimental chickens. Neither V4 nor any of the new strains produced detectable clinical disease. All the viruses produced an antibody response and spread by contact. Some of the newly isolated viruses produced a more rapid serological response than V4 virus did. Dual or multiple infections with one of the new strains of Newcastle disease virus, infectious bronchitis virus and Escherichia coli did not enhance the pathogenicity of any of the agents.

Animals↗
PubMed1995

Utilization of a clinical pathway in the care of the ambulatory cataract surgical patient.

Rapid changes are occurring in healthcare today. Both customers and consumers of healthcare are demanding a change in the way business is being conducted. According to Smith (1993), healthcare organizations are being prompted to explore and implement systems which will enhance quality care as well as promote cost effective resource utilization. A notable change in recent years is the shift of ophthalmic surgical patients from inpatient to an ambulatory setting. This paper will focus on the implementation of a case management model for ophthalmic patients utilizing clinical pathways on an ambulatory unit. Emphasis will be on the provision of quality care resulting in positive patient outcomes.

Ambulatory Surgical Procedures↗
PubMed1993

Expression of HOX C homeobox genes in lymphoid cells.

The class I homeobox genes located in four clusters in mammalian genomes (HOX A, HOX B, HOX C, and HOX D) appear to play a major role in fetal development. Previous surveys of homeobox gene expression in human leukemic cell lines have shown that certain HOX A genes are expressed only in myeloid cell lines, whereas HOX B gene expression is largely restricted to cells with erythroid potential. We now report a survey of the expression patterns of 9 homeobox genes from the HOX C locus in a panel of 24 human and 7 murine leukemic cell lines. The most striking observation is the lymphoid-specific pattern of expression of HOX C4, located at the 3' end of the locus. A major transcript of 1.9 kilobases is observed in both T-cell and B-cell lines. HOX C4 expression is also detected in normal human marrow and peripheral blood lymphocytes, but not in mature granulocytes or monocytes. HOX C8 is also expressed in human lymphoid cells but is expressed in other blood cell types as well. However, the HOX C8 transcript pattern is lineage specific. These data, in conjunction with earlier findings, suggest that homeobox gene expression influences lineage determination during hematopoiesis.

Animals↗
PubMed1992

Abnormalities in immune regulation precede the development of multiple myeloma.

Immunosuppression of immunoglobulin synthesis seen in patients with multiple myeloma is in part due to immunosuppressive CD5 positive B cells. In a 13 year longitudinal study of an IgA-deficient blood donor who developed multiple myeloma, the presence of immunosuppressive CD5 positive B cells and T cells preceded the diagnosis of overt multiple myeloma and the appearance of immunosuppressive monocytes. These data argue that certain immune defects may be involved in the development of myeloma and are not simply a consequence of overt malignancy.

Antibody Formation↗
PubMed1991

A cytogenetic and molecular study of a series of 45,X fetuses and their parents.

The parental origin of the single X chromosome in 10 45,X fetuses was studied using DNA restriction fragment length polymorphisms. In six the single X was maternal in origin, in one it was paternal, and in one the results were consistent with a paternal origin. Therefore the parental origin of the X in 45,X fetuses that survive to the second or third trimester of pregnancy is similar to that of spontaneous abortions and live births with a 45,X constitution. The mothers of two of the fetuses were themselves found to have an abnormal sex chromosome complement, but in neither case did it appear to be related to the chromosome abnormality in the fetus.

Chromosome Banding↗
PubMed1991

Pathophysiology of thermoregulation in patients with poikilothermia.

To investigate the thermoregulatory mechanisms underlying poikilothermia in man, we have studied 4 female patients (age 28-37 yr) with poikilothermia, most probably of hypothalamic origin, as well as 4 female volunteers of similar age. In a climatic chamber the participants were subjected to cold stress (16.5 degrees C) and subsequent heat exposure (40 degrees C). In the volunteers cold stress did not influence the rectal temperature; cooling induced a marked shivering response and an immediate peripheral vasoconstriction. Subsequent heat challenge induced a slight rise in the rectal temperature (from 36.3 +/- 0.2 to 37.0 +/- 0.3 degrees C) and a marked sweat secretion in all control subjects. All patients were hypothermic at the start of the experiment. Cooling induced a decrease in the rectal temperature of 0.3-0.9 degrees C. Three patients showed neither peripheral vasoconstriction nor a shivering response to cold stress. In contradistinction to the control subjects, in all patients an afterdrop of the rectal temperature of 0.3-0.5 degrees C was observed once heating of the environment had started; thereafter a progressive rise in core temperature occurred up to 38.5 (38.0) degrees C. In none of the patients sweat secretion was clinically visible. These results reveal that in these patients with poikilothermia the disorder of thermoregulation is accompanied by inadequate cutaneous vasomotor adjustment and disturbed sweat response and likely reduced metabolic response to cold stress.

Adult↗
PubMed1988

CD5 positive immunoregulatory B cell subsets.

B-chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease often expressed as a clonal expansion of CD5+ B cells. We report the characterization of CD5+ B cells from two unique B-CLL patients. Cells from patient 1 coexpressed CD5 (leu-1), CD19 (Leu-12), CD20 (B1), and HLA-DR; they were CD10 (J5), CD21 (B2), CD22 (Leu-14), CD25 (IL2-R1), PCA-1, surface, and cytoplasmic Ig negative. They suppressed normal peripheral blood lymphocyte (PBL) pokeweed mitogen (PWM) -stimulated immunoglobulin (Ig) synthesis greater than 80%. Cells from patient 2 were CD5 (Leu-1), CD19 (Leu-12), CD20 (B1), CD21 (B2), CD22 (Leu-14), HLA-DR, IgM, and kappa positive. They were negative for CD10 (J5), CD25 (IL2-R1), and PCA-1. These cells did not suppress normal PBL PWM-stimulated Ig synthesis but produced a monoclonal IgM kappa protein with rheumatoid factor-like activity. These observations suggest that there are different CD5+ B cell subsets, one immunosuppressive and the other autoreactive.

Antibodies, Monoclonal↗
PubMed1986

Hematologic abnormalities in simian acquired immune deficiency syndrome.

Hematologic abnormalities were defined in 31 rhesus monkeys (Macaca mulatta) with simian acquired immune deficiency syndrome (SAIDS). Animals manifested anemia (hypochromic/microcytic), severe neutropenia and progressive lymphopenia, monocytosis and occasional thrombocytopenia. Bone marrow studies showed erythroid hyperplasia with a marked left shift and adequate megakaryocytes. Two animals showed profound hypoplasia of all hematopoietic elements. Most animals were iron deficient, but the course of the anemia suggested additional factors. There was no evidence of immune hemolysis. The pathogenesis of these abnormalities is not clear and will require further study. This reproducible disease will allow studies to elucidate the mechanisms of viral-induced hematologic abnormalities.

Acquired Immunodeficiency Syndrome↗
PubMed1978

The isolation of lentogenic strains of Newcastle disease virus in Australia.

Twelve isolations of Newcastle disease virus were made from 77 clinical samples from chickens from conjunctivitis, respiratory disease, proventriculitis and bursal atrophy. Nine of the isolations were made from chickens with conjunctivitis. The viruses were identified as Newcastle disease virus by inhibition of their haemagglutinins with specific antiserum to Newcastle disease virus. The viruses failed to kill chicken embryos after inoculation into the allantoic cavity and they were judged to be lentogenic strains. There was no evidence that the Newcastle disease viruses were responsible for any of the clinical conditions from which they were isolated. The presence of other agents in 10 of the samples was indicated by reduced production of haemagglutinin in allantoic fluids of infected embryos, by deaths of infected embryos, by the production of cytopathic changes in avian cell cultures and by electron microscopy. Three isolations of infectious bronchitis virus, 2 of avian adenovirus and one of avian reovirus were made. Other samples were suspected of containing infectious bronchitis virus and mycoplasmas, but these were not isolated. The Newcastle disease viruses failed to produce plaques in chicken embryo fibroblast cell cultures and they were separated from the contaminating agents by haemagglutination and elution followed by passage at terminal dilution in chick embryos. No Newcastle disease virus was isolated from 60 caecal tonsils and 60 lung samples from 9-week-old broiler chickens. Eight lung samples yielded mycoplasmas that caused haemadsorption in chicken cell cultures. The mycoplasmas were probably Mycoplasma gallisepticum.

Animals↗
PubMed1978

C controlled trial of taurolin in established bacterial peritonitis.

Taurolin administered intraperitoneally has effected a significant reduction in morbidity in peritonitis even when all other methods of intensive care, including powerful antibiotics, have been used. Easy to use clinically, it is effective locally against all fecal pathogens and is nontoxic.

Adolescent↗
PubMed1977

Adenyl cyclase and cyclic AMP (cAMP) in acute experimental pancreatitis.

The level of adenosine 3':5'-cyclic monophosphate (cAMP) and the activity of adenyl cyclase were studied in the pancreas under normal conditions and during acute hemorrhagic pancreatitis induced by intraductal injection of fresh trypsin-bile-blood mixture. In addition, the adenyl cyclase was localized histochemically in the pancreas. Basal cAMP concentration and adenyl cyclase activity were 0.88 +/- 0.11 pmoles/mg wet tissue and 3.39 +/- 0.21 pmoles/mg protein/min, respectively. The acute pancreatitis drastically reduced the adenyl cyclase activity at 15 minutes to 1.66 +/- 0.54 pmoles/mg protein/min, and totally suppressed adenyl cyclase activity at 30 minutes after the onset of pancreatitis without affecting cAMP levels. The presence of sodium fluoride in the incubation medium prolonged the enzyme activity up to 45 minutes. The progressive disappearance of adenyl cyclase activity presumably resulted from the destruction of cellular integrity caused by autodigestion by the active proteolytic enzymes released during pancreatitis.

Acute Disease↗