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Biomedical subjects

A MacKenzie

Publications and source records attributed to A MacKenzie.

At least 55 records · Page 3Linked to original sources
PubMed1996

Cyclosporin A inhibits the in vivo production of interleukin-1beta and tumour necrosis factor alpha, but not interleukin-6, by a T-cell-independent mechanism.

The effect of cyclosporin A (CsA) on cytokine production in the tissue chamber model of acute inflammation was investigated. CsA caused a dose-related inhibition of interleukin 1beta(IL-1beta) production in both normal and athymic mice, confirming earlier conclusions that this effect is not T cell dependent (ED50s 40 and 53 mg/kg p.o., respectively). Tumour necrosis factor alpha (TNF-alpha) levels were similarly affected with ED50s of 40 and 58 mg/kg p.o. for normal and athymic mice, respectively. By contrast, CsA inhibited interleukin 6 (IL-6) production only in normal mice (ED50 27 mg/kg p.o.) Differences in the absolute production of the three cytokines in normal and athymic mice were also noted. IL-1beta and IL-6 levels were two-fold higher in athymic mice, while for TNF-alpha, there was no difference between the two groups. The present findings support the authors' original hypothesis, that the inhibitory mechanism of CsA on IL-1beta is not mediated via T cells. The same mechanism also seems responsible for the inhibition of TNF-alpha production, but not for IL-6, where inhibition by CsA appears to require the presence of T cells.

Animals↗
PubMed1996

Endothelin production in sepsis and the adult respiratory distress syndrome.

OBJECTIVE: Septic shock is characterised by a decrease in systemic vascular resistance. Nevertheless, regional increases in vascular resistance can occur which may predispose to organ dysfunction, including the adult respiratory distress syndrome (ARDS). Because endothelial damage is a major feature of acute lung injury, we examined whether the potent endothelial vasoconstrictor peptide endothelin-1 plays a pathophysiological role in sepsis or ARDS. DESIGN: Plasma endothelin was measured in mixed venous, pulmonary capillary and arterial blood, and the relationship with outcome measures was determined. SETTING: The intensive care unit of a university teaching hospital. PATIENTS AND PARTICIPANTS: A consecutive series of well-characterised patients with sepsis syndrome, both with (n = 11) and without (n = 15) ARDS, and ventilated controls without sepsis or ARDS (n = 7). MEASUREMENTS AND RESULTS: Plasma endothelin was significantly elevated in patients with sepsis alone and in patients with sepsis and ARDS. Plasma endothelin did not differ among mixed venous, pulmonary capillary and systemic arterial blood. On multiple regression analysis, plasma endothelin correlated positively with organ failure score and with oxygen consumption, and negatively with the PaO2 : FiO2 ratio. There was no correlation with plasma creatinine, suggesting that decreased renal clearance did not account for the high plasma endothelin concentrations. CONCLUSIONS: Although the lung does not appear to be the major site of endothelin production in critically ill patients with sepsis, increased endothelin production may contribute to regional increases in vascular [correction of vacular] resistance, hyperfusion, and the development of organ failure, including ARDS, in patients with sepsis.

Case-Control Studies↗
PubMed1996

Mutations in GPC3, a glypican gene, cause the Simpson-Golabi-Behmel overgrowth syndrome.

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked condition characterized by pre- and postnatal overgrowth with visceral and skeletal anomalies. To identify the causative gene, breakpoints in two female patients with X;autosome translocations were identified. The breakpoints occur near the 5' and 3' ends of a gene, GPC3, that spans more than 500 kilobases in Xq26; in three families, different microdeletions encompassing exons cosegregate with SGBS. GPC3 encodes a putative extracellular proteoglycan, glypican 3, that is inferred to play an important role in growth control in embryonic mesodermal tissues in which it is selectively expressed. Initial western- and ligand-blotting experiments suggest that glypican 3 forms a complex with insulin-like growth factor 2 (IGF2), and might thereby modulate IGF2 action.

Abnormalities, Multiple↗
PubMed1996

FISH detection of chromosome polymorphism and deletions in the spinal muscular atrophy (SMA) region of 5q13.

The search for the SMA defect has culminated in the identification of two candidate 5q13.1 SMA genes, NAIP and SMN both of which are deleted in individuals with SMA. It was postulated that the intact and degenerate versions of NAIP are present in variable and frequently high copy numbers in this region while SMN was proposed to be present in only two copies. In order to assess the copy number of NAIP and SMN we have conducted interphase FISH analysis using NAIP and SMN gene-containing cosmid and plasmid probes. Our results confirm the variability in the number of NAIP signals in non-SMA chromosomes (2-6) and show that SMN is present on average twice per chromosome although in one chromosome 4-5 signals for the SMN-containing cosmid probe were detected. Our analysis reveals that one of four and three of six type I SMA chromosomes had a lower than normal number of NAIP and SMN signals, respectively. In two of six SMA type I chromosomes, complete loss of hybridization signal was observed on one chromosome 5 with our SMN cosmid probe possibly reflecting a large scale deletion. Large scale deletions were not detectable when metaphase chromosomes of an SMA type II and III patient were analyzed.

Chromosome Deletion↗
PubMed1996

Automated DNA sequencing requiring no DNA template purification.

A critical component in automated fluorescent DNA sequencing is good quality of DNA template. In an effort to reduce the dependence of sequencing success on DNA template quality, the effect of heat-soaked PCR on automated sequencing reactions has been examined. We have found that the heat-soaked PCR protocol considerably improves the overall quality of sequence data and significantly reduces the dependence on the quality of DNA templates. The improvement is corroborated by our ability to obtain over 500 bp of readable sequence per reaction using DNA from E. coli lysates as template obviating DNA purification.

Automation↗
PubMed1995

A recombination event occurring within two complex 5q13.1 microsatellite repeat polymorphisms suggests a telomeric mapping of spinal muscular atrophy.

The gene for the childhood spinal muscular atrophies (SMAs) has been mapped to 5q13.1. The interval containing the SMA gene has been defined by linkage analysis as 5qcen-D5S629-SMA-D5S557-5qter. We have identified a recombination event within this interval on a type-I SMA chromosome. The recombination maps to a region of multilocus microsatellite repeat (MSR) markers, and occurs between different subloci of two such markers, CMS-1 and 7613. While the possibility of a novel mutation caused by the recombination cannot be discounted, we believe when viewed in the context of a similar recombination in a Dutch SMA family, a centromeric boundary at the recombination site for the critical SMA interval is likely. This new proximal boundary would reduce the minimal region harboring the SMA locus from approximately 1.1 Mb to approximately 600 kb.

Alleles↗
PubMed1995

Different effects of cyclosporin A on bone remodeling in young and adult rats.

Reported effects of cyclosporin A (Sandimmun, CsA) on bone have been both contradictory and controversial. Thus, stimulation of new bone formation as well as increased mineral and matrix resorption have been observed. To investigate the response of basal mineral and matrix turnover to CsA treatment at different stages of skeletal development, comparative experiments were conducted in young growing female rats and in adults. Fifty-six young animals (study A) and 40 adults (study B) received orally either the carrier substance or 5, 15, and 30 mg/kg CsA for 30 days. The following parameters were measured: (a) total skeletal mineral content by dual energy X-ray absorptiometry (DEXA) on days 1 and 30; (b) tibial trabecular volume at day 30; (c) serum osteocalcin at 5-day intervals; (d) urinary deoxypyridinoline (Dpd) excretion (days 1, 15, and 30); and (e) plasma levels of CsA. Results can be summarized as follows: in young rats (study A), total skeletal mineral was not modified by the 5- and 15-mg/kg doses of CsA, whereas 30 mg/kg induced a significant decrease (-15%, p < 0.01). This parameter was not significantly modified in adult animals (study B) subjected to the same doses. The administration of 5 mg/kg CsA did not alter tibial trabecular volume in young rats, but 15 and 30 mg/kg significantly lowered this parameter (-16.3%, p < 0.02, and -42%, p < 0.001, respectively). In adult rats, tibial trabecular volume remained unchanged with the exception of the group receiving 30 mg/kg which exhibited significantly lower values (-28%, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1995

A phase I study of chemically synthesized verotoxin (Shiga-like toxin) Pk-trisaccharide receptors attached to chromosorb for preventing hemolytic-uremic syndrome.

A double-blind, placebo-controlled study was conducted to document possible side effects associated with oral consumption of synthetic verotoxin (VT, shiga-like toxin) Pk-trisaccharide receptor sequences attached to Chromosorb (Synsorb-Pk) by healthy adult volunteers. Synsorb-Pk reclaimed from volunteer stool samples was also analyzed to determine if its VT-binding activity was affected by exposure to the pH extremes and digestive processes of the human gastrointestinal tract. No participant reported any Synsorb-Pk-related adverse reactions, and no clinically important trends in laboratory data were evident. Synsorb-Pk recovered from stools retained its ability to absorb VT in polymyxin extracts of VT-producing Escherichia coli and also neutralized VT when mixed in vitro with VT-positive stools from children with hemorrhagic colitis or hemolytic-uremic syndrome (HUS). These results suggest a potential use for Synsorb-Pk in preventing HUS in patients infected with VT-producing E. coli.

Absorption↗
PubMed1995

Genomic rearrangements in childhood spinal muscular atrophy: linkage disequilibrium with a null allele.

Autosomal recessive childhood onset spinal muscular atrophy has been mapped to chromosome 5q13. We report the analysis of a polymorphic microsatellite which shows linkage disequilibrium with the disease. The linkage disequilibrium is observed with a null allele which is seen as the non-inheritance of alleles from one or both parents. The inheritance of a null allele was observed in 26 out of 36 (72%) informative childhood onset spinal muscular atrophy (SMA) families tested, of all types of severity and from a variety of ethnic backgrounds. In seven families segregating for the severe Werdnig-Hoffmann or SMA type I, no alleles were inherited from either parent using this microsatellite. This null allele may represent a deletion which is either closely associated with, or causes, the disease.

Alleles↗
PubMed1994

The structure of the tricellular region of endothelial tight junctions of pulmonary capillaries analyzed by freeze-fracture.

This study provides the first description of tight junction organization in the tricellular regions of pulmonary capillary endothelial cells. Three important characteristics of tight junction organization at these corners were observed. First, endothelial tight junctions are discontinuous at these corners where an intramembranous gap which averages 27.4 +/- 2.3 (SE) nm in width and 1.1 + 0.17 (SE) micron in length was observed to cross the depth of the junctional complex and endothelium. Second, the depth of the tricellular region of endothelial tight junctions at these corners was made possible by an overlapping flap provided by one of the three cells, the flap cell, which covers the remaining two adjacent cells. Third, the observations in this study demonstrated that the tricellular regions of endothelial tight junctions are oriented parallel to the plane of the endothelium rather than perpendicular as in epithelium. A model of this organization, based upon freeze-fracture replicas of 16 tricellular regions, thin section data, and scanning electron microscopic data of perfusion fixed guinea pig lungs is provided.

Animals↗
PubMed1993

Modulation of secretory processes of phagocytes by IX 207-887.

In chronic inflammation, the mediators released by phagocytes are in part responsible for the initiation and perpetuation of the disease. IX 207-887, which is a novel antiarthritic drug, inhibits the release of cytokines from mononuclear cells at concentrations which are achieved therapeutically in human rheumatoid arthritis and in animal models of arthritis. Furthermore, the production of superoxide and release of azurophil and specific granules by N-formyl-Met-Leu-Phe-stimulated neutrophils are significantly reduced. As a consequence, IX 207-887 may break the vicious circle which is manifest in chronic inflammation. In a recent double-blind placebo controlled study IX 207-887 has been shown to be an effective slow-acting drug for use in rheumatoid arthritis.

Animals↗
PubMed1993

Genetic linkage analysis of Canadian spinal muscular atrophy kindreds using flanking microsatellite 5q13 polymorphisms.

The spinal muscular atrophies (SMA) are among the most common autosomal recessive disorders. We have performed linkage analysis using both standard restriction fragment length polymorphisms (RFLPs) as well as microsatellite polymorphisms [Ca(n)] on 49 Canadian SMA families (types 1, 2, and 3) that both flank and are linked to SMA. The closest SMA linkage was observed with the MAP1B locus (zmax = 8.04, theta max = 0.0). Multipoint linkage analysis gave a high probability of SMA mapping between D5S6 and D5S39. Only one family (type 3) that fulfilled our diagnostic criteria for SMA showed nonlinkage with 5q13 markers. This study shows the feasibility of accurate molecular diagnosis of SMA utilizing 5q13 satellite polymorphisms.

Canada↗
PubMed1992

Expression patterns of the homeobox gene, Hox-8, in the mouse embryo suggest a role in specifying tooth initiation and shape.

We have studied the expression patterns of the newly isolated homeobox gene, Hox-8 by in situ hybridisation to sections of the developing heads of mouse embryos between E9 and E17.5, and compared them to Hox-7 expression patterns in adjacent sections. This paper concentrates on the interesting expression patterns of Hox-8 during initiation and development of the molar and incisor teeth. Hox-8 expression domains are present in the neural crest-derived mesenchyme beneath sites of future tooth formation, in a proximo-distal gradient. Tooth development is initiated in the oral epithelium which subsequently thickens in discrete sites and invaginates to form the dental lamina. Hox-8 expression in mouse oral epithelium is first evident at the sites of the dental placodes, suggesting a role in the specification of tooth position. Subsequently, in molar teeth, this patch of Hox-8 expressing epithelium becomes incorporated within the buccal aspect of the invaginating dental lamina to form part of the external enamel epithelium of the cap stage tooth germ. This locus of Hox-8 expression becomes continuous with new sites of Hox-8 expression in the enamel navel, septum, knot and internal enamel epithelium. The transitory enamel knot, septum and navel were postulated, long ago, to be involved in specifying tooth shape, causing the inflection of the first buccal cusp, but this theory has been largely ignored. Interestingly, in the conical incisor teeth, the enamel navel, septum and knot are absent, and Hox-8 has a symmetrical expression pattern. Our demonstration of the precise expression patterns of Hox-8 in the early dental placodes and their subsequent association with the enamel knot, septum and navel provide the first molecular clues to the basis of patterning in the dentition and the association of tooth position with tooth shape: an association all the more intriguing in view of the evolutionary robustness of the patterning mechanism, and the known role of homeobox genes in Drosophila pattern formation. At the bell stage of tooth development, Hox-8 expression switches tissue layers, being absent from the differentiating epithelial ameloblasts and turned on in the differentiating mesenchymal odontoblasts. Hox-7 is expressed in the mesenchyme of the dental papilla and follicle at all stages. This reciprocity of expression suggests an interactive role between Hox-7, Hox-8 and other genes in regulating epithelial mesenchymal interactions during dental differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Watson syndrome: is it a subtype of type 1 neurofibromatosis?

Over 20 years ago, Watson described three families with a condition characterised by pulmonary valvular stenosis, café au lait patches, and dull intelligence. Short stature is an additional feature of this autosomal dominant condition. A fourth family with Watson syndrome has since been reported. We have had the opportunity to review members of three of these four families. The clinical phenotype of Watson syndrome has been expanded to include relative macrocephaly and Lisch nodules in the majority of affected subjects, and neurofibromas in one-third of family members. Because the additional clinical findings enhance the similarity between Watson syndrome and neurofibromatosis 1, molecular linkage studies have been performed using probes flanking the NF1 gene on chromosome 17. Probe HHH202 showed the tightest linkage to Watson syndrome with a maximum lod score of 3.59 at phi = 0.0 (95% confidence limits of phi = 0.0-0.15). This suggests either that Watson syndrome and neurofibromatosis 1 are allelic, or that there is a series of contiguous genes for pulmonary stenosis, neurocutaneous anomalies, short stature, and mental retardation on 17q.

Chromosomes, Human, Pair 17↗