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Biomedical subjects

J Boyle

Publications and source records attributed to J Boyle.

At least 19 recordsLinked to original sources
PubMed1995

Characterization of proteoglycan accumulation during formation of cartilagenous tissue in vitro.

In order to study proteoglycan retention and accumulation, we optimized a chondrocyte cell culture system in which isolated bovine articular chondrocytes accumulate extracellular matrix to form a continuous layer of cartilagenous tissue. The tissue can attain a thickness of up to 110 microns by 35 days. The cells synthesize large keratan sulfate containing proteoglycans and type II collagen indicating that the chondrocytes maintain their phenotype in these culture conditions. Matrix accumulation is enhanced by increased cell density and the presence of serum and ascorbic acid. The amount of proteoglycans synthesized by the chondrocytes increases up to day 21 and then decreases to the same levels as are synthesized during the first week of culture. The percentage of newly synthesized proteoglycans retained in the matrix increases from 20% on day 6 to a maximum of 85% by day 35. The proteoglycan and collagen content in the tissue increases with time in culture. The changes in the percentage of proteoglycans retained parallels the increase in proteoglycan content. After day 35, there is no further increase in the amount of proteoglycans and collagen nor in the percentage of newly synthesized proteoglycans retained in the extracellular matrix. These studies demonstrate that the cultures are going through two phases: one of matrix accumulation and then one of maintaining the existing matrix. The period of matrix accumulation occurs between days 10-21 whereas matrix maintenance is observed after day 35. Using this culture system to study proteoglycan accumulation and maintenance during these culture periods may prove useful in identifying the mechanisms regulating these processes.

Animals↗
PubMed1992

Vascular smooth muscle cell detachment from elastin and migration through elastic laminae is promoted by chondroitin sulfate-induced "shedding" of the 67-kDa cell surface elastin binding protein.

Impaired elastin fiber assembly is observed in the fetal ductus arteriosus (DA), associated with a reduced concentration of elastin binding protein (EBP), a 67-kDa galactolectin. It is also seen in cultured aortic (Ao) smooth muscle cells (SMC) following the release of the EBP by glycosaminoglycans rich in N-acetylgalactosamine, such as chondroitin sulfate (CS). In the DA, impaired elastin fiber assembly is observed in conjunction with intimal thickening associated with increased migration of SMC into the subendothelium, a feature we previously related to increased production of fibronectin. In this report, we determined whether SMC use the EBP to attach to an elastin substrate, whether shedding of the EBP promotes SMC migration through a three-dimensional network of pure elastic laminae prepared from sheep aorta, and whether the latter is associated with increased production of fibronectin. We observed reduced attachment to elastin-coated surfaces of DA SMC deficient in EBP compared to Ao SMC. Addition of CS but not heparan sulfate (a glycosaminoglycan which does not induce EBP shedding) decreased Ao SMC attachment to elastin, as did preincubation with VGVAPG elastin-derived peptides which saturate the EBP. The immunolocalization of cell surface EBP suggested that cells can quickly replace EBP released from their surfaces by CS treatment. The magnitude of CS-induced impaired attachment of SMC to elastin was dose dependent and could be further increased by the administration of cyclohexamide and sodium azide. Also, the reversibility of CS-induced detachment was prevented by monensin. This suggests that a process of new synthesis and intracellular transport of the EBP was necessary to replace the EBP molecules released from the cell surface by CS treatment. In the migration assay, both DA and Ao SMC attached to the top of an elastin membrane, but only DA SMC deficient in EBP migrated through the laminae. Addition of CS, which induced shedding of EBP, resulted in Ao SMC migration associated with increased synthesis of fibronectin. We postulate that CS-induced release of EBP from SMC surfaces causes cell detachment from elastin and an increase in fibronectin synthesis, processes which may be critical in promoting SMC migration associated with intimal thickening developmentally in the DA and perhaps also in vascular disease.

Amino Acid Sequence↗
PubMed1992

Transforming growth factor-beta regulates increased ductus arteriosus endothelial glycosaminoglycan synthesis and a post-transcriptional mechanism controls increased smooth muscle fibronectin, features associated with intimal proliferation.

BACKGROUND: In previous studies we established that there are developmentally regulated increases in endothelial hyaluronan (HA) and heparan sulfate (HS), and smooth muscle cell fibronectin (FN) related to the formation of intimal cushions, structures essential to the postnatal closure of the ductus arteriosus (DA). In this report, we investigated the mechanisms underlying these features to ascertain whether they were independently or coordinately regulated. EXPERIMENTAL DESIGN: We determined by assessing HA polymer size and by pulse labeling with [3H]glucosamine whether the increased glycosaminoglycans (GAGs) incorporated in DA compared with aorta (Ao) endothelial cell matrices reflected increased synthesis of HA and HS rather than decreased degradation. We assessed whether transforming growth factor-beta (TGF-beta) may be responsible for the increased DA endothelial GAGs and smooth muscle FN production by confirming the presence of TGF-beta in DA tissue using immunohistochemistry and by assessing the effect of adding neutralizing antibodies to the cell cultures. We next determined whether the level of regulation of the increase in FN in DA smooth muscle cells was transcriptional or post-transcriptional by relating protein synthesis to steady state mRNA levels and to mRNA levels after serum stimulation. Using northern blot analyses with specific probes, we also explored the possibility that the FN produced by the DA and Ao was qualitatively different in the proportion of isoforms containing the V95+ region associated with secretion or the EIIIB+ region that has been related to migration. RESULTS: We observed that HA polymer size produced by DA and Ao endothelial cells was similar and we further verified using pulse labeling that the increase in DA compared with Ao endothelial GAGs reflected increased synthesis of HA and HS rather than decreased degradation. There was increased immunostaining for TGF-beta in DA compared with Ao tissue and we showed that TGF-beta neutralizing antibodies reduced synthesis of GAGs by the DA endothelial cells to the level of that seen in the Ao cells, but did not reduce DA smooth muscle cell FN synthesis. The increase in FN synthesis by DA compared to Ao smooth muscle cells was not associated with increased levels of steady-state mRNA for FN. Furthermore, following serum-stimulated increases in FN mRNA, the DA yielded greater amounts of FN protein compared to Ao smooth muscle cells. The increased FN production by the DA smooth muscle cells could not be attributed to a relative lack of degradation of FN protein or mRNA, or to qualitative differences which might influence secretion, as both cell types contained similar proportions of EIIIB+ and V95+ isoforms of FN. CONCLUSIONS: These results would suggest that, in contrast to the TGF-beta dependent increase in DA endothelial GAG synthesis, the increase in DA smooth muscle FN synthesis arises through differences in post-transcriptional regulation that are likely independent of TGF-beta.

Animals↗
PubMed1991

Who is entitled to double effect?

The doctrine of double effect continues to be an important tool in bioethical casuistry. Its role within the Catholic moral tradition continues, and there is considerable interest in it by contemporary moral philosophers. But problems of justification and correct application remain. I argue that if the traditional Catholic conviction that there are exceptionless norms prohibiting inflicting some kinds of harms on people is correct, then double effect is justified and necessary. The objection that double effect is superfluous is a rejection of that normative conviction, not a refutation of double effect itself. This justification suggests the correct way of applying double effect to controversial cases. But versions of double effect which dispense with the absolutism of the Catholic tradition lack justification and fall to the objection that double effect is an unnecessary complication.

Bioethical Issues↗
PubMed1991

Ventilatory control (Ventrol) simulation for education.

An educational microcomputer-based simulation of respiratory control has been developed. The program contains three major sections: tutorial, stimulation, and unknown testing. The tutorial section provides a brief discussion of the major factors involved in respiratory control. The simulation section provides a menu of variables to demonstrate the effects of altering inspired gases, changing compliance or airway resistance, metabolic acidosis, neural activity, and lesions (including vagotomy) or exercise. The last section of the program allows students to test their understanding of abnormal respiratory and blood gas values. The program has been used as a problem-solving exercise in a medical physiology course. Student groups were assigned to a microcomputer and given a specific problem during a regularly scheduled laboratory period. The students collected data using the program, analyzed and graphed or tabulated the results, and presented their findings in a minisymposium format to their fellow students. This approach has proven valuable and provides a number of pedagogical benefits that are lacking in a lecture-based basic science curriculum.

Computer Simulation↗
PubMed1991

Use of polymerase chain reaction to detect latent channel catfish virus.

Polymerase chain reaction was used to detect an economically important herpesvirus, channel catfish virus (CCV). A segment of the viral DNA was sequenced and oligonucleotide primers were produced from that sequence. After the primers were tested for the possibility of hybridization to catfish DNA, they were used to prime the polymerase chain reaction, using pure CCV DNA, CCV DNA added to catfish DNA, and DNA from catfish infected and not infected with CCV. In all cases, the method proved to be simple and sensitive in its detection by CCV DNA. When catfish DNA was present, less than 0.1 pg of CCV DNA was detectable. Channel catfish virus DNA in a latent carrier of CCV was readily detectable.

Animals↗
PubMed1990

Roles of prolactin and the uterus in the control of luteal regression in the Bennett's wallaby (Macropus rufogriseus rufogriseus).

The factors responsible for controlling luteal regression in macropodid marsupials are unclear. Experiments were designed to examine the role of the uterus and the pre-partum prolactin pulse in this process. In experiment 1, two groups of adult female Bennett's wallabies were hysterectomized (n = 3) or sham-hysterectomized (n = 3) on Day 16 of a non-pregnant oestrous cycle and daily peripheral blood samples were collected between Days 10-37. In both groups, circulating progesterone concentrations declined to below 0.96 nmol L-1 at luteolysis on Days 28-33. Circulating prolactin concentrations remained low over the period of luteal regression. In experiment 2, two groups of animals, which were maintained in the presence of a fertile male and synchronized by the removal of pouch young (RPY), were treated on Day 16 after RPY with a single injection of long-acting bromocriptine (Parlodel LA, Sandoz Ltd, Basle, Switzerland; 50 mg per animal n = 5) or vehicle (n = 4). Vehicle-treated animals gave birth on Day 28 (n = 3) or Day 29 (n = 1) with a significant elevation of prolactin on Day 28. In contrast, 4 of the 5 bromocriptine-treated animals failed to give birth and one gave birth on Day 29. No comparable prolactin pulse was detected in any of them. Circulating progesterone concentrations declined later in the bromocriptine-treated group than in the controls. These data suggest that different mechanisms lead to luteolysis in pregnant and non-pregnant animals; in pregnancy the luteolytic signal is prolactin, whereas in the non-pregnant cycle another signal of non-uterine origin is involved.

Animals↗
PubMed1989

Acrivastine versus terfenadine in the treatment of symptomatic dermographism--a double-blind, placebo-controlled study.

Twelve patients with symptomatic dermographism were entered into a double-blind, crossover study. Patients received 8 mg acrivastine three times daily, 60 mg terfenadine three times daily or placebo, according to a fully randomized balanced treatment plan. Subjective clinical assessments were performed and the response to experimentally induced dermographism was assessed. Both active treatments were well tolerated and were shown to be significantly more effective than placebo in the treatment of symptomatic dermographism and in reducing the signs and symptoms of wealing induced by a dermographometer.

Adult↗
PubMed1989

Quantitation of strand breaks in human DNA using 32P-Alu hybridization: application to exponential and plateau-phase cells.

A sensitive quantitation of DNA (0.2 to 10 ng) can be achieved using a 32P-labeled Alu probe to hybridize human DNA spotted onto nylon membrane. This allows the determination of radiation-induced single-strand breaks without the use of [3H]thymidine prelabeling of cells in culture. The sensitivity of this technique in HeLa cells is comparable to results obtained using the alkaline unwinding technique. The method is applicable to cells in both exponential and plateau phases of growth.

Cesium Radioisotopes↗
PubMed1988

Microcirculatory hematocrit and blood flow.

Direct measurements from many laboratories indicate that the oxygen tension in skeletal muscle is significantly less than in the large veins draining these tissues. Harris (1986) has proposed that because of the parallel anatomic arrangement of large arterioles and venules in skeletal muscle, a counter-current exchange between these vessels can occur. He theorized that diffusion of O2 between arteriole and venule would lower the PO2 in the blood as it enters capillaries and result in a decreased tissue PO2 and an increase in large vein PO2. Calculations (Appendix) show that the amount of O2 transferred between arteriole and venule is inadequate to account for this difference in PO2 between tissue and veins due to the small surface area that is involved. It is well documented that the microcirculatory hematocrit ranges between 20 and 50% of that in the supply vessels. The reduced hematocrit lowers the oxygen content in these vessels and results in a low oxygen tension in the surrounding tissue. True arteriovenous shunts are not present in most skeletal muscles, but 15-20% of the microvessels represent thoroughfare or preferential flow channels. It is suggested that these vessels contain a greater than normal hematocrit to account for a conservation of red cell mass across the microcirculation. Furthermore, it is shown that the hematocrit in the preferential flow channels is an inverse function of the flow rate for any level of the microcirculatory hematocrit. The increased hematocrit raises the flow resistance in these vessels which reduces flow further and represents a positive feedback condition which may contribute to the intermittent and uneven flow patterns which are present within the microcirculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Tetanus--a continuing problem in minor injuries.

Tetanus is rare in North America because of highly effective specific immunization programs. Nevertheless, 15 patients with generalized tetanus were treated at the Vancouver General Hospital over a 20-year period; 10 of them were over 50 years of age. Two patients had no injury and 12 had suffered only minor wounds. None had received previous immunization and, even after wounding, prophylaxis was unsatisfactory in all cases. Nine patients required intensive care and two died. Positive cultures were obtained in only two cases. Four recommendations are made to prevent tetanus: (a) all wounds should be considered "tetanus-prone", (b) an accurate history of immunization should be obtained, (c) more attention should be given to prophylaxis at the time of injury and (d) patients should record vaccinations.

Adult↗