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Biomedical subjects

T M Quinn

Publications and source records attributed to T M Quinn.

31 records · Page 2Linked to original sources
PubMed1999

Elevated platelet-derived growth factor-B in congenital cystic adenomatoid malformations requiring fetal resection.

BACKGROUND: During lung development, platelet-derived growth factor-BB (PDGF-BB) is maximal during the canalicular stage and decreases by the saccular stage. PDGF-BB stimulates lung growth by increasing cell proliferation. Fetal CCAMs have been shown to have an elevated proliferative index, but it is not known why some CCAMs rapidly enlarge in utero and cause fetal hydrops. The authors hypothesized that the high proliferative index and rapid enlargement of some fetal CCAMs may be caused by persistently elevated PDGF-BB production compared with normal fetal lung. METHODS: To test this hypothesis, tissue was obtained at the time of resection from two fetal CCAMs (22 weeks), three full-term CCAMs, and three normal fetal lungs (21 to 22 weeks). PDGF-BB production by fetal CCAMs was compared with normal age-matched fetal lung using immunohistochemistry, reverse transcriptionase-polymerase chain reaction (RT-PCR), and Western blot analysis. RESULTS: CCAMs resulting in fetal hydrops and requiring fetal resection had strong mesenchymal immunostaining for PDGF-BB next to epithelial lined cysts, increased PDGF-B gene expression by RT-PCR, and elevated PDGF-BB protein by Western blot, compared with normal age-matched fetal lung. Term CCAMs had minimal PDGF-BB staining, PDGF-B gene expression, and PDGF-BB protein production. CONCLUSIONS: CCAMs that grew rapidly and progressed to hydrops, requiring in utero resection, demonstrated increased mesenchymal PDGF-B gene expression and PDGF-BB protein production compared with age-matched normal fetal lung, which may, in part, be responsible for the autonomous growth and proliferation seen in hydropic fetal CCAMs.

Blotting, Western↗
PubMed1998

Effects of injurious compression on matrix turnover around individual cells in calf articular cartilage explants.

The effects of mechanical injury on the metabolism of cartilage matrix are of interest for understanding the pathogenesis of osteoarthrosis and the development of strategies for cartilage repair. The purpose of the present study was to examine the effects of injury on matrix turnover in a calf articular cartilage explant system for which the effects of mechanical loading on cell activity and the cell-mediated pathways of matrix metabolism are already well characterized. New methods of quantitative autoradiography were used in combination with established biochemical and biomechanical techniques for the analysis of cell and matrix responses to acute mechanical injury, with particular attention to the processes of localized matrix turnover in the cell-associated matrices of individual chondrocytes. Matrix deposition and turnover around cells in control explants was spatially dependent, with the highest rates of proteoglycan deposition and turnover and the lowest rates of collagen deposition (as indicated by [3H]proline autoradiography) occurring in the pericellular matrix. Injurious compression was associated with (a) an abrupt decrease in the tensile load-carrying capacity of the collagen matrix, apparently associated with mechanical failure of the tissue, (b) a considerable but subtotal decrease in cell viability, marked by the emergence of an apparently inactive cell population interspersed within catabolically active but abnormally large cells, and (c) sustained, elevated rates of proteoglycan turnover, particularly in the cell-associated matrices of apparently viable cells, which involved the increased release of aggregating species in addition to a spectrum of degradation fragments that were also in controls. These results may represent an in vitro model for the responses of chondrocytes and the cartilage extracellular matrix to mechanical injury.

Animals↗
PubMed1998

Tracheal occlusion in the fetal rat: a new experimental model for the study of accelerated lung growth.

BACKGROUND: Prenatal tracheal occlusion accelerates fetal lung growth, but the mechanism of this phenomenon is unknown. Previous animal models have been limited by expense, lack of species-specific molecular probes, or the stage of lung development when studies could be performed. To provide a model that is more amenable to systematic analysis, we have developed an in vivo rat model of prenatal tracheal occlusion. METHODS: Time-dated pregnant rats underwent laparotomy at 19 days' gestational age (term, 22 days). The fetal head and neck were exteriorized through a hysterotomy, and the trachea was ligated under a dissecting microscope. The fetus was returned to the amniotic cavity, and the uterine and maternal abdominal incisions were closed. The dam and the fetuses were killed at 21.5 days' gestational age, and the fetal lungs were assessed for lung growth and compared with nonoperated littermate controls. RESULTS: Thirty-two of 50 manipulated fetuses survived. Of the 32 survivors, successful tracheal ligation was confirmed in 20, and these 20 fetuses were compared with 33 littermate controls. Fetal body weight (4.81+/-0.26 g v 4.87+/-0.41 g) and heart weight (0.05+/-0.01 g v 0.05+/-0.01 g) were not significantly different between ligated fetuses and littermate controls, whereas the wet lung weight (0.30+/-0.06 g v 0.13+/-0.02 g, P<.01), lung-to-body-weight ratio (6.34+/-1.16% v 2.64+/-0.41%, P<.01), dry lung weight (17.4+/-2.45 mg v 12.1+/-1.87 mg, P<.01), total lung DNA (1210+/-371 microg v 828+/-208 microg, P<.01), and total lung protein (14.3+/-5.3 mg v 8.7+/-1.7 mg, P<.01) were increased significantly in the ligated fetuses. The enlarged lung demonstrated normal histology findings after inflation fixation. CONCLUSIONS: Prenatal tracheal occlusion during the canalicular stage of lung development accelerates lung growth in the rat. In comparison with other large animal models, this relatively inexpensive small animal model has the distinct advantages of a short gestation, a large number of fetuses per litter, the availability of a developmental model of congenital diaphragmatic hernia, and the availability of well-defined molecular probes to investigate the mechanism of tracheal occlusion-induced lung growth.

Animals↗
PubMed1998

Prenatal magnetic resonance imaging enhances fetal diagnosis.

BACKGROUND: Ultrasound (US) evaluation of some fetal anomalies provides limited information. Anatomic details that affect prognosis and selection for fetal therapy, such as liver herniation and pulmonary hypoplasia in congenital diaphragmatic hernia (CDH) and airway patency in giant neck masses, may be difficult to delineate using conventional sonographic methods. The authors evaluated the utility of prenatal magnetic resonance imaging (MRI) with new ultrafast imaging sequences in the diagnosis and management of fetal anomalies. METHODS: From April 1996 to April 1997 45 MRI scans were performed in 31 pregnant women with an US diagnosis of a fetal anomaly. The US diagnoses included CDH, giant neck masses, lung masses, abdominal and pelvic abnormalities, twin anomalies, and central nervous system (CNS) anomalies. The fetuses ranged in age from 18 to 39 weeks' gestation (mean, 28.7 weeks). Using a 1.5-T magnet, a variety of ultrafast imaging sequences were performed including fast gradient-echo, half-fourier single shot turbo spin-echo (Haste) and echo-planar imaging yielding images with T1 to T2 type weighting. RESULTS: With CDH, MRI demonstrated liver herniation into the chest in 11 of 14 cases. In four cases, US findings had not been definitive. In two cases of CDH detected by MRI, the primary diagnosis by US had been congenital cystic adenomatoid malformation (CCAM). With lung masses, MRI accurately distinguished between CCAM and bronchopulmonary sequestration (BPS). For giant neck masses with potential airway obstruction, MRI scans permitted differentiation of teratoma from cystic hygroma and allowed delineation of fetal airway involvement. The accurate anatomic evaluation facilitated planning for the ex utero intrapartum treatment (EXIT) procedure, a technique for securing the airway while the term fetus is still on placental support. With huge abdominal masses such as enterogenous cyst and lymphangioma, MRI scanning clarified the diagnosis. Fourteen of the 31 (45%) patients underwent fetal treatment after US and MRI evaluation. CONCLUSIONS: Prenatal MRI enhances fetal anatomic evaluation and facilitates perinatal management and family counseling. Ultrafast imaging sequence MRI is helpful to corroborate and refine US diagnoses. Fetal MRI is a valuable adjunct to US for prenatal diagnosis before fetal surgical intervention for selected life-threatening birth defects.

Congenital Abnormalities↗
PubMed1998

Increased cell proliferation and decreased apoptosis characterize congenital cystic adenomatoid malformation of the lung.

BACKGROUND/PURPOSE: Congenital cystic adenomatoid malformations (CCAM) are lung lesions that demonstrate abnormalities of both mesenchymal and epithelial tissues. The pathogenesis of these tumors remains unknown. Because normal organogenesis requires a balance between cell proliferation and programmed cell death (apoptosis), the authors hypothesized that CCAM results from an increase in cell proliferation or a decrease in apoptosis within the developing lung, possibly mediated by keratinocyte growth factor (KGF). METHODS: To examine cell cycle control in CCAM, we measured indices of cell proliferation and apoptosis in lesions requiring fetal (n = 4) or neonatal (n = 8) resection compared with those of normal fetal (14 to 28 weeks' gestation; n = 14) and neonatal (n = 3) human lung. Cell proliferation was analyzed by immunostaining for a proliferation marker (Ki-67). Apoptosis was examined using an in situ digoxigenin end-labeling technique to localize apoptotic bodies. The expression of KGF protein and KGF mRNA in CCAM and normal lung was examined using immunohistochemistry and semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: CCAM lesions in general showed a twofold increase in cell proliferation index (19.2% +/- 1.4% v 9.6% +/- 0.7%, P < .00005) and a fivefold decrease in apoptotic bodies (0.9 +/- 0.2 v 4.5 +/- 0.5, P < .0005) compared with age-matched normal lung. CCAMs that required resection before birth had the highest cell proliferation index. There were no differences in the expression of KGF protein or KGF mRNA in CCAM and normal lung. CONCLUSIONS: These results demonstrate that CCAM differs from normal lung by increased cell proliferation and decreased apoptosis. The increased proliferation does not appear to be mediated by the pneumocyte mitogen KGF. An examination of factors that control cell proliferation and apoptosis in CCAM may provide further insight into the pathogenesis of this tumor.

Apoptosis↗
PubMed1998

Mechanical compression alters proteoglycan deposition and matrix deformation around individual cells in cartilage explants.

We have used new techniques of cell-length scale quantitative autoradiography to assess matrix synthesis, deposition, and deformation around individual chondrocytes in mechanically compressed cartilage explants. Our objectives were to: (1) quantify the effects of static and dynamic compression on the deposition of newly synthesized proteoglycans into cell-associated and further-removed matrices; (2) measure cell-length scale matrix strains and morphological changes of the cell and matrix associated with tissue compression; and (3) relate microscopic physical stimuli to changes in proteoglycan synthesis as functions of compression level and position within mechanically compressed explants. Results indicate a high degree of structural organization in the extracellular matrix, with the pericellular matrix associated with the most rapid rates of proteoglycan deposition, and greatest sensitivity to mechanical compression. Static compression could stimulate directional deposition of secreted proteoglycans around chondrocytes, superimposed on an inhibition of proteoglycan synthesis; these events followed trends for compressive strain in the cell-associated matrix. Conversely, proteoglycan synthesis and pericellular deposition was stimulated by dynamic compression. Results suggest that cell-matrix interactions in the cell-associated matrix may be a particularly important aspect of the chondrocyte response to mechanical compression, possibly involving macromolecular transport limitations and morphological changes associated with fluid flow and local compaction of the matrix around cells.

Animals↗
PubMed1997

Percutaneous fetal access and uterine closure for fetoscopic surgery. Lessons learned from 16 consecutive procedures in pregnant sheep.

BACKGROUND: Maternal morbidity and preterm labor from fetal surgery might be minimized by a percutaneous technique for fetal access and uterine closure. METHODS: In each of 16 ewes, we inserted three trocars percutaneously into the amniotic cavity using ultrasound and fetoscopic guidance. In six ewes, percutaneous uterine closure after the procedure was attempted. We assessed feasibility and acute complications of our technique during surgery and at autopsy. RESULTS: We achieved percutaneous fetal access in 14 ewes and closed the uterus percutaneously in all six ewes attempted. Fetal injury was related to amnioinfusion or fixation of chorioamniotic membranes. Other complications were trocar dislodgment and damage to uterine wall and chorioamniotic membranes. The latter complication was prevented using balloon-tipped trocars. CONCLUSIONS: Percutaneous intraamniotic access and uterine closure for fetoscopic surgery can be achieved reliably with little maternal and fetal morbidity in sheep. Minor modifications are desired to apply this approach in humans.

Amnion↗
PubMed1997

Fetal surgery.

Fetal surgery holds the promise of correcting some fetal problems at an early point in gestation, before fetal injury or death has occurred. Prenatal operative intervention may become the more cost-effective and humane approach to a series of otherwise devastating fetal diseases. With refinement of techniques that reduce maternal and fetal risk from fetal surgery, it may be possible to treat nonfatal fetal diseases with less postnatal morbidity.

Algorithms↗
PubMed1995

Analysis of collagen synthesis and assembly in culture by immortalized mouse chondrocytes in the presence or absence of alpha 1(IX) collagen chains.

We have previously shown that SV40 large T oncogene is able to induce mouse chondrocyte proliferation without loss of expression of types II, IX, and XI collagen, as well as cartilage aggrecan and link protein. The cell line obtained (termed MC 615) also expressed some type I collagen in monolayer and we have investigated if anchorage-independent conditions could inhibit type I collagen synthesis and promote hypertrophy and type X collagen synthesis. The MC 615 cells were grown in agarose in the presence of serum, and GAG accumulation, DNA content, and matrix synthesis rates were monitored after incubation with [35S]sulfate and [3H]- or [14C]proline. SDS-PAGE analysis of pepsin-extracted samples showed that type I collagen was still synthesized by the MC 615 cells, from the beginning of the culture and at low or high density. Type II collagen synthesis was demonstrated by immunoblotting, but type X collagen synthesis was not detected, indicating that the MC 615 chondrocytes immortalized by large T were still blocked in their maturation pathway. The cells were also grown over agarose and electron microscopy (E. M.) analysis of the cell aggregates showed an extracellular matrix rich in proteoglycans and in type II-containing collagen fibrils. To gain insight into the role of type IX collagen in cartilage collagen assembly and/or matrix organization, we also immortalized embryonic chondrocytes isolated from mice lacking alpha 1 (IX) collagen and obtained a clone termed 4KO 91. As found for the MC 615 cells, the 4KO 91 cells synthesized type II collagen as demonstrated by Western blotting and some type I collagen identified by the presence of alpha 2(I) chains after electrophoretic analysis of pepsin-digested collagen chains. E. M. analysis of the extracellular matrices synthesized by the two cell lines revealed differences in collagen structure and organization. In the absence of alpha 1 (IX) collagen chains, the collagen fibrils seemed to fuse laterally, suggesting that collagen IX acts as a "spacer" between fibrils, to keep them apart.

Animals↗
PubMedDate not supplied

Bi-zonal cartilaginous tissues engineered in a rotary cell culture system.

In this study, we aimed at validating a rotary cell culture system (RCCS) bioreactor with medium recirculation and external oxygenation, for cartilage tissue engineering. Primary bovine and human culture-expanded chondrocytes were seeded into non-woven meshes of esterified hyaluronan (HYAFF-11), and the resulting constructs were cultured statically or in the RCCS, in the presence of insulin and TGFbeta3, for up to 4 weeks. Culture in the RCCS did not induce significant differences in the contents of glycosaminoglycans (GAG) and collagen deposited, but markedly affected their distribution. In contrast to statically grown tissues, engineered cartilage cultured in the RCCS had a bi-zonal structure, consisting of an outgrowing fibrous capsule deficient in GAG and rich in collagen, and an inner region more positively stained for GAG. Structurally, trends were similar using primary bovine or expanded human chondrocytes, although the human cells deposited inferior amounts of matrix. The use of the presented RCCS, in conjunction with the described medium composition, has the potential to generate bi-zonal tissues with features qualitatively resembling the native meniscus.

Adult↗