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Biomedical subjects

J J Mitchell

Publications and source records attributed to J J Mitchell.

At least 37 records · Page 2Linked to original sources
PubMed1993

Familial cold urticaria.

Familial cold urticaria (FCU) is a rare autosomal dominant condition, first described in 1940. The onset is in early life in all reported cases. Symptoms are triggered by generalized exposure to cold air, particularly in damp and windy weather. The cutaneous lesions consist of erythematous macules or plaques, urticarial lesions and sometimes petechiae. Associated fever, chills, joint pains, nausea, stiffness and swelling of the hands and feet frequently occur. The symptoms are variable, ranging from mild to incapacitating. The pathogenesis of FCU remains unknown. To our knowledge only 10 pedigrees have been published, seven from the USA and one each from Holland, France and South Africa. We wish to report another extensive pedigree after having had the opportunity to investigate one member of the family in detail. A short form of this pedigree has been published elsewhere.

Cold Temperature↗
PubMed1993

In vitro expression of the alpha-smooth muscle actin isoform by rat lung mesenchymal cells: regulation by culture condition and transforming growth factor-beta.

alpha-Smooth muscle actin (alpha SM actin)-containing cells recently have been demonstrated in intraalveolar lesions in both rat and human tissues following lung injury. In order to develop model systems for the study of such cells, we examined cultured lung cell lines for this phenotype. The adult rat lung fibroblast-like "RL" cell lines were found to express alpha SM actin mRNA and protein and to organize this actin into stress fiber-like structures. Immunocytochemical staining of subclones of the RL87 line demonstrated the presence in the cultures of at least four cell phenotypes, one that fails to express alpha SM actin and three distinct morphologic types that do express alpha SM actin. The proportion of cellular actin that is the alpha-isoform was modulated by the culture conditions. RL cells growing at low density expressed minimal alpha SM actin. On reaching confluent densities, however, alpha SM actin increased to at least 20% of the total actin content. This effect, combined with the observation that the most immunoreactive cells were those that displayed overlapping cell processes in culture, suggests that cell-cell contact may be involved in actin isoform regulation in these cells. Similar to the response of some smooth muscle cell lines, alpha SM actin expression in RL cells also was promoted by conditions, e.g., maintenance in low serum medium, which minimize cell division. alpha SM actin expression was modulated in RL cells by the growth factor transforming growth factor-beta. Addition of this cytokine to growing cells substantially elevated the proportion of alpha SM actin protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1993

Cyclic mechanical deformation stimulates human lung fibroblast proliferation and autocrine growth factor activity.

Cellular hypertrophy and hyperplasia and increased extracellular matrix deposition are features of tissue hypertrophy resulting from increased work load. It is known, for example, that mechanical forces play a critical role in lung development, cardiovascular remodeling following pressure overload, and skeletal muscle growth. The mechanisms involved in these processes, however, remain unclear. Here we examined the effect of mechanical deformation on fibroblast function in vitro. IMR-90 human fetal lung fibroblasts grown on collagen-coated silastic membranes were subjected to cyclical mechanical deformation (10% increase in culture surface area; 1 Hz) for up to 5 days. Cell number was increased by 39% after 2 days of deformation (1.43 +/- .01 x 10(5) cells/membrane compared with control, 1.03 +/- 0.02 x 10(5) cells; mean +/- SEM; P < 0.02) increasing to 163% above control by 4 days (2.16 +/- 0.16 x 10(5) cells compared with 0.82 +/- 0.03 x 10(5) cells; P < 0.001). The medium from mechanically deformed cells was mitogenic for IMR-90 cells, with maximal activity in the medium from cells mechanically deformed for 2 days (stimulating cell replication by 35% compared with media control; P < 0.002). These data suggest that mechanical deformation stimulates human lung fibroblast replication and that this effect is mediated by the release of autocrine growth factors.

Biomechanical Phenomena↗
PubMed1991

Quantitative autoradiographic analysis of excitatory amino acid receptors in the cat spinal cord.

Using quantitative autoradiography, we have studied the density and distribution of N-methyl-D-aspartate (NMDA), kainate and AMPA receptors and the binding site for the sodium-dependent EAA transporter in sections from the cat spinal cord. NMDA, kainate and AMPA receptors were found in highest concentrations in laminae I and II of the dorsal horn. Lower levels of all receptors were seen in other regions of the spinal cord grey matter. The distribution of the sodium-dependent transporter was unlike that of any of the receptor populations with highest levels found in the ventral horn with slightly lower levels in other regions of grey matter. The pattern of binding sites was consistent throughout all levels of the spinal cord.

Animals↗
PubMed1991

From ethical dilemma to hospital policy. The withholding or withdrawing of artificially provided nutrition and hydration.

In 1990 St. Joseph's Hospital and Medical Center, Paterson, NJ, established a committee to create an institutional policy to facilitate the decision-making process when patients or their legally authorized surrogates request the withholding or withdrawing of artificially provided nutrition and hydration. Before drafting a policy, the committee agreed on the philosophical, ethical, and medical assumptions that would be the foundation for the policy. The group adopted nine policy assumptions and provided guidelines that address concerns common to all healthcare facilities. No policy that addresses the issue of when to withhold or withdraw life-sustaining treatment will be perfect, nor will it resolve all the complexities of such a decision. However, an imperfect policy is preferable to the absence of a policy, which can lead to an abuse of patients' rights and contribute to arbitrariness in medical decision making.

Catholicism↗
PubMed1990

Cytomatrix synthesis in MDCK epithelial cells.

Detailed information regarding the synthesis rates of individual protein components is important in understanding the assembly and dynamics of the cytoskeletal matrix of eukaryotic cells. As an approach to this topic, the dual isotope technique of Clark and Zak (J. Biol. Chem., 256:4863-4870, 1981), was employed to measure fractional synthesis rates (FSRs) in growing and quiescent cultures of MDCK epithelial cells. Cell protein was labeled to equilibrium with [14C]leucine over several days and then pulse-labeled for 4 hours with [3H]leucine. FSRs (as percent per hour) were calculated from the 3H/14C ratio of cell extracts or individual proteins separated by two-dimensional polyacrylamide gel electrophoresis and the 3H/14C ratio of free leucine in the medium. Synthesis of total cell protein rose from approximately 1.4%/hour in quiescent cells to 3.5%/hour in the growing cultures. The latter rate was sufficient to account for the rate of protein accumulation and a low level of turnover in the growing cultures. The FSR of the buffered-Triton soluble extract was higher and the cytoskeletal FSR significantly lower than that for total protein in quiescent monolayers. This difference, however, was not observed in growing cultures. A distinct pattern of differences was seen in the FSRs of individual cytoskeletal proteins in the quiescent cultures. Vimentin synthesis was significantly lower than that of the keratins and the keratin FSRs were not obviously matched in pairwise fashion. Unexpectedly, the FSRs of alpha- and beta-tubulin diverged in quiescent cells with alpha-tubulin turnover exceeding beta-tubulin. Likewise, components of the microfilament lattice showed unequal fractional synthesis rates, myosin and alpha-actinin being faster than actin. In addition, the FSR for globular actin exceeded that of the cytoskeletal associated form. The results suggest that metabolic coupling between individual cellular filament systems is not strict. The data are, however, consistent with models that predict that assembly of a subcellular structure influences the turnover of its component proteins.

Animals↗
PubMed1990

Alpha smooth muscle actin expression in developing and adult human lung.

Myofibroblast-like cells containing smooth muscle actin have been identified in lung injury and repair. These cells differ from typical smooth muscle cells by architectural configuration, location and lack of smooth muscle myosin. Their progenitors are unknown. We hypothesized that these cells might have a developmental analog critical to lung morphogenesis. Lung tissue from developing and adult human lungs was studied using a highly specific monoclonal antibody directed against alpha smooth muscle actin (ASMA). Cells immunoreactive for ASMA (ASMA cells) were identified prenatally in the form of smooth muscle investing the developing vasculature and airway structures. ASMA was not expressed in undifferentiated mesenchymal cells at any prenatal stage. Late in development, ASMA cells within the lung acinus increased proportionally to terminal airway and vascular complexity. In the early postnatal period, the specific distribution of ASMA cells within inflated lung became clearer, and three populations were identified: (1) typical smooth muscle investing the large airways and blood vessels; (2) small clusters of cells within the acinus distributed at the tips of septa protruding into the alveolar duct; (3) individual cells within the alveolar sac sparsely distributed near the junctions of individual alveoli, frequently in association with small blood vessels. We conclude that ASMA cells appear only in developing small and large airways and pulmonary vessels and that they may play a critical role in branching morphogenesis during development.

Actins↗
PubMed1990

Alveolar epithelial cell keratin expression during lung development.

Defining the expression and organization of keratins has provided insight into epithelial cell differentiation during tissue development and remodeling. We have used monoclonal antibodies to examine keratin distribution in lung epithelial cells in the rat from the preglandular phase of gestation to the adult. Of particular interest were the distributions of keratin No. 18 and keratin No. 19, since previous results have suggested these keratins may be important in alveolar epithelial cell transitions occurring in adult remodeling lung and in cultured type II cells. The epithelial tubes at 15 days of gestation do not react with 24A3 monoclonal antibody to keratin No. 18, nor is this antigen apparent by gel or immunoblot analysis. Staining is apparent at day 16, however, showing a light punctate pattern at the basal edge of the cells, and becomes prominent by day 17, with intensity greatest in the larger airway tubes. The intensity and number of cells in the parenchyma staining with 24A3 peaks at postnatal days 5 to 10, when proliferation and cytodifferentiation of type I and type II cells is most active. In the adult, staining of type II cells is present mainly at the cell periphery, and occasional reactive attenuated type I-like cells can be observed. Keratin No. 19 immunoreactivity is not present in the primitive epithelial tube until 19 days' gestation but predominantly stains type II pneumocytes in the adult rat lung throughout the entire cell. AE3 antibody to basic keratins stains similarly to keratin No. 19. We conclude that keratin No. 18 is expressed at high levels in type II cells during development in periods of intense proliferation and alveolarization. This correlates with our previous observations on keratin expression following bleomycin lung injury.

Animals↗
PubMed1990

Smooth muscle cell markers in developing rat lung.

We employed a panel of antibodies directed against cytoskeletal and contractile proteins in a developmental study to follow the differentiation and distribution of smooth muscle-like cells in the rat lung. We observed that, in the mesenchyme around developing airways and vessels, desmin replaces vimentin as the predominant intermediate filament as specialization toward smooth muscle occurs. Normally, desmin and smooth muscle myosin were expressed together in the cells and their acquisition appeared indicative of terminal differentiation of smooth muscle. In this regard, the maturation of vascular smooth muscle is delayed in the lung relative to that surrounding the developing air passages. alpha-smooth muscle actin-containing cells form a thicker coat around the primitive airway tubes and extend farther down the tree than desmin or smooth muscle myosin-positive cells. This suggests that the alpha-actin is a marker for initial differentiation of smooth muscle cells and that these cells arise from the enveloping mesenchyme. In the pseudoglandular and canalicular lung, alpha-actin-containing cells were also found in regions of epithelial tube cleft formation, suggesting an association with the process of branching morphogenesis. In addition, a large complement of alpha-actin-positive but smooth muscle myosin-negative cells were observed in the saccular interstitium during the period of secondary saccule formation and capillary reorganization that leads to final alveolarization. In summary, we note an association of smooth muscle-like, alpha-actin-containing cells with areas and periods of remodeling during normal pulmonary development. This observation may have relevance to the repair process in the adult lung.

Actins↗
PubMed1989

The enhanced association of keratin with hepatoma cell nuclei.

A monoclonal antibody to rat hepatoma keratin demonstrates a close association of intermediate filaments with the nucleus in hepatoma cells. Immunoblot analysis of nuclear fractions and immunofluorescence of nuclei both prepared by standard procedures, indicate that intermediate filament proteins are consistently present. Sodium citrate extraction of these preparations diminishes the amount of intermediate filament proteins but does not totally remove the antigenic moieties, suggesting a tight association of intermediate filaments with nuclei. The results from both immunoblot analysis and immunofluorescent localization demonstrate the increased amount of keratins associated with hepatoma cell nuclei.

Animals↗
PubMed1988

Alpha-smooth muscle actin is transiently expressed in embryonic rat cardiac and skeletal muscles.

Actin isoform expression may change during development, and in certain physiological, experimental and pathological situations. It is accepted that during sarcomeric (skeletal and cardiac) muscle development, the alpha-skeletal and alpha-cardiac isoforms of actin accumulate rapidly at the onset of muscle fibre formation, while there is a rapid fall in the expression of nonmuscle (beta and gamma) actin isoforms. Here we show that, before birth, both skeletal and myocardial cells express significant amounts of alpha-smooth muscle actin mRNA and protein. This expression is transient and disappears over the 1-7 days following birth. Our findings show that the program regulating actin isoform expression in sarcomeric muscle development is complex and that alpha-smooth muscle actin participates in this process.

Actins↗
PubMed1986

Keratin species in type II pneumocytes in culture and during lung injury.

A detailed understanding of alveolar epithelial cell transitions during remodeling after lung injury requires the identification of specific markers. We have developed a panel of monoclonal antibodies against species of the intermediate filament protein, keratin. These individual species are recognized markers of the state of differentiation of various epithelial cells. These and complementary protein analytic methods have been applied to studies of isolated, enriched Type II pneumocyte preparations as well as to normal and injured lung tissues. Monoclonal antibody 24A3, initially raised against Morris hepatoma 7777 keratins, decorated a filament network in isolated cultured rat Type II pneumocytes by indirect immunofluorescence; it reacts by 2-dimensional polyacrylamide gel immunoblot procedures with an acidic, 46,000-dalton keratin. Monoclonal antikeratin antibodies AE1 and AE3, raised against human epidermal keratins, reacted poorly with isolated Type II cells; however, AE3 reacted by immunoblot technique with the 55,000-dalton keratin subclass. The bronchial epithelium reacted intensely with 24A3 as well as with a mix of AE1 plus AE3 in ethanol-fixed, paraffin-embedded sections of normal and injured rat lung. Alveolar regions of normal lung reacted poorly with all 3 antibodies, however, as visualized by light microscopy. At the same time, very large, presumptive epithelial cells in the alveolar regions stained intensely with 24A3 3 days after intratracheal instillation of bleomycin, whereas thin cells lining the alveoli in injured regions were intensely reactive 14 days after bleomycin treatment. These elongated cells may represent Type II pneumocytes in the process of converting to Type I cells.

Animals↗
PubMed1985

Synthesis of cytoskeletal and contractile proteins by cultured IMR-90 fibroblasts.

Models of the assembly of cytoskeletal and contractile proteins of eukaryotic cells require quantitative information about the rates of synthesis of individual component proteins. We applied the dual isotope technique of Clark and Zak (1981, J. Biol. Chem., 256:4863-4870) to measure the synthesis rates of cytoskeletal and contractile proteins in stationary and growing cultures of IMR-90 fibroblasts. Fibroblast proteins were labeled to equilibrium with [14C]leucine over several days, at the end of which there was a 4-h pulse with [3H]leucine. Fractional synthesis rates (percent per hour) were calculated from the 3H/14C ratio of cell protein extracts or protein purified by one- or two-dimensional polyacrylamide gel electrophoresis and the 3H/14C ratio of medium-free leucine. The average fractional synthesis rate for total, SDS- or urea-soluble; Triton-soluble; and cytoskeletal protein extracts in stationary cells each was approximately 4.0%/h. The range of values for the synthesis of individual proteins from total cell extracts or cytoskeletal extracts sliced from one-dimensional gels was similar, though this range was greater than that for major proteins of Triton-soluble protein extracts. Three specific cytoskeletal proteins--actin, vimentin, and tubulin--were synthesized at similar rates that were significantly slower than the average fractional synthesis rate for total protein. Myosin, on the other hand, was synthesized faster than average. Synthesis rates were the same for beta-and gamma-actin and polymerized (cytoskeletal extract) vs. Triton-soluble actin. The same was true for alpha- and beta-tubulin and two different forms of vimentin. Synthesis rates were uniformly higher in growing cells, though the same pattern of differential rates was observed as for stationary cells. Synthesis rates in growing cells were higher than the rate necessary to maintain the growth rate, even for those cytoskeletal proteins being synthesized slowly. Therefore, there appears to be some turnover of these cytoskeletal elements even during growth. We conclude that proteins in cytoskeletal extracts may have nonuniform rates of synthesis, but at least one important subclass of cytoskeletal proteins that comprise filament subunits have the same synthesis rates.

Actins↗
PubMed1983

Bleomycin treatment of chick fibroblasts causes an increase of polysomal type I procollagen mRNAs. Reversal of the bleomycin effect by dexamethasone.

Bleomycin treatment of primary chick skin fibroblasts and chick lung fibroblasts resulted in a selective dose-dependent increase of cell layer procollagen synthesis. Solid support hybridization of total cellular RNA to 32P-labeled pro-alpha 1(I) and pro-alpha 2(I) cDNAs did not indicate an increase of total cellular procollagen type I mRNAs in bleomycin-treated cells. However, bleomycin treatment of chick skin fibroblasts causes a redistribution of procollagen type I mRNAs within the nuclear, cytoplasmic, and polysomal subcellular fractions. Both the nuclear and cytoplasmic procollagen type I mRNAs are significantly decreased in concentration after bleomycin administration. In contrast, the polysomal procollagen type I mRNAs are significantly increased in both chick skin and lung fibroblasts treated with bleomycin. Administration of dexamethasone to bleomycin-treated fibroblasts resulted in a reversal of the bleomycin-induced increase in cell layer procollagen synthesis. The increased amounts of polysomal procollagen type I mRNAs in bleomycin-treated cells were also reduced by subsequent administration of dexamethasone. These data indicate that bleomycin treatment of chick skin and chick lung fibroblasts results in a specific increase in procollagen synthesis in the cell layer which is mediated by elevated levels of polysomal type I procollagen mRNAs via a repartitioning of these mRNAs within the fibroblast. Furthermore, dexamethasone reverses the bleomycin-induced elevations of both cell layer procollagen synthesis and polysomal type I procollagen mRNAs.

Animals↗
PubMed1983

Dexamethasone decreases the amounts of type I procollagen mRNAs in vivo and in fibroblast cell cultures.

Dexamethasone treatment of neonatal chicks resulted in a time- and dose-dependent selective decrease of skin collagen synthesis. Total RNA of chick skin was isolated and hybridized to the cloned cDNAs pCg54 for pro-alpha 1 (I) mRNA and pCg45 for pro-alpha 2(I) mRNA. RNA isolated from the total skin of chicks receiving various doses of dexamethasone had dose-related decreases of pro-alpha 1 (I) and pro-alpha 2(I) mRNAs. The decrease of type I procollagen mRNAs for various doses of dexamethasone were similar to the decreases observed for collagen synthesis in vivo. Dexamethasone treatment of chick skin and chick lung fibroblasts resulted in a selective decrease of procollagen synthesis. A dose-related decrease of procollagen synthesis was observed with chick skin fibroblasts. Dexamethasone-treated chick skin and chick lung fibroblasts had decreased levels of pro-alpha 1 (I) and pro-alpha 2(I) mRNAs as determined by solid support hybridization with pCg54 and pCg45. The dexamethasone-mediated decreases of type I procollagen mRNAs in skin fibroblasts and lung fibroblasts were similar to the decreases observed in procollagen synthesis.

Animals↗