Growth stimulation by catecholamines in plant tissue/organ cultures

Addition of catecholamines at micromolar concentrations caused a dramatic stimulation of growth of tobacco (Nicotiana tabacum) thin cell layers (TCLs) and Acmella oppositifolia “hairy” root cultures. A threefold increase in the rate of ethylene evolution was observed in the catecholamine-treated explants. Aminooxyacetic acid and silver thiosulfate, inhibitors of ethylene biosynthesis and action, respectively, reduced the growth-promoting effect of dopamine. However, these compounds alone could also inhibit the growth of the TCL explants. When ethylene in the culture vessel was depleted by trapping with mercuric perchlorate, dopamine-stimulated growth was still obtained, suggesting that ethylene does not mediate the dopamine effect. Dopamine potentiated the growth of TCLs grown in Murashige and Skoog medium supplemented with indoleacetic acid (IAA) and kinetin. When IAA was replaced by 2,4-dichlorophenoxyacetic acid, dopamine addition showed no growth-promoting effect. Instead, 2,4-dichlorophenoxyacetic acid stimulated the growth of TCL explants to the same extent as that obtained with IAA plus dopamine. Because synthetic auxins do not appear to be substrates for IAA oxidizing enzymes, we hypothesized that catecholamines exert their effect by preventing IAA oxidation. Consistent with this explanation, dopamine (25 micromolar) inhibited IAA oxidase activity by 60 to 100% in crude enzyme extracts from tobacco roots and etiolated corn coleoptiles, but had no effect on peroxidase activity in the same extracts. Furthermore, addition of dopamine to TCL cultures resulted in a fourfold reduction in the oxidative degradation of [1-¹⁴C]IAA fed to the explants. Because the growth enhancement by catecholamines is observed in both IAA-requiring and IAA-independent cultures, we suggest that these aromatic amines may have a role in the regulation of IAA levels in vivo.     

Connective tissue activation in guinea pig lung fibroblast cultures: regulatory effects of glucocorticoids

Earlier studies showed that guinea pig lung fibroblasts in cell culture could be "activated" by naturally occurring peptides with a resultant increase in glycolysis and glycosaminoglycan formation. Such connective tissue activation (CTA) in human cell systems (synovial, cartilage, dermal) has proved a useful tool for studying the mechanisms of inflammation and dissecting the efficacy and actions of anti-inflammatory drugs. The present study examined the consequences of treating basal and activated guinea pig lung fibroblasts with glucocorticoids. The data indicate that glucocorticoids minimally suppress glycosaminoglycan (GAG) synthesis in nonactivated cultures. Further, CTA was inhibited to only a minor degree in activated lung fibroblast cultures by steroids, and even markedly supraphysiologic concentrations of glucocorticoids were not notably inhibitory. It was of interest that thiols enhanced suppression of incremental GAG synthesis by some glucocorticoids in activated lung fibroblast cultures.     

Connective tissue activation in guinea pig lung fibroblast cultures: Regulatory effects of glucocorticoids

Summary Earlier studies showed that guinea pig lung fibroblasts in cell culture could be “activated” by naturally occurring peptides with a resultant increase in glycolysis and glycosaminoglycan formation. Such connective tissue activation (CTA) in human cell systems (synovial, cartilage, dermal) has proved a useful tool for studying the mechanisms of inflammation and dissecting the efficacy and actions of anti-inflammatory drugs. The present study examined the consequences of treating basal and activated guinea pig lung fibroblasts with glucocorticoids. The data indicate that glucocorticoids minimally suppress glycosaminoglycan (GAG) synthesis in nonactivated cultures. Further, CTA was inhibited to only a minor degree in activated lung fibroblast cultures by steroids, and even markedly supraphysiologic concentrations of glucocorticoids were not notably inhibitory. It was of interest that thiols enhanced suppression of incremental GAG synthesis by some glucocorticoids in activated lung fibroblast cultures. This study was supported by USPHS Grant HL-19685.     

Age-related changes in microtubules in the guinea pig organ of Corti

Biochemical and immunocytochemical analyses have been used to provide new insights into age-related changes in the sensory and supporting cells of the guinea pig organ of Corti. Quantitative densitometry of immunoblots showed that, while levels of alpha-tubulin remained relatively constant in guinea pigs from 3 weeks to 18 months old, there were progressive shifts in some tubulin isoforms. Levels of tyrosinated tubulin increased with age, nontyrosinatable tubulin (delta2-tubulin) showed a compensatory decrease, but detyrosinated tubulin did not change; acetylated, polyglutamylated, and glycylated tubulin levels also decreased. Immunolabeled tissue sections showed that cell type-specific distribution of tubulin seen in young guinea pigs (tyrosinated in the microtubules of the sensory cells, and post-translationally modified isoforms in the supporting cells) did not change as animals aged. However, there were age-related decreases in labeling for alpha-tubulin and all post-translationally modified isoforms. Biochemical and immunocytochemical results both support an age-related decrease in the number and/or length of microtubules as well as an increase in the pool of soluble tyrosinated and detyrosinated tubulin. They further suggest that microtubules containing nontyrosinatable tubulin from older animals are the sites for further modification of tubulin by acetylation, polyglutamylation, and glycylation. Changes in tubulin isoform levels and stability of microtubules in the organ of Corti may alter its micromechanical properties; the resulting changes in conduction of sound-induced vibration would provide one mechanism for age-related hearing loss.     

Development of a guinea pig colony free of complement-fixing antibodies to parainfluenza virus.

Complement-fixing antibodies to parainfluenza 3 virus were found in Hartley strain [Cds: (HA)] guinea pigs from the authors' production colony. The prevalence and distribution of these antibodies were determined by testing guinea pigs of five age categories: 4 weeks, 8 weeks, 12 weeks, 6 months to 1 year, and over 1 year of age. Forty-seven percent (28 of 60) were positive to parainfluenza 3 antigen. Positive reactors were found in all age groups except those 8 weeks old. The 12-week-old group had the highest titers; the group over 1 year of age had the highest percentage of positives (92%). When 8-week-old guinea pigs were isolated, 55% were positive at some time between 8 and 34 weeks of age. The titers characteristically rose rapidly and then dropped slowly to low or undetectable levels. Four pairs of breeders over 6 months of age (most of whom were positive for parainfluenza 3 virus antibodies and, therefore, presumed to be immune to the virus) were isolated and allowed to breed. Their offspring were found to be free of complement-fixing antibodies to parainfluenza 3 virus.     

Bone tissue formation in organ cultures of human bone marrow

Bone formation in adult human bone marrow organ cultures is described. When culturing marrow fragments, thick bone lamina is formed. It has well-mineralized trabecular bone matrix with bone cells incorporated and is lined with osteoblast-like cells. In cultures of marrow deaggregated cell suspensions thin layers of the bone are only formed. Osteoclast-like cells develop in the cultures.     

Characterization of bovine parainfluenza virus type 3.

Bovine parainfluenza virus type 3 (PIV-3) has a buoyant density of 1.197. The RNA of PIV-3, like that of Sendai virus, is a single continuous chain which lacks polyadenylic acid sequences and tends to self-anneal to a marked extent. It has a sedimentation coefficient of 42S and a molecular weight of 4.5 X 10(6), being slightly smaller than Sendai virus RNA (47S, 5.3 X 10(6)). PIV-3 has 5 main structural proteins, of which 2 are glycoproteins. The molecular weights of protein 1, protein 2, protein 3, glycoprotein 1, and glycoprotein 2 were estimated to be 79,000, 68,000, 35,000, 69,000, and 55,000, respectively. Protein 2 was suggested to be nucleocapsid protein.     

Heterogeneity of beta-adrenoreceptors in guinea pig alveolar type II cells

[3H]Dihydroalprenolol ([3H]DHA) binding to guinea pig alveolar type II cell membrane revealed the presence of both high (KD = 0.38 nM) and low (KD = 4.2 nM) affinity beta-adrenoreceptors. The low affinity site had a higher binding capacity (Bmax = 245.6 fmol/mg protein) than the high affinity site (Bmax = 71.7 fmol/mg protein). Displacement of [3H]DHA by practolol, a selective beta 1 agent, confirmed the existence of two species of adrenoreceptors, corresponding to 21% high affinity (beta 1) and 79% low affinity (beta 2), respectively.