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Biomedical subjects

W B Anderson

Publications and source records attributed to W B Anderson.

At least 127 records · Page 7Linked to original sources
PubMed1979

Gonadotropin stimulation of cyclic AMP levels in Chinese hamster ovary cells in culture.

When Chinese Hamster Ovary (CHO) cells, incubated in serum-free medium, are exposed to gonadotropins a transient increase in the intracellular concentration of cyclic AMP is observed. Maximum accumulation of cyclic AMP is noted 30 minutes after addition of either human chorionic gonadotropin (hCG) or follicle stimulating hormone (FSH). Within one to two hours after hormone addition, the intracellular concentrations of cyclic AMP have returned to basal levels. The enhancement of intracellular cyclic AMP levels by hCG is hormone concentration dependent, with maximal stimulation observed at 10 micrograms/ml hCG. The exogenous addition of gonadotropins also slows the growth rate of CHO cells. This effect on growth seems to be mediated through cyclic AMP since the growth rate of a mutant of CHO cells defective in the catalytic subunit of cyclic AMP dependent protein kinase is only slightly decreased.

Animals↗
PubMed1979

Chinese hamster ovary cell population density affects intracellular concentrations of calcium-dependent regulator and ability of regulator to inhibit adenylate cyclase activity.

The adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] of crude Chinese hamster ovary cell membranes was inhibited 30-40% by low concentrations (6-600 ng/ml) of calcium-dependent regulator (CDR). This inhibitory effect was lost at concentrations of CDR above 600 ng/ml. The adenylate cyclase activity of membranes prepared from low population density Chinese hamster ovary cells was not appreciably altered by CDR. However, with increasing cell population density there was a significant increase in the ability of CDR to inhibit cyclic AMP formation. Further, the intracellular levels of CDR determined in the 12,000 x g supernatant and particulate fractions varied inversely with increasing cell population density. As cell number increased from 2 x 10(6) to 10 x 10(6) cells per dish the CDR concentration present in the supernatant fraction increased from 0.4 to 0.8 mug of CDR per mg of protein, while the amount of endogenous CDR associated with the particulate fraction decreased from 0.6 to 0.4 mug of CDR per mg of protein. This suggests that possible changes in the distribution of CDR between the supernatant and membrane fractions might serve as a regulatory mechanism for activities under CDR control.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1979

Increase in hormonal activation of adenylate cyclase by treatment of cultured cells with N-alkyl,N-nitrosourea.

Treatment of cultured normal rat kidney cells with the nitrosourea-containing compounds streptozotocin, chlorozotocin, or 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea resulted in a time-dependent potentiation in the ability of prostaglandin E1 and (-)-isoproterenol to elevate intracellular cAMP levels. This hormone response increased at 4 hours and reached a maximum at 15--25 hours after addition of the nitrosoureas. Basal cAMP levels were not affected. The greater response was apparently due to an increase in the GTP-dependent step in hormonal activation of adenylate cyclase, inasmuch as GTP- and GTP plus hormone-stimulated adenylate cyclase activities were enhanced twofold to threefold in crude membranes prepared from nitrosourea-treated cells. Fluoride-stimulated adenylate cyclase activity was increased only 10--25%. Nicotinamide did not prevent the elevated response, and NAD+ plus NADH levels were not appreciably altered after 42 hours; treatment with streptozotocin. The results suggest a possible involvement of cAMP in the biologic actions of nitrosoureas.

Adenylyl Cyclases↗
PubMed1978

Adenylate cyclase activity of normal and transformed fibroblasts in culture.

The intracellular concentration of cyclic AMP regulates many cellular properties of normal rat, mouse, and human fibroblasts in culture. Thus it is important to elucidate how the activity of adenylate cyclase of fibroblasts might be altered and regulated by both intracellular and extracellular agents and events. In studies with several virally transformed fibroblast lines, as well as those transformed spontaneously or by 3-methylcholanthrene, a common feature of each type of transformation is a defective adenylate cyclase system. However, the means by which adenylate cyclase activity is altered differs with the cell system and the type of transformation. Here we concentrate on efforts to understand the regulatory properties of the adenylate cyclase from normal rat kidney fibroblasts. The modulation (increase or decrease) of the hormonal responsiveness of this enzyme may play an important role in its regulation. Of substantial interest is the isolation from serum of a high-molecular weight factor that selectively decreases the GTP and hormone-stimulated activities of adenylate cyclase. These findings are of value in our attempts at elucidation of the reasons for altered cyclase activity following virus transformation and during various stages of growth.

Adenylyl Cyclase Inhibitors↗
PubMed1977

Argon laser treatment of central serous chorioretinopathy.

Thirty patients (33 eyes) with central serous chorioretinopathy were treated with argon laser photocoagulation. Visual acuity improved in 28 eyes (85%) and remained the same in 5 (15%). In all cases symptomatic improvement occurred and final visual acuity was 20/30 or better. No complications resulted from treatment. In deciding when to treat, one must consider the duration of a given episode, degree of visual impairment, visual needs of the patient, and location of the leakage site. While argon laser therapy of central serous chorioretinopathy is effective and safe, inadvertent foveal photocoagulation and intraretinal macular absorption of argon laser energy are potential therapeutic hazards.

Adult↗
PubMed1976

Guanylate cyclase and cyclic guanosine 3':5'-monophosphate phosphodiesterase activities and cyclic guanosine 3':5'-monophosphate levels in normal and transformed fibroblasts in culture.

To investigate the role of guanosine 3':5'-monophosphate (cyclic GMP) in cultured cells we have measured guanylate cyclase and cyclic GMP phosphodiesterase activities and cyclic GMP levels in normal and transformed fibroblastic cells. Guanylate cyclase activity is found almost exclusively in the particulate fraction of normal rat kidney (NRK) and BALB 3T3 cells. Enzyme activity is stimulated 3- to 10-fold by treatment with the detergent Lubrol PX. However, enhancement of guanylate cyclase by fibroblast growth factor could not be demonstrated under a variety of assay conditions. In both NRK and BALB 3T3 cells guanylate cyclase activity is low during logarithmic growth and increases as the cells crowd together and growth slows. Guanylate cyclase activity is undetectable in homogenates of NRK cells transformed by the Kirsten sarcoma virus (KNRK cells) either in the presence or absence of Lubrol PX. Guanylate cyclase activity is also greatly decreased in NRK cells transformed by Moloney, Schmidt-Ruppin, or Harvey viruses. BALB 3T3 cells transformed by RNA viruses (Kirsten, Harvey, or Moloney), by a DNA virus (SV40), by methylcholanthrene, or spontaneously, all have diminished but readily detectable guanylate cyclase activity. Cyclic GMP phosphodiesterase activity is found predominately in the soluble fraction of NRK cells. This activity increases slightly as NRK cells enter the stationary growth phase. Cyclic GMP phosphodiesterase activity is undetectable in two clones of KNRK cells under a variety of assay conditions, and is decreased relative to the level present in NRK cells in a third KNRK clone. However, both Moloney- and Schmidt-Ruppin-transformed NRK cells have a phosphodiesterase activity similar to that found in NRK cells. Boiled supernatant from both NRK and KNRK cells is observed to appreciably enhance the activity of activator-deficient phosphodiesterase from bovine heart. This result indicates that the absence of cyclic GMP phosphodiesterase activity in KNRK cells is not due to a loss of the phosphodiesterase activator. The intracellular concentration of cyclic GMP is found to be very low in transformed NRK cells when compared to levels measured in confluent NRK cells. The low levels of cyclic GMP in transformed NRK cells reflect the greatly decreased guanylate cyclase activity observed in these cells. These results do not appear to support the suggestion that cyclic GMP promotes the growth of fibroblastic cells.

Cell Line↗