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Biomedical subjects

A M Douglas

Publications and source records attributed to A M Douglas.

15 recordsLinked to original sources
PubMed2001

Oncostatin M and leukemia inhibitory factor regulate the growth of normal human breast epithelial cells.

We have previously reported the inhibitory effects of oncostatin M (OSM) and leukemia inhibitory factor (LIF) on the proliferation of breast cancer cell lines. In this study, we examined the action of OSM and LIF on normal, non-malignant human breast epithelial cells (HBECs). We demonstrated expression of three components of the OSM receptor; gp130, the leukemia inhibitory factor receptor (LIFRbeta) and the OSM specific receptor (OSMRbeta). Treatment of the normal HBECs with OSM and LIF resulted in inhibition of proliferation, even in the presence of the breast mitogen, epidermal growth factor (EGF), which is required for HBEC growth. The inhibition was associated with a reduction of cells in the S-phase of the cell cycle and an accumulation of cells in G0/G1. These results suggest a previously unrecognised physiological role for these growth factors in the regulation of normal breast epithelium.

Antigens, CD↗
PubMed1998

Oncostatin M induces the differentiation of breast cancer cells.

We have recently described the action of Oncostatin M (OSM) to inhibit the proliferation of breast cancer cells. In this study we examined the action of OSM on 2 breast cancer cell lines to further characterize the nature of OSM inhibition of cellular proliferation. Treatment with OSM for 6 days resulted in an approximately 2- to 5-fold decrease in cell number, which was independent of estrogen receptor status. Consistent with this, colony formation was reduced to approximately 50% when cells were exposed to OSM in primary agar cultures. Clonogenicity was further inhibited following 7 days treatment with OSM in monolayer cultures: the total number of clonogenic cells was suppressed approximately 10-fold. Analysis of cell cycle status in OSM-treated cells demonstrated a 40% reduction in the proportion of cells in S phase within 12 hr, with an increase in cells in G0/G1. After 6 days, there was a 10-fold reduction in the absolute number of cells in S phase in OSM-treated cultures. These changes were associated with striking changes in cellular morphology, including disruption of intercellular junctions and the production of lipid droplets. There was a 5-fold increase of c-fos and c-myc mRNA within 30 min of commencing treatment with OSM. In addition, in the ER positive cells there was a decrease in ER mRNA (evident within approximately 2 hr) and ER protein expression following treatment with OSM. Conversely, there was a 5-fold increase in epidermal growth factor receptor (EGFR) mRNA within 4 hr, and a 2.5-fold rise in mRNA for transforming growth factor alpha (TGF alpha). Thus, the inhibition of breast cancer cells by OSM was associated with decreased clonogenicity, a decrease in S phase cells and a variety of phenotypic changes, all consistent with the induction of differentiation.

Antineoplastic Agents↗
PubMed1997

Expression and function of members of the cytokine receptor superfamily on breast cancer cells.

Receptors for the cytokines leukemia inhibitory factor (LIF), interleukin-6 (IL-6), oncostatin M (OSM), ciliary neurotrophic factor (CNTF) and interleukin-11 (IL-11) are members of the structurally conserved hemopoietin receptor superfamily. In addition, they all share the transmembrane signalling protein gp130. In this paper the expression and function of this family of receptors in breast cancer cells was examined. RT-PCR analyses demonstrated that gp130 was expressed in 12/12 breast cell lines and the specific receptor alpha-chains for IL-6, LIF, IL-11 and CNTF were expressed in the majority of these cell lines. This was in contrast to other hemopoietin receptors. Examination of 50 clinical samples of malignant breast tissue by RT-PCR showed a similar pattern of expression of gp130 associated receptors. Treatment of breast cancer cell lines with OSM resulted in changes in cellular morphology. Cellular proliferation was inhibited following exposure to OSM (3/4 cell lines), IL-11 (2/4 cell lines), and by IL-6 and LIF (1/4 cell lines). Cell surface binding of LIF and OSM was also documented. The expression of these receptors in 12/12 cell lines and greater than 95% of clinical samples suggests that these molecules may be important in regulating the growth of breast cells.

Base Sequence↗
PubMed1993

Direct sequencing of double-stranded PCR products incorporating a chemiluminescent detection procedure.

A simple and reliable method is described for direct sequencing of material generated by the polymerase chain reaction (PCR). Sequencing reactions can be performed directly on PCR products without the need for purification of the template by removal of residual deoxyribonucleoside triphosphates or primers. The coupling of a chemiluminescent detection system with the use of the same primers in the initial and sequencing PCR's allows for sequencing of a number of PCR products on the one gel.

Biotechnology↗
PubMed1992

Purification of human leucocyte DNA: proteinase K is not necessary.

A rapid nontoxic method for the purification of DNA from human leucocytes is described. Preliminary experiments which tested different methods of DNA purification indicated that digestion of proteins with proteinase K was unnecessary. This led to the development of a simple procedure involving lysis of the cells in SDS followed by extraction with 6 M NaCl. The method described overcomes the requirement for lengthy incubations in the presence of expensive proteinase K and subsequent extraction with toxic chemicals.

DNA↗
PubMed1983

Low calcium reperfusion of ischemic myocardium.

The mechanisms underlying protection of ischemic myocardium by reperfusion with solutions containing reduced concentrations of calcium (CA) were studied in isolated vascularly perfused rabbit interventricular septa at 37 degrees C. After 45 min of total ischemia adenosine triphosphate (ATP), and phosphocreatine (PC) contents fell to 6.8 +/- 0.82, and 12.4 +/- 2.0 micrometer/g dry tissue (dt) (+/- S.E.M.). After 5 min of reperfusion with 0.75 mM Ca these values had recovered significantly to 10.3 +/- 1.0, and 33.3 +/- 3.6, (micrometer/g dt), while reperfusion with 2.5 mM Ca produced 5.9 +/- 1.0 and 22.0 +/- 2.6 (micrometer/g dt). The significantly greater recovery of ATP and PC after 0.75 mM Ca reperfusion persisted after an additional 25 min of reperfusion with 2.5 mM Ca when compared to septa reperfused for the entire 30 min with 2.5 mM Ca. When mechanical work was reduced by cessation of stimulation during the first 5 min of reperfusion, ATP, PC and total creatine (TC) recovery were significantly improved in muscles exposed to 2.5 mM Ca but showed no additional improvement in muscles reperfused with 0.75 mM Ca. A further reduction to 100 micrometers Ca reperfusion in quiescent muscles did significantly improve ATP, PC and TC recovery. Quiescence achieved with 16.0 mM K impaired ATP, PC and TC recovery. This effect was reversed by 100 micrometers CA reperfusion. Measurements of mitochondrial oxygen consumption, respiratory control and ADP/O showed results parallel to the ATP, PC and TC determinations. Both mechanical work and CA itself influence mitochondrial respiration, ATP, PC and TC content after ischemia. As previously demonstrated for mechanical function, metabolic recovery can be improved by interventions limited to the first 5 min of reperfusion.

Adenosine Triphosphate↗
PubMed1977

42K exchange during myocardial ischemia.

42K exchange was studied before and after total ischemia in isolated, blood-perfused rabbit interventricular septa at 37 degrees C and 72 beats/min. Of 11 septa made ischemic for up to 45 min after 42K labeling to asymptotic values, 10 showed no decline in 42K as measured by tissue probe counts 5 min after reperfusion. Of these 10 septa, 7 showed a 1.4-14.2% increase in 42K counts on reperfusion. Three of four muscles reperfused after 60 min of ischemia showed progressive 42K losses. Of 14 septa previously labeled with 42K, 9 showed a parallel decrease in 42K-exchange rate constants as measured by tissue probe and effluent during washing out after 2-45 min of ischemia. In five other muscles a nonparallel decrease in rate constants as measured by tissue probe and effluent during washout indicated inhomogeneity of 45K exchange. These results indicated no persistent impairment in Na pump activity for 30-45 min of total ischemia. After ischemia for 45 min or less there was no consistent relationship between recovery of mechanical function and preservation of 42K content. After 60 min of ischemia, irreversible mechanical injury was associated with loss of tissue potassium.

Animals↗
PubMed1976

Ischemia in isolated interventricular septa: mechanical events.

Isolated blood-perfused rabbit interventricular septa were adapted for studies of global ischemia by enclosure in a constant-humidity nitrogen atmosphere. During ischemia, developed tension (DT) and maximal rate of relaxation (-dP/dt) declined monoexponentially, lambda = 0.39 min-1 at 37 degrees C and 72 beats/min with a Q10 of 1.4 for DT and a Q10 of 1.9 for -dP/dt. After a 60- to 90-s delay the maximal rate of tension development (+dP/dt) declined at the same rate as DT. Time-to-peak tension (TPT) shortened immediately with ischemia but action potential duration shortened after 60-90 s. Calcium at a concentration of 5 mM slowed the rate of decline of +dP/dt to lambda = 0.26 min-1. Upon reperfusion after 10 min of ischemia the rates of recovery of DT, +dP/dt, and -dP/dt were similar, lambda = 0.21-0.23 min-1, and were not temperature dependent. The magnitude of recovery was 10-17% less at 37 degrees C than 28 degrees C. Potassium at a concentration of 10 mM did not alter the rate of decline of mechanical function, but significantly (P less than 0.01) increased the magnitude of mechanical recovery. The results suggest depletion and/or repletion of single compartments as the rate-limiting steps in ischemia and reperfusion.

Action Potentials↗
PubMed1975

Magnesium effects in rabbit ventricle.

Ten to twenty millimoles per liter Mg did not affect 42-K exchange in control isolated blood-perfused rabbit septa, but abolished acetyl strophanthidin (ACS)-induced net 42-K loss (constant heart rate) without attenuating the mechanical response. In six septa ACS-induced net K loss was reduced from 159.3 plus or minus 45 to 43.5 plus or minus 35 mumol/kg tissue water (P smaller than 0.05) by increasing Mg from 1.0 to 20 mM without a change in inotropic response. Ten to twenty millimoles per liter Mg did not reverse ACS inhibition of 42-K5 tissue uptake. In eight septa 16 mM K doubled the efflux rate for 42-K in 1mM Mg. Twenty millimoles per liter Mg abolished this effect. Sixteen millimoles per liter K increase 42-K effluent counts by 99.5 plus or minus 18.5 percent of control in 1.0 mM Mg, but by 44.9 plus or minus 14.1 percent (P smaller than 0.001) in 20 mM Mg. Mg inhibited 42-K exchange at sites that became rate limiting after ACS treatment. These sites were activated by 16mM K. ACS inotrophy was not quantitatively related to net K loss. The Mg effect during digitalis exposure did not result from reversal of ACS inhibition of NA-K-ATPase activity but from a separate effect on K efflux.

Action Potentials↗