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Biomedical subjects

G Davis

Publications and source records attributed to G Davis.

At least 163 records · Page 9Linked to original sources
PubMed1989

Maternal brain death and prolonged fetal survival.

A 30-year-old woman suffered massive brain injuries after a motor vehicle accident at 15 weeks' gestation. The patient was diagnosed as brain-dead on her tenth hospital day. She was supported with intensive care for 107 days after this diagnosis, and a normal 1555-g male infant was delivered at approximately 32 weeks' gestation by repeat cesarean section. The child is developing normally at 11 months of age. This represents the longest reported case of prolongation of pregnancy after brain death.

Adult↗
PubMed1988

Coronary embolism following atrial septal defect repair.

To our knowledge, coronary embolism following repair of atrial septal defect has not been reported previously. A 29-year-old woman had an angiographically documented embolus to the circumflex coronary artery on the fifth postoperative day after pericardial patch repair of a secundum atrial septal defect. This complication might have been prevented by temporary postoperative anticoagulation.

Adult↗
PubMed1987

Polyamines and the synthesis of estradiol-regulated growth factors in rat mammary cancer in culture.

We have recently provided evidence to suggest that the polyamine pathway plays an essential role in the expression of the growth-promoting effect of estradiol (E2) regulated growth factors in the N-nitrosomethylurea (NMU) induced rat mammary tumor cultured in vitro in the soft agar clonogenic assay. To further explore the interaction between the polyamine pathway and autocrine control of tumor growth by E2, we tested whether, in our system, polyamines play a role in the synthesis of E2-regulated growth factors. Conditioned medium (CM) obtained from tumors treated with E2 and the polyamine biosynthesis inhibitor alpha-difluoromethyl-ornithine (DFMO) (1 mM) no longer exhibited the colony-stimulating effect which was consistently observed with E2-CM. Such growth promoting activity was restored in a dose-dependent fashion with CM obtained from tumors treated with E2, DFMO, and increasing concentrations of spermidine (from 1 to 100 microM). Conditioned medium obtained from tumors treated with DFMO with and without spermidine in the absence of E2 had no discernible effects on colony formation. The colony stimulating effect of the CM employed could not be accounted for by the contaminating presence in the media of E2, DFMO, or polyamines. These results indicate that, in our system, the polyamine pathway plays an important role in the synthesis of E2-regulated growth factors.

Animals↗
PubMed1986

The formation of plasma membrane blebs in hepatocytes exposed to agents that increase cytosolic Ca2+ is mediated by the activation of a non-lysosomal proteolytic system.

Exposure of isolated hepatocytes to extracellular ATP, cystamine or ionophore A23187 was associated with an increase in cytosolic Ca2+ concentration, a stimulation of intracellular proteolysis, and the appearance of plasma membrane blebs which preceded the loss of cell viability. Both bleb formation and cell killing were prevented when inhibitors of Ca2+-activated neutral proteases, such as antipain or leupeptin, were included in the incubation medium, whereas inhibitors of lysosomal proteases had no effect. Thus, the activation of a Ca2+-dependent, non-lysosomal proteolytic system appears to be responsible for the plasma membrane blebbing and, ultimately, the cytotoxicity associated with treatment of hepatocytes with agents that disrupt intracellular Ca2+ homeostasis.

Adenosine Triphosphate↗
PubMed1986

Myectomy of the inferior oblique muscle.

The current surgical procedures usually selected to weaken clinically overactive inferior oblique muscles are recession, disinsertion, or myectomy. A review of published reports revealed that each technique appeared to produce the intended result but that investigators differed in their choices for reasons of simplicity, quickness, and complications. Our experience indicated distal myectomy to be simple, quick, predictable, and devoid of significant complications. To affirm our impressions, 130 myectomies performed in 81 patients were reviewed. The procedure was satisfactory, although 5% had a postoperative residual overaction, and 3% had a residual underaction. No significant complications, such as the "adherence syndrome," were observed.

Esotropia↗
PubMed1986

Advances in biomedical sensor technology: a review of the 1985 patent literature.

The 1985 patent literature pertaining to biomedical sensor technology is reviewed and an assessment made of the types of devices that are most likely to reach commercialisation. Novel systems that are described comprise electrochemical, optical, thermal and other transducers for monitoring key components of clinical samples. These include blood gases and electrolytes, metabolites, enzymes, proteins, antibodies and antigens.

Biotechnology↗
PubMed1986

Promotion by prolactin of the growth of human breast neoplasms cultured in vitro in the soft agar clonogenic assay.

The role of prolactin (PRL) in supporting the growth of human breast cancer is still unclear. The ability to grow primary breast cancer specimens in the soft agar clonogenic assay in the absence of serum gave us the opportunity to evaluate the growth-promoting effect of PRL and to compare it to that of estradiol in the same tumor samples. PRL was tested both at physiological concentrations (20 ng/ml) as well as in pharmacological amounts (200 ng/ml) comparable to circulating blood levels in hyperprolactinemic states. Estradiol was simultaneously tested in physiological amounts (10(-8)M). In 17 infiltrating ductal carcinomas, the lower dose of PRL stimulated colony formation to 126 +/- 5.2% (SE) of control, while the higher dose increased colony number to 159 +/- 10.4% of control. This latter effect was comparable to that observed with estradiol (159 +/- 8.5% of control). The effect of PRL was more pronounced in estrogen receptor-positive tumors. Nine of ten estrogen receptor-positive tumors were PRL sensitive, while three of seven estrogen receptor-negative tumors exhibited a clear response to PRL administration. PRL did not stimulate colony formation in a malignant cystosarcoma phylloides and in two benign lesions (fibroadenoma and fibrocystic disease). We conclude that, at least under the conditions of the soft agar clonogenic assay, PRL exerts a dose-dependent growth-promoting effect on human breast cancer. Such effect is comparable to that of estradiol when PRL is added in concentrations similar to circulating blood levels in hyperprolactinemic patients.

Adult↗
PubMed1985

Nucleotide sequence of the alpha ribosomal protein operon of Escherichia coli.

In Escherichia coli some 19 transcription units encoding the 52 ribosomal proteins are scattered throughout the genome. One of the units, the alpha operon, encodes genes for the ribosomal proteins S13, S11, S4 and L17 as well as the alpha subunit of RNA polymerase. We report here the complete 3.0 kb nucleotide sequence of the alpha operon. In addition, we have determined by S1 nuclease mapping the site of transcription termination in this operon.

Amino Acid Sequence↗
PubMed1985

Autorepressor properties of the pi-initiation protein encoded by plasmid R6K.

A DNA fusion containing the promoter of the pir gene of plasmid R6K that encodes for the pi-initiation protein and the beta-galactosidase gene of Escherichia coli (lacZ) is described. The synthesis of beta-galactosidase promoted by this pir-lac fusion was almost completely inhibited when an R6K sequence containing the pir gene was provided in trans in E. coli. Transcription in vitro from the pir promoter but not the trp promoter of E. coli, was inhibited by purified pi protein indicating that the pi protein alone is responsible for repression of its own gene and that the effect is promoter specific. The DNA-protein interaction sites in the pir regulatory region have been determined for the pi protein and E. coli RNA polymerase using the DNase I protection method. The binding sites for these two proteins overlap for three helical turns. Competition DNA binding experiments show that the pi protein will displace bound RNA polymerase. From these studies we conclude that repression of the pir gene is accomplished by binding of the pi protein and this association blocks access of RNA polymerase to the pir promoter region.

Base Sequence↗