Biomedical subjects

H Halvorson

Publications and source records attributed to H Halvorson.

13 recordsLinked to original sources

PubMed1989

Cyclic and sequential therapy with tamoxifen and medroxyprogesterone acetate in metastatic breast cancer.

A clinical trial of sequential tamoxifen and medroxyprogesterone acetate (MPA) was carried out in 36 women with metastatic breast cancer in order to evaluate the therapeutic efficacy of this regimen and to determine if tamoxifen would increase progesterone receptor (PR) levels and thereby increase response to MPA. Fourteen patients (39%) responded to this treatment, with the duration of remission ranging from 2 to 24 + months (the mean and median were 11 months). In 22 patients, PR levels were measured both before and after 7 days of tamoxifen administration. In PR-positive patients, PR changes induced by tamoxifen did not appear to increase the response rate. In PR-negative patients, PR became positive in 3 patients following tamoxifen treatment, with 2 of 3 responding to treatment, whereas in 11 others whose PR levels remained negative, only one response was observed. Our results suggest that potentiation by tamoxifen was not observed, since in our previous study, MPA alone was equally effective. Thus, tamoxifen and MPA should be given independently for palliation of metastatic breast cancer, and MPA should be administered following therapy with tamoxifen.

Adult↗

PubMed1989

Low brain magnesium in migraine.

Brain magnesium was measured in migraine patients and control subjects using in vivo 31-Phosphorus Nuclear Magnetic Resonance Spectroscopy. pMg and pH were calculated from the chemical shifts between Pi, PCr and ATP signals. Magnesium levels were low during a migraine attack without changes in pH. We hypothesize that low brain magnesium is an important factor in the mechanism of the migraine attack.

Adult↗

PubMed1989

Low brain magnesium in migraine.

Adult↗

PubMed1987

Effect of growth conditions on levels of components of the phosphoenolpyruvate:sugar phosphotransferase system in Streptococcus mutans and Streptococcus sobrinus grown in continuous culture.

The membrane-bound, sugar-specific enzyme II (EII) component of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) in Streptococcus mutans Ingbritt is repressed by growth on glucose under various conditions in continuous culture. Compared with optimal PTS conditions (i.e., glucose limitation, dilution rate [D] of 0.1 h-1, and pH 7.0), EII activity for glucose (EIIGlc) and mannose (EIIMan) in cells grown at a D of 0.4 h-1 and pH 5.5 with the same glucose concentration was reduced 24- to 27-fold. EII activity with methyl alpha-glucoside and 2-deoxyglucose was reduced 6- and 26-fold, respectively. Growth with excess glucose (i.e., nitrogen limitation) resulted in 26- to 88-fold repression of EII activity with these substrates. The above conditions of low pH, high dilution rate, and excess glucose also repressed EII activity for fructose (EIIFru), but to a lesser extent (two- to fivefold). Conversely, growth of S. mutans DR0001 at a D of 0.2 h-1 and pH 5.5 resulted in increased EIIGlc and EIIMan activity. Unlike the EII component, the HPr concentration in S. mutans Ingbritt varied only twofold (5.5 to 11.4 nmol/mg of protein) despite growth at pH 5.5 with limiting and excess glucose. The HPr concentrations in S. mutans DR0001 and the glucose-PTS-defective mutant DR0001/6 were similar. In a companion study, the soluble components of the PTS (i.e., HPr, EI, and EIIILac) in Streptococcus sobrinus grown on limiting lactose in a chemostat were not influenced significantly by growth at various pHs (7.0 and 5.0) and growth rates (D of 0.1, 0.54, and 0.8 h-1). However, growth on lactose resulted in repression of both EIIGlc and EIIFru, confirming earlier results with batch-grown cells. Thus, the glucose-PTS in some strains of S. mutans is regulated at the level of EII synthesis by certain environmental conditions.

Glucose↗

PubMed1974

Comparison of butyric type of fermentation in sporogenic and asporogenic mutants of Clostridium botulinum.

Glucose-adapted cells of a sporogenic mutant. MSp(+), and an asporogenic mutant, RSpoIIIa, of Clostridium botulinum type E rapidly fermented glucose, fructose, maltose, and sucrose, resulting in cytoplasmic granulation, heavy growth, a pH of <6.0, and sporulation of the MSp(+) mutant ranging from 60 to 80%. In Trypticase peptone glucose broth, the MSp(+) mutant formed >80% refractile endospores in 25 h, whereas the RSpoIIIa mutant which was blocked at early forespore stage had commenced to lyse. Both mutants accumulated acetate and intracellular granules, reaching maximal levels at early stationary phase of growth. In MSp(+), as the levels of acetokinase, phosphotransacetylase, and butyryl-coenzyme A dehydrogenase reached a maximum, butyrate accumulation continued concurrently with an increase of endospore formation, whereas the levels of poly-beta-hydroxybutyrate decreased simultaneously with its precursor, acetate. Butyrate biosynthesis was blocked in the asporogenic mutant. As shown by isotopic assays, butyrate and acetate serve as precursors of spore lipids. beta-Phenethyl alcohol, fluoroacetic acid, and 2-picolinic acid inhibited anaerobic sporogenesis almost completely, butyrate biosynthesis by >87%, and acetate accumulation by 50 to 62%, showing a direct relationship between butyric type of fermentation and anaerobic sporulation.

Acetates↗

PubMed1972