Viscosity of cellular protoplasm.

The protoplasmic viscosity was studied by using a small spin label having high permeability and broad solubility properties and nickel chloride as an extracellular spin-subtracting agent to localize signal inside cells. The viscosity is variable and in some cells is many times that of water or phospholipids, suggesting that lateral diffusion in biological membranes is important to cell function.

Butylated hydroxytoluene inactivated lipid-containing viruses.

Butylated hydroxytoluene (BHT) is widely used as a food preservative for its antioxidizing property. This small, hydrophobic molecule has been found to be a potent inactivator of lipid-containing mammalian and bacterial viruses.

Interaction of divalent cations and proteins with phospholipid vesicles.

The broadening of spin-label absorption lines resulting from spin-exchange reactions that occur during collision with paramagnetic Ni2+ is diminished when Ni2+ binds to phospholipid vesicles. Subsequent addition of non-paramagnetic ions that compete for binding sites releases Ni2+ into solution and restores the line-broadening. The concentrations of various ions required to achieve this effect was used to order the ions with respect to their binding to vesicles containing phosphatidylethanolamine and phosphatidylglycerol. The relative strengths of binding for those ions studied were: Ca2+ > Mg2+ > Zn2+ > Sr2+ > Ba2+. The spin-broadening assay was also used to study the effects of two proteins on the availability of Ni2+-binding sites on the vesicles. Ribonuclease, which is thought to associate electrostatically as an extrinsic protein on the surface of vesicles, completely blocked the Ni2+-binding sites at comparatively low protein concentrations. Quantitative considerations of these data suggest the possibility that Ni2+ may bind preferenetially to phosphatidylglycerol, and that these binding sites are aggregated in the ribonuclease-containing vesicles. In contract to ribonuclease, cytochrome c does not block Ni2+-bindings sites on the phospholipid vesicles, but rather contains sites of its own that bind Ni2+, both when the protein is in solution and when it is associated with the vesicles. These results are consistent with other studies which suggest that cytochrome c becomes partially embedded in membrane bilayers and associates with phospholipid molecules through hydrophobic interactions.

Effect of lipid alkyl chain perturbations on the assembly of bacteriophage PM2.

The lipid-containing bacteriophage PM2 can produce infectious virus in cultures infected at temperatures up to 31.5 degrees C, but not at 34 degrees C. Its host, Pseudomonas BAL-31, grows at 34 degrees C and cultures infected at that temperature undergo lysis. Sucrose-gradient analysis shows that 34 degrees C lysates contain no PM2-like particles. Temperature-shift experiments establish that the thermally sensitive process is late in infection when virus assembly is taking place. Adamantanone, a small hydrophobic molecule that perturbs membrane hydrocarbon zones, prevents the production of infective virus. Concentrations which prevent virus production have no effect on host-cell growth or stability of mature virions. Adamantanone exerts its effects late in the infectious cycle, and lysates amde in its presence contain no PM2-like particles. These experiments, carried out at 25 degrees C, indicate that adamantanone prevents the assembly of stable PM2 virus. Spin-label studies suggest that the lipid alkyl chains of the host-cell membrane are in an "ordered" state at temperatures below about 33 degrees C and undergo a transition to a "disordered" state above that temperature. Furthermore, the addition of adamantanone perturbs the hydrocarbon zones, producing a greater degree of disorder even below 25 degrees C. Our findings suggest that the cell membrane can function and grow with the lipid alkyl chains in either the "ordered" or "disordered" state, but that the "ordered" state must be maintanined for PM2 assembly to occur.

Spin label evidence for the role of lysoglycerophosphatides in cellular membranes of hibernating mammals.

The phospholipid composition of ground squirrel heart muscle changes during hibernation: more lysoglycerophosphatides are found in the hibernating state than in the active state. Phase transitions inferred from spin label motion occur in the usual manner typical of mammalian mitochondria for the mitochondria and mitochondrial lipids from active squirrels. However, a conspicuous absence of a spin label-detectable phase transition is observed in equivalent preparations from hibernating animals. The addition of lysolecithin to preparations from active squirrels removes the break and induces a straight line in the Arrhenius plot. The lack of a spin label-detectable phase transition in hibernating animals, therefore, is attributed to an increased content of lysoglycerophosphatides present in the phospholipids during hibernation.

Ultraviolet mutagenesis and its repair in an Escherichia coli strain containing a nonsense codon.

Ultraviolet mutagenesis and its repair were studied mainly in WU36-10-89, a uvr(-) strain of Escherichia coli containing a UAG mutation in a gene for leucine biosynthesis. Following ultraviolet (UV) irradiation revertants appearing with or without direct photoreactivation (PR) were classified according to the presence and type of suppressor they contained. We find UV mutation production to be quite specific. An analysis of revertants produced by UV indicates they are formed mainly from GC --> AT and that the miscoding is due to a cytosine residue at the site of mutation in a cytosine-thymine (CT) dimer. We propose that the dimer serves as template during some aspects of repair replication and at the time of replication the C in the dimer directs the insertion of A in the complementary strand. We also note that C --> A and T -->G changes caused by a CT dimer occur much less frequently.

Antiproliferative effects of low-dose micronized progesterone.

OBJECTIVE: To study the pharmacodynamic effects of oral micronized P on endometrial maturation. DESIGN: This was a controlled, open, parallel group, pilot study. SETTING: The experiment was performed in an outpatient academic clinical research unit. PATIENTS: Twelve healthy, P-challenged, estrogen-primed, postmenopausal women participated in the study. INTERVENTIONS: Patients were given 300 mg micronized P daily (8:00 A.M.) or twice (8:00 A.M. and 4:00 P.M.) daily from study days 1 through 14 after estrogen priming for 30 days. Blood samples were taken at 0, 0.5, 1, 1.5, 2, 3, 4, 6, and 8 hours after the 8:00 A.M. dose on study day 1 and 14 and again at 8:00 and 9:30 A.M. on days 3 and 5 fasting, days 7 and 9 after a fatty meal, and day 11 after a high fiber meal. Endometrial biopsies were taken on day 1 and 14. MAIN OUTCOME MEASURES: Progesterone concentrations were measured. Endometrial biopsies were studied for effects on histology, glycogen content of glands, ribosomal RNA, and nuclear estrogen receptors in glands, surface epithelium, and stroma. RESULTS: Day 1 and 14 P kinetics were similar for 8 hours. Dose-dependent increases in glandular glycogen, decrease in ribosomal RNA, and decrease in nuclear estrogen receptors were demonstrated. CONCLUSIONS: Oral micronized P can induce antiproliferative changes in the human endometrium at doses lower than those required for transformation of the endometrium to a full secretory state.

Pharmacokinetics of a single dose of buccal testosterone.

The bioavailability, pharmacokinetics, and metabolism of a novel transbuccal delivery system of testosterone was investigated in five healthy eugonadal men. Total serum testosterone (T), dihydrotestosterone (DHT), and sex hormone-binding globulin (SHBG) concentrations were determined from blood samples obtained at 8:00 a.m. (zero hour), and 30 min and 1, 2, 3, 4, 6, 12 and 24 hours later on day 1, and again on day 2, after dosing. This single transbuccal administration of Buccal T induced a prompt rise in serum T and DHT concentrations. The maximal concentration (Cmax) of T was 19.56 7.64 ng/mL (mean +/- SD; 5.3-fold increase from the baseline) at< 30 min (Tmax) after administration. The elimination half-life of Buccal T was about 1.75 h. Serum DHT peaked at 1 h at a concentration of 1.46 +/- 0.46 ng/mL (2.3-fold increase from the baseline). The drug was well tolerated. This study suggests that the Buccal T is a promising delivery system for natural T.