An isoelectric focusing study of plasma membrane actin.

Plasma membranes were purified from secondary chick embryo fibroblasts labeled with [³⁵S]methionine for 1 or 18 h. The total cell homogenate, postnuclear supernatant and plasma membrane fractions were analyzed by two-dimensional electrophoresis (isoelectric focusing followed by SDS-slab gel electrophoresis). The α, β, and γ isoelectric variants of actin were present in similar proportion in membranes, supernatant, and cell homogenate as determined by incorporation of ³⁵S into each species of actin. These results indicate that the plasma membrane actin of chick fibroblasts is heterogeneous and that no isoelectric variant of actin is unique to the plasma membrane.     

High Numbers of Prosthecate Bacteria in Pulp Mill Waste Aeration Lagoons

Prosthecate bacteria comprised 0.6 to 10.5% of the bacterial community in samples from 11 pulp mill waste aeration lagoons. Because of their distinct morphology, the genera Ancalomicrobium, Caulobacter, Prosthecobacter, Prosthecomicrobium, Stella, and Hyphomicrobium or Hyphomonas could be identified and enumerated by direct microscopic examination. Monthly samples from one lagoon showed that several genera varied from undetectable to predominant among the appendaged organisms. Temperature (season), type of wood pulped, and pulping process did not significantly affect the density of prosthecate bacteria.     

Schistosoma mansoni: Cytotoxicity of hemocytes from susceptible snail hosts for sporocysts in plasma from resistant Biomphalaria glabrata

Sporocysts of Schistosoma mansoni (PR1 strain) survive and grow in Biomphalaria glabrata PR albino strain snails, whereas they are encapsulated and die in B. glabrata 10R2 strain snails. These processes also occur in an in vitro system in which the only living cells are those of sporocysts and snail hemolymph. Hemocytes of the susceptible snail are normally not effective in damaging sporocysts. However, when the encounter occurred in the presence of cell-free plasma from resistant snails, previously impotent hemocytes severely damaged sporocysts in 24 hr. The cytotoxic capacity of resistant strain hemocytes was not altered by plasma from susceptible snails. Furthermore, it was retained even when plasma was replaced by culture medium free of snail components. The nature of the plasma factor(s) which facilitated damage by otherwise impotent hemocytes is discussed, and evidence is evaluated for the hypothesis that snail resistance is dependent upon the specificity of cytophilic factors present both in the plasma and on the hemocyte plasma membranes.     

Inhibition of dihydropteridine reductase by dopamine

Dihydropteridine reductase has been purified 900-fold from rat liver. Dopamine inhibited the enzyme up to 50% at a concentration of 0.11mm. In the presence of dopamine the enzyme gave non-hyperbolic v-against-[S] plots. This enzyme may have a role in control of dopamine biosynthesis.     

CORRECTION OF THE NAME PSEUDOTETRAÉDRON POLYMORPHUM (CHLOROPHYCEAE)1

A unicellular chlorococcalean alga, Pseudotetraëdron polymorphum MacEntee, Bold & Archibald is renamed Chlorotetratëdron polymorphum (MacEntee, Bold & Archibald) MacEntee, Bold & Archibald became the former generic designation has been preempted by a xanthophycean alga.     

The potential of an equimolar combination of propane-1,2-diol and glycerol as a vitrification solution for corneas

Corneas must first be equilibrated with multimolar concentrations of cryoprotectants if the formation of ice during cryopreservation is to be avoided by vitrification at practicable cooling rates. Rabbit corneas were exposed to equimolar mixtures of the cryoprotectants propane-1,2-diol and glycerol in a Hepes-buffered Ringer's solution containing glutathione, adenosine, 5 mmol/liter sodium bicarbonate, and 6% w/v bovine serum albumin. Endothelial function was assessed by monitoring its ability to control stromal hydration during perfusion of the endothelial surface at 34 degrees C for 6 h. Endothelial morphology was observed by specular microscopy during perfusion and by scanning electron microscopy after perfusion. Endothelial pump activity and structural integrity of the endothelial layer were demonstrated after 20 min exposure at 4 degrees C to a total concentration of 1.4 mol/liter cryoprotectant (i.e., 0.7 mol/liter propane-1,2-diol + 0.7 mol/liter glycerol). Exposure to 2.0 and 3.4 mol/liter cryoprotectant for 20 min at 4 degrees and -5 degrees C, respectively, resulted in initial endothelial damage; but this repaired and a functioning endothelial pump was subsequently demonstrated. Although exposure to 4.1 mol/liter cryoprotectant for 10 min at -10 degrees C caused irreparable damage to 2/4 corneas, reduced dilution temperatures together with increased dilution time allowed exposure to 4.8 and 5.5 mol/liter cryoprotectant with retention of endothelial pump activity. Exposure to 6.1 mol/liter cryoprotectant for 10 min at -15 degrees C caused endothelial damage which was not mitigated by the presence of 2.5% w/v chondroitin sulfate. Endothelial function may be improved by further modification of addition and dilution protocols or by exposure to the cryoprotectants at lower temperatures.     

Corneal tolerance of vitrifiable concentrations of propane-1,2-diol

The merit of corneal cryopreservation by vitrification as opposed to conventional freezing is the avoidance of ice damage which is believed to disrupt the integrity of the corneal endothelium resulting in loss of corneal transparency. The cornea must be equilibrated with high concentrations of cryoprotectant in order to achieve vitrification at practicable cooling rates. In an earlier study, corneas were exposed to 3.4 mol/liter propane-1,2-diol (Rich and Armitage (1990) Cryobiology 27, 42-54). The present study exposed rabbit corneas to concentrations of propane-1,2-diol between 3.4 and 5.4 mol/liter in a Hepes-buffered Ringer's solution containing glutathione, adenosine, 5 mmol/liter sodium bicarbonate, 6% (w/v) bovine serum albumin, and 2.5% (w/v) dextran sulfate. Dextran sulfate was as effective as chondroitin sulfate at improving endothelial tolerance of 3.4 mol/liter propane-1,2-diol. This beneficial effect may be linked to the polyanionic nature of these molecules. Corneas exposed to 5.4 mol/liter propane-1,2-diol were cooled in liquid nitrogen vapor at a temperature of -140 degrees C for 2 h. Warming was achieved by direct transfer to a dilution solution at -10 degrees C. Endothelial function was assessed by monitoring corneal thickness during perfusion of the endothelial surface at 34 degrees C for 6 h. Endothelial structure was observed by specular microscopy during the perfusion and by scanning electron microscopy after perfusion. Corneas tolerated exposure to 3.4 mol/liter propane-1,2-diol for 20 min at 0 degrees C and to 4.1 mol/liter for 10 min at -10 degrees C. Exposure to 4.8 and 5.4 mol/liter for 10 min at -10 degrees C caused endothelial damage, although a degree of endothelial function was retained. Function following exposure to 5.4 mol/liter was improved by reducing the temperature of exposure to -15 degrees C. Corneas cooled after exposure to 5.4 mol/liter propane-1,2-diol for 10 min at -15 degrees C apparently vitrified, but devitrified on warming. The corneas swelled to such an extent during perfusion that the endothelium could not be viewed by specular microscopy, subsequent scanning electron microscopy showed a severely disrupted endothelium.     

Purification and characterization of recombinant Pneumocystis carinii thymidylate synthase

Gatalytically active Pneumocystis carinii thymidylate synthase is expressed to the extent of about 4% of the soluble protein in Escherichia coli χ2913 harboring plasmid pUETS-1.8 (U. Edman, J. C. Edman, B. Lundgren, and D. V. Santi, Proc. Natl. Acad. Sci. USA 86, 6503–6507, 1989). Ion-exchange, affinity, hydrophobic, and reactive dye agarose chromatography steps were explored to devise a large-scale purification protocol for P. carinii thymidylate synthase. Sequential DE52, Q-Sepharose, phenyl-Sepharose, and Cibacron Blue F3GA chromatography yielded enzyme that was homogeneous by SDS-PAGE in a yield of over 50%. The sequence of the first 10 amino acid residues of the purified protein was in accord with that predicted from the DNA sequence. Isoelectric focusing gave a pI of 6.2. Kinetic analysis of the purified enzyme revealed that the the K_m values were 4.7 ± 1.3 μM for dUMP and 15.7 ± 4.3 μM for 5,10-methylenetetrahydrofolate, similar to those of many other thymidylate synthases; the κ_cat of the most active preparation was 0.8 s⁻¹. The enzyme is stable for at least 2 months when stored at −80°C in the presence of 40% glycerol, Tris-HCl, and thiol.     

Sustained effects of biofeedback-assisted relaxation therapy in essential hypertension

The usefulness of biofeedback-assisted relaxation as an adjunct or substitute for pharmacotherapy in essential hypertension can be enhanced if the effects are shown to persist after formal treatment has ended. Patients with essential hypertension successfully treated with biofeedback-assisted relaxation were recalled for follow-up yearly after the termination of treatment. Twenty-six of 40 patients met the BP criterion for success. At one-, two-, and three-year follow-up, 31%, 38%, and 27% of the successful completers continued to meet the criterion for success. The pretreatment-posttreatment decreases in BP were accompanied by decreases in forehead muscle tension and urinary cortisol. Forehead muscle tension, urinary cortisol, and anxiety levels were significantly lower than pretreatment one year after the end of treatment. Self-report data were used to assess continued relaxation practice. No relationship was found between practice and any other dependent measure. It appears that some patients trained in biofeedback-assisted relaxation can maintain lowered blood pressure, muscle tension, anxiety, and cortisol levels over the long term; however, the role of relaxation practice in maintaining these lowered levels remains unclear.