APOLAR EMBRYOS OF FUCUS RESULTING FROM OSMOTIC AND CHEMICAL TREATMENT

Embryos of the brown alga Fucus vesiculosas L. were grown as populations in glass petri dishes in seawater at 15 C in continuous low-intensity unilateral fluorescent illumination for periods up to 2 weeks. A quantitative estimate of increase in nuclear number was made from acetocarmine squash preparations of samples taken at 12-or-24 hr intervals. Over the period of 2-6 days embryos showed a doubling time of about 12-18 hr. Under normal seawater culture conditions each embryo formed a single rhizoid. When grown in seawater supplemented with sugar concentrations above 0.4 m , Fucus embryos developed as multicellular spherical embryos lacking rhizoids. In 0.6 m sucrose-seawater, 97% of the embryos were apolar at 2 days; only 37% were apolar at 4 days, many having recovered from the sucrose inhibition. Some embryos remained apolar after growth in 0.6 m sucrose for 2 weeks. Nuclear counts showed that sucrose-seawater markedly inhibited the rate of cell division. Other sugars including D-glucose, D-fructose, D-galactose and the sugar alcohol D-mannitol were also effective. When apolar embryos grown in sucrose-seawater were returned to seawater, embryo growth resumed at the normal seawater rate, judged from nuclear counts. Such embryos formed multiple rhizoids, varying from two to eight rhizoids per embryo, which developed on the embryo quadrant or half away from the unilateral light. Each of the multiple rhizoids originated from a single small cell in the periphery of the multicellular spherica embryo. Thus the rhizoid-forming stimulus apparently had been subdivided among a number of the cells of the apolar embryos. The implications of this finding are discussed. Attempts to produce multiple rhizoids by treatment of embryos with indoleacetic acid or 2,4-dichlorophen-oxyacetic acid failed. However, embryos treated with 10⁻⁴ M or 5 × 10⁻⁵ m 2,3,5-triiodobenzoic acid formed 40 and 30% multiple rhizoids, respectively, suggesting that some chemical, perhaps hormonal, mechanism is involved in polarization and rhizoid initiation in Fucus embryogenesis.     

Site-specific gap-misrepair mutagenesis by O4-ethylthymine

The mutagenicity of the DNA base O-alkylation adduct, O4-ethylthymine, specifically incorporated into the plasmid vector pUC8 at the unique SalI and HincII recognition sites, was studied in vivo. Escherichia coli, Micrococcus luteus and AMV DNA polymerases catalyze the incorporation of O4-ethylTMP against template adenine and guanine residues, resulting in DNA sequence alteration during subsequent replication in the host E. coli K-12 strain JM83. The greatest mutation frequency was observed with error-prone AMV DNA polymerase. High levels of cognate restriction endonuclease-resistant mutant plasmid isolates were obtained by gap replication repair in the presence of O4-ethylTTP. The yields of mutant isolates were dependent upon the relative concentration of the competing pyrimidine deoxynucleoside triphosphates, TTP and dCTP, in the misreplication reaction. Repair of incorporated O4-ethylTMP of plasmid DNA by in vitro treatment with specific alkyltransferase, prior to transformation in the host, effectively increases the mutagenic efficiency of the adduct. The results obtained are consistent with the high miscoding potential O4-ethylthymine observed in in vitro studies and its ability to base-pair with noncomplementary guanine residues in DNA.     

Complementation in Nonconidiating Mutants of Trichoderma

Nonconidiating (Con(-)) mutants were isolated from wild-type and color mutants of the fungus Trichoderma viride Pers. ex Fries. Heterokaryons were easily produced and maintained, and the complementation relationships among the Con(-) mutants were established. Most Con(-) mutants could complement one or more of the other Con(-) mutants. When marked Con(-) mutants were mixed with marked Con(+) testers, conidiating heterokaryons were formed. The conidia thus obtained produced only the parental type colonies after replating, indicating that nonconidiation is a nuclear characteristic. Allowing two Con(-) colonies to meet and produce a heterokaryon, it was found that the migration of nuclei reached a rate of 5 mm per hr, which is several times greater than the rate of hyphal elongation; it was also found that heterokaryosis of a mycelial region preceded its ability to conidiate.     

Study of the inheritance of sex expression in the cucumber. The interaction of major genes with modifying genetic and non-genetic factors

Summary Two major genes and a complex of polygenes affecting sex expression inCucumis sativus L. as well as their interaction with some nongenetic factors were investigated in the present study. The genetic factorst was found to affect sex by inducing a shift of the predetermined flowering pattern of this plant, in the direction of its base. As this pattern is composed of a staminate stage followed by a mixed (staminate-pistillate) stage and a pistillate stage, a double dose ofst will induce a change from the normal monoecious sex expression (to absolute gynoecism.The second major gene studied,m, known previously to control sex in the individual flower (m/m—andromonoecious,M—monoecious), also interacts with factors affecting the flowering pattern by inducing male tendency.Using an ordinary commercial monoecious stock additional modifying factors for sex expression were demonstrated, by eight generations of selection for high (in male direction) and for low (in female direction) node number to the first pistillate flower. A comparison of the means and frequency distributions of node number of the two selected lines, their F₁ and F₂, indicated polygenic control of this character.It was found that two non-genetic factors, day length and gibberellic acid (GA), may mimic the genetic factors for sex expression. Furthermore, evidence was presented, indicating that this sex controlling ability of GA and the modifying genes may be based on physiological conditions common to those two genetic and nongenetic factors.The overall mechanism of sex control in the cucumber and in other plants was discussed and a hypothetic model for the evolution of dioecism in flowering plants was proposed.     

Comparison of European and US biological indicators for ethylene oxide sterilization

Summary Biological indicators (BIs) are used to monitor ethylene oxide (EO) gas sterilization processes for medical devices. Several European and United States BIs for EO sterilization were evaluated for resistance according to both United States Pharmacopeia (USP) XXI and United Kingdom's (UK) tests for D-values. US BIs areB. subtilis var. niger spores on paper strips or disc carriers while European BIs use aluminum strips, quartz sand, or cotton yarn. Numerous BIs per run and runs per lot, as well as 2–3 different lots of BIs from each manufacturer, were examined. Both British and US BIs met their respective label claims for rates of inactivation when tested against British and USP EO test parameters, respectively. However, Danish BIs, on cotton yarn or quartz sand, were not inactivated following USP specifications during the exposure dwell times tested (600 mg L^–1 EO, 54°C, 60% RH, 0–110 min). The Danish BIs will require further testing in order for us to determine if theirB. subtilis spores are unusually resistant to EO or if the spore carrier substrates protect the spores from the sterilizing gas. In conclusion, the British and American BIs for EO sterilization are equivalent in resistance despite differences in carrier substrate, recovery conditions, calculation methods for D-values, and the labeled sterilization conditions for use.     

Differential effects of deuterium oxide on the growth and morphogenesis of Trichoderma viride

Trichoderma viride can be grown in deuterium oxide (D₂O) concentrationsas high as 99.7%. Increasing concentrations of D₂O (25–90%)progressively extend the lag phase in growth, but do not greatlyaffect the linear growth rate itself. The minimum age and sizeof colony required for photoinduction of the conidiation processis also increased. In 95% D₂O, although growth rates are stillrelatively high, both photomorphogenesis and dark conidiationare completely blocked. This block does not appear to involvethe photoprocess itself, but rather post photoinductive processessuch as differentiation of conidiophores. These observations point to an alternative, or at least additional,hypothesis to the one frequently cited—that D₂O acts throughstabilizing or "temperature lowering mechanisms. (Received January 6, 1978; )     

Determination of the configurations of lactic and glyceric acids from human serum and urine by capillary gas—liquid chromatography

The separation of the enantiomers of lactic and glyceric acids can be achieved by capillary gas chromatography on SP-1000 using the corresponding O-acetylated menthyl esters. The structures of the derivatives were proved by proton magnetic resonance spectroscopy and mass spectrometry. The method has been used for the determination of the absolute configurations of lactic and glyceric acids isolated from serum and urine from different patients.     

Microbiological quality of frozen cauliflower, corn, and peas obtained at retail markets.

The microbiological quality of blanched frozen cauliflower, cut corn, and peas at the retail level was determined. At 35 degrees C, mean aerobic plate count (APC) values for cauliflower, corn, and peas, respectively, were 30,000, 6,100, and 4,700 per g; at 30 degrees C, the mean APC values were 45,000, 8,500, and 6,800 per g, respectively. Geometric means for coliform, Escherichia coli, and Staphylococcus aureus counts for all three vegetables were less than 10 per g.     

Microbiological quality of some spices and herbs in retail markets.

The microbiological quality of 10 spices or herbs was determined by a national survey at the retail level. Aerobic plate count values for the 10 products ranged from less than 100 to 3.1 X 10(8) per g; mean values of the individual spices or herbs ranged from 1,400 to 820,000 per g. Coliform counts ranged from less than 3 to 1.1 X 10(6) per g; however, mean values were less than 20 per g for all products. Escherichia coli counts ranged from less than 3 to 2,300 per g. Except for celery seed, which had a mean value of 7 per g, all mean values were less than 3 per g. Yeast and mold counts were made for 5 of the 10 products. Mean values were generally low; the highest mean (290 per g) was obtained for cinnamon.     

Fast kinetics studies of Escherichia coli electrotransformation.

Direct gene transfer is achieved in Escherichia coli by use of square wave electric pulsing. As observed by video monitoring, the field pulse causes bacteria to orientate parallel to the field lines. Rapid kinetic turbidity changes indicate that this process happens quickly. In these circumstances, and in pulsing conditions prone to inducing transformation, only caps are affected by the field. Considerable cytoplasmic ion leakage occurs during the pulse, affecting the interfacial ionic concentration. The pulsing-buffer osmolarity has to be close to that used with protoplasts. Contact between the plasmid and the bacteria can be very short before the pulse but must be present during the pulse. The plasmid remains accessible to externally added DNases up to 5 days after the pulse, suggesting that the transfer step is slow. Electric-field-mediated transfer can be described in two steps: the anchoring process during the pulse, followed by the crossing of the membrane.