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A procedure has been developed for the cryopreservation of wheat female gametes. The procedure involves loading the cells with 25% concentrated vitrification solution consisting of 30% glycerol, 10% sucrose, 120 mM ascorbic acid (AA) and 5% propylene glycol (PG), dehydration in 80% concentrated vitrification solution, droplet vitrification and storage in liquid nitrogen, unloading and rehydration of the cells by gradual addition of isolation solution. Supplementation with AA significantly increased the proportion of viable egg cells after deand rehydration. During the early phase of rehydration AA reduced the probability of membrane damage caused by rapid water uptake. Maintaining the temperature of the cells at 0℃ during the de- and rehydration processes increased cell survival. Microscopic examination of the semi-thin sections of untreated and viable cryopreserved cells revealed that the vitrification process might cause changes in cell structure.
Although the record of Paleozoic drillholes is long and extensive, evidence pertaining to the identity of the drillers is sparse. The most conclusive evidence, a driller “caught in the act”, has been documented only once (Baumiller 1990). In that example, a drillhole in the calyx of a crinoid was found directly beneath an attached platyceratid gastropod. Additional evidence for drilling by platyceratids has been circumstantial, i.e., based on the association of platyceratids with certain blastoids and crinoids, and the presence of drillholes in other crinoid and blastoid taxa. To a skeptic, the lack of congruence between drilled and platyceratidinfested crinoids and blastoids is not sufficient evidence that platyceratids were the drillers. More conclusive evidence requires examples of drillholes in taxa that are known to have been platyceratid−infested, preferably from localities where both infested specimens and drilled specimens co−occur.
Hyperhomocysteinemia is reported to be an independent risk factor for the development of ischemic stroke. Several studies on genetic variants of methylenetetrahydrofolate reductase (MTHFR, which plays a crucial role in regulation of plasma homocysteine concentration) reported an association between C677T gene polymorphism and stroke in some Asian populations. No study but one detected this association in Caucasians. The purpose of the present case-control study was to find a relationship between MTHFR genotypes and stroke in a Polish population. MTHFR genotypes were determined by PCR in 152 patients with ischemic stroke from northwestern Poland and in 135 consecutive newborns from the same population. The TT genotype and the T allele were significantly more frequent in patients than in the control group (11.8% vs. 4.4%, and 34.5% vs. 21.5%, P < 0.01). When males and females were analyzed separately, the differences were statistically significant in both genders. It is concluded that presence of the T allele is a risk factor for ischemic stroke in Polish subjects.
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