The search for a reliable mounting medium for Recent ‘live’ foraminifera

There is no suitable mounting medium for the long term storage of Recent ‘live’ foraminifera. Glycerol has been used for this purpose since the last century, but its properties do not meet our requirements (see below). We therefore began a series of trials in order to find the ‘perfect’ mountant. The inception of this “Micropalaeontological Notebook” provides a timely opportunity to highlight the results of our experiments and to elicit a response from the readership to facilitate our search.In choosing mounting media for experiment it was first necessary to detail our requirements. The latter are as follows: the medium must be clear and possess a refractive index (nD) close or equal to that of glass. The nD of the mounted specimens should differ from that of the mountant or they will be invisible. It should function as a permanent mount, fixing specimens in a position suitable for light microscopical examination. It should not form aggregations or induce overlap of specimens and should permit easy relocation of small organisms (i.e., fixing them so that their co-ordinates can be read with an England Finder). It should neither be messy nor aspirate air and should not contract, thereby crushing delicate specimens. The mountant must be treated to inhibit bacterial and fungal growths. It must be relatively inexpensive and quick to prepare and must not solidify too rapidly, leaving insufficient time to position specimens. Since the specimens are ‘live’ it is important that the protoplasmic contents of the cell auld the mountant are. . .

The search for a reliable mounting medium for Recent ‘live’ foraminifera

There is no suitable mounting medium for the longterm storage of Recent, ‘live’ foraminifera. Glycerol has been used for this purpose since the last century, but its properties do not meet our requirements (see below). We therefore began a series of trials in order to find the ‘perfect’ mountant. The inception of this ‘Micropalaeontological Notebook’ provides a timely opportunity to highlight the results of our experiments and to elicit a response from the readership to facilitate our search.In choosing mounting media for experiment it was first necessary to detail our requirements. The latter are as follows: the medium must be clear and possess a refractive index (nD:) close or equal to that of glass. The nD of the mounted specimens should differ from that of the mountant or they will be invisible. It should function as a permanent mount, fixing specimens in a position suitable for light microscopical examination. It should not form aggregations or induce overlap of specimens and should permit easy relocation of small organisms (i.e., fixing them so that their co-ordinates can be read with an England Finder) It should neither be messy nor aspirate air and should not contract, thereby crushing delicate specimens. The mountant must be treated to inhibit bacterial and fungal growths. It must be relatively inexpensive and quick to prepare and must not solidify too rapidly, leaving insufficient time to position specimens. Since the specimens are ‘live’ it is important that the protoplasmic contents of the cell and the mountant are isotonic. Similarly, . . .

The Toxic Effects of Two Dental Materials on Human Buccal Epithelium In Vitro and Monkey Buccal Epithelium In Vivo

The aim of the present study was to compare the toxicity in vitro with the toxicity in vivo of two commercial chemicals marketed for use in the oral cavity (GLUMA BondR and 3M Etching LiquidR). Confluent cultures of human buccal epithelial cells were exposed to graded concentrations of GLUMA Bond or 3M Etching Liquid for 5 minutes. The cytotoxic effects induced by this treatment were observed (cytomorphology, proliferation rate). In vivo, monkey buccal epithelium was exposed to GLUMA Bond or 3M Etching Liquid for 5 minutes. Biopsies were taken after 24 hours, and the buccal epithelium processed for light microscopical examination. In both models, the toxic reactions to GLUMA Bond were far more extensive than those caused by 3M Etching Liquid.

SELECTIVE ABORTION OF TWO NONSISTER NUCLEI IN A DEVELOPING ASCUS OF THE hfd1—1 MUTANT IN SACCHAROMYCES CEREVISIAE

ABSTRACT A recessive mutation, hfd1—1, in strain SOS4 of Saccharomyces cerevisiae leads the mutant cells to produce predominantly two-spored asci. Light microscopical examination of Giemsastained cells revealed no significant differences in the meiotic figures between mutant and wild-type strains. However, only two of the four meiotic products in a developing ascus matured to ascospores in SOS4. Dyad analysis was carried out on an hfd1-1 mutant strain heterozygous for three markers, asp5, gal1 and arg4, which are closely linked to their centromeres, and for his4, which is loosely linked to its centromere. The twospored asci produced by the hfd1—1 mutant segregated dominant (+) and recessive (-) alleles of each marker in a 1:1 ratio; they generally contained one + and one - spore for any given marker. The occurrence of rare dyads with two + or two - spores can be explained quantitatively by recombination between the marker and its centromere. From the results of these cytological and genetical analyses, we infer that, in the mutant strain, one genome set is partitioned to each of the four second-meiotic division poles, but only two nonsister genomes are incorporated into mature spores. Thus, the hfd1—1 mutation in SOS4 blocks incorporation of two nonsister nuclei into mature ascospores, but does not block enclosure of the remaining two nonsister nuclei.