Glenn K. Walker

Inhibitors of V-Type ATPases, Bafilomycin A1 and Concanamycin A, Protect Against β-Amyloid-Mediated Effects on 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) Reduction

Abstract: The functional viability of cells can be evaluated using a number of different assay determinants. One common assay involves exposing cells to 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT), which is converted intracellularly to a colored formazan precipitate and often used to assess amyloid peptide‐induced cytotoxic effects. The MTT assay was employed to evaluate the role of endosomal uptake and lysbsomal acidification in amyloid peptide‐treated differentiated PC12 cell cultures using selective vacuolar‐type (N‐type) ATPase inhibitors. The macrolides bafilomycin A1 (BAF) and concanamycin A (CON) block lysosomal acidification through selective inhibition of the V‐type ATPase. Treating nerve growth factor‐differentiated PC12 cells with nanomolar concentrations of BAF or CON provides complete protection against the effects of β‐amyloid peptides Aβ(1‐42), Aβ(1‐40), and Aβ(25‐35) and of amylin on MTT dye conversion. These macrolides do not inhibit peptide aggregation, act as antioxidants, or inhibit Aβ uptake by cells. Measurements of lysosomal acidification reveal that the concentrations of BAF and CON effective in reversing Aβ‐mediated MTT dye conversion also reverse lysosomal pH. These results suggest that lysosomal acidification is necessary for Aβ effects on MTT dye conversion.

Characteristics of a human epidermal squamous carcinoma cell line at different extracellular calcium concentratrions

A continuous line derived from a human skin squamous cell carcinoma has been grown in media of high, normal and low Ca2+ concentrations. The growth rate was unaffected by the Ca2+ levels even though morphological changes were observed. Desmosomes were absent at low Ca2+ and areas of cell piling were observed at high Ca2+. Cell protein staining patterns on polyacrylamide gels were identical for cells grown at the three Ca2+ levels. The variations were minor for the glycoproteins reacted with 125I-conA. Lactoperoxidase iodination revealed changes in cell surface proteins, most markedly in the emergence of new proteins at high Ca2+.

Embryonic Developmental Progression in Lake Trout (Salvelinus namaycush) (Walbaum, 1792) and Its Relation to Lake Temperature

Abstract Developmental progression of lake trout ( Salvelinus namaycush ) embryos was examined with light and scanning electron microscopy. From this examination, key developmental stages were described in detail. The key developmental stages were then applied to individual lake trout egg lots incubated in constant temperatures of 2, 4, 6, 8, and 10°C. We used Belehradeks, Thermodynamic, and Power models, and also developed the Zero model to determine stage specific developmental rates of lake trout eggs for each background temperature. From the models, hatch dates and staging were predicted for temperature regimes from Lake Superior (1990–91) and Lake Huron (1996–97). Based on the existing lake temperature data and the observed spawning dates, the Zero and the Power models predict that post peak spawning may contribute significantly to overall recruitment success for these years.

Scanning electron microscopy studies on Prasadiseius kayosiekeri (Prasad, 1970) (Acari: Mesostigmata: Otopheidomenidae): idiosoma

ABSTRACT A scanning electron microscopic study of idiosomal structures of Prasadiseius kayosiekeri (Prasad, 1970) (Acari: Otopheidomenidae) provides details of the dorsal idiosomal, sternal, genital and anal shield. The setae are identified according to the system proposed by Prasad [Prasad, V. 2011. Proposed nomenclature for idiosomal setae in otopheidomenid mites (Acari: Otopheidomenidae) known from sphingid moths (Lepidoptera: Sphingidae). Internat. J. Acarol. 37(1):11–30]. These studies complement previous microscopy studies reported by Prasad [Prasad, V. 1970b. Two new species of Otopheidomenis (Acarina: Phytoseiidae) ectoparasitic on sphingid moths with a note on Noctuiseius. Can. Entomol. 102(10): 1209–1215] and augment with details in the electron micrographs.

The Fine Structure of the Sperm of the Round Goby (Neogobius melanostomus)

Abstract The fine structural details of the spermatozoon of the round goby are presented for the first time in this study. Scanning and transmission electron microscopic examination of testis reveals an anacrosomal spermatozoon with a slightly elongate head and uniformly compacted chromatin. The midpiece contains a single, spherical mitochondrion. Two perpendicularly oriented centrioles lie in a deep, eccentric nuclear fossa with no regularly observed connection to the nucleus. The flagellum develops bilateral fins soon after emerging from the fossa; each extends approximately 1 μm from the axoneme and persists nearly the length of the flagellum.