Surface changes in the naturally ankylosed teeth of the frog Rana pipiens during growth and maturation: an SEM study

An SEM study of the surface morphology of the major stages of mature and developing teeth of the leopard frog was made using anorganic preparations of the teeth and jaws. After initial development, the crown area changed little during subsequent tooth eruption, ankylosis and maturation. The thin enamel covering extended further down the shaft than expected. After ankylosis, the surfaces of the tooth continued to mature. The unmineralized gap between the crown and the pedestal, which is prominent in most amphibians, gradually filled in as the ankylosed tooth aged. The upper portion of the pedestal initially formed a dentine surface which was globular in appearance due to partial calcification of the surface collagen fibres but became smooth with uniformly calcified fibres as the ankylosed tooth matured. The lower portion of the pedestal was more variable and there was a gradual transition of dentine into a more cellular, bone-like tissue which contained lacunae and larger fibre bundles. This bone-like tissue was very distinct in surface morphology from the bone of the adjacent jaw, and as the tooth matured it changed from a coarse, woven appearance to one more like lamellar bone. Resorption bays were present in both the dentine and bony areas of teeth which were being shed. During development, the pedestal, which attaches the tooth to the jaw, formed as a separate calcification site and did not form a complete ring until fusion of its buccal surface with that of the overlying crown. A bony buccal lip formed early as part of the pedestal.     

Fine needle aspiration biopsy in uveal melanoma

Fine needle aspiration (FNA) biopsies were performed in a series of patients with uveal tumors. Cytopathologic examination established the correct diagnosis in 26 of 29 uveal melanomas. FNA biopsy was able to exclude the diagnosis of a malignant neoplasm in five nonmelanoma tumefactions. Histologic and FNA cytologic typing of melanomas as epithelioid or predominantly spindle cell showed good agreement, with the same classifications made in 14 of 18 cases. FNA biopsy specimens also proved to be adequate for DNA-content and cell-cycling studies. The cessation of cell cycling in successfully irradiated melanomas may be useful in establishing the postradiation status of tumors that have questionable growths after therapy, as was shown using FNA samples in three such cases in this study. The results of this study show that FNA biopsy is a useful diagnostic adjunct in patients with atypical lesions that require therapy.     

Transport of groundwater-borne nutrients from watersheds and their effects on coastal waters

Anthropogenic activities on coastal watersheds increase nutrient concentrations of groundwater. As groundwater travels downslope it transports these nutrients toward the adjoining coastal water. The resulting nutrient loading rates can be significant because nutrient concentrations in coastal groundwaters may be several orders of magnitude greater than those of receiving coastal waters. Groundwater-borne nutrients are most subject to active biogeochemical transformations as they course through the upper 1 m or so of bottom sediments. There conditions favor anaerobic processes such as denitrification, as well as other mechanisms that either sequester or release nutrients. The relative importance of advective vs. regenerative pathways of nutrient supply may result in widely different rates of release of nutrients from sediments. The relative activity of denitrifiers also may alter the ratio of N to P released to overlying waters, and hence affect which nutrient limits growth of producers. The consequences of nutrient (particularly nitrate) loading include somewhat elevated nutrient concentrations in the watercolumn, increased growth of macroalgae and phytoplankton, reduction of seagrass beds, and reductions of the associated fauna. The decline in animals occurs because of habitat changes and because of the increased frequency of anoxic events prompted by the characteristically high respiration rates found in enriched waters.     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.