Phenotypic plasticity, heterochrony and ontogenetic repatterning during juvenile development of divergent Arctic charr (Salvelinus alpinus).

Phenotypic plasticity is a developmental process that plays a role as a source of variation for evolution. Models of adaptive divergence make the prediction that increasing ecological specialization should be associated with lower levels of plasticity. We tested for differences in the magnitude, rate and trajectory of morphological plasticity in two lake populations of Arctic charr (Salvelinus alpinus) that exhibited variation in the degree of resource polymorphism. We reared offspring on diet treatments that mimicked benthic and pelagic prey. Offspring from the more divergent population had lower levels of morphological plasticity. Allometry influenced the rate of shape change over ontogeny, with differences in rate among ecomorphs being minimal when allometric variation was removed. However, plasticity in the spatial trajectory of development was extensive across ecomorphs, both with and without the inclusion of allometric variation, suggesting that different aspects of shape development can evolve independently.

Evolution of adaptive diversity and genetic connectivity in Arctic charr (Salvelinus alpinus) in Iceland.

The ecological theory of adaptive radiation predicts that the evolution of phenotypic diversity within species is generated by divergent natural selection arising from different environments and competition between species. Genetic connectivity among populations is likely also to have an important role in both the origin and maintenance of adaptive genetic diversity. Our goal was to evaluate the potential roles of genetic connectivity and natural selection in the maintenance of adaptive phenotypic differences among morphs of Arctic charr, Salvelinus alpinus, in Iceland. At a large spatial scale, we tested the predictive power of geographic structure and phenotypic variation for patterns of neutral genetic variation among populations throughout Iceland. At a smaller scale, we evaluated the genetic differentiation between two morphs in Lake Thingvallavatn relative to historically explicit, coalescent-based null models of the evolutionary history of these lineages. At the large spatial scale, populations are highly differentiated, but weakly structured, both geographically and with respect to patterns of phenotypic variation. At the intralacustrine scale, we observe modest genetic differentiation between two morphs, but this level of differentiation is nonetheless consistent with strong reproductive isolation throughout the Holocene. Rather than a result of the homogenizing effect of gene flow in a system at migration-drift equilibrium, the modest level of genetic differentiation could equally be a result of slow neutral divergence by drift in large populations. We conclude that contemporary and recent patterns of restricted gene flow have been highly conducive to the evolution and maintenance of adaptive genetic variation in Icelandic Arctic charr.

Whole genome duplication: challenges and considerations associated with sequence orthology assignment in Salmoninae.

To illustrate some of the challenges and considerations in assigning correct orthology necessary for any comparative genomic investigation among salmonids, sequence data from the non-coding regions of different chromosomes in three members of the subfamily Salmoninae, rainbow trout Oncorhynchus mykiss, Atlantic salmon Salmo salar and Arctic charr Salvelinus alpinus, were compared. By analysing c. 55 distinct loci, corresponding to c. 142 kbp sequence information per species, 18 duplicated patterns representative of the two sequential rounds of teleost-specific whole genome duplications (i.e. 3R and 4R WGD) were identified. Sequence similarities between the 4R paralogues were c. 90%, which was slightly lower than those of the 4R orthologues and c. 60% for the 3R products. Through careful examination of the sequence data, however, only 14 loci could reliably be assigned as true orthologues. Locus-specific trees were constructed through maximum parsimony, maximum likelihood and neighbour-joining methods and were rooted using the information from a close relative, lake whitefish Coregonus clupeaformis. All approaches generated congruent trees supporting the {Coregonus [Salmo (Oncorhynchus, Salvelinus)]} topology. The general phenotypic characteristics of sequences, however, were highly suggestive of the basal position of Oncorhynchus, raising the hypothesis of an accelerated rate of nucleotide evolution in this species.

The genetic architecture of embryonic developmental rate and genetic covariation with age at maturation in rainbow trout Oncorhynchus mykiss.

The genetic architecture underlying variation in embryonic developmental rate (DR) and genetic covariation with age of maturation (MAT) was investigated in rainbow trout Oncorhynchus mykiss. Highly significant additive parental effects and more limited evidence of epistatic effects on progeny hatching time were detected in three diallel sets of families. Genome scans with an average of 142 microsatellite loci from all 29 linkage groups in two families detected significant quantitative trait loci (QTL) for developmental rate on RT-8 and RT-30 with genome-wide and chromosome-wide effects, respectively. The QTL on linkage group RT-8 explained 23·7% of the phenotypic variation and supports results from previous studies. The co-localization of QTL for both DR and MAT to several linkage groups and the observation that alleles associated with faster developmental rate were found significantly more often in early maturing rather than typical and later maturing male ancestors supports the hypothesis of genetic covariation between DR and MAT. The maturation background and schedule of additional sires, however, did not have a consistent association with their progeny hatching times, suggesting that other genetic, environmental and physiological effects contribute to variation in these life-history traits.

Genome organization of glutamine synthetase genes in rainbow trout (Oncorhynchus mykiss).

Unlike mammals, bony fish appear to possess multiple genes encoding glutamine synthetase (GS), the nitrogen metabolism enzyme responsible for the conversion of glutamate and ammonia into glutamine at the expense of ATP. This study reports on the development of genetic markers for each of the four isoforms identified thus far in rainbow trout (Oncorhynchus mykiss) and their genome localization by linkage mapping. We found that genes coding for GS01, GS02, GS03, and GS04 map to four different linkage groups in the trout genome, namely RT-24, RT-23, RT-08, and RT-13, respectively. Linkage groups RT-23 and RT-13 appear to represent distinct chromosomes sharing duplicated marker regions, which lends further support to the previous suggestion that GS02 and GS04 may be duplicate gene copies that evolved from a whole-genome duplication in the trout ancestor. In contrast, there is at present no further evidence that RT-24 and RT-08 share ancestrally homologous segments and additional genomic studies will be needed to clarify the evolutionary origin of genes coding for GS01 and GS03.

A microsatellite linkage map of rainbow trout (Oncorhynchus mykiss) characterized by large sex-specific differences in recombination rates.

We constructed a genetic linkage map for a tetraploid derivative species, the rainbow trout (Oncorhynchus mykiss), using 191 microsatellite, 3 RAPD, 7 ESMP, and 7 allozyme markers in three backcross families. The linkage map consists of 29 linkage groups with potential arm displacements in the female map due to male-specific pseudolinkage arrangements. Synteny of duplicated microsatellite markers was used to identify and confirm some previously reported pseudolinkage arrangements based upon allozyme markers. Fifteen centromeric regions (20 chromosome arms) were identified with a half-tetrad analysis using gynogenetic diploids. Female map length is approximately 10 M, but this is a large underestimate as many genotyped segments remain unassigned at a LOD threshold of 3.0. Extreme differences in female:male map distances were observed (ratio F:M, 3.25:1). Females had much lower recombination rates (0.14:1) in telomeric regions than males, while recombination rates were much higher in females within regions proximal to the centromere (F:M, 10:1). Quadrivalent formations that appear almost exclusively in males are postulated to account for the observed differences.

Aplasia of the parotid gland in Down syndrome.

Salivary gland aplasia has not to our knowledge been previously reported in association with Down syndrome. We present a case of bilateral parotid aplasia in a patient with Down syndrome. Clinically he had aplasia of the major salivary glands and symptoms of xerostomia. Thirteen other family members over three generations were examined, and all had functional parotid glands. We reviewed publications about Down syndrome and salivary aplasia, together with the data regarding his other clinical problems and family background. His oral problems were inadequate plaque control, dental caries, and erosion of the teeth.

Oestrogen as an inhibitor of human NK cell cytolysis.

Natural killer (NK) cells are large granular lymphocytes attributed with the ability to lyse certain tumour cells. Previous studies on NK cells have demonstrated only an in vivo suppression of NK cell activity by 17 beta-oestradiol. The suppressive action of oestrogen on other peroxidase-containing leukocytes by virtue of its redox potential has already been documented. In the present study oestrogen suppressed NK cell cytolysis in vitro (determined by the release of [51Cr]chromate from radiolabelled cells) in a dose-dependent manner (p less than 0.01). Parallel experiments demonstrated a similar reduction in NK cell luminol chemiluminescence during activation by K562 tumour cells. Therefore, it would appear that there may be an association between NK cell lysis and their peroxidase/oxygenase activity.

Inhibition of NK cell-induced cytolysis by thiocarbamide antithyroid drugs.

The thiocarbamide antithyroid drugs, methimazole and propylthiouracil, suppressed natural killer (NK) cell-induced cytolysis in vitro (determined by the release of 51Cr-chromate from labelled target cells) in a dose-dependent manner. Parallel experiments demonstrated a similar reduction in NK cell luminol chemiluminescence during activation by K562 tumour cells. It would appear, therefore, that an association may exist between NK cell-induced cytolysis and the peroxidase/oxygenase activity of these lymphocytes.

Influence of sodium perchlorate on thiourylene antithyroid drug accumulation in mice.

Radiolabelled [35S]propylthiouracil and [35S]methimazole were shown to accumulate in mouse thyroid gland in vivo, with maximal tissue/plasma ratios and maximal intrathyroidal levels of 35S-labelled drug being seen at the lowest dose of drug studied (0.1 micrograms/animal). Pretreatment with sodium perchlorate (10 mg) abolished iodide trapping by the thyroid and caused a fall in accumulation of both [35S]methimazole and [35S]propylthiouracil, although this effect was not seen at higher doses of drug, when tissue/plasma ratios approached unity. These data suggest that thiourylene antithyroid drug accumulation by the thyroid gland does not depend directly on the anion trap, and it is suggested that this accumulation might depend on subsequent intrathyroidal drug metabolism.

Accumulation of thiourylene antithyroid drugs in mouse salivary gland.

[35S]Methimazole and [35S]propylthiouracil were shown to accumulate in mouse submandibular gland in vivo, with maximal tissue: plasma ratios being achieved at the lowest dose of drug studied (0.1 microgram/animal). Autoradiography of submandibular glands showed that the drugs were localized to the intralobular ductal epithelium and within the lumen of the convoluted granular tubule, which was identical to the localization of radiolabelled iodide. Histochemical studies indicated that this was the site of peroxidase activity within the gland. Drug accumulation persisted when iodide trapping was competitively inhibited using perchlorate. These data suggest that antithyroid drug accumulation by this tissue is not dependent on the anion trap; the localization of drug and iodide at the site of peroxidase activity suggest that this may be an important factor in the mechanism of drug accumulation, possibly related to subsequent drug metabolism.

Peroxidase activity in relation to iodide, 17 beta-oestradiol and thioureylene drug uptake in human polymorphoneutrophils.

In polymorphoneutrophils (PMNs) phagocytosis is accompanied by an increase in peroxidase activity. Accumulation of iodide, thioureylene antithyroid drugs and 17 beta-oestradiol also occurs during the process. There is no evidence of an active iodide transport system in the PMNs as pertechnetate is not concentrated and neither ouabain nor perchlorate abolishes iodide accumulation. The uptakes of 125I, [35S]PTU and [3H]-17 beta-oestradiol were compared in phagocytosing PMNs and the effects of various compounds examined. In addition, chemiluminescence generation from luminol by PMNs and by horseradish peroxidase was studied. This indicated that uptake of all three compounds could be associated with activation of the peroxidase system, and inhibition of this enzyme system caused a reduction in their accumulation.

S-100-positive T-cell lymphoproliferative disorder. A case report and review of the literature.

The authors describe a patient with a S-100-positive T-cell lymphoproliferative disorder, characterized by clinically aggressive behavior, with leukemic dissemination and death within 1 year of the onset of symptoms. The neoplastic cells had abundant amphophilic cytoplasm, suggestive of plasmacytoid differentiation, but demonstrated a mature T-cell immunophenotype characteristic of the suppressor-cytotoxic subset. In addition, the cells expressed the S-100 protein within the cytoplasm. Genotypic studies were performed by Southern blot analysis, which demonstrated beta-chain T-cell receptor gene rearrangement, further confirming the T-cell nature of this disorder. This case had features very similar to those of the seven cases previously reported. It has been proposed that the S-100-positive T-cell lymphoproliferative disorder is a distinctive clinicopathologic entity.

Progesterone metabolism in the murine submandibular salivary gland.

Homogenates of submandibular salivary glands from female mice were incubated with progesterone. This resulted in the formation of 20 alpha-hydroxy-progesterone, thus indicating the presence of the enzyme, 20 alpha-hydroxysteroid dehydrogenase.

The anatomy of the facial nerve in relation to CT/sialography of the parotid gland.

The technique of computed tomography with simultaneous parotid sialography allows for accurate localisation of tumours within the parotid gland. The relationship of these tumours to the facial nerve, which divides within the gland, is of surgical significance. A study of the course of the facial nerve through the parotid gland in the cadaver was therefore undertaken in order to identify relevant landmarks for the CT prediction of its relationship to those tumours. The heads of five cadavers were sectioned in the Frankfurt plane into 1 cm slices which were then X-rayed. Individual slices were examined and the course of the facial nerve was plotted on the X-ray plate of the same slice. It was found that the nerve could be represented on a CT scan by an arc of radius 8.5 mm, the centre of which is the most posterior point of the ramus of the mandible. The arc extends from directly lateral to directly posterior to that point. Pre-operative visualisation of parotid tumours by simultaneous CT scan and sialography in conjunction with an appreciation of the course of the facial nerve through the parotid gland may allow for more precise presurgical planning.

A pilot study of the disposition of pilocarpine in plasma, saliva and urine after a single oral dose.

Concentrations of pilocarpine in plasma, saliva and urine from three healthy male volunteers were measured using a fluorescence derivatisation method, following administration of a single 10 mg oral dose. Pharmacokinetic parameter values were estimated from concentration-time profiles. Linear correlations between plasma and saliva pilocarpine concentrations (r2=0.945, n=10, p<0.001; r2=0.954, n=12, p<0.001) and plasma concentrations and salivation rate (r2=0. 863, n=12, p<0.001; r2=0.862, n=15, p<0.001) were established. Pilocarpine and an unidentified metabolite, respectively 20.3% and 34.7% of the oral dose, were excreted into urine.

A quantitative study on growth and cell population identification in murine salivary gland culture.

Differentiation of neonatal salivary gland cell populations was studied in vitro using primary explant cultures. Growth on glass of the submandibular, sublingual and parotid salivary glands was optimal if the initial explant diameter was less than 0.4 mm and culture was in 199 medium plus 20 per cent newborn-calf serum. Growth was measured by planimetry of the area of cellular outgrowth as a monolayer with continuous cell contacts. Duct epithelial cells identified using ultrastructural, histochemical and immunological criteria, produced evidence of altered morphology by in-vitro conditions. Preservation of enzymic and antigenic markers of ductal epithelial cell origin in vitro irrespective of gross cell morphology allowed quantification of these cells in a mixed cell population.

Behavioural plasticity of lake charr (Salvelinus namaycush) x brook charr (S. fontinalis) F1 hybrids in response to varying social environment.

Lake x brook F1 hybrid charr were observed in heterogeneous groups with lake charr or brook charr to assess the effects of different species on hybrid social behaviour. Levels of behavioural plasticity were low in relation to the behavioural differences between the parental and hybrid types. Feeding behaviour showed the most dramatic change, with higher levels in the lake charr treatment and lower levels in the brook charr treatment than controls, suggesting social facilitation. Even though only two measures varied significantly between treatments, there was a tendency for the frequencies and durations of all agonistic measures to increase in the presence of lake charr and decrease with brook charr. A cost-benefit argument is presented to account for this trend.

Comparison of cryosurgery and the carbon dioxide laser in mucosal healing.

Cryosurgery is an established technique for the removal of a range of mucosal lesions. As the portable carbon dioxide laser may provide an alternative form of treatment, the effectiveness of and the healing response following use of the 2 techniques was compared by producing lesions on the lateral border of sheep tongues. Cryosurgery produced more extensive lesions with a marked inflammatory reaction but no differences in the time course of healing were evident. Laser surgery was as effective as cryosurgery in the removal of superficial tissues but caused less swelling and, therefore, may be advantageous in some clinical situations.

Histological evaluation of the effect of a miniature carbon dioxide laser on oral mucosa.

Carbon dioxide lasers emit infra-red radiation at a wavelength of 10600 nm, making them suitable for tissue vaporisation, incision and vessel coagulation. A miniature CO2 laser (length 24 cm), with an output of 4 Watts focused on to a spot of 0.2 mm diameter at a distance of 2.5 mm from the nozzle tip, has been developed. This hand-held, water-cooled device operates off a 12 V D.C. source and provides good access to most areas of the mouth. In order to evaluate the use of the miniature laser, a series of lesions were produced on the lateral margins of sheep's tongues, and histological examination of tissues carried out immediately after treatment and at 1 h; 1, 2, 4, 7, 14, 21, and 28 day intervals. Wounds showed clean cut margins with even removal of epithelium and superficial connective tissue. Damage appeared to be restricted to a 100 microns deep zone in the lamina propria. Epithelial regeneration had commenced at between 2 and 4 days, and re-covered the surface by 14 days. A residue of chronic inflammatory cells was present within the stroma at 21 days, but this had resolved by 28 days. The miniature carbon dioxide laser is effective in vaporising oral mucosa and also achieving haemostasis by vessel coagulation; its manoeuvrability and relatively low cost warrant further clinical evaluation for the treatment of mucosal lesions, such as leukoplakia.