A new species ofScymnodalatias from the southern oceans,and comments on other squaliform sharks

Scymnodalatias albicauda sp. nov. is described from two specimens taken at high latitudes (45°S and 49°S). It is distinguished fromS. sherwoodi, only known species of the genus, by having white markings on the caudal fin, the second dorsal posterior tip almost reaching the upper caudal fin, shorter snout and head, smaller eye and larger fins. Relationships ofScymnodalatias to the generaScymnodon, Centroscymnus, andZameus are discussed, based chiefly on dermal denticle structure.Scymnodalatias andZameus uniquely share transverse ridges on their dermal denticles, and on this character they are treated as sister-groups. Comments on the above genera,Z. squamulosus and some species ofScymnodon are made to clarify their systematic status. As a result, it is proposed thatScymnodon includesichiharai, macracanthus, plunketi, andringens, thatCentroscymnus includescoelolepis, crepidater, crypt acanthus, andowstonii, and thatZameus includessquamulosus.     

Effects of sulfhydryl and other reagents on the diffusional permeability of dog erythrocytes to small solutes

The effects of p-chloromercuriphenylsulfonic acid (PCMBS), 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB), phloretin and thiourea on the diffusional permeability of dog erythrocytes to tritiated water and to small 14C-labeled lipophilic and hydrophilic solutes were measured at 37 degrees C by means of the linear diffusion technique. Permeability to 3HHO was significantly decreased by PCMBS but was not affected by the other reagents. The permeability to the small hydrophilic solutes acetamide and urea was decreased by phloretin and thiourea but only the permeability to acetamide was reduced to a statistically significant extent by PCMBS. The permeability to the lipophilic solutes methanol, ethanol and antipyrine was not affected by any of these agents. We interpret these results as an indication that the small lipophilic solutes probably move through lipid areas, that the small hydrophilic solutes probably move through protein associated areas in the erythrocyte membrane and that pathways for the small hydrophilic solutes are distinct from those for water. While the pathways for water may be associated with membrane protein they do not appear to be associated specifically with band 3 protein as has been suggested for human erythrocytes. Diffusional water movement through the dog erythrocyte occurs by two distinct pathways.     

Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans

Recent studies of mitochondrial DNA (mtDNA) variation in mammals and Drosophila have shown an excess of amino acid variation within species (replacement polymorphism) relative to the number of silent and replacement differences fixed between species. To examine further this pattern of nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5 genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans. Of interest are the frequency spectra of silent and replacement polymorphisms, and potential variation among genes and taxa in the departures from neutral expectations. The Drosophila ND3 and ND5 data show no significant excess of replacement polymorphism using the McDonald-Kreitman test. These data are in contrast to significant departures from neutrality for the ND3 gene in mammals and other genes in Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however, both Drosophila and human mtDNA show very significant excesses of amino acid polymorphism. Silent polymorphisms at ND5 show a significantly higher variance in frequency than replacement polymorphisms, and the latter show a significant skew toward low frequencies (Tajima's D = -1.954). These patterns are interpreted in light of the nearly neutral theory where mildly deleterious amino acid haplotypes are observed as ephemeral variants within species but do not contribute to divergence. The patterns of polymorphism and divergence at charge-altering amino acid sites are presented for the Drosophila ND5 gene to examine the evolution of functionally distinct mutations. Excess charge-altering polymorphism is observed at the carboxyl terminal and excess charge-altering divergence is detected at the amino terminal. While the mildly deleterious model fits as a net effect in the evolution of nonrecombining mitochondrial genomes, these data suggest that opposing evolutionary pressures may act on different regions of mitochondrial genes and genomes.      

Iron supplementation moderates but does not cure the Belgrade anemia

Belgrade rats inherit microcytic, hypochromic anemia as an autosomalrecessive trait (gene symbol b). Erythrocytes and tissue are iron deficientin the face of elevated TIBC (total iron binding capacity) and percent ironsaturation; iron injections increased the number of erythrocytes but theirappearance remained abnormal. We have investigated iron supplements toimprove husbandry of b/b rats and to learn more about the underlying defectand its tissue distribution. Weekly IM (intramuscular) injections ofiron–dextran (Imferon at 30 mg kg) improved the anemia but did not alter thered cell morphology. Certain diets also improved the health of b/b rats whencompared to standard rat chows by the criteria of weight, survival toadulthood, hematology and reproduction. The critical nutritional factorturned out to be iron bioavailability, with ferrous iron added to the dietimproving the health of Belgrade rats without affecting the underlyingerythroid defect. Tissue iron measurements after dietary or parenteralsupplementation confirmed the iron deficient status of untreated b/b rats andestablished that dietary ferrous iron partially relieved this deficiency,with injections leading to greater amounts of tissue iron. Serum iron andTIBC were also found to be elevated in untreated b/b rats, with dietarysupplementation decreasing but not eliminating the elevation in TIBC. Thesestudies indicate that iron supplements can improve the health of b/b ratswithout altering the underlying defect and also suggest that the mutationcould alter iron uptake in the GI (gastrointestinal) tract.     

Surrogate transformation of perennial ryegrass, Lolium perenne, using genetically modified Acremonium endophyte.

Summary Conditions have been developed for transforming protoplasts of the perennial ryegrass endophyteAcremonium strain 187BB. Unlike most other ryegrass endophytes, this strain does not produce the lolitrem B neurotoxin and is therefore suitable as a host for surrogate introduction of foreign genes into grasses. Transformation frequencies of 700–800 transformants/g DNA were obtained for both linear and circular forms of pAN7-1, a hygromycin (hph) resistant plasmid. Up to 80% of the linear transformants were stable on further culturing but only 25% of the circular transformants retained hygromycin resistance. Integration of pAN7-1 into the genome was confirmed by Southern blotting and probing of genomic digests of transformant DNA. Both single and tandemly repeated copies of the plasmid were found in the genome and both the number and sites of integration varied among the transformants. At least 13 chromosomes were identified in 187BB using contour-clamped homogeneous electric field (CHEF) gel electrophoresis. Probing of Southern blots of these gels confirmed that pAN7-1 had integrated into different chromosomes. The -glucuronidase (GUS) gene,uidA, was also introduced into 187BB by co-transformation of pNOM-2 with pAN7-1. GUS activity was detected by growing the transformants on plates containing 5-bromo-4-chloro-3-indolyl -D-glucuronic acid and by enzyme assays of mycelial extracts. Severalhph- anduidA-containing transformants were reintroduced into ryegrass seedlings and expression of GUS visualized in vivo, demonstrating that 187BB can be used as a surrogate host to introduce foreign genes into perennial ryegrass. Molecular analysis of fungal isolates from the leaf sheath confirmed that the pattern of pAN7-1 and pNOM-2 hybridizing fragments was identical to that observed in the fungus used as inoculum.     

Osmotic permeability of Novikoff hepatoma cells

The osmotic permeability coefficient (P_f) for water movement across Novikoff hepatoma cells was found to be 82 ± 3 (S.E.) · 10^?5 cm · s^?1 at 20°C. The corresponding diffusional permeability coefficient for ³HHO (P_d) was 97 ± 10 (S.E.) · 10^?5 cm · s^?1, therefore the ratio $\text{P}{}_{\mathrm{<mtext>f</mtext>}}\text{P}{}_{\mathrm{<mtext>d</mtext>}}$ is close to unity. The apparent activation energy for water filtration was 10.4 ± 0.4 (S.E.) kcal · mol^?1. This value is significantly greater than the activation energy for the self diffusion of water. The product of the hydraulic permeability coefficient and the viscosity coefficient for water was temperature-dependent. However, the product of the hydraulic permeability coefficient and the viscosity coefficient for membrane lipid did not vary with temperature. These data are interpreted as evidence for water movement across a lipid membrane barrier rather than through aqueous channels.     

Inner Nuclear Layer Thickening Is Inversley Proportional to Retinal Ganglion Cell Loss in Optic Neuritis

Aim

To examine the relationship between retinal ganglion cell loss and changes in the inner nuclear layer (INL) in optic neuritis (ON).

Methods

36 multiple sclerosis (MS) patients with a history of ON and 36 age and sex-matched controls underwent Optical Coherence Tomography. The paramacular retinal nerve fiber layer (RNFL), combined ganglion cell and inner plexiform layers (GCL/IPL) and inner nuclear layer (INL) thickness were measured at 36 points around the fovea. To remove inter-subject variability, the difference in thickness of each layer between the ON and fellow eye of each patient was calculated. A topographic analysis was conducted.

Results

The INL of the ON patients was thicker than the controls (42.9µm versus 39.6µm, p=0.002). ON patients also had a thinner RNFL (27.8µm versus 32.2µm, p<0.001) and GCL/IPL (69.3µm versus 98.1µm, p<0.001). Among the controls, there was no correlation between RNFL and GCL/IPL as well as RNFL and INL, but a positive correlation was seen between GCL/IPL and INL (r=0.65, p<0.001). In the ON group, there was a positive correlation between RNFL and GCL/IPL (r=0.80, p<0.001) but a negative correlation between RNFL and INL (r=-0.61, p<0.001) as well as GCL/IPL and INL (r=-0.44, p=0.007). The negative correlation between GCL/IPL and INL strengthened in the ON group when inter-subject variability was removed (r=-0.75, p<0.001). Microcysts within the INL were present in 5 ON patients, mainly in the superior and infero-nasal paramacular regions. While patients with microcysts lay at the far end of the correlation curve between GCL/IPL and INL (i.e. larger INL and smaller GCL/IPL compared to other patients), their exclusion did not affect the correlation (r= -0.76, p<0.001).

Conclusions

INL enlargement in MS-related ON is associated with the severity of GCL loss. This is a continuous relationship and patients with INL microcysts may represent the extreme end of the scale.