Seasonal changes in vertical distribution, biomass and faecal production of tubificids in the profundal region of a shallow Japanese lake

Two tubificid species Limnodrilus hoffmeisteri and L. claparedeianus formed more than 93% of the total number of oligochaetes in the profundal. Limnodrilus spp. worms were found down to 33 cm in the sediment but in great numbers in the upper zone in June and October. Worms confined to the top 15 cm of sediment accounted for 53-92% of the total number. There were two annual maxima in population density and biomass, one in late spring (66000 inds m⁻², 17 g wet wt m⁻²) and the other in mid autumn (97000 inds m⁻², 176 g wet wt m⁻²). Two regression lines describing the effect of temperature on faecal production rate were obtained; Log F = 0.0604 T (°C) −0.7660 (below 15°C), Log F = 0.0266 T – 0.2170 (above 15°C). In total 26.8 kg dry wt m⁻² of sediment was defecated annually by Limnodrilus spp. The sediment in the 0–10 cm stratum may pass through the guts of the worms 2.3 times a year. Sedimentation rates in profundal region were very low with respect to the faecal production rates of the tubificids.     

A study of cytoplasmic and nuclear estrogen and progestin receptors in gynecologic neoplasms

A rapid method for simultaneous preparation of cytosol and nuclear estrogen (E) and progestin (P) receptors and their in vitro determination is described. The method was applied to several uterine or ovarian surgical specimens to evaluate their steroid hormone "dependence". The results suggest that low cytoplasmic E receptor levels (ERc) are associated with higher nuclear E receptor (ERn) levels but no apparent correlation was observed between PRc and ERn levels. The method appeared to be suitable for screening steroid hormone receptor content in tumor tissues and may provide better estimation of steroid dependence since both cytoplasmic and nuclear compartments can be studied simultaneously.     

The different effects of recombinant human tumor necrosis factor on rat fibrosarcoma sublines

Summary The antitumor effect of recombinant human tumor necrosis factor (rH-TNF) on two clones of rat fibrosarcoma with different metastatic potential to lymph nodes was examined. The colony formation of clone A, which has high metastatic potential, was completely inhibited by continuous exposure to rH-TNF at 50 U/ml. In contrast, colony formation of clone G, which has low metastatic potential, was not inhibited by high concentrations of rH-TNF (10,000 U/ml). The inhibitory effect of rH-TNF on colony formation by clone A was also observed with a 1-h exposure to rH-TNF. This effect was time and concentration dependent, as determined by the colony assay, ³H-thymidine uptake assay, and ⁵¹Cr-release assay. ³H-thymidine and ³H-uridine uptake per cell of clone A exposed to rH-TNF was not decreased. This suggests that the mechanisms of the antitumor effect of rH-TNF were not due to inhibition of DNA and RNA synthesis of tumor cells. In vivo growth and lymph node metastases of clone A inoculated i.p. to Donryu strain rats were completely suppressed by 14 consecutive i.p. injections of 10⁵ or 10⁶ U/kg per day of rH-TNF. On the other hand the growth of clone G was not influenced by rH-TNF administration.     

The complete sequence of the rice (Oryza sativa) chloroplast genome: intermolecular recombination between distinct tRNA genes accounts for a major plastid DNA inversion during the evolution of the cereals

Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation of repeated sequences near the inversion endpoints.     

Opioid-binding protein (OBCAM) is rich in β-sheets

Based on circular dichroism (CD) and the sequence-predictive method, the opioid-binding cell adhesion molecule (OBCAM) consisted of one half -sheets and one fourth -helices. This is consistent with significant sequence homology of the protein to several members of the immunoglobulin (Ig) superfamily, particularly cell adhesion molecules, which are rich in -sheets. Hydropathy analysis suggests that hydrophobic and hydrophilic regions were evenly distributed along the sequence, but the NH₂- and COOH-termini were hydrophobic. Hydrophobic moments and Fourier-transform amphipathic analyses further suggest that residues 23–30 and 83–93 were amphiphathie -sheets. The overall conformation of OBCAM was unaltered by adding linoleic acid, which is required for opioid ligand binding.     

A theoretical study of the dielectric constant of protein

The dielectric properties of a protein molecule were investigated by calculating a 'local dielectric constant' with the aid of normal mode analysis. This local dielectric constant was calculated from the electronic polarization of atoms and the orientational polarization of local dipoles. The former was obtained from atomic polarizations of the whole atoms in a protein molecule. The latter was determined from the fluctuation-dissipation theorem. The degree of dipole fluctuation was calculated from the positional fluctuation of each atom obtained by the normal mode analysis. Assuming a minimum volume for a continuum model, the resulting local dielectric constants ranged from 1 to 20 inside the protein.