Isolation and characterization of rat cDNA clones for two distinct thyroid hormone receptors

Two distinct v-erbA-related cDNA clones representing the products of different genes were isolated from a rat liver cDNA library. The first, rc-erbA-alpha, was 82% identical to v-erbA and encoded a polypeptide with a calculated molecular mass of 45,000 daltons. This cDNA clone arises from the same gene product as a v-erbA-related cDNA isolated from rat brain by Thompson et al. (Thompson, C. C., Weinberger, C., Lebo, R., and Evans, R. (1987) Science 237, 1610-1614). The second cDNA clone, rc-erbA-beta, was 76% identical to v-erbA and encoded a polypeptide with a calculated molecular mass of 52,000 daltons. Both rc-erbA-alpha and rc-erbA-beta translational products bound 3,5,3'-triiodo-L-thyronine with affinities equal to each other (Kd approximately equal to 0.4 nM) and comparable to the nuclear thyroid hormone receptor extracted from rat liver. The relative affinities of a series of thyroid hormone analogs for both translational products were also identical. In various tissues and cell lines, the relative levels of rc-erbA-beta RNA, but not rc-erbA-alpha RNA, correlated with measurements of nuclear 3,5,3'-triiodo-L-thyronine binding sites. Based on this correlation, we suggest that rc-erbA-beta may encode the "classical" nuclear thyroid hormone receptor, whereas rc-erbA-alpha may encode an isoreceptor species with differing functional properties.     

Sequence specificity of 125I-labelled Hoechst 33258 in intact human cells

Using polyacrylamide/urea DNA sequencing gels, the DNA sequence selectivity of 125I-labelled Hoechst 33258 damage has been determined in intact human cells to the exact base-pair. This was accomplished using a novel procedure with human alpha RI-DNA as the target DNA sequence. In this procedure, after size fractionation, the alpha RI-DNA is selectively purified by hybridization to a single-stranded M13 clone containing an alpha RI-DNA insert. The sequence specificity of [125I]Hoechst 33258 was indistinguishable in intact cells from purified high molecular weight DNA; and this is surprising considering the more complex environment of DNA in the nucleus where DNA is bound to nucleosomes and other DNA binding proteins. The ligand preferentially binds to DNA sequences which have four or more consecutive A.T base-pairs. The extent of damage was measured with a densitometer and, relative to the damage hotspot at base-pair 94, the extent of damage was similar in both purified high molecular weight DNA and intact cells. [125I]Hoechst 33258 causes only double-strand breaks, since single-strand breaks or base damage were not detected. These experiments represent the first occasion that the sequence specificity of a DNA damaging agent, which causes only double-strand breaks, has been determined to the exact base-pair in intact cells.     

Induction and rejoining of gamma-ray-induced DNA single- and double-strand breaks in Chinese hamster AA8 cells and in two radiosensitive clones

The induction and rejoining of gamma-ray-induced DNA strand breaks were measured in a Chinese hamster ovary cell line, AA8, and in two radiosensitive clones (EM9 and NM2) derived from it. The kinetics of recovery from sublethal damage (SLD) and potentially lethal damage (PLD) has previously been characterized in each of these lines [vanAnkeren et al., Radiat. Res., 115, 223-237 (1988)]. No significant differences were observed among the cell lines in the yields of either DNA single-strand breaks (SSBs) or double-strand breaks (DSBs) as assayed by filter elution. Data for SSB rejoining in AA8 and NM2 cells irradiated with 7.5 Gy were fit by a biexponential process (t1/2 values of approximately 4 and 80 min). In comparison, SSB rejoining in EM9 cells was initially slower (t1/2 = 10 min) and a higher level of SSBs was unrejoined 6 h after irradiation. DSB rejoining in AA8 cells assayed at pH 9.6 was also biphasic (t1/2 values of 15 and 93 min), although when assayed at pH 7.0, most (approximately 80%) of the damage was rejoined at a constant rate (t1/2 = 45 min) during the first 2 h. EM9 cells exhibited a slower initial rate of DSB rejoining when assayed at pH 9.6 but showed no difference compared with AA8 cells in DSB rejoining when assayed at pH 7.0. These results indicate that radiosensitive EM9 cells, whose kinetics of recovery from SLD and PLD was the same as that of AA8 cells, have a defect in the fast phase of SSB rejoining but no measurable defect in DSB rejoining. Conversely, NM2 cells, which displayed a reduced shoulder width on their survival curve and decreased recovery from SLD, had no demonstrable defects in the rate or extent of rejoining of DSBs or SSBs. When compared with the SLD and PLD data reported previously, these results suggest that there is no direct correlation between either of these recovery processes and the rejoining of SSBs or DSBs as assayed here.     

A genetic analysis of body size in pink salmon (Oncorhynchus gorbuscha)

Two small-sized and two large-sized male pink salmon (Oncorhynchus gorbuscha) were mated to each of four females, producing eight families sired by small males and eight sired by large males. The juveniles were reared for 500 d after fry emergence. Juvenile weight in the two male size classes was similar until the spring of the year of maturity, when juveniles sired by large males grew faster than those sired by small ones. Heritability estimates of weight based upon the dam component of variance increased during 500 d of rearing from 0.4 to 0.8. Heritability of weight based upon the sire component of variance generally ranged between 0.1 and 0.3. The large variation in male body size in spawning pink salmon populations may have resulted from different male breeding strategies.     

Regional assignment of the gene for human liver/bone/kidney alkaline phosphatase to chromosome 1p36.1-p34

We have used three different methods to map the human liver/bone/kidney alkaline phosphatase (ALPL) locus: (1) Southern blot analysis of DNA derived from a panel of human-rodent somatic cell hybrids; (2) in situ hybridization to human chromosomes; and (3) genetic linkage analysis. Our results indicate that the ALPL locus maps to human chromosome bands 1p36.1-p34 and is genetically linked to the Rh (maximum lod score of 15.66 at a recombination value of 0.10) and fucosidase A (maximum lod score of 8.24 at a recombination value of 0.02) loci. These results, combined with restriction fragment length polymorphisms identified by ALPL DNA probes, provide a useful marker for gene mapping studies involving the short arm of chromosome 1. In addition, our results help to elucidate further the structure and evolution of the human alkaline phosphatase multigene enzyme family.     

On a simplified model for pattern formation in honey bee colonies

We present a simplified version of a previously presented model (Camazine et al. (1990)) that generates the characteristic pattern of honey, pollen and brood which develops on combs in honey bee colonies. We demonstrate that the formation of a band of pollen surrounding the brood area is dependent on the assumed form of the honey and pollen removal terms, and that a significant pollen band arises as the parameter controlling the rate of pollen input passes through a bifurcation value. The persistence of the pollen band after a temporary increase in pollen input can be predicted from the model. We also determine conditions on the parameters which ensure the accumulation of honey in the periphery and demonstrate that, although there is an important qualitative difference between the simplified and complete models, an analysis of the simplified version helps us understand many biological aspects of the more complex complete model. Corresponding author     

Analysis of dynamic and stationary pattern formation in the cell cortex

We study a sol-gel mechanochemical model for cellular cytoplasm. Using conservation equations and a force balance equation, we derive equations for the sol-gel dynamics. Regular perturbation analysis suggests the growth of patterns which may be either dynamic or stationary, depending on parameter values. Nonlinear analysis, which indicates that these patterns remain bounded, is confirmed by numerically solving the mechanochemical equations. We use these analytical and numerical results to model two different biological problems: the dynamic formation of filopodia in nerve growth cones, and the growth of microvilli in epithelial cells.     

A mite survey in the dumpsters for urban solid rubbish

Summary The presence of house dust mites and storage mites in dumpsters was investigated in 3 different areas of Venice hinterland. The aim of this study was to find a relationship between some reported respiratory symptoms among 6 workers who were responsible for moving the dumpsters to the truck and the bio-aerosol released from such operation. These symptoms were closely related to the work and after allergological evaluation we found sensitisation to house dust mites in all 6 employees. The mine exposure in the workplace was assessed by a standardized sampling and analysis of dust obtained after brushing the inside surfaces of dumpsters. In 50% of the specimens (10/20) we found mites belonging to the following families: Pyroglyphidae (Dermatophagoides spp.), Acaridae (Acarus siro) and a lower amount of Cheyletidae (Cheyletus spp.). An indirect test (guanine test) was also performed and gave positivity in 16 dust samples (80%). The insides of dumpsters showed to be an optimal environment for mites survival and reproduction because of cracks and grooves on the walls, the high humidity level and the presence of mould. These mites probably come from dwelling places and other environments (markets, slaughters-houses, farms, etc.). This suggests that mites allergens can be released during rubbish discharging from the dumpsters and represent a possible risk for the employees.     

Radiolarian flux in Antarctic waters (Drake Passage,Powell Basin,Bransfield Strait)

Summary The study of radiolarians collected during sediment trap experiments in the Drake Passage, the northern Powell Basin, and the King George Basin of the Bransfield Strait provides new information on the fluxes of radiolarian shells in Antarctic waters, on the annual flux pattern, the species distribution and its ecological significance, and on alteration processes of the radiolarian shells in the water column and at the sediment/water interface. A 28-month monitoring with time-series sediment traps in the Bransfield Strait indicates an annual flux pattern characterized by short-term flux pulses during austral summer, which reach daily fluxes of up to 5 × 10³ shells m^–2 and which account for more than 90% of the total annual flux. The distinct seasonal variations are linked to variations in the sea ice coverage. Other controlling factors are the production of phytoplankton and the impact by zooplankton grazers, e.g., krill. During the summer flux pulses the vertical fluxes of radiolarians range between ca. 3 and 21 × 10⁴ shells m^–2, values that are one or more orders of magnitudes lower than fluxes observed at sites in the tropical and northern high-latitude ocean. Significant lateral transport of radiolarians was documented during the austral summer in the Bransfield Strait by a factor of 10 increase of the radiolarian flux in the lower portion of the water column and the species composition trapped in deeper waters. Radiolarian assemblages associated with pelagic and neritic environments characterized by typical Antarctic taxa (Antarctissa spp.) and a group of species with bipolar distribution (e.g. Plectacantha oikiskos, Phormacantha hystrix), respectively, are distinguished. While the signal of polycystine radiolarians is relatively well recorded in the sediments, the shells of phaeodarians, which were observed at fluxes of up to 1 × 10³ shells m^–2day^–1 in the upper portion of the water column, are almost completely dissolved during settling through the water column.