Oskar organizes the germ plasm and directs localization of the posterior determinant nanos

Oskar is one of seven Drosophila maternal-effect genes that are necessary for germline and abdomen formation. We have cloned oskar and show that oskar RNA is localized to the posterior pole of the oocyte when germ plasm forms. This polar distribution of oskar RNA is established during oogenesis in three phases: accumulation in the oocyte, transport toward the posterior, and finally maintenance at the posterior pole of the oocyte. The colocalization of oskar and nanos in wild-type and bicaudal embryos suggests that oskar directs localization of the posterior determinant nanos. We propose that the pole plasm is assembled stepwise and that continued interaction among its components is required for germ cell determination.     

Transcriptional regulation by the nuclear receptor superfamily

In the past year, additional experimental data have expanded our understanding of the molecular mechanisms that underlie nuclear receptor control of regulatory programs. It is increasingly clear -that steroid members (e.g. glucocorticoid and estrogen) and non-steroid members (e.g. retinoic acid, thyroid hormone, and vitamin D) of the nuclear receptor superfamily may utilize distinct strategies in achieving their complex control of gene regulation.     

The malmö polymorphism of coagulation factor IX, an immunologic polymorphism due to dimorphism of residue 148 that is in linkage disequilibrium with two other F.IX polymorphisms

A mouse monoclonal antibody (MAB 9.9) to coagulation factor IX (F.IX) detects a polymorphism in the plasma of normal people. Its epitope has been narrowed down to <6 amino acids in the activation peptide of the X-linked F.IX protein. The activation peptide contains a dimorphism—Thr:Ala—at position 148 of the protein. Using synthetic oligonucleotides, we have demonstrated that (1) the F.IX which reacts with 9.9 has Thr at position 148 and (2) that which does not has Ala. Positive reactors (148^thr) are designated Malmö A, and negative reactors (148^ala) are designated Malmö B. The plasma levels of AA women are indistinguishable from those of A men, and both B men and BB women are null against MAB 9.9. The plasma level of Malmö A in AB women is approximately half that of AA women, and “lyonization” is clearly operating in the heterozygotes. The dimorphism is in strong linkage disequilibrium with two other intragenic RFLPs, TaqI and XmnI. Furthermore, intragenic crossing-over—including double crossing-over—appears to have occurred between the three sites. Seven of the eight possible haplotypes have been identified, five in men and two others in women. The immunoassay that identifies ～50% of the AB women in the pool of Malmö A females with 95% confidence identifies men unambiguously as A or B. The assay would be very useful for population-genetic studies of the Malmö epitope if the studies were limited to men.     

Differential sensitivities to gamma radiation of human bladder and testicular tumour cell lines

Gamma radiation sensitivities of continuous cell lines from nine human tumours were measured, comparing four derived from transitional cell carcinomas of the bladder with five from non-seminomatous germ cell tumours of the testis. The testicular cells were significantly more radiosensitive than the bladder cells, corresponding to the response to therapy of these tumour types in patients. These observations indicate that radiosensitivity is retained in vitro and is an inherent property of the testicular tumour cells. These gamma radiation sensitivities were compared with those of SV40-transformed fibroblasts derived from a normal individual and one with the heritable disease, ataxia-telangiectasia (A-T). The bladder cells had gamma radiation sensitivities similar to that of the SV40-transformed normal line. The testicular cells were hypersensitive to gamma radiation, although not as sensitive as the SV40-transformed A-T line. A-T cells, unlike those derived from normal individuals, continue to synthesize DNA at a normal rate following radiation exposure, prompting a comparison of the kinetics of DNA synthesis in three bladder and three testicular tumour cell lines. One of the bladder and two testicular lines showed a reduced inhibition when compared to the other tumour cell lines and the SV40-transformed normal line. Thus there was no clear association between DNA synthesis inhibition and radiosensitivity.     

Litter parameters and spontaneous abnormalities in Himalayan rabbits

A joint study was undertaken in three testing facilities to evaluate cumulative background data of Himalayan rabbits. All litters were derived from control does. The conception rate was high (84.0-95.1%) but the average numbers of corpora lutea (7.9-8.7), implantation sites (6.5-7.5) and viable fetuses (5.8-6.9) were somewhat lower than that of most other strains of rabbit. Altogether 90 malformed fetuses (1.12%) and 425 fetuses with variations (5.27%) occurred among 8,060 virable fetuses.     

Lysosomal uptake of isolated cell organelles microinjected into HeLa cells

Lysosomes and microsomes were isolated from rat liver and microinjected into the cytoplasm of HeLa cells. The fate of the transplanted organelles and their effects on the recipient cells were followed in the electron microscope at various time intervals after administration. Needle injection with buffer or sucrose did not seem to evoke any ultrastructural alterations, such as induced autophagy or other signs of sublethal cell injury. Recipients of microinjected cell organelles elicited a rapid and conspicuous increase in membrane-bounded cytoplasmic vacuoles, concomitant with the disappearance of the injected material. Golgi complexes became abundant with many small vesicles clustering around their cisternae. The volume density of the lysosomal compartment increased 2-3-fold after organelle injection as compared with control-injected (0.3 M sucrose) or noninjected cells. Our preliminary results show that isolated cell organelles can be microinjected into cells n culture and indicate that the microinjected organelles were segregated from the cytoplasm into membrane-bounded vacuoles probably through autophagolysosome formation. Thus, this technique offers an additional approach for studies on the segregation and degradation of cell organelles in somatic cells and may enable more detailed analyses on the mechanisms of autophagic sequestration of specific cell organelles.