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Let M and P be Seifert 3-manifolds. Is there a degree one map f : M → P? The problem was completely solved by Hayat Legrand, Wang, and Zieschang for all casesexcept when P is the Poincaré homology sphere. We investigate the remaining case by elaborating and implementing a computer algorithm that calculates the degree. As a result, we get an explicit experimental expression for the degree through numerical invariants of the induced homomorphism f# : π1(M) → π1(P).

We describe here the use of PCR-generated templates incorporating T3 polymerase sites in order to prepare digoxigenin (DIG)-labelled cRNA probes against any gene of known sequence. This method was applied to the preparation of probes specific for chicken glyceraldehyde-3-phosphate dehydrogenase messenger RNAs and we demonstrate that such probes can be used forin situhybridization (ISH). This technique therefore represents a rapid and convenient means to prepare DIG-labelled cRNA probes for use in a non-radioactive ISH. It adds speed and convenience of probe preparation to the previously described advantages of non-radioactive detection techniques.

For a fiber bundle with a finite cohomology dimension and $ 1$ and $ 1$, we obtain the homology of the section space by an $ {E^1}$-terms are the homology of a product of Eilenberg-Mac Lane space of type $ K({H^{p - i}}(B;{\pi _p}F),i)$-spectral sequences which converges to the homology of the functional space $ \operatorname{Hom} (B,F)$10]). The differential is the product of two operations: one appears in the $ {E^1}$ $ \operatorname{Hom} (B,F)$9].

Ligand-activated retinoic acid receptor α (RARα) and c-ErbAα repress the AP-1-mediated transcriptional activation of the interstitial collagenase gene promoter by specifically decreasing the activity of the AP-1 transcription factor. On the other hand, the v-ErbA oncoprotein fails to repress the AP-1 activity and acts as a dominant negative oncoprotein by overcoming the repression of the AP-1 activity induced by RARα and c-ErbAα. This maintenance by v-ErbA of a fully active AP-1 complex is correlated with the abrogation by this same oncogene product of the growth-inhibitory response of chicken embryo fibroblasts to retinoic acid treatment. This new mechanism of action of v-ErbA together with its previously discovered dominant repressor effect on transcription of thyroid hormone-activated target genes may explain the contribution of the v-erbAoncogene to sarcomatogenic and leukemogenic transformation.

All manifolds M considered in this Note are orientable Seifert 3-manifolds with base surface S2 and infinite fundamental group π1(M). Our goal is to compute the cohomology ring H* (M; Z/2Z). The ring structure will enable us to determine whether M admits a degree 1 map into RP3 or not. We describe the equivariant chain complex for the universal cover M of M, and give a diagonal approximation. The cohomology ring H* (M; Z/2Z) is computed.