Poliovirus antigen chimeras.

Poliovirus, the aetiological agent of paralytic poliomyelitis, is arguably the best characterized of all animal viruses. Using recombinant-DNA technology, this information, together with the availability of infectious cDNA clones of the notably safe and efficacious live attenuated Sabin 1 vaccine strains of poliovirus, has enabled the creation of hybrid viruses (chimeras) possessing novel antigenicity. The potential applications of these 'epitope-presentation systems' include their use as immunogens, as antigens for serodiagnosis, and as vaccines.     

Structure of equine corticotropin releasing factor

A 41 amino acid peptide, probably identical in structure to human corticotropin releasing factor, was isolated from 70 equine hypothalami by methanol extraction, immunoaffinity chromatography and single step of reverse phase HPLC. The amino acid sequence was determined by gas phase sequence analysis. Probable carboxyl terminal amidation was demonstrated by similar retention times for equine and human corticotropin releasing factor on reverse phase HPLC at pH 8. The likely structure of equine corticotropin releasing factor is: Ser-Glu-Glu-Pro-Pro- Ile-Ser-Leu-Asp-Leu-Thr-Phe-His-Leu-Leu-Arg-Glu-Val-Leu-Glu-Met-Ala-Arg-Ala-Glu-Gln-Leu-Ala-Gln-Gln-Ala-His-Ser-Asn- Arg-Lys-Leu-Met-Glu-Ile-Ile-NH₂. The purified peptide is equipotent with human corticotropin releasing factor in an in vitro bioassay and in a human plasma binding protein assay.     

Genetic and molecular evidence of an X-chromosome deletion spanning the tabby (Ta) and testicular feminization (Tfm) loci in the mouse

A new radiation-induced mutation in the mouse, tabby-25H (Ta25H), has proved to be a deletion which spans both the tabby and testicular feminization (Tfm) loci on the X chromosome. The Ta phenotype closely resembles that of the original TaFa mutation in both the heterozygous and hemizygous conditions but Ta25H/Y animals additionally show the Tfm/Y phenotype, being externally female but possessing abdominally located testes. There is a shortage of both Ta25H/+ and Ta25H/Y classes relative to their normal sibs among the progeny of Ta25H/+ females at weaning age and this was indicated to be due to prenatal or neonatal losses. Exencephaly was observed in some members of both classes prior to birth. Both Ta25H classes tend to be runted at weaning but, remarkably, Ta25H/+ females often show a range of abnormalities not evident in Ta25H/Y animals. When probes for the Zfx, Ccg-1, Phk, and DXPas19 loci, which lie close to Ta, were hybridised to DNAs from Ta25H hemizygotes, the profiles of the X-linked bands were similar to those of control DNAs, suggesting these loci lie outside the deletion. However, a clear absence of an X-linked band was found with human androgen receptor probes, indicating that the Tfm locus is indeed missing. The deletion, therefore, extends a minimum of 1.5 cM and, with its proximal and distal boundaries partially defined, it could be as large as 4 cM. As Ta25H/+ females show the striped X-inactivation coat pattern, the putative X-inactivation centre, Xce, which lies close to Ta, cannot be located within the region deleted. The greasy (Gs) locus similarly appears to lie outside the deletion.     

Characterization of mutant TMK368K pig citrate synthase expressed in and isolated from Escherichia coli

A cDNA that encodes pig citrate synthase (PCS) was inserted into a plasmid T7 vector and was expressed in an E. coli gltA mutant. Up to 10 mg of purified PCS was obtained from 2 liters of E. coli. The mammalian protein produced in E. coli comigrated with the enzyme purified from pig heart on a SDS-polyacrylamide gel (SDS-PAGE) with an Mr of 50,000, and reacted with a polyclonal antibody directed against pig heart citrate synthase. The Vmax and Km of the expressed PCS were indistinguishable from those of the pig heart enzyme. The PCS produced in E. coli did not contain the trimethylation modification of Lys 368, characteristic of the pig heart enzyme. These data suggest that the PCS protein produced in E. coli is catalytically similar to the enzyme purified from pig heart and methylation of Lys 368 is not essential for catalysis.     

Enucleation of protoplasts derived from suspension cultures of winged bean and from a crown gall cell line ofParthenocissus tricuspidata

Protoplasts derived from suspension cultures of the winged bean and a crown gall lineof Parthenocissus tricuspidata were enucleated by centrifugation on iso-osmotic discontinuous Percoli gradients and on discontinuous sucrose-mannitol density gradients. Enucleation was achieved according to the buoyant density of the protoplasts and preparations of both cytoplasts and miniprotoplasts were recovered. The Percoll gradients gave more satisfactory results than the sucrose-mannitol gradients. Enucleation was increased by raising the centrifugal force from 20 kg to 60 kg. The presence of nuclei was determined by the DNA specific probe 4′6-diamidino-2-phenylindole (DAPI). Membrane integrity, as measured by staining with fluorescein diacetate, showed that some 85 % of the cytoplasts were bounded by an intact plasma membrane.     

Clinical pharmacodynamics of anticancer drugs: a basis for extending the concept of dose-intensity

The studies reviewed herein support the precept that "systemic dose-intensity" (i.e., systemic exposure) may be more informative than "administered dose-intensity" for certain anticancer drugs. This does not mean that the administered dose-intensity should be ignored; in fact these data indicate the importance of documenting and assessing administered dose-intensity as an initial step toward identifying those situations where systemic dose-intensity may be most important. The studies described in this review were selected as representative examples of successful clinical pharmacodynamic studies; other published examples include vincristine AUC versus severity of neurotoxicity, etoposide systemic exposure versus leukopenia, red cell concentration of mercaptopurine metabolites versus neutropenia in children with ALL, and ARA-CTP retention in leukemic blasts versus clinical response in acute non-lymphocytic leukemia. As is the case with other types of clinical trials in cancer patients, there are also examples of negative pharmacodynamic studies (i.e., no relationship found between concentration and effects). There are several possible reasons for such negative findings, including the lack of such a relationship for some drugs, measuring the inappropriate drug moiety (e.g., failure to measure all active metabolites), measuring drug concentrations in the wrong biological fluid, evaluating systemic exposure over too narrow a range (i.e., all patients have either sub- or supra-therapeutic systemic exposure), selecting inappropriate sampling times or pharmacokinetic parameters, inadequately assessing drug toxicity or response, or simply studying an inadequate number of patients or patients with drug-resistant cancers. Therefore, negative findings in some pharmacodynamic studies should not deter the investigation of other drugs and/or other malignant diseases, just as negative therapeutic trials do not preclude subsequent clinical trials in oncology. Also, finding a relation between systemic exposure and drug toxicity, in the absence of a clear relation to antitumor effects, is potentially of great clinical utility. Such data should allow more objective escalation of drug dosages in individual patients, to ensure maximum dose-intensity while avoiding host toxicity. Obviously, if such dose escalation could be guided by more easily measured patient characteristics (e.g., age, weight, CrCl, shoe size, etc.), then using drug concentrations in individual patients might be obviated.(ABSTRACT TRUNCATED AT 400 WORDS)