Evidence for spontaneous neuro-melanophore activity inPseudopleuronectes americanus (teleostei; pleuronectiformes) during total darkness

Summary In total darkness, melanophores of much of the integumentary pattern ofPseudopleuronectes americanus display intermediate melanosome distribution, whilst the-adrenoceptor antagonist phentolamine evokes their complete dispersion. The intermediate condition is not attained in total darkness in locally decentralized melanophores. It is proposed that, in the absence of photic stimulation, spontaneous neural activity sustains a partial melanosome aggregation in this species.     

Immunization of hu-PBL-SCID mice and the rescue of human monoclonal Fab fragments through combinatorial libraries.

Antibodies are usually prepared from recently boosted animals and reflect ongoing immune responses. In humans, this is restrictive as ethical constraints generally prevent antigen-boosting. Therefore the rich memory compartment of human antibody responses remains largely untapped. Severe combined immune deficiency (SCID) mice populated with human cells allow the stimulation of human antibody memory without the usual constraints. Here we show how peripheral blood lymphocytes can be stimulated by antigen to produce large secondary responses after transfer to SCID mice. Specific monoclonal human Fab fragments can then be isolated from the mice by repertoire cloning even when the human donor's last contact with antigen was more than 17 years ago.     

DNA sequence and analysis of human chromosome 9

Chromosome 9 is highly structurally polymorphic. It contains the largest autosomal block of heterochromatin, which is heteromorphic in 6-8% of humans, whereas pericentric inversions occur in more than 1% of the population. The finished euchromatic sequence of chromosome 9 comprises 109,044,351 base pairs and represents >99.6% of the region. Analysis of the sequence reveals many intra- and interchromosomal duplications, including segmental duplications adjacent to both the centromere and the large heterochromatic block. We have annotated 1,149 genes, including genes implicated in male-to-female sex reversal, cancer and neurodegenerative disease, and 426 pseudogenes. The chromosome contains the largest interferon gene cluster in the human genome. There is also a region of exceptionally high gene and G + C content including genes paralogous to those in the major histocompatibility complex. We have also detected recently duplicated genes that exhibit different rates of sequence divergence, presumably reflecting natural selection.     

Pituitary hyperplasia and gigantism in mice caused by a cholera toxin transgene.

Cyclic AMP is thought to act as an intracellular second messenger, mediating the physiological response of many cell types to extracellular signals. In the pituitary, growth hormone (GH)-producing cells (somatotrophs) proliferate and produce GH in response to hypothalamic GH-releasing factor, which binds a receptor that stimulates Gs protein activation of adenylyl cyclase. We have now determined whether somatotroph proliferation and GH production are stimulated by cAMP alone, or require concurrent, non-Gs-mediated induction of other regulatory molecules by designing a transgene to induce chronic supraphysiological concentrations of cAMP in somatotrophs. The rat GH promoter was used to express an intracellular form of cholera toxin, a non-cytotoxic and irreversible activator of Gs. Introduction of this transgene into mice caused gigantism, elevated serum GH levels, somatotroph proliferation and pituitary hyperplasia. These results support the direct triggering of these events by cAMP, and illustrate the utility of cholera toxin transgenes as a tool for physiological engineering.     

The influence of cations on contracture in the superfused ventricle ofHelix aspersa

Zusammenfassung Die isometrische Kontraktionsspannung in der isoliertenHerzkammer — mit Wechselstrom gereizt—nimmt mit der Kalziumkonzentration im Medium bis zu einem « Plateau » zu. Dem Kalziumeffekt wird durch Magnesium entgegengewirkt während Veränderungen der Natriumkonzentration keinen entscheidenden Einfluss haben.