Citations

The secretory granule matrix is a miniature biopolymer that consists of a charged polymer network that traps peptides and transmitters when it condenses and releases them on exocytotic decondensation. Models of exocytotic fusion have treated this matrix as a short circuit and have neglected its electrical contributions. This matrix responded to negative voltages by swelling, which was accompanied by a large increase in conductance, and to positive voltages by condensing. Thus, the matrix resembled a diode. The swollen matrix exerted large pressures on the order of 12 bar. The responses took place within milliseconds of the application of the electric field. These findings suggest that matrix decondensation, and therefore product release, is controlled by potential gradients.

Epidemiologic studies strongly associate eosinophilia-myalgia syndrome (EMS) with ingestion of tryptophan containing a contaminant ("peak E"). Prior reports have suggested that peak E is the di-tryptophan Nα-animal of acetaldehyde. Spectral and chemical studies now demonstrate that peak E is 1,1′-ethylidenebis[tryptophan]. This novel amino acid may be the etiological agent responsible for EMS, or it may be a marker of a still unidentified causal agent.

Transforming growth factor α (TGF-α) is produced by and required for the growth of epithelial cells and is angiogenic in vivo. Since epidermal hyperplasia and angiogenesis are hallmarks of psoriasis, TGF-α gene expression was analyzed in epidermal biopsies of normal and psoriatic skin. TGF-α messenger RNA and protein are much more abundant in lesional psoriatic epidermis than in normal-appearing skin of psoriatic patients or in normal epidermis. In contrast, messenger RNA levels of transforming growth factor β1 (TGF-β1), which inhibits epithelial cell growth, are not significantly different in normal, uninvolved, and lesional psoriatic epidermis. Thus, psoriatic epidermal hyperplasia may involve increased expression of a keratinocyte mitogen (TGF-α) rather than deficient expression of a growth inhibitor (TGF-β1).

RNA amplification with transcript sequencing (RAWTS) is a rapid and sensitive method of direct sequencing that involves complementary DNA synthesis, polymerase chain reaction (PCR) with a primer or primers containing a phage promoter, transcription from the phage promoter, and reverse transcriptase-mediated sequencing. By means of RAWTS, it was possible to sequence each of four tissue-specific human messenger RNAs (blue pigment, factor IX, phenylalanine hydroxylase, and tyrosine hydroxylase) in four cell types examined (white blood cells, liver, K562 erythroleukemia cells, and chorionic villus cells). These results indicate that there is a basal rate of transcription, splicing, and polyadenylation of tissue-specific mRNAs in adult and embryonic tissues. In addition to revealing sequence information, it is possible to generate a desired in vitro translation product by incorporating a translation initiation signal into the appropriate PCR primer. RAWTS can be used to obtain novel mRNA sequence information from other species as illustrated with a segment of the catalytic domain of factor IX. In general, the ability to obtain mRNA sequences rapidly across species boundaries should aid both the study of protein evolution and the identification of sequences crucial for protein structure and function.

The gene for von Recklinghausen neurofibromatosis (NF1), one of the most common autosomal-dominant disorders of humans, was recently mapped to chromosome 17 by linkage analysis. The identification of two NF1 patients with balanced translocations that involved chromosome 17q11.2 suggests that the disease can arise by gross rearrangement of the NF1 locus, and that the NF1 gene might be identified by cloning the region around these translocation breakpoints. To further define the region of these translocations, a series of chromosome 17 Not I-linking clones has been mapped to proximal 17q and studied by pulsed-field gel electrophoresis. One clone, 17L1 (D17S133), clearly identifies the breakpoint in an NF1 patient with a t(1;17) translocation. A 2.3-megabase pulsed-field map of this region was constructed and indicates that the NF1 breakpoint is only 10 to 240 kilobases away from 17L1. This finding prepares the way for the cloning of NF1 .