Novel specificity of an endoribonuclease of yeast

Investigations of the cleavage specificity of a cyclizing endoribonuclease of yeast show that it hydrolyzes Y-A bonds of single-stranded regions of RNA and that oligonucleotides are hydrolyzed poorly. The stringent specificity of the enzyme suggests that it may be useful for generating specific fragments of polyribonucleotides. An isolation technique employing ethanol extraction has now been used to isolate the enzyme free of other RNases, and the studies show that it is a small protein, 10 kDa or less in molecular mass.

Severe cutaneous reactions to captopril and enalapril; histological study and comparison with early mycosis fungoides

A severe non-dose related skin eruption attributable to treatment with captopril was recently reported: this is distinct from the dose related rashes that have been widely described. Ultrastructural and immunohistochemical studies were carried out to determine in detail the histological features of this eruption: the histological appearances were similar to those found in early mycosis fungoides, so that this disease was erroneously diagnosed in one case. Unlike most other complications resulting from treatment with Captopril, an indistinguishable rash can result from treatment with enalapril, a newer angiotensin converting enzyme inhibitor.

Inhibition of chloride secretion by BaCl2 in the rectal gland of the spiny dogfish, Squalus acanthias

In the rectal gland of the spiny dogfish (Squalus acanthias), chloride enters the cell via a cotransport system together with sodium and potassium in a 2 Cl-: 1 Na+: 1 K+ stoichiometry. The system is energized by the electrochemical potential for sodium directed into the cell. Sodium is extruded from the cell by Na-K-ATPase located on the basolateral cell membrane. Chloride leaks into the lumen following a favorable electrical gradient. Potassium is thought to recirculate across the basolateral cell membrane. Since barium ions inhibit the efflux of potassium from cells we used barium chloride to explore the role of potassium in the process of stimulated secretion of chloride by the gland. The secretion of chloride was stimulated with theophylline 2.5 X 10(-4)M and dibutyryl cyclic AMP 5 X 10(-5)M. Ba++ inhibited the secretion of chloride in a way that was reversible and dose dependent. The reduction in secretion was associated with a parallel fall in transglandular electrical potential. Inhibition was half maximal at a concentration of Ba++ of 10(-3)M. The reduction in efflux of potassium produced by Ba++ presumably decreases the potassium diffusion potential, thus reducing the electronegativity of the cell and dissipating the driving force for chloride across the apical cell membrane. Recirculation of K+ across the basolateral border of the cell would thus be essential for the maintenance of chloride secretion by the gland.

Biosynthesis and Degradation of a Wheat Embryo Cytokinin-Binding Protein during Embryogenesis and Germination

The accumulation and degradation of a wheat (Triticum durum) embryo cytokinin-binding protein (CBF-1) was followed during embryo development and germination by its N(6)-benzyladenine (BA) binding activity and immunological reactivity (rocket immunoelectrophoresis and Western blotting). Both BA binding activity and CBF-1 appeared at 2 weeks post-anthesis and rose sharply between 2 to 4 weeks before leveling off to approximately 47 micrograms per embryo (9% of the soluble embryo protein at maturity). In vitro translation of polyadenylated RNA from 20-day-old embryos yielded a polypeptide which was immunoprecipitable with anti-CBF-1 IgG and migrated closely to the 54-kilodalton CBF-1 polypeptide on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Upon germination, both the amount of CBF-1 and BA binding activity dropped to low levels within 3 days. The data are discussed in relation to the possible role of CBF-1 as a regulator of cytokinin availability, and comparisons are drawn between the structural and biosynthetic similarities found between CBF-1 and the vicilin storage proteins of legumes. An improved method for isolating undegraded CBF-1 from whole seeds is also presented.

Paranasal sinus mucormycosis in an immunologically competent host

A case of paranasal sinus mucormycosis in an immunocompetent patient is reported. After an extensive evaluation, no evidence of either diabetes mellitus or underlying immunologic abnormality was found. The combination of excisional surgery and amphotericin B therapy resulted in an excellent response. High-resolution axial and coronal computed tomography was useful in both planning treatment and monitoring the response to therapy.

Pyrimidine-specific cleavage by an endoribonuclease of Saccharomyces cerevisiae

An endoribonuclease with pyrimidine cleavage site specificity was isolated from Saccharomyces cerevisiae. The enzyme had a pH optimum of 6 to 7 and did not require a divalent cation. It was inhibited by 5 X 10(-5) M ethidium bromide, although it appeared to be single strand specific. The enzyme gave a limited cleavage of yeast mRNA and rRNA, yielding products that were terminated with pyrimidine nucleoside 2',3'-cyclic phosphate. The bonds between pyrimidine and A residues constituted more than 90% of the scission sites when the average product size was 50 nucleotides. Homopolyribonucleotides were cleaved poorly. Poly(A,U) was cleaved rapidly, and analysis of the products of poly(A,U) hydrolysis showed a very stringent cleavage of U-A bonds.

Frozen sections of bone biopsies in metabolic and other bone diseases

Frozen sections of bone trephine and needle biopsies can be satisfactorily cut in a standard cryostat and, when stained with haematoxylin and eosin, they enable a rapid diagnosis to be made in a wide range of metabolic bone disorders including Paget's disease, osteoporosis, osteomalacia, hyperparathyroidism and renal osteodystrophy. Neoplastic disease of bone may also be diagnosed using the same technique. A tissue diagnosis can be established within an hour of the biopsy being taken, instead of the 1-3 weeks required for resin section diagnosis, with a consequent potential saving in further costly biochemical and radiological investigations, a possible shortening of the patient's stay in hospital and earlier initiation of correct treatment. The method is quick, reliable and highly cost-effective; it is of particular value in laboratories with insufficient workload to justify the expenditure on specialized microtomes and reagents for resin embedding.