Diffuse Conduction Abnormalities in an Adolescent with Familial Sinus Node Disease

We report a case of familial sinus node disease with associated conduction abnormalities in the atrioventricular node and distal conduction system Spontaneous atrial pacemaker activity was absent though the atrium could be depolarized. The pacemaker activity of the heart resided in the atrioventricular junction. The AV node showed impaired automaticity and abnormal conduction properties which partially improved after vagal blockage.     

Costs of Magnetic Resonance Imaging Services in Public Hospitals

Audited cost data from two public hospital installations participating in a trial of the utilisation and efficacy of magnetic resonance imaging are presented. The data cover the period July 1987 to June 1988 when both installations had attained stable patterns of operation. One hospital operated a superconductive system and the other a resistive magnetic resonance imaging unit. Depreciation and salaries represented the major components of cost.     

Comparison of the stability of a mite and a pollen extract stored in normal conditions of use

Pollen extracts are stable in solutions containing 50% glycerol. The stability of Dermatophagoides pteronyssinus (Dp) extracts have not been determined. Two lyophilised extracts (Dp and cocksfoot pollen) were reconstituted in 50% glycerol and stored for up to 6 months at +4°C. Every day the extracts were placed at room temperature for 1 hr to mimic the natural use of allergen extracts by allergists. Every 2 months the extracts initially prepared were compared to freshly reconstituted extracts by means of prick skin tests in fifteen allergic patients. It was observed that cocksfoot pollen extract is stable but there appears a slight but significant (P > 0.05) decay in activity when the extract stored for up to 6 months was compared with a freshly prepared extract. On the other hand there is a significant (P > 0.01) decay in activity of the Dp extract after 2 months of storage. Dermatophagoides pteronyssinus and cocksfoot pollen extracts behave differently when stored. These findings have particular importance in the diagnosis and treatment of allergic disorders.     

Investigation of the structural parameters involved in the δ-opioid selectivity of several families of opioid peptides

Three series of highly δ-opioid selective peptides are now available, and each family is used as template to investigate the structural parameters involved in δ-receptor recognition and in the modulation of the selectivity of the parent peptide. The first series includes cyclic derivatives such as Tyr-D-Pen-Gly-Phe-D-Pen(DPDPE) and Tyr-D-Pen-Gly-Phe-Pen(DPLPE); the second are the synthetic linear constrained peptides [Tyr-D-Ser(OtBu)-Gly-Phe-Leu-Thr(DSTBULET), Tyr-D-Ser(OtBu)-Gly-Phe-Leu-Thr(OtBu) (BUBU) and especially Tyr-D-Cys(StBu)-Gly-Phe-Leu-Thr(OtBu) (BUBUC)] and the last one the natural peptides [Tyr-D-Met-Phe-His-Leu-Met-Asp-NH₂ (deltorphin or dermenkephalin) and Tyr-D-Ala-Phe-Asp-Val-Val-GlyNH₂ ([D-Ala²] deltorphin I)]. In the present study, the possibly of transposing some of the decisive factors of δ-selectivity evidenced in the two other families, to the linear constrained peptides series was examinated. With this aim in view, residues such as Phe³, pClPhe⁴ or Asp were introduced in the sequence of DSTBULET, BUBU or BUBUC. Direct comparison between the biochemical profiles of the [pClPhe⁴] analogs of the linear constrained peptides and their parent compounds shows that the addition of an electronegative atom on the Phe⁴ residue of enkephalin sequences is not an absolute parameter for δ-selectivity improvement. The hydrophobic δ-receptor subsite seems able to receive a range of molecular volumes and electronegativities. By contrast, this subsite cannot interact with a Phe³ aromatic ring introduced in this series of peptides. Moreover, the results obtained with linear peptides including additional negatively charged residues demonstrate that the proposed location of the δ-receptors in a cationic membrane environment is not adequate to explain the selectivity profile of a number of compounds.     

Release of platelet-activating factor (PAF-acether) from alveolar macrophages by the calcium ionophore A 23187 and phagocytosis

Platelet-activating factor (PAF-acether) was recovered from rabbit, rat and human alveolar macrophages stimulated with the Ca++ ionophore A23187. PAF-acether release was also obtained from rat and rabbit macrophages in the presence of zymosan, but not from human alveolar preparations in spite of the phagocytic activity exhibited by the latter cells. Observed releases were active, Ca++ dependent, and plateaued at 45 min. No PAF-acether was released from lungs washed out of their macrophages, another argument against the mastocyte origin of this mediator. Given the potent bronchoconstrictive activity of PAF-acether, its release from alveolar macrophages may provide an alternative explanation for non IgE-dependent asthmas and the implication of platelets in pulmonary diseases.     

Chemical modification of ribonuclease A with 4-arsono-2-nitrofluorobenzene

4-Arsono-2-nitrofluorobenzene reacts selectively at the anion binding site of bovine pancreatic ribonuclease A. The major derivative is the inactive 41-(4-arsono-2-nitrophenyl) ribonuclease A (45% yield). Additional products are 1-α-(4-arsono-2-nitrophenyl) ribonuclease A (11% yield) which is enzymatically active and the disubstituted, inactive 1,41-bis-(4-arsono-2-nitrophenyl) ribonuclease A (25% yield). 2′ (3′)-O-Bromoacetyluridine reacts with 41-(4-arsono-2-nitrophenyl) ribonuclease A exclusively at the histidine-12 residue at a rate which is approximately one-fourth the rate observed with the unmodified enzyme. Saturation kinetics are observed and the dissociation constant for the protein-inhibitor complex is 0.096 ± 0.023 M. The first-order unimolecular decomposition constant for complex breakdown is 8.9 ± 2.9 times 10^-4s^-1. 2′-Bromoacetamido-2′-deoxyuridine reacts with 41-(4-arsono-2-nitrophenyl) ribonuclease A 25 times more slowly than 2′(3′)-O-bromoacetyluridine. Bromo-acetate reacts with 41-(4-arsono-2-nitrophenyl) ribonuclease A predominantly at the histidine-119 residue at a rate 45 times less than that found for the unmodified enzyme. The results of the alkylation studies imply that the dianionic arsonate does not occupy the phosphate binding site in the enzyme but is sufficiently proximate to account for a decrease in bromoacetate binding as well as a reduction in the nucleophilic reactivity of histidine-12 and -119. All these effects may be accounted for in terms of a local electrostatic perturbation of the active site region by the arsononitrophenyl group.