Molecular architecture of the human specialised atrioventricular conduction axis

The atrioventricular conduction axis, located in the septal component of the atrioventricular junctions, is arguably the most complex structure in the heart. It fulfils a multitude of functions, including the introduction of a delay between atrial and ventricular systole and backup pacemaking. Like any other multifunctional tissue, complexity is a key feature of this specialised tissue in the heart, and this complexity is both anatomical and electrophysiological, with the two being inextricably linked. We used quantitative PCR, histology and immunohistochemistry to analyse the axis from six human subjects. mRNAs for ~ 50 ion and gap junction channels, Ca²⁺-handling proteins and markers were measured in the atrial muscle (AM), a transitional area (TA), inferior nodal extension (INE), compact node (CN), penetrating bundle (PB) and ventricular muscle (VM). When compared to the AM, we found a lower expression of Na_v1.5, K_ir2.1, Cx43 and ANP mRNAs in the CN for example, but a higher expression of HCN1, HCN4, Ca_v1.3, Ca_v3.1, K_ir3.4, Cx40 and Tbx3 mRNAs. Expression of some related proteins was in agreement with the expression of the corresponding mRNAs. There is a complex and heterogeneous pattern of expression of ion and gap junction channels and Ca²⁺-handling proteins in the human atrioventricular conduction axis that explains the function of this crucial pathway.     

Metallurgical aspects and corrosion behavior of yellow low-gold alloys

Three copper-free type III yellow low-gold alloys (Ag-Au-In-Pd-Zn) were investigated. Microstructural analysis was performed with x-ray diffraction, light microscopy, and an electron x-ray micro-analysis. The electrochemical behavior of the alloys was tested with standard potentiodynamic techniques in 0.9% saline solution and an artificial saliva and compared with that of a traditional high-gold alloy. The three alloys turned out to be two-phase mixtures of a fcc (matrix) and a bcc (island) phase. The yellow color, present in spite of the low-gold content, was caused by the disordered Pd-In, island-type structure. An additional third structure was seen after etching. However, no distinct phase could be correlated with it. The corrosion behavior for the experimental alloys, based on cyclic polarization, can be considered acceptable in both electrolytes used, but is inferior to that of the control alloy.     

Trends in selected obstetric complications from University Hospital, Kuala Lumpur, Malaysia.

Trends in selected pregnancy complications from 1969 to 1987 in a tertiary hospital in Malaysia are presented. Complications reviewed were abortion, ectopic pregnancy, anemia, hypertension, hyperemesis, antepartum and postpartum hemorrhage. Possible explanations for the observed trends were discussed, including the role of improved obstetric care and changes in the characteristics of the childbearing population. The data presented give some indication of maternal morbidity in the childbearing population served by this tertiary center and should lead to improvements in provision of services as well as in health data collection in the future.     

A double blind cross-over study of high-frequency emphasis hearing aids in individuals with noise-induced hearing loss

This study compared the benefits of a high-frequency emphasis hearing aid and a more conventional, flatter response aid. Subjects with moderate noise-induced hearing loss were fitted binaurally within a double blind procedure. Each aid type was worn for 1 month, during which the subjects completed diaries concerning their problems in various listening situations. At the end of each month, a satisfaction questionnaire was completed and free field assessment, consisting of speech in noise discrimination measurement and warble tone threshold determinations, was performed. Results indicated that although there were few significant differences found between the aids using any of the assessment techniques, the subjects generally preferred the aid with the high-frequency emphasis.