Coralline hydroxyapatite bone graft substitutes: preliminary report of radiographic evaluation

A new bone graft substitute made by conversion of the calcium carbonate exoskeleton of reef-building sea coral into hydroxyapatite has recently become clinically available. The normal radiographic appearance of two forms of this material is described. In the immediate postoperative period, the exoskeletal architecture of these implants is readily appreciated. With graft incorporation over the ensuing months, their intrinsic structure is gradually lost in association with poor marginal definition. Evolving radiographic findings reflect the biocompatible nature of these implants, which provides the potential for ingrowth of native bone with preservation of the coralline scaffold, resulting in enhanced biomechanical properties.     

Restorative treatment need assessment by dentally and nondentally trained subjects

A study was carried out which compared how two groups of people, one with clinical dental experience and one without, assessed restorative dental treatment need. Using a visual analogue scale, a group of final year dental students ( n = 50) and nonclinical university students ( n = 50) assessed the extent to which they considered common dental imperfections, viz. spacing of the upper anterior teeth and discolouration of upper anterior teeth, warranted restorative correction. The group of dental students judged the necessity for treatment of discolouration to be more urgent than correction of spacing. The nondental group did not differentiate between the degrees of need. Data were non‐normal in distribution but the use of appropriate statistical tests showed the differences in mean assessments to be significant.     

Method for maximising measurements of muscular pulmonary arteries.

Using a digitiser for assessing the media and intima of muscular pulmonary arteries, we have previously shown that the most sensible measurements are those of medial and intimal area and that artery size should be defined in terms of the total length of internal elastic lamina. These measurements do not vary with the collapse or constriction of the artery. A cross sectional cut and a well defined internal elastic lamina are essential for measurement using our technique. This study explores methods for obtaining the above three measurements for cross sectionally cut arteries with an ill defined internal elastic lamina, with a view to increasing the number of arteries measured. The methods were tested on three subjects, using arteries for which the true values of the three variables were known. Acceptable estimates of medial and intimal area could be obtained by simply delineating the boundaries of the intima and media and ignoring the crinkles in the elastic laminae. It was also found that muscular pulmonary arteries may not be uniformly collapsed or constricted round the circumference of their walls and that the overall degree of collapse or constriction seemed to be affected by the size of the artery. An acceptable estimate of the total length of an internal elastic lamina was most readily obtained by multiplying the length of the boundary between intima and media by a crinkle factor based on an optical assessment of the amount of crinkling in that internal elastic lamina.     

Identification of non-amplifying CYP21 genes when using PCR-based diagnosis of 21-hydroxylase deficiency in congenital adrenal hyperplasia (CAH) affected pedigrees

Steroid 21-hydroxylase deficiency is among the most common inborn errors of metabolism in man. Characterization of mutations in the 21- hydroxylase gene (CYP21) has permitted genetic diagnosis, facilitated by the polymerase chain reaction (PCR). The most common mutation is conversion of an A or C at nt656 to a G in the second intron causing aberrant splicing of mRNA. Homozygosity for nt656G is associated with profoundly deficient adrenal cortisol and aldosterone synthesis, secondary hypersecretion of adrenal androgens, and a severe form of congenital adrenal hyperplasia (CAH) characterized by ambiguous genitalia and/or sodium wasting in newborns. During the course of genetic analysis of CYP21 mutations in CAH families, we and others have noticed a number of relatives genotyped as nt656G homozygotes, yet showing no clinical signs of disease. A number of lines of evidence have led us to propose that the putative asymptomatic nt656G/G individuals are incorrectly typed due to dropout of one haplotype during PCR amplification of CYP21. For prenatal diagnosis, we recommend that microsatellite typing be used as a supplement to CYP21 genotyping in order to resolve ambiguities at nt656.      

Effects of the PKA inhibitor H-89 on excitation–contraction coupling in skinned and intact skeletal muscle fibres

This study investigated the effects of the protein kinase A (PKA) inhibitor, H-89, in mechanically-skinned muscle fibres and intact muscle fibres, in order to determine whether PKA phosphorylation is essential for normal excitation–contraction (E–C) coupling. In skinned EDL fibres of the rat, force responses to depolarization (by ion substitution) were inhibited only slightly by 10M H-89, a concentration more than sufficient to fully inhibit PKA. Staurosporine (1 M), a potent non-specific kinase inhibitor, also had little if any effect on depolarization-induced responses. At 1–2 M, H-89 significantly slowed the repriming rate in rat skinned fibres, most likely due to it deleteriously affecting the T-system potential. With 100 M H-89, the force response to depolarization by ion substitution was completely abolished. This inhibitory effect was reversed by washout of H-89 and was not due to block of the Ca²⁺ release channel in the sarcoplasmic reticulum (SR). In intact single fibres of the flexor digitorum longus (FDB) muscle of the mouse, 1–3 M H-89 had no noticeable effect on action-potential-mediated Ca²⁺ transients. Higher concentrations (4–10 M) caused Ca²⁺ transient failure in fibres stimulated at 20 Hz in a manner indicative of action-potential failure. At 10–100 M, H-89 also inhibited net Ca²⁺ uptake by the SR and affected the Ca²⁺-sensitivity of the contractile apparatus in rat skinned fibres. All such effects were proportionately greater in toad muscle fibres. These results do not support the hypothesis that phosphorylation is essential for the Ca²⁺ release channel to open in response to voltage-sensor activation in skeletal muscle fibres.     

Requirements for the development of IL-4-producing T cells during intestinal nematode infections: what it takes to make a Th2 cell in vivo

Summary: Components of the type 2 immune response may mediate host protection against both helminthic parasites and harmful allergic responses. A central player in this response is the T‐helper 2 (Th2) effector cell, which produces interleukin (IL)‐4, IL‐5, IL‐13, and other Th2 cytokines during the primary and memory response. Specific aspects of the parasite that trigger Th2‐cell differentiation are not yet defined. Furthermore, the cell types and cell surface and secreted molecules that provide the immune milieu required for the development of Th2 effector cells and also Th2 memory cells are not well understood. They will probably vary with the particular helminth or other antigen inducing the Th2 response. We have used third stage larvae of intestinal nematode parasites as adjuvants to promote naïve nonparasite antigen‐specific T cells to differentiate into Th2 cells. This model system avoids possible parasite antigen‐specific T‐cell clones or cross‐reactive memory T cells that may preferentially differentiate into Th2 effector cells during the course of infection and confound the stereotypical components of parasite‐induced Th2 cell differentiation. We have found that these parasites have a potent adjuvant effect and have used our model system to begin to investigate the events that lead to the development of polarized Th2 cells in vivo.