Patellofemoral joint arthroplasty: patient selection,surgical technique and outcomes

Isolated patellofemoral arthritis is an increasingly recognized entity, and is usually associated with previous patellofemoral dysplasia or instability. Patellofemoral arthroplasty (PFA) has evolved significantly in recent years, both in terms of implant design and importantly in the understanding of appropriate patient selection. This review outlines the indications and investigations for PFA, provides a brief history of the development of contemporary implants, and presents the clinical outcomes for the prostheses most commonly used in the UK. In addition, it provides a detailed surgical technique for implantation of an onlay implant, with tips on how to optimize patellofemoral biomechanics and thus achieve a consistently good outcome.     

Quantitation of benzo(a)pyrene and 7,12-dimethylbenz(a)anthracene binding to nuclear macromolecules in human and rat mammary epithelial cells

Our laboratory has developed virtually identical techniques for the isolation and culture of mammary epithelial cells (MEC) from rats and humans. In a cell-mediated mutagenesis assay, rat MEC activated 7,12-dimethylbenz(a)anthracene (DMBA) but not benzo(a)pyrene [B(a)P] to mutagenic forms, and the opposite pattern was found with human MEC. These species-specific patterns were not readily explained by either qualitative or quantitative differences in Phase I metabolism of these compounds. In contrast, relative levels of covalent binding of these compounds to DNA in the human and rat cells under identical assay conditions generally parallel the pattern of the mutagenesis results, while not reflecting the absolute levels of metabolism in each system. The ability of the rat MEC to bind relatively higher levels of DMBA than B(a)P to nuclear DNA, and the reversed pattern in human MEC, was found at all incubation times tested between 6 and 48 h. Culture density was found to exert a greater effect on the levels of PAH-DNA binding in rat than in human cells, but in neither case did it affect the ratio of DMBA to B(a)P binding within a species. C2SO4 gradient separation of nuclear macromolecules from PAH-treated MEC revealed that the relative DNA binding levels of DMBA and B(a)P did not correlate with relative levels of nuclear protein binding. For both species, nuclear (DNA + protein) binding levels of B(a)P were approximately 2-fold higher than DMBA. However, these binding levels were 4 to 5-fold higher for both carcinogens in the human than in the rat MEC. The species-specific patterns of PAH activation shown by these cells suggest that caution should be used in extrapolating rodent carcinogenesis data to humans, for either quantitative or qualitative purposes.     

Anesthesia affects respiratory and sympathetic nerve activities differentially.

Phrenic and cervical sympathetic nerve responses to hypercapnia were examined before and after anesthesia in twelve midcollicularly decerebrated, vagotomized, glomectomized, paralyzed and ventilated cats. We measured responses of integrated phrenic and cervical sympathetic nerve activities to increases in end-tidal PCO2 (PETCO2) from apneic threshold to approximately 30 torr above threshold. All cats were studied first in the unanesthetized state. Six cats were then restudied after a quarter of a usual dose of chloralose/urethane (10 mg/kg and 62.5 mg/kg, respectively) and then after half the usual dose of chloralose/urethane (20 mg/kg and 125 mg/kg). The other six animals were restudied after quarter of a standard dose of pentobarbital (9 mg/kg), after half the standard dose (18 mg/kg) and then after the full (35 mg/kg) dose. Both anesthetic agents led to significant increases in apneic thresholds for both phrenic and sympathetic nerve activities. These agents also caused dose-dependent decreases in peak, tonic and respiratory-related sympathetic nerve activities. Peak (tidal) phrenic nerve activities, in comparison, were much less affected by the anesthetic agents. CO2 response curves showed that both of these anesthetic agents depressed, at any given level of PETCO2, respiratory-related sympathetic nerve responses more than the responses found in the phrenic nerve. We conclude that the relations between peak, tonic (i.e. between phasic bursts) and respiratory-related sympathetic nerve activities and phrenic nerve activity can be altered by anesthesia.     

Mapping the Distribution of the Telomeric Sequence (T2AG3) n in the 2n = 14 Ancestral Marsupial Complement and in the Macropodines (Marsupialia: Macropodidae) by fluorescence in situ hybridization

In this study we test the theory that the presence of the conserved vertebrate telomeric sequence (T(2)AG(3))(n) at the centromeres of Australian marsupial 2n = 14 complements is evidence that these karyotypes are recently derived, which is contrary to the generally held view that the 2n = 14 karyotype is ancestral for Australasian and American marsupials. Here we compare the distribution of the (T(2)AG(3))( n ) sequence and constitutive heterochromatin in the presumed ancestral 2n = 14 complement and in complements with known rearrangements. We found that where there were moderate to large amounts of constitutive heterochromatin, the distribution of the (T(2)AG(3))(n) sequence reflected its presence as a native component of satellite DNA rather than its involvement in past rearrangements. The presence of centromeric heterochromatin in all Australian 2n = 14 complements therefore suggests that centromeric sites of the (T(2)AG(3))(n) sequence do not represent evidence for recent rearrangements.