Can we afford to ignore the biology of joint healing and graft incorporation after ACL reconstruction?

Anterior cruciate ligament (ACL) reconstruction is successful at restoring stability to return ACL injured patients to high-demand work, sports, and recreational activities. The development of posttraumatic osteoarthritis (OA) in roughly half of patients just 10–15 years after ACLR highlight the need to improve clinical care pathways. Graft failure and reinjury rates, which further increase OA risk, also remain high for younger and more active patients. The biological components of joint recovery and graft incorporation, therefore, impact short- and long-term clinical outcomes. Biochemical and magnetic resonance imaging (MRI) data show substantial compromise of articular cartilage metabolism and matrix composition after ACL injury and reconstructive surgery suggesting a potential need for activity modulation in early recovery. Furthermore, joint recovery is variable with compositional MRI studies showing progressive cartilage degeneration 1 and 2 years after ACLR. Biopsy and MRI studies also show high variability in ACL graft characteristics within the 1st year after ACLR followed by continued graft maturation into the 2nd year and beyond. To improve the care of ACL injured patients, there is a critical need for clinical attention and scientific inquiry into timing the reintroduction of higher load activities in relationship to neuromuscular recovery, joint biology, and graft maturation. In addition to symptomatic and mechanical recovery, development and validation of biological markers for joint and cartilage homeostasis as well as ACL graft healing are needed for personalized decision making on rehabilitation needs, reduction of OA risk, and resumption of athletic, recreational, and vocational activities.     

Reliability and Extension of Quantitative Prediction of CYP3A4-Mediated Drug Interactions Based on Clinical Data

An approach was proposed in 2007 for quantitative predictions of cytochrome P450 (CYP)3A4-mediated drug-drug interactions. It is based on two characteristic parameters: the contribution ratio (CR; i.e., the fraction of victim drug clearance by CYP) and the inhibition ratio (IR) of the inhibitor. Knowledge of these parameters allows forecasting of the ratio between the area under the plasma concentration-time curve (AUC) of the victim drug when given with the inhibitor and the AUC of the victim drug when it is given alone. So far, these parameters were established for 21 substrates and 17 inhibitors. The goals of our study were to test the assumption of substrate independence of the potency of inhibitors in vivo and to estimate the CR and IR for an extended list of substrates and inhibitors of CYP3A4. The assumption of independence of IRs from the substrate was evaluated on a set of eight victim drugs and eight inhibitors. Forty-four AUC ratios were available. This assumption was rejected in four cases, but it did not result in more than a twofold error in AUC ratio predictions. The extended list of substrates and inhibitors was defined by a thorough literature search. Fifty-nine AUC ratios were available for the global analysis. Final estimates of CRs and IRs were obtained for 37 substrates and 25 inhibitors, respectively. The mean prediction error of the ratios was 0.02, while the mean absolute prediction error was 0.58. Predictive distributions for 917 possible interactions were obtained, giving detailed information on some drugs or inhibitors that have been poorly studied so far.     

The Alcoholics Anonymous Affiliation Scale: Development, Reliability, and Norms for Diverse Treated and Untreated Populations

Affiliation with Alcoholics Anonymous (AA) is an important variable to measure in many clinical and research activities. This paper reports on the development of an AA affiliation scale, and demonstrates its utility in a sample of 927 alcohol treatment seekers and 674 untreated problem drinkers. The scale is short (9 items), covers a range of AA experiences, and is internally consistent across diverse demographic groups, multiple health services settings, and treated and untreated populations. The validity of the scale is supported by the findings that treatment seekers report significantly higher AA affiliation than do untreated problem drinkers, and inpatients report higher affiliation than outpatients. Potential clinical and research applications of the scale are proposed.     

Long-term follow-up of two infants with an implanted cardiac pacemaker

The clinical course of two patients with congenital heart block who had pacemaker implantation at age 7 and 8 months, respectively, is reviewed. One patient at age 10 years has had nine pulse generators Inserted; the other has had six implantations, the most recent a lithium iodine pacemaker, during 81/2 years of observation. Both patients have shown normal physical development and emotional maturation despite multiple hospitalizations and pacemaker replacements, thus demonstrating that electrical pacing, initiated in infancy, can be maintained through childhood without adverse effects.     

Identification and characterization of undifferentiated mast cells in mouse bone marrow

Sequential immunomagnetic isolation with 2 monoclonal antibodies was used to purify and characterize an undifferentiated mast cell in adult mouse bone marrow that had not been previously recognized. This cell represents 0.02% of the cells in the bone marrow, is CD34(+), CD13(+), and c-kit(+), and does not express FcepsilonRI. However, by polymerase chain reaction (PCR) the cell contains message for the alpha and beta subunits of FcepsilonRI, mast cell-specific proteases, and carboxypeptidase A. Morphologically, this cell has a large nucleus, little cytoplasm, few cytoplasmic organelles, and no cytoplasmic granules. In vitro, in the presence of interleukin-3 (IL-3) and stem cell factor (SCF) these cells differentiate only into a granulated mast cell that now expresses CD13, c-kit, mast cell-specific gangliosides, FcepsilonRI, and binds immunoglobulin E (IgE). When injected into lethally irradiated mice, these cells are able to reconstitute the mast cell population in the spleen.     

Hydroxyurea nitrosylates and activates soluble guanylyl cyclase in human erythroid cells

Hydroxyurea, a drug widely used for treating myeloproliferative diseases, has also been approved for the treatment of sickle cell disease by raising fetal hemoglobin (HbF). We have shown that nitric oxide (NO) and the soluble guanylyl cyclase (sGC) pathways are involved in hydroxyurea induction of HbF levels in erythroid progenitor cells (EPCs). We demonstrate now that during erythroid differentiation, endothelial NO synthase mRNA and protein levels decline steadily, as does the production of NO derivatives and cyclic adenosine monophosphate (cAMP) levels, but guanosine 3',5'-cyclic monophosphate (cGMP) levels are stable. Hydroxyurea increased intracellular cGMP levels and cAMP levels in EPCs. The NO donor, DEANONOate, induced much higher cGMP levels, but reduced cAMP levels. Hydroxyurea (1 mM) induced production of approximately 45 pM cGMP/minute/ng of purified sGC, similar to induction by 1 muM DEANONOate. We found that hydroxyurea and ProliNONOate produced iron-nitrosyl derivatives of sGC. Thus, we confirm that hydroxyurea can directly interact with the deoxy-heme of sGC, presumably by a free-radical nitroxide pathway, and activate cGMP production. These data add to an expanding appreciation of the role of hydroxyurea as an inducer of the NO/cGMP pathway in EPCs. These mechanisms may also be involved in the cytostatic effects of hydroxyurea, as well as the induction of HbF.     

Knockout of the abetalipoproteinemia gene in mice: Reduced lipoprotein secretion in heterozygotes and embryonic lethality in homozygotes

Abetalipoproteinemia, an inherited human disease characterized by a near-complete absence of the apolipoprotein (apo) B-containing lipoproteins in the plasma, is caused by mutations in the gene for microsomal triglyceride transfer protein (MTP). We used gene targeting to knock out the mouse MTP gene (Mttp). In heterozygous knockout mice (Mttp+/− ), the MTP mRNA, protein, and activity levels were reduced by 50%, in both liver and intestine. Compared with control mice (Mttp+/+), chow-fed Mttp+/− mice had reduced plasma levels of low-density lipoprotein cholesterol and had a 28% reduction in plasma apoB100 levels. On a high-fat diet, the Mttp+/− mice exhibited a marked reduction in total plasma cholesterol levels, compared with those in Mttp+/+ mice. Both the livers of adult Mttp+/− mice and the visceral endoderm of the yolk sacs from Mttp+/− embryos manifested an accumulation of cytosolic fat. All homozygous embryos (Mttp−/−) died during embryonic development. In the visceral endoderm of Mttp−/− yolk sacs, lipoprotein synthesis was virtually absent, and there was a marked accumulation of cytosolic fat droplets. In summary, half-normal MTP levels do not support normal levels of lipoprotein synthesis and secretion, and a complete deficiency of MTP causes lethal developmental abnormalities, perhaps because of an impaired capacity of the yolk sac to export lipids to the developing embryo.