Imaging in osteoarthritis

Conventional radiography is still the first and most important imaging examination in a clinical setting when evaluating a patient with a known or suspected diagnosis of osteoarthritis (OA). In research and clinical trials, it still is a valuable tool for stratifying patients who have OA into different categories for inclusion criteria and eligibility. MRI has become crucial in understanding the natural history of the disease and in guiding future therapies because of its ability to image the knee as a whole organ and to assess cartilage morphology and composition directly and in a three-dimensional manner. The other modalities discussed in this article are valuable additional techniques indicated on a case-by-case basis.     

Accessory mitral valve tissue: Appearance on cardiac computed tomography

Accessory mitral valve tissue is an uncommon congenital malformation and a rare cause of left ventricular outflow tract obstruction. Although echocardiography provides a "gold standard" for evaluation of valves, the high temporal and spatial resolutions of computed tomography technology makes it useful in the assessment of valvular structure and function.     

Lung injury and bronchopulmonary dysplasia in newborn infants

Bronchopulmonary dysplasia is the most common morbidity among surviving premature infants. Injury to the developing lung is the result of the interaction between a susceptible host and a number of contributing factors such as mechanical ventilation and infection. The resulting persistent impairment of pulmonary function and need for ongoing therapy are the underlying characteristics of bronchopulmonary dysplasia. Important insights into the pathogenesis of bronchopulmonary dysplasia have led to numerous therapies and preventive approaches. Although significant progress has been made, in order to further affect the incidence and severity of the disease, we need to further study (a) the genetically determined predisposing factors, (b) the relative contribution of the various pathogenetic pathways, and, most important, (c) how to best translate the knowledge gained from these studies into effective clinical approaches.     

The serology of chronic hepatitis B infection revisited.

The serology of chronic hepatitis B infection has been established through the use of commercial immunoassays to measure the structural antigens of the hepatitis B virus and their respective antibodies in serum. However, the commercial assays have not been designed to detect serum antibodies in the presence of an excess of circulating antigens. A series of serum samples from 200 HBeAg-positive, chronically infected hepatitis B patients with varying degrees of liver disease were analyzed using novel immunoassays designed to detect antibodies in the presence of circulating viral antigens. All patients, regardless of their liver disease, were seronegative for antibodies specific for the envelope antigens or the secreted nucleoprotein antigen (HBeAg) when the commercial assays were used. In contrast, virtually all chronically infected patients with liver disease and approximately 50% of patients without liver disease demonstrated anti-HBe and anti-envelope antibodies when sera were tested in the more sensitive immunoassays. Furthermore, asymptomatic patients could be serologically distinguished from symptomatic patients based on antibody fine specificity, titer, and IgG subclass. This study revealed that the majority of chronically infected hepatitis B patients produce a variety of antibodies for many years, and are not immunologically unresponsive, as suggested by the current assays.     

Pediatric brain tumor patients: their parents' perceptions of the hospital experience.

Studies have shown that admission to the hospital of a child can induce feelings of fear and helplessness in parents, challenging usual patterns of coping and parenting competence. Stress has been associated with parents' need to establish effective communication with staff and their need for information, ready access to their children, and participation in decision making relating to their child's care. This study of coping and adjustment was undertaken with the parents, including mothers and fathers, of children under 18 years of age diagnosed with a brain tumor, presenting at Royal Children's Hospital, Melbourne, between 2001 and 2002 (N=53). It was a prospective study using repeated measures over time. Participants in the study were involved in a questionnaire interview at 4 different points: at the time of diagnosis, 6 months postdiagnosis, 1 year postdiagnosis, and 2 years postdiagnosis, in which they were asked, among other things, about their experience of the hospital. The point of diagnosis was marked by a high level of dependence, with parents coping with rapid decision making and shock, and the surrender of care of their child. Parents identified high levels of information need but noted that they were often too stressed to take in information early on, and that this information need persisted up to the 2-year postdiagnosis point. More parents expressed dissatisfaction with the hospital and particularly with their interactions with the health care team at the 6-month post-diagnosis period, reflecting a possible reduction in attention given to families once they had settled into the treatment routine and the crisis of diagnosis had passed.     

Copper and quaternary ammonium cations exert synergistic bactericidal and antibiofilm activity against Pseudomonas aeruginosa

Biofilms are slimy aggregates of microbes that are likely responsible for many chronic infections as well as for contamination of clinical and industrial environments. Pseudomonas aeruginosa is a prevalent hospital pathogen that is well known for its ability to form biofilms that are recalcitrant to many different antimicrobial treatments. We have devised a high-throughput method for testing combinations of antimicrobials for synergistic activity against biofilms, including those formed by P. aeruginosa. This approach was used to look for changes in biofilm susceptibility to various biocides when these agents were combined with metal ions. This process identified that Cu²⁺ works synergistically with quaternary ammonium compounds (QACs; specifically benzalkonium chloride, cetalkonium chloride, cetylpyridinium chloride, myristalkonium chloride, and Polycide) to kill P. aeruginosa biofilms. In some cases, adding Cu²⁺ to QACs resulted in a 128-fold decrease in the biofilm minimum bactericidal concentration compared to that for single-agent treatments. In combination, these agents retained broad-spectrum antimicrobial activity that also eradicated biofilms of Escherichia coli, Staphylococcus aureus, Salmonella enterica serovar Cholerasuis, and Pseudomonas fluorescens. To investigate the mechanism of action, isothermal titration calorimetry was used to show that Cu²⁺ and QACs do not interact in aqueous solutions, suggesting that each agent exerts microbiological toxicity through independent biochemical routes. Additionally, Cu²⁺ and QACs, both alone and in combination, reduced the activity of nitrate reductases, which are enzymes that are important for normal biofilm growth. Collectively, the results of this study indicate that Cu²⁺ and QACs are effective combinations of antimicrobials that may be used to kill bacterial biofilms.     

Population pharmacokinetics of rifapentine and its primary desacetyl metabolite in South African tuberculosis patients

This study was designed to describe the population pharmacokinetics of rifapentine (RFP) and 25-desacetyl RFP in a South African pulmonary tuberculosis patient population. Special reference was made to studying the influence of previous exposure to rifampin (RIF) and the variability in pharmacokinetic parameters between patients and between occasions and the influence of different covariates. Patients were included in the study if they had been receiving first-line antimycobacterial therapy (rifampin, isoniazid, pyrazinamide, and ethambutol) for not less than 4 weeks and not more than 6 weeks and were divided into three RFP dosage groups based on weight: 600 mg, <45 kg; 750 mg, 46 to 55 kg; and 900 mg, >55 kg. Participants received a single oral dose of RFP together with concomitant antimycobacterial agents, excluding RIF, on study days 1 and 5 after they ingested a soup-based meal. The RFP and 25-desacetyl RFP concentration-time data were analyzed by nonlinear mixed-effect modeling using NONMEM. The pharmacokinetics of the parent drug were modeled separately, and the individual pharmacokinetic parameters were used as inputs for the 25-desacetyl RFP pharmacokinetic model. A one-compartment disposition model was found to best describe the data for both the parent and the metabolite, and the metabolite was assumed to be formed only from the central compartment of the parent drug. Prior treatment with RIF did not alter the pharmacokinetics of RFP but appeared to increase the excretion of 25-desacetyl RFP in a nonlinear fashion. The RFP oral clearance and volume of distribution were found to increase by 0.049 liter/h and 0.691 liter, respectively, with a 1-kg increase from the median weight of 50 kg. The oral clearance of 25-desacetyl RFP was found to be 35% lower in female patients. The model developed here describes the population pharmacokinetics of RFP and its primary metabolite in tuberculosis patients and includes the effects of prior administration with RIF and covariate factors.