Interpretive standards and quality control guidelines for imipenem susceptibility tests with 10-micrograms disks

Tests with 10-micrograms imipenem disks accurately categorized 98.5% of 551 bacterial isolates when interpretive breakpoints of less than or equal to 13 mm for resistant and greater than or equal to 16 mm for susceptible were used. Because a sufficient number of resistant or moderately susceptible strains were not available for testing, these interpretive standards must be considered tentative. Quality control limits for tests with Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 are 26 to 32 and 20 to 28 mm, respectively. Zones obtained with Staphylococcus aureus ATCC 25923 were too large and variable to be useful for quality control purposes.     

Opioid receptors regulate the extinction of Pavlovian fear conditioning

Rats received a single pairing of an auditory conditioned stimulus (CS) with a footshock unconditioned stimulus (US). The fear (freezing) that had accrued to the CS was then extinguished. Injection of naloxone prior to this extinction significantly impaired the development of extinction. This impairment was mediated by opioid receptors in the brain and was not observed when naloxone was injected after extinction training. Finally, an injection of naloxone on test failed to reinstate extinguished responding that had already accrued to the CS. These experiments show that opioid receptors regulate the development, but not the expression, of fear extinction and are discussed with reference to the roles of opioid receptors in US processing, memory, and appetitive motivation.     

The value of the axial view in assessing calcaneal fractures

We studied the value of the axial view of the calcaneum in diagnosing fractures. Fifty sets calcaneal radiographs were studied by four senior trauma staff and four orthopeadic trainees on two occasions 2-3 weeks apart. On the first occasion only the lateral view was studied; on the second, both lateral and axial views were studied. The axial view did not improve the sensitivity or specificity of the lateral view alone. Senior staff were more accurate in assessing the radiographs. We suggest that the axial view should not be used routinely in assessing a patient with a possible calcaneal fracture.     

Economics of Stratified Medicine in Rheumatoid Arthritis

Calcinosis is one of the hallmark sequelae of juvenile dermatomyositis (JDM), and despite recent progress in the therapy of JDM, dystrophic calcification still occurs in approximately one third of patients. This review discusses our current, albeit limited, understanding of risk factors for the development of calcinosis in JDM, as well as approaches to assessment, and current views on its pathogenesis. Anecdotal approaches to treating calcinosis associated with JDM, including both anti-inflammatory therapies and agents aimed at inhibiting the deposition of calcium hydroxyapatite, are reviewed. An improved understanding of the pathogenesis of calcinosis, the establishment of standardized measurement tools to assess calcinosis, and randomized controlled trials employing more sensitive outcome measures are needed to develop efficacious therapies for this often disabling complication.     

The role of medial prefrontal cortex in extinction and reinstatement of alcohol‐seeking in rats

The prelimbic (PL) and infralimbic (IL) medial prefrontal cortex (mPFC) are thought to play opposing roles in drug‐seeking behaviour. Specifically, the PL promotes drug‐seeking whereas the IL is necessary for the inhibition of drug‐seeking during extinction. We studied the roles of the PL, IL and dorsal peduncular PFC (DP) in the expression of context‐induced reinstatement, reacquisition and extinction of alcoholic beer‐seeking. In context‐induced reinstatement (renewal), animals were trained to nosepoke for alcoholic beer (context A), extinguished (context B) and then tested in context A and B. In reacquisition, animals received the same instrumental training and extinction without any contextual manipulation. On test, alcoholic beer was again available and responding was compared with naive controls. Just prior to the test, rats received bilateral infusion of baclofen/muscimol into the PL, IL or DP. Reversible inactivation of the PL attenuated ABA renewal but augmented reacquisition. Reversible inactivation of IL had no effect on the reinstatement or reacquisition of alcoholic beer‐seeking and had no effect on extinction expression (ABB and AAA). IL inactivation did, however, increase the latencies with which animals responded on test but only when animals were tested in the extinction context. DP inactivation had no effect on reinstatement or reacquisition. These studies are inconsistent with the view that PL and IL exert opposing effects on drug‐seeking. Rather, they support the view that PL is important for retrieval of drug‐seeking contingency information and that the use of contextual information is enhanced with IL manipulation.     

The effects of FG7142 on two types of forgetting in 18-day-old rats

The authors studied the role of gamma-aminobutyric acid (GABA) in 2 types of forgetting of fear in the developing rat. One type of forgetting studied was that observed after an intermediate retention interval (the "Kamin effect"); the other type studied was that observed after a longer interval (infantile amnesia). Rats were given pairings of an auditory conditioned stimulus with shock, and learned fear was assessed by freezing. Forgetting at an intermediate retention interval (1 hr) was not alleviated by the GABA-sub(A) receptor partial inverse agonist FG7142 (0, 1, 5, or 10 mg/kg), whereas forgetting at a longer retention interval (48 hr) was alleviated. These results suggest that in the developing rat, forgetting observed at different retention intervals is mediated by different physiological mechanisms.     

Temporal-difference prediction errors and Pavlovian fear conditioning: role of NMDA and opioid receptors

Three experiments studied temporal-difference (TD) prediction errors during Pavlovian fear conditioning. In Stage I, rats received conditioned stimulus A (CSA) paired with shock. In Stage II, they received pairings of CSA and CSB with shock that blocked learning to CSB. In Stage III, a serial overlapping compound, CSB --> CSA, was followed by shock. The change in intratrial durations supported fear learning to CSB but reduced fear of CSA, revealing the operation of TD prediction errors. N-methyl- D-aspartate (NMDA) receptor antagonism prior to Stage III prevented learning, whereas opioid receptor antagonism selectively affected predictive learning. These findings support a role for TD prediction errors in fear conditioning. They suggest that NMDA receptors contribute to fear learning by acting on the product of predictive error, whereas opioid receptors contribute to predictive error.     

Stem fracture of conserve hemiarthroplasty

Resurfacing hemiarthroplasty of the femoral head has been recommended as a bone-preserving alternative to total hip arthroplasty for the management of osteonecrosis of the femoral head in the young patient. This case report describes failure of a cemented resurfacing hemiarthroplasty resulting from a fracture through the stem of the implant.