Structure of nitrilotriacetate monooxygenase component B from Mycobacterium thermoresistibile

Mycobacterium tuberculosis belongs to a large family of soil bacteria which can degrade a remarkably broad range of organic compounds and utilize them as carbon, nitrogen and energy sources. It has been proposed that a variety of mycobacteria can subsist on alternative carbon sources during latency within an infected human host, with the help of enzymes such as nitrilotriacetate monooxygenase (NTA-Mo). NTA-Mo is a member of a class of enzymes which consist of two components: A and B. While component A has monooxygenase activity and is responsible for the oxidation of the substrate, component B consumes cofactor to generate reduced flavin mononucleotide, which is required for component A activity. NTA-MoB from M. thermoresistibile, a rare but infectious close relative of M. tuberculosis which can thrive at elevated temperatures, has been expressed, purified and crystallized. The 1.6 Å resolution crystal structure of component B of NTA-Mo presented here is one of the first crystal structures determined from the organism M. thermoresistibile. The NTA-MoB crystal structure reveals a homodimer with the characteristic split-barrel motif typical of flavin reductases. Surprisingly, NTA-MoB from M. thermoresistibile contains a C-terminal tail that is highly conserved among mycobacterial orthologs and resides in the active site of the other protomer. Based on the structure, the C-terminal tail may modulate NTA-MoB activity in mycobacteria by blocking the binding of flavins and NADH.

Structure of aldose reductase from Giardia lamblia

The 1.75 Å resolution crystal structure of aldose reductase from G. lamblia, the etiological agent of giardiasis, is reported.

Giardia lamblia is an anaerobic aerotolerant eukaryotic parasite of the intestines. It is believed to have diverged early from eukarya during evolution and is thus lacking in many of the typical eukaryotic organelles and biochemical pathways. Most conspicuously, mitochondria and the associated machinery of oxidative phosphorylation are absent; instead, energy is derived from substrate-level phosphorylation. Here, the 1.75 Å resolution crystal structure of G. lamblia aldose reductase heterologously expressed in Escherichia coli is reported. As in other oxidoreductases, G. lamblia aldose reductase adopts a TIM-barrel conformation with the NADP⁺-binding site located within the eight β-strands of the interior.

Fresh gas flow is not the only determinant of volatile agent consumption: a multi-centre study of low-flow anaesthesia

METHODS

Seven academic centres studied 302 patients, using desflurane, enflurane, halothane, or isoflurane using circle-systems and Dräger Julian anaesthetic machines, with fresh gas flows (V(F)) of 3, 1, and 0.5 litre min(-1). Volatile agent partial pressures in the breathing system were recorded and agent consumptions measured by weighing.

RESULTS

At these flows, desflurane consumption depended on V(F). In contrast, halothane consumption was not influenced by V(F). Isoflurane and enflurane showed differences in consumption between flows of 0.5 and 3 litre min(-1). Stepwise linear regression suggested that besides V(F), other factors influenced consumption of the more soluble agents (sex, age, weight, height, altitude, and temperature). The partial pressure ratios were independent of V(F) for desflurane (end-tidal to fresh gas=0.8), but the ratios of the more soluble agents varied with V(F) (end-tidal to fresh gas=0.3-0.7).

CONCLUSIONS

At V(F) that involves significant re-breathing, consumption of soluble agents depends only partially on V(F). These results can be explained using Mapleson's hydraulic analogue model.

Improving competitiveness through performance-measurement systems

Parallels exist between the competitive pressures felt by U.S. manufacturers over the past 30 years and those experienced by healthcare providers today. Increasing market deregulation, changing government policies, and growing consumerism have altered the healthcare arena. Responding to similar pressures, manufacturers adopted a strategic orientation driven by customer needs and expectations that led them to achieve high performance levels and surpass their competition. The adoption of integrated performance-measurement systems was instrumental in these firms' success. An integrated performance-measurement model for healthcare organizations can help to blend the organization's strategy with the demands of the contemporary healthcare environment. Performance-measurement systems encourage healthcare organizations to focus on their mission and vision by aligning their strategic objectives and resource-allocation decisions with customer requirements.

Dimethylsulfoxide reductase: an enzyme capable of catalysis with either molybdenum or tungsten at the active site

DMSO reductase (DMSOR) from Rhodobacter capsulatus, well-characterised as a molybdoenzyme, will bind tungsten. Protein crystallography has shown that tungsten in W-DMSOR is ligated by the dithiolene group of the two pyranopterins, the oxygen atom of Ser147 plus another oxygen atom, and is located in a very similar site to that of molybdenum in Mo-DMSOR. These conclusions are consistent with W L(III)-edge X-ray absorption, EPR and UV/visible spectroscopic data. W-DMSOR is significantly more active than Mo-DMSOR in catalysing the reduction of DMSO but, in contrast to the latter, shows no significant ability to catalyse the oxidation of DMS.

Newly reported skin disease syndromes in the dog

Several recently recognized canine dermatoses are described. Syndromes discussed include superficial necrolytic dermatitis, Malasezzia dermatitis, sebaceous adenitis, nodular dermatofibrosis in German shepherd dogs, solar-induced dermatitis, and acrodermatitis.

Juvenile cellulitis in dogs: 15 cases (1979-1988)

The records of 15 dogs diagnosed as having juvenile cellulitis (juvenile pyoderma, puppy strangles) were evaluated for clinical, laboratory, and therapeutic results. Mandibular lymphadenopathy was observed in 14 dogs, and was not associated with skin lesions in 5 dogs. Edema, pustules, papules, or crusts were noticed periorally, periocularly, on the chin or muzzle, or in the ears of those dogs with skin lesions. Eight dogs were lethargic; fever and anorexia were inconsistent findings. Four dogs had signs of pain on manipulation of their joints. Complete blood counts revealed leukocytosis with neutrophilia in 4 dogs, and normocytic, normochromic anemia in 6 dogs. Three dogs had suppurative lymphadenitis with many neutrophils. Cytology of the aspirate of pustules or abscesses in 6 dogs revealed many neutrophils without bacteria. Coagulase-positive Staphylococcus spp were isolated from draining lesions in 2 dogs. Intact abscesses and lymph nodes were negative for bacterial growth in 4 dogs. Three of these dogs were being administered antibiotics at the time of bacterial culturing. Cytology of the aspirates of joints in 3 of the 4 dogs with joint pain revealed suppurative arthritis with no bacteria, and the aspirates were negative for bacterial growth on culturing, although all 3 dogs were being administered antibiotics at the time of culturing. Of 12 dogs initially treated with antibiotics, only 4 (33%) responded favorably; the other 8 dogs were then given antibiotics and corticosteroids. Three dogs were initially given antibiotics and corticosteroids. All dogs treated concurrently with antibiotics and corticosteroids responded favorably. One of these dogs had a relapse after treatment was discontinued. The concurrent arthritis in 4 of the dogs resolved with treatment of the juvenile cellulitis and did not redevelop once the medication was discontinued. Concurrent treatment with antibiotics (cephalosporins) and prednisone (2.2 mg/kg of body weight/day) was the most consistently effective treatment in the dogs in this study.

The role of pyoderma in pruritus

In the approach to the pruritic patient, it is important to first determine if a pyoderma is present. A thorough investigation of the integument should be undertaken during the physical examination. There are a wide variety of clinical appearances of pyodermas, so the clinician should recognize the lesions that are suggestive of infection (epidermal collarettes, draining tracts, and so on). When infection is present, it is necessary to direct therapy at the pyoderma and then re-evaluate the patient. Any animal that presents with a pruritic pyoderma deserves proper therapy directed at the infection before the clinician can assess the role that the pyoderma is contributing to the pruritus. Rational therapy in these cases requires that one determine the cause of the itch rather than merely masking the symptom of pruritus.

Corticosteroid (methylprednisolone sodium succinate) pulse therapy in five dogs with autoimmune skin disease

Corticosteroid pulse therapy is the parenteral administration of suprapharmacologic doses of methylprednisolone sodium succinate for short periods. Five dogs diagnosed as having autoimmune skin disease were treated, using pulse therapy, with subsequent dramatic and rapid improvement of skin lesions. The dogs had no adverse clinical signs attributable to the treatment. All dogs had a relapse of clinical signs after a maintenance protocol (0.5 mg/kg, q 48 h) of orally administered prednisone was started. Skin lesions on 4 of 5 dogs eventually were controlled by prednisone, azathioprine, or gold therapy.