Cloning and functional expression of the small subunit of acetolactate synthase from Nicotiana plumbaginifolia.

Acetolactate synthase (ALS) is the first committed step of branched-chain amino acid biosynthesis in plants and bacteria. The bacterial holoenzyme has been well characterized and is a tetramer of two identical large subunits (LSUs) of 60 kDa and two identical small subunits (SSUs) ranging in molecular mass from 9 to 17 kDa depending on the isozyme. The enzyme from plants is much less well characterized. Attempts to purify the protein have yielded an enzyme which appears to be an oligomer of LSUs, with the potential existence of a SSU for the plant enzyme remaining a matter of considerable speculation. We report here the discovery of a cDNA clone that encodes a SSU of plant ALS based upon the homology of the encoded peptide with various bacterial ALS SSUs. The plant ALS SSU is more than twice as large as any of its prokaryotic homologues and contains two domains that each encode a full-length copy of the prokaryotic SSU polypeptide. The cDNA clone was used to express Nicotiana plumbaginifolia SSU in Escherichia coli. Mixing a partially purified preparation of this SSU with the LSU of ALS from either N. plumbaginifolia or Arabidopsis thaliana results in both increased specific activity and increased stability of the enzymic activity. These results are consistent with those observed for the bacterial enzyme in similar experiments and represent the first functional demonstration of the existence of a SSU for plant ALS.

Treatment of corneal abrasions with soft contact lenses and topical diclofenac.

BACKGROUND: Treatment of corneal abrasions often involves antibiotic ointment and pressure patching. The corneal abrasions following excimer laser photorefractive keratectomy have been managed with disposable soft contact lenses and diclofenac (Voltaren) eye drops. METHODS: We report 13 patients with corneal abrasions from trauma or recurrent corneal erosions treated with application of a disposable soft contact lens and instillation of diclofenac and antibiotic eye drops. RESULTS: All 13 patients reported significant pain relief and all abrasions healed within 3 days (most within 24 hours). Two of the recurrent erosion patients suffered subsequent spontaneous abrasions and one of the traumatic abrasion patients developed a possible infectious keratitis which cleared without visual loss. CONCLUSIONS: In this small series, the combination of a disposable soft contact lens and the instillation of diclofenac drops provided significant pain relief while the abrasion healed and allowed the patients to function with binocular vision. This treatment regimen offers an alternative to pressure patching in the treatment of corneal abrasions.

Endocrine function in children with human immunodeficiency virus infection.

We sought to determine if failure to thrive in pediatric patients with the human immunodeficiency virus could be explained based on endocrine dysfunction. Fourteen human immunodeficiency virus-infected pediatric patients, all of whom had adequate nutritional status, underwent endocrine evaluation. Growth hormone and cortisol responses to glucagon stimulation were adequate. Despite this, eight of the 12 subjects had low somatomedin C levels. Although all patients were clinically and biochemically euthyroid, 36% (5/14) demonstrated elevated baseline and peak thyrotropin levels in response to thyroid releasing hormone, suggesting a state of compensated hypothyroidism. Although the importance of these findings is unclear, it is possible that subtle alterations of thyroid regulation may contribute to failure to thrive in some pediatric patients infected with human immunodeficiency virus and may represent a potentially correctable defect.

Toxic effects of selected industrial solvents in batch and continuous anaerobic reactors.

Acetone and ethyl acetate were readily degraded in batch reactors containing anaerobic solids from an industrial reactor at concentrations to 1000 mg/L; isoamyl acetate was degraded at concentrations below 200 mg/L. Xylene was noninhibitory in batch cultures at concentrations of 50 mg/L or less. Batch reactors receiving 45 mg/L methylene chloride (MC) experienced a 60% reduction in gas production, and an increase in volatile fatty acids. Semicontinuously-fed reactors dosed with 20 mg/L MC at the start suffered some loss of anaerobic efficiency, but acclimated well with increased gas production after 20 d. A continuously fed sludge blanket reactor with no previous exposure to MC has acclimated to 20 mg/L MC after initial inhibition at 10 mg/L.

Three methods of assessing the mutagenic action of ultraviolet radiation on the fungus Emericellopsis glabra.

Colony isolates of the fungus Emericellopsis glabra, developing from ultraviolet (UV)-irradiated conidia, were examined for variability on the basis of colony morphology, loss of antibiotic-producing capacity on plate assay, and loss of ability to grow in minimal medium. The latter two of these methods are considered to be more objective and reliable in determining the degree of variability induced by UV radiation in this fungus. The highest frequency of variants is obtained at UV dosages which reduce spore survival to levels of 5 to 15%.