Molecular dissection of water and glycerol permeability of the aquaglyceroporin from Plasmodium falciparum by mutational analysis

The selectivity of aquaporins for water and solutes is determined by pore diameter. Paradoxically, the wider pores of glycerol facilitators restrict water passage by an unknown mechanism. Earlier we characterized an aquaglyceroporin from Plasmodium falciparum with high permeability for both glycerol and water. We use point mutations to demonstrate that amino acids directly lining the pore are not responsible for the excellent water permeability of the Plasmodium aquaglyceroporin but affect permeability of pentitols. Within a conserved WET triad in the extracellular C-loop we identified a Plasmodium aquaglyceroporin-specific glutamate (E125) located in proximity to a conserved arginine (R196) at the pore mouth. Mutation of E125 to serine largely abolished water permeability. Concomitantly, the activation energy for water permeation was increased by 4 kcal/mol. Mutation of the adjacent tryptophan to cysteine led to irreversible inhibition of water passage by Hg(2+). This unequivocally proves the proximity of the couple W124/E125 close to the pore mouth. We conclude that in the Plasmodium aquaglyceroporin the electrostatic environment at the extracellular pore entry regulates water permeability.     

The relationship of mode of infant feeding and location of care to frequency of infection

During one year 200 healthy, full-term infants were followed up prospectively for frequency of infection. Infants were categorized by mode of feeding--breast, breast-and-bottle, or bottle--and were subcategorized by location of care and by number of siblings in the home. The average number of infections in infants fed in a day-care or sitter location was 35% greater than that in infants fed at home. The mode of feeding had no bearing on the frequency of infection.     

Functional impairment of lens aquaporin in two families with dominantly inherited cataracts

Opacities in the crystalline lens of eye appear with high frequency in the general population. Dominantly inherited cataracts with differing clinical features were found in two families carrying different point mutations in the gene encoding lens water channel protein AQP0 (major intrinsic protein, MIP). Families with E134G have a uni-lamellar cataract which is stable after birth, whereas families with T138R have multi-focal opacities which increase throughout life. To establish pathophysiological relevance of cataract formation, the Xenopus laevis oocyte expression system was employed to evaluate functional defects in the mutant proteins, E134G and T138R. Both substitutions cause loss of membrane water channel activity due to impaired trafficking of the mutant proteins to the oocyte plasma membrane. Although missense mutations in AQP1 and AQP2 proteins are known to result in recessive traits in vivo and in vitro, when E134G or T138R are co-expressed with wild-type AQP0 protein, the mutant proteins exhibit dominant negative behaviour. To our knowledge, these studies represent the first in vitro demonstration of functionally defective AQP0 protein from humans with congenital cataracts. Moreover, these observations predict that less severe defects in the AQP0 protein may contribute to lens opacity in patients with common, less fulminant forms of cataracts.     

Isokinetic strength testing in older women: a comparison of two systems

Funding: National Institute of Aging; University of Wisconsin Graduate School. Isokinetic equipment is used for measuring muscular strength for both experimental and rehabilitative purposes. In this study two LIDO(R) isokinetic dynamometer systems, the LIDO-digital and the LIDO-active, were compared at 60, 180, 240, and 300 degrees /see for peak torque (PT) and average work output (WO) of knee flexion and extension. Twenty-five elderly women (age range = 65-86) were tested on both systems within seven days. The data were compared by using a repeated measures ANOVA followed by a Dunn-Bonferroni posthoc comparison (p 相似文献   

Patient education: a multidisciplinary approach to influence patient compliance

The Department of Pharmacy and Nursing should collaborate on a consistent basis to proactively implement and evaluate the patient education program. Although many hospitals educate their patients, the systems can often be fragmented. Unanswered questions may include how and where the education takes place, the method of documentation, and who specifically educates the patient. Selection of the best media for educational materials requires that the broad array of printed (i.e., manuals, programmed texts, booklets) and nonprint material (i.e., videotape, motion pictures, etc.) be considered. A multidisciplinary patient education committee facilitates the program at MSKCC. Approximately 50 chemotherapy fact cards have been used at MSKCC for six years. This program has yielded positive perceptions from patients as well as from the pharmacy and nursing staff. Future trends will probably include widespread use of interactive patient education programs to provide indexing, order entry, and documentation of patient education materials.     

Amino-acid substitution in α-spectrin commonly coinherited with nondominant hereditary spherocytosis

Nondominant hereditary spherocytosis (ndHS) is a disorder characterized in some patients by severe hemolytic anemia and marked deficiency of erythrocyte spectrin. This report describes the identification of a variant spectrin chain, α-spectrin Bughill or α^BH, that is associated with this disorder in a number of patients. Tryptic maps of spectrin from affected individuals revealed an acidic shift in isoelectric point of the αll domain peptides at 46 kD and 35 kD. A point mutation at codon 970 of the α-spectrin gene (GCT→GAT), that changes the encoded amino acid from an alanine to an aspartic acid, was identified in genomic DNA of affected patients. The α^BH variant was present in 8 patients with ndHS from five different kindreds but was absent in 4 patients from two other kindreds. The 8 ndHS patients with the α^BH variant appeared to be homozygous for the α^BH variant by analysis of peptide maps of limited tryptic digests of erythrocyte spectrin. However, following genomic DNA analysis, only 2 of these patients were true homozygotes, whereas 6 were found to be doubly heterozygous for the α^BH allele and a second, presumably abnormal, α-spectrin gene. These results suggest that, in these 6 patients, the second α-spectrin allele is in fact associated with one or more genetic defect(s), causing decreased accumulation of α-spectrin. The pattern of transmission of the α^BH allele in certain families suggests that the α^BH amino-acid substitution is not itself responsible for ndHS but is more likely a polymorphic variant that, in some but not all cases, is in linkage disequilibrium with another uncharacterized α-spectrin gene defect that itself is a cause of ndHS. Am. J. Hematol. 54:233–241, 1997 © 1997 Wiley-Liss, Inc.     

A multicenter, randomized, double-blinded trial of pyridostigmine in postpolio syndrome.

BACKGROUND: Postpoliomyelitis syndrome (PPS) is likely due to degeneration and dysfunction of terminal axons of enlarged postpolio motor units. Age-related decline in growth hormone and insulin-like growth factor (IGF-I) may be a contributing factor. Neuromuscular junction abnormalities and decreased IGF-I levels may respond to the anticholinesterase pyridostigmine, with consequent improvement in strength, fatigue, and quality of life. OBJECTIVES: To determine the effect of pyridostigmine in PPS on health-related quality of life, isometric muscle strength, fatigue, and serum IGF-I levels; and to assess the safety of pyridostigmine in PPS. METHODS: The study was a multicenter, randomized, double-blinded, placebo-controlled trial of a 6-month course of pyridostigmine 60 mg three times per day in 126 PPS patients. The primary data analysis compared mean changes of outcomes between treatment and control groups at 6 months using an intention to treat approach. Secondary analyses included a comparison of outcomes at 6 and 10 weeks, and in compliant patients. RESULTS: The study showed no significant differences in pyridostigmine and placebo-treated patients with regard to changes in quality of life, isometric strength, fatigue, and IGF-I serum levels at 6 months in the primary analysis and in compliant patients. There were no differences in outcomes at 6 and 10 weeks between groups. However, very weak muscles (1 to 25% predicted normal at baseline) were somewhat stronger (p = 0.10, 95% CI of difference -9.5 to 73.3%), and in compliant patients IGF-I was somewhat increased (p = 0.15, 95% CI of difference -6.4 to 44.8 ng/mL) at 6 months with the medication. Pyridostigmine was generally well tolerated. CONCLUSIONS: This study showed no significant differences between pyridostigmine and placebo-treated PPS patients on measures of quality of life, isometric strength, fatigue, and serum IGF-I.     

Neuromuscular function: comparison of symptomatic and asymptomatic polio subjects to control subjects

The purpose of this study was to determine if there were any differences between symptomatic and asymptomatic polio survivors by history of acute poliomyelitis illness, electromyographic evidence of terminal motor unit reorganization, and neuromuscular function of the quadriceps femoris muscle. Thirty-four symptomatic postpolio subjects, 16 asymptomatic postpolio subjects, and 41 controls were studied. A questionnaire assessed polio history. Peak knee extension torque was measured isokinetically and isometrically. Endurance (time to exhaustion) was measured at 40% of maximal isometric torque. Work capacity was determined as the product of torque and duration. Recovery of isometric strength was measured at regular intervals for ten minutes after exhaustion. Quantitative electromyography was also performed on the quadriceps to determine motor unit action potential duration and amplitude. It was found that symptomatic subjects had evidence of more severe original polio involvement by history (documented electromyographically), were weaker and capable of performing less work than asymptomatic subjects, and recovered strength less readily than controls.