ATP inhibition and rectification of a Ca2+-activated anion channel in sarcoplasmic reticulum of skeletal muscle

We describe ATP-dependent inhibition of the 75-105-pS (in 250 mM Cl-) anion channel (SCl) from the sarcoplasmic reticulum (SR) of rabbit skeletal muscle. In addition to activation by Ca2+ and voltage, inhibition by ATP provides a further mechanism for regulating SCl channel activity in vivo. Inhibition by the nonhydrolyzable ATP analog 5'-adenylylimidodiphosphate (AMP-PNP) ruled out a phosphorylation mechanism. Cytoplasmic ATP (approximately 1 mM) inhibited only when Cl- flowed from cytoplasm to lumen, regardless of membrane voltage. Flux in the opposite direction was not inhibited by 9 mM ATP. Thus ATP causes true, current rectification in SCl channels. Inhibition by cytoplasmic ATP was also voltage dependent, having a K(I) of 0.4-1 mM at -40 mV (Hill coefficient approximately 2), which increased at more negative potentials. Luminal ATP inhibited with a K(I) of approximately 2 mM at +40 mV, and showed no block at negative voltages. Hidden Markov model analysis revealed that ATP inhibition 1) reduced mean open times without altering the maximum channel amplitude, 2) was mediated by a novel, single, voltage-independent closed state (approximately 1 ms), and 3) was much less potent on lower conductance substates than the higher conductance states. Therefore, the SCl channel is unlikely to pass Cl- from cytoplasm to SR lumen in vivo, and balance electrogenic Ca2+ uptake as previously suggested. Possible roles for the SCl channel in the transport of other anions are discussed.     

Relationship of endometrial thickness with the menstrual timing of leuprolide acetate administration for preoperative preparation for hysteroscopic surgery

OBJECTIVES: To investigate the changes in the cholesterol:phospholipids (C/PL) ratio of erythrocyte membrane in post-menopausal women with and without hormone replacement therapy (HRT). STUDY DESIGN: A cross-sectional study including 83 patients divided into three groups according to HRT (group 1, no HRT (n = 52); group 2, combined HRT (n = 16); and group 3, estrogen-only therapy (n = 15)). RESULTS: The C/PL ratio was lower in group 2 with respect to group 1 and group 3 (P = 0.03). No difference was found in erythrocyte membrane cholesterol between the three groups; however, the phospholipid concentration was higher in group 2 with respect to the other groups (P < 0.05). In the control group, C/PL values correlated positively with plasma LDL levels (P < 0.005) and negatively with HDL levels (P < 0.005). CONCLUSIONS: From our data the addition of progestogens in HRT appears to decrease the C/PL of the erythrocyte membrane possibly resulting in a beneficial effect on rheological properties of erythrocyte membrane. The results of our study thus suggest additional benefits from supplementation of progestogens in HRT, in addition to prevention of estrogen dependent endometrial hyperplasia and adenocarcinoma.     

Ventilation inhomogeneities and mixed venous blood N2 in multibreath N2 washout

OBJECTIVE: To examine the relationship between allergy-related symptoms, food intolerance and psychological distress in primary care. METHODS: Two thousand three hundred and thirty two adults in five General Practices in the South of England completed questionnaires regarding allergy-related symptoms and psychological symptoms, but no association was demonstrated between a history of diagnosed or treated asthma, eczema or hay fever and psychological morbidity. Cases of food intolerance had lower levels of psychological distress than expected compared to hospital samples. Current, but not past wheezing and eczema, was associated with an excess of life stresses in the previous six months. CONCLUSIONS: The association between psychological distress and the label of food allergy/intolerance found in specialist care does not extend to primary care.     

Methanogenium frigidum sp. nov., a psychrophilic, H2-using methanogen from Ace Lake, Antarctica

Methanogenium frigidum sp. nov. was isolated from the perennially cold, anoxic hypolimnion of Ace Lake in the Vesfold Hills of Antarctica. The cells were psychrophilic, exhibiting most rapid growth at 15 degrees C and no growth at temperatures above 18 to 20 degrees C. The cells were irregular, nonmotile coccoids (diameter, 1.2 to 2.5 microns) that occurred singly and grew by CO2 reduction by using H2 as a reductant. Formate could replace H2, but growth was slower. Acetate, methanol, and trimethylamine were not catabolized. Cells grew with acetate as the only organic compounds in the culture medium, but growth was much faster in medium also supplemented with peptones and yeast extract. The cells were slightly halophilic; good growth occurred in medium supplemented with 350 to 600 mM Na+, but no growth occurred with 100 or 850 mM Na+. The pH range for growth was 6.5 to 7.9; no growth occurred at pH 6.0 or 8.5. Growth was slow (maximum specific growth rate, 0.24 day-1; doubling time, 2.9 days). This is the first report of a psychrophilic methanogen growing by CO2 reduction.     

Caecal disease in equids

OBJECTIVE: To review the breed, age, gender, clinical and laboratory findings, treatment and outcome of horses with caecal disease presented to a referral centre. DESIGN: Retrospective study of 96 cases. PROCEDURE: The breed, age, and gender of the study population were compared with the corresponding hospital population for the same period. The means (+/- SD) for clinical and laboratory findings were recorded for each caecal disorder. Treatment was categorised as medical or surgical, and outcome was recorded. RESULTS: Caecal diseases included impaction (40% of total cases), rupture associated with concurrent unrelated disease (13%), rupture with parturition (9%), rupture with no associated disease (5%), infarction (11%), torsion (9%), abscess or adhesion (7%), tumour (3%), and miscellaneous conditions (3%). The breed or gender of affected horses did not differ from the hospital population, although horses > 15 years were more frequently represented (P < 0.05). This age group was specifically more predisposed to caecal impaction (P < 0.05), as were Arabian, Morgan, and Appaloosa breeds (P < 0.05). In horses with caecal impaction transrectal examination was the most useful diagnostic procedure; 90% of affected horses treated medically were discharged while horses treated by typhlotomy alone, or typhlotomy and blind end ileocolostomy, had survival rates to discharge of 71% and 86%, respectively. Horses with caecal rupture associated with concurrent un-related disease showed no signs of impending rupture; all were receiving phenylbutazone, all were euthanased, and 50% had caecal ulceration at necropsy. Of horses with caecal rupture with parturition 56% had prior dystocia; in two-thirds the site of rupture was the ileocaecal junction and all were euthanased. Horses with caecal rupture with no associated disease died or were euthanased; rupture was idiopathic. Horses with caecal infarction usually had signs of abdominal pain and abdominal fluid changes consistent with peritonitis; transrectal examination was nonspecific, and typhlectomy was successful in seven of eight horses. Horses with caecal torsion had signs of severe, acute abdominal pain and typhlectomy was successful in three of five horses. Diagnosis of caecal adhesion or abscess was assisted by transrectal palpation in two of seven horses and surgical treatment was successful in two of five horses. A caecal tumour was diagnosed in three horses aged 20 years or older that presented with chronic weight loss. Other caecal diseases were uncommon. CONCLUSION: Caecal disease is uncommon in equids but some specific features of the history and physical findings can alert the veterinarian to the possibility of caecal involvement in horses with gastrointestinal dysfunction. Medical or surgical therapy can be effective in horses where caecal rupture has not occurred.     

An enhancer that directs lineage-specific expression of CD8 in positively selected thymocytes and mature T cells

Positive selection of CD4+CD8+ T cells to the CD4+CD8- helper and CD4- CD8+ cytotoxic lineages is a multistep process that involves complex regulation of coreceptor gene expression. By analyzing expression of a reporter gene in transgenic mice, we have identified a DNA segment, located between the murine CD8beta and CD8alpha genes, that has enhancer activity restricted to CD8 lineage cells. Remarkably, this enhancer functions in thymocytes undergoing positive selection to the CD4-CD8+ phenotype but not in immature double-positive thymocytes. The enhancer also functions in gut intraepithelial lymphocytes that express CD8alpha but not CD8beta, suggesting that it is specific for CD8alpha expression. The tight correlation between activation of this enhancer and the final step in positive selection has important implications for understanding the mechanism of lineage commitment in thymocytes.     

Describing-function method for estimating the performance of a dynamic system having nonlinear-power take-off,with application to wave-power conversion

This work reports part of a programme aimed at stimulating the use of control engineering methods and techniques in the wave-power arena. Here we use the Describing-Function method to estimate the performance of a dynamical energy-conversion system (a second-order system in this particular case) with nonlinear damping. The Describing-Function is used to model the nonlinearity, and the system is conceptually re-arranged to appear in closed-loop form; this arrangement is particularly convenient for the application of a graphical method of solution. By this means the motion and the mean-rate of energy conversion of the system can be rapidly evaluated. The method is primarily directed towards solving problems of wave-power conversion by nonlinear devices.