Patch-clamp recording of charge movement, Ca(2+) current, and Ca(2+) transients in adult skeletal muscle fibers

Intramembrane charge movement (Q), Ca(2+) conductance (G(m)) through the dihydropyridine-sensitive L-type Ca(2+) channel (DHPR) and intracellular Ca(2+) fluorescence (F) have been recorded simultaneously in flexor digitorum brevis muscle fibers of adult mice, using the whole-cell configuration of the patch-clamp technique. The voltage distribution of Q was fitted to a Boltzmann equation; the Q(max), V(1/2Q), and effective valence (z(Q)) values were 41 +/- 3.1 nC/&mgr;F, -17.6 +/- 0.7 mV, and 2.0 +/- 0.12, respectively. V(1/2G) and z(G) values were -0.3 +/- 0.06 mV and 5.6 +/- 0.34, respectively. Peak Ca(2+) transients did not change significantly after 30 min of recording. F was fit to a Boltzmann equation, and the values for V(F1/2) and z(F) were 6.2 +/- 0.04 mV and 2.4, respectively. F was adequately fit to the fourth power of Q. These results demonstrate that the patch-clamp technique is appropriate for recording Q, G(m), and intracellular [Ca(2+)] simultaneously in mature skeletal muscle fibers and that the voltage distribution of the changes in intracellular Ca(2+) can be predicted by a Hodgkin-Huxley model.     

Early postnatal ibuprofen and indomethacin effects in suckling and weanling rat kidneys

The use of indomethacin in preterm newborn infants with symptomatic patent ductus arteriosus is associated with compromised renal function. Ibuprofen has been shown to be as effective as indomethacin with fewer renal side effects. We examined the hypothesis that early postnatal ibuprofen has less adverse effects on neonatal rat renal prostanoids, COX-2 expression, and angiotensin II than indomethacin. Newborn rats received IP injections of human therapeutic doses of ibuprofen or indomethacin on the first 3 days of life. Control rats were treated with equivalent volume saline. Kidneys were assessed in suckling and weanling rats for prostanoids, COX-2 expression, and angiotensin II. In suckling rats, indomethacin suppressed PGE(2) and COX-2 expression, and increased PGF(2alpha), whereas ibuprofen increased COX-2 and angiotensin II. Although both NSAIDs suppressed 6-ketoPGF(1alpha) and TxB(2) levels in suckling rats, the effect was sustained in weanling rats with indomethacin. Our findings demonstrate that indomethacin exhibits more potent suppressive effects on renal COX-2 and vasodilator prostanoids which are important regulators of renal development and function. These long-term, sustained effects may explain in part, why indomethacin exerts more severe adverse renal effects than ibuprofen, when administered during early postnatal life.     

Maternal and feto-placental prostanoid responses to a single course of antenatal betamethasone

We tested the hypothesis that antenatal betamethasone alters prostanoid levels in the maternal and feto-placental compartments. Forty-three singleton pregnancies were studied. Group I were women treated with a single course of antenatal betamethasone and who delivered <37 weeks gestation; Group II were untreated women who delivered <37 weeks; and Group III were untreated women who delivered >38 weeks. Maternal and mixed cord blood; and placental samples were collected at delivery and analyzed for PGE2, PGF(2alpha), 6-ketoPGF(1alpha), and TxB2 levels. Antenatal betamethasone decreased maternal PGE2 levels with concomitant increases in the feto-placental compartment. Umbilical cord TxB2 levels in the treated group were significantly lower than the non-treated pre-term and term groups resulting in a higher 6-ketoPGF(1alpha):TxB2 ratio. Considering the regulatory role of PGE2 and PGI2 in fetal lung development and neonatal transition homeostasis, these results suggest a mechanism, at least in part, for the beneficial effects of antenatal steroids on fetal lung maturation and neonatal cardio-pulmonary homeostasis at birth.     

Evaluation of penicillin-based inhibitors of the class A and B beta-lactamases from Bacillus anthracis

Bacillus anthracis contains a class A (Bla1) and class B (Bla2) beta-lactamase, which confer resistance to beta-lactam antibiotics when expressed in Escherichia coli. In an effort to find new beta-lactamase inhibitors, several penicillin derivatives have been evaluated including experimental compounds incorporating a 6-mercaptomethyl group or a 6-pyridylmethylidene group, along with clavulanate and tazobactam, as inhibitors against Bla1 and Bla2. The 6-mercaptomethyl-substituted penicillins showed much greater activity against the zinc-containing Bla2 than Bla1. The compound that incorporated a 6-pyridylmethylidene substituent and a catecholic substituent at the 2' position was the most effective inhibitor of Bla1 with Ki=0.057 microM. Inhibitors containing iron-chelating functional groups have previously been shown to work in combination with antibiotics to inhibit growth of antibiotic-resistant bacteria expressing beta-lactamase. The development of similar compounds, incorporating these types of substituents, may help overcome resistance to currently used antibiotics.     

Long-term docosahexaenoic acid therapy in a congenic murine model of cystic fibrosis

We used a congenic C57Bl/6J cystic fibrosis transmembrane conductance regulator (Cftr)(-/-) mouse model, which develops cystic fibrosis (CF)-like pathology in all organs, to evaluate the short- and long-term therapeutic effects of dietary docosahexaenoic acid (DHA). Thirty-day-old Cftr(-/-) mice and wild-type littermates were randomized to receive a liquid diet with or without DHA (40 mg/day). Animals were killed for histological and lipid analysis after 7, 30, and 60 days of therapy. DHA had no significant therapeutic or harmful effect on the lung, pancreas, or ileum of the Cftr(-/-) mice or their wild-type littermates. In contrast, dietary DHA resulted in highly significant amelioration of the severity of liver disease in the Cftr(-/-) mice, primarily a reduction in the degree of peri-portal inflammation. Additionally, these detailed measurements confirm our previous findings that Cftr(-/-) mice have significant alterations in the pancreas (except external acinar diameter), ileum, liver, lung, and salivary (except sublingual) glands at all ages compared with their age-matched wild-type littermates. In conclusion, inhibition of cytokines and/or eicosanoid metabolism and release of endogenous inhibitors of inflammation by DHA may account for the anti-inflammatory effects in the liver of this congenic murine model of CF. The potential therapeutic benefits of DHA in severe CF-associated liver disease remain to be explored.