Diazepam, gamma-aminobutyric acid, and progesterone open K(+) channels in myocytes from coronary arteries

Benzodiazepines enhance coronary blood flow and lower blood pressure, but the cellular basis of this action remains unclear. The present study now demonstrates a direct effect of diazepam, gamma-aminobutyric acid (GABA), and progesterone on the large conductance, Ca(2+)- and voltage-activated K(+) channel (BK(Ca)) in single myocytes isolated from porcine coronary arteries. These GABA receptor agonists significantly increased whole-cell (perforated patch) K(+) currents and stimulated the activity of single BK(Ca) channels in cell-attached patches dramatically. This effect is not mediated via cyclic AMP or cyclic GMP, but involves stimulation of Ca(2+) influx in response to activation of a bicuculline-sensitive GABA(A)-like receptor. We propose that localized, subsarcolemmal increases in Ca(2+) levels open BK(Ca) channels, thereby promoting K(+) efflux, membrane repolarization, and coronary relaxation. This transduction pathway can now account, at least in part, for the direct vasodilatory effects of diazepam, progesterone, and GABA.

High-throughput screening in drug metabolism and pharmacokinetic support of drug discovery

The application of rapid methods currently used for screening discovery drug candidates for metabolism and pharmacokinetic characteristics is discussed. General considerations are given for screening in this context, including the criteria for good screens, the use of counterscreens, the proper sequencing of screens, ambiguity in the interpretation of results, strategies for false positives and negatives, and the special difficulties encountered in drug metabolism and pharmacokinetic screening. Detailed descriptions of the present status of screening are provided for absorption potential, blood-brain barrier penetration, inhibition and induction of cytochrome P450, pharmacokinetics, biotransformation, and computer modeling. Although none of the systems currently employed for drug metabolism and pharmacokinetic screening can be considered truly high-throughput, several of them are rapid enough to be a practical part of the screening paradigm for modern, fast-moving discovery programs.

H(2)O(2) opens BK(Ca) channels via the PLA(2)-arachidonic acid signaling cascade in coronary artery smooth muscle

H(2)O(2) is a reactive oxygen species that contracts or relaxes vascular smooth muscle, but the molecular basis of these effects remains obscure. We previously demonstrated that H(2)O(2) opens the large-conductance, calcium- and voltage-activated (BK(Ca)) potassium channel of coronary myocytes (2) and now report physiological and biochemical evidence that the effect of H(2)O(2) on coronary smooth muscle involves the phospholipase A(2) (PLA(2))/arachidonic acid (AA) signaling cascades. H(2)O(2) stimulation of BK(Ca) channel activity was inhibited by arachidonyl trifluoromethyl ketone, an inhibitor of cytosolic PLA(2). Furthermore, H(2)O(2) stimulated release of [(3)H]AA from coronary myocytes, and exogenous AA mimicked the effect of H(2)O(2) on BK(Ca) channels. Inhibitors of protein kinase C activity attenuated the effect of H(2)O(2) on BK(Ca) channels, [(3)H]AA release, or intact coronary arteries. In addition, the effect of H(2)O(2) or AA on BK(Ca) channels was inhibited by blockers of lipoxygenase metabolism. In contrast, inhibitors of cyclooxygenase or cytochrome P-450 had no effect. We propose that H(2)O(2) relaxes coronary arteries by stimulating BK(Ca) channels via the PLA(2)/AA signaling cascade and that lipoxygenase metabolites mediate this response.

Calcium-activated potassium channels and nitric oxide coregulate estrogen-induced vasodilation

Nitric oxide synthase (NOS) contributes to estradiol-17beta (E(2)beta)-induced uterine vasodilation, but additional mechanisms are involved, and the cellular pathways remain unclear. We determined if 1) uterine artery myocytes express potassium channels, 2) E(2)beta activates these channels, and 3) channel blockade plus NOS inhibition alters E(2)beta-induced uterine vasodilation. Studies of cell-attached patches identified a 107 +/- 7 pS calcium-dependent potassium channel (BK(Ca)) in uterine artery myocytes that rapidly increased single-channel open probability 70-fold (P < 0.05) after exposure to 100 nM E(2)beta through an apparent cGMP-dependent mechanism. In ovariectomized nonpregnant ewes (n = 11) with uterine artery flow probes and catheters, local BK(Ca) blockade with tetraethylammonium (TEA; 0.05-0.6 mM) dose dependently inhibited E(2)beta-induced uterine vasodilation (n = 37, R = 0.77, P < 0.0001), with maximum inhibition averaging 67 +/- 11%. Mean arterial pressure (MAP) and E(2)beta-induced increases (P </= 0.001) in heart rate (13%) and contralateral uterine blood flow (UBF, approximately 5-fold) were unaffected. Local NOS inhibition plus BK(Ca) blockade, using submaximal doses of nitro-L-arginine methyl ester (5 mg/ml) and TEA (0.3 mM), did not alter basal UBF but completely inhibited ipsilateral E(2)beta-induced uterine vasodilation without affecting MAP and E(2)beta-induced increases in contralateral UBF and heart rate. Acute E(2)beta-mediated uterine vasodilation involves rapid activation of uterine artery BK(Ca) and NOS, and the pathway for their interaction appears to include activation of guanylyl cyclase.

cAMP-dependent vasodilators cross-activate the cGMP-dependent protein kinase to stimulate BK(Ca) channel activity in coronary artery smooth muscle cells

cAMP-dependent vasodilators are used to treat a variety of cardiovascular disorders; however, the signal transduction pathways and effector mechanisms stimulated by these agents are not fully understood. In the present study we demonstrate that cAMP-stimulating agents enhance the activity of the large-conductance, calcium-activated potassium (BK(Ca)) channel in single myocytes from coronary arteries by "cross-activation" of the cGMP-dependent protein kinase (protein kinase G, PKG). Single-channel patch-clamp data revealed that 10 micromol/L isoproterenol, forskolin, or dopamine opens BK(Ca) channels in coronary myocytes and that this effect is attenuated by inhibitors of PKG (KT5823; Rp-8-pCPT-cGMPS), but not by inhibiting the cAMP-dependent protein kinase (protein kinase A, PKA). In addition, a membrane-permeable analog, CPT-cAMP, also opened BK(Ca) channels in these myocytes, and this effect was reversed by KT5823. Direct biochemical measurement confirmed that dopamine or forskolin stimulates PKG activity in coronary arteries but does not elevate cGMP. Finally, the stimulatory effect of cAMP on BK(Ca) channels was reconstituted in a cell-free, inside-out patch by addition of purified PKG activated by either cGMP or cAMP. In contrast, channel gating was unaffected by exposure to the purified catalytic subunit of PKA. In summary, findings from on-cell and cell-free patch-clamp experiments provide direct evidence that cAMP-dependent vasodilators open BK(Ca) channels in coronary myocytes by cross-activation of PKG (but not via PKA). Biochemical assay confirmed this cross-activation mechanism of cAMP action in these arteries. This signaling pathway is a novel mechanism for regulation of potassium channel activity in vascular smooth muscle and other cells.

Gender and ethnic differences in health behaviors and risk factors for coronary disease among urban teenagers: the PATH program

OBJECTIVE

To assess gender and ethnic differences among teenagers in heart health behaviors, risk factors for coronary heart disease (CHD), and cardiovascular fitness.

DESIGN

Observations consist of cross-sectional data collected prior to a school-based health promotion intervention program.

PARTICIPANTS

Teenage girls (N = 865) and boys (N = 497) from three New York City high schools. The ethnic composition of this sample was 20% Asian-American, 40% African-American, 25% Hispanic, and 15% white.

METHOD

Subjects were compared on the following: height, weight, body mass index, percentage body fat, total cholesterol, blood pressure, heart health knowledge, family history, socioeconomic status, dietary habits, smoking, physical activity, and estimated aerobic capacity. Differences were assessed with independent t tests, analysis of variance, and chi-square statistical techniques.

RESULTS

Compared with girls, boys were more active and had higher estimated aerobic capacity, higher systolic blood pressure, and better self-perception of health. Compared with boys, girls had higher cholesterol, percentage body fat, and heart health knowledge scores and ate fewer foods high in saturated fat, cholesterol, salt, and simple sugars. Among girls, African-Americans had the highest blood pressure, cholesterol, body mass index, and intake of foods high in saturated fat, cholesterol, and sugar. Among boys, Hispanics had the highest body mass index and percentage body fat and the lowest heart health knowledge scores. White girls and white boys were the most frequent smokers.

CONCLUSIONS

Poor health behaviors and risk factors for CHD occurred frequently among urban teenagers. In general, teenage girls had poorer health behaviors and a greater prevalence of risk factors than teenage boys, even though they scored better in heart health knowledge testing. Ethnic comparisons revealed poorer health behaviors and higher prevalence of risk factors in African-American and Hispanic teens compared with white and Asian-American teens. Results support the need for health promotion intervention among urban teenagers.

K-Cl cotransport in vascular smooth muscle and erythrocytes: possible implication in vasodilation

K-Cl cotransport, the electroneutral-coupled movement of K and Cl ions, plays an important role in regulatory volume decrease. We recently reported that nitrite, a nitric oxide derivative possessing potent vasodilation properties, stimulates K-Cl cotransport in low-K sheep red blood cells (LK SRBCs). We hypothesized that activation of vascular smooth muscle (VSM) K-Cl cotransport by vasodilators decreases VSM tension. Here we tested this hypothesis by comparing the effects of commonly used vasodilators, hydralazine (HYZ), sodium nitroprusside, isosorbide mononitrate, and pentaerythritol, on K-Cl cotransport in LK SRBCs and in primary cultures of rat VSM cells (VSMCs) and of HYZ-induced K-Cl cotransport activation on relaxation of isolated porcine coronary rings. K-Cl cotransport was measured as the Cl-dependent K efflux or Rb influx in the presence and absence of inhibitors for other K/Rb transport pathways. All vasodilators activated K-Cl cotransport in LK SRBCs and HYZ in VSMCs, and this activation was inhibited by calyculin and genistein, two inhibitors of K-Cl cotransport. KT-5823, a specific inhibitor of protein kinase G, abolished the sodium nitroprusside-stimulated K-Cl cotransport in LK SRBCs, suggesting involvement of the cGMP pathway in K-Cl cotransport activation. Hydralazine, in a dose-dependent manner, and sodium nitroprusside relaxed (independently of the endothelium) precontracted arteries when only K-Cl cotransport was operating and other pathways for K/Rb transport, including the Ca-activated K channel, were inhibited. Our findings suggest that K-Cl cotransport may be involved in vasodilation.

A novel transduction mechanism mediating dopamine-induced vascular relaxation: opening of BKCa channels by cyclic AMP-induced stimulation of the cyclic GMP-dependent protein kinase

Dopamine dilates the coronary, renal and other vascular beds; however, the signaling pathway underlying this effect is unclear. In this study the signal-transduction process mediating dopamine-induced relaxation of porcine coronary arteries was investigated in isolated vessels and single arterial myocytes. Dopamine-induced relaxation of arteries was mediated through the DA- receptor and involved K+ efflux, and subsequent patch-clamp studies demonstrated that either dopamine or fenoldopam, a selective DA-1 agonist, increased the opening probability of the large-conductance, calcium- and voltage-activated K+ (BKCa) channel in coronary myocytes. Moreover, blockade of this channel by iberiotoxin prevented dopamine-induced coronary relaxation. Dopamine stimulation of BKCa channels was completely prevented by a DA-1-receptor antagonist, but was unaffected by propranolol. Furthermore, inhibiting adenylyl cyclase activity prevented stimulation of BKCa channel activity, whereas chlorophenylthio (CPT)-cyclic adenosine monophosphate (AMP), a membrane-permeable analog of cyclic AMP, mimicked the effects of dopamine. Interestingly, inhibiting the cyclic AMP-dependent protein kinase (PKA) did not affect the response to dopamine, whereas dopamine-induced channel activity was completely blocked by inhibiting the activity of the cyclic guanosine monophosphate (GMP)-dependent protein kinase (PKG). These findings demonstrate that activation of DA-1 receptors causes stimulation of BKCa channel activity by a mechanism involving cyclic AMP-dependent stimulation of PKG, but not PKA, and further suggest that this cross-reactivity mediates dopamine-induced coronary vasodilation.

Clinical comparison of the midvastus and medial parapatellar surgical approaches

The medial parapatellar approach and the midvastus approach are the two most commonly used surgical approaches in total knee replacement. This study compared surgical and clinical parameters associated with both surgical approaches in primary total knee replacement. One hundred nine patients who underwent bilateral primary total knee replacements had a medial parapatellar approach to one knee and a midvastus approach to the opposite knee. The prosthetic design and physical therapy were identical in all 109 patients. The patients and physical therapists were blinded to the type of approach used on each knee. The comparison included the surgical parameters of difficulty of exposure, surgical time, incidence of lateral retinacular release, and total blood loss. The clinical parameters of pain, range of motion, ability to perform a straight leg raise, and complications were compared at 8 days, 6 weeks and 6 months. The comparison between the two surgical approaches showed a statistically significant difference in four parameters, all of which favored the midvastus approach. The patients who had the midvastus approach required fewer lateral retinacular releases, had less pain at 8 days, had less pain at 6 weeks, and had a higher incidence of ability to straight leg raise at 8 days. There was no statistical difference between the two surgical approaches in all other surgical and clinical parameters. There was no increased difficulty of exposure using the midvastus approach when compared with the medial parapatellar approach even in patients with severe varus or valgus deformities. Notably, all clinical parameters were equal at 6 months. From a clinical standpoint, the midvastus approach had an advantage over the medial parapatellar approach because the patients had significantly less pain and had the ability to straight leg raise at 8 days. Because the managed care environment dictates a shorter hospital stay, patients who have the midvastus surgical approach have less pain and earlier control of the operative leg, and may be discharged from the hospital earlier. However, the clinical results at 6 months based on the patient's pain relief, range of motion, and ability to straight legraise were identical between the two surgical approaches.

Resveratrol inhibits MAPK activity and nuclear translocation in coronary artery smooth muscle: reversal of endothelin-1 stimulatory effects

In porcine coronary arteries, short-term treatment with resveratrol (RSVL) substantially inhibited MAPK activity (IC50 = 37 microM); and immunoblot analyses revealed consistent reduction in the phosphorylation of ERK-1/-2, JNK-1 and p38, at active sites. Endothelin-1 (ET-1), a primary antecedent in coronary heart diseases, enhanced MAPK activity, phosphorylation and nuclear translocation in a concentration-responsive but RSVL-sensitive manner. RSVL had no effect on basal or forskolin-stimulated cAMP levels, a known downregulator of the MAPK cascade. Likewise, inhibition of MAPK by RSVL was not reversed by the estrogen receptor blockers tamoxifen and ICI-182,780. Conversely, RSVL remarkably attenuated basal and ET-1-evoked protein tyrosine phosphorylation. Because MAPKs promote smooth muscle proliferation and contraction, their current inhibition may contribute to the putative protection by RSVL against coronary heart diseases. These effects apparently do not involve interaction with estrogen receptors.

Short- and long-term projections about the use of drug metabolism in drug discovery and development

The science of drug metabolism, like any other science, has advanced from simple beginnings (by today's standards) to its present state. One can examine the path that has been taken to understand the forces driving the direction of evolution of this science. The trends discovered can then be used to make reasonable extrapolations about the changes that might be expected in the future. That exercise is the subject of this article. The main focus will be on drug metabolism as practiced in the industrial environment, representing the author's main experience as well as the principal arena of practical applications of the science. The discussion will draw mainly on broad phenomena occurring in this application of drug metabolism to drug discovery and development.

Evidence for a tyrosine kinase-dependent activation of the adenylyl Cyclase/PKA cascade downstream from the G-protein-linked endothelin ETA receptor in vascular smooth muscle

Endothelin (ET-1), a contractor and mitogen in the vasculature, enhanced cAMP production (t1/2, 2.2 min; EC50, 89 +/- 6.3 nM) and stimulated activity of the cAMP-dependent protein kinase (PKA) in pig coronary arteries. These responses were blunted by the protein tyrosine kinase (PTK) inhibitors genistein and herbimycin-A, but not by inhibitors of protein kinase C or cyclooxygenase. In contrast, forskolin-stimulated cAMP production was unaffected by PTK inhibition. Immunoblot analysis revealed that ET-1 induced a concentration-dependent protein tyrosine (PT) phosphorylation. Sarafotoxin-c, a selective ETB receptor agonist, had no effect on either cAMP levels or PT phosphorylation. Moreover, pervanadate (PV), a potent inhibitor of PT phosphatases, enhanced both cAMP formation and PT phosphorylation, both of which were blocked by PTK inhibitors. The effects of ET-1 and PV were not additive, suggesting a similar mode of activation, whereas responses to ET-1 and forskolin were synergistic. These findings indicate that AC and PKA are activatable via a nonreceptor PTK-dependent pathway downstream from the G-protein-linked ETA receptor. Because cAMP is a dilator and antimitogen in smooth muscle, stimulation of AC activity may be a negative feedback mechanism regulating ET-1-induced vasoconstriction and/or mitogenesis.

Metabolism of alpha-phosphonosulfonate squalene synthase inhibitors. I. Disposition of a farnesylethyl alpha-phosphonosulfonate and ester prodrugs in rats

The disposition of I [(E,E)-6,10,14-trimethyl-1-phosphono-5,9, 13-pentadecatriene-1-sulfonic acid] and its mono- (II), di- (III), and triester (IV) prodrugs in rats was studied with 14C-labeled compounds. After iv administration of I (15 micromol/kg), radioactivity in plasma was measurable up to 96 hr and averaged 0. 026 microg-eq/ml. I accounted for >50% of the radioactivity in plasma and had an apparent half-life of 4 hr. After oral administration of the same dose, the maximal plasma concentration of radioactivity averaged 0.108 microg-eq/ml at 6 hr. In 96 hr, 19 and 73% of the iv dose and 2 and 97% of the po dose was excreted in urine and feces, respectively. The absorption was 2.4%, based on the plasma data. In 12 hr after an iv dose of I to bile duct-cannulated rats, 41 and 14% of the dose was excreted in bile and urine, respectively. I accounted for 51% of the radioactivity in bile and a negligible amount in urine. At 12 hr after iv dosing, liver retained 31% of the dose. No accumulation of radioactivity in bone was observed. I (3%) and II (6%) were poorly absorbed. Enhanced absorption was observed for III (80%) and IV (45%). No I or metabolites of I were found in bile or urine of rats dosed with the prodrugs. The structures of two metabolites each for I, III, and IV were proposed. Together, they accounted for >80% of the radioactivity in urine and approximately 50% of the radioactivity in bile for each compound. Metabolism appeared to occur primarily at the farnesyl moiety, presumably by the same pathways as for farnesyl-1-pyrophosphate.

Hydrogen peroxide relaxes porcine coronary arteries by stimulating BKCa channel activity

It has been known for a number of years that neutrophils and macrophages secrete H2O2 while fighting disease, and the levels obtained within the vasculature under these conditions can reach several hundred micromolar. Because the effect of H2O2 on vascular smooth muscle is not fully understood, the present study examined the cellular effects of H2O2 on coronary arteries. Under normal ionic conditions, H2O2 relaxed arteries that were precontracted with prostaglandin F2alpha or histamine (EC50 = 252 +/- 22 microM). The effect of H2O2 was concentration dependent and endothelium independent. In contrast, H2O2 did not relax arteries contracted with 80 mM KCl, suggesting involvement of K+ channels. Single-channel patch-clamp recordings revealed that H2O2 increased the activity of the large-conductance (119 pS), Ca2+- and voltage-activated K+ (BKCa) channel. This response was mimicked by arachidonic acid and inhibited by eicosatriynoic acid, a lipoxygenase blocker, suggesting involvement of leukotrienes. Further studies on intact arteries demonstrated that eicosatriynoic acid not only blocked the vasodilatory response to H2O2 but unmasked a vasoconstrictor effect that was reversed by blocking cyclooxygenase activity with indomethacin. These findings identify a novel effector molecule, the BKCa channel, which appears to mediate the vasodilatory effect of H2O2, and suggest that a single signaling pathway, arachidonic acid metabolism, can mediate the vasodilatory and vasoconstrictor effects of H2O2 and possibly other reactive oxygen species.

Procedures for skin diseases performed by physicians in 1993 and 1994: analysis of data from the National Ambulatory Medical Care Survey

BACKGROUND

The provision of ambulatory dermatologic procedural care is not well characterized.

OBJECTIVE

Our purpose was to determine the frequency that different cutaneous procedures are performed by different physician specialties and the diagnoses corresponding to these procedures.

METHODS

Outpatient dermatologic procedures recorded in the 1993 and 1994 National Ambulatory Medical Care Survey were analyzed. To define dermatologic procedures and diagnoses, the International Classification of Diseases diagnosis and procedure codes were identified that related to the skin and subcutaneous tissues. Sampling weights were applied to achieve the nationally representative estimates.

RESULTS

During 1993 and 1994, an estimated 37 million dermatologic procedures were performed. Most were performed by dermatologists (69%) and by family and general practice physicians (15%). A single procedure, "Other local excision or destruction of lesion or tissue of skin and subcutaneous tissue," constituted 65% of all of the dermatologic procedures. UV light treatments, ambulatory microscopic examination of skin specimens, and acne surgical procedures were performed almost exclusively by dermatologists. Most skin biopsies (82%) and excision/destruction procedures (71%) were performed by dermatologists. Actinic keratoses and viral warts accounted for 25% of all cutaneous dermatologic diagnoses treated.

CONCLUSION

Dermatologists have far more experience performing skin biopsies and excision/destruction procedures than other physicians. Cost containment efforts that deny coverage for treatment of actinic keratoses and viral warts would affect a significant portion of cutaneous procedures.

Growth factor-mediated K+ channel activity associated with human myeloblastic ML-1 cell proliferation

ML-1 cell proliferation is dependent on the presence of serum growth factors. Removing serum from the culture medium results in growth arrest and promotes differentiation. In this study, we found that a 4-aminopyridine-sensitive K+ channel was highly expressed in proliferating ML-1 cells and significantly diminished in G1-arrested ML-1 cells induced by serum deprivation but was restored within 30 min in these cells with addition of 10% fetal bovine serum (FBS) or 5 ng/ml epidermal growth factor (EGF). Intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels, but not guanosine 3',5'-cyclic monophosphate, were significantly increased in serum-deprived cells stimulated by FBS or EGF, and the effects of FBS and EGF on the channel activation were mimicked by exogenous cAMP. In inside-out patches, K+ channel activity was significantly increased by the cAMP-dependent protein kinase catalytic subunit, whereas the effect of EGF on K+ channel activation was blocked by Rp-8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphothioate. Together, our results demonstrate that serum growth factors stimulate K+ channel activity in proliferation of ML-1 cells through protein kinase-induced phosphorylation and suggest an important molecular mechanism for serum growth factor-stimulated mitogenesis in ML-1 cells.

Nitrovasodilators relax mesenteric microvessels by cGMP-induced stimulation of Ca-activated K channels

Nitric oxide (NO) released from endothelial cells or exogenous nitrates is a potent dilator of arterial smooth muscle; however, the molecular mechanisms mediating relaxation to NO in the microcirculation have not been characterized. The present study investigated the relaxant effect of nitrovasodilators on microvessels obtained from the rat mesentery and also employed whole cell and single-channel patch-clamp techniques to identify the molecular target of NO action in myocytes from these vessels. Both sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) relaxed phenylephrine-induced contractions by approximately 80% but were significantly less effective in relaxing contractions induced by 40 mM KCl. Relaxation to SNP was also inhibited by the K(+)-channel blocker tetraethylammonium or by inhibition of the activity of the guanosine 3',5'-cyclic monophosphate (cGMP)-dependent protein kinase (PKG). These results suggest that SNP stimulated K+ efflux by opening K+ channels via PKG-mediated phosphorylation. Perforated-patch experiments revealed that both SNP and SNAP increased outward currents in microvascular myocytes, and single-channel studies identified the high-conductance Ca(2+)- and voltage-activated K+ (BKCa) channel as the target of nitrovasodilator action. The effects of nitrovasodilators on BKCa channels were mimicked by cGMP and inhibited by blocking the activity of PKG. We conclude that stimulation of BKCa-channel activity via cGMP-dependent phosphorylation contributes to the vasodilatory effect of NO on microvessels and that a direct effect of NO on BKCa channels does not play a major role in this process. We propose that this mechanism is important for the therapeutic effect of nitrovasodilators on peripheral resistance and arterial blood pressure.

Estrogen relaxation of coronary artery smooth muscle is mediated by nitric oxide and cGMP

Estrogens are proposed to exert protection against cardiovascular disease, and evidence now suggests that this protection involves a direct vasodilatory effect. We have shown previously that estrogen relaxes endothelium-denuded porcine coronary arteries by opening the large-conductance calcium- and voltage-activated potassium (BKCa) channel of myocytes through guanosine 3',5'-cyclic monophosphate (cGMP)-dependent phosphorylation (35). The present study confirms these results and now demonstrates that this mechanism involves production of nitric oxide (NO). S-nitroso-N-acetylpenicillamine (SNAP), an NO donor, or 8-bromo-cGMP mimicked the effect of estrogen on BKCa channels. Furthermore, inhibition of NO synthase (NOS) attenuated estrogen- or tamoxifen-induced BKCa-channel activity, and this effect was disinhibited by L-arginine. Inhibition of guanylyl cyclase activity blocked the stimulatory effect of estrogen, SNAP, or L-arginine on BKCa channels. Furthermore, 17 beta-estradiol stimulated accumulation of nitrite and cGMP in coronary myocytes. Therefore, we propose that the vasodilatory effect of estrogen on the coronary circulation is mediated by NO. A portion of the beneficial cardiovascular effects of estrogen may be attributed to relaxation of vascular smooth muscle by a process that involves NO- and cGMP-dependent stimulation of BKCa channels.

Therapeutic options and results for the management of minimally invasive carcinoma of the breast: influence of axillary dissection for treatment of T1a and T1b lesions

BACKGROUND

Axillary dissection has maintained a role of primacy for the surgical therapy of invasive carcinoma of the breast for many years. More recently, early (T1) minimally invasive carcinoma of the breast has been diagnosed with increasing frequency, and the necessity of axillary dissection for sampling purposes in these small tumors has been questioned, based primarily on the finding of low rates of axillary metastases.

STUDY DESIGN

The Rhode Island State Tumor Registry records of 1,126 patients with T1a or T1b tumors were examined to assess the effect of axillary dissection on patient outcome. These data span 9 years (1985 to 1992) with a median follow-up duration of 64 months. Five-year overall, disease-free, and breast cancer-specific (determinate) survival were determined according to treatment modality. Axillary node positivity was calculated for patients with minimally invasive carcinoma of the breast who underwent axillary dissection. Multivariate statistical methods were used to provide adjustment for known confounding prognostic variables.

RESULTS

Omission of axillary dissection occurred in 157 cases and correlated with reductions in overall, disease-free, and breast cancer-specific survival (p < .001 in all cases). Nodal status significantly influenced disease-free survival in minimally invasive carcinoma of the breast (90 percent node-negative compared with 76 percent node-positive, p = .02). Nodal positivity was evident in 18.2 percent of patients undergoing axillary dissection for minimally invasive carcinoma of the breast (9.8 percent for T1a, 19.4 percent for T1b, p = .01). In multivariate analysis, the performance of axillary dissection with breast conservation or modified radical mastectomy were independent predictors of overall survival, as well as disease-free and breast cancer-specific survival.

CONCLUSIONS

A significant number of patients with small (less than or equal to 1 cm) invasive tumors of the breast will have axillary metastases at the time of diagnosis. Omission of axillary dissection in these patients was associated with significant impairment of overall, disease-free, and breast cancer-specific survival. Axillary dissection should continue to be a standard approach for the surgical therapy of all patients with invasive carcinoma of the breast, regardless of tumor size.

A gene map of the human genome

The human genome is thought to harbor 50,000 to 100,000 genes, of which about half have been sampled to date in the form of expressed sequence tags. An international consortium was organized to develop and map gene-based sequence tagged site markers on a set of two radiation hybrid panels and a yeast artificial chromosome library. More than 16,000 human genes have been mapped relative to a framework map that contains about 1000 polymorphic genetic markers. The gene map unifies the existing genetic and physical maps with the nucleotide and protein sequence databases in a fashion that should speed the discovery of genes underlying inherited human disease. The integrated resource is available through a site on the World Wide Web at http://www.ncbi.nlm.nih.gov/SCIENCE96/.

Mood disorder and chronic hypercalcemia

Fifty-five patients with chronic hypercalcemia were compared with test norms, and two comparison groups of orthopedic patients and hypertensive patients on objective and subjective tests of mood. Sixteen percent of the hypercalcemic patients were found to score over the cut-off point for anxiety on the anxiety subsection of the Hospital Anxiety and Depression Scale, and 16% were diagnosed as suffering from depression on the Paykel Clinical Interview for Depression. There were, however, no significant differences between the comparison groups and those with hypercalcemia on the scales used. There has been debate about the management of individuals with hypercalcemia. This study supports a conservative rather than a surgical approach as far as psychological symptoms are concerned.

Prodrugs of BMS-183920: metabolism and permeability considerations

The oral bioavailability of BMS-183920, a diacidic, potent angiotensin II receptor antagonist, is low in rats (approximately 11%). In vivo studies in bile duct-cannulated rats indicated that BMS-183920 was metabolically stable and that the low bioavailability was due to incomplete intestinal absorption. Five acyl-ester prodrugs were synthesized which were 5-15 times more permeable than BMS-183920 through Caco-2 cells. However, limited studies in rats indicated that the oral bioavailability of BMS-183920 was improved only 2-fold, in the best case. The lack of a substantial increase in bioavailability was apparently due to presystemic prodrug hydrolysis or metabolism via N-glucuronidation. Bioavailability of BMS-183920 after oral dosing of a tetrazole-ester prodrug averaged 37%, the most significant improvement within this prodrug series. Interestingly, in vitro studies indicated that the tetrazole-ester prodrug was a substrate for glucuronosyl transferase; however, its rate of bioactivation (hydrolysis) was sufficiently high to provide a substantial increase in bioavailability of BMS-183920. Therefore, while prodrug modification of BMS-183920 improved Caco-2 cell permeability and oral absorption in vivo, the relative extents of hydrolysis (bioactivation) vs metabolism of the prodrug determined whether a substantial improvement in bioavailability was achieved.

Coronary disease risk factor reduction and behavior modification in minority adolescents: the PATH program

PURPOSE

To evaluate the impact of a unique school-based program of exercise, health education, and behavior modification on health knowledge, health behaviors, coronary risk factors, and cardiovascular fitness in minority adolescents.

METHODS

A total of 346 students from an inner-city public high school participated in health promotion intervention or regular physical education volleyball classes. Subjects were African-American (47%), Asian-American (9%), Hispanic (21%), white (3%), and other (19%). The health promotion curriculum consisted of 11 weeks of daily circuit training exercise and health lecture-discussions.

RESULTS

The groups were similar in age, height, weight, ethnicity, and socioeconomic status. Following intervention both boys (P < .001) and girls (P < .006) significantly improved health knowledge test scores. Significant benefits for girls included improved dietary habits (P < .05), reduced cholesterol (P < .004), and higher estimated V(O2)max (P < .0001). There were no other significant changes in boys.

CONCLUSIONS

The results suggest that a school-based health promotion program of exercise and health lecture-discussion is beneficial for multiethnic, inner-city adolescents, especially females.

X-ray diffraction analysis of cytochrome P450 2B4 reconstituted into liposomes

Two general models of the membrane topology of microsomal cytochrome P450 have been proposed: (1) deep immersion in the membrane, and (2) a P450cam-like heme domain anchored to the membrane with one or two membrane-spanning helices. Lamellar X-ray diffraction of oriented membrane multilayers was employed to distinguish these alternatives. Cytochrome P450 2B4 was reconstituted into unilamellar phospholipid proteoliposomes (molar protein to lipid ratio 1:90). Sedimentation of the proteoliposomes produced an ordered stack of bilayers with a one-dimensional repeat distance (d) perpendicular to the plane of the bilayer. The stacked multilayers were exposed to an X-ray beam (lambda = 1.54 A) at near grazing incidence, and lamellar diffraction patterns were recorded. With proteoliposome multilayers, up to six diffraction orders could be observed. Their spacing corresponded to a d of 63.6 A, calculated according to Bragg's Law, comprising the lipid bilayer, the projection of the incorporated protein beyond the bilayer, and the intermembrane water layer. With liposome multilayers containing no P450, the observed d was 59.6 A. These data suggest that the increase of distance between successive bilayers in the stack due to the presence of P450 2B4 was only about 4 A. This distance is much less than would be expected with the "N-terminal membrane-anchor" model of the membrane topology, in which the P450 molecules largely extend beyond the surface of the membrane (> or = 35 A). Furthermore, the mass distribution deduced from Fourier synthesis confirms that the protein is deeply immersed in the membrane.

Somatostatin stimulates BKCa channels in rat pituitary tumor cells through lipoxygenase metabolites of arachidonic acid

The stimulation of large-conductance, calcium-activated (BK) potassium channels by somatostatin through protein dephosphorylation in rat pituitary tumor cells (White et al., Nature 351, 570-573, 1991) is blocked by drugs that interfere with arachidonic acid release by phospholipase A2 and metabolism by 5-lip-oxygenase. In contrast, higher concentrations of the same drugs had no effect on BK channel gating in cell-free patches, on the inhibition of adenylyl cyclase by somatostatin, or on the stimulation of BK channels by protein dephosphorylation through a cGMP-dependent pathway (White et al., Nature 361, 263-266, 1993). Exogenous arachidonic acid (1-20 muM) stimulated BK channel activity through protein dephosphorylation as effectively as somatostatin and was also blocked by inhibitors of lipoxygenases but not by inhibitors of phospholipase A2. These results support the hypothesis that lipoxygenase metabolites of arachidonic acid are second messengers linking pertussis toxin sensitive G-proteins to protein phosphatases regulating potassium channel activity (Armstrong and White, Trends Neurosci. 15, 403-408, 1992).

Estrogen relaxes coronary arteries by opening BKCa channels through a cGMP-dependent mechanism

Women rarely suffer cardiovascular dysfunction before menopause, but by the age of 65 a woman becomes as vulnerable to cardiovascular mortality as a man. It has been proposed that estrogens protect against cardiovascular disease; however, the physiological basis of estrogen protection is unknown. In the present study the mechanism of estrogen-induced relaxation of coronary arteries was investigated at the tissue, cellular, and molecular levels. Tissue studies demonstrate that 17 beta-estradiol relaxes porcine coronary arteries by an endothelium-independent mechanism involving K+ efflux, and subsequent studies employing the patch-clamp technique confirmed that estrogen stimulates K+ channel gating in coronary smooth muscle. Perforated-patch recordings from metabolically intact coronary myocytes revealed that 17 beta-estradiol more than doubles steady state outward currents in these cells at positive voltages. Studies of on-cell patches demonstrated a potent stimulatory effect of 17 beta-estradiol on the gating of the large-conductance, Ca(2+)- and voltage-activated K+ (BKCa) channels, while 17 alpha-estradiol had no effect. Furthermore, blocking BKCa channels in intact arteries inhibited estrogen-induced relaxation. The effect of 17 beta-estradiol on BKCa channels was blocked by inhibiting cGMP-dependent protein kinase (PKG) activity and was mimicked by exogenous cGMP or by stimulating PKG activity. Therefore, we propose that 17 beta-estradiol relaxes coronary arteries by opening BKCa channels via cGMP-dependent phosphorylation. This novel mechanism could account for the hypotensive effect of estrogens and help explain, at least in part, why postmenopausal estrogen therapy lowers the risk of cardiovascular disease.

A three-dimensional model of aromatase cytochrome P450

P450 hemeproteins comprise a large gene superfamily that catalyzes monooxygenase reactions in the presence of a redox partner. Because the mammalian members are, without exception, membrane-bound proteins, they have resisted structure-function analysis by means of X-ray crystallographic methods. Among P450-catalyzed reactions, the aromatase reaction that catalyzes the conversion of C19 steroids to estrogens is one of the most complex and least understood. Thus, to better understand the reaction mechanism, we have constructed a three-dimensional model of P450arom not only to examine the active site and those residues potentially involved in catalysis, but to study other important structural features such as substrate recognition and redox-partner binding, which require examination of the entire molecule (excepting the putative membrane-spanning region). This model of P450arom was built based on a "core structure" identified from the structures of the soluble, bacterial P450s (P450cam, P450terp, and P450BM-P) rather than by molecular replacement, after which the less conserved elements and loops were added in a rational fashion. Minimization and dynamic simulations were used to optimize the model and the reasonableness of the structure was evaluated. From this model we have postulated a membrane-associated hydrophobic region of aliphatic and aromatic residues involved in substrate recognition, a redox-partner binding region that may be unique compared to other P450s, as well as residues involved in active site orientation of substrates and an inhibitor of P450arom, namely vorozole. We also have proposed a scheme for the reaction mechanism in which a "threonine switch" determines whether oxygen insertion into the substrate molecule involves an oxygen radical or a peroxide intermediate.

Effects of bioflavonoids on hepatic P450 activities

1. The effects of tangeretin, green tea flavonoids, and other flavonoids on 7-ethoxyresorufin-O-deethylase (EROD; 450 1A), 7-pentoxyresorufin-O-dealkylase (PROD; P450 2B), p-nitrophenol hydroxylase (PNPH, P450 2E1), and erythromycin-N-demethylase (ERDM; P450 3A) were examined in induced rat liver microsomes. EROD, PNPH, ERDM, and nifedipine oxidase (NIFO; P450 3A4) were examined in human liver microsomes. 2. All flavonoids tested inhibited EROD activity at higher concentrations in liver microsomes. Flavone and tangeretin were potent inhibitors of EROD, with IC50's of 0.7 and 0.8 microM respectively in rat liver microsomes and 0.15 and 16 microM respectively in human liver microsomes. The green tea flavonoid (-)-epicatechin-3-gallate (ECG) was the most potent inhibitor of EROD in human liver microsomes (IC50 = 75 microM). The effect of the green tea flavonoids on EROD was complex; in addition to inhibition at high concentrations of flavonoid, moderate activation was seen at lower concentrations. 3. 450 2B-, 2E1- and 3A-dependent activities in rat and human liver microsomes were only moderately inhibited by any of the flavonoids tested, and, in general, ECG was the most potent inhibitor for these activities with IC50's ranging from 75 to 300 microM. 4. Tangeretin inhibited EROD activity (P450 1A2) in human liver microsomes in a competitive manner with a Ki = 68 nM. Tangeretin inhibited NIFO activity (P450 3A4) in human liver microsomes in an uncompetitive manner with Ki = 72 microM.

Prevalence estimates of alcohol problems in a Veterans Administration outpatient population: AUDIT vs. MAST

Prior reports have indicated that the prevalence of alcohol-related problems in VA patients is significantly higher than that found in the general population. Prevalence rates, however, are likely to be affected by the screening instrument employed. A sample of 722 VA outpatients awaiting general medical and urgent care treatment was asked to complete two screening questionnaires: the World Health Organization's AUDIT and the brief MAST. Of 508 completed AUDITs, 55 (11%) scored above the cut-offs of 11 for harmful consumption, and 85 (17%) above the more liberal cut-off score of 8; whereas of 501 completed MASTs, 104 (21%) scored above the cut-off. Differences in identification rates are discussed.

Uncertainty and psychologic stress after coronary angioplasty and coronary bypass surgery

OBJECTIVE

To examine the trajectory of uncertainty and symptoms of psychologic stress during the first 3 months after coronary angioplasty and coronary bypass surgery and to study the impact of social support on uncertainty and psychologic stress in these patient populations.

DESIGN

Descriptive, correlative.

SETTING

Urban community, at-home interviews.

PATIENTS

Male patients with angioplasty (n = 22) and bypass (n = 25) at 1 and 3 months after treatment. Age range was 39 to 75 years (mean 58 years).

OUTCOME MEASURES

Mishel Uncertainty in Illness scores, General Health Questionnaire scores, and Perceived Social Support Scale scores.

INTERVENTION

Patients underwent either percutaneous transluminal coronary angioplasty or coronary artery bypass grafting as treatment for coronary artery disease.

RESULTS

Data were analyzed with repeated measures analysis of variance and Pearson correlation coefficients. Results showed that at both time periods angioplasty patients were more uncertain than bypass patients (p < 0.05), and that regardless of procedure, patients reported fewer symptoms of psychologic stress at 3 months than at 1 month (p < 0.01). Patients with high social support had less uncertainty and psychologic stress than patients with low support (p < 0.05). Analysis of the social support and treatment group interaction showed that angioplasty patients with low perceived social support had significantly more psychologic stress than angioplasty patients with high support (p < 0.01). Analysis of the correlations between uncertainty and psychologic stress in the angioplasty and bypass grafting procedure groups after control for social support revealed that social support was a significant mediator of the relationship between uncertainty and stress only among patients undergoing percutaneous transluminal coronary angioplasty. There was little evidence of a mediating role for social support in the coronary artery bypass grafting group.

CONCLUSIONS

These results suggest that angioplasty patients may be in particular need of interventions aimed at reducing uncertainty, and that interventions that increase social support could be important in achieving this reduction.

Health promotion in minority adolescents: a Healthy People 2000 pilot study

PURPOSE

The purpose was to evaluate the effects of a health promotion curriculum on health knowledge, behavior, cardiovascular fitness, and cardiovascular risk factors.

METHODS

A multi-ethnic, multi-cultural sample (n = 54) of 10th grade males and females participated in a study of cardiovascular health promotion and coronary risk factor reduction. The sample was comprised of Asian-Americans (39%), blacks (33%), Hispanics (11%), whites (2%), and others (15%). Intervention consisted of a 10-week health promotion curriculum of classroom education modules in physical activity, nutrition, smoking cessation, stress management and personal problem solving, and an exercise program of walking and running. A nonintervention control group served as a basis for comparison. Classroom and exercise sessions met on alternate days.

RESULTS

Following intervention, a significant treatment effect (P = .007) was observed in lowered total cholesterol, and significant within group improvements (P < .01) were observed in diet habits, percent body fat, and cardiovascular health knowledge. Comparisons of knowledge and social effects revealed higher cardiovascular health knowledge (P < .05) in subjects of nonsmoking compared to smoking parents, higher self-perception of health (P < .01) in more active vs less active subjects and better dietary habits (P < .07) in children whose parents were college educated compared to parents who did not attend college.

CONCLUSIONS

Preliminary findings suggest that a health promotion curriculum consisting of health education, behavior modification, and regular aerobic exercise lowers cholesterol, improves health behavior and increases health knowledge.

Photoaffinity labeling of cytochrome P450 2B4: capture of active site heme ligands by a photocarbene

Spiro[adamantane-2,2'-diazirine], which produces adamantyl carbene upon photolysis, binds tightly to P450 2B4 (KS = 3.2 microM), giving a normal substrate binding difference spectrum. Irradiation of 2-[3H]adamantane diazirine at 365 nm in the presence of native, ferric P450 2B4 resulted in first-order photolysis (t1/2 = 1.8 min). The main product was 2-[3H]adamantanol, with about 6% of the radioactivity covalently bound to P450 2B4. With the ferrous carbonyl form of P450 2B4, 2-adamantanol production decreased and protein labeling increased to 12%. When ferric cyanide 2B4 was used, 2-adamantanecarbonitrile was formed in addition to 2-adamantanol. The nitrile appears to have resulted from capture of the iron-bound cyanide ligand by the carbene. The use of multiple cycles of photolysis increased the percentage of protein labeling to 76%. Photolabeling was inhibited by known 2B4 substrates and inhibitors. Also, N-demethylation of benzphetamine and generation of a substrate binding difference spectrum by benzphetamine were both inhibited stoichiometrically with the fraction of radiolabeled protein. The labeled protein was permanently converted to the high-spin state, as indicated by the characteristic change in the absorbance spectrum, demonstrating irreversible occupation of the substrate binding site by the adamantyl residue. Mild acid hydrolysis of radiolabeled 2B4 at the five Asp-Pro bonds generated a 2-kDa peptide which carried 78% of the radioactivity. These results are interpreted as the result of the active site carbene reacting by three competing pathways: capture of the heme sixth ligand to yield either 2-adamantanol or 2-adamantanecarbonitrile, capture of an unbound active site water molecule to yield adamantanol, and covalent attachment to a protein residue. Thus, the P450 2B4 active site appears to contain at least one unbound water molecule in addition to the heme aquo sixth ligand, even when substrate is present.

Data-driven performance improvement in health care: the Joint Commission's Indicator Measurement System (IMSystem)

BACKGROUND

Since 1986, the Joint Commission has worked to create an evaluation system that would remain standards based but would accent an organization's performance as well as its capability to provide care. One component is the Indicator Measurement System (IMSystem), which involves continuous data collection and periodic feedback about specific performance measures, or indicators. An indicator is a quantitative measure of an aspect of patient care. It is not a direct measure of quality; rather it is a screen or flag which indicates areas for more detailed analysis.

METHODOLOGY

Sets of indicators, each set related to specific important health care functions such as perioperative care, are established by expert task forces and are then subject to two phases of testing. Alpha testing addresses face validity and feasibility of data collection and may result in indicator revision. In the beta phase, a large group of organizations test the indicators for validity, reliability, and usefulness in improving performance.

OPERATIONAL ISSUES

In 1994, the IMSystem will contain ten indicators and participation by hospitals will be voluntary. Once the value of these data in the accreditation process has been demonstrated--possibly as early as 1996--participation will become an integral component of accreditation. Hospitals will transmit indicator data to the Joint Commission but no patient or physician identifiers will leave the hospital. The system will provide organizations with information they can use to monitor and improve their performance, while helping meet external needs for performance measurement.

Kallmann's syndrome and anorexia nervosa: a diagnostic dilemma

Kallmann's syndrome is a rare cause of primary amenorrhea, with impairment of release of gonadotropin-releasing hormone and anosmia. We present a case in which Kallmann's syndrome had been diagnosed, but who also fulfilled the diagnostic criteria for anorexia nervosa. We discuss the diagnostic dilemma.

Potassium channel stimulation by natriuretic peptides through cGMP-dependent dephosphorylation

Natriuretic peptides inhibit the release and action of many hormones through cyclic guanosine monophosphate (cGMP), but the mechanism of cGMP action is unclear. In frog ventricular muscle and guinea-pig hippocampal neurons, cGMP inhibits voltage-activated Ca2+ currents by stimulating phosphodiesterase activity and reducing intracellular cyclic AMP; however, this mechanism is not involved in the action of cGMP on other channels or on Ca2+ channels in other cells. Natriuretic peptide receptors in the rat pituitary also stimulate guanylyl cyclase activity but inhibit secretion by increasing membrane conductance to potassium. In an electrophysiological study on rat pituitary tumour cells, we identified the large-conductance, calcium- and voltage-activated potassium channels (BK) as the primary target of another inhibitory neuropeptide, somatostatin. Here we report that atrial natriuretic peptide also stimulates BK channel activity in GH4C1 cells through protein dephosphorylation. Unlike somatostatin, however, the effect of atrial natriuretic peptide on BK channel activity is preceded by a rapid and potent stimulation of cGMP production and requires cGMP-dependent protein kinase activity. Protein phosphatase activation by cGMP-dependent kinase could explain the inhibitory effects of natriuretic peptides on electrical excitability and the antagonism of cGMP and cAMP in many systems.

An enzymatic mechanism for potassium channel stimulation through pertussis-toxin-sensitive G proteins

Many neurotransmitters inhibit secretion from electrically excitable cells by activating pertussis-toxin-sensitive G proteins that modulate voltage-gated ion channels. Recent electrophysiological studies of metabolically intact cells from mammalian and molluscan neuroendocrine systems have implicated protein phosphatases in this process. In this article David Armstrong and Richard White review these studies and suggest a biochemical pathway that might link one of the G proteins to protein phosphatase activity.

Increased occurrence of exfoliation in the male, Spanish American population of New Mexico

Exfoliation syndrome was found to occur much more frequently in the male Spanish American population of New Mexico. This was based on a Veterans Administration Medical Center study in Albuquerque, New Mexico. The prevalence of exfoliation in the Spanish Americans was estimated to be from 3-6 percent and this is consistent with many other such studies performed in the United States and other countries. The Spanish American population is 5.8 times more likely to develop exfoliation than the non-Spanish American population of New Mexico. Exfoliation was found on such eye structures as the lens, iris, ciliary processes, posterior capsule, vitreous face, posterior corneal surface, and arterial chamber angle. Glaucoma capsulare was also studied and it was found that there was not a significant difference between the Spanish American and the non-Spanish American population for developing the condition. However, there was a strong association of glaucoma with the presence of exfoliation in both groups. Based on our results, patients with exfoliation are 22 times more likely to develop glaucoma than are their age-matched controls. Also, 40 percent of the exfoliation patients had glaucoma compared with only 5 percent of the age-matched controls (p less than .001). The patients with glaucoma capsulare were found to have a more medically resistant type of glaucoma, which was consistent with other reports of this condition. There are two theories we propose for the existence of exfoliation in the Spanish American population of New Mexico. The first is a geographic climatic theory that relates exfoliation to greater solar radiation levels due to a high overall altitude and sunny weather in New Mexico.(ABSTRACT TRUNCATED AT 250 WORDS)

A derivation of the underlying constructs of just-in-time management systems

Researchers have recommended that the theoretical constructs underlying just-in-time (JIT) management systems be identified and developed if JIT is to be fully understood and its full capabilities realized. In this study, we advanced this conceptual development through an instrument based on the relevant literature and empirically deriving three underlying constructs: (1) operating structure and control, (2) product scheduling, and (3) quality implementation. We report a content analysis of these constructs and develop propositions regarding their relationships, predecessors, and outcomes.

Benzazepinone calcium channel blockers. 5. Effects on antihypertensive activity associated with N1 and aromatic substituents

We have shown that the pyrrolidinylmethyl substituent on the lactam nitrogen (N1) of benzazepinone and benzothiazepinone calcium channel blocking agents is resistant to metabolic deamination and generally increases the duration and potency of antihypertensive activity in spontaneously hypertensive rats (SHR) relative to (N,N-dimethylamino)ethyl analogs. Additionally, compounds possessing a substituent on the fused aromatic ring are more resistant to metabolic deacylation of the C3 hydroxy function, which may explain why aromatic substituents also frequently increase the potency and/or duration of antihypertensive activity. Our data also indicate the increased antihypertensive activity associated with these structural modifications is independent of any effects of potency in vitro. Overall, we interpret these results to indicate that these structural modifications improve antihypertensive activity as a result of increased metabolic stability and, consequently, oral bioavailability.

Benzazepinone calcium channel blockers. 2. Structure-activity and drug metabolism studies leading to potent antihypertensive agents. Comparison with benzothiazepinones

As part of a program to discover potent antihypertensive analogues of diltiazem (3a), we prepared 1-benzazepin-2-ones (4). Benzazepinones competitively displace radiolabeled diltiazem, and show the same absolute stereochemical preferences at the calcium channel receptor protein. Derivatives of 4 containing a trifluoromethyl substituent in the fused aromatic ring show potent and long-acting antihypertensive activity. Studies of the metabolism of 4 lead to the metabolically stable antihypertensive calcium channel blockers 5a and 5c. Benzazepinone 5a is a longer acting and more potent antihypertensive agent than the second generation diltiazem analogue TA-3090 (3e).

Spinal epidural abscess complicating vertebral osteomyelitis: an insidious cause of deteriorating spinal cord function

Spinal epidural abscess may complicate vertebral osteomyelitis. The purpose of this report is to discuss its course in two patients with sensory/motor and cognitive impairment and to demonstrate the need for its early detection. Delayed detection may lead to spinal cord injury or meningitis. It may also delay functional return and hinder intensive rehabilitation efforts. Two patients are presented.

Enzymatic gating of voltage-activated calcium channels

The model of calcium-channel gating described above, although almost certainly too simple, suggests a direct role for protein kinases and phosphatases in determining the kinetics of calcium channel gating on a subsecond time scale. In addition, it provides a unique perspective for understanding studies of calcium channel gating under widely different metabolic and pharmacological conditions. Although many of these effects may be specific to the dihydropyridine-sensitive or L-type calcium channel, they give an indication of the range of possibilities for integrating calcium-channel activity with cellular biochemistry.

Somatostatin stimulates Ca(2+)-activated K+ channels through protein dephosphorylation

The neuropeptide somatostatin inhibits secretion from electrically excitable cells in the pituitary, pancreas, gut and brain. In mammalian pituitary tumour cells somatostatin inhibits secretion through two distinct pertussis toxin-sensitive mechanisms. One involves inhibition of adenylyl cyclase, the other an unidentified cyclic AMP-independent mechanism that reduces Ca2+ influx by increasing membrane conductance to potassium. Here we demonstrate that the predominant electrophysiological effect of somatostatin on metabolically intact pituitary tumour cells is a large, sustained increase in the activity of the large-conductance Ca(2+)- and voltage-activated K+ channels (BK). This action of somatostatin does not involve direct effects of Ca2+, cAMP or G proteins on the channels. Our results indicate instead that somatostatin stimulates BK channel activity through protein dephosphorylation.

Synthesis and antibacterial activity of new C-10 quinolonyl-cephem esters

A series of cephalosporins derived from cephalothin containing an ester-linked quinolonyl substituent at the C-10 position (C-10 quinolonyl-cephem esters) has been prepared and evaluated for in vitro antibacterial activity. The C-10 quinolonyl-cephem esters exhibited a broadened spectrum of activity when compared with cephalothin and the corresponding quinolones, including activity against beta-lactamase-producing bacteria.

Regulation of Ca2+ current in frog ventricular cardiomyocytes by 5'-guanylylimidodiphosphate and acetylcholine

1. Calcium currents (ICa) were measured in frog ventricular myocytes using the whole-cell patch clamp technique and a perfused pipette. The effect of internal perfusion with the hydrolysis-resistant GTP analogue, GppNHp (5'guanylylimidodiphosphate), on basal ICa and ICa stimulated with forskolin or isoprenaline was examined to gain insight into the role of G proteins in ICa regulation. 2. Without added guanine nucleotides, isoprenaline stimulated ICa approximately 14-fold with an EC50 of 0.09 microM. Forskolin stimulated ICa approximately 10-fold with an EC50 of 0.30 microM. 3. Internal 30 microM-GppNHp produced an approximately 80% decrease in ICa elevated by 0.3 microM-isoprenaline or 3 microM-forskolin. The inhibition of isoprenaline stimulation was due to a decrease in the maximal stimulation from approximately 14-fold to approximately 14-fold without a significant change in the EC50. In contrast, the reduction in forskolin stimulation was due to a 22-fold increase in the EC50 to 11.4 microM, with little change in maximal stimulation. 4. The inhibition of stimulated ICa by GppNHp is likely to be mediated by a G protein, because the effects of GppNHp are irreversible, and are blocked by excess GTP. ICa is affected similarly by GppNHp and by ACh. This suggests that GppNHp activates the same G protein that is normally activated by ACh, but activation by GppNHp occurs in the absence of agonist occupation of the muscarinic receptor. 5. The increase in the EC50 for forskolin produced by internal GppNHp was reversed by exposure to isoprenaline, which itself did not affect ICa amplitude. On average, exposure to isoprenaline in the presence of GppNHp caused an irreversible 81-fold decrease in the EC50 for forskolin to 0.14 microM. Stimulation of ICa by forskolin after internal GppNHp and exposure to isoprenaline was completely blocked by the protein kinase A inhibitor PKI(5-22). 6. These effects do not involve the phospholipase C system, because they are not mimicked by phorbol esters or internal inositol 1,4,5-trisphosphate (IP3) and are not blocked by bromophenacyl bromide or neomycin. 7. Direct effects of G proteins on ICa were not evident, because internal perfusion with PKI(5-22) completely inhibited isoprenaline- or forskolin-stimulated increases in ICa, and neither ACh nor internal GppNHp (30-500 microM) affected basal ICa or ICa elevated by internally perfused cyclic AMP. 8. These results suggest that the predominant site of action of the inhibitory G protein activated by either GppNHp or ACh is adenylyl cyclase. Furthermore, the internally perfused frog cardiomyocytes may provide a useful approach for probing the detailed interactions of G proteins, forskolin, and adenylyl cyclase in an intact cell.

The involvement of free radicals in the mechanisms of monooxygenases

The occurrence of free radicals in the mechanisms of monooxygenases reflects the chemistry of dioxygen and the inertness of typical substrates. Thus, oxidation of such substrates requires attack by reduced dioxygen-derived free radicals. Consequently, a molecule of NAD(P)H must be invested for each substrate molecule oxidized. Furthermore, since free radicals are difficult to control, deviations from the intended reaction course are frequent. These considerations are illustrated by examination of the generation and fate of enzyme- and substrate-derived free radicals at various stages in the catalytic cycles of two monooxygenases important in xenobiotic biotransformation, dopamine beta-hydroxylase and cytochrome P-450.