Vascular contraction induced by activation of membrane calcium ion channels is enhanced in streptozotocin-diabetes

Previous results from our laboratory (White and Carrier, Enhanced Vascular Alpha-Adrenergic Neuroeffector System in Diabetes: Importance of Calcium. Am. J. Physiol. 255: H1036-1042, 1988) demonstrated that mesenteric arteries from streptozotocin (STZ)-diabetic rats exhibit an enhanced responsiveness to alpha adrenergic agonists. The present study demonstrates that this enhanced responsiveness is dependent upon the presence of extracellular calcium. Arteries from STZ-diabetic (10-12 weeks) rats developed greater contractile force in response to norepinephrine or KCl. Development of these effects was prevented by daily insulin treatment, indicating these alterations are related to the diabetic state. Similarly, the contractile response to extracellular calcium in the presence of norepinephrine (3 x 10(-6) M) or KCl (60 mM) was greater in arteries from STZ-diabetic animals. BAY K 8644, a calcium channel agonist, induced greater contraction in arteries from STZ-diabetic animals, as did activation of protein kinase C by phorbol dibutyrate. In contrast, contraction induced by release of calcium from intracellular sources (alpha-1 adrenoceptor-mediated or caffeine-induced) was unaltered by diabetes. These findings indicate that enhanced vascular contraction in STZ-diabetes is of a nonspecific nature, i.e., the contractile response to any agent which induces extracellular calcium-dependent contraction should be enhanced in diabetes. We propose that STZ-diabetes enhances the activity and/or number of calcium ion channels in vascular smooth muscle.

A review of the use of phosphate rocks as fertilizers for direct application in Australia and New Zealand

Field trials in New Zealand have shown that reactive phosphate rocks (RPRs) can be as effective as soluble P fertilisers, per kg of P applied, on permanent pastures that have a soil pH<6.0 (in water) and a mean annual rainfall >800 mm. Whereas RPRs such as North Carolina, Sechura, Gafsa and Chatham Rise have been evaluated on permanent pastures in New Zealand, most Australian field trials have examined unreactive PRs such as Christmas Island A and C grade, Nauru and Duchess, using annual plant species. Only in recent experiments has an RPR, North Carolina, been examined. Except on the highly leached sands in southern and south-western Australia, both reactive and unreactive PRs have shown a low effectiveness relative to superphosphate. In addition to chemical reactivity, other factors may contribute to the difference in the observed agronomic effectiveness of PRs in Australia and New Zealand. Generally, PRs have been evaluated on soils of lower pH, higher pH buffering capacity (as measured by titratable acidity) and higher P status in New Zealand than in Australia. Rainfall is more evenly distributed throughout the year on New Zealand pastures than in Australia where the soil surface dries out between rainfall events. Dry conditions reduce the rate at which soil acid diffuses to a PR granule and dissolution products diffuse away. Even when pH and soil moisture are favourable, the release of P from PR is slow and more suited to permanent pasture (i.e. the conditions usually used to evaluate PRs in New Zealand) than to the annual pastures or crops used in most Australian trials. Based on the criteria of soil pH<6.0 and mean annual rainfall >800 mm, it is estimated that the potentially suitable area for RPRs on pasture in New Zealand is about 8 million ha. Extending this analysis to Australia, but excluding the seasonal rainfall areas of northern and south-western Australia, the potentially suitable area is about 13 million ha. In New Zealand, many of the soils in the North and South Islands satisfy both the pH and rainfall criteria. However, suitable areas in Australia are confined mainly to the coastal and tableland areas of New South Wales and eastern Victoria, and within these areas the actual effectiveness of RPR will depend markedly on soil management and the distribution of annual rainfall. Further research on RPR use should be focused on these areas.

Effects of magnesium on inactivation of the voltage-gated calcium current in cardiac myocytes

The effects of changes in intracellular and extracellular free ionized [Mg2+] on inactivation of ICa and IBa in isolated ventricular myocytes of the frog were investigated using the whole-cell configuration of the patch-clamp technique. Intracellular [Mg2+] was varied by internal perfusion with solutions having different calculated free [Mg2+]. Increasing [Mg2+]i from 0.3 mM to 3.0 mM caused a 16% reduction in peak ICa amplitude and a 36% reduction in peak IBa amplitude, shifted the current-voltage relationship and the inactivation curve approximately 10 mV to the left, decreased relief from inactivation, and caused a dramatic increase in the rate of inactivation of IBa. The shifts in the current-voltage and inactivation curves were attributed to screening of internal surface charge by Mg2+. The increased rate of inactivation of IBa was due to an increase in both the steady-state level of inactivation as well as an increase in the rate of inactivation, as measured by two-pulse inactivation protocols. Increasing external [Mg2+] decreased IBa amplitude and shifted the current-voltage and inactivation curves to the right, but, in contrast to the effect of internal Mg2+, had little effect on the inactivation kinetics or the steady-state inactivation of IBa at potentials positive to 0 mV. These observations suggest that the Ca channel can be blocked quite rapidly by external Mg2+, whereas the block by [Mg2+]i is time and voltage dependent. We propose that inactivation of Ca channels can occur by both calcium-dependent and purely voltage-dependent mechanisms, and that a component of voltage-dependent inactivation can be modulated by changes in cytoplasmic Mg2+.

Enhanced vascular alpha-adrenergic neuroeffector system in diabetes: importance of calcium

Mesenteric arteries from streptozotocin (STZ)-diabetic rats developed greater contractile force in response to norepinephrine and related alpha-agonists than arteries from age-matched controls. Subsequent experiments attempted to define the mechanisms underlying these findings. Transmural nerve stimulation of mesenteric arteries from both groups of animals revealed a similar optimal frequency and voltage of stimulation; however, arteries from STZ-diabetic rats developed greater contractile force than controls. Second, determination of selective alpha-adrenergic antagonist affinities (pA2 values) revealed qualitatively similar postjunctional alpha 1-adrenoceptors in both groups of arteries. Third, disruption of the endothelium did not abolish the enhanced responsiveness of arteries from STZ-diabetic rats. In contrast, the increased vascular responsiveness in STZ-diabetes was associated with a greater dependency on extracellular calcium, with no change in the response to alpha-agonist-induced release of calcium from cellular stores. Thus the enhanced responsiveness of mesenteric arteries from STZ-diabetic rats to alpha-adrenergic agonists cannot be attributed to neuronal deterioration, altered postjunctional alpha-adrenoceptor subtypes, endothelium degeneration, or enhanced release of intracellular calcium but is associated with a greater dependency on extracellular calcium.

Service- and facility-sharing

The Veterans Administration and the United States Air Force hospitals in Albuquerque recently established a service- and facility-sharing arrangement. In this article, the authors share lessons learned from planning and executing the arrangement-lessons that any organization considering a large-scale joint venture will want to keep in mind.

Physicians and the organizational evolution of medicine

Within medicine there is growing uneasiness and debate about changes in medical care delivery. Much of this concern centers on the evolution of organizations and the role of physicians. The emergence of multi-institutional organizations, the rise of investor-owned health care corporations, and the expansion of group medical practice illustrate the increasing organizational influence in medicine. Added to these trends are new financial incentives confronting both physicians and organizations so that the environment increasingly favors conflict. This article reviews the primary strategies for resolving physician-organization conflicts, including cooperation between physicians and organizations, having physician representatives in governance and management, restructuring incentives, and restructuring organizations. Although these strategies have various merits, we suggest that every physician has a personal responsibility to become more involved in organization and management issues. Physicians can play an important role in guiding the evolution of medicine.

Decreased production of suppressive-B-cell factor by synovial membrane B-lymphocytes in rheumatoid arthritis

Suppressive-B-cell factor (SBF) is an autoregulatory B-cell lymphokine produced by heat-aggregated-IgG stimulated B-lymphocytes which suppresses polyclonal immunoglobulin production. SBF production by rheumatoid arthritis (RA) patients' peripheral blood B-lymphocytes inversely correlates with disease activity and in vitro rheumatoid factor production. To further define the role of SBF in the pathogenesis of RA, the present study measured SBF production by surgically-obtained synovial membrane mononuclear leukocytes. SBF production by RA synovial leukocytes was similar to the levels previously described for RA peripheral blood leukocytes. Both RA and osteoarthritis (OA) synovial leukocytes produced significantly less SBF than leukocytes obtained from otherwise healthy patients with plica. OA patients produced less SBF than RA patients, but the difference was not statistically significant. SBF values for combined RA patients and controls with OA or plica correlated with the degree of histological plasma cell infiltration providing further evidence for SBF production by cells of the B-lymphocyte lineage. Depletion studies also demonstrated that synovial SBF was produced by B-lymphocytes. The molecular weight (34,000) of synovial SBF was similar to the molecular weight of peripheral blood SBF. Decreased SBF production by RA synovial B-lymphocytes is a functional abnormality in RA which may contribute to the perpetuation of synovial rheumatoid factor production and chronic synovial inflammation.

Managing organizational mergers

Reimbursement, competition, and other significant trends in the health field have stimulated an increase in mergers among health care organizations. Mergers inevitably produce significant ramifications for clinicians. Nurses have discovered that mergers produce a greater need for efficient patient care, but not necessarily the mechanism or guidance for achieving this goal. Nursing administrators are responsible for minimizing the negative impact of a merger on nurses while simultaneously promoting merger goals. Despite this increase in mergers and the subsequent challenge to clinicians, little information is available about how to manage mergers. This article reviews the impact of the merger between the Veterans Administration Medical Center and the Kirtland Air Force Base Hospital in Albuquerque, New Mexico. A nursing perspective is used to understand what problems arise and how nursing administrators can effectively manage these problems.

Effects of intracellular free magnesium on calcium current in isolated cardiac myocytes

Magnesium ions play a fundamental role in cellular function, but the effects of changes in the concentration of intracellular ionized magnesium ([Mg2+]i) on cell physiology have only recently received experimental attention. Increasing [Mg2+]i from 0.3 to 3.0 mM in cardiac cells by internal perfusion has only small effects on the basal voltage-gated calcium current (ICa) or on ICa elevated by dihydropyridine calcium channel agonists. In contrast, ICa elevated by cyclic adenosine monophosphate (cAMP)-dependent phosphorylation decreases by more than 50 percent. The effect of [Mg2+]i is not due to changes in the concentration of cAMP or in the velocity of phosphorylation but rather appears to be a direct effect on the phosphorylated channel or on channel dephosphorylation.

Synovial fluid lipid abnormalities in various disease states: review and classification

Although lipids are not usually present in large quantities in normal synovial fluids or in the usual synovial fluid seen in most rheumatologic conditions, their presence in synovial fluid may have diagnostic importance. As summarized in Table 2, analysis of synovial fluids for lipid constituents is relatively simple. On standing or after centrifugation, significant amounts of lipids may layer out and be visible as a supernatant. On microscopic examination, lipid droplets are usually easily seen and should be stainable with appropriate dyes (oil red O or Sudan III or IV), or may occasionally be visualized as intracellular or extracellular inclusions by polarized microscopy. Small (0.5 to 2.0 microns) intracellular inclusions containing triglycerides may be seen in neutrophils from most synovial fluids, and are of no diagnostic importance. Cholesterol crystals may be readily recognized microscopically by their characteristic flat, plate-like appearance and notched corners Synovial fluid may also be analyzed for cholesterol and triglycerides in routine clinical laboratories, and free fatty acids and lipolytic enzymes in special lipid laboratories. The presence of massive increases in cholesterol associated with microscopically visible cholesterol crystals is usually associated with chronic RA, occasionally in the setting of super-imposed bacterial infection. The presence of gross or microscopic lipid droplets is usually associated with trauma and hemorrhagic effusions. When present in this setting, the clinician should entertain a high suspicion for a significant intraarticular injury, such as fracture, meniscal tear, or severe ligamentous injury. In addition, however, several instances of non-traumatic inflammatory effusions associated with intracellular and extracellular lipid droplets have been reported.(ABSTRACT TRUNCATED AT 250 WORDS)

Follow-up chest radiographs in Vietnam veterans: are they useful?

Agent Orange exposure and its long-term health consequences on Vietnam veterans have been widely discussed in the past few years. Myriad physical and mental disabilities have been studied with regard to exposure to various herbicides. The number of persons potentially exposed is large, since 2.4-2.8 million U.S. military personnel served in Vietnam. A case-control study was undertaken to determine if persons who served in the U.S. military in Vietnam have either cardiovascular or pulmonary effects that can be demonstrated on long-term follow-up chest radiographs. Information regarding military service in Vietnam was obtained from interviews and, in some cases, review of military records. Vietnam veterans did not have an increased prevalence of abnormalities on follow-up chest radiographs. A subset of Vietnam veterans who had greater estimated opportunities for Agent Orange exposure also did not appear to be at greater risk than the control population.

Resection of the distal ulna with and without implant arthroplasty in rheumatoid arthritis

Eighteen patients who had rheumatoid wrist surgery with resection of the distal ulna, with or without implant arthroplasty, were reviewed at an average follow-up of 32 months. Subjective and objective clinical findings did not confirm any advantage to the routine use of implant arthroplasty of the distal ulna. Moreover, a bone resorptive process, which was identified in all implant cases, may cause clinical symptoms and prosthetic instability and may warrant reoperation. The histologic findings supported a granulomatous reaction to a foreign body as a cause of the resorptive process. Histologic examination showed a synovial type of membrane and the feasibility was raised of an enzymatic cause.

Successful symptomatic treatment of melorheostosis with nifedipine

Melorheostosis is an unusual sclerotic dysplasia of bone. We describe a patient with melorheostosis who showed improvement in pain and vasomotor function after treatment with nifedipine. Peripheral vascular disturbances may be responsible for the pain associated with this disorder and vascular abnormalities could possibly be related to the pathogenesis of this disease.

Alpha 1- and alpha 2-adrenoceptor agonist-induced contraction in rat mesenteric artery upon removal of endothelium

Contractile response to norepinephrine, methoxamine and clonidine were determined in rat mesenteric arteries with and without an intact endothelium. Removal of the endothelial cell layer markedly enhanced the maximum contractile effect of norepinephrine (2.8 fold), methoxamine (4.0 fold) and clonidine (13.0 fold). Furthermore, there was a significant decrease in the EC50 values for these agonists. These findings indicate that both alpha 1- and alpha 2-adrenoceptor agonists can induce contraction of mesenteric arteries which is modulated by the endothelial cell layer.

Active site mechanics of liver microsomal cytochrome P-450

For a set of 10 para-substituted toluene derivatives, three enzymatic constants were determined describing their interaction with purified rabbit liver microsomal P-450LM2. The three constants were the catalytic rate constant (Kcat) for hydroxylation, the apparent dissociation constant (Kd) for the enzyme-substrate complex, and the interaction energy (delta Gint) between the substrate-binding and spin-state equilibria. The para-substituents of the toluene substrates were: hydrogen, fluoro, bromo, chloro, iodo, nitro, methyl, cyano, isopropyl, and t-butyl. Linear free energy correlations were sought between the enzymatic constants and several physical constants of the individual substrate molecules. These correlations would be useful both for empirical prediction purposes and for insight into active site chemistry and mechanics. Catalytic rates were correlated by a linear combination of the Hansch pi hydrophobic constant and the Hammett sigma value. A deuterium isotope effect (DV) of 2.6 for d8-toluene compared to d0-toluene confirmed that hydrogen abstraction was partially rate-limiting with this series of substrates. Apparent dissociation constants were predicted by a linear combination of the molar volume and pi, while the spin-state interaction energies were best predicted by a linear combination of the Hansch pi hydrophobic constant and the reciprocal of the dielectric constant.

Decreased suppressive B cell factor (SBF) in rheumatoid arthritis: evidence for a defect in B cell autoregulation

Rheumatoid arthritis (RA) is a disorder characterized by defective immunoregulation. Hypergammaglobulinemia, circulating immune complexes (IC), and autoantibodies such as rheumatoid factor (RF) are common serum abnormalities. To assess IC-mediated feedback suppression in RA, we evaluated the ability of a suppressive B cell factor (SBF) generated by culturing heat-aggregated IgG (HAIgG) with peripheral blood mononuclear leukocytes (PBL) from patients with RA and normal controls to suppress the pokeweed mitogen (PWM)-induced RF plaque-forming cell (PFC) response of normal PBL. RA patients generated less SBF than age-matched controls. Background suppression (supernatants obtained from PBL cultured without HAIgG) was similar in the RA patients and age-matched controls. To determine the effects of nonsteroidal antiinflammatory drug (NSAID) therapy on suppression, RA patients and age-matched controls were studied before and after NSAID therapy. NSAID therapy significantly reduced background suppression in RA patients who were not on immunosuppressive drugs and in age-matched controls, but there was no effect on SBF in RA patients or controls. There was a small increase in background suppression when NSAID were administered to RA patients on immunosuppressives, suggesting an ameliorative effect of NSAID in this group of patients, which tended to increase their level of suppression when compared with RA patients only on NSAID. Spontaneous RF-PFC were measured in normal controls and RA patients and were compared with suppressor activity. There were increased numbers of spontaneous RF-PFC in RA patients. Total suppressor activity was greatest in young adult controls, who also had the least RF-PFC. The percentage of suppression correlated inversely with the number of RF-PFC in patients and controls. Additionally, disease activity in RA as measured by total joint count and erythrocyte sedimentation rate (ESR) was shown to correlate inversely with total suppressor activity. We conclude that the PBL from patients with RA produce decreased SBF after HAIgG stimulation and that loss of suppression is also associated with aging. This study suggests a defect in IC-stimulated B cell suppressor activity in RA leading to decreased ability to suppress antibody and further IC formation. The combination of increased RF-PFC and decreased SBF suggests that there is defective B cell autoregulation in RA, which may be involved in the pathogenesis and chronicity of this disease.

Suppression of a pokeweed mitogen-stimulated plaque-forming cell response by a human B lymphocyte-derived aggregated IgG-stimulated suppressor factor: suppressive B cell factor (SBF)

The mechanisms whereby formed immune complexes (IC) or immunoglobulin aggregates can suppress further antibody production were explored by culturing normal human peripheral blood mononuclear leukocytes (PBL) with heat-aggregated IgG (HAIgG) and collecting the culture supernatants at 24 hr. These supernatants were found to suppress a pokeweed mitogen (PWM)-induced rheumatoid factor plaque-forming cell (RF-PFC) response in normal individuals. PWM-induced anti-trinitrophenylated sheep red blood cell (TNP-SRBC) PFC were also inhibited by suppressor supernatants from HAIgG-stimulated PBL, suggesting that the polyclonal PFC response was inhibited by a suppressor factor. The suppressor factor inhibited PWM stimulated RF-PFC throughout the culture period, but suppression was maximal at the peak of the RF-PFC response. Suppressor factor was only effective at the initiation of cultures, suggesting that it inhibited early events in the PWM-stimulated RF-PFC response. Molecular weight determination of the suppressor factor by differential membrane fractionation suggested a m.w. range of 30,000 to 50,000, and chromatography on Sephadex G-100 showed a peak activity at an approximate m.w. of 32,000. Studies suggested the factor was not an interferon. Depletion of T lymphocytes by E rosetting and macrophages/monocytes by G-10 adherence did not affect the generation of suppressor factor. Depletion of T lymphocytes (OKT4, OKT8) and NK cells (Leu-11b) by antibody-dependent, complement-mediated cytotoxicity also did not affect the generation of suppressor factor. Depletion of B lymphocytes with OKB7 resulted in the generation of significantly less suppressor factor. Suppression produced by unstimulated purified B lymphocytes was approximately one-half that seen when B lymphocytes were stimulated with HAIgG. Differential membrane fractionation studies suggested that only HAIgG-stimulated B cell cultures contained peak activity in the 30,000 to 50,000 m.w. fraction. Supernatants from unstimulated purified T cells also generated suppression, which was approximately one-half of that seen with HAIgG-stimulated B cells, but no increase in suppressor activity was seen in T cell cultures after incubation with HAIgG. These studies demonstrate that HAIgG is capable of stimulating B lymphocytes to produce a lymphokine, suppressive B cell factor (SBF), which is capable of suppressing a polyclonal PFC response. SBF may be important in feedback control of human immunoglobulin production.

Decreased suppressive B cell factor (SBF) in rheumatoid arthritis: evidence for a defect in B cell autoregulation

Rheumatoid arthritis (RA) is a disorder characterized by defective immunoregulation. Hypergammaglobulinemia, circulating immune complexes (IC), and autoantibodies such as rheumatoid factor (RF) are common serum abnormalities. To assess IC-mediated feedback suppression in RA, we evaluated the ability of a suppressive B cell factor (SBF) generated by culturing heat-aggregated IgG (HAIgG) with peripheral blood mononuclear leukocytes (PBL) from patients with RA and normal controls to suppress the pokeweed mitogen (PWM)-induced RF plaque-forming cell (PFC) response of normal PBL. RA patients generated less SBF than age-matched controls. Background suppression (supernatants obtained from PBL cultured without HAIgG) was similar in the RA patients and age-matched controls. To determine the effects of nonsteroidal antiinflammatory drug (NSAID) therapy on suppression, RA patients and age-matched controls were studied before and after NSAID therapy. NSAID therapy significantly reduced background suppression in RA patients who were not on immunosuppressive drugs and in age-matched controls, but there was no effect on SBF in RA patients or controls. There was a small increase in background suppression when NSAID were administered to RA patients on immunosuppressives, suggesting an ameliorative effect of NSAID in this group of patients, which tended to increase their level of suppression when compared with RA patients only on NSAID. Spontaneous RF-PFC were measured in normal controls and RA patients and were compared with suppressor activity. There were increased numbers of spontaneous RF-PFC in RA patients. Total suppressor activity was greatest in young adult controls, who also had the least RF-PFC. The percentage of suppression correlated inversely with the number of RF-PFC in patients and controls. Additionally, disease activity in RA as measured by total joint count and erythrocyte sedimentation rate (ESR) was shown to correlate inversely with total suppressor activity. We conclude that the PBL from patients with RA produce decreased SBF after HAIgG stimulation and that loss of suppression is also associated with aging. This study suggests a defect in IC-stimulated B cell suppressor activity in RA leading to decreased ability to suppress antibody and further IC formation. The combination of increased RF-PFC and decreased SBF suggests that there is defective B cell autoregulation in RA, which may be involved in the pathogenesis and chronicity of this disease.

Suppression of a pokeweed mitogen-stimulated plaque-forming cell response by a human B lymphocyte-derived aggregated IgG-stimulated suppressor factor: suppressive B cell factor (SBF)

The mechanisms whereby formed immune complexes (IC) or immunoglobulin aggregates can suppress further antibody production were explored by culturing normal human peripheral blood mononuclear leukocytes (PBL) with heat-aggregated IgG (HAIgG) and collecting the culture supernatants at 24 hr. These supernatants were found to suppress a pokeweed mitogen (PWM)-induced rheumatoid factor plaque-forming cell (RF-PFC) response in normal individuals. PWM-induced anti-trinitrophenylated sheep red blood cell (TNP-SRBC) PFC were also inhibited by suppressor supernatants from HAIgG-stimulated PBL, suggesting that the polyclonal PFC response was inhibited by a suppressor factor. The suppressor factor inhibited PWM stimulated RF-PFC throughout the culture period, but suppression was maximal at the peak of the RF-PFC response. Suppressor factor was only effective at the initiation of cultures, suggesting that it inhibited early events in the PWM-stimulated RF-PFC response. Molecular weight determination of the suppressor factor by differential membrane fractionation suggested a m.w. range of 30,000 to 50,000, and chromatography on Sephadex G-100 showed a peak activity at an approximate m.w. of 32,000. Studies suggested the factor was not an interferon. Depletion of T lymphocytes by E rosetting and macrophages/monocytes by G-10 adherence did not affect the generation of suppressor factor. Depletion of T lymphocytes (OKT4, OKT8) and NK cells (Leu-11b) by antibody-dependent, complement-mediated cytotoxicity also did not affect the generation of suppressor factor. Depletion of B lymphocytes with OKB7 resulted in the generation of significantly less suppressor factor. Suppression produced by unstimulated purified B lymphocytes was approximately one-half that seen when B lymphocytes were stimulated with HAIgG. Differential membrane fractionation studies suggested that only HAIgG-stimulated B cell cultures contained peak activity in the 30,000 to 50,000 m.w. fraction. Supernatants from unstimulated purified T cells also generated suppression, which was approximately one-half of that seen with HAIgG-stimulated B cells, but no increase in suppressor activity was seen in T cell cultures after incubation with HAIgG. These studies demonstrate that HAIgG is capable of stimulating B lymphocytes to produce a lymphokine, suppressive B cell factor (SBF), which is capable of suppressing a polyclonal PFC response. SBF may be important in feedback control of human immunoglobulin production.

Enhanced relaxation response of canine coronary artery to isoproterenol and salbutamol after removal of endothelial cells

The importance of the endothelium for isoproterenol- and salbutamol-induced relaxation of canine coronary artery was examined. The relaxation effect of isoproterenol and salbutamol was significantly enhanced (P less than 0.05) upon removal of the coronary artery endothelium. In contrast, the relaxation effect of acetylcholine was completely abolished. These results indicate that canine coronary endothelium modulates beta-adrenoceptor-mediated relaxation, and that the role of the endothelium in agonist-induced relaxation of vascular smooth muscle appears to be heterogeneous.

Supersensitivity and endothelium dependency of histamine-induced relaxation in mesenteric arteries isolated from diabetic rats

Diabetes mellitus is known to produce alterations in vascular reactivity. In the present study we have examined the effects of short-term diabetes on histamine-induced relaxation of isolated mesenteric arteries, and the role of the endothelial cell layer in this response. Removal of the endothelium completely abolished the histamine relaxation effect in both diabetic and age-matched control rats. In contrast, vessels isolated from streptozotocin-diabetic rats were supersensitive to histamine, and this relaxation was mediated only through the H1-receptors. The present findings suggest that histamine-induced relaxation of rat mesenteric arteries is dependent upon endothelial cell processes which are enhanced in arteries from STZ-diabetic rats.

Chemical characterization of protein-protein interactions between cytochrome P-450 and cytochrome b5

Native cytochrome b5 interacts with either RLM5 or LM2 to form tight equimolar complexes (Kd = 250 and 540 nM, respectively) in which the content of high spin cytochrome P-450 was substantially increased. Cytochrome b5 caused 3- and 7-fold increases in the binding affinities of RLM5 and LM2 for benzphetamine, respectively, and benzphetamine decreased the apparent Kd for cytochrome b5 binding. Upon formation of the ternary complex between cytochromes P-450, b5, and benzphetamine the percentage of cytochrome P-450 in the high spin state was increased from 28 to 74 (RLM5) and from 9 to 85 (LM2). Cytochrome b5 caused 13- and 7-fold increases in the rate of RLM5- and LM2-dependent p-nitroanisole demethylation, respectively. Amino-modified (ethyl acetimidate or acetic anhydride) cytochrome b5 produced results similar to those obtained above with native cytochrome b5. In contrast, modification of as few as 5 mol of carboxyl groups/mol of amidinated cytochrome b5 resulted in both a substantial loss of the spectrally observed interactions with either cytochrome P-450 LM2 or cytochrome P-450 RLM5, and in a loss of the cytochrome b5-mediated stimulation of p-nitroanisole demethylation catalyzed by either monooxygenase. In further studies, native and fully acetylated cytochromes b5 reoxidized carbonmonoxy ferrous LM2 at least 20 times faster than amidinated, carboxyl-modified cytochrome b5 derivatives. In contrast, amidination, or acetylation of amino groups, or amidination of amino groups plus methylamidination of the carboxyl groups did not appreciably slow the rate of reduction of the cytochrome b5 by NADPH-cytochrome P-450 reductase. Collectively, the results provide strong evidence for an essential role of cytochrome b5 carboxyl groups in functional interactions with RLM5 and LM2.

Enhancement of alpha-1 and alpha-2 adrenergic agonist-induced vasoconstriction by removal of endothelium in rat aorta

It is well known that the vascular endothelial cell layer plays an essential role in the vasodilatory response of several agents. In this study we have investigated the possibility that the endothelium may also modulate alpha adrenergic agonist-induced vasoconstriction. The responses of rat aortae to selective alpha-1 and alpha-2 adrenergic agonists were studied. Removal of the endothelium did not significantly alter the maximum contractile response to norepinephrine. However, the maximum responses to selective alpha-1 agonists (phenylephrine and methoxamine) were increased 2-fold. The vasoconstrictor effects of both clonidine and B-HT920 (selective alpha-2 agonists) were enhanced 5- to 7-fold after removal of the endothelial cell layer. The sensitivity of the tissue, as reflected by the EC50 value, to each alpha adrenergic agonist was enhanced in the absence of endothelium. An explanation for the present results is that alpha-1 and alpha-2 adrenergic agonists activate adrenoceptors in the endothelial cells and thereby may promote the release of a relaxing factor to inhibit vascular smooth muscle contraction. Removal of the endothelium would abolish release of this putative inhibitory substance and adrenergic agonist would activate only adrenoceptors in the muscle to cause vasoconstriction. On the other hand, endothelial cells may function as an uptake site for the various adrenergic agonists. Ablation of this uptake process could conceivably result in a greater effective concentration of the agonist in the receptor area and thus promote a stronger vasoconstrictor effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of pulmonary angiotensin-converting enzyme and 5'-nucleotidase in vivo

Angiotensin-converting enzyme and 5'-nucleotidase line the luminal surface of pulmonary microvascular endothelium and participate in the synthesis and/or degradation of potent vasoactive substances. We applied Michaelis-Menten kinetics in simultaneous estimations of apparent constants Km and Amax (product of Vmax and microvascular plasma volume) of these two enzymes for the substrates 3H-labeled benzoyl-Phe-Ala-Pro and 14C-labeled 5'-AMP, respectively, in vivo. Values of angiotensin-converting enzyme for benzoyl-Phe-Ala-Pro (Km = 10-11 microM; Amax = 12-13 mumol X min-1) were somewhat higher than published estimates in vitro and changed predictably in response to the known enzyme inhibitor captopril. Kinetic values of 5'-nucleotidase for 5'-AMP (Km = 3-4 microM; Amax = 3-4 mumol/min) were substantially lower than those reported in vitro but also responded predictably to the competitive inhibitor of 5'-nucleotidase, adenosine 5'-[alpha, beta-methylene]diphosphate. These data offer in vivo estimates of enzyme kinetics that are useful in revealing enzyme behavior in their normal physiological environment and provide means of evaluating the action of pharmacological, physiological, and pathological modulators of enzyme activity, in vivo.

Ordering decision and clinic cost variation among resident physicians

Physicians vary considerably in the services they order for their patients. We examined ordering variation among 47 resident physicians during 4,991 continuity clinic visits with patients who had specific, chronic medical problems. We ranked the physicians by their average charge per visit and grouped them into three equal categories. High-charge physicians averaged $164 per visit, medium-charge $124 and low-charge $97. In comparing the frequencies with which physicians in each group ordered a wide array of specific laboratory tests, x-ray studies, medications and miscellaneous items, we found that ordering variation among the physician groups was not confined to certain decisions or categories of services. High-charge physicians ordered a little more of nearly every item or service. Although the magnitude of ordering variation for each item was small, the sum over many items was great, suggesting that cost-containment efforts may have to focus on the "little ticket" decision-making style of expensive physicians.

Effect of aminoglycoside-use restrictions on drug cost

The effect on drug costs of restricting aminoglycoside use in a teaching hospital is described. In October 1980, the pharmacy and therapeutics committee deleted tobramycin from the formulary because of its high cost and relative lack of therapeutic advantages compared with gentamicin. Amikacin use was restricted. Concurrently, physicians were instructed in the proper use and dosage of gentamicin via lectures and dosing nomograms provided by the clinical pharmacist. Chart reviews of patients receiving gentamicin showed that the incidence of nephrotoxicity (defined by an increase in serum creatinine of 0.5 mg/dl) was 0%, 4.5%, and 6.5% in fiscal years 1981, 1982, and 1983, respectively. Based on the percentage of total aminoglycoside use represented by tobramycin, gentamicin, and amikacin during the year before implementation of the policy, projected cost savings for three years was more than $42,000. Expensive and improper aminoglycoside use should be a prime target for reduced spending as budgetary constraints in hospitals increase.

Transient vascular compromise of the lunate after fracture-dislocation or dislocation of the carpus

Although classic avascular necrosis of the lunate is rare after fracture-dislocation or dislocation of the carpus, these severe carpal injuries can compromise the vascular supply of the lunate. The lunate thus develops a relative increase in radiodensity. Our finding of an incidence of 12.5%--three of 24 cases--suggests a relatively frequent occurrence. The clinical course was transient with resolution of abnormal radiodensity and subjective findings. Moreover, none of the three cases progressed to classic avascular necrosis of the lunate, Kienböck's disease. The clinician should not confuse this transient vascular compromise of the lunate with Kienböck's disease, but should be aware of the entity and its benign, self-limited course and should treat it expectantly.

Evaluation of the CASPAR alcohol education curriculum

The CASPAR education-prevention program was initiated when experimental results indicated that a 5-hr alcohol education curriculum at a Catholic high school was able to reduce frequent intoxication among teenagers. Attempts to institutionalize such a program in the public schools shows that (1) alcohol education can generate widespread community and school support; (2) workshops can successfully train teachers to adopt a decision-making approach, though close supervision is needed to ensure that this approach is adhered to in classroom teaching; (3) the CASPAR model of alcohol education produces classroom situations conducive to many children feeling free to express alcohol-related concerns; (4) trained teachers can serve as intermediaries between students with alcohol-related concerns and community resources, in particular those resources that are designed to help children from families with alcoholism; (5) the CASPAR curriculum, implemented by trained teachers, produces statistically significant knowledge and attitude gains, whereas alternate programs such as a special-events approach produce smaller knowledge gains and little attitude change; and (6) to a considerable extent, knowledge and attitude gains persist over time, although retention is greater on knowledge items and among older students. The results suggest that there may be a behavioral impact of instruction in the form of reduced alcohol misuse among teenagers, although if there is, it requires intensive and repeated exposure and can be demonstrated in these data only among younger students while they remain in junior high school. Although such results may be viewed as less supportive than the original experiment with which this work began, they do suggest that alcohol education remains an effective prevention strategy.

Regioselectivity in the cytochromes P-450: control by protein constraints and by chemical reactivities

Three alicyclic compounds (D-camphor, adamantanone, adamantane) were found to be hydroxylated by the cytochrome P-450 isoenzymes P-450cam and P-450LM2. With P-450cam as the catalyst only one product was formed from each of the substrates: 5-exohydroxycamphor, 5-hydroxyadamantanone, and 1-adamantanol. With P-450LM2 as the catalyst, two or more isomeric products were formed from each substrate: 3-endo-, 5-exo-, and 5-endo-hydroxycamphor; 4-anti- and 5-hydroxyadamantanone; and 1- and 2- adamantanol. The products from P-450cam hydroxylations were found to be isosteric with one another, suggesting that each of them was attacked at a topologically congruent position within a rigid enzyme-substrate complex. The distribution of products from P-450LM2 hydroxylations, on the other hand, were similar to the distributions expected during solution-phase hydroxylations. Thus, it would appear that the complex which P-450LM2 forms with its substrate allows considerable movement of the substrate molecule, such that most of the hydrogens in the substrate are exposed to the enzymatic hydrogen abstractor. Under these conditions, the distribution of products more nearly reflects the rank order of chemical reactivities of the various hydroxylatable positions, with only a moderate protein-based steric constraint being expressed. These suggestions were also evident in the tightness of binding of the substrates to the two enzymes and in the magnitude of coupling between the substrate binding and the spin-state equilibria. Thus, the product from P-450cam-catalyzed hydroxylation may be predicted by a consideration of the relation of the topology of the prospective substrate to that of D-camphor. The products from P-450LM2-catalyzed hydroxylations, on the other hand, may be approximately predicted from the chemical reactivities of the various abstractable hydrogens in the prospective substrate.

2,3-dihydro-4H-1-benzopyran-4-one O-carbamoyloximes, a series of gastric antisecretory agents

A series of 2,3-dihydro-4H-1-benzopyran-4-one O-carbamoyloximes were synthesized and evaluated for gastric antisecretory activity in a pylorus-ligated rat model. Various substituents in the 6-position did not afford any compounds more active than I.

Competing modes of peroxyacid flux through cytochrome P-450

In the presence of peroxyphenylacetic acid and a hydroxylatable substrate, cytochrome P-450LM2 catalyzes two reactions which proceed concurrently, decarboxylation of the peroxyacid and hydroxylation of substrate. While the first process is definitely the result of homolytic cleavage of the peroxide O--O bond, the second may involve a different mechanistic pathway. We have undertaken to determine the relationship between these two processes through a kinetic analysis of the system. Seven different mechanistic schemes are advanced to account for the two processes. The two reactions were found to have different apparent Michaelis constants for peroxyacid and different inhibition constants for cyanide. Since the ratio of the two products is saturable at high substrate concentrations, the decarboxylation reaction can proceed from both substrate-bound and substrate-free enzyme. By appropriate manipulation of the rate equations it is possible to derive expressions for the ratio of hydrogen abstraction rate constants for a series of p-substituted toluene substrates compared to toluene. The nature of the correlation of these expressions with delta in a Hammett plot allowed some of the schemes to be eliminated. After consideration of all the data, we concluded that the processes of decarboxylation and hydroxylation occur in separate pathways and do not involve any common intermediate beyond the ferric resting state of the enzyme.

Functional differences between peroxidase compound I and the cytochrome P-450 reactive oxygen intermediate

A series of seven hemeproteins, cytochromes P-450LM2, P-450LM4, and P-420LM2, horseradish peroxidase, chloroperoxidase, catalase, and metmyoglobin, as well as hemin were tested for their ability to catalyze a set of five oxidative reactions. These reactions were a typical peroxidative reaction (oxidation of pyrogallol to purpurogallin) and three characteristic P-450 reactions (aliphatic hydroxylation, aromatic hydroxylation, and olefinic epoxidation). In addition, the ability to decarboxylate a peroxyacid was measured. All hemeproteins were able to carry out peroxidation, but three (horseradish peroxidase, chloroperoxidase, and catalase) were much better catalysts than the others. Only the P-450 enzymes were competent catalysts for the hydroxylation and epoxidation reactions. Furthermore, the decarboxylation reaction was strictly limited to the P-450 enzymes, establishing it as a new, unique P-450 activity. Since the decarboxylation of peroxyacids is diagnostic of peroxide homolysis, these results indicate a fundamentally different manner of processing of peroxides by cytochrome P-450 than by the peroxidases. Thus, the possibility of close similarity of reactive oxygen intermediates in the two series is called into question.

Comparison of family medicine and internal medicine: charges for continuing ambulatory care

The authors compared charges for ambulatory and continuing patient care prescribed by residents in internal medicine and family medicine. An analysis of covariance showed that the charges per encounter in internal medicine were $38.83 greater than charges in family medicine after accounting for differences such as patient age, diagnosis, and severity of condition. However, family practitioners scheduled patient encounters more frequently. The median number of days between encounters was 30 for family medicine and 60 for internal medicine. The duration of medical care for each patient (up to 18 months was possible) and the summation of encounter charges over that duration of medical care were evaluated. Because only two out of eight duration-of-medical-care categories were significantly less in family medicine, the differences in charges between the specialties essentially disappeared. Comparative studies which consider only charges per encounter potentially have a large bias.