Isoniazid urine spectrophotometry for prediction of serum pharmacokinetics in adults with TB

BACKGROUND

Isoniazid (INH) is an important drug in many TB regimens, and unfavorable treatment outcomes can be caused by suboptimal pharmacokinetics. Dose adjustment can be personalized by measuring peak serum concentrations; however, the process involves cold-chain preservation and laboratory techniques such as liquid chromatography (LC)/mass spectrometry (MS), which are unavailable in many high-burden settings. Urine spectrophotometry could provide a low-cost alternative with simple sampling and quantification methods.

METHODS

We enrolled 56 adult patients on treatment for active TB. Serum was collected at 0, 1, 2, 4, 6, and 8 h for measurement of INH concentrations using validated LC-MS/MS methods. Urine was collected at 0-4, 4-8, and 8-24 h intervals, with INH concentrations measured using colorimetric methods.

RESULTS

The median peak serum concentration and total serum exposure over 24 h were 4.8 mg/L and 16.4 mg*hour/L, respectively. Area under the receiver operator characteristic curves for urine values predicting a subtherapeutic serum concentration (peak <3.0 mg/L) were as follows: 0-4 h interval (AUC 0.85, 95% CI 0.7-0.96), 0-8 h interval (AUC 0.85, 95% CI 0.71-0.96), and 0-24 h urine collection interval (AUC 0.84, 95% CI 0.68-0.96).

CONCLUSION

Urine spectrophotometry may improve feasibility of personalized dosing in high TB burden regions but requires further study of target attainment following dose adjustment based on a urine threshold.

622 Potential Application of Electrocardiographs (ECG) to Diagnose Breech Presentations of Fetuses

Breech presentation, i.e. the abnormal lie of a foetus longitudinally with the buttocks closest to the mother’s cervix, is a common issue affecting up to 5% of women during delivery resulting in poor outcomes such as traumatic labour, infection and increased neonatal mortality.

Currently, abdominal palpation is the screening method of choice for breech presentation; however, 15,000 breech presentations remain undiagnosed across England annually. While routine ultrasonography has been suggested, its cost-effectiveness and scalability remain concerning, especially in low/middle-income countries.

Various algorithms have been applied to maternal trans-abdominal ECGs to obtain foetal ECGs, but current applications only allow heart rates, congenital heart defects, hypoxia, and foetal distress to be identified. The use of ECG is proposed to determine foetal position as breech foetuses tend to display QRS complexes in a similar pattern to the maternal trace, whereas cephalic foetuses would demonstrate inverted QRS complexes.

ECGs are cost-effective, safe and do not require highly skilled technicians to operate, which makes it an ideal starting platform for the development of a device with high sensitivity and reasonable diagnostic speeds to identify breech foetuses. Future considerations include the use of artificial intelligence to increase diagnostic accuracy and development of a patient-facing mobile application.

Think ultrasound; could point of care ultrasound really change the management of critically ill patient?

Myxomas are the most common primary cardiac neoplasms. The prevalence of cardiac tumors at autopsy ranges from 0.001% to 0.3%. More than 50% of benign cardiac tumors are myxomas. Approximately 7% of these have genetic origin and arise as a component of a heritable disorder with some clinical manifestations. Over 72% of primary cardiac tumors are benign. In adults, the majority of benign lesions are myxomas. Its clinical manifestations are variable and nonspecific. Commonly observed symptoms and signs are dyspnea, orthopnea, paroxysmal nocturnal dyspnea, pulmonary edema, cough, hemoptysis, edema, and fatigue. Key words: POCUS; ARDS; Atrial myxoma; Pulmonary edema Abbreviations: ARDS: acute respiratory distress syndrome; CRP: C reactive protein; ABG: arterial blood gases; PEEP: positive end expiratory pressure; HFNC: high frequency nasal cannula; TTE: transthoracic echocardiography; P/F: ratio of partial pressure of oxygen to inspired oxygen fraction; CT: computed tomography; POCUS: point of care ultrasound Citation: Aisa T, Lal S, Thomas J, Singh V, Narayanan N. Think ultrasound; could point of care ultrasound really change the management of critically ill patient? Anaesth. pain intensive care 2021;25(1):105–108; DOI: 10.35975/apic.v25i1.1438 Received: 16 June 2020; Reviewed: 4 June 2020; Accepted: 21 June 2020

Efavirenz–eudragit E-100 nanoparticle-loaded aerosol foam for sustained release: in-vitro and ex-vivo evaluation

The control of HIV infection using antiretroviral agents, especially through targeted delivery, has attracted extensive attention in the last decade. Recently, the vaginal route of administration has become the one most recommended for HIV infections during pregnancy. Efavirenz is a non-nucleoside reverse transcriptase inhibitor anti-HIV drug and its prolonged half-life helps achieve long-term preexposure prophylaxis of HIV-1 infections; it is used as a first-line drug in the treatment using combination therapy. Nanotechnology has received attention as a major area of research into drug delivery in recent years. The aerosol foam formulation is packed under pressure and contains therapeutically active ingredients that are released as foam on the activation of an appropriate valve system. The objective of this study was to develop an aerosol foam formulation of efavirenz nanoparticles for vaginal drug delivery. The nanoparticles were prepared using the emulsion solvent evaporation method and converted into an aerosol foam formulation with the addition of 0.1 mass % of sodium lauryl sulphate as a foaming agent and pressurised with 1,1,1,2-tetrafluroethane. The nanoparticles containing the formulation and aerosol foam formulation were individually characterised by applying various tests such as particle size, zeta potential, pH, viscosity, drug content, entrapment efficiency, drug release studies and release kinetics. The compatibility of the materials was evaluated using FT-IR, polymorphic changes by TGA-DSC and also the morphological properties using SEM study. Foam density, bubble size and collapse time were evaluated in the aerosol-foam formulation; in addition, the drug content and release studies were compared with nanoparticle formulation. The results revealed that the nanoparticle-containing formulation and aerosol formulations were stable and the foam emerged as grade one with fine bubbles and became coarser over time.

Attenuation of conducted vasodilation in skeletal muscle arterioles during hyperhomocysteinemia

BACKGROUND

Vasomotor responses conducted from terminal arterioles to proximal vessels may contribute to match tissue demands and blood supply during skeletal muscle contraction. Conduction of vasodilatation (CVD) from distal resistance arterioles to the proximal arterioles and feeding arteries during metabolic demand is mediated by intercellular gap junctions in the vascular endothelium. The role of hyperhomocysteinemia (HHcy) in the musculoskeletal system during CVD is unclear. We hypothesize that during HHcy, there is impaired CVD due to decreased expression of endothelial-associated connexins and thus decreased tissue perfusion to the contracting skeletal muscles.

METHODS

CVD studies were performed in a gluteus maximus muscle preparation of wild-type (C57BL6/J) and CBS-/+ (HHcy) mice using intravital microscopy. Expression of connexins and myostatin protein (an antiskeletal muscle statin) was studied by Western blot and immunohistochemistry methods. Tissue perfusion to acetylcholine was assessed by the laser Doppler technique.

RESULTS

There was decreased CVD and tissue perfusion in response to acetylcholine in CBS-/+ mice compared to wild-type controls. There was decreased expression of connexins 37, 40 and 43 and increased expression of myostatin in CBS-/+ mice compared to wild-type controls.

CONCLUSION

Our findings suggest that CVD in skeletal muscle is decreased during HHcy due to decreased expression of gap junction connexins.

TIMP-2 mutant decreases MMP-2 activity and augments pressure overload induced LV dysfunction and heart failure

Pressure overload induces cardiac extracellular matrix (ECM) remodelling and results in heart failure. ECM remodelling by matrix metalloproteinases (MMPs) is primarily regulated by their target inhibitors, tissue inhibitor of matrix metalloproteinases (TIMPs). It is known that TIMP-2 is highly expressed in myocardium and is required for cell surface activation of pro-MMP-2. We and others have reported that imbalance between angiogenic growth factors and anti-angiogenic factors results in transition from compensatory cardiac hypertrophy to heart failure. We previously reported the pro-angiogenic role of MMP-2 in cardiac compensation, however, the specific role of TIMP-2 during pressure overload is yet unclear. We hypothesize that genetic ablation of TIMP-2 exacerbates the adverse cardiac matrix remodelling due to lack of pro-angiogenic MMP-2 and increase in anti-angiogenic factors during pressure overload stress and results in severe heart failure. To verify this, ascending aortic banding (AB) was created to mimic pressure overload, in wild type C57BL6/J and TIMP-2-/- (model of MMP-2 deficiency) mice. Left ventricular (LV) function assessed by echocardiography and pressure-volume loop studies showed severe LV dysfunction in TIMP-2-/- AB mice compared to controls. Expression of MMP-2, vascular endothelial growth factor (VEGF) was decreased and expression of MMP-9, anti-angiogenic factors endostatin and angiostatin was increased in TIMP-2-/- AB mice compared with wild type AB mice. Connexins (Cx) are the gap junction proteins that are widely present in the myocardium and play an important role in endothelial-myocyte coupling. Our results showed that expression of Cx 37 and 43 was decreased in TIMP-2-/- AB mice compared with corresponding wild type controls. These results suggest that genetic ablation of TIMP-2 decrease the expression of pro-angiogenic MMP-2, VEGF and increases anti-angiogenic factors that results in exacerbated abnormal ventricular remodelling leading to severe heart failure.

Supraoesophageal manifestations of gerd- A myth or reality?

Gastroesophageal reflux disease (GERD) is a disease that has come to limelight in the rreent past to account for various ear, nose and throat disorders. Fifty patients from my outpatient department, presenting with chronic dry paroxysmal cough, choking spells, globus sensation, voice change, burning throat syndrome, dysphagia were evaluated, with both invasive and non-invasive techniques like Fibreoptic Nasoendoscopy, Nuclear Scintigraphy with technetium, Barium swallow, sans pH monitoring which is an expensive and laborious method.We have shown evidence of GER with help of Nasoendoscopy, which revealed posterior laryngitis, erythema of arytenoids and interarytenoid oedema. This is corroborated with Scintigraphy done in Nuclear Medicine department, which is our gold standard for labelling the cases as GERD. Basing on the investigations, we have treated successfully fifty cases with medical treatment consisting of H2 Hockers, proton pump inhibitors and microlaryngeal surgery wherever necessary. In this article we are discussing the various symptoms, the fifty patients complained of, and how we are able to pinpoint the diagnosis and the modality we adopted with the facilities available, and also a brief review of literature.

Hyperhomocysteinemia decreases intestinal motility leading to constipation

Elevated levels of plasma homocysteine (Hcy) called hyperhomocysteinemia (HHcy) have been implicated in inflammation and remodeling in intestinal vasculature, and HHcy is also known to aggravate the pathogenesis of inflammatory bowel disease (IBD). Interestingly, colon is the pivotal site that regulates Hcy levels in the plasma. We hypothesize that HHcy decreases intestinal motility through matrix metalloproteinase-9 (MMP-9)-induced intestinal remodeling leading to constipation. To verify this hypothesis, we used C57BL/6J or wild-type (WT), cystathionine β-synthase (CBS(+/-)), MMP-9(-/-), and MMP-9(-/-) + Hcy mice. Intestinal motility was assessed by barium meal studies and daily feces output. Plasma Hcy levels were measured by HPLC. Expression of ICAM-1, inducible nitric oxide synthase, MMP-9, and tissue inhibitors of MMPs was studied by Western blot and immunohistochemistry. Reactive oxygen species (ROS) including super oxide were measured by the Invitrogen molecular probe method. Tissue nitric oxide levels were assessed by a commercially available kit. Plasma Hcy levels in the treated MMP-9 group mice were comparable to CBS(+/-) mice. Barium meal studies suggest that intestinal motility is significantly decreased in CBS(+/-) mice compared with other groups. Fecal output-to-body weight ratio was significantly reduced in CBS(+/-) mice compared with other groups. There was significant upregulation of MMP-9, iNOS, and ICAM-1 expression in the colon from CBS(+/-) mice compared with WT mice. Levels of ROS, superoxide, and inducible nitric oxide were elevated in the CBS(+/-) mice compared with other groups. Results suggest that HHcy decreases intestinal motility due to MMP-9-induced intestinal remodeling leading to constipation.

Should we stop doing blind transversus abdominis plane blocks?

BACKGROUND

Any landmark-based regional anaesthetic technique raises two important issues. The first is the accuracy of placement of the needle and thus the local anaesthetic in a 'blind' technique and the second is the potential for damage to adjacent structures. We designed a prospective, blinded study in an adult general surgical population to evaluate with ultrasound the placement of the needle tip and local anaesthetic during transversus abdominis plane (TAP) blocks using the landmark-based 'double-pop' technique.

METHODS

After induction of general anaesthesia, 36 adult patients had a TAP block performed bilaterally using the standard landmark-based technique. Ultrasonography was then used to record the actual needle position and local anaesthetic spread. The anaesthetist performing the block was blinded to the ultrasound images.

RESULTS

Thirty-six adult patients were included in the study, which was terminated early due to what was considered an unacceptably high level of peritoneal needle placements. The needle tip and local anaesthetic spread were in the correct plane in only 17 (23.6%) of the injections. In the remaining 55 (76.4%), the needle was in the subcutaneous tissue 1 (1.38%), external oblique muscle 1 (1.38%), plane between the external and internal oblique muscles 5 (6.94%), internal oblique muscle 26 (36.1%), transversus abdominis muscle 9 (12.5%), and peritoneum 13 (18%).

CONCLUSIONS

We conclude that the needle and local anaesthetic placement using the standard landmark-based approach to the TAP block is inaccurate, and the incidence of peritoneal placement is unacceptably high.

Antitumour activity of Prosopis cineraria (L.) Druce against Ehrlich ascites carcinoma-induced mice

The antitumour activity of the hydroalcoholic extract of the leaf (PCL) and stem bark (PCB) of Prosopis cineraria (L.) in Swiss albino mice was evaluated against an Ehrlich ascites carcinoma (EAC) tumour model. The activity was assessed using survival time, peritoneal cells, haematological studies, lipid peroxidation, antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, solid tumour mass and in vitro cytotoxicity. PCL and PCB were found to be potent and possessed significant cytotoxicity towards EAC tumour cells.

Simultaneous delivery of Nifedipine and Metoprolol tartarate using sandwiched osmotic pump tablet system

The sandwiched osmotic tablet system that could deliver Nifedipine and Metoprolol tartarate simultaneously for extended period of time was developed in order to reduce the problems associated with multidrug therapy of hypertension. This system composed of a middle push layer and attached drug layers of Nifedipine and Metoprolol. The advantage of the sandwiched osmotic tablet system over the commercialized push-pull osmotic tablet system is its simplicity of preparation, as the surface identification was avoided. Polyethylene oxide 600,000 and 8,000,000 g/mole were used as thickening agent of drug layer and the expandable hydrogel of push layer, respectively. It has been observed that amount of polyethylene oxide (PEO) and KCL of the drug and push layer had profound influence on Nifedipine and Metoprolol release. Further, the release of drugs was optimized by the size of the delivery orifice, level of plasticizer and membrane thickness. The optimal osmotic pump tablet was found to deliver both drugs at a rate of approximately zero order for up to 16 h independent of pH and agitational intensity, but dependent on the osmotic pressure of the release media. The formulations were found to be stable after 3 months of accelerated stability studies. Prediction of steady-state levels showed the plasma concentrations of Nifedipine and Metoprolol to be within the desired range. Further sandwiched system had a good sustained effect in comparison with the conventional product. Hence the prototype design of the system could be applied to other combinations of drugs used for cardiovascular diseases, diabetes, etc.

Carbopol-based gels for nasal delivery of progesterone

The purpose of this study was to investigate the nasal absorption of progesterone from carbopol-based nasal gels in rabbits. Progesterone nasal gels were prepared by dispersing carbopol 974 (1%, 1.5%, and 2%) in distilled water followed by addition of progesterone/progesterone-beta cyclodextrin complex dissolved in propylene glycol then neutralization. The potential use of beta cyclodextrin (CD) as nasal absorption enhancer by simple addition, as a physical mixture and as a complex with progesterone was investigated. The absolute bioavailability of progesterone from nasal gels in rabbits was studied by estimating the serum progesterone level by competitive solid-phase enzyme immunoassay in comparison to intravenous injection. The carbopol gel formulations produced a significant increase in bioavailability. CD complex promotes the nasal absorption of progesterone from carbopol gels as compared with gels where the CD is added by simple addition and gels which do not contain CD. This method of addition of CD as an inclusion complex in the gels could be considered as a preferred platform in nasal drug administration.

Mechanistic basis of differences in Ca2+ -handling properties of sarcoplasmic reticulum in right and left ventricles of normal rat myocardium

This study investigated Ca2+ -cycling properties of sarcoplasmic reticulum (SR) in right ventricle (RV) and left ventricle (LV) of normal rat myocardium. Intracellular Ca2+ transients and contractile function were monitored in freshly isolated myocytes from RV and LV. SR in RV displayed nearly fourfold lower rates of ATP-energized Ca2+ uptake in vitro than SR of LV. The Ca2+ concentration required for half-maximal activation of Ca2+ transport was nearly twofold higher in SR of RV. The lower Ca2+ -sequestering activity of SR in RV was accompanied by a matching decrement in Ca2+ -induced phosphoenzyme formation during the catalytic cycle of the Ca2+ -pumping ATPase (SERCA2). Western immunoblot analysis showed that protein levels of Ca2+ -ATPase and its inhibitor phospholamban (PLN) were only approximately 15% lower in SR of RV than in SR of LV. Coimmunoprecipitation experiments revealed that PLN-bound, functionally inert Ca2+ -ATPase molecules in SR of RV greatly exceed (> 50%) that in SR of LV. Endogenous Ca2+/calmodulin-dependent protein kinase-mediated phosphorylation of SR substrates did not abolish the huge disparity in SR Ca2+ pump function between RV and LV. Intracellular Ca2+ transients, evoked by electrical field stimulation, were significantly prolonged in RV myocytes compared with LV myocytes, mainly because of slow decay of intracellular Ca2+ concentration. The slow decay of intracellular Ca2+ concentration in RV and consequent decrease in the speed of RV relaxation may promote temporal synchrony of the end of diastole in RV and LV. The preponderance of functionally silent SR Ca2+ pumps in RV reflects a higher diastolic reserve required to protect and maintain RV function in the face of a sudden rise in afterload or resistance in the pulmonary circulation.

Coordinate downregulation of CaM kinase II and phospholamban accompanies contractile phenotype transition in the hyperthyroid rabbit soleus

This study investigated the effects of l-thyroxine-induced hyperthyroidism on Ca2+/calmodulin (CaM)-dependent protein kinase (CaM kinase II)-mediated sarcoplasmic reticulum (SR) protein phosphorylation, SR Ca2+pump (Ca2+-ATPase) activity, and contraction duration in slow-twitch soleus muscle of the rabbit. Phosphorylation of Ca2+-ATPase and phospholamban (PLN) by endogenous CaM kinase II was found to be significantly lower (30–50%) in soleus of the hyperthyroid compared with euthyroid rabbit. Western blotting analysis revealed higher levels of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) 1 (∼150%) Ca2+pump isoform, unaltered levels of SERCA2 Ca2+pump isoform, and lower levels of PLN (∼50%) and δ-, β-, and γ-CaM kinase II (40 ∼ 70%) in soleus of the hyperthyroid rabbit. SR vesicles from hyperthyroid rabbit soleus displayed approximately twofold higher ATP-energized Ca2+uptake and Ca2+-stimulated ATPase activities compared with that from euthyroid control. The Vmaxof Ca2+uptake (in nmol Ca2+·mg SR protein−1·min−1: euthyroid, 818 ± 73; hyperthyroid, 1,649 ± 90) but not the apparent affinity of the Ca2+-ATPase for Ca2+(euthyroid, 0.97 ± 0.02 μM, hyperthyroid, 1.09 ± 0.04 μM) differed significantly between the two groups. CaM kinase II-mediated stimulation of Ca2+uptake by soleus muscle SR was ∼60% lower in the hyperthyroid compared with euthyroid. Isometric twitch force of soleus measured in situ was significantly greater (∼36%), and the time to peak force and relaxation time were significantly lower (∼30–40%), in the hyperthyroid. These results demonstrate that thyroid hormone-induced transition in contractile properties of the rabbit soleus is associated with coordinate downregulation of the expression and function of PLN and CaM kinase II and selective upregulation of the expression and function of SERCA1, but not SERCA2, isoform of the SR Ca2+pump.

An unusual complication of Thyroid Surgery and its management

Stricture oesophagus is an unusal complication of thyroid surgery. There is only one case of such nature recorded in literature, which shows that the surgeon who operated may not have had any previous experience of head and neck surgery. Locating the stricture was difficult, more so planning the treatment modality was problematic. Informed consent for oesophagectomy with gastric pull through was taken. However when we explored the neck the stricture was seen just below the level of pyriform sinus. It could be successfully excised without end to end anastomosis.

Glucocorticoid modulation of protein phosphorylation and sarcoplasmic reticulum function in rat myocardium

To decipher the mechanism(s) underlying glucocorticoid action on cardiac contractile function, this study investigated the effects of adrenalectomy and dexamethasone treatment on the contents of sarcoplasmic reticulum (SR) Ca(2+)-cycling proteins, their phosphorylation by endogenous Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II), and SR Ca(2+) sequestration in the rat myocardium. Cardiac SR vesicles from adrenalectomized rats displayed significantly diminished rates of ATP-energized Ca(2+) uptake in vitro compared with cardiac SR vesicles from control rats; in vivo administration of dexamethasone to adrenalectomized rats prevented the decline in SR function. Western immunoblotting analysis showed that the relative protein amounts of ryanodine receptor/Ca(2+)-release channel, Ca(2+)-ATPase, calsequestrin, and phospholamban were neither diminished significantly by adrenalectomy nor elevated by dexamethasone treatment. However, the relative amount of SR-associated CaM kinase II protein was increased 2.5- to 4-fold in dexamethasone-treated rats compared with control and adrenalectomized rats. Endogenous CaM kinase II activity, as judged from phosphorylation of ryanodine receptor, Ca(2+)-ATPase, and phospholamban protein, was also significantly higher (50--80% increase) in the dexamethasone-treated rats. The stimulatory effect of CaM kinase II activation on Ca(2+) uptake activity of SR was significantly depressed after adrenalectomy and greatly enhanced after dexamethasone treatment. These findings identify the SR as a major target for glucocorticoid actions in the heart and implicate modification of the SR CaM kinase II system as a component of the mechanisms by which dexamethasone influences SR Ca(2+)-cycling and myocardial contraction.

Lipoma of the external ear with osseous metaplasia

Lipoma with osseous metaplasia of the external ear is an uncommon and has not been reported so far in Medline search for 30 years. The diagnosis was confirmed only after excision biopsy of the lesion. We report this case for its rarity.

Calcium inhibits human placental 11beta-hydroxysteroid dehydrogenase type 2 activity

The effect of Ca2+ on the conversion of cortisol to its inert metabolite cortisone, the reaction catalyzed by the microsomal enzyme 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), was investigated in human placental microsomes. Placental microsomal 11beta-HSD2 activity, as determined by the rate of conversion of cortisol to cortisone, was inhibited up to 50% by increasing free Ca2+ concentrations from 22 to 268 nM. The Ca2+-induced inhibition was reversible since chelation of endogenous Ca2+ with EGTA increased 11beta-HSD2 activity up to 200%. Ca2+ decreased the maximal velocity (Vmax) of the 11beta-HSD2 catalyzed conversion of cortisol to cortisone without altering the Km of 11beta-HSD2 for cortisol, indicating that Ca2+ modulates the catalytic efficiency rather than the substrate binding of 11beta-HSD2. Moreover, the Ca2+-induced inhibition does not appear to involve altered cofactor (NAD+) binding since the inhibition of microsomal 11beta-HSD2 activity by a sub-maximal concentration of free Ca2+ was not overcome by increasing the concentration of NAD+. These findings in the microsomes were then extended to an intact cell system, JEG-3 cells, an established model for human placental trophoblasts. In these cells, an increase in cytosolic free Ca2+ concentration ([Ca2+]i) elicited by a known physiological stimulus, PGF(2alpha), was accompanied by a 40% decrease in the level of 11beta-HSD2 activity. Furthermore, the PGF(2alpha)-induced inhibition of 11beta-HSD2 activity was abrogated when increases in [Ca2+]i were blocked with the intracellular Ca2+ chelator, BAPTA. Collectively, these results demonstrate for the first time that Ca2+ inhibits human placental 11beta-HSD2 activity by a post-translational mechanism not involving substrate or cofactor binding.

Differential regulation of Ca2+/calmodulin-dependent enzymes by plant calmodulin isoforms and free Ca2+ concentration

Multiple calmodulin (CaM) isoforms are expressed in plants, but their biochemical characteristics are not well resolved. Here we show the differential regulation exhibited by two soya bean CaM isoforms (SCaM-1 and SCaM-4) for the activation of five CaM-dependent enzymes, and the Ca(2+) dependence of their target enzyme activation. SCaM-1 activated myosin light-chain kinase as effectively as brain CaM (K(act) 1.8 and 1.7 nM respectively), but SCaM-4 produced no activation of this enzyme. Both CaM isoforms supported near maximal activation of CaM-dependent protein kinase II (CaM KII), but SCaM-4 exhibited approx.12-fold higher K(act) than SCaM-1 for CaM KII phosphorylation of caldesmon. The SCaM isoforms showed differential activation of plant and animal Ca(2+)-ATPases. The plant Ca(2+)-ATPase was activated maximally by both isoforms, while the erythrocyte Ca(2+)-ATPase was activated only by SCaM-1. Plant glutamate decarboxylase was activated fully by SCaM-1, but SCaM-4 exhibited an approx. 4-fold increase in K(act) and an approx. 25% reduction in V(max). Importantly, SCaM isoforms showed a distinct Ca(2+) concentration requirement for target enzyme activation. SCaM-4 required 4-fold higher [Ca(2+)] for half-maximal activation of CaM KII, and 1.5-fold higher [Ca(2+)] for activation of cyclic nucleotide phosphodiesterase than SCaM-1. Thus these plant CaM isoforms provide a mechanism by which a different subset of target enzymes could be activated or inhibited by the differential expression of these CaM isoforms or by differences in Ca(2+) transients.

Thyroid hormone-induced overexpression of functional ryanodine receptors in the rabbit heart

Modifications in the Ca(2+)-uptake and -release functions of the sarcoplasmic reticulum (SR) may be a major component of the mechanisms underlying thyroid state-dependent alterations in heart rate, myocardial contractility, and metabolism. We investigated the influence of hyperthyroid state on the expression and functional properties of the ryanodine receptor (RyR), a major protein in the junctional SR (JSR), which mediates Ca(2+) release to trigger muscle contraction. Experiments were performed using homogenates and JSR vesicles derived from ventricular myocardium of euthyroid and hyperthyroid rabbits. Hyperthyroidism, with attendant cardiac hypertrophy, was induced by the injection of L-thyroxine (200 microg/kg body wt) daily for 7 days. Western blotting analysis using cardiac RyR-specific antibody revealed a significant increase (>50%) in the relative amount of RyR in the hyperthyroid compared with euthyroid rabbits. Ca(2+)-dependent, high-affinity [(3)H]ryanodine binding was also significantly greater ( approximately 40%) in JSR from hyperthyroid rabbits. The Ca(2+ )sensitivity of [(3)H]ryanodine binding and the dissociation constant for [(3)H]ryanodine did not differ significantly between euthyroid and hyperthyroid hearts. Measurement of Ca(2+)-release rates from passively Ca(2+)-preloaded JSR vesicles and assessment of the effect of RyR-Ca(2+)-release channel (CRC) blockade on active Ca(2+)-uptake rates revealed significantly enhanced (>2-fold) CRC activity in the hyperthyroid, compared with euthyroid, JSR. These results demonstrate overexpression of functional RyR in thyroid hormone-induced cardiac hypertrophy. Relative abundance of RyR may be responsible, in part, for the changes in SR Ca(2+) release, cytosolic Ca(2+) transient, and cardiac systolic function associated with thyroid hormone-induced cardiac hypertrophy.

Antipyretic, antinociceptive and anti-inflammatory activity of Premna herbacea roots

The alcoholic extract of the roots of Premna herbacea was investigated for its antipyretic, antinociceptive and anti-inflammatory potential in animal models. The extract, when administered orally to mice has been found to be safe up to a dose of 8.0 g/kg. A significant antipyretic effect has been observed in rabbits while mild antinociceptive effects were evidenced in mice when tested by chemical as well as thermal methods. The extract did not exhibit any anti-inflammatory activity in acute but significantly reduced the chronic inflammation.

Reversible inhibition of the calcium-pumping ATPase in native cardiac sarcoplasmic reticulum by a calmodulin-binding peptide. Evidence for calmodulin-dependent regulation of the V(max) of calcium transport

Calmodulin (CaM) and Ca(2+)/CaM-dependent protein kinase II (CaM kinase) are tightly associated with cardiac sarcoplasmic reticulum (SR) and are implicated in the regulation of transmembrane Ca(2+) cycling. In order to assess the importance of membrane-associated CaM in modulating the Ca(2+) pump (Ca(2+)-ATPase) function of SR, the present study investigated the effects of a synthetic, high affinity CaM-binding peptide (CaM BP; amino acid sequence, LKWKKLLKLLKKLLKLG) on the ATP-energized Ca(2+) uptake, Ca(2+)-stimulated ATP hydrolysis, and CaM kinase-mediated protein phosphorylation in rabbit cardiac SR vesicles. The results revealed a strong concentration-dependent inhibitory action of CaM BP on Ca(2+) uptake and Ca(2+)-ATPase activities of SR (50% inhibition at approximately 2-3 microM CaM BP). The inhibition, which followed the association of CaM BP with its SR target(s), was of rapid onset (manifested within 30 s) and was accompanied by a decrease in V(max) of Ca(2+) uptake, unaltered K(0.5) for Ca(2+) activation of Ca(2+) transport, and a 10-fold decrease in the apparent affinity of the Ca(2+)-ATPase for its substrate, ATP. Thus, the mechanism of inhibition involved alterations at the catalytic site but not the Ca(2+)-binding sites of the Ca(2+)-ATPase. Endogenous CaM kinase-mediated phosphorylation of Ca(2+)-ATPase, phospholamban, and ryanodine receptor-Ca(2+) release channel was also strongly inhibited by CaM BP. The inhibitory action of CaM BP on SR Ca(2+) pump function and protein phosphorylation was fully reversed by exogenous CaM (1-3 microM). A peptide inhibitor of CaM kinase markedly attenuated the ability of CaM to reverse CaM BP-mediated inhibition of Ca(2+) transport. These findings suggest a critical role for membrane-bound CaM in controlling the velocity of Ca(2+) pumping in native cardiac SR. Consistent with its ability to inhibit SR Ca(2+) pump function, CaM BP (1-2.5 microM) caused marked depression of contractility and diastolic dysfunction in isolated perfused, spontaneously beating rabbit heart preparations. Full or partial recovery of contractile function occurred gradually following withdrawal of CaM BP from the perfusate, presumably due to slow dissociation of CaM BP from its target sites promoted by endogenous cytosolic CaM.

Serine phosphorylation of the sarcoplasmic reticulum Ca(2+)-ATPase in the intact beating rabbit heart

Recent studies have demonstrated that Ca(2+)/calmodulin-dependent protein kinase phosphorylates the Ca(2+)-pumping ATPase of cardiac sarcoplasmic reticulum (SR) in vitro. Also, evidence from in vitro studies suggested that this phosphorylation, occurring at Ser(38), results in stimulation of Ca(2+) transport. In the present study, we investigated whether serine phosphorylation of the SR Ca(2+)-ATPase occurs in the intact functioning heart. Hearts removed from anesthetized rabbits were subjected to retrograde aortic perfusion of the coronary arteries with oxygenated mammalian Ringer solution containing (32)P(i) and contractions were monitored by recording systolic left ventricular pressure development. Following 45-50 min of (32)P perfusion, the hearts were freeze-clamped, SR isolated, and analyzed for protein phosphorylation. SDS-polyacrylamide gel electrophoresis and autoradiography showed phosphorylation of several peptides including the Ca(2+)-ATPase and Ca(2+) release channel (ryanodine receptor). The identity of Ca(2+)-ATPase as a phosphorylated substrate was confirmed by Western immunoblotting as well as immunoprecipitation using a cardiac SR Ca(2+)-ATPase-specific monoclonal antibody. The Ca(2+)-ATPase showed immunoreactivity with a phosphoserine monoclonal antibody indicating that the in situ phosphorylation occurred at the serine residue. Quantification of Ca(2+)-ATPase phosphorylation in situ yielded a value of 208 +/- 12 pmol (32)P/mg SR protein which corresponded to the phosphorylation of approximately 20% of the Ca(2+) pump units in the SR membrane. Since this phosphorylation occurred under basal conditions (i.e., in the absence of any inotropic intervention), a considerable steady-state pool of serine-phosphorylated Ca(2+)-ATPase likely exists in the normally beating heart. These findings demonstrate that serine phosphorylation of the Ca(2+)-ATPase is a physiological event which may be important in the regulation of SR function.

Detection of biomolecules in the near-infrared spectral region via a fiber-optic immunosensor

The design, development, and application of a fluorescent fiber-optic immunosensor (FFOI) procedure for the detection of antibody/antigen binding within the near-infrared (NIR) spectral region is reported. The technique was developed through the combined use of fiber-optics, semiconductor laser excitation, fluorescence detection, NIR dye, and immunochemical techniques. The antibody is immobilized on the FFOI's sensing tip and utilized as a recognition component for trace amounts of specific antigen. The FFOI is constructed to utilize antibody sandwich technique. Three individual immunoassays are reported. The first two assays utilize the FFOI and NN382, a commercial NIR dye, for the detection of human immunoglobulin G (IgG). In these assays, goat anti-human IgG antibody (GAHG) is immobilized on the sensitive terminal of the FFOI followed by the exposure of the antibody-coated terminal to human IgG. The probe is then introduced to GAHG labeled with NN382, generating a signal. The third assay utilizes the FFOI for the detection of trace amounts of Legionella pneumophila serogroup 1 (LPS1). In this assay, rabbit anti-LPS1 antibody is immobilized on the sensitive terminal of the FFOI followed by exposure to LPS1. The antigen-coated probe is then treated with monoclonal anti-LPS1 antibody followed by incubation with GAHG labeled with NN382. The assays are optimized to detect the corresponding antigen via the NIR-FFOI. Typical measurements are performed in 10-15 min. A 780-nm semiconductor laser provides the excitation of the immune complex and the resulting emission is detected by a 820-nm silicon photodiode detector. The intensity of the resulting fluorescence is directly proportional to the concentration of the antigen. Solutions of IgG and LPS1 with concentrations as low as 10(-11) M and 0.5 ng/ml, respectively, have been detected with a minimum interference.

Antinociceptive, anti-inflammatory and antipyretic effects of ethanol extract of Clerodendron serratum roots in experimental animals

The alcoholic extract (50, 100 and 200 mg/kg, p.o) of Clerodendron serratum roots produced a significant antinociceptive, anti-inflammatory and antipyretic activities in animal models. The results support the traditional claims of C. serratum as a remedy for pain, inflammation and fever.

Ca2+/calmodulin-dependent phosphorylation of the Ca2+-ATPase, uncoupled from phospholamban, stimulates Ca2+-pumping in native cardiac sarcoplasmic reticulum

Recent studies have demonstrated phosphorylation of the cardiac and slow-twitch muscle isoform (SERCA2a) of the sarcoplasmic reticulum (SR) Ca2+-ATPase (at Ser38) by a membrane-associated Ca2+/calmodulin-dependent protein kinase (CaM kinase). Analysis of the functional consequence of Ca2+-ATPase phosphorylation in the native SR membranes, however, is complicated by the concurrent phosphorylation of the SR proteins phospholamban (PLN) which stimulates Ca2+ sequestration by the Ca2+-ATPase, and the ryanodine receptor-Ca2+ release channel (RYR-CRC) which likely augments Ca2+ release from the SR. In the present study, we achieved selective phosphorylation of the Ca2+-ATPase by endogenous CaM kinase in isolated rabbit cardiac SR vesicles utilizing a PLN monoclonal antibody (PLN AB) which inhibits PLN phosphorylation, and the RYR-CRC blocking drug, ruthenium red, which inhibits phosphorylation of RYR-CRC. Analysis of the Ca2+ concentration-dependence of ATP-energized Ca2+ uptake by SR showed that endogenous CaM kinase mediated phosphorylation of the Ca2+-ATPase, in the absence of PLN and/or RYR-CRC phosphorylation, results in a significant increase (approximately 50-70%) in the Vmax of Ca2+ sequestration without any change in the k0.5 for Ca2+ activation of the Ca2+ transport rate. On the other hand, treatment of SR with PLN AB (which mimics the effect of PLN phosphorylation by uncoupling Ca2+-ATPase from PLN) resulted in approximately 2-fold decrease in k0.5 for Ca2+ without any change in Vmax of Ca2+ sequestration. These findings suggest that, besides PLN phosphorylation, direct phosphorylation of the Ca2+-ATPase by SR-associated CaM kinase serves to enhance the speed of cardiac muscle relaxation.

The antifungal antibiotic clotrimazole potently inhibits L-type calcium current in guinea-pig ventricular myocytes

The antimycotic agent clotrimazole (CLT) is a promising potential therapeutic agent for a variety of diseases including cancer. Although it is known that CLT alters calcium homeostasis in many cell types, its cardiac effects are virtually unknown. We investigated the effects of CLT on L-type calcium current (ICa,L) and action potentials in guinea-pig ventricular myocytes. CLT (5, 25 and 50 microM) inhibited basal ICa,L by 16, 59 and 93%, respectively. The inhibitory effect of CLT was rapid and the peak effect was attained within 3 min. At a concentration of 25 microM, the inhibitory effect of CLT was partially reversible whereas the response to 50 microM CLT persisted following drug withdrawal. CLT abbreviated action potential duration at 50 and 90% of repolarization and suppressed the plateau significantly. These results indicate that CLT may have important cardiac effects at concentrations used to induce the antiproliferative action of the drug.

Effects of aging on sarcoplasmic reticulum Ca2+-cycling proteins and their phosphorylation in rat myocardium

Diminished Ca2+-sequestering activity of the sarcoplasmic reticulum (SR) is implicated in the age-associated slowing of cardiac muscle relaxation. In attempting to further define the underlying mechanisms, the present study investigated the impact of aging on the contents of major SR Ca2+-cycling proteins and SR protein phosphorylation by endogenous Ca2+/calmodulin-dependent protein kinase (CaM kinase). The studies were performed using homogenates and SR vesicles derived from the ventricular myocardium of adult (6-8 mo old) and aged (26-28 mo old) Fischer 344 rats. Western immunoblotting analysis showed no significant age-related difference in the relative amounts of ryanodine receptor-Ca2+-release channel (RyR-CRC), the Ca2+-storage protein calsequestrin, Ca2+-pumping ATPase (Ca2+-ATPase), and Ca2+-ATPase-regulatory protein phospholamban (PLB) in SR or homogenate. On the other hand, the relative amount of immunoreactive CaM kinase II (delta-isoform) was approximately 50% lower in the aged heart. CaM kinase-mediated phosphorylation of RyR-CRC, Ca2+-ATPase, and PLB was reduced significantly ( approximately 25-40%) in the aged compared with adult rat. ATP-dependent Ca2+-uptake activity of SR and the stimulatory effect of calmodulin on Ca2+ uptake were also reduced significantly with aging. Treatment of SR vesicles with anti-PLB antibody (PLBab) invoked relatively less stimulation of Ca2+ uptake in the aged (</=26%) compared with the adult (</=65%) rat. Ca2+-ATPase but not PLB underwent phosphorylation by CaM kinase in PLBab-treated SR with resultant stimulation of Ca2+ uptake. The rates of Ca2+ uptake by PLBab-treated SR were significantly lower (45-55%) in the aged compared with adult rat in the absence and presence of calmodulin. These findings imply that changes in the intrinsic functional properties of SR Ca2+-cycling proteins and/or their phosphorylation-dependent regulation contribute to impaired SR function in the aging heart.

Clotrimazole, an antimycotic drug, inhibits the sarcoplasmic reticulum calcium pump and contractile function in heart muscle

Clotrimazole (CLT), an antimycotic drug, has been shown to inhibit proliferation of normal and cancer cell lines and its systemic use as a new tool in the treatment of proliferative disorders is presently under scrutiny (Benzaquen, L. R., Brugnara, C., Byers, H. R., Gattoni-Celli, S., and Halperin, J. A. (1995) Nature Med. 1, 534-540). The action of CLT is thought to involve depletion of intracellular Ca2+ stores but the underlying mechanism has not been defined. The present study utilized membrane vesicles of rabbit cardiac sarcoplasmic reticulum (SR) to determine the mechanism by which CLT depletes intracellular Ca2+ stores. The results revealed a strong, concentration-dependent inhibitory action of CLT on the ATP-energized Ca2+ uptake activity of SR (50% inhibition with approximately 35 microM CLT). The inhibition was of rapid onset (manifested in <15 s), and was accompanied by a 7-fold decrease in the apparent affinity of the SR Ca2+-ATPase for Ca2+ and a minor decrement in the enzyme's apparent affinity toward ATP. Exposure of SR to CLT in the absence or presence of Ca2+ resulted in irreversible inhibition of Ca2+ uptake demonstrating that the Ca2+-bound and Ca2+-free conformations of the Ca2+-ATPase are CLT-sensitive. Introduction of CLT to the reaction medium subsequent to induction of enzyme turnover with Ca2+ and ATP resulted in instantaneous cessation of Ca2+ transport indicating that an intermediate enzyme species generated during turnover undergoes rapid inactivation by CLT. The inhibition of Ca2+ uptake by CLT was accompanied by inhibition of Ca2+-stimulated ATP hydrolysis and Ca2+-induced phosphoenzyme intermediate formation from ATP in the ATPase catalytic cycle. Phosphorylation of the Ca2+-deprived enzyme with Pi in the reverse direction of catalytic cycle and Ca2+ release from Ca2+-preloaded SR vesicles were unaffected by CLT. It is concluded that CLT depletes intracellular Ca2+ stores by inhibiting Ca2+ sequestration by the Ca2+-ATPase. The mechanism of ATPase inhibition involves a drug-induced alteration in the Ca2+-binding site(s) resulting in paralysis of the enzyme's catalytic and ion transport cycle. CLT (50 microM) caused marked depression of contractile function in isolated perfused, electrically paced rabbit heart preparations. The contractile function recovered gradually following withdrawal of CLT from the perfusate indicating the existence of mechanisms in the intact cell to inactivate, metabolize, or clear CLT from its target site.

Defibrillation depresses heart sarcoplasmic reticulum calcium pump: a mechanism of postshock dysfunction

Presently, the only therapy for ventricular fibrillation is delivery of high-voltage shocks. Despite "successful defibrillation," patients may have poor cardiac contractility, the mechanisms of which are unknown. Intracellular Ca2+ handling by the sarcoplasmic reticulum (SR) plays a major role in contractility. We tested the hypothesis that defibrillation shocks interfere with Ca2+ transport function of cardiac SR. Rats anesthetized with pentobarbital sodium had bilateral electrodes implanted subcutaneously for transthoracic shocks. A series of 10 shocks, 10 s apart, at 0-250 V was delivered from a trapezoidal defibrilator. The hearts were rapidly removed, SR-enriched membrane vesicles were isolated, and ATP-dependent Ca2+ uptake and Ca(2+)-stimulated ATP hydrolysis were determined. There was a marked, shock-related decline in Ca2+ uptake, whereas adenosinetriphosphatase activity remained unaltered. The polypeptide compositions were similar in control and shocked SR. In Langendorff hearts, shocks also decreased contractility and slowed relaxation. These data indicate that shocks with current densities similar to defibrillation depress Ca(2+)-pumping function of cardiac SR because of uncoupling of ATP hydrolysis and Ca2+ transport. Shock-induced impairment of Ca2+ pump function may underlie postshock myocardial dysfunction.