Preoperative bisphosphonate treatment may adversely affect the outcome after shoulder arthroplasty

AIMS

The aim of this study was to investigate the effects of preoperative bisphosphonate treatment on the intra- and postoperative outcomes of arthroplasty of the shoulder. The hypothesis was that previous bisphosphonate treatment would adversely affect both intra- and postoperative outcomes.

PATIENTS AND METHODS

A retrospective cohort study was conducted involving patients undergoing arthroplasty of the shoulder, at a single institution. Two patients with no previous bisphosphonate treatment were matched to each patient who had received this treatment preoperatively by gender, age, race, ethnicity, body mass index (BMI), and type of arthroplasty. Previous bisphosphonate treatment was defined as treatment occurring during the three-year period before the arthroplasty. The primary outcome measure was the incidence of intraoperative complications and those occurring at one and two years postoperatively. A total of 87 patients were included: 29 in the bisphosphonates-exposed (BP⁺) group and 58 in the non-exposed (BP^-) group. In the BP⁺ group, there were 26 female and three male patients, with a mean age of 71.4 years (51 to 87). In the BP^- group, there were 52 female and six male patients, with a mean age of 72.1 years (53 to 88).

RESULTS

Previous treatment with bisphosphonates was positively associated with intraoperative complications (fracture; odds ratio (OR) 39.40, 95% confidence interval (CI) 2.42 to 6305.70) and one-year postoperative complications (OR 7.83, 95% CI 1.11 to 128.82), but did not achieve statistical significance for complications two years postoperatively (OR 3.45, 95% CI 0.65 to 25.28). The power was 63% for complications at one year.

CONCLUSION

Patients who are treated with bisphosphonates during the three-year period before shoulder arthroplasty have a greater risk of intraoperative and one-year postoperative complications compared with those without this previous treatment.

Risk factors for recurrent instability or revision surgery following arthroscopic Bankart repair

Aims

The factors that predispose to recurrent instability and revision stabilization procedures after arthroscopic Bankart repair for anterior glenohumeral instability remain unclear. We sought to determine the rate and risk factors associated with ongoing instability in patients undergoing arthroscopic Bankart repair for instability of the shoulder.

Materials and Methods

We used the Statewide Planning and Research Cooperative System (SPARCS) database to identify patients with a diagnosis of anterior instability of the shoulder undergoing arthroscopic Bankart repair between 2003 and 2011. Patients were followed for a minimum of three years. Baseline demographics and subsequent further surgery to the ipsilateral shoulder were analyzed. Multivariate analysis was used to identify independent risk factors for recurrent instability.

Results

A total of 5719 patients were analyzed. Their mean age was 24.9 years (sd 9.3); 4013 (70.2%) were male. A total of 461 (8.1%) underwent a further procedure involving the ipsilateral shoulder at a mean of 31.5 months (sd 23.8) postoperatively; 117 (2.1%) had a closed reduction and 344 (6.0%) had further surgery. Revision arthroscopic Bankart repair was the most common subsequent surgical procedure (223; 65.4%). Independent risk factors for recurrent instability were: age < 19 years (odds ratio 1.86), Caucasian ethnicity (hazard ratio 1.42), bilateral instability of the shoulder (hazard ratio 2.17), and a history of closed reduction(s) prior to the initial repair (hazard ratio 2.45). Revision arthroscopic Bankart repair was associated with significantly higher rates of ongoing persistent instability than revision open stabilization (12.4% vs 5.1%, p = 0.041).

Conclusion

The incidence of a further procedure being required in patients undergoing arthroscopic Bankart repair for anterior glenohumeral instability was 8.1%. Younger age, Caucasian race, bilateral instability, and closed reduction prior to the initial repair were independent risk factors for recurrent instability, while subsequent revision arthroscopic Bankart repair had significantly higher rates of persistent instability than subsequent open revision procedures. Cite this article: Bone Joint J 2018;100-B:324–30.

The influence of a history of clinical depression on peri-operative outcomes in elective total shoulder arthroplasty: a ten-year national analysis

AIMS

Depression can significantly affect quality of life and is associated with higher rates of medical comorbidities and increased mortality following surgery. Although depression has been linked to poorer outcomes following orthopaedic trauma, total joint arthroplasty and spinal surgery, we wished to examine the impact of depression in elective total shoulder arthroplasty (TSA) as this has not been previously explored.

PATIENTS AND METHODS

The United States Nationwide Inpatient Sample (NIS) was used to identify patients undergoing elective TSA over a ten-year period. Between 2002 and 2012, 224 060 patients underwent elective TSA.

RESULTS

Among the identified patients who had undergone TSA, 12.4% had a diagnosis of a history of depression. A diagnosis of depression was twice as common in women compared with men (16.0% vs 8.0%, p < 0.001), and more frequent in those with low income and Medicaid insurance (p < 0.001). A diagnosis of depression was an independent risk factor for post-operative delirium (odds ratio (OR) 2.29, p < 0.001), anaemia (OR 1.65, p < 0.001), infection (2.09, p = 0.045) and hospital discharge to a placement other than home (OR 1.52, p < 0.001) CONCLUSION: A history of clinical depression is present in 12.4% of patients undergoing elective TSA and the disease burden is projected to increase further in the future. Depression is often underdiagnosed and pre-operative screening and appropriate peri-operative management of patients is encouraged.

TAKE HOME MESSAGE

The awareness that clinical depression is associated with increased complications following total shoulder arthroplasty provides physicians an opportunity for early intervention in this at-risk population. Cite this article: Bone Joint J 2016;98-B:818-24.

Nano-scaled Pt/Ag/Ni/Au contacts on p-type GaN for low contact resistance and high reflectivity

We synthesized the vertical-structured LED (VLED) using nano-scaled Pt between p-type GaN and Ag-based reflector. The metallization scheme on p-type GaN for high reflectance and low was the nano-scaled Pt/Ag/Ni/Au. Nano-scaled Pt (5 A) on Ag/Ni/Au exhibited reasonably high reflectance of 86.2% at the wavelength of 460 nm due to high transmittance of light through nano-scaled Pt (5 A) onto Ag layer. Ohmic behavior of contact metal, Pt/Ag/Ni/Au, to p-type GaN was achieved using surface treatments of p-type GaN prior to the deposition of contact metals and the specific contact resistance was observed with decreasing Pt thickness of 5 A, resulting in 1.5 x 10(-4) ohms cm2. Forward voltages of Pt (5 A)/Ag/Ni contact to p-type GaN showed 4.19 V with the current injection of 350 mA. Output voltages with various thickness of Pt showed the highest value at the smallest thickness of Pt due to its high transmittance of light onto Ag, leading to high reflectance. Our results propose that nano-scaled Pt/Ag/Ni could act as a promising contact metal to p-type GaN for improving the performance of VLEDs.

Performance of GaN vertical light emitting diodes using wafer bonding process with Al-alloyed graphite substrate

We report on the vertical-structure light emitting diodes (VLEDs) fabricated with wafer bonding method using Al-alloyed graphite and Si supporter. VLEDs with Al-alloyed graphite produced no crack during/after laser lift-off (LLO) techniques while the wafer crack took place using Si supporter because of the difference of thermal expansion coefficients between Si and sapphire. The performance of VLEDs with wafer bonding method using Al-alloyed graphite supporter was compared to those fabricated by Cu plating methods. The output power of the chips with wafer bonding method was nearly same as the one with Cu-plating method. However, the forward voltage of VLEDs with wafer bonding method was higher than those with Cu-plating method. In the terms of reliabilities the wafer bonding process is more preferable to Cu-plating and our report proposes that Al-alloyed graphite could be one of promising candidates for the supporters in wafer bonding process.

Vibrational characteristics of carbon nanotubes as nanomechanical resonators

Using eigenvalue analysis of mass and stiffness matrices directly computed from atomistic simulations, natural frequencies and mode shapes of various carbon nanotubes are studied. The stiffness matrix was developed from the Tersoff-Brenner potential for carbon-carbon interactions. The computed frequencies of the radial breathing modes of a variety of armchair (n, n) nanotubes agree well with results obtained by others using different techniques. In addition, the study reveals diverse mode shapes such as accordion-like axial modes, lateral bending modes, torsional modes, axial shear modes, and radial breathing modes for a variety of single-wall, multi-wall, and bamboo-type carbon nanotubes. The effects of different constraints on the carbon nanotube ends on the computed frequencies and mode shapes have been investigated for possible applications in vibration sensors or electromechanical resonators.

Muscle fibre size and capillarity in Korean diving women

AIM

Effects of prolonged habitual cold-water immersion on fibre size and capillarity in vastus lateralis muscle were studied in human beings. The hypothesis tested in the present study was that cold acclimatized human skeletal muscle would have reduced muscle fibre size and higher capillarity, favouring the idea of efficacy of recruitment under cold environment.

METHODS

Ten women breath-hold divers (BHDs) and 10 active women (controls CONs) participated in this study. Muscle biopsy was obtained from vastus lateralis and determined fibre type composition and capillary density.

RESULTS

A major finding was that all BHDs revealed a markedly smaller cross-sectional area (CSA) in all fibre types than the CONs, or even than any other morphological data reported in previous investigations. Furthermore, mean CSA of type II fibre (range 1205-2766 microm2) was much smaller than type I fibre (2343-4327 microm2). The number of capillaries per fibre in different fibre types in the BHDs was higher than in the CONs (P < 0.001), and diffusional area was smaller in type II fibres than in type I fibres (P < 0.001). The BHDs and the CONs have similarity in the percentage of type I fibres, but type II fibre was predominant in both groups. Interestingly the proportion of type IIx fibre in the BHDs was higher (31%) than in the CONs (22%). No significant difference was found in the thigh circumference between the groups.

CONCLUSION

The present study demonstrates that prolonged habitual cold-water immersion may induce a decrease in fibre size and an increase in capillarity in human skeletal muscle.

Insulin-like growth factor II induces interleukin-6 expression via NFkappaB activation in psoriasis

IGF-II is known to induce the growth of keratinocytes and the level was significantly elevated in the tissue fluid of psoriatic lesion. However, the role of IGF-II in psoriasis is not well defined. Because an inflammatory cytokine, interleukin-6 (IL-6) is overexpressed in psoriatic lesions, we explored whether IGF-II has some role in psoriasis through induction of IL-6. Therefore, the expression of IL-6 was analyzed after treatment of IGF-II in primary cultured psoriatic cells and human keratinocyte cell line, HaCaT. We found that IGF-II induced the IL-6 mRNA expression significantly. To investigate the inducing mechanism of IL-6 by IGF-II, we examined the promoter activity of IL-6 and the DNA binding activity of NFkappaB, a strong regulator of IL-6. Interestingly, IL-6 promoter activity and the binding activity of NFkappaB were remarkably increased by IGF-II. Western blot data that IkappaB was reduced by IGF-II significantly suggest that NFkappaB activation by IGF-II may be mediated through the downregulation of IkappaB. Therefore, these results suggest a novel role of IGF-II in psoriasis possibly by inducing IL-6 through the activation of NFkappaB mediated by downregulation of IkappaB.

Optimal electrode placement in facial nerve conduction study

This study was designed to determine the optimal sites for the active electrode in a nerve conduction study of each branch of the facial nerve. Twenty healthy male and female volunteers between 20 and 40 years old were investigated. Our criteria for the optimal site of the active electrode were initial negative deflection and maximal amplitude of the response and the most synchronized response. Optimal sites were found to be as follows: 1. Frontalis (temporal branch): a point midway between the hairline and the eyebrow along a line passing vertically through the pupil. 2. Orbicularis oculi (zygomatic branch): the medial quarter between the medial and lateral canthus. 3. Nasalis (buccal branch): muscle belly. 4. Triangularis (mandibular branch): 15 mm lateral and 25 mm below the corner of the mouth. 5. Orbicularis oris (zygomatic, mandibular and buccal branches): 2 mm below the lower lip midway between the midline and the corner of the mouth.

Identification of genes differentially expressed by hypoxia in hepatocellular carcinoma cells

In order to identify genes differentially expressed under hypoxia (1% O2, 5% CO2, balance N2), we performed mRNA differential display analysis using total RNA extracted from hypoxic and normoxic HepG2, human hepatocellular carcinoma (HCC) cells. Of the differentially expressed genes by hypoxia, some of cDNA fragments were cloned and sequenced. The expression patterns of these clones by hypoxia were confirmed by Northern blot analysis and the quantitative RT-PCR. Down-regulated genes by hypoxia have homology to cDNA sequences encoding cytochrome oxidase subunit II and ADP/ATP translocase, respectively. Up-regulated gene by hypoxia was identified as Homo sapiens oscillin. Moreover, novel genes induced by hypoxia represent partial sequences of cDNAs that have not been reported or functionally identified. Up- or down-regulated expression of these genes in response to hypoxia may contribute to human hepatocarcinogenesis.

Brain-derived neurotrophic factor transiently stabilizes silent synapses on developing neuromuscular junctions

A general feature of the developing nervous system is the activity-dependent rearrangement of genetically defined, synaptic connections. A parallel process occurs at the developing neuromuscular junction as activity-dependent synapse withdrawal reduces the initial polyneuronal innervation of individual muscle fibers to a mononeuronal innervation within the first few weeks after birth. Because members of the neurotrophin gene family influence motor neuron differentiation and survival, we examined whether or not they also influence synaptic rearrangements in neonatal muscles. We found that treatment with brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or neurotrophin-4/5 (NT-4/5) causes the transient retention of multiple synaptic contacts on neonatal myofibers. However, the combination of both electrophysiological and histological assays revealed that the majority of such supernumerary synaptic contacts are functionally inactive or "silent." There also occurs an increase in the number of retracting axons. Because BDNF mRNA is expressed in developing muscle and the trkB tyrosine kinase receptor for BDNF is expressed by neonatal motor neurons, our results suggest that BDNF may play an endogenous role in the refinement of synaptic connectivity that occurs in skeletal muscles after birth.

Leukemia inhibitory factor influences the timing of programmed synapses withdrawal from neonatal muscles

We show that leukemia inhibitory factor (LIF) plays a physiological role in the programmed withdrawal of synapses from neonatal muscles. First, LIF mRNA is present in embryonic skeletal muscle and is developmentally regulated. We detect high levels of LIF mRNA at embryonic day 17 (E17) in mouse hind leg muscles. The content of LIF mRNA falls 10-fold between E17 and birth and then remains low in the neonate and adult. The decrease in LIF mRNA in skeletal muscle coincides with the end of secondary myogenesis and the completion of the adult number of myofibers. Second, treatment of the mouse tensor fascia latae (TFL), a superficial muscle of the hind leg, with LIF from birth (100 ng/day), transiently delays the withdrawal of excess inputs from polyneuronally innervated myofibers by approximately 3 days. The midpoint of the process is shifted from 7.5 +/- 10.2 +/- 0.6 days of age. LIF treatment delays synapse withdrawal by altering its timing without an appreciable effect on its rate. Third, in mice homozygous for a disruption of the LIF gene, the midpoint in the reduction of multiply innervated TFL myofibers occurs 1 day earlier, at 6.5 +/- 0.5 days of age. Muscle fiber number is unchanged in LIF null mice. Treatment with LIF does not alter the rate of neonatal growth, the number of muscle fibers in the TFL, or the reappearance of inputs that have been eliminated. Instead, LIF appears to delay maturation of the motor unit by transiently delaying the onset of synapse withdrawal. We hypothesize that this is a necessary component of a selective process that will operate simultaneously and equally on multiple, competing motor units.

Age-dependent penetrance of disease in a transgenic mouse model of familial amyotrophic lateral sclerosis

The mutation gly93-->ala of Cu,Zn superoxide dismutase (SOD) is found in patients with familial amyotrophic lateral sclerosis and causes motor neuron disease when expressed in transgenic mice. The progression of clinical and pathological disease was studied in a line of mice designated G1H. Clinical disease started at 91 +/- 14 days of age with fine shaking of the limbs, followed by paralysis and death by 136 +/- 7 days of age. Pathological changes begin by 37 days of age with vacuoles derived from swollen mitochondria accumulating in motor neurons. At the onset of clinical disease (90 days), significant death of somatic motor neurons innervating limb muscles has occurred; mice at end-stage disease (136 days) show up to 50% loss of cervical and lumbar motor neurons. However, neither thoracic nor cranial motor neurons show appreciable loss despite vacuolar changes. Autonomic motor neurons also are not affected. Mice that express wild-type human Cu,Zn SOD remain free of disease, indicating that mutations cause neuron loss by a gain-of-function. Thus, the age-dependent penetrance of motor neuron disease in this transgenic model is due to the gradual accumulation of pathological damage in select populations of cholinergic neurons.

Motor neuron degeneration in mice that express a human Cu,Zn superoxide dismutase mutation

Mutations of human Cu,Zn superoxide dismutase (SOD) are found in about 20 percent of patients with familial amyotrophic lateral sclerosis (ALS). Expression of high levels of human SOD containing a substitution of glycine to alanine at position 93--a change that has little effect on enzyme activity--caused motor neuron disease in transgenic mice. The mice became paralyzed in one or more limbs as a result of motor neuron loss from the spinal cord and died by 5 to 6 months of age. The results show that dominant, gain-of-function mutations in SOD contribute to the pathogenesis of familial ALS.

Systemic injections of ciliary neurotrophic factor induce sprouting by adult motor neurons

The ability of ciliary neurotrophic factor (CNTF) to induce sprouting by undamaged adult motor neurons was studied in gluteal muscles of adult ICR mice. Low doses of CNTF (0.02 mg kg-1 day-1) only induced sprouting in gluteus muscles that were beneath the site of injection, whereas high doses of CNTF (0.4-1.2 mg kg-1 day-1) acted systemically to induce motor neuron sprouting. We found little difference between the type or quality of sprouting induced by CNTF compared with muscle paralysis. Both stimuli induced sprouts of the same length, although muscle paralysis tended to induce more sprouts per end-plate. Paralysis also induced more nodal sprouting than did CNTF, but both were weaker stimuli for nodal sprouting than was partial denervation. In addition to its effects on motor neuron sprouting, high doses of CNTF induced loss of up to 36% of the body weight of treated mice. The substantial wasting caused by CNTF indicates that the factor has potent cachectic activity.

Continuous versus intermittent nitroglycerin administration in experimental heart failure: vascular relaxation and radioligand binding to adrenoceptors and ion channels

Continuous nitroglycerin (NTG) administration causes pharmacologic tolerance in humans and animals, whereas intermittent dosing is capable of avoiding or reducing tolerance development. The mechanism of NTG-induced hemodynamic tolerance may involve specific vascular desensitization and/or neurohormonal compensation. We compared effects of long-term (10 days) NTG administration (continuous or intermittent 12 h on/12 h off transdermal dosing, 10 micrograms/min) to rats with congestive heart failure (CHF) on radioligand binding from selected tissues. Tension responses in isolated blood vessels, plasma renin activity (PRA), plasma Na+ and K+ concentrations were also determined. The maximal binding values (Bmax) for [3H]glyburide and [3H]PN 200 110 in homogenates of left ventricle, right ventricle, and brain were not significantly different after NTG administration (continuous or intermittent), as compared with control. Intermittent, but not continuous, NTG caused significant increases in beta-adrenoceptor densities in the left ventricle, as judged by [3H]dihydroalprenolol binding (Bmax values: intermittent NTG 34.5 +/- 4.8, continuous NTG 24.4 +/- 2.6, placebo control 20.9 +/- 2.9 fmol/mg protein); Kd values for all ligands were not significantly altered by NTG administration. Both intermittent and continuous NTG increased the vascular contractile response to phenylephrine in isolated rat thoracic aorta. Slight reductions (two- to four-fold shifts in EC50 values) in thoracic aorta relaxant response to NTG were observed in both treatment groups as compared with control. Intermittent and continuous NTG administration caused selective changes in beta-adrenoceptor density and vascular response. These changes may contribute partly to the phenomenon of pharmacologic tolerance after chronic nitrate administration.

Rat cardiac calcium channels and their relationships with beta-adrenergic and muscarinic receptors in hypothyroidism

Thyroid hormone deficiency is associated with changes in the cardiovascular system. No one has reported the measures of both atrial and ventricular calcium channel density and function, in association with measures of negative and positive channel modulators, in hypothyroid hearts. Hormonally-induced modulation of calcium channels has clinical significance in the development and application of therapeutic agents in dysthyroid states. We thyroidectomized male rats and sham-operated euthyroid controls, in order to measure radioligand binding to ventricular and atrial membrane Ca2+ channels ([3H]-isradipine), beta-adrenoceptors ([125I]-iodocyanopindolol) and atrial muscarinic receptors ([3H]-quinuclidinyl benzilate) and related these data to contraction and heart rate responses to isoproterenol, carbachol and calcium. When data from hypothyroid tissues were compared to those of controls, the densities of calcium channels increased 50% in ventricles, but no differences were seen in atrial homogenates. In both atria and ventricles, beta-adrenoceptors decreased modestly with no change in affinity. Atrial muscarinic receptor density was also unchanged. Dose response curves of left atrial contractions showed: decreased sensitivity (increased EC50 value) but equal maximal responsiveness to extracellular calcium; an increased carbachol sensitivity (decreased EC50 value); and no significant difference in isoproterenol response. Comparisons of within-individual preparation ratioed EC50 values confirm the changed calcium and carbachol sensitivities. Heart-rate dose response curves displayed: increased maximal heart rate responsiveness to calcium associated with increased EC50 values; isoproterenol sensitivity was decreased nearly 3-fold. There was no significant difference in heart rate response to carbachol; however, ratioed values of carbachol and calcium EC50s were significantly different. These data are consistent with a tissue-level state of enhanced negative chronotropism and inotropism occurring in hypothyroid myocardia. We also confirm an earlier controversial finding of increased calcium channel density in ventricles from hypothyroid rats.

Effect of an homologous series of aliphatic alcohols on neuronal and smooth muscle voltage-dependent Ca2+ channels

The acute inhibitory actions of alcohol on K(+)-stimulated 45Ca2+ uptake into synaptosomes shows regional variation in sensitivity throughout the brain, suggesting the possibility of a selective action on a specific Ca2+ channel subtype. This was examined by comparing the effects of a homologous series of aliphatic alcohols on synaptosomal Ca2+ channels with their actions on K(+)-stimulated Ca2+ channels in guinea-pig intestinal longitudinal muscle, which have been demonstrated to be of the L-type. K(+)-stimulated contraction of and [3H]nitrendipine binding to smooth muscle were both inhibited by the alcohols at similar concentrations, with the potency increasing with chain length. In synaptosomes, however, K(+)-stimulated 45Ca2+ uptake was 5-30 times more sensitive to the inhibitory actions of alcohol than were [3H]nitrendipine and [125I]omega-conotoxin binding. These observations suggest that K(+)-stimulated 45Ca2+ uptake is mediated by a non-L non-N type channel which is more sensitive to the acute effects of alcohols. This is supported by the observation that K(+)-stimulated 45Ca2+ uptake which is insensitive to L- and N-channel antagonists was inhibited by funnel web spider venom.

Synthesis of 2-(3-substituted-1,2,4-oxadiazol-5-yl)-8-methyl-8-azabicyclo [3.2.1]octanes and 2 alpha-(3-substituted-1,2,4-oxadiazol-5-yl)-8-methyl-8- azabicyclo[3.2.1]oct-2-enes as potential muscarinic agonists

Radioligand binding affinities of seven muscarinic receptor ligands which possess an oxadiazole ring side chain have been determined in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations to determine the selectivity for subtypes of muscarinic receptor. The ratios of binding constants in brain membranes were measured as an indicator of potential agonist activity against [3H]QNB and [3H]Oxo-M. These muscarinic ligands did not discriminate the subtypes of muscarinic receptors. Six muscarinic ligands which have a 3-amino- or 3-methyl-1,2,4-oxadiazol-5-yl groups attached to the 8-methyl-8-azabicyclo[3.2.1]oct-2-ene or 8-methyl-8-azabicyclo[3.2.1]octane head group show binding constants between 2.04 x 10(-6) and 1.79 x 10(-5) M in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations. 1-Methyl-2-[3-amino-1,2,4-oxadiazol-5-yl]piperidine shows low binding constants of approximately 10(-4) M in rat heart and rat brain. (1R,5S)-2-[3-Amino-1,2,4-oxadiazol-5-yl]-8-methyl-8-azabicyclo- [3.2.1]oct-2-ene [(1R,5S)-17] was the most active compound.

Synthesis and muscarinic receptor activity of ester derivatives of 2-substituted 2-azabicyclo[2.2.1]heptan-5-ol and -6-ol

Radioligand binding affinities of four new muscarinic antagonists and six potential muscarinic agonists which possess the 2-alkyl-2-azabicyclo[2.2.1]heptane ring system have been determined in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations to examine the selectivity for subtypes of muscarinic receptor. The efficacies of the potential muscarinic agonists were determined by the ratio of binding affinities against [3H]QNB and [3H]Oxo-M. Four muscarinic antagonists which have the 2,2-diphenylpropionate side chain at either the C5 (5-endo or 5-exo) or the C6 (6-endo or 6-exo) positions did not discriminate between the subtypes of muscarinic receptors. The 2,2-diphenylpropionate 5-endo substituted compound was the most potent, showing affinities between 4.23 x 10(-10) and 1.18 x 10(-9) M in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations. The rank order of ester potency was 5-endo greater than 5-exo greater than 6-endo greater than 6-exo. A molecular modeling study based on the pharmacophore developed for azaprophen was used to account for the relative potency of these antagonists. Six potential muscarinic agonists which have acetoxy groups in the C5 or C6 position with an N-methyl or N-benzyl substituent did not discriminate subtypes of muscarinic receptors and had affinities between 6.63 x 10(-6) and 4.76 x 10(-5) M in rat heart, rat brain, and m1- or m3-transfected CHO cell membrane preparations. exo-2-Methyl-5-acetoxy-2-azabicyclo[2.2.1]heptane was the most efficacious partial agonist.

Regulation of K+ and Ca2+ channels in experimental cardiac failure

To examine the status of ATP-sensitive K+ (K+ATP) channels and 1,4-dihydropyridine-sensitive Ca2+ (Ca2+DHP) channels during experimental cardiac failure, we have measured the radioligand binding properties of [3H]glyburide and [3H]PN 200 110, respectively, in tissue homogenates from the rat cardiac left ventricle, right ventricle, and brain 4 wk after myocardial infarction induced by left coronary artery ligation. The maximal values (Bmax) for [3H]glyburide and [3H]PN 200 110 binding were reduced by 39 and 40%, respectively, in the left ventricle, and these reductions showed a good correlation with the right ventricle-to-body weight ratio in heart-failure rats. The ligand binding affinities were not altered. In the hypertrophied right ventricle, Bmax values for both the ligands were not significantly different when data were normalized to DNA content or right ventricle weights but showed an apparent reduction when normalized to unit protein or tissue weight. Moderate reductions in channel densities were observed also in whole brain homogenates from heart failure rats. Assessment of muscarinic receptors, beta-adrenoceptors and alpha 1-adrenoceptors by [3H]quinuclidinyl benzilate, [3H]dihydroalprenolol, and [3H]prazosin showed reductions in left ventricular muscarinic and beta-adrenoceptor densities but not in alpha 1-adrenoceptor densities, consistent with earlier observations. It is suggested that these changes may in part contribute to the pathology of cardiac failure.

Synthesis, molecular modeling studies, and muscarinic receptor activity of azaprophen analogues

Synthesis, radioligand binding, and pharmacologic activities of a series of muscarinic receptor ligands including and related to azaprophen (6-methyl-6-azabicyclo[3.2.1]octan-3 alpha-ol 2,2-diphenylpropionate, 1) have been measured to determine activity and selectivity for muscarinic receptor subtypes. Pharmacologic affinities of antagonists were determined as pA2 values for antagonism of methacholine-induced tension responses in guinea pig ileum. Binding affinities were measured by competition against [3H]QNB binding in guinea pig ileum, rat heart and brain, and m1- or m3-transfected Chinese hamster ovary (CHO) cells. The efficacies of muscarinic agonists in brain were determined by the ratio of binding affinities against [3H]QNB or [3H]NMS and [3H]oxotremorine-M ([3H]Oxo-M). Nine muscarinic antagonists, including azaprophen, did not discriminate significantly between the subtypes of muscarinic receptors. KI values for receptor binding for azaprophen (1) were between 8.81 x 10(-11) and 4.72 x 10(-10) M in ileum, heart, brain, and m1- or m3-transfected CHO cells. The alpha- and beta-benzilate esters 5 and 6 are as potent as azaprophen, and diphenylacetate esters 3 and 4 and N-(6)-benzyl alpha-isomer 7 are less potent than azaprophen. Significant stereoselectivity was exhibited with (+)-azaprophen being approximately 200 times more potent than the (-)-enantiomers and the 3 beta-ol isomer 2 being ca. 50 times less potent than azaprophen in all systems. A molecular modeling-molecular mechanics study was conducted to account for the difference. Putative muscarinic agonists (analogues and isomers of 6-methyl-6-azabicyclo[3.2.1]octan-3-ol acetate) did not discriminate muscarinic receptor subtypes with KI values between 2.77 x 10(-6) and 4.33 x 10(-5) M without significant stereoselectivity in the systems examined. The most active analogue was (1R,3R,5S)-6-[1(R)-phenylethyl]-6-azabicyclo[3.2.1]octan-3 alpha-ol acetate. However, efficacies of these putative agonists were in general very low.

Interactions of local anesthetics with neuronal 1,4-dihydropyridine binding sites

A series of local anesthetics competed with 1,4-dihydropyridine [3H]PN 200,110 binding to synaptosomes from guinea pig cerebral cortex synaptosomes. Dibucaine (10(-3)M) increased the dissociation rate of bound [3H]PN 200,110 consistent with an indirect, rather than competitive, interaction between local anesthetics and the 1,4-dihydropyridine site. The binding activities were compared to those previously available for local anesthetic competition with [3H]batrachotoxinin benzoate binding at a Na+ channel site. A linear correlation was observed between the two sets of activities with significantly higher activities being exhibited at the Na+ channel site. This relationship is consistent with the significant structural homologies exhibited between Na+ and Ca2+ channels.

Crystal, solution, and molecular modeling structural properties and muscarinic antagonist activity of azaprophen

The structure of azaprophen, which was originally assigned by 1H NMR analysis, was confirmed by X-ray crystallography. A comparison of 13C NMR isotropic chemical shift data for azaprophen in the solid state and in CDCl3 and DMSO-d6 solution was used to correlate solution and solid-state conformation as determined by the X-ray data. The data suggested that the solid-state and solution conformation of azaprophen were similar. The observed solid-state structure was also compared to low-energy conformations identified by molecular-mechanics calculations. A comparison of azaprophen and atropine radioligand binding in guinea pig ileum, rat heart, rat brain, and in CHO cells expressing transfected m1 and m3 receptors was conducted. Azaprophen is more active than atropine in all preparations except the m3 receptor expressed in CHO cells. However, like atropine, it does not provide major discrimination among the muscarinic receptor subtypes.

Molecular level model for the agonist/antagonist selectivity of the 1,4-dihydropyridine calcium channel receptor

Crystal structures of the 1,4-dihydropyridine (1,4-DHP) calcium channel activators Bay K 8643 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3-nitrophenyl)-pyridine-5-carboxy lat e], Bay O 8495 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(3-trifluoromethylphenyl)-pyridine-5- carboxylate], and Bay O 9507 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(4-nitrophenyl)-pyridine-5-carboxy lat e] were determined. The conformations of the 1,4-DHP rings of these activator analogues of Bay K 8644 [methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5- carboxylate] do not suggest that their activator properties are as strongly correlated with the degree of 1,4-DHP ring flattening as was indicated for members of the corresponding antagonist series. The solid state hydrogen bonding of the N(1)-H groups of the activators is not, unlike that of their antagonist counterparts, to acceptors that are directly in line with the donor. Rather, acceptor groups are positioned within +/- 60 degrees of the N(1)-H bond in the vertical plane of the 1,4-DHP ring. Previously determined structure-activity relationships have indicated the importance of this N(1)-H group to the activity of the 1,4-DHP antagonists. Based on these observations, a model is advanced to describe the 1,4-DHP binding site of the voltage-gated Ca2+ channel and its ability to accommodate both antagonist and activator ligands.

Chiral aspects of drug action at ion channels: a commentary on the stereoselectivity of drug actions at voltage-gated ion channels with particular reference to verapamil actions at the Ca2+ channel

Ion channels may be considered as pharmacological receptors possessing specific drug binding sites with defined structure-activity relationships. Accordingly drug binding to ion channels is stereoselective. Interpretation of this stereoselectivity may be complex because of the existence of differences in affinity and access to different channel states. Such state-dependent interactions may give rise to quantitative and qualitative differences in stereoselectivity. The implications of such differences are reviewed for drug action at Na+, K+ and Ca2+ channels. Detailed attention is paid to the actions of verapamil enantiomers in the cardiovascular system where activities differ in vascular and cardiac tissues because of state-dependent interactions and stereoselective first-oass metabolism.

Effects of Ca2+ channel ligands on [3H]QNB binding at m1 and m3 muscarinic receptors

1. The effects of Ca2+ channel ligands on [3H]QNB binding in m1- or m3-transfected Chinese hamster ovary (CHO) cells have been studied. 2. The IC50 values of Ca2+ channel ligands for the inhibition of [3H]QNB binding were between 10(-6) and 10(-4) M and the rank order of potency was HOE 166 greater than McN 6186 greater than nicardipine greater than tiamdipine greater than verapamil greater than diltiazem greater than Bay K 8644 greater than nifedipine at m1 and m3 receptors. 3. The results indicate that Ca2+ channel ligands employed in this experiment do not distinguish subtypes of muscarinic receptors.

The interactions of 1,4-dihydropyridines bearing a 2-(2-aminoethylthio)methyl substituent at voltage-dependent Ca2+ channels of smooth muscle, cardiac muscle and neuronal tissues

The Ca2+ channel antagonistic potencies of tiamdipine [2-(2-aminoethylthio)methyl-3-carboethoxy-5-carbomethoxy-6-m ethyl-4-(3- nitrophenyl)-1,4-dihydropyridine] and nifedipine [2,6-dimethyl-3,5-dicarbomethoxy-4-(2-nitrophenyl)-1,4-dihydrop yri dine] analogs bearing phenyl ring substituents were studied using pharmacologic and radioligand binding techniques. Additionally, analogs of tiamdipine possessing (2-aminoethylthio)methyl-, (2-acetamidoethylthio)methyl- and (2-pyrrolidinylmethylthio)methyl- groups at the C2 position of the 1,4-dihydropyridine ring have been studied. Tiamdipine and nifedipine analogs inhibited K(+)-induced contractile responses in rat tail artery. IC50 values of 4-phenyl ring substituted 2-(2-aminoethylthio)methyl tiamdipine analogs ranged from 10(-7) mol/l to 10(-8) mol/l. However, the corresponding 4-phenyl ring substituted nifedipine analogs covered a wider range of potency from 10(-6) mol/l to 10(-9) mol/l. KI values of the corresponding tiamdipine analogs for the inhibition of specific [3H]PN 200-110 [(+)-[3H]isopropyl-4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-5- methoxycarbonyl-2,6-dimethyl-3-pyridinecarboxylate] binding ranged from 10(-7) mol/l to 10(-9) mol/l in guinea pig ileal and rat heart membranes and rat brain synaptosomes. The two stereoisomers of tiamdipine and its analog 2-(2-acetamidoethylthio)methyl-3-carboethoxy-5-carbomethoxy- 6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine, and the four stereoisomers of 2-(2-pyrrolidinylmethylthio)methyl-3-carboethoxy-5-carbom eth oxy-6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine showed high stereoselectivity ratios of approximately (-)/(+) = 100 and 1000 in pharmacologic and binding experiments, respectively. The inhibitory actions of 2-(2-aminoethylthio)methyltiamdipine analogs against K(+)-induced contractile responses in rat tail artery developed very slowly requiring at least 2 h for maximum effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacologic and radioligand binding analysis of the actions of 1,4-dihydropyridine activators related to Bay K 8644 in smooth muscle, cardiac muscle and neuronal preparations

The structure-activity relationships of a series of 1,4-dihydropyridine Ca2+ channel activators, including Bay K 8644, have been determined by pharmacologic and radioligand binding techniques. Pharmacologic techniques included tension responses and the measurement of pA2 values for nifedipine antagonism of Bay K 8644 responses in guinea pig ileal, rat femoral and rat atrial and papillary muscle preparations. Radioligand binding experiments employed competition against [3H]nitrendipine binding in ileal smooth muscle and rat ventricular membranes and rat brain synaptosomal preparations. The series of compounds was employed as the racemates. Binding affinities were not significantly different between smooth muscle, cardiac muscle and brain preparations and the same rank order of pharmacologic activities is observed in smooth and cardiac muscle, where the effects of the 4-phenyl substituents, o greater than or equal to m greater than p, parallel those observed for 1,4-dihydropyridine antagonists. In the ileal and femoral artery smooth muscle preparations a 1:1 correlation is observed between pharmacologic and radioligand binding affinities. However, in the cardiac muscle preparations, left atrium and papillary muscle, there is an approximately 10-fold difference between the binding affinities and the lower pharmacologic affinities. A similar difference between smooth and cardiac muscle is observed with the pA2 values of 6.97 and 7.06 in atrial and papillary muscle respectively, which are significantly lower than the values of 8.54 and 8.72 measured in ileal and femoral artery respectively. The structure-activity expressions measured for this small series of 1,4-dihydropyridine activators parallel those observed in the larger series of 1,4-dihydropyridine antagonists. This is consistent with proposals that activators and antagonists interact at common binding sites that are components of a voltage-dependent Ca2+ channel.