Epidural electrical stimulation of the cervical spinal cord opposes opioid-induced respiratory depression

Opioid overdose suppresses brainstem respiratory circuits, causes apnoea and may result in death. Epidural electrical stimulation (EES) at the cervical spinal cord facilitated motor activity in rodents and humans, and we hypothesized that EES of the cervical spinal cord could antagonize opioid-induced respiratory depression in humans. Eighteen patients requiring surgical access to the dorsal surface of the spinal cord between C2 and C7 received EES or sham stimulation for up to 90 s at 5 or 30 Hz during complete (OFF-State) or partial suppression (ON-State) of respiration induced by remifentanil. During the ON-State, 30 Hz EES at C4 and 5 Hz EES at C3/4 increased tidal volume and decreased the end-tidal carbon dioxide level compared to pre-stimulation control levels. EES of 5 Hz at C5 and C7 increased respiratory frequency compared to pre-stimulation control levels. In the OFF-State, 30 Hz cervical EES at C3/4 terminated apnoea and induced rhythmic breathing. In cadaveric tissue obtained from a brain bank, more neurons expressed both the neurokinin 1 receptor (NK1R) and somatostatin (SST) in the cervical spinal levels responsive to EES (C3/4, C6 and C7) compared to a region non-responsive to EES (C2). Thus, the capacity of cervical EES to oppose opioid depression of respiration may be mediated by NK1R+/SST+ neurons in the dorsal cervical spinal cord. This study provides proof of principle that cervical EES may provide a novel therapeutic approach to augment respiratory activity when the neural function of the central respiratory circuits is compromised by opioids or other pathological conditions. KEY POINTS: Epidural electrical stimulation (EES) using an implanted spinal cord stimulator (SCS) is an FDA-approved method to manage chronic pain. We tested the hypothesis that cervical EES facilitates respiration during administration of opioids in 18 human subjects who were treated with low-dose remifentanil that suppressed respiration (ON-State) or high-dose remifentanil that completely inhibited breathing (OFF-State) during the course of cervical surgery. Dorsal cervical EES of the spinal cord augmented the respiratory tidal volume or increased the respiratory frequency, and the response to EES varied as a function of the stimulation frequency (5 or 30 Hz) and the cervical level stimulated (C2-C7). Short, continuous cervical EES restored a cyclic breathing pattern (eupnoea) in the OFF-State, suggesting that cervical EES reversed the opioid-induced respiratory depression. These findings add to our understanding of respiratory pattern modulation and suggest a novel mechanism to oppose the respiratory depression caused by opioids.

Evaluation of Telemedicine Use for an Anesthesiology Pain Division: Time, Cost, and Patient Satisfaction Analysis

Background

An increasing number of patients require outpatient and interventional pain management. To help meet the rising demand for anesthesia pain subspecialty care in rural and metropolitan areas, health care providers have used telemedicine for pain management of both interventional patients and those with chronic pain.

Objective

In this study, we aimed to describe the implementation of a telemedicine program for pain management in an academic pain division in a large metropolitan area. We also aimed to estimate patient cost savings from telemedicine, before and after the California COVID-19 “Safer at Home” directive, and to estimate patient satisfaction with telemedicine for pain management care.

Methods

This was a retrospective, observational case series study of telemedicine use in a pain division at an urban academic medical center. From August 2019 to June 2020, we evaluated 1398 patients and conducted 2948 video visits for remote pain management care. We used the publicly available Internal Revenue Service’s Statistics of Income data to estimate hourly earnings by zip code in order to estimate patient cost savings. We estimated median travel time and travel distance with Google Maps’ Distance Matrix application programming interface, direct cost of travel with median value for regular fuel cost in California, and time-based opportunity savings from estimated hourly earnings and round-trip time. We reported patient satisfaction scores derived from a postvisit satisfaction survey containing questions with responses on a 5-point Likert scale.

Results

Patients who attended telemedicine visits avoided an estimated median round-trip driving distance of 26 miles and a median travel time of 69 minutes during afternoon traffic conditions. Within the sample, their median hourly earnings were US $28 (IQR US $21-$39) per hour. Patients saved a median of US $22 on gas and parking and a median total of US $52 (IQR US $36-$75) per telemedicine visit based on estimated hourly earnings and travel time. Patients who were evaluated serially with telemedicine for medication management saved a median of US $156 over a median of 3 visits. A total of 91.4% (286/313) of patients surveyed were satisfied with their telemedicine experience.

Conclusions

Telemedicine use for pain management reduced travel distance, travel time, and travel and time-based opportunity costs for patients with pain. We achieved the successful implementation of telemedicine across a pain division in an urban academic medical center with high patient satisfaction and patient cost savings.

Activation of TLR-4 to produce tumour necrosis factor-α in neuropathic pain caused by paclitaxel

BACKGROUND

Neuropathic pain is a common complication of treatment with the anti-neoplastic drug paclitaxel. Animal studies suggest neuroinflammation and transient receptor potential channels TRPA1 and TRPV4 are involved in the pathogenesis of pain in this condition. However, how neuroinflammation and TRPA1 and TRPV4 are linked to cause pain in paclitaxel-treated animals is not known.

METHODS

Paclitaxel-induced pain was modelled by IP injection of paclitaxel (16 mg/kg) once a week for 5 weeks. The role of toll-like receptor 4 (TLR-4) in tumour necrosis factor-α (TNF-α) production and the effect of TNF-α on the expression of TRPA1 and TRPV4 were evaluated in vitro and in vivo. TNF-α signalling in dorsal root ganglion (DRG) was blocked by expressing soluble TNF receptor I (TNFsR) from a herpes simplex virus (HSV)-based vector (vTNFsR).

RESULTS

Paclitaxel treatment increased the expression and release of TNF-α in satellite glial cells and increased the expression of TRPA1 and TRPV4 in DRG neurons in animals. In vitro, paclitaxel enhanced the expression and release of TNF-α in enriched primary satellite glial cells, an effect that was blocked by an inhibitor of TLR-4. Direct application of TNF-α to primary DRG neurons in culture up-regulated the expression of TRPA1 and TRPV4. In vivo, vector-mediated TNFsR release from DRG neurons reduced paclitaxel-induced up-regulation of TRPA1 and TRPV4 expression and prevented paclitaxel-induced pain.

CONCLUSION

These results suggest that paclitaxel activation of TLR-4 to cause release of TNF-α from satellite glial cells increases the expression of TRPA1 and TRPV4 in DRG neurons to cause neuropathic pain.

Utilization of a novel digital measurement tool for quantitative assessment of upper extremity motor dexterity: a controlled pilot study

Background

The current methods of assessing motor function rely primarily on the clinician’s judgment of the patient’s physical examination and the patient’s self-administered surveys. Recently, computerized handgrip tools have been designed as an objective method to quantify upper-extremity motor function. This pilot study explores the use of the MediSens handgrip as a potential clinical tool for objectively assessing the motor function of the hand.

Methods

Eleven patients with cervical spondylotic myelopathy (CSM) were followed for three months. Eighteen age-matched healthy participants were followed for two months. The neuromotor function and the patient-perceived motor function of these patients were assessed with the MediSens device and the Oswestry Disability Index respectively. The MediSens device utilized a target tracking test to investigate the neuromotor capacity of the participants. The mean absolute error (MAE) between the target curve and the curve tracing achieved by the participants was used as the assessment metric. The patients’ adjusted MediSens MAE scores were then compared to the controls. The CSM patients were further classified as either “functional” or “nonfunctional” in order to validate the system’s responsiveness. Finally, the correlation between the MediSens MAE score and the ODI score was investigated.

Results

The control participants had lower MediSens MAE scores of 8.09%±1.60%, while the cervical spinal disorder patients had greater MediSens MAE scores of 11.24%±6.29%. Following surgery, the functional CSM patients had an average MediSens MAE score of 7.13%±1.60%, while the nonfunctional CSM patients had an average score of 12.41%±6.32%. The MediSens MAE and the ODI scores showed a statistically significant correlation (r=-0.341, p<1.14×10^-5). A Bland-Altman plot was then used to validate the agreement between the two scores. Furthermore, the percentage improvement of the the two scores after receiving the surgical intervention showed a significant correlation (r=-0.723, p<0.04).

Conclusions

The MediSens handgrip device is capable of identifying patients with impaired motor function of the hand. The MediSens handgrip scores correlate with the ODI scores and may serve as an objective alternative for assessing motor function of the hand.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-0003-11-121) contains supplementary material, which is available to authorized users.

Cardiovascular effects of a PEGylated apelin

Several studies have documented cardiovascular effects of apelin, including enhanced inotropy and vasodilation. However, these cardiovascular effects are short lived due to the predicted short circulating half-life of the apelin peptide. To address this limitation of apelin, we pursued N-terminal PEGylation of apelin and examined the cardiovascular effects of the PEGylated apelin. A 40kDa PEG conjugated apelin-36 (PEG-apelin-36) was successfully produced with N-terminal conjugation, high purity (>98%) and minimum reduction of APJ receptor binding affinity. Using an adenylate cyclase inhibition assay, comparable in vitro bioactivity was observed between the PEG-apelin-36 and unmodified apelin-36. In vivo evaluation of the PEG-apelin-36 was performed in normal rats and rats with myocardial infarction (MI). Cardiac function was assessed via echocardiography before, during a 20 min IV infusion and up to 100 min post peptide infusion. Similar increases in cardiac ejection fraction (EF) were observed during the infusion of PEG-apelin-36 and apelin-36 in normal rats. However, animals that received PEG-apelin-36 maintained significantly increased EF over the 100 min post infusion monitoring period compared to the animals that received unmodified apelin-36. Interestingly, EF increases observed with PEG-apelin-36 and apelin-36 were greater in the MI rats. PEG-apelin-36 had a prolonged circulating life compared to apelin-36 in rats. There were no changes in aortic blood pressure when PEG-apelin-36 or apelin-36 was administered. To our knowledge this is the first report of apelin PEGylation and documentation of its cardiovascular effects.

Safety and clinical efficacy of Onyx for embolization of extracranial head and neck vascular anomalies

BACKGROUND AND PURPOSE

Onyx was developed for embolization of central nervous system AVMs but is increasingly used extracranially because of its unique physical properties. We review our experience and results with the use of Onyx for the treatment of fast-flow extracranial vascular lesions.

MATERIALS AND METHODS

We retrospectively analyzed clinical and imaging records of 22 patients who underwent 71 extracranial embolizations from March 2007 through January 2010. The diagnoses were the following: cervicofacial AVM (n = 18), traumatic fistula (n = 3), and vessel laceration (n = 1). In 62 of 71 procedures (87%), Onyx was the sole embolic agent; it was delivered transarterially in 67/71 and percutaneously in 4/71 procedures. Clinical goals included amelioration of pain and control of bleeding. The clinical efficacy of embolization was judged by symptom control, and adverse events were assessed by clinical examination and history, both postembolization and 4 weeks postprocedure.

RESULTS

Cessation of acute bleeding was achieved in 13/14 cases, with 1 case of immediate recurrent massive epistaxis prompting reintubation and further embolization. Control of subacute bleeding episodes and pain was achieved for all patients. Following staged embolization, 7 patients underwent surgical resection without significant blood loss. Surgeons reported high satisfaction with the intraoperative handling properties of Onyx. Transient swelling, local tenderness, or numbness was encountered after 7 procedures. There were no stuck catheters, vessel dissections, or vessel ruptures and no skin discoloration.

CONCLUSIONS

Staged Onyx embolization was clinically efficacious in managing extracranial fast-flow vascular malformations and lesions, with low associated morbidity.

Reproductive tract disorders among Afghan refugee women attending health clinics in Haripur, Pakistan

Afghans comprise one of the largest groups of refugees in the world, with the majority living in Pakistan. The objective of this study was to identify commonly-occurring reproductive tract infections (RTIs), describe knowledge of women about RTIs, and assess physical and behavioural factors contributing to the development of RTIs. Afghan women presenting at Basic Health Units in refugee camps in Haripur, Pakistan, with reproductive health-related complaints, were included in the study (n=634). Data collection included implementation of an interviewer-administered questionnaire, along with a physical examination and laboratory tests. A descriptive analysis was conducted first. Qualitative data were coded and analyzed using predetermined themes. Chi-square test was used for determining the possible relationships between a binary outcome and categorical risk factors. Over three-fourths (76.7%) of those who reported to the health clinics with reproductive complaints had an RTI. Nearly half (49.5%) of these women were diagnosed with some form of vaginitis, and 14.7% were diagnosed with clinical suspicion of pelvic inflammatory disease (PID). Women with cervical prolapse (p = 0.033) or who cleansed after intercourse (p = 0.002) were more likely to have vaginitis. There was a significant difference (p = 0.017) in the prevalence of suspected PID among women who used mud only (11.1%), any water (18.8%), and an old cloth or toilet paper (9.8%) for cleansing after defaecation. Specific physical and behavioural contributors to the high prevalence of RTIs in this population were identified, and recommendations to ameliorate these factors are offered.

Single-particle visualization of assembly: I. Dimerization in a planar zone

Summary Single-particle fluorescence microscopy of association/dissociation is required for analysis of biological assembly reactions. Toward achieving this goal, Wang et al. (J. Microsc., 2004, 213, 101-109) used molten agarose to concentrate thermally diffusing particles in a thin zone of solution next to the surface of a coverglass (plane of concentration). The present study details the first real-time, single-particle analysis of the association/dissociation of thermally diffusing particles in the plane of concentration. The test particles were procapsids of bacteriophage lambda (radius = 31 nm). Quantification of thermal motion was developed and used to determine whether co-diffusing particles were bound to each other. The data are explained by (1) the presence of a molten agarose-generated barrier that is 93-155 nm from the coverglass surface, and (2) non-random orientation of procapsid dimers in the plane of concentration.

Intensity modulated radiation therapy: Film verification of planar dose maps

A new slow response radiographic film (Kodak EDR) is compared with a more traditional faster responding dosimetry film (Kodak XV) in an intensity modulated radiation therapy x-ray field. Dose profiles derived from the two films are compared with doses obtained using a radiotherapy dose planning system (Philips-Pinnacle) which calculates planar dose using a collapsed cone convolution algorithm. Comparisons of the dose maps delivered from film with the Pinnacle dose maps are useful to ensure accurate dose delivery. The Pinnacle dose maps agreed with measurement using both film types to within +/- 3% (in the umbral region) at depths ranging from d(max) to 15 cm. Both XV and EDR films can be used to verify IMRT. EDR film is better suited for dosimetry for combined field dose maps due to its useful dose range of 1-5 Gy. We found XV to be more suitable for individual field dose maps (dose range 0-1 Gy) as no scaling of monitor units were required to achieve acceptable optical density response.

Cloning of a cDNA encoding an isoform of human protein phosphatase inhibitor 2 from vascularized breast tumor

Using modified differential display, a gene fragment was identified as being over-expressed in human vascularized breast carcinoma when compare to its neighboring normal tissue. The differentially expressed pattern was confirmed by quantitative RT-PCR. Full-length cDNA was then cloned by both 3'-end RACE and 5'-end RACE. Analysis of the full-length cDNA of this gene reveals that this cDNA encodes an open reading frame of 615 bp, which is highly homologous to human protein phosphatase inhibitor-2, with 92% identity at the nucleotide level, and 89% identity at amino acid level. The results of this study suggest that this novel isoform of human protein phosphatase inhibitor-2 (nPPI-2) may be involved in the angiogenic switch during breast tumor development.

Functional comparison of transmyocardial revascularization by mechanical and laser means

BACKGROUND

As a result of the clinical benefit observed in angina patients treated by transmyocardial revascularization (TMR) with a laser, interest in mechanical TMR has been renewed. Although the injury induced by mechanical TMR is similar to laser TMR, the resultant impact on myocardial contractility is unknown. The purpose of this study was to determine whether mechanical TMR improves ventricular function as compared with laser TMR in chronically ischemic myocardium.

METHODS

After establishing an area of chronic myocardial ischemia, 25 domestic pigs were randomized to treatment by: excimer laser (group I), a hot needle (50 degrees C) (group II), a normothermic needle (group III), an ultrasonic needle (40 KHz) (group IV), or no treatment (group V). All devices create a transmural channel of the same diameter; 22 +/- 1 transmural channels were created in each animal. Regional myocardial contractility was assessed by measuring ventricular wall thickening at rest and with dobutamine stress echocardiography. Six weeks after revascularization, the animals were restudied at rest and with stress. Postsacrifice and histologic analysis of angiogenesis and TMR effects was then assessed.

RESULTS

Laser TMR provided significant recovery of ischemic myocardial function. This improvement in contractility after laser TMR was a 75% increase over the baseline function of the ischemic zone (p < 0.01). Mechanical TMR provided no significant improvement in function posttreatment. In fact, TMR achieved with an ultrasonic needle demonstrated a 40% worsening of the contractility versus the pretreatment baseline (p < 0.05). Histologic analysis demonstrated a significant increase in new blood vessels in the ischemic zone after laser TMR, which was not demonstrated for any of the other groups (p < 0.05). Additionally, evaluation of the mechanical TMR channels demonstrated significant scarring, which correlated with the functional results.

CONCLUSIONS

Using devices to create an injury analogous to the laser, mechanical TMR failed to improve the function of chronically ischemic myocardium. Only laser TMR significantly improved myocardial function.

Angiogenic molecules and mechanisms in breast cancer

One of the most promising and exciting anti-cancer strategies is one that is based on the inhibition of angiogenesis. Unlike conventional therapeutic approaches, anti-angiogenic therapy holds the unique promise of treating the disease in the absence of cytotoxicity or drug resistance. The link between angiogenesis and the progression of human breast cancer has been known for over 25 years, yet it is only in recent years, as endogenous stimulators and inhibitors of angiogenesis have been discovered and studied, that the promise of this therapeutic approach for breast cancer has come to be appreciated. This article presents a concise review of recent studies focused on the molecules and mechanisms that are related to the role of angiogenesis in breast cancer.

Photochemical keratodesmos for repair of lamellar corneal incisions

PURPOSE

To determine the efficacy of photochemical keratodesmos (PKD) for closing surgical incisions in the cornea of enucleated rabbit eyes compared with that achieved using sutures and self-sealing incisions.

METHODS

A 3.5-mm incision, at an angle parallel to the iris, was made in the cornea of enucleated New Zealand White rabbit eyes. The intraocular pressure required to cause leakage (IOP(L)) from the untreated incision was then recorded. Photochemical keratodesmos treatment was then performed by application of a dye, Rose Bengal (RB), in saline solution to the surfaces of the incision wound, followed by laser irradiation at 514 nm from an argon ion laser. Immediately after treatment, the IOP(L) was measured. Both dose and laser irradiance dependencies were studied in five or more eyes for each condition and appropriate control eyes. The IOP(L)s were compared with those obtained using conventional interrupted 10-0 nylon sutures. Other dyes were tested in a similar fashion.

RESULTS

The IOP(L) of 300 mm Hg was obtained using a fluence of 1270 J/cm(2) with an irradiance of 1.27 W/cm(2) (laser exposure time, 16 minutes 40 seconds). No sealing was observed using dye or light alone where control pressures of approximately 30 mm Hg were found. At higher dose (1524 J/cm(2)) and irradiance (3.82 W/cm(2); 6 minutes 35 seconds), PKD was less effective, which may be attributable to thermal effects. PKD produced IOP(L)s similar to those in closure by sutures. Other dyes such as riboflavin-5-phosphate and N:-hydroxy-pyridine thione also produced efficient bonding after PKD. Nonphotochemically active dyes did not produce significant increases in the IOP(L) at which leakage occurred.

CONCLUSIONS

The increase in IOP(L) after PKD treatment, comparable with that with sutures, in enucleated rabbit eyes demonstrates the feasibility of this technique ex vivo.

Troponin I is present in human cartilage and inhibits angiogenesis

Cartilage is an avascular and relatively tumor-resistant tissue. Work from a number of laboratories, including our own, has demonstrated that cartilage is an enriched source of endogenous inhibitors of angiogenesis. In the course of a study designed to identify novel cartilage-derived inhibitors of new capillary growth, we have purified an inhibitory protein that was identified by peptide microsequencing and protein database analysis as troponin I (TnI). TnI is a subunit of the troponin complex (troponin-C and troponin-T being the other two), which, along with tropomyosin, is responsible for the calcium-dependent regulation of striated muscle contraction; independently, TnI is capable of inhibiting actomyosin ATPase. Because troponin has never previously been reported to be present in cartilage, we have cloned and expressed the cDNA of human cartilage TnI, purified this protein to apparent homogeneity, and demonstrated that it is a potent and specific inhibitor of angiogenesis in vivo and in vitro, as well as of tumor metastasis in vivo.

Molecular cloning and expression analysis of the cDNA encoding rat tissue inhibitor of metalloproteinase-4

We have cloned and sequenced the cDNA encoding the rat tissue inhibitor of metalloproteinase 4 (TIMP-4). As a first step towards exploring the role of TIMP-4 in both the physiological and the pathological remodeling of extracellular matrix, we have extensively analyzed the mRNA expression of TIMP-4 in various rat tissues. The results reveal that the expression pattern of rat TIMP-4 is distinct from that of its human and mouse counterparts (Greene et al., 1996; Leco et al., 1997). In this report, we show that rat TIMP-4 is expressed much more extensively than previously reported, which suggests that it may play a significant role in modulating proteolysis of extracellular matrix in a wide range of tissue settings.

Stress-induced binding of the transcriptional factor CHOP to a novel DNA control element

CHOP (GADD153) is a mammalian nuclear protein that dimerizes with members of the C/EBP family of transcriptional factors. Absent under normal conditions, CHOP is induced by the stress encountered during nutrient deprivation, the acute-phase response, and treatment of cells with certain toxins. The basic region of CHOP deviates considerably in sequence from that of other C/EBP proteins, and CHOP-C/EBP heterodimers are incapable of binding to a common class of C/EBP sites. With respect to such sites, CHOP serves as an inhibitor of the activity of C/EBP proteins. However, recent studies indicate that certain functions of CHOP, such as the induction of growth arrest by overexpression of the wild-type protein and oncogenic transformation by the TLS-CHOP fusion protein, require an intact basic region, suggesting that DNA binding by CHOP may be implicated in these activities. In this study an in vitro PCR-based selection assay was used to identify sequences bound by CHOP-C/EBP dimers. These sequences were found to contain a unique core element PuPuPuTGCAAT(A/C)CCC. Competition in DNA-binding assays, DNase 1 footprint analysis, and methylation interference demonstrate that the binding is sequence specific. Deletions in the basic region of CHOP lead to a loss of DNA binding, suggesting that CHOP participates in this process. Stress induction in NIH 3T3 cells leads to the appearance of CHOP-containing DNA-binding activity. CHOP is found to contain a transcriptional activation domain which is inducible by cellular stress, lending further support to the notion that the protein can function as a positively acting transcription factor. We conclude that CHOP may serve a dual role both as an inhibitor of the ability of C/EBP proteins to activate some target genes and as a direct activator of others.

Cloning and expression of the cDNA encoding rat tissue inhibitor of metalloproteinase 3 (TIMP-3)

We have cloned the cDNA encoding the rat tissue inhibitor of metalloproteinase 3 (TIMP-3) by a PCR cloning method. Sequence analysis reveals an open reading frame containing 211 amino acids that show 99% identity to mouse TIMP-3 and 95% identity to human TIMP-3, respectively. High-level expression of TIMP-3 was detected in rat kidney, lungs and heart.

In vitro assembly of the core catalytic complex of the chloroplast ATP synthase

The regulatory gamma subunit and an alpha beta complex were isolated from the catalytic F1 portion of the chloroplast ATP synthase. The isolated gamma subunit was devoid of catalytic activity, whereas the alpha beta complex exhibited a very low ATPase activity (approximately 200 nmol/min/mg of protein). The alpha beta complex migrated as a hexameric alpha 3 beta 3 complex during ultracentrifugation and gel filtration but reversibly dissociated into alpha and beta monomers after freezing and thawing in the presence of ethylenediamine tetraacetic acid and in the absence of nucleotides. Conditions are described in which the gamma and alpha beta preparations were combined to rapidly and efficiently reconstitute a fully functional catalytic core enzyme complex. The reconstituted enzyme exhibited normal tight binding and sensitivity to the inhibitory epsilon subunit and to the allosteric inhibitor tentoxin. However, neither the alpha beta complex nor the isolated gamma subunit alone could bind the epsilon subunit or tentoxin with high affinity. Similarly, high affinity binding sites for ATP and ADP, which are characteristic of the core alpha 3 beta 3 gamma enzyme, were absent from the alpha beta complex. The results indicate that when the gamma subunit binds to the alpha beta complex, it induces a three-dimensional conformation in the enzyme, which is necessary for tight binding of the inhibitors and for high-affinity, asymmetric nucleotide binding.

Different densities of 5-HT3 receptors are labeled by [3H]quipazine, [3H]GR 65630 and [3H]granisetron

The binding of three, structurally distinct, 5-hydroxytryptamine3 (5-HT3) receptor radioligands was characterized in rat cerebral cortex, rabbit ileum myenteric plexus and NG-108-15 neuroblastoma cells. The density of sites labeled by the three ligands in rat cortex or in rabbit ileum was markedly different. [3H]Quipazine labeled more sites than [3H]GR 65630 in rat cortex (4.0-fold) and rabbit ileum (1.8-fold), but not in NG-108-15 cells. [3H]Quipazine also labeled a greater density of sites than [3H]granisetron in rat cortex (7-fold) but not in NG-108 cells. [3H]Quipazine binding in rat cortex and rabbit ileum, but not in NG-108-15 cells, was displaced by non-radiolabeled GR 65630 in a manner consistent with an interaction with more than one site. These data indicate that not all 5-HT3 receptor radioligands recognize the same population of 5-HT3 binding sites with equivalent density and further suggest the existence of subtypes of 5-HT3 receptor binding sites in rat cortical and rabbit myenteric plexus preparations.

Labelling of 5-hydroxytryptamine3 receptors with a novel 5-HT3 receptor ligand, [3H]RS-42358-197

RS-42358-197[(S)-N-(1-azabicyclo[2.2.2]oct-3-yl)-2,4,5,6-tetrahydro-1 H-benzo[de]isoquinolin-1-one hydrochloride] displaced the prototypic 5-hydroxytryptamine3 (5-HT3) receptor ligand [3H]quipazine in rat cerebral cortical membranes with an affinity (pKi) of 9.8 +/- 0.1, while having weak affinity (pKi < 6.0) in 23 other receptor binding assays. [3H]RS-42358-197 was then utilized to label 5-HT3 receptors in a variety of tissues. [3H]RS-42358-197 labelled high-affinity and saturable binding sites in membranes from rat cortex, NG108-15 cells, and rabbit ileal myenteric plexus with affinities (KD) of 0.12 +/- 0.01, 0.20 +/- 0.01, and 0.10 +/- 0.01 nM and densities (Bmax) of 16.0 +/- 2.0, 660 +/- 74, and 88 +/- 12 fmol/mg of protein, respectively. The density of sites labelled in each of these tissues with [3H]RS-42358-197 was similar to that labelled with [3H]GR 65630, but was significantly less than that found with [3H]-quipazine. The binding of [3H]RS-42358-197 had a pharmacological profile similar to that of [3H]quipazine, as indicated by the rank order of displacement potencies: RS-42358-197 > (S)-zacopride > tropisetron > (R)-zacopride > ondansetron > MDL72222 > 5-HT. However, differences in 5-HT3 receptors of different tissues and species were detected on the basis of statistically significant differences in the affinities of phenylbiguanide, and 1-(m-chlorophenyl)biguanide when displacing [3H]RS-42358-197 binding. [3H]RS-42358-197 also labelled a population (Bmax = 91 +/- 17 fmol/mg of protein) of binding sites in guinea pig myenteric plexus membranes, with lower affinity (KD = 1.6 +/- 0.3 nM) than those in the other preparations. Moreover, the rank order of displacement potencies of 15 5-HT3 receptor ligands in guinea pig ileum was found not to be identical to that in other tissues. Binding studies carried out with [3H]RS-42358-197 have detected differences in 5-HT3 receptor binding sites in tissues of different species and further underscore the unique nature of the guinea pig 5-HT3 receptor.

Over-expression and refolding of beta-subunit from the chloroplast ATP synthase

We established a bacterial system for high-level over-expression of the spinach chloroplast atpB gene which encodes the ATP synthase beta subunit. Upon induction, atpB was expressed as at least 50% to 70% of total cell protein. Although the over-expressed beta polypeptide formed insoluble inclusion bodies, more than fifty percent of it was restored to a functional form by solubilizing the inclusion bodies with 4 M urea and slowly removing the urea by stepwise dialysis. The resulting beta subunit exhibited specific and selective nucleotide binding properties identical to those of the native beta subunit.

Unusual pattern of fatty acid biosynthesis. Evidence for C-19 desaturase activity in freshwater sponges

The two long chain fatty acids common in marine demosponges, (5Z, 9Z)-5,9-hexacosadienoic (delta 5,9-26:2) and (5Z, 9Z, 19Z)-5,9,19-hexacosatrienoic (delta 5,9,19-26:3) acids), were identified also as the major phospholipid components in the freshwater sponge Ephydatia fluviatilis. Whereas the typical marine sponge Microciona prolifera biosynthesizes the delta 5,9,19-26:3 acid solely by homologation of exogenous palmitoleic acid (delta 9-16:1) and subsequent desaturation at positions 5 and 9, it was found that the freshwater sponge could further desaturate the delta 5,9-26:2 acid to the triene, indicating for the first time the existence of delta 19 -desaturase activity in a living organism.