Diverse African genomes reveal selection on ancient modern human introgressions in Neanderthals

Comparisons of Neanderthal genomes to anatomically modern human (AMH) genomes show a history of Neanderthal-to-AMH introgression stemming from interbreeding after the migration of AMHs from Africa to Eurasia. All non-sub-Saharan African AMHs have genomic regions genetically similar to Neanderthals that descend from this introgression. Regions of the genome with Neanderthal similarities have also been identified in sub-Saharan African populations, but their origins have been unclear. To better understand how these regions are distributed across sub-Saharan Africa, the source of their origin, and what their distribution within the genome tells us about early AMH and Neanderthal evolution, we analyzed a dataset of high-coverage, whole-genome sequences from 180 individuals from 12 diverse sub-Saharan African populations. In sub-Saharan African populations with non-sub-Saharan African ancestry, as much as 1% of their genomes can be attributed to Neanderthal sequence introduced by recent migration, and subsequent admixture, of AMH populations originating from the Levant and North Africa. However, most Neanderthal homologous regions in sub-Saharan African populations originate from migration of AMH populations from Africa to Eurasia ∼250 kya, and subsequent admixture with Neanderthals, resulting in ∼6% AMH ancestry in Neanderthals. These results indicate that there have been multiple migration events of AMHs out of Africa and that Neanderthal and AMH gene flow has been bi-directional. Observing that genomic regions where AMHs show a depletion of Neanderthal introgression are also regions where Neanderthal genomes show a depletion of AMH introgression points to deleterious interactions between introgressed variants and background genomes in both groups-a hallmark of incipient speciation.

Sequencing of 53,831 diverse genomes from the NHLBI TOPMed Program

The Trans-Omics for Precision Medicine (TOPMed) programme seeks to elucidate the genetic architecture and biology of heart, lung, blood and sleep disorders, with the ultimate goal of improving diagnosis, treatment and prevention of these diseases. The initial phases of the programme focused on whole-genome sequencing of individuals with rich phenotypic data and diverse backgrounds. Here we describe the TOPMed goals and design as well as the available resources and early insights obtained from the sequence data. The resources include a variant browser, a genotype imputation server, and genomic and phenotypic data that are available through dbGaP (Database of Genotypes and Phenotypes)1. In the first 53,831 TOPMed samples, we detected more than 400 million single-nucleotide and insertion or deletion variants after alignment with the reference genome. Additional previously undescribed variants were detected through assembly of unmapped reads and customized analysis in highly variable loci. Among the more than 400 million detected variants, 97% have frequencies of less than 1% and 46% are singletons that are present in only one individual (53% among unrelated individuals). These rare variants provide insights into mutational processes and recent human evolutionary history. The extensive catalogue of genetic variation in TOPMed studies provides unique opportunities for exploring the contributions of rare and noncoding sequence variants to phenotypic variation. Furthermore, combining TOPMed haplotypes with modern imputation methods improves the power and reach of genome-wide association studies to include variants down to a frequency of approximately 0.01%.

Evolutionary history of modern Samoans

Archaeological studies estimate the initial settlement of Samoa at 2,750 to 2,880 y ago and identify only limited settlement and human modification to the landscape until about 1,000 to 1,500 y ago. At this point, a complex history of migration is thought to have begun with the arrival of people sharing ancestry with Near Oceanic groups (i.e., Austronesian-speaking and Papuan-speaking groups), and was then followed by the arrival of non-Oceanic groups during European colonialism. However, the specifics of this peopling are not entirely clear from the archaeological and anthropological records, and is therefore a focus of continued debate. To shed additional light on the Samoan population history that this peopling reflects, we employ a population genetic approach to analyze 1,197 Samoan high-coverage whole genomes. We identify population splits between the major Samoan islands and detect asymmetrical gene flow to the capital city. We also find an extreme bottleneck until about 1,000 y ago, which is followed by distinct expansions across the islands and subsequent bottlenecks consistent with European colonization. These results provide for an increased understanding of Samoan population history and the dynamics that inform it, and also demonstrate how rapid demographic processes can shape modern genomes.

Evolution of Hominin Polyunsaturated Fatty Acid Metabolism: From Africa to the New World

The metabolic conversion of dietary omega-3 and omega-6 18 carbon (18C) to long chain (>20 carbon) polyunsaturated fatty acids (LC-PUFAs) is vital for human life. The rate-limiting steps of this process are catalyzed by fatty acid desaturase (FADS) 1 and 2. Therefore, understanding the evolutionary history of the FADS genes is essential to our understanding of hominin evolution. The FADS genes have two haplogroups, ancestral and derived, with the derived haplogroup being associated with more efficient LC-PUFA biosynthesis than the ancestral haplogroup. In addition, there is a complex global distribution of these haplogroups that is suggestive of Neanderthal introgression. We confirm that Native American ancestry is nearly fixed for the ancestral haplogroup, and replicate a positive selection signal in Native Americans. This positive selection potentially continued after the founding of the Americas, although simulations suggest that the timing is dependent on the allele frequency of the ancestral Beringian population. We also find that the Neanderthal FADS haplotype is more closely related to the derived haplogroup and the Denisovan clusters closer to the ancestral haplogroup. Furthermore, the derived haplogroup has a time to the most recent common ancestor of 688,474 years before present. These results support an ancient polymorphism, as opposed to Neanderthal introgression, forming in the FADS region during the Pleistocene with possibly differential selection pressures on both haplogroups. The near fixation of the ancestral haplogroup in Native American ancestry calls for future studies to explore the potential health risk of associated low LC-PUFA levels in these populations.

The Mobile Element Locator Tool (MELT): population-scale mobile element discovery and biology

Mobile element insertions (MEIs) represent ∼25% of all structural variants in human genomes. Moreover, when they disrupt genes, MEIs can influence human traits and diseases. Therefore, MEIs should be fully discovered along with other forms of genetic variation in whole genome sequencing (WGS) projects involving population genetics, human diseases, and clinical genomics. Here, we describe the Mobile Element Locator Tool (MELT), which was developed as part of the 1000 Genomes Project to perform MEI discovery on a population scale. Using both Illumina WGS data and simulations, we demonstrate that MELT outperforms existing MEI discovery tools in terms of speed, scalability, specificity, and sensitivity, while also detecting a broader spectrum of MEI-associated features. Several run modes were developed to perform MEI discovery on local and cloud systems. In addition to using MELT to discover MEIs in modern humans as part of the 1000 Genomes Project, we also used it to discover MEIs in chimpanzees and ancient (Neanderthal and Denisovan) hominids. We detected diverse patterns of MEI stratification across these populations that likely were caused by (1) diverse rates of MEI production from source elements, (2) diverse patterns of MEI inheritance, and (3) the introgression of ancient MEIs into modern human genomes. Overall, our study provides the most comprehensive map of MEIs to date spanning chimpanzees, ancient hominids, and modern humans and reveals new aspects of MEI biology in these lineages. We also demonstrate that MELT is a robust platform for MEI discovery and analysis in a variety of experimental settings.

Nerve tissue protein S-100 and neurone-specific enolase concentrations in cerebrospinal fluid and blood during carotid endarterectomy

Nerve tissue protein S-100 and neurone-specific enolase levels in serum were studied in 10 patients before, during and for 2 days after elective carotid endarterectomy performed under general anaesthesia and using a Javid Shunt. In six patients, simultaneous cerebrospinal fluid samples were also obtained. Serum nerve tissue protein S-100 was normal throughout the operation, but in one patient with severe hypertension, levels increased to 1.38 microg. l-1 at 1 h postoperatively. Two patients showed an increase in cerebrospinal fluid nerve tissue protein S-100 during clamping: these patients also had neurological deficits at 6 months. Serum neurone-specific enolase increased from 5.8 to 9.3 microg.l-1 during shunting while cerebrospinal fluid neurone-specific enolase did not change. Uncomplicated carotid endarterectomy does not produce cerebral damage as measured by serum nerve tissue protein S-100; cerebrospinal fluid nerve tissue protein S-100 may be more sensitive for minor cerebral damage. Neurone-specific enolase appeared to be nonspecific. The lack of correlation between the neuroproteins may need to be explained before relying on these simple assays as diagnostic indicators of cerebral ischaemia.

Transanal MR imaging after repair of anorectal anomalies in children: appearances in pull-through versus posterior sagittal reconstructions

OBJECTIVE

Our objective was to use transanal MR imaging to compare the anatomic appearance of the components of the anal sphincter and the pattern of scarring after a pull-through perineoplasty versus a posterior sagittal anorectoplasty.

SUBJECTS AND METHODS

Sixteen children ranging in age from 10 months to 15 years (mean, 10 years) were imaged using transanal receiver coils appropriate to the size of the child. Five had low, four intermediate, and seven high anomalies. Seven had undergone a transanal pull-through procedure, and nine had undergone posterior sagittal reconstruction. The integrity of the muscles was assessed on T1-weighted and short inversion time inversion recovery transverse and coronal images using a qualitative MR imaging score. The pattern of scarring was also assessed.

RESULTS

In the transanal pull-through group, four of seven patients showed external sphincter deficiency. A circumferential low-signal-intensity band was seen inferior to the sphincter in six patients. All posterior sagittal reconstructions had a long posterior midline scar. Five of nine patients showed external sphincter deficiency, whereas a further two had internal sphincter deficiency. No differences were seen in MR imaging scores for each operative procedure for all grades of severity of anorectal anomaly. However, a comparison between high and intermediate anomalies showed a small improvement in MR imaging score using the transanal pull-through procedure (Mann-Whitney U test = 3, p < .03). Manometric pressures obtained in 13 patients were poor.

CONCLUSION

Transanal MR imaging identifies focal defects and patterns of scarring of the anal sphincter complex in infants and children and provides valuable information about individual muscle components.

Time course of neurone-specific enolase and S-100 protein release during and after coronary artery bypass grafting

Serum neurone-specific enolase (NSE) and S-100 protein are well established as markers of cerebral injury, and have been used as markers of neuronal and glial cell damage, respectively, after cardiac surgery with cardiopulmonary bypass (CPB), but the speed of their increase during CPB has not been studied. Therefore, we have investigated the time course of NSE and S-100 release during and after CPB. We studied 18 adult patients undergoing elective coronary artery bypass grafting (CABG). Standard hypothermic (32 degrees C) pulsatile bypass with membrane oxygenation was used. Blood samples were obtained at induction, before bypass, before rewarming, at the end of rewarming, 10 min, 1 h and 8 h after bypass and 1, 2 and 3 days after surgery. NSE and S-100 were assayed using immunoradiometric assay kits (Sangtec Medical). NSE and S-100 release followed similar time courses. Both increased sharply during bypass, reached peak concentrations at the end of rewarming (mean 25.55 (SEM 2.79) and 1.65 (0.23) microgram litre-1, respectively), had decreased significantly by the end of operation and returned to pre-bypass concentrations by the second day after surgery. No patient developed a major neurological deficit. When using NSE and S-100 assays to study cerebral dysfunction in relation to CPB, postoperative samples miss peak (end-bypass) concentrations, and studies should be designed to include intraoperative samples.

Magnetic resonance spectroscopy of high-energy phosphates and lactate immediately after coronary artery bypass surgery

Hypothermic cardiopulmonary bypass (CPB) is associated with a high incidence of neuropsychological defects, marked cerebral swelling immediately after surgery and jugular bulb desaturation during rewarming. This suggests cerebral ischaemia may occur, but evidence is indirect. We studied four patients with 31P magnetic resonance spectroscopy (MRS) and four with 1H MRS before and immediately after coronary surgery. There was no visible lactate in 1H MR spectra. In 31P MR spectra, the ratio of phosphocreatine to adenosine triphosphate was maintained (before: 2.13 +/- 0.86 vs after: 2.57 +/- 1.31; mean +/- 1 SD) and there was no intracellular acidosis (intracellular pH: 7.1 +/- 0.04 vs 7.16 +/- 0.08), while phosphocreatine/inorganic phosphate was increased immediately after the operation (2.92 +/- 0.37 vs 6.39 +/- 2.67, p = 0.03). This suggests rebound replacement of energy stores following recovery from temporary cerebral ischaemia during CPB: intra-operative studies would be needed to test this hypothesis further.

Localised cerebral phosphorus-31 MR spectroscopy in man before and immediately after coronary bypass surgery with hypothermic cardiopulmonary bypass

Coronary artery bypass surgery classically is undertaken with hypothermic cardiopulmonary bypass (CPB). There is a high incidence of neuropsychological defects after cardiac surgery, which may be related to cerebral ischaemia during the rewarming period. In this study, phosphorus-31 magnetic resonance spectroscopy (31P MRS) was used to identify changes in cerebral 31P MR spectra in patients before and immediately after hypothermic CPB. Four neurologically normal patients undergoing coronary artery bypass surgery were studied. Localised cerebral 31P MRS (TR 5000 ms) was performed at 1.5 Tesla on each patient the day before and within an hour of completion of surgery. Peak areas for phosphomonoesters (PME), inorganic phosphate (Pi), phosphodiesters (PDE), phosphocreatine (PCr) and beta ATP (betaATP) were measured. Metabolite peak area ratios and relative percentages of each 31P MR resonance with respect to the total 31P MR signal were calculated. In the post-operative MR spectra, each patient displayed a marked reduction in Pi/betaATP and increase in PCr/Pi ratios. Spectral changes in percentage metabolite signals following surgery varied both in magnitude and pattern between patients. In two patients there was an increased postoperative percentage PME and percentage PCr with a decrease in percentage betaATP. The converse was found in the other two patients, but all four subjects displayed a markedly decreased percentage Pi after CPB. These metabolite changes probably reflect rebound phosphorylation in the immediate postoperative period and suggest increased metabolic activity in the hyperaemic brain on rewarming from hypothermic CPB.

Cerebral swelling after normothermic cardiopulmonary bypass

BACKGROUND

Marked cerebral swelling visible on magnetic resonance images has been found immediately after hypothermic (28 degrees C) cardiopulmonary bypass. The mechanism is unknown, but indices of cerebral ischemia are seen during rewarming from hypothermic bypass that are not present with normothermic bypass (37 degrees C).

METHODS

T1-weighted and fluid-attenuated inversion recovery magnetic resonance images were taken of seven patients undergoing routine coronary artery bypass surgery before, 1 h, and 7 days after the operation using normothermic bypass.

RESULTS

Marked cerebral swelling was seen in fluid-attenuated inversion recovery images in five of seven patients 1 h after bypass. Scans in four patients taken 7 days after bypass showed that the cerebral swelling had returned to normal. There was no change in cerebral ventricular size, and all patients had uncomplicated postoperative courses.

CONCLUSIONS

Normothermic bypass is followed by acute postoperative cerebral swelling. However, the amount of swelling was similar to that found in a previous study after hypothermic bypass. The mechanism of swelling is still obscure, and its relation to neurologic outcome is unknown.

Magnetic resonance spectroscopy of isoflurane kinetics in humans. Part II: Functional localization

We describe the first experiments to relate the cerebral kinetics of isoflurane (determined by fluorine magnetic resonance spectroscopy) to cerebral function. Using a surface receive coil we found two-compartment kinetics within the head with equilibrium half-times of 3.5 min and approximately 1 h with respect to expired isoflurane concentrations. Using critical fusion flicker frequency as an objective measure of the cerebral effect of isoflurane, we found evidence to identify the fast component as the brain. Responsiveness to command was lost at a brain partial pressure of 0.3% isoflurane. We conclude that the measured cerebral kinetics of isoflurane exactly matched the predictions of the classical perfusion-limited model.

Magnetic resonance spectroscopy of isoflurane kinetics in humans. Part I: Elimination from the head

We describe the first human experiments to demonstrate wash-out of isoflurane using fluorine magnetic resonance spectroscopy. Using a surface receive coil, we found two-compartment kinetics within the head with decay half-times of 9.5 and 130 min, but the signal was too weak to localize the compartments. If the fast compartment is assumed to be the brain then our results match the predictions of the classical perfusion-limited pharmacokinetic model of inhalation anaesthesia.

Neurone-specific enolase and Sangtec 100 assays during cardiac surgery: Part I--The effects of heparin, protamine and propofol

Neurone-specific enolase (NSE) and Sangtec 100 (S-100) (Sangtec Medical, Sweden) assays are designed for clotted samples, but when studying cerebral damage following cardiac surgery, perioperative samples will contain heparin and/or protamine. The lipid emulsion propofol is also frequently used during cardiac surgery and could affect the assays. We, therefore, studied the effects of heparin, protamine and propofol on the accuracy of NSE and S-100 assays in five healthy patients. Blood samples were taken and divided into four groups: normal saline was added to group A; heparin to group B; heparin followed by protamine to group C; and propofol to group D. NSE and S-100 concentrations were measured for all samples. Neither heparin, protamine nor propofol affected the accuracy of S-100 and NSE assays; therefore, samples can be taken throughout operations involving cardiopulmonary bypass without influencing the results.

Neurone-specific enolase and Sangtec 100 assays during cardiac surgery: Part II--Must samples be spun within 30 min?

Sangtec 100 (S-100) (Sangtec Medical, Sweden) and neurone-specific enolase (NSE) assays are showing promise in the assessment of cerebral damage following cardiopulmonary bypass (CBP). The manufacturer's instructions state, however, that samples must be spun and frozen within 30 min, which is inconvenient for serial studies. We, therefore, investigated whether strong blood samples at room temperature (RT) or 4 degrees C for up to 48 h affected the measured levels. Blood samples were taken before and after CBP in six patients and stored for 15 min, 4, 8, 24 or 48 h at RT or 4 degrees C. S-100 and NSE levels did not alter in either 'before surgery' or CPB samples when stored for up to 48 h at 4 degrees C. There was a small, nonsignificant rise when stored at RT. Samples may, therefore, be collected throughout long operations or stored overnight without affecting NSE or S-100 plasma levels.

Neurone-specific enolase and Sangtec 100 assays during cardiac surgery: Part III--Dose haemolysis affect their accuracy?

Neurone-specific enolase (NSE) and Sangtec 100 (S-100) are useful for detecting cerebral damage during cardiopulmonary bypass (CPB). However, red cells contain NSE, and the haemolysis frequently caused by CPB could produce a false rise in NSE; S-100 is not found in red cells and should not be affected. We, therefore, compared the effects of haemolysis on NSE and S-100 to see if correction was necessary and possible. From seven patients, serial dilutions of haemolysed red cells were added to plasma (1/64-1/2048), measured for absorption at 540 nm and assayed for NSE and S-100. S-100 concentrations showed no change with haemolysis. Measured NSE increased significantly with haemolysis > 1/512 (an increase of 6.6 micrograms/ml): a correction formula is presented. In 39/48 patients after CPB, mean haemolysis was < 1/256 and would not need any correction. NSE and S-100 assay can, therefore, be used throughout CPB, which allows both glial and neuronal damage to be studied.

Biochemical markers of cerebral damage

Neuroprotective therapy is likely to be most effective in preventing or minimizing the effects of cerebral ischaemia when given as early as possible after the insult. Neuropsychological testing is the gold standard for assessing minor cerebral damage, but is carried out several days or weeks after surgery and is too late to be useful for instituting therapy. Current intraoperative cerebral monitors (EEG, CFAM, NIRS and TCD) can detect cerebral ischaemia with good sensitivity, and give immediate results, but their specificity for ischaemia is low. Biochemical markers offer the possibility of rapid and specific diagnosis of cerebral ischaemia which would allow the early institution of neuroprotective therapies.

Laser ablation of the endometrium: MR appearance during and after treatment and the relation of MR appearance to clinical outcome

OBJECTIVE

Our objective was to study the appearance of the uterus on MR images obtained during and 3 months after laser ablation of the endometrium and to determine if a correlation exists between the MR imaging findings and the subsequent clinical outcome. The appearance could then be used to guide the application of laser energy during the procedure to optimize the clinical result.

SUBJECTS AND METHODS

Eight women 34-55 years old (mean, 42 years old) with symptoms of heavy, painful menses underwent laser ablation under epidural anesthesia. Imaging was done on a 0.5-T Picker Asset system with a pelvic phased-array receiver coil using conventional T1-weighted spin-echo, T2-weighted spin-echo, and gradient-recalled-echo sequences. Images were obtained preoperatively, after ablation of the anterior surface, after completion of the procedure, and 3 months later. Images were visually assessed for signal intensity changes in the endometrium and myometrium by two observers in conference. Images were quantitatively analyzed by measuring uterine volume and the width of the endometrium, junctional zone (JZ), and outer myometrium (OM) on the T2-weighted images. Preoperative and 3-month postoperative symptom scores including duration, amount of bleeding, and associated pain were recorded.

RESULTS

MR images obtained immediately after treatment showed an increase in the volume of the uterus (mean, 21%). Endometrial thickness increased in five patients, and the JZ:OM ratio increased on the T2-weighted scans in six patients. The increase in the ratio probably represented myometrial edema. Two patients with persistent symptoms were treated with hysterectomy 6 weeks postoperatively. Of the remaining six patients, five showed an improvement in symptom scores after 3 months. The uterus returned to its preoperative size after 3 months in three patients, endometrial thinning was noted in two, and the JZ:OM ratio remained increased in two. The difference between the mean improvement in symptom scores at 3 months was significant in the patients with and without the endometrial swelling seen immediately after treatment. No statistically significant correlation existed between the amount of perioperative uterine swelling or the increase in JZ:OM ratio and the improvement in symptom scores at 3 months.

CONCLUSION

On laser ablation of the endometrium, MR imaging showed significant immediate uterine swelling as well as an increase in the endometrial thickness and JZ:OM ratio. The presence of immediate endometrial swelling and the reduction in the JZ:OM ratio after 3 months correlated with a subsequent improvement in symptom scores. Perioperative endometrial swelling rather than myometrial changes is therefore an indicator of clinical outcome.

Endoscopic laser ablation of the prostate: MR appearances during and after treatment and their relation to clinical outcome

OBJECTIVE

Endoscopic laser ablation is a new treatment for benign prostatic hypertrophy. The objectives of this study were to determine the appearances of the prostate on MR images obtained during, 1 week after, and 3 months after this procedure and to determine if a correlation exists between the MR findings and the clinical outcome. Such appearances could then be used to guide the application of laser energy during the procedure in order to optimize the clinical result.

SUBJECTS AND METHODS

Eight consecutive men 58-74 years old with symptoms of bladder outflow obstruction caused by benign prostatic hypertrophy underwent endoscopic laser ablation of the prostate under spinal or epidural anaesthesia. Imaging was done on a 0.5-T Picker Asset system with an endorectal receiver coil and conventional T1-weighted spin-echo, T2-weighted spin-echo, and gradient-recalled-echo sequences. T1-weighted magnetization transfer images were obtained in three patients. Images were obtained preoperatively, after ablation of the left-sided quadrants, immediately after completion of the procedure, and 1 week and 3 months later. Preoperative and 3-month postoperative symptom scores, peak urine flow rates, and bladder residual volumes were studied. Images were visually assessed for signal-intensity changes and the presence of cavitation by three radiologists in conference. The results were quantitatively analyzed by measuring prostatic volumes on the gradient-recalled-echo images and by measuring the width and area of regions of signal-intensity change on the T2-weighted images.

RESULTS

MR images made immediately after treatment showed an increase in the volume of the prostate (mean, 34%) and a poorly defined, low-signal-intensity region around the urethra on the T2-weighted images in six patients. This probably represented coagulative necrosis. The prostate was smaller on MR images made 1 week after treatment, and after 3 months the prostate returned to its preoperative size. After 1 week, the low-signal-intensity periurethral region on the T2-weighted images was less obvious, and at 3 months it was replaced in four patients by a well-demarcated low-signal-intensity ring on the T2-weighted and gradient-recalled-echo images. No evidence of cavity formation in the prostate was seen on MR images in any patient. Symptom scores and peak urinary flow rates improved after 3 months, with a significant difference between the mean increase in symptom scores in the patients with and without the periurethral changes seen immediately after treatment. However, we found no significant difference between the mean increase in peak urinary flow rates in the patients with and without periurethral changes seen either immediately or at 3 months after treatment. No statistically significant correlation was found between the amount of prostatic swelling and the improvement in symptom scores or peak urine flow rates.

CONCLUSION

In patients who have had laser prostatectomy, MR imaging shows significant immediate glandular swelling, which may account for the delayed improvement in symptoms reported with this technique. The presence of the periurethral changes immediately after treatment was correlated with a subsequent improvement in symptom scores. After 3 months, no cavity could be seen in the prostate. This may account for the poorer long-term clinical outcome reported with endoscopic laser ablation of the prostate compared with transurethral prostatectomy.

Brain swelling in first hour after coronary artery bypass surgery

Six patients undergoing routine coronary artery bypass surgery were examined by magnetic resonance imaging of the brain before surgery, immediately afterwards, and 6-18 days later. Brain swelling was visible in all six patients on the immediate postoperative scan. In five patients who had later scans the swelling had subsided. No major neurological deficits were seen, and the patients were extubated successfully within 3 h of the operation. The mechanism of the cerebral swelling is uncertain, but it may provide insight into the cause of neurophysiological deficits seen after coronary artery surgery.

Near infrared spectroscopy in adults. Does the Invos 3100 really measure intracerebral oxygenation?

Does the Invos near infrared spectroscopy monitor detect intracranial oxygenation, or reflect oxygenation of extracerebral tissues? The change in Invos regional cerebral oxygenation was studied during a doubling of middle cerebral artery flow with hypercapnia. There was no significant change in regional cerebral oxygenation, which suggests that the Invos does not reflect intracerebral oxygenation, possibly because of its narrow optode separation. The use of near infrared spectroscopy in adults may require a more powerful machine.

Interphenylene 7-oxabicyclo[2.2.1]heptane oxazoles. Highly potent, selective, and long-acting thromboxane A2 receptor antagonists

A series of interphenylene 7-oxabicyclo[2.2.1]heptane oxazoles (2) were prepared and evaluated for their thromboxane (TxA2) antagonistic activity in vitro and duration of action in vivo. Examination of the carboxyl side chain indicated that the interphenylene ring substitution pattern and, to a lesser extent, chain length were important factors in determining TxA2 antagonistic potency. For the carboxyl side chain, ortho substitution, a single methylene spacer between the interphenylene and oxabicycloheptane rings, and a propionic acid side-chain length were determined to be optimal. With respect to the oxazole side chain a wide range of amide substituents with diverse structures and lipophilicities were compatible with potent antagonistic activity. Finally, an acidic functional group on the alpha-chain and a hydrogen bond acceptor on the 4-position of the oxazole ring were critical for potent activity. From the analogs prepared 42 (BMS-180,291: [(+)-1S-(1 alpha, 2 alpha, 3 alpha, 4 alpha)-2-[[3-[4-[(n- pentylamino)carbonyl]-2-oxazolyl]-7-oxabicyclo[2.2.1]hept-2- yl]methyl]benzenepropanoic acid) was found to be a potent, selective, and orally-active TxA2 antagonist with a long duration of action and has been selected as a candidate for clinical development. In human platelet-rich plasma, 42 inhibited arachidonic acid (800 microM) and U-46,-619 (10 microM) induced aggregation with I50 values of 7 and 21 nM, respectively. Radioligand binding studies of 42 with [3H]-SQ 29,548 showed a Kd value of 4.0 +/- 1.0 nM in human platelet membranes. Both in vitro and in vivo studies indicated 42 was devoid of direct agonistic activity. In vivo 42 (0.2 mg/kg, po) showed extended protection (T50 = 14.4 h) from U-46,619 (2 mg/kg, iv) induced death in mice, and a single oral dose of 42 (3 mg/kg) abolished U46,619-induced platelet aggregation ex vivo in African green monkeys for > 24 h.

Binding and function of a potent new thromboxane receptor antagonist, BMS 180,291, in human platelets

Binding and function of BMS 180,291 ([(+)1S-(1 alpha,2 alpha,3 alpha,4 alpha)]-2-[[3-[4-[(n-pentylamino)carbonyl]-2-oxazolyl]-7- oxabicyclo[2.2.1] hept-2-yl]methyl]benzenepropanoic acid]) in human platelets was examined. Kinetic determination of [3H]BMS 180,291 binding produced ligand-receptor association and dissociation rates of 1.4 x 10(7) +/- 0.2 M-1 x min-1 (n = 5) and 0.04 +/- 0.005 min-1 (n = 5), respectively. The resultant Kd was 3.1 +/- 1.1 nM (n = 5). Saturation binding analysis in platelet membranes was consistent with a single class of [3H]BMS 180,291 binding sites with a Kd of 3.6 +/- 0.19 nM (n = 4) and a binding site maxima (Bmax) of 2099.1 +/- 70.3 fmol/mg of protein (n = 4). Specific [3H]BMS 180,291 binding was inhibited by thromboxane A2/endoperoxide receptor antagonists and agonists with a rank order of potency of: BMS 180,291 > or = SQ 29,548 = I-BOP race 15-(1 alpha,2 beta(5Z), 3 alpha(1E,3S),4 alpha) d7-[3-(3-hydroxy-4-(p-iodophenoxy)-1-butenyl)-7- oxabicyclo[2.2.1]hept-2-yl]5-heptenoic acid) > or = BM 13,505 > or = SQ 30,741 = U 44,609 > U 46,619 >> BM 13,177. Prostaglandin E2 and prostacyclin did not appreciably inhibit the specific binding of [3H]BMS 180,291. BMS 180,291 (10 nM-5 microM) shifted the I-BOP-induced platelet shape change curve to the right in a parallel manner without reduction of the maximal response (KB = 13 +/- 3.5 nM; pA2 = 8 +/- 0.2; slope = -1.0 +/- 0.05), whereas 30 nM drug decreased the maximal I-BOP-induced platelet aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological profile of BMS 180,291: a potent, long-acting, orally active thromboxane A2/prostaglandin endoperoxide receptor antagonist

180,291 1S-(1 alpha, 2 alpha, 3 alpha, 4 alpha)-2-[[3-[4- [(pentylamino)carbonyl]-2-oxazolyl]-7-oxabicyclo[2.2.1]hept- 2- yl]methyl]benzenepropanoic acid (BMS) is a potent and highly selective antagonist of thromboxane A2/prostaglandin endoperoxide (TP) receptors. In human platelet-rich plasma, BMS 180,291 inhibited platelet aggregation induced by arachidonate (800 microM) and U-46,619 (10 microM) with respective IC50 values of 7 +/- 1 (S.E.M.) and 21 +/- 2 nM. Inhibition of both the rate and full extent of 11,9-epoxymethano-prostaglandin H2 (U-46,619)-induced platelet aggregation were insurmountable at antagonist concentrations > 10 nM, but BMS 180,291 antagonized U-46,619-induced platelet shape change competitively with a KB of 11 +/- 2 nM. BMS 180,291 concentrations < or = 1 mM did not inhibit platelet aggregation induced by high concentrations of ADP (20 microM) or human alpha-thrombin (1 U/ml). BMS 180,291 inhibited binding of [3H]1S-[1 alpha,2 alpha(5Z),3 alpha,4 alpha]-7-[3-[[2- [(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]-hept-2- yl]-5-heptenoic acid to human platelet membranes with a kd of 4.0 +/- 1.0 nM and slope factor of 1.06 +/- 0.13. U-46,619-induced concentrations of rat aortae were competitively antagonized by BMS 180,291 with a KB of 0.6 +/- 0.1 nM. Aortic responses to norepinephrine, serotonin and angiotensin II were not inhibited by BMS 180,291 at 1 microM. U-46,619-induced contractions of guinea pig tracheal rings were antagonized in an almost all-or-none manner, with maximal blockade at > or = 1 nM BMS 180,291, but little effect at lower concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

DuP 753, the selective angiotensin II receptor blocker, is a competitive antagonist to human platelet thromboxane A2/prostaglandin H2 (TP) receptors

DuP 753 is a potent, selective angiotensin II type 1 (AT1) receptor antagonist. The possibility was investigated that DuP 753 may crossreact with thromboxane A2/prostaglandin H2 (TP) receptors. DuP 753 inhibited the specific binding of the TP receptor antagonist [3H]SQ 29,548 (5 nM) in human platelets with kd/slope factor values of 9.6 +/- 1.4 microM/1.1 +/- 0.02. The AT2-selective angiotensin receptor ligand, PD 123,177 was a very weak inhibitor of specific [3H]SQ 29,548 binding in platelets (Kd/slope factor:200 microM/0.86). [3H]SQ 29,548 saturation binding in the absence and presence of DuP 753 resulted in an increase in equilibrium affinity constant (Kd: 9.3, 22, 33 nM, respectively) without a concentration-dependent reduction in binding site maxima (Bmax: 3597, 4597, 3109 fmol/mg protein, respectively). Platelet aggregation induced by the TP receptor agonist U 46,619 was concentration-dependently inhibited by DuP 753 (IC50 = 46 microM). These data indicate for the first time that DuP 753 is a weak but competitive antagonist at human platelet TP receptors.

Hypotension following valve replacement surgery in carcinoid heart disease

We report the use of adrenaline in a 62-year-old woman with carcinoid heart disease who underwent double valve replacement. She was given an intravenous infusion of octreotide throughout the peri-operative period. Following the termination of cardiopulmonary bypass she developed profound hypotension which proved to be refractory to various therapies but responded to adrenaline. Adrenaline is said to be contraindicated in carcinoid syndrome, but we would suggest the consideration of its use in such cases where the hypotension may result from myocardial depression rather than from a carcinoid crisis.

Pharmacological characterization of potent, long-acting thromboxane receptor antagonists, SQ 33,261 and SQ 33,552

SQ 33,261 ([1S-[1 alpha,2 alpha(Z),3 alpha,4 alpha]]-6-[3-[[2- [(phenylamino)carbonyl]hydrazono]methyl]-7-oxabicyclo[2.2.1]hept-2 - yl]-4-hexenoic acid) and SQ 33,552 ([1S-[1 alpha,2 alpha(Z),3 alpha,4 alpha]]-6-[3-[[[[(4- chlorophenyl)amino]carbonyl]hydrazono]methyl]-7- oxabicyclo[2.2.1]hept-2-yl]-4-hexenoic acid) are potent thromboxane (Tx) A2 receptor antagonists. They inhibited platelet aggregation in platelet-rich plasma induced by the TxA2 mimetic, U-46,619 (10 microM), with IC50 values of 200 and 70 nM, respectively. Neither compound inhibited ADP (20 microM)-induced platelet aggregation (IC50 greater than 1000 microM). SQ 33,261 and SQ 33,552 competitively antagonized U-46,619-induced contraction of rat aortic strips with respective pA2 values of 9.0 and 10.1 and KB values of 1.2 and 0.1 nM. They also competitively antagonized U-46,619-induced contraction of guinea pig tracheal strips with pA2 values of 8.9 and 9.9 and KB values of 1.9 and 0.4 nM, respectively. SQ 33,261 and SQ 33,552 (p.o.) were potent inhibitors of U-46,619 (2 mg/kg i.v.)-induced death in mice with ID50 values of 8 and 1 micrograms/kg, respectively. SQ 33,261 and SQ 33,552 (0.2 mg/kg p.o.), also had long duration of action in this assay with 50% survival times of 7 and 15 hr, respectively. SQ 33,261 at 0.01 and 1.0 mg/kg i.v., inhibited arachidonic acid-induced bronchoconstriction and reversed arachidonic acid-induced hypertension to a hypotensive response. SQ 33,552 inhibited TxA2 synthase at high concentrations (IC50 = 307 microM), whereas SQ 33,261 was inactive. Neither compound inhibited cyclooxygenase or caused an elevation of platelet cyclic AMP levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Interphenylene 7-oxabicyclo[2.2.1]heptane thromboxane A2 antagonists. Semicarbazone omega-chains

A series of chiral interphenylene 7-oxabicyclo[2.2.1]heptane semicarbazones 19-26 were prepared and evaluated for their in vitro thromboxane (TxA2) antagonistic activity and in vivo duration of action. The potency of 19-26 was found to highly dependent on the substitution pattern of the interphenylene ring and decreased in the order ortho greater than meta much greater than para. SQ 35,091 (25), [1S-(1 alpha,2 alpha,3 alpha,4 alpha)]-2-[[3-[[[(phenylamino) carbonyl]hydrazono]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]methyl] benzenepropanoic acid, was identified as a potent and long-acting TxA2 antagonist. In human platelet rich plasma SQ 35,091 inhibited arachidonic acid (800 microM) and U-46,619 (10 microM) induced aggregation with I50 values of 3 and 12 nM, respectively. In contrast, no inhibition of ADP (20 microM) induced aggregation was observed at greater than 1000 microM. Receptor binding studies with [3H]-SQ 29,548 showed SQ 35,091 was a competitive antagonist with a Kd value of 1.0 +/- 0.1 nM in human platelet membranes. In vivo SQ 35,091 (0.2 mg/kg po) showed extended protection (T50 = 16 h) from U-46,619 (2 mg/kg iv) induced death in mice. These compounds have for the first time demonstrated that a metabolically stable interphenylene alpha-sidechain can be introduced into a prostanoid-like series of TxA2 antagonists with the maintainance of potent antagonistic activity.

7-Oxabicyclo[2.2.1]heptyl carboxylic acids as thromboxane A2 antagonists: aza omega-chain analogues

A novel bicyclic prostaglandin analogue, [1S-[1 alpha, 2 alpha (Z), 3 alpha, 4 alpha]]-7-[3-[[[[(1- Oxoheptyl)amino]acetyl]amino]-methyl]-7-oxabicyclo[2.2.1]hept-2- yl]-5-heptenoic acid [-)-7) was found to be a potent and selective thromboxane A2 (TxA2) receptor antagonist. Unlike the related series of omega-chain allylic alcohols, amide 7 and its congeners were uniformly free of direct contractile activity in vitro (bovine coronary) and in vivo (anesthetized guinea pig). Amide 7 was effective in the inhibition of (a) arachidonic acid induced platelet aggregation of human platelet-rich plasma (I50 = 0.18 +/- 0.006 microM), (b) 11,9-epoxymethano-PGH2 induced platelet aggregation of human platelet-rich plasma (I50 = 0.24 microM), (c) 11,9-epoxymethano-PGH2 induced contraction of guinea pig trachea (Kb = 3.0 +/- 0.3 nM) or rat aorta (Kb = 8.8 +/- 1.1 nM), and (d) arachidonic acid induced bronchoconstriction in the anesthetized guinea pig (0.1-1.0 mg/kg iv). Amide 7 inhibited the binding of [5,6-3H2]-[1S- (1 alpha, 2 alpha (Z), 3 alpha, 4 alpha)]-7-[3-[[2-[(Phenyl- amino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5- heptenoic acid to human platelet membranes in a specific and saturable manner with a Kd = 49.6 +/- 1.4 nM.

9,11-epoxy-9-homoprosta-5-enoic acid analogues as thromboxane A2 receptor antagonists

A novel bicyclic prostaglandin analogue, (1S)-[1 alpha, 2 alpha(Z),3 alpha(1E,3S*,4R*),4 alpha]-7-[3-(3-hydroxy-4-phenyl-1-pentenyl)-7- oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (4), was found to be a potent and selective thromboxane A2 (TxA2) receptor antagonist. Alcohol 4 was the only member in a series of allylic alcohols which did not display direct contractile activity in the rat stomach strip model. Alcohol 4 was effective in the inhibition of (a) arachidonic acid induced platelet aggregation of human platelet-rich plasma (I50 = 0.65 +/- 0.1 microM); (b) 11,9-epoxymethano-PGH2 induced contraction of guinea pig trachea (pA2 = 8.0 +/- 0.2) or rat aorta (pA2 = 8.1 +/- 0.2); and (c) arachidonic acid induced bronchoconstriction in the anesthetized guinea pig (1 mg/kg iv). A radioiodinated analogue of 4 bound in a specific and saturable manner to human platelet membranes with a Kd = 2.3 +/- 0.9 nM. Modification of the alpha-chain, in an attempt to minimize in vivo metabolism, resulted in TxA2 receptor antagonists of reduced in vitro potency.

9,11-Epoxy-9-homo-14-thiaprost-5-enoic acid derivatives: potent thromboxane A2 antagonists

A novel bicyclic prostaglandin analogue, (1S)-[1 alpha,2 alpha(Z),3 alpha,4 alpha]-7-[3-[(hexylthio)methyl]-7- oxabicyclo [2.2.1]hept-2-yl]-5-heptenoic acid ((-)-10), and its cogeners were found to be potent antagonists at the TxA2 receptor. Compound (-)-10 was the only stereoisomer out of eight possible structures that was active. Thioether (-)-10 was 30-40-fold more potent than another TxA2 antagonist, BM 13.177, in inhibiting arachidonic acid (AA) induced aggregation of human platelet-rich plasma. Compound (-)-10 was effective (I50 = 0.5 +/- 0.4 microM) in inhibiting 9,11-azo-PGH2-induced (0.1 microgram/mL) contraction of guinea pig tracheal spirals. The bronchoconstriction in anesthetized guinea pigs induced by AA was also effectively antagonized by (-)-10 (1 mg/kg, iv); however, in this assay (-)-10 exhibited some direct agonist activity. Radioligand binding studies in washed (human) platelets revealed that (-)-10 is one of the most potent ligands for the PGH2/TxA2 receptor yet described (Kd = 1.6 +/- 0.4 nM).

Magnitude of thromboxane receptor antagonism necessary for antithrombotic activity in monkeys

SQ 30741 was characterized as a competitive antagonist of thromboxane receptor-mediated platelet activation in vitro that does not inhibit the activity of enzymes involved in prostaglandin, prostacyclin, and thromboxane biosynthesis. The threshold intravenous dose for antithrombotic activity was measured in anesthetized monkeys as the minimum amount of SQ 30741 required to inhibit thrombotic cyclic blood flow reductions in stenotic renal arteries. Platelet responsiveness was measured ex vivo before and during inhibition of thrombosis by the shape-change response to a thromboxane mimetic, U 46619. The threshold antithrombotic SQ 30741 dose (0.32 +/- 0.04 mg/kg; n = 5) was accompanied by an 8.5 +/- 1.1-fold shift to the right of the U 46619 concentration-effect curve, implying antagonism of 87 +/- 3% of platelet thromboxane receptors. The antithrombotic activity of SQ 30741 persisted for 109 +/- 10 min and was not reversed by indomethacin. However, in two out of seven monkeys SQ 30741 (7 mg/kg iv) did not interrupt the cyclical flow reductions. Vehicle treatment did not impede thrombosis and caused a 1.4 +/- 0.3-fold shift of the U 46619 concentration-effect curve (n = 4). In separate monkeys, SQ 30741 (0.33 mg/kg iv) produced identical dose ratios (8.6 +/- 0.7, n = 8) for inhibition of U 46619-induced mesenteric vasoconstriction. Thus the threshold antithrombotic dose of SQ 30741 caused the same magnitude of antagonism of platelet (ex vivo) and vascular (in vivo) thromboxane receptors.

Characterization of [5,6-3H]SQ 29,548 as a high affinity radioligand, binding to thromboxane A2/prostaglandin H2-receptors in human platelets

The binding of 5,6-3H(1S-[1 alpha, 2 beta(5Z), 3 beta, 4 alpha])-7-[3-([2-[(phenyl amino)carbonyl]hydrazino]methyl)-7-oxabicyclo[2.2.1]hept-2-yl]-5- heptenoic acid to receptors in human washed platelets (WP) and platelet membranes (PM) was characterized with regard to kinetics, saturability and competitive inhibition by putative thromboxane A2/prostaglandin H2 (TP)-receptor ligands. Specific binding of [3H]SQ 29,548 routinely amounted to 90 to 97% of total binding. The rate of association was 1.6 x 10(7) and 2.5 x 10(7) M-1 x min-1 in WP and PM, respectively. The corresponding rate of dissociation was 0.07 and 0.12 min-1, resulting in dissociation constants of 4.1 and 5.8 nM in WP and PM, respectively. Saturable binding to a single class of receptors indicated a receptor density of 2633 fmol/mg of protein in WP (1394 receptors/platelet; kd, 4.5 nM) and 1466 fmol/mg of protein in PM (kd, 11.3 nM). Specific binding of [3H]SQ 29,548 was inhibited by five antagonists (high/low affinity kd values in nanomolar), SQ 29,548 (WP, 5.2; PM, 7.3), SQ 28,668 (WP, 32; PM, 73), SQ 30,741 (WP, 28; PM, 50), BM 13,177 (WP, 140; PM, 4834) and BM 13,505 (WP, 5/379; PM, 11). Two agonists, U 44069 and U 46619, inhibited the binding in a biphasic manner, indicating binding to two receptor sites (approximately 20/80%) with kd values of 4/72 and 4/170 nM, respectively, in WP and 7/136 and 19/502 nM, respectively in PM. The demonstrated high affinity binding of [3H]SQ 29,548 to human platelet TP-receptors should make this radioligand a suitable and potentially useful tool in future studies of function, structure and regulation of TP-receptors.

Synthesis and pharmacological evaluation of 5,6-exo-epoxy-7-oxabicyclo[2.2.1]heptane derivatives

1 alpha,2 beta(5Z),3 beta(1E,3S),4 alpha,5 alpha,6 alpha]-7-[5,6-Epoxy-3- (3-cyclohexyl-3-hydroxy-3-methyl-1-propenyl)-7-oxabicyclo[2.2.1]-hept-2- yl]-5-heptenoic acid (31) and [1 alpha,2 beta(5Z),3 beta(1E,3S),4 alpha,5 alpha,6 alpha]-7-[5,6-epoxy-3-[3-hydroxy-5-(p-hydroxyphenyl)-1- pentenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (37) were found to be selective TxA2 antagonists at the platelet and pulmonary thromboxane receptors. An efficient stereospecific synthesis of these compounds and a series of structural analogues is described. Compounds 31 and 37 both inhibited the bronchoconstriction induced by arachidonic acid in the anesthetized guinea pig.

Effect of thromboxane receptor antagonists on renal artery thrombosis in the cynomolgus monkey

The effect of the thromboxane (Tx) A2-receptor antagonists SQ 28,668 and SQ 30,741 on platelet function and renal artery thrombosis was studied in the dialurethane-anesthetized cynomolgus monkey. Both antagonists competitively inhibited the aggregation of platelet rich plasma in vitro to arachidonic acid and U-46,619, a Tx-mimetic. SQ 30,741 was 4 to 7 times more potent than SQ 28,668 against either of these agonists. Thrombotic cyclical blood flow reductions (CFRs) were elicited by placing a critical stenosis at a crush injury site on the left renal artery. After allowing 10 consecutive CFRs, of which 95% required shaking of the vessel to restore flow, a single i.v. injection of either SQ 28,668 (1 mg/kg, n = 6), SQ 30,741 (1 mg/kg, n = 8) or vehicle (2 ml of 0.2% Na2CO3 + 10% ethanol, n = 4) was administered. Antithrombotic activity was defined as the spontaneous restoration of flow and was accompanied by a reduction in the rate of flow decline during the CFRs. Spontaneous flow restoration was observed in animals treated with SQ 28,668 (five of six) and SQ 30,741 (six of eight) but not vehicle (zero of four). The rate of flow decline was reduced only with SQ 28,668 (56 +/- 8%) and SQ 30,741 (53 +/- 10%) treatments. The antithrombotic activities of SQ 28,668 and SQ 30,741 lasted 68 +/- 6 and 224 +/- 21 min, respectively. The threshold antithrombotic dose was found to be lower for SQ 30,741 (0.20 +/- 0.03 mg/kg) than SQ 28,668 (0.61 +/- 0.09 mg/kg) in additional experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of captopril on sympathetic control of the heart and vasculature in dogs

Experiments were conducted in pentobarbital anesthetized dogs to investigate the effects of captopril on sympathetic neuronal control of the heart and hindlimb vasculature. Captopril, 3.1 mg/kg, i.v. produced marked reductions in blood pressure and hindlimb perfusion pressure, an observation consistent with the high plasma renin activity in the test animals. Increments in hindlimb perfusion pressure elicited by electrical stimulation of the lumbar sympathetic chain were also significantly reduced following captopril administration (p less than .002). The subsequent administration of a ten fold higher dose of captopril, 31.0 mg/kg, produced no further attenuation of the neurally mediated responses. In contrast to the decreased vascular responses to nerve stimulation after captopril, the tachycardia produced by stimulation of pre- or post-ganglionic neurons to the stellate ganglion were not altered. The results of the present study suggest that captopril acts by inhibiting vascular sympathetic neuronal function when the activity of the renin-angiotensin system is elevated. The attenuation of neurally mediated vasoconstriction may be due to the interruption of angiotensin II formation, thereby, preventing the facilitatory effects of angiotensin on sympathetic neurons.

9,11-Epoxy-9-homo-14-oxaprosta-5-enoic acid derivatives. Novel inhibitors of fatty acid cyclooxygenase

A novel bicyclic prostaglandin analogue, [1R-[l alpha,2 beta (5Z),3 beta,4 alpha]]-7-[3-[(hexyloxy)methyl]- 7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (1), and cogeners were found to be potent inhibitors of fatty acid cyclooxygenase. Compound 1 was the only stereoisomer out of eight possible structures that was active. Ether 1 was 20 times more potent than indomethacin (IND) in inhibiting arachidonic acid (AA) induced aggregation of human platelet-rich plasma. Compound 1 was also more potent than IND in several in vivo assays, AA-induced sudden death in the conscious mouse (2 times) and AA-induced bronchoconstriction in the anesthetized guinea pig (16-45 times).

Inhibition of prostaglandin biosynthesis by SQ 28,852, a 7-oxabicyclo[2.2.1]heptane analog

7-Oxabicyclo[2.2.1]heptane analogs of prostaglandin (PG) H2 can act as thromboxane (Tx) A2 receptor antagonists or agonists, PGI2 and/or PGD2 receptor agonists, or exhibit a mixture of the above activities. SQ 28,852, a new analog with a hexyloxymethyl omega side chain, is a potent inhibitor of PG synthesis. SQ 28,852 inhibited collagen and arachidonic acid (AA)-induced platelet aggregation and TxB2 and PGE2 formation, but did not block platelet aggregation induced by ADP or the TxA2 mimics, 9,11-azo PGH2, SQ 26,655, and U-46,619. It also blocked conversion of AA to TxB2, PGE2, and 6-keto PGF1 alpha by microsomal preparations of human platelets, bovine seminal vesicles, and bovine aortas, respectively, but did not inhibit the conversion of PGH2 to TxA2 by the platelet microsomal preparation. SQ 28,852 (p.o.) protected mice against the lethal effects of AA (75 mg/kg, i.v.). The I50 values for SQ 28,852, indomethacin and aspirin were 0.025, 0.05 and 15 mg/kg, respectively. Neither SQ 28,852 nor indomethacin protected mice from death caused by 9,11-azo PGH2. SQ 28,852 (0.01 to 1 mg/kg, i.v.) inhibited AA-induced bronchoconstriction in anesthetized guinea pigs for at least 60 min. As an inhibitor of AA-induced bronchoconstriction, SQ 28,852 was 16- and 45-times more potent than indomethacin at 3 and 60 min after i.v. administration, respectively. SQ 28,852 did not inhibit bronchoconstriction induced by histamine or 9,11-azo PGH2, indicating its specificity of action in vivo. SQ 28,852 is the first example of a new class of cyclooxygenase inhibitors whose structure is similar to that of the naturally occurring endoperoxide, PGH2.

Synthesis and in vitro pharmacology of 7-oxabicyclo[2.2.1]heptane analogues of thromboxane A2/PGH2

A series of chemically stable TXA2/PGH2 analogues modeled after the structure of the natural products was prepared in search of useful inhibitors of TXA2/PGH2-mediated pathophysiology. Each of the 16 isomers implied in structure 1 was prepared in chiral form and evaluated for activity in vitro in platelets and smooth muscle. Depending on relative side chain and carbinol stereochemistry, TXA2/PGH2 agonist and antagonist and, surprisingly, PGD2/PGI2 agonist activities were observed. The enantiomers possessing the alpha heterocycle shown in 1 were generally more potent than their mirror-image isomers.

Pharmacological actions of SQ 29,548, a novel selective thromboxane antagonist

SQ 29,548, [1S-[1 alpha,2 beta (5Z),3 beta,4 alpha]-7-[3-[[2-[(phenylamino) carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1] hept-2-yl]-5-heptenoic acid, and the racemic modification, +/- SQ 29,548, were identified as active inhibitors of human platelet aggregation induced by arachidonic acid, collagen, epinephrine (2 degrees phase) and the thromboxane A2 mimics, 9,11-azo prostaglandin (PG) H2 and 11,9-epoxymethano PGH2. SQ 29,548 did not inhibit aggregation induced by ADP, and it did not prevent PGD2 from inhibiting ADP-induced platelet aggregation. Inhibition of platelet function by +/- SQ 29,548 was not associated with inhibition of cyclooxygenase or thromboxane synthetase or with changes in platelet cyclic AMP. In guinea-pig trachea and rat aorta, +/- SQ 29,548 competitively antagonized the activity of 9,11-azo PGH2 with pA2 values of 7.8 and 8.4, respectively. The chiral compound, SQ 29,548 competitively antagonized contractions of guinea-pig tracheal spirals caused by 11,9-epoxymethano PGH2 with a pA2 value of 9.1. The +/- SQ 29,548 competitively antagonized tracheal responses to 11,9-epoxymethano PGH2 and PGD2 with pA2 values of 8.2 and 8.3, respectively, indicating that PGD2 and the thromboxane A2 mimic probably act at the same receptor in guinea-pig tracheal smooth muscle. Contractions of guinea-pig tracheal spirals induced by PGE2 were not antagonized, and those caused by PGF2 alpha were only partially antagonized by +/- SQ 29,548. The +/- SQ 29,548 also significantly inhibited the aorta contracting activity of 11,9-epoxymethano PGH2 (pA2 = 9.1) and thromboxane A2 released from perfused guinea-pig lungs upon arachidonic acid challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of SQ 27,427, a thromboxane A2 receptor antagonist, in the human platelet and isolated smooth muscle

The TxA2 receptor antagonist properties of SQ 27,427 [a cyclohexylcarbinol-7-oxabicyclo(2.2.1)heptenoic acid analog] were studied in vitro both in the human platelet and various isolated smooth muscle preparations. SQ 27,427 was found to be a potent inhibitor of human platelet aggregation induced by arachidonic acid, ADP, epinephrine, collagen and the stable TxA2 agonists 9,11-azoPGH2 and SQ 26,655. Inhibition of platelet aggregation was achieved at concentrations of SQ 27,427 which did not alter TxB2 levels. SQ 27,427 was found to weakly inhibit the formation of TxB2 from arachidonic acid and had no effect on the synthesis of PGE2 or PGI2 from arachidonic acid. SQ 27,427 was also found to be a weak stimulator of platelet adenylate cyclase, being 1000 times less potent than PGI2. In isolated smooth muscle experiments, SQ 27,427 was shown to be a potent and specific TxA2 receptor antagonist. It caused competitive antagonism of 9,11-azoPGH2-induced contractions of vascular, respiratory and gastrointestinal smooth muscles. This antagonism was specific, as responses to norepinephrine, serotonin, PGE2, PGI2, PGF2 alpha, histamine, carbachol and KCl were not altered by SQ 27,427.

Thromboxane receptor antagonist properties of SQ 27,427 in the anesthetized guinea pig

The TXA2 receptor antagonist properties of SQ 27,427 (a novel oxabicyclo[2.2.1]heptane derivative) were studied in vivo in the anesthetized guinea pig where changes in pulmonary resistance, dynamic compliance, and mean arterial blood pressure were measured. Both the bronchoconstrictor and pressor responses to arachidonic acid (AA) and to the stable TXA2 mimic 9,11-azoPGH2 (AZO) were taken as indices of in vivo TXA2 receptor activation. The administration of SQ 27,427 (0.1-1.0 mg/kg i.v., and 10.0 mg/kg p.o.) caused dose-related inhibitions of both AA- and AZO-induced bronchoconstriction. Relative specificity of this antagonism was evidenced by the failure of SQ 27,427 (1.0 mg/kg i.v.) to inhibit histamine-induced bronchoconstriction. In the same experiments the pressor response to AA was reversed to a depressor response by SQ 27,427. This reversal was abolished by indomethacin. The pressor response to AZO was antagonized by SQ 27,427, but not by indomethacin. The reversal of the pressor response to AA by SQ 27,427 may be due to the unmasking of the depressor effect of a cyclooxygenase product, i.e., prostacyclin. It is concluded that SQ 27,427 is a relatively specific TXA2 receptor antagonist in vivo in the guinea pig.