Combination atezolizumab, bevacizumab, pemetrexed and carboplatin for metastatic EGFR mutated NSCLC after TKI failure

INTRODUCTION

Acquired resistance to TKI is an important unmet need in the management of EGFR mutated lung cancer. Recent clinical trial IMPower150 suggested that combination approach with VEGF inhibitor, check point inhibitor immunotherapy and platinum-based chemotherapy was effective in oncogene driven lung cancer. The current trial examined the efficacy of a modified regimen in an EGFR mutated cohort.

METHODS

An open-labelled, single arm, phase II study was conducted in patients with EGFR mutated NSCLC who had progressed on at least one EGFR TKI. For those with T790M mutation, radiological progression on osimertinib was required for enrolment. Patients were treated with combination atezolizumab (1200 mg), bevacizumab (7.5 mg/kg), pemetrexed (500 mg/m2) and carboplatin (AUC 5) given once every 3 weeks until progression.

RESULTS

Forty patients were enrolled. Median age was 62 (range 45-76) years. More than one half (23/40, 57.5%) had progressed on osimertinib. PD-L1 expression was < 1% in 52.5%. Median follow-up time was 17.8 months. ORR was 62.5%. Median PFS was 9.4 months (95% CI: 7.6 - 12.1). One year OS was 72.5% (95% CI: 0.56-0.83). Treatment related grade 3 or above adverse events (AE) occurred in 37.5% (15/40). Immune-related AE occurred in 32.5% (13/40) patients. Quality of life measures of function and symptoms did not change significantly throughout the course of treatments. Post-trial rechallenge with EGFR TKI containing regimen resulted in PFS of 5.8 months (95% CI 3.9-10.0 months).

CONCLUSION

Combination approach of atezolizumab, bevacizumab, pemetrexed and carboplatin achieved promising efficacy in metastatic EGFR mutated NSCLC after TKI failure. The results were comparable with taxane based regimen of IMPower150 while toxicity profile was improved.

Lung disease severity in idiopathic pulmonary fibrosis is more strongly associated with impedance measures of bolus reflux than pH parameters of acid reflux alone

BACKGROUND

Gastroesophageal reflux (GER) has been associated with idiopathic pulmonary fibrosis (IPF). Pathogenesis may be related to chronic micro-aspiration. We aimed to assess objective measures of GER on multichannel intraluminal impedance and pH study (MII-pH) and their relationship with pulmonary function testing (PFT) results, and to compare the performance of pH/acid reflux parameters vs corresponding MII/bolus parameters in predicting pulmonary dysfunction in IPF.

METHODS

This was a retrospective cohort study of IPF patients undergoing prelung transplant evaluation with MII-pH off acid suppression, and having received PFT within 3 months. Patients with prior fundoplication were excluded. Severe pulmonary dysfunction was defined using diffusion capacity of the lung for carbon monoxide (DLCO) ≤40%. Six pH/acid reflux parameters with corresponding MII/bolus reflux measures were specified a priori. Multivariate analyses were applied using forward stepwise logistic regression. Predictive value of each parameter for severe pulmonary dysfunction was calculated by area-under-the-receiver-operating-characteristic-curve or c-statistic.

KEY RESULTS

Forty-five subjects (67% M, age 59, 15 mild-moderate vs 30 severe) met criteria for inclusion. Patient demographics and clinical characteristics were similar between pulmonary dysfunction groups. Abnormal total reflux episodes and prolonged bolus clearance time were significantly associated with pulmonary dysfunction severity on univariate and multivariate analyses. No pH parameters were significant. The c-statistic of each pH parameter was lower than its MII counterpart in predicting pulmonary dysfunction.

CONCLUSIONS & INFERENCES

MII/bolus reflux, but not pH/acid reflux, was associated with pulmonary dysfunction in prelung transplant patients with IPF. MII-pH may be more valuable than pH testing alone in characterizing GER in IPF.

Increased proximal acid reflux is associated with early readmission following lung transplantation

BACKGROUND

Gastroesophageal reflux disease has been associated with poor outcomes following lung transplantation. However, the association between pretransplant reflux and post-transplant readmission, an indicator of early clinical outcome, has not been previously assessed.

METHODS

This was a retrospective cohort study of lung transplant recipients undergoing pretransplant multichannel intraluminal impedance and pH (MII-pH) study off acid suppression at a tertiary care center since 2007. Subjects with pretransplant fundoplication were excluded. Time to readmission was defined as duration from post-transplant discharge to next hospital admission for any reason. Subgroup analysis was performed to exclude elective readmissions. Time-to-event analysis was performed using Cox proportional hazards model, with appropriate censoring.

KEY RESULTS

Forty-three subjects (60% men, mean age: 57, median follow-up: 1.7 years) met inclusion criteria for the study. Patient demographics and pretransplant cardiopulmonary function were similar between readmission cohorts. Time to all-cause readmission was associated with increased distal acid episodes (HR: 3.15, p = 0.04) and proximal acid episodes (HR: 3.61, p = 0.008) on impedance, increased acid exposure on pH (HR: 2.22, p = 0.04), and elevated Demeester score (HR: 2.26, p = 0.03). When elective readmissions were excluded, early readmission remained significantly associated with increased proximal acid reflux episodes (HR: 2.49, p = 0.04). All findings were confirmed on Kaplan-Meier analysis.

CONCLUSIONS & INFERENCES

Elevated proximal acid reflux on pretransplant MII-pH testing was associated with early readmission following lung transplantation, even after excluding elective readmissions. Exposure to severe acid reflux has measurable effects on early postoperative outcomes such as readmission, and aggressive early antireflux therapy should be considered.

Idiopathic pulmonary fibrosis is associated with increased impedance measures of reflux compared to non-fibrotic disease among pre-lung transplant patients

BACKGROUND

Gastroesophageal reflux (GER) has been associated with idiopathic pulmonary fibrosis (IPF), although the mechanism remains unclear. Gastroesophageal reflux/microaspiration may lead to lung fibrosis, while increased pulmonary workload may also worsen GER. Comparing the GER profile of IPF patients to chronic obstructive pulmonary disease (COPD) patients with similar lung function may help delineate the role of GER in IPF pathogenesis.

METHODS

This was a retrospective cohort study of IPF and COPD patients undergoing pre-lung transplant multichannel intraluminal impedance and pH study (MII-pH) off acid suppression at a tertiary center in 2008-2014. Patients with prior fundoplication were excluded. Baseline demographics, pulmonary function test, and MII-pH results were recorded. Univariate analyses were performed using Fisher's exact (binary variables) and Student's t (continuous variables) tests. Logistic regression was performed to adjust for potential confounders.

KEY RESULTS

A total of 90 subjects (54 IPF, 36 COPD) met inclusion criteria. Compared to COPD, IPF patients had increased total reflux episodes (65.9 vs 46.1, p = 0.02), proximal reflux episodes (30.3 vs 20.3, p = 0.04), and prevalence of abnormal total reflux episodes (38.9% vs 16.7%, p = 0.02). On multivariate analyses, abnormal total reflux episodes (OR: 4.9, p = 0.05) and bolus reflux exposure time (OR: 4, p = 0.04) remained significantly associated with IPF.

CONCLUSIONS & INFERENCES

Abnormal reflux was significantly more prevalent among IPF patients after controlling for lung disease severity. Gastroesophageal reflux/microaspiration likely plays a role in fibrosis in IPF. A significant portion of IPF patients had increased non-acid reflux. Therapies aiming to prevent reflux of gastric contents may be more beneficial than antisecretory medications alone in these patients.

Idiopathic pulmonary fibrosis is associated with increased impedance measures of reflux compared to non-fibrotic disease among pre-lung transplant patients

BACKGROUND

Gastroesophageal reflux (GER) has been associated with idiopathic pulmonary fibrosis (IPF), although the mechanism remains unclear. Gastroesophageal reflux/microaspiration may lead to lung fibrosis, while increased pulmonary workload may also worsen GER. Comparing the GER profile of IPF patients to chronic obstructive pulmonary disease (COPD) patients with similar lung function may help delineate the role of GER in IPF pathogenesis.

METHODS

This was a retrospective cohort study of IPF and COPD patients undergoing pre-lung transplant multichannel intraluminal impedance and pH study (MII-pH) off acid suppression at a tertiary center in 2008-2014. Patients with prior fundoplication were excluded. Baseline demographics, pulmonary function test, and MII-pH results were recorded. Univariate analyses were performed using Fisher's exact (binary variables) and Student's t (continuous variables) tests. Logistic regression was performed to adjust for potential confounders.

KEY RESULTS

A total of 90 subjects (54 IPF, 36 COPD) met inclusion criteria. Compared to COPD, IPF patients had increased total reflux episodes (65.9 vs 46.1, p = 0.02), proximal reflux episodes (30.3 vs 20.3, p = 0.04), and prevalence of abnormal total reflux episodes (38.9% vs 16.7%, p = 0.02). On multivariate analyses, abnormal total reflux episodes (OR: 4.9, p = 0.05) and bolus reflux exposure time (OR: 4, p = 0.04) remained significantly associated with IPF.

CONCLUSIONS & INFERENCES

Abnormal reflux was significantly more prevalent among IPF patients after controlling for lung disease severity. Gastroesophageal reflux/microaspiration likely plays a role in fibrosis in IPF. A significant portion of IPF patients had increased non-acid reflux. Therapies aiming to prevent reflux of gastric contents may be more beneficial than antisecretory medications alone in these patients.

How we identify and count Aboriginal people--does it make a difference in estimating their disease burden?

INTRODUCTION

We examined the concordance between the Canadian Community Health Survey (CCHS) "identity" and "ancestry" questions used to estimate the size of the Aboriginal population in Canada and whether the different definitions affect the prevalence of selected chronic diseases.

METHODS

Based on responses to the "identity" and "ancestry" questions in the CCHS combined 2009-2010 microdata file, Aboriginal participants were divided into 4 groups: (A) identity only; (B) ancestry only; (C) either ancestry or identity; and (D) both ancestry and identity. Prevalence of diabetes, arthritis and hypertension was estimated based on participants reporting that a health professional had told them that they have the condition(s).

RESULTS

Of participants who identified themselves as Aboriginal, only 63% reported having an Aboriginal ancestor; of those who claimed Aboriginal ancestry, only 57% identified themselves as Aboriginal. The lack of concordance also differs according to whether the individual was First Nation, Métis or Inuit. The different method of estimating the Aboriginal population, however, does not significantly affect the prevalence of the three selected chronic diseases.

CONCLUSION

The lack of concordance requires further investigation by combining more cycles of CCHS to compare discrepancy across regions, genders and socio-economic status. Its impact on a broader list of health conditions should be examined.

Incidence of diabetes among postmenopausal breast cancer survivors

AIMS/HYPOTHESIS

Evidence is emerging of an association between breast cancer and diabetes; however, it is uncertain whether diabetes incidence is increased in postmenopausal breast cancer survivors compared with women without breast cancer. The objective of this study was to determine whether postmenopausal women who develop breast cancer have a higher incidence of diabetes than those who do not develop breast cancer.

METHODS

We used population-based data from Ontario, Canada to compare the incidence of diabetes among women with breast cancer, aged 55 years or older, from 1996 to 2008, with that of age-matched women without breast cancer. We used Cox proportional hazard models to estimate the effect of breast cancer on the cause-specific hazard of developing diabetes overall and in the subgroup of women who received adjuvant chemotherapy.

RESULTS

Of 24,976 breast cancer survivors and 124,880 controls, 9.7% developed diabetes over a mean follow-up of 5.8 years. The risk of diabetes among breast cancer survivors compared with women without breast cancer began to increase 2 years after diagnosis (HR 1.07 [95% CI, 1.02, 1.12]), and rose to an HR of 1.21 (95% CI, 1.09, 1.35) after 10 years. Among those who received adjuvant chemotherapy (n = 4,404), risk was highest in the first 2 years after diagnosis (HR 1.24 [95% CI 1.12, 1.38]) and then declined.

CONCLUSIONS/INTERPRETATION

We found a modest increase in the incidence of diabetes among postmenopausal breast cancer survivors that varied over time. In most women the risk began to increase 2 years after cancer diagnosis but the highest risk was in the first 2 years in those who received adjuvant therapy. Our study suggests that greater diabetes screening and prevention strategies among breast cancer survivors may be warranted.

Mycobacterium heckeshornense peritonitis in a peritoneal dialysis patient: a case report and review of the literature

We report the first case of peritonitis attributed to Mycobacterium heckeshornense. This is a rare, non-tuberculous mycobacterium that has been reported as an aetiological agent in a growing number and widening spectrum of infections.

Bisphosphonates and osteoporotic fractures: a cross-design synthesis of results among compliant/persistent postmenopausal women in clinical practice versus randomized controlled trials

In a cross-design synthesis, total fractures were similarly reduced by bisphosphonates among postmenopausal women in randomized trials (23.8%) and highly compliant/persistent patients in observational studies of large databases from routine practice (20.3%). Bisphosphonates also reduced nonvertebral, vertebral and hip fractures in randomized trials and observational studies. In the real-word setting, compliant/persistent patients can gain a benefit from bisphosphonates comparable to that of randomized trial participants.

INTRODUCTION

The purpose of the study was to determine whether clinical fracture risk reduction by bisphosphonate treatment in women with postmenopausal osteoporosis differs between randomized controlled trials and routine practice.

METHODS

Randomized trials comparing bisphosphonate with placebo and observational studies comparing highly compliant/persistent with less compliant/persistent patients were sought by electronic searches and ancillary methods. Clinical fracture data were extracted from the study reports and quantitatively combined by random effects metaanalysis.

RESULTS

The odds ratio (OR) for all clinical fractures in randomized trials of 0.762, with a 95% confidence interval (CI) of 0.680-0.855, was closely similar to that in the observational studies (OR, 0.797; CI, 0.748-0.850). Pooled clinical fracture reduction across both study designs was 22%. Nonvertebral, vertebral, and hip fractures were also significantly reduced by bisphosphonate treatment in both randomized trials and observational studies.

CONCLUSIONS

Compliant/persistent patients in the "real-world" setting benefit from bisphosphonate treatment to a similar extent as patients in randomized trials.

Penetrating head injury caused by a dart

In paediatric practice, head injury is a major public health hazard that places considerable demand on health services. It accounts for almost one third of all accidental deaths and for up to two thirds of all trauma deaths in hospital. Common house-hold objects are at times a source of penetrating head injuries in children. These include electric plugs, golf clubs, toys, nails, etc. Fortunately less than 10% of these eventually lead to permanent brain injury. We report a rare case of penetrating head injury caused by a dart.

Clinical outcomes of 203 adult patients receiving highly (H) and moderately (M) emetogenic (E) chemotherapy (C) following an institutional antiemetic guideline update incorporating aprepitant (A) and palonosetron (P)

19506

Background: A quality improvement project targeted at chemotherapy induced nausea (N) and vomiting (V) was initiated in 2004. The project included an antiemetic guideline update consisting of replacing ASCO 1998 3 tier guidelines with a 4 tier system similar to ASCO 2006. Following implementation of the guidelines an evaluation phase began. Methods: Adult chemotherapy-naïve patients receiving HEC or MEC were asked to participate. HEC patients received P 250 mcg IV each day of chemotherapy, A 125 mg PO day 1 and 80 mg PO days 2 and 3 and dexamethasone (D) 12 mg PO days 1, 2 and 3. MEC patients received P 250 mcg IV and D 12 mg PO on the day of C. Participating patients were asked to complete a 7 question NV tool at least 5 days following C to report on the 5 days following C. Outcomes reported include % of patients without N, % without V and N score using a 0–10 visual analog scale (VAS). Patient satisfaction with the the control of N and V was also assessed using a 0–10 VAS. Results: A total of 151 patients received HEC and 89% and 44% were protected from V and N respectively. A total of 52 patients received MEC and 90% and 56% were protected from V and N respectively The median N score for all patients who reported nausea was 3. The median and mean score for satisfaction with N and V control was 10 and 8.7 respectively. Patient outcomes for the most commonly used C regimens are reported in the table below. Conclusion: Implementation of revised AEG provided patients receiving HEC and MEC a high level of protection from vomiting, low nausea scores and a high level of overall satisfaction with prevention of N and V. Although N scores were low, the incidence of N reported offers an opportunity for further improvement.

[Table: see text]

No significant financial relationships to disclose.

Acupuncture for general veterinary practice

Since the International Society of Veterinary Acupuncture (IVAS) was founded in 1974, acupuncture (AP) has received greater acceptance by veterinary professionals throughout the world. This article introduces some important animal diseases that respond well to AP therapy. These include resuscitation of small animals, treatment of anoestrous gilts and sows, bovine reproductive disease, canine vertebral problems and equine backpain, etc. Conventional medicine considers these to be difficult cases to treat. Veterinarians have become more aware of the benefits of AP especially for those diseases, thanks to the efforts of experienced practitioners and scientists, and the many published reports on veterinary AP that have introduced some good indications for AP therapy in veterinary practice. Possible mechanisms behind the effectiveness of AP are discussed. This article aims to introduce veterinarians to good indications for AP to initiate their interest in the practice of AP. Although this is a rapidly expanding field, a long march must begin with one step. We wish this article to be the shoes for such a march. For more information on veterinary AP, contact IVAS <ivasoffice@aol.com>, P.O. Box 1478, Longmont, CO.. 80502, USA (http://www.ivas.org), or your national veterinary acupuncture society (http://www.komvet.at/ ivadkom/vapsocs.htm).

High-level expression and mutagenesis of recombinant human phosphatidylcholine transfer protein using a synthetic gene: evidence for a C-terminal membrane binding domain

Phosphatidylcholine transfer protein (PC-TP) is a 214-amino acid cytosolic protein that promotes intermembrane transfer of phosphatidylcholines, but no other phospholipid class. To probe mechanisms for membrane interactions and phosphatidylcholine binding, we expressed recombinant human PC-TP in Escherichia coli using a synthetic gene. Optimization of codon usage for bacterial protein translation increased expression of PC-TP from trace levels to >10% of the E. coli cytosolic protein mass. On the basis of secondary structure predictions of an amphipathic alpha-helix (residues 198-212) in proximity to a hydrophobic alpha-helix (residues 184-193), we explored whether the C-terminus might interact with membranes and promote binding of phosphatidylcholines. Consistent with this possibility, truncation of five residues from the C-terminus shortened the predicted amphipathic alpha-helix and decreased PC-TP activity by 50%, whereas removal of 10 residues eliminated the alpha-helix, abolished activity, and markedly decreased the level of membrane binding. Circular dichroic spectra of synthetic peptides containing one ((196-214)PC-TP) or both ((183-214)PC-TP) predicted C-terminal alpha-helices in aqueous buffer were most consistent with random coil structures. However, both peptides adopted alpha-helical configurations in the presence of trifluoroethanol or phosphatidylcholine/phosphatidylserine small unilamellar vesicles. The helical content of (196-214)PC-TP increased in proportion to vesicle phosphatidylserine content, consistent with stabilization of the alpha-helix at the membrane surface. In contrast, the helical content of (183-214)PC-TP was not influenced by vesicle composition, implying that the more hydrophobic of the alpha-helices penetrated into the membrane bilayer. These studies suggest that tandem alpha-helices located near the C-terminus of PC-TP facilitate membrane binding and extraction of phosphatidylcholines.

Modeling directed design and biological evaluation of quinazolinones as non-peptidic growth hormone secretagogues

Quinazolinone derivatives were synthesized and evaluated as non-peptidic growth hormone secretagogues. Modeling guided design of quinazolinone compound 21 led to a potency enhancement of greater than 200-fold compared to human growth hormone secretagogue affinity of a screening lead 4.

Acyclic structural variants of growth hormone secretagogue L-692,429

Systematic investigation of acyclic analogs of L-692,429, the prototype benzolactam growth hormone secretagogue, has helped to further define the structural requirements for the release of growth hormone from rat pituitary cells for this class of secretagogues.

Nonpeptidyl somatostatin agonists demonstrate that sst2 and sst5 inhibit stimulated growth hormone secretion from rat anterior pituitary cells

Somatostatin (SST) regulates growth hormone (GH) secretion from pituitary somatotrophs by interacting with members of the SST family of G-protein-coupled receptors (sst1-5). We have used potent, nonpeptidyl SST agonists with sst2 and sst5 selectivity to determine whether these receptor subtypes are involved in regulating growth hormone releasing hormone (GHRH) stimulated secretion. GHRH stimulated GH release from pituitary cells in a dose-dependent manner, and this secretion was inhibited by Tyr(11)-SST-14, a nonselective SST analog. A sst2 selective agonist, L-779,976, potently inhibited GHRH-stimulated GH release. In addition, L-817, 818, a potent sst5 receptor selective agonist, also inhibited GH secretion, but was approximately 10-fold less potent (P < 0.01, ANOVA) in inhibiting GH release than either Tyr(11)-SST-14 or L-779, 976. These results show that both sst2 and sst5 receptor subtypes regulate GHRH-stimulated GH release from rat pituitary cells.

Synthesis and biological activities of spiroheterocyclic growth hormone secretagogues

The synthesis and biological activities of a series of spiroheterocyclic growth hormone secretagogues are reported. Modification of the spiroindane part-structure of the prototypal secretagogue L-162,752 revealed that the spiroindane could be replaced with spirobenzodihydrothiophen derivatives to enhance not only in vitro potency but also oral activity. In this study non-aromatic D-2-amino-4-cyclohexylbutanoic analogs (8a-8d) were also identified to be active secretagogues.

Rapid identification of subtype-selective agonists of the somatostatin receptor through combinatorial chemistry

Nonpeptide agonists of each of the five somatostatin receptors were identified in combinatorial libraries constructed on the basis of molecular modeling of known peptide agonists. In vitro experiments using these selective compounds demonstrated the role of the somatostatin subtype-2 receptor in inhibition of glucagon release from mouse pancreatic alpha cells and the somatostatin subtype-5 receptor as a mediator of insulin secretion from pancreatic beta cells. Both receptors regulated growth hormone release from the rat anterior pituitary gland. The availability of high-affinity, subtype-selective agonists for each of the somatostatin receptors provides a direct approach to defining their physiological functions.

Synthesis and biological activities of phenyl piperazine-based peptidomimetic growth hormone secretagogues

A new class of potent, orally active phenyl piperazine-based GH secretagogues have been discovered from attempts to mimic the arrangement of the phenyl substituent in the spiroindanyl piperidine and spiroindoline sulfonamide privileged structures of 4 and 1, respectively. The best of these compounds, 18 (EC50 = 2.8 nM) is nearly as potent as MK-0677 for releasing GH from rat pituitary cells.

Comparison of substance P concentration in acupuncture points in different tissues in dogs

Histologically, acupuncture points show neuronal innervation. One hundred seventy-seven tissue samples of acupuncture points and control points from 4 dogs were collected. Concentrations of substance P, a neurotransmitter, in the skin, muscle and subcutis of acupuncture points and control points were measured by means of enzyme immunoassay. The determined tissue concentrations of substance P (mean +/- SEM) in acupuncture points and control points were 1.81 +/- 0.13 and 1.51 +/- 0.1 ng/g in the muscle, 3.33 +/- 0.29 and 2.63 +/- 0.28 ng/g in the skin and 1.59 +/- 0.22 and 1.32 +/- 0.16 ng/g in the subcutis, respectively. The results indicate that there is a difference in the neurochemical profile between acupuncture points and control points.

A potent, orally bioavailable benzazepinone growth hormone secretagogue

The identification of L-739,943 (8b), a potent, orally bioavailable benzolactam growth hormone secretagogue, is obtained from zwitterionic L-692,429 through modification of its amino acid side chain and replacement of the acidic 2'-tetrazole with the neutral and potency enhancing 2'-(N-methylaminocarbonylamino)methyl substituent. L-739,943 is orally active for the release of growth hormone in beagle dogs at doses as low as 0.5 mg/kg. Oral bioavailability in dogs of 8b is 24% at a dose of 2 mg/kg with a mean drug Cmax of 145 +/- 46 ng/mL. L-739,943 represents a significant breakthrough in terms of both potency and oral bioavailability as compared to the prototype benzolactam L-692,429.

Tripeptide growth hormone secretagogues

A series of C-terminus capped dipeptides and tripeptides was synthesized as growth hormone (GH) secretagogues. Among them, tripeptide Aib-D-Trp-D-homoPhe-OEt showed low nanomolar activity in the rat pituitary assay. Thus, we have demonstrated that the GH secretagogue activity of the hexa-hepta-GH releasing peptides can be mimicked at the tripeptide level.

Potent 3-spiropiperidine growth hormone secretagogues

Systematic SAR studies of the different regioisomers and homologues of the spiro(indane-1,4-piperidine) moiety in the growth hormone secretagogue L-162,752 are presented. Among them, spiro(3H-1-benzopyran-2,3-piperidine) was found to afford secretagogues with low nanomolar in vitro activity.

Imaging performance of the liquid-crystal-adaptive lens with conductive ladder meshing

The liquid-crystal-adaptive lens (LCAL) is an electro-optical device that utilizes a graded index of refraction to bring light to focus. A set of electrodes controls the index variation in a liquid-crystal thin film. One can vary the focal length of the LCAL by changing the voltages applied to the device. The discrete nature of the electrodes causes phase aberrations. We introduce a novel electrode architecture, called conductive ladder meshing (CLM), that we developed to greatly reduce the static phase aberration (caused by the electrode structure). To reduce the dynamic phase aberration (associated with inaccurate voltages), we used a simulated-annealing voltage-dithering technique. The coherent transfer function of the LCAL was derived so that the performance of the CLM LCAL could be predicted theoretically. Theoretical analysis indicates that the CLM LCAL scatters less than 30% of incident light compared with scattering of 65% in the previous version. The focal-spot performance of the spherical LCAL was measured under coherent illumination for plane-wave illumination. Because of the improved quality of the spherical LCAL, true imaging experiments are demonstrated for a single incoming polarization under white-light illumination. Images formed by the spherical LCAL are comparable with those formed by a fixed lens in terms of resolution, although the contrast is worse.

Gem-dialkyl succinic acids: a novel class of inhibitors for carboxypeptidases

gem-Dimethylsuccinic acid and its higher homolog, 2-methyl-2-ethylsuccinic acid (MESA) are highly potent inhibitors of both carboxypeptidase A (CPA) and B. The inhibition constant of MESA for CPA (0.11 microM for the racemic mixture) is remarkable considering the relatively simple structure of the compound. The molecular feature which is crucial for high affinity binding to both carboxypeptidases appears to be the nonpolar gem-dialkyl locus. The structure of the complex between MESA and CPA has been determined by X-ray crystallography to 2.0 A resolution and shows the R enantiomer of the inhibitor to be bound in a generally substrate-like manner. The carboxymethyl group is coordinated to the Zn ion in the active site, and the gem-dialkyl locus corresponds in position to the alpha-carbon of the C-terminal amino acid in a peptide substrate. The methyl group of the inhibitor occupies a cavity in the enzyme which is apparently not filled upon substrate-binding. We postulate that this cavity (the alpha-methyl hole) is designed to allow the proximal Glu-270 residue to undergo a critical movement during catalysis. The hydrophobic nature of the above cavity may play a role in modulating the reactivity of this residue. These results suggest that similar cenophilic(empty-loving) inhibitors may be found for other enzymes.

Transoesophageal echocardiography

Transoesophageal echocardiography gives unparalleled views of the posterior structures of the heart. It is the investigation of choice for the diagnosis of acute dissection of the aorta, in patients with endocarditis, management of the hypotensive patient in the intensive care unit, and in the search for a potential cardiac source of thromboembolism. However, it is a semi-invasive procedure, and proper training is required to carry it out safely, to ensure that maximum information is obtained at the time of examination, and to avoid diagnostic pitfalls.

Inhibition of L-692,429-stimulated rat growth hormone release by a weak substance P antagonist: L-756,867

H2N,D-Arg,Pro,Lys,Pro,D-Phe,Gln,D-Trp,Phe,D-Trp,Leu, Leu,NH2 (L-756,867), a weak substance P antagonist, inhibited L-692,429-stimulated GH release from rat primary pituitary cells in a dose-dependent manner. At a concentration of 50 nM, L-756,867 shifted the dose-response curve of L-692,429-induced GH release to the right by about tenfold. It also impaired the ability of L-692,429 to potentiate the effect of growth hormone-releasing factor (GRF) on GH release. Substance P (1 microM) had no effect on basal or L-692,429-stimulated GH release. When tested in anesthetized rats, L-756,867 inhibited L-692,429- and growth hormone-releasing hexapeptide- (GHRP-6)-stimulated GH secretion in a dose-dependent manner. Complete inhibition was observed at an i.v. dose of 100 micrograms/kg of L-756,867. However, at the same concentration, it had no effect on GRF-induced GH secretion D-Lys3-GHRP-6, a GHRP-6 antagonist, had no effect on GHRP-6 or L-692,429-induced GH secretion even at an i.v. dose of 2 mg/kg. These results indicate that L-692,429 and GHRP-6 stimulate GH release both in vitro and in vivo via a common receptor and signaling pathway which is different from that of substance P in spite of the fact that their effects are inhibited by a weak substance P antagonist.

Analysis of the interactions between an enzyme and multiple inhibitors using combination plots

The concurrent effects of two enzyme inhibitors have been analysed previously with the Yonetani-Theorell plot to obtain insight into the interactions between bound inhibitors. This procedure, like many other traditional graphical methods in enzymology, is based on the estimation of intersecting tendencies in a family of lines. In a recent paper from this laboratory [Chan (1995) Biochem. J. 311, 981-985] it was shown that a plot of this nature may sometimes be replaced, with advantage, by a 'combination plot' in which all data points are accommodated in a single line. We have now extended this approach to analyse the effects of multiple inhibitors and have developed combination plots which illustrate the interaction behaviour in an optimal manner. Thus, in these plots, the synergistic or antagonistic nature of the interactions is clearly evident from the slope, which also provides a direct estimate of the interaction coefficient. The analysis is more efficient and consequently requires fewer enzyme assays. This approach is applicable to various special cases, including that in which three inhibitors bind simultaneously to the enzyme.

Characteristics of fetal heart rate changes during the expulsive stage of bovine parturition in relation to fetal outcome

OBJECTIVE

To characterize fetal heart rate (FHR) patterns of nonacidotic (N-AC) and acidotic (AC) calves during the expulsive stage of parturition.

ANIMALS

32 calves born to heifers, either unassisted or by moderate traction.

PROCEDURE

Cardiotocograms (CTG) evaluated qualitatively (visual) and quantitatively by a moving window technique (width 10, shift 5 minutes) for baseline FHR, variability, and periodic alterations (accelerations and decelerations).

RESULTS

Significant differences were apparent between increase in baseline FHR of N-AC and AC calves; change in FHR (delta-FHR), taking into account individual FHR, is a more discriminating parameter. The predominant reaction to uterine contraction is a decrease in FHR; variable decelerations were the most common type in both groups, and late decelerations were seen only in AC calves. Additional characteristics of variable decelerations were more frequently seen in AC calves.

CONCLUSIONS

CTG parameters during expulsion can discriminate between AC and N-AC calves, but specific characteristics are not exclusively restricted to AC or N-AC calves.

CLINICAL RELEVANCE

CTG recordings during bovine parturition in cattle provide information on the fetal condition and can be used in the future to study the effects of medication and manipulations to the fetus.

Requirement of lysine residues outside of the proposed pentasaccharide binding region for high affinity heparin binding and activation of human antithrombin III

Variant forms of human antithrombin III with glutamine or threonine substitutions at Lys114, Lys125, Lys133, Lys136, and Lys139 were expressed in insect cells to evaluate their roles in heparin binding and activation. Recombinant native ATIII and all of the variants had very similar second order rate constants for thrombin inhibition in the absence of heparin, ranging from 1.13 x 10(5) M-1min-1 to 1.66 x 10(5) M-1min-1. Direct binding studies using 125I-flouresceinamine-heparin yielded a Kd of 6 nM for the recombinant native ATIII and K136T, whereas K114Q and K139Q bound heparin so poorly that a Kd could not be determined. K125Q had a moderately reduced affinity. Heparin binding affinity correlated directly with heparin cofactor activity. Recombinant native ATIII was nearly identical to plasma-purified ATIII, whereas K114Q and K139Q were severely impaired in heparin cofactor activity. K125Q and K136T were only slightly impaired. Based on these data, Lys114 and Lys139, which are outside of the putative pentasaccharide binding site, play pivotal roles in the high affinity binding of heparin to ATIII and the activation of thrombin inhibitory activity.

The effect of transcutaneous electrical nerve stimulation on coronary and systemic haemodynamics in syndrome X

BACKGROUND

Neurostimulation techniques have been shown to be beneficial in patients with angina and syndrome X but the mechanism remains unclear. We examined the effect of transcutaneous electrical nerve stimulation (TENS) on coronary artery blood flow in a group of patients with syndrome X.

METHODS

Coronary blood flows were measured in 11 patients with angiographically normal coronary arteries, positive results from exercise tests and angina (syndrome X) using intracoronary Doppler catheters combined with quantitative coronary angiography.

RESULTS

The mean coronary flow velocity did not increase in any patient during TENS therapy; in fact, there was a fall from 5.2 +/- 2.8 to 4.3 +/- 1.9 cm/s (P = 0.02) and the coronary blood flow index fell from 47 +/- 22 to 38 +/- 16 cm/s per mm2 (P = 0.007). This was associated with a fall in the rate x pressure product from 0.92 +/- 0.22 to 0.83 +/- 0.18 mmHg/min (P = 0.038). The coronary vascular resistance rose from 2.4 +/- 1.1 to 3.0 +/- 1.6 mmHg/cm per s per mm2 (P = 0.041). There were no major changes in the epicardial coronary artery diameter during TENS and there was no significant effect on the response to the cold-pressor test.

CONCLUSIONS

In this group of patients with syndrome X, TENS produced a small but significant fall in coronary artery blood flow associated with a reduction in the rate x pressure product. TENS had no significant effect on coronary vasomotion during sympathetic stimulation by the cold-pressor test. Thus, TENS is unlikely to have a direct effect on coronary artery vasomotion or haemodynamics in syndrome X but reduces the rate x pressure product and thus myocardial oxygen consumption.

Synergistic binding of inhibitors to the protease from HIV type 1

Inhibition of the protease in HIV is a potentially useful approach for the treatment of AIDS. In the course of evaluating inhibitors of the HIV-1 protease, we observed a strong synergism between certain inhibitors that might be expected to bind to different sites in this enzyme. The binding affinity of carbobenzyloxyisoleucinylphenylalaninol, for example, is increased 125-fold in the presence of carbobenzyloxyglutaminylisoamylamide. These synergistic effects between inhibitors have specific structural requirements that correlate well with the known substrate preference of the enzyme. The modular basis for this phenomenon remains to be elucidated but it could involve substrate-induced conformational change as part of the reaction mechanism. Similar effects have been reported previously for several zinc proteases. Thus this work extends the observation to a different class of enzymes and suggests that the phenomenon might be widespread.

Effect of low dose beta blockers on atrial and ventricular (B type) natriuretic factor in heart failure: a double blind, randomised comparison of metoprolol and a third generation vasodilating beta blocker

OBJECTIVES

This study examines the acute effects of two differing beta adrenergic blocking agents (metoprolol and a third generation vasodilating beta blocker) on plasma concentrations of atrial natriuretic factor (ANF), brain (ventricular) natriuretic factor (BNF), and haemodynamic variables in patients with heart failure.

SETTING

University teaching hospital.

METHODS

20 patients with impaired left ventricular systolic function [ejection fraction 32 (SEM 2.3)%] were randomised in a double blind manner to receive either oral metoprolol 6.25 mg twice daily or celiprolol 25 mg daily. Haemodynamic variables were evaluated by Swan-Ganz pulmonary artery catheter over 24 hours. ANF and BNF concentrations were measured at baseline, 5 h, and 24 h by radioimmunoassay.

RESULTS

At baseline ANF and BNF concentrations were considerably raised compared to the normal range. Treatment with metoprolol caused ANF to rise further to 147% of the basal level at 5 h (P = 0.017) and 112% at 24 h (P = 0.029). This was associated with a small but non-significant rise in pulmonary capillary wedge pressure. Cardiac output and systemic vascular resistance were unchanged at 24 h. In contrast, after celiprolol ANF fell to 90% of basal levels at 5 h and to 74% of basal level at 24 h (P = 0.019), associated with a small but non-significant fall in pulmonary capillary wedge pressure [-3.3 (2.7) mm Hg] and systemic vascular resistance, and rise in cardiac output from 3.2 (0.2) to 4.0 (0.4) l/min (P = 0.04). BNF concentrations rose to 112% of baseline at 5 h (P = 0.09) after metoprolol but fell slightly, to 91% of baseline values, after celiprolol (NS).

CONCLUSIONS

Metoprolol, even in very low doses (6.25 mg), produced a rise in ANF and BNF, although minimal haemodynamic changes were detected. In contrast, a vasodilating beta blocker was associated with a significant fall in ANF and BNF and a small rise in cardiac output. This study confirms both the advantages of vasodilating beta blockers over metoprolol for initial treatment of heart failure and the usefulness of ANF and BNF measurements for the assessment of drug effects in heart failure compared to traditional haemodynamic measurements.

Combination plots as graphical tools in the study of enzyme inhibition

Although statistical regression has become the method of choice in the analysis of enzyme kinetics, graphical methods continue to be useful on account of their illustrative capabilities. It is pointed out in this paper that enzyme inhibition data may be presented more efficiently as a single linear plot than the traditional way as a family of lines. This approach has been taken previously by Hunter and Downs [Hunter and Downs (1945) J. Biol. Chem. 157, 427-446] but has remained neglected. A new version of this type of plot (combination plot) has been devised which is linear for competitive, non-competitive, uncompetitive and linear mixed inhibition and has a characteristic appearance for each type of inhibition behaviour. The slopes and intercepts not only indicate directly the dissociation constant but also provide quantitative criteria for the nature of inhibition. This plot should serve as a useful graphical tool in enzyme research as well as in biochemical education.

The aetiology of heart failure in the Chinese population of Hong Kong--a prospective study of 730 consecutive patients

Heart failure is a common and serious condition in many parts of the world and is a frequent cause for hospital admission in the Chinese population of Hong Kong. There is no published information on the epidemiology of heart failure in this community or from mainland China. Therefore, a prospective study of consecutive patients admitted with the clinical diagnosis of heart failure has been carried out to identify the main risk factors or possible causes, and other clinical data. Seven-hundred thirty consecutive patients with cardiac failure were identified and studied. Standard clinical criteria were used for diagnosis and identification of the main or most likely aetiologies and echocardiography was done in 30%. The data analysis of the 730 patients showed the following. The majority were females (56%) and the prevalence of heart failure increased with age (mean age 73.5 +/- 11.7 years) with 76% of the women > 70 years old. In contrast, the men were younger with 40% < 70 years old. The main identifiable risk factors were hypertension (37%), ischemic heart disease (31%), valvular heart disease (15%), cor pulmonale (27%), idiopathic dilated cardiomyopathy (4%), and miscellaneous (10%). In women, hypertension was the commonest cause at all ages but in men aged < 70 years ischemic heart disease was equal in frequency to hypertension (36% and 35%, respectively). Twenty-one percent had diabetes compared to a community rate of 10% for this age group (odds ratio 2.25, P < 0.0001). There was considerable overlap between diabetes, hypertension and ischemic heart disease. The estimated incidence rate was 3.8/1000 women and 3.0/1000 men aged > 45 years old.(ABSTRACT TRUNCATED AT 250 WORDS)

Design and biological activities of L-163,191 (MK-0677): a potent, orally active growth hormone secretagogue

A potent, orally active growth hormone (GH) secretagogue L-163,191 belonging to a recently synthesized structural class has been characterized. L-163,191 releases GH from rat pituitary cells in culture with EC50 = 1.3 +/- 0.09 nM and is mechanistically indistinguishable from the GH-releasing peptide GHRP-6 and the prototypical nonpeptide GH secretagogue L-692,429 but clearly distinguishable from the natural GH secretagogue, GH-releasing hormone. L-163,191 elevates GH in dogs after oral doses as low as 0.125 mg/kg and was shown to be specific in its release of GH without significant effect on plasma levels of aldosterone, luteinizing hormone, thyroxine, and prolactin after oral administration of 1 mg/kg. Only modest increases in cortisol were observed. Based on these properties, L-163,191 has been selected for clinical studies.

Aconitine poisoning due to Chinese herbal medicines: a review

Both "chuanwu", the main root of Aconitum carmichaeli, and "caowu", the root of A kusnezoffii, are believed to possess anti-inflammatory, analgesic and cardiotonic effects and have been used in Chinese materia medica mainly for the treatment of musculoskeletal disorders. They contain the highly toxic C19 diterpenoid alkaloids of aconitine, mesaconitine and hypaconitine. After ingestion, patients may present with signs and symptoms that are typical of aconitine poisoning. Death may occur from ventricular arrhythmias, which are most likely to occur within the first 24 h. Management of aconitine poisoning is essentially supportive. There are no adequate studies in humans to indicate the most effective treatment of the ventricular arrhythmias. All clinicians should be alerted to the potential toxicity of "chuanwu" and "caowu".

A novel 3-substituted benzazepinone growth hormone secretagogue (L-692,429)

The 3-substituted benzazepinone, L-692,429 (compound 1), is the prototype compound of a novel class of compounds that stimulate release of growth hormone (GH). The molecule evolved from efforts to identify a non-peptide mimic of the growth hormone-releasing hexapeptide, GHRP-6. Compound 1 is prepared by sequential attachment of dimethyl-beta-alanine and 2'-biphenylyltetrazole side chains to a chiral 3-aminobenzolactam nucleus. Comparison of the biological activity of 1 with the corresponding six- and eight-membered lactam analogs shows the seven-membered benzazepinone skeleton to be preferred. Molecular modeling of the structurally diverse GH secretagogues, L-692,429 and GHRP-6, was performed.

Effect of lipoic acid on redox state of coenzyme Q in mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and diethyldithiocarbamate

We investigated the effects of a combined treatment of male C57Bl/6 mice with diethyldithiocarbamate and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the absence or presence of different forms of lipoic acid (Thioctacid TR; commonly used for treatment of diabetic polyneuropathies) on levels and redox states of alpha-tocopherol and coenzyme Q in vivo and on activities of various enzymes of energy metabolism ex vivo. Treatment of mice with diethyldithiocarbamate plus MPTP resulted in a decrease in dopamine (67%) and its major metabolites dihydroxyphenylacetic acid (38%) and homovanillic acid (37%) in striatum. alpha-Tocopherol levels were unaltered in striatum; however, the reduced forms of coenzyme Q were decreased in frontal cortex and hippocampus following diethyldithiocarbamate plus MPTP. In frontal cortex activity of NADH dehydrogenase was significantly inhibited by diethyldithiocarbamate plus MPTP ex vivo, suggesting that the neurotoxic metabolite of MPTP, 1-methyl-4-phenylpyridinium ion, is acting in brain regions other than striatum as well. Lipoic acid, administered 6 times, each at 90 min prior to MPTP, could not restore dopamine in striatum but in contrast maintained a normal ratio of the reduced form to the oxidized form of coenzyme Q, suggesting an interaction of lipoic acid with energy metabolism which seems, however, not only to be due to an activation of pyruvate dehydrogenase.

Pituitary adenylate cyclase activating polypeptide-induced desensitization on growth hormone release from rat primary pituitary cells

Pituitary adenylate cyclase activating polypeptide (PACAP38) stimulated growth hormone release as well as cAMP accumulation in a static rat primary pituitary cell culture in a dose-dependent manner with EC50 values of 1.9 +/- 0.4 nM (n = 13) and 0.9 +/- 0.3 nM (n = 5), respectively. The maximal GH response was observed between 5 to 15 min. Prolonged incubation (3 to 4 hrs) markedly reduced the stimulatory effect of PACAP38. The effect of PACAP38 on GH release was desensitized by pretreatment of the cells with PACAP38 or GRF, but not with PMA. The PACAP38-induced desensitization appeared to be time- and dose-dependent. Somatostatin (20 nM) inhibited PACAP-stimulated GH release through a cAMP-independent pathway.

Synergistic binding of hydrophobic probes and zinc ligands to thermolysin

The strong synergism previously observed in the binding of inhibitors to two Zn-proteases, has also been found for thermolysin. As in earlier cases, the effects are produced by a small Zn-ligand (e.g. a hydroxamate) in the presence of another compound which contains the key structural features of specific substrates (a specificity probe). For thermolysin, the most effective specificity probes are hydrophobic derivatives of amines and amino acids (e.g. carbobenzyloxy-L-alaninol). Even the simple combination of benzyl alcohol and formohydroxamate displays considerable synergism. The above effects are temperature dependent and correlate well with a thermally induced conformational isomerization reported recently for this enzyme. Our results seem to be related to previous observations of substrate synergism in the reverse reaction and to superactivation by chemical modification of this enzyme. All these effects are consistent with a change in the environment of the catalytically important zinc atom upon binding of the hydrophobic side chain of the substrate. With the inclusion of thermolysin, binding synergism is now known to occur in an endopeptidase as well as in exopeptidases of diverse specificity. The general occurrence of this phenomenon in zinc proteases and its possible significance are discussed in an accompanying study.

General occurrence of binding synergism in zinc proteases and its possible significance

The observation of binding synergism has been successfully extended to include carboxypeptidases A and B. The behaviour of these two enzymes follows the same pattern previously found for three other Zn-proteases. Thus in all cases examined, the affinity of a suitable Zn-ligand is increased in the presence of a compound (specificity probe) which contains the key structural features of specific substrates. A bifunctional ligand such as phosphonoacetate is particularly useful for generating synergism in both carboxypeptidases. Presumably the carboxylate moiety binds to the C-terminal recognition site while the other functional group interacts with the metal ion. Several basic compounds (e.g. methyl guanidine) act as effective specificity probes for carboxypeptidase B while phenol and other hydrophobic substances serve this purpose in carboxypeptidase A. The above phenomenon appears to be a mechanism designed to enhance catalytic efficiency through a substrate-induced conformational change. We postulate that there is a requirement for at least one ionizable group at the active site. The proposed mechanism keeps this group in the correct ionization state in the presence of water and increases its reactivity after exclusion of water by substrate binding. We suggest the term xerophilic shift for this process. Since proton transfer is a common process in enzyme reactions, the xerophilic-shift mechanism may play a similar role in many instances. It should therefore be possible to detect binding synergism in a wide variety of enzymes.

Functional changes in cocultures of mesencephalon and striatal neurons from embryonic C57/BL6 mice due to low concentrations of 1-methyl-4-phenylpyridinium (MPP+)

1-Methyl-4-phenylpyridinium (MPP+), the active metabolite of 1-Methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP) is taken up into dopaminergic terminals and selectively destroys dopaminergic neurons, serving as a valuable tool in animal model of Parkinson's disease. Cocultures from ventral mesencephalon and neostriatum of embryonic C57/BL6 mouse brains were used to study the sensitivity of dopaminergic neurons to the toxic agent MPP+. Cultures were grown for 9 days in vitro and exposed to different concentrations of MPP+ for various times. Treatment with (0.1-1.0 microM) MPP+ for 24 hours decreased 3H-dopamine (3H-DA) uptake with an IC50 at 0.2 microM. Exposure of cells to 1 microM MPP+ over time decreased the 3H-DA uptake to 38% of controls within the first two hours of incubation and to 8% after 48 hours. Loss of tyrosine hydroxylase (TH) positive cells became evident at 0.1 microM MPP+ (80% of control) leading to maximal toxicity at 10 microM (20% of control). MPP+ reduced the dopamine content in the cultures in a dose dependent manner (IC50 at 0.1 microM) and failed to show reversibility in recovery studies. These findings provide evidence that exposure of MPP+ even at low concentrations and for short time in our coculture model results in irreversible toxicity for dopaminergic neurons.

Influence of labor and neonatal hypoxia on sympathoadrenal activation and methionine enkephalin release in calves

Labor and delivery stimulate increased release of catecholamines and endogenous opioid peptides in neonates. Catecholamines promote adaptation to the extrauterine environment after birth. Enkephalins are stored together with catecholamines in the adrenal medulla and have an inhibitory effect on catecholamine release. We investigated the influence of labor and neonatal hypoxia on epinephrine, norepinephrine, and met-enkephalin release in calves. Blood samples were taken from the umbilical artery before rupture of the umbilical cord and from the jugular vein repeatedly after birth. Highest plasma norepinephrine concentration was found in calves delivered at the end of gestation (term calves) before umbilical cord rupture. In calves delivered before the physiologic end of gestation (preterm calves), norepinephrine values increased after cord rupture, but remained lower than values in term calves. Epinephrine release followed a similar pattern, but norepinephrine was clearly predominant. In term calves, met-enkephalin values were significantly higher than values in preterm calves. In calves of both groups, met-enkephalin release increased after cord rupture. During birth, the increase in catecholamine release seems to take place earlier than that of enkephalins. Norepinephrine-dominated stimulation during expulsion of the calf might be followed by increasing enkephalinergic inhibition after cord rupture and onset of respiration. Reduced release of catecholamines and enkephalins in preterm calves may be connected with delayed adaptation to the extrauterine environment.

A nonpeptidyl growth hormone secretagogue

A nonpeptidyl secretagogue for growth hormone of the structure 3-amino-3-methyl-N-(2,3,4,5-tetrahydro-2-oxo-1-([2'-(1H-tetrazol-5 -yl) (1,1'-biphenyl)-4-yl]methyl)-1H-1-benzazepin-3(R)-yl)-butanamid e (L-692,429) has been identified. L-692,429 synergizes with the natural growth hormone secretagogue growth hormone-releasing hormone and acts through an alternative signal transduction pathway. The mechanism of action of L-692,429 and studies with peptidyl and nonpeptidyl antagonists suggest that this molecule is a mimic of the growth hormone-releasing hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6). L-692,429 is an example of a nonpeptidyl specific secretagogue for growth hormone.

Stimulation of growth hormone release from rat primary pituitary cells by L-692,429, a novel non-peptidyl GH secretagogue

L-692,429, a benzolactam derivative, stimulated GH release from rat primary pituitary cells in a dose-dependent manner. The concentration of L-692,429 required for half-maximal stimulation were 59.6 +/- 7.3 nM. Under the same conditions, GHRP-6 and GRF had EC50 values of 10.3 +/- 1.9 nM and 0.47 +/- 0.09 nM, respectively. L-692,428, the enantiomer of L-692,429, was inactive at a concentration as high as 2 microM. Like GHRP-6, L-692,429 had no effect on intracellular cAMP level; however, it synergized with GRF to further increase not only the accumulation of cAMP but also the release of GH. The magnitude of GH release stimulated by maximal concentrations of L-692,429 and GHRP-6 was comparable. Interestingly, when presented together in maximal concentrations, L-692,429 and GHRP-6 did not cause additional GH release when compared with either secretagogue alone. The L-692,429-stimulated GH release was completely inhibited by 20 nM somatostatin. To our knowledge, L-692,429 is the first non-peptidyl GH secretagogue which has a direct effect on the release of growth hormone from rat primary pituitary cells. Its effect is most likely mediated through a mechanism which is similar to that of GHRP-6.