Consistency of response and image recognition, pulmonary nodules

OBJECTIVE

To investigate the effect of recognition of a previously encountered radiograph on consistency of response in localized pulmonary nodules.

METHODS

13 radiologists interpreted 40 radiographs each to locate pulmonary nodules. A few days later, they again interpreted 40 radiographs. Half of the images in the second set were new. We asked the radiologists whether each image had been in the first set. We used Fisher's exact test and Kruskal-Wallis test to evaluate the correlation between recognition of an image and consistency in its interpretation. We evaluated the data using all possible recognition levels-definitely, probably or possibly included vs definitely, probably or possibly not included by collapsing the recognition levels into two and by eliminating the "possibly included" and "possibly not included" scores.

RESULTS

With all but one of six methods of looking at the data, there was no significant correlation between consistency in interpretation and recognition of the image. When the possibly included and possibly not included scores were eliminated, there was a borderline statistical significance (p = 0.04) with slightly greater consistency in interpretation of recognized than that of non-recognized images.

CONCLUSION

We found no convincing evidence that radiologists' recognition of images in an observer performance study affects their interpretation on a second encounter.

ADVANCES IN KNOWLEDGE

Conscious recognition of chest radiographs did not result in a greater degree of consistency in the tested interpretation than that in the interpretation of images that were not recognized.

Zoledronic acid for the prevention of bone loss in patients with previously untreated lymphoma undergoing chemotherapy

e20611

Background: Treatment of lymphoma with alkylating agents and steroids causes bone loss and increased fracture risk. In addition, over half of all untreated lymphoma patients are osteopenic or osteoporotic at diagnosis. Pamidronate reduces bone loss and risk of vertebral fractures in lymphoma patients undergoing chemotherapy (CT). However, the effects of the more potent bisphosphonate (BP) zoledronic acid (ZA) in this setting are unknown. Therefore, we report on a phase III trial evaluating the effect of ZA on bone mineral density (B) in patients with newly-diagnosed lymphoma undergoing CT. Methods: In total, 72 patients will be randomized to either the control arm [calcium carbonate (1,200 mg orally/day) plus vitamin D (400 IU orally/day)], or the BP arm [calcium carbonate and vitamin D as in the control arm plus ZA (4 mg IV at baseline and at 6 months)]. The primary endpoint is the absolute change in B of the lumbar spine (LS) and femoral neck (FN) at baseline and 12 months. Results: Thus far, 112 patients have been screened for enrollment. Twenty-seven patients (24.1%) failed screening due to periodontal disease, a predetermined exclusion criterion of the study. To date, 14 patients in the control arm and 9 patients in the BP arm have completed the one-year follow up period including baseline and one-year B evaluations. Comparing patients in the control arm to those in the BP arm, the average absolute change in B at the LS was -0.048 g/cm2 vs. 0.0093 g/cm2 (p=0.005), at the left FN was -0.039 g/cm2 vs. 0.0074 g/cm2 (p=0.01), and at the right FN was -0.043 g/cm2 vs. 0.0211 g/cm2 (p<0.001), respectively. There have been no therapy-related serious adverse events or skeletal fractures in either arm. Conclusions: ZA in combination with calcium carbonate and vitamin D improves the B of patients with lymphoma undergoing CT. Given the incidence of below-average pre-treatment B and the known deleterious effects of lymphoma therapy on bone density, baseline B evaluation is warranted in all lymphoma patients. The high rate of periodontal disease in this patient population emphasizes the need for careful dental evaluation prior to BP therapy given the well-described, albeit rare, risk of osteonecrosis of the jaw from ZA.

[Table: see text]

Osteopenia and osteoporosis in untreated non-Hodgkin's lymphoma patients: An important and potentially treatable survivorship issue in lymphoma

9055

Background: Alkylating agents and steroids can cause premature osteoporosis, increasing the risk of vertebral and hip fracture. The bisphosphonate pamidronate every 3 months can reduce bone loss and the risk of new vertebral fractures in lymphoma patients receiving chemotherapy.(Kim et al., 2004 Am J Med) We are conducting a randomized study of the more potent bisphosphonate zoledronic acid in untreated non-Hodgkin's lymphoma (NHL) patients to study chemotherapy induced bone loss. Methods: During the accrual period, we report the baseline bone mineral density (BMD) characteristics for screened untreated NHL patients. Exclusion criteria included bone fractures, BMD T-scores worse than -2.0, CrCl < 60 mL/min, dental problems, prior bisphosphonate or significant steroid use. Patients accrued to the study were randomized to receive either: 1) oral calcium and vitamin D (Ca+D) or 2) Ca+D and 4 mg zoledronic acid IV at baseline and at 6 months. Results: Patient characteristics: 59 males and 55 females with median age 63 (range: 18–87). Lymphoma types: B-cell n=111, T-cell 3; follicular (FL) 56, diffuse large B-cell (DLBCL) 33, mantle cell 8, and others, totaling 114 patients. Of untreated NHL individuals screened for baseline BMD to date 11/114 (10%) had osteoporosis and 62/114 (54%) had osteopenia or osteoporosis. The lowest BMD was a T-score of -4.4. Other bone, dental, and endocrine abnormalities excluded some patients from treatment randomization. Patients with T scores < -2.0 were considered for off-study treatment with bisphosphonates. Osteopenia and osteoporosis were common across lymphoma subtypes: FL 25/56 (45%), DLBCL 20/33 (61%), mantle cell 6/8 (75%), and marginal zone 5/6 (83%). The low rate of osteopenia/osteoporosis of 25% for Burkitt/Burkitt-like lymphoma may reflect fast lymphoma kinetics without associated increase in bone loss. Conclusions: Baseline testing of BMD revealed osteopenia or osteoporosis in the majority of untreated NHL patients. This widely available and non-invasive test should be considered in untreated NHL patients. Our ongoing clinical trial will address the potential role of zoledronic acid in preserving bone density for survivors of NHL. ClinicalTrials.gov Identifier: NCT00352846

[Table: see text]

Analysis of responses to hAmylin, hCGRP, and hADM in isolated resistance arteries from the mesenteric vascular bed of the rat

Responses to human calcitonin gene-related peptide (hCGRP) and human adrenomedullin (hADM) hAmylin were investigated in isolated mesenteric resistance arteries from the rat. The results of the present investigation show that hCGRP, hAmylin, and hADM induce dose-related vasodilator responses in isolated resistance arteries from the rat mesenteric vascular bed. Vasodilator responses to hCGRP and hAmylin were not altered after denuding the vascular endothelium, after administration of the nitric oxide synthase inhibitor L-NA, or after administration of the soluble guanylate cyclase inhibitor ODQ, suggesting that vasodilator responses to hCGRP and hAmylin are not mediated by the release of nitric oxide from the vascular endothelium and the subsequent increase in cGMP. Vasodilator responses to hCGRP, hAmylin, and hADM were not altered by the vascular selective K+(ATP) channel antagonist U-37883A. The role of the CGRP1 receptor was investigated and responses to hCGRP and hAmylin, but not hADM, were significantly reduced following administration of hCGRP-(8-37). Moreover, vasodilator responses to hCGRP and hAmylin, but not hADM, were significantly reduced by hAmylin-(8-37), suggesting that an hAmylin-(8-37)-sensitive receptor mediates responses to hCGRP and hAmylin in the rat mesenteric artery. These data suggest that hCGRP and hAmylin have direct vasodilator effects in the isolated mesenteric resistance artery that are mediated by hAmylin-(8-37)- and hCGRP-(8-37)-sensitive receptors.

GI side-effects of a possible therapeutic GRF analogue in monkeys are likely due to VIP receptor agonist activity

Growth hormone (GH) is used or is being evaluated for efficacy in treatment of short stature, aspects of aging, cardiac disorders, Crohn's disease, and short bowel syndrome. Therefore, we synthesized several stable growth hormone-releasing factor (GRF) analogues that could be therapeutically useful. One potent analog, [D-Ala(2),Aib(8, 18,)Ala(9, 15, 16, 22, 24-26,)Gab(27)]hGRF(1-27)NH(2) (GRF-6), with prolonged infusion caused severe diarrhea in monkeys; however, it had no side-effects in rats. Because GRF has similarity to VIP/PACAP and VIPomas cause diarrhea, this study investigated the ability of this and other GRF analogues to interact with the VIP/PACAP receptors. Rat VPAC(1)-R (rVPAC(1)-R), human VPAC(1)-R (hVPAC(1)-R), rVPAC(2)-R and hVPAC(2)-R stably transfected CHO and PANC 1 cells were made and T47D breast cancer cells containing native human VPAC(1)-R and AR4-2J cells containing PAC(1)-R were used. hGRF(1-29)NH(2) had low affinity for both rVPAC(1)-R and rVPAC(2)-R while VIP had a high affinity for both receptors. GRF-6 had a low affinity for both rVPAC(1)-R and rVPAC(2)-R and very low affinity for the rPAC(1)-R. VIP had a high affinity, whereas hGRF(1-29)NH(2) had a low affinity for both hVPAC(1)-R and hVPAC(2)-R. In contrast GRF-6, while having a low affinity for hVPAC(2)-R, had relatively higher affinity for the hVPAC(1)-R. In guinea pig pancreatic acini, all GRF analogues were full agonists at the VPAC(1)-R causing enzyme secretion. These results demonstrate that in contrast to native hGRF(1-29)NH(2,) GRF-6 has a relatively high affinity for the human VPAC(1)-R but not for the human VPAC(2)-R, rat VPAC(1)-R, rat VPAC(2)-R or rat PAC(1)-R. These results suggest that the substituted GRF analog, GRF-6, likely causes the diarrheal side-effects in monkeys by interacting with the VPAC(1)-R. Furthermore, they demonstrate significant species differences can exist for possible therapeutic peptide agonists of the VIP/PACAP/GRF receptor family and that it is essential that receptor affinity assessments be performed in human cells or from a closely related species.

Antitumor and antiangiogenic effects of somatostatin receptor-targeted in situ radiation with (111)In-DTPA-JIC 2DL

INTRODUCTION

Expression of somatostatin receptor subtype 2 (sst 2) in angiogenic tumor vessels appears to be homogeneous, while tumor cell expression of this receptor is often heterogeneous. We have developed a novel in vitro three-dimensional tumor angiogenesis model to study the antitumor and the antiangiogenic effects of radiolabeled somatostatin analogs. We hypothesized that targeted in situ radiation with an Auger electron-emitting radiolabeled somatostatin analog would produce receptor-specific cytotoxicity in sst 2-expressing cells.

MATERIALS AND METHODS

IMR-32 human neuroblastoma (sst 2-positive) and MDA MB-231 human breast cancer (sst 2-negative) xenografts were created in nude mice from monolayer cell cultures. Fragments of these tumors were embedded in three-dimensional fibrin gels supplemented with endothelial growth media and incubated for a period of 14 days. Tumor fragments were treated with 50 microCi/ml of (111)In-JIC 2DL, a sst 2-preferring somatostatin analog, or medium on Day 1. Initial angiogenic activity was determined at 48 h and the mean angiogenic score and tumoricidal responses were assessed on Day 14.

RESULTS AND CONCLUSION

Tumoricidal effects of (111)In-JIC 2DL were seen only in sst 2-positive IMR-32 tumors. However, the angiogenic response was inhibited in both IMR-32 and MDA MB-231 tumors independent of the tumor cells' sst 2 status. Somatostatin receptor-mediated in situ radiation therapy has profound cytotoxic effects on angiogenic blood vessels and sst 2-expressing tumor cells.

Differential inhibition of growth hormone secretion by analogs selective for somatostatin receptor subtypes 2 and 5 in human growth-hormone-secreting adenoma cells in vitro

Somatostatin (SRIH), a cyclic tetradecapeptide hormone originally isolated from mammalian hypothalamus, is a potent suppressor of pituitary growth hormone (GH) secretion. SRIH acts through a family of G-protein-coupled membrane receptors containing seven transmembrane domains. Five genes encoding distinct SRIH receptor (SSTR) subtypes have so far been cloned in human and other species and termed SSTR1-5. In human somatotrophe pituitary adenomas GH secretion is controlled by both SSTR2 and SSTR5. However, in clinical practice only somatostatin analogs selective for SSTR2 (octreotide and lanreotide) are available. This may explain why clinical and in vitro responses to these analogs in acromegaly are only partial. In this study, we investigated the inhibitory effect of two new SRIH analogs with high selectivity for SSTR2 (NC-4-28B) and SSTR5 (BIM-23268) and compared it to that of native somatostatin (SRIH-14) on a large number of GH-secreting adenomas obtained by transphenoidal neurosurgery. Tissues from 16 adenomas were enzymatically dispersed and plated in 24-well dishes at 50,000 cells/well. After 3 days, groups of three wells were incubated for 4 h with medium alone, SRIH-14 or analogs NC-4-28B or BIM-23268, at the concentrations of 0.01, 0.1 and 1 microM. Our results show that 9 out of 16 adenomas were responsive (GH suppression: 20-40% vs. control, p < 0.05) to SRIH. In this group only 4 adenomas showed similar responses to both selective analogs, with 2 nonresponders (expression of other SRIH receptor subtypes) and 2 responders (concomitant expression of SSTR2 and SSTR5) to both analogs. GH release was selectively inhibited by NC-4-28B in 3 adenomas and by BIM-23268 in the remaining 2 adenomas, suggesting predominant expression of SSTR2 and SSTR5, respectively. SRIH failed to inhibit GH release in 7 adenomas (43%). Interestingly, in that group a better inhibitory effect was obtained with BIM-23268 (5 out of 7 adenomas) than with NC-4-28B, suggesting expression of a few SSTR5 receptors only, or of both SSTR2 and SSTR5, respectively. We conclude that the availability of somatostatin analogs selective for SSTR5 will enhance the treatment potency and spectrum in acromegaly.

N-Methyl scan of somatostatin octapeptide agonists produces interesting effects on receptor subtype specificity

The search for synthetic analogues of somatostatin which exhibit selective affinities for the five receptor subtypes is of considerable basic and therapeutic interest and has generated a large number of potent agonist analogues with a wide spectrum of binding profiles. In the past, conformational restriction of side chain groups and the peptide backbone has yielded the most interesting results. Under the latter category and as part of the present study, we were interested in the potential effects of N-methylation of peptide bond NH groups on binding affinity since this approach had not been systematically examined with these peptides. This was aided by new chemistries for introducing an N-Me group during regular solid-phase peptide synthesis using Boc protection. A number of interesting effects were noted on relative binding affinities of the two series of agonist sequences chosen, DPhe(5)(or Tyr(5))-c[Cys(6)-Phe(7)-DTrp(8)-Lys(9)-Thr(10)-Cys(11)]Thr(12)-NH(2) (SRIF numbering), at the five known human somatostatin receptors transfected into and stably expressed by CHO cells. N-Methylation of residues 7 (Phe), 10 (Thr), 11 (Cys), and 12 (Thr) largely destroyed affinities for all five receptors. N-Methylation of DTrp in the DPhe series gave an analogue with extraordinarily high affinity for the type 5 receptor for which it was also quite selective. N-Methylation of Lys in both series resulted in retention of type 2 affinity despite this residue constituting the "active center" of somatostatin peptides. N-Methylation of either the N-terminal Tyr residue or of Cys(6) in the Tyr series resulted in analogues with extraordinarily high affinity for the type 3 receptor, also with a degree of specificity. N-Methylation of the peptide bond constrains the conformational space of the amino acid and eliminates the possibility of donor hydrogen bond formation from the amide linkage. The beta-bend conformation of the agonists around DTrp-Lys is stabilized by a transannular intramolecular hydrogen bond(s) between Phe(7) and Thr(10) so methylation of these residues eliminates this source of stabilization. It is expected that several of these analogues will provide additional tools for determining some of the physiological roles played by type 3 and 5 somatostatin receptors which are still far from being fully elucidated.

Highly potent and subtype selective ligands derived by N-methyl scan of a somatostatin antagonist

The search for synthetic peptide analogues of somatostatin (SRIF) which exhibit selective affinities for the five known receptor subtypes (sst1-5) has generated a large number of potent agonists. Some of these agonists display good subtype selectivities and affinities for the subtypes 1, 2, 3, and 5, including analogues created by N-methyl amino acid substitutions in a standard octapeptide analogue format. We have now extended this peptide backbone N-methylation approach to a potent somatostatin receptor antagonist series using the antagonist Cpa-cyclo(DCys-Pal-DTrp-Lys-Thr-Cys)-Nal-NH2 9 reported from this laboratory as the lead structure. Synthetic analogues were tested for their ability to inhibit somatostatin-stimulated GH release from rat pituitary cells in culture and to displace 125I-labeled somatostatin from CHO cells transfected with the five known human somatostatin receptors. Several interesting observations resulted from the study. N-Methylation at the Lys(9) residue (5) increased the rat GH release inhibitory potency nearly 4-fold to 0.73 nM but resulted in little change in the binding affinity for human type 2 receptor. This analogue also had a high affinity of 5.98 nM for sst5 receptor (compared to 1.4 nM for somatostatin itself) and is the first antagonist analogue to be reported with high affinity for sst5. It also had high potency on in vitro inhibition of sst5 mediated intracellular calcium mobilization. These results were considered surprising, since the Lys(9) residue has long been considered to constitute the active center of somatostatin, important both for receptor binding and activation, and suggests important conformational differences between D-Cys(9) somatostatin antagonists and normal agonist structures. More modifications were carried out on this analogue with the aim of improving antagonist potency and/or specificity. Tyr(7) substitution of 5 resulted in an analogue, which had the highest affinity in the series for hsst2 (K(I) 5.51 nM) and an extraordinarily low IC50 of 0.53 nM in the rat pituitary cell assay. However, this analogue lost considerable affinity for sst5 relative to analogue 5. Analogue 16 with DTrp(12) at C-terminus had the highest affinity for hsst2, however, the IC50 in the rat GH release assay was only 11.6 nM. Replacement of Lys(9) in 9 with Dab(9) gave 11 which displayed high binding affinity for sst3, and it was also quite selective for that receptor. Both the sst3 and sst5 antagonists should be of value in assigning the physiological roles to type 3 and 5 receptor, respectively.

Nitric oxide-mediated erectile effects of galantide but not galanin in vivo

The purpose of this study was to investigate the in vivo effects of intracavernosal injections of galanin and galantide (a specific galanin receptor antagonist) on penile erection in the anesthetized cat. Erectile responses to galanin and galantide were compared with responses to a standard triple drug combination [1.65 mg papaverine, 25 microg phentolamine, and 0.5 microg prostaglandin E(1) (PGE(1))]. Intracavernosal injections of galanin (3-100 nmol) and galantide (0. 1-3 nmol) induced penile erection in a dose-dependent manner. In terms of relative potency, galantide was approximately 100-fold more potent than galanin at increasing cavernosal pressure. The maximal increases in intracavernosal pressure in response to galanin and galantide were 83 and 95%, respectively, of the control triple drug combination. The total durations of erectile response caused by these peptides were significantly shorter (P<0.05) than those by the triple drug combination. The nitric oxide synthase inhibitor L-NAME (20 mg) significantly decreased the erectile response in the cat to galantide but not to galanin, while the K(+)(ATP) channel antagonist U-37883A (3 mg) had no effect on the erectile response to galanin nor galantide. The results of the present study demonstrate that galantide, a putative antagonist for the galanin receptor, has more potent agonist activity than galanin in increasing intracavernosal pressure in the cat. Moreover, these data suggest that galantide, but not galanin, causes penile erection by an NO/cGMP-dependent mechanism. This is the first study to demonstrate that galanin may play a role in the physiology of penile erection.

Prevalence of pelvic Paget's disease of bone in the United States

The objective of this article was to estimate the prevalence of Paget's disease of bone in the United States from a statistically derived sample of the general population. Pelvic radiographs obtained in the First National Health and Nutrition Examination Survey (NHANES-I) were reviewed for the presence of Paget's disease. Age, sex, and geographic distribution of Paget's disease of the pelvic region were determined. The overall prevalence of Paget's disease in the United States was estimated. Pelvic Paget's disease is estimated to be present in 0.71 + 0.18% of the radiographs of the general population. The disease was higher in frequency in people who were in the older decades of life with the highest prevalence of 2.32 + 0.54% in the 65- to 74-year-old people. There is a slight male predominance in the 45- to 74-year age group. The regional distribution suggests the highest prevalence in the Northeast (1.48 + 0.52%) with the lowest prevalence in the South (0.26+0.25%). The prevalence was equal in white people and black people. An estimate of the overall prevalence of Paget's disease in the United States was at least 1% and perhaps as much as 2 % of the general population with near equal sex distribution and the highest prevalence in the northeastern United States.

Highly potent cyclic disulfide antagonists of somatostatin

The search for synthetic analogues of somatostatin (SRIF) which exhibit selective affinities for the five known receptor subtypes (sst1-5) has generated a large number of potent agonist analogues. Many of these agonists display good subtype selectivities and affinities for the subtypes 2, 3, and 5, with very few selective for sst1 or sst4. Until the recent report by Bass and co-workers (Mol. Pharmacol. 1996, 50, 709-715; erratum Mol. Pharmacol. 1997, 51, 170), no true antagonists of somatostatin had been discovered, let alone any displaying differential receptor subtype selectivity. In this present study, we further explore the effect of this putative L,5D6 antagonist motif on somatostatin octapeptide analogues with a cyclic hexapeptide core. The most potent antagonist found to date is H-Cpa-cyclo[DCys-Tyr-DTrp-Lys-Thr-Cys]-Nal-NH2, PRL-2970 (21), which has an IC50 of 1.1 nM in a rat pituitary growth hormone in vitro antagonist assay versus SRIF (1 nM). This analogue bound to cloned human somatostatin subtype 2 receptors with a Ki of 26 nM. The highest hsst2 affinity analogue was H-Cpa-cyclo[DCys-Pal-DTrp-Lys-Tle-Cys]-Nal-NH2, PRL-2915 (15), with a Ki of 12 nM (IC50 = 1.8 nM). This analogue was also selective for hsst2 over hsst3 and hsst5 by factors of 8 and 40, respectively, and had no agonist activity when tested alone at concentrations up to 10 microM. Regression analysis of the binding affinities versus the observed antagonist potencies revealed high correlations for hsst2 (r = 0.65) and hsst3 (r = 0.52) with a less significant correlation to hsst5 (r = 0.40). This is quite different from the somatostatin agonist analogues which show a highly significant correlation to hsst2 (r > 0.9). Receptor-selective somatostatin antagonists should provide valuable tools for characterizing the many important physiological functions of this neuropeptide.

Proadrenomedullin N-terminal 20 peptide (PAMP), acting through PAMP(12-20)-sensitive receptors, inhibits Ca2+-dependent, agonist-stimulated secretion of human adrenal glands

Proadrenomedullin N-terminal 20 peptide (PAMP) is a 20-amino acid hypotensive peptide expressed in the adrenal medulla. We investigated the localization and function of PAMP receptors in the human adrenal gland. Autoradiography showed the presence of [125I]PAMP-binding sites in both zona glomerulosa and adrenal medulla that were displaced by cold PAMP and PAMP(12-20) but not by other preproadrenomedullin-derived peptides. PAMP, but not PAMP(12-20), counteracted, in a concentration dependent manner, both aldosterone response of zona glomerulosa cells and catecholamine response of adrenal medulla cells to BAYK-8644, the selective agonist of voltage-activated Ca2+ channels, as well as to K+ and angiotensin II. PAMP(12-20) partially reversed this antisecretagogue effect of PAMP. Collectively, these findings suggest (1) that PAMP inhibits Ca2+-dependent, agonist-stimulated aldosterone and catecholamine secretion, acting via specific receptors and through a mechanism involving the impairment of Ca2+ influx; and (2) that PAMP(12-20) acts as a weak antagonist of PAMP receptors, thereby suggesting that both C- and N-terminal sequences of the PAMP molecule are required for this peptide to exert its antisecretagogue action on the human adrenal gland.

Synthesis and characterization of multiply-tyrosinated, multiply-iodinated somatostatin analogs

Radio-labeled somatostatin analogs have recently gained popularity as agents useful in intraoperative tumor localization, external scintigraphy and in situ radiotherapy. We have synthesized and characterized a series of novel N-terminally extended multiply-tyrosinated somatostatin analogs that possess high binding affinity for somatostatin receptors, exhibit biological activity comparable to the native peptide and retain these characteristics after iodination. These analogs can be radio-iodinated to high specific activities. Following radioiodination, these analogs exhibit minimal radiolysis and may be clinically useful for tumor localization, scanning and therapy.

Adrenomedullin and calcitonin gene-related peptide (CGRP) interact with a common receptor of the CGRP1 subtype in the human adrenal zona glomerulosa

Frozen sections of normal adrenal glands, obtained from patients undergoing unilateral nephrectomy for kidney cancer, were labeled in vitro with human [125I]ADM(1-52). Autoradiography showed the presence of abundant ADM binding sites in the zona glomerulosa (ZG) and the outermost portion of the zona fasciculata, which were completely displaced by the addition of an excess of cold ADM(1-52). Calcitonin gene-related peptide (CGRP) and the non-selective ligand of the CGRP-receptor subtypes 1 and 2 CGRP(8-37) eliminated [125I]ADM(1-52) binding in the ZG, while the selective ligand of CGRP receptor subtype 2 [Cys(acm)2,7]-CGRP and CGRP(1-8) were ineffective. These findings confirm the presence of ADM binding sites in the human ZG, and provide the first morphological evidence that ADM and CGRP interact with a common receptor of the CGRP1 subtype.

Inhibitory effect of adrenomedullin (ADM) on the aldosterone response of human adrenocortical cells to angiotensin-II: role of ADM(22-52)-sensitive receptors

Human adrenomedullin (ADM) is a 52-amino acid hypotensive peptide, which possesses a disulfide bridge-formed six-membered ring in 16-21 position. The ring structure, and both the N- and C-terminal amino-acid sequences seem to play a key role in the vascular effects of ADM(1-52), and we have investigated whether the same is true for the inhibitory effect of this peptide on the aldosterone response of zona glomerulosa (ZG) cells to angiotensin-II (ANG-II). Autoradiography showed the presence of abundant [125I]ADM(1-52) binding sites in the ZG of human adrenals, which were displaced not only by cold ADM(1-52), but also by both ADM(13-52) and ADM(22-52); ADM fragments 1-12, 15-22 and 16-31 were ineffective. ADM(1-52) and ADM(13-52), but not other fragments, concentration-dependently inhibited ANG-II-stimulated aldosterone secretion of dispersed human adrenocortical cells. The aldosterone antisecretagogue actions of ADM(1-52) and ADM(13-52) were counteracted by ADM(22-52) in a concentration-dependent manner, while other ADM fragments were ineffective. In light of these findings the following conclusions could be drawn: (i) human ZG cells are provided with ADM(22-52)-sensitive receptors; (ii) the six-membered ring structure and the C-terminal, but not N-terminal, amino-acid sequence are both essential for ADM(1-52) to exert its antimineralocorticoid action; and probably (iii) the C-terminal sequence is needed for ADM(1-52) to bind its ZG receptors, while the ring structure is required for the receptor activation.

Adrenomedullin Does Not Inhibit Human Platelet Aggregation

BACKGROUND: Adrenomedullin (ADM) is a hypotensive peptide isolated from human pheochromocytoma extracts discovered in 1993 using an assay system designed to monitor its ability to increase rat platelet adenosine 3',5'-cyclic monophosphate (cAMP) levels. Physiological mediators that elevate cAMP levels, such as prostaglandin (PG)E(1) and PGI(2), have also been shown to inhibit platelet aggregation. Therefore, we have chosen to investigate the effect of ADM, a peptide shown to increase platelet cAMP levels, on human platelet aggregation. METHODS AND RESULTS: Platelet-rich plasma prepared from blood donors was incubated with ADM (10(-9)-10(-6) M) for 1 min at 37 degrees C before the addition of a submaximal dose of adenosine 5'-diphosphate (ADP). ADM did not alter the platelet aggregatory response to ADP. PGE(1), a substance known to inhibit ADP-induced platelet aggregation (10(-6) M), however, inhibited ADP-induced platelet aggregation. In addition, the ADM induced a dose-dependent relation in rings of human chorionic arteries. CONCLUSIONS: These data may be interpreted to suggest that human platelets do not possess a functional ADM receptor couple with adenylate cyclase.

Multiply radioiodinated somatostatin analogs induce receptor-specific cytotoxicity

BACKGROUND

Radiolabeled somatostatin analogs have gained popularity for tumor imaging and have recently been used for the treatment of somatostatin receptor-expressing tumors. We have developed a novel, N-terminally extended, multiply iodinated somatostatin analog, 125I-WOC 4a, that we hypothesize will be a useful tool for the detection of and therapy for somatostatin receptor-positive tumors. To evaluate the therapeutic potential of this agent, we compared the cytotoxicity of 125I-WOC 4a in a somatostatin receptor subtype-2 (sst 2)-expressing human neurobalstoma cell line to its cytotoxicity in a somatostatin receptor-negative human pancreatic carcinoma cell line.

METHODS

IMR-32 neuroblastoma cells (sst 2-positive) and PANC-1 human pancreatic cells (sst 2-negative) were incubated with 125I-WOC 4a at doses ranging from 0.1-100 CPM/cell for 48 h and cell viability was assessed by a colorimetric (MTT) cell viability assay. Subsequently, IMR-32 cells were incubated with either control medium, 125I-WOC 4a (1 cpm/cell) alone, 125I-WOC 4a with 10(-6) M octreotide acetate, 125I (1 cpm/cell) alone, 125I with octreotide acetate, or octreotide acetate alone for 48 h, washed, and cryopreserved for 4 weeks. Cells were then thawed, replated, and allowed to acclimate for 48 h. Cell viability was assessed by trypan blue exclusion and a colorimetric assay.

RESULTS

Following short-term exposure, 125I-WOC 4a induced dose-dependent cytotoxicity in IMR-32 cells (P < 0.05 by ANOVA), but not in the PANC-1 cells. After exposure to 125I-WOC 4a (1 cpm/cell) for 48 h followed by a 4-week cryopreserved exposure, significant cytotoxicity was induced in IMR-32 cells (P < 0.05 by ANOVA) which was not seen in cells treated with 125I alone or 125I with 10(-6) M octreotide acetate. Simultaneous exposure to 125I-WOC 4a and octreotide acetate was also cytotoxic.

CONCLUSION

125I-WOC 4a induces receptor-specific cytotoxicity following both short- and long-term drug exposures. This radiopharmaceutical may be useful for localizing or treating somatostatin receptor-positive tumors.

Potent antagonists of somatostatin: synthesis and biology

The search for synthetic analogues of somatostatin (SRIF) which exhibit selective affinities for the five known receptor subtypes (sst1-5) has generated a large number of potent agonist analogues. Many of these agonists display good subtype selectivities and affinities for the subtypes 2, 3, and 5, with very few selective for sst1 or sst4. Until the recent report by Bass and co-workers (Mol. Pharmacol. 1996, 50, 709-715; erratum, Mol. Pharmacol. 1997, 51, 170), no true antagonists had been discovered, let alone any displaying differential receptor subtype selectivity. In this present study, we explore the effect of this putative L5,D6 antagonist motif on various series of somatostatin agonist analogues, both linear and cyclic. It was found that many D5,L6 agonists could be converted into competitive antagonists by applying this motif, the most potent of which was H-Nal-cyclo[DCys-Pal-DTrp-Lys-Val-Cys]-Nal-NH2 (32). This antagonist was selective for hsst2 with an affinity of 75 nM and an IC50 of 15.1 nM against SRIF-14 in a rat in vitro antagonist bioassay. Receptor-selective somatostatin antagonists should provide valuable tools for characterizing the many important physiological functions of this neuropeptide.

Introduction to wavelet-based compression of medical images

Medical image compression can significantly enhance the performance of picture archiving and communication systems and may be considered an enabling technology for telemedicine. The wavelet transform is a powerful mathematical tool with many unique qualities that are useful for image compression and processing applications. Although wavelet concepts can be traced back to 1910, the mathematics of wavelets have only recently been formalized. By exploiting spatial and spectral information redundancy in images, wavelet-based methods offer significantly better results for compressing medical images than do compression algorithms based on Fourier methods, such as the discrete cosine transform used by the Joint Photographic Experts Group. Furthermore, wavelet-based compression does not suffer from blocking artifacts, and the restored image quality is generally superior at higher compression rates.

Comparison of responses to adrenomedullin and calcitonin gene-related peptide in the feline erection model

The purpose of the present study was to investigate the effects of intracavernosal injections of adrenomedullin (ADM) and calcitonin gene-related peptide (CGRP), two structurally similar peptides, on penile erection in the anesthetized cat. Erectile responses to ADM and CGRP were compared with responses to a standard drug combination (1.65 mg papaverine, 25 microg phentolamine, and 0.5 microg prostaglandin E1 [PGE1]). Intracavernosal injections of ADM (0.1-3 nmol) and CGRP (0.01-0.3 nmol) induced erection in a dose-dependent manner. The maximal increase in intracavernosal pressure in response to ADM was a 75% increase, while the maximal response to CGRP was comparable to that induced by the reference combination, and the maximal increase in penile length was comparable with ADM, CGRP, and the standard drug combination. The duration of the maximal pressure increase and the total duration of the response to ADM and CGRP were more abbreviated than with the control combination, and systemic blood pressure was reduced significantly after administration of CGRP, the control combination, and the higher doses of ADM. The nitric oxide synthase inhibitor, L-NAME, and the K+(ATP)-channel antagonist, glybenclamide, had no effect on the erectile response to CGRP or ADM. The CGRP receptor antagonist CGRP(8-37) attenuated the erectile response to CGRP but not to ADM. These data suggest that the erectile responses to ADM and CGRP are not mediated by nitric oxide release or the opening of K+(ATP) channels, two mechanisms reported to be involved in penile erection, and that CGRP and ADM induce penile erection by activating different receptors.

Comparison of responses to rat and human adrenomedullin in the hindlimb vascular bed of the cat

Responses to rat (r) adrenomedullin (ADM) and human (h) ADM were compared in the hindlimb vascular bed of the cat under conditions of controlled blood flow. Intra-arterial injections of rADM and hADM in doses of 0.03-1 nmol caused dose-related decreases in hindlimb perfusion pressure. In terms of relative vasodilator activity, rADM was similar to hADM. The time course of the vasodilator response and the recovery half times (T1/2) for the vasodilator response to rADM and hADM were not significantly different. Decreases in hindlimb perfusion pressure in response to rADM and hADM were not altered by the calcitonin gene-related peptide receptor antagonist, rCGRP(8-37), at the same time, vasodilator responses to calcitonin gene-related peptide (CGRP) were significantly reduced. The T1/2 of the vasodilator response to rADM and hADM were significantly greater after administration of the cAMP-selective, type IV phosphodiesterase inhibitor, rolipram. These data demonstrate that decreases in hindlimb perfusion pressure in response to rADM and hADM are similar and that vasodilator responses to rADM are not dependent on the activation of CGRP receptors in the hindlimb vascular bed of the cat. These data further suggest that decreases in hindlimb perfusion pressure in response to rADM are mediated by smooth muscle increases in cAMP levels.

Proadrenomedullin NH2-terminal 20 peptide has direct vasodilator activity in the cat

The mechanism by which proadrenomedullin NH2-terminal 20 peptide (PAMP) decreases vascular resistance was investigated in the hindlimb vascular bed in the cat. Injections of PAMP, a shortened form of the peptide PAMP-(12-20), and adrenomedullin (ADM) into the hindlimb perfusion circuit elicit dose-related decreases in perfusion pressure. The order of potency was ADM > PAMP > PAMP-(12-20), and the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37) had no effect on vasodilator responses to PAMP or ADM. Vasodilator responses to PAMP were increased in duration by the adenosine 3',5'-cyclic monophosphate (cAMP) phosphodiesterase inhibitor Rolipram, whereas inhibitors of nitric oxide synthase and guanosine 3',5'-cyclic monophosphate phosphodiesterase had no effect. Vasodilator responses to PAMP were not altered by treatment with alpha-receptor or adrenergic nerve terminal blocking agents and were similar in innervated and denervated hindlimb preparations. Responses to PAMP were similar when vasoconstrictor tone was increased by stimulation of the sympathetic nerves or infusion of phenylephrine and were not altered by the passage of time. These data suggest that PAMP dilates the hindlimb vascular bed by a direct cAMP-dependent mechanism and that inhibition of norepinephrine release plays little if any role in mediating responses to the peptide in the regional vascular bed of the cat.

Adrenomedullin induces penile erection in the cat

The present study was undertaken to investigate the effects of intracavernosal injections of adrenomedullin, a novel hypotensive peptide, on penile erection in anesthetized cats. Responses to adrenomedullin were compared to those elicited by intracavernosal injection of the control triple-drug combination (1.65 mg papaverine, 25 micrograms phentolamine, and 0.5 microgram prostaglandin E1). Intracavernosal injections of adrenomedullin in doses of 0.1-1.0 nmol elicited dose-related increases in cavernosal pressure and penile length. The maximal effect of adrenomedullin injection on cavernosal pressure was an 8-fold increase in pressure, which was 74% of that induced by the triple-drug combination. The maximal effect on penile length was a 43% increase when compared to baseline value, which was comparable to that induced by the triple-drug combination. The duration of the peak pressure and total duration of the peptide effect were significantly shorter in response to the 1 nmol dose of adrenomedullin than was observed with the control triple-drug combination. Intracavernous injection of the control triple-drug combination resulted in a significantly greater decrease in systemic arterial blood pressure than did adrenomedullin. Erectile responses to adrenomedullin were not altered following administration of the nitric oxide synthase inhibitor. N omega-nitro-L-arginine, at a time when erectile responses to acetylcholine were significantly reduced. These data demonstrate that intracavernous injection of adrenomedullin induces a short-lived erection in cats that is not due to the release of nitric oxide.

Tone-dependent vasodilator responses to proadrenomedullin NH2-terminal 20 peptide in the hindquarters vascular bed of the rat

Responses to proadrenomedullin NH2-terminal 20 peptide (PAMP) were investigated in the systemic and hindquarters vascular bed of the rat. Intravenous injections of PAMP and adrenomedullin (ADM) produced dose-related decreases in systemic arterial and hindquarters perfusion pressure, which were not altered by alpha-receptor or adrenergic nerve terminal blocking agents. PAMP was 100-fold less potent than ADM, and hindquarters vasodilator responses to both peptides were similar in innervated and denervated preparations. When baseline tone was increased with phenylephrine and U46619 or decreased with sodium nitroprusside, vasodilator responses to PAMP and ADM were correlated with the basal level of tone, suggesting that responses to both peptides are dependent on the baseline level of vasoconstrictor tone in the hindquarters vascular bed of the rat.

Adrenomedullin (16-31) has pressor activity in the rat but not the cat

Responses to a newly synthesized human adrenomedullin (hADM) analog, hADM (16-31), were investigated in the rat and cat. Unlike the full-sequence peptide, which has potent hypotensive activity, hADM (16-31) had pressor activity in the rat but not in the cat. Injection of hADM (16-31) in doses of 10-300 nmol/kg i.v. induced dose-dependent increases in systemic arterial pressure in the rat, and the peptide was approximately 10-fold less potent than norepinephrine when doses are compared on a nanomole basis. In contrast, injection of hADM (16-31) in doses up to 1,000 nmol/kg i.v. had no significant effect on systemic arterial pressure in the cat. Increases in systemic arterial pressure in response to hADM (16-31) in the rat were significantly reduced after administration of phentolamine or reserpine. These data suggest that increases in systemic arterial pressure in response to hADM (16-31) are mediated by release of catecholamines and activation of alpha-adrenergic receptors in the rat. These data show that hADM (16-31) has significant pressor activity and that there are marked species differences in the response to hADM (16-31).

Proadrenomedullin NH2-terminal peptide (PAMP)(12-20) has vasodepressor activity in the rat and cat

Decreases in systemic arterial pressure in response to human proadrenomedullin NH2-terminal 20 peptide (hPAMP), a truncated analog, hPAMP(12-20), and human adrenomedullin (hADM) were compared in the rat and cat. The order of potency was hADM > hPAMP > hPAMP(12-20). hPAMP(12-20) was approximately 3-fold less potent than the full sequence peptide, hPAMP, and 10-fold less potent than the related peptide, hADM. The duration of the vasodepressor responses to hPAMP(12-20) and hPAMP were similar, and responses to both peptides were significantly shorter in duration than hADM. Vasodepressor responses to hPAMP(12-20), hPAMP, and hADM were greater in the rat when compared to responses to the peptides in the cat.

Adrenomedullin-(22-52) antagonizes vasodilator responses to CGRP but not adrenomedullin in the cat

The effects of adrenomedullin (ADM)-(22-52), a putative ADM receptor antagonist, on vasodilator responses to ADM and the structurally related peptide, calcitonin gene-related peptide (CGRP), were investigated in the hindlimb vascular bed of the cat under constant-flow conditions. ADM-(22-52) had no significant effect on hindlimb perfusion pressure when injected in doses up to 120 nmol; after administration of ADM-(22-52), vasodilator responses to ADM were unchanged, whereas vasodilator responses to CGRP were inhibited. The inhibitory effects of ADM-(22-52) on responses to CGRP were selective and reversible and were similar to the inhibitory effects of the CGRP antagonist CGRP-(8-37). Hindlimb vasodilator responses to CGRP and to ADM were increased in duration by the adenosine 3',5'-cyclic monophosphate (cAMP) phosphodiesterase inhibitor rolipram but were not altered by inhibitors of guanosine 3',5'-cyclic monophosphate phosphodiesterase, nitric oxide synthetase, K(+)-ATP channels, the cyclooxygenase pathway, or the adrenergic nervous system. These results demonstrate that ADM-(22-52) is a selective CGRP receptor antagonist in the hindlimb vascular bed of the cat. The present data suggest that vasodilator responses to CGRP and ADM are mediated by different receptors but that these peptides dilate the hindlimb vascular bed of the cat by a similar cAMP-dependent mechanism.

Analysis of cardiovascular responses to PACAP-27, PACAP-38, and vasoactive intestinal polypeptide

Responses to pituitary adenylate cyclase polypeptide (PACAP)-27, PACAP-38, and vasoactive intestinal peptide (VIP) were compared in the peripheral and pulmonary vascular beds of the cat and in the isolated perfused neonatal pig heart. Intravenous injections of PACAP-27 and PACAP-38 produced biphasic changes in systemic arterial pressure whereas iv injections of VIP caused only decreases in arterial pressure. When blood flow to the hind limb and mesenteric vascular beds was maintained constant, PACAP-27 and PACAP-38 caused dose-related biphasic changes in perfusion pressure, whereas VIP only decreased perfusion pressure. PACAP-27 was approximately threefold more potent than PACAP-38, and the pressor component of the biphasic response was blocked by alpha-adrenergic antagonists and adrenalectomy. PACAP-27, PACAP-38, and VIP produced decreases in pulmonary vascular resistance, and all three peptides had significant vasodilator activity in the isolated perfused neonatal pig heart. Although all three peptides decreased coronary vascular resistance, only PACAP-27 and PACAP-38 increased left ventricular contractility, with PACAP-27 approaching isoproterenol in potency. The results of these experiments show that PACAP-27, PACAP-38, and VIP have significant effects on vasomotor tone that depend on the vascular bed studied and the contribution of adrenal catecholamines.

Catecholamine release mediates pressor effects of adrenomedullin-(15-22) in the rat

Human adrenomedullin, a novel hypotensive peptide, contains a six-member ring structure similar to that found in calcitonin gene-related peptide and pancreatic amylin. Unlike the full-sequence peptide, human adrenomedullin-(15-22) [hADM-(15-22)], which contains the ring structure, increases systemic arterial pressure in the rat but not the cat. We undertook the present study to investigate the mechanism by which hADM-(15-22) increases systemic arterial pressure in the rat. Injection of hADM-(15-22) in doses of 10 to 300 nmol/kg i.v. increased systemic arterial pressure in a dose-dependent manner and was threefold less potent than norepinephrine when doses were compared on a nanomole basis. However, the ring structures of human calcitonin gene-related peptide and human amylin, human calcitonin gene-related peptide-(1-8) and human amylin-(1-8), respectively, had no significant effect on systemic arterial pressure in the rat. Pressor responses to hADM-(15-22) were reduced significantly after administration of phentolamine or reserpine. Responses to hADM-(15-22) were not altered by the angiotensin type 1 blocking agent DuP 753 or the endothelin-A/endothelin-B receptor blocking agent bosentan, and responses to hADM-(15-22) and the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP) were reduced after bilateral adrenalectomy. Pressor responses to DMPP were reduced by hexamethonium, whereas the nicotinic blocking agent had no effect on the pressor response to hADM-(15-22). These data suggest that increases in systemic arterial pressure in response to hADM-(15-22) in the rat are mediated by the activation of alpha-adrenergic receptors by catecholamines released from the adrenal medulla. The present data suggest that hADM-(15-22) releases catecholamines from the adrenal medulla by a noncholinergic mechanism.

Biochemical and radiologic improvement in Paget's disease of bone treated with alendronate: a randomized, placebo-controlled trial

PURPOSE

The potent bisphosphonates offer great promise in the management of Paget's disease of bone, but are currently available only as parenteral preparations in most countries. There is a need for a well-tolerated, oral therapy. Furthermore, none of the currently available therapies have been rigorously demonstrated to heal the lytic bone lesions characteristic of this condition. Alendronate is a potent new oral aminobisphosphonate that has shown promising effects on Paget's disease in preliminary studies.

METHODS

We report a double-blind, randomized comparison of oral alendronate 40 mg/day and placebo over 6 months in 55 patients with Paget's disease. Efficacy was determined from measurements of biochemical indices of bone turnover (serum alkaline phosphatase and urine N-telopeptide) and blinded radiologic assessment of lytic bone lesions.

RESULTS

N-telopeptide excretion declined by 86% and serum alkaline phosphatase by 73% in patients receiving alendronate, but remained stable in patients receiving placebo (P < 0.001 between groups for both indices). Responses were similar whether or not patients had previously received bisphosphonate treatment. Alendronate treatment normalized alkaline phosphatase in 48% of patients. Forty-eight percent of alendronate-treated patients showed radiologic improvement in osteolysis whereas in the placebo group only 4% improved (P = 0.02 for between-groups comparison). No patient in either group showed worsening of osteolysis. Bone histomorphometry indicated that alendronate tended to normalize turnover indices. There was no evidence of abnormal mineralization in bone biopsies taken from 12 alendronate-treated subjects. The treatment was well tolerated.

CONCLUSION

Oral alendronate appears to be a safe and effective therapy for Paget's disease and results in healing of lytic bone lesions.

Prevalence of red marrow around the knee joint in adults as demonstrated on magnetic resonance imaging

RATIONALE AND OBJECTIVES

We determined the prevalence of red marrow around the knee joint in adults and evaluated variations with age, gender, and other variables.

METHODS

One hundred ninety-nine adult patients presenting for routine knee magnetic resonance (MR) imaging completed a questionnaire that covered age, gender, menstrual history, past pregnancies, smoking history, and medications. The presence or absence of visible red marrow in the distal femur and proximal tibia on both coronal and sagittal MR images was recorded for each patient. Associations between the presence of red marrow and the other recorded variables then were evaluated.

RESULTS

Red marrow was present in more than half of the women and less than one sixth of the men, a statistically significant difference. The age distribution of red marrow in men and women also was different. Red marrow was the most common in women aged 30-60 years. In men, there was no clear-cut age trend. Red marrow also was more likely to be present in obese individuals and smokers. No association was found between the presence of red marrow and any of the other recorded variables.

CONCLUSION

There are clear gender, age, obesity, and smoking-related differences in the prevalence of red marrow around the knee joint in adults. Red marrow is relatively common in this site in all age groups, and its presence should not be a cause for clinical concern.

[MPR14]-rADM(14-50), a novel analog of adrenomedullin, possesses potent vasodilator activity in the hindlimb vascular bed of the cat

Responses to [Mpr14]-ADM(14-50), a novel analog of adrenomedullin, were investigated in the hindlimb vascular bed of the cat under conditions of controlled blood flow. Intraarterial injections of [Mpr14]-rADM(14-50) in doses of 0.003-1 nmol caused dose-related decreases in hindlimb perfusion pressure. In terms of relative vasodilator activity, [Mpr14]-rADM(14-50) was more potent than human synthetic adrenomedullin (hADM) in doses of 0.003-0.1 nmol. The recovery half-times (T 1/2) for the vasodilator response to [Mpr14]-rADM(14-50) were significantly greater than the recovery half-times for hADM in all doses studied. Decreases in hindlimb perfusion pressure in response to [Mpr14]-rADM(14-50) were not altered by the calcitonin gene-related peptide receptor antagonist rCGRP(8-37) at the same time vasodilator responses to calcitonin gene-related peptide were significantly reduced. The present data demonstrate that [Mpr14]-(14-50) has potent and long-lasting vasodilator activity when compared to hADM, and that vasodilator responses to [Mpr14]-rADM(14-50) are not dependent on the activation of CGRP receptors in the hindlimb vascular bed of the cat.

Pulmonary vasodilator responses to adrenomedullin are reduced by NOS inhibitors in rats but not in cats

Responses to and the mechanism of action of adrenomedullin (ADM), the carboxy-terminal fragments of ADM, and calcitonin gene-related peptide (CGRP), a structurally related peptide, were investigated in the pulmonary vascular bed of the rat. Under conditions of elevated tone and controlled pulmonary blood flow in the isolated blood-perfused rat lung, injections of ADM, the 15-52 amino acid carboxy-terminal ADM analogue (ADM15-52), and CGRP caused dose-related decreases in pulmonary arterial perfusion pressure. In contrast, the carboxy-terminal 22-52 and 40-52 amino acid fragments had no consistent vasodilator activity. After administration of the nitric oxide synthase inhibitors, N omega-nitro-L-arginine benzyl ester or N omega-nitro-L-arginine methyl ester (L-NAME), pulmonary vasodilator responses to ADM, to ADM15-52, to CGRP, to acetylcholine, and to bradykinin were significantly decreased in the rat, whereas vasodilator responses to isoproterenol and nitroglycerin were not changed. However, in the pulmonary vascular bed of the cat, L-NAME had no significant effect on vasodilator responses to ADM in doses that attenuated vasodilator responses to acetylcholine and bradykinin. L-NAME had no effect on responses to isoproterenol or nitric oxide. When the relative vasodilator activity of the active peptides was compared, ADM15-52 was approximately three-fold less potent than ADM, and ADM was threefold less potent than CGRP in decreasing pulmonary vascular resistance in the rat lung. When vasodilator responses were compared in the rat and cat, ADM was threefold more potent in decreasing pulmonary vascular vascular resistance in the cat than in the rat, and vasodilator responses to ADM were independent of the intervention used to raise tone in the rat. The present data demonstrate that ADM and ADM15-52 have significant vasodilator activity in the pulmonary vascular bed of the rat, and that responses to ADM, ADM15-52, and CGRP are dependent on the release of nitric oxide in the rat. The present results indicate that pulmonary vasodilator responses to ADM are not dependent on the release of nitric oxide in the cat and suggest that responses to the peptide are mediated by different mechanisms in the pulmonary vascular bed of the rat and cat.

Comparative study of alendronate versus etidronate for the treatment of Paget's disease of bone

Alendronate, an aminobisphosphonate, is much more potent than etidronate, an older bisphosphonate, in inhibiting osteoclast-mediated bone resorption, and unlike etidronate, therapeutic doses of alendronate are not associated with abnormal mineralization. In the present study, we compared the effectiveness, safety, and tolerability of 6 months of daily oral administration of alendronate (40 mg) with those of etidronate (400 mg) in 89 patients with clinically active Paget's disease. The primary efficacy end point was the percent change in serum alkaline phosphatase. Other end points included changes in urinary deoxypyridinoline excretion, pain, functional impairment scores, and radiological osteolysis. Tetracycline-labeled bone biopsies were obtained for histomorphometric analysis from a subset of 43 patients at the 6-month visit. The alendronate-treated group had significantly greater decreases in both serum alkaline phosphatase (79% vs. 44%) and urinary deoxypyridinoline (75% vs. 51%) than the etidronate-treated group (P < 0.001 in both cases). Normalization of serum alkaline phosphatase was much more frequent in alendronate-treated patients (63.4% vs. 17.0%; P < 0.001). Alendronate was well tolerated and had a safety profile similar to that of etidronate. Histomorphometry revealed decreased bone turnover and no qualitative abnormalities, including no direct negative effects on bone mineralization, with alendronate treatment. One patient receiving etidronate developed frank osteomalacia. Alendronate appears to be a highly effective treatment for Paget's disease of bone that offers an important therapeutic advance over etidronate.

Proadrenomedullin NH2-terminal 20 peptide has cAMP-mediated vasodilator activity in the mesenteric vascular bed of the cat

Responses to proadrenomedullin NH2-terminal 20 peptide (hPAMP), a truncated analogue [hPAMP(12-20)], and adrenomedullin (hADM) were investigated in the mesenteric vascular bed of the cat. Under constant-flow conditions, injections of hPAMP, hPAMP(12-20), and hADM caused dose-related decreases in mesenteric perfusion pressure. hADM was 100-fold more potent than hPAMP, and 1000-fold more potent than hPAMP(12-20). Vasodilator responses to hPAMP and hADM were not altered by adrenergic-blocking agents, were similar in innervated and denervated preparations, and were similar when tone was increased by sympathetic nerve stimulation or phenylephrine infusion. Vasodilator responses to hPAMP and hADM were increased in duration by rolipram, a cAMP phosphodiesterase inhibitor. The present data suggest that vasodilator responses to the hPAMP and hADM are mediated by an increase in cAMP and that an interaction with the adrenergic nervous system is not involved.

Atlas of individual radiographic features in osteoarthritis

Radiographs of the hand, hip and knee were screened for evidence of osteoarthritis (OA). Specific sites selected for screening on the postero-anterior radiographs of the hand included the base of the thumb with distal and proximal interphalangeal joints; these regions were examined for formation of marginal osteophytes, joint space narrowing and subchondral lucency. Sites selected from antero-posterior radiographs of the hip included the acetabular and femoral portions of the joint; these regions were examined for joint space narrowing, subchondral lucency, marginal osteophytes and subchondral sclerosis. Sites selected from antero-posterior weight-bearing radiographs of the knee included distal femora and proximal tibiae including the medial and lateral compartments; these regions were examined for joint space narrowing, marginal osteophytes and subchondral sclerosis. Sites selected from axial views of the patellofemoral joint examined the medial and lateral portions; these regions were examined for joint space narrowing, osteophytes, subluxations and subchondral sclerosis. A set of photographic prints was made from the collection of radiographs. These specific features of OA were graded on each print and a subset of prints was selected that best demonstrated the spectrum of severity for each feature of OA. This resultant atlas is offered as an updated guide to standardize interpretation of radiographs prior to and during clinical trials.

Medical students who choose a radiology elective: career decisions, motivations, and intentions

RATIONALE AND OBJECTIVES

A national survey of American medical students was conducted to determine the effects of taking a radiology elective. The survey also probed attitudes of students not planning a career in radiology relative to the interpretation of medical images independently of radiologists.

METHODS

The names of all students taking an elective in radiology in 1993-1994 were solicited from all American medical schools. Eighty-one of 124 radiology elective programs responded, and 3872 questionnaires were returned to the 81 medical schools for delivery to the students. Approximately 25% of the questionnaires were returned, and data were derived from these.

RESULTS

Rarely did the radiology elective influence a change (2.1%) from another specialty or primary care to radiology. Eighty-nine percent of the students sampled indicated that the elective had no effect on their decision. Of students who were undecided about their careers, 13.2% indicated that the elective changed their career choice, but 63.2% said the elective had no effect. The data revealed that there are multiple, often overlapping, reasons for a medical student not planning a career in radiology to choose a radiology elective. Most of the students (93.5%) expected to interpret radiographs or other medical images themselves and then correlate their impression with a radiologic report. However, 30% of the students planned to interpret some radiographs independently of radiologists, and another 15% expected to interpret medical images other then plain radiographs without a radiologic consultation.

CONCLUSION

Our data suggest that attitudes regarding interpretation of radiographs or other medical images without involvement of a radiologist are ingrained in medical students and correspond to attitudes among practicing clinicians. There is an expectation among medical students that taking a 4-week elective is useful or even necessary to independently interpret radiographs in future clinical practice. The effect of these attitudes on the cost and quality of future medical care should engender considerable concern. A basic conceptual change in the structure and content of the radiology elective is suggested.

Three-dimensional quantitative structure-activity relationships of somatostatin analogues. 1. Comparative molecular field analysis of growth hormone release-inhibiting potencies

Somatostatin is a hypothalamic hormone that inhibits the release of growth hormone (GH). It has also been shown to inhibit the release of a broad range of hormones including insulin, glucagon, and gastrin. Presently, five different receptor subtypes of somatostatin have been characterized and cloned. Our previous work on the structure-activity relationship of somatostatin and that of many others has generated a large database of analogues with different biological activities and receptor affinities. This present work is an investigation of the growth hormone release-inhibiting potencies of somatostatin analogues by the three-dimensional quantitative structure-activity paradigm, comparative molecular field analysis (CoMFA). A total of 64 analogues were modeled in SYBYL using structural information from two NMR studies. The molecules were aligned by a root-mean-square fit of atoms and field-fit of the steric and electrostatic molecular fields and the resulting databases analyzed by partial least squares analysis with cross-validation to extract the optimum number of components. The analysis was then repeated without cross-validation to give the final QSAR models. Preliminary investigations with the CoMFA models led to the synthesis of a new somatostatin analogue. This compound together with five other newly synthesized compounds not included in the original training sets were used to test the predictive ability of the CoMFA models. Two models with good predictive powers are presented.

Updated osteoarthritis reference standard

The Kellgren and Lawrence atlas has been the reference standard for radiographic classification of osteoarthritis (OA) for nearly 40 years. Limitations include employment of a global grade, over-emphasis of the osteophyte, and submergence of other features so measurement of disease progression is difficult. Observer bias, drift, and variability cause concern. To address deficiencies and optimize observer accuracy, precision, and agreement, an updated atlas was created. From a photographic set of clinical radiographs, 4 readers selected a subset by consensus. Major radiographic features of hand, hip, and knee OA are graded on a 4-point scale. Using this atlas, it should be possible to individually score each relevant feature in a given joint. It is hoped the atlas will be adopted for population studies, assessment of disease progression, and protocols that evaluate new agents capable of modifying disease.

Comparison of responses to adrenomedullin and adrenomedullin analogs in the mesenteric vascular bed of the cat

Responses to adrenomedullin, a newly discovered hypotensive peptide isolated from human pheochromocytoma cells, and the carboxy terminal 15-52 (adrenomedullin-(15-52)) and 22-52 (adrenomedullin-(22-52)) amino acid fragments of adrenomedullin were investigated in the mesenteric vascular bed of the cat. Under constant flow conditions, injections of adrenomedullin, adrenomedullin-(15-52), and calcitonin gene-related peptide (CGRP) in doses of 0.003-1 nmol into the perfused superior mesenteric artery caused significant dose-related decreases in mesenteric arterial perfusion pressure. Mesenteric vasodilator responses to adrenomedullin and adrenomedullin-(15-52) were similar in magnitude and duration, while vasodilator responses to CGRP were greater in magnitude and longer in duration than those produced by adrenomedullin or adrenomedullin-(15-52) when these agents were injected in doses of 0.1-1 nmol. Adrenomedullin-(22-52) caused no significant change in mesenteric arterial perfusion pressure when injected in doses up to 10 nmol. These results suggest that amino acids 15-52 and the six-membered ring structure of adrenomedullin are important for the expression of vasodilator activity in the mesenteric vascular bed of the cat.

Evaluation of the injured cervical spine: comparison of conventional and storage phosphor radiography with a hybrid cassette

PURPOSE

To compare conventional and storage phosphor radiography of the injured cervical spine.

MATERIALS AND METHODS

Sixty-five patients underwent imaging in a supine position while wearing a cervical collar. Matched storage phosphor and conventional lateral cervical spine radiographs were obtained with an 18 x 24-cm hybrid cassette. Edge-enhanced and nonenhanced copies of each computed radiograph were printed on film, and the images were sent via a computer network to a remote imaging workstation. Four radiologists read the conventional radiographs, the two hard-copy computed radiographs, and the soft-copy images and used a binary scale to score the visibility of bone and soft-tissue structures.

RESULTS

All readers scored better in all areas with computed radiographs, and a statistically significant (P = .030) improvement in performance was seen for soft-tissue structures.

CONCLUSION

Storage phosphor imaging offers advantages over conventional radiography, and digital images may be a viable alternative to film.

Fractures of the tibial plateau: value of spiral CT coronal plane reconstructions for detecting displacement in vitro

OBJECTIVE

The purpose of this in vitro study was to determine the value of spiral CT for detecting displacement of fractures of the tibial plateau. The exact amount of inferior plateau depression, if any, is a primary criterion for deciding between surgical management and conservative management.

MATERIALS AND METHODS

An artificial fracture was produced in a cadaveric tibial plateau. Inferior displacements of 0, 1, 3, and 5 mm were created at the fracture. Spiral CT scans of each displacement were obtained with table speeds of 2, 3, and 5 mm/sec. Section collimation equaled table increment. Coronal image reconstructions were produced by use of standard scanner software. The images were interpreted by six musculoskeletal radiologists.

RESULTS

Interpretation accuracy was greatest with coronal images created from the 2 mm/sec scans. For distinguishing 5-mm fracture displacements, the average diagnostic sensitivity and specificity were 96% and 93%, respectively; when a 2-mm depression was used as the criterion for clinical significance, the sensitivity was 100% and the specificity was 69%.

CONCLUSION

When minimal table increment and collimation are used, spiral CT can detect clinically important inferior depressions of tibial plateau fractures. On the basis of the results of this study, when spiral CT is used for tibial plateau fracture assessment, we recommend 2-mm section collimation, 2-mm table speed, and reconstruction of images at 1-mm increments.

Skull of a 5,300-year-old mummy: reproduction and investigation with CT-guided stereolithography

PURPOSE

In September 1991, a mummified corpse was discovered soon after it was released by the receding ice of the Similaun glacier in the Tyrolean Alps. This body proved to be an astonishingly well-preserved man from the late Neolithic Age or early Bronze Age. To preserve the fragile mummy, scientific investigations were required to be as noninvasive and nondestructive as possible.

MATERIALS AND METHODS

A radiologic investigation that included conventional radiography, digital radiography, and whole-body computed tomography (CT) was performed from the CT data, the skull was duplicated by means of stereolithography.

RESULTS

The copy of the prehistoric skull was validated by means of comparison of measurements obtained from the original CT images and from external physical measurements of the intact head of the mummy.

CONCLUSION

The CT images, radiologic findings, and duplicated skull are expected to provide anthropologists and other interested scientists relatively accurate information without the need to handle the mummy, to expose it to the considerable risks of repeated partial thawing, or to perform invasive exploratory studies such as autopsy.

Comparison of spiral computed tomography versus conventional computed tomography multiplanar reconstructions of a fracture displacement phantom

PURPOSE

The capabilities of spiral computed tomography (CT) versus conventional CT to represent minimal fracture displacements on multiplanar reconstruction images in a phantom model were evaluated.

MATERIALS AND METHODS

A displacement phantom was created from Teflon and was scanned with conventional and spiral CT, at slice collimations of 2 mm, 3 mm, and 5 mm. Three Z-axis interpolation algorithms (360_LI, 180_LI and 180_HI) were employed to process the spiral image data into planar images. Displacements of 5 mm or less were represented in the phantom, and the resultant multiplanar reconstructions were analyzed for the precision of displacement representation. Specifically, the edge profiles of the reconstructed images were measured and compared.

RESULTS

Spiral CT reconstruction edge profiles were similar to those of conventional CT when minimal table increments (3 mm/sec or less), and an advanced interpolation algorithm (180_LI) was employed. Images obtained with 360_LI interpolation manifested the effect of widened slice profile even when employing minimal table speeds.

CONCLUSIONS

With minimal table increment (3 mm/sec or less) and a high-order interpolation algorithm (180_LI), spiral-CT-derived reconstructions demonstrate similar edge profile resolution to reconstructions obtained from conventional CT.

Comparison of responses to adrenomedullin and calcitonin gene-related peptide in the pulmonary vascular bed of the cat

Pulmonary vascular responses to the newly discovered hypotensive peptide, adrenomedullin, were compared with responses to the structurally related peptides, calcitonin gene-related peptide (CGRP) and amylin, in the intact-chest cat. Under conditions of controlled blood flow, when tone in the pulmonary vascular bed had been raised to a high steady level, intralobar injections of adrenomedullin (0.03-1 nmol), CGRP (0.1-3 nmol), and amylin (0.1 and 0.3 nmol) caused dose-related decreases in lobar arterial pressure without changing left atrial pressure. In terms of relative vasodilator activity in the pulmonary vascular bed, the dose of the peptide that decreased lobar arterial pressure 7.5 mm Hg (ED7.5 mm Hg) was significantly lower for adrenomedullin than for CGRP. The duration of the pulmonary vasodilator responses to CGRP was longer than for adrenomedullin, and both peptides decreased systemic arterial pressure when injected into the perfused lobar artery in the higher doses studied. The present data demonstrate that synthetic human adrenomedullin and CGRP have potent but relatively short-lasting vasodilator activity in the pulmonary vascular bed. These data show also that amylin, a structurally related pancreatic peptide, also has significant pulmonary vasodilator activity.