A scanning electron microscope investigation of the effects of pollutants on the hepatopancreatic ceca of Gammarus pulex (L.)

Scanning electron microscope studies were performed on the peripheral muscle network (myoepithelium) of the hepatopancreatic ceca of Gammarus pulex (L.) exposed to lindane, copper, or 3, 4-dichloroaniline (3,4-DCA) for a 24-hr period. The structural integrity of the myoepithelium of gammarids from control and test treatments was assessed using semiquantitative techniques. The lowest observed effect concentrations for structural changes were determined as 29.8 microg liter-1 lindane, 55 microg liter-1 copper, and 8.7 mg liter-1 3,4-DCA. The sensitivity of the bioassay and the significance of the morphological changes observed in the hepatopancreatic ceca of G. pulex are discussed.

Laparoscopic bipolar coagulation for the conservative treatment of adenomyomata

STUDY OBJECTIVE

To assess the effectiveness of treating adenomyomata with laparoscopic bipolar coagulation.

DESIGN

Prospective, observational study. Setting. The gynecology department of a community hospital.

PATIENTS

Ten women, each with severe dysmenorrhea, chronic menorrhagia, and adenomyomata diagnosed by magnetic resonance imaging.

INTERVENTIONS

Laparoscopic bipolar coagulation of adenomyomata.

MEASUREMENTS AND MAIN RESULTS

The mean (+/- SEM) total adenomyoma volume before leuprolide acetate administration was 119 +/- 16 cm3 (range 6-190 cm3); after 3 months of therapy this was reduced to 86 +/- 8 cm3 (range 6-162 cm3, p <0. 0001) a 27.7% reduction. Further reduction occurred 7 to 12 months postoperatively to 31 +/- 3.4 cm3 (range 3-155 cm3, p <0.0001), a 73.9% reduction from baseline. Twelve months postoperatively, seven (70.0%, p <0.05) women had continued resolution or significant reduction of dysmenorrhea and resolution of menorrhagia. One woman (10.0%) with unresolved dysmenorrhea and menorrhagia required hysterectomy, and two (20.0%) with recurrent menorrhagia required resection of the endomyometrium; one continued to have menorrhagia but refused further surgical or medical treatment.

CONCLUSIONS

Conservative treatment obviated the need for major surgery in 90% of women with adenomyomata, but further evaluation of this technique is necessary to determine its definitive role.

The effect of dilute vasopressin solution on blood loss during operative hysteroscopy: a randomized controlled trial

OBJECTIVE

To assess the effect of intracervical injection of dilute (0.05 U/mL) vasopressin solution on blood loss during operative hysteroscopy.

METHODS

In a randomized, double-blind study, dilute vasopressin solution or placebo (normal saline) was injected into the cervical stroma of 106 women before dilation of the cervix in preparation for operative hysteroscopy. Intraoperative bleeding was calculated by dividing the number of red blood cells per milliliter of outflow distention fluid by the number of red blood cells per milliliter of the woman's blood immediately before the procedure and multiplying this quotient by the total amount of outflow fluid collected. Pressures were kept constant with a hysteroscopic infusion pump.

RESULTS

The mean (+/-standard error of the mean) intraoperative blood loss of the treated (vasopressin) and control (placebo) groups was 20.3 +/- 4.1 mL (range 0-135) and 33.4 +/- 5.4 mL (range 0-290), respectively. The volume of distention fluid intravasation in the treated and control groups was 448.5 +/- 47.0 mL (range 30-1410) and 819.1 +/- 79.7 mL (range 20-1977), respectively. The operating time in the treated and control groups was 31.1 +/- 1.2 minutes (range 18-52) and 34.1 +/- 1.3 minutes (range 19-65), respectively. For all three outcome measures, the differences between the two groups were statistically significant, but for visual clarity of the uterine cavity during surgery, the difference was not significant.

CONCLUSION

Administration of dilute vasopressin solution (0.05 U/mL) to the cervical stroma significantly reduces blood loss, distention fluid intravasation, and operative time during hysteroscopy. Further evaluation is required to determine the optimum dosage.

Policy issues in the private health sector: examples from long-term care in the U.K

The international trend towards private markets in health care can be illustrated very clearly by developments over the last decade in the U.K., where the balance of health care provision has shifted from a predominantly free, public and comprehensive system to more of a mixed economy model. The shift can be attributed to a variety of factors, and not government policy alone. The relationship between the private and NHS sectors of health care is not a simple one and there are both positive and negative implications of the public-private mix. The growth of private hospitals and acute beds has dominated debates about private health care, but further policy issues have emerged in relation to the significant growth in private residential and nursing home care. This paper briefly reviews developments in private health care and then explores the key policy issues associated with this development. Secondly, an analysis of developments in the private residential care sector is undertaken highlighting the relationship between the public and private sectors of care provision. Policy issues pertaining to the long-term care sector of private health care are raised, including the regulation of residential care, regulatory models, enforcement and quality, and standards of care. Lessons for the regulation of private health care generally are considered and the implications for the private sector of a growing trend towards market deregulation are explored. Future models of long-term care are discussed and the likely balance between the public and private sectors explored.

Identification of retained N-formylmethionine in bacterial recombinant mammalian cytochrome P450 proteins with the N-terminal sequence MALLLAVFL...: roles of residues 3-5 in retention and membrane topology

An N-terminal block to Edman degradation was observed when any of five different mammalian cytochrome P450 (P450) proteins was expressed in Escherichia coli using the N-terminal sequence MALLLAVFL... This block was also seen in Salmonella typhimurium. With all proteins examined, the block could be removed by mild acid hydrolysis (0.6--6 N HCl, 23 degrees C) to expose Met as the N-terminus, suggesting N-formylMet retention. The N-terminal peptide of a modified P450 1A2 ("mutant 1", containing a thrombin-sensitive site inserted at residue 25) was released with thrombin and analyzed by electrospray mass spectrometry and found to yield the M(r) expected for the N-formyl derivative (+/- 0.8 amu). The region of positions 3--5 was altered by random mutagenesis, and three P450 1A2-expressing clones were analyzed for nucleotide and amino acid sequences. The changes from LLL were to RER (P450 1A2a), VDS (P450 1A2b), and WRH (P450 1A2c); these all show slightly dissimilar hydropathy plots compared to the MALLLAVFL... sequence. Mutant P450 1A2a had the N-terminal Met removed to yield N-terminal Ala; P450 1A2b contained an unmodified Met at the N-terminus; P450 1A2c had an approximately 80% block of the N-terminal Met. Experiments with bacterial membranes containing expressed P450 1A2 mutant 1 and P450 1A2 mutant 2 (thrombin-sensitive site inserted at residue 46) suggest that thrombin site 2, but not 1, is sequestered in the membrane. Spheroplasts of bacteria expressing P450 1A2 and the mutants at positions 3--5 were treated with proteinase K; amino acid analysis indicated that no cleavage occurred. These results are interpreted in a model in which most of the mammalian P450 expressed in the bacterium is located in the cytosol, the region near residue 46 is in the inner membrane, the region near residue 25 is in the cytosol, and the N-terminus is either imbedded in the membrane or free in the cytosolic space, depending upon the sequence. However, the possibility that the differences in N-terminal processing are the result of direct changes in interactions with the deformylase and Met aminopeptidase cannot be excluded.

Outside-in integrin signal transduction. Alpha IIb beta 3-(GP IIb IIIa) tyrosine phosphorylation induced by platelet aggregation

alpha IIb beta 3-(GP IIb IIIa) is the most abundant integrin expressed on platelets and plays a critical role in platelet aggregation and normal hemostasis. In response to platelet stimulation by agonists such as thrombin, alpha IIb beta 3 becomes a receptor for the adhesive proteins fibrinogen, von Willebrand factor, vitronectin, and fibronectin. Binding of extracellular matrix ligands allows the integrin to transmit a signal to the inside of the cell, but the exact mechanisms whereby integrins transduce these signals remains unclear. In this paper we demonstrate that the beta 3 subunit of alpha IIb beta 3 was phosphorylated on tyrosine residues in response to thrombin-induced platelet aggregation. However, tyrosine phosphorylation was not observed when platelets were stimulated by thrombin in the presence of an inhibitor of aggregation. Phosphotyrosine was only detected when platelets were solubilized under protein-denaturing conditions. A peptide corresponding to residues 740-762 of the beta 3 cytoplasmic domain was capable of binding the signaling proteins SHC and GRB2. GRB2 binding occurred only when both tyrosine residues (Tyr-747 and Tyr-759) were phosphorylated. SHC binding also occurred to a peptide monophosphorylated at Tyr-759. The data suggest that tyrosine phosphorylation of an integrin beta subunit may be important in initiating outside-in signaling cascades by inducing association of signaling components directly with the integrin.

Laparoscopic management of benign cystic teratomas during pregnancy

OBJECTIVE

Our purpose was to evaluate the surgical management and outcome of laparoscopic removal of benign cystic teratomas during pregnancy.

STUDY DESIGN

The records of women with benign cystic teratomas who were managed with operative laparoscopy during pregnancy were reviewed.

RESULTS

Twelve women had laparoscopic removal of a benign cystic teratoma during pregnancy. Gestational ages at surgery ranged from 9 to 17 weeks, with a mean of 14 weeks. Cyst size ranged from 5 to 13 cm, with a mean of 8.5 cm. Intraoperative rupture of the cyst occurred in 10 of 12 (93%) women. No patient had evidence of chemical peritonitis. The mean operating time was 87 minutes and the mean postoperative hospital stay was 44 hours. No intraoperative or postoperative maternal or fetal complications occurred.

CONCLUSIONS

Laparoscopic removal of a benign cystic teratoma of the ovary may be safely accomplished during pregnancy. In spite of a significant risk of cyst rupture, careful operative technique followed by copious irrigation of the pelvis may avoid chemical peritonitis and potential adverse sequelae.

Biophysical and biological evaluation of porphyrin-bisacridine conjugates

Two novel porphyrin-bisacridine conjugates (1 and 2) were designed as bifunctional antitumour agents to combine the DNA-binding character of the acridines and the photosensitizing capacity of porphyrin, and have been subjected to biophysical and biological evaluation. The interactions of the conjugates with calf thymus DNA were evaluated using viscometric, spectrophotometric and stopped-flow sodium dodecyl sulphate (SDS) sequestration methods. Both conjugates acted as bis-intercalators via the two acridine chromophores and displayed a longer residence time on DNA relative to the parent acridine ligand. Their biological activity in vitro was studied against the C6 rat glioma, MCF-7, GBM and A431 cell lines. Both conjugates were cytotoxic to all four cell lines. The ID50 (C6 glioma) was essentially the same as that of the parent acridine for one conjugate, but was increased 20-fold for the other, while both conjugates were approximately 10-fold more cytotoxic than the parent porphyrin component. The tissue distribution of the two conjugates was assessed in nude mice xenografted with a human small cell lung carcinoma (POVD). There were large differences in the tissue distribution of the two conjugates, with conjugate 2 localizing 8-fold more in the tumour than conjugate 1.

Adriamycin-induced DNA adducts inhibit the DNA interactions of transcription factors and RNA polymerase

Adriamycin is known to specifically induce DNA interstrand cross-links at 5'-GC sequences. Because 5'-GC sequences are a predominant feature of 5'-untranslated regions (transcription factor-binding sites, promoter, and enhancer regions), it is likely that adriamycin adducts at GC sites would affect the binding of DNA-interacting proteins. Two model systems were chosen for the analysis: the octamer-binding proteins Oct-1, N-Oct-3 and N-Oct-5, which bind to ATGCAAAT and TAATGARAT recognition sites, and Escherichia coli RNA polymerase binding to the lac UV5 promoter. Electrophoretic mobility shift studies showed that adriamycin adducts at GC sites inhibited the binding of octamer proteins to their consensus motifs at drug levels as low as 1 micoM, but no effect was observed with a control sequence lacking a GC site. Adriamycin adducts at GC sites also inhibited the binding of RNA polymerase to the lac UV5 promoter. Adriamycin may therefore function by down-regulating the expression of specific genes by means of inactivation of short but critical motifs containing one or more GC sites.

Effect of sulphur mustard on the initiation and elongation of transcription

Sulphur mustard is a potent alkylating agent that causes severe vesication as well as systemic and genotoxic effects. Despite its long history as a chemical warfare agent, the mechanism of its toxicity remains unknown and no successful pharmacological intervention has yet been found. In this study we have examined the effects of mustard alkylation of DNA on transcriptional processes. Gel mobility shift analysis shows that mustard alkylation of the lac UV5 promoter increases the stability of the promoter-RNA polymerase binary complex. Following formation of the initiation complex and addition of elongation nucleotides, approximately 45% of the RNA polymerase in the initiated complex remained associated with the alkylated promoter, compared to only 7% remaining associated with the unalkylated promoter. For the RNA polymerase able to escape the initiation complex, mustard alkylation of the DNA template resulted in the production of truncated transcripts. Analysis of these truncated transcripts revealed that sulphur mustard alkylates DNA preferentially at 5'-AA, 5'-GG and 5'-GNC sequences on the DNA template strand and this is significantly different from the alkylation sites observed with nitrogen mustard. This study represents the first report at the molecular level of sulphur mustard-induced effects on transcriptional processes.

A comparison of manual diagnosis with a diagnosis established by a uni-level lumbar spinal block procedure

The study was designed to test if a manipulative therapist (MT) using manual examination techniques alone or when accompanied by a verbal response from the subject as to the pain produced, could diagnose the lumbar segmental level responsible for a subjects low back pain and referred pain. The study consisted of prospective and retrospective parts where the MTs manual diagnosis of the symptomatic lumbar segmental level was compared to a segmental level diagnosis attained by subsequent or previous spinal anaesthetic blocks. In the prospective part of the study the MT's manual diagnosis was 94.12% and 52.9% sensitive in detecting the symptomatic lumbar segmental level with verbal and non-verbal subject responses, respectively. In the retrospective part of the study the MTs manual diagnosis was found to be 60.86% and 47.82% sensitive in detecting the symptomatic lumbar segmental level with verbal and non-verbal subject responses, respectively. In the prospective study the MT's manual diagnosis showed 100% and 80% specificity in detecting subjects with no history of low back pain with verbal and non-verbal subject responses, respectively, and 100% and 75% specificity in the retrospective study with verbal and non-verbal subject responses, respectively. Inter-therapist reliability analysis for the recording of passive physiological intervertebral movements (PPIVMs), passive accessory intervertebral movements (PAIVMs) and 'tissue response' showed percentage agreement rates ranging from 55% to 99%; 74% to 100% and 43% to 100%, respectively, with weighted kappa values ranging from -0.11 to 0.32; -0.15 to 0.24 and kappa values ranging from -0.16 to 0.28, respectively. This study demonstrates that a MT's manual examination when accompanied by a verbal subject response, is highly accurate in detecting the lumbar segmental level responsible for a subjects complaint.

Evaluation of porphyrin C analogues for photodynamic therapy of cerebral glioma

A series of monomeric porphyrins (2-8) based on porphyrin C (1) have been tested as sensitisers for photodynamic therapy (PDT) of cerebral glioma using the in vitro/in vivo C6 intracerebral animal tumour model. The in vivo screening, consisting of cytotoxicity, phototoxicity (red light) and subcellular localisation studies, revealed two sensitisers (porphyrin 7, molecular weight 863 Da and porphyrin 8, molecular weight 889 Da), which had greater photoactivity than porphyrin C and similar photoactivity to haematoporphyrin derivative (HpD) although at a 5-fold higher dose than HpD. Both sensitisers showed intracellular localisation to discrete organelle sites and exhibited considerably less 'dark' cytotoxicity than HpD. The kinetics of uptake of porphyrins 7 and 8 was studied in the mouse C6 glioma model as well as in biopsy samples from normal brain, liver, spleen and blood. Maximal drug uptake levels in tumour occurred 9 and 6 h after intraperitoneal injection for 7 and 8 respectively, at which time the tumour to normal brain ratios were 15:1 and 13:1 respectively. The effect of PDT using porphyrin 7 activated by the gold metal vapour laser tuned to 627.8 nm was studied in Wistar rats bearing intracerebral C6 glioma. At a drug dose of 10 mg porphyrin 7 kg-1 body weight and laser doses of up to 400 J cm-2 light, selective tumour kill with sparing of normal brain was achieved, with a maximal depth of tumour kill of 1.77+/-0.40. mm. Irradiation following a higher drug dose of 75 mg porphyrin 7 kg-1 body weight resulted in a greater depth of tumour kill, but also significantly increased the likelihood and extent of necrosis in normal brain.

Magnetic resonance imaging for diagnosing adenomyomata

STUDY OBJECTIVES

To evaluate the accuracy of magnetic resonance imaging (MRI) for diagnosing nodular adenomyosis by percutaneous myometrial biopsies.

DESIGN

Prospective observational study.

SETTING

Gynecology department of community hospitals.

PATIENTS

Twenty women with severe dysmenorrhea, chronic menorrhagia, and an MRI diagnosis of adenomyomata.

INTERVENTIONS

Several laparoscopically guided, percutaneous myometrial biopsy specimens were taken in an attempt to confirm histologically an MRI diagnosis of adenomyoma; and resectoscopic endomyometrial biopsy specimens were taken in an attempt to confirm an MRI diagnosis of adenomyosis.

MEASUREMENTS AND MAIN RESULTS

Eighteen (90%) of the 20 women had an MRI diagnosis of adenomyosis histologically confirmed by myometrial biopsy. The remaining two (20.0%) had an MRI diagnosis of adenomyosis histologically confirmed by endomyometrial biopsy.

CONCLUSIONS

An MRl diagnosis of adenomyoma was confirmed by transabdominal uterine biopsy in most patients. These results, when combined with those obtained by resectoscopic endomyometrial biopsy, established a diagnosis of adenomyosis in all patients.

Procoagulant activity of reversibly acylated human factor Xa

The plasma clotting factors used to treat hemophiliacs who have developed inhibitory antibodies have a shared history of limited clinical safety and utility. To improve on existing bypass factors, we have developed a reversibly acylated form of human plasma factor Xa capable of providing a time-dependent release of procoagulant activity. Factor Xa was treated with p-amidinophenyl p'-anisate to generate anisoyl Xa. The chemical modification of the protein involves acylation of the active site serine residue of factor Xa. Anisoyl Xa deacylated in a time, pH, and temperature-dependent manner. Active factor Xa generated on deacylation of anisoyl Xa exhibited amidolytic and prothrombinase complex activities in in vitro assays, the level being comparable to those of untreated factor Xa. When Anisoyl Xa was infused into rabbits, active factor Xa was generated on deacylation of the acylated enzyme, which shortened the activated partial thromboplastin time (APTT) in a dose-dependent manner. The duration of effect on rabbit APTT could be directly correlated to the level of human plasma factor Xa. Because anisoyl Xa bypasses the "tenase" complex that is compromised in hemophilia A and B and is unaffected by inhibitory antibodies, it has the potential to be used as an effective bypass therapy.

Aging trends--Singapore

"Three major inter-related issues have emerged concerning population aging in Singapore. The first two concerns are whether aging will increase dependency on the state for welfare and financial assistance and whether traditional family caring structures will survive and provide the care deemed necessary in the future. The third concern focuses on the potential impact of population aging on Singapore's future economic growth and development....A national policy on elderly persons has been formulated since 1989 and focuses on four main areas: employment of elderly people in the workforce; attitudes towards elderly people; community care; and residential care."

Myeloperoxidase oxidizes mitoxantrone to metabolites which bind covalently to DNA and RNA

The anticancer agent mitoxantrone is readily oxidized by the human haem enzyme myeloperoxidase and hydrogen peroxide. Intercalation of mitoxantrone with DNA inhibited oxidation of the drug by myeloperoxidase. However, at a physiological ionic strength, significant oxidation of the drug was evident. At a H2O2:mitoxantrone ratio of 1.0, myeloperoxidase oxidized mitoxantrone to a metabolite (product B) which associated reversibly with DNA. At greater hydrogen peroxide concentrations, two further metabolites were produced (products C and D), neither of which associated reversibly with DNA, as indicated by the absence of any spectral change in the presence of DNA. Long exposure of the products derived from the oxidation of [14C]mitoxantrone by myeloperoxidase resulted in a time-dependent covalent binding of the activated drug to both DNA and RNA. The amount of DNA adduct increased linearly with the extent of oxidation of mitoxantrone (up to a H2O2:mitoxantrone ratio of 5.0). No adducts resulted from exposure of the oxidized product B to DNA, but adducts formed following further oxidation of B by myeloperoxidase. The myeloperoxidase-catalysed oxidation of mitoxantrone to products capable of interacting covalently and non-covalently with nucleic acids may represent an important mode of action of mitoxantrone against acute myeloid leukemias since these cells (including neutrophils, monocytes and their precursors) contain high levels of myeloperoxidase.

Aging in the United Kingdom: a review of demographic trends, recent policy developments and care provision

"Although the U.K.'s population is not predicted to grow very much in the future, the population structure is changing and there is a shift towards a much older age distribution. The characteristics of demographic aging in the U.K. include a marked reduction in fertility rates, increasing rates of life expectation at birth..., increasing dependency ratios and variations in mortality and social class in old age. The U.K.'s demographic context has important implications for aged care policy and planning. This paper documents the demographic trends, reviews recent major policy changes and their impact on care provision, and discusses some of the emerging implementation issues that challenge the potential of such policies to meet the needs of an aging population."

100 laparoscopic hysterectomies in private practice and visiting professorship programs

STUDY OBJECTIVE

To evaluate 100 laparoscopic hysterectomies and their variations in private practice and visiting professorship programs.

DESIGN

A prospective observational study.

SETTING

Gynecology departments of 17 teaching, community, and proprietary hospitals in the northeastern United States.

PATIENTS

One hundred women who successfully underwent laparoscopic hysterectomy, 91 of whom were followed for 6 months.

INTERVENTIONS

From July 1990 to August 1994, 108 women (mean age 41.6 yrs, range 38-68 yrs) for whom a vaginal hysterectomy was relatively contraindicated underwent a hysterectomy attempted by the laparoscopic route. The most common indications for hysterectomy were pelvic pain, chronic menorrhagia, and uterine leiomyomas. The women were classified according to hysterectomy, with groups comparable in age, weight, uterine size and weight, concomitant surgery performed, uterine and coexisting pathology, and history of pelvic surgery. Of the 108 women, 35 had laparoscopic hysterectomies (LH), 56 had laparoscopic-assisted vaginal hysterectomies (LAVH), and 9 had subtotal laparoscopic hysterectomies (SLH). Eight procedures were converted to laparotomy, two attempted LHs and six attempted LAVHs. In 22 cases, bipolar coagulation of vascular pedicles was done exclusively, in 58 the Endo GIA 30 stapler was used exclusively, and in 20 a combination of both modalities was used. Bilateral ureteral catheters were inserted 49 times.

MEASUREMENTS AND MAIN RESULTS

There were eight complications (8.0%): two blood transfusions, two cases of transient, asymptomatic pyrexia, two abdominal wall hematomas, one Richter hernia, and one urinary tract infection. The hernia repair was the only delayed laparotomy. The mean (+/-SEM) surgical time was 123 +/- 8 minutes (range 45-235 min), and the mean hospital stay was 1.48 days +/- 0.4 (range 1-5 days). Ninety-five of the 100 women who successfully underwent a laparoscopic procedure returned to work within 2 weeks (range 4-14 days, range 15-53 days for the remaining 5).

CONCLUSION

Hysterectomy performed or aided by the laparoscope, whether LH, LAVH, or SLH, is effective and safe as long as at least one member of the surgical team is an experienced and appropriately trained laparoscopic surgeon. Further studies are necessary to determine if the credentialing process for advanced laparoscopic surgery would be facilitated by a visiting professorship program.

Nitrogen mustard inhibits transcription and translation in a cell free system

Nitrogen mustard and its derivatives such as cyclophosphamide, chlorambucil and melphalan are widely used anti-cancer agents, despite their non-specific reaction mechanism. In this study, the effect of alkylation by nitrogen mustard of DNA and RNA (coding for a single protein) was investigated using both a translation system and a coupled transcription/translation system. When alkylated DNA was used as the template for coupled transcription and translation, a single translation product corresponding to the 62 kDa luciferase protein was synthesised. Production of the translated product encoded by this template was inhibited by mustard concentrations as low as 10 nM, and 50% inhibition occurred with 30 nM mustard. A primer extension assay employed to verify alkylation sites on the DNA revealed that all guanine residues on the DNA template are susceptible to alkylation by nitrogen mustard. Similarly, when alkylated RNA was used as the template for protein synthesis, the amount of the 62 kDa luciferase protein decreased with increasing mustard concentration and a range of truncated polypeptides was synthesised. Under these conditions 50% inhibition of translation occurred with approximately 300 nM mustard (i.e. approximately 10 times that required for similar inhibition using an alkylated DNA template). Furthermore, a gel mobility shift assay revealed that mustard alkylation of the RNA template results in the formation of a more stable retarded RNA complex. The functional activity of the luciferase protein decreased with alkylation of both the DNA and RNA templates, with a half-life of loss of activity of 1.1 h for DNA exposed to 50 nM mustard, and 0.5 h for RNA exposed to 50 microM mustard. The data presented support the notion that DNA is a critical molecule in the mode of action of mustards.

Aging trends-Hong Kong

Aspects of demographic aging in Hong Kong are examined in this study. "By regional standards, many of Hong Kong's 1992 population of 5.9 million have a good standard of living and adequate housing. However, there are considerable discrepancies in wealth and well-being; elderly people are not always financially secure, and there are growing difficulties in maintaining the oft-cited mode of family care for elderly members. Hong Kong is a rapidly aging society and it is essential to see this process in the context of local and regional socioeconomic change and the future political linkages of the territory with China."

Endometrial ablation for postmenopausal uterine bleeding induced by hormone replacement therapy

STUDY OBJECTIVE

To determine the effectiveness of transcervical endometrial ablation or endomyometrial resection for treating refractory postmenopausal uterine bleeding induced by hormone replacement therapy (HRT).

DESIGN

Prospective observational study.

SETTING

Community, teaching, and proprietary hospitals.

PATIENTS

Twenty-nine postmenopausal women experiencing troublesome uterine bleeding while taking hormones.

INTERVENTIONS

Hormone manipulation, office hysteroscopy or sonohysterography, endometrial curettage, and transcervical endometrial ablation or endomyometrial resection were performed in all 29 patients.

MEASUREMENTS AND MAIN RESULTS

Twenty-seven women (93.1%) who continued HRT became amenorrheic within 2 months of surgery. The two who did not have irregular, intermittent spotting, but neither one required or desired further surgical intervention. Five women discontinued HRT from 3 to 53 months postoperatively (mean 12.5 +/- 8.2 mo) because of apprehension about developing breast cancer and for personal reasons. The 24 (82.8%) who continued HRT were observed for as long as 99 months (mean 36.4 +/- 5.5 mo); 22 (91.6%) of them remained amenorrheic. Pathologic examination of tissue specimens revealed atrophic endometrium in 4 patients, adenomyosis in 7, simple hyperplasia in 4, submucous leiomyomas in 11, endometrial polyps in 4, and proliferative endometrium in 1. There were no perioperative complications.

CONCLUSION

Endometrial ablation or endomyometrial resection was an effective alternative to discontinuing HRT for these postmenopausal women whose uterine bleeding was unrelieved by modification of their sex steroid regimens.

Use of oligonucleotides to define the site of interstrand cross-links induced by Adriamycin

It has been known for several years that Adriamycin forms adducts and interstrand cross-links when reacted for long periods of time with bacterial and mammalian DNA in vitro, with the cross-link being restricted to 2 bp elements containing GpC sequences. The self-complementary 20mer deoxyoligonucleotide TA4T4GCA4T4A has been used in this study as a model of the apparent G-G cross-linking site at GpC sequences. The rate of formation of cross-links, as well as the dependence on both Adriamycin and Fe(III) concentration, were similar with this oligonucleotide as compared with calf thymus DNA. The cross-linking was demonstrated on both denaturing and non-denaturing sequencing gels. The half-life of the G-G cross-link was 40 h, consistent with that implied with high molecular weight, heterogeneous sequence DNA. Exonuclease III digests of adducts formed with 20mer deoxyoligonucleotides containing single, central G-G, G-I and I-I potential cross-links revealed that a guanine residue is required at both ends of the cross-link. No cross-linking was observed with a similar oligonucleotide containing only a single central (G.C) bp.

Teenage pregnancy: a comparative study of teenagers choosing termination of pregnancy or antenatal care

A comparative study of 167 pregnant teenagers in Devon attending either antenatal booking clinics or for National Health Service (NHS) termination of pregnancy was carried out to determine differences in their characteristics, use and experience of local family planning services. Teenagers presenting for termination of pregnancy were younger and more likely to say that they had wished to avoid getting pregnant. Whether the teenager was in a stable relationship was strongly associated with the outcome of the pregnancy, with single girls being more likely to choose a termination of pregnancy. The termination of pregnancy group were also more likely to be condom users, and to have learned about their method of contraception from school rather than from health care professionals. Teenagers' frequency of contact with family planning services suggested that teenagers choosing a termination were less likely than antenatal attenders to have attended regularly. This was mainly due to differences in behaviour among teenagers attending their general practitioner (GP) for contraceptive advice: teenagers having a termination were more likely to describe their visit to their GP as embarrassing. These findings have implications for local family planning services attempting to reduce the number of unwanted teenage pregnancies.

Transcervical electrosurgical resection of submucous leiomyomas for chronic menorrhagia

STUDY OBJECTIVE

To evaluate the effectiveness and safety of transcervical electrosurgical resection (TSR) of submucous leiomyomas with or without concomitant transcervical endomyometrial resection (TEMR) for chronic menorrhagia.

DESIGN

Prospective observational study, with 6-month follow-up of all 208 women and up to 6-year follow-up of 185 (88.9%).

SETTING

Gynecology departments of teaching, community, and proprietary hospitals.

PATIENTS

Two hundred eight women with submucous leiomyoma requiring surgical treatment of menorrhagia between March 1988 and March 1994.

INTERVENTIONS

All 208 women (age range 32-63 yrs) underwent TSR with a continuous-flow gynecologic resectoscope. In 88 of these women who had no desire to preserve fertility, concomitant TEMR was performed.

MEASUREMENTS AND MAIN RESULTS

Six months postoperatively 113 (94.2%) of the 120 women who underwent only TSR reported normal menses and 85 (96.6%) had satisfactory results; 62 (70.5%) who had both TSR and TEMR were amenorrheic. Eleven (73%) of the 15 women who had TSR and wanted to conceive subsequently became pregnant. One hundred eighty-five (88.9%) of the 208 patients have been followed for as long as 6 years. Ninety (84.1%) of the 107 women who had only the initial TSR and 69 (88.5%) of the 78 who had initial TSR and TEMR had satisfactory results. Only five women (2.7%) required major abdominal surgery. Among those undergoing TSR and TEMR, 49 (62.8%) were amenorrheic for as long as 6 years after TSR and one or two TEMRs. Eight (3.8%) of the 208 women had perioperative complications: 6 (2.9%) had fluid overload, 1 (0.5%) had dilutional hyponatremia, and 1 (0.5%) had excessive postoperative bleeding requiring tamponade.

CONCLUSIONS

We believe that TSR with or without concomitant TEMR is an effective and safe treatment for women with submucous leiomyomas suffering from chronic menorrhagia.

Stability of adriamycin-induced DNA adducts and interstrand crosslinks

The stability of adriamycin-induced DNA adducts and interstrand crosslinks was measured at 37 degrees C by three independent procedures. The loss of [14C]-labelled adducts was described by two first-order decays with half-lives of 7.4 h (60% amplitude) and 39 h (40%). The loss of the drug chromophore also exhibited a biphasic character, with half-lives of 6 h (65%) and approximately 150 h (35%). The decay of transcriptional blockages at an isolated, apparent interstrand GpC crosslinking site was described by two first-order processes, with half-lives of 3 h (65%) and 40 h (35%), whereas the decay of transcriptional blockages at an isolated guanine residue (apparent site of monoadduct) was completely described by a first-order decay with a half-life of 5.3 h. The loss of interstrand crosslinks was measured using a gel electrophoresis assay, and the decay was characterised by a single first-order process with a half-life of 4.7 h. Collectively, these values serve to define a model of the interstrand crosslink with unstable sites of attachment at both ends of the crosslink, with half-lives at either end being approximately 5 and 40 h. The adducts exhibited increasing lability with increasing pH, and were particularly unstable at pH 12, with a half-life of approximately 0.5 h. The adducts were also heat labile, with an overall melting temperature of 67 degrees C (10 min exposure) and this was also the thermal lability measured at three individual adduct sites probed by lambda exonuclease.

Biodistribution of haematoporphyrin analogues in a lung carcinoma model

In an attempt to identify novel compounds useful for the optimization of Photodynamic Therapy (PDT), the tissue localization of new synthetic porphyrins was compared with Photofrin II in nude mice xenografted with a human small cell lung cancer (POVD). Three haematoporphyrin analogues were selected for this study based on prior in vitro photosensitivity screening of a series of 15 such derivatives, as well as on the basis of improved localization in C6 gliomas in mice. Two of the porphyrins yielded better tumour:normal lung ratios than Photofrin II and, of these two, one (P13) is known to exhibit good photosensitization properties both in vitro and in vivo, and is therefore a good candidate as a lead compound for the development of porphyrins suitable for the photodynamic treatment of lung tumours.

Oxidative metabolism of mitoxantrone by the human neutrophil enzyme myeloperoxidase

The anti-cancer drug mitoxantrone is readily oxidized by the human heme enzyme myeloperoxidase (MPO) and H2O2. Direct oxidation yielded up to three products, which depended on the ratio of H2O2 to mitoxantrone. At an H2O2: mitoxantrone ratio of 1.0, one major product was obtained, with a spectrum and HPLC retention time identical to that resulting from oxidation by horseradish peroxidase. This metabolite is a substituted hexahydronaphtho[2,3-f]quinoxaline-7,12-dione and has been discovered in the urine of patients treated with mitoxantrone, hence implicating MPO in the in vivo metabolism of mitoxantrone. At higher concentrations of H2O2, the oxidation of mitoxantrone was more complex, with two further metabolites being identified. When mitoxantrone was incubated with neutrophils that had been stimulated with phorbol myristate acetate, it was oxidized by an MPO-dependent mechanism. Therefore, it appears that MPO may play a significant role in the clinical activity displayed by mitoxantrone against acute myelogenous leukemias, as neutrophils, monocytes and their bone marrow precursors contain high levels of the enzyme.

Molecular basis of nitrogen mustard effects on transcription processes: role of depurination

DNA was alkylated with nitrogen mustard (HN2) and the rate of release of the alkylpurines was quantitated by HPLC. The half life of depurination of the major product (7-alkylguanine) was 9.1 h at 37 degrees C. End-labelled DNA was used to show that depurination occurred dominantly at 5'-GA, 5'-GG and 5'-GT sequences. Although extensive alkylation was observed at all 5'-GNC and 5'GNT sequences, no depurination was observed at these sites during a depurination time of 20 h at 37 degrees C. Since these sites are potential interstrand crosslinking sequences (G-adduct-G and G-adduct-A, both spanning an intervening base pair), this suggests that these regions have a greatly enhanced stability or that simultaneous depurination of both ends of the crosslink is necessary before these lesions are removed (with a predicted half-life of approximately 80 h at 37 degrees C). Depurination at the lac UV5 promoter impaired the association of Escherichia coli RNA polymerase with that promoter, while in the elongation phase two distinctly different sequence-specific processes were apparent. At 5'-GNC and 5'-GNT sequences transcriptional blockages were maintained with increasing elongation time, whereas at monoadduct sites, the blockage decreased with elongation time (predominantly at 5'-GG and 5'-GC sequences), with an average half-life of approximately 10.7 h. Collectively, these results suggest that the observed read-through past monoadduct sites is due to depurination of the DNA at those sites. E. coli RNA polymerase is therefore able to transcribe efficiently past apurinic sites and presumably does so by incorporating an incorrect base into the nascent RNA.

Evaluation of a morpholinothiolporphyrin for use in photodynamic therapy

The photonecrotic effectiveness of a morpholinothiolporphyrin derived from haematoporphyrin was measured in an animal model of cerebral glioma. The dose administered was 20 mg kg-1 and the laser dose varied from 0 to 200 J cm-2. The tumour necrosis was at least as good as that of HpD, and this therapeutic response may be attributed to the targeting of specific 'photopotent' subcellular sites.

Formation of adriamycin--DNA adducts in vitro

Adriamycin is known to induce the formation of adducts with DNA when reacted under in vitro transcription conditions. The factors affecting the extent of adduct formation were examined in order to establish the critical components and optimal conditions required for the reaction, and to gain insight into the nature of the DNA-adduct complex. There was a strong dependence on reaction temperature (with a 40-fold increase of adducts at 40-50 degrees C compared to 10 degrees C), pH (maximum adducts at pH 7), but little dependence on the oxygen level. There was an absolute requirement for a reducing agent, with adducts detected with DTT, beta-mercaptoethanol and glutathione, maximal adducts were formed at high levels of DTT (5-10 mM). Adducts were also formed with a xanthine oxidase/NADH reducing system, with increasing amounts of adducts detected with increasing NADH; no adducts were detected in the absence of either the enzyme or NADH. Of fourteen derivatives studied, only four yielded a similar extent of adduct formation as adriamycin; there was no absolute requirement for a carbonyl at C13 or hydroxyl at C14. Adducts were also observed with ssDNA but required a longer reaction time compared to dsDNA. The sequence specificity of adduct formation with ssDNA was examined using a primer-extension assay; almost all adducts were associated with a guanine residue. Overall, the results are consistent with a two-step reaction mechanism involving reductive activation of adriamycin, with the activated species then reacting with the guanine residues of either dsDNA or ssDNA.

A modelling procedure for the analysis of dynamic drug--DNA interactions probed during active transcription of the DNA

A multicompartment simulation analysis (CONSAM) has been used to describe the in vitro inhibition of transcription of DNA by echinomycin. The model assumes that at all drug blockage sites the fractional amount of blocked RNA polymerase is defined by the relative drug occupancy at that site (and is released at a rate defined by the drug dissociation rate), with all remaining enzyme being rapidly transferred past that site. The solution to the 48 parameters (three per drug site, 16 sites), which fully described the echinomycin-DNA transcription data set, can readily be accomplished without manual intervention within an hour on a MS-DOS, 486D-based microcomputer, compared to several months for a similar solution by Monte-Carlo simulation (requiring repeated intervention). The adequacy of the parameters to describe the model was confirmed by four independent criteria. The approach is applicable to the analysis of any enzyme system where an inhibitor of any type (interacting in either a reversible or irreversible manner) prevents the processive movement of enzyme along the template.

Sequence specificity of (cyanomorpholino)adriamycin adducts in human cells

The highly reiterated alpha DNA tandem repeat was extracted from HeLa cells incubated with (cyanomorpholino)adriamycin (CMA) using mild techniques and subsequently probed for drug adducts by exonuclease III. The sequence specificity of the CMA-induced blockages was compared with that for blockages induced on the same DNA fragment when reacted in vitro. The sequence specificity of the drug-induced blockages was the same on both the isolated and the intact cell alpha DNA templates, with blockages predominantly associated with GpG sequences on either strand of the DNA.

A comparison of endometrial ablation using the Nd:YAG laser or electrosurgical techniques

STUDY OBJECTIVE

To compare the results of endometrial ablations performed either with the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser or electrosurgically.

STUDY DESIGN

Retrospective study, with 4-year follow-up of 82 of 98 patients.

SETTING

Gynecology departments of teaching, community, and proprietary hospitals.

PATIENTS

One hundred sixty-six women requiring surgical treatment for menorrhagia between March 1986 and October 1992.

INTERVENTIONS

Fifty-eight women were treated with a Nd:YAG laser, 11 with a rollerball electrode, and 97 with a wire loop electrode. Concomitant resection of submucous leiomyomata was performed in 54 (32.5%) of the patients.

MEASUREMENTS AND MAIN RESULTS

The mean operating times, complication rates, mean volume of fluid absorption, concomitant surgery, morbidity, duration of hospital stay, and results of laser and electrosurgical endometrial ablations were similar. Thirty-nine women (69.9%) undergoing laser endometrial ablation became amenorrheic and 54 (96.4%) had satisfactory results after 6 months. Seven (63.3%) of the women who had a rollerball ablation became amenorrheic, and 10 (90.9%) had satisfactory results. Sixty-one women (70.9%) who underwent wire loop resection became amenorrheic, with 83 (96.5%) attaining satisfactory results. Four years postoperatively, 85.4% of the patients continued to have satisfactory results.

CONCLUSIONS

Laser and electrosurgical endometrial ablations are similarly effective treatment for patients suffering from chronic menorrhagia. This preliminary study should be followed by a randomized, controlled, prospective study to evaluate the two techniques more fully.

DNA sequence specificity of mitoxantrone

An in vitro transcription assay was used to determine the sequence specificity of binding of mitoxantrone to a 497 bp fragment of DNA containing the lac UV5 promoter. Transcriptional blockages of the E. coli RNA polymerase were observed dominantly prior to 5'-CpA sequences (64% occurrence), and to a lesser extent 5'-CpG sequences (29%). Overall, 93% of all blockage sites were prior to pyrimidine (3'-5') purine sequences. An effect of flanking sequences was evident since the blockage sites contained an A/T base pair 5' prior to the consensus CpA and CpG intercalation sites. The consensus sequences for the preferred mitoxantrone intercalation sites are therefore 5'-(A/T)CA and 5'-(A/T)CG. The location of transcriptional blockages one base pair prior to the intercalation site is consistent with the fact that the mitoxantrone side chains lie in the major groove.

Does adriamycin induce interstrand cross-links in DNA?

Under nonenzymatic conditions in vitro, Adriamycin appears to form interstrand cross-links with DNA over 1-2 days. This is the first report of such Adriamycin-induced interstrand cross-links in vitro. Cross-links were measured by a fluorescence based renaturation assay and also by gel electrophoresis. Both procedures revealed an increase of cross-linking with reaction time and with increasing Adriamycin concentration and a 5-6-fold enhancement in the presence of Fe3+ ions. The cross-link contains the Adriamycin chromophore, with a lambda max of 508 nm, intercalated at the GpC site of cross-linking. Maximal stoichiometry of the cross-link was one per 11-20 bp. The cross-link appears to involve adducts of the Adriamycin chromophore linked to the N2 of guanine, with no indication that N7 of guanine is involved. Given that the mode of action of Adriamycin still remains obscure, even after 20 years of clinical use, the possibility that interstrand DNA cross-links may be associated with the clinical mechanism of action of this drug should now be fully addressed.

Isolation and characterization of a platelet-derived macrophage-binding proteoglycan

A macromolecule in human platelet secretory products was demonstrated previously to inhibit the binding and uptake of acetoacetylated (AcAc) low density lipoproteins (LDL) by scavenger receptors on mouse peritoneal macrophages. In the current study, this macromolecule was purified to apparent homogeneity by DEAE-Sephacel chromatography, Sephacryl S-300 chromatography, and sucrose gradient centrifugation. SDS-polyacrylamide gel electrophoresis revealed a single band with an apparent molecular mass of approximately 120 kDa. Chemical analysis indicated that the macromolecule (designated platelet-derived macrophage-binding proteoglycan (PDMBP)) was a chondroitin 4-sulfate proteoglycan with an approximately 32-kDa core protein. A polyclonal antibody produced against this proteoglycan identified only PDMBP on Western blots of platelet secretory products and removed all ability of these products to inhibit the binding of AcAc LDL to macrophages. Treatment of purified PDMBP with protease or chondroitinase AC or ABC abolished the ability of the proteoglycan to inhibit the binding of AcAc LDL to macrophages. Binding studies using radiolabeled PDMBP demonstrated that the proteoglycan bound directly to the macrophage cell surface and was competitively inhibited by AcAc LDL, acetyl-LDL, fucoidin, and unlabeled PDMBP. PDMBP inhibited binding of 125I-labeled AcAc LDL to macrophages but had no effect on binding to endothelial cells. The finding that PDMBP binds to the scavenger receptor on macrophages suggests a mechanism for the inhibition of foam cell formation and suggests that the receptor could be involved in the plasma clearance of chondroitin sulfate proteoglycans.

Effect of alkylating agents on initiation and elongation of the lac UV5 promoter

DNA containing the lac UV5 promoter was alkylated using bifunctional sulfur and nitrogen mustards and a monofunctional sulfur mustard. The alkylation sites were mapped using Taq polymerase, and the effect of alkylation on the formation of the DNA-RNA polymerase complex was determined using gel retardation. Alkylation was observed at all G residues in the template strand. Exposure of the alkylated DNA to Escherichia coli RNA polymerase resulted in the formation of a DNA-enzyme complex that was more stable, prior to initiation, than the complex formed with nonalkylated DNA. The DNA-RNA polymerase complex formed with the alkylated DNA also demonstrated decreased ability to progress along the full length of the DNA template. These observations show that, in addition to inducing transcriptional blockages, mustards also influence the interaction between RNA polymerase and its promoter. The ability to interfere with protein-DNA interactions may contribute significantly to the effects of these compounds in eukaryotic systems with their complex array of transcription factors.

Cloning and characterization of the gene encoding the human platelet glycoprotein V. A member of the leucine-rich glycoprotein family cleaved during thrombin-induced platelet activation

Glycoprotein V (GPV) is a major platelet membrane 82-kDa glycoprotein, missing in the Bernard-Soulier syndrome, that is cleaved when platelets are treated with thrombin. We report the cloning and sequencing of the GPV cDNA and gene obtained by a combination of polymerase chain reaction amplification of platelet mRNA and genomic library screening. The single-copy gene for GPV is contained within 6.5 kilobase pairs (kb) of genomic sequence and has a simple structure with a single intron of 958 base pairs in the 5'-untranslated sequence; the coding sequence is contained within a single exon. The promoter region contains a canonical TATA box, and putative GATA, Ets-1, and Sp1 cis-acting elements. Reverse transcription-polymerase chain reaction analysis on RNAs from cells of different hematopoietic origins revealed that GPV was specifically transcribed from platelets and from cells of the megakaryocytic lineage (megakaryocytes, HEL cells). A single transcript of 4.5 kb for GPV was detected in human platelets by Northern blot analysis. The entire amino acid sequence of GPV was deduced from the cDNA and genomic sequences. Mature GPV was composed of 544 amino acids which contained a single transmembrane domain, a short cytoplasmic domain (16 residues), and a large extracellular domain with 8 potential N-glycosylation sites. Analysis of the extracellular domain revealed the presence of 15 tandem Leu-rich repeats of 24 amino acids with homology to GPIb alpha and identified a cleavage site for thrombin near the COOH terminus with similarity to the A alpha chain of fibrinogen, but no hirudin-like sequence was found.

Thermal stability of DNA adducts induced by cyanomorpholinoadriamycin in vitro

The Adriamycin derivative, cyanomorpholinoadriamycin (CMA) was reacted with DNA in vitro to form apparent interstrand crosslinks. The extent of interstrand crosslink formation was monitored by a gel electrophoresis assay and maximal crosslinking of DNA was observed within 1 hr with 5 microM of drug. The interstrand crosslinks were heat labile, with a midpoint melting temperature of 70 degrees C (10 min exposure to heat) in 45% formamide. When CMA-induced adducts were detected as blockages of lambda-exonuclease, 12 blockage sites were observed with 8 being prior to 5'-GG sequences, one prior to 5'-CC, one prior to 5'-GC and 2 at unresolved combinations of these sequences. These exonuclease-detected blockages reveal the same sites of CMA-induced crosslinking as detected by in vitro transcription footprinting and primer-extension blockages on single strand DNA, where the blockages at 5'-GG and 5'-CC were identified as sites of intrastrand crosslinking and the 5'-GC blockage as a probable site of interstrand crosslinking. The thermal stability of both types of crosslink (10 min exposure to heat) ranged from 63-70 degrees C at individual sites. High levels of adduct were detected with poly (dG-dC) but not with poly (dI-dC). These results suggest adduct formation involving an aminal linkage between the 3 position of the morpholino moiety and N2 of guanine.

The use of bidirectional transcription footprinting to detect platinum-DNA crosslinks by acridine-tethered platinum diamine complexes and cisplatin

Bidirectional transcription footprinting has been used to probe the platination of DNA by cisplatin, and to examine the modulation of these interactions by (a) cyclisation of the non-reactive amino group by either ethyl or propyl groups, and (b) the further addition of a pendant intercalator (9-amino acridine) linked by either phenylethyl or phenylpentyl groups. Intrastrand crosslinking was detected for all derivatives at all 5'-GG and 5'-AG sequences on the template strand, but the same sites did not result in transcriptional blockages when on the non-template strand. There was little effect of cyclysation of the amino groups, but the further addition of an intercalator resulted in three responses: a time-dependent increase of the blocked transcript by one and three nucleotides; a reduction of the sequence selectivity of platination; a decrease of apparent interstrand crosslinking for these derivatives with a pendant intercalator tethered to the amino moiety of cisplatin.

Characterization of the integrin specificities of disintegrins isolated from American pit viper venoms

A new series of homologous disintegrins was isolated from the venoms of new world pit viper genus Bothrops, Crotalus, and Lachesis. The relative activities of each disintegrin in blocking adhesive protein binding activities of GPIIb-IIIa, alpha v beta 3, and alpha 5 beta 1 were determined and correlated with their primary amino acid sequences. Four disintegrins contained the RGDW sequence and were found to be approximately twice as effective in blocking the binding of fibrinogen to GPIIb-IIIa than inhibiting the binding of vitronectin to alpha v beta 3 in solid-phase ligand binding assays (IC50 = 7.3 and 17.2 nM, respectively). A second group of seven disintegrins contained the RGDNP sequence and were found to be more potent inhibitors of vitronectin binding to alpha v beta 3 than fibrinogen binding to GPIIb-IIIa (IC50 = 4.3 and 19 nM, respectively). The RGDNP containing disintegrins were also greater than 10-fold more potent than RGDW containing disintegrins in blocking the adhesion of cells mediated by alpha 5 beta 1. These data illustrate that amino acid sequences immediately adjacent to the RGD site of disintegrins can create an extended RGD locus which coupled with conformational display of the RGD sequence may be involved in determining integrin selectivity and affinity. This information has been used in separate studies to design conformationally constrained integrin antagonists with high affinity for platelet GPIIb-IIIa.

Design of potent and specific integrin antagonists. Peptide antagonists with high specificity for glycoprotein IIb-IIIa

Members of the snake venon-derived, "disintegrin" peptide family containing the Arg-Gly-Asp (RGD) amino acid sequence are among the most potent inhibitors of the binding of adhesive proteins to platelet glycoprotein (GP) IIb-IIIa. However, GPIIb-IIIa antagonists containing the RGD sequence are not integrin specific and inhibit the adhesive functions of many other RGD-dependent integrins. The single disintegrin peptide, barbourin, containing a conservative amino acid substitution of Lys (K) for Arg (R) in the RGD sequence, is however, highly specific for GPIIb-IIIa. Using this information we have tested the hypothesis that both structural and conformational elements of barbourin are important for its high affinity and selectivity for platelet GPIIb-IIIa by synthesizing a series of conformationally constrained, disulfide-bridged peptides containing the KGD amino acid sequence. Incorporation of the KGD sequence into a cyclic peptide template, followed by systematic optimization of the cyclic ring size, optimization of secondary hydrophobic binding site interactions, and the derivatization of the lysyl side chain functionality of the KGD sequence has resulted in peptide analogs which display inhibitory potency and GPIIb-IIIa selectivity comparable to that of barbourin. This study demonstrates that the specificity and potency of the disintegrin family of antagonists, in particular barbourin, can be mimicked by small, conformationally restrained peptides.

Evidence for novel binding sites on the platelet glycoprotein IIb and IIIa subunits and immobilized fibrinogen

The present study was designed to examine the interaction of the purified platelet glycoprotein IIb-IIIa complex (GP IIb-IIIa or integrin alpha IIb beta 3) and the individual subunits of the complex with immobilized fibrinogen. Although 125I-GP IIb-IIIa binding to fibrinogen immobilized on Sepharose was specific, this interaction exhibited properties distinct from those of reversible fibrinogen binding to platelets: 125I-GP IIb-IIIa binding appeared irreversible, but non-covalent, Ca(2+)-independent, and was inhibited only weakly, or not at all, by the anti-(GP IIb-IIIa) monoclonal antibodies 10E5 and 7E3 and synthetic peptides from known platelet-binding domains of fibrinogen. Reversibly dissociated GP IIb or GP IIIa subunits inhibited 125I-GP IIb-IIIa binding to immobilized fibrinogen and bound directly to the fibrinogen. However, these subunits did not bind to peptides derived from known platelet-binding domains within the fibrinogen alpha- and gamma-chains, although the GP IIb-IIIa complex did. These results show that the complexed form of full-length GP IIb and GP IIIa is required for binding to these synthetic peptides, but not necessarily for binding to immobilized fibrinogen. Thus GP IIb-IIIa can bind to immobilized fibrinogen by a distinct mechanism that appears to involve novel binding sites on each subunit of the GP IIb-IIIa complex and on fibrinogen.

Cupric Ion Chelation Assisted Synthesis of N(α)-Protected N(ω)-Acridin-9-yl α,ω-Diamino Carboxylic Acids

The synthesis of Nα-protected Nω-acridin-9-yl derivatives of the α,w-diamino carboxylic acids ornithine and lysine is reported. Direct introduction of the acridin-9-yl moiety to the amino side chain of the free amino acid was achieved in methanol through temporary copper(II) chelation protection of the α-amino and carboxy groups. Nα-Fmoc protection was introduced by using N-(fluoren-9-ylmethoxycarbonyloxy)succinimide in aqueous dioxan.