CADM1 is a TWIST1-regulated suppressor of invasion and survival

Metastatic cancer remains a clinical challenge; however, patients diagnosed prior to metastatic dissemination have a good prognosis. The transcription factor, TWIST1 has been implicated in enhancing the migration and invasion steps within the metastatic cascade, but the range of TWIST1-regulated targets is poorly described. In this study, we performed expression profiling to identify the TWIST1-regulated transcriptome of melanoma cells. Gene ontology pathway analysis revealed that TWIST1 and epithelial to mesenchymal transition (EMT) were inversely correlated with levels of cell adhesion molecule 1 (CADM1). Chromatin immunoprecipitation (ChIP) studies and promoter assays demonstrated that TWIST1 physically interacts with the CADM1 promoter, suggesting TWIST1 directly represses CADM1 levels. Increased expression of CADM1 resulted in significant inhibition of motility and invasiveness of melanoma cells. In addition, elevated CADM1 elicited caspase-independent cell death in non-adherent conditions. Expression array analysis suggests that CADM1 directed non-adherent cell death is associated with loss of mitochondrial membrane potential and subsequent failure of oxidative phosphorylation pathways. Importantly, tissue microarray analysis and clinical data from TCGA indicate that CADM1 expression is inversely associated with melanoma progression and positively correlated with better overall survival in patients. Together, these data suggest that CADM1 exerts tumor suppressive functions in melanoma by reducing invasive potential and may be considered a biomarker for favorable prognosis.

Abstract 105: CADM1 is a TWIST1-regulated suppressor of melanoma invasion and survival

Metastatic melanoma is the deadliest form of skin cancer; however, patients diagnosed and treated prior to metastatic dissemination have a good prognosis. The transcription factor, TWIST1 has been implicated in enhancing the migration and invasion of melanoma cells but the range of TWIST1-regulated targets is poorly described. In this study, we performed expression profiling to identify the TWIST1-regulated transcriptome. Gene ontology pathway analysis revealed that TWIST1 and epithelial to mesenchymal transition (EMT) were inversely correlated with levels of cell adhesion molecule 1 (CADM1). Chromatin immunoprecipitation (ChIP) studies and promoter assays demonstrated that TWIST1 physically interacts with the CADM1 promoter, suggesting TWIST1 directly represses CADM1 levels. Modulation of CADM1 resulted in significant effects on the migration and invasion of melanoma cells. In addition, elevated CADM1 elicited cell death in non-adherent conditions, an effect that could not be rescued with a pan-caspase inhibitor. Analyses suggest that CADM1 directed non-adherent cell death is associated with loss of mitochondrial membrane potential and subsequent failure of oxidative phosphorylation pathways. Furthermore, clinical data from TCGA indicates that CADM1 expression is correlated with better overall survival in patients. Together, these data suggest that CADM1 exerts tumor suppressive functions in melanoma by reducing invasive potential and may be a biomarker for improved survival of melanoma patients.

Citation Format: Edward J. Hartsough, Michele B. Weiss, Shea A. Heilman, Timothy J. Purwin, Curtis H. Kugel, Sheera R. Rosenbaum, Dan A. Erkes, Manoela Tiago, Inna Chervoneva, Andrew E. Aplin. CADM1 is a TWIST1-regulated suppressor of melanoma invasion and survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 105.

Abstract 4089: CADM1 is a TWIST1 regulated suppressor of melanoma invasion

Melanoma is the deadliest form of skin cancer; however, with early detection prior to metastatic dissemination, patients generally have a good prognosis. Recently, our lab has implicated the transcription factor TWIST1 in the progression of melanoma towards metastasis. In melanoma cells, we found that RAS-RAF-MEK-ERK (ERK1/2 pathway) signaling increases TWIST1 expression, which promotes invasive properties in the dermal microenvironment at least in part by enhancing levels of the matrix metalloproteinase, MMP1. Other TWIST1 regulated targets are poorly described. In this study, we compared expression profiling data from cells expressing shRNA against TWIST1 or cells overexpressing TWIST1 in order to determine TWIST1 regulated genes. KEGG and GO analysis revealed that TWIST1 is responsible for regulating a number of genes involved in cellular adhesion. We found that TWIST1 levels inversely correlate with levels of cell adhesion molecule 1 (CADM1) (NECL-2, IGSF4, TSLC1, SynCAM). Chromatin immunoprecipitation (ChIP) studies and promoter assays demonstrate that TWIST1 physically interacts with CADM1 promoter and this is associated with reduced CADM1 levels. Additionally, CADM1 expression is inversely associated ERK1/2 signaling and TWIST1 expression. Modulation of cellular CADM1 levels does not seem to affect proliferations rates however, overexpression of CADM1 augments cell-cell interaction, and cell aggregation. Furthermore, exogenous CADM1 inhibited serum directed migration and invasion through matrigel coated boyden chambers, while knockdown of CADM1 was associated with an enhancement in the migratory and invasion properties. Taken together, these data provide evidence that CADM1 is negatively regulated by TWIST1, and may act as a suppressor of melanoma invasion.

Citation Format: Edward J. Hartsough, Michele B. Weiss, Curtis H. Kugel, Sheera R. Rosenbaum, Andrew E. Aplin. CADM1 is a TWIST1 regulated suppressor of melanoma invasion. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4089. doi:10.1158/1538-7445.AM2015-4089

Abstract A08: CADM1 is a TWIST1 regulated suppressor of melanoma invasion

Melanoma is the deadliest form of skin cancer; however, with early detection prior to metastatic dissemination, patients generally have a good prognosis. Recently, our lab has implicated the transcription factor TWIST1 in the progression of melanoma towards metastasis. In melanoma cells, we found that RAS-RAF-MEK-ERK (ERK1/2 pathway) signaling increases TWIST1 expression, which promotes invasive properties in the dermal microenvironment, at least in part by enhancing levels of the matrix metalloproteinase, MMP1. Other TWIST1-regulated targets are poorly described. In this study, we compared expression-profiling data from cells expressing shRNA against TWIST1 or cells overexpressing TWIST1 in order to identify TWIST1-regulated genes. KEGG and GO analysis revealed that TWIST1 is responsible for regulating a number of genes involved in cellular adhesion. We found that TWIST1 levels inversely correlate with levels of cell adhesion molecule 1 (CADM1, also known as NECL-2, IGSF4, TSLC1, SynCAM). Chromatin immunoprecipitation (ChIP) studies and promoter assays demonstrated that TWIST1 physically interacts with the CADM1 promoter and this is associated with reduced CADM1 levels. Additionally, CADM1 expression is inversely associated with ERK1/2 signaling and TWIST1 expression. Modulation of cellular CADM1 levels did not affect proliferation rates; however, overexpression of CADM1 augmented cell-cell interaction, cell aggregation, and reduced trans-endothelial invasion. Furthermore, exogenous CADM1 inhibited serum-directed migration and invasion through Matrigel-coated Boyden chambers, whereas knockdown of CADM1 was associated with enhanced migratory and invasive properties. Taken together, these data provide evidence that CADM1 is negatively regulated by TWIST1 and may act as a suppressor of melanoma invasion.

Citation Format: Edward J. Hartsough, Michele B. Weiss, Sheera R. Rosenbaum, Andrew E. Aplin. CADM1 is a TWIST1 regulated suppressor of melanoma invasion. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Melanoma: From Biology to Therapy; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(14 Suppl):Abstract nr A08.

FOXD3 modulates migration through direct transcriptional repression of TWIST1 in melanoma

The neural crest is a multipotent, highly migratory cell population that gives rise to diverse cell types, including melanocytes. Factors regulating the development of the neural crest and emigration of its cells are likely to influence melanoma metastasis. The transcription factor FOXD3 plays an essential role in premigratory neural crest development and has been implicated in melanoma cell dormancy and response to therapeutics. FOXD3 is downregulated during the migration of the melanocyte lineage from the neural crest, and our previous work supports a role for FOXD3 in suppressing melanoma cell migration and invasion. Alternatively, TWIST1 is known to have promigratory and proinvasive roles in a number of cancers, including melanoma. Using ChIP-seq analysis, TWIST1 was identified as a potential transcriptional target of FOXD3. Mechanistically, FOXD3 directly binds to regions of the TWIST1 gene locus, leading to transcriptional repression of TWIST1 in human mutant BRAF melanoma cells. In addition, depletion of endogenous FOXD3 promotes upregulation of TWIST1 transcripts and protein. Finally, FOXD3 expression leads to a significant decrease in cell migration that can be efficiently reversed by the overexpression of TWIST1. These findings uncover the novel interplay between FOXD3 and TWIST1, which is likely to be important in the melanoma metastatic cascade.

IMPLICATIONS

FOXD3 and TWIST1 define distinct subgroups of cells within a heterogeneous tumor.

TWIST1 is an ERK1/2 effector that promotes invasion and regulates MMP-1 expression in human melanoma cells

Tumor cells often use developmental processes to progress toward advanced disease. The E-box transcription factor TWIST1 is essential to epithelial-mesenchymal transition (EMT) and cell migration in the developing neural crest. In melanoma, which derives from the neural crest cell lineage, enhanced TWIST1 expression has been linked to worse clinical prognosis. However, mechanisms underlying TWIST1 expression and whether aberrant TWIST1 levels promote steps in melanoma progression remain unknown. Here, we report that elevated TWIST1 mRNA/protein expression is dependent on extracellular signal-regulated kinase (ERK)1/2 signaling, which is hyperactive in the majority of melanomas. We show that TWIST1 protein levels are especially high in melanoma cell lines generated from invasive, premetastatic stage tumors. Furthermore, TWIST1 expression is required and sufficient to promote invasion through Matrigel and spheroid outgrowth in three-dimensional dermal-mimetic conditions. Alterations to spheroid outgrowth were not as a result of altered cell death, cell-cycle profile, or paradigm EMT protein changes. Importantly, we identify matrix metalloproteinase-1 (MMP-1) as a novel downstream target of TWIST1. We have determined that TWIST1 acts, in a dose-dependent manner, as a mediator between hyperactive ERK1/2 signaling and regulation of MMP-1 transcription. Together, these studies mechanistically show a previously unrecognized interplay between ERK1/2, TWIST1, and MMP-1 that is likely significant in the progression of melanoma toward metastasis.

The TWEAK receptor Fn14 is a therapeutic target in melanoma: immunotoxins targeting Fn14 receptor for malignant melanoma treatment

Fn14, the cell surface receptor for TWEAK, is over-expressed in various human solid tumor types and can be a negative prognostic indicator. We detected Fn14 expression in ~60% of the melanoma cell lines we tested, including both B-Raf WT and B-Raf^V600E lines. Tumor tissue microarray analysis indicated that Fn14 expression was low in normal skin but elevated in 173/190 (92%) of primary melanoma specimens and in 86/150 (58%) of melanoma metastases tested. We generated both a chemical conjugate composed of the rGel toxin and the anti-Fn14 antibody ITEM-4 (designated ITEM4-rGel) and a humanized, dimeric single-chain antibody of ITEM-4 fused to rGel (designated hSGZ). Both ITEM4-rGel and hSGZ were highly cytotoxic to a panel of different melanoma cell lines. Mechanistic studies showed that both immunotoxins induced melanoma cell necrosis. Also, these immunotoxins could up-regulate the cellular expression of Fn14 and trigger cell signaling events similar to the Fn14 ligand TWEAK. Finally, treatment of mice bearing human melanoma MDA-MB-435 xenografts with either ITEM4-rGel or hSGZ showed significant tumor growth inhibition compared to controls. We conclude that Fn14 is a novel therapeutic target in melanoma and the hSGZ construct appears to warrant further development as a novel therapeutic agent against Fn14-positive melanoma.

Abstract 3866: TWEAK receptor (Fn14) Is a novel target in melanoma: Characterization of unique targeted therapeutics

Previous studies have indicated that Fn14, the cell surface receptor for the cytokine TWEAK, is over-expressed in multiple human solid tumor types, including brain, breast, and lung cancers, and overexpression can be a negative prognostic indicator. We analyzed a series of melanoma cell lines and tumor tissue microarrays and detected Fn14 expression in ∼60% of the melanoma cell lines, including both B-Raf WT and B-Raf V600E lines. Fn14 expression was elevated in 178/190 (93.6%) of primary melanoma specimens and in 87/150 (58%) of melanoma metastases tested. Fn14 expression was not elevated in normal skin tissues. Initial development and characterization of an immunoconjugate designated ITEM4-rGel targeting Fn14 receptor has been published (Zhou et al., Mol. Cancer Ther. 10:1276 (2011)). We have now developed an Fn14-targeted immunotoxin more suitable for long-term clinical use. Specifically, we generated a humanized, dimeric single-chain version of ITEM-4 and fused this scFv to rGel. The resulting anti-Fn14 immunotoxin, designated hSGZ, bound to Fn14 with a Kd of ∼1.4 nM as determined by Biacore analysis. Confocal immunofluoresence studies showed that hSGZ specifically and rapidly (within 2 hrs) internalized into Fn14-expressing MDA-MB-435 melanoma cells. Cytotoxicity studies showed that hSGZ was highly cytotoxic to a panel of different melanoma cell lines (IC50 ranged from 0.1 pM to 1.1 nM) and was 2.2 to 2.8 ×105 fold more potent than free rGel. Treatment of cells expressing the multidrug resistance protein MDR1 showed no cross-resistance to the fusion construct in vitro. When hSGZ was combined with 5-FU, cisplatin, doxorubicin, etoposide or dacarbazine, we found an additive effect on melanoma cell growth inhibition. Mechanistic studies showed that hSGZ induced melanoma cell death consistent with a necrotic mechanism. Additionally, Fn14-targeted immunotoxins increased Fn14 expression and triggered cell signaling events similar to those induced by the TWEAK ligand. Finally, treatment of mice bearing human melanoma MDA-MB-435 and breast MDA-MB-231 xenografts with either ITEM4-rGel or hSGZ showed significant tumor growth inhibition compared to controls (P< 0.05). Fn14 appears to be an excellent new target for melanoma and the Fn14-targeting construct hSGZ appears to warrant further development as a novel therapeutic agent against Fn14-positive tumors. Melanoma lines appear to be the most sensitive tumor type tested but the reasons for this are unclear. Additional studies are in progress to investigate the biodistribution and pharmacokinetics of hSGZ in tumor-bearing mice. This work was conducted, in part, by the Clayton Foundation for Research (MGR); and supported by NIH grant NS055126 (JAW) and DOD Breast Cancer Concept Award BC086135 (JAW).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3866. doi:1538-7445.AM2012-3866

Abstract 4310: TWIST1, a B-RAF effector, promotes invasion and is a novel regulator of MMP-1 in human melanoma cells

Metastatic melanoma is the deadliest form of skin cancer due to its highly aggressive and chemotherapy-resistant nature. Therefore, determining the factors impacting melanoma advancement toward metastasis is an important and clinically-relevant task. Importantly, RAF/MEK/ERK signaling is hyperactive in the great majority of melanoma cells and is a driver of melanoma growth and invasion. In addition, the TWIST1 protein is up-regulated in melanoma and its expression correlates strongly with poor clinical prognosis. However, the mechanism underlying TWIST1 up-regulation, as well as the role of high TWIST1 expression in traits associated with the progression of melanoma, has yet to be uncovered. In this study, we report that disruption of RAF/MEK/ERK signaling strongly represses TWIST1 at the mRNA and protein level. We further show that TWIST1 protein levels are especially high in B-RAF mutant cells as well as in vertical growth phase melanoma cells, which are those that first begin to invade downward into the deeper dermal layers eventually leading to metastasis. To that effect, depletion of TWIST1 in several invasive melanoma cell lines significantly reduces Matrigel invasion. The inverse phenotype is apparent when TWIST1 is overexpressed in low TWIST1-expressing, non-invasive melanoma cell lines. Additionally, we tested the effect of altered Twist expression in three-dimensional collagen spheroid outgrowth assays, which mimic both tumor architecture and the in vivo collagen-rich dermal layer. We observe significant reduction in spheroid outgrowth when invasive cell lines are depleted for TWIST1 as well as increases in outgrowth when non-invasive cells overexpress TWIST1. Alterations to spheroid outgrowth were not as a result of apoptotic changes or proliferative rate. Importantly, we have found matrix metalloproteinase-1 (MMP-1) to be a downstream effector of TWIST1. Furthermore, TWIST1 acts as a mediator between activated B-RAF signaling and MMP-1 in a dose-dependent and direct manner at the level of transcription. Our findings uncover the novel interplay between B-RAF, TWIST1, and MMP-1 which is likely important in the progression of melanoma towards metastasis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4310. doi:1538-7445.AM2012-4310

Abstract 2334: TWIST1, a B-RAF effector, promotes melanoma cell invasion

Metastatic melanoma is the deadliest form of skin cancer and a paradigm for highly aggressive, chemotherapy-resistant tumors. Therefore, determining the factors impacting melanoma advancement toward metastasis is an important and clinically-relevant task. The TWIST1 protein is up-regulated in melanoma and its expression correlates strongly with poor clinical prognosis. We tested the role of high TWIST1 expression in traits associated with the progression of melanoma, as well as sought to delineate the mechanism underlying TWIST1 up-regulation. Our data shows that TWIST1 protein levels are higher in melanoma cells, especially invasive lines, compared to normal melanocytes. To evaluate the biological relevance of TWIST1 expression, we generated invasive melanoma cell lines depleted of TWIST1 by shRNA and non-invasive melanoma cell lines which constitutively overexpress TWIST1. First, we utilized these cell lines in standard Matrigel invasion assays through boyden chambers. Depletion of TWIST1 in several invasive melanoma cell lines significantly reduces Matrigel invasion by approximately 40-50%. The inverse phenotype is apparent when TWIST1 is overexpressed in low TWIST1-expressing, non-invasive melanoma cell lines. Additionally, we tested the effect of altered Twist expression in 3D collagen spheroid outgrowth assays, which mimic both tumor architecture and the in vivo collagen-rich dermal layer. We have found significant reduction of spheroid outgrowth when invasive cell lines are depleted for TWIST1 as well as increases in outgrowth when non-invasive cells overexpress TWIST1. Alterations to spheroid outgrowth were not as a result of apoptotic changes or proliferative rate as assessed by live/dead and EdU staining. Importantly, the mechanisms regulating high TWIST1 expression in melanoma are unclear. A comparison between wild-type and mutant B-RAF melanoma cell lines demonstrates that TWIST1 is more highly expressed in mutant B-RAF cells. We have found that disruption of B-RAF/MEK signaling, through siRNA/shRNA knockdown or pharmacological inhibition, strongly represses TWIST1 at the mRNA and protein level. An area of active investigation is the determination of the transcription factor responsible for TWIST1 regulation downstream of mutant B-RAF in melanoma. The data generated from these studies will allow for a greater understanding of the role and regulation of TWIST1 during the progression of melanoma towards metastasis. In addition, it may highlight TWIST1 as an attractive molecule/pathway for novel targeted therapies for melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2334. doi:10.1158/1538-7445.AM2011-2334

Paying "particle" attention to novel melanoma treatment strategies

Malignant melanoma remains the deadliest form of skin cancer because of its highly aggressive nature and the lack of effective treatments. Recent investigations into alternative treatment strategies have highlighted the exciting potential of nanoparticles to increase melanoma cell delivery and the efficacy of small interfering RNAs (siRNAs) and pharmacological inhibitors. In this issue, Chen et al. report a new liposomal nanoparticle for c-Myc siRNA delivery, noting it to be highly effective in reducing c-Myc expression and inhibiting melanoma tumor growth in mouse models. This preclinical study underscores the importance of investigating nanoparticle treatment options for chemoresistant melanomas.

Deletion of p53 in human mammary epithelial cells causes chromosomal instability and altered therapeutic response

The TP53 tumor suppressor gene is the most commonly mutated gene in human cancers. To evaluate the biological and clinical relevance of p53 loss, human somatic cell gene targeting was used to delete the TP53 gene in the non-tumorigenic epithelial cell line, MCF-10A. In all four p53-/- clones generated, cells acquired the capability for epidermal growth factor-independent growth and were defective in appropriate downstream signaling and cell cycle checkpoints in response to DNA damage. Interestingly, p53 loss induced chromosomal instability leading to features of transformation and the selection of clones with varying phenotypes. For example, p53-deficient clones were heterogeneous in their capacity for anchorage-independent growth and invasion. In addition, and of clinical importance, the cohort of p53-null clones showed sensitivity to chemotherapeutic interventions that varied depending not only on the type of chemotherapeutic agent, but also on the treatment schedule. In conclusion, deletion of the TP53 gene from MCF-10A cells eliminated p53 functions, as well as produced p53-/- clones with varying phenotypes possibly stemming from the distinct chromosomal changes observed. Such a model system will be useful to further understand the cancer-specific phenotypic changes that accompany p53 loss, as well as help to provide future treatment strategies for human malignancies that harbor aberrant p53.

Deletion of PTEN promotes tumorigenic signaling, resistance to anoikis, and altered response to chemotherapeutic agents in human mammary epithelial cells

Many cancers, including breast cancer, harbor loss-of-function mutations in the catalytic domain of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) or have reduced PTEN expression through loss of heterozygosity and/or epigenetic silencing mechanisms. However, specific phenotypic effects of PTEN inactivation in human cancer cells remain poorly defined without a direct causal connection between the loss of PTEN function and the development or progression of cancer. To evaluate the biological and clinical relevance of reduced or deleted PTEN expression, a novel in vitro model system was generated using human somatic cell knockout technologies. Targeted homologous recombination allowed for a single and double allelic deletion, which resulted in reduced and deleted PTEN expression, respectively. We determined that heterozygous loss of PTEN in the nontumorigenic human mammary epithelial cell line MCF-10A was sufficient for activation of the phosphoinositide 3-kinase/AKT and mitogen-activated protein kinase pathways, whereas the homozygous absence of PTEN expression led to a further increased activation of both pathways. The deletion of PTEN was able to confer growth factor-independent proliferation, which was confirmed by the resistance of the PTEN(-/-) MCF-10A cells to small-molecule inhibitors of the epidermal growth factor receptor. However, neither heterozygous nor homozygous loss of PTEN expression was sufficient to promote anchorage-independent growth, but the loss of PTEN did confer apoptotic resistance to cell rounding and matrix detachment. Finally, MCF-10A cells with the reduction or loss of PTEN showed increased susceptibility to the chemotherapeutic drug doxorubicin but not paclitaxel.

Persistent mismatch repair deficiency following targeted correction of hMLH1

The use of gene therapy to correct mutated or lost gene function for the treatment of human cancers has been an active, yet problematic area of biomedical research. Many technical difficulties, including efficient tissue-specific delivery, integration site specificity and general toxicity, are being addressed. Little is known, however, about the genetic and phenotypic stability that accompanies a successful gene-specific targeting event in a cancer cell. This question was addressed following the creation of a colon cancer cell line in which a mutated hMLH1 gene was corrected via targeted homologous recombination. This correction resulted in the expression of wild-type hMLH1 protein, restoration of the hPMS2 protein and mismatch repair (MMR) proficiency. One of two hMLH1-corrected clones, however, was found to retain defects in MMR activity. These cells continued to express the corrected hMLH1 protein, but had lost expression of another MMR protein, hMSH6. DNA sequence analysis of the hMSH6 gene revealed biallelic expansions of a cytosine repeat region in exon 5 that result in frameshifts leading to premature stop codons. These findings suggest that, similar to acquired drug resistance, the presence of genetically heterogeneous cancer cell populations or acquisition of compensatory mutations can result in 'resistance' to gene replacement therapy.

Solution Structure of Zinc- and Calcium-Bound Rat S100B as Determined by Nuclear Magnetic Resonance Spectroscopy†,‡

The EF-hand calcium-binding protein S100B also binds one zinc ion per subunit with a relatively high affinity (K(d) approximately 90 nM) [Wilder et al., (2003) Biochemistry 42, 13410-13421]. In this study, the structural characterization of zinc binding to calcium-loaded S100B was examined using high-resolution NMR techniques, including structural characterization of this complex in solution at atomic resolution. As with other S100 protein structures, the quaternary structure of Zn(2+)-Ca(2+)-bound S100B was found to be dimeric with helices H1, H1', H4, and H4' forming an X-type four-helix bundle at the dimer interface. NMR data together with mutational analyses are consistent with Zn(2+) coordination arising from His-15 and His-25 of one S100B subunit and from His-85 and Glu-89 of the other subunit. The addition of Zn(2+) was also found to extend helices H4 and H4' three to four residues similar to what was previously observed with the binding of target proteins to S100B. Furthermore, a kink in helix 4 was observed in Zn(2+)-Ca(2+)-bound S100B that is not in Ca(2+)-bound S100B. These structural changes upon Zn(2+)-binding could explain the 5-fold increase in affinity that Zn(2+)-Ca(2+)-bound S100B has for peptide targets such as the TRTK peptide versus Ca(2+)-bound S100B. There are also changes in the relative positioning of the two EF-hand calcium-binding domains and the respective helices comprising these EF-hands. Changes in conformation such as these could contribute to the order of magnitude higher affinity that S100B has for calcium in the presence of Zn(2+).

Circulating endothelial cells are elevated in patients with type 2 diabetes mellitus independently of HbA(1)c

AIMS/HYPOTHESIS

Patients with diabetes mellitus are well known to be at high risk for vascular disease. Circulating endothelial cells (CECs) have been reported to be an ex vivo indicator of vascular injury. We investigated the presence of CECs in the peripheral blood of 25 patients with diabetes mellitus and in nine non-diabetic control donors.

METHODS

Endothelial cells were isolated from peripheral blood with anti-CD-146-coated immunomagnetic Dynabeads, and were stained with acridine orange dye and counted by fluorescence microscopy. The cells were also stained for von Willebrand factor and Ulex europaeus lectin 1.

RESULTS

Patients with diabetes mellitus had an elevated number of CECs (mean 69+/-30 cells/ml, range 35-126) compared with healthy controls (mean 10+/-5 cells/ml, range 3-18) (p<0.001). The increase in CECs did not correlate with the levels of HbA(1)c. Circulating endothelial cell numbers were elevated regardless of glucose levels, suggesting that, even with control of glucose levels, there is increased endothelial cell sloughing.

CONCLUSIONS

Our study suggests that the higher number of CECs in patients with type 2 diabetes may reflect ongoing vascular injury that is not directly dependent on glucose control.

Long-term clinical outcome of rescue balloon angioplasty compared with rescue stenting after failed thrombolysis

Failed thrombolysis following acute myocardial infarction is associated with a poor prognosis. Balloon angioplasty with or without stenting is an established procedure in acute myocardial infarction and for failed thrombolysis (rescue percutaneous transluminal coronary angioplasty [PTCA]). Intracoronary stenting improves initial success rates, decreases incidence of abrupt closure, and reduces the rate of restenosis after angioplasty. The purpose of this study was to compare the effect of rescue PTCA with rescue stenting in the treatment of acute myocardial infarction after failed thrombolysis. Clinical data are from a retrospective review of 102 patients requiring rescue balloon angioplasty or stenting after failed thrombolysis for acute myocardial infarction. There was a greater incidence of recurrent angina in 11 patients (22%) in the rescue PTCA group versus 2 patients (4%) in the rescue stenting group. The in-hospital recurrent myocardial infarction rate was 14% in the rescue PTCA group versus 2% in the stented group. In the rescue PTCA cohort, 11 patients (22%) required in-hospital repeat revascularization versus 2 patients in the stented group. The in-hospital mortality rate was higher in the PTCA group (10%) versus that in the stent group (2%). There was no significant difference in the incidence of postdischarge deaths. Rescue stenting is superior to rescue angioplasty. The procedure is associated with lower in-hospital angina and recurrent myocardial infarction, and the need for fewer repeat revascularizations. Long-term patients treated with stents required fewer revascularization procedures. Overall, rescue stenting was associated with a significantly lower mortality.

A case of a large coronary artery fistula in an elderly patient surgically corrected 12 years after initial diagnosis

This case report discusses the natural history of a large coronary artery fistula in an elderly patient treated conservatively for 12 years. There has been no previous report of long term follow-up in a patient with a large coronary artery fistula with symptoms of congestive heart failure. The surgical management and clinical response to surgical correction will be discussed, and an extensive review of the literature will be performed.

Percutaneous transluminal coronary angioplasty (PTCA) combined with stenting improves clinical outcomes compared with PTCA alone in acute myocardial infarction

Balloon angioplasty in acute myocardial infarction is an established procedure. The procedure is limited by the potential for early abrupt reocclusion (18-20%) and other complications. Coronary stenting improves the initial success rate, decreases the incidence of abrupt closure, and is associated with a reduced rate of restenosis. For these reasons, coronary stenting is increasingly utilized to treat acute myocardial infarction. The purpose of this study was to compare the effect of coronary stenting with percutaneous transluminal coronary angioplasty (PTCA) in the management of acute myocardial infarction. Clinical data from a retrospective review of 228 consecutive patients admitted with acute myocardial infarction who underwent primary or rescue coronary intervention were used. There was a significantly greater incidence of in-hospital recurrent myocardial infarction in the PTCA group (10%) versus the stented group (1%). In the PTCA cohort, 10 patients required in-hospital repeat revascularization by PTCA compared with one patient in the stented group. The in-hospital death rate was significantly higher in the PTCA group (8%) compared with the stented group (1%). There was no significant difference in the incidence of postdischarge death or repeated revascularization. The results suggest that patients who undergo PTCA with stent deployment have fewer episodes of in-hospital recurrent angina, myocardial infarctions, repeat angioplasties, and fewer in-hospital deaths. PTCA with stenting was associated with a low in-hospital mortality (1%). For patients who had PTCA alone and survived to be discharged, there was no significant difference in overall mortality or the need for revascularization over the 2-year follow-up period.

Influence of pre-PTCA strategy and initial PTCA result in patients with multivessel disease: the Bypass Angioplasty Revascularization Investigation (BARI)

BACKGROUND

In PTCA patients with multivessel coronary artery disease, incomplete revascularization (IR) is the result of both pre-PTCA strategy and initial lesion outcome. The unique contribution of these components on long-term patient outcome is uncertain.

METHODS AND RESULTS

From the Bypass Angioplasty Revascularization Investigation (BARI), 2047 patients who underwent first-time PTCA were evaluated. Before enrollment, all significant lesions were assessed by the PTCA operator for clinical importance and intention to dilate. Complete revascularization (CR) was defined as successful dilatation of all clinically relevant lesions. Planned CR was indicated in 65% of all patients. More lesions were intended for PTCA in these patients compared with those with planned IR (2.8 versus 2.1). Successful dilatation of all intended lesions occurred in 45% of patients with planned CR versus 56% with planned IR (P<0. 001). In multivariable analysis, planned IR (versus planned CR), initial lesions attempted (not all versus all intended lesions attempted), and initial lesion outcome (not all versus all attempted lesions successful) were unrelated to 5-year risk of cardiac death or death/myocardial infarction but were all independently related to risk of CABG.

CONCLUSIONS

Overall, a pre-PTCA strategy of IR in BARI-like patients appears comparable to a strategy of CR except for a higher need for CABG. Whether the use of new devices may attenuate the elevated risk of CABG in patients with multivessel disease and planned IR remains to be determined.

Long-term clinical outcome of stenting in primary and rescue angioplasty in acute myocardial infarction

Long-term clinical outcome after use of stents in primary and rescue coronary angioplasty for treatment of acute myocardial infarction has not been described in detail. This study was conducted to evaluate long-term (more than one year) outcome in patients treated for acute myocardial infarction with stents. Between January 1, 1997 and September 1997, 101 consecutive patients had coronary artery stents implanted either for primary treatment of myocardial infarction or after failed thrombolytic therapy. Medical records of these patients were reviewed and telephone follow-up was performed using a standard questionnaire. Mean duration of follow-up was 17.8 +/- 1.7 months. During initial hospitalization only one patient had emergent percutaneous transluminal coronary angioplasty due to stent thrombosis (1%); two patients underwent emergent coronary artery bypass surgery (2%) and two patients died (2%). During the follow-up period, ten patients (10%) had recurrent angina, eight patients were treated medically (8%), two required repeat angioplasty (2%), two patients died (2%), and three patients (3%) were lost to follow-up. Stenting of the culprit vessel during acute myocardial infarction appears to be a safe and effective treatment associated with favorable in-hospital and long-term outcomes.

Adverse effects of enalapril in the Studies of Left Ventricular Dysfunction (SOLVD). SOLVD Investigators

In the Studies of Left Ventricular Dysfunction (LVD), enalapril or placebo was administered in a double-blind fashion to 6797 participants with ejection fraction < or = 0.35. During 40 months' average follow-up, 28.1% of participants randomized to enalapril reported side effects compared with 16.0% in the placebo group (p < 0.0001). Enalapril use was associated with a higher rate of symptoms related to hypotension (14.8% vs 7.1%, p < 0.0001), azotemia (3.8% vs 1.6%, p < 0.0001), cough (5.0% vs 2.0%, p < 0.0001), fatigue (5.8% vs 3.5%, p < 0.0001), hyperkalemia (1.2% vs 0.4%, p = 0.0002), and angioedema (0.4% vs 0.1%, p < 0.05). Side effects resulted in discontinuation of blinded therapy in 15.2% of the enalapril group compared with 8.6% in the placebo group (p < 0.0001). Thus enalapril is well tolerated by patients with LVD; however, hypotension, azotemia, cough, fatigue, and other side effects result in discontinuation of therapy in a significant minority of patients.

Patterns of medication use in patients with heart failure: a report from the Registry of Studies of Left Ventricular Dysfunction (SOLVD)

To determine patterns of medication use based on clinical variables in patients with heart failure, we analyzed data from 5,999 patients participating in the Registry of Studies of Left Ventricular Dysfunction (SOLVD). The Registry comprised a broad spectrum of patients with heart failure, including some with predominantly diastolic dysfunction. Drug use was determined in a population cross-sectional manner at the time of identification (74% hospitalized). The median number of drugs per patient was four, with diuretics taken by 62%, digitalis by 45%, angiotensin-converting enzyme inhibitors (ACE-I) by 32%, calcium channel blockers by 36%, antiarrhythmics by 22%, and beta-blockers by 18%. Only 18% were on the combination of ACE-I, diuretic, and digitalis. Stratification for diagnosis, heart failure symptoms, and ejection fractions demonstrated that triple-drug therapy (digitalis, diuretic, and ACE-I) was common only in those with ejection fractions less than .20 and several signs or symptoms of heart failure. Older patients were taking diuretics frequently (73% of patients older than 70 years of age), and our European center used fewer drugs overall, while prescribing digitalis about half as frequently as North American clinics. These data serve as the baseline for analysis of evolving therapeutic practice in patients with heart failure.

Tolerability of enalapril initiation by patients with left ventricular dysfunction: results of the medication challenge phase of the Studies of Left Ventricular Dysfunction

Although converting-enzyme inhibitors are useful for the treatment of congestive heart failure (CHF), there are concerns about adverse reactions especially on initiation of therapy. In the Studies of Left Ventricular Dysfunction, enalapril, 2.5 mg twice per day was given on an open-label outpatient basis for 7 days (mean 6.1, range 2 to 7, and median 7) as a prerandomization drug challenge to 7487 patients with left ventricular dysfunction (ejection fraction < or = 0.35). Four hundred forty-four (5.93%) patients reported side effects, including symptoms attributed to hypotension (in 166 patients [2.2%]). The majority (346 [77.9%] of 444 and 129 [77.7%] of 166 with symptoms attributed to hypotension) of patients who reported side effects were willing to participate in the study and to continue receiving enalapril. Thus only 98 (1.3%) of 7487 patients (0.5% because of symptoms attributed to hypotension) were not willing to continue because of side effects. Women and patients of CHF class III or IV were more likely to report side effects. In conclusion, enalapril is well tolerated by patients with left ventricular dysfunction; treatment can be initiated on an outpatient basis in the majority of patients.

Adjunctive thrombolytic therapy during angioplasty for ischemic rest angina. Results of the TAUSA Trial. TAUSA Investigators. Thrombolysis and Angioplasty in Unstable Angina trial

BACKGROUND

Acute closure is increased after angioplasty in unstable angina, and adjunctive intracoronary thrombolytic therapy has been used successfully to increase angiographic success. The role of prophylactic thrombolytic therapy during angioplasty in unstable angina is unknown.

METHODS AND RESULTS

Four hundred sixty-nine patients with ischemic rest pain with or without a recent (< 1 month) infarction were randomized in double-blind fashion to intracoronary urokinase or placebo. Randomization was carried out in two sequential phases. In phase I, 257 patients were randomized to 250,000 U of urokinase or placebo given in divided doses at the time of angioplasty. In phase II, 212 patients were randomized to 500,000 U of urokinase or placebo in divided doses. All patients were pretreated with aspirin, and activated clotting times were followed to maintain them at > 300 seconds during angioplasty. Angiographic end points of thrombus after angioplasty were insignificantly decreased by urokinase (30 [13.8%] versus 41 [18.0%] with placebo; P = NS). Acute closure, on the other hand, was increased with urokinase (23 [10.2%] versus 10 [4.3%] with placebo; P < .02). The difference in acute closure between urokinase and placebo was more striking at the higher dose of urokinase (P < .04) than in phase I at the lower urokinase dose (P = NS). Adverse in-hospital clinical end points (ischemia, infarction, or emergency coronary artery bypass surgery) were also increased with urokinase versus placebo (30 [12.9%] versus 15 [6.3%], respectively; P < .02). Angiographic and clinical end points were worse with urokinase in unstable angina without recent infarction than with angioplasty after a recent infarction.

CONCLUSIONS

Adjunctive urokinase given prophylactically during angioplasty for ischemic rest angina as administered in this trial is associated with adverse angiographic and clinical events. These detrimental effects may be related to hemorrhagic dissection, lack of intimal sealing, or procoagulant or platelet-activating effects of urokinase.

Reversible late potentials due to ischemia

The role of ischemia in the development of reversible late potentials was assessed in 19 patients undergoing percutaneous transluminal coronary angioplasty. Signal-averaged electrocardiograms were performed before angioplasty, during ischemia caused by balloon inflation and after angioplasty. Five of 19 patients developed late potentials that reverted to normal after angioplasty. Age, sex, ejection fraction, left ventricular end diastolic pressure, vessels involved, and extent of myocardium in jeopardy did not predict the development of late potentials. Patients with a prior history of myocardial infarction were more likely to develop late potentials. Therefore, patients with prior myocardial infarction appear more likely to develop the substrate for reentrant ventricular tachycardia during periods of ischemia.

Left main coronary artery aneurysm following percutaneous transluminal angioplasty: a report of a case and review of the literature

Since its introduction in 1977, the number of PTCAs and its indications have grown. Along with more frequent usage, newer complications have been reported. Aneurysm of left main coronary artery is rare. This report describes the formation of a new non-obstructing aneurysm in the left main coronary artery after PTCA of left circumflex artery. The patient has had 7 yr of follow-up with a benign clinical course.

Origin of all three coronary arteries from separate ostia in the right sinus of Valsalva: a rarely reported coronary artery anomaly

Anomalous origin of the circumflex and left anterior descending coronary arteries from separate ostia in the right sinus of Valsalva is a rarely reported phenomenon. Few clinical details concerning patients with this anomaly are available in the literature. Angiographic and clinical data in an adult patient with this finding are reported here.

Cardiopulmonary exercise testing. The clinical value of gas exchange data

Cardiopulmonary exercise testing is a noninvasive tool whose clinical value is not yet widely recognized. The technique involves breath-by-breath measurement of respiratory gas exchange during a symptom-limited exercise test, with determination of maximal oxygen uptake and anaerobic threshold. These measurements serve as objective, reproducible indices of exercise capacity that can be applied to the management of various clinical problems. In addition, by permitting simultaneous assessment of circulatory and ventilatory reserves, the test can be especially helpful in the differential diagnosis of exertional dyspnea and fatigue. This paper reviews the physiology of gas exchange, the limitations of standard exercise tests, and the methodology and clinical applications of cardiopulmonary exercise testing.

Monoclonal antibody identification of mononuclear cells in endomyocardial biopsy specimens from a patient with rheumatic carditis

A 17-year-old woman with rheumatic carditis underwent endomyocardial biopsy both prior to and following treatment with prednisone and aspirin. Frozen sections from the endomyocardial biopsy specimens were studied with monoclonal antibodies by an indirect immunofluorescence technique to define the composition of the inflammatory infiltrate in the myocardium and to determine whether the composition of the infiltrate is distinctive and diagnostically useful. The specimen from the initial biopsy contained a heterogeneous infiltrate composed of T lymphocytes, macrophages, B lymphocytes, and mast cells. T lymphocytes predominated, and the ratio of T-helper to T-cytotoxic/suppressor cells was 2.0. Following treatment the overall cellularity of the infiltrate was diminished, but the infiltrate remained heterogeneous; T cells predominated, and the T-helper to T-cytotoxic/suppressor ratio was reversed, to 0.59. The composition of the inflammatory infiltrate in this case of rheumatic carditis distinguishes it immunologically from other "idiopathic," presumably virus-associated, forms of myocarditis.

Serological evidence of Hantaan virus infection in the United States

We found low titers of fluorescent antibodies against Hantaan virus, the etiologic agent of Korean hemorrhagic fever, in sera from 7 of 1,035 patients with febrile illnesses of unknown origin and from 6 of 664 blood donors in the United States. All but 1 of these individuals possessed neutralizing antibodies against Hantaan virus. This was a 31-year-old research technician who had worked with laboratory rodents with virus-induced tumors, but had not traveled abroad, suggesting that infection with Hantaan virus or a closely related agent was locally acquired. However, the precise source of his infection remains unclear.

Percutaneous transluminal coronary angioplasty of a coronary artery with a total occlusion

Percutaneous transluminal coronary angioplasty has become an accepted therapeutic modality for patients with coronary artery disease. Until the present, its use has been restricted to vessels that are subtotally obstructed. We recently successfully utilized coronary angioplasty in a patient with a totally occluded coronary artery. The experience is described and criteria proposed for the selection of patients with totally obstructed coronary arteries for coronary angioplasty.

Kawasaki syndrome in an adult: endomyocardial histology and ventricular function during acute and recovery phases of illness

Kawasaki syndrome, an acute systemic inflammatory illness of unknown origin usually affecting children, may develop into a serious illness complicated by coronary artery aneurysms or myocarditis. This report describes an adult with Kawasaki syndrome studied by right ventricular endomyocardial biopsy and cardiac catheterization during the acute and recovery phases of illness. The initial biopsy specimen showed acute myocarditis and was associated with hemodynamic evidence of biventricular dysfunction, a severely depressed left ventricular ejection fraction and global hypokinesia. With time, there was spontaneous and rapid resolution of the inflammatory cell infiltrate with concurrent return to normal myocardial function. Right ventricular endomyocardial biopsy studies early in the course of the cardiac disease associated with Kawasaki syndrome may correlate with ventricular function and may be useful for monitoring immunosuppressive therapy in patients with this syndrome.

Relationship between segmental thallium-201 uptake and regional myocardial blood flow in patients with coronary artery disease

The relationship between the spatial distribution of thallium-201 in myocardial perfusion scintigrams and the distribution of left ventricular regional myocardial blood flow was examined in 25 patients undergoing coronary arteriography. Thallium-201 myocardial scintigrams were obtained after symptom-limited exercise and after a 4 hr delay. Regional myocardial blood flow was measured by the xenon-133 clearance method in patients at rest and during rapid atrial pacing to a double product comparable with that achieved during exercise stress testing. Patterns of regional thallium-201 activity and regional myocardial blood flow, recorded in similar left anterior oblique projections, were compared for left ventricular segments supplied by the left anterior descending (LAD) and left circumflex (CIRC) arteries. In 11 patients without significant lesions of the left coronary artery (group 1), thallium-201 was homogeneously distributed in the LAD and CIRC distributions in scintigrams taken during peak exercise; these scintigrams correspond to homogeneous regional myocardial blood flow in the LAD and CIRC regions during pacing-induced stress. In 14 patients with significant lesions of the left coronary artery (group 2), ratios of regional thallium-201 activity in the LAD and CIRC distributions of exercise scintigrams correlated well (r = .84) with ratios of regional myocardial blood flow measured during rapid pacing. Background subtraction altered the relationship between relative thallium-201 uptake and regional myocardial blood flow, causing overestimation of the magnitude of flow reduction on exercise scintigrams. These data indicate that: (1) in patients with normal left coronary arteries, thallium-201 is homogeneously distributed to the left ventricle, reflecting the homogeneous distribution of regional myocardial blood flow over a wide range of mean left ventricular flow rates and (2) in patients with significant lesions of the left coronary artery, the relative spatial distribution of thallium-201 activity in exercise perfusion scintigrams reflects the distribution of regional myocardial blood flow.

Diagnosis and classification of myocarditis by endomyocardial biopsy

Myocarditis was diagnosed by endomyocardial biopsy in 34 patients with otherwise unexplained heart failure. On the basis of both clinical and histologic findings these patients were divided into three groups. Seven patients had acute myocarditis (mean age, 20 years; mean ejection fraction, 22 per cent) characterized by an interstitial inflammatory infiltrate and extensive, acute cell damage. Five of these patients died after a mean duration of illness of eight weeks. Eighteen patients had rapidly progressive myocarditis (mean age, 35 years; mean ejection fraction, 19 per cent) characterized by patchy acute and healing cell damage and fibrosis; 17 of them died after a mean duration of illness of 23 months. Nine patients had chronic myocarditis (mean age, 31 years; mean ejection fraction, 31 per cent) characterized by focal inflammation and cell damage. All nine were alive after a mean follow-up period of 39 months. In four of these nine, clinical and hemodynamic improvement occurred after one month of immunosuppressive therapy. Our study suggests that a clinically useful classification of myocarditis can be accomplished by endomyocardial biopsy.

Validation of the angiographic accuracy of digital left ventriculography

Digital subtraction angiography enhances the contrast to background signal, enabling the performance of angiography with reduced doses of contrast medium. The objectives of the present study were (1) to validate the accuracy of digital left ventriculography for measurement of left ventricular volumes and segmental contraction; and (2) to compare the hemodynamic effects resulting from low-and high-dose intraventricular contrast injections. Twenty-eight patients underwent digital left ventriculography, performed by intraventricular injection of 7 ml of contrast medium diluted in saline solution, followed by conventional cineangiography of the left ventricle performed with 45 ml of undiluted contrast medium. Left ventricular volumes calculated from digital ventriculograms correlated well with volumes calculated from conventional ventriculograms: end-diastolic volume (r = 0.97, standard error of estimate [SEE] 23.4 ml; end-systolic volume (r = 0.97, SEE 15.4 ml); stroke volume (r = 0.95, SEE 14.7 ml); and ejection fraction (r = 0.97, SEE 3.8%). Segmental left ventricular contraction, measured as percent chordal shortening of hemiaxes, correlated moderately well (r = 0.81, SEE 11.5%). After injection of undiluted contrast medium, left ventricular systolic pressure decreased (133 +/- 31 to 123.5 +/- 27 mm Hg; p less than 0.01) and left ventricular end-diastolic pressure increased (12.0 +/- 7 to 16.9 +/- 10 mm Hg; p less than 0.001). Left ventricular systolic and end-diastolic pressures did not change significantly after injection of diluted contrast medium, and patients had no discomfort. Thus, digital subtraction angiography permits the performance of left ventriculography with markedly reduced doses of contrast medium, obviating the hemodynamic effects resulting from injection of conventional doses of contrast medium. This new approach to left ventriculography provides high resolution ventriculograms for accurate measurement of left ventricular volumes, stroke volume, and ejection fraction.

The effect of captopril on renal, coronary, and systemic hemodynamics in patients with severe congestive heart failure

The effects of captopril (CPT), an oral angiotensin-converting enzyme (ACE) inhibitor, on systemic failure (CHF). In 15 patients, CPT decreased mean arterial pressure from 75 +/- 3 to 60 +/- 3 mm Hg associated with a 16% increase in cardiac output, a 24% reduction in systemic vascular resistance, and a 36% decrease in pulmonary capillary wedge pressure (all p less than 0.01). Despite the improved cardiac output, renal blood flow, creatinine clearance, and sodium excretion did not rise during the first 2 days of CPT therapy. In eight patients, coronary sinus blood flow diminished from 98 +/- 11 to 82 +/- 9 ml/min (p less than 0.01) following drug administration in association with a fall in arterial pressure and heart rate but no change in coronary sinus oxygen inhibitor failed to improve renal hemodynamics. In addition, initial CPT administration produced a decrease in coronary blood flow that was related to a decrease in myocardial oxygen requirements.

Left ventricular myocardial blood flow in multivessel coronary artery disease

The relationship between resting left ventricular (LV) myocardial blood flow (MBF) and hemodynamic determinants of myocardial oxygen consumption was investigated in 15 patients with multivessel coronary artery disease (CAD) and in 10 patients with normal coronary arteriograms. Mean LV MBF per unit mass of tissue was measured with a multicrystal scintillation camera from the regional clearance rates of xenon-133 injected into the left main coronary artery. Peak LV wall stress, mean velocity of circumferential fiber shortening (Vcf), rate of ejection during the first third of systole (1/3 SV), LV ejection fraction (EF), and the ratio of peak LV systolic pressure to LV end-systolic volume were measured by contrast left ventriculography. Mean LV MBF per unit mass was significantly reduced (48 +/- 11 vs 67 +/- 12 ml/100 g.min; p less than 0.01) in patients with multivessel CAD. However, none of the patients with CAD experienced chest pain or had electrocardiographic evidence of myocardial ischemia during the resting MBF measurements. Ejection phase indexes were lower in the patients with CAD: LVEF (56 +/- 10% vs 64 +/- 7%, p less than 0.05); 1/3 SV (35 +/- 3 vs 44 +/- 4%, p less than 0.05); and mean Vcf (1.05 +/- 0.30 vs 1.19 +/- 0.27 circ/sec, NS). LV wall thickness (9.8 +/- 1.9 vs 7.5 +/- 1.4 mm, p less than 0.01) and LV mass index (94 +/- 32 vs 64 +/- 17 g/m2, p less than 0.05) were significantly increased in the patients with CAD, accounting for the reduction in peak LV wall stress (276 +/- 73 vs 373 +/- 91 dyn-cm-2 x 10(-3), p less than 0.05) observed in these patients. Multiple regression analysis indicated that indexes of three of the major determinants of myocardial oxygen consumption explained 65% of the variation in MBF in patients with CAD: peak LV stress, mean Vcf and heart rate. After adjustment for these three indexes, the average LV MBF rates were not significantly different in the two patient groups (54.8 +/- 1.8 vs 57.6 +/- 2.3 ml/100 g.min). In both groups, resting LV MBF/beat correlated most highly with peak LV wall stress (r = 0.79). Thus, the reduction in LV MBF per unit mass observed in patients with multivessel CAD at rest is related to lower levels of hemodynamic variables that determine myocardial oxygen consumption. Peak LV wall stress is the most important hemodynamic variable determining the level of resting MBF in patients with and without CAD.

Development of a new endosseous dental implant. Part II: Human studies

The development of an endosseous implant has followed a logical and formal plan. 1. Extensive experiments with animals provided preliminary statistics of successful function, extensive histologic studies, evaluation of biocompatibility, and a preliminary assessment of contraindications. 2. Carefully developed and controlled clinical study of human subjects with frequent examinations and detailed records of both successes and failures again provided new bases for contraindications. The statistics on the clinical study are satisfactory in their results, although they should be regarded as having a somewhat conservative slant. This is because implant failures became a learning base for improved procedures. The program so far has been limited to a single implant design that, with size variants, will serve most applications. However, it is not feasible to modify the design in terms of dimensions for application in the anterior portion of the mouth. A design for this purpose is established on paper and will become a future additional development.

Percutaneous intraaortic balloon insertion in patients with aortoiliac disease

A new technique for percutaneous insertion of intraaortic balloon catheters in patients with tortuous or narrowed external iliac arteries is described. This method uses a long (45 cm) 12F sheath, which extends up to the descending aorta and protects the iliac artery and aorta from injury during insertion of the balloon catheter. Insertion of intraaortic balloon catheters was not possible by conventional percutaneous technique in six patients with severe acute myocardial ischemia. Use of the long sheath approach permitted rapid and successful institution of circulatory support in these patients.

The human sinus node electrogram: a transvenous catheter technique and a comparison of directly measured and indirectly estimated sinoatrial conduction time in adults

To improve methods for evaluating human sinus node function (SNF), we developed a transvenous electrode catheter technique for direct recording of sinus node electrograms in adults. Sinus node electrograms (SNE) characterized by low-frequency, anatomically localized pre-P-wave potentials were obtained in 19 of 23 patients. The SNE configuration was similar to that previously found for endocardial SNE recordings in in vitro atrial preparations, in open-chest dogs and during human open heart surgery. In 16 patients with normal SNF, directly recorded sinoatrial conduction times (SACTs) were 46-116 msec. In three patients with sick sinus syndrome, SACT was 110-126 msec. In 15 of the 19 patients, SACT was estimated by the atrial premature stimulus technique and was compared with the directly measured SACT. When atrial premature depolarizations produced no sinus node depression, the mean differences between the direct and estimated SACT was 1.8 +/- 5.6 msec.

Percutaneous intraaortic balloon insertion

A new single chambered percutaneous intraaortic balloon has been constructed around a central guidewire. The balloon can be wrapped around the guidewire, enabling its insertion into the femoral artery through a 12F sheath inserted with the conventional Seldinger technique. Percutaneous intraaortic balloon insertion has been performed in 27 patients (mean age 58 years) for a variety of medical and surgical indications. Percutaneous balloons could not be advanced into the aorta in two patients (7.4 percent) with severe bilateral aortoiliac occlusive disease. In all 25 patients undergoing intraaortic balloon pumping satisfactory circulatory support was achieved, and 21 (84 percent) of the patients survived to be discharged from the hospital. The mean duration of intraaortic balloon pumping was 3.5 days. Percutaneous intraaortic balloon insertion requires less than 5 minutes and has been successfully performed in the cardiac catheterization laboratory, coronary care unit, operating room and recovery room. After direct balloon removal, external pressure was applied for 30 minutes. No patient experienced hematoma of the groin, aortic dissection, compromised distal pulses or late wound complications. Percutaneous balloon insertion permits the rapid institution of circulatory support and broadens the medical and surgical applications of intraaortic balloon pumping.