Karsch-Neugebauer syndrome in two sibs with unaffected parents

We report on 2 sisters with Karsch-Neugebauer syndrome comprising split foot and split hand anomalies in association with congenital nystagmus. These sisters share a nearly identical phenotype with the 8 previously reported instances of this disorder. Although genetic heterogeneity can not be formally excluded, most evidence suggests that Karsch-Neugebauer syndrome is an autosomal dominant disorder. If so, then this report of 2 affected sibs born to healthy parents is the second instance of apparent gonadal mosaicism in this disorder. The apparent high frequency of gonadal mosaicism is important to recognize in counseling families with this disorder.

Generation and transplantation of EGF-responsive neural stem cells derived from GFAP-hNGF transgenic mice

EGF-responsive neural stem cells isolated from murine striatum have the capacity to differentiate into both neurons and glia in vitro. Genetic modification of these cells is hindered by a number of problems such as gene stability and transfection efficiency. To circumvent these problems we generated transgenic mice in which the human GFAP promoter directs the expression of human NGF. Neural stem cells isolated from the forebrain of these transgenic animals proliferate and form clusters, which appear identical to stem cells generated from control animals. Upon differentiation in vitro, the transgenic stem cell-derived astrocytes express and secrete bioactive hNGF. Undifferentiated GFAP-hNGF or control stem cells were transplanted into the striatum of adult rats. One and 3 weeks after transplantation, hNGF was detected immunocytochemically in an halo around the transplant sites. In GFAP-hNGF-grafted animals, intrinsic striatal neurons proximal to the graft appear to have taken up hNGF secreted by the grafted cells. Ipsilateral to implants of GFAP-hNGF-secreting cells, choline acetyltransferase-immunoreactive neurons within the striatum were hypertrophied relative to the contralateral side or control-grafted animals. Further, GFAP-hNGF-grafted rats displayed a robust sprouting of p75 neurotrophin receptor-positive fibers emanating from the underlying basal forebrain. These studies indicate that EGF-responsive stem cells which secrete hNGF under the direction of the GFAP promoter display in vitro and in vivo properties similar to that seen following other methods of NGF delivery and this source of cells may provide an excellent avenue for delivery of neurotrophins such as NGF to the central nervous system.

Direct interactions of human natural killer cells with Cryptococcus neoformans inhibit granulocyte-macrophage colony-stimulating factor and tumor necrosis factor alpha production

Human natural killer (NK) cells and T lymphocytes can bind to and inhibit the growth of the yeast-like organism Cryptococcus neoformans. Binding of target cells to NK or T cells also has the potential to modulate cytokine production by the effector cells. In this study, we assessed the ability of C. neoformans to modulate NK cell production, or in some cases T-cell production, of granulocyte-macrophage colony-stimulating factor (GM-CSF) or tumor necrosis factor alpha (TNF-alpha). We found that freshly isolated human NK cells from most individuals make GM-CSF and TNF-alpha constitutively when cultured in vitro. The addition of C. neoformans to T-cell fractions which do not make GM-CSF constitutively did not affect GM-CSF production, but the addition of C. neoformans to NK cell fractions significantly reduced the amounts of GM-CSF produced in most NK cell samples. The reduction in the amount of GM-CSF in C. neoformans-NK cell cocultures could not be attributed to loss of lymphocyte viability or to C. neoformans adsorbing or degrading the cytokine and was dependent on direct contact between the NK cells and cryptococcal cells. GM-CSF was not the only cytokine to be down-regulated. TNF-alpha production was also diminished when NK cells were incubated with C. neoformans. The regulation of both cytokines was at the transcriptional level because GM-CSF and TNF-alpha mRNA levels were lower in NK cell samples incubated with C. neoformans than in NK cell samples incubated without C. neoformans. Diminished production of constitutively produced cytokines resulting from the interaction of NK cells with cryptococcal cells has the potential to affect phagocytic cells in the immediate regional environment and to damp the immune response.

Grafts of EGF-responsive neural stem cells derived from GFAP-hNGF transgenic mice: trophic and tropic effects in a rodent model of Huntington's disease

The present study examined whether implants of epidermal growth factor (EGF)-responsive stems cells derived from transgenic mice in which the glial fibrillary acid protein (GFAP) promoter directs the expression of human nerve growth factor (hNGF) could prevent the degeneration of striatal neurons in a rodent model of Huntington's disease (HD). Rats received intrastriatal transplants of GFAP-hNGF stem cells or control stem cells followed 9 days later by an intrastriatal injection of quinolinic acid (QA). Nissl stains revealed large striatal lesions in rats receiving control grafts, which, on average, encompassed 12.78 mm3. The size of the lesion was significantly reduced (1.92 mm3) in rats receiving lesions and GFAP-hNGF transplants. Rats receiving QA lesions and GFAP-hNGF-secreting grafts stem cell grafts displayed a sparing of striatal neurons immunoreactive (ir) for glutamic acid decarboxylase, choline acetyltransferase, and neurons histochemically positive for nicotinamide adenosine diphosphate. Intrastriatal GFAP-hNGF-secreting implants also induced a robust sprouting of cholinergic fibers from subjacent basal forebrain neurons. The lesioned striatum in control-grafted animals displayed numerous p75 neurotrophin-ir (p75NTR) astrocytes, which enveloped host vasculature. In rats receiving GFAP-hNGF-secreting stem cell grafts, the astroglial staining pattern was absent. By using a mouse-specific probe, stem cells were identified in all animals. These data indicate that cellular delivery of hNGF by genetic modification of stem cells can prevent the degeneration of vulnerable striatal neural populations, including those destined to die in a rodent model of HD, and supports the emerging concept that this technology may be a valuable therapeutic strategy for patients suffering from this disease.

Increased frequency of expression of elevated dihydrofolate reductase in T-cell versus B-precursor acute lymphoblastic leukemia in children

The relationships between dihydrofolate reductase (DHFR) levels or methotrexate membrane transport and acute lymphoblastic leukemia (ALL) immunophenotype were evaluated on 51 T-cell and 44 B-precursor ALL specimens from 90 pediatric ALL patients at diagnosis and relapse, using a fluorescent methotrexate analog (PT430) and flow cytometry assay (Matherly et al, Blood 85:500, 1995). For T-cell ALL, 35 of 45 (78%) of newly diagnosed patients' specimens exhibited elevated DHFR relative to DHFR levels in ALL blasts from methotrexate-responsive patients. For 30 of 45 diagnostic T-ALL specimens, DHFR expression was heterogeneous, with up to 3 separate subpopulations covering a 44-fold range; the DHFR-overproducing fractions comprised 10% to 88% of the total blasts. Elevated DHFR was less common in B-precursor ALL at diagnosis, being detected in only 17 of 36 specimens (47%); 11 of these samples exhibited DHFR heterogeneity. Median maximal DHFR levels were fourfold higher in T-cell than B-precursor ALL at diagnosis. Within a particular phenotypic group, there were no correlations between DHFR levels and patient prognostic features, including age, sex, chromosomal abnormalities, white blood cell counts (WBCs), and percentage of S-phase. However, for B-precursor ALL, there was a notably higher fraction of African-American than white patients with elevated DHFR. For patients (both phenotypes) with low WBCs (<50,000/ microL), event-free survival times were significantly shorter for those expressing DHFR above a threshold level than for patients expressing DHFR below this level (P < .016); this relationship was not seen for patients with high WBCs (>50,000/microL). Elevated DHFR was detected in 11 of 14 relapse specimens (5 of 6 T-cell and 6 of 8 B-precursor). Two of five paired relapse specimens (both T-cell) from patients treated with methotrexate exhibited increased DHFR levels over those at diagnosis (2.5- to 5-fold); the fraction of DHFR-overproducing blasts was also increased in 4 of 5 paired relapse specimens (2 B-precursor and 2 T-cell). In contrast to the variations in DHFR, highly impaired methotrexate transport was detected in only 6 of 95 ALL specimens, including both diagnosis and relapse. There was no correlation between phenotype and impaired transport. These data provide further rationale for the use of mechanistically based prognostic factors to complement known biologic or disease-based prognostic indicators in the design of ALL therapy including methotrexate, particularly with patients presenting with low WBCs. The finding of a markedly increased frequency of DHFR overexpression in T-cell over B-precursor ALL suggests that this difference is associated with the poorer prognosis of patients with T-cell ALL treated with standard-dose antimetabolite therapy and implies that higher-dose methotrexate (> or = 1 g/m2) during consolidation therapy may be useful in the treatment of this disease.

Feasibility and efficacy of locally delivered enoxaparin via the Channeled Balloon catheter on smooth muscle cell proliferation following balloon injury in rabbits

To determine the potential utility of local treatment of enoxaparin on restenosis, four groups of rabbits underwent balloon injury of bilateral iliac arteries with the Channeled Balloon (balloon/artery = 1.1), followed by assigned treatment (5 controls received local saline, 7 local-treatment rabbits received a one-time local delivery of 10 mg/kg of enoxaparin, 5 systemic-treatment rabbits received 10 mg/kg of enoxaparin subcutaneously once daily for 1 wk, and 5 combined-treatment rabbits received both local and systemic enoxaparin). The percentage of nuclei positive for proliferating cell nuclear antigen/microns2 of media 1 wk later was 1.97 +/- 2.01 for the control group, 2.68 +/- 2.52 for the local group, 0.22 +/- 0.32 for the systemic group, and 0.07 +/- 0.09 for the combined group (P < 0.0001 by Kruskal-Wallis test, with P < 0.05 for combined treatment group vs. controls or local treatment group and systemic vs. local groups). Feasibility study with 3H-enoxaparin showed intramural retention of 0.1-0.2% of locally delivered amount for 24 h. We conclude that one-time local delivery of enoxaparin following angioplasty is ineffective in inhibiting medial smooth muscle cell proliferation, most likely due to low efficiency. Only sustained treatment resulted in significant reduction.

Role of high-performance liquid chromatographic protein analysis in developing fermentation processes for recombinant human growth hormone, relaxin, antibody fragments and lymphotoxin

Development of efficient and reliable fermentation processes for protein pharmaceuticals is aided by the availability of accurate quantitative and qualitative product analyses. We have developed a variety of single and dual column chromatographic separations that meet the needs of process development and examples will be provided of how the resulting data has been used to optimize the culture process. For single column methods, reversed-phase chromatography has been the most versatile, permitting the reliable quantitation of many yeast, Chinese hamster ovary (CHO) cell and Escherichia coli-expressed products in the matrix of culture broth or cell extract. Analysis of secreted human growth hormone synthesized in E. coli, along with clipped and unprocessed forms, will be discussed. Another reversed-phase assay for direct analysis of a peptide product (B-chain relaxin) and its degradation products secreted into E. coli fermentation medium has allowed the purification of the responsible protease. Cation-exchange has proven extremely useful for the direct analysis of antibody fragment synthesized in E. coli, allowing the separation and quantitation of the desired Fab' and Fab'2, as well as the unwanted products of glutathione addition and translational read-through. Assay development is often complicated by the presence of host proteins with chromatographic behavior that is similar to that of the product. Commercial instrumentation now permits the facile development of multidimensional chromatographic assays. We show examples of coupled receptor affinity-reversed-phase assays for a mistranslation product and for covalent multimers of E. coli-synthesized lymphotoxin.

Human K562 transfectants expressing high levels of reduced folate carrier but exhibiting low transport activity

A human reduced folate carrier (hRFC) cDNA was transfected into transport-deficient K562 cells to circumvent complications that may result from carrier expression in a heterologous mammalian species. Relative to wild-type cells, hRFC transcript levels were increased 11- and 19-fold, respectively, in the K43-6 and K43-1 transfectants. Although photoaffinity labeling of hRFC protein revealed similar increases of 15- and 19-fold, respectively, only a 2-fold enhancement in methotrexate (Mtx) transport was observed. This suggests that only a small portion of the cDNA-encoded hRFC protein is actively engaged in membrane transport. Kinetic analysis of [3H]Mtx transport indicated that K43-6 cells exhibited a similar affinity (Kt) but an increased Vmax (1.7-fold) when compared with K562 cells. The restored transport was similar to that of wild-type cells in its capacity to be trans-stimulated by intracellular folates and in its sensitivity to competitive transport inhibitors (1843U89, bromosulfophthalein, folic acid, leucovorin, and ZD1694) and to irreversible inhibition by N-hydroxysuccinimide-methotrexate. Further, deglycosylated photoaffinity-labeled hRFC protein in both K562 and K43-6 cells migrated at approximately 65-70 kDa on SDS-gels, consistent with the molecular mass from the predicted amino acid sequence. These data further establish that the expression of hRFC, alone, is sufficient to confer transport properties typical of the "classical" hRFC. However, the discrepancy between the stoichiometry of carrier expression and transport activity implies that membrane translocation of bound substrate may be regulated by additional undefined mechanisms.

Continuous subcutaneous angiopeptin treatment significantly reduces neointimal hyperplasia in a porcine coronary in-stent restenosis model

BACKGROUND

In-stent restenosis results primarily from neointimal hyperplasia. This study evaluated the efficacy and the optimal mode of administration of angiopeptin, a somatostatin analogue with antiproliferative activity, in a porcine coronary in-stent restenosis model.

METHODS AND RESULTS

Forty pigs were randomly assigned to one of four groups (n = 10 per group): (1) controls receiving saline infusion at the site of stent implantation via a local delivery catheter, (2) local treatment group receiving one-time treatment (200 (micrograms angiopeptin) at the site of stent placement, (3) systemic treatment group receiving continuous angiopeptin over a 1-week period via a subcutaneous osmotic pump (200 micrograms/kg total dose) and (4) combined local and systemic treatment group. Then, one oversized Palmaz-Schatz stent (mean ratio of stent to artery diameters, 1.3:1) was implanted in the left anterior descending coronary artery. The degree of neointimal reaction was evaluated 4 weeks later by angiography (maximal percent diameter stenosis), intravascular ultrasound (total in-stent neointimal volume), and histology (maximal area stenosis). Systemic treatment produced the least neointimal hyperplasia and significantly reduced in-stent restenosis compared with the control group by all end points, despite similar degrees of injury. Angiography showed 25 +/- 17% versus 50 +/- 17% diameter stenosis in the systemic angiopeptin group versus the control group (P < .0001), intravascular ultrasound revealed 23 +/- 10 versus 58 +/- 27 mm3 neointimal volume in the systemic angiopeptin versus control group (P = .0002), and histology showed 41 +/- 16% versus 69 +/- 18% area stenosis (P = .0016) in the systemic angiopeptin versus control group. Plasma angiopeptin levels revealed rapid clearance (within 6 hours) after local therapy, whereas the levels persisted for up to 2 weeks in the systemic group.

CONCLUSIONS

This study shows that continuous subcutaneous treatment with angiopeptin after stent implantation significantly reduces in-stent restenosis by inhibiting neointimal hyperplasia.

Confocal microscopy visualization of antifolate uptake by the reduced folate carrier in human leukaemic cells

Confocal microscopy was used to visualize the intracellular uptake of the fluorescent methotrexate analogue, fluorescein-MTX (F-MTX), in human leukaemic cell lines and leukaemic blasts. Cytosolic labelling of wild-type K562 human erythroleukaemia cells was detected during 3-60 min incubations with F-MTX (1 microM) and was completely inhibited by co-exposure to either methotrexate or the thymidylate synthase inhibitor, ZD1694. There was no significant intracellular F-MTX accumulation over this period in a K562 subline (K500E) with a documented defect (approximately 10% of wild type) in membrane transport by the reduced folate carrier (RFC). F-MTX uptake was re-established in K500E cells transfected with a cDNA to human RFC, establishing a role for RFC in the cellular uptake of this compound. High levels of intracellular labelling were detected in all cell lines after prolonged (24 h) F-MTX incubations, however F-MTX accumulation at this time was not inhibited by ZD1694. F-MTX uptake by RFC was also detected in leukaemic blasts from children with acute lymphoblastic leukaemia and could be blocked with ZD1694. In leukaemic blasts with a documented defect in MTX uptake, F-MTX accumulation was abolished in almost all the cells. These results display the power of confocal microscopy for directly visualizing RFC-mediated anti-folate uptake. Over short intervals, F-MTX uptake is mediated by RFC, however, RFC-independent processes predominate during long drug exposures. Direct assay by confocal microscopy may be better suited than other indirect methods (i.e. flow cytometry) for detecting low levels of RFC transport in leukaemic blasts from patients undergoing chemotherapy with methotrexate.

Mouse RAD50 has limited epitopic homology to p53 and is expressed in the adult myocardium

Previous studies have identified a 180-kDa mouse cardiomyocyte phosphoprotein with limited epitopic homology to p53. In this study, the protein was purified and partially sequenced. Oligonucleotide probes based on the available amino acid sequence data were used to isolate cDNA clones. Sequence analyses revealed that the clones encoded a protein with regional homology to the yeast RAD50 gene product. Expression of the mouse cDNA rescued the methyl methanesulfonate-sensitive phenotype in rad50 mutant yeast, indicating that the cardiomyocyte phosphoprotein is the mammalian homologue of the yeast RAD50 gene product. Fluorescence in situ hybridization analyses localized the mouse RAD50 gene to the A5-B1 region of chromosome 11. Northern blot analyses demonstrated a complex pattern of RAD50 expression during mouse development which was further complicated by the presence of several alternatively spliced transcripts. High levels of RAD50 expression was evident in the adult myocardium, a somewhat surprising observation given the absence of DNA synthesis in adult cardiomyocytes.

Age- and sex-related changes in lymphocyte subpopulations of healthy Asian subjects: from birth to adulthood

Flow cytometric analysis of lymphocyte subsets were evaluated in 391 healthy Asian subjects ranging in age from birth to 40 years. Lymphocyte subsets were analysed using specific monoclonal antibodies: CD20 (B cells), CD3 and CD2 (T cells), CD16 and CD56+ (NK cells), CD4/CD3+ (helper-inducer T cells), CD8/ CD3+ (suppressor/cytotoxic T cells), HLA-DR expression on CD3 and CD25 (Tac) on CD3. The total white cell count, absolute lymphocyte counts, and B cell percentages peaked in infancy and declined steadily with age. Absolute counts of each subset, which were derived from absolute lymphocyte counts, also followed this trend. Increases with age were seen in the NK, T cell (CD2, CD3), and CD8 percentages. Males tended to have higher NK and CD8 percentages than females, and, conversely, females had higher CD3 and CD4 percentages than males. Comparison of our results with studies involving Caucasian subjects indicated higher NK percentages in our Asian population and lower CD4 absolute counts in the males of our population. These results indicate the presence of age, sex, and probable racial differences in lymphocyte subset expression. Our results may serve as reference standards for the Asian population.

Percutaneous transcatheter repair of a coronary aneurysm using a composite autologous cephalic vein-coated Palmaz-Schatz biliary stent

We describe a novel percutaneous transcatheter technique using an autologous vein graft-coated Palmaz-Schatz stent for the treatment of a coronary aneurysm. This technique avoids the procedural risks that are currently associated with surgical repair with revascularization or spring coil embolization in the treatment of coronary aneurysm.

Can coronary flow parameters after stent placement predict restenosis?

Intracoronary stent was used to treat a dissection resulting from balloon angioplasty. Coronary flow parameters measured with Doppler Flowire pre- and post-stenting suggested abnormal coronary flow even after stenting. The patient returned 4 months later with an instent restenosis. This case suggests the intriguing possibility of coronary flow parameters obtained immediately after new device angioplasty in predicting restenosis.

Cloning, sequencing, and expression of a 24-kDa Ca(2+)-binding protein activating photoreceptor guanylyl cyclase

Two vertebrate photoreceptor-specific membrane guanylyl cyclases, RetGC-1 and RetGC-2, are activated by a soluble 24-kDa retinal protein, p24, in a Ca(2+)-sensitive manner (Dizhoor, A.M., Lowe, D.G., Olshevskaya, E.V., Laura, R.P., and Hurley, J.B. (1994) Neuron 12, 1345-1352; Lowe, D.G., Dizhoor, A.M., Liu, K., Gu, O., Laura, R., Lu, L., and Hurley, J.B. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 5535-5539). The primary structure of bovine p24 has been derived from peptide sequencing and from its cDNA. p24 is a new EF-hand-type Ca(2+)-binding protein, related but not identical to another guanylyl cyclase-activating protein, GCAP (Palczewski, K., Subbaraya, I., Gorczyca, W.A., Helekar, B.S., Ruiz, C.C., Ohguro, H. Huang, J., Zhao, X., Crabb, J.W., Johnson, R.S., Walsh, K.A., Gray-Keller, M.P., Detwiler, P.B., and Baehr, W. (1994) Neuron 13, 395-404) and other members of the recovering family of Ca(2+)-binding proteins. Antibodies against a truncated fusion protein and against a p24-specific synthetic peptide specifically recognize retinal p24 on immunoblot. Both antibodies inhibit activation of photoreceptor membrane guanylyl cyclase by purified p24. p24 is found only in retina, and it copurifies with outer segment membranes. Immunocytochemical analysis shows that it is present in rod photoreceptor cells. An immobilized antibody column was used to purify p24 from a heat-treated retinal extract. Purified p24 appears on SDS-polyacrylamide gel electrophoresis as a homogeneous protein not contaminated with GCAP, and it activates photoreceptor guanylyl cyclase in vitro at submicromolar concentrations. Ca2+ inhibits this activation with an EC50 near 200 nM and a Hill coefficient of 1.7. Recombinant p24 expressed in 293 cells effectively stimulates photoreceptor guanylyl cyclase. These findings demonstrate that p24, like GCAP, imparts Ca2+ sensitivity to photoreceptor membrane guanylyl cyclase. We propose that p24 be referred to as GCAP-2 and that GCAP be referred to as GCAP-1.

Vascular effects of diet-induced hypercalcemia after balloon artery injury in giant Flemish rabbits

To determine whether metastatic calcification during neointima formation can result in neointimal calcification that simulates advanced human atherosclerosis, 32 giant Flemish rabbits (weight 5.5 +/- 0.6 kg) underwent overstretch balloon injury of bilateral iliac arteries and received diet therapy for 8 weeks: high cholesterol (2%) and low calcium-vitamin D2 regimen (250 mg of calcium carbonate orally 5 times weekly and 50,000 U of calciferol intramuscularly 3 times weekly; group 1; n = 5); low cholesterol (0.5%) and high calcium-vitamin D2 regimen (500 mg of calcium carbonate orally 5 times weekly and 100,000 U of calciferol intramuscularly three times weekly; group 2; n = 19); or 0% cholesterol and high calcium-vitamin D2 regimen (group 3; n = 8). The incidence of vascular calcification was highest (71.4%) in group 2. Eighty-one percent of calcification was medial. Residual strain measurements of 7 thoracic aortas from group 2 compared to normal thoracic aortas from 8 control rabbits showed that residual strain was significantly increased in the calcified atherosclerotic aortas (12.3% vs 5.2%; p = 0.001). We conclude that diet-induced hypercalcemia predominantly affects the media despite the presence of concomitant neointima formation from balloon artery injury with or without hypercholesterolemia and increases the residual strain more than twofold compared to normal thoracic aortas.

Small stent size and intimal hyperplasia contribute to restenosis: a volumetric intravascular ultrasound analysis

OBJECTIVES

The purpose of this study was to use volumetric intravascular ultrasound analysis of Palmaz-Schatz stents to assess the in-stent restenotic process.

BACKGROUND

By reducing lesion elastic recoil and chronic arterial remodeling, stents improve the long-term results of coronary angioplasty. However, stents are prone to the development of neointimal hyperplasia. Angiographic studies of stent restenosis have suggested that these hyperplastic responses are the cause of in-stent restenosis; however, it is difficult to visualize the radiolucent Palmaz-Schatz stent by angiography. Intravascular ultrasound provides detailed cross-sectional imaging of the coronary arteries, especially the intense metallic reflection of endovascular stents.

METHODS

Forty-four patients with 60 Palmaz-Schatz stents underwent intravascular ultrasound imaging at follow-up ([mean +/- SD] 8.8 +/- 7.2 months after implantation). Thirty-four stents were placed in saphenous vein grafts and 26 in native coronary arteries; 30 were placed in restenotic lesions. Intravascular ultrasound with automatic transducer pullback at 0.5 mm/s allowed measurement of stent, lumen and intimal hyperplasia cross-sectional areas at 1-mm axial increments within the stents. Using Simpson's rule, stent, lumen and intimal hyperplasia volumes were calculated. Patterns of in-stent restenosis were then identified.

RESULTS

Restenotic stents had smaller stent volumes (120 +/- 41 vs. 147 +/- 43 mm3, p = 0.016) and lumen volumes (62 +/- 28 vs. 118 +/- 42 mm3, p < 0.0001) but larger intimal hyperplasia volumes (58 +/- 36 vs. 29 +/- 18 mm3, p < 0.001) than nonrestenotic stents. A focal restenosis pattern was more common (20 [77%] of 26) than a diffuse restenosis pattern (6 [23%] of 26). Stents with focal restenosis and stents with diffuse restenosis had equally small stent volumes (120 +/- 44 vs. 120 +/- 31 mm3, respectively, p = NS); however, stents with diffuse restenosis had larger intimal hyperplasia volumes (84 +/- 30 vs. 50 +/- 34 mm3, p < 0.05). Focal restenosis was most commonly located at the central articulation (45%); the location of focal restenosis was related to the focal accumulation of neointimal tissue.

CONCLUSIONS

Stent volume and magnitude and distribution of intimal hyperplasia are important in the development of in-stent restenosis. Stent volume was smaller and intimal hyperplasia volume greater in restenotic stents. Stent restenosis is more commonly focal in nature and located at the central articulation.

Immediate results and late outcomes after stent implantation in saphenous vein graft lesions: the multicenter U.S. Palmaz-Schatz stent experience. The Palmaz-Schatz Stent Study Group

OBJECTIVES

This study reports the multicenter registry experience evaluating the safety and efficacy of the Palmaz-Schatz stent in the treatment of saphenous vein graft disease.

BACKGROUND

Saphenous vein graft angioplasty is associated with frequent periprocedural complications and a high frequency of restenosis. Stent implantation has been shown to reduce restenosis, with improved long-term outcomes in the treatment of native coronary artery disease. Preliminary experience with stent placement in the treatment of saphenous vein graft lesions has been favorable.

METHODS

Twenty U.S. investigator sites enrolled a total of 589 symptomatic patients (624 lesions) for treatment of focal vein graft stenoses between January 1990 and April 1992. Follow-up angiography was performed at 6 months, and the clinical course of all study patients was prospectively collected at regular intervals for up to 12 months.

RESULTS

Stent delivery was successful in 98.8% of cases, and the procedural success rate was 97.1%. The lesion diameter stenosis decreased from 82 +/- 12% (mean +/- SD) before to 6.6 +/- 10.2% after treatment. Major in-hospital complications occurred in 17 patients (2.9%); stent thrombosis was found in 8 (1.4%); and major vascular or bleeding complications were noted in 83 (14.3%). Six-month angiographic follow-up revealed an overall restenosis rate (> or = 50% diameter stenosis) of 29.7%. Multivariate logistic regression analysis indicated that 1) restenotic lesions, 2) smaller reference vessel size, 3) history of diabetes mellitus, and 4) higher percent poststent diameter stenosis were independent predictors of restenosis. The 12-month actuarial event-free survival was 76.3%.

CONCLUSIONS

Stent implantation in patients with focal saphenous vein graft lesions can be achieved with a high rate of procedural success, acceptable major complications, reduced angiographic restenosis and favorable late clinical outcome compared with historical balloon angioplasty control series. The rigorous anticoagulation regimen after stent placement results in more frequent vascular and other bleeding complications. Future randomized studies comparing standard balloon angioplasty with stent implantation are warranted to properly assess the full impact of stent placement in the treatment of saphenous vein graft lesions.

Isolation of human cDNAs that restore methotrexate sensitivity and reduced folate carrier activity in methotrexate transport-defective Chinese hamster ovary cells

This report describes the isolation, nucleotide sequencing, and functional expression of human cDNAs that restore reduced folate carrier activity in transport-defective cells. Based on homology to a partial murine cDNA probe, two functional cDNAs were isolated from a lambda gt11 library prepared from methotrexate transport upregulated K562 cells (K562.4CF). A 2.8-kilobase (kb) clone, KS43, contained a 1776-base pair open reading frame. The 2.5-kb clone, KS32, contained an internal deletion (626 base pairs) resulting a shortened open reading frame and 3'-untranslated region. KS43 and KS32 encoded proteins with multiple hydrophobic domains, one consensus N-glycosylation site, and predicted molecular masses of 65 and 58 kDa, respectively. The deduced amino acid sequence of KS43 is 79% and 80% homologous to the mouse and hamster sequences, respectively (Dixon, K. H., Lanpher, B. C., Chiu, J., Kelley, K., and Cowan, K. H. (1994) J. Biol. Chem. 269, 17-20; Williams, F. M. R., Murray R. C., Underhill, T. M., and Flintoff, W. F. (1994) J. Biol. Chem. 269, 5810-5816). Northern blots identified one primary transcript at 3.1 kb in parental K562, K562.4CF, and transport-impaired K500E cells; transcript levels varied by 7-fold. The expression of both KS43 and KS32 in methotrexate transport-defective Chinese hamster ovary cells restored methotrexate sensitivity and transport. Certain transport characteristics of the transfected cells resembled both the wild type human (K562) and hamster "classical" reduced folate carriers, suggesting the expression of a hybrid system. For instance, based on Ki values, up to a 4-fold increased affinity for 1843U89 over wild type hamster cells (typical of human cells), and a 19-fold increased affinity for methotrexate over K562 cells (typical of hamster cells) was observed. Further, a photoaffinity probe with high specificity for the reduced folate carrier labeled 94-kDa proteins in K562 cells and the transfectant containing the full-length KS43, and a 85-kDa protein in the transfectant containing the 3'-truncated KS32. No specifically labeled proteins were detected in wild type or mock-transfected hamster cells. Collectively, our results suggest that the KS43/KS32 cDNAs encode the human reduced folate carrier; however, additional modulatory/regulatory factors may be required to manifest the full spectrum of transport substrate activities typical of this system.

Intracoronary stents

A number of significant milestones were achieved in the field of coronary stent technology in 1994. Two large, randomized multicenter studies demonstrated that stenting has a superior "antirestenosis" effect compared with balloon angioplasty. The application of intravascular ultrasound-guided high-pressure adjunct balloon dilatation for optimal stent expansion and the use of more potent antiplatelet agents improved bleeding complications, shortened hospital stays, and lowered the incidence of stent thrombosis despite reduced anticoagulation following stent placement. Ongoing development of new technologies, including drug-coated and radioactive stents that provide both mechanical support and inhibition of myointimal proliferation, will likely further reduce restenosis frequency. These promising developments will ensure an exciting future for coronary stents as a vital interventional cardiology modality.

The 3' flanking region of the human tyrosine hydroxylase gene directs reporter gene expression in peripheral neuroendocrine tissues

Cell type-specific expression of the catecholamine synthetic enzyme, tyrosine hydroxylase (TH), appears to be mediated in part by cis-acting elements located at the 3' end of the human gene. Further delineation of this region indicated sequences corresponding to a CACGTG motif significantly stimulated transcription of a heterologous promoter in various cell types. Mutation of this site led to a complete loss of activity. DNase footprinting, gel retardation, and UV cross-linking experiments indicated that a 74-kDa cellular factor(s) bound specifically to the CACGTG motif in the pheochromocytoma cell line PC12. The size of this protein and its pattern of expression are compatible with those of the CACGTG binding protein TFE3. Transgenic animals were created using a 261-bp human TH 3' fragment encompassing the CACGTG motif in front of a thymidine kinase promoter/chloramphenicol acetyltransferase reporter gene. In three lines of mice this fragment was sufficient to direct a pattern of mRNA expression in peripheral neuroendocrine tissues that mimicked TH mRNA distribution. However, these sequences were not sufficient for CNS-specific patterns of expression. Thus, multiple cell type-specific enhancers may regulate TH gene expression in the CNS and periphery.

Distinct regions of c-Mpl cytoplasmic domain are coupled to the JAK-STAT signal transduction pathway and Shc phosphorylation

c-Mpl, a member of the hematopoietic cytokine receptor family, is the receptor for thrombopoietin. To investigate signal transduction by c-Mpl, a chimeric receptor, composed of the extracellular domain of human growth hormone receptor and the intracellular domain of c-Mpl, was introduced into the interleukin 3-dependent cell line Ba/F3. In response to growth hormone, this chimeric receptor induced growth in the absence of interleukin 3. Deletion analysis of the 123-amino acid intracellular domain indicated that the elements responsible for this effect are present within the 63 amino acids proximal to the transmembrane domain. Mutation of the recently described box 1 motif abrogated the proliferative response. Tyrosine phosphorylation of the tyrosine kinase JAK-2 and activation of STAT proteins were dependent on box 1 and sequences within 63 amino acids of the plasma membrane. STAT proteins activated by thrombopoietin in a megakaryocytic cell line were purified and shown to be STAT1 and STAT3. A separate region located at the C terminus of the c-Mpl intracellular domain was found to be required for induction of Shc phosphorylation and c-fos mRNA accumulation, suggesting involvement of the Ras signal transduction pathway. Thus, at least two distinct regions are involved in signal transduction by the c-Mpl.