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.

Optical frequency domain imaging with a rapidly swept laser in the 815-870 nm range

Optical frequency domain imaging (OFDI) in the 800-nm biological imaging window is demonstrated by using a novel wavelength-swept laser source. The laser output is tuned continuously from 815 to 870 nm at a 43.2-kHz repetition rate with 7-mW average power. Axial resolution of 10-mum in biological tissue and peak sensitivity of 96 dB are achieved. In vivo imaging of Xenopus laevis is demonstrated with an acquisition speed of 84 frames per second (512 axial lines per frame). This new imaging technique may prove useful in comprehensive retinal screening for medical diagnosis and contrast-agent-based imaging for biological investigations.

Interleukin-1 alpha mediates the growth proliferative effects of transforming growth factor-beta in p21 null MCF-10A human mammary epithelial cells

Transforming growth factor-beta type 1 (TGF-beta) has been implicated as both a tumor suppressor and a tumor promoter in many solid epithelial cancers. We have previously demonstrated that the cyclin dependent kinase (CDK) inhibitor p21 acts as a molecular switch in determining a growth inhibitory versus growth proliferative response to TGF-beta in the spontaneously immortalized human mammary epithelial cell line MCF-10A. We now demonstrate that this proliferative effect of TGF-beta is mediated through the proinflammatory cytokine, interleukin-1alpha (IL-1alpha). Using gene expression array analysis, we identified IL-1alpha as a cytokine specifically upregulated only in cells lacking p21 and only upon TGF-beta stimulation. Cell proliferation assays verified that recombinant IL-1alpha was capable of inducing a growth proliferative response in p21 null MCF-10A cells, while neutralizing antibodies against IL-1alpha prevented the growth proliferative effects of TGF-beta. Mechanistically, both the CDK and proliferating cell nuclear antigen (PCNA) inhibitory functions of p21 were responsible for preventing TGF-beta induced cell proliferation, but only PCNA inhibition by p21 regulated IL-1alpha gene expression. These studies demonstrate a novel role for IL-1alpha in mediating a proliferative response to TGF-beta signaling, and suggest that therapies directed against IL-1alpha could abate the growth proliferative effects of TGF-beta without compromising its tumor suppressive function.

Mutation of the PIK3CA oncogene in human cancers

It is now well established that cancer is a genetic disease and that somatic mutations of oncogenes and tumour suppressor genes are the initiators of the carcinogenic process. The phosphatidylinositol 3-kinase signalling pathway has previously been implicated in tumorigenesis, and evidence over the past year suggests a pivotal role for the phosphatidylinositol 3-kinase catalytic subunit, PIK3CA, in human cancers. In this review, we analyse recent reports describing PIK3CA mutations in a variety of human malignancies, and discuss their possible implications for diagnosis and therapy.

Ultra-high speed and ultra-high resolution spectral-domain optical coherence tomography and optical Doppler tomography in ophthalmology

We present ultra-high resolution optical coherence tomography (OCT) structural intensity and optical Doppler tomography (ODT) flow velocity images of the human retina in vivo. The ultra-high speed OCT system is based on Spectral Domain or Fourier Domain technology, which provides a sensitivity advantage over conventional OCT of more than 2 orders of magnitude. This sensitivity improvement allows video rate OCT and ODT cross sectional imaging of retinal structures. Images will be presented with axial resolutions of 6 and 3.5 microns. We observed small features in the inner and outer plexiform layers, which are believed to be small blood vessels. Flow velocity images will be presented showing pulsatile flow in retinal arteries and veins.

A case report: isolated a heavy chain monoclonal gammopathy in a patient with polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin change syndrome

A 45-year-old South-Korean man presented with abdominal distension, progressive paresthesia and motor weakness of both lower extremities. Our case was identified as polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin change (POEMS) syndrome based on diagnostic criteria. Circulating M components of POEMS syndrome consist mainly of IgG or IgA-lambda and rarely IgM-lambda, IgG-kappa or isolated light chains. In this case, the M-band on serum protein electrophoresis and isolated IgA heavy chain on serum immunofixation electrophoresis were demonstrated, but there was no abnormal light chain. We suggest that this case may be associated with a pattern of abnormal secretion of monoclonal protein or a coincidence of a heavy chain disease in POEMS syndrome, even though the latter possibility may be very rare.

Stabilization of interchange modes in mirror plasmas by a nonlinear rf-plasma wave coupling process

Experimental and theoretical studies are made of the consequences of a nonlinear coupling process between pump rf waves and interchange modes in mirror plasmas. It is demonstrated that the interchange-stable operation window exists depending on the applied rf power and gamma=omega(0)/Omega(i), where omega(0) (Omega(i)) is the angular frequency of the applied rf wave (ion cyclotron frequency). Results are shown that the nonlinear wave coupling process gives rise to the operation window near the resonance (gamma approximately equal to 1), which is elucidated by theoretical analyses combined with full rf wave simulations.

Hepatopulmonary syndrome induced by common bile duct ligation in a rabbit model: correlation between pulmonary vascular dilatation on thin-section CT and angiography and serum nitrite concentration or endothelial nitric oxide synthase (eNOS)1 expression

OBJECTIVE

To investigate the correlation between radiologic vascular dilatation and serum nitrite concentration and eNOS expression in the endothelial cell and pneumocyte in a rabbit model of hepatopulmonary syndrome induced by common bile duct ligation (CBDL).

MATERIALS AND METHODS

Thin-section CT scans of the lung and pulmonary angiography were obtained 3 weeks after CBDL (n = 6), or a sham operation (n = 4), and intrapulmonary vasodilatation was assessed. The diameter and tortuosity of peripheral vessels in the right lower lobe by thin-section CT and angiography at the same level of the right lower lobe in all subjects were correlated to serum nitrite concentration and eNOS (endothelial nitric oxide synthase) expression as determined by immunostaining.

RESULTS

The diameters of pulmonary vessels on thin-section CT were well correlated with nitrite concentrations in serum (r = 0.92, p < 0.001). Dilated pulmonary vessels were significantly correlated with an increased eNOS expression (r = 0.94, p < 0.0001), and the severity of pulmonary vessel tortuosity was found to be well correlated with serum nitrite concentration (r = 0.90, p < 0.001).

CONCLUSION

The peripheral pulmonary vasculature in hepatopulmonary syndrome induced by CBLD was dilated on thin-section CT and on angiographs. Our findings suggest that peripheral pulmonary vascular dilatations are correlated with serum nitrite concentrations and pulmonary eNOS expression.

Ultrasonographic evidence of phenotypic instability during hepatocarcinogenesis in N-nitrosomorpholine-treated rats

Carcinogen-induced hepatoma in immunocompetent animal models has shown a progress similar to the clinical course of human hepatoma. Ultrasonography (US) was used for consecutive evaluation of the phenotypic changes in Sprague-Dawley rats exposed for 8 weeks to N-nitrosomorpholine (NNM, 200 mg/L). Three distinctive US findings were ascites, coarseness (defined as small and heterogeneously widespread increased echogenecity), and nodularity (defined as a >0.6-cm-sized echogenic region and clearly showing a tumor-like mass). Abdominal ascites was observed in 5 of 26 rats at week 8 NNM posttreatment and the number of rats showing ascites gradually increased. Coarseness (22 of 26 rats) and nodularity (1 of 18) appeared at weeks 8 and 17 NNM posttreatment, respectively. The gross and histological findings indicated that coarseness and nodularity shown in US reflected fibrosis and hepatocellular carcinoma or cholangiofibroma, respectively. The computer-aided quantification of coarseness and nodularity showed that the regression-linked phenotypic instability was present in coarseness but not in nodularity. We conclude that the heterogeneity of preneoplasia in NNM-treated rats might be induced by phenotypic instability rather than random initiating events of preneoplastic lesion.

Hypoxia decreases Runx2/Cbfa1 expression in human osteoblast-like cells

To elucidate the molecular mechanism in relation to vascular supply and osteoporosis, we investigated the effect of hypoxia on Runx2 expression in MG63 cells. Also investigated was expression of type I collagen and osteocalcin, which are regulated by Runx2, alkaline phosphatase (ALPase) to see if they are affected by hypoxia. Quiescent cultures of MG63 cells were exposed to hypoxia (2% O(2)) and normoxia (18% O(2)) for 24, 48, 72 and 96 h. In cells exposed to hypoxia, reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that mRNA expression of Runx2, type I collagen, osteocalcin, and ALPase were decreased in a time dependent manner to 96 h. Activity of ALPase was also reduced in the same manner. Western blotting showed a marked decrease in Runx2 protein at 96 h in cells under hypoxia compared to normoxia. These data indicate that Runx2 expression in osteoblasts is reduced by hypoxia, and may be a mechanism of osteoporosis by decreased vascular supply.

Vibrio vulnificus cytolysin induces superoxide anion-initiated apoptotic signaling pathway in human ECV304 cells

Previous studies showed that exposure to Vibrio vulnificus cytolysin (VVC) caused characteristic morphologic changes and dysfunction of vascular structures in lung. VVC showed cytotoxicity for mammalian cells in culture and acted as a vascular permeability factor. In this study, the underlying mechanisms of VVC-induced cytotoxicity was investigated on ECV304 cell, a human vascular endothelial cell line. When cells were exposed to 0.4 hemolytic units (HU) of VVC, consecutive apoptotic events were observed; the elevation of superoxide anion (O (-.)(2)), the release of cytochrome c, the activation of caspase-3, the cleavage of poly(ADP-ribose) polymerase, and the DNA fragmentation. The pretreatment with 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), O(-.) 2) scavenger, completely abolished O(-.)(2) levels and downstream apoptotic events. Moreover, pretreatment with cyclosporin A (CsA), a mitochondrial permeability transition inhibitor, was capable of attenuating O(-.)(2)-mediated cytochrome c release and caspase-3 activation, and consequent apoptosis. Apoptosis, as demonstrated by oligonucleosomal DNA fragmentation and fluorescence microscopy, was induced 24 h after VVC treatment, which was also prevented by caspase-3 inhibitor, Ac-DEVD-CHO. Caspase-1 inhibitor, Ac-YVAD-CHO, did not protect ECV 304 cells from apoptosis. These results suggest a scenario where VVC-induced apoptosis is triggered by the generation of O(-.)(2), release of cytochrome c from mitochondria, activation of caspase-3, degradation of poly(ADP-ribose) polymerase, and DNA fragmentation. The induction of apoptosis in endothelial cells by VVC may provide a pivotal mechanism for understanding the pathophysiology of septicemia.

In vivo burn depth determination by high-speed fiber-based polarization sensitive optical coherence tomography

We report the first application of high-speed fiber-based polarization sensitive optical coherence tomography (PS-OCT) to image burned tissue in vivo. Thermal injury denatures collagen in skin and PS-OCT can measure the reduction in collagen birefringence using depth resolved changes in the polarization state of light propagated in, and reflected from, the tissue. Stokes vectors were calculated for each point in a scan and birefringence relative to incident polarization determined using four incident polarization states. Using a high-speed fiber-based PS-OCT system on rat skin burned for varying periods of time, a correlation between birefringence and actual burn depth determined by histological analysis was established. In conclusion, PS-OCT has potential use for noninvasive assessment of burn depth.

The protective effect of Amomum xanthoides extract against alloxan-induced diabetes through the suppression of NFkappaB activation

This study was undertaken to investigate the preventive mechanism of Amomum xanthoides extract against the development of alloxan-induced diabetics of mice. Pretreatment of mice with A. xanthoides extract via intraperitoneum prevented alloxan-induced hyperglycemia and hypoinsulinemia in a dose dependent manner. Histological examination of pancreatic tissue from A. xanthoides extract treated mice showed that the islet cells remain unaffected by alloxan treatment. NFkappaB activation in the pancreas 30 min after alloxan injection (60 mg/kg, iv), as assessed by an electrophoretic mobility shift assay, was not detected in the mice pretreated with A. xanthoides extract. These results suggest that NFkappaB activation may be one of the critical determinant in the progression of the disease. Considering the preventive effect of A. xanthoides extract from alloxan-induced diabetics development, these results may provide the possible therapeutic value of A. xanthoides extract for the prevention of diabetes mellitus progression.

A role for C/EBPbeta in regulating peroxisome proliferator-activated receptor gamma activity during adipogenesis in 3T3-L1 preadipocytes

The differentiation of 3T3-L1 preadipocytes is regulated in part by a cascade of transcriptional events involving activation of the CCAAT/enhancer-binding proteins (C/EBPs) and peroxisome proliferator-activated receptor gamma (PPARgamma) by dexamethasone (DEX), 3-isobutyl-1-methylxanthine (MIX), and insulin. In this study, we demonstrate that exposure of 3T3-L1 preadipocytes to DEX and insulin fails to induce adipogenesis as indicated by a lack of C/EBPalpha, PPARgamma2, and adipose protein 2/fatty acid-binding protein expression; however, PPARgamma1 is expressed. Treatment of these MIX-deficient cells with a PPARgamma ligand, troglitazone, induces C/EBPalpha expression and rescues the block in adipogenesis. In this regard, we also show that induction of C/EBPalpha gene expression by troglitazone in C3H10T1/2 cells ectopically expressing PPARgamma occurs in the absence of ongoing protein synthesis, suggesting a direct transactivation of the C/EBPalpha gene by PPARgamma. Furthermore, ectopic expression of a dominant negative isoform of C/EBPbeta (liver-enriched transcriptional inhibitory protein (LIP)) inhibits the induction of C/EBPalpha, PPARgamma2, and adipose protein 2/fatty acid-binding protein by DEX, MIX, and insulin in 3T3-L1 cells without affecting the induction of PPARgamma1 by DEX. Exposure of LIP-expressing preadipocytes to troglitazone along with DEX, MIX, and insulin induces differentiation into adipocytes. Additionally, we show that sustained expression of C/EBPalpha in these LIP-expressing adipocytes requires constant exposure to troglitazone. Taken together, these observations suggest that inhibition of C/EBPbeta activity not only blocks C/EBPalpha and PPARgamma2 expression, but it also renders the preadipocytes dependent on an exogenous PPARgamma ligand for their differentiation into adipocytes. We propose, therefore, an additional role for C/EBPbeta in regulating PPARgamma activity during adipogenesis, and we suggest an alternative means of inducing preadipocyte differentiation that relies on the dexamethasone-associated induction of PPARgamma1 expression.

Elective endovascular treatment of descending thoracic aortic aneurysms and chronic dissections with stent-grafts

PURPOSE

To report our experience of endovascular stent-graft placement in patients with descending thoracic aortic dissections and aneurysms and to evaluate the feasibility, safety, and clinical outcomes of the treatment.

MATERIALS AND METHODS

Stent-grafts were placed in the descending thoracic aortas of 23 patients with saccular aneurysms (n = 11) and Stanford type B chronic aortic dissections of the descending thoracic and abdominal aorta (n = 12). All stent-grafts were individually constructed of self-expandable stainless steel stents covered with polytetrafluoroethylene. Vascular access was achieved through the femoral artery in all patients. Clinical status of each patient was monitored and postoperative CT was performed within 1 month of the procedure and at 3-12-month intervals after the procedures.

RESULTS

Successful exclusion of the primary entry tears of dissections and the inlets of saccular aneurysms was achieved in all but two patients with aortic dissection. The overall technical success rate was 91.3% (dissection: 10 of 12 = 83%; aneurysm: 11 of 11 = 100%). All patients in whom technical success was achieved showed complete thrombosis and significant decrease in diameter of the thoracic false lumen (preoperative: 5.3 cm +/- 0.9; postoperative: 4.3 cm +/- 0.9; P = .004) or aneurysm sac (preoperative: 5.3 cm +/- 1.7; postoperative: 2.8 cm +/- 2.5; P = .001). In addition, five patients demonstrated complete resolution of the dissected thoracic false lumen (n = 2) and aneurysm sac (n = 3). However, in all patients with aortic dissection, the abdominal aorta was not significantly changed in size (P = .302) and shape and their false lumen flows remained persistent. Immediate postoperative complications were detected in 12 patients (52%); 10 had fever, leukocytosis, and elevation of C-reactive protein, another had wound infection, and another had transient abdominal pain. Three patients died 2, 3, and 12 months after the procedure: one from septic shock, another from underlying mediastinitis, and the other from an unexplained cause. The remaining 20 patients were well after the procedure (1-9 days; mean, 3 days), without any stent-graft-related complications or discomfort (follow up period: 10-65 mo; mean: 25.1 mo +/- 15.6). The cumulative survival rate after the stent graft was 100% at 30 days and 91% at 12 months.

CONCLUSIONS

For treatment of aortic dissection and saccular aneurysm of the descending thoracic aorta, endovascular stent-graft repair may be a technically feasible and effective treatment modality.

Normal and acutely torn posterior cruciate ligament of the knee at US evaluation: preliminary experience

PURPOSE

To determine the ultrasonographic (US) findings of normal and acutely torn posterior cruciate ligament (PCL) of the knee and evaluate the usefulness of US in the injured PCL.

MATERIALS AND METHODS

US images were obtained in 30 knees in 15 asymptomatic volunteers as a control group and in 35 patients clinically suspected of having an acute PCL injury. Only the distal half of the PCL was evaluated. Of the 35 patients, 28 had their PCL status confirmed: 13 had a normal PCL at magnetic resonance (MR) imaging plus clinical examination, and 15 had a torn PCL at either MR imaging and surgery or MR imaging and clinical follow-up.

RESULTS

Normal PCLs were homogeneously hypoechoic, with a well-defined posterior border. Torn PCLs were heterogeneously hypoechoic (12 [80%] of 15 patients), with an indistinct posterior margin (11 [73%] of 15 patients). Torn PCLs were significantly thicker (range, 12.0-20.0 mm; mean, 15.6 mm +/- 2.5 [SD]; P <.01), as compared with normal PCLs in 13 patients (range, 3.8-5.8 mm; mean, 4.6 mm +/- 1.0; P <.01) and in the volunteers (range, 3.7-6.2 mm; mean, 4.5 mm +/- 1.2; P <.01).

CONCLUSION

An acutely torn PCL thickens (>10 mm), loses its sharply defined posterior border, and has a heterogeneously hypoechoic appearance. US may be useful as a screening examination for patients suspected of having PCL injury and for deciding whether to perform more expensive MR imaging or surgical intervention.

Disodium cromoglycate inhibits production of immunoglobulin E

Disodium cromoglycate (DSCG) has been shown to inhibit the release of mediators from mast cells. In the present study, the effect of DSCG on active anaphylactic reaction was studied in mice. DSCG dose-dependently inhibited the active systemic anaphylactic reaction and serum immunoglobulin (Ig)E production induced by immunization with ovalbumin, Bordetella pertussis toxin and aluminum hydroxide gel. DSCG strongly inhibited IL-4-dependent IgE production by lipopolysaccharide-stimulated murine whole spleen cells. In the case of U266 human IgE-bearing B cells, DSCG also showed an inhibitory effect on the IgE production. These results suggest that DSCG has an anti-anaphylactic activity by inhibition of IgE production from B cells.

Significance of ecto-cyclase activity of CD38 in insulin secretion of mouse pancreatic islet cells

Cyclic ADP-ribose (cADPR), a product of CD38, has a second messenger role for in intracellular Ca(2+) mobilization from microsomes of pancreatic islets as well as from a variety of other cells. ADP-ribosylation of CD38 by ecto-mono ADP-ribosyltransferase in activated T cells results in apoptosis as well as inactivation of its activities. We, therefore, examined the effect of ADP-ribosylation of CD38 in mouse pancreatic islet cells. NAD-dependent inactivation and ADP-ribosylation of CD38, intracellular concentrations of cADPR and Ca(2+), and insulin secretion were measured following incubation of mouse pancreatic islet cells with NAD. ADP-ribosylation of CD38 inactivated its ecto-enzyme activities, and abolished glucose-induced increase of cADPR production, intracellular concentration of Ca(2+), and insulin secretion. Taken together, ecto-cyclase activity of CD38 to produce intracellular cADPR seems to be indispensable for insulin secretion.

Protective effect of C-reactive protein against the lethality induced by Vibrio vulnificus lipopolysaccharide

Vibrio vulnificus infection has attracted special interest because of its high mortality. A strong clinical association exists between hepatic dysfunction and increased morbidity and mortality from V. vulnificus infection. In this study, the effect of C-reactive protein (CRP), a typical hepatogenic acute phase protein, on the lethality induced by V. vulnificus lipopolysaccharide (LPS) was investigated in galactosamine-sensitized mice. The pretreatment of CRP, in a dose of at least 2 mg/kg, 2 hr before the challenge of LPS completely protected mice against the lethality by V. vulnificus LPS. The elevation of serum tumor necrosis factor-alpha (TNF-alpha) induced by LPS administration was not affected by CRP pretreatment. However, the LPS- or TNF-alpha-induced hepatotoxicity was completely prevented by CRP. These results indicate that CRP does not prevent the synthesis, but prevents the hepatotoxic action of TNF-alpha. The possibility that impaired production of acute phase proteins in patients with pre-existing hepatic dysfunction may predispose the higher risk of V. vulnificus infection needs to be evaluated further.

Genetic disruption of PPARdelta decreases the tumorigenicity of human colon cancer cells

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that have been implicated in a variety of biologic processes. The PPARdelta isotype was recently proposed as a downstream target of the adenomatous polyposis coli (APC)/beta-catenin pathway in colorectal carcinogenesis. To evaluate its role in tumorigenesis, a PPARdelta null cell line was created by targeted homologous recombination. When inoculated as xenografts in nude mice, PPARdelta -/- cells exhibited a decreased ability to form tumors compared with PPARdelta +/- and wild-type controls. These data suggest that suppression of PPARdelta expression contributes to the growth-inhibitory effects of the APC tumor suppressor.

Gene expression and fast construction of distributed evolutionary representation

The gene expression process in nature produces different proteins in different cells from different portions of the DNA. Since proteins control almost every important activity in a living organism, at an abstract level, gene expression can be viewed as a process that evaluates the merit or "fitness" of the DNA. This distributed evaluation of the DNA would not be possible without a decomposed representation of the fitness function defined over the DNAs. This paper argues that, unless the living body was provided with such a representation, we have every reason to believe that it must have an efficient mechanism to construct this distributed representation. This paper demonstrates polynomial-time computability of such a representation by proposing a class of efficient algorithms. The main contribution of this paper is two-fold. On the algorithmic side, it offers a way to scale up evolutionary search by detecting the underlying structure of the search space. On the biological side, it proves that the distributed representation of the evolutionary fitness function in gene expression can be computed in polynomial-time. It advances our understanding about the representation construction in gene expression from the perspective of computing. It also presents experimental results supporting the theoretical performance of the proposed algorithms.

Peroxisome proliferator-activated receptors: roles in tumorigenesis and chemoprevention in human cancer

Peroxisome proliferator-activated receptors are nuclear receptors that were isolated for their ability to modulate lipid metabolism. Similar to other members of the nuclear receptor family, peroxisome proliferator-activated receptors bind ligand as heterodimers and exert their effects via transcriptional regulation through their DNA binding domains. During the past decade, it has become clear that peroxisome proliferator-activated receptors also contribute to a variety of different biologic processes, including atherosclerosis, insulin resistance, and more recently, cancer. In this review, we discuss the evidence for the different peroxisome proliferator-activated receptors' roles in tumorigenesis and also their potential application for the treatment and prevention of neoplastic diseases.

Role of BAX in the apoptotic response to anticancer agents

To assess the role of BAX in drug-induced apoptosis in human colorectal cancer cells, we generated cells that lack functional BAX genes. Such cells were partially resistant to the apoptotic effects of the chemotherapeutic agent 5-fluorouracil, but apoptosis was not abolished. In contrast, the absence of BAX completely abolished the apoptotic response to the chemopreventive agent sulindac and other nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs inhibited the expression of the antiapoptotic protein Bcl-XL, resulting in an altered ratio of BAX to Bcl-XL and subsequent mitochondria-mediated cell death. These results establish an unambiguous role for BAX in apoptotic processes in human epithelial cancers and may have implications for cancer chemoprevention strategies.

Optical coherence tomography of the rat cochlea

Optical coherence tomography (OCT) was used to image the internal structure of a rat cochlea (ex vivo). Immediately following sacrifice, the temporal bone of a Sprague-Dawley rat was harvested. Axial OCT cross sectional images (over regions of interest, 1x1 mm-2x8 mm) were obtained with a spatial resolution of 10-15 microm. The osseous borders of the lateral membranous labyrinth overlying the cochlea and the scala vestibuli, media, and tympani, which were well demarcated by the modiolus, Reissner's and the basilar membranes, were clearly identified. OCT can be used to image internal structures in the cochlea without violating the osseous labyrinth using simple surgical exposure of the promontory, and may potentially be used to diagnose inner ear pathology in vivo in both animal and human subjects labyrinth.

High-speed fiber based polarization-sensitive optical coherence tomography of in vivo human skin

A high-speed single-mode fiber-based polarization-sensitive optical coherence tomography (PS OCT) system was developed. With a polarization modulator, Stokes parameters of reflected flight for four input polarization states are measured as a function of depth. A phase modulator in the reference arm of a Michelson interferometer permits independent control of the axial scan rate and carrier frequency. In vivo PS OCT images of human skin are presented, showing subsurface structures that are not discernible in conventional OCT images. A phase retardation image in tissue is calculated based on the reflected Stokes parameters of the four input polarization states.

Ultrasound of the adult hip

The adult hip is a new and challenging site for evaluation with ultrasound (US). Clinically, diseases involving the hip region may be difficult to diagnose without the help of imaging. The hip region is a crossroad for numerous vascular, nervous, and muscular structures that pass between the trunk and the lower extremity. Thus, inflammatory processes and neoplasms may spread to and from the hip, buttock, thigh, pelvis, and retroperitoneum, and trauma may also effect the adjacent areas of the trunk and thigh. Because it is a crossroad, many conditions that are not specific to the hip occur in this area, including inguinal lymphadenopathy, pathology from the abdomen or the genitalia (intestinal hernia, inflammation, and infection), and even referred pain from spinal disorders. The goals of US imaging are the detection and localization of these pathological processes, the differentiation of intra-articular andextra-articular pathology, and the performance of diagnostic and therapeutic interventional procedures. This article reviews the hip anatomy, followed up by a discussion of the US evaluation and differential diagnosis of common pathology occurring in the hip area. This includes joint effusion, arthritis, loose bodies, bursitis, pseudoaneurysm, muscle and tendon diseases, as well as tumor and tumor-like lesions such as hematoma, abscess, and lymphadenopathy.

Protective mechanism of glucose against alloxan-induced beta-cell damage: pivotal role of ATP

Glucose prevents the development of diabetes induced by alloxan. In the present study, the protective mechanism of glucose against alloxan-induced beta-cell damage was investigated using HIT-T 15 cell, a Syrian hamster transformed beta-cell line. Alloxan caused beta-cell damages with DNA fragmentation, inhibition of glucose-stimulated insulin release, and decrease of cellular ATP level, but all of these beta-cell damages by alloxan were prevented by the presence of 20 mM glucose. Oligomycin, a specific inhibitor of ATP synthase, completely abolished the protective effects of glucose against alloxan-induced cell damage. Furthermore, treatment of nuclei isolated from HIT-T15 cells with ATP significantly prevented the DNA fragmentation induced by Ca2+. The results indicate that ATP produced during glucose metabolism plays a pivotal role in the protection of glucose against alloxan-induced beta-cell damage.

Effects of C5 protein on Escherichia coli RNase P catalysis with a precursor tRNA(Phe) bearing a single mismatch in the acceptor stem

Escherichia coli RNase P, an RNA-processing enzyme that cleaves precursor tRNAs to generate the mature 5'-end, is composed of a catalytic component (M1 RNA) and a protein cofactor (C5 protein). In this study, effects of C5 protein on the RNase P catalysis with a precursor E. coli tRNA(Phe) having a single mismatch in the acceptor stem were examined. This mutant precursor unexpectedly generated upstream cleavage products at the -8 position as well as normal cleavage products at the +1 position. The cleavage at the -8 position was essentially effective only in the presence of C5 protein. Possible secondary structures for cleavage at the -8 position deviate significantly from the structures of the known RNase P substrates, implying that C5 protein can allow the enzyme to broaden the substrate specificity more than previously appreciated.

Hepatic involvement in hypereosinophilia: sonographic findings

Hypereosinophilic syndrome may cause eosinophil-related tissue damage to various organs. The purpose of this paper is to describe sonographic findings in 13 patients with hypereosinophilia in whom the liver was involved. The diagnosis in these 13 patients was based on liver biopsy in seven patients with bone marrow biopsy in six patients. Eight patients had hypereosinophilic syndrome and five patients had clonorchiasis. All 13 patients had mild to marked hepatomegaly. Seven of 13 patients showed multiple round or oval hypoechoic (n = 6) or variably echogenic (n = 1) lesions measuring 1 to 2 cm with poorly defined margins in both lobes of the liver. Four patients had one or two hypoechoic lesions 3 to 4 cm in size, with geographic pattern and poorly defined margins. Two patients showed diffuse hepatomegaly with increased parenchymal echogenicity. The number of lesions and the extent of diffuse lesions seem to be proportional to the degree of eosinophilia. Hypereosinophilia may produce multiple small focal hepatic lesions or diffuse segmental or lobar echogenic lesions simulating primary or metastatic tumor of the liver.

Change of plasma lipoproteins by heparin-released lipoprotein lipase

Lipoprotein lipase (LPL) is known to be attached to the luminal surface of vascular endothelial cells in a complex with membrane-bound heparan sulfate, and released into blood stream by heparin. LPL that catalyzes hydrolysis of triglyceride (TGL) on chylomicron and VLDL into two fatty acids and monoacylglycerol, is also implicated to participate in an enhancement of cholesterol uptake by arterial endothelial cells in vitro. But little is known about the LPL-mediated cholesterol uptake in physiological state. In this study, changes in blood lipid composition and levels of lipoproteins were determined after the injection of heparin in human. The level of LPL in plasma was increased from 0 to 11 mU/ml within 30-40 min post-heparin administration and decreased to the basal level within 2 h. The level of TGL in plasma decreased from 70 mg/dl to 20 mg/dl within 1 h and gradually increased to 80 mg/dl within 4 h. However the level of total cholesterol in plasma remained at 140 mg/dl during an experimental period of 4 h. Analysis of Lipoproteins in plasma by NaBr density gradient ultracentrifugation showed that the level of VLDL decreased from 50 mg/dl to 10 mg/dl within 1-2 h and returned to normal plasm level at 4 h. However there were no significant changes in the level of LDL and HDL. These results suggest that, at least, in normo-lipidemic subjects, increased free plasm LPL acts primarily on VLDL and failed to show any significant uptake of cholesterol-rich lipoproteins in human.

Cytotoxicity of Vibrio vulnificus cytolysin on rat peritoneal mast cells

Histamine has been thought to be a permeability enhancing factor in Vibrio vulnificus infection. The injection of living bacteria or purified V. vulnificus cytolysin (VVC) can cause lethality in mice by inducing hemoconcentration and increased vascular permeability. In the present study, we tried to identify whether histamine release causes the increased vascular permeability that is responsible for the lethal effect of VVC. Treatment of rat peritoneal mast cells with high concentrations of VVC caused the release of whole cellular histamine and lactate dehydrogenase (LDH). At concentrations less than 10 HU/ml, histamine and LDH were not released whereas preloaded 2-deoxy-D-glucose was rapidly effluxed with the concomitant decrease in cellular ATP. VVC-treated mast cells were refractory to the stimulation of histamine secretion by Compound 48/80 but remained fully responsive to Ca2+ plus GTP-gamma-S. These results indicate that histamine can be released from mast cells only when the concentration of VVC is high enough to cause the lysis of cells. At low concentrations, VVC does not induce the release of stored histamine from damaged cells. The intravenous injection of 80 HU purified VVC to rats, which can produce the calculated blood concentration of about 3 HU/ml, caused a marked increase in pulmonary vascular permeability, hemoconcentration and death. However, no increase in blood histamine level was detected. This level of VVC in rat blood was enough to cause severe hemoconcentration and lethality but might not be enough to cause cytolysis of the mast cells and resulting histamine release.

Complementation of the growth defect of an rnpA49 mutant of Escherichia coli by overexpression of arginine tRNA(CCG)

We previously found that overexpression of arginine tRNA(CCG) from Brevibacterium albidum complements the rnpA49 mutation, which is responsible for the thermosensitivity of Escherichia coli RNase P function. In this present work, we show that the E. coli homologue tRNA also complements the same mutation, but other tRNAs do not. These results suggest that the rnpA49 mutation causes a major cellular defect in an RNase P reaction to generate the mature arginine tRNA(CCG).

Human D3 dopamine receptor in the medulloblastoma TE671 cell line: cross-talk between D1 and D3 receptors

In search of a cell line in which the D3 dopamine receptor is expressed endogenously, we found that the neuron-derived human medulloblastoma cell line TE671 expresses the human D3 (hD3) and D1 (hD1) receptor, but neither the D2 or D4 receptors. Exposure of TE671 cells to the D3 agonist 7-OH-DPAT (DPAT), or to the D1 agonist SKF-38393 (SKF) increased the expression of hD3 or hD1 mRNA, respectively. Moreover, whereas DPAT had no effect on hD1 mRNA levels, stimulating the cells with SKF caused an increase in both hD1 and hD3 transcript levels. These results suggest (i) that following ligand stimulation, hD3 and hD1 receptors are upregulated to enhance their own receptor expression, and (ii) that upregulation of hD1 receptor transcripts leads to a stimulation of the hD3 dopamine receptor transcripts.

Transjugular intrahepatic portosystemic shunt: effect of bile leak on smooth muscle cell proliferation

PURPOSE

To evaluate the effect of bile on smooth muscle cell (SMC) proliferation in vitro and in vivo in a porcine transjugular intrahepatic portosystemic shunt (TIPS) model.

MATERIALS AND METHODS

In vitro, SMCs explanted from porcine thoracic aorta were cultured with standard techniques. After initial pilot studies, they were subcultured in one of three groups: 1% porcine serum plus 1% bile, 10% porcine serum plus 1% bile, and 10% porcine serum. Cells were harvested at 3, 10, or 14 days, and DNA, protein, and disintegrations per minute (an indicator of proliferation) were measured. In vivo, TIPS creation was successful in 45 swine. All pigs were euthanized at 10-16 days. The proliferative response within the stent was histologically quantified and correlated for evidence of bile leak.

RESULTS

In pilot studies, 2.5%-10.0% bile solutions caused 100% SMC mortality by 3 days. In the presence of 1% bile (with or without porcine serum), both DNA and protein production decreased significantly compared with that in porcine serum alone (P < .05). In vivo, 13 of 45 specimens (29%) showed bile leak at gross or microscopic examination. SMC proliferation was less overall in animals with versus those without bile leak (difference not significant).

CONCLUSION

These data suggest that the proliferative response in a TIPS is not primarily due to bile leak. Bile leak may promote thrombosis, but it appears to inhibit myointimal proliferation.

Guillain-Barré syndrome: MR imaging findings of the spine in eight patients

PURPOSE

To evaluate magnetic resonance (MR) imaging findings of the spine in patients with Guillain-Barré syndrome.

MATERIALS AND METHODS

MR imaging findings in eight patients (three male, five female; age range, 2-47 years) with Guillain-Barré syndrome were retrospectively reviewed. Guillain-Barré syndrome was diagnosed mainly on the basis of symptoms and also on the basis of supportive ancillary data, such as the results cerebrospinal fluid analysis and electrophysiologic evaluation. In addition, follow-up MR imaging was performed in three patients, who had slight clinical improvement.

RESULTS

All patients had thickening of the intrathecal spinal nerve roots and cauda equina, with varying degrees of enhancement on gadolinium-enhanced axial T1-weighted images. Two enhancement patterns were noted. One was enhancement of both the anterior and posterior spinal nerve roots (n = 2); the other was enhancement of the anterior spinal nerve roots only (n = 6). Follow-up MR imaging in the three patients with slight improvement of symptoms revealed that the thickening and the degree of enhancement of the spinal nerve roots were diminished.

CONCLUSION

Although the enhancement of the intrathecal spinal nerve roots is not specific to Guillain-Barré syndrome and can be seen in neoplasia and other inflammatory processes, the enhancement of only the anterior spinal nerve roots is strongly suggestive of Guillain-Barré syndrome.

Purification and characterization of adenosine diphosphate ribose pyrophosphatase from human erythrocytes

Free ADP-ribose is a turnover product of NAD+, protein-bound polymeric and monomeric ADP-ribose, and cyclic ADP-ribose. But little is known about the specific cellular roles or metabolism of free ADP-ribose. ADP-ribose pyrophosphatase (EC 3.6.1.13), which hydrolyzes ADP-ribose into AMP and ribose-5'-phosphate, was purified from human erythrocytes. Purification was achieved to homogeneity by successive chromatographic steps, resulting in a final purification of 75,790-fold from the hemolysate. The purified enzyme showed a single band with the molecular weight of 34 kDa on SDS-PAGE both in the presence and absence of 2-mercaptoethanol. The molecular weight of the native enzyme calculated by gel filtration was 68 kDa, indicating that the active enzyme is a dimer of identical subunits. The enzyme requiring Mg2+ showed highest activity toward ADP-ribose, and about 40-70% activities with IDP-ribose, ADP-mannose and GDP-mannose. The enzyme showed a Km of 169 +/- 11 microM for ADP-ribose, broad pH optimum around pH 9.5, and pI of 5.1. ADP was a potent noncompetitive inhibitor with a Ki of 16 +/- 1.2 microM. These results suggest that our enzyme is unique, and different from the other ADP-ribose pyrophosphatases reported. ADP-ribose pyrophosphatase may play an important role in the regulation of intracellular steady-state of free ADP-ribose.

Expression of C5 protein, the protein component of Escherichia coli RNase P, from the tac promoter

The accurate function of C5 protein, the protein component of Escherichia coli RNase P, is uncertain in vivo. A controllable expression system for C5 protein was constructed which can be used to investigate effects of C5 protein on various cellular functions including biosynthesis of RNase P in vivo. The semisynthetic rnpA gene encoding C5 protein was fused to the tac promoter of the pKK223-3 expression vector. This tac promoter expression system produced a high level of C5 protein upon induction with isopropyl-beta-D-thiogalacto-pyranoside. When the overexpressed C5 protein was purified and used for reconstitution of RNase P, the reconstituted enzyme was active. The N-terminal amino acid of the overexpressed C5 protein was leucine specified by the second codon of the rnpA gene. The more controllable expression system was constructed by introducing the lacIq gene into the vector sequence itself.

Factors affecting the ability of energy functions to discriminate correct from incorrect folds

Eighteen low and medium resolution empirical energy functions were tested for their ability to distinguish correct from incorrect folds from three test sets of decoy protein conformations. The energy functions included 13 pairwise potentials of mean force, covering a wide range of functional forms and methods of parameterization, four potentials that attempt to detect properly formed hydrophobic cores, and one environment-based potential. the first of the three test sets consists of large ensembles of plausible conformations for eight small proteins, all of which have correct native secondary structure and are reasonably compact. The second is the set of all subconformations in a database of known protein structures applied to the sequences in that database (ungapped threading). The third is a set of ensembles of 1000 conformations each for seven small proteins taken from molecular dynamics simulations at 298 K and 498 K. Our results show that there are functions effective for each challenge set; moreover, success in one test is no guarantee of success in another. We examine the factors that seem to be important for accurate discrimination of correct structures in each of the test sets, and note that extremely simple functions are often as effective as more complex functions.

Mutations in the rpoB gene of Mycobacterium tuberculosis that interfere with PCR-single-strand conformation polymorphism analysis for rifampin susceptibility testing

Rifampin susceptibility of 32 rifampin-resistant and 26 rifampin-susceptible Mycobacterium tuberculosis strains was analyzed by PCR-single-strand conformation polymorphism (SSCP) and DNA sequencing within the 157-bp region of the rpoB gene (Ala500 to Val550). Two false-positive PCR-SSCP results were observed among the susceptible strains due to the silent mutation Gln513 (CAA-->CAG) and the deletion mutation Thr508 and Ser509. Another silent mutation [Leu511 (CTG-->CTA)], combined with the mutation Ser531-->Leu, was observed in a resistant strain. These results suggest that to rule out false-positive PCR-SSCP results, sequencing of the target DNA is required.

Effect of carbonyl cyanide m-chlorophenylhydrazone (CCCP) on the dimerization of lipoprotein lipase

Lipoprotein lipase (LPL), an enzyme playing the central role in triglyceride metabolism, is a glycoprotein and a homodimer of identical subunits. Dimerization and proper processing of oligosaccharide chains are important maturation steps in post-translational regulation of enzyme activity. Indirect evidences suggest that dimerization of LPL occurs in endoplasmic reticulum (ER) or Golgi. In this study, we investigated the dimerization status of LPL in 3T3-L1 adipocytes, using sucrose density gradient ultracentrifugation and carbonyl cyanide m-chlorophenylhydrazone (CCCP), an inhibitor of ER-Golgi protein transport. In the presence of CCCP, no increase of cellular LPL activity was detected during 2 b of recovery period after the depletion of LPL, with heparin and cycloheximide. Only endoglycosidase H (endo H)-sensitive subunits were found in CCCP-treated cells after endo H digestion, suggesting that inactive LPL was retained in ER. In the presence of castanospermine, an inhibitor of ER glucosidase I, LPL subunits of both control and CCCP-treated cells had same molecular weight, indicating that complete oligosaccharides were transferred to LPL subunits in the presence of CCCP. In sucrose density gradient ultracentrifugation, all the LPL protein synthesized in the presence of CCCP was found at the dimeric fractions as in control cells. Most of LPL protein in control cells showed high affinity for heparin, and there was no difference between the control and CCCP-treated cells. These results suggest that dimerization and acquisition of high affinity for heparin of LPL can occur in ER of CCCP-treated cells without acquisition of catalytic activity.

Pulmonary damage by Vibrio vulnificus cytolysin

Vibrio vulnificus is an estuarine bacterium that causes septicemia and serious wound infection. Cytolysin produced by V. vulnificus has been incriminated as one of the important virulence determinants of bacterial infection. Cytolysin (8 hemolytic units) given intravenously to mice via their tail veins caused severe hemoconcentration and lethality. Cytolysin treatment greatly increased pulmonary wet weight and vascular permeability as measured by (125)I-labeled albumin leakage without affecting those factors of other organs significantly. Blood neutrophils were markedly decreased in number after cytolysin injection, with a concomitant increase in the level of pulmonary myeloperoxidase activity, indicating that cytolysin-induced neutropenia might be due to pulmonary sequestration of neutrophils. By microscopic examination, severe perivascular edema and neutrophil infiltration were evident in lung tissues. These results suggest that increased vascular permeability and neutrophil sequestration in the lungs are important factors in lethal activity by cytolysin.

A targeted mutation of the D3 dopamine receptor gene is associated with hyperactivity in mice

While most effects of dopamine in the brain are mediated by the D1 and D2 receptor subtypes, other members of this G protein-coupled receptor family have potentially important functions. D3 receptors belong to the D2-like subclass of dopamine receptors, activation of which inhibits adenylyl cyclase. Using targeted mutagenesis in mouse embryonic stem cells, we have generated mice lacking functional D3 receptors. A premature chain-termination mutation was introduced in the D3 receptor gene after residue Arg-148 in the second intracellular loop of the predicted protein sequence. Binding of the dopamine antagonist [125I]iodosulpride to D3 receptors was absent in mice homozygous for the mutation and greatly reduced in heterozygous mice. Behavioral analysis of mutant mice showed that this mutation is associated with hyperactivity in an exploratory test. Homozygous mice lacking D3 receptors display increased locomotor activity and rearing behavior. Mice heterozygous for the D3 receptor mutation show similar, albeit less pronounced, behavioral alterations. Our findings indicate that D3 receptors play an inhibitory role in the control of certain behaviors.

Glycosylation of lipoprotein lipase in human subcutaneous lipomas

Glycosylation of lipoprotein lipase (LPL) was studied in human subcutaneous lipomas. Heparin-releasable LPL activities were higher in lipomas than those in adjacent normal adipose tissues, and showed good correlation with cellular LPL protein mass. Molecular weight of LPL subunit was 57 kDa in both tissues. After endoglycosidase H-digestion, two types of LPL subunits were found in normal adipose tissues; partially sensitive (55 kDa) and totally sensitive (52 kDa) form. In lipoma tissues, the fraction of partially sensitive form (55 kDa) was increased comparing with control adipose tissues. These results suggest that partially sensitive subunits constitute the major secretable form of LPL in human subcutaneous lipomas.

Manipulation of the immune response by foreign gene expression in the thymus

Retroviral gene transfer vectors have been developed for optimal in vivo gene therapy. Ideally, these vectors should target gene expression specifically to selected tissues or organs. Our studies focus on the development of retroviral vectors for gene delivery to the thymus. The goal of these studies is to utilize thymic expression of exogenous genes to manipulate the immune repertoire. We have characterized the selective thymic tropism of a molecular clone of Gross murine leukemia virus, GD-17, to thymic medullary epithelial cells using immunohistochemical staining and confocal microscopy. Specific expression of viral antigens in the thymus lead to the induction of immunologic tolerance to GMuLV proteins. This tissue specific vector may thus be used to study the requirements of epithelial mediated tolerance induction, and provide a more efficient tool for gene therapy.

The complexity and accuracy of discrete state models of protein structure

The prediction of protein structure depends on the quality of the models used. In this paper, we examine the relationship between the complexity and accuracy of representation of various models of protein alpha-carbon backbone structure. First, we develop an efficient algorithm for the near optimal fitting of arbitrary lattice and off-lattice models of polypeptide chains to their true X-ray structures. Using this, we show that the relationship between the complexity of a model, taken as the number of possible conformational states per residue, and the simplest measure of accuracy, the root-mean-square deviation from the X-ray structure, is approximately (Accuracy) varies; is directly proportional to (Complexity)-1/2. This relationship is insensitive to the particularities of individual models, i.e. lattice and off-lattice models of the same complexity tend to have similar average root-mean-square deviations, and this also implies that improvements in model accuracy with increasing complexity are very small. However, other measures of model accuracy, such as the preservation of X-ray residue-residue contacts and the alpha-helix, do distinguish among models. In addition, we show that low complexity models, which take into account the uneven distribution of residue conformations in real proteins, can represent X-ray structures as accurately as more complex models, which do not: a selected 6-state model can represent protein structures almost as accurately (1.7 A root-mean-square) as a 17-state lattice model (1.6 A root-mean-square). Finally, we use a novel optimization procedure to generate eight 4-state models, which fit native proteins to an average of 2.4 A, and preserve 85% of native residue-residue contacts. We discuss the implications of these findings for protein folding and the prediction of protein conformation.

Protective mechanism of glucose against alloxan-induced pancreatic beta-cell damage

Glucose prevented the alloxan- or H2O2-induced inhibition of insulin secretion in rat pancreatic islets. Hydrogen peroxide was detected during the incubation of islets with alloxan, and this generation of hydrogen peroxide was not affected by glucose. Treatment of beta-cells with alloxan or H2O2 caused elevation of cytosolic free Ca2+ and decrease of cellular NAD+. Glucose blocked the decrease of cellular NAD+ level, but did not abolish the increase of cytosolic Ca2+. These results indicate that glucose protected pancreatic beta-cell damage after the H2O2 generation and Ca2+ influx on a chain of reactions in the diabetogenesis of alloxan.

Structural organization of the murine D3 dopamine receptor gene

We have cloned the gene encoding the murine D3 dopamine receptor and have analyzed its intron-exon structural organization, to gain a better understanding of the detailed architecture of the D2 dopamine receptor genes. Restriction and sequence analysis reveal the presence of six introns, in contrast to the five introns previously reported for the rat D3 receptor. The extra intron is located in the receptor's putative third cytoplasmic loop and generates an intron-exon organization directly analogous to that found in the D2 receptor gene. In addition, we have sequenced the 5' and 3' nontranslated sequences flanking the coding region and have identified a putative poly(A) adenylation signal. These sequences are found to have a far lower homology with the corresponding rat nontranslated sequences than is found for the D2 receptor, suggesting that the control of D3 receptor expression may vary more between species than the control of D2 receptor expression.