Weight change after 20 years of age and the incidence of dyslipidemia: a cohort study of Japanese male workers.

BACKGROUND: While heavier weight is known to increase the incidence of dyslipidemia, limited data are available on the relationship between weight gain and its development. METHODS: A total of 2647 males were categorized into the following four groups according to the difference between their self-reported weight at 20 years of age and their measured weight in 1994-95: a loss of ≥5% (decrease), loss of <5% or gain of <5% (no change), gain of ≥5 to <15% (increase) and gain of ≥15% (sizable increase). They were followed up until their 2002-03 health examination. Using the 'no change' group as reference, the multivariable-adjusted odds ratio (adjusted for age, body mass index at 20 years of age, physical activity, smoking and alcohol intake) and 95% confidence interval (95% CI) for the incidence of dyslipidemia were determined using logistic regression models. RESULTS: A total of 1342 participants developed dyslipidemia during the follow-up period. The 'increase' and 'sizable increase' groups had odds ratios for the incidence of dyslipidemia of 1.97 (95% CI, 1.59-2.45) and 2.68 (2.15-3.34), respectively, demonstrating that there was a significant dose-response association between weight gain since 20 years of age and the incidence of dyslipidemia (P < 0.001 for trend). CONCLUSION: These results suggest that dyslipidemia could be prevented by avoiding weight gain in adulthood.

Prototyping the Experimental Setup to Quantify the Tissue Oxygen Consumption Rate and Its Preliminary Test.

In order to establish a reliable and practical method to make a diagnosis on the viability of an amputated extremity, we propose a method to evaluate the oxygen consumption rate. To validate this concept, we prototyped an experimental system with which the oxygen transfer rate into tissue can be assessed by the rate of change of the decrease in dissolved oxygen (DO) concentration within the buffer fluid surrounding the target tissue. The purpose of this study is to examine the feasibility of our prototyped experimental system by comparison between fresh and non-fresh rat skeletal muscles. The results show that the fresher tissue transferred more oxygen to the tissue, which suggests that tissue oxygen consumption is highly related to tissue freshness and can indirectly assess the tissue viability.

Irsogladine maleate reduces the incidence of fluorouracil-based chemotherapy-induced oral mucositis.

BACKGROUND: Oral mucositis is one of the most common side-effects of 5-fluorouracil (5-FU)-based chemotherapy. The objective of this study was to evaluate the effects of irsogladine maleate (IM) on fluorouracil-induced oral mucositis through a double-blind, placebo controlled trial. PATIENTS AND METHODS: Patients (N = 66) were randomly assigned to receive either placebo or IM (4 mg/day for 14 consecutive days). The incidence and maximum severity of fluorouracil-induced oral mucositis and safety of the irsogladine dosing regimen were evaluated. RESULTS: A cohort of 33 patients received placebo and 33 patients received IM. The incidence of oral mucositis was significantly lower for IM than for placebo (27% versus 73%; P < 0.001 by chi-square test). Specific adverse events considered related to IM were not found. CONCLUSION: IM significantly reduced the incidence and maximum severity of oral mucositis in patients treated with 5-FU-chemotherapy.

CO2 microbubble contrast enhancement in x-ray angiography.

AIM: To demonstrate that carbon dioxide (CO2) microbubble contrast enhancement depicts blood vessels when used for x-ray examinations. MATERIALS AND METHODS: Microbubbles were generated by cavitation of physiological saline to which CO2 gas had been added using an ejector-type microbubble generator. The input pressure values for CO2 gas and physiological saline that produced a large quantity of CO2 microbubbles were obtained in a phantom. In an animal study, angiography was performed in three swine using three types of contrast: CO2 microbubbles, conventional CO2 gas, and iodinated contrast medium. For CO2 microbubble contrast enhancement, physiological saline, and CO2 gas were supplied at the input pressures calculated in the phantom experiment. Regions of interest were set in the abdominal aorta, external iliac arteries, and background. The difference in digital values between each artery and the background was calculated. RESULTS: The input pressures obtained in the phantom experiment were 0.16 MPa for physiological saline and 0.5 MPa for CO2 gas, with physiological saline input volume being 8.1 ml/s. Three interventional radiologists all evaluated the depictions of all arteries as "present" in the CO2 microbubble contrast enhancement, conventional CO2 contrast enhancement, and iodinated contrast enhancement performed in three swine. Digital values for all vessels with microbubble CO2 contrast enhancement were higher than background values. CONCLUSIONS: In x-ray angiography, blood vessels can be depicted by CO2 microbubble contrast enhancement, in which a large quantity of CO2 microbubbles is generated within blood vessels.

Role of aquaporin-5 in gallbladder carcinoma.

BACKGROUND/PURPOSE: Aquaporins (AQPs) are important in controlling bile formation. However, the exact role in human gallbladder carcinogenesis has not yet been defined. METHODS: AQP-5-expressing gallbladder carcinoma (GBC) cell lines (NOZ) were transfected with anti-AQP-5 small interfering RNA (siRNA). Growth, migration, invasion assay, and drug susceptibility tests were performed. Next, microRNA (miRNA) expression was analyzed by miRNA oligo chip (3D-Gene®). AQP-5 and AQP-5-related miRNA target gene expressions were also analyzed using tissue microarray (TMA) in 44 GBC samples. RESULTS: Treatment with AQP-5 siRNA decreased cell proliferation, migration, and invasion. On the other hand, those cells increased IC50 of gemcitabine. By performing miRNA assays, miR-29b, -200a, and -21 were shown to be highly overexpressed in cells treated with AQP-5 siRNA NOZ. When focusing on miR-21, phosphatase and tensin homolog (PTEN) was found to be a target of miR-21. In the TMA, AQP-5/PTEN coexpression was significantly associated with the depth of invasion and MIB-1 index (p = 0.003, 0.010). Survival of patients with a high AQP-5/PTEN coexpression was longer than that of patients with a low coexpression (p = 0.003). CONCLUSIONS: Our result suggested that miR-21 and PTEN may contribute to the role of AQP-5 in GBC. AQP-5 and PTEN cascades are favorable biomarkers of GBC.

Identification of NF1 mutations in both alleles of a dermal neurofibroma.

A hallmark clinical feature of neurofibromatosis 1 (NF1) is multiple dermal neurofibromas, benign tumours that typically appear in early adolescence and increase in numbers throughout life. The pathogenesis of these tumours is not known. One domain of the NF1 gene product, neurofibromin, stimulates the intrinsic GTPase of Ras, and inactivation of both NF1 alleles has been demonstrated in specific malignancies. These observations support the contention that the NF1 gene product is a tumour suppressor that is involved in the Ras signal transduction pathway. Even though accumulating evidence demonstrates that NF1 acts as a tumour suppressor in some cells, mutations have not been identified in both NF1 alleles in dermal neurofibromas. Using standard techniques to analyse DNA extracted from benign neurofibromas, numerous investigators failed to identify loss of heterozygosity (LOH) in multiple tumours. In contrast to these reports, Colman et al. demonstrated NF1 LOH of dermal neurofibromas derived from 2 of 5 NF1 patients, yet the constitutional NF1 mutations in these patients were not identified, and the extent of the somatic deletions beyond the NF1 locus were not established. In this study, we show that a dermal neurofibroma from an NF1 individual who has a constitutional deletion of the entire NF1 locus harbours a 4-bp deletion of NF1 exon 4b in the other allele. This is the first definitive identification of a somatic mutation which is limited to the NF1 locus in a benign neurofibroma from an NF1 individual in whom the constitutional NF1 mutation is known.

Search for the Θ+ pentaquark via the π(-)p→K(-)X reaction at 1.92 GeV/c.

The Θ(+) pentaquark baryon was searched for via the π(-)p→K(-)X reaction with a missing mass resolution of 1.4 MeV/c(2) (FWHM) at the Japan Proton Accelerator Research Complex (J-PARC). π(-) meson beams were incident on the liquid hydrogen target with a beam momentum of 1.92 GeV/c. No peak structure corresponding to the Θ(+) mass was observed. The upper limit of the production cross section averaged over the scattering angle of 2° to 15° in the laboratory frame is obtained to be 0.26 µb/sr in the mass region of 1.51-1.55 GeV/c(2). The upper limit of the Θ(+) decay width is obtained to be 0.72 and 3.1 MeV for J(Θ)(P)=1/2(+) and J(Θ)(P)=1/2(-), respectively, using the effective Lagrangian approach.

Perioperative risk predictors of cardiac outcomes in patients undergoing liver transplantation surgery.

BACKGROUND: Cardiac risk assessment for perioperative outcomes of liver transplantation patients is limited. We examined the outcomes of an older intermediate-cardiac-risk group of patients undergoing liver transplantation surgery. METHODS AND RESULTS: Patients who had liver transplantation surgery between 2001 and 2005 were studied. The 3 outcomes analyzed were nonfatal myocardial infarction, death, and either outcome within the first 30 days after the liver transplantation surgery. Of 403 patients (mean age, 52+/-9 years; 67% male), 106 (26%) were diabetic, 84 (21%) were hypertensive, and 173 (43%) had a history of smoking. There were 48 total events (12%), 25 myocardial infarctions (7%), and 38 deaths (9%) recorded during the perioperative period. From the final multivariate model, history of coronary artery disease, prior stroke, and postoperative sepsis predicted greater risk (P=0.014; odds ratio [OR], 4.0; 95% confidence interval [CI], 1.3 to 11.8; P=0.025; OR, 6.6; 95% CI, 1.3 to 33.8; and P<0.001; OR, 7.5; 95% CI, 3.3 to 17.1, respectively). Use of perioperative beta-blockers was protective (P=0.004; OR, 0.20; 95% CI, 0.1 to 0.6) for combined cardiac outcomes. For the outcome of death on multivariate analysis, postoperative sepsis and increased interventricular septal thickness predicted risk (P<0.001; OR, 8.6; 95% CI, 3.5 to 20.9; and P=0.027; OR, 2.8; 95% CI, 1.1 to 7.2, respectively), whereas the use of perioperative beta-blockers was again protective (P=0.012; OR, 0.07; 95% CI, 0.01 to 0.56). CONCLUSIONS: In our study of cardiac risk assessment for liver transplantation surgery, history of stroke, coronary artery disease, postoperative sepsis, and increased interventricular septal thickness were markers of adverse perioperative cardiac outcomes, whereas use of perioperative beta-blockers was significantly protective.

Disturbed CD4+ T cell homeostasis and in vitro HIV-1 susceptibility in transgenic mice expressing T cell line-tropic HIV-1 receptors.

T cell line-tropic (T-tropic) HIV type 1 strains enter cells by interacting with the cell-surface molecules CD4 and CXCR4. We have generated transgenic mice predominantly expressing human CD4 and CXCR4 on their CD4-positive T lymphocytes (CD4+ T cells). Their primary thymocytes are susceptible to T-tropic but not to macrophage-tropic HIV-1 infection in vitro, albeit with a viral antigen production less efficient than human peripheral blood mononuclear cells. Interestingly, even without HIV infection, transgenic mice display a CD4+ T cell depletion profile of peripheral blood reminiscent of that seen in AIDS patients. We demonstrate that CD4+ T cell trafficking in transgenic mice is biased toward bone marrow essentially due to CXCR4 overexpression, resulting in the severe loss of CD4+ T cells from circulating blood. Our data suggest that CXCR4 plays an important role in lymphocyte trafficking through tissues, especially between peripheral blood and bone marrow, participating in the regulation of lymphocyte homeostasis in these compartments. Based on these findings, we propose a hypothetical model in which the dual function of CXCR4 in HIV-1 infection and in lymphocyte trafficking may cooperatively induce progressive HIV-1 infection and CD4+ T cell decline in patients.

Metabolic syndrome attenuates effect of chronic kidney disease on prevalence of coronary disease in men referred for stress imaging study.

BACKGROUND: Metabolic syndrome (MS) and chronic kidney disease (CKD) are both strongly associated with coronary artery disease (CAD). Components of MS also cause CKD. The incremental effect of CKD on CAD prevalence in MS patients referred for stress imaging studies is unknown. METHODS: From January to December 2005, consecutive subjects referred for a stress imaging study were prospectively enrolled. CAD was defined as fixed or reversible defects on nuclear imaging and as resting or stress-induced wall motion abnormalities on echocardiography. MS was defined using NCEP-ATP III criteria. CKD definition was based on calculated glomerular filtration rate. The independent effect of CKD on stress results was assessed using multiple variable logistic regression. Stepwise model selection was used for variable reduction, and areas under the receiver operating characteristic curves (ROC) were calculated. RESULTS: Of 1,122 patients enrolled (mean age 61.4 years, 97% male), 535 (47%) had MS. Among MS patients, 156/535 (29%) had CKD while 116/587 (19%) subjects without MS had CKD. Subjects with CKD were older (p < 0.001) in subjects with and without MS. The presence of CKD affected prevalence of CAD in the non-MS group only, almost doubling it (20% vs. 38%, p < 0.001). Further, using the ordered nature of the 5 CKD stages, worsening severity of CKD had greater prevalence of CAD, in non-MS subjects only (p < 0.001). CONCLUSIONS: MS attenuates the effect of CKD on CAD prevalence, regardless of CKD severity. CKD almost doubles the prevalence of CAD in non-MS subjects. CKD severity is associated with greater CAD burden in the non-MS group.

Composite material stent comprising metallic wire and polylactic acid fibers, and its mechanical strength and retrievability.

BACKGROUND: Although metallic stents are characterized by strong expanse of force, thin walls, and easy stent deployment, their removal from the body is usually difficult or impossible due to the difficulty of unraveling their mesh structure. A stent built of a composite material comprising a metallic wire and a polylactic acid (PLA) fiber, in which the metallic wire component could be unraveled after PLA fiber degradation in the body, should allow easy stent removal. PURPOSE: To evaluate the mechanical strength and retrievability of a composite material stent comprising a metallic wire and a PLA fiber. MATERIAL AND METHODS: We produced a composite material stent comprising a metallic wire and a biodegradable fiber (hybrid stent). As the metallic wire is not cross-linked with itself, but with the PLA fibers only, the hybrid stent can be easily unraveled after PLA fiber degradation. This stent was built with a 0.2-mm stainless-steel wire and a 0.23-mm PLA fiber knitted in the same textile as an Ultraflex stent. For comparison, an identical stent was built using PLA fiber only (PLA stent). The mechanical strength of these stents was tested by the radial expansive force response against circumferential shrinkage stress load. Change in radial force due to PLA fiber degradation was estimated by adding an artificial PLA degeneration process, by immersing each stent in a water bath at 80 degrees C for 48 hours. Retrievability of the hybrid stent after PLA degeneration was examined by hooking and pulling out the residual stainless-steel wire from a silicon tube. RESULTS: The hybrid stent exhibited a linear response in radial expansive force within the range of 15% diameter reduction. The PLA stent did not exhibit linear response at over 15% diameter reduction. Decrease of radial expansive force after PLA degradation was within 5% of the original force in the hybrid stent, but the PLA stent did not create effective radial expansive force. Hybrid stents, even after PLA degradation, exhibited a linear response in radial expansive force, within the range of 15% diameter reduction. The metallic component of the heat-processed hybrid stent was easily unraveled by pulling out the wire. CONCLUSION: The hybrid stent comprising a stainless-steel wire and a PLA fiber appears to provide effective radial expansive force and retrievability.

Transcatheter coil embolization for steal syndrome in patients with hemodialysis access.

BACKGROUND: Drainage of large amounts of shunt blood into deep veins via collaterals reduces resistance to venous outflow and decreases blood flow to the artery distal to the arterial anastomotic site, potentially resulting in steal syndrome. PURPOSE: To evaluate the effectiveness of transcatheter coil embolization for collateral veins of hemodialysis access in the treatment of steal syndrome. MATERIALS AND METHODS: Five hemodialysis patients (four male, one female; mean age 58.8 years, range 40-71 years) with symptomatic steal syndrome were treated. Steal syndrome was diagnosed based on decreased or absent distal pulse, coolness, pain, abnormal skin color, ischemic ulceration of digits, numbness, sensory impairment, or motor impairment. Coil embolization was performed to block collaterals communicating with deep veins, with conscious sedation and local anesthesia. Fistulography was performed before, immediately after, and 1 month after embolization. Ultrasonography was performed 2 days after embolization. Symptoms and signs were assessed 2 days after embolization. Clinical findings related to steal syndrome and access failure were observed at each hemodialysis. RESULTS: Blood flow in the collaterals was successfully blocked by coil embolization in all patients. Distal pulse, coolness, pain, and skin color improved in all patients. Numbness, sensory impairment, and motor impairment were unimproved in two patients. In all patients, hemodialysis following embolization was performed normally. The mean observation period after embolization was 33 months (range 9-75 months). CONCLUSION: Coil embolization of collaterals that drain shunt blood into deep veins is effective for steal syndrome for hemodialysis access originating in the brachial artery.

Antiproteinuric effect of angiotensin-converting enzyme inhibitors and an angiotensin II receptor blocker in patients with lupus nephritis.

Although the effects of angiotensin II receptor blockers (ARBs) on non-diabetic glomerulonephritis have been reported, studies of their effects on collagen-vascular diseases, particularly lupus nephritis, are limited. In this retrospective, observational study, systemic lupus erythematosus (SLE) patients (n = 7) with lupus nephritis and uncontrolled proteinuria were treated with an angiotensin-converting enzyme inhibitor followed by the ARB losartan (25 - 50 mg/day). Urinary protein excretion and renal function were evaluated. After 12 months of losartan, mean urinary protein excretion decreased significantly by 84.8%. Mean systolic and diastolic blood pressures also decreased significantly during the 12 months of losartan treatment, although not in normotensive patients. Complement 4, total complement activity and anti-dsDNA antibody levels, which are indices of SLE activity, and serum creatinine levels, which is an index of renal function, showed no change in response to losartan treatment. A more extensive evaluation of the effects of ARBs in patients with lupus nephritis and poorly controlled proteinuria is required.

The role of stress echocardiography and competing technologies for the diagnostic and prognostic assessment of coronary artery disease.

Coronary artery disease remains the leading cause of death in adults in the United States. Non-invasive cardiac imaging is now central to the diagnosis and management of patients with known or suspected coronary disease. The generally accepted indications for stress testing include confirming a diagnosis of coronary disease, assessing prognosis, preoperative risk stratification, and evaluation of medical therapy. Stress echocardiography and single photon computed tomography are well-established non-invasive techniques for all the previously mentioned indications. These modalities provide a relatively high sensitivity and specificity along with an incremental value over clinical risk factors. Cardiac magnetic resonance imaging (CMRI) and multislice computed tomography are new imaging tools in the evaluation of patients with coronary disease. CMRI offers a comprehensive cardiac evaluation which includes wall motion analysis, myocardial tissue morphology, rest and stress first pass myocardial perfusion as well as systolic ventricular function. It is also considered a first line technique for the diagnosis of certain structural heart disease and chamber volume quantification. Cardiac computed tomography allows non-invasive anatomic imaging of the coronary tree. It has a high clinical utility especially in select intermediate risk patient population. Available tests all have advantages and drawbacks and none can be considered suitable for all patients. The choice of the imaging method should be tailored to each person based on the clinical judgment of the a priori risk of cardiac event, clinical history, and risk factors profile.

[Large cell neuroendocrine carcinoma of the lung].

Large cell neuroendocrine carcinoma (LCNEC) is a neuroendocrine tumor comprising a subgroup of large cell carcinoma and is a type of lung cancer showing a neuroendocrine characteristic similar to that of small cell lung carcinoma In our institution, we started to diagnose LCNEC by immunostaining in 2002, and we herein report 9 patients diagnosed with LCNEC from January 2002 to May 2008. The average patient age was 74.9, male/female ratio was 8/1, and all 9 patients had a smoking history. Pathological stages IA/IB/IIB/IIIA comprised 4/1/2/2, respectively. Peripherally located and lobulated tumors were noted on preoperative computed tomography (CT), and moderate uptake of fluoro-2-deoxy-D-glucose (FDG), which balanced with the size, was recognized on positron emission tomography (PET). All 9 patients underwent surgery and 7 underwent radical surgery. Postoperative adjuvant chemotherapy was performed for 4 patients. Three showed recurrence, and 2 of these 3 died of the primary disease. The remaining 7 patients have survived to date. The possibility of LCNEC must be considered when peripherally located lung cancer with lobulation is noted on CT and shows moderate uptake of FDG for its size on PET, and multimodal treatment is needed if the diagnosis is determined postoperatively.

Improvement in respiratory function by percutaneous vertebroplasty.

BACKGROUND: Percutaneous vertebroplasty (PVP) improves back pain and corrects spinal misalignment to some extent, and thus may improve respiratory function. PURPOSE: To retrospectively investigate changes in respiratory function after PVP. MATERIAL AND METHODS: 41 patients (mean age 72.0 years, range 59-86 years; 39 women, two men) who had undergone PVP for vertebral compression fractures (37 thoracic vertebral bodies [Th6-Th12] and 50 lumbar vertebral bodies [L1-L5]) caused by osteoporosis visited our hospital for follow-up consultation between January and June 2005. At this follow-up consultation, respiratory function testing, including percent forced vital capacity (FVC%) and percent forced expiratory volume in 1 s (FEV(1)%), was performed. We retrospectively compared these values with those taken before PVP using a Wilcoxon signed-rank test. RESULTS: FVC% was 85.2+/-30.3% before PVP and 91.5+/-16.8% at follow-up (mean 10 months after PVP), which represented a significant difference (P<0.003). No significant difference in FEV(1)% was detected. Regarding the number of treatment levels, that is, single vertebroplasty versus multiple vertebroplasty, no significant difference in improvement of FVC% was confirmed (P=0.1). FVC% was abnormally low (

Diffusion-weighted imaging for predicting new compression fractures following percutaneous vertebroplasty.

BACKGROUND: Percutaneous vertebroplasty (PVP) is a technique that structurally stabilizes a fractured vertebral body. However, some patients return to the hospital due to recurrent back pain following PVP, and such pain is sometimes caused by new compression fractures. PURPOSE: To investigate whether the apparent diffusion coefficient (ADC) of adjacent vertebral bodies as assessed by diffusion-weighted imaging before PVP could predict the onset of new compression fractures following PVP. MATERIAL AND METHODS: 25 patients with osteoporotic compression fractures who underwent PVP were enrolled in this study. ADC was measured for 49 vertebral bodies immediately above and below each vertebral body injected with bone cement before and after PVP. By measuring ADC for each adjacent vertebral body, ADC was compared between vertebral bodies with a new compression fracture within 1 month and those without new compression fractures. In addition, the mean ADC of adjacent vertebral bodies per patient was calculated. RESULTS: Mean preoperative ADC for the six adjacent vertebral bodies with new compression fractures was 0.55 x 10(-3) mm(2)/s (range 0.36-1.01 x 10(-3) mm(2)/s), and for the 43 adjacent vertebral bodies without new compression fractures 0.20 x 10(-3) mm(2)/s (range 0-0.98 x 10(-3) mm(2)/s) (P < 0.001). Mean preoperative ADC for the six patients with new compression fractures was 0.55 x 10(-3) mm(2)/s (range 0.21-1.01 x 10(-3) mm(2)/s), and that for the 19 patients without new compression fractures 0.17 x 10(-3) mm(2)/s (range 0.01-0.43 x 10(-3) mm(2)/s) (P < 0.001). CONCLUSION: The ADC of adjacent vertebral bodies as assessed by diffusion-weighted imaging before PVP might be one of the predictors for new compression fractures following PVP.

Identification and characterization of a T-cell-specific enhancer adjacent to the murine CD4 gene.

Expression of the CD4 and CD8 glycoproteins is a tightly regulated process tied to the maturation of functionally distinct classes of thymocytes. Therefore, understanding of the mechanism of expression of the genes encoding CD4 and CD8 is likely to yield important insight into regulation of the differentiated functions of T cells. Here, we report the identification of a T-cell-specific enhancer in a DNase I-hypersensitive region about 13 kb 5' of the transcription initiation site of the murine CD4 gene. Within the minimal enhancer element, at least three nuclear protein binding sites were identified by DNase I footprint analysis. One site contains the consensus motif for TCF-1 alpha/LEF-1, a recently identified HMG box transcription factor primarily expressed in pre-B and T cells. By Southwestern (DNA-protein) blotting and binding competition analyses, the protein binding to this site was found to be indistinguishable from TCF-1 alpha/LEF-1. Mutagenesis of this site resulted in loss of factor binding but had a relatively minor effect on enhancer activity. In contrast, mutations in another site, containing two consensus binding motifs for basic helix-loop-helix proteins, abolished factor binding and dramatically reduced enhancer activity. None of the protein binding sites had activity on its own, suggesting that the CD4 enhancer requires the interaction of multiple regulatory sites.

A heterodimer of HEB and an E12-related protein interacts with the CD4 enhancer and regulates its activity in T-cell lines.

A T-lymphocyte-specific enhancer located 13 kb upstream of the murine CD4 gene was recently shown to be required for the developmentally regulated expression of CD4. We have previously identified three nuclear protein binding sites in this enhancer; one of these sites, CD4-3, is essential for expression and contains two E-box core motifs (CANNTG) adjacent to each other in the sequence TAACAGGTGTCAGCTGGT. In electrophoretic mobility shift assays using the CD4-3 oligonucleotide as a probe, three nuclear protein complexes, termed CD4-3A, -B, and -C, were detected with nuclear extracts from T-cell lines. CD4-3A, which involves nuclear protein binding to the 5' E-box, was detected only with nuclear extracts from lymphoid cells. Specific antisera were used to show that the CD4-3A complex contains a heterodimer or heterooligomer of basic helix-loop-helix transcriptional factors, E12 or a related factor and HEB, which is expressed predominantly in thymus. Consistent with this finding, in vitro-translated E12 and HEB proteins, as homodimers or heterodimers, bound preferentially to the 5' E-box. Point mutations in the 5' E-box, but not in the 3' E-box, abolished CD4 enhancer activity. Furthermore, overexpression of Id, a protein that forms inactive heterodimers with E12/E47, blocked CD4 enhancer activity in T cells. These results suggest that a heterodimer composed of HEB and E12 or a closely related protein plays a critical role in CD4 enhancer function by interacting with the 5' E-box motif of the CD4-3 site in vivo.