Changes in muscle force following therapeutic electrical stimulation in patients with complete paraplegia

Changes in muscle force following therapeutic electrical stimulation (TES) in 5 patients with complete paraplegia were evaluated by computed tomography, Cybex II, a strain-gauge transducer, and manual muscle testing. The stimulation parameters included a frequency of 20 Hz, a pulse width of 0.2 ms, and an output voltage of -15 V. The cross-sectional areas of muscles, the muscle torques, and the muscle forces increased after TES, though the increased ratio differed in each muscle. The reasons why it differed are as follows: (1) The possibility of peripheral nerve injury; (2) The different patterns of nerve distribution in the muscles; (3) Implantation techniques; and (4) The possibility of breakage, movement, or changes in the impedance of electrodes. This study demonstrates that TES increases muscle force during electrical stimulation in paralyzed muscle, but that an initial TES-induced muscle force greater than a poor-minus level on manual muscle testing is necessary for practical use. TES treatment should be started as soon as possible after the onset of paralysis, in order to maintain muscle quality.

Cloning, expression and chromosomal mapping of a novel cyclophilin-related gene (PPIL1) from human fetal brain

We isolated a human cDNA clone encoding a novel protein homologous to cyclophilins, specific cellular targets of cyclosporin A, which are conserved in species ranging from human to prokaryotes. This cDNA, designated hCyPX, contained an open reading frame of 498 nucleotides encoding 166 amino acids. Computer analysis indicated that its predicted amino acid sequence had 41.6%, 40.4%, and 39.2% homology to those of human, bovine, and Drosophila cyclophilins, respectively. Northern blot analysis indicated ubiquitous expression in adult human tissues, but most abundant expression in heart. Fluorescence in situ hybridization to human metaphase chromosomes localized this gene (PPIL1, peptidylprolyl isomerase [cyclophilin]-like 1) to chromosome bands 2p23.3-->p23.1.

Cloning, expression, and mapping of UBE2I, a novel gene encoding a human homologue of yeast ubiquitin-conjugating enzymes which are critical for regulating the cell cycle

From a human fetal-brain cDNA library we isolated a novel gene sharing significant homology with two yeast genes, UBC9 and hus5, which encode ubiquitin-conjugating enzyme 9 (UBC9). In yeast this protein is critical for normal mitosis, and seems to be closely involved in progression of G2 to M phase of the cell cycle. The human UBC9 (h-UBC9) cDNA, (gene symbol UBE2I), contained an open reading frame of 474 nucleotides encoding 158 amino acids. Its predicted peptide showed respectively 56% and 66% identity (75% and 82% similarity) with the products of UBC9 and hus5. Northern-blot analysis revealed expression of three transcripts, 6.4 kb, 3.3 kb, and 1.35 kb, in all human tissues examined. This gene, UBE2I, was mapped to chromosome band 16p13.3 by FISH.

Anatomic study of the bronchial arteries with special reference to their preservation during the radical dissection of the upper mediastinum lymph nodes

BACKGROUND

The anatomy of the bronchial arteries was studied, with special reference to their preservation during the radical dissection of the upper mediastinum lymph nodes.

METHODS

The bronchial arteries of 71 cadavers were studied macroscopically by use of the surgical field of right thoracotomy. The small branches difficult to identify macroscopically were described by x-ray imaging with digital subtraction angiography. Their anatomic relationship to the adjacent organs was observed microscopically.

RESULTS

The bronchial arteries arising from the intercostal arteries (the intercostobronchial arteries) were observed in 66 of 71 cases. By use of the surgical field of right thoracotomy the intercostobronchial arteries were easily found and preserved. All cadavers also had other bronchial arteries arising from the aorta. These were difficult to preserve because of the depth of the surgical field and the location of their course in the dissected area. Bronchial arteries had established connection with each other via the vascular network in the tracheal proper sheath. India ink injected into the intercostobronchial arteries was observed in the tracheal proper sheath and the submucosa of the trachea.

CONCLUSIONS

Saving the blood supply to the trachea is possible with careful preservation of the intercostobronchial arteries and the tracheal proper sheath during radical dissection of the upper mediastinum.

Alteration of T cells and natural killer cells during chickenpox in infancy

To determine the reasons for the low immune response and the mild morbidity of chickenpox in infancy, we investigated alteration of T cells and natural killer (NK) cells during chickenpox in children < 1 year and > or = 2 years old using flow cytometry. The CD4/CD8 ratio decreased only in the < 1-year-old group from the acute to the convalescent phase (P < 0.05). The CD3-CD16+CD56+ and CD57-CD16+ counts increased in the < 1-year-old group, but those in the > or = 2-year-old group did not increase from the acute to the convalescent phase. The CD3-CD16+CD56+ counts and the CD57-CD16+ counts and percentage were larger in the < 1-year-old group than those in the > or = 2-year-old group (P = 0.001, P = 0.002, and P < 0.05) in the convalescent phase. These results seem to indicate that the low immune response in infancy after chickenpox are related to the small number of CD8 in contrast with CD4 and that increased subsets of NK cells during chickenpox may correlate to the mild morbidity of chickenpox in infancy.

Color-coded pattern suppresses visual evoked cortical potentials and electroretinograms

We developed a new visual stimulating system for recording visual evoked cortical potentials and electroretinograms. The stimulus was a color checkerboard, in which each check kept its chromaticity but changed its luminance with its corresponding check. Color-coded pattern stimuli using red and green checks did not produce visual evoked cortical potentials, while yellow checks produced clear responses in a normal subject. Moreover, five color stairs from red and green to yellow showed only that the more colors are different, the smaller the visual evoked cortical potentials become. In addition electroretinogram recordings indicated that color-coded patterns behave in the same way as in visual evoked cortical potentials. The mechanism that causes the small color visual evoked cortical potentials may already be present in the retina. Color perception may be able to induce a suppression of responses for luminance contrast that appears to be formed already in the retina. Retinal responses were affected whether the stimulus field was color coded or not. Pattern electroretinograms appear to be more than the sum of local on and off responses.

Efficacy of CPT-11 (irinotecan) as a single agent in metastatic colorectal cancer

The efficacy of CPT-11 (Campto, irinotecan) given as a single agent has been assessed in three phase II clinical studies of patients with advanced colorectal cancer conducted in Japan, Europe and the U.S. Among a total of 337 evaluable patients treated with CPT-11 in dosage schedules of 100-150 mg/m2 weekly or bi-weekly (Japan, n = 63; U.S., n = 118) or 350 mg/m2 every 3 weeks (Europe, n = 156), overall objective response rates ranged from 17 to 27% and the median duration of response was approximately 7-9 months. Prior treatment with chemotherapy did not preclude a response to CPT-11 as evidenced by response rates of 14 to 22% and response durations of approximately 6-8 months in this cohort. In the European study, comparison of chemotherapy-naive patients with those who had received only one 5-fluorouracil (5-FU)-based regimen revealed similar response rates (22 and 20%) and of note, CPT-11 maintained its activity in pretreated patients who had previously experienced progressive disease. Together, these results suggest a lack of cross-resistance between the two agents. Leucopenia and delayed diarrhoea were the major adverse events observed in these studies, with grade 3-4 events occurring in 15-36% and 13-47% of patients, respectively. CPT-11, therefore, has significant activity in advanced colorectal cancer with response rates that are reproducible, durable and comparable to those achieved with 5-FU plus folinic acid in the first-line treatment of metastatic disease. Further work is needed to define the optimum dosage schedule for CPT-11 and also to assess fully the utility of CPT-11 in combination with other chemotherapeutic agents. Nevertheless, the activity of CPT-11 in patients refractory to treatment with 5-FU may be considered a significant advance, making it the first effective second-line agent in this setting.

[The importance of scientific clinical trials]

Well-designed clinical trials have been the only ways to answer many questions as to the "uncertainty" of cancer treatment. However, general physicians and mass media have not been willing to accept clinical trials because they were experiments on patients. In order to break through the present bottleneck it is very important to recognize the clinical significance of clinical trials by physicians themselves and to establish a system for reviewing and managing protocol study and for collecting clinical data. It is also important to obtain honest informed consent from patients tested in clinical trials. To accumulate the scientific evidences from clinical trials was the best way to achieve significant advances in cancer therapy.

Variation of the right subclavian artery as the last branch of the aortic arch in two Japanese cadavers

Two anomalous cases of the right subclavian artery were found in Japanese cadavers. In both cases, the right subclavian artery arose from the posterior wall of the aortic arch as its last branch, and ran rightwards between the esophagus and the vertebral column. The cases described belong to type G of the Adachi-Williams-Nakagawa-Takemura classification of aortic arch branching patterns.

Production of thrombopoietin (TPO) by rat hepatocytes and hepatoma cell lines

Recently, we purified rat thrombopoietin (TPO) from plasma of irradiated rats (XRP) by measuring its activity that stimulated the production of megakaryocytes from megakaryocyte progenitor cells (CFU-MK) in vitro. We then cloned the cDNAs for rat and human TPO. In this study, we found the production of TPO by hepatocytes isolated with the collagenase perfusion method from both normal and thrombocytopenic rats, by a two-step fractionation of hepatocyte culture medium (CM). Subsequently, CM of rat hepatoma cell lines was screened for the presence of TPO; three cell lines, H4-II-E, McA-RH8994, and HTC, were found to produce TPO. According to the purification procedure for TPO from XRP, TPO was partially purified from 2 L CM of each of three cell lines with a six-step procedure. In the final reverse-phase column, TPO from each cell line was eluted with the same retention time as that from XRP, and the TPO fraction exhibited megakaryocyte colony-stimulating activity (Meg-CSA). TPO-active fraction eluted from the final reverse-phase column was separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), extracted from the gel, and assayed. TPO activity from each cell line was found in the respective molecular weight region, indicating the heterogeneity of the TPO molecule. Using reverse transcriptase-polymerase chain reaction (RT-PCR), we detected the expression of TPO mRNA in hepatocytes, three hepatoma cell lines, normal rat liver, and X-irradiated rat liver. Northern blot analysis showed that TPO mRNA was expressed mainly in liver among the various organs tested. These data demonstrate that TPO is produced by rat hepatocytes and hepatoma cell lines and suggest that liver may be the primary organ that produces TPO.

Differential effects of ketamine and midazolam on heart rate variability

Alterations in autonomic activity caused by anaesthesia can be assessed by spectral analysis of heart rate variability (HRV). This study examined the effects of ketamine and midazolam on HRV. Thirty patients of ASA PS 1 were studied. Fifteen were given ketamine (2 mg.kg-1) and 15 received midazolam (0.3 mg.kg-1), iv. The RR intervals of ECG were measured before and after induction of anaesthesia for ten minutes during spontaneous respiration. Power spectral density of the data was computed using fast Fourier transform. The spectral peaks within each measurement were calculated: low frequency area (LF, 0.04-0.15 Hz), high frequency area (HF, 0.15-0.5 Hz), and total power (TP, 0.04-0.5 Hz). Normalized unit power was derived as follows: low frequency area (nuLF): LF/TP x 100%, high frequency area (nuHF): HF/TP x 100%. Both ketamine and midazolam caused reductions in all measurements of HRV power (P < 0.05). However, ketamine increased nuLF from 64 +/- 14% to 75 +/- 13% (P < 0.05) and decreased nuHF from 36 +/- 14% to 25 +/- 13% (P < 0.05), while midazolam decreased nuLF from 66 +/- 15% to 54 +/- 14% (P < 0.05) and increased nuHF from 34 +/- 15% to 46 +/- 14% (P < 0.05). These results documented that both ketamine and midazolam reduced the total power and all frequency components of power in spite of their opposing effects on autonomic nervous activity. However, normalized unit power showed the expected sympathetic activation with ketamine and sympathetic depression with midazolam since ketamine increased nuLF and midazolam decreased nuLF.

Construction of a divalent cell adhesive lysozyme by introducing the Arg-Gly-Asp sequence at two sites

To increase the cell adhesion activity of 74RGD4, an RGDS-inserted mutant between Val74 and Asn75 of human lysozyme, one more site for the RGD introduction was investigated in the lysozyme molecule. We found that 47RGD4 with RGDS in place of AGDR (residues 47 to 50) in a beta-turn region possesses the same level of adhesion activity as that of 74RGD4. The acceptance of the RGD introduction in the beta-turn region of human lysozyme is in good agreement with recent studies on the functional conformation of RGD. We constructed (47,74)RGD4, a mutant containing RGD at two sites, by combining the N-terminal domain of 47RGD4 and the C-terminal domain of 74RGD4. The (47,74)RGD4 lysozyme, with two functional RGD sequences, exhibits even higher cell adhesion activity than that of 74RGD4 or 47RGD4.

A simple and quantitative liquid culture system to measure megakaryocyte growth using highly purified CFU-MK

A new and quantitative liquid culture system has been developed to measure the production of megakaryocytes from megakaryocyte progenitor cells (colony-forming units-megakaryocyte [CFU-MK]). The system uses as a target population a glycoprotein (Gp) IIb/IIIa+ subpopulation of rat bone marrow cells previously demonstrated to be highly enriched for CFU-MK. GpIIb/IIIa+ cells were cultured at 5 x 10(4) cells/mL (10(4) cells/well) with test samples in 96-well tissue culture plates for 4 days at 37 degrees C. During the final 3 hours of incubation, the cells were pulsed with [14C]5-hydroxytryptamine creatinine sulfate (14C-serotonin). After incubation, the plates were washed and the cell pellets were lysed with Triton-X 100. The cell lysate was infiltrated into a commercially available solid scintillator and dried, and radioactivity was measured. In this assay system, rat interleukin-3 (IL-3) was found to be the most potent among known cytokines tested. Murine granulocyte-macrophage colony-stimulating factor (GM-CSF), human erythropoietin (Epo), human IL-6, and murine stem cell factor (SCF) each alone stimulated megakaryocyte growth but were much less active than rat IL-3. Plasma of rats rendered thrombocytopenic by injection of monoclonal antirat platelet GpIIb/IIIa antibody exhibited significant activity, and the active protein fractions partially purified from the plasma showed much higher activity, but normal rat plasma had no effect. This liquid culture system allows the measurement of a large number of test samples--including a wide variety of cytokines and unknown growth factors, alone or in combinations--and provides a simple method for evaluating the early proliferative events involving CFU-MK in the megakaryocyte differentiation pathway.

Plasma methylguanidine and creatinine concentrations in cats with experimentally induced acute renal failure

Plasma methylguanidine (MG) and creatinine (CRN) concentrations were measured in 11 cats with experimentally induced acute renal failure by a two-stage surgical procedure. According to the progression of renal failure, both plasma MG and CRN levels increased. A significant positive correlation (y = 0.187X - 0.379, lambda = 0.9176, P < 0.001) was found between plasma MG and CRN levels. These results suggested that the increase in plasma MG level was an available indicator for uremic status in cats.

[Experimental study on effects of omental transposition in cats with spinal cord injury]

The effects of autogenous omental transposition on spinal cord injury in cats were examined using a cord crush injury model produced by a modification of Allen's weight-dropping technique. Twenty-three cats were divided into two groups: an omental transposition group, and a control group. The animals were sacrificed at 1, 2, 3, and 4 weeks after injury. The injured cords were examined histologically using India ink perfusion, morphometry of the spinal cord cavities and also by somatosensory evoked potential (SEP) studies. After 1 week, hemorrhagic necrosis, cavitation and demyelination of almost the same extent and severity were noted in both groups. These changes diminished with time in the omental transposition group, but tended to persist in the control group. In the omental transposition group, fibrous coats of Goldsmith were newly formed on the injured cord between the incised dura edges. After 3 weeks, the fibrous coat was thickened with active proliferation of fibroblasts and collagen fibers. India ink particles were noticed within the fine vessels of the omentum, fibrous coat and injured cord at 4 weeks. No India ink particles were found in the control group even after 4 weeks. In the somatosensory evoked potentials, biphasic or triphasic waves noted before injury were absent immediately after trauma. At 3 and 4 weeks, 3 of 5 cats with the omentum showed reappearance of the waves, whereas no wave-reappearance was noted in the controls. These results suggest that autogenous omental transposition helps to accelerate the healing process after crush injury to the spinal cord.

In vivo adhesive interface between resin and dentin

V-shaped cervical cavities prepared in monkey teeth were restored with several dentin bonding systems, and the in vivo resin-dentin interfacial structures were observed under the scanning electron microscope using an argon-ion etching technique. The hybrid layer could be clearly observed; its depth was dependent on the conditioner/primer used and tended to be thinner at the deep part of the cavity. Resin tags were also clearly observed, and their structure at the inner part was noted to be rougher than that closer to the tubule orifices. When 37% phosphoric acid gel was used, the tags in the deeper parts of the cavity were much rougher. Hemispherical and spherical roughened structures were observed directly above the tubule orifices, which were thought to be a mixture of dentinal fluid and bonding resin that had flowed out from the tubules. The acidic primer containing maleic acid and HEMA could not remove the smear plugs, and undissolved smear particles were observed in the tubules.

Reduced fidelity of DNA synthesis in cell extracts from chemically induced primary thymic lymphomas of mice

To examine whether the fidelity of DNA synthesis is reduced in tumor cells, M13 mp2-based fidelity assays were carried out using 15 samples of whole-cell extracts from primary mouse thymic lymphomas induced by alkylating agents. We found that DNA synthesis activities of thymic lymphomas, detected as incorporation of [3H]TTP into acid-insoluble materials, were 2- to 10-fold higher compared to those of normal thymus. Furthermore, mutant frequencies in the forward mutation assay of DNA synthesis were increased 2- to 7-fold in cell extracts from thymic lymphomas compared to those from normal thymus. As the DNA polymerase beta (pol beta) activity was extremely high in the thymic lymphomas, we screened mutations in the pol beta gene to examine the possibility of involvement of mutated pol beta in reduction of the fidelity of DNA synthesis. Of 20 lymphomas, one case of point mutation (T to A) was found by reverse transcription-PCR single-strand conformation polymorphism analysis. These results suggest that the mutagenic DNA synthesis is involved in murine thymic lymphoma genesis, although mutation of the pol beta gene is not a major causal event.

[A case of gastric cancer developed in the gastric tube 11 years after subtotal esophagectomy for esophageal cancer]

A case of adenocarcinoma developed in the reconstructed gastric tube after esophagectomy was reported. The patient was 66 years old man and he had received subtotal esophagectomy for the carcinoma of the esophagus 11 years previously. The follow-up examination of upper GI series revealed an ulcerative lesion in the lower part of the gastric tube and endoscopic biopsy showed adenocarcinoma. The partial resection of the lower gastric tube with mediansternotomy was performed because of limiting the invasion of the carcinoma. Pathological examination showed that poorly differentiated adenocarcinoma with signet ring cells had invaded muscularis propria. The postoperative course was uneventful and he is well without any recurrence 6 months after the operation. A double carcinoma, such as esophageal cancer concomitant gastric cancer is not rare, but a carcinoma of the gastric tube which was substituted for the esophagus is rare. Recently, the incidence of carcinoma of the gastric tube is increasing due to the increasingly long-term survival rate of patients who had esophageal carcinoma. In order to ensure the early detection of a second carcinoma which can minimalize damage from curative resections, follow up examinations should be conducted with the utmost diligence.

Restoration and analysis of standing-up in complete paraplegia utilizing functional electrical stimulation

OBJECTIVE

Restoration of stand-up motion in patients with complete paraplegia utilizing multichannel functional electrical stimulation, and analysis of the restored motion.

DESIGN

Nonrandomized control trial.

SETTING

General community, a referral center, institutional practice, and ambulatory care:

PATIENTS

Twelve volunteer samples were used for the collection of normal data. Two complete paraplegics received treatment for the restoration of stand-up motion.

MAIN OUTCOME MEASURES

The electromyogram, joint angle, and floor reaction force were investigated during standing-up with arms crossed in front of the chest, and hands-assisted standing-up using parallel bars. The maximum knee joint torque during standing-up without hands-assists was calculated using a three-segment link model. Standing-up motion in complete paraplegics was restored, and then analyzed using the three-dimensional floor reaction force and the hip, knee, and ankle angles.

RESULTS

Main muscles used to stand up were the quadriceps, tibialis anterior, and paraspinal muscles. Hands-assists reduced the muscle activity and the vertical floor reaction force. Peak muscle activity was less during hands-assisted standing-up, except for the rectus femoris and the iliopsoas muscle. The maximum knee joint torque during standing-up was 1.6Nm/kg for both knees. Two complete paraplegics were able to stand up smoothly from a wheelchair based on stimulation data obtained from normal subjects. The characteristic pattern during standing-up was knee flexion preceding extension.

CONCLUSION

Stand-up motion was restored utilizing electromyogram data and knee joint torque data from normal subjects.

Color vision and color pattern visual evoked cortical potentials in a patient with acquired cerebral dyschromatopsia

We examined a 74-year-old man because of difficulty seeing green and the presence of prosopagnosia. His visual acuity was 0.8 in both eyes. He was not congenitally color blind, and there was no family history of color blindness. A left superior homonymous quadrantanopsia was found. The dyschromatopsia ws identical in both eyes. The patient showed red-green deficiency on testing with Ishihara plates a deutan defect with Tokyo Medical College plates, strong blue-yellow defects and medium red-green defects with Standard Pseudochromatic Plates II and a tritan defect with the Panel D-15. He failed the New Color separation test with scores of 160 and could not carry out the Farnsworth-Munsell 100-hue test, but his color naming test results were normal. Visual evoked cortical potentials to black-and-white checkerboard and color pattern reversal (Red and Blue-Green, Green and Red-Purple, Purple and Yellow-Green: isochromatic paired checks) stimuli were normal. Bilateral inferior occipital lesions were found by computed tomography and T2-weighted magnetic resonance imaging. Our findings suggested that luminance and color channels up to area 17 in our patient were intact. We believe that our patient's acquired cerebral dyschromatopsia is rare.

Multiple tumor-suppressor-1 gene and esophageal-carcinoma

The multiple tumor suppressor 1 (MTS1) gene is homozygously deleted frequently in cell lines derived from a wide variety of tumors. We investigated the deletion of the MTS1 gene in esophageal cancer cell lines and primary esophageal squamous carcinomas using the polymerase chain reaction. Sixteen and 15 of 23 esophageal cancer cell lines showed homozygous deletion of MTS1 exon 1 and exon 2, respectively, while none of 21 primary esophageal carcinomas showed the deletion. An analysis of MTS1 gene mutations was carried out by direct DNA sequencing in 8 cell lines and 21 primary carcinomas showing no homozygous deletion. In contrast to previous reports of esophageal carcinoma, there were no mutations recognized in the region sequenced. Our study suggests that the inactivation of the MTS 1 gene may play an important role in esophageal carcinoma cell lines but may be less important in primary carcinomas of the human esophagus.

Induction of differentiation of HL-60 cells by the anti-fungal antibiotic, radicicol

The anti-fungal antibiotic, radicicol, produced in the culture broth of Neocosmospora tenuicristata, was found to induce differentiation of HL-60 cells into macrophages from the following evidence: (1) it caused morphological changes into macrophage-like cells, (2) induced NBT (Nitrobluetetrazolium) reduction activity, (3) induced phagocytosis, and (4) induced alpha-naphthyl acetate esterase activity. The concentration of radicicol required to differentiate HL-60 cells is 50-100 ng/ml, and the incubation time required for commitment of differentiation is 16 hours. Flow cytometry analysis indicated that radicicol blocks the cell cycle of HL-60 cells at the G1 and G2 sites. In addition, radicicol induced reversal of the transformed phenotype of ras-transformed NIH3T3 cells (DT cells) at 25 ng/ml.

Serum lipid and lipoprotein concentrations in obese dogs

Serum lipid and lipoprotein concentrations in 10 obese and 16 control dogs were examined. The serum triglyceride (TG) concentration in obese dogs was significantly higher than in control dogs. The serum concentrations of TG and phospholipid (PL) in beta lipoprotein and PL in pre-beta lipoprotein were significantly higher in obese dogs, while the serum PL concentration in alpha 1 lipoprotein was significantly lower in obese animals. In the serum total cholesterol concentration in obese dogs, a higher tendency for beta and pre-beta lipoproteins and lower tendency for alpha 1 lipoprotein were observed. These abnormal lipoprotein profiles were similar to those in diabetes mellitus in men and acute pancreatitis in dogs.

Genomic DNA and messenger RNA expression alterations of the CDKN2B and CDKN2 genes in esophageal squamous carcinoma cell lines

The genes CDKN2B (MTS2) and CDKN2 (MTS1) encoding the proteins p15 and p16 are both located on chromosomal band 9p21, a locus at which frequent homozygous and heterozygous deletions occur in many primary human tumors, including esophageal carcinoma. CDKN2 and CDKN2B belong to a family of cyclin-dependent kinase 4 inhibitors (INK41) and control cell proliferation during the G1 phase of the cell cycle. Their inactivation may contribute to uncontrolled growth in human cancers. To investigate whether CDKN2B and CDKN2 are involved in esophageal tumorigenesis, we studied homozygous deletion, intragenic mutation, and messenger RNA (mRNA) expression of CDKN2 and CDKN2B in nine esophageal squamous cancer cell lines. Polymerase chain reaction (PCR) amplification revealed that five of the nine cell lines (55%) manifested homozygous deletions of CDKN2B, CDKN2, and/or flanking loci on chromosomal band 9p21. Reverse transcriptase-PCR (RT-PCR) was used to examine CDKN2 and CDKN2B mRNA in the nine cell lines. Lack of CDKN2 and CDKN2B mRNA correlated perfectly with homozygous deletion involving these genes. No subtle intragenic mutations of CDKN2B or CDKN2 were detected by DNA sequencing of their entire coding sequences in any cell lines lacking homozygous deletion. Two of the cell lines manifested homozygous deletions excluding CDKN2; one of these two deletions also excluded CDKN2B. These results suggest that inactivation of CDKN2B and CDKN2 may contribute to the malignant phenotype in esophageal cells and that homozygous deletion may be the predominant mechanism for inactivation of CDKN2B and CDKN2. Alternatively, a gene or genes adjacent to CDKN2B/CDKN2 may constitute the target(s) of deletion at this locus.