Free radical-independent protection by nerve growth factor and Bcl-2 of PC12 cells from hydrogen peroxide-triggered apoptosis

To investigate the mechanism of oxidative stress induced death of PC12 cells, we performed confocal and flow cytometric analysis with a reactive oxygen species (ROS)-specific fluorogen, 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA). Hydrogen peroxide significantly decreased the number of viable PC12 cells after 24 h. Hydrogen peroxide caused membrane blebbing, nuclear condensation and DNA fragmentation, indicating that the PC12 cells died due to apoptosis. The hydrogen peroxide-triggered apoptosis of PC12 cells was associated with enhanced ROS production in a dose-dependent manner by measuring with C-DCDHF-DA. Nerve growth factor (NGF) and Bcl-2 inhibited the hydrogen peroxide-induced apoptosis of PC12 cells. Neither of them, however, reduced the ROS production in PC12 cells. These data suggest that NGF or Bcl-2 protects PC12 cells from hydrogen peroxide-triggered apoptosis independently from ROS production.

Elevated serum Lp(a) concentration and the rare apo(a) phenotype in a patient with myocardial infarction

Lp(a) is considered to be an independent risk factor for the development of cardiovascular disease. A case of myocardial infarction with elevated serum Lp(a) concentration and the rare apo(a) phenotype and its successful recanalization using tissue plasminogen activator is reported.

[Incidence of synchronous or metachronous multiple primary cancers and aggregation of cancers in families of patients with endometrial cancer]

We evaluated the incidence of synchronous or metachronous multiple primary cancer, hereditary or familial cancer, and the familial aggregation of cancer in 142 patients who were treated for endometrial cancer at Tsukuba University Hospital in the period 1977 to 1995. Synchronous multiple primary cancers were identified in 6 of the 142 patients (4.2%). Eleven patients (7.7%) had a history of extraendometrial cancer. Patients with endometrial cancer had a significantly high incidence of a history of breast cancer. Endometrial cancer was diagnosed in two patients who were screened before menopause. Four patients with endometrial cancer (2.8%) subsequently developed extraendometrial forms of cancer. One patient (0.7%) was considered to have a hereditary form of cancer, and 5 patients (3.5%) had familial forms of cancer. A total of 86 cases of cancer were found among 53 kindred (37.3%). More detailed studies are needed to elucidate the aggregation of cancers in the families of patients with endometrial cancer in Japan. Patients with a history of breast cancer should be screened for the presence of endometrial cancer.

Unequal atrial stretch in dogs increases dispersion of refractoriness conducive to developing atrial fibrillation

INTRODUCTION

We have shown previously that acute atrial dilation prolonged atrial refractoriness. We hypothesized that this increase in refractoriness might be heterogeneous and could create an electrophysiologic substrate leading to atrial fibrillation. The purpose of the present study was to test that hypothesis.

METHODS AND RESULTS

We studied 23 anesthetized open chest dogs. Bipolar plunge electrodes were placed in the medial free wall of the right atrium (thin region) and in the lower crista terminalis of the right atrium (thick region). Two bipolar plunge electrodes were also placed in the left ventricular apex to stimulate and record. Atrial effective refractory period (ERP) was measured in a group of nine dogs using the atrial extrastimulus method (A1A2) in two ways: during atrial pacing (AP) and during simultaneous atrioventricular (AV) pacing that achieved and AV interval of 0 msec (AV = 0). One liter/hour of normal saline was infused intravenously to elevate right atrial pressure and produce right atrial stretch. Atrial ERPs were measured before and after the normal saline infusion. To compare the extent of atrial stretch produced by volume overload, two pairs of sonomicrometer transducers were implanted in the thick and thin regions in a separate group of six dogs. The area encompassed by sonomicrometers was measured before and after saline infusion. The inducibility of atrial fibrillation was compared before and after saline infusion using rapid AP in another group of five dogs. Atrial pressure during sinus rhythm increased from 5.1 +/- 0.96 mmHg to 6.3 +/- 0.93 mmHg after normal saline infusion (P < 0.01). ERP increased in the thin free wall from 151 +/- 14.3 to 172 +/- 14.7 msec (AV = 0), and from 169 +/- 12.0 to 170 +/- 14.3 msec (AP). ERP increased in the thick crista terminalis from 134 +/- 9.9 to 147 +/- 10.2 msec (AV = 0), and from 133 +/- 7.9 to 146 +/- 9.8 msec (AV) (P < 0.01). The increase in ERP in the thin free wall exceeded that in the thick crista terminalis (P < 0.01), increasing the dispersion of atrial ERP. After 500-mL saline infusion for 30 minutes, the increase of area in the thin region was 12.8% +/- 3.7%, and that in the thick was 3.5% +/- 3.2%. The increase of the area in the thin region after 1000 mL for 1 hour was 18.8% +/- 6.2%, and that in the thick region was 6.3 +/- 5.1% (P < 0.01). Atrial fibrillation was not induced in any dog before infusion, but induced in all five dogs after saline infusion.

CONCLUSIONS

Atrial ERP in the thin right atrial free wall exceeds the ERP of the thick crista terminalis, and an increase in atrial pressure produced by saline infusion exaggerates this difference by stretching thin segments of the atrial myocardium more than it stretches thick regions. Thus, atrial stretch, by increasing the dispersion of atrial ERP, may be conducive to the development of atrial fibrillation.

Large diffuse arteriovenous malformation affecting the right cerebral and cerebellar hemispheres: case report

A cerebral vascular malformation was triggered in a 24-year-old man by left hemiparesis resembling transient ischemic attack. Cerebral angiography revealed slight dilation of the right anterior cerebral artery, middle cerebral artery, superior cerebellar artery, and posterior inferior cerebellar artery, as well as marked capillary blush and dilation of medullary veins involving the right cerebral hemisphere, especially the frontal lobe and cerebellar hemispheres. This vascular malformation, a clinical rarity, seemed to be in the same family as diffuse arteriovenous malformation or "medullary venous malformation." Single photon emission computed tomography showed a decline in cerebral blood flow in the right cerebral hemisphere, which was the probable cause of the left hemiparesis.

Regulation of Na-K-ATPase activity in the proximal tubule: role of the protein kinase C pathway and of eicosanoids

To evaluate further the signal transduction mechanisms involved in the short-term modulation of Na-K-ATPase activity in the mammalian kidney, we examined the role of phospholipase C-protein kinase C (PLC-PKC) pathway and of various eicosanoids in this process, using microdissected rat proximal convoluted tubules. Dopamine (DA) and parathyroid hormone (either synthetic PTH1-34 or PTH3-34) inhibited Na-K-ATPase activity in dose-dependent manner; this effect was reproduced by PKC530-558 fragment and blocked by the specific PKC inhibitor calphostin C, as well as by the PLC inhibitors neomycin and U-73122. Pump inhibition by DA, PTH, or arachidonic acid, and by PKC activators phorbol dibutyrate (PDBu) or dioctanoyl glycerol (DiC8) was abolished by ethoxyresorufin, an inhibitor of the cytochrome P450-dependent monooxygenase pathway, but was unaffected by indomethacin or nordihydroguaiaretic acid, inhibitors of the cyclooxygenase and lipoxygenase pathways of the arachidonic acid cascade, respectively. Furthermore, each of the three monooxygenase products tested (20-HETE, 12(R)-HETE, or 11,12-DHT) caused a dose-dependent inhibition of the pump. The effect of DA, PTH, PDBu or DiC8, as well as that of 20-HETE was not altered when sodium entry was blocked with the amiloride analog ethylisopropyl amiloride or increased with nystatin. We conclude that short-term regulation of proximal tubule Na-K-ATPase activity by dopamine and parathyroid hormone occurs via the PLC-PKC signal transduction pathway and is mediated by cytochrome P450-dependent monooxygenase products of arachidonic acid metabolism, which may interact with the pump rather than alter sodium access to it.

The effects of pravastatin, an HMG-CoA reductase inhibitor, on cell viability and DNA production of rat hepatocytes

Some metabolites and products of mevalonic acid are involved in various cellular functions, particularly cell growth. In this study, we assessed the effects of pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on cell viability and DNA production of rat hepatocytes stimulated with epidermal growth factor. Pravastatin (0.1 to 10 microM) induced a dose-dependent reduction of DNA synthesis, assessed by 3H-thymidine incorporation in rat hepatocytes, which dropped by approximately 60% at a drug concentration of 10 microM. This suppression of DNA synthesis was nearly reversed by exogenous mevalonic acid, but was not prevented by purified low-density lipoprotein cholesterol. Pravastatin did not affect the mitochondrial reduction of Dimethylthiazolyl-diphenyl-tetrazolium bromide (MTT), but induced apoptotic change as assessed by nuclear chromatin staining. This apoptotic change was also reversed by exogenous mevalonic acid. These results indicate that mevalonic acid metabolites are necessary for DNA synthesis by rat hepatocytes stimulated by epidermal growth factor and for suppressing cell death.

Synthetic peptides derived from the fourth domain of CD4 antagonize off function and inhibit T cell activation

We have developed synthetic peptide analogs to analyze novel surface structures of the human CD4 protein potentially involved in T cell activation. Linear and cyclic peptides derived from the FG and CC' loops of the membrane proximal fourth domain of CD4 displayed inhibitory activities in a CD4-dependent immunological assay. These results suggest that the fourth domain of CD4 plays an important role in T cell activation. In addition, we report the synthesis of a highly stable CD4 peptide analog cyclized by the formation of an amide bond between amino and carboxyl termini. Serum stability studies showed that this main-chain cyclic CD4 peptide was highly resistant to proteolytic degradation while the linear and disulfide cyclic peptides were much less stable. The strategy of main chain cyclization of CD4 peptides may represent a promising approach to generate proteolytically stable, orally active immunoregulatory agents.

Rapid rates during bradycardia prolong ventricular refractoriness and facilitate ventricular tachycardia induction with cesium in dogs

BACKGROUND

Bradycardia can promote the development of some ventricular techycardias (VTs). We investigated whether relative bradycardia per se or the transition from a rapid to a slower ventricular rate might be important in developing VT.

METHODS AND RESULTS

We studied groups of anesthetized closed-chest dogs that had AV produced by radiofrequency catheter ablation of the AV junction. One group had uninterrupted AV block; the other group underwent a period of rapid left ventricular pacing. Both groups then received incremental doses of CsCl until sustained VT resulted. We also measured ventricular effective refractory period (V-ERP) and QT interval in separate groups of dogs that had AV block for 1 week or 3 days with and without rapid pacing (pacing cycle length [PCL] = 500 or 250 ms) for 1 hour or 30 minutes. Finally, we investigated the effects of rapid pacing on V-ERP by testing the effects of verapamil and autonomic denervation on these changes. We found that CsCl induced larger early afterdepolarizations and a greater prevalence of VT in dogs with rapid pacing than in dogs without. In dogs that had AV block for 1 week, 1 hour of rapid pacing prolonged V-ERP and QT interval compared with V-ERP and QT interval before pacing. Changes persisted for at least 3 hours. Rapid pacing for only 30 minutes and at a PCL of 250 ms, as well as superimposition on sinus rhythm, each prolonged V-ERP but to a lesser extent. Only 3 days of complete AV block and autonomic denervation did not affect the prolongation of V-ERP produced by rapid pacing, whereas verapamil significantly blunted but did not eliminate the prolongation.

CONCLUSIONS

At the same PCLs, the heart exposed to transient tachycardia superimposed on bradycardia exhibited a longer V-ERP, QT interval, and monophasic action potential duration and greater ease for developing VT than the heart exposed only to bradycardia. The prolongation of refractoriness lasted for at least 3 hours, and the delta-ERP was influenced by the heart rate before pacing, the duration of pacing, and the PCL. The mechanism for this response to rapid rates appears to involve calcium, at least in part.

Electrophysiologic effects of ischemic preconditioning on QT dispersion during coronary angioplasty

OBJECTIVES

The aim of this study was to examine the effect of ischemic preconditioning on the manner of ventricular repolarization by assessing the change in QT dispersion during coronary angioplasty.

BACKGROUND

QT interval dispersion reflects regional variations in ventricular repolarization and cardiac electrical instability. Previous studies have suggested that increased QT dispersion is associated with an increased incidence of malignant ventricular arrhythmias, whereas brief episodes of myocardial ischemia can render the heart more resistant to subsequent ischemic episodes, a phenomenon called ischemic preconditioning.

METHODS

To assess the effects of ischemic preconditioning on myocardial repolarization by examining the change in QT dispersion during coronary angioplasty, we studied 47 consecutive patients (39 men and 8 women; mean age 57 +/- 16 years). QT dispersion was measured after each balloon inflation during coronary angioplasty. Statistical analysis was performed by using repeated measurement of analysis of variance.

RESULTS

There were significant differences in QT dispersion as the number of balloon inflations increased (mean +/- SD 52 +/- 14, 42 +/- 11, 36 +/- 9, 31 +/- 10 and 29 +/- 11 ms, respectively [p < 0.01], for the first, second, third, fourth and fifth balloon inflations). The magnitude of decrease in QT dispersion was significant in the first and second balloon inflations, then became insignificant with later inflations.

CONCLUSIONS

These data indicate that the gradual decrease in QT dispersion provoked by coronary artery occlusion and reperfusion during coronary angioplasty may be associated with electrophysiologic effects of ischemic preconditioning on myocardium in the human heart.

[An immunohistological study on expression of glutathione S-transferase pi (form) in dysplastic and neoplastic human uterine cervix lesions]

The glutathione S-transferase (GST) pi has been studied in association with the mechanisms of multidrug resistance and as a marker for malignant tumors. In this study, specimens from 92 cases of cervical neoplasms and 10 cases of normal squamous epithelium adhering to myoma were stained immunohistochemically with a rabbit polyclonal antibody to GST-pi. In 6 cases of normal squamous epithelium, the intermediate layer was positively stained with the GST-pi antibody. In all 20 cases of dysplasia, the cells with koilocytotic atypia were stained positively. In all 10 cases of carcinoma in situ and all 16 cases of stage Ia squamous cell carcinoma, various intensities of GST-pi staining were demonstrated. Forty-six specimens of stage Ib or more squamous cell carcinoma were positive for GST-pi binding except only one case. In general, squamous cell carcinoma of the uterine cervix is resistant to chemotherapeutic agents. GST-pi is most frequently stained in cervical squamous cell carcinoma as compared with ovarian or endometrial carcinoma. In conclusion, these results suggest that GST-pi may be a marker for cervical squamous cell carcinoma.

Giant retroperitoneal cyst in an adult male

This paper presents a case of a symptomatic giant retroperitoneal cyst in an adult male. The unilocular cyst was excised successfully with resolution of the attendant symptoms. Histological findings of the cyst wall suggested a lymphangiomatous etiology. Any good risk patient found to harbor such a cyst should undergo complete excision in view of the potential for the development of symptoms and complications.

Bile acid synthesis in young and old rats

Bile acid synthesis from orally administered (14)C-cholesterol or from (14)C-mevalonic acid administered intravenously were examined in male and female 2-, 12- and 24-month-old rats. About 5-9% of the '4C-cholesterol administered was recovered as bile acids from the small intestine 3 days after administration. The value in the case of (14)C-mevalonic acid was about 1/10 that of (14)C-cholesterol. Major bile acids were cholic acid and beta-muricholic acid, and the formation ratio of cholic acid increased in aged rats, although no further difference was found between 12- and 24-month-old animals of either sex. Male rats formed more beta-muricholic acid than females at all ages examined. In addition, no significant difference was found in the bile acid composition between both precursors, (14)C-cholesterol and (14)C-mevalonic acid.

Specificity of substrate and inhibitor probes for cytochrome P450s: evaluation of in vitro metabolism using cDNA-expressed human P450s and human liver microsomes

1. We evaluated the specificity of 15 substrates and 14 inhibitors of the cytochrome P450s using nine human P450 forms expressed in HepG2 cells using a recombinant vaccinia virus and also in human liver microsomes. 2. Coumarin, 7-ethoxyresorufin, 7-benzyloxyresorufin, tolbutamide, aniline and diazepam were form-selective substrates towards CYP2A6, the CYP1A subfamily, CYP2B6, the CYP2C subfamily, CYP2E1 and the CYP3A subfamily respectively. However, a selective substrate for CYP2D6 was not found among the chemicals tested. 3. SKF-525A inhibited > 40% of the metabolic activity of all substrates tested, and the inhibitory effects differed among P450 forms. Sulphaphenazole, 7,8-benzoflavone, quinidine and troleandomycin were selective inhibitors of the CYP2C subfamily (except CYP2C19), the CYP1A subfamily, CYP2D6 and the CYP3A subfamily respectively. Methoxsalen (CYP2A6 inhibitor) inhibited the metabolic activity of CYP1A2 as well as that of CYP2A6. Diethyldithiocarbamate (CYP2E1 inhibitor) inhibited the metabolic activities of CYP2A6 and CYP2C19 in addition to that of CYP2E1. 4. Our results indicated that substrates and inhibitors reported as P450 selective probes are not necessarily specific for individual human P450 forms. These results may provide useful information regarding human P450 substrates and inhibitors in vitro using human liver microsomal samples.

Effects of beta-lactam antibiotics on intestinal microflora and bile acid metabolism in rats

Wistar male rats were treated for six days with broad spectrum beta-lactam antibiotics, latamoxef, and cefotaxime. On the seventh day, the number of fecal anaerobic microbes decreased, total fecal bile acids decreased, and bile acid pools increased. Secondary bile acids such as beta-hyocholic, hyodeoxycholic, lithocholic, and deoxycholic acids decreased in the feces while the primary bile acids, cholic, beta-muricholic, and chenodeoxycholic acids, became predominant. Coprostanol, a microbial metabolite of cholesterol, also disappeared from the feces during the treatment. The cecum enlarged to almost twice the size of that in control rats, whereas the liver weight was not significantly changed. After treatment was stopped, the number of fecal microbes returned to the initial counts within a week, but restoration of bile acid and cholesterol metabolism required at least three weeks.

Establishment of eighteen clones of Ishikawa cells

Ishikawa cells, which derive from a well differentiated human endometrial adenocarcinoma, were cloned using the limiting dilution method in an attempt to preserve well differentiated cells. Eighteen clones were obtained. According to their morphologic characteristics, there were six well differentiated, seven moderately differentiated, three poorly differentiated and two adenosquamous carcinoma clones. All of them were transplantable into node mice. Fifteen of the 17 clones were positive for estrogen receptors and all of the clones examined were positive for progesterone receptors. There were no significant differences in terms of population doubling time, plating efficiency or saturation density among these clones. On the basis of these results, we concluded that Ishikawa cells are not as homogeneous morphologically as we thought, since cells with varying degrees of differentiation have already mingled with the parent cell line. It is verified that the adenosquamous cell carcinoma of the endometrium can arise from one stem cell. It would be impossible to revive the cultured cells after having undergone their changes to the original conditions. Therefore, to preserve the characteristics of an established cell line, the cells should be frozen at a very early stage. It is also important to avoid frequent passages when special characters of the cells are necessary for a given investigation.

A YAC contig of the human CC chemokine genes clustered on chromosome 17q11.2

CC chemokines are cytokines that attract and activate leukocytes. The human genes for the CC chemokines are clustered on chromosome 17. To elucidate the genomic organization of the CC chemokine genes, we constructed a YAC contig comprising 34 clones. The contig was shown to contain all 10 CC chemokine genes reported so far, except for one gene whose nucleotide sequence is not available. The contig also contains 4 CC chemokine-like genes, which were deposited in GenBank as ESTs and are here referred to as NCC-1, NCC-2, NCC-3, and NCC-4. Within the contig, the CC chemokine genes were localized in two regions. In addition, the CC chemokine genes were more precisely mapped on chromosome 17q11.2 using a somatic cell hybrid cell DNA panel containing various portions of human chromosome 17. Interestingly, a reciprocal translocation t(Y;17) breakpoint, contained in the hybrid cell line Y1741, lay between the two chromosome 17 chemokine gene regions covered by our YAC contig. From these results, the order and the orientation of CC chemokine genes on chromosome 17 were determined as follows: centromere-neurofibromatosis 1-(MCP-3, MCP-1, NCC-1, I-309)-Y1741 breakpoint-RANTES-(LD78gamma, AT744.2, LD78beta)-(NCC-3, NCC-2, AT744.1, LD78alpha)-NCC-4-retinoic acid receptor alpha- telomere.

Influence of cholesterol feeding on bile acid metabolism in young and aged germ-free rats

The effects of cholesterol feeding on serum and liver cholesterol levels, fecal and biliary bile acid levels, bile acid pool size and bile acid composition were examined in 2-, 12- and 24-month-old male germ-free rats. The major bile acids in these animals were cholic and beta-muricholic acids. Cholesterol feeding increased synthesis of bile acids by 3- to 4-fold, especially that of chenodeoxycholic acid (mainly beta-muricholic acid in the rat), decreasing the cholic acid/chenodeoxycholic acid (CA/CDCA) ratio in all rats regardless of age, even though the CA/CDCA ratio increased as a linear function of age in both diet groups. Cholesterol feeding increased the serum cholesterol level markedly in aged rats. This hypercholesterolemia may be produced by the increase in CA/CDCA ratio in aged rats.

Purification of the cytosolic CuZn-superoxide dismutase (CuZn-SOD) of Marchantia paleacea var. diptera and its resemblance to CuZn-SOD from chloroplasts

Suspension-cultured cells of Marchantia paleacea var. diptera contain a single form of CuZn-superoxide dismutase (SOD; EC 1.15.1.1) which is localized in the cytosol. SOD activity was found in cells cultured under heterotrophic, photoheterotrophic and photoautotrophic conditions. The CuZn-SOD was purified to homogeneity from liverwort cells that had been cultured heterotrophically. Its molecular mass was 32.6 kDa, and it contained 17.5 dDa subunits, an indication that the enzyme is a homodimer. The enzyme had peaks of absorption at 252, 258 and 264 nm in the ultraviolet region, due to the presence of phenylalanine, and a peak at 680 nm in the visible region, which is characteristic of CuZn-SODs from chloroplasts. The amino acid sequence of the amino-terminal region of the enzyme exhibited a very high degree of homology to those of chloroplast CuZn-SODs. An antiserum raised against the CuZn-SOD from liverwort cross-reacted more strongly with the enzyme from spinach chloroplasts, than with the enzyme from spinach cytosol. These results indicate that the CuZn-SOD of liverwort resembles CuZn-SOD in chloroplasts even though the former is located in the cytosol.

NMR studies of the effects of the 5'-phosphate group on conformational properties of 5-methylaminomethyluridine found in the first position of the anticodon of Escherichia coli tRNA(Arg)4

5-Methylaminomethyluridine (mnm5U) exists in the first position of the anticodon (position 34) of Escherichia coli tRNA4Arg for codons AGA/AGG. In the present study, the temperature dependence of the ribose-puckering equilibrium of pmnm5U was analyzed by proton NMR spectroscopy. Thus, the enthalpy difference (delta H) between the C2'-endo and C3'-endo forms was obtained at 0.65 kcal.mol-1. By comparison of the delta H values of pU and pmnm5U, the 5-substitution was found to increase the relative stability of the C3'-endo form over the C2'-endo form significantly (by 0.56 kcal.mol-1). Furthermore, this conformational "rigidity" was concluded to depend on the 5'-phosphate group, because nucleoside U exhibits only a negligible change in the ribose-puckering equilibrium upon the 5-methylaminomethyl substitution. Further NMR analyses and molecular dynamics calculations revealed that interactions between the 5-methylaminomethyl and 5'-phosphate groups of pmnm5U restrict the conformation about the glycosidic bond to a low anti form, enhancing steric repulsion between the 2-carbonyl and 2'-hydroxyl groups in the C2'-endo form. This intrinsic conformational rigidity of the mnm5U residue in position 34 may contribute to the correct codon recognition.

Tyrosine phosphorylation of ACK in response to temperature shift-down, hyperosmotic shock, and epidermal growth factor stimulation

The mammalian Cdc42 protein regulates various kinds of cellular responses, including formation of filopodia, polarization of T cells, and cell cycle progression. A non-receptor tyrosine kinase ACK, which specifically binds to the GTP-bound form of Cdc42, was isolated as a putative target of Cdc42. Here we show the induction of tyrosine phosphorylation of ACK in response to temperature shift-down to 25 degrees C, and hypertonic shock, as well as stimulation with epidermal growth factor (EGF) in human embryonic kidney (HEK) 293 cells. The increased tyrosine phosphorylation level upon temperature shift-down was sustained for at least 60 min, whereas reversion of the temperature to 37 degrees C caused rapid tyrosine dephosphorylation to the initial level. The responses to EGF and the high osmolarity were transient. Furthermore, we observed association of ACK with an adaptor protein Grb2, which may suggest the involvement of Grb2 in EGF receptor-mediated tyrosine phosphorylation of ACK.