Surgical outcome after curative resection of rectal leiomyosarcoma

PURPOSE

The aim of this study is to present the prognosis and possible associated prognostic factors after curative resection of rectal leiomyosarcoma.

METHODS

From 1979 to 1996 our hospital saw 40 patients with rectal leiomyosarcoma, including 19 females, who did not have metastasis initially and received curative resection and regular postoperative follow-up.

RESULTS

The mean age of the 40 patients was 58.7 years. Anal bleeding and perianal pain were the two most common symptoms at initial diagnosis. Twenty-nine patients received a radical surgical resection, such as abdominoperineal resection or low anterior resection; the other 11 patients received a wide local excision, such as transrectal excision or Kraske's operation. Sixteen tumors were classified as high-grade leiomyosarcoma, and 23 as low grade. Nineteen patients (48 percent) developed recurrence or metastasis postoperatively (median follow-up, 35 months). The overall and disease-free (1-year, 3-year, and 5-year) survival rates were 97, 90, and 75 percent and 90, 59, and 46 percent, respectively. In univariate analysis, younger group (<50 years, n = 9, P = 0.033) and high-grade leiomyosarcoma (P = 0.043) showed poorer prognosis in the disease-free survival curve. In the multivariate Cox model, gender, tumor size, tumor location, and operation type did not significantly affect disease-free survival, whereas histologic grade (P = 0.037) and age divided by a level of 50 years (P = 0.009) were shown to be independent factors. There was a strong trend toward higher local recurrence rate for the wide local excision group than for the radical resection group (55 vs. 24 percent, P = 0.067) despite the wide local excision group being composed of smaller tumors (5.1 vs. 7.5 cm, P = 0.069). There was no difference in the incidence of distant metastasis between the two groups with different operation types. The metastasis rates of the wide local excision and radical resection groups were 27 and 38 percent, respectively.

CONCLUSION

A younger age (<50 years) and a high histologic grade of tumor were the two most significant poor prognostic factors for rectal leiomyosarcoma. Radical resection may be superior to wide local excision in the prevention of local recurrence but not distant metastasis.

A comprehensive neurobehavioral and neurophysiological study for low level lead-exposed workers

A comprehensive neurobehavioral and neurophysiological study was performed to evaluate the adverse effect of low level lead-exposure, and to compare the sensibility, easiness of the test methods utilized. The tests were: WHO recommended Neurobehavioral Core Test Battery (NCTB), Autonomic Nouvers System Function (ANS) Test Battery, Brain Electricity Active Mapping (BEAM), and Nerve Conduction Velocity. 44 lead-exposed workers were selected, with 34 age, education degree, family economic level, smoking and drinking matched referents.

RESULT

The mean blood lead concentration of lead-exposed workers was 1.3870 mumol/L, whereas that of referents was 0.6080 mumol/L, the difference was very significant. The negative Profile of Mood State (POMS) score of lead-expose workers was higher than that of referents, whereas the positive POMS score of the referents was higher than that of lead-exposed group, with a covariance analysis. The lead-exposure affected some NCTB test items, such as simple reaction time (SRT), digital symbol (DSY), correct dots (PAC) and total dots (PA). The heart-rate response to Valsalva manoeuvre (HR-V), heart-rate response to deep breathing (HR-DB), and blood-pressure response to immediate standing (BP-IS) were lowered in lead-exposed workers significantly. Some abnormal brain electric waves (dominant beta frequency, semetry-diffuse abnormal and non semetry-diffuse abnormal wave distribution, dominant low wave amplitude) appeared in lead-exposed workers. Left ulnar nerve maximal conduction velocity was significantly lowered in lead-exposed group.

CONCLUSION

The NCTB (including POMS), and ANS function test should be the regular screening battery for low level lead-exposed workers. The threshold blood lead concentration for health surveillance should be 30 micrograms/dL, or 1.4 mumol/L.

Systemic infusion of naloxone reduces degeneration of rat substantia nigral dopaminergic neurons induced by intranigral injection of lipopolysaccharide

A massive degeneration of dopamine-containing neurons in the substantia nigra (SN) in the midbrain is characteristic of Parkinson's disease. Inflammation in the brain has long been speculated to play a role in the pathogenesis of this neurological disorder. Recently, we reported that treatment of primary rat mesencephalic mixed neuron-glia cultures with lipopolysaccharide (LPS) led to the activation of microglia, resident immune cells of the brain, and subsequent death of dopaminergic neurons. The LPS-induced degeneration of dopaminergic neurons was significantly attenuated by the opiate receptor antagonist (-)-naloxone and its inactive isomer (+)-naloxone, with equal potency, through an inhibition of microglial activation and their production of neurotoxic factors. In this study, injection of LPS into the rat SN led to the activation of microglia and degeneration of dopaminergic neurons: microglial activation was observed as early as 6 h and loss of dopaminergic neurons was detected 3 days after the LPS injection. Furthermore, the LPS-induced loss of dopaminergic neurons in the SN was time- and LPS concentration-dependent. Systemic infusion of either (-)-naloxone or (+)-naloxone inhibited the LPS-induced activation of microglia and significantly reduced the LPS-induced loss of dopaminergic neurons in the SN. These in vivo results combined with our cell culture observations confirmed that naloxone protects dopaminergic neurons against inflammation-mediated degeneration through inhibition of microglial activation and suggest that naloxone would have therapeutic efficacy in the treatment of inflammation-related neurological disorders. In addition, the inflammation-mediated degeneration of dopaminergic neurons in the rat SN resulting from the targeted injection of LPS may serve as a useful model to gain further insights into the pathogenesis of Parkinson's disease.

Expression of the TGF-beta receptor gene and sensitivity to growth inhibition following polyamine depletion

Our previous studies have shown that inhibition of polyamine biosynthesis increases the sensitivity of intestinal epithelial cells to growth inhibition induced by exogenous transforming growth factor-beta (TGF-beta). This study went further to determine whether expression of the TGF-beta receptor genes is involved in this process. Studies were conducted in the IEC-6 cell line, derived from rat small intestinal crypt cells. Administration of alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase (the rate-limiting enzyme for polyamine synthesis), for 4 and 6 days depleted cellular polyamines putrescine, spermidine, and spermine in IEC-6 cells. Polyamine depletion by DFMO increased levels of the TGF-beta type I receptor (TGF-betaRI) mRNA and protein but had no effect on the TGF-beta type II receptor expression. The induced TGF-betaRI expression after polyamine depletion was associated with an increased sensitivity to growth inhibition induced by exogenous TGF-beta but not by somatostatin. Extracellular matrix laminin inhibited IEC-6 cell growth without affecting the TGF-beta receptor expression. Laminin consistently failed to induce the sensitivity of TGF-beta-mediated growth inhibition. In addition, decreasing TGF-betaRI expression by treatment with retinoic acid not only decreased TGF-beta-mediated growth inhibition in normal cells but also prevented the increased sensitivity to exogenous TGF-beta in polyamine-deficient cells. These results indicate that 1) depletion of cellular polyamines by DFMO increases expression of the TGF-betaRI gene and 2) increased TGF-betaRI expression plays an important role in the process through which polyamine depletion sensitizes intestinal epithelial cells to growth inhibition induced by TGF-beta.

Subtotal colectomy for colonic inertia

The aim of this study was to assess the outcome of subtotal colectomy for colonic inertia (idiopathic slow transit constipation) that was resistant to laxative treatment. Twenty-four patients, 19 women and 5 men, with a mean age of 37 years, underwent subtotal colectomy with ileorectal or ascendo-rectal anastomosis. All patients were available for follow-up, with a mean follow-up of 23 months. Bowel frequency was significantly increased from 1.4+/-0.9 times per week to 22.8+/-9 times per week (average 3.2/day) after surgery (P <0.0001). The incidence of abdominal pain was decreased from 75% to 17%, as well as the severity (P <0.0001). Two patients who underwent ascendo-rectal anastomosis developed recurrent constipation. Two patients used antidiarrheal medication regularly. There was no major postoperative morbidity. Five patients were re-admitted due to small bowel obstruction; four received successful conservative management, and one required enterolysis. 'Excellent' or 'good' outcomes were reported by 21 patients (87.5%). Subtotal colectomy with ileorectal anastomosis produces satisfactory results in the majority of patients with proven colonic inertia.

RB-dependent S-phase response to DNA damage

The retinoblastoma tumor suppressor protein (RB) is a potent inhibitor of cell proliferation. RB is expressed throughout the cell cycle, but its antiproliferative activity is neutralized by phosphorylation during the G(1)/S transition. RB plays an essential role in the G(1) arrest induced by a variety of growth inhibitory signals. In this report, RB is shown to also be required for an intra-S-phase response to DNA damage. Treatment with cisplatin, etoposide, or mitomycin C inhibited S-phase progression in Rb(+/+) but not in Rb(-/-) mouse embryo fibroblasts. Dephosphorylation of RB in S-phase cells temporally preceded the inhibition of DNA synthesis. This S-phase dephosphorylation of RB and subsequent inhibition of DNA replication was observed in p21(Cip1)-deficient cells. The induction of the RB-dependent intra-S-phase arrest persisted for days and correlated with a protection against DNA damage-induced cell death. These results demonstrate that RB plays a protective role in response to genotoxic stress by inhibiting cell cycle progression in G(1) and in S phase.

A comparison between acute exposures to ethanol and acetaldehyde on neurotoxicity, nitric oxide production and NMDA-induced excitotoxicity in primary cultures of cortical neurons

Chronic exposure of primary neuronal cultures to ethanol has been shown to potentiate N-methyl-D-aspartate (NMDA) receptor-mediated processes, such as nitric oxide (NO) formation and excitotoxicity. In the present study, we compared the effects of acute ethanol and acetaldehyde on NMDA receptor-mediated excitotoxicity and NO production in primary cultures of rat cortical neurons. The delayed cell death induced by NMDA (300 mM, 25 min) was evaluated by morphological examination and by measuring the release of the cytotoxic indicator, lactate dehydrogenase, in the culture media 24 hours after the NMDA exposure. The accumulation of nitrite, as an index of NO production, was also measured 24 hours after NMDA treatment. NMDA caused a dose-dependent cell death and nitrite accumulation, both effects were blocked by pretreatment of MK-801 (100 microM). Acute exposure to ethanol (1-1000 mM) or acetaldehyde (0.1-1 mM) for 35 minutes did not affect neuronal viability in the following 24-hr period. However, acute exposure to acetaldehyde (> or =10 mM) was neurotoxic. Neither ethanol nor acetaldehyde changed basal nitrite levels in the culture media. Acute ethanol (50-400 mM, 10 min) given before the NMDA treatment (25 min) resulted in a concentration-dependent suppression of the delayed cell death. The NMDA-induced NO production was, however, not affected by ethanol. Neither the NMDA excitotoxicity nor NO production was affected by acute ethanol given after NMDA treatment. Acute acetaldehyde (0.01-0.5 mM, 10 min) given before or after NMDA treatment had no effect on delayed NMDA neurotoxicity and NO production. Our data suggest that acute exposure to ethanol is not neurotoxic and is even protective against delayed NMDA-excitotoxicity when given before but not after NMDA treatment. Neither NO nor metabolism of ethanol to acetaldehyde is required for ethanol-mediated suppression of NMDA excititoxicity. Acetaldehyde, on the other hand, is toxic by itself at low concentrations (> or =10 mM). Furthermore, acute exposure to non-toxic concentrations of acetaldehyde could not protect cortical neurons against NMDA-induced excitotoxicity.

Uroguanylin treatment suppresses polyp formation in the Apc(Min/+) mouse and induces apoptosis in human colon adenocarcinoma cells via cyclic GMP

The enteric peptides, guanylin and uroguanylin, are local regulators of intestinal secretion by activation of receptor-guanylate cyclase (R-GC) signaling molecules that produce cyclic GMP (cGMP) and stimulate the cystic fibrosis transmembrane conductance regulator-dependent secretion of Cl- and HCO3-. Our experiments demonstrate that mRNA transcripts for guanylin and uroguanylin are markedly reduced in colon polyps and adenocarcinomas. In contrast, a specific uroguanylin-R-GC, R-GCC, is expressed in polyps and adenocarcinomas at levels comparable with normal colon mucosa. Activation of R-GCC by uroguanylin in vitro inhibits the proliferation of T84 colon cells and elicits profound apoptosis in human colon cancer cells, T84. Therefore, down-regulation of gene expression and loss of the peptides may interfere with renewal and/or removal of the epithelial cells resulting in the formation of polyps, which can progress to malignant cancers of the colon and rectum. Oral replacement therapy with human uroguanylin was used to evaluate its effects on the formation of intestinal polyps in the Min/+ mouse model for colorectal cancer. Uroguanylin significantly reduces the number of polyps found in the intestine of Min/+ mice by approximately 50% of control. Our findings suggest that uroguanylin and guanylin regulate the turnover of epithelial cells within the intestinal mucosa via activation of a cGMP signaling mechanism that elicits apoptosis of target enterocytes. The intestinal R-GC signaling molecules for guanylin regulatory peptides are promising targets for prevention and/or therapeutic treatment of intestinal polyps and cancers by oral administration of human uroguanylin.

Mechanisms of all-trans retinoic acid-induced differentiation of acute promyelocytic leukemia cells

Retinoic acids (RA) play a key role in myeloid differentiation through their agonistic nuclear receptors (RAR alpha/RXR) to modulate the expression of target genes. In acute promyelocytic leukemia (APL) cells with rearrangement of retinoic acid receptor a (RAR alpha) (including: PML-RAR alpha, PLZF-RAR alpha, NPM-RAR alpha, NuMA- RAR alpha or STAT5b-RAR alpha) as a result of chromosomal translocations, the RA signal pathway is disrupted and myeloid differentiation is arrested at the promyelocytic stage. Pharmacologic dosage of all-trans retinoic acid (ATRA) directly modulates PML-RAR alpha and its interaction with the nuclear receptor co-repressor complex, which restores the wild-type RAR alpha/RXR regulatory pathway and induces the transcriptional expression of downstream genes. Analysing gene expression profiles in APL cells before and after ATRA treatment represents a useful approach to identify genes whose functions are involved in this new cancer treatment. A chronologically well coordinated modulation of ATRA-regulated genes has thus been revealed which seems to constitute a balanced functional network underlying decreased cellular proliferation, initiation and progression of maturation, and maintenance of cell survival before terminal differentiation.

Primary colorectal lymphoma

PURPOSE

The purpose of this study was to review the clinical presentation and characteristics of primary colorectal lymphoma, analyze the prognostic factors, and assess the results of treatment with adjuvant chemotherapy.

METHODS

We identified 37 cases at our institution between 1980 and 1996. They comprised 0.48 percent of all cases of colon malignancies (37/7,658) during this period. The following clinical information was obtained: age, gender, signs and symptoms, tumor site, tumor size, histology grade, pathology, and adjuvant chemotherapy.

RESULTS

The most common presenting signs and symptoms were abdominal pain (62 percent), abdominal mass (54 percent), and weight loss (43 percent). The most frequent site of involvement was the cecum (45 percent). Histologically, 29 (78 percent) were classified as high-grade, and 8 (22 percent) as intermediate-grade-to-low-grade lymphoma. Nine (24.3 percent) of the cases were Stage EI, 23 (62.2 percent) were Stage EII, and 5 (13.5 percent) were Stage EIV. Twenty-one (57 percent) cases received adjuvant chemotherapy. The five-year survival rate was 33 percent for all patients and 39 percent for patients treated with combination chemotherapy. Overall median survival time was 24 months and 36 months for those with adjuvant chemotherapy. Only histology grade, among the factors examined, was a significant prognostic factor for survival. The mean survival time of the patients with Stage II disease who received chemotherapy was 117.4 months, and it was 47.9 months for the patients with Stage II disease who did not received chemotherapy.

CONCLUSIONS

In our retrospective study high-grade lymphoma was the only significant adverse prognostic factor for survival. Receiving adjuvant chemotherapy significantly improved survival in patients with Stage II disease. Patients with diffuse large-cell type had better survival than patients with small noncleaved-cell type in Stage II high-grade lymphoma.

Chronic methamphetamine exposure decreases high affinity uptake function in norepinephrine afferents in the cerebellar cortex: an electrophysiological and electrochemical study

It has been reported that chronic methamphetamine (MA) treatment decreases monoamine release in different brain regions. However, the clearance of norepinephrine (NE) after chronic MA intake is not clear. In the present study, we administered MA to Sprague-Dawley rats for 1 month. The animals were later anesthetized with urethane for electrophysiological recording. Previous studies have indicated that gamma-aminobutyric acid (GABA)-induced electrophysiological responses are enhanced by norepinephrine (NE) acting via postsynaptic beta-adrenergic receptors. We found that local application of the NE high affinity uptake inhibitor desmethylimipramine (DMI) significantly potentiated GABA-induced electrophysiological depressions in cerebellar Purkinje neurons in control rats. In contrast, DMI did not augment GABA responses in rats chronically treated with MA for 1 month, or in rats withdrawn from MA for 7-14 days after a 1-month MA treatment. To further examine if DMI-induced GABA modulation is altered by post- or pre-synaptic mechanisms in chronic MA-treated rats, we examined the electrophysiological interaction of GABA and isoproterenol (ISO), a postsynaptic beta-adrenergic receptor agonist, in Purkinje neurons. We found that GABA-induced inhibition is potentiated by local application of ISO in both control and chronic MA rats, suggesting that the reduction in DMI/GABA interactions is probably not mediated through post-synaptic noradrenergic mechanisms. Presynaptic NE clearance was further examined using in vivo chronoamperometric methods. Extracellular NE levels in the cerebellar cortex were measured using Nafion-coated carbon fiber sensors. We found that local application of DMI inhibited NE clearance in control rats, but not in chronic MA animals, suggesting that presynaptic NE clearance is reduced after chronic MA treatment. In addition, NE levels in cerebellar tissue were measured using HPLC-ECD. The NE concentration was significantly decreased in chronic MA rats. Taken together, our data suggest that regulation of uptake by DMI at central noradrenergic nerve terminals is abnormal after chronic MA exposure.

Establishment of irreversible growth arrest in myogenic differentiation requires the RB LXCXE-binding function

The crystal structure of the A-B domain of RB has defined the binding pocket for the LXCXE peptide motif. Using the crystal structure as a guide, we have inactivated the LXCXE-binding pocket by replacing N757 with Phe [to obtain RB(N757F)]. RB(N757F) does not bind to viral oncoproteins but retains the ability to bind and inhibit E2F. RB(N757F) is less effective than the wild-type RB [RB(WT)] in repressing E2F-regulated transcription, and its repression activity is not affected by trichostatin A, an inhibitor of histone deacetylases. However, RB(N757F) is as effective as RB(WT) in suppressing cell growth. Interestingly, RB(N757F) cannot establish an irreversible growth arrest in differentiated myocytes. Differentiated myocytes with RB(WT) become refractory to serum. By contrast, differentiated myocytes with RB(N757F) undergo DNA synthesis and phosphorylate RB(N757F) in response to serum, despite a high level of p21Cip1 expression. Mutation of the phosphorylation sites in RB(N757F) rescued its defect and allowed myocytes to permanently withdraw from the cell cycle. These results demonstrate that it is possible to inactivate the LXCXE-binding pocket without compromising the overall integrity of RB. Moreover, the LXCXE-binding pocket is dispensable for the intrinsic growth suppression function of RB. However, the LXCXE-binding function is essential for RB to establish the serum-refractory state in differentiated myocytes.

Constitutive expression of the Vi polysaccharide capsular antigen in attenuated Salmonella enterica serovar typhi oral vaccine strain CVD 909

Live oral Ty21a and parenteral Vi polysaccharide vaccines provide significant protection against typhoid fever, albeit by distinct immune mechanisms. Vi stimulates serum immunoglobulin G Vi antibodies, whereas Ty21a, which does not express Vi, elicits humoral and cell-mediated immune responses other than Vi antibodies. Protection may be enhanced if serum Vi antibody as well as cell-mediated and humoral responses can be stimulated. Disappointingly, several new attenuated Salmonella enterica serovar Typhi oral vaccines (e.g., CVD 908-htrA and Ty800) that elicit serum O and H antibody and cell-mediated responses following a single dose do not stimulate serum Vi antibody. Vi expression is regulated in response to environmental signals such as osmolarity by controlling the transcription of tviA in the viaB locus. To investigate if Vi antibodies can be stimulated if Vi expression is rendered constitutive, we replaced P(tviA) in serovar Typhi vaccine CVD 908-htrA with the constitutive promoter P(tac), resulting in CVD 909. CVD 909 expresses Vi even under high-osmolarity conditions and is less invasive for Henle 407 cells. In mice immunized with a single intranasal dose, CVD 909 was more immunogenic than CVD 908-htrA in eliciting serum Vi antibodies (geometric mean titer of 160 versus 49, P = 0.0007), whereas O antibody responses were virtually identical (geometric mean titer of 87 versus 80). In mice challenged intraperitoneally with wild-type serovar Typhi 4 weeks after a single intranasal immunization, the mortality of those immunized with CVD 909 (3 of 8) was significantly lower than that of control mice (10 of 10, P = 0.043) or mice given CVD 908-htrA (9 of 10, P = 0.0065).

Recurrent infections and chronic colonization by an Escherichia coli clone in the respiratory tract of a patient with severe cystic bronchiectasis

A 39-year-old woman with cystic bronchiectasis had repeated pulmonary infections from 1996 to 1999, and 6 of a total of 28 isolates of Escherichia coli from sputum specimens were studied. Their identical antibiotype and randomly amplified polymorphic DNA patterns indicated a single clone of E. coli, which persistently colonized the respiratory tract, causing recurrent infections.

Fluorescence in-situ hybridization analysis of chromosomal constitution in spermatozoa from a mosaic 47,XYY/46,XY male

Sex-chromosome mosaicism in spermatozoa from a mosaic 47,XYY[20%]/46, XY[80%] male with fertility problems was assessed using triple-probe fluorescence in-situ hybridization (FISH) studies. Chromosome-specific probes for X, Y and 18 were used, and the possible outcomes were deduced. In normal haploid spermatozoa of the patient and a normal 46,XY male control, the X:Y ratio was close to 1:1. There was a significant difference in the total incidence of karyotypically abnormal spermatozoa between the patient and the 46, XY male control (2.31% versus 1.46%, P < 0.0001). The incidence of some types of disomic spermatozoa X+Y+18 (24,XY) and X+18+18 (24,X, +18), or diploid X+Y+18+18 (46,XY) spermatozoa was significantly increased in the patient's semen sample. There was, however, no significant difference in the incidence of disomic Y+Y+18 (24,YY) spermatozoa. Because the majority of the patient's spermatozoa was karyotypically normal, the aetiology of his fertility problems was unclear. These results add to the growing body of information regarding chromosome abnormalities in spermatozoa from men who are mosaic for sex chromosome abnormalities. In these men, FISH analysis of spermatozoa may be warranted to determine the relative percentages of abnormal cells, and to determine if in-vitro fertilization with preimplantation genetic diagnosis may increase the likelihood of a successful pregnancy.

[Model of diffuse axonal injury and focal brain injury in rats]

OBJECTIVE

To establish a rather ideal experimental brain injury model in rats, in which diffuse axonal injury(DAI) and focal brain contusion were made concurrently.

METHODS

The pathophysiological changes were monitored, and the histological changes were observed under naked eye, microscope and electric microscope.

RESULTS

1. The mortality in the group suffering from DAI with focal contusion(Group A) was much higher than that in DAI(Group B) and sham group(Group C); 2. The time of post-injury primary coma in Group A [(5.19 +/- 0.49) h] was longer than that in Group B [(2.75 +/- 0.16) h] and Group C [(2.77 +/- 0.20) h] significantly(P < 0.01); 3. Immunohistological examination showed that the diffuse axonal injury could be seen in several parts of the brain(subcortical, corpus callosum and brainstem) in Group A; 4. We observed in Group A under electric microscope that the axons were swollen and degenerated fragmently, neurofilaments ranged disorderly and there was vacuolation.

CONCLUSION

The model is cheap, simple and can be easily repeated. Furthermore it can be used to research the changes of pathophysiology, histology and moleculobiochemistry of head injury in human beings.

p38 and extracellular signal-regulated kinases regulate the myogenic program at multiple steps

The extracellular signals which regulate the myogenic program are transduced to the nucleus by mitogen-activated protein kinases (MAPKs). We have investigated the role of two MAPKs, p38 and extracellular signal-regulated kinase (ERK), whose activities undergo significant changes during muscle differentiation. p38 is rapidly activated in myocytes induced to differentiate. This activation differs from those triggered by stress and cytokines, because it is not linked to Jun-N-terminal kinase stimulation and is maintained during the whole process of myotube formation. Moreover, p38 activation is independent of a parallel promyogenic pathway stimulated by insulin-like growth factor 1. Inhibition of p38 prevents the differentiation program in myogenic cell lines and human primary myocytes. Conversely, deliberate activation of endogenous p38 stimulates muscle differentiation even in the presence of antimyogenic cues. Much evidence indicates that p38 is an activator of MyoD: (i) p38 kinase activity is required for the expression of MyoD-responsive genes, (ii) enforced induction of p38 stimulates the transcriptional activity of a Gal4-MyoD fusion protein and allows efficient activation of chromatin-integrated reporters by MyoD, and (iii) MyoD-dependent myogenic conversion is reduced in mouse embryonic fibroblasts derived from p38alpha(-/-) embryos. Activation of p38 also enhances the transcriptional activities of myocyte enhancer binding factor 2A (MEF2A) and MEF2C by direct phosphorylation. With MEF2C, selective phosphorylation of one residue (Thr293) is a tissue-specific activating signal in differentiating myocytes. Finally, ERK shows a biphasic activation profile, with peaks of activity in undifferentiated myoblasts and postmitotic myotubes. Importantly, activation of ERK is inhibitory toward myogenic transcription in myoblasts but contributes to the activation of myogenic transcription and regulates postmitotic responses (i.e., hypertrophic growth) in myotubes.

IGF-I receptor signaling in a prostatic cancer cell line with a PTEN mutation

LNCaP prostatic cancer cells are characterized by having a PTEN mutation, low levels of type 1 insulin-like growth factor receptor (IGF-IR) and no IRS-1, one of the major substrates of the IGF-IR. The absence of IRS-1, an activator of PI3-kinase, is compensated in these cells by the mutation in PTEN, an inhibitor of PI3-kinase. However, IGF-IR signaling in the absence of IRS-1 can cause cell differentiation and growth arrest. We hypothesized that these three characteristics may not be unrelated, specifically that, together, they may favor the metastatic spread of prostatic cancer cells without decreasing their growth potential. In support of this hypothesis, we report here that: (1) IRS-1 expression increases cell adhesion and decreases cell motility; (2) over-expression of the IGF-IR, in the absence of IRS-1, causes growth arrest and (3) a combination of IGF-IR and IRS-1 restores the transformed phenotype of LNCaP cells. These findings suggest a mechanism by which prostatic cancer cells can achieve metastatic potential without interfering with their growth potential. Oncogene (2000).

The p53/p63/p73 family of transcription factors: overlapping and distinct functions

The p53 gene is the most frequently mutated gene in human cancer. The identification of two homologues, p63 and p73, revealed that p53 is a member of a family of related transcription factors. Given that they share amino acid sequence identity reaching 63% in the DNA-binding domain, p53, p63 and p73 should have redundant functions in the regulation of gene expression. Indeed, p73 can activate p53-regulated genes and suppress growth or induce apoptosis. Moreover, p53 and p73 are both induced by DNA damage - albeit through distinct mechanisms. Other evidence, however, suggests that p63 and p73 are important for regulation of normal development. An extended C-terminal region, not found in p53, is alternatively spliced in p63 and p73. Within this C-terminal extension is a sterile α motif (SAM) previously found in other proteins that regulate development. The p63-deficient mice showed developmental abnormalities. Interestingly, the human p63 gene is mutated in children who have the disease Ectrodactyly, Ectodermal dysplasia and facial Clefts (EEC) syndrome, and the disease phenotype is similar to the one of p63-deficient mice. The p63 and p73 genes are rarely mutated in human cancer, although p73 loss is observed in neuroblastoma and a subtype of T-cell lymphoma. p53, p63 and p73 appear to have overlapping and distinct functions: p53 regulates the stress response to suppress tumors; p63 is essential for ectoderm development; and p73 might regulate both the stress response and development. Because p53 and p73 are linked to different upstream pathways, this family of transcription factors might regulate a common set of genes in response to different extracellular signals and developmental cues.

Interaction of the N-methyl-D-aspartic acid receptor NR2D subunit with the c-Abl tyrosine kinase

The COOH-terminal domain of the NR2D subunit of the NMDA receptor contains proline-rich regions that show striking homology to sequences known to bind to Src homology 3 (SH3) domains. To determine whether the proline-rich region of the NR2D subunit interacts with specific SH3 domains, in vitro SH3 domain binding assays were performed. A proline-rich fragment of the NR2D subunit (2D(866-1064)) bound to the Abl SH3 domain but not to the SH3 domains from Src, Fyn, Grb2, GAP, or phospholipase C-gamma (PLCgamma). Co-immunoprecipitation of NR2D with Abl suggests stable association of NR2D and Abl in transfected cells. The SH3 domain plays an important role in the negative regulation of Abl kinase activity. To determine whether the interaction of NR2D with the Abl SH3 domain alters Abl kinase activity, Abl was expressed alone or with NR2D in 293T cells. Autophosphorylation of Abl was readily observed when Abl was expressed alone. However, co-expression of Abl with 2D(866-1064) or full-length NR2D inhibited autophosphorylation. 2D(866-1064) did not inhibit DeltaSH3 Abl, indicating a requirement for the Abl SH3 domain in the inhibitory effect. Similarly, 2D(866-1064) did not inhibit the catalytic activity of Abl-PP, which contains two point mutations in the SH2-kinase linker domain that release the negative kinase regulation by the SH3 domain. In contrast, the full-length NR2D subunit partially inhibited the autokinase activity of both DeltaSH3 Abl and Abl-PP, suggesting that NR2D and Abl may interact at multiple sites. Taken together, the data in this report provide the first evidence for a novel inhibitory interaction between the NR2D subunit of the NMDA receptor and the Abl tyrosine kinase.

The central mechanism of hypothalamic-pituitary-adrenocortical system hyperfunction in depressed patients

While hypercortisolemia is commonly observed in depression, exactly where in the hypothalamic-pituitary-adrenocortical (H-P-A) axis this dysfunction arises remains undefined. In attempting to distinguish between central or peripheral locus of dysfunction, we studied in 12 patients (10 females, two males) with primary major depression and eight age-matched controls (six females, two males) in their adrenal cortisol response to infused adrenocorticotropic hormone (ACTH) (cosyntropin 0.05 microg/kg bodyweight) while endogenous ACTH was suppressed with 1 mg of dexamethasone. Compared with the control group, pre-dexamethasone plasma baseline cortisol level was significantly higher in depressed patients while ACTH level remained normal. Post-dexamethasone responses of both hormones were greatly non-suppressed in the depressed group. Exogenous cosyntropin-elicited rise in plasma cortisol was significantly lower in depressed patients while the ACTH response was not significantly different. These findings suggest that an adrenal cortisol response to ACTH was significantly decreased during depression as compared with normals in Chinese depressed patients. Therefore, the central mechanism of hyperfunctioning H-P-A axis causing hypercortisolemia should be emphasized.

Genomic organization of the UGT2b gene cluster on human chromosome 4q13

The UDP-glucuronosyltransferases (UGTs) comprise a large family of proteins capable of detoxifying a wide variety of both endogenous and exogenous substrates. The primary function of this gene superfamily is to catalyze the glycosylation of substrates such as biogenic amines, steroids, bile acids, phenolic compounds and various other pharmacologically relevant compounds, including numerous carcinogens, toxic environmental pollutants and prescription drugs. This conjugation increases the solubility of these compounds, allowing them to be excreted more readily through hepatic or renal mechanisms. This paper describes the genomic characterization and chromosomal localization of three UGT2B genes which together comprise part of a large cluster of related sequences, including pseudogenes found on human chromosome 4q13. A genomic map spanning approximately 500-1000 kb of this region reveals the presence of three previously described UGT2B genes, at least two previously uncharacterized pseudogenes and a significant number of remnant gene fragments and places UGT2B4 between UGT2B7 and UGT2B15. Additionally, access to a large reference DNA bank allowed us to calculate allele frequencies for two UGT2B SNPs: D85R in UGT2B15 and Q458D in UGT2B4 amongst 803 unrelated individuals representing five ethnic populations. The data presented here suggest a recent evolutionary history of gene duplication, mutation and rearrangement. Furthermore, they suggest that a re-evaluation of the current description of the UGT2B gene family with respect to the number of specific genes, degree of allelic diversity and molecular evolution may be necessary.