Cloning and characterization of PHIP, a novel insulin receptor substrate-1 pleckstrin homology domain interacting protein

Insulin receptor substrate-1 (IRS-1) protein is a major substrate of the insulin receptor tyrosine kinase and is essential for transducing many of the biological effects of insulin including mitogenesis, gene expression, and glucose transport. The N terminus of IRS-1 contains a pleckstrin homology (PH) domain that is critical for recognition and subsequent phosphorylation of IRS-1 by the activated insulin receptor. Here we report the isolation of a novel protein, PHIP (PH-interacting protein), which selectively binds to the PH domain of IRS-1 in vitro and stably associates with IRS-1 in vivo. Importantly, mutants of the IRS-1 PH domain that disrupt the PH fold fail to bind to PHIP. Anti-phosphotyrosine immunoblots of PHIP revealed no discernible insulin receptor-regulated phosphorylation, suggesting that PHIP is not itself a substrate of the insulin receptor. In contrast to full-length PHIP, overexpression of the PH-binding region of PHIP has a pronounced inhibitory effect on insulin-induced IRS-1 tyrosine phosphorylation levels. Furthermore, expression of this dominant-negative PHIP mutant leads to a marked attenuation of insulin-stimulated mitogen-activated protein kinase activity. We conclude that PHIP represents a novel protein ligand of the IRS-1 PH domain that may serve to link IRS-1 to the insulin receptor.

Depletion of a gamma delta T cell subset can increase host resistance to a bacterial infection

Gammadelta T lymphocytes have been shown to regulate immune responses in diverse experimental systems. Because distinct gammadelta T cell subsets, as defined by the usage of certain TCR V genes, preferentially respond in various diseases and disease models, we have hypothesized that the various gammadelta T cell subsets carry out different functions. To test this, we compared one particular gammadelta T cell subset, the Vgamma1(+) subset, which represents a major gammadelta T cell type in the lymphoid organs and blood of mice, to other subsets and to gammadelta T cells as a whole. Using Listeria monocytogenes infection as an infectious disease model, we found that bacterial containment improves in mice depleted of Vgamma1(+) gammadelta T cells, albeit mice lacking all gammadelta T cells are instead impaired in their ability to control Listeria expansion. Our findings indicate that Vgamma1(+) gammadelta T cells reduce the ability of the innate immune system to destroy Listeria, even though other gammadelta T cells as a whole promote clearance of this pathogen.

Coupling estimated effects of QTLs for physiological traits to a crop growth model: predicting yield variation among recombinant inbred lines in barley

Advances in the use of molecular markers to elucidate the inheritance of quantitative traits enable the integration of genetic information on physiological traits into crop growth models. The objective of this study was to assess the ability of a crop growth model with QTL-based estimates of physiological input parameters to predict the yield of recombinant inbred lines (RILs) of barley. The model used predicts yield as spike biomass accumulated over the post-flowering period. We describe a two-stage procedure for predicting trait values from estimated additive and epistatic effects of QTLs. Values of physiological traits estimated by that procedure or measured in the field were used as input to the crop growth model. The output values (yield and shoot biomass) from the growth model using these two types of input values were highly correlated, indicating that QTL information can successfully replace measured input parameters. With the current crop growth model, however, both types of input values often resulted in large discrepancies between observed and predicted values. Improvement of performance may be achieved by incorporating physiological processes not yet included in the model. The prospects of using QTL-based predictions of model-input traits to identify new, high yielding barley genotypes are discussed.

[The application study of mimic operation with 3D-cut in maxillofacial bone tumor]

OBJECTIVE

To study the feasibility of guiding operation planning and complication prevention.

METHODS

Ten patients suffer from Maxillofacial bone tumour were examined with spiral CT. Firstly, to get three-dimensional reconstructive image of tumour and other tissues. Secondly, use 3D-cut software to cut off every layer of normal tissue and tumour mass. Lastly, to compare virtual operation with mimic operation in virtual operation process.

RESULTS

Three-dimensional mimic operation clearly displays the relationship between tumor and surrounding tissues, reflect the actual operation condition.

CONCLUSIONS

It is very useful designing operation program and predicting the potential complications before the actual operation.

Promotion of growth and apoptosis in c-myc nullizygous fibroblasts by other members of the myc oncoprotein family

c-myc nullizygous fibroblasts (KO cells) were used to compare the abilities of c-myc, N-myc and L-myc oncoproteins to accelerate growth, promote apoptosis, revert morphology, and regulate the expression of previously described c-myc target genes. All three myc oncoproteins were expressed following retroviral transduction of KO cells. The proteins all enhanced the growth rate of KO cells and significantly shortened the cell cycle transition time. They also accelerated apoptosis following serum deprivation, reverted the abnormal KO cell morphology, and modulated the expression of previously described c-myc target genes. In most cases, L-myc was equivalent to c-myc and N-myc in restoring all of the c-myc-dependent activities. These findings contrast with the previously reported weak transforming and transactivating properties of L-myc. Myc oncoproteins may thus impart both highly similar as well as dissimilar signals to the cells in which they are expressed.

[A case-control study on the relationship between abnormal homocysteine metabolism and essential hypertension]

OBJECTIVE

To examine the relationship between abnormal homocysteine metabolism and essential hypertension in a Chinese population, a community-based case-control study was conducted.

METHODS

127 essential hypertensive patients aged 35 to 75 were randomly selected from a community. Another 170 control subjects with blood pressure < 140/90 mmHg were selected from the same community. Serum homocysteine was determined using HPLC. Folate and vitamin B(12) were measured by radioimmunoassay. MTHFR genotypes were identified by PCR and restriction fragment length polymorphism analysis with Hinf I digestion.

RESULTS

After adjusting for age and sex, the mean homocysteine level was 10.56 micromol/L for hypertensive patients and 10.34 micromol/L for controls (F = 0.234, P = 0.63). No association between either SBP or DBP and Hcy concentration was found in subjects without anti-hypertensive medications. The prevalence of homozygousity for thermolabile MTHFR variant for this population was 13.1%, and the mutant allele frequency was 38.7%. There was no significant difference on genotype distributions and the mutant allele frequency for the two studied groups. However, the concentrations of folate and B(12) for the hypertensive subjects were generally higher than the controls.

CONCLUSIONS

The present study did not discover that the elevation of Hcy levels or MTHFR mutation were independent risk factors for essential hypertension. The higher folate and B(12) in the hypertensive subjects might contribute to a lower risk.

Oncogenic base substitution mutations in circulating leukocytes of normal individuals

The background frequency of mutations in human tissues is an important issue in cancer susceptibility and genotoxic exposure determinations. Here we report the detection of rare mutant leukocytes containing oncogenic base substitutions of the Harvey-ras, N-ras, and p53 genes by the Needle-in-a-Haystack mutation assay with a sensitivity of one cell in a million. Altogether, we detected and identified 17 independent mutations of 66 separate base site analyses of peripheral blood specimens obtained from 19 apparently normal individuals. Two individuals harbored a substantially increased frequency of mutant cells, representing 9 of the 17 independent mutations found. These results suggest that up to 1 in 10 normal individuals may harbor a significant frequency of oncogenic mutations in circulating leukocytes.

[Effects of glycidyl methacrylate on gap junctional intercellular communication]

In order to probe into the mechanism of glycidyl methacrylate (GMA)-induced cell transformation, the effects of GMA on gap junctional intercellular communication (GJIC) in human lung, embryonic fibroblasts(HLEF) were studied by using scrape-loading and dye transfer(SLDT) technique. HLEF cells were treated with GMA at concentrations of 0.5, 2.5 and 5.0 mg/L for 12 hours and Lucifer Yellow was introduced by scrape-loading after exposure. The GJIC in exposed cells and that of control were determined directly as the diffusion extent of fluorescent dye into adjacent cells. The results indicated that GMA could inhibit the GJIC in exposed cells in a dose-dependent manner. Significantly decreased GJIC was found in 2.5 and 5.0 mg/L dose groups. It was suggested that the inhibition of GJIC might be one of the mechanisms responsible for GMA-induced cell transformation.

Casein kinase II phosphorylates lens connexin 45.6 and is involved in its degradation

Connexin (Cx) 45.6, an avian counterpart of rodent Cx50, is phosphorylated in vivo, but the sites and function of the phosphorylation have not been elucidated. Our peptide mapping experiments showed that the Ser(363) site in the carboxyl (COOH) terminus of Cx45.6 was phosphorylated and that this site is within casein kinase (CK) II consensus sequence, although showing some similarity to CKI sequence. The peptide containing Ser(363) could be phosphorylated in vitro by CKII, but not by CKI. Furthermore, CKII phosphorylated Cx45.6 in embryonic lens membrane and the fusion protein containing the COOH terminus of Cx45.6. Two-dimensional peptide mapping experiments showed that one of the Cx45.6 peptides phosphorylated in vivo migrated to the same spot as one of those phosphorylated by CKII in vitro. Furthermore, CKII activity could be detected in lens lysates. To assess the function of this phosphorylation event, exogenous wild type and mutant Cx45.6 (Ser(363) --> Ala) were expressed in lens primary cultures by retroviral infection. The mutant Cx45.6 was shown to be more stable having a longer half-life compared with wild type Cx45.6. Together, the evidence suggests that CKII is likely a kinase responsible for the Ser(363) phosphorylation, leading to the destablization and degradation of Cx45.6. The connexin degradation induced by phosphorylation has a broad functional significance in the regulation of gap junctions in vivo.

Schwann cell myelination requires timely and precise targeting of P(0) protein

This report investigated mechanisms responsible for failed Schwann cell myelination in mice that overexpress P(0) (P(0)(tg)), the major structural protein of PNS myelin. Quantitative ultrastructural immunocytochemistry established that P(0) protein was mistargeted to abaxonal, periaxonal, and mesaxon membranes in P(0)(tg) Schwann cells with arrested myelination. The extracellular leaflets of P(0)-containing mesaxon membranes were closely apposed with periodicities of compact myelin. The myelin-associated glycoprotein was appropriately sorted in the Golgi apparatus and targeted to periaxonal membranes. In adult mice, occasional Schwann cells myelinated axons possibly with the aid of endocytic removal of mistargeted P(0). These results indicate that P(0) gene multiplication causes P(0) mistargeting to mesaxon membranes, and through obligate P(0) homophilic adhesion, renders these dynamic membranes inert and halts myelination.

P(0) glycoprotein overexpression causes congenital hypomyelination of peripheral nerves

We show that normal peripheral nerve myelination depends on strict dosage of the most abundantly expressed myelin gene, myelin protein zero (Mpz). Transgenic mice containing extra copies of Mpz manifested a dose-dependent, dysmyelinating neuropathy, ranging from transient perinatal hypomyelination to arrested myelination and impaired sorting of axons by Schwann cells. Myelination was restored by breeding the transgene into the Mpz-null background, demonstrating that dysmyelination does not result from a structural alteration or Schwann cell-extrinsic effect of the transgenic P(0) glycoprotein. Mpz mRNA overexpression ranged from 30-700%, whereas an increased level of P(0) protein was detected only in nerves of low copy-number animals. Breeding experiments placed the threshold for dysmyelination between 30 and 80% Mpz overexpression. These data reveal new points in nerve development at which Schwann cells are susceptible to increased gene dosage, and suggest a novel basis for hereditary neuropathy.

Detection of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 2(PAI-2) in gingival crevicular fluid from healthy, gingivitis and periodontitis patients

BACKGROUND

The regulation of plasminogen activation is a key element in controlling proteolytic events in the extracellular matrix. Our previous studies had demonstrated that in inflamed gingival tissues, tissue-type plasminogen activator (t-PA) is significantly increased in the extracellular matrix of the connective tissue and that interleukin 1beta(IL-1beta) can up regulate the level of t-PA and plasminogen activator inhibitor-2 (PAI-2) synthesis by human gingival fibroblasts.

METHOD

In the present study, the levels of t-PA and PAI-2 in gingival crevicular fluid (GCF) were measured from healthy, gingivitis and periodontitis sites and compared before and after periodontal treatment. Crevicular fluid from106 periodontal sites in 33 patients were collected. 24 sites from 11 periodontitis patients received periodontal treatment after the first sample collection and post-treatment samples were collected 14 days after treatment. All samples were analyzed by enzyme-linked immunosorbent assay (ELISA) for t-PA and PAI-2.

RESULTS

The results showed that significantly high levels of t-PA and PAI-2 in GCF were found in the gingivitis and periodontitis sites. Periodontal treatment led to significant decreases of PAI-2, but not t-PA, after 14 days. A significant positive linear correlation was found between t-PA and PAI-2 in GCF (r=0.80, p<0.01). In the healthy group, different sites from within the same subject showed little variation of t-PA and PAI-2 in GCF. However, the gingivitis and periodontitis sites showed large variation. These results suggest a good correlation between t-PA and PAI-2 with the severity of periodontal conditions.

CONCLUSION

This study indicates that t-PA and PAI-2 may play a significant rôle in the periodontal tissue destruction and tissue remodeling and that t-PA and PAI-2 in GCF may be used as clinical markers to evaluate the periodontal diseases and assess treatment.

Species-specific detection of hydrocarbon-utilizing bacteria

Rapid detection and quantitative assessment of specific microbial species in environmental samples is desirable for monitoring changes in ecosystems and for tracking natural or introduced microbial species during bioremediation of contaminated sites. In the interests of developing rapid tests for hydrocarbon-degrading bacteria, species-specific PCR primer sets have been developed for Pseudomonas aeruginosa, Stentrophomonas (Xanthomonas) maltophilia, and Serratia marsescens. Highly variable regions of the 16S rRNA gene were used to design these primer sets. The amplification products of these primer sets have been verified and validated with hemi-nested PCR and with ligase chain reaction (LCR) techniques, and have been applied to the analyses of environmental water samples. These species-specific primer sets were also chosen to amplify in conjunction with a universal set of PCR primers chosen from highly conserved neighboring sequences in the same gene. These multiplex or competitive PCR procedures enable testing with an internal marker and/or the quantitative estimation of the relative proportion of the microbial community that any one of these species occupies. In addition, this universal PCR primer set amplified the same size amplicon from a wide spectrum of procaryotic and eucaryotic organisms and may have potential in earth biota analyses.

[Hepatic arterial infusion of 32P-radionuclide microspheres for radiation therapy of hepatocellular carcinoma]

OBJECTIVE

To investigate the efficacy of internal radiation of (32)P-glass microspheres ((32)P-GMS) in unresected hepatocellular carcinoma (HCC) via subcutaneous arterial port.

METHODS

Hepatic arterial (99)technetium-macroaggregate albumin ((99)Tc-MAA) scanning via subcutaneous arterial port was undertaken to measure lung/liver shunting ratio and tumor/liver ratio. Hepatic arterial infusion of (32)P-GMS was performed in 17 cases of HCC with a dose from 1.11 to 1.30 GBq. Twenty cases of HCC undergoing hepatic arterial chemoembolization (HACE) in the same period served as controls group.

RESULTS

There was no treatment-related death in the 17 cases. In 7 of the 17 cases, AFP level and/or tumor size decreased by 50% after treatment, with a response rate of 64.7%. The median survival time was 5.5 months, and the 3-, 6-, 9-, 12-month survival rates were 94.1%, 44.1%, 31.0%, 24.4%, respectively. The therapeutic efficacy was better than that of HACE. The survival time was significantly longer in patients with T/N ratio >or= 2 than in those with T/N < 2 (P < 0.05).

CONCLUSIONS

Hepatic arterial infusion of (32)P-GMS is an alternative treatment for unresected HCC.

[Histological studies on rinds of 18 species of Gualou]

OBJECTIVE

To make clear the histological characteristics of rinds for eighteen species of Gualou.

METHOD

Observing the cross sections and separate divide of the rinds with light microscope.

RESULT AND CONCLUSION

Of eighteen rinds of Gualou, each trichome on exocarp, wood fiber and thickness of ring of stone cell are different from one another, this distinction can be used to identify the different rinds of Gualou.

[Study on expression of apoptosis related genes in non-small cell carcinoma]

OBJECTIVE

To study the relationship between the expression of apoptosis related genes in the tissue of non-small cell lung carcinoma (NSCLC) and clinicopathology in the tumor.

METHODS

The expression of bcl-2, bax, Fas and FasL were detected with immunohistochemistry method in 45 cases of NSCLC.

RESULTS

23 (51%) cases of NSCLC were bcl-2 positive, 38 (84%) were bax positive (P < 0.01), and there was no significant correlation between the expression of bcl-2 and bax protein, but a positive relationship was found between the expression of Fas and FasL (P < 0.01). The positive rate of bcl-2 expression decreased in advanced stages of NSCLC(P < 0.05), the bax expression was lower in cases with poor cell differentiation (P < 0.05), and the FasL expression was higher in adenocarcinoma (P < 0.01). The simultaneous expression of bcl-2 and bax protein was closely correlated with TNM stages (P < 0.05), the differences of bcl-2 protein expression alone in NSCLC with cell differentiation were statistically significant (P = 0.033).

CONCLUSIONS

Both bcl-2, bax, Fas and FasL may involve in the regulation of apoptosis and may play an important role in the occurrence and progression of NSCLC.

Needle-in-a-haystack detection and identification of base substitution mutations in human tissues

Background and induced germline mutagenesis and other genotoxicity studies have been hampered by the lack of a sufficiently sensitive technique for detecting mutations in a small cluster of cells or a single cell in a tissue sample composed of millions of cells. The most frequent type of genetic alteration is intragenic. The vast majority of oncogenic mutations in human and mammalian cancer involves only single base substitutions. We have developed universally applicable techniques that not only provide the necessary sensitivity and specificity for site specific mutagenesis studies, but also identify the point mutation. The exponential amplification procedures of polymerase chain reaction (PCR) and ligase chain reaction (LCR) have been combined with restriction endonuclease (RE) digestion to enable the selective enrichment and detection of single base substitution mutations in human oncogenic loci at a sensitivity of one mutant in more than 10(7) wild type alleles. These PCR/RE/LCR procedures have been successfully designed and used for codons 12 and 248 of the Ha-ras and p53 genes, respectively, both of which contain a natural MspI restriction endonuclease recognition sequence. These procedures have also been adapted for the detection and identification of mutations in oncogenic loci that do not contain a natural restriction endonuclease recognition sequence. Using PCR techniques, a HphI site was incorporated into the codons 12/13 region of the human N-ras gene, which was then used for the selective enrichment of mutants at this oncogenic locus. These PCR/RE/LCR procedures for base substitution mutations in codon 12 of the N-ras gene were found to have the sensitivity of detection of at least one mutant allele in the presence of the DNA equivalent of 10(6) wild type cells. Only one peripheral blood leukocyte DNA specimen out of nine normal individuals displayed an observable Ha-ras mutation that was present at frequency between 10(-5) and 10(-6). These PCR/RE/LCR techniques for detecting and identifying base substitution mutations are universally applicable to almost any locus or base site within the human or animal genome. With the added advantage of the adjustability of both the amount of DNA (number of genomes) to be tested and the sensitivity (10(-2) to 10(-7)) of the assay selection or enrichment procedures, these PCR/RE/LCR techniques will be useful in addressing a broad range of important questions in mutagenesis and carcinogenesis.

Determination of icariin in Chinese traditional medicine by capillary zone electrophoresis

Icariin in Chinese traditional medicine was determined by an accurate and simple capillary zone electrophoresis method which used 30 mmol/L of borate solution containing 10% of acetonitrile as running buffer and needed no pretreatment.

A familial case of Alzheimer's disease without tau pathology may be linked with chromosome 3 markers

Alzheimer's disease is the most common form of dementia that occurs in later years. The diagnosis is confirmed by the pathological findings of betaA4-amyloid-containing neuritic plaques and neurofibrillary tangles, the former being present in sufficient quantity commensurate with age. Other forms of dementia are more difficult to diagnose clinically; their pathology is noted for the lack of plaques and tangles. A patient with a family history of dementia presented with the clinical signs of Alzheimer's disease which lasted for 13 years. At autopsy the brain tissue had betaA4-amyloid-containing neuritic plaques, but no neurofibrillary tangles (i.e., the tissue was negative for staining with the tau antibody). Genetic analysis of DNA from family members revealed no linkage with chromosome 17 markers, indicating that this was not frontotemporal dementia. However, there was linkage with chromosome 3 markers. Thus, this form of Alzheimer's disease with a pathology of plaques only is linked with markers on chromosome 3.

[Effects of tantalum and its oxide on exposed workers]

OBJECTIVE

To explore effects of tantalum and its oxide on the exposed workers.

METHODS

Health examination for 113 workers exposed to tantalum and its oxide and a field survey for occupational hygiene in the workplace were carried out.

RESULTS

Workplace air concentration of tantalum and its oxide averaged 0.1 - 7.6 mg/m(3). There was no significant difference in prevalence of symptoms and signs and biochemical, pulmonary function, chest X-ray and electrocardiograph examinations between the exposed and control workers.

CONCLUSION

No adverse effect of tantalum and its oxide on the exposed workers was found.

[Morphological studies on 18 species of gualoupi]

OBJECTIVE

To gain a clear idea of the drug Gualoupi and its adulterants.

METHOD

Collecting data and spot investigating in 30 provinces, cities and autonomous regions in China.

RESULT

Gualoupi used as drug in China consists of 15 species of Trichosanthes, 1 species of Momordica, 1 species of Citrullus and 1 species of Adenia(Passifloraceae).

CONCLUSION

The main commodity is the rind of T. kirilowii or T. rosthornii, and the main adulterant is the rind of T. hupehensis.

Portal hemodynamics in cirrhotics with portal hypertension using color Doppler velocity profile

OBJECTIVE

To investigate portal hemodynamics and its correlation with esophageal variceal bleeding (EVB) in cirrhotics with portal hypertension by using a newly-developed technique, color Doppler velocity profile (CDVP).

METHODS

Hemodynamics of portal trunk (PT), right anterior branch (RAB) and splenic vein (SV) were evaluated in 48 cirrhotics with portal hypertension and 35 normal volunteers by CDVP. The parameters included maximum cross-sectional velocity (CS-Vmax), flow volume, congestion index (CI), profile parameter N and pattern of flow curve. Stepwise logistic regression model was employed to determine EVB-relating factors in cirrhotics.

RESULTS

CS-Vmax in PT and RAB was significantly lower in cirrhotic group than that of normal group, being 14.91 +/- 3.08 cm/s, 9.44 +/- 2.70 cm/s vs 30.52 +/- 6.75 cm/s, 12.82 +/- 2.69 cm/s, respectively (P < 0.01 for both). Flow volume of PT and SV was significantly higher in cirrhotic group compared with that of normal group, being 25.16 +/- 10.48 ml.min-1.kg-1, 15.83 +/- 9.18 ml.min-1.kg-1 vs 20.43 +/- 5.57 ml.min-1.kg-1, 5.81 +/- 2.04 ml.min-1.kg-1, respectively (P < 0.01 for both). CI of PT, RAB and SV was significantly higher in cirrhotic group than in normal group, being 0.142 +/- 0.0654, 0.105 +/- 0.0496, 0.0884 +/- 0.0431 vs 0.0326 +/- 0.0142, 0.0757 +/- 0.0342, 0.0483 +/- 0.0230, respectively (P < 0.01 for all). In dynamic variation of flow volume over time, RAB and SV in cirrhotic group increasingly presented flat pattern and periodically changed pattern, respectively (P < 0.01 for both). Between cirrhotic subgroups without and with EVB history, there were significant differences in flow volume, CI and N value of SV, splenic size, degree of esophageal varices (EV) and portal hypertensive gastropathy (PHG), and stepwise logistic regression revealed that N value of SV, splenic size, degree of EV and PHG were four independent factors in relation to EVB. EVB scores calculated from the regression equation had a close correlation with EVB. In patients with EVB score > 0, 88.9% of them had EVB, and in those with EVB < 0, 76.9% of them had no history of EVB.

CONCLUSION

In cirrhotics with portal hypertension, portal venous system has the features of elevated vascular resistance and hyperdynamics, and the latter mainly results from increased blood flow in SV. EVB score may become a valuable parameter in predicting occurrence of EVB.

Axonal pathology in myelin disorders

Myelination provides extrinsic trophic signals that influence normal maturation and long-term survival of axons. The extent of axonal involvement in diseases affecting myelin or myelin forming cells has traditionally been underestimated. There are, however, many examples of axon damage as a consequence of dysmyelinating or demyelinating disorders. More than a century ago, Charcot described the pathology of multiple sclerosis (MS) in terms of demyelination and relative sparing of axons. Recent reports demonstrate a strong correlation between inflammatory demyelination in MS lesions and axonal transection, indicating axonal loss at disease onset. Disruption of axons is also observed in experimental allergic encephalomyelitis and in Theiler's murine encephalomyelitis virus disease, two animal models of inflammatory demyelinating CNS disease. A number of dysmyelinating mouse mutants with axonal pathology have provided insights regarding cellular and molecular mechanisms of axon degeneration. For example, the myelin-associated glycoprotein and proteolipid protein have been shown to be essential for mediating myelin-derived trophic signals to axons. Patients with the inherited peripheral neuropathy Charcot-Marie Tooth disease type 1 develop symptomatic progressive axonal loss due to abnormal Schwann cell expression of peripheral myelin protein 22. The data summarized in this review indicate that axonal damage is an integral part of myelin disease, and that loss of axons contributes to the irreversible functional impairment observed in affected individuals. Early neuroprotection should be considered as an additional therapeutic option for these patients.

[Experimental study on antiendotoxin effect of extracts from Artemisia annua L]

OBJECTIVE

To explore the antiendotoxin effect of extracts from Artemisia annua (AA) and qinghaosu (QHS).

METHOD

LPO and SOD in chondriosome, ACP in lysosomes, tumor nicrosis factor-alpha(TNF-alpha) and endotoxin in plasma, and P450 concentration in hepatic microsome of rats were determined. Mortality of endotoxemic mice and histomorphology were observed.

RESULT

LPO, ACP, endotoxin, TNF-alpha and P450 content were decreased with AA and QHS. SOD activity was increased with AA and QHS. At the same time, mortality was decreased. Histomorphology of lysosomes and chondriosome of rats were protected from endotoxin.

CONCLUSION

AA and QHS possess an antiendotoxin effect.

The clinical application of computerized three-dimensional mimic operation for maxillofacial bone tumor

Facial bone, as the frame to support maxillofacial region and with several sinuses and cavities, is structurally complicated and the maxillofacial tumors, benign or malignant, in this region usually grows into the deep tissues, sinus-cavities and orbit and destroys the bone. In this study, the maxillofacial tumors were subjected to a mimic operation on a computer following CT scanning and 3-dimensional reconstruction. The data similar to those of real operation were obtained, which could be used for developing operative plans. As compared with data on the basis of conditions in the real operation, computerized mimic operation reflected the real conditions during operation. Computerized mimic operation is valuable for the preoperative planning and the prediction of probable intraoperative events.

[Study on toxicity of P-Dichlorobenzene]

The authors studied the toxicity of P-Dichlorobenzene(P-DCB). The results showed that the toxicity of P-DCB was low. It has no accumulation (K > 5), no eye irritation and no skin sensitization effects. But light skin irritation effect was observed. In sub-acute inhalate exposure, damage on the function of liver and kidney was not observed. Genotoxic tests showed that tests in s. typhimurium strains TA98 and TA100 did not show any mutagenic potential. In Chinese hamster lung fibroblast CHL cell test system, it did not cause chromosomal aberrations.

Transcriptional regulation of human transcription factor IIB in SMMC-7721 human hepatocellular carcinoma cells by all-trans-retinoic acid and phorbol 12-myristate 13-acetate

The differential-display reverse transcription/polymerase chain reaction (DDRT-PCR) method was utilised to find genes differentially expressed at the messenger RNA level in SMMC-7721 human hepatocellular carcinoma cells treated and not treated with all-trans-retinoic acid, a differentiation inducer of the cell. Human transcription factor IIB (TFIIB) was discovered to be decreased on the 3rd day after the cells had been treated with retinoic acid and increased by phorbol 12-myristate 13-acetate, which stimulated the proliferation of human hepatocellular carcinoma cells. It was also found that the transcription of TFIIB in SMMC-7721 cell had no relationship to the cell cycle.

Differential apoptotic behaviors of c-myc, N-myc, and L-myc oncoproteins

c-, N-, and L-myc are related nuclear oncoproteins that bind similar DNA sites and cooperate with activated ras oncogenes to transform primary fibroblasts. Although c-myc can also promote apoptosis in some cells after growth factor withdrawal or exposure to cytotoxic agents, roles for N- and L-myc in apoptosis remain undetermined. To address this, c-, N-, or L-myc were stably expressed in the interleukin 3 (IL-3)-dependent 32D hematopoietic cell line. The apoptotic response of each cell line was assessed after IL-3 withdrawal or treatment with four structurally unrelated cytotoxic agents. All three oncoproteins accelerated apoptosis after IL-3 withdrawal. In contrast, whereas c-myc overexpression generally sensitized cells to cytotoxic drugs, N-myc and L-myc overexpression produced resistance. myc expression tended to be associated with a more robust G2-M arrest after drug exposure, but this did not correlate with drug sensitivity or resistance. Bcl-2 and Bcl-X(L) protected control cells against apoptosis after either IL-3 withdrawal or drug exposure, although in some cases this effect could be overridden by myc oncoproteins, particularly N-myc and L-myc. Our results suggest that the apoptotic pathways activated upon IL-3 withdrawal and cytotoxic drug treatment are distinct and differentially affected by members of the myc and Bcl-2 families.

[Dynamic change of androgen-receptor in tumor and surrounding liver tissue of nude mice model with transplanted human HCC]

OBJECTIVE

To research into the law of androgen-receptor (AR) dynamic change in developing course of human HCC.

METHOD

Dynamic measurement of AR in tumor and peritumorous tissue was performed in nude mice model with orthotopic transplanted human HCC.

RESULT

Tumor nodules were present in 90% nude mice 4 weeks after transplantation, tumor necrosis was found in the 10th week, and remarkable necrosis occurred in the 12th week. The quantity of AR in tumor and peritumorous tissue was highest in the early stage of tumor (102.32 +/- 21.42 fmol/mg protein and 72.45 +/- 10.11 fmol/mg protein respectively), and then decreased progressively with time to the 10th week (40.98 +/- 21.11 fmol/mg protein and 53.39 +/- 7.01 fmol/mg protein respectively). The difference in AR between each two weeks was significant.

CONCLUSION

Androgen promotes the development of tumor because of existence of AR, and its action may decline after establishment of tumor. Therefore, antiandrogen treatment may be ineffective after establishment of tumor.

Commonly occurring loss and mutation of the MXI1 gene in prostate cancer

One of the most common chromosomal abnormalities in prostate cancer involves loss of 10q22-qter. Rarely, a smaller deletion, involving 10q24-q25, has been observed, suggesting the presence of a tumor suppressor gene at this site. We previously demonstrated that the MXI1 gene maps to 10q24-q25 and is mutated in some tumors with cytogenetically detectable deletions of this locus. MXI1 encodes a basic-helix-loop-helix protein that suppresses the transcriptional activity of the MYC oncoprotein by competing for the common dimerization partner, MAX, and binding to identical DNA sites. Because more than 90% of prostate tumors contain no cytogenetic abnormality of 10q, the relevance of MXI1 loss and/or mutation to the vast majority of cases remains unclear. We prospectively evaluated prostate tumors for loss of MXI1 by fluorescence in situ hybridization (FISH) and cytogenetic techniques. Twenty-one of 40 tumors (53%) demonstrated loss of a single MXI1 allele as determined by FISH. Ten cases with cytogenetically normal 10qs, but with FISH-documented deletion of MXI1, were examined at the molecular level, and eight mutations were identified, albeit at low frequency. Five of the mutant proteins were unable to bind DNA in association with MAX. We conclude that MXI1 gene loss in prostate cancer is common and most frequently involves a cytogenetically undetectable deletion.

Prion protein expression in different species: analysis with a panel of new mAbs

By immunizing prion knockout mice (Prnp-/-) with recombinant murine prion protein (PrPc), we obtained a panel of mAbs specific for murine PrPc. These mAbs can be applied to immunoblotting, cell surface immunofluorescent staining, and immunohistochemistry at light and electron microscopy. These mAbs recognize both the normal (PrPc) and protease-resistant (PrPres) isoforms of PrP. Some mAbs are species restricted, while others react with PrP from a broad range of mammals including mice, humans, monkeys, cows, sheep, squirrels, and hamsters. Moreover, some of the mAbs selectively recognize different PrP glycoforms as well as the metabolic fragments of PrPc. These newly generated PrPc antibodies will help to explore the biology of PrPc and to establish the diagnosis of prion diseases in both humans and animals.

Induction of antioxidants by adriamycin in mouse heart

Cardiac oxidative injury is a major limiting factor for clinical application of Adriamycin (ADR) in cancer chemotherapy. ADR depresses some antioxidant systems, thereby further enhancing the cardiotoxicity. Previous studies have shown that ADR inhibits the overall synthesis of DNA, RNA, and protein. It was presumed that the depressed antioxidant activity resulted from the inhibited gene expression. However, there were no experimental data to demonstrate the relationship between the change in antioxidant activities and that in their gene expression. Therefore, the present study was undertaken to examine the effects of ADR on the activities and mRNA abundances of antioxidants in mouse heart. FVB mice (7 weeks old) were treated with ADR (15 mg/kg) by a single i.p. injection. Four days after the treatment, cardiac antioxidant activities and mRNA abundances were measured. The results showed that ADR increased the levels of mRNAs for Cu,Zn-superoxide dismutase (Cu,Zn-SOD), catalase, glutathione peroxidase (GSHpx), and gamma-glutamylcysteine synthetase (gamma-GCS). On the other hand, ADR increased the activities of catalase and gamma-GCS, and slightly decreased total glutathione concentrations in the heart. Cu,Zn-superoxide dismutase, Mn-superoxide dismutase, and glutathione peroxidase activities were not changed significantly. In addition, ADR increased both mRNA and protein levels of metallothionein in the heart. The data demonstrate that up-regulation of antioxidant gene expression occurred in response to ADR in the mouse heart, although the antioxidant activities were not all increased.

[The effect of recombinant tissue inhibitor of metalloproteinase-3 (TIMP-3) on tumor growth and metastases]

OBJECTIVE

To investigate the anti-cancer effect of tissue inhibitor of metalloproteinase-3 (TIMP-3) and its mechanism of action.

METHODS

Recombinant TIMP-3(rTIMP-3) was prepared and used to study its effect on tumor growth and metastases in mice, and its effect on angiogenesis in chicken embryo allantoic membrane (CAM).

RESULTS

rTIMP-3 was able to inhibit growth of subcutaneously implanted S180 sarcoma and hepatic carcinoma H22 in a dose-dependent manner. When the rTIMP-3 was given i.p. at a daily dose of 20 mg/kg body weight for 10 days, the growth of S180 sarcoma and H22 carcinoma was inhibited by 63.2% and 73.4%, respectively. The metastases of i.v. injected Lewis lung carcinoma(3LLC) was also suppressed by rTIMP-3, with an inhibition rate of 59.8%. rTIMP-3 was found to significantly inhibit angiogenesis in CAM assay.

CONCLUSION

rTIMP-3 has anti-cancer activity, and the mechanism of action might be associated with its inhibition on extracellular matrix degradation and anti-angiogenesis.

Lack of transcriptional repression by max homodimers

Max, a basic-helix-loop-helix-leucine zipper (bHLH-ZIP) protein, plays a central role in the transcriptional regulation of myc oncoprotein-responsive genes. Myc-max heterodimers bind to consensus E-box motifs near or within the promoters of these genes and activate gene expression, whereas heterodimers between max and members of the mad family of bHLH-ZIP proteins promote transcriptional repression. In contrast to all other members of the myc network, max readily homodimerizes and binds to identical E-box sites in vitro. However, the role for max homodimers in transcriptional repression in vivo is unclear. Upstream stimulatory factor (USF) is a bHLH-ZIP protein which does not interact with members of the myc-max-mad family. By replacing the HLH-ZIP domain of max with that from USF, we created a chimeric protein, max(USF), which was indistinguishable from max with respect to its ability to homodimerize and bind DNA. As expected, however, max(USF) was unable to heterodimerize with any of the tested max partner proteins and was incapable of suppressing c-myc target genes. Thus, transcriptional repression is an exclusive property of max-mad heterodimers and cannot be achieved by max homodimers alone.

[Hepatectomy for hepatolithiasis treatment of 354 cases]

OBJECTIVE

To evaluate the effect of hepatectomy for hepatolithiasis.

METHOD

354 patients with hepatolithiasis underwent hepatectomy in the past 10 years. The results were analysed retrospectively, including clinical findings, distribution of stones, patterns of operation, postoperative complications, and residual stones. The clinical data of the patients before 1990 were compared with those thereafter.

RESULT

Left hepatolithiasis was the most common form (323 patients). Left lateral lobectomy and left hepatectomy were most commonly employed (91.2%). 166 of the patients underwent concurrent cholangiojejunostomy. 13.8% patients had residual stones, and postoperative complications occurred in 60 patients, including 4 deaths. Few patients were reoperated on and the incidence of residual stones was lower after 1990. 88% the patients showed excellent or good result.

CONCLUSION

Hepatectomy is a procedure for the management of hepatolithiasis, but still requires combined plasty of stenotic intrahepatic bile ducts and cholangiojejunostomy to reduce the incidence of residual stones and recurrence.

Myelin-associated glycoprotein is a myelin signal that modulates the caliber of myelinated axons

Myelination increases neuronal conduction velocity through its insulating properties and an unidentified extrinsic effect that increases axonal caliber. Although it is well established that demyelination can cause axonal atrophy, the myelin molecule that regulates axonal caliber is not known. Loss of the structural proteins of compact peripheral nervous system (PNS) myelin, P0 protein, and myelin basic protein does not lead to axonal atrophy. This study demonstrates that mice with a null mutation of the myelin-associated glycoprotein (MAG) gene have a chronic atrophy of myelinated PNS axons that results in paranodal myelin tomaculi and axonal degeneration. Absence of MAG was correlated with reduced axonal calibers, decreased neurofilament spacing, and reduced neurofilament phosphorylation. Because axonal atrophy and degeneration in MAG-deficient mice occur in the absence of inflammation, hypomyelination, significant demyelination-remyelination, or gain of function mutations, these data support a functional role for MAG in modulating the maturation and viability of myelinated axons.

Mmip1: a novel leucine zipper protein that reverses the suppressive effects of Mad family members on c-myc

C-myc, a member of the basic helix-loop-helix-leucine zipper (bHLH-ZIP) protein family activates target genes in heterodimeric association with another bHLH-ZIP protein, Max. Max readily homodimerizes, competes with C-myc-Max heterodimers, and represses transcription. Four additional bHLH-ZIP proteins, Mad1, Mxi1, Mad3 and Mad4, heterodimerize with Max and also repress transcription of c-myc-responsive genes. We employed a yeast two-hybid approach to identify proteins which interact with Mxi. We identified a novel ZIP-containing protein, Mmip1 (Mad member-interacting protein 1) that strongly dimerizes with all four Mad members, but not with c-myc, Max, or with unrelated HLH proteins. The Mmip1-Mxi association is mediated by the ZIP domain of each polypeptide and is as strong or stronger than the associations between c-myc and Max or Max and Mxi1. In vitro, Mmip1 can inhibit DNA binding by Max-Mad heterodimers and, in vivo, can reverse the suppressive effects of Mad proteins on c-myc functions. Mmipl is found in a variety of cells types, is induced by serum stimulation, and can be co-immunoprecipitated from fibroblasts in association with Mxi1. By interfering with the dimerization between Max and Mad family member proteins, Mmip1 can indirectly up-regulate the transcriptional activity of c-myc and suppress the antiproliferative actions of Mad proteins.

Erythroid 5-aminolevulinate synthase is required for erythroid differentiation in mouse embryonic stem cells

We have examined the induction of the enzymes of the heme biosynthetic pathway during erythroid differentiation of mouse embryonic stem (ES) cells. Following transfer to appropriate medium all of the pathway enzymes are induced within three days. Unlike differentiating mouse erythroleukemia cells (Lake-Bullock, H. and Dailey, H.A. Mol Cell Biol 13:7122-7132, 1993), all of the enzymes appear to be induced simultaneously and not sequentially in differentiating ES cells. The role of erythroid 5-aminolevulinate synthase (ALAS-2) in this differentiation process was examined by disruption of the ALAS-2 gene. The targeting vector used for disruption replaced all of exons 4 to 6 with a selectable neomycin resistance gene. The resulting genetically modified (ALAS-2 knockout) cells, as well as normal ES cells were used to study induction of heme biosynthesis. Following 10 days of culture in methylcellulose media significant morphological differences between the embryoid bodies (EBs) of the two cell lines were observed. ES cells exhibited morphology of typical EBs with a dark field (blood island) in the center, while ALAS-2 knockout ES cells developed very poorly both in size and shape. At 8 days of differentiation, only 3% of all EBs contained visible erythropoietic cells (i.e., stained positively for hemoglobin) in the ALAS-2 knockout cell line, compared with 50% in ES cells. Most of the genes in the heme synthetic pathway were expressed to a stable level within 3 to 6 days after induction in normal ES cells, while the ALAS-2 knockout cell line failed to significantly increase the level of expression of these genes. Fetal beta-globin mRNA was not detectable in the differentiating ALAS-2 knockout cells, whereas mRNA for this gene was detected in normal ES cells within 3 days of differentiation. These results suggest that ALAS-2 is necessary for ES cell erythroid differentiation and that there is an interrelationship between heme and globin synthesis in differentiating ES cells.

[The analysis of fatty acid composition in syncytiotrophoblast plasma membranes of human placenta]

The fatty acids were determined in syncytiotrophoblast plasma membranes of the eighteen human placenta from the normal pregnant women. With the method of Landon, the fat was purified in syncytiotrophoblast plasma membranes, which was extracted from the placenta by using the procedure of Whitsett. The methylated fatty acids were separated with gas chromatography in which a glass column packed with DEGS was used. In comparing the retention time of the sample with the standards and referring to the results of GC/MS, thirteen peaks were identified and quantified. The area normalization method was used to determine the distribution, the compositions and contents of fatty acids in syncytiotrophoblast plasma membranes. It is shown that the amount of identified fatty acids attains 74.1% of total peak area, in which the amount of saturated fatty acids was 30.64%, and the unsaturated was 43.46%.

[Light microscopic observation of bone interface of titanium-coated 317L plate screw]

The observational results of bone interface of titanium-coated 317L plate screw and 317L plate screw under light microscope are reported in the present paper. Osseointegration was formed in both kinds of screws after implanting. In the titanium-coated 317L plate screw group, the inflammatory reaction was slighter, the new bone formed earlier in the interface and the bone was combined with the metal tightly, whereas in the uncoated 317L plate screw group, the relationship between the bone and metal was only a state of contact. These indicate that the bone interface and tissue compatibility of titanium-coated 317L plate screw may be better than that of the 317L plate screw.

Chinese dietary composition and intakes of elements and radionuclides by ingestion

As update and complement of Chinese Total Diet Study in 1990, a renewing study was conducted during 1992-1993 according to regulated procedure. Contents of 32 elements, including 19 newly determined, in 12 categories of food from 12 provinces were analyzed by NAA or AAS technique and the daily intakes of Chinese adult man were estimated and hygienically evaluated. Meanwhile, a typical survey on dietary composition and intake for difference among 4 age groups and between Spring and Autumn was surveyed too. The results provide important basis for decision for further improvement of Chinese diet from hygienic view point and compilation of physiological characteristics of Chinese Reference Man. At the end of this article, the estimated nationwide average intakes for adult man are compared with those for current ICRP Reference Man.

Mu opioid receptor phosphorylation, desensitization, and ligand efficacy

Mu opioid receptors are subject to phosphorylation and desensitization through actions of at least two distinct biochemical pathways: agonist-dependent mu receptor phosphorylation and desensitization induced by a biochemically distinct second pathway dependent on protein kinase C activation (1). To better understand the nature of the agonist-induced mu receptor phosphorylation events, we have investigated the effects of a variety of opiate ligands of varying potencies and intrinsic activities on mu receptor phosphorylation and desensitization. Exposure to the potent full agonists sufentanil, dihydroetorphine, etorphine, etonitazine, and [D-Ala2, MePhe4, Glyol5]enkephalin (DAMGO) led to strong receptor phosphorylation, while methadone, l-alpha-acetylmethadone (LAAM), morphine, meperidine, DADL, beta-endorphin(1-31), enkephalins, and dynorphin A(1-17) produced intermediate effects. The partial agonist buprenorphine minimally enhanced receptor phosphorylation while antagonists failed to alter phosphorylation. Buprenorphine and full antagonists each antagonized the enhanced mu receptor phosphorylation induced by morphine or DAMGO. The rank order of opiate ligand efficacies in producing mu receptor-mediated functional desensitization generally paralleled their rank order of efficacies in producing receptor phosphorylation. Interestingly, the desensitization and phosphorylation mediated by methadone and LAAM were disproportionate to their efficacies in two distinct test systems. This generally good fit between the efficacies of opiates in mu receptor activation, phosphorylation, and desensitization supports the idea that activated receptor/agonist/G-protein complexes and/or receptor conformational changes induced by agonists are required for agonist-induced mu receptor phosphorylation. Data for methadone and LAAM suggest possible contribution from their enhanced desensitizing abilities to their therapeutic efficacies.

CNP overexpression induces aberrant oligodendrocyte membranes and inhibits MBP accumulation and myelin compaction

2',3'-Cyclic nucleotide 3'-phosphodiesterase (CNP) is highly enriched in myelin-forming cells where it is concentrated at the cytoplasmic side of all surface membranes except those of compact myelin. Previous studies have provided evidence that CNP is functionally involved in migration or expansion of membranes during myelination. This hypothesis is supported, in part, by the production of aberrant myelin membranes in transgenic mice that have a 6-fold increase in CNP expression. In addition, many myelin lamellae in these CNP-overexpressing mice lacked major dense lines (MDLs). The purpose of the present study was to determine if CNP overexpression altered: (1) oligodendrocyte and myelin membrane production during early stages of myelination, and (2) the ultrastructural distribution of CNP and myelin basic protein (MBP) in myelin membranes. We identified aberrant membrane expanses that extended from premyelinating oligodendrocyte processes, the periaxonal membrane, and the contact point between oligodendrocyte processes and myelin internodes. Myelin membranes without MDLs were deficient in MBP and enriched in CNP. These data support a functional role for CNP during oligodendrocyte membrane expansion and indicate, for the first time, that CNP may help target MBP to compact myelin.

Expression of preproopiomelanocortin mRNA and preprodynorphin mRNA in brain of spontaneously hypertensive rats

AIM

To compare the expressions of prepropiomelanocortin (POMC) mRNA and preprodynorphin (PPD) mRNA between 16-wk-old spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY).

METHODS

The expression of POMC mRNA and PPD mRNA were detected with nonradioactive in situ hybridization by digoxigenin-labeled RNA probe.

RESULTS

POMC mRNA mainly was expressed in arcuate nucleus, compared with WKY, SHR had higher level of POMC mRNA (542). PPD mRNA was found in hippocampus, hypothalamus, central gray, nucleus of the solitary tract (NTS), and thoracic spinal cord (T4-T6). Compared with WKY, PPD mRNA level of SHR decreased in dentate gyrus (2342), NTS (381), and medial preoptic area (467); no difference was observed in arcuate nucleus (263), thoracic spinal cord (750-1800) and CA1, CA2, CA3 of hippocampus (1674, 2014, 2626).

CONCLUSION

Increase of POMC mRNA in arcuate nucleus and decrease of PPD mRNA in dentate gyrus of SHR may be associated with the genesis of spontaneous hypertension.

Differential interactions of Id proteins with basic-helix-loop-helix transcription factors

Dimerization of three Id proteins (Id1, Id2, and Id3) with the four class A E proteins (E12, E47, E2-2, and HEB) and two groups of class B proteins, the myogenic regulatory factors (MRFs: MyoD, myogenin, Myf-5 and MRF4/Myf-6), and the hematopoietic factors (Scl/Tal-1, Tal-2, and Lyl-1) were tested in a quantitative yeast 2-hybrid assay. All three Ids bound with high affinity to E proteins, but a much broader range of interactions was observed between Ids and the class B factors. Id1 and Id2 interacted strongly with MyoD and Myf-5 and weakly with myogenin and MRF4/Myf-6, whereas Id3 interacted weakly with all four MRFs. Similar specificities were observed in co-immunoprecipitation and mammalian 2-hybrid analyses. No interactions were found between the Ids and any of the hematopoietic factors. Each Id was able to disrupt the ability of E protein-MyoD complexes to transactivate from a muscle creatine kinase reporter construct in vivo. Finally, mutagenesis experiments showed that the differences between Id1 and Id3 binding map to three amino acids in the first helix and to a small cluster of upstream residues. The Id proteins thus display a signature range of interactions with all of their potential dimerization partners and may play a role in myogenesis which is distinct from that in hematopoiesis.

Novel regulation of the helix-loop-helix protein Id1 by S5a, a subunit of the 26 S proteasome

Id proteins negatively regulate the dimerization, DNA binding, and biological properties of basic helix-loop-helix proteins. In a search for novel factors that interact with Id1, we identified a component of the 26 S proteasome, S5a, that has previously been implicated only in the recognition of ubiquitinated polypeptides destined for proteolysis. S5a interacts strongly with Id1, less strongly with the basic helix-loop-helix proteins MyoD and E12, and not at all with other Id proteins. S5a restores DNA binding by MyoD-Id1 and E12-Id1 heterodimers, enhances DNA binding by MyoD and E12 homodimers, and reverses Id1-mediated repression of the muscle creatine kinase promoter during myogenic differentiation. Mutagenesis experiments showed that amino acids flanking the helix-loop-helix domain plus three residues in the first helix of Id1 impart S5a recognition. This requires only the NH2-terminal half of S5a. S5a thus appears to promote the positive regulation of myogenic genes through ubiquitin-independent mechanisms involving inhibition of Id1 and the enhancement of DNA binding by MyoD and E12. This latter property may permit the selection of novel promoter binding sites during myogenesis.