[Environmental pollution, human exposure and its health effect of sodium pentachlorophenate in schistosomiasis prevalent area]

Sodium pentachlorophenate (Na-PCP) has been used in China for years as an molluscacide to kill oncomelania, which is an intermediate host of Schistosome. To evaluate the effects of its long-term successive usage on environment, human exposure and health, studies were carried out in Sichuan, Jiangxi, Jiangsu and Fujian provinces, with a time gap of more than one month between sample collection and last spray of Na-PCP. Results indicated that PCP contents in surface water, soil, sediment, animals and plants were significantly higher in studied areas than in control areas. The daily intake and the content in urine of PCP were also sigificantify higher in studied areas. But, there was no difference on physical and biochemical examinations except that a 22%-28% decrease of blood cholinesterase activity was found in studied areas. The health effect of impurities in Na-PCP, dioxins and furans, was assessed and discussed.

Controlling epidermal growth factor (EGF)-stimulated Ras activation in intact cells by a cell-permeable peptide mimicking phosphorylated EGF receptor

Epidermal growth factor (EGF)-stimulated Ras activation involves specific interactions between the EGF receptor (EGFR), the adaptor proteins Grb2 and Shc, and the nucleotide exchange factor Sos-1. Study and control of these protein-protein interactions in vivo can be greatly promoted by introducing intracellular reagents that mimic EGFR functions. Here, we showed that a synthetic phosphopeptide encompassing the autophosphorylation site 1068 of EGFR formed a complex with endogenous Grb2 after this peptide was delivered into intact cells by a cell-permeable peptide import technique. Consequently, this intracellular peptide inhibited EGF-induced EGFR/Grb2 associations but not EGFR/Shc or Shc/Grb2 associations. Peptide-mediated disruption of the EGF/Grb2/Sos-1 cascade led to reduced Ras activation and mitogen-activated protein kinase activation. These results indicate that the binding of Grb2 to the phosphorylated Tyr-1068 of EGFR is crucial to the EGF-induced Ras/mitogen-activated protein kinase signaling pathway. The application of cell-permeable peptides to this study demonstrates a useful biochemical tool to probe and control various intracellular processes involved in signal transduction and gene transcription.

Identification of a functionally important sequence in the cytoplasmic tail of integrin beta 3 by using cell-permeable peptide analogs

Integrins are major two-way signaling receptors responsible for the attachment of cells to the extracellular matrix and for cell-cell interactions that underlie immune responses, tumor metastasis, and progression of atherosclerosis and thrombosis. We report the structure-function analysis of the cytoplasmic tail of integrin beta 3 (glycoprotein IIla) based on the cellular import of synthetic peptide analogs of this region. Among the four overlapping cell-permeable peptides, only the peptide carrying residues 747-762 of the carboxyl-terminal segment of integrin beta 3 inhibited adhesion of human erythroleukemia (HEL) cells and of human endothelial cells (ECV) 304 to immobilized fibrinogen mediated by integrin beta 3 heterodimers, alpha IIb beta 3, and alpha v beta 3, respectively. Inhibition of adhesion was integrin-specific because the cell-permeable beta 3 peptide (residues 747-762) did not inhibit adhesion of human fibroblasts mediated by integrin beta 1 heterodimers. Conversely, a cell-permeable peptide representing homologous portion of the integrin beta 1 cytoplasmic tail (residues 788-803) inhibited adhesion of human fibroblasts, whereas it was without effect on adhesion of HEL or ECV 304 cells. The cell-permeable integrin beta 3 peptide (residues 747-762) carrying a known loss-of-function mutation (Ser752Pro) responsible for the genetic disorder Glanzmann thrombasthenia Paris I did not inhibit cell adhesion of HEL or ECV 304 cells, whereas the beta 3 peptide carrying a Ser752Ala mutation was inhibitory. Although Ser752 is not essential, Tyr747 and Tyr759 form a functionally active tandem because conservative mutations Tyr747Phe or Tyr759Phe resulted in a nonfunctional cell permeable integrin beta 3 peptide. We propose that the carboxyl-terminal segment of the integrin beta 3 cytoplasmic tail spanning residues 747-762 constitutes a major intracellular cell adhesion regulatory domain (CARD) that modulates the interaction of integrin beta 3-expressing cells with immobilized fibrinogen. Import of cell-permeable peptides carrying this domain results in inhibition "from within" of the adhesive function of these integrins.

Alterations in enzymatic functions in hepatocytes and hepatocellular carcinomas from Ras-transduced livers resemble the effects of insulin

An understanding of how oncogenes affect differentiated liver functions might lead to improved treatments for liver cancer or other disorders where liver-specific functions are compromised. A retroviral vector that coexpressed beta-galactosidase (beta-gal) and activated Ras genes (Ras-gal) was transduced into a small fraction of adult rat hepatocytes in vivo. Hepatocytes from Ras-gal-transduced diethylnitrosamine-untreated livers and hepatocellular carcinomas (HCC) from Ras-gal-transduced diethylnitrosamine-treated rats were analyzed for liver functions by performing histochemical assays on liver sections. Ras-gal-transduced hepatocytes failed to express gluconeogenic, ketogenic, and urea pathway enzymes. In contrast, several enzymes involved in fat synthesis were strongly activated, and microvesicular fat accumulated. These metabolic changes are induced in normal livers by insulin, a hormone that activates p21-ras. The deregulation of p21-ras may inhibit these liver-specific functions and may induce fat synthesis in both malignant and nonmalignant liver diseases. Furthermore, treatment with drugs that inhibit the attachment of p21-ras to the plasma membrane might reverse these changes. The alterations in enzymatic functions in the HCCs were similar to those observed in the hepatocytes, although each of the two cancers had a region that abruptly lost its expression of liver-specific enzymes and acquired the expression of genes that are more characteristic of oval or bile ductule cells. This suggests that a single genetic event in a malignant cell may dramatically alter its apparent phenotype. The identification of this putative gene might lead to insights into the regulation of the phenotype of normal cells in the liver.

Terbutaline nebulization and epinephrine injection in treating acute asthmatic children

Ninety children with acute asthma, equally divided into two study groups, were studied to compare the efficacy and safety of nebulized terbutaline with injected epinephrine in the treatment of acute exacerbation. The terbutaline group received 2 ml (5,0 mg) terbutaline solution diluted with 2 ml 0.9% saline for inhalation over 10 minutes; the epinephrine group received 0.01 ml/kg of 1:1000 epinephrine (maximum 0,3 ml) through subcutaneous injection at deltoid area. Spirometry, pulse oximetry, and clinical severity scoring system were evaluated at baseline and again 15 minutes after treatment. The baseline data of the two groups were not significantly different. The clinical severity score and spirometry of both groups were significantly improved after treatment. Compared with the terbutaline group, the epinephrine group had better mean oxygen saturation (SaO2; p < 0.001), frequency of oxygen desaturation (p = 0.0028) and forced expiratory flow 25-75% (FEF25-75%, p = 0.027). For those patients with initial forced expiratory volume in one second (FEV1) lower than 60% of predicted value, epinephrine treatment was more effective in the improvement of FEV1, FEF25-75%, and oxygen saturation (SaO2) (p = 0.011, 0.012, and 0.006, respectively). A Significantly higher rate of adverse effects occurred in patients given epinephrine (47% vs 11%, p = 0.0002); these included pallor, tremor, dizziness, headache, palpitation, soreness of legs, numbness of extremities, cold sweating, general weakness and nausea. Considering the general trend to noninvasive therapy in children and the more frequent adverse effects after epinephrine injection, such nebulized beta-2 agonists as terbutaline appear preferable for initial therapy of acute asthma if oxygen is supplemented to prevent possible hypoxemia. However, parenteral epinephrine still is worth trying, particularly in any severe, life-threatening attack.

Role of the nuclear localization sequence in fibroblast growth factor-1-stimulated mitogenic pathways

Fibroblast growth factor-1 (FGF-1) is a potent mitogen for mesoderm- and neuroectoderm-derived cell types in vitro. However, a mutant FGF-1 with deletion in its nuclear localization sequence (NLS, residues 21-27) is not mitogenic in vitro. We demonstrated that synthetic peptides containing this NLS were able to stimulate DNA synthesis in a FGF receptor-independent manner after they were delivered into living NIH 3T3 cells by a cell-permeable peptide import technique. The stimulation of maximal DNA synthesis by these peptides required the presence of peptides during the entire G1 phase of the cell cycle. The mitogenic effect was specific for the NLS of FGF-1 because a peptide with double point mutations at lysine residues was inactive in stimulating DNA synthesis. Our results suggest that the NLS plays an important role in the mitogenic pathway initiated by exogenous FGF-1 by its direct involvement in the nuclear transport and signaling of internalized FGF-1.

Ras-transduced diethylnitrosamine-treated hepatocytes develop into cancers of mixed phenotype in vivo

The cell of origin of hepatocellular carcinoma (HCC) is controversial. A method for marking cells of different lineages in vivo and then determining their carcinogenic potential should resolve this issue. A retroviral vector expressing activated ras and beta-gal genes (Ras-gal) was transferred into adult rat hepatocytes in vivo, and some animals were treated with diethylnitrosamine (DEN). Bile ductule cells and the putative stem cells of the liver (the oval cells) did not appear to be transduced by this method. At 1 month after transfer, 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside staining was performed on transduced rat livers to determine the blue cluster size. Eight % of the clusters in Ras-gal-transduced, DEN-treated livers contained at least twice as many cells as the largest cluster in Ras-gal-transduced, DEN-untreated rats, demonstrating that they had acquired markedly abnormal growth properties. When the retroviral vector containing beta-gal without ras (Gal-509) was transferred into DEN-treated rats, 2.5% of the cells were present in clusters containing at least twice as many cells as the largest cluster in Gal-509-transduced, DEN-untreated animals. Thus, p21-ras may increase the percentage of cells that acquire mutations in response to DEN, or it may behave synergistically with other mutations to increase the replication rate of cells. Occasional foci in Ras-gal-transduced, DEN-treated rats had extramedullary hematopoiesis. Forty % of the Ras-gal-transduced, DEN-treated rats developed unifocal HCC, mixed HCC/cholangiocarcinoma (CC), or CC at 3-6 months after transduction, suggesting that hepatocytes can develop into HCC or CC if sufficient genetic alterations occur.

Inhibition of nuclear translocation of transcription factor NF-kappa B by a synthetic peptide containing a cell membrane-permeable motif and nuclear localization sequence

To control agonist-induced nuclear translocation of transcription factor kappa B (NF-kappa B) in intact cells, cell-permeable synthetic peptides were devised. Their import into intact cells was dependent on a hydrophobic region selected from the signal peptide sequences and was verified by their inaccessibility to extracellular proteases and by confocal laser scanning microscopy. When a cell-permeable peptide carried a functional cargo representing the nuclear localization sequence of NF-kappa B p50, it inhibited in a concentration-dependent manner nuclear translocation of NF-kappa B in cultured endothelial and monocytic cells stimulated with lipopolysaccharide or tumor necrosis factor-alpha. Synthetic peptide analogues with deleted hydrophobic cell membrane-permeable motif or with a mutated nuclear localization sequence were inactive. Cell membrane-permeable peptides were not cytotoxic within the concentration range used in these experiments. These results suggest that cell-permeable synthetic peptides carrying a functional cargo can be applied to control signal transduction-dependent subcellular traffic of transcription factors mediating the cellular responses to different agonists. Moreover, this approach can be used to study other intracellular processes involving proteins with functionally distinct domains.

Metered dose inhaler and nebuliser in acute asthma

One hundred and eleven children with acute asthma were studied to compare delivery of terbutaline by either a metered dose inhaler (MDI) with a valved holding chamber or a nebuliser driven by air. Eligible patients were randomised; the MDI group received three puffs (0.75 mg) of terbutaline and the nebuliser group received 2 ml (5.0 mg) terbutaline solution diluted with 2 ml 0.9% saline for inhalation over 10 minutes. Patients were evaluated by spirometry, pulse oximetry, and clinical severity scoring system at baseline and again 15 minutes after the beginning of treatment. The baseline data of the two groups were not significantly different. All parameters of spirometry, except the peak expiratory flow (PEF) for the nebuliser group, and clinical severity score for both groups significantly improved after terbutaline treatment. Compared with the nebuliser group, the MDI group after treatment had better mean (SD) oxygen saturation (SaO2; 96.82 (1.63)% v 95.44 (1.88)%), frequency of oxygen desaturation (23.2% v 47.3%), absolute increase of PEF (32.6 (37.7) l/min v 10.2 (34.7) l/min), and SaO2 (0.54 (1.64)% v -0.47 (1.84)%). There was also a mean (SD) per cent increase of forced expiratory volume in one second (22.9 (21.0)% v 15.4 (16.1)%), PEF (27.7 (38.4)%) v 7.7 (25.1)%), and SaO2 (0.58 (1.72)% v -0.47 (1.93)%). In conclusion, aerosol treatment by MDI (with a valved holding chamber) in this study proved to be superior to nebuliser treatment in terms of SaO2 and some measurements of spirometry. Respiratory therapists working with children with severe asthma should be aware of the possibility of oxygen desaturation, especially when using room air as the driving gas for nebulisation.

Clinical evaluation of the diagnostic value of measuring IgG antibody to 3 mycobacterial antigen preparations in the capillary blood of children with tuberculosis and control subjects

SETTING

Department of Paediatrics in a University Hospital.

OBJECTIVE

To evaluate ABC-ELISA as serodiagnostic tests for tuberculosis in children.

DESIGN

An avidin-biotin-peroxidase conjugated anti-human immunoglobulin (ABC) enzyme-linked immunosorbent assay (ELISA) was established to measure serum immunoglobulin G (IgG) antibodies to polymerized old tuberculin (OT), tuberculin purified protein derivative (PPD) and the 30,000 dalton (30 kDa) native antigen of Mycobacterium tuberculosis, in 122 tuberculosis patients and 187 healthy children.

RESULTS

In those patients who had received less than 3 months of chemotherapy the sensitivities of the tests based on OT, PPD and the 30 kDa antigen were 40.3%, 50.0% and 36.1% respectively; the positive predictive values were 92.6%, 94.7% and 93.8% respectively and the negative predictive values were 58.6%, 62.9% and 57.2% respectively.

CONCLUSION

The ABC-ELISA may be useful for the diagnosis of pulmonary and extrapulmonary tuberculosis in groups of children with a high prior probability of tuberculosis. Antibodies to the 30 kDa antigen persisted longer than did those to OT and PPD.

Effects of nebulized terbutaline on oxygen saturation in acute asthmatic children

To evaluate the paradoxical effect of oxygen desaturation following beta-2 bronchodilator nebulization treatment in acute asthmatic children, a total of 47 patients, aged between 1.8 and 14 years, 27 males and 20 females, were studied. Twenty ml of nebulized normal saline (NS), followed by 10 mg (4 ml) of terbutaline sulphate solution (TSS) in 20 ml NS, were delivered by an ultrasonic nebulizer in 10 min to each patient through a connecting air tube placed in front of the nose and mouth. Oxygen saturation (SaO2) and pulse rate were monitored, using a pulse oximeter, before study and every two minutes until the end of the study. The clinical severity score and peak expiratory flow rate (PEFR) were checked before the study, at the end of inhalation of NS, and at the end of inhalation of TSS. SaO2 was increased both after nebulized NS and TSS when compared with the pre-study data (p < 0.05 and p < 0.0001, respectively). Twenty two cases (47%) during NS and 12 cases (25%) during TSS nebulization had SaO2 below the pre-study level. The mean decrease of SaO2 for the former was 1.62 +/- 0.95% (range: 1.00% to 4.26%), and 1.64 +/- 0.83% (range: 1.02% to 3.13%) for the latter (p > 0.9). No SaO2 decrease after nebulized TSS was observed in any of the seven severe asthmatic children with a prestudy SaO2 < or = 90%. The clinical severity score and PEFR were also significantly improved both after nebulized NS and TSS (p < 0.0001 and p < 0.001, respectively for NS, and both p < 0.0001 for TSS).(ABSTRACT TRUNCATED AT 250 WORDS)

[Respiratory failure after nebulized terbutaline treatment in severely wheezy infants: report of three cases]

Subjective clinical observations have suggested that nebulized bronchodilators are helpful in the treatment of some wheezy infants. Although the role of beta 2-agonists in the management of acute asthma in infants and very young children remains controversial, the use of beta 2-adrenergic agents in this age group has been widespread. beta 2-agonists nebulization continues to be the first-line treatment for acute attack of asthma, irrespective of age, in some institutes, but their uses are not without side effect especially in young wheezy infants. We report three cases of respiratory failure occurred after treatment with nebulized beta 2 bronchodilator in infants with chronic lung disease and acute wheezing. All the 3 cases were victims of prematurity. Case 1 was a case of Wilson-Mikity syndrome; case 2 was a case of bronchopulmonary dysplasia; and case 3 was a case of repeatedly wheezing infant. All 3 cases had severely wheezy dyspnea with retraction before nebulized beta 2 bronchodilator treatment. Respiratory failure was found 5 to 10 minutes after the treatment. We suggest that it must be very careful in the treatment of severely wheezy infants with beta 2-agonist nebulization, especially in cases with histories of prematurity and chronic lung disease. It is necessary to carefully monitor the vital signs of the infants during beta 2 agonist nebulization.

[The expression of C-myc, N-ras mRNA and its relations to the differentiation of preneoplastic altered hepatocytes]

The expression of C-myc and N-ras mRNA was studied in preneoplastic hepatic lesions induced by multiple small doses of diethylnitrosamine (DEN). Dot blot analysis showed that the expression of C-myc and N-ras mRNA was in elevated levels during the early stage of hepatocarcinogenesis. In situ hybridization in tissue sections demonstrated that the over-expression of C-myc and N-ras mRNA was clearly seen in some of the preneoplastic altered liver cell lesions. In comparison of these over-expressed oncogene lesions with the expression of carbamyl phosphate synthetase I (CPS I), known as a differentiation marker of hepatocytes, in serial sections revealed that almost all of the foci with over-expressed C-myc and/or N-ras mRNA also showed low expression of CPS I mRNA, which means a low differentiation nature of the liver cells. These findings suggested that the overexpression of C-myc and N-ras are closely correlated to the differentiation state of altered liver cells.

[Expression of insulin-like growth factor II mRNA and its relation to the differentiation of preneoplastic hepatocytes in rats]

Expression of insulin-like growth factor II (IGF II) mRNA was studied during the early stage of diethylnitrosamine-induced hepatocarcinogenesis in rats according to Solt-Farber's protocol. The DNA-RNA dot blot hybridization denoted that the expression of IGF II mRNA in the liver of experimental animals were 13-15 folds more than those in the normal controls, while the expression level of the uninitiated animals or the rats 24 hours after a similar 2/3 hepatectomy were similar to the normal rat's. The RNA-RNA in situ hybridization showed that the over expression of IGF II was detected in some "preneoplastic" hepatocytic foci and nodules, which was usually accompanied by altered ornithine carbamyol transferase and carbamyol phosphate synthetase I expressions, while no over expression of IGF II was seen in those foci of normal OCT and CPS I expression. Since OCT and CPS I have been used as the differentiation markers of the liver cells, it is considered that over expression of IGF II in DEN initiated liver cells is closely related to de- or aberrant differentiation of the altered hepatocytes which might play an important role in the early stage of hepatocarcinogenesis.

Enzymic activities of two-chain pepsinogen, two-chain pepsin, and the amino-terminal lobe of pepsinogen

In order to study the relationships of aspartic proteases, we have modified pepsin, a single-chain eukaryotic enzyme, to a two-chain heterodimer, which resembles aspartic proteases from retrovirus, including human immunodeficiency virus. Two fragments of pepsinogen, residues 1P-172 and 173-326, were expressed separately in Escherichia coli. Mixtures of chains were refolded from urea solutions to generate an active two-chain pepsinogen, which was converted to two-chain pepsin in acid solutions. The intramolecular and bimolecular activation constants (k1 and k2) of two-chain pepsinogen are about 1.5-fold and one-sixth, respectively, of those for pepsinogen. Structural evidence suggests that the faster k1 of two-chain pepsinogen is due to decreased interaction of the propeptide with the pepsin moiety, implying that the rate-limiting step in the intramolecular activation of pepsinogen is the "conformational dissociation" of its propeptide. Two-chain pepsin has the same Km but only one-sixth of the kcat of pepsin. Both pepsinogen chains are capable of independent refolding. The refolding of the NH2-terminal chain, which contains the propeptide and the NH2-terminal lobe, generated a small amount of proteolytic activity which is likely derived from the homodimer of the NH2-terminal lobe. It has been postulated that mammalian aspartic proteases, which contain two structurally homologous lobes, are derived in evolution from a homodimer enzyme by gene duplication and fusion (Tang, J., James, M. N. G., Hsu, I.-N., Jenkins, J. A., and Blundell, T. L. (1978) Nature 271, 618-621). The observation of the homodimer activity of the NH2-terminal lobe of pepsinogen suggests that the interface of the lobes is conservative in evolution.

The pairing of the separated A and B chains of insulin and its derivatives, FTIR studies

From the amide I bands of their deconvolved FTIR spectra, the S-thiomethyl derivatives of the insulin A, B, despentapeptide(26-30) B and desoctapeptide(23-30) B chains all contain significant amounts of ordered secondary structure. The intact B chain is considerably more ordered than either the A or the truncated B chains. Comparison of the spectra of the separated and mixed intact chains of insulin suggests further folding upon mixing of the chains leading to significant increases in ordered secondary structures, presumably because of stabilization by interaction of the chains. The interactions of the A chain with the DPI B chain appear to be weaker as compared to that with the intact B chain. The above results suggest that only the intact A and B chains contain sufficient structural information to recognize each other and interact to form a native-like structure which make the correct formation of the disulfide linkages possible.

Arboviruses as aetiological agents of encephalitis in the People's Republic of China

A serological study was undertaken to determine the role of arboviruses as etiological agents of encephalitis in the People's Republic of China (PRC). Paired sera were collected during mosquito seasons in 1988-1990 from 614 patients with possible viral encephalitis in 15 regions of PRC and tested for haemagglutination inhibiting antibodies to selected arboviruses. Seroconversions were documented to alphavirus and flavivirus antigens in 13.0 and 18.7% of patients respectively in most of the study areas. No California group seroconversion was detected. The age of alphavirus seroconvertors ranged from 2 months to 32 years and of flavivirus seroconvertors from 6 months to 50 years, with higher numbers in males. Serious central nervous system manifestations were seen more commonly in flavivirus seroconvertors. This study affirms the importance of flavivirus as causative agents of encephalitis in PRC and provides evidence that one or more alphaviruses are causing symptomatic infections with neurological involvement in PRC.

Clinical trial of corticosteroid and beta-2 bronchodilator in acute wheezing infants

To evaluate the effect of a combination of corticosteroid and beta-2 bronchodilator on acute, young, wheezing patients, a total of 80 patients, ages below 36 months who were hospitalized for this condition during the period November 1988 to March 1990 were studied. They were divided into three groups. Group A consisted of 29 cases, under 12 months old, and treated with hydrocortisone and procaterol; Group B included 23 cases, between 12 and 36 months old, treated as in Group A; Group C, of 28 cases younger than 12 months, received neither drug. The clinical severity scores for Group B were significantly more improved than Group A on days 4 and 5 (p less than 0.05 and p less than 0.05, respectively), and better than that of Group C on days 3, 4, and 5 (p less than 0.05, 0.005, and 0.05, respectively). No significant difference was found between Group A and C from days 1 to 5. The previous wheezy coughing episodes were significantly more frequent in Group B than in Groups A and C (p less than 0.05). Two-thirds of the quick responders to hydrocortisone and procaterol were 12 months old or older. The personal and family allergic history, serum IgE level, and total eosinophil count could not be used as parameter to predict responsiveness to the combined therapy of hydrocortisone and procaterol.

FTIR studies of secondary structures of bovine insulin and its derivatives

The amide I bands of the deconvolved FTIR spectrum of bovine insulin, despentapeptide (B26-B30) insulin and desoctapeptide (B23-B30) insulin in D2O solution have been assigned to alpha-helix, the 3(10) helix, irregular helix, extended chains, beta-turns and other secondary structures. From the peak areas the relative contents of these structures obtained are in general agreement with those calculated from the known structures of porcine insulin and DPI in the crystalline state. The main difference in the structure of DOI with those of insulin and DPI is the shortening of the helix segment and an extended chain for the C terminal segment in the B chain.

Mapping the receptor-recognition site of human transforming growth factor-alpha

The receptor-recognition site human transforming growth factor-alpha (TGF alpha), a 50-residue tricyclic peptide with three disulfide bonds, was mapped by a set of 46 peptide analogs consisting of linear, monocyclic, bicyclic, and tricyclic structures representing individual and overlapping subdomains of human TGF alpha. Linear overlapping fragments ranging from 7 to 18 residues and spanning the entire length of TGF alpha as well as monocyclic analogs with one disulfide linkage were found to be inactive in both receptor-binding and mitogenic assays. Bicyclic analogs with two disulfide linkage and representing either the amino or carboxyl two-thirds of TGF alpha showed low activity at 0.1-0.9 mM concentrations. Tricyclic analogs containing all three disulfide linkages but lacking either the amino or carboxyl terminal heptapeptide was, respectively, 3% and 0.1% as active as TGF alpha. These results show that determinants for the receptor binding cannot be represented by a short continuous fragment or a single subdomain, but are located on a discontinuous surface on a folded structure with disulfide restraints. Furthermore, these results when combined with our previous results which shows that the middle subdomain (second disulfide loop) is not involved in the receptor binding suggest that the receptor-binding residues are constituted of three fragments located at the first and third subdomains as well as the external carboxyl peptide.

Serologic survey of spotted fever group rickettsiosis on Hainan Island of China

A serosurvey for antibodies to Rickettsia japonica was conducted on Hainan Island of China. Serum specimens were collected from 1,030 outpatients at hospitals in different parts of the island regardless of their diagnosis. Only two among 538 serum specimens collected in Baoting and Tongshi counties, located in the southern part of the island, were demonstrated to contain antibodies reactive with R. japonica at a high dilution. The specimens also reacted with R. rickettsii at the same titer as with R. japonica. These two specimens reacted with other pathogenic spotted fever group (SFG) rickettsiae to a lesser extent. On the other hand, the specimens were shown to possess antibodies reactive with R. typhi at a significantly lower dilution or were not reactive at all. The findings suggested the occurrence of an SFG rickettsiosis on Hainan Island. More than half of the serum specimens collected from patients with suspected rickettsial infections in the southern area were found to contain IgM and IgG antibodies to R. typhi, indicating a high incidence of murine typhus.

Synthesis and structure-activity study of myxoma virus growth factor

Myxoma virus growth factor (MGF) is an 85-residue peptide derived from the gene product of a DNA tumor virus that infects rabbits. The carboxyl domain of MGF possesses about 40% sequence homology with the epidermal growth factor (EGF). This EGF-like domain covering residues 30-83 was synthesized and found to possess putative activities of EGF. It was, however, about 200-fold less active than EGF in the competitive binding of EGF receptor in A431 cells and the stimulation of [3H]-thymidine uptake in NRK 49F cells. MGF(30-83) is a basic and a hydrophobic peptide rich in beta-sheet structure. These features in MGF tend to promote aggregation, leading to precipitation even in strongly denaturing solutions. Thus, the refolding of MGF was achieved with difficulty and resulted in low yield. To increase the synthetic yield of MGF(30-83), a cluster of acidic amino acids was added to the NH2-terminus of MGF(30-83). This approach was found to be effective in minimizing the refolding difficulties and allowed accessibility to the synthesis of analogues in this class of compounds. The relationships of structure and function of MGF were studied by using analogues with point substitution by the corresponding D-amino acid or by Ala at position 44 or 52 and analogues with deletion of basic residues from the amino terminus. Modifications of both the receptor contact and the structural residues greatly reduced the potency of MGF(30-83), and the overall result correlated well with the known structure-activity of the EGF family.

A soluble protein related to the HER-2 proto-oncogene product is released from human breast carcinoma cells

Amplified expression of p185HER-2, the protein product of the HER-2/neu proto-oncogene, appears to be involved in carcinogenesis of human mammary epithelial cells. Our data suggest that an extracellular 130 Kda glycoprotein released from breast carcinoma cells may be related to the ectodomain of p185HER-2: (1) Both cellular p185HER-2 and extracellular p130, when reduced and alkylated, reacted with antipeptide antibody against the N-terminus of the HER-2 protein [alpha N(HER-21)] and reactivity was blocked by cognate peptide; (2) Neither p130 nor other extracellular proteins reacted with antiserum against the C-terminus of p185HER-2 [alpha C(HER-2)]; (3) Partial proteolysis of p185HER-2 generated an immunoreactive fragment of 130 kDa that was similar to extracellular p130; (4) Both p130 and p185HER-2 contained carbohydrate that bound to Con-A Sepharose; (5) The amount of p130 released from breast cells corresponded to the levels of expression of cellular p185HER-2. Release of the ectodomain of p185HER-2 from breast carcinoma cells may be involved in their malignant growth and may be a useful marker for assessing the expression of p185HER-2 in human tumors.