Function and differential regulation of the alpha 6 integrin isoforms during parietal endoderm differentiation

F9 embryonal carcinoma cells treated with retinoic acid differentiate in monolayer into parietal endoderm (PE) or in suspension into embryoid bodies with an outer layer of visceral endoderm (VE) surrounding a core of largely undifferentiated cells. Previous reports have shown that cell-extracellular matrix interactions mediated by the beta 1 integrins play a critical role in the differentiation and migration of PE. In the present study we investigated the pattern of expression and function of the integrin alpha 6 beta 1 during the differentiation of F9 cells into VE and PE. F9 cells express integrin subunits alpha 3, alpha 5, alpha 6, and beta 1. Cell adhesion and migration assays demonstrate that alpha 6 beta 1 is the major laminin receptor in undifferentiated F9 cells as well as F9-derived PE cells. However, the amount of alpha 6 protein decreases significantly upon F9 cell differentiation into either VE or PE, as revealed by immunofluorescent staining and immunoprecipitation analysis. In contrast, the amount of steady-state alpha 6 message stays constant before and after F9 cell differentiation, suggesting that the down-regulation of alpha 6 beta 1 occurs post-transcriptionally. In view of previous reports of two alpha 6 isoforms generated by alternative RNA processing, we carried out reverse transcription-PCR analysis and show that, while alpha 6B is the major mRNA isoform before and after F9 cell differentiation, alpha 6A mRNA is weakly expressed in undifferentiated F9 cells and is substantially increased following F9 differentiation into PE. Immunoprecipitations using the isoform-specific antibodies show an increase in alpha 6A and a dramatic decrease in alpha 6B protein following PE differentiation. Pulse-chase experiments indicate that, whereas the stability of alpha 6B protein is unaltered, synthesis of alpha 6B protein is decreased at least threefold following PE differentiation. Further experiments demonstrate that alpha 6A localizes to focal contacts in PE cells. The switch from alpha 6B to alpha 6A and the localization of alpha 6A at focal contacts correlate with the acquisition of PE cell motility, which suggests distinct functions for the two alpha 6 isoforms.

[A study of epidermal growth factor receptor in human colorectal cancer]

Membrane extracts of surgically resected colorectal cancer and nearby non-cancerous tissues were prepared and the expression of epidermal growth factor receptor (EGF-R) was examined by 125I-EGF binding assay. Scatchard analysis indicated that a single class of EGF-R was present in the cancer as well as the non-cancerous tissues. EGF-R was found over-expressed in cancer (38.07 +/- 4.75 fmol/mg protein) as compared to that in the non-cancerous tissue (29.31 +/- 1.64 fmol/mg protein) (P < 0.05). However, the difference in binding affinities of EGF-R in the cancer and non-cancerous tissues was not statistically significant. The results suggest an important role of an autocrine/paracrine loop of growth regulation in colorectal cancer.

A family of proteins containing a conserved domain that mediates interaction with the yeast SNF1 protein kinase complex

The SNF1 protein kinase is required for the regulatory response to glucose starvation in Saccharomyces cerevisiae. SNF1 is a protein serine/threonine kinase that has been widely conserved in both plants and mammals. Previously, we identified SIP1 and SIP2 as proteins that interact with SNF1 in vivo by the two-hybrid system. We have cloned the SIP2 gene and the encoded protein is homologous to SIP1 and to GAL83, which affects glucose repression of the GAL genes. We show that SIP2 and GAL83, like SIP1, co-immunoprecipitate with SNF1 and are phosphorylated in vitro. An 80 amino acid sequence, designated the ASC domain, is highly conserved at the C-termini of all three proteins. We show that this small domain can mediate protein-protein interaction with the SNF1 kinase complex. Thus, SIP1, SIP2 and GAL83 define a family of homologous proteins that are tightly associated with the SNF1 kinase, probably in alternative forms of the complex. Genetic evidence suggests that the three proteins have distinct, but related, functions in the SNF1 pathway, and deletion of GAL83 dramatically reduces SNF1 activity in immune complex assays. We propose that SIP1, SIP2 and GAL83 act as adaptors that promote the activity of SNF1 towards specific targets.

Time course of lipid peroxidation in puromycin aminonucleoside-induced nephropathy

Reactive oxygen species have been implicated in the pathogenesis of acute puromycin aminonucleoside (PAN)-induced nephropathy, with antioxidants significantly reducing the proteinuria. The temporal relationship between lipid peroxidation in the kidney and proteinuria was examined in this study. Rats were treated with a single IV injection of puromycin aminonucleoside, (PAN, 7.5 mg/kg) and 24 hour urine samples were obtained prior to sacrifice on days 3,5,7,10,17,27,41 (N = 5-10 per group). The kidneys were removed, flushed with ice cold TRIS buffer. Kidney cortices from each animal were used to prepare homogenates. Tissue lipid peroxidation was measured in whole homogenates as well as in lipid extracts from homogenates as thiobarbituric acid reactive substances. Proteinuria was evident at day 5, peaked at day 7 and persisted to day 27. Lipid peroxidation in homogenates was maximal at day 3 and declined rapidly to control levels by day 17. This study supports the role of lipid peroxidation in mediating the proteinuric injury in PAN nephropathy.

Infusion of large quantities of autologous blood monocyte-derived macrophages in two cancer patients did not induce increased concentration of IL-6, TNF-alpha, soluble CD14 and nitrate in blood plasma

In an attempt to increase the number of macrophages available for reinfusion in immunotherapy trials, GM-CSF was injected in vivo to mobilize circulating blood monocytes in 2 cancer patients. Subsequently mononuclear cells were collected by apheresis, cultured in the presence of GM-CSF and activated with IFN-gamma. This procedure resulted in the harvesting of 1.3 to 3.1 x 10(9) (mean 2 x 10(9)) macrophages per apheresis, product which was very well tolerated at autologous reinfusion. These infusions did not induce increased levels of TNF-alpha, IL-6, soluble CD14 nor nitrates in blood plasma (or urine). The lack of TNF-alpha and IL-6 release in blood plasma could explain the good tolerance of these infusions. No in vivo anti-tumoural activity of these high numbers of infused macrophages could be observed.

[Investigations on the present status of infections with Chlamydia trachomatis (Ct), Mycoplasma hominis (Mh) and Ureaplasma urealyticum (Uu) in patients with venereal diseases, sexual abusers and healthy people in Da Lian]

From January to June 1992, we conducted the detection of serum antibodies against Ct, Mh and Uu in patients with venereal diseases, sexual abusers and healthy people. The results showed that the positive rates of antibodies against Ct, Mh and Uu in patients were the highest, while in healthy people those of antibodies against Ct and Uu were the lowest. The positive rates between the antibody against Uu and that against Mh have no obvious difference between male and female. All samples have dual infection of Ct and Mh.

Dosage-dependent modulation of glucose repression by MSN3 (STD1) in Saccharomyces cerevisiae

The SNF1 protein kinase of Saccharomyces cerevisiae is required to relieve glucose repression of transcription. To identify components of the SNF1 pathway, we isolated multicopy suppressors of defects caused by loss of SNF4, an activator of the SNF1 kinase. Increased dosage of the MSN3 gene restored invertase expression in snf4 mutants and also relieved glucose repression in the wild type. Deletion of MSN3 caused no substantial phenotype, and we identified a homolog, MTH1, encoding a protein 61% identical to MSN3. Both are also homologous to chicken fimbrin, human plastin, and yeast SAC6 over a 43-residue region. Deletion of MSN3 and MTH1 together impaired derepression of invertase in response to glucose limitation. Finally, MSN3 physically interacts with the SNF1 protein kinase, as assayed by a two-hybrid system and by in vitro binding studies. MSN3 is the same gene as STD1, a multicopy suppressor of defects caused by overexpression of the C terminus of TATA-binding protein (R. W. Ganster, W. Shen, and M. C. Schmidt, Mol. Cell. Biol. 13:3650-3659, 1993). Taken together, these data suggest that MSN3 modulates the regulatory response to glucose and may couple the SNF1 pathway to transcription.

[Application of A-scan ultrasonography in the diagnosis and treatment of myositis of extraocular muscles (with a report of four cases)]

Four cases of myositis of extraocular muscles were diagnosed by A-scan ultrasonography. The diagnostic criteria were thickening, low reflectivity and homogeneous internal structure of affected muscles. Under the monitor of A-scan ultrasonography all cases were treated with high dose prednisone. Three of the four were cured, and one regressed. Meanwhile, the clinical manifestations and differential diagnosis of the disease are discussed briefly.

[Effect of the changes of amino acids on both signal peptide C-terminal and mature protein N-terminal region to the secretion of alpha-amylase in B. subtilis]

By site-directed mutagenesis, G and C have taken the place of T and G at nucleotide sequence 287 and 291 of B. licheniformis alpha-amylase gene to generate pAm-y413B and the N-terminal sequence of mature protein have been changed from 7Leu 8Met to 7Arg8Ile. By the insertion of polylinker into the C-terminal of the signal sequence of alpha-amylase gene of pAmy413, the signal peptide of alpha-amylase produced by pAmy413L is 13 amino acids more than the pAmy413 (which is 29 amino acids long) and also, a new recognition cleavage sequence for signal peptidase I (Ala-Gln-Ala decreases Ser) is created; The secondary structure of the signal peptide has been analyzed by computer programs. The alpha-amylase relative activity of the two mutant strains is 3% and 36% of pAmy413, respectively. The molecular weight of extracellular alpha-amylase is the same as pAmy413. Terminal analysis shows that the N-terminal amino acid of mature protein is Ala, not Ser, and suggests that SPase I prefers to cleavage at the wild type recognition site (Ala-Ala-Ala decreases Ala). Therefore, all of the above results show that the secretion of alpha-amylase in B. subtilis is in accordance with the co-translational transportation model.

[Transposition of Tn917 in Bacillus pumilus]

Transposition Tn917 was introduced into Bacillus pumilus 289 by protoplast transformation with plasmid pTV32. The temperature-sensitive replication property of pTV32 was maintained in B. pumilus. Tn917 was transposed efficiently in B. pumilus with 4.8 x 10(-4) transposition rate. The yield of auxotrophs was about 0.65% in all insertional mutants. It indicated a prospects for the use of Tn917 as a tool for insertional mutagenesis and genetic manipulation in B. pumilus.

[Clinical significance of serum CEA determination in the diagnosis of colo-rectal cancer]

Serum CEA levels of 581 specimens obtained from 350 colo-rectal cancer patients and 61 specimens from 54 non-tumor subjects were determined by sandwich method of CEA-EIA McAb kit supplied by the Beijing Institute of Biological Products. In patients with primary colo-rectal cancer, the serum CEA level was 15.0 +/- 52.1 ng/ml and 37.9% of patients gave a CEA level greater than 5 ng/ml. In recurrent colo-rectal cancer patients, serum CEA increased to 124.2 +/- 454.8 ng/ml with a positive rate of 78.0%. Both the CEA value and the positive rate of patients in clinically tumor-free period after surgery were 2.9 +/- 2.2 ng/ml and 16.5%, respectively. Serial follow-up CEA assays in selected cases were helpful to reflect the clinical status. Generally, CEA is useful to predict prognosis and to guide follow-up management.

Isolation and characterization of rabbit gastrin

The heptadecapeptide form the rabbit gastrin was extracted from 16 rabbit antra and purified by a combination of DEAE Sephadex, C-18 SEP PAK cartridges, fast performance liquid chromatography (FPLC) and reverse phase high pressure liquid chromatography (HPLC) steps. After the HPLC purification, a sharp, single peak of gastrin-like immunoreactivity was detected that had the same absorption to immunoreactivity ratio as human gastrin. An amino terminal pyrrolidone carboxylic acid blocking group was removed by incubation with pyrrolidone carboxylic peptidase. The amino acid analysis, microsequence analysis and mass spectrometry all confirmed the structure of rabbit gastrin being pQGPWLQEEEEAYGWMDFamide. This sequence is identical to human gastrin-17 except for glutamine in position 6 which replaces glutamate in human gastrin. Both sulfated and unsulfated rabbit gastrin-17 were characterized by mass spectrometry.