[Microsurgical repair of defects of soft tissue and infected wounds of extremities]

A study was carried out to observe the application of microsurgical technique in the repair defects of soft tissue and infected wounds of extremities. Eighty-three patients with soft tissue defects and infected wounds of extremities were treated by either transferring of vascularized cutaneous flap or transplantation of myocutaneous flap with vascular anastomosis. The result showed that eighty-three patients had gained success after a follow-up of 6 months to 4 years. It was concluded that soft tissue defects and infected wounds of extremities should be repaired as early as possible. Selecting the donor flap near the recipient site was of first choice. The method used for repair should be simple and easily applicable rather these very complicated one. The success depended on the correct treatment of local conditions, resonable design of donor flap and close monitoring after operation.

[Chemical constituents of the leaves of Crataegus scabrifolia (Franch.) Rehd]

OBJECTIVE

To explore the medicinal resources of Crataegus and seek compounds with pharmaceutical effects.

METHOD

Column chromatography was employed for the isolation and purification of constituents and the structures were elucidated by spectral analysis and chemical evidence.

RESULT

Six compounds were obtained and identified as rutin, hyperoside, vitexin, ursolic acid, daucosterol, and nonacosanol.

CONCLUSION

The main constituents of the leaves of Crataegus scabrifolia are flavonoids.

Replication defect of moloney murine leukemia virus with a mutant reverse transcriptase that can incorporate ribonucleotides and deoxyribonucleotides

Reverse transcriptase (RT) plays a critical role in retrovirus replication, directing the synthesis of a double- stranded DNA copy of the viral RNA genome. We have previously described a mutant RT of the Moloney murine leukemia virus in which F155 was replaced by valine, and we demonstrated that this substitution allowed the enzyme to incorporate ribonucleotides to form RNA while still retaining its normal ability to incorporate deoxyribonucleotides to form DNA. When introduced into the viral genome, this mutation rendered the virus incapable of replication. Characterization of the mutant virus revealed that the enzyme was still active and able to synthesize minus-strand strong stop DNA and some longer products but failed to make full-length minus-strand DNA. We propose that the failure of the enzyme to complete DNA synthesis in vivo resulted from its ability to incorporate ribonucleotides into the products, which served as inhibitors for DNA synthesis. We also tested seven other amino acid residues for their abilities to substitute for F155 in virus replication; of these, only tyrosine could support virus replication. In an attempt to select for second-site suppressor mutations, the F155V mutant was subjected to random mutagenesis and was used as a parent for the isolation of revertant viruses. Two independent revertants were found to have changed the valine residue at position 155 back to the wild- type phenylalanine. These results suggest that an aromatic ring at this position is important for virus replication.

[Feasibility study of laser-induced fluorescence (LIF) spectrum for diagnosis of colon cancer]

OBJECTIVE

To study the usefulness of laser-induced fluorescence (LIF) spectrum for diagnosis of colon cancer.

METHODS

Nitrogen laser, wavelength 337 nm, optical multichannel analyzer (OMA III) were used to demonstrate LIF spectra. A standard spectrum of LIF of colon cancer was used to analyse that of 51 surgically removed colon specimens and the results were compared with pathological findings.

RESULTS

Compared with pathological findings, LIF spectrum examination had 80.0% sensitivity, 100% specificity, with positive predictive value of 100%, negative predictive value of 83.9% and accuracy of 90.2% for the diagnosis of colon cancer, respectively.

CONCLUSION

Laser-induced fluorescence (LIF) spectrum of colon is of use in the diagnosis of colon cancer.

[P53 protein expression in malignant germ cell tumor of ovary and its relationship with clinical course and prognosis]

To study the relationship of P53 protein expression with clinical course and prognosis in malignant germ cell tumor of ovary P53 protein expression was examined by immunohistochemical ABC methods in 82 cases of the neoplasm and 20 cases of normal ovary tissue. The results showed that no expression of P53 protein was detected in normal ovarian tissue. The total expression rate of P53 protein was 24.39% in neoplasm, and the expression was not significantly correlated with the different histological types of neoplasm. The study however found that the protein expression of p53 gene was significantly correlated with the clinical stages and prognosis of the neoplasm.

Use of foldback analysis to foster consolidation between academic and public health practice

INTRODUCTION

Departments of health can provide applied settings for students from academic public health programs to explore the connection of course work to real-life circumstances. Barriers exist for public health practitioners, however, that restrict their willingness to engage in joint efforts with academe. To address these barriers, they must be identified and characterized. That is, it is important for academics in public health to respect both barrier-issues and to understand underlying value constructs, if they hope to employ public health practice settings to advance their students' training.

METHODS

A 100% sample of all midmanagers was surveyed at the Hawaii Department of Health by the School of Public Health. Nine clusters of "key issues for continued collaboration" were identified and rank-ordered in importance. Further analysis of the rank-orders, using multidimensional scaling, distinguished important underlying value constructs crucial to improving joint activities between the school and department.

RESULTS

Working together, representatives from the Department and School identified the first three value dimensions as cooperation, implying the need for true reciprocal and equal interaction; obligation, signifying mutual responsibility and parallel investment; and, professional practice, suggesting the balanced interdigitation of research with practice. These value dimensions account for three fifths (58%) of the variance in opinion.

CONCLUSIONS

Detailed analysis of these dimensions suggests that low-cost strategies improve collaboration, and foster possible consolidation, between academic and clinical public health settings. A stronger partnership between the school and the department is likely, provided the two agencies can address these issues satisfactorily. Insights from the Hawaii experience may prove useful to other academic public health practice settings. Recommendations that may improve collaboration include holding joint semi-annual meetings, a school bulletin board listing practica at the department, a public health leadership course, improved electronic communications between the school and the department, joint appointments to the two agencies, faculty release time to conduct research to improve practices at the department, and the establishment of a steering committee for the collaboration.

Differential expression of cyclic nucleotide phosphodiesterase 3 and 4 activities in human T cell clones specific for myelin basic protein

Little is known concerning the relative distribution and function of the different cyclic nucleotide phosphodiesterases (PDEs) in lymphocytes. Recent reports, however, have indicated that specific PDE4 inhibitors were effective in treatment of experimental allergic encephalomyelitis, an animal model of multiple sclerosis. The therapeutic effect of PDE4 inhibitors is thought to be related to inhibition of autoreactive CD4+ T cells specific for myelin basic protein (MBP) or other myelin proteins. Human autoreactive CD4+ T lymphocyte clones (TCC), specific for the immunodominant MBP epitope (amino acids 83-99), contain PDE3 and PDE4, two PDEs that exhibit a high affinity for cAMP. Amplification of TCC mRNA by reverse transcription-PCR indicated that TCC PDE3 mRNA was of the PDE3B, not PDE3A, subtype. Different TCC contained different proportions of PDE3 and PDE4, and their activities increased during Ag (MBP) stimulation. Specific PDE3 (cilostamide) and PDE4 (rolipram) inhibitors suppressed [3H]thymidine incorporation in TCC. Since it is believed that many autoimmune diseases are at least partially mediated by autoreactive CD4+ T cells, these observations may have important implications not only for the treatment of multiple sclerosis but also for other autoimmune diseases.

Differential expression of cyclic nucleotide phosphodiesterase 3 and 4 activities in human T cell clones specific for myelin basic protein

Little is known concerning the relative distribution and function of the different cyclic nucleotide phosphodiesterases (PDEs) in lymphocytes. Recent reports, however, have indicated that specific PDE4 inhibitors were effective in treatment of experimental allergic encephalomyelitis, an animal model of multiple sclerosis. The therapeutic effect of PDE4 inhibitors is thought to be related to inhibition of autoreactive CD4+ T cells specific for myelin basic protein (MBP) or other myelin proteins. Human autoreactive CD4+ T lymphocyte clones (TCC), specific for the immunodominant MBP epitope (amino acids 83-99), contain PDE3 and PDE4, two PDEs that exhibit a high affinity for cAMP. Amplification of TCC mRNA by reverse transcription-PCR indicated that TCC PDE3 mRNA was of the PDE3B, not PDE3A, subtype. Different TCC contained different proportions of PDE3 and PDE4, and their activities increased during Ag (MBP) stimulation. Specific PDE3 (cilostamide) and PDE4 (rolipram) inhibitors suppressed [3H]thymidine incorporation in TCC. Since it is believed that many autoimmune diseases are at least partially mediated by autoreactive CD4+ T cells, these observations may have important implications not only for the treatment of multiple sclerosis but also for other autoimmune diseases.

Fusion of phospholipid vesicles induced by the ribosome inactivating protein saporin

The single chain ribosome-inactivating protein Saporin-S6 (SO-6) induces the fusion of acid phospholipid vesicles. The extent of fusion was measured by resonance energy transfer assay between the N-(7-nitro-2-1,3-benzoxadiazol-4-yl)-dimyristoylphosphatidyl lithanolamine (NBD-PE)(donor) and N-(lissamine rhodamine B sulphonyl)-diacylphoshaidylethanolamine (Rh-PE) (acceptor) incorporated in the vesicle. The saturated lipid/protein molar ratio is approx. 100:1. The time course of fusion of vesicles induced by the protein showed that the process was completed within 10 minutes, and the size of the particles in the medium was enlarged which conforms the occurrence of the fusion occurring. The fusion is temperature dependent and the liquid-crystalline state lipid is more apt to fuse than the gel phase lipid. The effect of SO-6 is also dependent on ionic strength and pH, high salt concentration and basic pH may abolish fusion, which suggests that both electrostatic and hydrophobic components may be involved in the process.

[Measurement of skin area of expansion and defect on scalp]

The skin expander has been widely used to produce extra skin by the plastic surgeon, but there is no a scientific method for measuring the skin area of external expansion. The plastic surgeon usually do not know exactly whether the skin area of expansion more or less than the skin area of defect. A morphologic measure method was developed to figure out accurately the area of expansion and the area of defect separately. Clinical application has proved that the method can help the plastic surgeon know the wanted skin area of expansion in practice before operation.

Conferring RNA polymerase activity to a DNA polymerase: a single residue in reverse transcriptase controls substrate selection

The traditional classification of nucleic acid polymerases as either DNA or RNA polymerases is based, in large part, on their fundamental preference for the incorporation of either deoxyribonucleotides or ribonucleotides during chain elongation. The refined structure determination of Moloney murine leukemia virus reverse transcriptase, a strict DNA polymerase, recently allowed the prediction that a single amino acid residue at the active site might be responsible for the discrimination against the 2'OH group of an incoming ribonucleotide. Mutation of this residue resulted in a variant enzyme now capable of acting as an RNA polymerase. In marked contrast to the wild-type enzyme, the K(m) of the mutant enzyme for ribonucleotides was comparable to that for deoxyribonucleotides. The results are consistent with proposals of a common evolutionary origin for both classes of enzymes and support models of a common mechanism of nucleic acid synthesis underlying catalysis by all such polymerases.

Fluorescence spectroscopic study of the interaction of saporin with phospholipid vesicles

Saporin-S6 (SO-6) is a type-1 ribosome-inactivating protein purified from the seeds of Saponaria officinalis. The fluorescence characteristics of SO-6 were studied in the presence and absence of phospholipids. The interaction of SO-6 with DMPG or DMPC vesicles results in a decrease in the fluorescence emission intensity of tryptophan without any shift in the emission maximal wavelength. The results of fluorescence titration indicate that DMPG/SO-6 saturation molar ratio is 100: 1, but the binding of DMPC with SO-6 does not reach a saturating plot. A shielding of the tryptophan fluorescence from quenching by acrylamide on interaction with the phospholipids was observed, and this shielding was more pronounced in the presence of DMPG. The interaction of SO-6 with DMPG vesicles is stronger in the liquid-crystalline phase than in the gel phase. Extrinsic fluorescence studies indicated that the interaction of the protein with DMPG vesicles does not modify the phase transition temperature of the lipid, but decreases the amplitude of the change of fluorescence anisotropy associated with the co-operative melting of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labelled vesicles. These results indicate that both electrostatic and hydrophobic components are involved in the SO-6-lipid vesicle interaction.

[The value of urine cystein proteinase and serum CA125 measurement in monitoring the treatment of malignant ovarian tumor]

Urine cystein proteinase (UCP) and serum CA125 were measured in 40 patients with malignant ovarian tumor (malignant group), 40 patients with benign ovarian tumor (benign group), and 40 normal control (normal group). 28 patients in the malignant group underwent UCP and CA125 measurement pre-operation, post-operation, and during three courses of chemotherapy. The enzyme activity of UCP in the malignant group was significantly higher than that in the benign and normal groups (P < 0.05 or 0.01). The values of UCP in patients with malignant tumor of stages II-IV were significantly higher compared with those of stages I-II (P < 0.01, 0.05). The activity of UCP was elevated pre-operation, post-operation, and was much higher on the seventh day postoperation. After the seventh day, UCP activity decreased gradually. Serum CA125 was also detected pre-operation, at 7.30 and 60 days post-operation. The levels of UCP and CA125 pre-operation and 30, 60 days post-operation in the patients whose residual carcinoma lesions were > 2 cm in diameter were apparantly higher than those with no residual lesions (P < 0.05). UCP and CA125 values were measured in six patients before relaparotomy. The sensitivity, specificity, accuaracy, positive predictive value and negative predictive value for UCP assay are 980%, 100%, 83%, 100% and 50% and those for CA125 assay are 40%, 100%, 80%, 100%, and 25%, respectively.

Regulation of 5'-AMP-activated protein kinase activity by the noncatalytic beta and gamma subunits

The mammalian 5'-AMP-activated protein kinase is a heterotrimer consisting of an alpha catalytic subunit and beta and gamma noncatalytic subunits, each of which is represented in a larger isoprotein family, related to the SNF1 kinase and its interacting proteins in yeast. In this study, we have used mammalian cell transfection to compare the activities of the two alpha subunit isoforms, alpha-1 and alpha-2, and to study the influence of the noncatalytic subunits on enzyme subunit association and activity. Expression of epitope-tagged protein subunits in COS7 cells indicates detectable but low level kinase activity for each of the two catalytic alpha subunits. Co-expression of alpha subunits with the beta or gamma subunits modestly increases kinase activity accompanied by the formation of alpha/beta or alpha/gamma heterodimers. Co-expression of all three subunits, however, is accompanied by a 50-110-fold increase in kinase activity with the formation of a heterotrimeric complex. In addition to binding of each noncatalytic subunit to the alpha subunit, the beta and gamma subunits bind to each other, likely resulting in a more stable heterotrimeric complex. The increase in kinase activity associated with expression of this heterotrimer is due both to an increase in enzyme-specific activity (units/enzyme mass) and to an apparent enhanced alpha subunit expression. Co-expression of a catalytically defective alpha subunit or the beta/gamma-binding COOH-terminal domain of the alpha subunit results in reduced heterotrimeric kinase activity. The synergistic positive regulatory roles for both the noncatalytic beta and gamma subunits of 5'-AMP-activated protein kinase contrasts with the Snf1p kinase, where only heterodimers of Snf1p and Snf4p seem to be required for maximum kinase activity.

Receptor specificity of the fibroblast growth factor family

Fibroblast growth factors (FGFs) are essential molecules for mammalian development. The nine known FGF ligands and the four signaling FGF receptors (and their alternatively spliced variants) are expressed in specific spatial and temporal patterns. The activity of this signaling pathway is regulated by ligand binding specificity, heparan sulfate proteoglycans, and the differential signaling capacity of individual FGF receptors. To determine potentially relevant ligand-receptor pairs we have engineered mitogenically responsive cell lines expressing the major splice variants of all the known FGF receptors. We have assayed the mitogenic activity of the nine known FGF ligands on these cell lines. These studies demonstrate that FGF 1 is the only FGF that can activate all FGF receptor splice variants. Using FGF 1 as an internal standard we have determined the relative activity of all the other members of the FGF family. These data should serve as a biochemical foundation for determining developmental, physiological, and pathophysiological processes that involve FGF signaling pathways.

Non-catalytic beta- and gamma-subunit isoforms of the 5'-AMP-activated protein kinase

The mammalian 5'-AMP-activated protein kinase (AMPK) is a heterotrimeric protein consisting of alpha-, beta-, and gamma-subunits. The alpha-subunit is the catalytic subunit and is related to the yeast Snf1p kinase. In this study, we report the cloning of full-length cDNAs for the non-catalytic beta- and gamma-subunits. The rat liver AMPK beta-subunit clone predicts a protein of 30,464 Da, which is related to the Sip1p, Sip2p, and Gal83p subfamily of yeast proteins that interact with Snf1p and are involved in glucose regulation of gene expression. The AMPK beta-subunit, when expressed in bacteria and in mammalian cells, migrates anomalously on SDS gels at an apparent molecular mass of 40 kDa. Rat and human liver AMPK gamma-subunit clones predict a protein of 37,577 Da (AMPK-gamma1), which is related to the yeast Snf4p protein that copurifies with Snf1p and to a larger family of other human AMPK gamma-isoforms. The mRNAs for both AMPK- beta and AMPK-gamma1 are widely expressed in rat tissues, consistent with a broad role for AMPK in cellular regulation. These data reveal a mammalian multisubunit protein kinase strikingly similar to the multisubunit glucose-sensing Snf1 kinase complex. The identification of isoform families for the AMPK subunits indicates the potential diversity of the roles of this highly conserved signaling system in nutrient regulation and utilization in mammalian cells.

Aggregation of phospholipid vesicles induced by the ribosome inactivating protein saporin

Saporin-S6(SO-6) is a single chain ribosome inactivating protein, which can inhibit protein synthesis by inactivating eukaryotic ribosomes. The interaction of SO-6 with phospholipid model systems was described. SO-6 can specifically interact with negatively-charged phospholipid vesicles and it induces the aggregation of the lipid vesicles. The kinetics of the vesicle aggregation induced by SO-6 was studied. The saturating protein/lipid molar ratio was determined to be 1:100 based on titration experiments. The aggregation is dependent on the temperature in a range that was many times higher than the phase transition temperature of the phospholipid. The effect of pH on the aggregation of the vesicles can not be explained by simple deprotonation of side chain amino groups of the protein, and may be related to conformational changes of the protein. The maintenance of physiological ionic strength was required for the aggregation of SO-6 with vesicles. Finally, the interaction was prompted by Ca2+ ions, and was totally inhibited by EDTA, which suggests that SO-6 may interact with phospholipid vesicles in a Ca(2+)-dependent manner.

Mammalian AMP-activated protein kinase subfamily

The mammalian 5'-AMP-activated protein kinase (AMPK) is related to a growing family of protein kinases in yeast and plants that are regulated by nutritional stress. We find the most prominent expressed form of the hepatic AMPK catalytic subunit (alpha 1) is distinct from the previously cloned kinase subunit (alpha 2). The alpha 1 (548 residues) and alpha 2 (552 residues) isoforms have 90% amino acid sequence identity within the catalytic core but only 61% identity elsewhere. The tissue distribution of the AMPK activity most closely parallels the low abundance 6-kilobase alpha 1 mRNA distribution and the alpha 1 immunoreactivity rather than alpha 2, with substantial amounts in kidney, liver, lung, heart, and brain. Both alpha 1 and alpha 2 isoforms are stimulated by AMP and contain noncatalytic beta and gamma subunits. The liver alpha 1 isoform accounts for approximately 94% of the enzyme activity measured using the SAMS peptide substrate. The tissue distribution of the alpha 2 immunoreactivity parallels the alpha 2 8.5-kilobase mRNA and is most prominent in skeletal muscle, heart, and liver. Isoforms of the beta and gamma subunits present in the human genome sequence reveal that the AMPK consists of a family of isoenzymes.

Four outbreaks of human trichinellosis in Henan Province

Four outbreaks of human trichinellosis caused by eating pork together had occurred successively in two rural areas and two cities of Henan Province, where the disease is endemic. Of the 110 persons involved, 54 had the onset. All of them had the history of eating pork. In the outbreak of Dengzhou, in those persons who dined together, men were all uninfected and 13 women were infected. The difference found between sexes was suggested to be related with spirit drinking. In these 54 patients, the latent period ranged from 3 to 28 days. The relevant clinical symptoms and signs were fever, edema, myalgia, rash, headache, nausea, abdominal pain and diarrhea. Vomiting was uncommon. Most patients were hospitalized and all cases recovered in two weeks after proper treatment with albendazole.

[Analysis of total saponins in traditional Chinese drug radix Astragali]

An analysis of the total saponins in 11 original species of Radix Astragali has been made. The results will be beneficial for drug control and resources utilization.

Heparin can activate a receptor tyrosine kinase

Heparin, a densely sulfated glycosaminoglycan produced by mast cells, is best known for its inhibitory effects on the blood coagulation system. Heparin or heparan sulfate proteoglycans are also essential cofactors for the interaction of fibroblast growth factors (FGFs) with their receptor tyrosine kinases (FGFRs). Here we show that heparin is a growth factor-independent activating ligand for FGFR-4. Heparin stimulates FGFR-4 autophosphorylation on transfected myoblasts, fibroblasts and lymphoid cells, and is most potent on cells lacking surface heparan proteoglycan. Two functional analogs of heparin, fucoidan and dextran sulfate, are also activators of FGFR-4, while neither heparin nor its analogs can stimulate FGFR-1 in the absence of FGF. A mutation in the FGFR-4 ectodomain which impairs receptor activation by FGFs does not interfere with activation by heparin, demonstrating that receptor domains required for heparin or FGF activation are not identical. Heparin activation of FGFR-4 or of a chimeric receptor bearing FGFR-4 ectodomain and FGFR-1 cytodomain triggers downstream tyrosine phosphorylation of several signaling proteins, and induces proliferation of cells bearing the chimeric receptor. Consistent with these findings, a soluble FGFR-4 ectodomain has strong FGF-independent affinity for immobilized heparin resin, while soluble FGFR-1 requires FGF for stable heparin interaction. Heparin activation of FGFR-4 is the first example of a mammalian polysaccharide serving as a signaling ligand.

Catalytic subunits of the porcine and rat 5'-AMP-activated protein kinase are members of the SNF1 protein kinase family

The 5'-AMP-activated protein kinase (AMPK) regulates the fatty acid and sterol synthesizing pathways via phosphorylation of acetyl-CoA carboxylase and HMG-CoA reductase, respectively. Highly purified kinase from porcine liver contains three apparent subunits of molecular mass 63 kDa, 40 kDa and 38 kDa. Peptide sequencing of the 63 kDa protein (AMPK63cat) revealed that this polypeptide is the catalytic subunit of the kinase. Porcine peptide sequences were used to clone by RT-PCR partial length cDNAs for the catalytic domains of the porcine AMPK63cat, and its rat homolog, which were virtually identical in deduced amino acid sequence. Screening of a rat liver cDNA library with these partial length cDNAs and with degenerate oligonucleotides yielded several unique clones, some of which had a 142 bp deletion in the catalytic domain of the kinase. A consensus full-length sequence with a 1.7 kb open reading frame has been constructed from overlapping library and PCR-derived clones. A large mRNA for rat AMPK63cat (8.5 kb) is expressed in nearly all rat tissues, with highest levels detectable in heart and skeletal muscle. Using PCR, the presence of two mRNA species with or without the 142 bp deletion in the catalytic domain was noted in all rat tissues examined. Comparison of the deduced protein sequence of AMPK63cat reveals highly conserved homologies in both the catalytic and non-catalytic domains to several members of the SNF1 kinase family, including kinases from Arabidopsis, barley, rye, and S. cerevesiae, as well as to other mammalian kinases and to a C. elegans kinase. The high evolutionary conservation of both kinase structure and function (metabolite sensing) coupled with their pattern of tissue/organism expression suggest that the mammalian members of this kinase family likely play wider roles than the regulation of cellular lipid metabolism.

In vivo detection of radicals in biological reactions

In vivo detection of free radicals on a quantitative basis is essential for an establishment of their role in membrane, protein, and cell and tissue damage. This article compares optical methods, including chemiluminescence, electron paramagnetic resonance (EPR) and NMR methods for the study of free radicals and free radical damage, especially reperfusion injury neutrophil accumulation 6 hr after the ischemia/reperfusion insult. The chemiluminescence method is applied to an evaluation of the improved resistance to free radical stress due to transfection of creatine kinase in the mouse liver.

Mammalian 5'-AMP-activated protein kinase non-catalytic subunits are homologs of proteins that interact with yeast Snf1 protein kinase

The 5'-AMP-activated protein kinase is responsible for the regulation of fatty acid synthesis by phosphorylation and inactivation of acetyl-CoA carboxylase. The porcine liver 5'-AMP-activated protein kinase 63-kDa catalytic subunit co-purifies 14,000-fold with a 38- and 40-kDa protein (Mitchelhill, K.I. et al. (1994) J. Biol. Chem. 269, 2361-2364). The 63-kDa subunit is homologous to the Saccharomyces cerevisiae Snf1 protein kinase, which regulates gene expression during glucose derepression. Peptide amino acid and polymerase chain reaction-derived partial cDNA sequences of both the pig and rat liver enzymes show that the 38-kDa protein is homologous to Snf4p (CAT3) and that the 40-kDa protein is homologous to the Sip1p/Spm/GAL83 family of Snf1p interacting proteins. Sucrose density gradient and cross-linking experiments with purified 5'-AMP-activated protein kinase suggest that both the 38- and 40-kDa proteins associate tightly with the 63-kDa catalytic polypeptide in either a heterotrimeric complex or in dimeric complexes. The 40-kDa subunit is autophosphorylated within the 63-kDa subunit complex. The sequence relationships between the mammalian 5'-AMP-activated protein kinase and yeast Snf1p extend to the subunit proteins consistent with conservation of the functional roles of these polypeptides in cellular regulation by this family of metabolite-sensing protein kinases.

[Reorganization of growth-plate-like tissue by isolated chondrocytes in culture]

Growth-plate cartilage is organized into four cellular zones containing resting, proliferating, maturing, and hypertrophic cells. Rabbit chondrocytes were isolated from growth-plate costal cartilage of 4-week-old New Zealand rabbits, the cells (15 x 10(4)) were suspended in 1 ml of Iscove's modified Dulbecco's medium (IMDM) with 10% fetal bovine serum, 50 micrograms ascorbic acid, and 60 micrograms kanamycin (medium A), then transferred to a 15 ml of plastic centrifuge tube, and centrifuged at 1500 rpm for 5 min. The cell pellet was incubated at 37 degrees C under 5% CO2 in air. The cultures reorganized into growth plate-like tissue which could be seen 7-14 days after cell seeding. This growth-plate, histologically, was organized longitudinally into cellular columns and horizontally into four cellular zones containing resting, proliferating, maturing and hypertrophic cells. The hypertrophic cells in the upper were large in size and round or oval in shape, the proliferating and the mature chondrocytes in the lower were small in size and spherical or elongated in shape. These chondrocytes were surrounded by an extensive matrix. Biochemically, DNA content of cultures began to rise on the 2nd day after cell seeding and reached a plateau after 10 days later. The uronic acid content increased from day 4 and reached the maximum on day 15. In contrast in the early culture, alkaline phosphatase activity was extremely low, it began to rise on day 9 and was the highest on day 20. The sequential increase of DNA, uronic acid and alkaline phosphatase contents was analogous to the in vivo changes of growth-plate chondrocytes.

Identification of an essential cysteine residue in pyridoxal phosphatase from human erythrocytes

Pyridoxal-specific phosphatase purified from human erythrocytes was inactivated by a variety of thiol-specific reagents in a time- and concentration-dependent manner. The presence of pyridoxal phosphate, a substrate, or inorganic phosphate, a competitive inhibitor, protected the enzyme from inactivation. Phosphatase inactivated by disulfide reagents was reactivated by the addition of excess dithiothreitol, indicating that the inactivation was due to formation of a mixed disulfide between the reagent and a free cysteinyl residue at or near the active site of the enzyme. Incorporation of either 1 mol of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), 0.6 mol of iodo[3H]acetate, or 0.6 mol of N-[3H]ethylmaleimide per mol of subunit led to complete inactivation of the enzyme. High concentration of phosphate prevented the incorporation of DTNB and iodo[3H]acetate. Amino acid analysis of carboxymethylated enzyme and DTNB titration of the denatured phosphatase indicated that there may be only 1 cysteinyl residue per subunit. Modification by iodoacetate did not affect the quaternary structure of the enzyme. The phosphatase modified by iodo[3H]acetate was subjected to trypsin digestion, and the resulting peptides were separated on a reverse phase C18 column. Two radioactive peaks were obtained and contained a peptide with the N-terminal sequence of Ala-Gln-Gly-Val-Leu-Phe-Asp-Cys(Cm)-Asp-Gly-Val-Leu-X-Asn-Gly. Most of the radioactivity was released with Cys(Cm). These results indicate that the cysteinyl residue in this sequence is at or near the active site and is essential for activity. Residues 5-12 and 15 of this peptide are identical with a sequence of a yeast alkaline p-nitrophenylphosphatase, and the peptide has little homology with other mammalian phosphatases.

Generation of selenium-containing abzyme by using chemical mutation

A new strategy for generating abzyme was developed. Glutathione peroxidase (GPX, EC 1.11.1.9) is one of the important members of antioxidation enzyme system; it catalyzes the reductions of a variety of hydroperoxides in presence of glutathione(GSH). We have first prepared the monoclonal antibody (McAb) with GSH binding sites, then incorporated GPX catalytic group selenocystein (SeCys) into the antibody combining sites by using chemical mutation. Thus the mutated antibody displays high GPX activity, which approaches the magnitude level of native GPX, exhibits the kinetic behavior similar to native GPX, and has some advantages over native GPX.

Hepatic 5'-AMP-activated protein kinase: zonal distribution and relationship to acetyl-CoA carboxylase activity in varying nutritional states

Acetyl-CoA carboxylase (ACC) activity in the liver varies markedly as a function of the nutritional state and is subject to complex regulation involving variable enzyme content, enzyme specific activity due to variable phosphorylation, and zonation within the hepatic lobule. A 5'-AMP-activated protein kinase (AMPK) has been identified as the major regulatory kinase active on ACC. Employing dual-digitonin pulse perfusion, the effect of varying nutrition on periportal and perivenous zonation of ACC and AMPK activity within the liver has been characterized. During the transition from fasting to refeeding with high-carbohydrate chow, total ACC activity is increased 11- to 17-fold. This induction of total ACC activity is accounted for by a 4.5- to 6-fold increase in the content of the two major ACC isoforms and by a 2.5-to 3-fold increase in enzyme specific activity (units per mg ACC). Despite a small perivenous preponderance of ACC protein, a gradient of activity to the periportal side, due to this increase in specific activity, is observed in fasted rats and during early refeeding. After 24-48 h of refeeding, maximal induction of both ACC protein and specific activity is observed with obliteration of this total activity gradient. 5'-AMP-activated protein kinase activity is maximal in the fasted rat and is zonated to the perivenous side. During refeeding, this activity is rapidly markedly diminished with abolition of this gradient, correlating inversely with the activation of ACC over a narrow range of kinase activity. Activities of casein kinase II, myelin basic protein kinase(s), and ribosomal S6 kinase(s) show no zonation. These data suggest that the zonal activity of the 5'-AMP-activated protein kinase is responsible, in part, for the intrahepatic gradient in ACC activity and that the regulation of this kinase is responsible for the variations in ACC-specific activity that occur during varying nutrition.

Influence of intracellular glutathione concentration of lipofuscin accumulation in cultured neonatal rat cardiac myocytes

The objective of this study was to investigate the relationship between intracellular glutathione (GSH) and lipofuscinogenesis in an established model system of cultured postmitotic neonatal rat cardiac myocytes exposed to moderate oxidative stress with respect to culture conditions (cells grown at 21% oxygen pressure). Intracellular glutathione was depleted by exposing cell cultures to buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase; this caused an increase in lipofuscin-specific autofluorescence, reflecting lipofuscin accumulation. Cell cultures exposed to 100 microM BSO exhibited the following reactions, as compared to control cells: the intracellular glutathione level decreased 78%, 86%, and 89%, and lipofuscin-specific autofluorescence increased 26%, 28%, and 77% after 5, 8, and 14 days of treatment, respectively. Compared to the glutathione levels found in newly excised heart tissue, concentrations in cultured cardiac myocytes were lower during the first few days after culture establishment, probably a result of the cell preparation technique used. Due to this effect, differences between BSO-treated cells and control cells in regard to glutathione concentration and lipofuscin accumulation were more pronounced during the remainder of the 2-week culture period. Lipid peroxidation measured as thiobarbituric acid reactive substances was not increased in BSO-treated cells. These results are in agreement with the oxidative-stress theory of lipofuscinogenesis previously proposed from the authors' laboratory. The authors show that reduced GSH level leads to a simultaneous increase in accumulation of lipofuscin in cardiac myocytes, possibly by increasing the level of cytosolic hydrogen peroxide.

Mammalian AMP-activated protein kinase shares structural and functional homology with the catalytic domain of yeast Snf1 protein kinase

The AMP-activated protein kinase is responsible for the regulation of fatty acid synthesis by phosphorylation of acetyl-CoA carboxylase. It may also regulate cholesterol synthesis via phosphorylation and inactivation of hormone-sensitive lipase and hydroxymethylglutaryl-CoA reductase. We have purified the AMP-activated protein kinase 14,000-fold from porcine liver. The 63-kDa catalytic subunit co-purifies with two proteins of 40 and 38 kDa that may function as subunits. Partial amino acid sequence of the 63-kDa subunit revealed a striking homology with the catalytic domain of the yeast protein kinase transcriptional regulator Snf1 and its plant homologs. The Snf1 (72 kDa) and Snf4 (36 kDa) complex was also purified and found to phosphorylate the AMP-activated protein kinase peptide substrate, HMRSAMSGLHLVKRR-amide, but was not activated by AMP. Both Snf1/4 and the AMP-activated protein kinase phosphorylate and inactivate yeast acetyl-CoA carboxylase in vitro. These results indicate that during evolution the catalytic domain sequences of the Snf1 protein kinase subfamily have been exploited in the control of mammalian lipid metabolism and raise the possibilities that the AMP-activated protein kinase may have other substrates involved in regulating gene expression pathways, as well as Snf1 homologs participating in the control of lipid metabolism in many eukaryotic organisms.

Fibroblast growth factor receptors have different signaling and mitogenic potentials

Fibroblast growth factor (FGF) receptors (FGFRs) are structurally related receptor protein tyrosine kinases encoded by four distinct genes. Activation of FGFR-1, -2, and -3 by FGFs induces mitogenic responses in various cell types, but the mitogenic potential of FGFR-4 has not been previously explored. We have compared the properties of BaF3 murine lymphoid cells and L6 rat myoblast cells engineered to express FGFR-1 or FGFR-4. Acidic FGF binds with high affinity to and elicits tyrosine phosphorylation of FGFR-1 or FGFR-4 receptors displayed on BaF3 cells, but only FGFR-1 activation leads to cell survival and growth. FGFR-4 activation also fails to elicit detectable signals characteristic of the FGFR-1 response: tyrosine phosphorylation of SHC and extracellular signal-related kinase (ERK) proteins and induction of fos and tis11 RNA expression. The only detected response to FGFR-4 activation was weak phosphorylation of phospholipase C gamma. A chimeric receptor containing the extracellular domain of FGFR-4 and the intracellular domain of FGFR-1 confers FGF-dependent growth upon transfected BaF3 cells, demonstrating that the intracellular domains of the receptors dictate their functional capacity. Activation of FGFR-1 in transfected L6 myoblasts induced far stronger phosphorylation of phospholipase C gamma, SHC, and ERK proteins than could activation of FGFR-4 in L6 cells, and only FGFR-1 activation induced tyrosine phosphorylation of a characteristic 80-kD protein. Hence, the signaling and biological responses elicited by different FGF receptors substantially differ.

Lipofuscin-induced autofluorescence of living neonatal rat cardiomyocytes in culture

Lipofuscin-specific autofluorescence of living, cultured rat neonatal myocardial myocytes was studied with respect to intensity and spectral characteristics. The autofluorescence emission spectrum changed over time indicating continuously ongoing intramolecular reorganisation of the pigment. Moreover, as compared with formaldehyde-fixed material native lipofuscin produced a considerable red-shifted autofluorescence, indicating formaldehyde-induced molecular modification or quenching of certain parts of the spectrum. The relationship between oxidative stress and lipofuscinogenesis was confirmed because the rate of lipofuscin accumulation was increased when cells were grown at increasing ambient oxygen concentrations.

Distinct rat genes with related profiles of expression define a TIE receptor tyrosine kinase family

We have isolated rat cDNAs that encode two related receptor-like tyrosine kinases. One of these receptors, TIE-1, is the rat homolog of a recently described human receptor-like kinase termed TIE (Partanen et al., 1992). The related TIE-2 receptor has the same organization of amino acid sequence motifs characteristic of TIE-1: two immunoglobulin-like domains, three epidermal growth factor (EGF)-like domains and three fibronectin III-like repeats in the extracellular region and a short kinase insert sequence and C-terminal tail in the intracellular region. The amino acid sequences of the intracellular and extracellular regions of TIE-1 and TIE-2 are 79% and 32% identical respectively. Both tie genes are broadly expressed in embryonic, neonatal and adult tissues, accounted for largely by their coexpression in endothelial cells. The tie-2 gene is also uniquely expressed in several additional embryonic tissues, including the lens epithelium and the heart epicardium.

Purification of an autocrine growth factor homologous with mouse epithelin precursor from a highly tumorigenic cell line

PC cell line is a highly tumorigenic insulin-independent variant from the teratoma-derived adipogenic cell line 1246. Culture medium of PC cells contains a growth promoting activity for 3T3 cells and producer cells. PC cell-derived growth factor (PCDGF) was purified to homogeneity from PC cell-conditioned medium as an apparent 88-kDa protein by chromatography on heparin-Sepharose, Sephacryl S-200, and phenyl-Sepharose. Digestion with peptide-N-glycosidase F yielded an apparent 68-kDa protein component indicating that PCDGF is a glycoprotein containing about 20 kDa of carbohydrate. Partial sequence from Edman degradation of peptide fragments obtained by digestion of PCDGF with cyanogen bromide and trypsin demonstrates that PCDGF contains regions of sequence identity to that deduced from the granulin or epithelin precursor cDNAs. Granulins are small polypeptides purified from granulocyte extracts with no apparent biological functions. Epithelins are cell growth modulators purified as small molecular mass 6-kDa polypeptides from kidney extracts. The existence of a large molecular mass precursor for granulin or epithelin has been predicted based upon recently cloned cDNAs encoding these biomolecules within a 63.5-kDa protein with putative glycosylation sites. No biological activity has previously been attributed to the precursor. The present results indicate that PCDGF is a potential precursor for epithelin and/or granulin, that this 88-kDa protein is secreted and glycosylated, and that it can function as a mitogen for 3T3 cells as well as an autocrine growth factor for PC cells.