Catalysis and energy coupling of H(+)-ATPase (ATP synthase): molecular biological approaches

The molecular biological approach has provided important information for understanding the F0F1 H(+)-ATPase. This article focuses on our recent results on the catalytic site in the beta subunit, and the roles of alpha/beta subunit interaction and amino/carboxyl terminal interaction of the gamma subunit in energy coupling. Extensive mutagenesis of the beta subunit revealed that beta Lys-155, beta Thr-156, beta Glu-181 and beta Arg-182 are essential catalytic residues. beta Glu-185 is not absolutely essential, but a carboxyl residue may be necessary at this position. A pseudo-revertant analysis positioned beta Gly-172, beta Ser-174, beta Glu-192 and beta Val-198 in the proximity of beta Gly-149. The finding of the roles of beta Gly-149, beta Lys-155, and beta Thr-156 emphasized the importance of the glycine-rich sequence (Gly-X-X-X-X-Gly-Lys-Thr/Ser, E. coli beta residues between beta Gly-149 and beta Thr-156) conserved in many nucleotide binding proteins. The A subunits of vacuolar type ATPases may have a similar catalytic mechanism because they have conserved glycine-rich and Gly-Glu-Arg (corresponding to beta Gly-180-beta Arg-182) sequences. The results of these mutational studies are consistent with the labeling of beta Lys-155 and beta Lys-201 with AP3-PL, and of beta Glu-192 with DCCD [15]. The DCCD-binding residue of a thermophilic Bacillus corresponds to beta Glu-181, an essential catalytic residue discussed above. The defective coupling of the beta Ser-174-->Phe mutant was suppressed by the second mutation alpha Arg-296-->Cys, indicating the importance of alpha/beta interaction in energy coupling. The gamma subunit, especially its amino/carboxyl interaction, seems to be essential for energy coupling between catalysis and transport judging from studies on gamma Met-23-->Lys or Arg mutation and second-site mutations which suppressed the gamma Lys-23 mutation. Thus the conserved gamma Met-23 is not absolutely essential but is located in the important region for amino/carboxyl interaction for energy coupling.

Monomeric activin A retains high receptor binding affinity but exhibits low biological activity

Activins are multipotent hormones/growth factors that belong to the transforming growth factor-beta (TGF-beta) superfamily. Like TGF-beta s, activins have 9 conserved cysteine residues and are disulfide-bonded dimers. Based on the three-dimensional structure of TGF-beta 2, we deduced Cys80 in activin A to form the intermolecular disulfide bond. To obtain a monomeric form of activin, Cys80 was exchanged for a serine residue by polymerase chain reaction mutagenesis. The mutant protein was expressed in a baculovirus/insect cell expression system. The molecular mass of this mutant activin was determined to be 13 kDa (consistent with a single chain form of the protein) by SDS-polyacrylamide gel electrophoresis and by laser desorption mass spectroscopy. When this mutant monomeric activin was incubated with cells that expressed either the activin type IIB receptor or both the type I and type IIB receptors, its affinity was found to be 20% of that of native activin on a mass basis. Binding affinity determined using the mouse pituitary cell line AtT 20 was 10% of that of native activin A. Biological potency, however, as determined by the mutant protein's ability to release FSH from anterior pituitary cells in primary culture and by its ability to suppress basal ACTH secretion form AtT 20 cells, was only 1% of that of the native protein. This discrepancy of an order of magnitude between binding and biological activity is consistent with a model in which dimerization of the hormone is not necessary for high affinity binding to its receptor(s) while being essential for efficient signal transduction.

Autophosphorylation modulates the kinase activity and oncogenic potential of the Met receptor tyrosine kinase

The met oncogene is activated by a genomic rearrangement that generates a hybrid protein containing tpr sequences at its amino terminus fused directly to the met (hepatocyte growth factor/scatter factor) receptor tyrosine kinase domain. The resultant p65Tpr-Met hybrid protein possesses tyrosine kinase activity and is constitutively phosphorylated on tyrosine in vivo. A substitution of the conserved lysine in the catalytic domain abolished kinase activity and the transforming potential of Tpr-Met demonstrating the requirement for kinase activity for transformation. To study the role of autophosphorylation at particular tyrosine residues on the transforming activity of Tpr-Met, the major autophosphorylation sites were identified by two dimensional phosphopeptide mapping. Two tyrosine residues in the catalytic domain, tyrosine 365 and tyrosine 366, were found to be the major autophosphorylation sites both in vitro and in vivo. Mutation of these sites singly or together modulates the biochemical and biological properties of Tpr-Met. Compared with the wild-type Tpr-Met, mutants have a reduced in vitro kinase activity when measured by levels of autophosphorylation and by their ability to phosphorylate an exogenous substrate and have little or no transforming activity. These results indicate that autophosphorylation at critical tyrosine residues is required for activation of the kinase activity of Tpr-Met and for cell transformation by this oncogene.

Role of scatter factor in the pathogenesis of AIDS-related Kaposi sarcoma

Kaposi sarcoma (KS) is a complex multicellular neoplasm that is commonly associated with AIDS. The pathogenesis of KS is not well understood. KS tumor cells grow poorly in vitro and require medium conditioned by retrovirus-infected T lymphocytes. We observed that conditioned medium (CM) from type II human T-cell leukemia virus (HTLV-II)-infected T cells (HTLV-II CM) induces conversion of endothelial cells (ECs) to a KS tumor cell-like phenotype. ECs grown in HTLV-II CM acquired a spindle-shaped morphology, the ability to express factor XIIIa and other KS cell markers, and a cytokine production profile similar to that of KS cells. We found that HTLV-II CM contains large quantities of scatter factor (SF), an angiogenic cytokine that stimulates cell motility. SF induced ECs to become spindle-shaped and express factor XIIIa. Moreover, SF was found to be a mitogen for KS cells in vitro and was identified within KS lesions in vivo. SF mRNA was present in KS cells in vitro, and antibodies against SF inhibited the growth of KS cells. The receptor for SF, the c-met protein, was expressed by ECs, dermal dendrocytes, and KS tumor cells in vitro and in vivo. HTLV-II CM was highly angiogenic in vivo, which was blocked by antibodies against SF. Based on these findings, we suggest that SF plays a role in the initiation and maintenance of KS lesions.

NADH and NAD modulates Ca(2+)-activated K+ channels in small pulmonary arterial smooth muscle cells of the rabbit

We have investigated the effect of NADH and NAD on the gating of large conductance Ca(2+)-activated K(KCa) channels in arterial smooth muscle cells isolated from small pulmonary artery (outer diameter < 300 microns) and ear artery, using the patch clamp technique. In the inside-out configuration, intracellularly applied 2 mM NADH inhibited the activity of KCa channels in pulmonary arterial smooth muscle cells, while it had no significant effect on ear arterial smooth muscle cells. On the other hand, 2 mM NAD increased the opening of KCa channels in pulmonary arterial smooth muscle cells. The effects of another intracellular redox couple, glutathione(GSH) and glutathione disulfide(GSSG) were also dependent on their redox potentials. GSH(5 mM) inhibited KCa channels activity, while GSSG(5 mM) increased the activity of pulmonary arterial smooth muscle cells. It could be concluded that the modulation of KCa channels by intracellular redox state contributes, at least in part, to the hypoxic suppression of outward current in pulmonary arterial smooth muscle cells.

Involvement of hepatocyte growth factor in kidney development

Using PCR, hepatocyte growth factor (HGF) and c-met (HGF receptor) expression were analyzed in the developing mouse kidney. Both HGF and c-met were expressed from Gestational Day 11.5 onward, the time at which branching morphogenesis of ureteric bud occurs. Coculturing the embryonic kidney with MDCK cells seeded in Type I collagen induced branching morphogenesis of the MDCK cells. When a monospecific antiserum against HGF was included in the culture medium, the branching morphogenesis induced by the embryonic kidney was markedly inhibited (73%). This anti-HGF serum also inhibited metanephric growth when incubated with 11.5- to 12.5-day embryonic kidneys in an organ culture assay. No inhibition was observed by nonimmune serum. Perturbation of ureteric duct development as well as extraductal metanephric development was observed in embryonic kidneys incubated with the anti-HGF serum. Together, our data indicates an important role for HGF in kidney development.

Receptor chimeras indicate that the met tyrosine kinase mediates the motility and morphogenic responses of hepatocyte growth/scatter factor

The met protooncogene is a receptor tyrosine kinase for hepatocyte growth factor/scatter factor (HGF/SF). HGF/SF is a multifunctional cytokine secreted mainly by mesenchymal cells that stimulates movement, invasion, and morphogenesis of some epithelial and endothelial cells and mitogenicity of others. Although the met receptor tyrosine kinase is a high affinity receptor for HGF/SF, it is not known whether this receptor can mediate the pleiotropic functions of HGF/SF. To investigate this in epithelial cells that normally respond to HGF/SF, we generated a chimeric receptor containing the extracellular domain from the colony stimulating factor 1 (CSF-1) receptor fused to the transmembrane and cytoplasmic domain of the met receptor. We show that the CSF-MET chimera, when expressed in Madin-Darby canine kidney (MDCK) epithelial cells, is fully functional. Treatment of MDCK cells expressing the chimera with CSF-1 leads to cell dissociation and scattering, as well as invasion and tubule formation of cells grown in collagen matrices. This effect is dependent on a functional met kinase. Stimulation of the receptor chimera with CSF-1 leads to activation of the met kinase and tyrosine phosphorylation of the chimeras in vivo, whereas a kinase inactive mutant chimera shows no biological response to CSF-1. These findings demonstrate that stimulation of the met kinase is sufficient and essential to mediate the motogenic, invasive, and morphogenic responses of MDCK cells to HGF/SF and that this is a suitable system for a detailed analysis of the molecular signaling events involved in these responses.

Assignment of disulfide bonds in corticotropin-releasing factor-binding protein

We have previously isolated, cloned, and characterized a protein that specifically binds and inactivates the peptide corticotropin-releasing factor. The integrity of the disulfide bonds in the binding protein is essential for this activity as reduction abolishes the protein's ability to bind corticotropin-releasing factor. The disulfide arrangement of the 10 cysteines present in the mature protein was established by analysis of proteolytically cleaved protein and sequence analysis of cystine containing fragments. A pattern is observed where each cysteine is connected to the next one in a sequential manner. Inspection of the genomic DNA encoding for this protein reveals that four of the domains defined by disulfide linkage coincide with four different exons.

Oncogenic activation of tyrosine kinases

Tyrosine kinases comprise the largest group of oncoproteins, a fact that underscores the importance of reversible tyrosine phosphorylation in the regulation of essential cellular functions. Oncogenic activation of tyrosine kinases results in the constitutive activation of what is normally a conditionally regulated enzyme activity. Studies of tyrosine kinase oncoproteins, and a comparison with their corresponding proto-oncogene products, have identified important functional and regulatory domains within these proteins, positive and negative regulators of their enzyme activities and signalling cascades that control cell growth and differentiation.

Breast carcinoma: a collective disorder

The development and differentiation of the epithelial component of glandular tissues such as the breast is regulated by two apparently unrelated processes. One of these is presumed to be epithelial cell collective autonomous, that is, it is mediated by gene products which act directly on the epithelial cells. An important component of autonomous regulation is the functional expression of homotypic cell-cell adhesion molecules such as cadherins. The second process is non-autonomous and involves an inductive effect of the neighboring mesenchymal cell collective. An important component of non-autonomous regulation is the aggregation/condensation of mesenchyme closely associated with the epithelium. We propose that molecular alterations in autonomous and non-autonomous pathways are important causes and indicators respectively of breast cancer progression and that these two fundamental regulators of epithelial collective organization are in fact inter-dependent. For example, we show that the expression of hepatocyte growth factor (HGF), an epithelially targeted mesenchymally derived morphogenic factor is regulated by mesenchymal cell density (condensation) and by factors released from epithelial cells. Breast epithelial cells produce factors which inhibit and stimulate HGF expression. The inhibitory factor is transforming growth factor beta (TGF-beta) and the activation state of TGF-beta is a crucial element in HGF homeostasis. The balance of negative and positive HGF regulators is markedly affected by the growth conditions and differentiation state of the epithelial cells. The expression of the HGF receptor, met, is high in normal breast epithelial cells and in dedifferentiated (ER negative) tumor cells but is reduced or lost in ER positive well differentiated epithelial cells. Our results indicate that the expression of at least one epithelial morphogen, HGF, is inter-dependently regulated by mesenchymal condensation and by factors released by neighboring epithelial cells.

Diabetes education in Grampian: a study

In a widely scattered area such as Grampian, patients' needs, staffing requirements and methods of delivery of health care are different from those found in a densely populated urban area. Although this may be seen as desirable from the point of view of meeting the individual needs of patients from diverse backgrounds, there are also problems in that consistency of quality of care may fluctuate. Recognising that the quantity and quality of patient education offered to diabetic patients in Grampian may vary according to their geographical location, the author and her colleagues set out to investigate the provision and quality of education on diabetes for both patients and nurses. The results indicated that there were significant gaps in patients', relatives' and nurses' knowledge of diabetes. Introducing a standard diabetes education system was found to be one way of improving levels of knowledge in the Grampian area.

Dimerization mediated through a leucine zipper activates the oncogenic potential of the met receptor tyrosine kinase

Oncogenic activation of the met (hepatocyte growth factor/scatter factor) receptor tyrosine kinase involves a genomic rearrangement that generates a hybrid protein containing tpr-encoded sequences at its amino terminus fused directly to the met-encoded receptor kinase domain. Deletion of Tpr sequences abolishes the transforming ability of this protein, implicating this region in oncogenic activation. We demonstrate, by site-directed mutagenesis and coimmunoprecipitation experiments, that a leucine zipper motif within Tpr mediates dimerization of the tpr-met product and is essential for the transforming activity of the met oncogene. By analogy with ligand-stimulated activation of receptor tyrosine kinases, we propose that constitutive dimerization mediated by a leucine zipper motif within Tpr is responsible for oncogenic activation of the Met kinase. The possibility that this mechanism of activation represents a paradigm for a class of receptor tyrosine kinase oncogenes activated by DNA rearrangement is discussed.

Hepatocyte growth factor/scatter factor is an autocrine factor for human normal bronchial epithelial and lung carcinoma cells

Hepatocyte growth factor (HGF) or scatter factor (SF) has been considered primarily as an endocrine/paracrine factor. We report here that HGF/SF mRNA was expressed by cultured human normal bronchial epithelial cells and many non-small cell lung carcinoma cell lines. Scatter activity was detected in the culture media of these cells, and this activity was inhibited by a neutralizing anti-recombinant human HGF antiserum. Immunostaining confirmed the presence of immunoreactive human HGF-like protein in the cytoplasm of these cultured cells, and in ciliated columnar epithelium of normal human bronchus/bronchioles. The met/HGF/SF receptor of these cultured cells was constitutively phosphorylated on tyrosine residues. A neutralizing anti-recombinant human HGF antiserum decreased the phosphorylation of the receptor, inhibited the proliferation of 45% of the non-small cell lung carcinoma cell lines studied, and stimulated the proliferation of normal bronchial epithelial cells. Altogether, the data demonstrate that HGF/SF and/or HGF-like protein is an autocrine factor for normal and neoplastic human bronchial epithelial cells in culture.

Primary structure of neuropeptide Y from brains of the American alligator (Alligator mississippiensis)

The purification of NPY from brains of the American alligator (Alligator mississippiensis) was achieved using reverse-phase high performance liquid chromatography (HPLC). The amino acid sequence was determined using automated Edman degradation as Tyr-Pro-Ser-Lys-Pro-Asp-Asn-Pro-Gly-Glu- Asp-Ala-Pro-Ala-Glu-Asp-Met-Ala-Arg-Tyr-Tyr-Ser-Ala-Leu-Arg-His-Tyr-Ile- Asn-Leu - Ile-Thr-Arg-Gln-Arg-Tyr. Alligator NPY is the first non-mammalian vertebrate to have 100% sequence identity to human NPY. The conservation of alligator NPY suggests that serine in position 7 of chicken NPY evolved after the birds and reptiles diverged from a common Archosaurian ancestor. Furthermore, the sequence identity between alligator and human NPY suggests this sequence is the same as the ancestral amniote NPY.

Expression of the met/hepatocyte growth factor/scatter factor receptor and its ligand during differentiation of murine P19 embryonal carcinoma cells

The met proto-oncogene is a member of the family of tyrosine kinase growth factor receptors and was recently identified as a receptor for hepatocyte growth factor and scatter factor (HGF/SF). From Northern hybridization studies the met/HGF/SF receptor (R) is expressed in many adult and embryonic mouse tissues. To identify which specific differentiated cell types express the met/HGF/SFR and to investigate the biological function of this receptor and its ligand during early murine development, we chose to study the expression of the met/HGF/SFR and HGF/SF during differentiation of the pluripotent P19 murine embryonal carcinoma cell line in culture. In this paper we demonstrate that met/HGF/SFR mRNA, protein, and its ligand are expressed at a low level in undifferentiated P19 cells and that their expression is increased as P19 cells are induced to differentiate into neuroectodermal derivatives following treatment with retinoic acid (RA) and into mesodermal derivatives following treatment with dimethyl sulfoxide (DMSO). From in situ hybridization analyses, only a subpopulation of differentiating P19 cells treated with RA or DMSO expresses high levels of the met/HGF/SFR RNA. In cultures treated with RA and cytosine arabinoside, both met/HGF/SFR mRNA and protein can be localized specifically to nondividing neuronal cells. Expression of the met/HGF/SFR and its ligand, HGF/SF, in undifferentiated P19 cells and differentiated derivatives suggests that stimulation of this signal transduction pathway may be an important event for the control of cell differentiation, proliferation, or positioning during embryogenesis.

Intrinsic positive end-expiratory pressure in ambulatory patients with airways obstruction

In patients with severe expiratory airflow limitation, dynamic hyperinflation often occurs when inspiratory efforts are initiated at a thoracic volume above the relaxation point of the respiratory system. The result is intrinsic positive end-expiratory alveolar pressure (PEEPi). To determine whether PEEPi occurs in ambulatory patients, we measured alveolar pressure (Palv) noninvasively during tidal breathing in 8 normal subjects, 15 asthmatic subjects, and 19 patients with COPD, using a body plethysmographic technique that includes computerized corrections for nonlinear pneumotachometer output and for plethysmograph leakage. In all 8 normal subjects, 9 asthmatic subjects, and 3 COPD patients, Palv descended smoothly to zero at end expiration. In contrast, among each of the remaining 22 patients, there was an abrupt change in slope of the Palv tracing near end expiration, identifying the onset of the next inspiratory effort and indicating the presence of PEEPi, ranging from 0.2 to 9.5 cm H2O. PEEPi was significantly correlated with FRC (% of predicted); PEEPi = (0.040 x %FRC) - 3.65, r = 0.73, p < 0.001, and with the reciprocal of FEV1 (% of predicted), PEEPi = (138/%FEV1) - 1.34, r = 0.69, p < 0.001. PEEPi could be elicited in normal subjects by severe expiratory resistive loading but not by the increased expiratory muscle activity occurring during an MVV maneuver. We conclude that PEEPi is common in patients with airways obstruction, even without overt ventilatory failure, and that its severity is generally in proportion to the severity of the hyperinflation and the airways obstruction.

Tumorigenicity of the met proto-oncogene and the gene for hepatocyte growth factor

The met proto-oncogene is the tyrosine kinase growth factor receptor for hepatocyte growth factor/scatter factor (HGF/SF). It was previously shown that, like the oncogenic tpr-met, the mouse met proto-oncogene transforms NIH 3T3 cells. We have established NIH 3T3 cells stably expressing both human (Methu) and mouse (Metmu) met proto-oncogene products. The protein products are properly processed and appear on the cell surface. NIH 3T3 cells express endogenous mouse HGF/SF mRNA, suggesting an autocrine activation mechanism for transformation by Metmu. However, the tumor-forming activity of Methu in NIH 3T3 cells is very low compared with that of Metmu, but efficient tumorigenesis occurs when Methu and HGF/SFhu are coexpressed. These results are consistent with an autocrine transformation mechanism and suggest further that the endogenous murine factor inefficiently activates the tumorigenic potential of Methu. The tumorigenicity observed with reciprocal chimeric human and mouse receptors that exchange external ligand-binding domains supports this conclusion. We also show that HGF/SFhu expressed in NIH 3T3 cells produces tumors in nude mice.

Hematologic changes during and after cardiopulmonary bypass and their relationship to the bleeding time and nonsurgical blood loss

The hemostatic dysfunction induced by cardiopulmonary bypass is due, in part, to a platelet dysfunction evidenced by a postoperative extension of the bleeding time; it leads to increased postoperative blood loss and morbidity. This study, which was conducted in 85 patients undergoing cardiopulmonary bypass, was designed to characterize the hematologic changes during and after cardiopulmonary bypass and to elucidate the relationships between these changes, the extension of the bleeding time, and the magnitude of the postoperative nonsurgical blood loss. Variables were measured before, during, and 2, 24, 48, and 72 hours after cardiopulmonary bypass. Univariate and multivariate analyses were performed with either the 2-hour postbypass bleeding time or the 4-hour postbypass blood loss as the dependent variables. The reversal of the extension of the bleeding time in the postoperative period was accompanied by a significant increase in the mean platelet volume and by a significant increase in the level of thromboxane B2 measured in the blood shed from the site of the bleeding time determination. The postoperative bleeding time correlated with the postoperative blood loss, and both parameters were dependent on the duration of cardiopulmonary bypass. In addition, the postoperative bleeding time correlated with the skin temperature and the plasma level of D-dimer, while the postoperative blood loss also correlated with temperature and the plasma levels of C3. These data establish a direct relationship between the postoperative bleeding time, the postoperative blood loss, and temperature. They indicate that the reversal of the postoperative extension of the bleeding time is due in part to rewarming and to the release of larger platelets into the circulation, and they suggest that hyperfibrinolysis and complement activation may play an important role in the cardiopulmonary bypass-induced platelet dysfunction.

Transforming growth factor-beta blocks protein kinase-A-mediated iodide transport and protein kinase-C-mediated DNA synthesis in FRTL-5 rat thyroid cells

Recent studies have shown that transforming growth factor-beta (TGF beta) alters DNA synthesis and iodide metabolism in human, porcine, and rat thyroid cells. In the present work we studied the mechanism of TGF beta action in FRTL-5 rat thyroid cells. The cells were treated with TGF beta in the presence of TSH, growth factors, and cellular modulators for various periods of time; then, [3H]thymidine incorporation and DNA content were measured as indicators of DNA synthesis, and [125I]iodide uptake was measured to assess cell function. TGF beta (10 ng/ml) inhibited TSH-induced DNA synthesis and iodide uptake. TGF beta also inhibited DNA synthesis induced by insulin-like growth factor-I, fibroblast growth factor, and endothelial cell growth factor. The protein kinase-A (PKA) activator 8-bromo-cAMP increased both iodide uptake and DNA synthesis; TGF beta inhibited 8-bromo-cAMP-induced [125I]iodide uptake, but not [3H]thymidine incorporation. The protein kinase-C (PKC) activator phorbol 12-myristate 13-acetate increased [3H]thymidine incorporation, and TGF beta inhibited this action of phorbol 12-myristate 13-acetate. The results show that activation of PKA or PKC increases DNA synthesis. TGF beta inhibited PKC-mediated, but not PKA-mediated, DNA synthesis in these cells. The results also show that TGF beta selectively inhibits PKA-mediated iodide uptake, but not PKA-mediated DNA synthesis. These findings suggest that TGF beta is a strong inhibitor of the proliferation and function of thyroid cells.

Thoracic spinal calcinosis circumscripta causing cord compression in two German shepherd dog littermates

Two young German shepherd dog littermates had progressive, painless, hindlimb ataxia. In both dogs plain radiography of the vertebral column revealed a solitary mineralised lesion on the dorsal laminae between the dorsal spines of the second and third thoracic vertebrae, and myelography with iopamidol demonstrated cord compression at the level of the lesions. The first dog died 18 hours after the myelography. A dorsal laminectomy performed in the second dog resulted in neurological improvement. A histopathological examination confirmed that both lesions were calcinosis circumscripta. The cause of the death of the first dog was meningitis.

Tumor necrosis factor-alpha activates nuclear factor kappa B and induces manganous superoxide dismutase and phosphodiesterase mRNA in human papillary thyroid carcinoma cells

Human papillary thyroid carcinoma (PTC) has a relatively benign prognosis despite a high frequency of lymphatic metastasis. This suggests that local anticancer factors, generated in lymph nodes, control PTC progression. The cytokine, tumor necrosis factor-alpha (TNF-alpha), may be one such factor. We have previously shown that a human PTC cell line (NP-PTC) has high affinity TNF-alpha receptors. We now report on the action of TNF-alpha in these cells. TNF-alpha decreased [3H]thymidine incorporation as well as cellular DNA content and cell number in a dose-dependent manner. The abundance of phosphodiesterase and manganous superoxide dismutase mRNA species was increased in a time- and dose-dependent manner in the NP-PTC cells after TNF-alpha treatment. TNF-alpha activated NF-kappa B, a nuclear factor thought to mediate multiple actions of TNF-alpha, in these cells with a maximum effect observed after 30 min of treatment. Thus, TNF-alpha has an antiproliferative action on NP-PTC cells, despite its ability to induce the accumulation of mRNA that encodes an enzyme (manganous superoxide dismutase), thought to be cytoprotective. The net antiproliferative effect must therefore be explained by a balance of protective and tumoricidal or static effects that ultimately result in control of tumor spread. These antiproliferative effects may be in part mediated by NF-kappa B and PDE.

The development of a decision support system for diagnosing nasal allergy

This paper deals with the problem of improving the capability of the medical decision support system (MDSS) for diagnosing nasal allergy by integrating the previously developed expert system with the neural network approach. Three knowledge acquisition methods were used to develop the expert system: statistical, rule-based, and the combined approach. Among the three, a combined approach showed the best prediction rate based on discriminant analysis. Using the results of a combined approach as input values, the neural network was developed using back-propagation method. Unlike the expert system, the neural network system provides the resulting allergy status in probabilistic terms. Managerial as well as legal issues were also discussed in this paper.

Overexpression of c-met proto-oncogene but not epidermal growth factor receptor or c-erbB-2 in primary human colorectal carcinomas

The epidermal growth factor receptor (EGFR) and the protein products of c-erbB-2 and c-met proto-oncogenes belong to a family of growth factor receptors with tyrosine kinase activity. In human colonic carcinomas, the expression of the EGFR and c-erbB-2 have been studied at the protein level only, while c-met expression has not been reported. We have examined the mRNA expression of these genes in human normal colorectal mucosa and primary carcinomas. The results demonstrate that the normal mucosa shows highly variable levels of EGFR and c-erbB-2 mRNAs, but expresses consistently low amounts of c-met mRNA. Colorectal carcinomas did not express significantly higher levels of the EGFR and c-erbB-2 mRNAs than the normal mucosa. In contrast, c-met was consistently and significantly overexpressed (mean sixfold) in carcinomas as compared with normal mucosa. Seventy percent of paired normal-tumor specimens showed a tumor to normal c-met mRNA ratio of greater than 4. The expression of c-met mRNA was also enhanced in the adenomas, suggesting that over-expression of this proto-oncogene may have mechanistic significance in the early stages of human colorectal carcinogenesis.

Alternative splicing generates isoforms of the met receptor tyrosine kinase which undergo differential processing

The met proto-oncogene is a member of the family of tyrosine kinase growth factor receptors. We describe the isolation and characterization of a cDNA clone (pOK) for the met receptor from a gastric carcinoma cell line. This clone differs from the published cDNA clone by the absence of 54 bp predicted to encode 18 amino acids in the extracellular domain. The pOK cDNA corresponds to the most abundant met RNA species of 8 kb expressed in human cell lines and tissue, and we show that there are in fact two 8-kb met receptor tyrosine kinase (RTK) isoforms that are generated by alternative splicing. This newly described met isoform when transiently expressed in COS cells encodes a protein of 190 kDa which corresponds in size to the p190 met alpha beta heterodimer expressed in human cell lines. Furthermore, we show that the 190-kDa product of pOK consists of the 140-kDa met beta subunit associated with the 50-kDa met alpha subunit. This finding suggests that both the alpha and beta met chains are encoded by this construct and confirms the hypothesis that a single chain precursor is cleaved to produce both subunits of met. In contrast, the previously characterized met isoform corresponds to a minor met RNA species and encodes a protein of 170 kDa that is not cleaved yet is processed in a manner that allows cell surface expression. Both met RTK isoforms are autophosphorylated in the in vitro kinase assay. These results suggest that different isoforms of the met RTK may have distinct biological activities.

Primary structure of two forms of gonadotropin-releasing hormone from brains of the American alligator (Alligator mississippiensis)

Two forms of gonadotropin-releasing hormone (GnRH) have been purified from brains of the American alligator, Alligator mississippiensis, using reverse-phase high-pressure liquid chromatography (HPLC). The concentration of total GnRH was 8.8 ng/g of frozen brain tissue or 21.1 ng per brain. The amino acid sequence of each form of GnRH was determined using automated Edman degradation. The presence of the N-terminal pGlu residue was established by digestion studies with bovine pyroglutamyl aminopeptidase and coelution with synthetic forms of the native peptide. The primary structure of alligator GnRH I is pGlu-His-Trp-Ser-Tyr-Gly-Leu-Gln-Pro-Gly-NH2 and alligator GnRH II is pGlu-His-Trp-Ser-His-Gly-Trp-Tyr-Pro-Gly-NH2.

Efficacy and distribution of single-dose preoperative antibiotic prophylaxis in high-risk gastroduodenal surgery

Although a single preoperative dose of antibiotic is now the accepted means of preventing postoperative surgical infection, the method has not been investigated adequately. In patients at high risk of infection who underwent gastroduodenal operations, the authors compared single-dose prophylaxis by intravenous cefotaxime (26 patients) with short-course perioperative prophylaxis (27 patients). No wound infection occurred, but in one patient in each group a subphrenic abscess developed after leakage at the anastomosis. The half-life of cefotaxime (1.23 +/- 0.12 hours) and its apparent volume of distribution (16.7 +/- 2.6 L/1.73 m2 resulted in perioperative levels of the antibiotic in blood (34.76 +/- 4.21 micrograms/mL), gastric mucosa (32.04 +/- 5.22 micrograms/mL) and subcutaneous fat (24.98 +/- 5.89 micrograms/mL) more than twice the usual minimal inhibitory concentration of the drug for organisms grown from the stomach contents and wound fat. These clinical and pharmacologic findings validate the efficacy of a single preoperative intravenous dose of the antibiotic in preventing postoperative infection in high-risk patients who undergo gastroduodenal surgery.

Analysis by pulsed field gel electrophoresis reveals complex rearrangements in two MET alleles in a chemically-treated human cell line, MNNG-HOS

We have previously shown that two alleles of the MET locus are independently rearranged in the chemically-treated human cell line MNNG-HOS. One allele is the TPR-MET oncogene which was activated by fusion of the MET locus on chromosome 7 with the TPR locus on chromosome 1. The second allele is found on a der(7)t(1;7)(q23;q32) chromosome and is characterized by a deletion of the amino-terminus of the MET extracellular ligand binding domain. Here we present a pulsed field gel electrophoresis analysis which reveals that the two MET allele rearrangements in MNNG-HOS cells are more complex than originally thought. The breakpoint in MET on der(7) has been molecularly cloned and, unexpectedly, we found that rearrangement in this allele involves sequences derived from chromosome 2. Moreover, the rearrangement producing der(7) involves an inversion of the MET locus or a more complex alteration. Analysis of hybrid cells containing TPR-MET demonstrated that both the upstream and downstream portions of MET are conserved in this rearrangement and that oncogene activation occurred by an insertion of TPR sequences into the MET locus. These findings illustrate that when examined at the molecular level some chromosome abnormalities can be extremely complex and, thus, are of limited value in gene mapping studies.

Structure, tissue-specific expression, and transforming activity of the mouse met protooncogene

A 6.7-kilobase met complementary DNA (cDNA) was isolated from a pcD cDNA library prepared from C3H mouse fibroblast cell line polyadenylated RNA. Sequence analysis of 6.7-kilobase met cDNA insert revealed that it contained the entire open reading frame and shared an overall homology of 88.1% with the human met gene. Using the mouse met cDNA as probe, high levels of met expression were observed in the kidney, brain, lung, skin, and embryonic tissue as well as in several factor responsive mouse myeloid cell lines. Under SV40 promoter control, the mouse met protooncogene cDNA in the pCD vector was able to transform NIH 3T3 cells. These transformed cells possess multiple copies of mouse met cDNA and exhibit properties of malignant cells, including growth in soft agar and induction of tumors in nude mice. Tumor explant cell lines analyzed by Western blot also reveal the presence of high levels of Mr 170,000 and 140,000 met protein product(s).

Simple elective cholecystectomy: to drain or not

We performed a large single-center prospective randomized controlled study to assess the role of peritoneal drainage in simple elective cholecystectomy. In 248 patients, drains were omitted; 122 patients had closed suction drains and 124 had Penrose drains. There were no deaths, and no patient required reoperation or drainage of a subhepatic collection. Wound infections occurred in eight patients with drains and in six patients without. Most infections were staphylococcal. Postoperative pulmonary complications and hospital stays were similar in patients with and without drains. Statistical analysis of the 10 available prospective controlled randomized studies (1,920 patients) by the method of odds ratios supported our findings. Simple elective cholecystectomy is safe without peritoneal drainage, but short-term drains do not increase morbidity.

Is neomycin necessary for bowel preparation in surgery of the colon? Oral neomycin plus erythromycin versus erythromycin-metronidazole

In 132 patients who underwent elective surgery of the colon, the value of bowel preparation with a conventional oral antibiotic preparation of neomycin-erythromycin (N-E) was compared with erythromycin-metronidazole (E-M). Of 125 patients who were available for assessment, 61 received N-E and 64 E-M. The two groups were evenly matched. Two wound infections occurred in patients receiving E-M, neither due to anaerobic bacteria, but seven wound infections developed in patients given N-E (p = 0.057), five of them caused by anaerobic bacteria. Anaerobic bacteria of the colon are the dominant cause of postoperative wound infection in elective surgery of the colon. Adequate antibiotic preparation directed against these bacteria makes the use of neomycin unnecessary.

Epstein-Barr virus DNA sequences in precursor monocyte-macrophage cell lines established from the bone marrow of children with maturation defects of haematopoiesis

Epstein-Barr virus (EBV) DNA sequences were detected in four established monoblast or early monocytic cell lines (CM-S, ROV-S, CV-S and AD-S) obtained from bone marrow of children suffering from maturation defects of haematopoiesis. EBV is present in these cells in a latent state. The viral DNA in these cell lines was analysed by Southern blot hybridization, using a set of cloned EBV DNA fragments from the EBV strain B95-8 as probes. A common spectrum of highly related but distinguishable EBV DNA restriction enzyme sequences was found, suggesting some genomic diversity. Propagation of the cells in long-term culture revealed a gradual decrease of EBV copies per cell in all lines with some minor changes in the restriction pattern of the EBV DNA. These findings demonstrate that human precursor monocyte cells may be susceptible to infection by EBV.

Ocular manifestations of Lyme disease

The incidence of Lyme disease has been increasing at alarming rates in recent years. Being the most commonly reported tickborne bacterial disease in the United States, it now outnumbers Rocky Mountain spotted fever by a ratio of almost 2:1. It is a multisystem illness and can manifest itself with dermatologic, neurologic, cardiac and rheumatologic involvement. The ocular complications of Lyme disease can present as one of the more ominous signs during the course of the illness. The detection of the disease and proper referral by the optometrist may permit more appropriate treatment, and thus, a better prognosis of the illness.

Regulation of cholesterol metabolism in fetal rabbit aorta: role of amniotic fluid factors

This study shows that amniotic fluid enhances cholesterol esterification in arterial wall, as measured by in vitro assay of acyl-CoA:cholesterol acyltransferase (ACAT) activity and by incorporation of oleic acid to cholesteryl esters in cultured fetal aortas and smooth muscle cells. This property is mostly evident in the fraction of molecular weight greater than 100,000, and it is abolished by delipidation, indicating that stimulating factor is probably lipoprotein in nature. Despite an increased cholesterol esterification by the presence of amniotic fluid in medium of cultured fetal aortas, the content of cholesterol and cholesteryl esters was much lower. The cellular structures are better preserved in explants cultured with amniotic fluid than in control animals. This study indicates that amniotic fluid contains factors that may have a pronounced effect on arterial wall during development.

Primary resection and anastomosis of lesions obstructing the left colon

It is becoming apparent that primary resection and anastomosis of the left colon for colonic obstruction is a feasible operation. This paper reviews 750 colonic resections at the Queen Elizabeth Hospital of Montreal, of which 40 were performed on unprepared bowel in patients with obstructed left colonic lesions. The pre- and postoperative hospital stay was greatly reduced. The death rate was 5% and complication rate 40%. Follow-up results suggest this procedure is safe and that an adequate cancer operation can be carried out. It should be stressed that not all obstructing left colonic lesions can be treated with a one-stage procedure and that the Hartmann procedure or a protective colostomy can always be used if the situation warrants it.

Two rearranged MET alleles in MNNG-HOS cells reveal the orientation of MET on chromosome 7 to other markers tightly linked to the cystic fibrosis locus

We have found that two alleles of the MET locus are rearranged in the human cell line MNNG-HOS. One allele is the previously characterized TPR-MET oncogene and the other is found on a der(7)t(1;7)(q23;q32) marker chromosome. These data and in situ chromosomal hybridization analysis would indicate that MET and, therefore, the cystic fibrosis locus are located at bands q31-q32 on human chromosome 7. Using somatic cell hybrids, we show that the chromosome containing the TPR-MET oncogene is grossly rearranged and contains both the upstream and downstream portions of the MET protooncogene locus. These results demonstrate that the TPR-MET oncogene rearrangement involving chromosomes 1 and 7 is either due to an insertion of TPR sequences into the MET locus or is more complex. We also show that the upstream MET protooncogene locus is deleted on der(7), while the downstream portion is retained. We cannot exclude that this is due to an interstitial chromosomal deletion or to a more complex rearrangement, but if MET maps at the breakpoint in der(7), then the 3' end of the MET transcription unit should be oriented towards the centromere. We also show that other DNA restriction fragment length polymorphism markers tightly linked with the inheritance of cystic fibrosis are deleted on der(7).

Distribution of 10-formyltetrahydrofolate synthetase in eubacteria

The distribution of 10-formyltetrahydrofolate synthetase, which activates formate for use as a one-carbon donor in a variety of biosynthetic reactions, was determined for a variety of eubacteria. Organisms from several genera were found to lack detectable synthetase activity; however, all organisms tested were found to contain 5,10-methylenetetrahydrofolate dehydrogenase activity.