Comparisons between the three-dimensional structures of the chemotactic protein CheY and the normal Gly 12-p21 protein

The three-dimensional structure of a chemotactic protein CheY from Salmonella typhimurium has recently been determined by X-ray crystallography. The structure of this small protein, containing 129 amino acid residues, shows a domain consisting of a central beta-pleated sheet surrounded on both sides by alpha-helices. We have examined the sequence and the arrangement of the structural domains of the CheY protein and have compared them with other nucleotide binding protein sequences and structures. We find that the CheY protein has significant sequence homology to the ras-gene encoded p21 protein. In addition, the structural domains of the two proteins are arranged in a fundamentally similar manner, including the phosphate-binding site (both proteins bind phosphate-containing ligands). The striking similarity in the arrangement of the structural domains of the two proteins suggests that both may serve similar functions as signal transducers.

Rapid diagnosis of streptococcal pharyngitis with enzyme immunoassay

From June 1988 to May 1989, 444 throat swab specimens were tested with an enzyme immunoassay kit for rapid diagnosis of group A streptococcal pharyngitis. The results were compared with those of throat culture method. The rapid test was positive in 37 of 42 culture-positive specimens and negative in 379 of 402 culture-negative specimens, thus yielding a total agreement of 93.7%, sensitivity 88.1%, specificity 94.7%, positive predictive value 61.7%, negative predictive value 98.7%. According to this practical application, we suggest that enzyme immunoassay test can be applied in outpatient clinics by busy pediatricians for rapid diagnosis of group A streptococcal pharyngitis.

Epidemic hemorrhagic fever. The mechanism of coagulation and fibrinolysis

To understand the mechanism of hemorrhage, coagulation and fibrinolysis in epidemic hemorrhagic fever (EHF), thrombin time (TT), prothrombin time (PT), fibrinogen (FIG), the platelet count (PLAT), plasminogen (PLG), antithrombin-III (AT-III), fibrin-fibrinogen degraded products (FDP) and platelet functions of aggregation and release were studied dynamically with advanced methods in 134 EHF patients. TT and PT were prolonged, FIG, AT-III and PLG were decreased and FDP was increased. Besides, the decrease of PLAT, the platelet functions of aggregation and release were below the normal level. The results showed that the balance of blood coagulation and fibrinolysis was lost from the early stage of the disease.

Autoimmune mice make anti-Fc gamma receptor antibodies

We demonstrate, using a recombinant truncated Fc gamma RII molecule as a probe, the presence of anti-Fc gamma R antibodies in several strains of autoimmune mice. Affinity chromatography on a truncated Fc gamma R column of pooled sera from aged NZB females resulted in isolation of 16 micrograms of IgM per ml of serum, approximately 2% of the total IgM; no anti-Fc gamma R IgM was found in sera from C58/J mice. Mice with high titers of anti-Fc gamma R IgM also had anti-Fc gamma R IgG. Affinity-purified anti-Fc gamma R IgG bound to Fc gamma R-bearing cells. A good correlation was found between the presence of anti-Fc gamma R Ig and impaired phagocytosis of immune complexes in autoimmune strains such as NZB or NZB/NZW F1. Sera with high titers of anti-Fc gamma R Ig from NZB and motheaten mice inhibited the binding of soluble immune complexes. Furthermore, BXSB, a lupus-prone mouse strain that does not produce anti-Fc gamma R Ig, shows normal macrophage binding and phagocytosis of immune complexes. A set of four IgM mAbs that bind to Fc gamma R was identified. These antibodies were polyspecific; some were directed against DNA, and others recognized a wide variety of antigens including histones, thyroglobulin, and transferrin, but all anti-Fc gamma R IgM antibodies effectively inhibited the binding of IgG1 anti-DNP/DNP20BSA complexes to J774 macrophages. The role of anti-Fc gamma R Ig in autoimmunity remains to be established. It may act to crosslink and activate Fc gamma Rs on neutrophils, macrophages, NK, and mesangial cells, or it may desensitize Fc gamma R function of Fc gamma R-bearing cells.

The structure of the carboxyl terminus of the p21 protein. Structural relationship to the nucleotide-binding/transforming regions of the protein

The carboxyl-terminal region of the ras oncogene-encoded p21 protein is critical to the protein's function, since membrane binding through the C-terminus is necessary for its cellular activity. X-ray crystal structures for truncated p21 proteins are available, but none of these include the C-terminal region of the protein (from residues 172-189). Using conformational energy analysis, we determined the preferred three-dimensional structures for this C-terminal octadecapeptide of the H-ras oncogene p21 protein and generated these structures onto the crystal structure of the remainder of the protein. The results indicate that, like other membrane-associated proteins, the membrane-binding C-terminus of p21 assumes a helical hairpin conformation. In several low-energy orientations, the C-terminal structure is in close proximity to other critical locales of p21. These include the central transforming region (around Gln 61) and the amino terminal transforming region (around Gly 12), indicating that extracellular signals can be transduced through the C-terminal helical hairpin to the effector regions of the protein. This finding is consistent with the results of recent genetic experiments.

Revised amino acid sequences of the three major phospholipases A2 from Bungarus fasciatus (banded krait) venom

The structures of three cardiotoxin-like proteins obtained from the venom of Bungarus fasciatus (banded krait) were elucidated previously (Lu and Lo, 1980, 1981). Since their molecular sizes are similar to that of phospholipase A2 and since they show weak phospholipase A2 activities (Chang et al., 1983), a further study of their primary structures was carried out. Fractions Va, Vb-2 and VI, corresponding to the former V-2, V-3 and VI were determined to be typical phospholipases A2. Among 118 amino acid residues, they all have in common a Pro29 between Gly28 and Gly30, the latter two residues being implicated in Ca2+ binding together with Tyr26 and Asp47.

A simulation model for evaluating a set of emergency vehicle base locations: development, validation, and usage

This paper describes our experiences in developing a simulation model for evaluating a set of emergency response vehicle base locations. The project was undertaken jointly by the University of Arizona and the Tucson Fire Department. The issues of model development, data collection, model validation, and experimentation are discussed. The critical nature of the problem and the clients' lack of experience with mathematical models, made model validation the major step in gaining user acceptance. We show that looking solely at standard performance statistics such as the calls successfully serviced, may lead to the acceptance of an invalid model. We also show that the high level of detail used in many simulation models for evaluating base locations is unnecessary in the current case. An analysis evaluating two alternative sets of locations for the Tucson system is discussed.

Conformational changes induced by the transforming amino acid substitution in the transmembrane domain of the neu oncogene-encoded p185 protein

The neu oncogene is frequently found in certain types of human carcinomas and has been shown to be activated in animal models by nitrosourea-induced mutation. The activating mutation in the neu oncogene results in the substitution of a glutamic acid for a valine at position 664 in the transmembrane domain of the encoded protein product of 185 kda (designated p185), which, on the basis of homology studies, is presumed to be a receptor for an as yet unidentified growth factor. It has been proposed that activating amino acid substitutions in this region of p185 lead to a conformational change in the protein which causes signal transduction via an increase in tyrosine kinase activity in the absence of any external signal. Using conformational energy analysis, we have determined the preferred three-dimensional structures for the transmembrane decapeptide (residues 658-667) of the p185 protein with valine and glutamic acid at the critical position 664. The results indicate that the global minimum energy conformation of the decapeptide from the normal protein with Val at position 664 is an alpha-helix with a sharp bend (CD conformation at residues 664 and 665) in this region, whereas the global minimum conformation for the decapeptide from the mutant transforming protein with Glu at position 664 assumes an all alpha-helical configuration. Furthermore, the second highest energy conformation for the decapeptide from the normal protein is identical to the global minimum energy conformation for the decapeptide from the transforming protein, providing a possible explanation why overexpression of the normal protein also has a transforming effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Conformational energy analysis of the leucine repeat regions of C/EBP, GCN4, and the proteins of the myc, jun, and fos oncogenes

It has been recently proposed that certain DNA binding proteins (including C/EBP, GCN4 and the myc, jun, and fos oncogene proteins) share a common structural motif based on helix-promoting regions containing heptad repeat sequences of leucines. It has been suggested that this structure is critical to the biological activity of these proteins, since it facilitates the formation of functional dimers held together by interdigitating leucine side-chains along the hydrophobic interfaces between long alpha-helical regions of the polypeptide chains in a configuration termed the "leucine zipper." In this paper, conformational energy analysis is used to deterrmine the preferred three-dimensional structures of the leucine repeat regions of these proteins. The results indicate that, in all cases, the global minimum energy conformation for these regions is an amphipathic alpha-helix with the leucine side-chains arrayed on one side in such a way to favor "leucine zipper" dimerization. Furthermore, amino acid substitutions in these regions (such as Pro for Leu), that are known to inhibit dimer formation and prevent DNA binding, are found to produce significant conformational changes that disrupt the amphipathic helical structure. Thus, these results provide support for the proposed "leucine zipper" configuration as a critical structural feature of this class of DNA binding proteins.

Correlation of beta-bend conformations of tetrapeptides with their activities in CD4-receptor binding assays

Conformational analysis, based on ECEPP (Empirical Conformational Energy Program for Peptides) using the chain build-up procedure, was applied to determine the low-energy conformations for a series of tetrapeptides. The tetrapeptides are components of larger peptides which have been found to bind to the CD4 receptor of monocytes. Several previous studies have implicated the tetrapeptide units investigated here as being critical to the biological activities of the full peptides. Five such tetrapeptides were studied: Ser-Ser-Asn-Tyr (from ribonuclease A), Thr-Thr-Asn-Tyr (from peptide T, known to block human immunodeficiency virus from attaching to CD4+ T cells), Thr-Ile-Asn-Tyr (from polio virus coat protein, which is less active than the other peptides in binding to CD4 receptors), Ser-Ser-Ala-Tyr (from the gp 120 coat protein of human immunodeficiency virus, a variant of the peptide T sequence, active in blocking viral attachment to CD4+ cells), and the tetrapeptide from an active synthetic pentapeptide, Asn-Thr-Lys-Tyr (from Asn-Thr-Lys-Tyr-Thr). Using a 7 kcal/mol cutoff, the low-energy conformations for each peptide were computed. Approximately 20,000 conformations were computed for each tetrapeptide. Residue probability profiles were determined for each tetrapeptide. All tetrapeptides except for the polio sequence showed flexibility in the sense that many low-energy conformations were possible. In previous studies, it was postulated that the critical tetrapeptide units would adopt conformations similar to the one observed in a segment of ribonuclease A, residues 22-25, a beta-bend, which is part of an octapeptide segment (residues 19-26) that is homologous to the sequence of peptide T.(ABSTRACT TRUNCATED AT 250 WORDS)

[Electron microscopic observation of the sporogonic stage of Plasmodium gallinaceum after five antimalarials]

Ultrastructural changes in Plasmodium gallinaceum oocysts and sporozoites were studies after 5 antimalarials (pyrimethamine, primaquine, artemisinine, 5-p-fluorobenzoxyl-primaquine citrate and nitroquine) were administered to Aedes albopictus. Obvious disfigurement, such as abnormal vacuoles of various sizes in the cytoplasma, thickened oocyst capsules and damaged sporozoite pellical membranes were found in many oocysts and sporozoites in the mosquitoes. When the grade of infection of sporozoites in the salivary glands of the 5 different groups of mosquitoes were compared with the control, the rank test (Hc = 271) showed a very significant variance (P less than 0.01).

Conformational effects of amino acid substitutions in the P-glycoprotein of the mdr 1 gene

The P-glycoprotein of the mdr 1 gene is responsible for the phenomenon of multidrug resistance in human cells. The presumed drug-binding site of the wild-type P-glycoprotein contains a glycine at position 185. A mutant P-glycoprotein which contains valine at this position causes cells to retain resistance to colchicine, but to lose cross-resistance to other drugs such as the chemotherapeutic agents vinblastine and Adriamycin. This has been hypothesized to be due to a conformational change in the protein induced by the amino acid substitution. Using conformational energy analysis, we have determined the allowed three-dimensional structures for the wild-type and mutant proteins in the region of position 185. The results indicate that the wild-type protein adopts a unique left-handed conformation at position 185 which is energically unfavorable for the protein with L-amino acids (including valine) at this position. This conformational change induced by amino acid substitutions for Gly 185 could explain the differences in binding to the P-glycoprotein of various drugs and, hence, the differences in drug resistance exhibited by various cell lines expressing these proteins.

Comparison of the computed structures for the phosphate-binding loop of the p21 protein containing the oncogenic site Gly 12 with the X-ray crystallographic structures for this region in the p21 protein and EFtu. A model for the structure of the p21 protein in its oncogenic form

The GTP-binding p21 protein encoded by the ras-oncogene can be activated to cause malignant transformation of cells by substitution of a single amino acid at critical positions along the polypeptide chain. Substitution of any non-cyclic L-amino acid for Gly 12 in the normal protein results in a transforming protein. This substitution occurs in a hydrophobic sequence (residues 6-15) which is known to be involved in binding the phosphate moities of GTP (and GDP). We find, using conformational energy calculations, that the 6-15 segment of the normal protein (with Gly 12) adopts structures that contain a bend at residues 11 and 12 with the Gly in the D* conformation, not allowed energetically for L-amino acids. Substitution of non-cyclic L-amino acids for Gly 12 results in shifting this bend to residues 12 and 13. We show that many computed structures for the Gly 12-containing phosphate binding loop, segment 9-15, are superimposable on the corresponding segment of the recently determined X-ray crystallographic structure for residues 1-171 of the p21 protein. All such structures contain bends at residues 11 and 12 and most of these contain Gly 12 in the C* or D* conformational state. Other computed conformations for the 9-15 segment were superimposable on the structure of the corresponding 18-23 segment of EFtu, the bacterial chain elongation factor having structural similarities to the p21 protein in the phosphate-binding regions. This segment contains a Val residue where a Gly occurs in the p21 protein. As previously predicted, all of these superimposable conformations contain a bend at positions 12 and 13, not 11 and 12. If these structures that are superimposable on EFtu are introduced into the p21 protein structure, bad contacts occur between the sidechain of the residue (here Val) at position 12 and another phosphate binding loop region around position 61. These bad contacts between the two segments can be removed by changing the conformation of the 61 region in the p21 protein to the corresponding position of the homologous region in EFtu. In this new conformation, a large site becomes available for the binding of phosphate residues. In addition, such phenomena as autophosphorylation of the p21 protein by GTP can be explained with this new model structure for the activated protein which cannot be explained by the structure for the non-activated protein.

A clinical evaluation of sulbactam/ampicillin in the treatment of pediatric infections

We have treated 42 episodes of pediatric infections with sulbactam/ampicillin since 1987. Included were 9 cellulitis, 9 urinary tract infections, 5 cervical lymphadenitis, 4 meningitis, 2 thoracic empyema, 2 osteomyelitis, 2 sepsis, 1 furuncle, 1 perianal abscess, 1 dental abscess, 1 peritonsillitis, 1 salmonellosis, 1 shigellosis, 1 peritonitis, 1 suppurative thyroiditis, 1 infective endocarditis. Responsible pathogens were Escherichia coli in 8, Staphylococcus aureus in 6, Hemophilus influenzae in 2, Streptococcus pneumoniae in 3, Streptococcus viridans in 2, Staphylococcus epidermidis in 1, Bacteroides fragilis in 1, Salmonella D1 in 1, Shigella sonnei in 1, Klebsiella pneumoniae in 1, Enterobacter agglomerans in 1, Acinetobacter calcoaceticus in 1, Enterobacter cloacae in 1, group A beta-hemolytic streptococcus in 1, and polymicrobial infection in 4 cases. Thirty-nine out of 41 (95%) clinically evaluable patients cured and all (34/34) bacteriologically evaluable patients eradicated their pathogens after treatment with sulbactam/ampicillin. Side reactions were seen in five patients; one maculopapular skin rash, one hemolytic anemia, two diarrhea, and one liver function impairment plus leukopenia. All these reactions were transient and did not require interruption of therapy. These results indicate that sulbactam/ampicillin is safe and effective in the treatment of common pediatric infections beyond the neonatal period.

Congenital cholesteatoma of the middle ear in children

Congenital cholesteatoma, once considered to be a rarity, has shown an exponential increase in its incidence as evidenced by numerous clinical studies over the past decade. No explanation has been offered for this phenomenon. A review of the literature indicates that the definition of "congenital cholesteatoma" has strayed from the original one formulated by Derlacki and Clemis, which included a cholesteatoma medial to an intact tympanic membrane, without prior history of aural infections. Allowing patients with recurrent otitis media into studies may have contributed to a "false positive" rise in the incidence of this condition. This article reviews 19 cases of cholesteatomas behind intact tympanic membranes, treated at the Montreal Children's Hospital over a 10-year period. They represent 22% of the entire cholesteatoma population. There appears to be two groups of patients, each with a distinct clinical presentation that correlates well with the surgical outcome. Whether this implies different pathogenetic mechanisms remains unclear.

Cellular events associated with lung branching morphogenesis including the deposition of collagen type IV

In this study mouse lung development was examined using an in vitro model system. The culture system permitted examination of a morphogenic process that eventually led to the formation of presumptive alveoli (terminal sacs). The observations included changes in epithelial cell morphology (transition from a columnar to a spindle shape), and evidence for motile activity on the part of primitive airway epithelial cells. The importance of Type IV collagen to the cellular events associated with branching morphogenesis was investigated by immunolocalization. In addition, we assessed the similarity of normal lung development to in vitro development by comparing cultured lungs with equivalent stages of embryonic and fetal mouse lungs. The results show that cultured embryonic lung explants proceed along a morphogenic pathway that parallels normal lung development; that primitive pulmonary epithelial cells engage in motile activity and transiently acquire an extended cell shape both in vitro and in vivo; that, as suggested by others, the pattern of late branching morphogenesis is not dichotomous, but irregular; and that short wisplike fibers of Type IV collagen are present in developing embryonic and fetal lung mesenchyme. Taken together, the results show that early and late lung branching patterns differ significantly, and suggest that later stages of lung branching involve distinct epithelial cell shape transitions. The immunofluorescence data suggest that fibrous Type IV collagen may be the extracellular matrix scaffold within which early epithelial cells accomplish lung branching morphogenesis.

Fibronectin-degrading proteases from the membranes of transformed cells

The local degradation of fibronectin substrata by Rous sarcoma virus-transformed chick embryonic fibroblasts requires cell-contact-related metalloendoprotease and serine-protease activities. Using fibronectin-containing SDS gels, two large proteases with apparent molecular weights of 120K and 150K were found only in the membrane fraction of transformed cells and were absent in normal cells. Both 120K and 150K proteases were active at neutral pH, but showed preferential inhibitor sensitivities of serine and metal proteases, respectively. The 150K protease appeared to account for most of the proteolytic activity since metalloendoprotease inhibitors completely blocked proteolytic activity of the 150K in fibronectin gels, more than 80% of the fibronectin-degrading activity of solubilized membranes, and largely suppressed the appearance of fibronectin degradation spots in cultures of transformed cells.

Coupled expression and colocalization of 140K cell adhesion molecules, fibronectin, and laminin during morphogenesis and cytodifferentiation of chick lung cells

We have analyzed the expression and distribution of fibronectin, laminin, and the 140K cell adhesion molecules (140K complex) in embryonic chick lung cells by a combination of biochemical and immunofluorescent approaches. The 140K complex was identified by monoclonal antibody JG22E as a complex of glycoproteins averaging 140,000 Mr and has been implicated in vitro as a receptor for fibronectin and laminin. Our studies provide the first description that the 140K complex is developmentally regulated, and that the 140K complex appears to be involved in adhesion of epithelial and endothelial cells during morphogenesis. We have shown that the 140K complex is expressed in high quantity in embryonic lung cell types, but is markedly reduced in all of the differentiated cell types except smooth muscle. Embryonic lung cells are enriched in 140K complex on portions of cells in close proximity to areas rich in fibronectin. For example, during the formation of airways and alveolar tissues, 140K complex is concentrated at the basal surfaces of epithelial cells adjacent to fibronectin. Likewise, during the angiogenic invasion of capillaries into lung mesenchyme, the 140K complex becomes localized at sites on the basal surfaces of endothelial cells in close contact with fibronectin. Finally, cytodifferentiating lung smooth muscle cells show unusually high levels of 140K complex, fibronectin, and laminin that persist into the adult. In contrast to fibronectin, laminin is found to be uniformly distributed in the basement membranes of differentiating epithelial cells. It becomes prominent in adult alveolar epithelium and airway epithelium concomitant with a reduction or loss of 140K complex and fibronectin at cell-basement membrane attachment sites. Surprisingly, laminin is also present in a punctate pattern in the mesenchyme of early lung buds, however, laminin, fibronectin, and 140K complex are greatly reduced or lost during mesenchymal maturation. Our results are consistent with the active participation of the 140K complex in cell-to-matrix adhesion during morphogenesis of alveolar walls and cytodifferentiation of mesenchymal and smooth muscle cells.

Cells that emerge from embryonic explants produce fibers of type IV collagen

Double immunofluorescence staining experiments designed to examine the synthesis and deposition of collagen types I and IV in cultured explants of embryonic mouse lung revealed the presence of connective tissue-like fibers that were immunoreactive with anti-type IV collagen antibodies. This observation is contrary to the widely accepted belief that type IV collagen is found only in sheet-like arrangements beneath epithelia or as a sheath-like layer enveloping bundles of nerve or muscle cells. The extracellular matrix produced by cells that migrate from embryonic mouse lung rudiments in vitro was examined by double indirect immunofluorescence microscopy. Affinity-purified monospecific polyclonal antibodies were used to examine cells after growth on glass or native collagen substrata. The data show that embryonic mesenchymal cells can produce organized fibers of type IV collagen that are not contained within a basement membrane, and that embryonic epithelial cells deposit fibers and strands of type IV collagen beneath their basal surface when grown on glass; however, when grown on a rat tail collagen substratum the epithelial cells produce a fine meshwork. To our knowledge this work represents the first report that type IV collagen can be organized by cells into a fibrous extracellular matrix that is not a basement membrane.

Local degradation of fibronectin at sites of expression of the transforming gene product pp60src

Local degradation of extracellular fibronectin, a major extracellular adhesive protein, is believed to play an important part in the migration of cells through the extracellular matrix during tumour invasion, morphogenetic movement and trophoblast implantation. Fibronectin is lost from the cell surface after transformation with Rous sarcoma virus (RSV). By using fluorescent and radiolabelled probes covalently coupled to the surface of substrata, we have recently identified a proteolytic activity that is expressed in RSV-transformed cells and is involved in the local degradation of fibronectin at cell-substratum contact sites. Here, we extend the relevance of these findings and gain some insight into the cellular functions of pp60src, the transforming gene product of RSV. We show that newly expressed viral pp60src is localized at the cytoplasmic surface of the cell membrane, corresponding to the cell contact sites where degradation of extracellular fibronectin occurs.

Intramural stress as a causative factor in atherosclerotic lesions of the aortic valve

Topographic distribution of atherosclerotic lesions of the aortic valve was investigated in rabbits on a 2%-cholesterol-enriched diet and related to distribution of intramural stress in the valve. Initially the lesions appeared at the base of the leaflet on the aortic face and with time spread further out into the leaflet and up the wall of the aortic sinus. In the leaflet, the lesion occurred only in the pressure-bearing part and was primarily composed of a mass of foam cells. By 10 weeks primary fatty plaques were still confined to the aortic face but fibroblasts within the leaflet had also taken up fat. Even after 33 weeks, the atheromatous plaque had not spread beyond the pressure-bearing part of the leaflet. From silicone rubber casts of the valve it was observed that only part of the leaflet was under pressure and the remaining leaflet sustained no pressure gradient. The maximum intramural stress occurred during diastole on the pressure-bearing part. In systole, the blood flow produced shear stress on the entire leaflet. Hence, occurrence of atherosclerotic lesions only in the area of maximum intramural stress suggests that intramural stress and not shear stress plays an important role in accelerating the process of atherosclerosis.

Transfer and expression of Klebsiella nif genes in Alcaligenes faecalis, a nitrogen-fixing bacterium associated with rice root

Plasmid pRD1 carrying Klebsiella nif genes was found to be transferable by conjugation from Escherichia coli JC5466 (pRD1) to Alcaligenes faecalis A-15 at a frequency of 5 X 10(-4). Nitrogenase activity of four A-15 (pRD1) strains tested was found to be higher than that of their parent A-15, as determined by the acetylene reduction assay. A-15-1 was a Nif- mutant derived from A-15. After mating with JC5466 (pRD1), the nitrogenase activity was restored. PRD1 was stable in A. faecalis and could be transferred to E. coli JC5466-1 by conjugation. The fact that Klebsiella nif genes carried in pRD1 can be expressed in A. faecalis makes it possible to use pRD1 as a tool for genetic analysis and genetic engineering of the nitrogen fixation system in A. faecalis.