Expression of the Thy-1 gene in human T lymphoid cell lines

We have previously shown that three human T cell lines (MOLT-3, HUT-78 and HUT-102) were able to react with anti-human brain Thy-1 sera by cell surface immunofluorescence. However, the possibility that the antisera might cross-react with molecules other than Thy-1 could not be entirely excluded. In this report, mRNA prepared from these three T cell lines as well as from a murine T cell line (EL4) and a human B cell line (Raji) was subjected to Northern blot analysis and probed with a murine Thy-1.2 gene fragment. The result confirms our cell surface immunofluorescence data and indicates that HUT-78 and HUT-102 cells have approximately 20-fold more of the Thy-1 mRNA than MOLT-3 cells do. The Thy-1 mRNA was not detectable in the human B cell line Raji. This work is the first demonstration that the Thy-1 gene is expressed in human T cell lines. The finding is helpful in clarifying the current confusion regarding the expression of Thy-1 in human lymphoid cells and it also provides a possible model system for exploring the function of Thy-1 in cultured human T lymphocytes.

Comparison of the distribution of tissue kallikrein and esterase A, a kallikrein-like enzyme, in rat kidney using specific monoclonal antibodies

Tissue kallikrein (E.C. 3.4.21.35) and arginine esterase A, another closely related, kinin-generating serine protease, have been localized by immunocytochemistry in rat kidney, using monoclonal antibodies that do not crossreact with other kallikrein-related enzymes or with tonin. Kallikrein was present primarily in the apical cytoplasm of the connecting tubule and the cortical collecting duct. Esterase A, on the other hand, was present primarily in the basolateral region of both proximal and distal straight tubules in the outer medulla and medullary rays. In addition, esterase A was demonstrable in distal convoluted tubules and, to a lesser extent, in proximal convoluted tubules. The presence of different kinin-generating enzymes at these sites would permit the formation of kinins from appropriate substrates on both the vascular and luminal poles of separate segments of the kidney tubule.

Molecular cloning and characterization of two rat renal kallikrein genes

Kallikreins compose a multigene family coding for a subgroup of serine proteases, which are involved in the processing of bioactive peptides. Two rat kallikrein-related genes, RSKG-7 (rat submandibular gland kallikrein gene 7) and RSKG-3, have been cloned and their sequences analyzed. RSKG-7 is approximately 4200 bases in length and consists of five exons and four introns. The 5' end region contains the variant CATAT box and TTTAAA box; the 3' end region contains the polyadenylation signal AATAAA. This gene encodes a putative 28,935-dalton preproenzyme of 261 amino acids (aa). The active enzyme consists of 237 aa and is preceded by a deduced signal peptide of 18 aa and a profragment of 6 aa. RSKG-3 is highly homologous to RSKG-7 in terms of its sequence and structure; it encodes a 28,730-dalton prepropeptide consisting of a signal peptide of 18 aa, a profragment of 6 aa, and an active peptide of 235 aa. Sequence comparisons of RSKG-7, RSKG-3, and other kallikrein-related enzymes reveal the key amino acid residues needed for both serine protease activity (His/Asp/Ser) and kallikrein-like cleavage specificity at basic amino acids. Northern blot analyses using specific oligonucleotide probes demonstrate that, among the 12 tissues studied, RSKG-7 and RSKG-3 are expressed in the rat kidney and submandibular gland. Castration of male rats results in a decrease in submandibular gland RSKG-7 mRNA, which can be restored to the normal level by treatment with thyroxine or testosterone. On the other hand, neither castration nor hormonal manipulation affects RSKG-7 mRNA levels in the kidney.

Evolution of sex in RNA viruses

The distribution of deleterious mutations in a population of organisms is determined by the opposing effects of two forces, mutation pressure and selection. If mutation rates are high, the resulting mutation-selection balance can generate a substantial mutational load in the population. Sex can be advantageous to organisms experiencing high mutation rates because it can either buffer the mutation-selection balance from genetic drift, thus preventing any increases in the mutational load (Muller, 1964: Mut. Res. 1, 2), or decrease the mutational load by increasing the efficiency of selection (Crow, 1970: Biomathematics 1, 128). Muller's hypothesis assumes that deleterious mutations act independently, whereas Crow's hypothesis assumes that deleterious mutations interact synergistically, i.e., the acquisition of a deleterious mutation is proportionately more harmful to a genome with many mutations than it is to a genome with a few mutations. RNA viruses provide a test for these two hypotheses because they have extremely high mutation rates and appear to have evolved specific adaptations to reproduce sexually. Population genetic models for RNA viruses show that Muller's and Crow's hypotheses are also possible explanations for why sex is advantageous to these viruses. A re-analysis of published data on RNA viruses that are cultured by undiluted passage suggests that deleterious mutations in such viruses interact synergistically and that sex evolved there as a mechanism to reduce the mutational load.

A major difference of kallikrein-binding protein in spontaneously hypertensive versus normotensive rats

A unique tissue kallikrein-binding protein was identified and partially characterized in the brain and serum of Sprague-Dawley rats and in the serum-free conditioned media of mouse anterior pituitary cells (AtT 20) and rodent neuroblastoma x glioma hybrids (NG108-15). Kallikrein and kallikrein-binding protein(s) form SDS- and heat-stable complexes with a molecular weight (Mr) of approximately 92,000. The complex formation of 125I-labelled kallikrein and the binding protein in the serum and brain is inhibited by excess unlabelled rat urinary kallikrein, rat arginine esterase A (a kallikrein-like kininogenase), and human urinary kallikrein. When the active site of kallikrein was blocked by phenylmethylsulfonyl fluoride or D-Phe-D-Phe-L-Arg-CH2Cl, no complex formation was detected. Kallikrein-binding protein only forms complexes with active kallikrein or trypsin-activated prokallikrein but not with prokallikrein. 125I-labelled kallikrein forms a 92-kilodalton protein with binding protein in various brain regions of perfused normotensive rats of the Wistar-Kyoto strain (WKY), including the cerebral cortex, cerebellum and brain stem; but complex formation was not found in corresponding brain regions of the spontaneously hypertensive rat (SHR). Similarly, the kallikrein-binding protein was identified in various tissues including thymus, lung, liver, prostate, Cowper's gland, adrenal gland, kidney, and pancreas of WKY rats but not in tissues of SHR. The results suggest a major difference in the kallikrein-binding protein in hypertensive versus normotensive rats. The role of this specific kallikrein-binding protein in cellular hemodynamic processes and blood pressure regulation remains to be investigated.

Immunocytochemical localization of a kallikrein-like serine protease (esterase A) in rat salivary glands

Light and electron microscopic (EM) immunocytochemical methods have been used to localize arginine esterase A, a kinin-generating enzyme immunologically similar to tissue kallikrein, in rat salivary glands. Both polyclonal and monoclonal antibodies to arginine esterase A were used in these studies. By means of a polyclonal antiserum, esterase A was found in granular tubules of submandibular glands and in striated ducts of all three major salivary glands, in a distribution similar to that of tissue kallikrein. With recently developed specific monoclonal antibodies to esterase A, this enzyme was localized in the granules of some (but not all) granular convoluted tubule cells (GCT) and along the basal membranes (but not in apical granules) of striated ducts. By an EM immunoperoxidase method, esterase A was localized subcellularly in granules of some GCT cells and along the basal cell membranes of the tubule and duct system. Thus, this enzyme is found in some sites (GCT granules) shared with tissue kallikrein, but in some unique sites, i.e., basal membranes of striated ducts. The polyclonal antibody used in the present study cross-reacted with tissue kallikrein, but when absorbed with kallikrein, it gave the staining pattern characteristic of monoclonal antibody to esterase A.

Special antigens on sperm from autoimmune infertile men

Sera from three fertile men and four infertile men without sperm antibodies, 17 infertile men with sperm antibodies in serum and seminal plasma (S.P.), and 25 infertile men with sperm antibodies in S.P. were tested by Western Blot analysis against sperm membrane extracts and S.P. from fertile nonautoimmune men and infertile autoimmune men. Sera from fertile men reacted against common antigens with molecular weights (MW) of 28, 38, 48, 60, and 68 kD present on sperm from autoimmune and nonautoimmune men and special antigen of MW 76 kD on the sperm of fertile men. Sera from 15 of 17 (88%) autoimmune infertile men with sperm antibodies in serum and S.P. detected special antigens with MW of 58 kD (sera reactivity in 47% of these men), 43kD (in 29%), 30 kD (in 24%), 35 kD (in 18%), 52 kD (in 12%), 41 kD (in 6%), and 71 kD (in 6%) on the sperm of autoimmune men in addition to the common antigens. Sera from 15 of 25 (60%) men with sperm antibodies in their S.P. showed reactivity to special antigens with MW 52 kD (in 20%), 35 kD (in 16%), 41 kD (in 16%), 58 kD (in 8%), 70/71 kD (in 8%), 30 kD (in 8%), and 56 kD (in 4%). Sera from 18 of 42 (43%) infertile men with sperm antibodies also detected special antigens of MW 26, 46, and 76 kD present only in fertile men's sperm. Sera from only 15 of 42 (36%) autoimmune infertile men reacted against special antigens with MW 17, 20, 23, 30, 43, and 58 kD in the seminal plasma of autoimmune infertile men.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue distribution and kininogen gene expression after acute-phase inflammation

A kinin-directed monoclonal antibody to kininogens has been developed by the fusion of murine myeloma cells with mouse splenocytes immunized with bradykinin-conjugated hemocyanin. The hybrid cells were screened by an enzyme-linked immunosorbent assay (ELISA) and a radioimmunoassay (RIA) for the secretion of antibodies to bradykinin. Ascitic fluids were produced and purified by a bradykinin-agarose affinity column. The monoclonal antibody (IgG1) bound to bradykinin, Lys-bradykinin, Met-Lys-bradykinin, and kininogens in ELISA. Further, this target-directed monoclonal antibody recognized purified low and high molecular weight bovine, human, or rat kininogens and T-kininogen in Western blotting. After turpentine-induced acute inflammation, rat kininogen levels increased dramatically in liver and serum as well as in the perfused pituitary, heart, lung, kidney, thymus, and other tissues, as identified by the kinin-directed kininogen antibody in Western blot analyses. The results were confirmed by measuring kinin equivalents of kininogens with a kinin RIA. During an induced inflammatory response, rat kininogens were localized immunohistochemically with the kinin-directed monoclonal antibody in parenchymal cells of liver, in acinar cells and some granular convoluted tubules of submandibular gland, and in the collecting tubules of kidney. Northern and cytoplasmic dot blot analyses using a kinin oligonucleotide probe showed that kininogen mRNA levels in liver but not in other tissues increase after turpentine-induced inflammation. The results indicated that rat kininogens are distributed in various tissues in addition to liver and only liver kininogen is induced by acute inflammation. The target-directed kininogen monoclonal antibody is a useful reagent for studying the structure, localization, and function of kininogens or any protein molecule containing the kinin moiety.

Circulating autoantibodies to mammalian tissue kallikreins

Autoantibodies to tissue kallikrein (EC 3.4.21.35) were discovered in normal human, rat, mouse, and guinea pig sera. Three independent methods--binding of iodolabeled antigen, enzyme-linked immunosorbent assay (ELISA), and immunoblotting--were used to demonstrate these kallikrein autoantibodies. Autoantibodies from rat and human sera were purified, using rat and human tissue kallikrein-affinity chromatography, respectively. Purified rat kallikrein autoantibody bound 50% of 125I-labeled rat urinary kallikrein upon incubation of antibody at 2.5 X 10(-10) M. The subtypes of rat and human kallikrein autoantibodies were determined by an ELISA, using antisera to immunoglobulin subclasses. In both species, autoantibody was predominantly IgG (approximately 80%) and some IgM (approximately 20%). Purified autoantibodies from rat and human sera were separated on sodium deodecyl sulfate-polyacrylamide gels, and their subunits were identified by Western blot analyses, using anti-rat and anti-human IgG antibodies, respectively. When primary cultures of mouse spleen cells were incubated for 1 to 5 days with lipopolysaccharide (1 to 5 micrograms/ml), the anti-kallikrein antibodies in the media increased up to seven-fold. We have demonstrated circulating autoantibodies that recognize and bind both autologous and heterologous kallikrein; however, their significance to the function of the tissue kallikrein-kinin system in normal and disease states remains to be explored.

Identification of latent tissue kallikrein, prolactin and growth hormone secretion in GH3 pituitary cells using modified radioimmunoassays

Our studies demonstrate that rat anterior pituitary cells (GH3) are capable of synthesizing and secreting tissue kallikrein together with prolactin and growth hormone. The secretion of prolactin and growth hormone in GH3 cells was measured by two newly developed sensitive radioimmunoassays (RIA), using the polyethylene glycol separation technique. In the direct radioimmunoassay for rat tissue kallikrein, using a polyclonal antiserum which recognizes both active and prokallikrein, the GH3 kallikrein displays parallelism with standard curves of rat urinary kallikrein. The production of immunoreactive kallikrein, prolactin, and growth hormone is time-dependent, and the levels after a 72 h incubation in serum-free media are approximately 12.2 +/- 4.4 ng, 272.2 +/- 33.0 ng, and 475.6 +/- 4.8 ng per 10(6) cells per ml (mean +/- SD, n = 3), respectively. In Western blot analyses, a specific monoclonal antibody to tissue kallikrein (V4D11) identifies GH3-secreted kallikrein as a approximately 39,000 Da protein, slightly larger than approximately 38,000 Da kallikreins of submandibular gland, mouse anterior pituitary cells (AtT 20) or rodent neuroblastoma X glioma hybrid cells (NG108). Kallikrein mRNA in GH3 cells was identified in Northern blot analyses, using a tissue kallikrein cDNA probe. In a RIA using a kallikrein monoclonal antibody (V1C3) recognizing only active kallikrein, kallikrein could not be detected in the media incubated up to 48 h with GH3 cells. However, after trypsin treatment, a time-dependent increase of immunoreactive kallikrein (using monoclonal antibody V1C3), Tos-Arg-OMe esterase, and kinin-releasing activities can be measured in the conditioned media. The activated esterase activity was inhibited by aprotinin and by affinity-purified kallikrein monoclonal antibody (V4D11) in a dose-dependent manner. The data indicated that rat anterior pituitary GH3 cells secrete latent tissue kallikrein, which can be converted to active kallikrein by trypsin. These hormonally responsive cells co-synthesize kallikrein with prolactin and growth hormone and provide a model system for studying the regulation of kallikrein gene expression.

Identification and expression of kallikrein gene family in rat submandibular and prostate glands using monoclonal antibodies as specific probes

Panels of monoclonal antibodies to three vasoactive peptide-producing enzymes: tissue kallikrein, tonin and arginine esterase A were developed, characterized and used as probes for identification of tissue-specific expression. In addition, immunoblot analyses were performed, using monospecific monoclonal antibodies which did not show cross-reactivity to related-purified enzymes in enzyme-linked immunosorbant assay (ELISA), and radioimmunoassay. We obtained the following results. In rat submandibular gland extract, the expression of 38 kDa kallikrein, 32 kDa tonin, and 18 kDa heavy chain of esterase A was identified by monoclonal antibodies to kallikrein (V4D11), tonin (1F11), and esterase A (5A10, 6C11, and 4B12), respectively. In the prostate gland, a 32 kDa kallikrein-like protein was identified by monoclonal antibodies to esterase A (5A10, 6C11 and 4B12) and by antibodies recognizing both tonin and esterase A (5A5), but not by antibody to kallikrein (V4D11) or to tonin (1F11, 1G6) in Western blot analysis. The esterase A-like enzyme in the prostate gland was found within the cytoplasm of ductal epithelial cells by using monoclonal anti-esterase A antibody (5A10) but not by employing anti-tonin antibody (1F11). These results indicate that tissue kallikrein, tonin, and esterase A are all expressed in the submandibular gland, while only esterase A or an esterase A-like enzyme is expressed in the prostate gland. The specific monoclonal antibodies can be used as probes for the identification and expression of the kallikrein gene-family enzymes.

Identification of tonin in brain and exocrine tissues and in the cell-free translation products encoded by the mRNA of these tissues

Tissue-specific expression of the esteropeptidase tonin [EC 3.4.99.-] was investigated in rat brain, submandibular gland, pancreas and kidney. Specific polyclonal and monoclonal antibodies to purified rat tonin from the submandibular gland have been developed and characterized and have been purified via a tonin-agarose affinity column. Immunoreactive tonin was measured by a recently developed tonin direct radioimmunoassay using a rabbit tonin antiserum. Resulting tonin levels were found to be 105.27 +/- 2.71 micrograms/mg (of protein) in submandibular gland, 3.18 +/- 0.32 ng/mg in pancreas, 1.35 +/- 0.08 ng/mg in kidney and 0.12 +/- 0.01 ng/mg in brain (means +/- S.E.M.). Western-blot analysis shows that affinity-purified anti-tonin antibody binds to a 32,000-Mr protein from brain and submandibular-gland extracts. The protein, a tonin precursor, was identified from cell-free translation products directly by polyadenylated [Poly(A)+]mRNA species in a wheat-germ system. After the translation products were subjected to immunoprecipitation with affinity-purified tonin antibody, SDS/polyacrylamide-gel electrophoresis of these precipitates revealed two precursors of tonin, with Mr values of 30,000 and 29,000, which are encoded by brain and submandibular-gland mRNA; however, only the 30,000-Mr preprotonin was encoded by pancreas and kidney mRNA. Collectively, the data show that tonin exists in brain, submandibular gland, pancreas and kidney, and can be synthesized by the mRNA of these tissues.

Identification and characterization of a tissue kallikrein in rat skeletal muscles

A tissue kallikrein was purified from rat skeletal muscle. Characterization of the enzyme showed that it has alpha-N-tosyl-L-arginine methylesterase activity and releases kinin from purified bovine low-Mr kininogen substrate. The pH optimum (9.0) of its esterase activity and the profile of inhibition by serine-proteinase inhibitors are identical with those of purified RUK (rat urinary kallikrein). Skeletal-muscle kallikrein also behaved identically with urinary kallikrein in a radioimmunoassay using a polyclonal anti-RUK antiserum. On Western-blot analysis, rat muscle kallikrein was recognized by affinity-purified monoclonal anti-kallikrein antibody at a position similar to that of RUK (Mr 38,000). Immunoreactive-kallikrein levels were measured in skeletal muscles which have different fibre types. The soleus, a slow-contracting muscle with high mitochondrial oxidative-enzyme activity, had higher kallikrein content than did the extensor digitorum longus or gastrocnemius, both fast-contracting muscles with low oxidative-enzyme activity. Streptozotocin-induced diabetes reduced muscle weights, but did not alter the level of kallikrein (pg/mg of protein) in skeletal muscle, suggesting that insulin is not a regulator of kallikrein in this tissue. Although the role of kallikrein in skeletal muscle is unknown, its localization and activity in relation to muscle functions and disease can now be studied.

Tissue kallikrein in rat brain and pituitary: regional distribution and estrogen induction in the anterior pituitary

We have detected tissue kallikrein and kallikrein mRNA in various brain regions with a kallikrein direct RIA and with nucleic acid hybridization using a kallikrein cDNA probe. In the direct RIA, rat urinary kallikrein-like activity was found in the pituitary and pineal glands, hypothalamus, cerebral cortex, cerebellum, and brain stem. Pituitary and pineal gland kallikrein concentrations were significantly higher than those in other regions. Only in pituitary was there a significant difference in tissue kallikrein concentration according to sex, with glands from female rats showing levels 4-fold higher than those from male rats. Kallikrein mRNAs were detected in all of the regions and were about 4-fold higher in female than in male pituitary gland. Northern blot analyses show sex dimorphism of pituitary kallikrein mRNA, similar in size to submandibular gland and kidney mRNA. In castrated male rats, whole pituitary kallikrein content was reduced to 50% of the control value and increased 1.7-fold with testosterone replacement and 18-fold with 17 beta-estradiol treatment. Neither T4 nor cortisol affected whole pituitary kallikrein levels in the castrated male rat, but testosterone decreased pituitary kallikrein in normal female rats by 35%. When anterior pituitary or neurointermediate lobe extracts were separately examined, immunoreactive kallikrein was 10.2- and 1.3-fold higher respectively, in female than in male rat lobes. Estradiol benzoate (30 micrograms/kg) administration increased kallikrein levels 90- and 22-fold, respectively, in the anterior pituitary of gonadectomized male and female rats, while it increased by only 40-50% kallikrein levels in the male and female neurointermediate lobe. In dot blot analysis, kallikrein mRNA levels were increased 5-fold by 17 beta-estradiol in the whole pituitary of castrated male rats. In the cytoplasmic dot hybridization analysis, estradiol benzoate treatment increased kallikrein mRNA levels 54-fold in the anterior pituitary of ovariectomized rats. The data show that a tissue kallikrein indistinguishable thus far from a urinary kallikrein is widely distributed in brain and pituitary and that levels of enzyme and mRNA are comparable in certain central sites. Kallikrein levels in the anterior and neurointermediate pituitaries are differentially regulated by estrogen.

Sperm and seminal plasma antigens from autoimmune men induce immunological infertility

Adult male rabbits were immunized with normal saline (controls), sperm extracts from 2 autoimmune men, seminal plasmas from the same autoimmune men, sperm extract from a fertile nonautoimmune man, and seminal plasma from the same fertile nonautoimmune man. All the sperm donors were free from infections. Rabbits immunized with fertile men's sperm extract and seminal plasma had significantly elevated postimmunization hemagglutinating but not cytotoxic sperm antibodies and reproduced normally. Rabbits immunized with autoimmune men's sperm and seminal plasma antigens developed high titers of cytotoxic and hemagglutinating sperm antibodies in their serum and seminal plasma and their reproduction was markedly reduced. Their sera and seminal plasma reduced motility of sperm from a normal donor. The immune responses were confirmed by electron microscopic immunocytochemistry. This technique revealed membrane-bound endogenous IgG on sperm from only those rabbits immunized with sperm extracts from autoimmune men. These antisera reacted against a protein in the 58,000 D range; antisera to fertile man's sperm extract reacted against three proteins with molecular weights of 15,000, 18,400, 25,000, and 44,000 D, as judged by Western blot. Rabbit antisera to seminal plasma from autoimmune men reacted against several proteins; additionally, it detected two proteins with 43,000 and 68,000 molecular weight detected by antiserum to fertile man's seminal plasma. Sperm and seminal plasma antigens from autoimmune men are different in their elicited immunogenic responses from those of fertile nonautoimmune men. These responses are relevant to infertility.

Identification of a new tissue-kallikrein-binding protein

We have identified a tissue-kallikrein-binding protein in human serum and in the serum-free culture media from human lung fibroblasts (WI-38) and rodent neuroblastoma X glioma hybrid cells (NG108-15). Purified and 125I-labelled tissue kallikrein and human serum form an approximately 92,000-Mr SDS-stable complex. The relative quantity of this complex-formation is measured by densitometric scanning of autoradiograms. Complex-formation between tissue kallikrein and the serum binding protein was time-dependent and detectable after 5 min incubation at 37 degrees C, with half-maximal binding at 28 min. Binding of 125I-kallikrein to kallikrein-binding protein is temperature-dependent and can be inhibited by heparin or excess unlabelled tissue kallikrein but not by plasma kallikrein, collagenase, thrombin, urokinase, alpha 1-antitrypsin or kininogens. The kallikrein-binding protein is acid- and heat-labile, as pretreatment of sera at pH 3.0 or at 60 degrees C for 30 min diminishes complex-formation. However, the formed complexes are stable to acid or 1 M-hydroxylamine treatment and can only be partially dissociated with 10 mM-NaOH. When kallikrein was inhibited by the active-site-labelling reagents phenylmethanesulphonyl fluoride or D-Phe-D-Phe-L-Arg-CH2Cl no complex-formation was observed. An endogenous approximately 92,000-Mr kallikrein-kallikrein-binding protein complex was isolated from normal human serum by using a human tissue kallikrein-agarose affinity column. These complexes were recognized by anti-(human tissue kallikrein) antibodies, but not by anti-alpha 1-antitrypsin serum, in Western-blot analyses. The results show that the kallikrein-binding protein is distinct from alpha 1-antitrypsin and is not identifiable with any of the well-characterized plasma proteinase inhibitors such as alpha 2-macroglobulin, inter-alpha-trypsin inhibitor, C1-inactivator or antithrombin III. The functional role of this kallikrein-binding protein and its impact on kallikrein activity or metabolism in vivo remain to be investigated.

Age and hormonal dependence of tonin levels in rat submandibular gland as determined by a new direct radioimmunoassay

A simple and sensitive direct radioimmunoassay for tonin (EC.3.4.99.-) has been developed. This assay incorporates a modified and convenient poly(ethylene glycol) technique for separation of free from bound tonin. A rabbit antiserum in a final dilution of 1:160,000 was used and the purified tonin was labelled with 125I by using a lactoperoxidase method. It detects 20 pg of immunoreactive tonin per tube. Serial dilutions of rat submandibular gland extracts showed complete parallelism with tonin standard curves. No cross-reactivity with rat tissue kallikrein was seen. Intra- and inter-assay errors were 3.2 and 5.6%, respectively. Using this assay, immunoreactive tonin was detected in the rat submandibular gland as early as 3 weeks after birth (body wt. approximately 50-60 g). Tonin levels are shown to be dependent on age and sex with significantly higher levels in male than in female rats. Castration results in decrease of tonin levels and 17 alpha-methyltestosterone replacement reversed the level to higher than the sham-operated control rats. Cortisol treatment increased, but thyroxine or oestradiol had no effect, on tonin levels in the submandibular gland of castrated rats. This newly developed radioimmunoassay can now be used to measure low levels of tonin in various tissues and body fluids to address questions about its regulation and functional significance.

Sex dimorphism and hormonal regulation of rat tissue kallikrein mRNA

The regulation of rat tissue kallikrein mRNA levels was investigated by RNA filter hybridization using a kallikrein cDNA probe and by in vitro translation of isolated RNA. The synthesis of a 37 kDa polypeptide has been hybrid-arrested by the tissue kallikrein cDNA in cell-free translation assays directed by submandibular mRNA and the quantitation of this protein was used as a measure of translational activity of kallikrein mRNA. In Northern blot analyses, relative kallikrein mRNA levels were found to be 60-fold higher in submandibular gland than in pancreas and 20-fold higher than in kidney. In addition, it was noted that kallikrein mRNA is differentially regulated in tissues from male and female animals. Rat submandibular gland kallikrein mRNA is 2-times more abundant in male animals as in females. This trend is reversed in kidney, where the kallikrein mRNA in females is twice that in male animals. Relative submandibular gland kallikrein mRNA levels were found to be responsive to hormonal manipulation as measured by both Northern blotting and cell-free translation assays. Castration of male animals resulted in a decrease of kallikrein mRNA which could be partially restored by treatment with thyroxine and almost completely restored by testosterone treatment. The submandibular gland kallikrein mRNA in normal female rats was increased up to 30% by administration of testosterone or thyroxine. Adrenalectomized female rats showed a decrease in submandibular kallikrein mRNA which was significantly increased by testosterone, thyroxine, aldosterone and cortisol, with the largest effect being a 2- to 2.4-fold increase in cortisol-treated rats. These results indicate that hormones regulate tissue kallikrein synthesis in the rat submandibular gland, at least in part, by altering kallikrein mRNA accumulation.

Molecular evolution, species distribution, and clinical consequences of an endemic aminoglycoside resistance plasmid

During the first 6 years after appearing in one hospital, a 92-kilobase conjugative plasmid, pBWH1, which encoded resistance to chloramphenicol and sulfonamides and determined TEM-1 beta-lactamase and 2''-aminoglycoside nucleotidyltransferase, underwent a variety of molecular changes. It was most prevalent initially in isolates of Klebsiella pneumoniae, then in isolates of Serratia marcescens, and finally, after nearly disappearing, in isolates of Enterobacter cloacae. Evolutionary changes in the plasmid did not account for its shifts in species distribution, since the original molecule was found in isolates of each species. The late resurgence of pBWH1 occurred after a copy of its original molecule entered a distinctive ornithine decarboxylase-negative strain of E. cloacae, new to the hospital. The resulting transconjugant strain, chromosomally resistant to topical silver salts and to cephalosporins, and with the addition of pBWH1-encoded aminoglycoside resistance, spread in the hospital by causing an outbreak of sepsis in the burn unit, where these were commonly used antibacterial agents. Thus, an endemic plasmid became prevalent in a new host species because one of its genes supplemented the fitness of an uncommon strain of the species for a particular clinical niche.

Immunological identification of rat tissue kallikrein cDNA and characterization of the kallikrein gene family

A tissue kallikrein cDNA was identified by direct immunological screening with affinity-purified anti-rat tissue kallikrein antibody from a rat submandibular cDNA library constructed with the expression vector pUC8. Sequence analysis of the kallikrein cDNA revealed an encoded protein 97% homologous to the partial amino acid sequence of rat submandibular kallikrein. This cDNA was used to hybrid-select kallikrein-specific RNA from submandibular gland. Translation of the hybrid-selected RNA in a cell-free assay system resulted in the production of a 37 kDa peptide representing the preproenzyme. In addition, hybrid-selection of RNA under less stringent conditions showed cross-hybridization with other submandibular gland mRNA species. In correlation with these results, analysis of rat genomic DNA showed extensive hybridization, suggesting a family of closely related kallikrein-like genes. Consequently, a Charon 4A rat genomic library was screened for kallikrein genes by hybridization with rat tissue kallikrein cDNA. Thirty-four clones were isolated and found to be highly homologous by hybridization and restriction enzymes analyses. Fourteen unique clones were identified by restriction enzyme site polymorphisms within DNA segments which hybridized to the kallikrein cDNA probe and it was estimated that at least 17 different kallikrein-like genes are present in the rat. Sequence and structural analysis of one of the genomic clones revealed a gene structure similar to that of other serine proteinases. Comparison of the partially sequenced exon regions of the gene with the sequence of rat tissue kallikrein cDNA reveals 89% identity when aligned for the greatest homology. However, the genomic sequence predicts termination codons in all three translational reading frames, implying that this gene is nonfunctional, i.e., a pseudogene. Comparison of the rat genomic sequence to a kallikrein-like gene from the mouse reveals extensive preservation of exons, less identity within introns and no significant homology between extragenic regions.

A monoclonal antibody to rat tissue kallikrein: use in biochemical and immunohistochemical studies

A monoclonal antibody (V4G6) to rat tissue kallikrein (EC 3.4.21.35) has been developed and characterized. This clone showed no cross-reactivity with rat tonin, rat esterase A or human urinary kallikrein in either radioimmunoassay or enzyme-linked immunosorbent assay. The monoclonal antibody used in the direct radioimmunoassay detects purified rat urinary kallikrein in a range of 0.32 to 40 ng per tube. The displacement curves for rat submandibular gland, pancreatic and kidney extracts and urine were parallel with the standard curve of purified rat urinary kallikrein. Analysis of immunoprecipitates from [14C] DFP labeled submandibular gland extract with SDS-polyacrylamide gel electrophoresis, demonstrates that this antibody recognizes only one 38,000 dalton serine protease while polyclonal antiserum identifies multiple species. Using this specific monoclonal reagent, tissue kallikrein was localized immunohistochemically in the granular convoluted tubules and striated ducts of the rat submandibular gland and in the acinar cells of the rat pancreas. The results showed that the monoclonal antibody (V4G6) can specifically recognize a single kallikrein in the tissue extracts without cross-reacting with other kallikrein-related serine proteases. This monoclonal antibody can be used as a specific reagent for quantitation, identification and immunohistochemical studies of tissue kallikrein.

Active kallikrein, preprokallikrein, and kallikrein-inhibitor complex

Active kallikreins isolated from various exocrine and endocrine tissues were identified by a monoclonal antibody in Western blot analyses to be approximately 38,000 dalton proteins. Kallikreins isolated from rat pancreas, kidney, submandibular gland, brain, spleen and urine were indistinguishable with respect to molecular weight and immunological characteristics. Preprokallikreins were synthesized in a cell-free translation system directed by mRNAs and immunoprecipitated by affinity-purified kallikrein antibody. Analysis of the precipitates by SDS-polyacrylamide gel electrophoresis revealed a approximately 37,000 dalton polypeptide in kidney, brain and submandibular gland translation products. This 37,000 dalton kallikrein precursor was hybrid-arrested by a kallikrein cDNA encoding tissue kallikrein which was isolated from a rat submandibular gland cDNA library. The immunoprecipitates of products directed by pancreatic mRNA showed a major protein with Mr of approximately 30,000. An endogenous approximately 92,000 dalton component in rat urine and kidney was also identified by a monoclonal antibody to tissue kallikrein and represents a kallikrein-inhibitor complex. These results indicate that tissue kallikreins can be initially synthesized as 37,000 or 30,000 dalton prepropeptides and then converted into a 38,000 dalton active form by proteolytic processing and glycosylation. The active kallikrein is capable of binding to an inhibitor to form a 92,000 dalton complex.

Kallikrein localization in rat brain by immunohistochemistry

Using an antibody-peroxidase bridge technique with either polyclonal antibodies or a specific monoclonal antibody, immunoreactive kallikrein was localized in all three lobes of the pituitary, in ependymal cells lining the third ventricle, and in cell bodies of the following hypothalamic neuronal nuclei: supraoptic, arcuate, paraventricular and ventromedial.

Sensitivity of DNA-repair-deficient strains of Escherichia coli to rifampicin killing

We have analyzed the role of RNA polymerase in DNA repair using the antibiotic rifampicin which binds specifically to the beta subunit of the enzyme. Several DNA-repair-deficient strains such as recA, uvr, and polA, and their isogenic parents were used for this study. All repair-deficient strains were found to be hypersensitive to rifampicin killing. Compared to the isogenic parent strains, recA strains are about 50 times more sensitive and the polA strain is about 100 times more sensitive to rifampicin killing. UvrA and uvrB strains are slightly more sensitive to rifampicin than the wild-type strains. The hypersensitivity of repair-deficient strains to rifampicin killing is totally abolished by the introduction of rifampicin-resistant mutations into these strains. We have examined the effect of rifampicin on RNA and protein synthesis in repair-deficient and -proficient strains. RNA and protein synthesis were found to be inhibited by rifampicin to the same extent among all the strains tested. The results also show that the resumption of DNA synthesis was significantly disrupted in DNA-repair-deficient strains following drug removal. Taken together these results suggest that RNA polymerase plays an essential role in DNA metabolism and such function may be replaced by polA and recA gene products and to a lesser extend by uvrA and uvrB gene products.

An improved method for the measurement of rat tissue kallikrein using a monoclonal antibody which recognizes only active enzyme

We have used a monoclonal antibody which recognizes active kallikrein to develop a method for measurement of inactive and active kallikrein in rat urine. The inactive kallikrein levels were calculated from the difference between values before and after trypsin pretreatment in the kallikrein direct radioimmunoassay. In this assay, the final dilution of ascitic fluid containing monoclonal antibody was 1:1.6 X 10(7) which gave 35% specific binding to 125I-labelled kallikrein, and the minimal detectable amount was 0.08 ng/tube. When inactive kallikrein was assessed by this method and a kininogenase assay in 23 randomly collected urines, a significant correlation was observed between the values obtained from the two assays (p less than 0.01). The regression line for this relation was similar to that observed between purified active kallikrein concentration and kininogenase activity. The active and inactive kallikrein excretion rates and the inactive/total kallikrein ratio in rats on normal sodium diet were 74.0 +/- 17.3 micrograms/day (m +/- SD), 82.8 +/- 14.4 micrograms/day and 53.1 +/- 7.1%, respectively. This method can now be applied to studies of prokallikrein activation.

Characterization of rat kallikrein-like multigene family and its expression in the submandibular gland

A cDNA clone encoding rat tissue kallikrein was isolated from a submandibular cDNA library. The kallikrein cDNA clone was used as a probe to analyze the complexity of the kallikrein-like gene family and its expression. The results indicate that rat kallikrein-like genes identified with this probe belong to a very large and highly homologous multigene family. A number of these genes, perhaps as many as a dozen or so, are expressed in the submandibular gland.

Characterization of monoclonal and polyclonal antibodies to human tissue kallikrein

Monoclonal antibodies to purified human urinary kallikrein have been developed. Selection of antibody producing clones was based on 125I-kallikrein binding activity of hybridoma media in both radioimmunoassay and enzyme-linked immunosorbent assay. Three clones (2 IgG1, 1 IgG2b) were subcloned, characterized, and compared with the polyclonal antiserum generated in rabbits immunized with the purified kallikrein. With radioimmunoassay, mouse ascitic fluids or rabbit antisera dilutions showing 50% binding to 125I-kallikrein were 1:1.2 X 10(6) (E7A9), 1:1.2 X 10(5) (H6A6), 1:8.0 X 10(4) (E12H1), and 1:1.4 X 10(6) (the rabbit antisera). With enzyme-linked immunosorbent assay, mouse ascitic fluids from clones E7A9 and H6A6 showed half-maximal absorbance at dilutions of 1:2.1 X 10(5) and 1:1.0 X 10(5) respectively, and the polyclonal antiserum showed half-maximal absorbance at a dilution of 1:2.0 X 10(4). These monoclonal antibodies showed no cross-reactivity with rat tissue kallikrein, rat urinary plasminogen activator, or dog pancreatic kallikrein, while the polyclonal antiserum showed some cross-reactivity. The binding of monoclonal or polyclonal antibodies to 125I-human urinary kallikrein was not affected by human plasma kallikrein, thrombin, or urokinase in a competitive radioimmunoassay. By using purified human urinary kallikrein immobilized to agarose, antibodies produced by clones E7A9 and H6A6 and in the rabbit antisera were purified to homogeneity. Each of these affinity-purified antibodies inhibited the esterase activity, and two of the three inhibited the kininogenase activity, of human urinary kallikrein. A sandwich immunosorbent assay was developed to measure this kallikrein using monoclonal antibody from the clone E7A9 in conjunction with the polyclonal antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific identification of tissue kallikrein in exocrine tissues and in cell-free translation products with monoclonal antibodies

A panel of six mouse monoclonal antibodies (IgG1) has been prepared against purified rat urinary kallikrein (EC 3.4.21.35) and characterized. In radioimmunoassay, the antibody titres of ascitic fluid giving 50% binding to 125I-kallikrein range from 1:2 X 10(3) to 1:1 X 10(6). Antibodies from four of the clones show no cross-reactivity with human urinary kallikrein, rat urinary esterase A or tonin. However, antibodies from a fifth clone cross-react with tonin and, from a sixth, with both urinary esterase A and tonin. Three of the kallikrein affinity-purified monoclonal antibodies inhibited, whereas one of the antibodies stimulated, kallikrein activity. Tissue kallikrein from rat submandibular-gland and pancreatic extracts and urine were labelled with [14C]di-isopropyl phosphofluoridate, immunoprecipitated with each of the six monoclonal antibodies and identified to be 38 kDa proteins, similar in size to purified rat urinary kallikrein. Western-blot analysis shows that 125I-labelled kallikrein monoclonal antibodies (V4D11) bind directly to a 38 kDa protein in submandibular-gland and pancreatic extracts and urine. Cell-free translation products of submandibular-gland polyadenylylated[poly(A)+]mRNA were immunoprecipitated with affinity-purified sheep anti-kallikrein antibodies and three monoclonal antibodies (V4D11, V4G6 and V1C3). Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of these immunoprecipitates revealed that two kallikrein precursors with Mr values of 37 000 and 35 000 are encoded by submandibular-gland mRNA. The third monoclonal antibody, V1C3, which binds to active kallikrein, did not recognize either precursor form. Collectively, the data show that these monoclonal antibodies comprise a set of powerful and specific reagents for studies of tissue kallikreins.

Evolution of transposable elements: an IS10 insertion increases fitness in Escherichia coli

Strains of Escherichia coli carrying Tn10, a transposon consisting of two IS10 insertion sequences flanking a segment encoding for a tetracycline-resistance determinant, gain a competitive advantage in chemostat cultures. All Tn10-bearing strains that increase in frequency during competition have a new IS10 insertion that is found in the same location in the genome of those strains. We mapped, by a gradient of transmission, the position of the new IS10 insertion. We examined 11 isolates whose IS10 insertion was deleted by recombinational crossing-over, and in all cases the competitive fitness of the isolates was decreased. These results show that the IS10-generated insertion increases fitness in chemostat cultures. We named the insertion fit::IS10 and suggest that transposable elements may speed the rate of evolution by promoting nonhomologous recombination between preexisting variations within a genome and thereby generating adaptive variation.

Immunocytochemical localization of tissue kallikrein in brain ventricular epithelium and hypothalamic cell bodies

A specific monoclonal antibody against rat tissue kallikrein was used as the primary antibody for indirect immunoperoxidase staining of rat hypothalamus. Kallikrein was localized in the epithelial cells (ependyma) lining the third ventricle as well as in cell bodies of arcuate, supraoptic, paraventricular, and ventromedial nuclei.

Immunological analysis of rat pancreatic prokallikrein activation

The present study shows that tissue kallikrein is present in rat pancreas as a proenzyme that can be converted by autolysis to a 38 000 Da active enzyme. The activation of pancreatic prokallikrein was examined by direct radioimmunoassay, enzymatic assays, active-site labeling with immunoprecipitation, and Western blot analyses. A monoclonal antibody (V1C3), which binds only active kallikrein, was used in a direct radioimmunoassay to monitor the appearance of the active enzyme. During a 22-h autolysis of pancreatic extract, a time-dependent increase in active kallikrein concentration paralleled the increase of kallikrein activities measured by both TosArgOMe esterase and kininogenase assays. The activation process was further analyzed by labeling the pancreatic extract with [14C]diisopropylphosphorofluoridate [( 14C]DFP) followed by immunoprecipitation with sheep anti-kallikrein antiserum. Pancreatic prokallikrein was not labeled by [14C]DFP; however, upon autolysis, a 38 000 Da active kallikrein can be labeled with [14C]DFP and increase in quantity with time. Western blot analysis, using a monoclonal antibody (V4D11) which recognizes both latent and active tissue kallikreins, identified a 39 000 Da pancreatic prokallikrein prior to autolysis and a 38 000 Da active kallikrein after 7 h of autolysis. The results indicate that the pancreatic prokallikrein exists as a 39 000 Da protein which may be converted to a 38 000 Da active kallikrein, indistinguishable from purified urinary, brain, spleen or submandibular gland kallikrein.

The effects of wall populations on coexistence of bacteria in the liquid phase of chemostat cultures

We have examined the effects of wall populations on coexistence between strains of Escherichia coli in the liquid phase of mixed (two-strain) chemostats. The wall populations of the two competing strains became established soon after the start of the cultures and, although the relative abundance of the strains in the liquid phase could change over time by several orders of magnitude, the composition of an established wall population did not change markedly. The bacterial strains examined could not displace an established wall population of a competing strain. The presence of a permanent wall population allowed a strain that was less fit in the liquid phase to coexist with a superior strain. The resulting coexistence did not require that the inferior strain attached to the vessel wall better than the superior strain. We believe that the coexistence developed because the inferior strain survived and reproduced on the vessel wall. The progeny from that wall population then provided replacements for the bacteria that the inferior strain lost through a selective disadvantage in the liquid phase of the culture. By replacing the chemostat vessel, hence eliminating the wall populations, we could distinguish between cases where the coexistence depended on the presence of a wall population and where it resulted from some alternative mechanism.

Resistance to antibiotics in clinical isolates of Klebsiella pneumoniae

The antibiotic resistance of Klebsiella pneumoniae isolates from 12 medical centers worldwide, over a 1- to 6-year period, were tested. Clinical isolates of K. pneumoniae were resistant to ampicillin and carbenicillin. Resistance to other antibiotics was less frequent with isolates of K. pneumoniae from 5 of 6 US centers than with those from 6 centers outside the US. In nearly all of the centers, resistance to sulfamethoxazole-trimethoprim, gentamicin, tobramycin, or chloramphenicol was more frequent in isolates of K. pneumoniae than in those of Escherichia coli, while the reverse was true for resistance to tetracycline. Resistance to multiple antibiotics declined gradually in isolates of K. pneumoniae at one center, but rose abruptly again with dissemination of a new plasmid.

Isolation of tissue kallikrein in rat spleen by monoclonal antibody-affinity chromatography

Rat spleen kallikrein was identified and purified by DEAE-cellulose and monoclonal antibody-affinity chromatography. The purified enzyme has Tos-Arg-OMe esterase activity and kinin-releasing activity from a purified low-molecular-weight kininogen substrate. In the direct radioimmunoassay for tissue kallikrein, the splenic enzyme displays parallelism with standard curves of rat urinary kallikrein. The pH profiles of the Tos-Arg-OMe esterase activities of spleen and urinary kallikrein were identical with optima at 9.0. Rat spleen kallikrein was inhibited strongly by aprotinin and affinity-purified kallikrein antibody and weakly by soybean trypsin inhibitor. The IC50 values were similar to those observed against rat urinary kallikrein. Neither the urinary nor the splenic enzyme was inhibited by lima bean trypsin inhibitor or preimmune serum immunoglobulins. Spleen kallikrein was labeled with [14C]diisopropylphosphorofluoridate and visualized by fluorography on a sodium dodecyl sulfate-polyacrylamide gel. The electrophoretic mobility of the splenic enzyme was indistinguishable from that of urinary kallikrein A with an estimated Mr of approx. 38 000. With Western blot analyses using a rabbit anti-kallikrein antibody followed by 125I-labeled protein A binding, the spleen and urinary kallikreins were again visualized at identical positions by autoradiography. The data show that there is a rat splenic tissue kallikrein which is indistinguishable from a renal kallikrein with respect to physicochemical properties, immunological character and susceptibility to inhibitors.

Identification of a kallikrein-like latent serine protease in human erythrocyte membranes

We have discovered and characterized a kallikrein-like latent serine protease in intact human erythrocytes and ghosts. The enzyme is activatable by trypsin. The solubilized enzyme has esterolytic activity with a pH optimum of 9; but the membrane-associated activity increases almost linearly up to pH 10. The activated enzyme releases kinin from bovine low molecular weight kininogen. Enzyme activity is inhibited by TosLysCH2Cl , phenylmethylsulfonyl fluoride, aprotinin and amiloride, and weakly by soybean or lima bean trypsin inhibitor. It is inhibited by Co2+, Zn2+ and Mn2+ but is stimulated by Fe2+, deoxycholate and phospholipase A2. An erythrocyte membrane protein (Mr = 88,000) with an active site serine residue was identified with [14C]-diisopropylphosphorofluoridate labeling. Consistent with the finding of tryptic activation of the latent erythrocyte serine protease, trypsin treatment reduced the density of labeling of this protein and revealed a lower molecular weight form (Mr = 64,000). Possible relationships between the activity of this newly identified serine protease and events such as erythrocyte membrane ion fluxes might be of interest.

Free transplantation of sub-axillary lateral thoraco-dorsal flap in burn surgery

Free transplantation of subaxillary lateral thoracodorsal flap is recommended. The thoraco-dorsal artery and its accompanying veins may nourish and drain a large musculo-cutaneous flap. The calibres of both the artery and the veins are big enough to be anastomosed to the recipient vessels using the naked eye. The donor area can be closed by first intention suture without interfering with the functional recovery of the donor area. Both the functional and cosmetic results after free transplantations of this flap are good. In acute electrical or other deep burns, this flap can be used to prevent infection, to protect the deep vital structures, and to lessen the amputation rate. A better condition is created for functional recovery and facilitating reconstructive surgery. The muscular branch of the thoraco-dorsal artery was always present in our 50 patients whereas only 20 cases (40 per cent) had an independent cutaneous branch which nourishes the flap. We stress the point of preserving and using the muscular branch as the main blood vessel to be anastomosed for this free flap.

Identification of tissue kallikrein in brain and in the cell-free translation product encoded by brain mRNA

A monoclonal antibody against purified rat urinary kallikrein was coupled to agarose and used to isolate kallikrein from rat brain. The purified enzyme has N alpha-tosyl-L-arginine methyl esterase activity with a pH optimum at 9.0, kinin-releasing activity from a purified low molecular weight kininogen, and a parallelism with standard curves of rat urinary kallikrein in a direct radioimmunoassay. Brain kallikrein is inhibited by a series of tissue kallikrein inhibitors with IC50 values similar to those for urinary kallikrein. The purified brain enzyme was labeled with [14C]diisopropylphosphorofluoridate and visualized by fluorography on a sodium dodecyl sulfate-polyacrylamide gel. Electrophoretic mobility of the enzyme was closely similar to that of urinary kallikrein with estimated Mr of approximately 38,000. With Western blot analyses using a rabbit anti-kallikrein antibody, both brain and urinary kallikrein were visualized at identical positions by immunoperoxidase staining and by autoradiography with 125I-protein A binding. Brain mRNA was used to direct cell-free protein synthesis in wheat germ and rabbit reticulocyte lysate systems. [35S]Methionine-labeled kallikrein was identified by fluorography of sodium dodecyl sulfate-polyacrylamide gels after the translation products were subject to immunoprecipitation with affinity-purified kallikrein antibody. Collectively, the data show that tissue kallikrein exists in brain and can be synthesized by brain mRNA.

Transposable elements as mutator genes in evolution

Strains of the bacterium Escherichia coli harbouring genes that increase mutation rates are known to have an evolutionary advantage in chemostat competition over otherwise isogeneic strains with lower mutation rates. This advantage is frequency-dependent, the mutator strain being favoured only above a starting ratio of approximately 5 x 10(-5), and it results from the fact that the necessary beneficial mutations cannot be generated in a mutator population below a certain size. Here we consider the possibility that the mutagenic properties of transposable elements confer an advantage in the same manner as mutator genes. A previous report has shown that the transposon Tn5 increases the fitness of E. coli in chemostats, although the reason for this effect has not been established. Our results show that the transposon Tn10 also confers an advantage in chemostats. In addition, we find that (1) this advantage, like that associated with mutator genes, is frequency-dependent, (2) whenever the Tn10 strains win, a segment of Tn10, probably its IS10 sequences, has undergone transposition to a new site, (3) the new insertions converge into a site contained within a 3.2 kilobase (kb) PvuII fragment of the genome, and (4) no transpositions are detected when the Tn10 population loses. We conclude that Tn10 confers an advantage by increasing the mutation rate of the host bacterium.

Enhanced resistance to nitrosoguanidine killing and mutagenesis in a DNA gyrase mutant of Escherichia coli

The role of DNA gyrase in handling DNA damages induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was examined with two Escherichia coli strains, KL161 and KL166. The two strains are isogenic except that KL166 harbors a mutation at the nalA (gyrA) locus which specifies one of the two subunits of DNA gyrase. We treated the two strains with several different types of mutagenic agents and found the nalA strain to be highly resistant to MNNG-induced killing and mutagenic effects as compared with the parental strain. The MNNG resistance was specific, since the two strains were about equally sensitive to methyl methane sulfonate, ethyl methane sulfonate, and UV and gamma radiations. We pulse-labeled the two strains with [(3)H]uridine and (14)C-amino acids after MNNG treatment to analyze RNA and protein synthetic rates. The pulse-labeled proteins were also separated on polyacrylamide gels. The results show that pulse-labeled RNA and proteins persisted in the nalA strain but declined rapidly in the parental strain after MNNG treatment. We compared membrane-free nucleoid preparations from the two strains by sucrose density gradient centrifugation and found a difference in nucleoid organization between the two strains. The nucleoid of the nalA strain, unlike that of the parental strain, may have a highly ordered structure, as indicated by its resistance to ethidium bromide-induced relaxation. The ability of the two strains to express an adaptive response to MNNG was determined. We found that the resistance to MNNG killing and mutagenesis by the nalA strain cannot be further increased by adaptive treatment. These results suggest that an alteration in DNA gyrase may have profound effects on E. coli chromosome organization and base methylation by MNNG.

Laboratory surveillance of synergy between and resistance to trimethoprim and sulfonamides

Results of susceptibility tests of Enterobacteriaceae isolated at 14 different centers demonstrate synergy between trimethoprim (TMP) and sulfamethoxazole (SMZ) against sulfonamide-susceptible isolates, which account for between less than 50% and greater than 75% of the isolates at different centers. Only 1%-4% of the isolates of Escherichia coli or Proteus mirabilis from the five centers in the United States were found to be resistant when tested with a disk containing both TMP and SMZ, but greater than 8% of such isolates from five of the other centers were resistant to the combination disk. A larger percentage of isolates of Klebsiella pneumoniae or Serratia marcescens were resistant, but the number varied from center to center. In the United States, resistance of human and animal isolates of Salmonella to the TMP-SMZ combination was almost completely absent, although greater than 50% of the animal isolates were resistant to sulfonamides. At a center that tested TMP and SMZ resistance with separate disks, resistance to TMP was found to be 30 times more common in sulfonamide-resistant than in sulfonamide-susceptible E. coli. This ratio may be useful as a monitor as treatment with TMP alone increases.

Structured habitats and the evolution of anticompetitor toxins in bacteria

We demonstrate that in liquid cultures, defined in this study as a mass habitat, the outcome of competition between Escherichia coli that produce an antibacterial toxin (colicin) and sensitive E. coli is frequency dependent; the colicinogenic bacteria are at an advantage only when fairly common (frequencies in excess of 2 X 10(-2)). However, we also show that in a soft agar matrix, a structured habitat, the colicinogenic bacteria have an advantage even when initially rare (frequencies as low as 10(-6)). These contrasting outcomes are attributed to the colicinogenic bacteria's lower intrinsic growth rate relative to the sensitive bacteria and the different manner in which bacteria and resources are partitioned in the two types of habitats. Bacteria in a liquid culture exist as randomly distributed individuals and the killing of sensitive bacteria by the colicin augments the amount of resource available to the colicinogenic bacteria to an extent identical to that experienced by the surviving sensitive bacteria. On the other hand, the bacteria in a soft agar matrix exist as single-clone colonies. As the colicinogenic colonies release colicin, they kill neighboring sensitive bacteria and form an inhibition zone around themselves. By this action, they increase the concentration of resources around themselves and overcome their growth rate disadvantage. We suggest that structured habitats are more favorable for the evolution of colicinogenic bacteria.

Altered stability and integration frequency of a F' factor in RNA polymerase mutants of Escherichia coli

A number of spontaneous rifampicin-resistant (Rifr) mutants were isolated from a strain of E. coli having a deletion in the lac proA proB region of the chromosome. The stability of a F'lac proA proB episome in these mutants was determined by their sensitivity to acridine orange curing and the frequency of spontaneous loss of episomes. The Rifr mutants can be divided into three classes based on their ability to maintain the F'lac pro episome. Class I mutants (25% of the total Rifr mutants) showed high degree of spontaneous episome loss and high sensitivity to acridine orange curing. Class II mutants (55% of the total Rifr mutants), like the parent strains, showed intermediate sensitivity to acridine orange curing. Class III mutants (21% of the total Rifr mutants) showed high resistance to acridine orange curing and low frequency of spontaneous episome loss. Three-fourths of the Class II mutants were found to be Hfr as shown by their lack of the F'lac pro DNA band on agarose gel together with their ability to mobilize chromosomal markers in mating. Representative Rifr mutants from each class were selected and the Rifr mutants from each class were selected and the Rifr mutations were mapped within the proB gene for the beta beta' operon by P1 transduction. These results indicate that RNA polymerase, or the beta subunit of RNA polymerase, plays an important role in maintaining the F' lac pro episome and in the integration of the F' lac pro episome where no extensive sequence homology is involved.

In vitro transformation of Syrian hamster epidermal cells by N-methyl-N'-nitro-N-nitrosoguanidine

The selection of Syrian hamster epidermal cells which do not terminally differentiate has provided a quantitative focus assay for in vitro chemical transformation. One-day-old Syrian hamster epidermal cells plated at 5 x 10(6)/100-mm dish were treated for 5 hr with various concentrations of N-methyl-N'-nitro-N-nitrosoguanidine. After 4 weeks, the normal epidermal cells began to terminally differentiate to keratinized squamous cells and died, but transformed epidermal colonies grew to higher cells densities and appeared as darker areas against a lightly stained normal cell background. Transformed epidermal foci were isolated and subcultured for at least 15 passages, whereas normal epidermal cells could not be subcultured under the same conditions. The transformed cells assumed the typical cobblestone-like morphology of epithelial cells, retained desmosomes and tonofilaments, and were able to use citrulline in place of arginine. Argininosuccinate synthetase (EC 6.3.4.5) activity was significantly higher in the epidermal cells than in fibroblasts. The injection of 5 x 10(6) cells of two transformed epidermal cell lines into athymic nude mice resulted in the formation of tumors which were identified as keratinizing squamous carcinomas.

Urinary excretion of 3-methylhistidine as an index of muscle protein catabolism in postoperative trauma: the effect of parenteral nutrition

The effect of different intravenous nutritional regimens on nitrogen balance and 3-methylhistidine (3-MeHIS) excretion were studied during a 6-day period following major elective surgery in 28 patients. All patients were kept on a synthetic diet 4 days prior to surgery and were given 0.1 g amino acid N and 120 kJ/kg . day. Postoperatively, all patients received parenteral nutrition with approximately 170 kJ/kg . day. Postoperatively, all patients received parenteral nutrition with approximately 170 kJ/kg . day. Three groups of patients were given varying amounts and proportions of amino acids while in one group no amino acids were administered. Preoperatively, urinary 3-MeHIS excretion (determined by a newly developed automatic analyzer) was 240.3 mumole/day +/- 9.2, nitrogen balance was -1.8 g N +/- 0.19. Postoperatively, nitrogen balance was less negative when amino acids were given. The degree of improvement depended on the amount, but not on the composition of nitrogen administered. In all four groups, 3-MeHIS outputs were elevated when compared with preoperative excretion. The 3-MeHIS excretion (mumole/day) was increased more in patients on high amino acid supply than in patients with low or no nitrogen supply. In each of the groups the 3-MeHIS excretion was negatively correlated to the nitrogen balance. Regression analyses suggest that postoperative muscle protein breakdown occurs in relation to the body protein loss. Amino acid administration seems not to decrease muscle protein breakdown, but rather, appears to stimulate protein synthesis, resulting in less net protein loss. The mean rate of muscle protein breakdown in the postoperative state was estimated to be 80 g/day, assuming 4.2 mumole 3-MeHIS per g mixed human muscle protein. This exceeded the mean preoperative breakdown by about 23 g muscle protein per day. This increase might be due to the metabolic response to the trauma and also in part to tissue damage by the surgical procedure.

Biochemical changes associated with severe trauma

The effects of different intravenous nutritional regimens on a number of biochemical indices of nutritional status were studied during the 8-day period following severe trauma. The inclusion of large amounts of amino acids (high nitrogen (N) was shown to greatly improve N balance over an isocaloric regimen containing no amino acids (O g N). The concentration of serum albumin, transferrin, prealbumin, and retinol-binding protein all fell during the study period in both patient groups, whereas the serum concentrations of acute phase reactants and of ribonuclease increased in the two groups. The sum of plasma levels of branched-chain amino acids and the essential amino acids was increased to a greater extent in the high N group. These amino acid totals and the ratio of glycine/valine showed a significant correlation with N balance in this group. Despite the marked difference in N balance, 3-methylhistidine excretion was increased but equal in the two nutritional groups, suggesting an increased rate of muscle protein breakdown in both groups, which appears not to be influenced by amino acid nutrition. It is concluded that N balance can be significantly improved in the immediate posttrauma period by provision of amino acids together with energy substrates. None of the biochemical variables measured, with the exception of plasma levels of essential amino acids, reflected these marked differences in N balance.