Production and characterization of microbial biosurfactants for potential use in oil-spill remediation.

Two biosurfactants, surfactin and fatty acyl-glutamate, were produced from genetically-modified strains of Bacillus subtilis on 2% glucose and mineral salts media in shake-flasks and bioreactors. Biosurfactant synthesis ceased when the main carbohydrate source was completely depleted. Surfactin titers were ∼30-fold higher than fatty acyl-glutamate in the same medium. When bacteria were grown in large aerated bioreactors, biosurfactants mostly partitioned to the foam fraction, which was recovered. Dispersion effectiveness of surfactin and fatty acyl-glutamate was evaluated by measuring the critical micelle concentration (CMC) and dispersant-to-oil ratio (DOR). The CMC values for surfactin and fatty acyl-glutamate in double deionized distilled water were 0.015 and 0.10 g/L, respectively. However, CMC values were higher, 0.02 and 0.4 g/L for surfactin and fatty acyl-glutamate, respectively, in 12 parts per thousand Instant Ocean®[corrected].sea salt, which has been partly attributed to saline-induced conformational changes in the solvated ionic species of the biosurfactants. The DORs for surfactin and fatty acyl-glutamate were 1:96 and 1:12, respectively, in water. In Instant Ocean® solutions containing 12 ppt sea salt, these decreased to 1:30 and 1:4, respectively, suggesting reduction in oil dispersing efficiency of both surfactants in saline. Surfactant toxicities were assessed using the Gulf killifish, Fundulus grandis, which is common in estuarine habitats of the Gulf of Mexico. Surfactin was 10-fold more toxic than fatty acyl-glutamate. A commercial surfactant, sodium laurel sulfate, had intermediate toxicity. Raising the salinity from 5 to 25 ppt increased the toxicity of all three surfactants; however, the increase was the lowest for fatty acyl-glutamate.

Resonant excitation and nonlinear evolution of waves in the equatorial waveguide in the presence of the mean current.

We study interactions of planetary waves propagating across the equator with trapped Rossby or Yanai modes, and the mean flow. The equatorial waveguide with a mean current acts as a resonator and responds to planetary waves with certain wave numbers by making the trapped modes grow. Thus excited waves reach amplitudes greatly exceeding the amplitude of the incoming wave. Nonlinear saturation of the excited waves is described by an amplitude equation with one or two attracting equilibrium solutions. In the latter case spatial modulation leads to formation of characteristic defects in the wave field. The evolution of the envelopes of long trapped Rossby waves is governed by the driven complex Ginzburg-Landau equation, and by the damped-driven nonlinear Schrödinger equation for short waves. The envelopes of the Yanai waves obey a simple wave equation with cubic nonlinearity.

Resonant excitation of rossby waves in the equatorial waveguide and their nonlinear evolution.

Nonlinear interactions between the baroclinic Rossby waves trapped in the equatorial waveguide and the barotropic Rossby waves freely propagating across the equator are studied within the two-layer model of the atmosphere, or the ocean. It is shown that a barotropic wave can resonantly excite a pair of baroclinic waves with amplitudes much greater than its proper amplitude. The envelopes of the baroclinic waves obey Ginzburg-Landau-type equations and exhibit nonlinear saturation and formation of characteristic "domain-wall" and "dark-soliton" defects.

Effect of streptavidins with varying biotin binding affinities on the properties of biotinylated gramicidin channels.

The pentadecapeptide gramicidin A, which is known to form highly conductive ion channels in a bilayer lipid membrane by assembling as transmembrane head-to-head dimers, can be modified by attaching a biotin group to its C-terminus through an aminocaproyl spacer. Such biotinylated gramicidin A analogues also form ion channels in a hydrophobic lipid bilayer, exposing the biotin group to the aqueous bathing solution. Interaction of the biotinylated gramicidin channels with (strept)avidin has previously been shown to result in the appearance of a long-lasting open state with a doubled transition amplitude in single-channel traces and a deceleration of the macroscopic current kinetics as studied by the sensitized photoinactivation method. Here this interaction was studied further by using streptavidin mutants with weakened biotin binding affinities. The Stv-F120 mutant, having a substantially reduced biotin binding affinity, exhibited an efficacy similar to that of natural streptavidin in inducing both double-conductance channel formation and deceleration of the photoinactivation kinetics of the biotinylated gramicidin having a long linker arm. The Stv-A23D27 mutant with a severely weakened biotin binding affinity was ineffective in eliciting the double-conductance channels, but decelerated noticeably the photoinactivation kinetics of the long linker biotinylated gramicidin. However, the marked difference in the effects of the mutant and natural streptavidins was smaller than expected on the basis of the substantially reduced biotin binding affinity of the Stv-A23D27 mutant. This may suggest direct interaction of this mutant streptavidin with a lipid membrane in the process of its binding to biotinylated gramicidin channels. The role of linker arm length in the interaction of biotinylated gramicidins with streptavidin was revealed in experiments with a short linker gramicidin. This gramicidin analogue appeared to be unable to form double-conductance channels, though several lines of evidence were indicative of its binding by streptavidin. The data obtained show the conditions under which the interaction of streptavidin with biotinylated gramicidin leads to the formation of the double-conductance tandem channels composed of two cross-linked transmembrane dimers.

A streptavidin mutant useful for directed immobilization on solid surfaces.

A streptavidin mutant has been designed and produced that allows the specific, covalent immobilization of streptavidin on solid surfaces. This streptavidin mutant was constructed by fusing a six-residue sequence, containing a single cysteine, to the carboxyl terminus of streptavidin. Because this mutant has no other cysteine residues, the reactive sulfhydryl group of the cysteine residue serves as a unique immobilization site for conjugation using sulfhydryl chemistry. This streptavidin mutant was efficiently immobilized on maleimide-coated solid surfaces via its unique immobilization site. Characterization of the immobilized streptavidin mutant for the ability to bind to biotinylated macromolecules and the dissociation rates of bound biotin showed that the biotin-binding properties of this mutant were minimally affected by immobilization on solid surfaces. This streptavidin could be readily incorporated into a wide variety of solid-phase diagnostic tests and biomedical assays. This could enhance the performance of streptavidin-based solid-phase assay systems.

The Rhodobacter capsulatus genome.

The genome of Rhodobacter capsulatus has been completely sequenced. It consists of a single chromosome containing 3.5 Mb and a circular plasmid of 134 kb. This effort, started in 1992, began with a fine-structure restriction map of an overlapping set of cosmids that covered the genome. Cosmid sequencing led to a gapped genome that was filled by primer walking on the chromosome and by using lambda clones. Methods had to be developed to handle strong stops in the high GC (68%) inserts. Annotation was done with the ERGO system at Integrated Genomics, as was the reconstruction of the cell's metabolism. It was possible to recognize 3709 orfs of which functional assignments could be made with high confidence to 2392 (65%). Unusual features include the presence of numerous cryptic phage genomes embedded in the chromosome.

Non-protein thiols flux to S-nitrosothiols in endothelial cells: an LPS redox signal.

Lipopolysaccharide (LPS) injures blood vessels by activating pathways in the endothelium that lead either to cell survival and proliferation or apoptosis. It has been suggested that these outcomes are determined when reactive oxygen and nitrogen intermediates oxidize low molecular weight non-protein thiols (NPSHs) such as glutathione (GSH) and cysteine (Cys), which serve as major intracellular reducing agents. The oxidoreduction of NPSHs could be an important redox signal if it were shown to occur rapidly following injury. Towards that end, cultured bovine aortic endothelial cells were stained with the thiol fluorescent probe, monobromobimane (MBB). Most of the acid extractable MBB-reactive adducts are GSH (approximately 90%) and Cys (approximately 90%). Within 1 min of LPS exposure, 50-70% of the MBB-reactive NPSHs are consumed without evidence for concomitant net generation of superoxide, hydrogen peroxide, singlet oxygen, or glutathione disulfide (GSSG). Although LPS induces an increased rate of thiol-disulfide exchange, the slight increase does not explain the magnitude of NPSH consumption. Within the first 10 min of recovery from LPS exposure, the MBB-reactive NPSH fluorescence returns at or slightly above baseline values. When HgCl2 was added to the acid extract, one mole of S-nitrosothiol oxidizing equivalent was found for every mole of MBB-reactive NPSH consumed. It is suspected that the rapid flux of MBB-reactive NPSHs and Hg2+-inducible oxidants reflects transition of GSH to GSNO (S-nitrosoglutathione) and could be an important redox signal in endothelial cells exposed to LPS.

A streptavidin mutant with altered ligand-binding specificity.

The biotin-binding site of streptavidin was modified to alter its ligand-binding specificity. In natural streptavidin, the side chains of N23 and S27 make two of the three hydrogen bonds with the ureido oxygen of biotin. These two residues were mutated to severely weaken biotin binding while attempting to maintain the affinity for two biotin analogs, 2-iminobiotin and diaminobiotin. Redesigning of the biotin-binding site used the difference in local electrostatic charge distribution between biotin and these biotin analogs. Free energy calculations predicted that the introduction of a negative charge at the position of S27 plus the mutation N23A should disrupt two of the three hydrogen bonds between natural streptavidin and the ureido oxygen of biotin. In contrast, the imino hydrogen of 2-iminobiotin should form a hydrogen bond with the side chain of an acidic amino acid at position 27. This should reduce the biotin-binding affinity by approximately eight orders of magnitude, while leaving the affinities for these biotin analogs virtually unaffected. In good agreement with these predictions, a streptavidin mutant with the N23A and S27D substitutions binds 2-iminobiotin with an affinity (Ka) of 1 x 10(6) M-1, two orders of magnitude higher than that for biotin (1 x 10(4) M-1). In contrast, the binding affinity of this streptavidin mutant for diaminobiotin (2.7 x 10(4) M-1) was lower than predicted (2.9 x 10(5) M-1), suggesting the position of the diaminobiotin in the biotin-binding site was not accurately determined by modeling.

Streptavidins with intersubunit crosslinks have enhanced stability.

Natural tetrameric streptavidin has two subunit interfaces; one is a strong interface between subunits in a tightly associated dimer, and the other is a weak interface between a pair of such dimers (dimer-dimer interface). To test whether strengthening the weak dimer-dimer interface could provide streptavidin with additional structural stability, covalent crosslinks were introduced between adjacent subunits through the dimer-dimer interface. Specific crosslinking sites were designed by site-directed mutations of His-127 residues that are in close proximity in natural streptavidin. The first and second streptavidin constructs have a disulfide bond and an irreversible covalent bond, respectively, between two Cys-127 residues across the dimer-dimer interface. The third variant is a hybrid tetramer consisting of two different streptavidin species, one having lysine and the other aspartic acid at position 127, which are covalently crosslinked. All streptavidin constructs with intersubunit crosslinks showed higher biotin-binding ability than natural core streptavidin after heat treatment. All of these crosslinked streptavidins retained bound biotin more stably than natural core streptavidin in guanidine hydrochloride at very acidic pH. These results suggest that the introduction of covalent bonds across the dimer-dimer interface enhances the overall stability of streptavidin.

[Nasal and nasopharyngeal cancer in animals and man]. / Rak nosa i nosoglotki u zhivotnykh i cheloveka.

This review brings together current knowledge about nasal cancer in animals and man. It must be emphasized that nasal cavity and sinus cancer (NCSC) and nasopharyngeal cancer (NPC) are different entities. NPC shows strong regional or ethnic concentration, especially Asian races have a particularly high incidence of NPC. Association of this disease with herpes virus (Epstein-Barr virus) has been made and other environmental agents such as smoking coupled with genetic predisposition, may also be involved. No suitable animal model for human NPC has been described, as most animals lack a region analogous to human nasopharynx. The histologic features of sinonasal mucosa are generally different from those of the nasopharynx. In many animals a region definitely analogous to human nasopharynx is not so obvious. The epiglottis is often functionally juxtaposed to the end of the palate and a region logically termed the pharynx may be very small or absent. Thus, the posterior nasal passage might be more legitimately considered a part of the nasal cavity. Thus, analysis of nasal area tumors within an animal species may not require a clear separation of a nasopharyngeal or epipharyngeal area, but when comparisons are made with human tumors the important specificities of nasopharyngeal pathology should be kept in mind.

Inhibition of protein-kinase-C--dependent cell proliferation of human lung cancer cell lines by the dihydropyridine dexniguldipine.

The dihydropyridine, dexniguldipine hydrochloride (B859-35), has shown therapeutic activity in experimentally induced neuroendocrine hamster lung tumors and demonstrated antiproliferative effects in a mammary cancer cell line via inhibition of Ca2+ calmodulin. Studies in NIH 3T3 fibroblasts have provided evidence that dexniguldipine may also inhibit protein kinase C (PKC). In this study, we have tested the hypothesis that dexniguldipine may inhibit the proliferation of lung cancer cells in response to autocrine or exogenous activation of PKC. Using a panel of human lung cancer cell lines, we show that dexniguldipine is a potent inhibitor of mitogenic signal transduction pathways dependent on PKC activation in several small-cell and non-small-cell lung cancer cell lines while it failed to inhibit cyclic-AMP-dependent cell proliferation.

Effect of the dihydropyridine dexniguldipine on the epidermal growth factor-stimulated proliferation of human lung cancer cell lines.

The dihydropyridine Dexniguldipine (B859-35) has been shown to inhibit calmodulin and protein kinase C in vitro, and has a significant therapeutic effect on induced neuroendocrine lung tumours in hamsters. As phase I clinical trials with this agent resulted in the development of stable disease in several patients with non-small-cell cancers and preliminary in vitro studies revealed several non-small-cell cancer cell lines susceptible to the antiproliferative effects of dexniguldipine, the possibility was investigated that this agent may inhibit cell proliferation stimulated by epidermal growth factor (EGF), which is expressed in many non-small-cell cancer types. Experiments conducted with six human lung cancer cell lines showed that dexniguldipine is a potent inhibitor of EGF-stimulated cell proliferation. This agent may therefore also be useful for the therapy of cancers that express the EGF receptor.

Percutaneous endoscopic implantation of Automatic Implantable Cardioverter/Defibrillator (AICD): an animal study of a new nonthoracotomy technique.

The Automatic Implantable Cardioverter/Defibrillator (AICD) prevents death due to malignant ventricular arrhythmias but requires thoracotomy for the implantation of the preferred two-patch lead system. The purpose of this study was to develop and test a new percutaneous endoscopic method of the AICD lead implantation without the need for open chest surgery. A high resolution video endoscopy system and currently available endoscopic instrumentation were used to develop pleural-pericardial dissection technique in 7 pigs and to endoscopically implant custom-made AICD patches in 20 pigs. An examining 10 mm rigid endoscope inserted in the 6th intercostal space in the anterior axillary line provided direct visual control for endoscopic dissection of the parietal pleura from the pericardium, delivery, and implantation of the AICD patches. This was successfully carried out through two trocars (10 and 11 mm) inserted into the pleural-pericardial space via the subxyphoid approach in 18 of 20 pigs. Effective patch positioning was confirmed by attaining a defibrillation threshold of 20J or less in 13 pigs. Of those, three required lead polarity reversal, and three others required lead repositioning to lower defibrillation thresholds to 20J or less. In three pigs, defibrillation thresholds of 30J or higher were required. Defibrillation was unsuccessful in two pigs due to patch malfunction. The authors conclude that percutaneous endoscopy is a feasible method of AICD lead implantation.

Ultrastructural investigations of the enterochromaffin-like (ECL) cells in three different rat strains (Sprague-Dawley, Fischer 344, Wistar) after treatment with the H+,K(+)-ATPase inhibitor pantoprazole.

The purpose of the present study was the evaluation of ultrastructural characteristics of the enterochromaffin-like (ECL) cells in the fundic mucosa of three different rat strains without treatment and after treatment with the H+, K(+)-ATPase inhibitor pantoprazole. In the study, 20 one year old female Sprague Dawley (SD), Fischer 344 (F) and Wistar (W) rats each were treated orally for three months with 4 mg pantoprazole/kg/d or with the vehicle only. The control animals showed close conformity of ECL cell density and morphology in all three strains. Treatment with pantoprazole led to a significant increase in serum gastrin concentration and GPC density in all strains. However, the electron microscopically determined ECL cell density was markedly increased in the SD strain only. Ultrastructurally all treated rats showed activation of the ECL cells, and enhanced histamine release. The SD and F strains had an enhanced proportion of large ECL cell granules, with the F rats also showing an increased granule density. In contrast, the treated W rats were found to have a lower granule density and a higher proportion of small and medium sized granules compared to their controls.

Cardiotoxicity of vasodilators and positive inotropic/vasodilating drugs in dogs: an overview.

Standard toxicological studies in dogs using high doses of vasodilators and positive inotropic/vasodilating agents give rise to a species-specific cardiotoxicity. The reason may be the extreme sensitivity of the dog to the pharmacological effects of these drugs; exaggerated pharmacodynamic effects and prolonged disturbance of homeostasis mechanisms often are responsible for the observed organ lesions. An assessment of the toxicological relevance and the risk for patients taking the drugs at therapeutic doses cannot be made without taking into account their pathomechanisms and the pathophysiological basis of the exceptional reaction patterns occurring in dogs. A large series of vasodilating and positive inotropic agents are presented, their pharmacological properties are described, and toxicological effects in dogs are compared. In view of the poor correlation between the distinct cardiac lesions induced in dogs and a lack of comparable toxicity in humans, it appears desirable to reassess the adequacy of the standard toxicological approaches for these substances.

Antiproliferative effects of the Ca2+/calmodulin antagonist B859-35 and the Ca(2+)-channel blocker verapamil on human lung cancer cell lines.

We have recently demonstrated that the dihydropyridine-derivative B859-35 has a selective chemotherapeutic effect on experimentally induced neuroendocrine lung tumors in hamsters. These tumors resembled human atypical lung carcinoids morphologically and expressed mammalian bombesin, calcitonin and neuron-specific enolase. In the hamster model, B859-35 had no antiproliferative effect on pulmonary adenomas of Clara cell origin. In this study, we have tested the antiproliferative effects of B859-35 and of the Ca(2+)-channel blocker Verapamil in vitro on three human lung cancer cell lines. The neuroendocrine cell line NCI-H727 is derived from a lung carcinoid and expresses mammalian bombesin and calcitonin. Two non-neuroendocrine cell lines are derived from peripheral pulmonary adenocarcinomas, with line NCI-H322 expressing features of Clara cells while line NCI-H358 expresses features of alveolar type II cells. B859-35 was a potent antiproliferative agent in the neuroendocrine line NCI-H727 at concentrations as low as 0.001 pM, while it inhibited cell proliferation in the two other cell lines at concentrations of 100 nM and above. Verapamil inhibited cell proliferation in the neuroendocrine line NCI-H727 at concentrations of 1 nM and above.

Diethylnitrosamine-induced metastasizing hepatocellular carcinomas in New Zealand white rabbits. A tumor model for clinical investigations.

The aim of this study was to produce large liver tumors reliably, and to diagnose the tumors during development. Therefore, New Zealand white rabbits were treated with N-nitrosodiethylamine orally three times per week by gavage and were examined by clinical-chemical assay at regular intervals during the average treatment period of 14 months. The total cumulative dose was 1200 mg N-nitrosodiethylamine over 14 months. After a short treatment period the initial dose of 3 mg/kg had to be reduced to 1.5 mg/kg. In all 11 treated animals (100%) liver tumors were seen at the end of the study. Four control animals did not show any neoplastic changes. Clinical parameters investigated were for an assessment of liver function, total protein, urea, creatinine, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, albumin and neuraminic acid as well as some serum electrolytes. The in vivo diagnosis of liver tumors based on changes in these parameters proved to be relatively unreliable. The liver enzyme tests and urea concentration only yielded significant changes when the liver tumors were very large. Changes in neuraminic acid levels were the most reliable indicator for the presence of a liver tumor in this animal model. In the 11 treated animals, serum values of this marker increased towards the end of the study by an average of 300 mg/dl. The induced tumors were mainly hepatocellular carcinomas. Only in 1 animal was a hepatocellular adenoma found. Further primary tumors diagnosed were six adenomas in the kidneys and two uterus adenomas, as well as nasal cavity tumors (two papillomas, one carcinoma, one adenoma and one adenocarcinoma). In 70% of the treated rabbits the hepatocellular carcinomas had metastasized to the lungs.