Intestinal growth and differentiation in zebrafish

Intestinal development in amniotes is driven by interactions between progenitor cells derived from the three primary germ layers. Genetic analyses and gene targeting experiments in zebrafish offer a novel approach to dissect such interactions at a molecular level. Here we show that intestinal anatomy and architecture in zebrafish closely resembles the anatomy and architecture of the mammalian small intestine. The zebrafish intestine is regionalized and the various segments can be identified by epithelial markers whose expression is already segregated at the onset of intestinal differentiation. Differentiation of cells derived from the three primary germ layers begins more or less contemporaneously, and is preceded by a stage in which there is rapid cell proliferation and maturation of epithelial cell polarization. Analysis of zebrafish mutants with altered epithelial survival reveals that seemingly related single gene defects have different effects on epithelial differentiation and smooth muscle and enteric nervous system development.

Avenues for entry of peripherally administered protein to the central nervous system in mouse, rat, and squirrel monkey

Pathways traversed by peripherally administered protein tracers for entry to the mammalian brain were investigated by light and electron microscopy. Native horseradish peroxidase (HRP) and wheat germ agglutinin (WGA) conjugated to peroxidase were administered intranasally, intravenously, or intraventricularly to mice; native HRP was delivered intranasally or intravenously to rats and squirrel monkeys. Unlike WGA-HRP, native HRP administered intranasally passed freely through intercellular junctions of the olfactory epithelia to reach the olfactory bulbs of the CNS extracellularly within 45-90 minutes in all species. The olfactory epithelium labeled with intravenously delivered HRP, which readily escaped vasculature supplying this epithelium. Blood-borne peroxidase also exited fenestrated vessels of the dura mater and circumventricular organs. This HRP in the mouse, but not in the other species, passed from the dura mater through patent intercellular junctions within the arachnoid mater; in time, peroxidase reaction product in the mouse brain was associated with the pial surface, the Virchow-Robin spaces of vessels penetrating the pial surface, perivascular clefts, and with phagocytic pericytes located on the abluminal surface of superficial and deep cerebral microvasculature. Blood-borne HRP was endocytosed avidly at the luminal face of the cerebral endothelium in all species. WGA-HRP and native HRP delivered intraventricularly to the mouse were not endocytosed appreciably at the abluminal surface of the endothelium; hence, the endocytosis of protein and internalization of cell surface membrane within the cerebral endothelium are vectorial. The low to non-existent endocytic activity and internalization of membrane from the abluminal endothelial surface suggests that vesicular transport through the cerebral endothelium from blood to brain and from brain to blood does not occur. The extracellular pathways through which probe molecules enter the mammalian brain offer potential routes of passage for blood-borne and air-borne toxic, carcinogenic, infectious, and neurotoxic agents and addictive drugs, and for the delivery of chemotherapeutic agents to combat CNS infections and deficiency states. Methodological considerations are discussed for the interpretation of data derived from application of peroxidase to study the blood-brain barrier.

Phorbol esters and horseradish peroxidase stimulate pinocytosis and redirect the flow of pinocytosed fluid in macrophages

Lucifer Yellow CH (LY) is an excellent probe for fluid-phase pinocytosis. It accumulates within the macrophage vacuolar system, is not degraded, and is not toxic at concentrations of 6.0 mg/ml. Its uptake is inhibited at 0 degree C. Thioglycollate-elicited mouse peritoneal macrophages were found to exhibit curvilinear uptake kinetics of LY. Upon addition of LY to the medium, there was a brief period of very rapid cellular accumulation of the dye (1,400 ng of LY/mg protein per h at 1 mg/ml LY). This rate of accumulation most closely approximates the rate of fluid influx by pinocytosis. Within 60 min, the rate of LY accumulation slowed to a steady-state rate of 250 ng/mg protein per h which then continued for up to 18 h. Pulse-chase experiments revealed that the reduced rate of accumulation under steady-state conditions was due to efflux of LY. Only 20% of LY taken into the cells was retained; the remainder was released back into the medium. Efflux has two components, rapid and slow; each can be characterized kinetically as a first-order reaction. The kinetics are similar to those described by Besterman et al. (Besterman, J. M., J. A. Airhart, R. C. Woodworth, and R. B. Low, 1981, J. Cell Biol. 91:716-727) who interpret fluid-phase pinocytosis as involving at least two compartments, one small, rapidly turning over compartment and another apparently larger one which fills and empties slowly. To search for processes that control intracellular fluid traffic, we studied pinocytosis after treatment of macrophages with horseradish peroxidase (HRP) or with the tumor promoter phorbol myristate acetate (PMA). HRP, often used as a marker for fluid-phase pinocytosis, was observed to stimulate the rate of LY accumulation in macrophages. PMA caused an immediate four- to sevenfold increase in the rate of LY accumulation. Both HRP and PMA increased LY accumulation by stimulating influx and reducing the percentage of internalized fluid that is rapidly recycled. A greater proportion of endocytosed fluid passes into the slowly emptying compartment (presumed lysosomes). These experiments demonstrate that because of the considerable efflux by cells, measurement of marker accumulation inaccurately estimates the rate of fluid pinocytosis. Moreover, pinocytic flow of water and solutes through cytoplasm is subject to regulation at points beyond the formation of pinosomes.

Centrifugal innervation of the retina by luteinizing hormone releasing hormone (LHRH)-immunoreactive telencephalic neurons in teleostean fishes

In cichlid, poecilid and centrarchid fishes luteinizing hormone releasing hormone (LHRH)-immunoreactive neurons are found in a cell group (nucleus olfactoretinalis) located at the transition between the ventral telencephalon and olfactory bulb. Processes of these neurons project to the contralateral retina, traveling along the border between the internal plexiform and internal nuclear layer, and probably terminating on amacrine or bipolar cells. Horseradish peroxidase (HRP) injected into the eye or optic nerve is transported retrogradely in the optic nerve to the contralateral nucleus olfactoretinalis where neuronal perikarya are labeled. Labeled processes leave this nucleus in a rostral direction and terminate in the olfactory bulb. The nucleus olfactoretinalis is present only in fishes, such as cichlids, poecilids and centrarchids, in which the olfactory bulbs border directly the telencephalic hemispheres. In cyprinid, silurid and notopterid fishes, in which the olfactory bulbs lie beneath the olfactory epithelium and are connected to the telencephalon via olfactory stalks, the nucleus olfactoretinalis or a comparable arrangement of LHRH-immunoreactive neurons is lacking. After retrograde transport of HRP in the optic nerve of these fishes no labeling of neurons in the telencephalon occurred. It is proposed that the nucleus olfactoretinalis anatomically and functionally interconnects and integrates parts of the olfactory and optic systems.

The ultrastructural basis of alveolar-capillary membrane permeability to peroxidase used as a tracer

The permeability of the alveolar-capillary membrane to a small molecular weight protein, horseradish peroxidase (HRP), was investigated by means of ultrastructural cytochemistry. Mice were injected intravenously with HRP and sacrificed at varying intervals. Experiments with intranasally instilled HRP were also carried out. The tissue was fixed in formaldehyde-glutaraldehyde fixative. Frozen sections were cut, incubated in Graham and Karnovsky's medium for demonstrating HRP activity, postfixed in OsO4, and processed for electron microscopy. 90 sec after injection, HRP had passed through endothelial junctions into underlying basement membranes, but was stopped from entering the alveolar space by zonulae occludentes between epithelial cells. HRP was demonstrated in pinocytotic vesicles of both endothelial and epithelial cells, but the role of these vesicles in net protein transport appeared to be minimal. Intranasally instilled HRP was similarly prevented from permeating the underlying basement membrane by epithelial zonulae occludentes. Pulmonary endothelial intercellular clefts stained with uranyl acetate appeared to contain maculae occludentes rather than zonulae occludentes. HRP did not alter the ultrastructure of these junctions.

Oxidation of low-density lipoprotein by hemoglobin stems from a heme-initiated globin radical: antioxidant role of haptoglobin

Hemoglobin, known as a poor peroxidase, has been recently found to be a highly reactive catalyzer of low-density lipoprotein (LDL) oxidation resulting in oxidation of LDL lipids and covalent cross-linking of the LDL protein, apo B. We evaluated three possible mechanisms that may account for hemoglobin reactivity: oxidative activation by globin-dissociated hemin following its transfer to LDL; peroxidase-like reactivity of the ferryl iron active state in intact hemoglobin; and oxidation by a globin radical formed in oxidized hemoglobin. The first mechanism was ruled out because only a minor fraction of hemin was actually transferred to LDL in the process of oxidation. The second mechanism was excluded because hemoglobin ferryl, unlike ferryl of horseradish peroxidase, was not consumed in the process of LDL oxidation. Haptoglobin completely inhibited cross-linking of globin in hemoglobin/H2O2 mixtures but not in myglobin/H2O2, as well as cross-linking of apo B and oxidation of LDL lipids. Haptoglobin could not however abolish the hemoglobin ferryl state, a finding that further supported exclusion of the second mechanism. We conclude that the active species in hemoglobin-induced LDL oxidation is the globin radical, as suggested in the third mechanism. The present findings also show that haptoglobin functions as a major antioxidant thus protecting the vascular system.

Oxidative activation of indole-3-acetic acids to cytotoxic species- a potential new role for plant auxins in cancer therapy

Indole-3-acetic acid (IAA) and some derivatives can be oxidised by horseradish peroxidase (HRP) to cytotoxic species. Upon treatment with IAA/HRP, liposomes undergo lipid peroxidation, strand breaks and adducts are formed in supercoiled plasmid DNA, and mammalian cells in culture lose colony-forming ability. IAA is only toxic after oxidative decarboxylation; no effects are seen when IAA or HRP is incubated independently in these systems at equivalent concentrations. Toxicity is similar in both hamster fibroblasts and some human tumour cells. The effect of IAA/HRP is thought to be due in part to the formation of 3-methylene-2-oxindole, which may conjugate with DNA bases and protein thiols. Our hypothesis is that IAA/HRP could be used as the basis for targeted cancer therapy involving antibody-, polymer-, or gene-directed approaches. HRP can thus be targeted to a tumour allowing non-toxic IAA delivered systemically to be activated only in the tumour. Exposure to newly synthesised analogues of IAA shows a range of four orders of magnitude difference in cellular toxicity but no structure-activity relationships are apparent, in contrast to well-defined redox dependencies of oxidation by HRP intermediates or rates of decarboxylation of radical-cation intermediates.

Acid azo dye degradation by free and immobilized horseradish peroxidase (HRP) catalyzed process

Acid azo (Acid Black 10 BX) dye removal by plant based peroxidase catalyzed reaction was investigated. Horseradish peroxidase (HRP) was extracted from horseradish roots and its performance was evaluated in both free and immobilized form. HRP showed its ability to degrade the dye in aqueous phase. Studies are further carried out to understand the process parameters such as aqueous phase pH, H2O2 dose, dye and enzyme concentrations during enzyme-mediated dye degradation process. Experimental data revealed that dye (substrate) concentration, aqueous phase pH, enzyme and H2O2 dose play a significant role on the overall enzyme-mediated reaction. Acrylamide gel immobilized HRP showed effective performance compared to free HRP and alginate entrapped HRP. Alginate entrapped HRP showed inferior performance over the free enzyme due to the consequence of non-availability of the enzyme to the dye molecule due to polymeric immobilization. Standard plating studies performed with Pseudomonas putida showed enhanced degradation of HRP catalyzed dye compared to control.

Anatomical relationships between the ventral mesencephalic tegmentum--a 10 region and the locus coeruleus as demonstrated by anterograde and retrograde tracing techniques

We have searched for anatomical connections between the ventral mesencephalic tegmentum (VMT), including the dopaminergic cell group A10 and the locus coeruleus (LC) region. Tritiated leucine (120--220 nl) and horseradish peroxidase delivered by electrophoresis were injected in the VMT-A10 region. We have demonstrated, on the one hand bilateral projections from the VMT-A10 region to LC, and on the other hand a possible contralateral projection from LC to VMT-A10 region. These relationships, reported for the first time may have some important functional significance.

Nickel induces increased oxidants in intact cultured mammalian cells as detected by dichlorofluorescein fluorescence

Exposure of intact cultured Chinese hamster ovary (CHO) cells to water-soluble nickel (Ni) salts and to relatively water-insoluble crystalline nickel subsulfide (Ni3S2) resulted in an increased formation of the fluorescent oxidized compound, dichlorofluorescein (DCF) from the parent nonfluorescent compound, 2,7-dichlorofluorescin diacetate. This fluorescent product was also formed in vitro following oxidation with relatively strong oxidants such as hydrogen peroxide in the presence of peroxidase, suggesting that Ni increased the concentration of hydrogen peroxide in intact cells. However, formation of other strong oxidants such as hydroperoxides is possible since they have also been shown to cause the oxidation of the nonfluorescent dichlorofluorescin to the fluorescent product DCF in vitro. Localization of the oxidized fluorescent DCF in intact cells was also examined by fluorescence microscopy. Both Ni3S2 and NiCl2 appeared to increase the degree of fluorescence in intact CHO cells around the nuclear membranes. This increase in fluorescence was greater in the presence of relatively water-insoluble Ni3S2 than water-soluble NiCl2. These results add to the emerging concept that Ni-induced genotoxicity may be mediated by oxygen radical intermediates.

Peroxidase activity and inducibility in the sea fan coral exposed to a fungal pathogen

The enzymatic defense mechanisms of Gorgonia ventalina to the fungal pathogen Aspergillus sydowii may play important roles in colony resistance to infection. In this study, we examined the role of the superfamily of peroxidase enzymes in the coral response to a naturally occurring pathogen. We examined the inducibility of peroxidases by experimentally exposing corals to A. sydowii and found that peroxidase activity was induced after an 8 day incubation period. In contrast, naturally infected corals collected from the reef had lower peroxidase activity when compared to healthy corals. Infected sea fans from the field also had less measurable protein in their tissues and increased purple sclerites near infection sites and it is likely that these infections are months old. Using native-PAGE activity gels, we detected 5 peroxidase isozymes in healthy corals, indicating that multiple isoforms of peroxidase with a plurality of possible functions are present in this coral. The role of the peroxidase enzymes in disease resistance was examined by testing anti-fungal activity of commercially available and partially purified sea fan peroxidases. In both cases there was significant, dose-dependent anti-fungal activity. While peroxidases are ubiquitous enzymes involved in many cellular pathways, we also hypothesize that G. ventalina utilizes these enzymes as an integral component in disease resistance pathways. As such, they may also contribute to the initiation of physiochemical defenses such as melanization and lipid soluble anti-fungal metabolites.

Urinary striated sphincter: what is its nerve supply?

Innervation of the voluntary urinary sphincter continues to be a controversial subject. Using retrograde axonal transport techniques to determine the exact nerve supply to the external sphincter has been successful in clarifying this controversy. 1-5 Tracing the transport of horseradish peroxidase (HRP) injected in the voluntary external sphincter and that injected directly in the cut end of the pudendal nerve was done. Transport from both sides ended in the same neurons in the dorsolateral column, thus labelling and identifying the pudendal nucleus which is the motor center for the voluntary urinary sphincter.

Parabrachial area as mediator of bradycardia in rabbits

This study examined the role of the parabrachial nucleus (PBN) in the mediation of bradycardia and in the reception of barosensory information. The 82 rabbits in the investigation were anesthetized with ethyl carbamate. Train stimulation of medial or lateral PBN produced primary bradycardia (mean peak change: -74 beats/min) associated with a pressor response (average peak mean change: +10 mm Hg) of longer latency. Section of the cervical vagus nerves indicated that the bradycardia was mediated primarily by the parasympathetic nervous system. Heart rate and blood pressure responses to train stimulation did not vary systematically as a function of respiratory pattern; paralyzing animals with decamethonium hydrochloride and artificially ventilating them also did not influence the cardiovascular responses to stimulation. Single-pulse stimulation of PBN in conjunction with extracellular single neuron recording established that neurons originating in or projecting through PBN project to the commissural region of nucleus tractus solitarius (NTS) where synapse is made neurons receiving barosensory input. In addition to establishing the existence of descending functional projections passing from PBN to NTS, injections of HRP into PBN revealed direct descending anatomical projections to PBN from regions of the forebrain previously implicated in the mediation of bradycardia. These included central nucleus of amygdala, lateral preoptic region, medial, forebrain bundle, bed nucleus of stria terminalis, anterior and lateral hypothalamus and zona incerta. The present investigation also indicated that PBN receives barosensory information. Single-pulse electrical stimulation of the aortic nerve (AN) activated neurons in NTS at an average latency of 7.5 ms and in PBN at a mean latency of 12.1 ms. Mean latency of 9 neurons in NTS activated antidromically by PBN stimulation was 3.4 ms. Conduction velocity of the monosynaptic fibers projecting from NTS to PBN was approximately 3.5 m/s, which would be characteristic of finely myelinated fibers. Injection of HRP into PBN confirmed the existence of direct ascending projections to PBN from regions of NTS (e.g. lateral commissural area) previously shown to receive primary barosensory input. However, the finding that only 1 of 9 NTS neurons antidromically activated by PBN stimulation also received barosensory stimulation, indicates that additional study is needed of the mono- and oligosynaptic functional projections from NTS to PBN. The present study did provide evidence that PBN both receives barosensory information at short latency over a direct route, and serves as a relay for descending projections mediating bradycardia.

Peroxidase-dependent metal-independent oxidation of low density lipoprotein in vitro: a model for in vivo oxidation?

Oxidative modification of low density lipoprotein is believed to be an important pathway by which the lipoprotein becomes atherogenic. The in vitro systems for oxidative modification of low density lipoprotein thus far described all appear to depend upon the presence in the medium of free transition metal ions (copper or iron). In vivo, on the other hand, these metals are present almost exclusively in tightly complexed forms that do not catalyze oxidative modification. The present studies describe oxidation of low density lipoprotein in a simple system that does not depend upon the presence of added free metal ions. It requires the presence of horseradish peroxidase and either hydrogen peroxide or lipid hydroperoxides.

Mucosal immunogenicity of plant lectins in mice

The mucosal immunogenicity of a number of plant lectins with different sugar specificities was investigated in mice. Following intranasal (i.n.) or oral administration, the systemic and mucosal antibody responses elicited were compared with those induced by a potent mucosal immunogen (cholera toxin; CT) and a poorly immunogenic protein (ovalbumin; OVA). After three oral or i.n. doses of CT, high levels of specific serum antibodies were measured and specific IgA was detected in the serum, saliva, vaginal wash, nasal wash and gut wash of mice. Immunization with OVA elicited low titres of serum IgG but specific IgA was not detected in mucosal secretions. Both oral and i.n. delivery of all five plant lectins investigated ¿Viscum album (mistletoe lectin 1; ML-1), Lycospersicum esculentum (tomato lectin; LEA), Phaseolus vulgaris (PHA), Triticum vulgaris (wheat germ agglutinin (WGA), Ulex europaeus I (UEA-1) stimulated the production of specific serum IgG and IgA antibody after three i. n. or oral doses. Immunization with ML-1 induced high titres of serum IgG and IgA in addition to specific IgA in mucosal secretions. The response to orally delivered ML-1 was comparable to that induced by CT, although a 10-fold higher dose was administered. Immunization with LEA also induced high titres of serum IgG, particularly after i. n. delivery. Low specific IgA titres were also detected to LEA in mucosal secretions. Responses to PHA, WGA and UEA-1 were measured at a relatively low level in the serum, and little or no specific mucosal IgA was detected.

Evaluation of some of the parameters of the enzyme-linked immunospecific assay

In an attempt to standardize the procedure for the enzyme-linked immunospecific assay, several parameters were examined. It was determined that horseradish peroxidase was the enzyme of choice and that several brands of polystyrene tubes and plates could be used. The test was considerably shortened by omitting long incubation steps previously used for eliminating background fixation of conjugate. The reproducibility of the procedure proved to be excellent, but reactivity curves indicated that use of a single dilution is not adequate for quantitative tests. A "standard" procedure was proposed.

Reaction between protein radicals and other biomolecules

The present study investigates the reactivity of bovine serum albumin (BSA) radicals towards different biomolecules (urate, linoleic acid, and a polypeptide, poly(Glu-Ala-Tyr)). The BSA radical was formed at room temperature through a direct protein-to-protein radical transfer from H(2)O(2)-activated immobilized horseradish peroxidase (im-HRP). Subsequently, each of the three different biomolecules was separately added to the BSA radicals, after removal of im-HRP by centrifugation. Electron spin resonance (ESR) spectroscopy showed that all three biomolecules quenched the BSA radicals. Subsequent analysis showed a decrease in the concentration of urate upon reaction with the BSA radical, while the BSA radical in the presence of poly(Glu-Ala-Tyr) resulted in increased formation of the characteristic protein oxidation product, dityrosine. Reaction between the BSA radical and a linoleic acid oil-in-water emulsion resulted in additional formation of lipid hydroperoxides and conjugated dienes. The results clearly show that protein radicals have to be considered as dynamic species during oxidative processes in biological systems and that protein radicals should not be considered as end-products, but rather as reactive intermediates during oxidative processes in biological systems hereby supporting recent data.

Oxidation of indole-3-acetic acid by horseradish peroxidase induces apoptosis in G361 human melanoma cells

The combination of indole-3-acetic acid (IAA) and horseradish peroxidase (HRP) has recently been proposed as a novel cancer therapy. However, the mechanism underlying the cytotoxic effect involved is substantially unknown. Here, we show that IAA/HRP treatment induces apoptosis in G361 human melanoma cells, whereas IAA or HRP alone have no effect. It is known that IAA produces free radicals when oxidized by HRP. Because oxidative stress could induce apoptosis, we measured the production of free radicals at varying concentrations of IAA and HRP. Our results show that IAA/HRP produces free radicals in a dose-dependent manner, which are suppressed by ascorbic acid or (-)-epigallocatechin gallate (EGCG). Furthermore, antioxidants prevent IAA/HRP-induced apoptosis, indicating that the IAA/HRP-produced free radicals play an important role in the apoptotic process. In addition, IAA/HRP was observed to activate p38 mitogen-activated protein (MAP) kinase and c-Jun N-terminal kinase (JNK), which are almost completely blocked by antioxidants. We further investigated the IAA/HRP-mediated apoptotic pathways, and found that IAA/HRP activates caspase-8 and caspase-9, leading to caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage. These events were also blocked by antioxidants, such as ascorbic acid or EGCG. Thus, we propose that IAA/HRP-induced free radicals lead to the apoptosis of human melanoma cells via both death receptor-mediated and mitochondrial apoptotic pathways.

Formation of long-lived radicals on proteins by radical transfer from heme enzymes--a common process?

Incubation of Fe(III)myoglobin (Fe(III)Mb) with H2O2 in the presence of bovine serum albumin (BSA) has been shown previously to give albumin-derived radicals as a result of radical transfer from myoglobin to BSA. In this study the occurrence of similar processes with peroxidases has been investigated using horseradish peroxidase (HRP)/H2O2, in the presence and absence of added tyrosine. Incubation of HRP with H2O2 and bovine or human serum albumins, in the presence and absence of tyrosine, gave long-lived albumin-derived radicals as detected by EPR spectroscopy. Evidence has been obtained for these albumin radicals being located on buried tyrosine residues on the basis of blocking experiments. The effect of protein conformation on radical transfer has been investigated using partial proteolytic digestion prior to protein oxidation. With HRP/H2O2/BSA and Fe(III)Mb/H2O2/BSA increased radical concentrations were observed after limited digestion, although this effect was less marked with the HRP/H2O2/BSA system than with Fe(III)Mb/H2O2/BSA, consistent with different modes of radical transfer. More extensive digestion of BSA decreased the radical concentration to levels below those detected with native albumin, indicating that the tertiary structure of the target protein plays an important role in determining the rate of radical transfer and/or the stability of the resultant species. These results are consistent with a mechanism for the HRP/H2O2/no free tyrosine system involving radical transfer to the albumin via the heme edge of the peroxidase. In contrast, albumin radical formation by the HRP/H2O2/free tyrosine system was only marginally affected by proteolysis, consistent with free tyrosine phenoxyl radicals being the mediators of radical transfer, without significant protein-protein interaction. These protein-to-protein radical transfer reactions may have important consequences for understanding protein oxidation in biological systems.

Reactive liposomes encapsulating a glucose oxidase-peroxidase system with antibacterial activity

Liposomes were prepared from phospholipid mixtures of dipalmitoylphosphatidylcholine (DPPC) and phosphatidylinositol (PI), encapsulating the enzymes glucose oxidase (GO) and GO in combination with horse radish peroxidase (HRP) by both extrusion (VET) and reverse-phase evaporation (REV). The optimum level of PI in DPPC/PI liposomes for targeting to biofilms of the oral bacterium Streptococcus gordonii has been established. The liposomes were characterised in terms of the content and activity of the encapsulated enzymes. The antibacterial activity of these 'reactive' liposomes arising from hydrogen peroxide and oxyacids in the presence of the substrates glucose and iodide ions, after targeting to the biofilms, were measured both as a function of liposome-biofilm incubation time and incubation time with the substrates. Bacterial inhibition increases with both liposome-biofilm and substrate-biofilm incubation time and with the extent of enzyme encapsulation. The reactive liposomes also display antibacterial activity in the presence of saliva. The reactive liposomes have potential value in the context of oral hygiene.

Saccadic eye movements evoked by microstimulation of the fastigial nucleus of macaque monkeys

1. Systematic exploration throughout the deep cerebellar nuclei and white matter disclosed that the region from which saccadic eye movements (saccades) were evoked with weak currents (less than 10 microA) was confined to the fastigial nucleus and the adjacent white matter. 2. When an electrode for stimulation was advanced in the cerebellum, saccades were evoked in the direction of the stimulated side (ipsilateral saccades) as it entered the low-threshold region. In some tracks, particularly when the electrode was advanced in the medial portion of the fastigial nucleus, the direction of the evoked saccades changed from the ipsilateral to the contralateral. 3. The mappings with microstimulation disclosed that the ipsilateral saccades were elicited from a relatively wide region that included almost the full extent of the fastigial nucleus. The low-threshold region continued in the white matter caudally into vermal lobule VII and rostrally into the dorsal aspect of the brachium conjunctivum. On the other hand, the contralateral saccades were evoked from a relatively circumscribed region in the ventromedial portion of the fastigial nucleus. 4. The reversal in the direction of the horizontal component occurred always in a narrow zone in the core of the fastigial nucleus. The caudal part of this zone coincided with an ellipsoidal region where anterogradely labeled axons of the Purkinje cells terminated when HRP was injected into vermal lobule VII. 5. When bicuculline (0.2-1 microgram) was injected in the ellipsoidal region, the ipsilateral saccades evoked from the dorsocaudal aspect of the region were suppressed for several hours. On the other hand, the contralateral saccades evoked from the ventromedial portion of the fastigial nucleus were either unchanged or enhanced. 6. Because the ipsilateral saccades were suppressed by bicuculline, they were most probably evoked by stimulation of the presynaptic component of gamma-amino-butyric acid-(GABA) mediated synapses, namely the axons of Purkinje cells. 7. Because stimulation of the presynaptic component of the inhibitory synapses evoked ipsilateral saccades, activation of the postsynaptic component would evoke contralateral saccades. In fact, the distribution of the fastigial sites yielding contralateral saccades coincided with the course of axons of fastigial neurons arising in the ellipsoidal region. It is most likely, therefore, that the contralateral saccades were evoked by stimulation of fastigial neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Oxidative protein cross-linking reactions involving L-tyrosine in transforming growth factor-beta1-stimulated fibroblasts

The mechanisms by which ligand-stimulated generation of reactive oxygen species in nonphagocytic cells mediate biologic effects are largely unknown. The profibrotic cytokine, transforming growth factor-beta1 (TGF-beta1), generates extracellular hydrogen peroxide (H2O2) in contrast to intracellular reactive oxygen species production by certain mitogenic growth factors in human lung fibroblasts. To determine whether tyrosine residues in fibroblast-derived extracellular matrix (ECM) proteins may be targets of H2O2-mediated dityrosine-dependent cross-linking reactions in response to TGF-beta1, we utilized fluorophore-labeled tyramide, a structurally related phenolic compound that forms dimers with tyrosine, as a probe to detect such reactions under dynamic cell culture conditions. With this approach, a distinct pattern of fluorescent labeling that seems to target ECM proteins preferentially was observed in TGF-beta1-treated cells but not in control cells. This reaction required the presence of a heme peroxidase and was inhibited by catalase or diphenyliodonium (a flavoenzyme inhibitor), similar to the effect on TGF-beta1-induced dityrosine formation. Exogenous addition of H2O2 to control cells that do not release extracellular H2O2 produced a similar fluorescent labeling reaction. These results support the concept that, in the presence of heme peroxidases in vivo, TGF-beta1-induced H2O2 production by fibroblasts may mediate oxidative dityrosine-dependent cross-linking of ECM protein(s). This effect may be important in the pathogenesis of human fibrotic diseases characterized by overexpression/activation of TGF-beta1.

Use of additives to enhance the removal of phenols from water treated with horseradish and hydrogen peroxide

Use of additives, such as polyethylene glycol (PEG), selected surfactants, chitosan gel, or activated carbon, has been shown to enhance enzymatic treatment of water polluted with organic compounds. In this study, additives were used to facilitate the removal of 2,4-dichlorophenol (2,4-DCP) from water using minced horseradish (Armoracia rusticana P. Gaertn. et al.) as a carrier of peroxidase activity. The specific objectives of the study were to (i) enhance the pollutant removal activity of minced horseradish by the addition of PEG and other additives (e.g., Tween 20, Triton X-100, and rhamnolipid); (ii) eliminate colored reaction products by the addition of chitosan; and (iii) eliminate color by amending treated water with activated carbon. The disappearance of 2,4-DCP in horseradish-treated water samples amended with PEG or various surfactants (75-90%) was greatly increased over that observed in nonamended samples (29%). The effect of PEG depended on its average molecular weight. As indicated by visible spectrophotometry, enclosing horseradish pieces between two sealed chitosan films completely eliminated colored reaction products; however, the decolorization was accompanied by a reduction in 2,4-DCP removal (from 95 to 60%). On the other hand, commercially available activated carbon completely removed colored reaction products from the treated water without reducing the removal efficiency. Based on the results obtained, it can be concluded that the use of additives may considerably improve the quality of wastewater treated by plant materials.