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PubMed1990

Antimony electrodes. Mucosal potential differences and buffer composition adversely affect pH measurements in the stomach.

Antimony electrodes are clinically useful because of their low cost and simple construction; they have no glass to break. There is only a few hundred ohms resistance between an antimony pH electrode and the reference electrode so that the voltage generated can be recorded with simple low-impedance recorders linked to microcomputers. We used antimony pH electrodes with silver-silver chloride electrodes applied to the skin to measure the gastric pH in vivo and obtained erroneously high values. Using an ion-permeable dialysis chamber to surround electrodes in vivo, we showed that the discrepancy was caused by interference from gastric transmucosal potential difference. To circumvent the interference, we used a combination electrode constructed by embedding a monocrystalline antimony electrode and a silver-silver chloride reference electrode in dental acrylic. Antimony pH electrodes calibrated with commercial pH buffers also gave erroneous readings in HCl solutions of known pH. The erroneous readings were due, in part, to organic complex-forming ligands or organic salts such as potassium phthalate present in commercial buffer solutions. Accurate pH calibration can be obtained with citrate or acetate buffers or by using a normogram to correct for the errors introduced with commercial buffers. The combination antimony pH electrode has a number of potential clinical and research applications and simplifies obtaining accurate and reliable pH data in vivo.

Antimony↗
PubMed1987

The silver-silver chloride electrode: a possible generator of offset voltages and currents.

Large input currents can be generated by an asymmetry in the chloride activity seen by Ag-AgCl electrodes used at the input of intracellular amplifiers because offset compensation no longer takes place at the input of the amplifier but rather later in the circuit in many modern amplifiers. This situation occurs when chloride-free solution, such as potassium acetate, potassium citrate or various intracellular dyes are used as pipette and electrode holder filling solutions. Omitting the agar bridge at the reference electrode, or using a platinum electrode will have similar results. Values of cellular membrane potentials can be significantly contaminated under such conditions, particularly where the amplifier input resistance did not exceed 10(10) omega and where small cells were studied. Unexpected iontophoresis of Cl- can occur when the asymmetry is such as to make the recording pipette negative. These offsets can be avoided in all situations by the use of salt bridges which insure that the two Ag/AgCl junctions are in contact with Cl- of the same activity.

Electrophysiology↗
PubMed2003

Characterization and application of Raman labels for confocal Raman microspectroscopic detection of cellular proteins in single cells.

A method using confocal Raman microspectroscopy for the detection of cellular proteins in single intact cells was developed. Two approaches were used to improve the detection of these cellular components. First, compounds with high Raman scattering were investigated for potential use as Raman labels. Raman labels were conjugated to either biomolecules or biotin and used as markers in the detection of cellular enzymes and receptors. Second, silver colloids were used to increase the surface-enhanced Raman scatter (SERS) of these Raman labels. Cresyl violet and dimethylaminoazobenzene are Raman labels that provide very sensitive SERS detection by a confocal Raman microscope with a HeNe laser at wavelength of 632.8 nm. The detection of 12-lipoxygenase and cyclooxygenase-1 in single bovine coronary artery endothelial cells and the binding of angiotensin II to its receptors in zona glomerulosa cells was demonstrated.

Angiotensin II↗
PubMed1976

A Golgi-electron microscope method for insect nervous tissue.

Golgi's light microscope method of selective silver impregnation for nervous tissue combined with electron microscopy appears to offer a promising method for working out the detailed anatomy of individual neurons and their connections. Insect nervous tissue is fixed in a mixture of 2% paraformaldehyde and 2 1/2% glutaraldehyde in Millonig's buffer (pH 7.2) before postfixation for 12 hours in a solution brought to pH 7.2 with KOH containing 2% potassium dichromate, 1% osmium tetroxide and 2% D-glucose. The tissue is then transferred to a solution of 4% potassium dichromate for 1 day; and for 1-2 days to a 0.75% silver nitrate solution. After dehydration and embedding in Araldite, 50 mum sections are made. Areas of interest are cut from these sections and re-embedded in silicone molds. Ultrathin sections are then cut and stained with uranyl acetate and lead citrate. The Golgi method described here gives good results at the level of both light and electron microscopy.

Acetates↗
PubMed2006

Surface-enhanced Raman spectroscopy of dodecanethiol-bound silver nanoparticles at the liquid/liquid interface.

Adsorption and domain formation of dodecanethiol (DT)-bound silver nanoparticles (SNPs) at the cyclohexane/water interface were studied by means of total internal reflection (TIR) light scattering microscopy and TIR surface-enhanced Raman scattering (SERS). By the TIR light scattering microscopy, the extent of the interfacial adsorption and domain formation of SNP was observed, which was produced by the reaction between citrate-reduced SNPs in the aqueous phase and DT in the cyclohexane phase. The Raman spectra of DT on SNP showed that the relative intensity ratios of gauche to trans conformers in the nu(C-S) band region decreased with the increase of the initial concentration of DT, suggesting the change from the liquidlike structure to the solidlike structure of the DT. The residue of the negative charges on the SNPs at the interface was detected by the resonance SERS (SERRS) peaks of the adsorbed cationic porphyrin, 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine (TMPyP). The efficiency of the interfacial SNPs domains as a SERS substrate for TMPyP strongly depended on the adsorption state of the DT.

Adsorption↗
PubMed2000

Pyogenic spondylodiskitis: a radiologic/pathologic and culture correlation study.

BACKGROUND: Intervertebral disk tissue is resistant to hematogenous infection because of its avascularity. However, spondylodiskitis is being diagnosed with increasing frequency because of advancement in magnetic resonance imaging technology. There is a dearth of information regarding the bacteriology, histomorphologic features, and radiopathologic correlation of spondylodiskitis. DESIGN: The study population consisted of 20 patients diagnosed as having spondylodiskitis by magnetic resonance imaging with and without gadolinium 67 enhancement and bone scans with technetium Tc 99m or gallium citrate Ga 67. Twenty-seven biopsy and debridement specimens were obtained from these patients. The specimens were cultured for microorganisms and also processed for histopathologic testing. Tissue sections were examined with hematoxylin-eosin and stains for infectious agents (Gomori's methenamine-silver, Gram, and Ziehl-Neelsen stains). RESULTS: Where intervertebral disk tissue was present (23 of 27 cases), the morphologic changes included vascularization (with or without granulation tissue), myxoid degeneration, and necrosis. Chronic osteomyelitis was present in all 27 specimens and was associated with acute osteomyelitis in 7 cases (25%). Twenty-one of 27 cases had positive culture results (mostly pyogenic bacteria), but special stains revealed microorganisms in sections of the disk in only 4 cases (3 cases with gram-positive cocci and 1 with yeast consistent with Blastomyces). Florid acute inflammation was present in all the 4 cases. CONCLUSION: Histopathologic features of acute spondylodiskitis include vascular proliferation, myxoid degeneration, and necrosis of the disk tissue with adjacent chronic osteomyelitis. Acute inflammation is variable and when florid is usually associated with identifiable organisms on histologic examination. At biopsy, tissue should be submitted for culture, since culture has a high sensitivity and specificity for detecting the etiologic organism.

Adult↗
PubMed1965

A STUDY OF EXTRACELLULAR SPACE IN CENTRAL NERVOUS TISSUE BY FREEZE-SUBSTITUTION.

It was attempted to preserve the water distribution in central nervous tissue by rapid freezing followed by substitution fixation at low temperature. The vermis of the cerebellum of white mice was frozen by bringing it into contact with a polished silver mirror maintained at a temperature of about -207 degrees C. The tissue was subjected to substitution fixation in acetone containing 2 per cent OsO(4) at -85 degrees C for 2 days, and then prepared for electron microscopy by embedding in Maraglas, sectioning, and staining with lead citrate or uranyl acetate and lead. Cerebellum frozen within 30 seconds of circulatory arrest was compared with cerebellum frozen after 8 minutes' asphyxiation. From impedance measurements under these conditions, it could be expected that in the former tissue the electrolyte and water distribution is similar to that in the normal, oxygenated cerebellum, whereas in the asphyxiated tissue a transport of water and electrolytes into the intracellular compartment has taken place. Electron micrographs of tissue frozen shortly after circulatory arrest revealed the presence of an appreciable extracellular space between the axons of granular layer cells. Between glia, dendrites, and presynaptic endings the usual narrow clefts and even tight junctions were found. Also the synaptic cleft was of the usual width (250 to 300 A). In asphyxiated tissue, the extracellular space between the axons is either completely obliterated (tight junctions) or reduced to narrow clefts between apposing cell surfaces.

Animals↗
PubMed1987

The use of avidin-gold complex for light microscopic localization of lectin receptors.

In the present study, we have investigated the use of avidin-gold complex (AG) as a possible cytochemical marker for visualizing and identifying lectin receptors in deparaffinized tissue sections. Monodispersed gold sols of 15 nm average diameter were prepared by sodium citrate reduction. The AG complex was prepared with highly purified egg-white avidin (avidin-D). Deparaffinized sections of cat duodenum were labeled with five different biotinylated lectins, then were washed and stained for 1-2 h with AG. Intensification of the gold staining was achieved by a modification of the silver-enhancement method. For each lectin, the labeling properties of the avidin-gold-silver (AGS) were compared with those of the avidin-biotin-peroxidase (ABC) and the lectin-gold (LG) methods. We found the lectin binding pattern demonstrated by the AG method to be similar to that of the ABC. The AG localization of the carbohydrate residues is more precise, compared to the peroxidase reaction due to lack of diffusion of the gold marker. Labeling with AGS resulted in improved staining over the AG method, similar to the staining intensity of the ABC. In addition, the two-step AG method provided more intense staining than the direct one-step procedure of the lectin-gold labeling. In conclusion, the use of the AGS method for histochemical visualization of lectin receptors requires a simple two-step procedure which allows highly accurate localization of tissue glycoconjugates. It entails using only a single gold-ligand complex applicable to any biotinylated lectin regardless of its biochemical nature.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The peptide route to multifunctional gold nanoparticles.

Extremely stable, peptide-capped gold nanoparticles with two different biomolecular recognition motifs expressed on their surface have been prepared, and their specific and selective binding to artificial, DNA-modified target particles and to DNA and protein microarrays has been demonstrated. Stabilization and biofunctionalization has been achieved in a single preparative step starting with citrate-stabilized gold hydrosols and a derivatization cocktail of peptide-capping ligands, which carry the functionalities of choice.

Base Sequence↗
PubMed1975

Calcium oxalate and the von Kossa method with reference to the influence of citric acid.

Crystals of calcium oxalate in pathological material and artificially precipitated in the absence or presence of citric acid in gelatin models were examined by polarized light and treated with silver nitrate under a variety of conditions. It was found that the intensity of the staining reaction was largely proportional to the strength of the silver solution, and was enhanced in in vitro studies by the presence of citric acid. Staining was also influenced by the crystal form, which was itself related to the absence or presence of citric acid.

Animals↗
PubMed1989

Topographical localization of muscle glycogen: an ultrahistochemical study in the human vastus lateralis.

The fine structural pattern of glycogen storage in resting and sprint-exercised human vastus lateralis muscle fibres of different types was analysed using ultrahistochemical methods. Three male subjects (31-36 years) performed 60 consecutive, supramaximal bouts of bicycle exercise, each starting every 1 min and having a duration of 8 s (including approximately 3 s of acceleration). The load was estimated to correspond to 200% of VO2-max. Five other subjects (22-27 years) constituted controls. Ultrathin sections stained with periodic acid-thiosemicarbazide-silver proteinate (PA-TSC-SP) clearly revealed a compartmental distribution of glycogen. Glycogen is stored at five topographically, and probably also functionally, different locations. They are the subsarcolemmal, intermyofibrillar, para-Z-disc, N2-line, and H-zone spaces. During the exercise, glycogen from the N2-line and para-Z-disc locations is preferentially utilized. Serial sections stained with uranyl acetate and lead citrate demonstrated that glycogen stores of the type 2 fibres were more depleted than those of type 1 fibres. The implications of the differential intracellular glycogen storage are discussed.

Adult↗
PubMed1983

Placental transfer and distribution of 241Am in the rat.

The placental transfer and distribution of 241Am in the feto-placental system were studied in pregnant rats. Rats were injected intravenously with 241Am citrate at 15 or 18 days of gestation. Groups injected at 15 days of gestation were sacrificed 2, 24, 48, or 120 hr after injection, and the group injected at 18 days was sacrificed 24 hr after. The radioactivities of 241Am in fetus, fetal membrane, and placenta were determined, and its distribution in the feto-placental system was investigated by high-speed autoradiography using a silver-activated zinc sulfide-coated membrane as an intensifying screen. The deposition of 241Am in feto-placental units increased with the number of days of gestation. Results of autoradiography revealed that major deposition sites of 241Am in the fetus are the skeleton and liver. Heavy deposition of 241Am in the yolk sac splanchnopleure and its existence in the exocoelom strongly suggest that the yolk sac placenta plays an important role in the placental transfer of this nuclide.

Americium↗
PubMed1987

Iron uptake in Mycelia sterilia EP-76.

The cyclic trihydroxamic acid, N,N',N''-triacetylfusarinine C, produced by Mycelia sterilia EP-76, was shown to be a ferric ionophore for this organism. The logarithm of the association constant k for the ferric triacetylfusarinine C chelate was determined to be 31.8. Other iron-chelating agents, such as rhodotorulic acid, citric acid, and the monomeric subunit of triacetylfusarinine C, N-acetylfusarinine, delivered iron to the cells by an indirect mechanism involving iron exchange into triacetylfusarinine C. In vitro ferric ion exchange was found to be rapid with triacetylfusarinine C. Gallium uptake rates comparable to those of iron were observed with the chelating agents that transport iron into the cell. Ferrichrome, but not ferrichrome A, was also capable of delivering iron and gallium to this organism, but not by an exchange mechanism. Unlike triacetylfusarinine C, the 14C-ligand of ferrichrome was retained by the cell. A midpoint potential of -690 mV with respect to the saturated silver chloride electrode was obtained for the ferric triacetylfusarinine C complex, indicating that an unfavorable reduction potential was not the reason for the use of a hydrolytic mechanism of intracellular iron release from the ferric triacetylfusarinine C chelate.

Biological Transport, Active↗
PubMed2004

Energy failure in astrocytes increases the vulnerability of neurons to spreading depression.

A neuroprotective role of astrocytes has been hypothesized, but the mechanism is debated and in vivo evidence is limited. To test this hypothesis, a sublethal stressor (spreading depression) and fluorocitrate (FC), a selective inhibitor of the astrocytic Krebs cycle, were used in urethane-anaesthetized adult rats. Neuronal damage was assessed 24 h after treatment with silver stain and immunoreactivity for a 72-kDa heat-shock protein. ATP levels and mitochondrial aconitase activity, a marker indicating exposure to reactive oxygen species, were measured after 4 and 24 h. Spreading depression alone did not affect ATP levels, mitochondrial aconitase activity, or induce neuronal injury in the cortex. Local or intraventricular injection of FC significantly decreased ATP levels and mitochondrial aconitase activity, but did not produce neuronal damage. In animals receiving injections of FC and then spreading depression, there was evidence of significant neuronal stress and damage. Isocitrate, which bypasses the metabolic inhibition produced by FC, prevented all of the changes seen after the combination of FC and spreading depression. One-hour pretreatment with dimethyl sulfoxide (a scavenger of hydroxyl radicals), deferoxamine (an iron chelator) or fructose-1,6-bisphosphate also blocked inactivation of mitochondrial aconitase, ATP depletion and the neuronal damage induced by FC and spreading depression. These experiments demonstrate that inhibition of the metabolism of astrocytes, with a decrease in ATP levels, will increase the susceptibility of neurons to the stress induced by spreading depression. The neuroprotective effects of dimethyl sulfoxide, deferoxamine and fructose-1,6-bisphosphate suggest that oxidative stress contributes to the neurotoxicity in this situation.

Aconitate Hydratase↗
PubMed1989

Terminal nerve sprouting at the frog neuromuscular junction induced by prolonged tetrodotoxin blockade of nerve conduction.

The effects of a prolonged blockade of nerve conduction by tetrodotoxin on frog motor innervation were studied in the cutaneous pectoris muscle of Rana esculenta. Prolonged nerve blockade (up to 22 days) was obtained by repeated subperineural injections of tetrodotoxin. Changes in morphological parameters of neuromuscular junctions were investigated in muscles after staining with a combined cholinesterase-silver method. In addition, changes in the incidence of polyneuronal innervation were investigated conjointly by electrophysiology and morphology. Morphometric analysis of singly innervated muscle fibres of 60 microns diameter revealed insignificant changes during the first week of tetrodotoxin-nerve blockade. After 15 days of paralysis, the mean length of synaptic contacts and the mean length of terminal arborization per synapse were significantly increased as compared to controls (contralateral muscles and citrate buffer-injected controls). After 20-22 days, differences in synaptic and aborization mean lengths were accentuated and reached 44 and 43%, respectively. At that time, the mean number of terminal branching points and of continuous synaptic contacts were also significantly increased (around 20 and 50%, respectively). No changes in the length of abandoned gutters were observed. The incidence of focal polyaxonal innervation (detected morphologically) and of polyneuronal innervation (determined electrophysiologically) was unchanged. The results show that prolonged tetrodotoxin blockade induces sprouting of the terminal arborization which results in an extension of pre-existing nerve terminals and an increase in the complexity of terminal arborization by addition of new branches. Nodal (collateral) sprouting was not changed.

Acetylcholinesterase↗
PubMed2001

Histochemical tracing of bismuth in Helicobacter pylori after in vitro exposure to bismuth citrate.

BACKGROUND: Bismuth-containing drugs are widely used in the treatment of Helicobacter pylori associated peptic ulcer. The mechanism of action of bismuth salts is, however, not fully understood, and at present no histochemical techniques for the demonstration of bismuth in H. pylori are available. The aims were to present a histochemical method for the detection of bismuth in H. pylori and to demonstrate bismuth uptake in H. pylori after in vitro exposure to bismuth citrate. METHODS: H. pylori cultures (the strain used in this study was CCUG 17874), were exposed to bismuth citrate at different concentrations (0, 4.6, 80, 200 microM) and for different lengths of time (0 min, 15 min, 1 h, 24 h, 48 h). The samples were fixed in glutaraldehyde, centrifuged, and exposed to autometallographic (AMG) development in order to detect bismuth histochemically. RESULTS: A detailed protocol on the AMG bismuth technique on H. pylori exposed to bismuth in vitro is given. This method results in easily detectable AMG grains of silver enhanced bismuth particles at the electron microscopical level, and shows that bismuth accumulates in H. pylori, predominantly near the wall of the bacteria. Bismuth uptake is followed by bacterial degeneration. CONCLUSION: The present technique with its ability to trace bismuth constitutes a valuable tool in the efforts of clarifying the mechanism of action of bismuth on H. pylori, and supports the notion that bismuth has an antimicrobial activity in itself.

Anti-Ulcer Agents↗