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Results for “Neutral Red”

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PubMed1978

Vital staining properties of neutral red. Vital staining of cornea and conjunctiva.

Vital staining by instillation in the conjunctival sac of 1% neutral red in 54 normal and 153 differently affected eyes was studied by slit lamp examination. Of these, 134 eyes were after-stained by a mixture of 1% tetrazolium and 1/4% alcian blue and 73 eyes were after-stained by a mixture of 1% rose bengal and 1% fluorescein. Microscopy of a further 10 conjunctival scrapings and 40 mucous conjunctival threads disclosed neutral-red-stained inclusion bodies in the cytoplasm of the epithelial cells and the granulocytes. In the slit lamp the cornea and the conjunctiva were seen to be stained only rarely and, if so, poorly by neutral red, both in normal and affected eyes. Better staining was obtained with tetrazolium, and the best with rose bengal. The plica semilunaris, Marx' line, and the mucous thread were stained by neutral red, more intensely by rose bengal, and the least by tetrazolium. The inferior fornix and the tarsus were rarely stained by any of the three dyes. Neutral red seems to offer no diagnostic advantages over the vital stains with which the dye has been compared in the present study. More particularly we found no pathological processes that were stained more intensely by neutral red than by the other vital stains.

Cataract↗

PubMed2000

Interaction of the excited singlet state of neutral red with aromatic amines

Quenching of neutral red (NR; neutral form of the dye) fluorescence by a number of aromatic amines has been investigated in acetonitrile solutions. The bimolecular quenching constants (kq) obtained from steady-state and time-resolved measurements for a particular donor-acceptor pair are seen to be the same within experimental error. Correlation of the changes in the kq values with the oxidation potentials of the donors (amines) indicates that electron transfer (ET) is the mechanism operative in the present systems. Direct evidence for ET has been obtained from picosecond transient absorption studies on a suitable amine-NR pair. Experimentally determined kq values are seen to correlate well with the free energy changes (delta G0) for the ET reactions, within the frame-work of the Marcus outer sphere ET theroy. From the correlation between the experimentally determined and theoretically calculated kq values, it appears that solvent reorganization plays a major role in governing ET dynamics in the systems investigated.

Journal Article↗

PubMed1978

The accumulation of neutral red in illuminated thylakoids.

Thylakoids isolated from spinach (Spinacia oleracea L.) bind only a small fraction of neutral red in the dark whereas they accumulate large amounts of the protonated dye in their inner space under light. Light-induced neutral red uptake depends on the size of the proton gradient across the thylakoid membrane but does not follow the mechanism established for amines. Instead, the correlation between pH gradient and neutral red uptake can be predicted quantitatively assuming that protonated neutral red is accumulated mainly as dimer species. Under appropriate conditions, accumulation of protonated neutral red in the inner thylakoid space is proportional to an absorbance increase at 520 nm. This 520-nm change can be used for the continuous measurement of pH changes in thylakoids during steady-state illumination.

Darkness↗

PubMed1983

Neutral red stains ganglia in the vagal motor pathway to ferret trachea without affecting ganglionic transmission.

To determine the effect of Neutral red (0.01%) on neural transmission through ganglia, we used an in vitro nerve-muscle preparation of ferret trachea. Before, during, and after incubating the trachea in Neutral red, we induced isometric muscle contractions first by activating preganglionic fibers with electrical stimulation of the vagus nerve, and then by activating postganglionic nerve fibers with electrical field stimulation. Incubation in Neutral red (0.01%) for 45 min at 38 degrees C reduced the responses to both pre- and postganglionic activation. When the control responses to pre- and postganglionic activation were matched. Neutral red depressed the 2 responses to the same degree, implying that the depression was confined to postganglionic structures. Washout of Neutral red from the medium restored the responses to both pre- and postganglionic activation. Histologic examination of all tissues proved that the ganglia were still stained after the washout procedure. We conclude that Neutral red (0.01%) depresses smooth muscle contractions evoked through neural pathways, and that this depression is reversible and confined to postganglionic structures, leaving ganglionic transmission intact.

Animals↗

PubMed1983

[Effect of inhibitors of energy metabolism and protein synthesis on the process of neutral red segregation in frog erythrocytes].

Effects of inhibitors of energy metabolism and protein synthesis on Neutral red segregation in frog erythrocytes were studied. Inhibitors of both glycolysis and respiration significantly reduced formation of segregation zones. This influence was most striking with antimycin A, rotenone and cyanide. This indicates that intact respiratory pathways may play an important part in the process of Neutral red segregation. Such uncouplers as FCCP (carbonyl cyanide p-trifluoromethoxyphenylhydrazone) and 2,4-dinitrophenol (DNP) as well as inhibitors of oxidative phosphorylation (arsenate and azide) are also very effective in inhibiting the Neutral red segregation at low concentrations. The effects of these uncouplers and of olygomycin suggest an important role of ATP as an energy source for the segregation process. An inhibitor of protein synthesis, such as cycloheximide, produces some reduction in segregation zones formation. Trapping of Neutral red by protonation could readily explain the high level of this dye accumulation in nucleated erythrocytes. The fact that low concentrations of FCCP and DNP inhibit the process of segregation brings a supporting evidence for the possibility of the ATP-driven proton pump involved in Neutral red segregation.

Animals↗

PubMed1976

Effect of neutral red and light on Herpesvirus hominis type 1 in cell culture.

Various concentrations of neutral red were added to monolayers of muscle-skin fibroblasts after adsorption of Herpesvirus hominis type 1. The concentration necessary to reduce plaque counts was found to be 10(-5.5) M. At the same time, the minimal toxic concentration of neutral red for muscle-skin fibroblasts was determined by the concentration that reduced the plaques of a challenge virus, vesicular stomatitis virus, that was applied after treatment with neutral red and light. The minimal toxic concentration was found to be 10(-5) M. Thus, the effective concentration of neutral red for H. hominis in tissue culture appears to be only slightly less than the minimal toxic concentration. The concentrations used for clinical trials in humans have been 10(3)-10(4) times this amount. Any observed efficacy of such treatment may be a reflection of cell toxicity.

Cell Division↗

PubMed1991

Cytotoxicity of T-2 toxin and its metabolites determined with the neutral red cell viability assay.

The neutral red (NR) cell viability assay was used with various cell types of human origin to quantitate the potency of T-2 mycotoxin and its metabolites. The human melanoma SK-Mel/27 cell line was the most sensitive, with a midpoint cytotoxicity value of 2.8 ng of T-2 per ml. With the human hepatoma cell line, HepG2, the sequence of potency for a series of mycotoxins was T-2 greater than HT-2 greater than T-2 triol greater than T-2 tetraol.

Animal Testing Alternatives↗

PubMed2003

A temperature-dependent interaction of neutral red with calf thymus DNA.

Neutral red (NR) is used as a probe to study the temperature and concentration dependent interaction of a cationic dye with nucleic acid. A temperature-dependent interaction of NR with calf thymus DNA (CT DNA) has been studied by differential pulse voltammetry (DPV), UV-Visible absorption, circular dichroism (CD) and fluorescence spectroscopy. The experimental results of increasing peak current, changes in the UV-Visible absorption and fluorescence spectra of NR and decreasing the induced circular dichroism (ICD) intensity show that (i) the binding mode of NR molecules is changed from intercalating into DNA base pairs to aggregating along the DNA double helix and (ii) the orientation of NR chromophore in DNA double helix is also changed with the temperature.

Animals↗

PubMed1981

[Mechanisms of neutral red transport through the mucosa of the gastrointestinal tract].

The conditions of the passage of neutral red into the cavity of gastro--intestinal tract were investigated during the atropine blockade of the stomach secretory activity in the dogs with fundal, antral and duodenal fistulas. The neutral red begins to cross the gastric mucosa only after the PH of the perfusing solution has achieved 2.5 and for intestine--5.0. The intensity of the neutral red passage increases with further decrease of the perfusing solution pH. During perfusion of acid solutions through the stomach and particularly through the duodenum, retrodiffusion of H+ occurs into the mucosa. The excretion of neutral red into the cavity of gastro--intestinal tract seems to be a process of passive diffusion. The role of the H+ retrodiffusion in this process is discussed.

Animals↗

PubMed1979

Selective vital staining of companion cells of potato tuber and parsnip root with neutral red.

When staining the internal phloem region of a potato tuber with the vital stain neutral red, it was observed that files of elongated cells of narrow diameter were heavily stained and were easily distinguishable from the more isodiametric parenchyma cells, many of which did not stain with neutral red. The elongated cells were identified as companion cells by locating the adjacent sieve-tube members through counterstaining with aniline blue and reviewing under violet light. Of a number of other plants surveyed, only parsnip roots possessed companion cells exhibiting a similar slective staining. In other plants both the companion cells and the surrounding parenchyma cells usually stained. Sieve-tube members never accumulated neutral red. It was concluded that the vacuoles of the companion cells of the potato tuber were stained by the ion trap mechanism because of the color of the accumulated stain, the lack of staining when neutral red was applied in an acidic solution, and the complete destaining after soaking in dilute ammonium hydroxide.

Histocytochemistry↗

PubMed1984

A study of dietary restriction and lifespan in the rotifer Asplanchna brightwelli monitored by chronic neutral red exposure.

The rotifer Asplanchna brightwelli could be exposed to concentrations of neutral red at 0.1 to 0.75 microgram/ml for two consecutive generations with no adverse effect on the lifespan or fecundity of either generation. Chronic exposure to higher concentrations of neutral red caused reductions in both lifespan and fecundity of the rotifers. Because neutral red stains the Paramecium which serve as a food source for the rotifers, the extent of red coloration in each rotifer's gut gave an approximation of how much food that rotifer had consumed. The Paramecium concentration had to be reduced to 100 per ml before pale gut coloration provided clear evidence of reduced food intake or dietary restriction. The group of rotifers with reduced food intake had a significantly longer lifespan than any other group. Their lifespan was 14.2% longer than that of control rotifers.

Aging↗

PubMed1990

Interaction with hyperthermia of tetrachloroplatinum(II)(Nile blue)2 and tetrachloroplatinum(II)(neutral red)2 in EMT6 murine cells and the murine FSaIIC fibrosarcoma.

Complexes of the tetrachoroplatinum(II) dianion with positively charged nuclear dyes were prepared in an effort to produce agents which gain ready access into the nucleus and become very cytotoxic at clinically relevant hyperthermia temperatures. Pt(Nile blue)2 and Pt(neutral red)2 are complexes of tetrachloroplatinum(II) with two closely related p-quinonediamine dyes. Pt(Nile blue)2 and Pt(neutral red)2 were only moderately cytotoxic to exponentially growing normally oxygenated or hypoxic EMT6 cells in vitro at pH 7.40 and 37 degrees C. At pH 7.40 and 42 degrees C and especially at 43 degrees C, however, Pt(Nile blue)2 became far more cytotoxic. At pH 6.45 Pt(Nile blue)2 became more toxic toward hypoxic cells (cell kill of 3.5 logs at 500 microM, 42 degrees C for 1 h). Pt(neutral red)2 became much more cytotoxic at pH 6.45 and 42 degrees C or 43 degrees C compared to pH 7.4, and the cell kill observed was similar in both euoxic and hypoxic cells (3 logs at pH 6.45, 43 degrees C with only 100 microM). Tumor cell survival studies in the FSaIIC murine fibrosarcoma demonstrated that both drugs killed in a dose-dependent log-linear manner. Hyperthermia treatment (43 degrees C, 30 min) immediately after either drug resulted in a dose modifying effect. The tumor growth delay produced by Pt(Nile blue)2 (100 mg/kg) was 4.6 days and by Pt(neutral red)2 (100 mg/kg) was 3.8 days. Both drugs were markedly improved by hyperthermia (tumor growth delay 1.4 days for hyperthermia; tumor growth delay 10.9 days for Pt(Nile blue)2 and 8.0 days for Pt(neutral red)2. Intracellular platinum levels were approximately 200 times higher after exposure of EMT6 cells to 25 microM of Pt(Nile blue)2 or Pt(neutral red)2 for 1 h at 37 degrees C than after exposure to the same concentration of cis-diamminedichloroplatinum(II). Treatment of cells with the drugs at 42 degrees C (1 h) resulted in no change in platinum levels with cis-diamminedichloroplatinum(II), but with Pt(Nile blue)2 and Pt(neutral red)2 an increase of 2- to 3-fold was found. Since previous work has shown that both of these complexes are active radiosensitizing agents, these new drugs seem quite well suited for further development as antitumor agents for use against solid tumors alone and in conjunction with hyperthermia and/or radiation therapy.

Animals↗

PubMed1955

Intracellular changes due to neutral red as revealed in the pancreas and kidney of the mouse by the electron microscope.

The effects of sublethal amounts of the cationic dye, neutral red, upon the structure of pancreatic exocrine cells, and upon the mitochondria of renal distal tubule cells, have been studied with the electron microscope. It was found that neutral red is a cytoplasmic toxin which causes reproducible and characteristic changes in the ergastoplasm, the zymogen granules, the mitochondria, and possibly in the Golgi complex. Ergastoplasmic membranes and granules and zymogen granules lose definition and become continuous with the cytoplasmic matrix. Mitochondria lose their internal folds, develop vacuoles which contain a solution of neutral red in high concentration, and form the nidus for the development of sudanophilic, argyrophilic, osmiophilic inclusions which appear in the cytoplasm after neutral red administration. Golgi granules, one of the three elements of the Golgi complex, appear to increase in number and to be scattered more widely through the cytoplasm than is normal. No consistent changes were found in the cell membrane or nucleus. The ability of the mitochondria to concentrate the cation, neutral red, taken with its well known ability to concentrate the cationic Janus dyes and methylene blue, and its probable role in concentrating those cationic dyes which have been used to demonstrate the "vacuome," is interpreted to signify that one of the functions of mitochondria may be to concentrate intracellar cations.

Animals↗

PubMed1990

A specific fluorescent dye for ex situ staining of vital islets of Langerhans: neutral red.

We present a new technique for specific ex situ fluorescent staining of islets of Langerhans with neutral red. Depending on the concentration of neutral red (1 microgram/ml), this technique allows the differentiation between exocrine and endocrine pancreatic tissue, according to differences in fluorescence intensity. Pancreatic islets can be stained not only in situ, but in particular ex situ after pancreas digestion. Since intravital staining of the pancreas in situ with neutral red is not applicable in human transplantation, the staining procedure ex situ may be a useful tool for islet purification by particle sorting, using a fluorescent-light-activated system; thus, a sufficient mass of purified islets for free transplantation may be isolated.

Animals↗

PubMed1992

Histochemical probing of potato periderm with neutral red: a sensitive cytofluorochrome for the hydrophobic domain of suberin.

A technique is described which uses the lipid fluorochrome neutral red as a cytochemical probe to detect the hydrophobic domain of the ligno-suberin matrix in native and wound periderm of potato tuber. Toluidine blue O is used as a counterstain to quench autofluorescence. The neutral red technique appears to be specific for the hydrophobic/lipid domain of suberin and is significantly more sensitive than Sudan III and IV. The fluorochrome was extensively used on paraffin-embedded tissue with excellent results but also worked on freehand sections of fresh periderm tissue. In tuber tissue undergoing wound-healing, the pattern of suberin fluorescence obtained with the neutral red probe was identical in specificity to the color pattern obtained with Sudan III/IV, but somewhat different than that observed when berberine was used. Results obtained with the neutral red probe and berberine probe visually demonstrated that during ligno-suberin biosynthesis, the depositions of hydrophobic/lipid and phenolic/lignin-like components in potato tuber periderm were separate processes. The deposition of these components does not necessarily require their simultaneous presence because the fluorescence from these probes showed that the components were not consistently present together on the cell walls.

Berberine↗

PubMedDate not supplied

Neutral red fluorescence of chromatin: specificity and binding mechanism.

After treatment with neutral red at low concentrations (10(-6), 10(-5) M), the chromatin of chicken erythrocytes shows an intensive red fluorescence, which is reduced or practically abolished when nuclei become stained by using the dye at concentrations higher than 10(-4) M. Both the fluorescence and staining reactions are dependent on the DNA content of chromatin. Neutral red fluorescence of nuclei increases considerably after treatment with inorganic cations (Al3+, Ba2+), while previous treatments with methylene blue reduce the fluorescence intensity. The possibility that chromatin fluorescence depends on the intercalative binding of neutral red is suggested.

Animals↗

PubMed1984

Subcellular localization of neutral red staining in Limulus ventral photoreceptors.

Limulus ventral photoreceptors are vitally stained by neutral red. In other systems such staining has been correlated with the presence of monoamines or neuropeptides. The stained cellular components in ventral photoreceptors are clusters of small ovoids which have been identified as residual bodies. These structures are unlikely candidates for monoamine or neuropeptide synthesis or storage sites, but may be part of the cyclic synthesis and degradation of photosensitive membrane. While vital staining with neutral red is a particularly useful method for identifying certain classes of neurons in vivo, in the case of ventral photoreceptors, the association of the vital staining property with the presence of a particular class of neurotransmitter candidates has proven difficult. Neutral red is useful, however, for visualizing the segmentation of ventral photoreceptors in vivo.

Animals↗

PubMedDate not supplied

Neutral red assay in minimum fungicidal concentrations of antifungal agents.

We assayed the fungicidal effects of antifungal agents using neutral red staining. Fungal elements of Trichophyton mentagrophytes and T. rubrum were treated with various concentrations of antifungal agents in 96-well filtration plates and then stained with neutral red. The amount of neutral red incorporated by the surviving viable cells was determined from the automated spectrophotometric readings at 550 nm. The minimum fungicidal concentrations (MFCs) of antifungal agents determined by this assay correlated well with those determined by conventional assay. This newly developed procedure should provide a rapid, reproducible, quantitative, qualitative and semi-automated susceptibility test for determination of the MFCs of the fungicidal agents.

Antifungal Agents↗