Fluorescent treponemal antibody-absorption double-staining procedure

The fluorescent treponemal antibody-absorption double-staining step-by-step procedure and proposed reference reagents for the test are described. The test and reagents were evaluated in two separate laboratories on 265 fresh sera, and test results were compared with the reference fluorescent treponemal antibody-absorption test results performed in a third laboratory. The data indicate that the tests are comparable in the areas where the test is recommended for use. Problems with inadequate light filtration occurred, but these could be resolved. This test is recommended for use with microscopes equipped with incident illumination.

Use of resonance energy transfer to monitor membrane fusion

An assay for vesicle--vesicle fusion involving resonance energy transfer between N-(7-nitro-2,1,3-benzoxadiazol-4-yl), the energy donor, and rhodamine, the energy acceptor, has been developed. The two fluorophores are coupled to the free amino group of phosphatidylethanolamine to provide analogues which can be incorporated into a lipid vesicle bilayer. When both fluorescent lipids are in phosphatidylserine vesicles at appropriate surface densities (ratio of fluorescent lipid to total lipid), efficient energy transfer is observed. When such vesicles are fused with a population of pure phosphatidylserine vesicles by the addition of calcium, the two probes mix with the other lipids present to form a new membrane. This mixing reduces the surface density of the energy acceptor resulting in a decreased efficiency of resonance energy transfer which is measured experimentally. These changes in transfer efficiency allow kinetic and quantitative measurements of the fusion process. Using this system, we have studied the ability of phosphatidylcholine, phosphatidylserine, and phosphatidylcholine--phosphatidylserine (1:1) vesicles to fuse with cultured fibroblasts. Under the conditions employed, the majority of the cellular uptake of vesicle lipid could be attributed to the adsorption of intact vesicles to the cell surface regardless of the composition of the vesicle bilayer.

A comparison of fluorescein isothiocyanate and lissamine rhodamine (RB 200) as labels for antibody in the fluorescent antibody technique

The relative merits of fluorescein isothiocyanate (FITC) and lissamine rhodamine (RB 200) as labels for antibody in fluorescence microscopy were studied and compared by microphotometry, testing each fluorochrome under its own optimal conditions as far as possible, and at a similar range of dye:protein ratios. The antibody was sheep anti-human globulin, and the tissues stained with it were rat liver sections bearing human anti-nuclear factor on the nuclei. The findings were as follows:

(i) the amount of RB 200 conjugating with protein was strictly proportional to the amount of the sulphonyl chloride derivative added to the reaction mixture; with increasing amounts of FITC in the reaction mixture, however, there was a less than proportional increase in the degree of conjugation.

(ii) Diethylaminoethyl (DEAE)-cellulose chromatography decreased the dye:protein ratio of the conjugates by 40% uniformly for both RB 200 and FITC, regardless of the initial dye:protein ratio.

(iii) When corrections were made for spectral responses of photo-detectors, effects of optimizing the mountants, and benefits to rhodamine of changing from a Xenon to a mercury lamp, it was concluded that RB 200 conjugates could give brighter staining than FITC conjugates at similar dye:protein ratios.

(iv) DEAE-cellulose chromatography greatly improved the contrast of the staining, especially with RB 200 conjugates.

(v) After chromatography, RB 200 consistently gave better contrast than FITC.

(vi) The fluorescence of rhodamine-stained sections did not fade demonstrably when irradiated for several minutes with green light.

(vii) The fluorescence of FITC-stained sections faded rapidly when irradiated with ultra-violet (u.v.)+blue light. The fluorescence appeared to contain two components, one fading with first-order kinetics with a half-life of about a minute under the experimental conditions used and the other not fading at all.

(viii) Raising the pH improved the fluorescence of FITC-stained sections but did not affect rates of fading.

(ix) Narrow-band excitation of FITC-stained sections with blue light instead of u.v.+blue reduced the rate of fading and the fluorescence intensity by equal amounts, an effect presumably due merely to loss of excitation intensity.

Cytochemical localization of ornithine decarboxylase with rhodamine or biotin-labeled alpha-difluoromethylornithine. An example for the use of labeled irreversible enzyme inhibitors as cytochemical markers

The present work describes a new method for cytochemical localization of enzymes using ornithine decarboxylase (ODC) as an example. The method is based on the preservation of the characteristic-specific and irreversible binding of the inhibitor alpha-difluoromethylornithine (alpha-DFMO) following its conjugation to "label" molecules. The inhibitor has been conjugated to the fluorescent molecule rhodamine-B-isothiocyanate, and its localization in tissue sections was detected directly by fluorescence cytochemistry. Alternatively, alpha-DFMO has been conjugated to biotin and its cytochemical localization determined indirectly following its binding with avidin conjugated to horseradish peroxidase (HRP) and visualization of the HRP reaction product. Both labeled inhibitor molecules were successfully localized cytochemically within specific cells of the developing rat cerebellum and rat liver following thioacetamide injection where ODC activity is greatly enhanced. This novel technique should be of general application 1) in other tissues, 2) for other enzymes, and 3) in electron microscopic studies for ultrastructural localization of the enzyme.

Rapid identification of human B-lymphocytes and monocytes with rhodamine-labeled Brucella melitensis

The bacterium Brucella melitensis has been shown to bind selectively to human B-lymphocytes. The specificity of this binding can be exploited in a rapid technique for the determination of human B-lymphocytes and monocytes by use of rhodamine-labeled Brucella melitensis. This fluorescent labeled regent is simple to use and provides highly specific identification of human B-lymphocytes and monocytes, as demonstrated in a series of experiments characterizing known cellular markers on T- and B-lymphocytes, their separated cellular subpopulations and lymphoblastoid cell lines. The use of fluorescence conjugated bacteria greatly simplifies the application of this highly specific technique and makes its use more practical in routine screening for B-cell and monocyte populations.

The association of rhodamine - labelled alpha-actinin with actin bundles in demembranated cells

Rhodamine-labelled alpha-actinin was specifically bound to actin containing filament bundles of demembranated fibroblasts, and was particularly associated with their termini. Optimal binding of rhodamine-alpha-actinin occurred at pH 6.0 - 6.2 and could be abolished by the addition of unlabeled alpha-actinin or myosin subfragment 1. The spatial relationships between the decorating alpha-actinin and several actin associated proteins was determined by double fluorescence microscopy.

Selective inhibition of nonspecific eosinophil staining or identification of eosinophilic granulocytes by paired counterstaining in immunofluorescence studies

Nonspecific staining of eosinophilic granulocytes produced by nonimmune rabbit IgG conjugates, highly labeled with fluorescein isothiocyanate (FITC) or tetramethylrhodamine isothiocyanate (MRITC), was efficiently inhibited by pretreatment of tissue sections with diaminobenzidine and hydrogen peroxide; the brown reaction product developed in the presence of this substrate by the endogenous peroxidase of the granulocytes sheltered these cells from subsequent nonspecific staining without interfering with specific immunofluorescence staining of other tissue elements. Similar results were obtained with the alternative noncarcinogenic peroxidase substrate, p-phenylenediamine-pyrocatechol. Alternatively, the eosinophils could be identified by their nonspecific staining with FITC-labeled bovine serum albumin when this conjugate was combined with an MRITC conjugate used for specific staining; optical conditions selective for green and red fluorescence discriminated distinctly between double-stained eosinophils and purely red specifically stained cells.

Identification of Mallory bodies with rhodamine B fluorescence and other stains for keratin

Rhodamine B staining in conjunction with fluorescence microscopy is shown to demonstrate Mallory bodies. Mallory body morphology, localization, and distribution in hepatocytes from griseofulvin-fed mice, human hepatoma, and human alcoholics were similar to those observed in the same tissues after conventional staining methods for Mallory bodies. The presence of these inclusions was further confirmed by specific cytochemical localization with indirect immunoperoxidase labeling, horseradish peroxidase labeling, and electron microscopy. Other tinctorial or histochemical procedures previously used for keratin or prekeratin (modified Mallory stain, Kreyberg method, Pauly method for histidine) also stained Mallory bodies for study with white light microscopy but with decreasing sensitivity respectively. Mallory bodies from mouse and human liver both appear to contain a keratin-like moiety. This entity may be simply, rapidly, and permanently stained with rhodamine B, and selectively and reproducibly demonstrated with fluorescence microscopy.

Proliferation of mitochondria during the cell cycle of the human cell line (HL-60)

Using rhodamine 123 to stain mitochondria of the human cell line HL-60, we have followed their increase over the cell cycle by flow cytometry. A near-linear synthesis of mitochondrial mass was shown to occur over the cell cycle. A comparison with the cell's DNA synthesis pattern obtained by the same technique established a common time-base. The mitochondrial synthesis curve changes with culture age. As a control, thd dye was tested for its binding specificity and for its use to resolve mitochondria microscopically. Its stoichiometric range was established and, above 0.25 microgram/ml, it was shown to reduce growth rate and cell viability in culture.

Replication of infectious laryngotracheitis virus in chickens following vaccination

The site of replication of infectious laryngotracheitis vaccine virus (ILTV) was studied in chickens vaccinated by drinking water (DW), intraconjunctival (IC) and cloacal (CL) routes. The anatomical sites exposed to vaccine were determined by simulating vaccination with rhodamine red dye. Virus replication was determined by recovering virus from various organs at necropsy. The dye simulation studies clearly demonstrated that DW vaccination did not usually expose susceptible target organs to virus while the CL and IC routes flooded susceptible organs with vaccine. Virus replication was confined to the cloaca in CL vaccination birds while in IC and DW vaccination birds most replication took place in the nasal cavity. Vaccine virus did not always become established in DW vaccinated birds and its establishment did not appear to be related to the amount of vaccine these birds were exposed. It was concluded that DW vaccination depends for its success upon the accidental contamination of the nasal cavity with vaccine virus during the act of drinking.

Cytochemical hybridization with fluorochrome-labeled RNA. I. Development of a method using nucleic acids bound to agarose beads as a model

A new procedure to label RNA at the 3'-terminus with a fluorochrome molecule is described. The thiosemicarbazides derived from tetramethylrhodamine isothiocyanate (TRITC) and fluorescein isothiocyanate (FITC) were prepared by reacting these compounds with hydrazine in dimethylsulfoxide (DMSO):pyridine, 99:1 (v/v). They coupled efficiently to the aldehydes generated by periodate oxidation of RNAs. We determined, using Sepharose to which different nucleic acids and proteins had been bound, that the label added no specific binding properties to the RNA, and did not interfere with duplex formation of labeled poly(U) and poly(A). The stability of the fluorochrome-RNA bond under conditions generally used for hybridization was investigated. The bond was found to be unstable at 66 degrees C in 3 x SSC, 0.1% SDS (50% loss within 45 min) but stable for at least 40 hr at 23 degrees C in 70% formamide/3 x SSC. The hybridization characteristics of complementary RNA, both fluorochrome- and 3H-labeled, were investigated using DNA-Sepharose beads as a cytochemical model. Hybridization was measured by scintillation counting of microliter quantities of beads and quantitative fluorescence microscopy of individual Sepharose beads. No influence of the label on the specificity and stability of the hybrids was found. Maximum specific fluorescence was found after hybridization at 23 degrees C in 70% formamide/3 x SSC. These results made possible the successful use of fluorochrome-labeled RNA to perform cytochemical hybridization followed by detection of the hybrids with fluorescence microscopy. This will be described in an accompanying article.

Cytochemical hybridization with fluorochrome-labeled RNA. II. Applications

The cytochemical detection of specific DNA sequences by hybridization with fluorochrome-labeled RNA and detection of the hybrids by fluorescence microscopy is described. RNAs complementary to the DNA of the kinetoplasts of Crithidia luciliae (an insect trypanosome) or to adenovirus-5 (Ad-5) DNA were labeled with the hydrazine derivative of tetramethylrhodamine isothiocyanate (TRITC). The specificity of the reactions between the complementary RNAs labeled both with 3H and tetramethylrhodamine was studied by cross-hybridization experiments using a model system in which the DNAs were bound to Sepharose beads. The extent of the reaction was measured by scintillation counting of the bead suspensions and quantitative fluorescence microscopy of individual Sepharose beads. The ability of the rhodamine-labeled cRNAs to hybridize and the absence of interference of the fluorochrome label with the specificity of the hybridization reaction was thus demonstrated. After cytochemical hybridization on microscopic preparations of C. luciliae cells the rhodamine-labeled kinetoplast cRNA stains only the kinetoplasts. No fluorescence was observed in the nuclei. After cytochemical hybridization of rhodamine-labeled Ad-5 cRNA with virus infected KB cells a distinct staining pattern in the nuclei was observed. No fluorescence was seen in uninfected cells, or after hybridization with heterologous rhodamine-labeled RNA. The possibilities and limitations of cytochemical hybridization with rhodamine-labeled RNA are discussed.

[Determination of phospholipase A2 activity in liver mitochondria using fluorescent dye 1,8-anilinonaphthalene sulfonate]

Quantitative estimation of free fatty acids was carried out in liver mitochondria of normal and thyroidectomized rabbits by means of two procedures--spectrophotometry using rhodamine 6Zh and a fluorescent method with 1,8-aniline naphthalene sulfonate /ANS/ as a dye. The use of ANS enabled to estimate quantitatively the free fatty acids beginning from 25 nmol in a sample /with eggor of about 17%/ by visual evaluation of the spot areas. As compared with the rhodamine procedure, use of ANS permitted to increase 5-fold the sensitivity of free fatty acid estimation, to elevate 6-fold the accuracy of the analysis, to overcome the step of fatty acid elution from chromatogramms and to decrease the time required for analysis. The data obtained suggest that the hyperthyroid state in rabbits was accompanied by an increase in the phospholipase A2 activity in liver mitochondria.

Permeability of the cell-to-cell membrane channel and its regulation in an insect cell junction

Cells of organs and tissues commonly communicate directly with one another via permeable membrane junctions. Cell-to-cell channels, spanning the width of both membranes of a junction, are thought to provide the pathways between the cytoplasms of adjacent cells for the immediate exchange of ions and small molecules. We study these cell-to-cell channels in a cell model system, the salivary gland of Chironomus. Using intracellularly injected fluorescent labelled peptides and oligosaccharides of various molecular dimensions as channel permeability probes we find the channels to have a bore of about 2 nm. The channel permeability can be modulated and, in the extreme, the channels can be closed under various experimental conditions. With the aid of the Ca2+-sensitive photoprotein aequorin as monitor of cytoplasmic free Ca2+ concentration, we show that a determining factor in this modulation of channel permeability is the cytoplasmic free Ca2+ concentration. Moreover, results obtained by injection of different-sized and different-labelled channel permeability probes together with Ca2+ indicate that closure of the individual channels may occur in more than one step, i.e., by a graded reduction of channel bore.

Distribution of marked perilymph to the subarachnoidal space

In guinea pigs the tympanic perilymph of the basal turn was marked with fluorescing rhodamine. In the first series one drop of a 2% solution of the dye was applied onto the round window membrane. Since the perilymphatic space was not opened, the physiologic state of the communicating fluids perilymph and CSF was maintained. The dye appeared within 3-5 min via cochlear aqueduct in the subarachnoidal space. In the dead animal the speed of distribution was significantly less. This most probably indicates a weak physiologic flow of the perilymph through the aqueduct to the subarachnoidal space in living animals. In the second series, 2 ng of lyophilized rhodamine was instilled directly into the tympanic perilymph near the round window. Though hardly any additional volume was brought into the perilymph, the distribution of the dye was distinctly greater as a sign of the considerable sensitivity of the fluid system, even by the slightest manipulation.

Local immunity to Bacteroides gingivalis in periodontal disease

The histopathologic status of gingival tissue was assessed according to the criteria of Page and Schroeder.(5) Rhodamine-labeled bacteria were used to assess the antigenic specificity of plasma cells in the tissue. Examination of tissue sections revealed that 31.6% of plasma cells in the advanced lesions bound the labeled bacterium, compared with only 3.1% of the cells in the early lesions. These results indicate that local immunity to Bacteroides gingivalis in greater in the more advanced than in the earlier forms of periodontal disease.

Estimation of phosphatidylglycerol in fluids containing pulmonary surfactant

A simple, direct and non-destructive method for quantitative separation of phosphatidylglycerol from other phospholipids in pulmonary washings is described. Total lipid extracts from dog lung washings and phosphatidylglycerol standard were spotted quantitatively on chromatoplates and separated by one-dimensional thin-layer chromatography in chloroform-methanol-water 65:25:4 (v/v/v). Quantification was performed with Rhodamine 6G and fluorometry. Washings from eleven dogs contained (mean +/- S.E.) 236 +/- 25 microgram phosphatidylglycerol per g of parenchymal wet lung tissue which accounted for 8.7% +/- 2.3 of the total phospholipids. The procedure is especially useful for quantification of phosphatidylglycerol in microgram amounts.