Introduction to confocal microscopy and three-dimensional reconstruction

Automated 3D scoring of fluorescence in situ hybridization (FISH) using a confocal whole slide imaging scanner

Fluorescence in situ hybridization (FISH) is a technique to visualize specific DNA/RNA sequences within the cell nuclei and provide the presence, location and structural integrity of genes on chromosomes. A confocal Whole Slide Imaging (WSI) scanner technology has superior depth resolution compared to wide-field fluorescence imaging. Confocal WSI has the ability to perform serial optical sections with specimen imaging, which is critical for 3D tissue reconstruction for volumetric spatial analysis. The standard clinical manual scoring for FISH is labor-intensive, time-consuming and subjective. Application of multi-gene FISH analysis alongside 3D imaging, significantly increase the level of complexity required for an accurate 3D analysis. Therefore, the purpose of this study is to establish automated 3D FISH scoring for z-stack images from confocal WSI scanner. The algorithm and the application we developed, SHIMARIS PAFQ, successfully employs 3D calculations for clear individual cell nuclei segmentation, gene signals detection and distribution of break-apart probes signal patterns, including standard break-apart, and variant patterns due to truncation, and deletion, etc. The analysis was accurate and precise when compared with ground truth clinical manual counting and scoring reported in ten lymphoma and solid tumors cases. The algorithm and the application we developed, SHIMARIS PAFQ, is objective and more efficient than the conventional procedure. It enables the automated counting of more nuclei, precisely detecting additional abnormal signal variations in nuclei patterns and analyzes gigabyte multi-layer stacking imaging data of tissue samples from patients. Currently, we are developing a deep learning algorithm for automated tumor area detection to be integrated with SHIMARIS PAFQ.

Digital, Rapid, Accurate, and Label-Free Enumeration of Viable Microorganisms Enabled by Custom-Built On-Glass-Slide Culturing Device and Microscopic Scanning

Accurately measuring the number of viable microorganisms plays an essential role in microbiological studies. Since the conventional agar method of enumerating visible colonies is time-consuming and not accurate, efforts have been made towards overcoming these limitations by counting the invisible micro-colonies. However, none of studies on micro-colony counting was able to save significant time or provide accurate results. Herein, we developed an on-glass-slide cell culture device that enables rapid formation of micro-colonies on a 0.38 mm-thick gel film without suffering from nutrient and oxygen deprivation during bacteria culturing. Employing a phase contrast imaging setup, we achieved rapid microscopic scanning of micro-colonies within a large sample area on the thin film without the need of fluorescent staining. Using Escherichia coli (E. coli) as a demonstration, our technique was able to shorten the culturing time to within 5 h and automatically enumerate the micro-colonies from the phase contrast images. Moreover, this method delivered more accurate counts than the conventional visible colony counting methods. Due to these advantages, this imaging-based micro-colony enumeration technique provides a new platform for the quantification of viable microorganisms.

Lactic acid bacteria in dairy food: surface characterization and interactions with food matrix components

This review gives an overview of the importance of interactions occurring in dairy matrices between Lactic Acid Bacteria and milk components. Dairy products are important sources of biological active compounds of particular relevance to human health. These compounds include immunoglobulins, whey proteins and peptides, polar lipids, and lactic acid bacteria including probiotics. A better understanding of interactions between bioactive components and their delivery matrix may successfully improve their transport to their target site of action. Pioneering research on probiotic lactic acid bacteria has mainly focused on their host effects. However, very little is known about their interaction with dairy ingredients. Such knowledge could contribute to designing new and more efficient dairy food, and to better understand relationships between milk constituents. The purpose of this review is first to provide an overview of the current knowledge about the biomolecules produced on bacterial surface and the composition of the dairy matter. In order to understand how bacteria interact with dairy molecules, adhesion mechanisms are subsequently reviewed with a special focus on the environmental conditions affecting bacterial adhesion. Methods dedicated to investigate the bacterial surface and to decipher interactions between bacteria and abiotic dairy components are also detailed. Finally, relevant industrial implications of these interactions are presented and discussed.

Study of CFU for individual microorganisms in mixed cultures with a known ratio using MBRT

Determination of metabolically active cell count is an important step in designing, operating and controlling fermentation processes. It's particularly relevant in processes involving mixed cultures, where multiple species contribute to the total growth. The motivation for the current study is to develop a methodology to estimate metabolically active cell counts for the individual species in a mixed culture with approximate equal numbers. Further, the methodology should indicate the presence of a contaminant in short time periods since in the agar plate methods used frequently it takes about 24 h. We present a methodology based on the rate of Methylene blue (MB) reduction to evaluate total count of metabolically active cells. The standard curve relating the slope of MB reduction and CFU of the individual species could be used to measure the metabolic activity of each species in the mixed culture. The slope of MB reduction could also be used to obtain the growth rate of individual species in a mixed culture and that of the total cell count. These measurements were achieved in less than 6 minutes during the growth of the cells. Evaluating the metabolic activity of individual species in a mixed culture is tedious, difficult and time consuming. The Methylene Blue dye Reduction Test (MBRT) presented here is capable of quickly estimating colony forming units (CFU) of individual species in a mixed culture if the ratio of the numbers of cells is known. The method was used to dynamically detect the occurrence of a contaminating microorganism during fermentation. The protocol developed here can be adapted to applications in processes involving mixed cultures.

Microstructural analysis of human white matter architecture using polarized light imaging: views from neuroanatomy

To date, there are several methods for mapping connectivity, ranging from the macroscopic to molecular scales. However, it is difficult to integrate this multiply-scaled data into one concept. Polarized light imaging (PLI) is a method to quantify fiber orientation in gross histological brain sections based on the birefringent properties of the myelin sheaths. The method is capable of imaging fiber orientation of larger-scale architectural patterns with higher detail than diffusion MRI of the human brain. PLI analyses light transmission through a gross histological section of a human brain under rotation of a polarization filter combination. Estimates of the angle of fiber direction and the angle of fiber inclination are automatically calculated at every point of the imaged section. Multiple sections can be assembled into a 3D volume. We describe the principles of PLI and present several studies of fiber anatomy as a synopsis of PLI: six brainstems were serially sectioned, imaged with PLI, and 3D reconstructed. Pyramidal tract and lemniscus medialis were segmented in the PLI datasets. PLI data from the internal capsule was related to results from confocal laser scanning microscopy, which is a method of smaller scale fiber anatomy. PLI fiber architecture of the extreme capsule was compared to macroscopical dissection, which represents a method of larger-scale anatomy. The microstructure of the anterior human cingulum bundle was analyzed in serial sections of six human brains. PLI can generate highly resolved 3D datasets of fiber orientation of the human brain and has high comparability to diffusion MR. To get additional information regarding axon structure and density, PLI can also be combined with classical histological stains. It brings the directional aspects of diffusion MRI into the range of histology and may represent a promising tool to close the gap between larger-scale diffusion orientation and microstructural histological analysis of connectivity.

Ex vivo and in vivo imaging of myelin fibers in mouse brain by coherent anti-Stokes Raman scattering microscopy

Coherent anti-Stokes Raman scattering (CARS) microscopy was applied to image myelinated fibers in different regions of a mouse brain. The CARS signal from the CH2 symmetric stretching vibration allows label-free imaging of myelin sheath with 3D sub-micron resolution. Compared with two-photon excited fluorescence imaging with lipophilic dye labeling, CARS microscopy provides sharper contrast and avoids photobleaching. The CARS signal exhibits excitation polarization dependence which can be eliminated by reconstruction of two complementary images with perpendicular excitation polarizations. The capability of imaging myelinated fibers without exogenous labeling was used to map the whole brain white matter in brain slices and to analyze the microstructural anatomy of brain axons. Quantitative information about fiber volume%, myelin density, and fiber orientations was derived. Combining CARS with two-photon excited fluorescence allowed multimodal imaging of myelinated axons and other cells. Furthermore, in vivo CARS imaging on an upright microscope clearly identified fiber bundles in brain subcortex white matter. These advances open up new opportunities for the study of brain connectivity and neurological disorders.

New imaging techniques in the diagnosis of multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic disabling disorder histopathologically characterized by inflammation, demyelination and axonal loss. Conventional MRI has made most contributions to the diagnosis of MS. However, it is not sufficiently sensitive and specific to reveal the extent and severity of the damage in the disease. Other nuclear magnetic resonance (NMR) techniques including magnetic resonance spectroscopy, magnetization transfer imaging, diffusion weighted and diffusion tensor imaging, and functional MRI have provided additional information that improves the diagnosis and understanding of MS. Optical techniques including optical coherence tomography (OCT) and coherent anti-Stokes Raman scattering (CARS) microscopy have shown promise in diagnosis and mechanistic study of myelin diseases.

OBJECTIVE

To review new imaging techniques and their potential in diagnosis of MS.

METHOD

The principles of three imaging techniques (MRI, OCT and CARS) and their applications to MS studies are described. Their advantages and disadvantages are compared.

CONCLUSION

Conventional MRI remains a critical tool in the diagnosis of MS. Alternative NMR/MRI techniques have improved specificity for the detection of lesions and provided more quantitative information about MS. Optical techniques including OCT and CARS microscopy are opening up new ways for diagnosis and mechanistic study of myelin diseases.

Quantification of metabolically active biomass using Methylene Blue dye Reduction Test (MBRT): measurement of CFU in about 200 s

Quantification of viable cells is a critical step in almost all biological experiments. Despite its importance, the methods developed so far to differentiate between viable and non-viable cells suffer from major limitations such as being time intensive, inaccurate and expensive. Here, we present a method to quantify viable cells based on reduction of methylene blue dye in cell cultures. Although the methylene blue reduction method is well known to check the bacterial load in milk, its application in the quantification of viable cells has not been reported. We have developed and standardized this method by monitoring the dye reduction rate at each time point for growth of Escherichia coli. The standard growth curve was monitored using this technique. The Methylene Blue dye Reduction Test (MBRT) correlates very well with Colony Forming Units (CFU) up to a 800 live cells as established by plating. The test developed is simple, accurate and fast (200 s) as compared to available techniques. We demonstrate the utility of the developed assay to monitor CFU rapidly and accurately for E. coli, Bacillus subtilis and a mixed culture of E. coli and B. subtilis. This assay, thus, has a wide applicability to all types of aerobic organisms.

Pseudomonas aeruginosa biofilm formation and slime excretion on antibiotic-loaded bone cement

BACKGROUND

Infection is an infrequent but serious complication of prosthetic joint surgery. These infections will usually not clear until the implant is removed and re-implantation has a high failure rate, especially when Pseudomonas aeruginosa is involved.

MATERIAL AND METHODS

We examined Pseudomonas aeruginosa biofilm formation on plain and gentamicin-loaded bone cement with confocal scanning laser microscopy (CSLM). Two different stains were applied in order to visualize and quantify the distribution of bacterial cells and extracellular polymeric substances (slime) from the bone cement surface to the top of the biofilm. Staining with LIVE/DEAD viability stain differentiated between live and dead bacteria within the biofilm, and slime production was evaluated after staining with Calcofluor white.

RESULTS

CSLM showed that the biofilm was a nonuniform structure of variable thickness, with differences in local bacterial cell and slime densities. Incorporation of gentamicin in bone cement resulted in a 44% reduction in bacterial viability, while the slime density increased significantly. In addition, conventional plate counting showed the development of small-colony variants on gentamicin-loaded bone cement with a decreased sensitivity for gentamicin (MIC: 8 m/L), as compared with normal-sized colonies taken from plain and gentamicin-loaded bone cement (MIC: 3 m/L). The enhanced slime production on antibiotic-loaded bone cement, together with the formation of small-colony variants, resulted in decreased susceptibility to antibiotics--probably concomitant with the onset of persistent and relapsing infections.

INTERPRETATION

In the clinical situation, our findings help to explain the frequent re-implantation failure of joint replacements infected with P. aeruginosa when the procedure has been performed using antibiotic-loaded bone cement.

The application of fuzzy-based methods to central nerve fiber imaging

This paper discusses the potential of fuzzy logic methods within medical imaging. Technical advances have produced imaging techniques that can visualize structures and their functions in the living human body. The interpretation of these images plays a prominent role in diagnostic and therapeutic decisions, so physicians must deal with a variety of image processing methods and their applications. This paper describes three different sources of medical imagery that allow the visualization of nerve fibers in the human brain: (1) an algorithm for automatic segmentation of some parts of the thalamus in magnetic resonance images based on the differences in myelin content in various thalamic subnuclei; (2) polarized light for classifying the 3D orientation of the nerve fibers at each point; and (3) confocal laser scanning microscopy (CLSM) for calculating semiquantitative variables for myelin content. Fuzzy logic methods were applied to analyze these pictures from low- to high-level image processing. The solutions presented here are motivated by problems of routine neuroanatomic research demonstrating fuzzy-based methods to be valuable tools in medical image processing.

Computational imaging in cell biology

Microscopy of cells has changed dramatically since its early days in the mid-seventeenth century. Image analysis has concurrently evolved from measurements of hand drawings and still photographs to computational methods that (semi-) automatically quantify objects, distances, concentrations, and velocities of cells and subcellular structures. Today's imaging technologies generate a wealth of data that requires visualization and multi-dimensional and quantitative image analysis as prerequisites to turning qualitative data into quantitative values. Such quantitative data provide the basis for mathematical modeling of protein kinetics and biochemical signaling networks that, in turn, open the way toward a quantitative view of cell biology. Here, we will review technologies for analyzing and reconstructing dynamic structures and processes in the living cell. We will present live-cell studies that would have been impossible without computational imaging. These applications illustrate the potential of computational imaging to enhance our knowledge of the dynamics of cellular structures and processes.

Spindle observation in living mammalian oocytes with the polarization microscope and its practical use

The meiotic spindle is crucial for normal chromosome alignment and separation of maternal chromosomes during meiosis. Conventional methods to image spindles rely on fixation and transmission electron microscope or immunofluorescence staining and fluorescence microscope, so they provide limited value to studies of spindle dynamics and human clinical in vitro fertilization. A new orientation-independent polarized light microscope, the LC Polscope, was used to examine the bi-refringent spindles in living mammalian oocytes. It was found that spindles could be imaged with the Polscope in living oocytes in all mammals so far examined, including hamster, mouse, cattle, human, and rat. The first polar body did not accurately predict the spindle location in most metaphase II oocytes. Intracytoplasmic sperm injection (ICSI) could be performed by monitoring spindle position. Studies in humans indicated that, aftr ICSI, higher fertilization and embryonic developmental rates could be achieved in oocytes with than without bi-refringent spindles. Because spindles in most mammalian oocytes are extremely sensitive to slight changes in temperature, maintenance of temperature at 37 degrees C is crucial for normal spindle function. As chromosomes#10; are usually associated with microtubule fibers in the spindles, the position of chromosomes could be indirectly located by imaging spindles. Removing spindles under the Polscope can achieve an enucleation#10; efficiency rate of 100% in mouse oocytes. The Polscope can also be used to examine the spindle dynamics, detect spindle morphology, predict chromosome misalignment, and perform spindle transfer.

A photoreactive fluorescent marker for identifying eosinophils and their cytoplasmic granules in tissues

Here we describe a simple histochemical technique that provides an improved approach to identifying eosinophil components in tissues through the formation of photoreactive complexes that produce stable fluorescent emissions. This method worked readily with histological tissue sections 6-60 microm thick, which were fixed in neutral buffered formalin (NBF), and with cell suspensions similarly fixed and unfixed. Deep red (>605 nm) fluorescent emissions were produced by eosinophil-specific granules when exposed to broadband excitation spectra from a 100-W mercury lamp source (510-590 nm), as well as single-wavelength excitations from both an argon laser (488 nm) and a UV-visible laser (514 nm). The fluorophore-granule complex emissions increased in intensity during the first minute of continuous photoexcitation, then remained stable (>10 min). All nonspecific autofluorescence phenomena associated with these tissues were photobleached in the first minute, including areas of background Biebrich scarlet binding where photoreactive complexes were not formed (i.e., collagen), indicating environmental influences on the fluorophore. This technique allows the visualization of eosinophil granules over a greater period of time than is usually permissible with standard fluorescent markers. Therefore, techniques such as confocal microscopy can be utilized to their fullest extent, providing much more detailed information on the location and distribution of the cytoplasmic contents of eosinophils.

Quantitative motion analysis and visualization of cellular structures

The availability of cellular markers tagged with the green fluorescent protein (GFP) has recently allowed a large number of cell biological studies to be carried out in live cells, thereby addressing the dynamic organization of cellular structures. Typically, microscopes capable of video recording are used to generate time-resolved data sets. Dynamic imaging data are complex and often difficult to interpret by pure visual inspection. Therefore, specialized image processing methods for object detection, motion estimation, visualization, and quantitation are required. In this review, we discuss concepts for automated analysis of multidimensional image data from live cell microscopy and their application to the dynamics of cell nuclear subcompartments.

Neutrophils lacking phosphoinositide 3-kinase gamma show loss of directionality during N-formyl-Met-Leu-Phe-induced chemotaxis

Confocal imaging and time-lapsed videomicroscopy were used to study the directionality, motility, rate of cell movement, and morphologies of phosphoinositide 3-kinase gamma (PI3K)gamma(-/-) neutrophils undergoing chemotaxis in Zigmond chambers containing N-formyl-Met-Leu-Phe gradients. Most of the PI3Kgamma(-/-) neutrophils failed to translocate up the chemotactic gradient. A partial reduction in cell motility and abnormal morphologies were also observed. In the wild-type neutrophils, the pleckstrin homology domain-containing protein kinase B (AKT) and F-actin colocalize to the leading edge of polarized neutrophils oriented toward the gradient, which was not observed in PI3Kgamma(-/-) neutrophils. In PI3Kgamma(-/-) neutrophils, AKT staining consistently failed to perfectly overlap with the F-actin. This failure was observed as an F-actin-filled region of 2.3 +/- 0.5 microm between AKT and the cell membrane. These data suggest that PI3Kgamma regulates neutrophil chemotaxis primarily by controlling the direction of cell migration and the intracellular colocalization of AKT and F-actin to the leading edge.

DNA topoisomerase II is essential for preimplantation mouse development

Topoisomerase II (topo II) is an essential enzyme that alters DNA topology. This activity is important for a variety of chromosome functions including DNA replication, transcription, recombination, and chromosome condensation and segregation. Previously we localized topo II in mouse gametes and preimplantation embryos using isoform-specific antibodies demonstrating the presence of the enzyme in oocytes and embryos, but not sperm. To probe functions of topo II during preimplantation development, we treated mouse zygotes with 100 nM teniposide, and assessed embryo morphology and DNA replication. Teniposide blocked cleavage in 69% embryos; the remainder cleaved once but had abnormal nuclei. Teniposide-treated embryos were devoid of topo II immunofluorescence. Teniposide also prevented DNA replication, implicating topo II in this process. Embryos treated with a 2 hr pulse of teniposide recovered and developed to the blastocyst stage, indicating 100 nM teniposide did not induce apoptosis. To more specifically analyze topo IIalpha function, we treated zygotes with topo IIalpha-targeted antisense oligodeoxynucleotides. Most zygotes arrested at the 2-cell stage while controls developed into blastocysts indicating topo IIalpha is essential for preimplantation development. The absence of topo IIalpha, but not beta immunofluorescence in antisense-treated embryos confirms the specificity and impact of the treatment. In addition, topo IIalpha is newly synthesized at the 2-cell stage. These results establish an essential function for topo II in mouse preimplantation embryonic development.

DNA topoisomerase II distribution in mouse preimplantation embryos

DNA topoisomerase II (topo II) is an essential enzyme that mediates a variety of chromosome activities including DNA replication, transcription, recombination, and chromosome condensation and segregation. Isoform-specific anti-topo II antibodies were used to determine the distribution of topo II alpha and beta in mouse gametes and embryos. Immunoblot analysis with two anti-topo IIalpha antibodies revealed that a 170 kDa topo IIalpha band was present in ovary and testis. Mature sperm exhibited an 89 kDa band only, which may be a degradation product of topo IIalpha. Immunoblots probed with a monoclonal antibody that recognizes both isoforms, showed bands at 170 and 180 kDa, which correspond to topo IIalpha and beta, respectively. An additional 100 kDa band was also present in ovary and testis. Mature sperm did not exhibit staining with this antibody. We also localized topo II in mouse gametes and embryos up to the blastocyst stage using immunofluorescence microscopy. While both isoforms were found in nuclei and nucleoli of germinal vesicle oocytes, topo IIalpha localized to metaphase chromosomes during meiosis, and only to nucleoli during embryonic interphase. Topo IIbeta was absent from chromosomes of metaphase II oocytes, but localized to embryonic interphase nuclei. Both full-length isoforms were absent from sperm, indicating topo II is stored maternally. These results identify topo II as an important component of mouse oocyte and embryonic chromatin, and suggest its involvement in oocyte maturation and preimplantation embryonic development. The different immunofluorescent staining patterns indicate topo IIalpha and beta may serve different roles during the embryonic cell cycle.

Abnormal migration phenotype of mitogen-activated protein kinase-activated protein kinase 2-/- neutrophils in Zigmond chambers containing formyl-methionyl-leucyl-phenylalanine gradients

Time-lapsed video microscopy and confocal imaging were used to study the migration of wild-type (WT) and mitogen-activated protein kinase-activated protein kinase 2 (MK2-/-) mouse neutrophils in Zigmond chambers containing fMLP gradients. Confocal images of polarized WT neutrophils showed an intracellular gradient of phospho-MK2 from the anterior to the posterior region of the neutrophils. Compared with WT neutrophils, MK2-/- neutrophils showed a partial loss of directionality but higher migration speed. Immunoblotting experiments showed a lower protein level of p38 mitogen-activated protein kinase and a loss of fMLP-induced extracellular signal-related kinase phosphorylation in MK2-/- neutrophils. These results suggest that MK2 plays an important role in the regulation of neutrophil migration and may also affect other signaling molecules.

The regrowth of axons within tissue defects in the CNS is promoted by implanted hydrogel matrices that contain BDNF and CNTF producing fibroblasts

In this study we demonstrate the potential for combining biocompatible polymers with genetically engineered cells to elicit axon regrowth across tissue defects in the injured CNS. Eighteen- to 21-day-old rats received implants of poly N-(2-hydroxypropyl)-methacrylamide (HPMA) hydrogels containing RGD peptide sequences that had been infiltrated with control (untransfected) fibroblasts (n = 8), fibroblasts engineered to express brain-derived neurotrophic factor (BDNF) (n = 5), ciliary neurotrophic factor (CNTF) (n = 5), or a mixture of BDNF and CNTF expressing fibroblasts (n = 11). Fibroblasts were prelabeled with Hoechst 33342. Cell/polymer constructs were inserted into cavities made in the left optic tract, between thalamus and superior colliculus. After 4-8 weeks, retinal projections were analyzed by injecting right eyes with cholera toxin (B-subunit). Rats were perfused 24 h later and sections were immunoreacted to visualize retinal axons, other axons (RT97 antibody), host astrocytes and macrophages, donor fibroblasts, and extracellular matrix molecules. The volume fraction (VF) of each gel that was occupied by RT97(+) axons was quantified. RT-PCR confirmed expression of the transgenes prior to, and 5 weeks after, transplantation. Compared to control rats (mean VF = 0.02 +/- 0.01% SEM) there was increased ingrowth of RT97(+) axons into implants in CNTF (mean VF = 0.33 +/- 0.19%) and BDNF (mean VF = 0.62 +/-0.19%) groups. Axon growth into hydrogels in the mixed BDNF/CNTF group (mean VF = 3.58 +/- 0.92%) was significantly greater (P < 0.05) than in the BDNF or CNTF fibroblast groups. Retinal axons exhibited a complex branching pattern within gels containing BDNF or BDNF/CNTF fibroblasts; however, they regrew the greatest distances within implants containing both BDNF and CNTF expressing cells.

Direct in situ viability assessment of bacteria in probiotic dairy products using viability staining in conjunction with confocal scanning laser microscopy

The viability of the human probiotic strains Lactobacillus paracasei NFBC 338 and Bifidobacterium sp. strain UCC 35612 in reconstituted skim milk was assessed by confocal scanning laser microscopy using the LIVE/DEAD BacLight viability stain. The technique was rapid (<30 min) and clearly differentiated live from heat-killed bacteria. The microscopic enumeration of various proportions of viable to heat-killed bacteria was then compared with conventional plating on nutrient agar. Direct microscopic enumeration of bacteria indicated that plate counting led to an underestimation of bacterial numbers, which was most likely related to clumping. Similarly, LIVE/DEAD BacLight staining yielded bacterial counts that were higher than cell numbers obtained by plate counting (CFU) in milk and fermented milk. These results indicate the value of the microscopic approach for rapid viability testing of such probiotic products. In contrast, the numbers obtained by direct microscopic counting for Cheddar cheese and spray-dried probiotic milk powder were lower than those obtained by plate counting. These results highlight the limitations of LIVE/DEAD BacLight staining and the need to optimize the technique for different strain-product combinations. The minimum detection limit for in situ viability staining in conjunction with confocal scanning laser microscopy enumeration was approximately 10(8) bacteria/ml (equivalent to approximately 10(7) CFU/ml), based on Bifidobacterium sp. strain UCC 35612 counts in maximum-recovery diluent.

Visualization of nerve fiber orientation in gross histological sections of the human brain

Diffusion weighted magnetic resonance imaging (DWMRI) allows visualization of the orientation of the nervous fibers in the living brain. For comparison, a method was developed to examine the orientation of fibers in histological sections of the human brain. Serial sections through the entire human brain were analyzed regarding fiber orientation using polarized light. Direction of fibers in the cutting plane was obtained by measuring the azimuth with the lowest intensity value at each point, and inclination of fibers in the section was evaluated using fuzzy logic approximations. Direction and inclination of fibers revealing their three-dimensional orientation were visualized by colored arrows mapped into the images. Using this procedure, various fiber tracts were identified (pyramidal tract, radiatio optica, radiatio acustica, arcuate fascicle, and 11 more). Intermingled fibers could be separated from each other. The orientation of the fiber tracts derived from polarized light microscopy was validated by confocal laser scanning microscopy in a defined volume of the internal capsule, where the fiber orientation was studied in four human brains. The polarization method visualizes the high degree of intermingled fiber bundles in the brain, so that distinct fiber pathways cannot be understood as solid, compact tracts: Neighbouring bundles of fibers can belong to different systems of fibers distinguishable by their orientation.

A novel, rapid, computerized method for quantitation of neuronal damage in a rat model of stroke

Determination of extent of infarction in animal models of cerebral ischemia is most commonly achieved by either classical histology (thionin staining) and light microscopy or staining with 2,3, 5-triphenyltetrazolium chloride (TTC). These techniques have limitations and we now describe a novel technique and its validation for assessment of the neuroprotective activity of AM-36, a novel arylalkypiperazine compound with combined antioxidant and sodium channel blocking activity. AM-36 (1.8 mg/kg i.p.) or vehicle, was administered 30 min, 24 and 48 h after endothelin-1-induced middle cerebral artery occlusion in conscious rats. Rats were killed at 72 h, brains removed and frozen in liquid nitrogen prior to coronal sectioning. Using a simple apparatus relying on basic principles of light propagation and a computerised image analysis system, ischemic damage in unstained slide-mounted sections was clearly visualised and measured. AM-36 significantly reduced the area of infarct in both cortex and striatum. The method was verified by thionin staining, and light microscopy. Linear regression analysis showed a highly significant correlation between methods at 72 h for infarct area in the cortex and striatum. Highly significant correlations between methods were found at 3 and 24 h after ischemia. Our method quickly and clearly delineates areas of damage in a manner superior to conventional staining methods.

Mapping of fiber orientation in human internal capsule by means of polarized light and confocal scanning laser microscopy

The nervous fibers in the human internal capsule were mapped according to their three-dimensional orientation. Four human cadaver brains were cut into comparable and standardized sections parallel to the ACPC-plane, stained with DiI, and analyzed using a combination of confocal and polarized light microscopy at the same time. This combination provides information about the structure and orientation of the fibers in great detail with confocal microscopy, and information about the localization and orientation of long myelinated fiber tracts with polarization microscopy. The internal capsule was parcellated in the areas CI 1 to CI 4 containing fibers of distinct orientation and structure, which enriches the macroscopically definable parcellation in the anterior and posterior limb. Fibers of the anterior thalamic peduncle intermingle with frontopontine tract fibers. Single fibers connect the caudate and the lentiform nucleus. The pyramidal tract is located in the anterior half of the posterior limb intermingled with fibers of the superior thalamic peduncle. Parietooccipitopontine fibers are located in the posterior part of the posterior limb. The slopes of the different systems of fibers change continuously in the anterior posterior direction of the internal capsule. Using the 3D orientation of fibers as a criterion for parcellation, as well as the description of bundles as a collection of fibers belonging to particular tracts leads to a more function-related description of the anatomy of the internal capsule. The method can be used for interindividual, sex- or age-related comparisons of particular systems of fibers.

Morphological asymmetry in anterior limb of human internal capsule revealed by confocal laser and polarized light microscopy

The fiber structure in the anterior limb of the internal capsule was investigated in a region where stereotactic lesions (anterior capsulotomy) result in successful treatment of obsessive-compulsive disorder (OCD). Eight human hemispheres were sectioned in comparable planes parallel to the ACPC plane. Microscopic slices were labeled with DiI and analyzed with confocal laser and polarized light microscopy. Three distinct systems of fibers were detected. Single fibers run from the caudate nucleus to the lentiform nucleus. The anterior thalamic peduncle connects the mediodorsal and partially the anterior thalamic nucleus with the frontal lobe. The frontopontine tract system connects the frontal lobe with the pons. This fiber tract occupies 38% of the anterior limb and is arranged in small bands. Right-left comparison of morphometric parameters of these bundles demonstrated that more and smaller bundles were located on the left-hand side than on the right-hand side. Tendencies for this configuration were noticeable in all brains investigated, with statistical significance in one brain. These morphological differences correlate with functional differences, as it was possible to demonstrate right hemispheric dysfunctions in cases of OCD. The benefit of anterior capsulotomy in OCD is generally seen in the interruption of fronto-basal ganglia-thalamic loops by disconnecting the anterior thalamic peduncle. In addition, the frontopontine fiber tract is disconnected in this stereotactic procedure.

Confocal laser scanning microscopy of calcium dynamics in living cells

Confocal laser scanning microscopy (CLSM) is widely used to monitor intracellular calcium levels in living cells loaded with calcium-sensitive fluorophores. This review examines the basic advantages and limitations of CLSM in in vivo imaging analyses of calcium dynamics. The benefits of utilizing ratioed images and dextran-conjugated fluorophores are addressed, and practical aspects of handling confocal datasets are outlined. After considering some relatively new microscopical methods that can be used in conjunction with conventional CLSM, possible future applications of confocal techniques in analyses of intracellular calcium dynamics are discussed.

Sperm nuclear activation during fertilization

The delivery of the paternal genome to the egg is a primary goal of fertilization. In preparation for this step, the nucleus of the developing spermatozoon undergoes extensive morphological and biochemical transformations during spermatogenesis to yield a tightly compacted sperm nucleus. These modifications are essentially reversed during fertilization. As a result, the incorporated sperm nucleus undergoes many steps in the egg cytoplasm as it develops into a male pronucleus. The sperm nucleus (1) loses its nuclear envelope, (2) undergoes nucleoprotein remodeling, (3) decondenses and increases in size, (4) becomes more spherical, (5) acquires a new nuclear envelope, and (6) becomes functionally competent to synthesize DNA and RNA. These changes are coordinate with meiotic processing of the maternal chromatin, and often result in behaviors asynchronous with the maternal chromatin. For example, in eggs fertilized during meiosis, the sperm nucleus decondenses while the maternal chromatin remains condensed. A model is presented that suggests some reasons why this puzzling behavior exists. Defects in any of the processes attending male pronuclear development often result in infertility. New assisted reproductive technologies have been developed that ensure delivery of the sperm nucleus to the egg cytoplasm so that a healthy embryo is produced. An emerging challenge is to further characterize the molecular mechanisms that control sperm nuclear transformations and link these to causes of human infertility. Further understanding of this basic process promises to revolutionize our understanding of the mystery of the beginning of new life.

Accessibility of SSA/Ro and SSB/La Antigens to Maternal Autoantibodies in Apoptotic Human Fetal Cardiac Myocytes

Access of intracellular Ags SSA/Ro and SSB/La to cognate maternal autoantibodies is unexplained despite their strong association with congenital heart block. To investigate the hypothesis that apoptosis facilitates surface accessibility of these Ags, human fetal cardiac myocytes from 16- to 22-wk abortuses were established in culture using a novel technique in which cells were isolated after perfusing the aorta with collagenase. Confirmation of cardiac myocytes included positive staining with antisarcomeric α-actinin and contractility induced by 1.8 mM calcium. Incubation with 0.5 μM staurosporine or 0.3 mM 2,3-dimethoxy-1,4-naphthoquinone induced the characteristic morphologic and biochemical changes of apoptosis. The cellular topology of Ro and La was evaluated with confocal microscopy and determined in nonapoptotic and apoptotic cardiocytes by indirect immunofluorescence. In permeabilized nonapoptotic cardiocytes, Ro and La were predominantly nuclear, and propidium iodide (PI) stained the nucleus. In early apoptotic cardiocytes, condensation of the PI- and Ro- or La-stained nucleus was observed, accompanied by Ro/La fluorescence around the cell periphery. In later stages of apoptosis, nuclear Ro and La staining became weaker, and PI demonstrated nuclear fragmentation. Ro/La-stained blebs emerged from the cell membrane, a finding observed in nonpermeabilized cells, supporting an Ab-Ag interaction at the cell surface. In summary, induction of apoptosis in cultured cardiocytes results in surface translocation of Ro/La and recognition by Abs. Although apoptotic cells are programmed to die and do not characteristically evoke inflammation, binding of maternal Abs and subsequent influx of leukocytes could damage surrounding healthy fetal cardiocytes.

Distribution of TMV movement protein in single living protoplasts immobilized in agarose

Recent studies of the tobacco mosaic virus (TMV) P30 movement protein (MP) fused with green fluorescent protein (GFP) during TMV infection described the involvement of elements of the cytoskeleton and components of the endoplasmic reticulum (ER) in the intracellular trafficking of MP:GFP from the sites of synthesis in the cytoplasm to plasmodesmata. To examine in real-time the pattern of synthesis, accumulation and degradation of MP:GFP, we developed a method to immobilize protoplasts in agarose such that they are maintained alive for extended periods of time. The pattern of MP:GFP accumulation in single living protoplasts visualized by confocal laser scanning microscopy (CLSM) was parallel to that previously described in a population of protoplasts harvested at different times post-infection. Additionally, a network of weakly fluorescent filaments, which are apparently different from microtubules, was observed to surround the nucleus and these filaments were associated with fluorescent bodies (previously identified as ER-derived structures). Later in infection, the fluorescent bodies increased in size and coalesced to form larger structures that accumulated near the periphery of the cells while highly fluorescent non-cortical filaments were observed distributed in the cytoplasm. The putative involvement of these filaments in targeting the fluorescent bodies to the periphery of the cell is discussed. Studies of single, embedded protoplasts make it possible to observe changes in amount and subcellular localization of viral and other proteins.

Four-dimensional imaging: the exploration of space and time

The process of studying dynamic three-dimensional samples has a long history in biological research. Recent advances in hardware and software have made it easier to visualise and record interior detail from multiple focal planes of three-dimensional samples as they change over time (four-dimensional imaging). Once captured, it is possible to watch these events repeatedly and to analyse them in numerous ways. This article discusses the history of and the hardware necessary to perform 4D experiments, the various techniques that make 4D imaging possible, and the applications and various options for 4D-image analysis.

Tomography of cells by confocal laser scanning microscopy and computer-assisted three-dimensional image reconstruction: localization of cathepsin B in tumor cells penetrating collagen gels in vitro

We used the nondestructive procedures of confocal laser scanning microscopy in combination with computer-assisted methods to visualize tumor cells in the process of penetrating collagen gels. Three independent sets of images were collected. The image information of all data sets was combined into one image, giving a three-dimensional (3D) impression at high light microscopic resolution and sensitivity. We collected information about the extracellular matrix using the reflection mode, the cell surface/morphology by staining with the fluorescent dye DiOC6(3), and the distribution of cathepsin B by Cy-3-labeled immunolocalization. The specific aim of our study was visualization of the spatial relationship of cell organelles as far as they contain the enzyme cathepsin B to cell morphology and motility in a 3D model of extracellular matrix. The majority of the enzyme was localized pericellularly, with no visible relationship to the direction of movement. However, substantial amounts also appeared in intramatrix pseudopodia and associated with the extracellular face of the plasma membrane, which may be indicative either of secretion and/or epicellular activity. Our approach has general applicability to study of the spatial relationships of cell compartments and their possible reorganization over time. This could open new horizons in understanding cell structure and function.

A case of linear IgA disease: an immunofluorescent study using confocal laser scan microscopy

A 79-year-old Japanese woman presented with erythema and bullae on her trunk and limbs. Histological examination of the skin lesions showed subepidermal bullae and polymorphonuclear leukocyte infiltration into the papillary dermis. A direct immunofluorescent study showed the linear deposition of IgA, but not of IgG or IgM, in the basement membrane zone. Indirect immunofluorescence of the serum using confocal laser scan microscopy showed IgA, but not IgG, reactivity in the basement membrane zone. In double immunostaining experiments, IgA reactivity was also observed on the epidermal side; laminin 5 was detected on the dermal side.

Assessment of in vivo attachment/phagocytosis by alveolar macrophages

Alveolar macrophages (AMs) are recognized as an important first line of cellular host defense within the lung. Although mechanisms underlying AM response to microorganisms or particulates are well characterized in vitro, experimental approaches to the study of AMs in vivo are limited. To circumvent these limitations, a new assay was developed using fluorescently labelled liposomes or Pneumocystis carinii (PC) organisms which were administered intratracheally into mechanically ventilated rats. After 30 min, the lungs were lavaged and the percentage of administered liposomes or PC bound to AMs was determined by quantifying fluorescence. Factors known to enhance attachment/phagocytosis by AMs in vitro were assayed to determine their effect in vivo. For example, vitronectin (VN)-coated liposomes increased attachment from 25.2 +/- 2.4% to 47.2 +/- 3.0% (p < 0.001), while addition of VN increased the binding of PC to AMs from 16.5 +/- 1.7% to 24.5 +/- 2.2% (p < 0.05). Confocal laser microscopy of cells obtained by lavage provided morphologic evidence of attachment/phagocytosis by AMs. This model will permit the quantitative assessment of the interaction of fluorescently labelled liposomes or microorganisms with AMs in the lower respiratory tract of living animals.

Surface:volume relationship in cardiac myocytes studied with confocal microscopy and membrane capacitance measurements: species-dependence and developmental effects

The quantitative analysis of the contribution of ion fluxes through membrane channels to changes of intracellular ion concentrations would benefit from the exact knowledge of the cell volume. It would allow direct correlation of ionic current measurements with simultaneous measurements of ion concentrations in individual cells. Because of various limitations of conventional light microscopy a simple method for accurate cell volume determination is lacking. We have combined the optical sectioning capabilities of fluorescence laser scanning confocal microscopy and the whole-cell patch-clamp technique to study the correlation between cell volume and membrane capacitance. Single cardiac myocytes loaded with the fluorescent dye calcein were optically sectioned to produce a series of confocal images. The volume of cardiac myocytes of three different mammalian species was determined by three-dimensional volume rendering of the confocal images. The calculated cell volumes were 30.4 +/- 7.3 pl (mean +/- SD) in rabbits (n = 28), 30.9 +/- 9.0 pl in ferrets (n = 23), and 34.4 +/- 7.0 pl in rats (n = 21), respectively. There was a positive linear correlation between membrane capacitance and cell volume in each animal species. The capacitance-volume ratios were significantly different among species (4.58 +/- 0.45 pF/pl in rabbit, 5.39 +/- 0.57 pF/pl in ferret, and 8.44 +/- 1.35 pF/pl in rat). Furthermore, the capacitance-volume ratio was dependent on the developmental stage (8.88 +/- 1.14 pF/pl in 6-month-old rats versus 6.76 +/- 0.62 pF/pl in 3-month-old rats). The data suggest that the ratio of surface area:volume of cardiac myocytes undergoes significant developmental changes and differs among mammalian species. We further established that the easily measurable parameters of cell membrane capacitance or the product of cell length and width provide reliable but species-dependent estimates for the volume of individual cells.

Resolution of sensory and mucoid glycoconjugates with terminal alpha-galactose residues in the mucomicrovillar complex of the vomeronasal sensory epithelium by dual confocal laser scanning microscopy

The organization of the mucomicrovillar complex of the vomeronasal sensory epithelium of adult rats was examined using confocal laser scanning microscopy. In specimens labeled with the FITC-conjugated isolectin B4 of Bandeiraea simplicifolia, which recognizes terminal alpha-galactose sugar residues of glycoconjugates, we demonstrated that the mucomicrovillar complex was composed of islet-like structures with a high-density alpha-galactose core. The mucomicrovillar complex was further resolved into sensory and mucoid components in double-labeling and dual scanning experiments. The sensory component, which consists of the dendritic terminals of olfactory marker protein-immunoreactive vomeronasal receptor neurons, contained cytosolic glycoconjugates with terminal alpha-galactose sugar residues. The extracellular mucoid component consisted of glycoconjugates containing terminal alpha-galactose derived from the glands associated with the vomeronasal organ. These results demonstrated the complex microchemical organization of the sensory and mucoid components of the mucomicrovillar complex.

Protein tyrosine phosphorylation during sea urchin fertilization: microtubule dynamics require tyrosine kinase activity

Protein tyrosine phosphorylation plays an important role in cell growth, mitosis, and tumorigenesis. It has also been implicated in meiotic maturation and fertilization. We have used anti-phosphotyrosine immunofluorescence and immunoblotting to identify sperm and egg proteins which are phosphorylated on tyrosine residues prior to and during sea urchin fertilization. On immunoblots of sperm proteins, the monoclonal anti-phosphotyrosine antibody detected three major proteins with molecular weights of 44, 82, and 100 kD, and six minor bands at 46, 48, 70, 76, 95, and 150 kD. These phosphotyrosyl proteins were localized to the sperm acrosomal and centriolar fossae. In contrast, staining was found globally in unfertilized eggs, and the antibody recognized two major egg phosphotyrosyl proteins of molecular weights 42 and 50 kD, and five minor bands at 40, 90, 116, 130, and 150 kD. While immunofluorescent staining remained throughout the fertilized egg cytoplasm, there were dynamic changes in the staining intensity of single bands. The 90 kD immunoreactive band increased in intensity, and the 40 and 42 kD bands disappeared by 15 min after fertilization. Loss of the 40 and 42 kD bands was due to dephosphorylation by okadaic acid-sensitive phosphatase(s). The 50 kD immunoreactive protein was unchanged up to the 8-cell stage and was still present in blastulae, indicating its importance throughout fertilization and early development. Alterations in the pattern of phosphotyrosine-containing proteins during fertilization did not depend on nascent proteins and could not be completely mimicked by increasing intracellular calcium, pH, and protein kinase C activity alone. Since changes in the fertilization pattern of phosphotyrosyl proteins occurred during formation of the sperm aster and mitotic spindle, we analyzed the role of protein tyrosine kinase activity in these processes using the tyrosine kinase specific inhibitor, erbstatin. Both the sperm aster and mitotic spindle were disrupted, indicating an involvement of tyrosine phosphorylation in these processes during interphase and mitosis. We conclude that the changes in phosphotyrosyl proteins play an important role in fertilization and early development of sea urchin eggs. Control of microtubule assembly into the sperm aster and mitotic spindle of the first cell cycle are examples of such roles.