Measuring stomatal and guard cell metrics for plant physiology and growth using StoManager1

Automated guard cell detection and measurement are vital for understanding plant physiological performance and ecological functioning in global water and carbon cycles. Most current methods for measuring guard cells and stomata are laborious, time-consuming, prone to bias, and limited in scale. We developed StoManager1, a high-throughput tool utilizing geometrical, mathematical algorithms, and convolutional neural networks to automatically detect, count, and measure over 30 guard cell and stomatal metrics, including guard cell and stomatal area, length, width, stomatal aperture area/guard cell area, orientation, stomatal evenness, divergence, and aggregation index. Combined with leaf functional traits, some of these StoManager1-measured guard cell and stomatal metrics explained 90% and 82% of tree biomass and intrinsic water use efficiency (iWUE) variances in hardwoods, making them substantial factors in leaf physiology and tree growth. StoManager1 demonstrated exceptional precision and recall (mAP@0.5 over 0.96), effectively capturing diverse stomatal properties across over 100 species. StoManager1 facilitates the automation of measuring leaf stomatal and guard cells, enabling broader exploration of stomatal control in plant growth and adaptation to environmental stress and climate change. This has implications for global gross primary productivity (GPP) modeling and estimation, as integrating stomatal metrics can enhance predictions of plant growth and resource usage worldwide. Easily accessible open-source code and standalone Windows executable applications are available on a GitHub repository (https://github.com/JiaxinWang123/StoManager1) and Zenodo (https://doi.org/10.5281/zenodo.7686022).

Bridging structural and cell biology with cryo-electron microscopy

Most life scientists would agree that understanding how cellular processes work requires structural knowledge about the macromolecules involved. For example, deciphering the double-helical nature of DNA revealed essential aspects of how genetic information is stored, copied and repaired. Yet, being reductionist in nature, structural biology requires the purification of large amounts of macromolecules, often trimmed off larger functional units. The advent of cryogenic electron microscopy (cryo-EM) greatly facilitated the study of large, functional complexes and generally of samples that are hard to express, purify and/or crystallize. Nevertheless, cryo-EM still requires purification and thus visualization outside of the natural context in which macromolecules operate and coexist. Conversely, cell biologists have been imaging cells using a number of fast-evolving techniques that keep expanding their spatial and temporal reach, but always far from the resolution at which chemistry can be understood. Thus, structural and cell biology provide complementary, yet unconnected visions of the inner workings of cells. Here we discuss how the interplay between cryo-EM and cryo-electron tomography, as a connecting bridge to visualize macromolecules in situ, holds great promise to create comprehensive structural depictions of macromolecules as they interact in complex mixtures or, ultimately, inside the cell itself.

Super-resolution microscopy demystified

Super-resolution microscopy (SRM) bypasses the diffraction limit, a physical barrier that restricts the optical resolution to roughly 250 nm and was previously thought to be impenetrable. SRM techniques allow the visualization of subcellular organization with unprecedented detail, but also confront biologists with the challenge of selecting the best-suited approach for their particular research question. Here, we provide guidance on how to use SRM techniques advantageously for investigating cellular structures and dynamics to promote new discoveries.

Navigating challenges in the application of superresolution microscopy

In 2014, the Nobel Prize in Chemistry was awarded to three scientists who have made groundbreaking contributions to the field of superresolution (SR) microscopy (SRM). The first commercial SR microscope came to market a decade earlier, and many other commercial options have followed. As commercialization has lowered the barrier to using SRM and the awarding of the Nobel Prize has drawn attention to these methods, biologists have begun adopting SRM to address a wide range of questions in many types of specimens. There is no shortage of reviews on the fundamental principles of SRM and the remarkable achievements made with these methods. We approach SRM from another direction: we focus on the current practical limitations and compromises that must be made when designing an SRM experiment. We provide information and resources to help biologists navigate through common pitfalls in SRM specimen preparation and optimization of image acquisition as well as errors and artifacts that may compromise the reproducibility of SRM data.

Living Cells and Dynamic Molecules Observed with the Polarized Light Microscope: the Legacy of Shinya Inoué

In 1948, Shinya Inoué arrived in the United States for graduate studies at Princeton. A year later he came to Woods Hole, starting a long tradition of summer research at the Marine Biological Laboratory (MBL), which quickly became Inoué's scientific home. Primed by his Japanese mentor, Katsuma Dan, Inoué followed Dan's mantra to work with healthy, living cells, on a fundamental problem (mitosis), with a unique tool set that he refined for precise and quantitative observations (polarized light microscopy), and a fresh and brilliant mind that was unafraid of challenging current dogma. Building on this potent combination, Inoué contributed landmark observations and concepts in cell biology, including the notion that there are dynamic, fine structures inside living cells, in which molecular assemblies such as mitotic spindle fibers exist in delicate equilibrium with their molecular building blocks suspended in the cytoplasm. In the late 1970s and 1980s, Inoué and others at the MBL were instrumental in conceiving video microscopy, a groundbreaking technique which married light microscopy and electronic imaging, ushering in a revolution in how we know and what we know about living cells and the molecular mechanisms of life. Here, we recount some of Inoué's accomplishments and describe how his legacy has shaped current activities in polarized light imaging at the MBL.

Impact of New Camera Technologies on Discoveries in Cell Biology

New technologies can make previously invisible phenomena visible. Nowhere is this more obvious than in the field of light microscopy. Beginning with the observation of "animalcules" by Antonie van Leeuwenhoek, when he figured out how to achieve high magnification by shaping lenses, microscopy has advanced to this day by a continued march of discoveries driven by technical innovations. Recent advances in single-molecule-based technologies have achieved unprecedented resolution, and were the basis of the Nobel prize in Chemistry in 2014. In this article, we focus on developments in camera technologies and associated image processing that have been a major driver of technical innovations in light microscopy. We describe five types of developments in camera technology: video-based analog contrast enhancement, charge-coupled devices (CCDs), intensified sensors, electron multiplying gain, and scientific complementary metal-oxide-semiconductor cameras, which, together, have had major impacts in light microscopy.

Asymmetric axonal edge guidance: a new paradigm for building oriented neuronal networks

We present a novel kind of directional axon guides for brain-on-a-chip applications. Contrarily to previous works, the directionality in our design is created by rerouting axons growing in the unwanted direction back to their original compartment while leaving the other growth direction unaffected. This design yields state-of-the-art levels of directionality without the disadvantages of previously reported technologies.

A soft, stretchable and conductive biointerface for cell mechanobiology

In mechanobiology the study of cell response to mechanical stimuli is fundamental, and the involved processes (i.e., mechanotransduction) need to be investigated by interfacing (mechanically and electrically) with the cells in dynamic and non-invasive natural-like conditions. In this work, we present a novel soft, stretchable and conductive biointerface that allows both cell mechanical stimulation and dynamic impedance recording. The biointerface stretchability and conductivity, jointly to the biocompatibility and transparency needed to perform cell culture studies, were obtained by exploiting the formation of wrinkles on the surface of a 90 nm thick conductive layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on a pre-stretched 130 μm thick poly(dimethylsiloxane) (PDMS) substrate. Cell adhesion and proliferation of SH-SY5Y human neuroblastoma cells were evaluated, and cell differentiation on the corrugated surface was assessed. We demonstrate how the biointerface remains conductive when applying uniaxial strain up to 10%, and when cell culturing is performed. Finally, a reduction of about 30% of the relative impedance variation signal was measured, with respect to the control, as a result of the mechanical stimulation of cells.

Total internal reflection fluorescence quantification of receptor pharmacology

Total internal reflection fluorescence (TIRF) microscopy has been widely used as a single molecule imaging technique to study various fundamental aspects of cell biology, owing to its ability to selectively excite a very thin fluorescent volume immediately above the substrate on which the cells are grown. However, TIRF microscopy has found little use in high content screening due to its complexity in instrumental setup and experimental procedures. Inspired by the recent demonstration of label-free evanescent wave biosensors for cell phenotypic profiling and drug screening with high throughput, we had hypothesized and demonstrated that TIRF imaging is also amenable to receptor pharmacology profiling. This paper reviews key considerations and recent applications of TIRF imaging for pharmacology profiling.

Biological soft X-ray tomography on beamline 2.1 at the Advanced Light Source

Beamline 2.1 (XM-2) is a transmission soft X-ray microscope in sector 2 of the Advanced Light Source at Lawrence Berkeley National Laboratory. XM-2 was designed, built and is now operated by the National Center for X-ray Tomography as a National Institutes of Health Biomedical Technology Research Resource. XM-2 is equipped with a cryogenic rotation stage to enable tomographic data collection from cryo-preserved cells, including large mammalian cells. During data collection the specimen is illuminated with `water window' X-rays (284-543 eV). Illuminating photons are attenuated an order of magnitude more strongly by biomolecules than by water. Consequently, differences in molecular composition generate quantitative contrast in images of the specimen. Soft X-ray tomography is an information-rich three-dimensional imaging method that can be applied either as a standalone technique or as a component modality in correlative imaging studies.

Print-to-print: printer-enabled out-of-cleanroom multiobject microprinting method

Micropatterning techniques have gained growing interests from a broad range of engineering and biology researches as it realizes the high-throughput and highly quantitative investigations on miniature biological objects (e.g., cells and bacteria) by spatially defined micropatterns. However, most of the existing techniques rely on expensive instruments or intensive cleanroom access which may not be easy to be utilized in a regular biological laboratory. Here, we present the detailed procedures of a simple versatile microprinting process, referred to as Print-to-Print (P2P), to form multiobject micropatterns for potential biological applications. Only a solid-phase printer and custom-made superhydrophobic (SH) films are utilized for the printing and no thermal or chemical treatment is involved during the entire printing process. Moreover, the noncontact nature of droplet transferring and printing steps can be highly advantageous for sensitive biological uses. By the P2P process, a minimal feature resolution of 229 ± 17 μm has been successfully achieved. What's more, this approach has been applied to form micropatterning on various commonly used substrates in biology as well as multiobject co-patterns. In addition, the SH substrates have also been demonstrated to be reusable.

Super-resolution confocal live imaging microscopy (SCLIM) - Cutting-edge technology in cell biology

Super-resolution confocal live imaging microscopy (SCLIM) we developed provides amazingly high-speed live cell imaging at high space resolution. With this technology we are now able to observe details of membrane traffic events, including behaviors of small vesicles, cisternal maturation of the Golgi apparatus, and membrane segregation within a compartment.

Microfabricated devices for cell biology: all for one and one for all

Individual cells in their native physiological states face a dynamic multi-factorial environment. This is true of both single-celled and multi-cellular organisms. A key challenge in cell biology is the design of experimental methods and specific assays to disentangle the contribution of each of the parameters governing cell behavior. After decades of studying cells cultured in Petri dishes or on glass coverslips, researchers can now benefit from a range of recent technological developments that allow them to study cells in a variety of contexts, with different levels of complexity and control over a range of environmental parameters. These technologies include new types of microscopy for detailed imaging of large cell aggregates or even whole tissues, and the development of cell culture substrates, such as 3D matrices. Here we will review the contribution of a third type of tool, collectively known as microfabricated tools. Derived from techniques originally developed for microelectronics, these tools range in size from hundreds of microns to hundreds of nanometers.

Patterned self-assembled monolayers: efficient, chemically defined tools for cell biology

Self-assembled monolayers (SAMs) of alkanethiolates on gold can be used to carefully probe immobilized biomolecule interactions with cell-surface receptors. However, due to a lack of experimental throughput associated with labor-intensive production, specialized fabrication apparatus, and other practical challenges, alkanethiolate SAMs have not had widespread use by biological researchers. In this Minireview, we investigate a range of techniques that could enhance the throughput of SAM-based approaches by patterning substrates with arrays of different conditions. Here we highlight microfluidic, photochemical, localized removal, and backfilling techniques to locally pattern SAM substrates with biomolecules and also describe how these approaches have been applied in SAM-based screening systems. Furthermore we provide perspectives on several crucial barriers that need to be overcome to enable widespread use of SAM chemistry in biological applications.

Cell biology apps for Apple devices

Apps for touch-pad devices hold promise for guiding and supporting learning. Students may use them in the classroom or on their own for didactic instruction, just-in-time learning, or review. Since Apple touch-pad devices (i.e., iPad and iPhone) have a substantial share of the touch-pad device market (Campbell, 2012), this Feature will explore cell biology apps available from the App Store. My review includes iPad and iPhone apps available in June 2012, but does not include courses, lectures, podcasts, audiobooks, texts, or other books. I rated each app on a five-point scale (1 star = lowest; 5 stars = highest) for educational and production values; I also provide an overall score.

Nanowire-based single-cell endoscopy

One-dimensional smart probes based on nanowires and nanotubes that can safely penetrate the plasma membrane and enter biological cells are potentially useful in high-resolution and high-throughput gene and drug delivery, biosensing and single-cell electrophysiology. However, using such probes for optical communication across the cellular membrane at the subwavelength level remains limited. Here, we show that a nanowire waveguide attached to the tapered tip of an optical fibre can guide visible light into intracellular compartments of a living mammalian cell, and can also detect optical signals from subcellular regions with high spatial resolution. Furthermore, we show that through light-activated mechanisms the endoscope can deliver payloads into cells with spatial and temporal specificity. Moreover, insertion of the endoscope into cells and illumination of the guided laser did not induce any significant toxicity in the cells.

Nanoscale heating of laser irradiated single gold nanoparticles in liquid

Biological applications where nanoparticles are used in a cell environment with laser irradiation are rapidly emerging. Investigation of the localized heating effect due to the laser irradiation on the particle is required to preclude unintended thermal effects. While bulk temperature rise can be determined using macroscale measurement methods, observation of the actual temperature within the nanoscale domain around the particle is difficult and here we propose a method to measure the local temperature around a single gold nanoparticle in liquid, using white light scattering spectroscopy. Using 40-nm-diameter gold nanoparticles coated with thermo-responsive polymer, we monitored the localized heating effect through the plasmon peak shift. The shift occurs due to the temperature-dependent refractive index change in surrounding polymer medium. The results indicate that the particle experiences a temperature rise of around 10 degrees Celsius when irradiated with tightly focused irradiation of ~1 mW at 532 nm.

Double-clad hollow core photonic crystal fiber for coherent Raman endoscope

Performing label free coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) in endoscope imaging is a challenge, with huge potential clinical benefit. To date, this goal has remained inaccessible because of the inherent coherent Raman noise that is generated in the fiber itself. By developing double-clad hollow core photonic crystal fiber, we demonstrate coherent anti-Stokes Raman scattering and stimulated Raman scattering in an 'endoscope-like' scheme. Both the excitation beams and the collected CARS and SRS signals travel through the same fiber. No CARS and SRS signals are generated within the hollow core fiber even for temporally overlapping pump and Stokes beams, leading to excellent image quality. The CARS and SRS signals generated in the sample are coupled back into a high numerical aperture multimode cladding surrounding the central photonic crystal cladding. We demonstrate this scheme by imaging molecular vibrational bonds of organic crystal deposited on a glass surface.

Digital cytology: current state of the art and prospects for the future

The growth of digital methods in pathology is accelerating. Digital images can be used for a variety of applications in cytology, including rapid interpretations, primary diagnosis and second opinions, continuing education and proficiency testing. All of these functions can be performed using small static digital images, real-time dynamic digital microscopy, or whole-slide images. This review will discuss the general principles of digital pathology, its methods and applications to cytologic specimens. As cytologic specimens have unique features compared to histopathology specimens, the key differences will be discussed. Technical and administrative issues in digital pathology applications and the outlook for the future of the field will be presented.

Towards monitoring real-time cellular response using an integrated microfluidics-matrix assisted laser desorption ionisation/nanoelectrospray ionisation-ion mobility-mass spectrometry platform

The combination of microfluidic cell trapping devices with ion mobility-mass spectrometry offers the potential for elucidating in real time the dynamic responses of small populations of cells to paracrine signals, changes in metabolite levels and delivery of drugs and toxins. Preliminary experiments examining peptides in methanol and recording the interactions of yeast and Jurkat cells with their superfusate have identified instrumental set-up and control parameters and online desalting procedures. Numerous initial experiments demonstrate and validate this new instrumental platform. Future outlooks and potential applications are addressed, specifically how this instrumentation may be used for fully automated systems biology studies of the significantly interdependent, dynamic internal workings of cellular metabolic and signalling pathways.

A physicist at Woods Hole: introducing the image intensifier and image processing to cell biology

In 1963, by invitation, particle physicist George Reynolds (Princeton University) brought an image intensifier to Woods Hole Marine Biological Laboratory. Together, he and a group of biologists began experimenting with the device as a way to create images of cells in low-light level situations, especially in the study of bioluminescence. In this paper I am interested in how the scientists, a physicist and biologists in collaboration, assessed, interpreted and presented the pictures that they created with the aid of image intensification. In particular, I consider the problem of 'noise' in the image. The paper ends with an example of how Reynolds and a biologist at Woods Hole contended with the presence of noise in images used for publication. Here is an example of how data is modified, that is, enhanced, to serve as scientific evidence. By presenting an early and simple case of the altered image I reveal one way scientists addressed the potentiality of presenting inappropriately modified data - a concern that has garnered much attention in the current age of digital imaging technologies.

Guiding neuron development with planar surface gradients of substrate cues deposited using microfluidic devices

Wiring the nervous system relies on the interplay of intrinsic and extrinsic signaling molecules that control neurite extension, neuronal polarity, process maturation and experience-dependent refinement. Extrinsic signals establish and enrich neuron-neuron interactions during development. Understanding how such extrinsic cues direct neurons to establish neural connections in vitro will facilitate the development of organized neural networks for investigating the development and function of nervous system networks. Producing ordered networks of neurons with defined connectivity in vitro presents special technical challenges because the results must be compliant with the biological requirements of rewiring neural networks. Here we demonstrate the ability to form stable, instructive surface-bound gradients of laminin that guide postnatal hippocampal neuron development in vitro. Our work uses a three-channel, interconnected microfluidic device that permits the production of adlayers of planar substrates through the combination of laminar flow, diffusion and physisorption. Through simple flow modifications, a variety of patterns and gradients of laminin (LN) and fluorescein isothiocyanate-conjugated poly-l-lysine (FITC-PLL) were deposited to present neurons with an instructive substratum to guide neuronal development. We present three variations in substrate design that produce distinct growth regimens for postnatal neurons in dispersed cell cultures. In the first approach, diffusion-mediated gradients of LN were formed on cover slips to guide neurons toward increasing LN concentrations. In the second approach, a combined gradient of LN and FITC-PLL was produced using aspiration-driven laminar flow to restrict neuronal growth to a 15 microm wide growth zone at the center of the two superimposed gradients. The last approach demonstrates the capacity to combine binary lines of FITC-PLL in conjunction with surface gradients of LN and bovine serum albumin (BSA) to produce substrate adlayers that provide additional levels of control over growth. This work demonstrates the advantages of spatio-temporal fluid control for patterning surface-bound gradients using a simple microfluidics-based substrate deposition procedure. We anticipate that this microfluidics-based patterning approach will provide instructive patterns and surface-bound gradients to enable a new level of control in guiding neuron development and network formation.

Infrared imaging of an A549 cultured cell by a vibrational sum-frequency generation detected infrared super-resolution microscope

We performed infrared (IR) spectroscopic imaging of molecular species in cultured cell interiors of A549 cells using in-house developed vibrational sum-frequency generation detected IR super-resolution microscope. The spatial resolution of this IR microscope was approximately 1.1 microm, which exceeds the diffraction limit of IR light. Therefore, we clearly observed differences in the signal intensity at various IR wavelengths which appear to originate from the differing IR absorptions of specific vibrational modes, and reveal the distribution of molecular species in the single cell. These results were never imaged with the conventional IR microscope.

Macro- and microscale fluid flow systems for endothelial cell biology

Recent advances in microfluidics have brought forth new tools for studying flow-induced effects on mammalian cells, with important applications in cardiovascular, bone and cancer biology. The plethora of microscale systems developed to date demonstrate the flexibility of microfluidic designs, and showcase advantages of the microscale that are simply not available at the macroscale. However, the majority of these systems will likely not achieve widespread use in the biological laboratory due to their complexity and lack of user-friendliness. To gain widespread acceptance in the biological research community, microfluidics engineers must understand the needs of cell biologists, while biologists must be made aware of available technology. This review provides a critical evaluation of cell culture flow (CCF) systems used to study the effects of mechanical forces on endothelial cells (ECs) in vitro. To help understand the need for various designs of CCF systems, we first briefly summarize main properties of ECs and their native environments. Basic principles of various macro- and microscale systems are described and evaluated. New opportunities are uncovered for developing technologies that have potential to both improve efficiency of experimentation as well as answer important biological questions that otherwise cannot be tackled with existing systems. Finally, we discuss some of the unresolved issues related to microfluidic cell culture, suggest possible avenues of investigation that could resolve these issues, and provide an outlook for the future of microfluidics in biological research.

AC-electrokinetic applications in a biological setting

Dielectrophoresis is a phenomenon which can be exploited to provide significant quantitative electrophysiological data in a range of biochemical setting, from oncology to drug discovery. This chapter seeks to elucidate those applications and the electrophysiological phenomena underpinning those applications.

Trapping double negative particles in the ray optics regime using optical tweezers with focused beams

The capabilities of optical tweezers to trap DNG (double negative) spherical particles, with both negative permittivity and permeability, are explored in detail by analyzing some interesting theoretical features not seeing in conventional DPS (double positive) particles possessing positive refractive index. The ray optics regime is adopted and, although this regime is quite simple and limited, its validity is already known and tested for DPS particles such as biological cells and molecules trapped by highly focused beams. Simulation results confirm that even for ray optics, DNG particles present unusual and interesting trapping characteristics.

Field-based angle-resolved light-scattering study of single live cells

We perform field-based angle-resolved light-scattering measurements from single live cells. We use a laser interferometer to acquire phase and amplitude images of cells at the image plane. The angular scattering spectrum is calculated from the Fourier transform of the field transmitted through the cells. A concurrent 3D refractive index distribution of the same cells is measured using tomographic phase microscopy. By measuring transient increases in light scattering by single cells during exposure to acetic acid, we correlate the scattering properties of single cells with their refractive index distributions and show that results are in good agreement with a model based on the Born approximation.

Mathematical Models of Cell Motility

Cell motility is an essential biological action in the creation, operation and maintenance of our bodies. Developing mathematical models elucidating cell motility will greatly advance our understanding of this fundamental biological process. With accurate models it is possible to explore many permutations of the same event and concisely investigate their outcome. While great advancements have been made in experimental studies of cell motility, it now has somewhat fallen on mathematical models to taking a leading role in future developments. The obvious reason for this is the complexity of cell motility. Employing the processing power of today's computers will give researches the ability to run complex biophysical and biochemical scenarios, without the inherent difficulty and time associated with in vitro investigations. Before any great advancement can be made, the basics of cell motility will have to be well-defined. Without this, complicated mathematical models will be hindered by their inherent conjecture. This review will look at current mathematical investigations of cell motility, explore the reasoning behind such work and conclude with how best to advance this interesting and challenging research area.

Validation in the cytopathology laboratory: Its time has come

The cytology laboratory has traditionally performed a relatively small variety of tests. The testing processes employed were generally manually performed and included preparation of glass slide materials, staining of these slides, coverslipping, and microscopic evaluation of the cellular material. Instrumentation in the cytology laboratory was very limited and included a centrifuge, membrane filtration system, and possibly an automated staining machine. If instruments were added, for example, a liquid based preparation device or an automated coverslipping device; the instruments were rarely checked to assure they were operating properly before implementation into clinical practice. In addition, little documentation was maintained with regards to the instrument performance evaluation process. Increasing automation and expansion of testing options have changed how cytopathology is practiced. There are many new devices employed for the preparation of specimens, staining and coverslipping of slides, and evaluation of cellular material. The increasing use of molecular testing methods in cytopathology further adds to the changing landscape of cytopathology. New instrumentation and testing methods are routinely being introduced and the cytopathology laboratory must assure that the testing performed is accurate and consistent. Cytopathology laboratory professionals need to appreciate the value of validation of the tests we perform and the instruments we use in order to best serve the patient. Our clinical laboratory colleagues have traditionally performed validation on both instruments and test methods before using them for clinical testing. If cytopathology wants to perform the complex testing being introduced and effectively utilize new instrumentation, we need to understand the value of validation and how we apply validation to our laboratory practice.

Acoustic microscope lens modeling and its application in determining biological cell properties from single- and multi-layered cell models

The acoustic microscopy technique provides some extraordinary advantages for determining mechanical properties of living cells. It is relatively fast, of excellent spatial resolution, and of minimal invasiveness. Sound velocity is a measure of the cell stiffness. Attenuation of cytoplasm is a measure of supramolecular interactions. These parameters are of crucial interest for studying cell motility and volume regulations and to establish the functional role of the various elements of the cytoskeleton. Using a scanning acoustic microscope, longitudinal wave speed, attenuation and thickness profile of a biological cell were measured earlier by Kundu et al. [Biophys. J. 78, 2270-2279 (2000)]. In that study it was assumed that the cell properties did not change through the cell thickness but could vary in the lateral direction. In that effort the acoustic-microscope-generated signal was modeled as a plane wave striking the cell at normal incidence. Such assumptions ignored the effect of cell inhomogenity and the surface skimming Rayleigh waves. In this paper a rigorous lens model, based on the DPSM (distributed point source method), is adopted. For the first time in the literature the cell is modeled here as a multi-layered material and the effect of some external drug stimuli on a living cell is studied.

A miniaturized wide-angle 2D cytometer

BACKGROUND

We present an optical waveguide based cytometer that is capable of simultaneously collecting the light scattered by cells over a wide range of solid angles. Such comprehensive scattering data are a prerequisite for the microstructural characterization of cells.

METHODS

We use latex beads as cell mimics, and demonstrate the ability of this new cytometer to collect back-scattered light in two dimensions (2D). This cytometer is based on a liquid-core optical waveguide, excited by prism coupling, that also serves as the microfluidic channel. In principle, our use of a hemispherical lens allows the collection of scattered light from 0 to 180 degrees in 2D.

RESULTS

The experimentally observed positions of the intensity peaks of the back-scattered light agree well with theoretical prediction of scattering from both 4.0- and 9.6-mum diameter latex beads. The position of the bead, relative to the axes of the hemispherical lens and the microchannel, strongly affects the scattering pattern. We discuss a computational method for determining these offsets.

CONCLUSIONS

We show that wide-angle 2D light scattering patterns of cell-sized latex beads can be observed in a microfluidic-based optical cytometer that uses leaky waveguide mode excitation. This chip-based system is compatible with emerging chip-based technologies.

Large-scale animal cell cultures: design and operational considerations

The manufacture of biologicals, especially proteins, using large-scale culture of animal cells is becoming popular. There is a need for a rational approach to the design and scale-up of bioreactors for these applications. The ultimate requirement of any scale-up strategy should be to preserve the biological activity of these high-value molecules. With this as the central theme, the design and operation of animal cell processes has been discussed. Equal importance has been given to both the biological and the engineering aspects which need to be considered for a successful scale-up. An integrated systems approach has been stressed.

Immobilization of histidine-tagged recombinant proteins onto micropatterned surfaces for cell-based functional assays

This letter describes a method for preparing protein microarrays that allow the functional analysis of proteins at a cellular level. This method involves the utilization of recombinant proteins genetically engineered to carry a fusion tag that has an affinity for metal ions. A micropatterned alkanethiol monolayer was used to prepare a microarray having multiple spots with immobilized metal ions. The fusion protein was chelated to the spots under physiological conditions. The feasibility of the method was demonstrated by culturing neural stem cells on the microarray that displayed oligohistidine-tagged epidermal growth factor.

Centrifugal force stretcher a new of in vitro mechanical cell stimulator

A number of mechanical cell stimulators have been used to study the effect of mechanical stimulation on cells in vitro. But the efficiency of these devices is not fully desirable. We recently developed a new device for mechanical cell stimulation, the centrifugal force stretcher, and compared its efficacy with that of the traditional Flexercell Strain Unit. When the mechanical stretcher circumrotates with certain speed, cardiac myocytes attached on the plate are stretched and elongated by centrifugal force. Neonatal rat cardiac myocytes were isolated by enzymatic dissociation from the hearts of 3~5 d old Sprague Dawley rats, and were mechanically stimulated by traditional 20% stretch and 180 r/min centrifugal force for 12 and 24 h. The effects of mechanical stimulation on the hypertrophic response of neonatal rat cardiac myocytes and production of angiotensin II (Ang II) were examined. Compared with the non-stretch group, the radioactivity of (3)H-leucine incorporated into the stretch-stimulated cardiac myocytes in the centrifugal force stretch group was significantly higher [(1295.17+/-51.19) vs (1122.67+/-51.63) in 12 h; (1447.5+/-35.96) vs (1210.67+/-90.92) in 24 h, P<0.05]. Ang II was also dramatically increased by 128% in 12 h (P<0.05) and 139% in 24 h (P<0.01). After the myocytes was stretched for 24 h, the LDH level in the medium in the Flexercell Strain Unit group was significantly higher than that in the centrifugal force group [(14.5+/-8.7) U/L vs (7.8+/-4.3) U/L, P<0.05]. The centrifugal force stretcher is a new and improved mechanical cell stimulator with the same effects on the protein synthesis and Ang II secretion of the cardiac myocytes, and the damage to the cells bronght by this stimulator is relatively slighter in comparison with the Flexercell Strain Unit.

Cervical cytology automation: an update for 2003. The end of the quest nears?

The field of cytology automation, through long investigation, trial and error, and finally, commercial success and failure, has arrived at the first levels of the "grail" of improvements in accuracy and productivity in cervical cytology screening. It remains to be seen how much further the road will lead toward so-called "diagnostic" instrumentation that would actually provide us with a fully automated system of "specimen in-diagnosis out" with little, or no, human input. Will commercial ventures or academic institutions continue to support investigations to further the applications that have been developed to date? This remains to be seen and is directly dependent on parallel processes that are detailed elsewhere in this issue. Will HPV vaccines eliminate the need for screening? Possibly, but probably not for many years [70]. Will more sensitive and specific genetic or protein markers (or combinations thereof) be found to be more accurate and cost-effective? Certainly the possibility of mass screening by high-risk HPV DNA testing, as a viable alternative, is being discussed at present. Despite all of these uncertainties, the present (or nearly available) technology has the potential to improve the practice of cervical cytology. Improvements in accuracy that are necessary to provide the highest possible level of patient care and to protect practitioners from unreasonable levels of medico-legal risk are a reality. Improvements in productivity that are necessary to help in the impending labor shortage in the field of cytotechnology are also a reality. Automation is clearly the short-term solution to the most difficult of the challenges that we face.

Shanxi Province cervical cancer screening study II: Self-sampling for high-risk human papillomavirus compared to direct sampling for human papillomavirus and liquid based cervical cytology

The objective of this study was to compare the sensitivity and specificity of a new method for self-sampling for high risk human papillomavirus (HPV) with direct sampling and liquid based cervical cytology. In Shanxi Province, China, 8,497 women (ages 27-56) underwent a self-sample for HPV using a conical-shaped brush placed into the upper vagina and rotated. Three to sixteen months later the women were screened with liquid-based cytology and direct HPV tests. Subjects with any abnormal test underwent colposcopy and multiple biopsies. Mean age was 40.9 years. 4.4 percent of subjects had >or=CIN II, 26% a positive self-sample and 24% a positive direct test for HPV. The sensitivity for detection of >or=CIN II was 87.5% for self-sampling, and 96.8% for the direct test (P < 0.001). The specificity was 77.2% for the self-sample and 79.7% for the direct test. With an abnormal Pap defined as ASCUS or greater the sensitivity of the Pap for the detection of >CIN II was 88.3% and the specificity was 81.2%. We conclude that self-sampling for HPV is less sensitive for >CIN II than the direct test, but similar to liquid based cytology.

Atomic force microscopy as a tool for biomedical and biotechnological studies

This work presents different applications in progress with the aid of the atomic force microscopy (AFM) technique for biomedical and biotechnological applications, comprising both the acquisition of three-dimensional images and spectroscopic force measurements, in the following systems: first, low-density lipoprotein (LDL)-glycosaminoglycans; second, lectins-polysaccharides; third, mycobacterium leprae cellular wall and Vesicular Stomatites Virus (VSV) with fibronectin laminin, and lipidic membranes; fourth, DNA-complex; and fifth, actin, as well as the development of surface functionalizing protocols and image restoration by means of mathematical techniques.

Effect of hemoglobin polymerization on oxygen transport in hemoglobin solutions

The effect of hemoglobin (Hb) polymerization on facilitated transport of oxygen in a bovine hemoglobin-based oxygen carrier was studied using a diffusion cell. In high oxygen tension gradient experiments (HOTG) at 37 degrees C the diffusion of dissolved oxygen in polymerized Hb samples was similar to that in unpolymerized Hb solutions during oxygen uptake. However, in the oxygen release experiments, the transport by diffusion of dissolved oxygen was augmented by diffusion of oxyhemoglobin over a range of oxygen saturations. The augmentation was up to 30% in the case of polymerized Hb and up to 100% in the case of unpolymerized Hb solution. In experiments performed at constant, low oxygen tension gradients in the range of physiological significance, the augmentation effect was less than that in the HOTG experiments. Oxygen transport in polymerized Hb samples was approximately the same as that in unpolymerized samples over a wide range of oxygen tensions. However, at oxygen tensions lower than 30 mm Hg, there were more significant augmentation effects in unpolymerized bovine Hb samples than in polymerized Hb. The results presented here are the first accurate, quantitative measurements of effective diffusion coefficients for oxygen transport in hemoglobin-based oxygen carriers of the type being evaluated to replace red cells in transfusions. In all cases the oxygen carrier was found to have higher effective oxygen diffusion coefficients than blood.

Atomic force microscopy and its related techniques in biomedicine

The atomic force microscope (AFM), invented in 1986, is a new instrument which provides three-dimensional surface images of samples by scanning a sharp probing tip over the sample surface. Unlike electron microscopes (EM), the AFM has the advantage to obtain high-resolution pictures not only in a vacuous but also in a non-vacuous (i.e., air or liquid) environment. This paper reviews our recent studies on the AFM application to the biomedical fields. AFM is useful for observing biological structures such as DNA, collagen molecules, collagen fibrils and chromosomes. AFM images of living cultured cells in liquid can be used for investigating the movement of cellular processes in relation to subcellular cytoskeletal elements. Recently, numerous AFM-related microscopes, or scanning probe microscopes (SPM), have been invented in parallel with the development of the AFM itself. These microscopes allow the simultaneous collection of topographical and other (e.g., viscoelastic, near-field optical) images of samples in the same portions. Thus, the combination of AFM and the other SPM has great potential for providing valuable new findings on structure and function of cells and tissues.

A quarter century of in vitro research: a new look at exposure methods

The specific absorption rate (SAR) distributions in radio frequency-exposed solutions containing suspended or plated cells in vessels used for in vitro research were calculated by the finite-difference-time-domain method, graphed in color, and statistically analyzed in terms of uniformity for application to research on safety of wireless devices. The uniformity of SAR was quantified by visual inspection of colored plots, histograms, means, standard deviations, and maximums for the cell suspensions exposed in test tubes, Petri dishes, and rectangular flasks. Exposure sources included plane waves, transverse electromagnetic (TEM) cells, and striplines used at frequencies of 837, 2450, or 3,000 MHz. The results demonstrated that the most nonuniform SARs for plated or suspended cells in solution occurred for exposures of test tubes and rectangular flasks with plane waves, polarized for maximal absorption. The most uniform SARs for a layer of cells occurred for exposure of Petri dishes oriented for weakest coupling to the fields in a TEM cell. Additional improvement in uniformity was found to be possible by restricting the edge of the layer of cells from being too near the edges of the dish. It was not possible to achieve satisfactory uniformity in the SAR in cell suspensions exposed in standard vessels to any of the sources. The best but not satisfactory SAR uniformity was observed for cells suspended in the lowest 1-ml volume of the liquid contained in a test tube exposed at the bottom in a TEM cell. Experimental measurements of average SAR by temperature change for this case varied from 18% higher to 26% lower than finite difference time domain-derived values. The most uniform SAR distribution for cell suspensions in nonstandard containers was found for a rectangular slab configuration exposed in a stripline with the plates separated from the media by a thin layer of insulation. It is possible to experimentally implement this model by placing a fluid-filled thin-wall rectangular container tightly between the plates of a stripline.

Bio-stretch, a computerized cell strain apparatus for three-dimensional organotypic cultures

In the present study, a unique mechanical strain apparatus for three-dimensional organotypic cultures was developed into a computerized system. It consists of a personal computer running Windows-based software, the Bio-Stretch Manager, a Bio-Stretch Controller, and three sets of magnet boards. Cells are cultured on a Gelfoam sponge that is placed in a 35 mm petri dish with one end glued to the dish, and the other end attached to a coated steel bar. The petri dish is placed in front of a magnet, and the movement of the steel bar is controlled by dynamically changing the magnetic field. Up to five stretch patterns of variable frequency, duty cycle, and magnitude can be designed for each stretch regimen. Three different stretch regimens can be tested simultaneously. The operational characteristics of sponges were examined. Attachment of cells to the sponges was observed on several cell types. These features provide wide options for using this system to study the effects of mechanical stretch on cells.