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Acoustically levitated droplets in the nanoliter to microliter range are studied in various fields. The volume measurements of these are conventionally done using image analysis. A precision-produced calibration sphere is often used to calibrate the recording equipment, which is time-consuming and expensive. This paper describes a self-calibrating method to measure the volumes of acoustically levitated droplets as a versatile and low-cost alternative. The distance between two levitated droplets in a horizontally oriented acoustic trap is processed via real-time or recorded frame data using image analysis. To assist in setting the cavity length for the acoustic trap, a simulation of the acoustic field is utilized based on the temperature in the trap, thereby also predicting the distance between the central nodes used to determine the scale factor. The volumes of the spheroidal-shaped levitated droplets can then be calculated from the pixel data. We use a modified version of the well-known TinyLev, and our method has been tested with two types of transducer packing. Its accuracy for volume measurements has been verified in comparison with the standard calibration sphere technique. Self-calibration of the system is demonstrated by changing the camera zoom during data collection, with negligible effects on measured volume. This is something that could not be achieved with conventional static methods., (© 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (https://creativecommons.org/licenses/by-nc-nd/4.0/).)

Significance: Sentinel lymph node (SLN) biopsy is an important method for metastasis staging in, e.g., patients with malignant melanoma. Tools enabling prompt histopathological analysis are expected to facilitate diagnostics; optical technologies are explored for this purpose., Aim: The objective of this exploratory study was to investigate the potential of adopting multiphoton laser scanning microscopy (MPM) together with fluorescence lifetime analysis (FLIM) for the examination of lymph node (LN) tissue ex vivo., Approach: Five LN tissue samples (three metastasis positive and two negative) were acquired from a biobank comprising tissues from melanoma patients. Tissues were deparaffinized and subjected to MPM-FLIM using an experimental MPM set-up equipped with a time correlated single photon counting module enabling FLIM., Results: The data confirm that morphological features similar to conventional histology were observed. In addition, FLIM analysis revealed elevated morphological contrast, particularly for discriminating between metastatic cells, lymphocytes, and erythrocytes., Conclusions: Taken together, the results from this investigation show promise for adopting MPM-FLIM in the context of SLN diagnostics and encourage further translational studies on fresh tissue samples.

The work presents an experiment that allows the study of many fundamental physical processes, such as photon pressure, diffraction of light or the motion of charged particles in electrical fields. In this experiment, a focused laser beam pointing upwards levitate liquid droplets. The droplets are levitated by the photon pressure of the focused laser beam which balances the gravitational force. The diffraction pattern created when illuminated with laser light can help measure the size of a trapped droplet. The charge of the trapped droplet can be determined by studying its motion when a vertically directed electrical field is applied. There are several reasons motivating this experiment to be remotely controlled. The investments required for the setup exceeds the amount normally available in undergraduate teaching laboratories. The experiment requires a laser of Class 4, which is harmful to both skin and eyes and the experiment uses voltages that are harmful.

Background and Objective: Endoscopic mucosal dissection (ESD) is a treatment option for oesophagus tumours localized to the mucosa enabling en bloc removal of large lesions. The resulting larger mucosal defects have resulted in an increase in the occurrence of post-treatment strictures. Transplantation of autologous cell sheets, cultured from oral mucosa, has been shown to prevent post-ESD strictures. The aim of the study was to assess the efficacy and safety of cell sheet transplantation after oesophageal ESD in a Western patient population where reflux-associated pre-malignant and malignant conditions predominate., Methods: Patients with Barrett's oesophagus associated high-grade dysplasia or early adenocarcinoma where ESD entailed a resection >3 cm in length and ≥75% of the circumference were eligible for treatment under hospital exemption. Cell sheets were cultured from buccal mucosa according to Good Manufacturing Practice and were endoscopically applied to the post-ESD defect directly after resection. Patients were followed with weekly endoscopy examinations, including confocal laser microscopy, for a total of four weeks., Results: Five patients were treated. ESD was extensive with resections being circumferential in three patients and 9-10 cm in length in two. The number of transplanted cell sheets ranged from two to six. Three patients developed strictures requiring two to five dilatation sessions., Conclusions: Cell sheet transplantation shows to be safe and feasible in a Western population. Results suggest that transplantation has a protective effect on the mucosal defect after ESD, decreasing both the risk for and extent of stricture formation.

Background: The use of optimized delivery devices has been shown to enhance the potency of DNA vaccines. However, further optimization of DNA vaccine delivery is needed for this vaccine modality to ultimately be efficacious in humans., Methods: Herein we evaluated antigen expression and immunogenicity after intradermal delivery of different doses of DNA vaccines by needle or by the Biojector jet-injection device, with or without the addition of electroporation (EP)., Results: Neither needle injection augmented by EP nor Biojector alone could induce higher magnitudes of immune responses after immunizations with a high dose of DNA. After division of a defined DNA dose into multiple skin sites, the humoral response was particularly enhanced by Biojector while cellular responses were particularly enhanced by EP. Furthermore, a close correlation between in vivo antigen expression and cell-mediated as well as humoral immune responses was observed., Conclusions: These results show that two optimized DNA vaccine delivery devices can act together to overcome dose restrictions of plasmid DNA vaccines.

We report on the development of an experimental platform where epi-fluorescence microscopy and optical tweezers are combined with a microfluidic system to enable the analysis of rapid cytological responses in single cells. The microfluidic system allows two different media to be merged in a Y-shaped channel. Microscale channel dimensions ensure purely laminar flow and, as a result, an environmental gradient can be created between the two media. Optical tweezers are used to move a single trapped cell repeatedly between the different environments. The cell is monitored continuously by fluorescence microscopy during the experiment. In a first experiment on yeast (Saccharomyces cerevisiae) we observed changes in cell volume as the cell was moved between environments with different osmolarity. This demonstrated that the platform allowed analysis of cytological alterations on a time scale shorter than 0.2 s. In a second experiment we observed the spatial migration of the Yap1p transcription factor fused to GFP as a cell was moved from an environment of low to high oxidative capacity. The system is universal allowing the response to numerous environmental changes to be studied on the sub second time scale in a variety of model cells. We intend to use the platform to study how the age of cells, their progression through the cell cycle, or their genetic landscape, alter their capacity (kinetics and amplitude) to respond to environmental changes.

Using a lab-on-a-chip approach we demonstrate the possibility of selecting a single cell with certain properties and following its dynamics after an environmental stimulation in real time using Raman spectroscopy. This is accomplished by combining a micro Raman set-up with optical tweezers and a microfluidic system. The latter gives full control over the media surrounding the cell, and it consists of a pattern of channels and reservoirs defined by electron beam lithography that is moulded into rubber silicon (PDMS). Different buffers can be transported through the channels using electro-osmotic flow, while the resonance Raman response of an optically trapped red blood cell (RBC) is simultaneously registered. This makes it possible to monitor the oxygenation cycle of the cell in real time and to investigate effects like photo-induced chemistry caused by the illumination. The experimental set-up has high potential for in vivo monitoring of cellular drug response using a variety of spectroscopic probes.

We demonstrate how optical tweezers can be incorporated into a multiphoton microscope to achieve three-dimensional imaging of trapped cells. The optical tweezers, formed by a cw 1064 nm Nd:YVO4 laser, were used to trap live yeast cells in suspension while the 4',6-diamidino-2-phenylindole-stained nucleus was imaged in three dimensions by use of a pulsed femtosecond laser. The trapped cell was moved in the axial direction by changing the position of an external lens, which was used to control the divergence of the trapping laser beam. This gives us a simple method to use optical tweezers in the laser scanning of confocal and multiphoton microscopes. It is further shown that the same femtosecond laser as used for the multiphoton imaging could also be used as laser scissors, allowing us to drill holes in the membrane of trapped spermatozoa.

We will demonstrate how optical tweezers can be combined with a microfluidic system to create a versatile microlaboratory. Cells are moved between reservoirs filled with different media by means of optical tweezers. We show that the cells, on a timescale of a few seconds, can be moved from one reservoir to another without the media being dragged along with them. The system is demonstrated with an experiment where we expose E. coli bacteria to different fluorescent markers. We will also discuss how the system can be used as an advanced cell sorter. It can favorably be used to sort out a small fraction of cells from a large population, in particular when advanced microscopic techniques are required to distinguish various cells. Patterns of channels and reservoirs were generated in a computer and transferred to a mask using either a sophisticated electron beam technique or a standard laser printer. Lithographic methods were applied to create microchannels in rubber silicon (PDMS). Media were transported in the channels using electroosmotic flow. The optical system consisted of a combined confocal and epi-fluorescence microscope, dual optical tweezers and a laser scalpel.

We introduce a novel setup combining a micro-Raman spectrometer with external optical tweezers, suitable for resonance Raman studies of single functional trapped cells. The system differs from earlier setups in that two separate laser beams used for trapping and Raman excitation are combined in a double-microscope configuration. This has the advantage that the wavelength and power of the trapping and probe beam can be adjusted individually to optimize the functionality of the setup and to enable the recording of resonance Raman profiles from a single trapped cell. Trapping is achieved by tightly focusing infrared (IR) diode laser radiation (830 nm) through an inverted oil-immersion objective, and resonance Raman scattering is excited by the lines of an argon:krypton ion laser. The functionality of the system is demonstrated by measurements of trapped single functional erythrocytes using different excitation lines (488.0, 514.5, and 568.2 nm) in resonance with the heme moiety and by studying spectral evolution during illumination. We found that great care has to be taken in order to avoid photodamage caused by the visible Raman excitation, whereas the IR trapping irradiation does not seem to harm the cells or alter the hemoglobin Raman spectra. Stronger photodamage is induced by Raman excitation using 488.0- and 514.5-nm irradiation, compared with excitation with the 568.2-nm line., ((c) 2004 Society of Photo-Optical Instrumentation Engineers.)

Escherichia coli cells that lack the carboxy-terminal part of FtsK fail to segregate their chromosomes properly during cytokinesis and tend to form chains. These chains are possibly formed as a result of DNA being trapped in the division planes or a failure to fuse the membrane during septum formation. If so, small molecules might diffuse between the apparent cell compartments. To investigate this theory, we developed an optical workstation that allows simultaneous imaging of and surgical operations on cellular objects in the sub-micrometre range. By surgical incisions of E. coli cell poles, diffusion of propidium iodide (PI) can be followed in real time. This analysis showed that PI was unable to diffuse from one cell equivalent to another in chain-forming ftsK mutants. Thus, the cytoplasm of the cell compartments in the chains seems to be fully separated.

The popularity of personal digital assistants (PDAs) continues to rise, due mostly to the convenience and reliability they offer caregivers.

We investigated the relationship between three factors--internal/external locus of control, self-esteem, and parental verbal interaction--for at-risk Black male adolescents in the United States. Forty-two male students in Grades 6, 7, and 8 who had been identified by their teachers as being at risk completed the Locus of Control Scale for Children (Nowicki & Strickland, 1973), the Self-Esteem Inventory (Coopersmith, 1967), and the Verbal Interaction Questionnaire (Blake, 1991). A moderate positive relationship found between self-esteem and parental verbal interaction was consistent with a previous finding for White high school students. A moderate negative relationship found between locus of control and self-esteem differed from a previous finding of no significant relationship for Black elementary children. A weak, yet significant, negative relationship was found between locus of control and parental verbal interaction.

Sex differences in the behavior of the highly predatory northern grasshopper mouse (Onychomys leucogaster) were investigated in a series of eight experiments. Female mice acquired two-way avoidance behavior more slowly, but passive avoidance more rapidly, than males. Females also buried a shock probe more completely than males and showed more escape behavior during open field testing. There were no sex differences in flinch-jump thresholds or escape from electric shock, general activity levels, or acquisition and reversal of a position discrimination. It is suggested that the sex differences in aversively motivated behavior result from an increased tendency of females to respond defensively to focal sources of aversive stimuli. The enhanced defensiveness of females may be an adaptation to higher levels of pup predation resulting from the large territories required by their predatory specialization and their association with other, more abundant, rodent species.

According to studies carried out using the optical microscope and the electron microscope quingestanol acetate, which is a powerful progestagen, modified significantly the histology and the histochemistry of the endometrium. The mechanisms of transport across the cellular membranes are not changed, but probably there is competition between the oestrogens at the binding sites as a result of which the synthesis of proteins and hydrocarbons is changed. This in turn provokes the formation of aggregations of platelets in the blood vessels and cellular degeneration starting from the onset of the cycle. The contraceptive efficiency of quingestanol acetate when it is administered by itself is due to alterations in cellular biology which it brings about at the level of the endometrium as well as due to its inhibitory effect on gonadotropins.