Flow microchamber for the Linnic interference microscope

A flow microchamber for the Linnic microscope was constructed. The volume of the microchamber is 6-10 microliters. The microchamber may be used in two working regimes: (a) under conditions of periodical change of solutions during the analysis of the same object and (b) under conditions of continuous flow of solutions. The microchamber was used for studying the birefringence of skeletal muscle sarcomere at rigor and relaxed states.     

A scanning electron microscope technique for restoring deformed fossils

Deformed fossils which originally had a regular geometric outline, such as crinoid columnals, can be restored using a scanning electron microscope technique called tilt correction. This magnifies the specimen in one direction only. It is unsuitable for specimens where deformation has occurred unevenly and can also distort small structures while restoring the whole specimen. D Crinoid columnals, scanning electron microscope, tilt correction.     

Parallel stranded DNA under scanning tunnelling microscope: the main characteristics of the double helix.

Using the scanning tunnelling microscopy we have directly observed the parallel stranded DNA of 43 bp in length, containing alternating AT-stretches. The double helix is right-handed and has the same width of each grooves equal to 17.4 A. The average pitch of the helical turn is about 34 A. The parallel double helix possesses no more than 8.6 bases per one turn. The diameter of the parallel stranded DNA molecule is 17-18 A. We conclude that in parallel DNA double helix the angle between N-glycoside bounds in trans-Crick-Watson base pairs is close to 180 degrees.     

Morphological investigation of Toxoplasma gondii in vivo by a multiple beam interference microscope.

A recently developed technique, namely multiple beam interference microscopy, has been applied to investigate the morphology of the parasite Toxoplasma gondii for the first time. The interference pattern obtained from the multiple internal reflection of a T. gondii, sandwiched between a glass plate and a cover plate, was focused on the objective of a conventional microscope. Because of the enhance contrast, several details of sub cellular structure and separating compartments are clearly visible. Details reveal the presence of a nucleus, lipid body, dense granule, rhoptry and amylopectin. The wall thickness of the membrane of the lipid body and the amylopectin is of the order of 0.02 microm and can be clearly distinguished with the help of the present technique. The same parasite has also been examined with the help of atomic force microscopy, and because of its thick membrane, the inner structural details were not observed at all. Sub cellular details of T. gondii observed with the present technique have been reported earlier only by low amplification transmission electron microscopy and not by any optical microscopic technique.     

Design for a fast fluorescence laser scanning microscope

The design of a fast fluorescence laser scanning microscope is described and illustrated, with discussion of the design consideration of the principal components, including the optical elements. The system, now under construction at the Optical Sciences Center of the University of Arizona, is expected to provide very-high-speed scanning, at a high spatial sampling density, of large object areas while retaining a flexibility of applications. The projected scanning rate approximates the rate achieved by flow cytometry; the projected rates of information generation should be orders of magnitude higher.     

Probing chromatin with the scanning force microscope

With the scanning force microscope (SFM), one can image the topography of biological material adsorbed at air-solid or liquid-solid interfaces with up to nanometer resolution. In principle, fixation, contrast enhancement, and labeling are not required. We have adapted specimen preparation techniques of conventional electron microscopy for visualizing chromatin ultra-structures in the SFM. A beaded substructure of the nucleoprotein filament was obtained after hypotonic lysis of chicken erythrocytes and air drying. The beads-on-astring morphology of the basic nucleosomal assembly was well delineated. The nucleosomes appeared as round protrusions with an apparent height of 4–6 nm. The histogram of center-to-center distances between adjacent nucleosome cores along the filament axis had a peak at 30 nm. Reversible changes in the three-dimensional structure were observed upon exposure of airdried samples of metaphase chromosomes to solutions of different ionic strengths.     

A scanning electron microscope study of microvascular anastomoses.

The abdominal aortas of 30 rats were sutured under an operating microscope. The results were studied under a scanning electron microscope at 8 different periods after operation, ranging from 3 minutes to one month. The observations are presented.     

A scanning near-field optical microscope approach to biomolecule patterning

In view of future generations of biosensors and advanced biomaterials, photochemistry in the near field using scanning near-field optical microscopy is investigated. The potential of direct near-field-induced photoactivation is demonstrated on standard photoresist. Photoimmobilization of maleimidoaryldiazirine on silicon substrates and bovine serum albumin on glass substrates is achieved, opening the way to a controlled biopatterning of surfaces with submicrometer feature size. The obtained patterns are characterized using atomic force microscopy, time-of-flight secondary ion mass spectroscopy (ToF-SIMS), and near-field fluorescence microscopy.     

Cosmos pollen ontogeny: A scanning electron microscope study

Summary Ontogenetic data concerning pollen not only clarifies the mode of deposition of the elaborate walls but has considerable functional and taxonomic relevance. Hitherto such studies have used optical or transmission electron microscopy but here a recently devised preparative technique has enabled pollen development inCosmos bipinnatus to be studied using the scanning electron microscope. The technique involves freeze-fracturing of osmium fixed, cryoprotected anthers, maceration in dilute osmium tetroxide, critical point drying, sputter coating and examination. The processes of pollen wall development can then be observed in three dimensions, an important aid to understanding the spatial relationships involved in the determination of ornamentation and apertures. Details of the pollen and tapetum are described at various stages between meiosis and anthesis. A close conformity is demonstrated between the results obtained and those of earlier transmission electron microscopic studies of the same and related species although very different interpretations are made.