Bindegewebsstudien I. Die Zellformen des Hahnenkammes

A comparative study of the structure and chemistry of the retinal photoreceptors of the eye is under continuous investigation in our laboratory. A part of this study is focused on the image-forming compound eyes of the arthropods, which include the arachnids, insects, and Crustacea (13-18). T h e present report is a study of the eye structure of Leptodora kindtii, a planktonic crustacean belonging to the order Cladocera which is found in m a n y fresh-water lakes of North America, Europe, and Asia. T h e general morphology and behavior of Leptodora kindtii were described more than a halfcentury ago by Gerschler (5). Leptodora is a relatively large organism (up to 18 m m in length), nearly all transparent, with one median, spherical eye. Because of its eye structure and various types of neurons (9), as well as its general behavior to light stimuli, Leptodora is of interest to us in studies of visual physiology. M A T E R I A L S A N D M E T H O D SLeptodora kingtii were collected from a depth of 1 meter at the University of Pittsburgh Field Biology Laboratory, Lake Pymatunlng, Pennsylvania. For electron microscopy, the organisms were immediately darkadapted for 1 hour and then fixed for 30 minutes at room temperature with l per cent osmium tetroxide (OsO4) in lake water, which included 45 mg/mi of sucrose and was buffered with Veronal-acetate to pH 7.5. After fixation, the organisms were washed with distilled water, then dehydrated by a series of graded alcohols, infiltrated with Vestopal W, flat-embedded, and polmerized. To obtain a preferred orientation for sectioning, areas were cut from the embedded material with a jeweler's coping saw and remounted. Sections were cut through the crystalline cone and photorcceptor regions of the compound eye, using a glass knife on a Porter-Blum ultramlcrotome. All sections were examined with an RCA-EMU-3F microscope.To determine the reactions of Leptodora to polarized light, an experimental method similar to that used by Waterman (10) for Daphnia was adopted, in which a low voltage, 25 watt, tungsten filament bulb provided a vertical beam of white light which passed successively through a heat filter, a depolarizer, and adjustable polarizer, (Polaroid), linearly polarizing the light almost completely. The experimental vessel was a Petri dish 10 cm in diameter and 1 cm deep, painted black to eliminate any reflections from the glass. The light intensity on the surface of the dish was about 20 foot-candles. Active, swimming Leptodora (50 per dish) were focused on a photographic easel and irradiated for 5 seconds with polarized light, then photographed on a plate, 31/~ x 4 inches. This operation was followed by a dark period of 15 to 20 seconds, and then another exposure on a photographic plate was made. 95 such plates which had been exposed in this manner were developed. The negatives were enlarged by printing, and the plane of polarization was indicated on each print. To obtain the angle of polarization, a line was drawn through the long axis of each Leptodora with respect to ...

Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

THE COMPOUND EYE OF A CRUSTACEAN, LEPTODORA KINDTII

Wolken

Gallik

1965

“…4, No. 4 with relatively resistant structures such as collagen (2), muscle (3,4), or nerve myelin (5,6). In addition to this, there have been more or less successful attempts to emphasize specifically certain components of the tissue by staining before embedding (7)(8)(9).…”

mentioning

confidence: 99%

Staining of Tissue Sections for Electron Microscopy with Heavy Metals

Watson

1958

3,876

977

Heavy metals may be incorporated from solution into tissue sections for electron microscopy. The resulting increase in density of the tissue provides greatly enhanced contrast with minimal distortion. Relative densities of various structures are found to depend on the heavy metal ions present and on the conditions of staining. Certain hitherto unobserved details are revealed and some sort of specificity exists, although the factors involved are not yet understood.

“…

MATERIALS AND METHODSCastor beans (Ricinus communis) were soaked for 24 hours in distilled water and sown in moist vermiculite.

…”

mentioning

confidence: 99%

Fine Structure of Negatively Stained Plant Mitochondria

Nadakavukaren

1964

Recently investigators have reported knob-like particles on mitochondrial membranes isolated from different organisms (1,2,4,5). This report presents observations on the structure of plant mitochondria, negatively stained with phosphotungstic acid, which show knob-like projections on the membranes. MATERIALS AND METHODSCastor beans (Ricinus communis) were soaked for 24 hours in distilled water and sown in moist vermiculite. The seeds were allowed to germinate for 41/~ days in the dark at 29°C. At the end of this period, mitochondria were isolated from endosperms according to Wiskich and Bonner (6), except that the final suspension was made in de-ionized water. Geronimo and Tanner (personal communication) of this department have obtained high enzymatic activity for endosperm mitochondria isolated from castor beans in the same manner. A small drop of the mitoehondrial fraction in water was placed on an electron microscope grid with a supporting film of carbon. A filter paper was used to remove the excess water until only a thin film remained on the grid. A drop of 2 per cent phosphotungstic acid in water, adjusted to pH 6.5 with 10 per cent potassium hydroxide, was then added to this film and the excess removed as above. The grid was allowed to dry at room temperature.The electron micrographs were made in a Hitachi HU 11-A microscope using double condenser, and the photographs were taken at a screen magnification of 25,000. Structural details of mitochondrial membranes and cristae were distinguishable at an optical magnification of 140,000. RESULTSExamination of the negatively stained mitochondrial fraction in the electron microscope showed intact mitochondria as wall as membrane fragments of varying size. Usually, the surfaces of membranes in intact and disrupted mitochondria showed lollipop-like particles (Fig. 1). These particles were more pronounced on the irregular ribbon-like structures in the disrupted mitochondria than in the intact ones. No particles were seen on the outer membrane of the mimchondria. The particles seem to be composed of roughly spherical heads attached to the mitochondrial membrane by narrow stalks. The diameter of the heads falls within the 75-95 A range, and the length of the stalks, which are only occasionally clearly distinguishable (Fig. 2), within the 40-60 A range. The particles seem to be distributed at the rate of 100 per micron length of membrane surface. Occasionally, areas of the membrane appeared to be lacking the particles.