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Biomedical subjects

V B Meyer-Rochow

Publications and source records attributed to V B Meyer-Rochow.

13 recordsLinked to original sources
PubMed1992

A light- and electron-microscopic study of the pineal complex of the ammocoete larva of the southern lamprey Geotria australis.

The pineal complex of larval Geotria australis lampreys has been examined by light- and electron-microscopy. The complex consists of a pineal organ and a smaller parapineal organ, the former being situated dorsal to the latter. It is concluded that the pineal organ is a functioning photoreceptor, with neural and endocrine output. The parapineal appears to be a more basic neuroendocrine organ without photosensory capability. Day-night comparisons of the pineal complex show no obvious differences in ultrastructure; this could be related to the chronobiological role of the complex as a constant monitor of ambient light levels, rather than a mere visual receptor that changes its sensitivity at night.

Animals↗
PubMed1992

Observations on an accidental case of raw sewage pollution in Antarctica.

The effects of an accidental exposure to saltwater polluted by human wastes on aquarium populations of a variety of Antarctic organisms are described. Only the giant Antarctic slater Glyptonotus antarcticus survived the exposure to the contaminated water unharmed. A comparative analysis of water qualities revealed that total nitrogen and phosphorus levels of the contaminated sample were 15 and 19.5 times higher than those of the control and that the contaminated sample contained high amounts of coliform bacteria, whereas the latter were not identified in the control. Considering the widespread practice in Antarctica of disposing of raw sewage into the sea, the dearth of knowledge concerning the biological impact of such behaviour is seen as worrysome.

Accidents↗
PubMed1991

Nephroblastoma in the clawed frog Xenopus laevis.

One 2.5-3 year old female clawed frog (Xenopus laevis), out of a consignment of 4,000 frogs, was found to have an abnormal abdominal growth, weighing 7.9 g. The growth was examined histologically and on the basis of the abundant stroma and serially-arranged tubules nephroblastoma was diagnosed. The growth is not considered to be transmissible.

Animals↗
PubMed1978

The eyes of mesopelagic crustaceans. III. Thysanopoda tricuspidata (Euphausiacea).

The compound eyes of the mesopelagic eupausiid Thysanopoda tricuspidata were investigated by light-, scanning-, and transmission electron microscopy. The eyes are spherical and have a diameter that corresponds to 1/6 of the carapace length. The hexagonal facets have strongly curved outer surfaces. Although there are four crystalline cone cells, only two participate in the formation of the cone, which is 90-120 micrometer long and appears to have a radial gradient of refractive index. The clear zone, separating dioptric structures and retinula, is only 90-120 micrometer wide. In it lie the very large oval nuclei of the seven retinula cells. Directly in front of the 70 micrometer long and 15 micrometer thick rhabdom a lens-like structure of 12 micrometer diameter is developed. This structure, known in only a very few arthropods, seems to be present in all species of Euphausiacea studied to date. It is believed that the rhabdom lens improves near-field vision and absolute light sensitivity. Rod-shaped pigment grains and mitochondria of the tubular type are found in the plasma of retinula cells. The position of the proximal screening pigment as well as the microvillar organization in the rhabdom are indicative of light-adapted material. The orthogonal alignment of rhabdovilli suggests polarization sensitivity. Behind each rabdom there is a cup-shaped homogenous structure of unknown, but possibly optical function. Finally, the structure and the function of the euphysiid eye are reviewed and the functional implications of individual components are discussed.

Biological Evolution↗
PubMed1978

The eyes of mesopelagic crustaceans. II. Streetsia challengeri (amphipoda).

In Streetsia challengeri left and right eyes have fused and become a single cylindrical photoreceptor, which occupies the basal half of a forward directed head projection. This unusual compound eye consists of approximately 2500 ommatidia, which are arranged in such a way that the animal has almost circumferential vision, but cannot look ahead or behind. It is thought that the eye operates on light-guide principles, and that the crystalline cones are the major dioptric component. Ommatidia in anterior-posterior rows show a greater overlap of visual fields than dorso-ventrally arranged ommatidia. Cone layer and retinula are separated by a 4 micrometer thick screen-membrane, which contains tiny pigment granules of 0.15 micrometer diameter. Cells of unknown function and origin, containing unusual multitubular organelles, are regularly found near the proximal ends of the crystalline cone threads. The twisted rhabdoms measure 18--20 micrometer in diameter, and consist of microvilli 0.05 micrometer in width, which belong to five retinula cells and which show no trace of disintegration. The position of interommatidial screening pigment, the density of retinula cell vesicles and inclusions, and the narrowness of the perirhabdomal space all suggest that the eyes have been light-adapted at the time of fixation for electron microscopy. The retinula cell nuclei lie on the proximal side of the heavily pigmented basement membrane. A tapetum or basal retinula cells are not developed. It is concluded that the eye optimally combines acuity with sensitivity, and that for distance estimation parallax may be important.

Animals↗
PubMed1978

Visual behavior, eye and retina of the parasitic fish Carapus mourlani.

1. This is the first transmission electron microscope description of the retina of a parasitic fish. 2. The retina is well supplied with capillaries, some of which occur on the inner surface of the retina. An unusual and possibly primitive type of capillary junction is described. 3. The outer segments of the retina of Carapus mourlani, which measure approximately 2 micron in diameter, are of one type only. A certain degree of banking was observed. Outer segments are not isolated from each other by screening pigments; they are, however, surrounded by about 15 calycal processes. 4. Typical spheroids or conoids were not seen in the outer plexiform layer. The inner nuclear layer consists of only one or two layers of nuclei. The inner plexiform layer is unusually wide and some amacrine synapses can be identified. There are few ganglion cells and the ratio of nuclei in the outer nuclear layer to those of the inner nuclear layer to ganglion cells is approximately 100:10:1. 5. The eye of C. mourlani combines features of degenerated photoreceptors, characteristic of cave-organisms, with adaptations which are commonly found in nocturnal and deep-sea forms. 6. The visual behavior of the animal indicates that the eye is fully functional in spite of its corneal keratosis and small number of optic nerve fibers.

Animals↗
PubMed1977

The eyes of mesopelagic crustaceans: I. Gennadas sp. (penaeidae).

The eye of the deep-sea penaeid shrimp Gennadas consists of approximately 700 square ommatidia with a side length of 15 micrometer. It is hemispherical in shape and is located at the end of a 1.5 mm long eye stalk. The cornea is extremely thin, but the crystalline cone is well-developed. A clear zone between dioptric structures and the rhabdom layer is absent. A few pigment granules are found within the basement membrane; otherwise they, too, are absent from the eye of Gennadas. The rhabdom is massive and occupies 50% of the eye. It consists of orthogonally oriented microvilli (the latter measuring 0.07 micrometer in diameter) and is 75 micrometer long. In cross sections adjacent rhabdoms, all approximately 8 micrometer in diameter, form an almost continuous sheet and leave little space for retinula cell cytoplasm. In spite of a one h exposure to light, rhabdom microvilli show no disintegration or disruption of membranes. Vesicles of various kinds, however, are present in all seven retinula cells near the basement membrane. Bundles of seven axons penetrate the basement membrane. On their way to the lamina they often combine and form larger aggregations.

Animals↗
PubMed1975

Larval and adult eye of the western rock lobster (Panulirus longipes).

A number of differences exists between the compound eyes of larval and adult rock lobsters, Panulirus longipes. The larval eye more closely resembles the apposition type of compound eye, in which retinula cells and rhabdom lie immediately below the cone cells. The adult eye, on the other hand, is a typical clear-zone photoreceptor in which cones and retinula cell layers are separated by a wide transparent region. The rhabdom of the larval eye, if cut longitudinally, exhibits a "banded" structure over its entire length; in the adult the banded part is confined to the distal end, and the rhabdom is tiered. Both eyes have in common an eighth, distally-located retinula cell, which possesses orthogonally-oriented microvilli, and a peculiar lens-shaped "crystal", which appears to focus light onto the narrow column of the distal rhabdom. Migration of screening pigment on dark-light adaptation is accompanied by changes in sensitivity and resolution of the eye. Retinula cells belonging to one ommatidium do not arrange into one single bundle of axons, but interweave with axons of four neighbouring facets in an extraordinarily regular fashion.

Animals↗