Ultrastructure of a colonial radiolarian Collozoum inerme and a cytochemical determination of the role of its zooxanthellae

Collozoum inerme (Müller) is a colonial Radiolarian containing numerous cells bound in a common gelatinous matrix. The cells do not possess a skeleton as observed in many unicellular Radiolaria, but the cytoplasmic organization is similar. The cells are multinucleate and a complex system of cellular processes containing mitochondria, Golgi, and numerous vacuoles radiate out from the nuclear region. The endoplasm is connected to the ectoplasm across a double membrane boundary by thin cytoplasmic strands called fusules whose structure resemble those in unicellular Radiolaria. The ectoplasm contains a lacy network of vacuoles containing an osmiophilic substance. Rhizopodia emerge from the ectoplasmic sheath. Some are thin and densely granular. Larger diameter rhizopodia, containing less dense cytoplasm, sequester the zooxanthellae which present a typical dinoflagellate fine structure. Some of the zooxanthellae are apparently cultivated since they are sometimes observed dividing and persist in large numbers when colonies are cultivated under illumination for several weeks in the laboratory. However, colonies maintained in the dark have a decline in number of zooxanthellae and light microscopic examination shows they are being drawn into the ectoplasm of the radiolarian cells. Electron microscopic examination of zooxanthellae drawn into the ectoplasm sheath indicates they are digested. C. inerme is a remarkable example of a simple cellular aggregate that has exploited its colonial habit to culture algae and use them as food thus possibly enhancing the viability of the colony.     

Intercentral correlations in the cerebral cortex according to the EEG coherence index after restoration of consciousness and speech following prolonged coma

Power spectra and coherence function of EEG of various cortical areas of both hemispheres were analyzed in 9 patients with extremely protracted loss of consciousness. Five patients were in the state of posttraumatic apallic syndrome lasting for more than 4 years in one patient, and 4-9 months with successive lethal outcome in 4 patients. One patient for more than 2 years was in a state of areactivity to external signals. In 3 patients the process of recovery of consciousness and speech began in 1-2 months. At the apallic syndrome, only low-frequency EEG components were present in spectrograms, and the values of coherence function were sharply decreased. With recovering consciousness and speech, a gradual appearance of alpha-activity was observed as well as an increase of coherence values at the frequency of the alpha-rhythm. The recovery of intercentral EEG relations in the motor-verbal cortical area was shown to play a special role in further normalization of connections in the cerebral cortex.     

Spatial, temporal and habitat-related variation in the abundance of large predatory fish at One Tree Reef, Australia

 Patterns of abundance of large piscivorous fish (>200 mm TL) were documented at two spatial and four temporal scales within the main lagoon of One Tree Reef on Australia’s Great Barrier Reef. Grouper (Serranidae), snapper (Lutjanidae) and wrasses (Labridae) were the most abundant large piscivores. On a large scale (hundreds of metres), patterns of predator abundance were consistently greater on the inner edge than centre of the lagoon over a range of temporal scales: days, weeks, months and years. On a small spatial scale (tens of metres), the abundance of large predatory fish was patchy. At both spatial scales, fish were consistently aggregated in particular areas and associated with specific structural features of the reef habitat. Predator abundance was high where live corals were predominant and the topography was more complex. Hence, predation pressure and its potential effects on the distribution and abundance of prey populations, both in time and space, may vary greatly within lagoonal environments. Accepted: 25 May 1997     

Perfusion method for preparing pig brain cortex for Golgi-Cox impregnation

The perfusion procedure described in this paper produces high quality impregnation of pig visual and somatosensory cortical neurons with a Golgi-Cox solution. Starting within 30 min after death, pig heads were perfused with a fixative solution composed of a mixture (v/v) of liquid phenol, 5%; formalin, 14%; ethylene glycol, 25%; methanol, 28%; and water, 28% for two periods of 4 hr each. After perfusion, the heads were chilled for at least 18 hr. The entire brain was removed from the skull and then placed in 10% buffered formalin, where it remained for at least 10 days before taking the blocks that were to be immersed in the Golgi-Cox solution. Three weeks spent in the Golgi-Cox solution typically produced uniform neuron impregnation. The tissue blocks were then embedded in celloidin and sectioned at 120 micron. This procedure avoids the following difficulties: Golgi-Cox methods that produced excellent results with rodent or primate tissue were unsuccessful with pig tissue, placing fresh tissue in Golgi-Cox solution resulted in incomplete neuron impregnation, and immersion fixation in 10% buffered formalin without perfusion resulted in excessive staining of glia.