An improved method of measuring photosynthetic electron transport in Euglena under in vivo conditions

A method is described to measure photochemical activity in intact cells of Euglena under in vivo conditions. The method employs a cell wall digesting enzyme (cellulysin) to induce enough permeability in the cell walls and membranes in order to allow dyes, commonly used to investigate light-dependent electron transport reactions to enter, but without inducing a concomittant efflux of metabolites. Between 1 and 2 h of incubation in 5% (w/v) cellulysin provided conditions which allowed measurement of photosystem I-, II- and I+II-dependent electron transport with rates up to 600% higher than in control cells; whereas other cell wall degrading enzymes (cellulase and pectinase) still did not increase the entry of the dyes. Cellulysin up to 2 h of incubation had little or no effect on whole cell respiration, photosynthetic O₂ evolution, or the export of potassium and (¹⁴C) labeled compounds out of cells; therefore cellulysin obviously did not change the normal habit or physiology of Euglena. Cellulysin (4 h digestion), cellulase and pectinase (2–4 h of incubation) on the other hand led to a lowering of respiration and light-dependent O₂ evolution, and increased the efflux of K⁺, but apparently decreased that of (¹⁴C)labeled fixation products.Abbreviations DBMIB dibromothymoquinone - DCPIP 2,6-dichlorophenol-indophenol - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DMMIB 2,3-dimethyl-5,6-methylenedioxy-p-benzoquinone - MV methylviologen - PSI photosystem I - PS II photosystem II     

Ultrastructural changes in neurons and neuroglia of the avian telencephalon (Hyperstriatum Accessorium) following tri-ortho-cresyl-phosphate intoxication

Summary Ultrastructural reactions of neurons of the avian forebrain following tri-ortho-cresyl-phosphate (TOCP) poisoning are described. These neurons show a marked increase in the rough endoplasmic reticulum (RER), with RER specializations such as lamellar bodies and subsurface cisternae, as well as a proliferation of the Golgi complex and neurofilaments. In addition, an increase in the number of dense bodies and mitochondrial osmiophilia is noted. Similar changes can also be observed in the neuroglia. These alterations appear 10–13 days after TOCP ingestion.     

Lysis of growing fissin-yeast cells induced by aculeacin A,a new antifungal antibiotic

Cells of Schizosaccharomyces pombe grown in the presence of aculeacin A, a peptide antibiotic, were lysed resulting the death of cells. Under high osmolarity, the cellular lysis induced by aculeacin A was considerably reduced. The use of synchronous-culture systems distinguished cell elongation from cell division revealed that the sites of aculeacin A-induced lysis on the fission yeast were the end(s) and the cell plate region, corresponded to the regions of the cell wall synthesis. Aculeacin A-resistant survivors exhibited morphological alterations which were swollen at one or both ends of the cell and appeared drumstick or dumbbel like; the wall of the bulge region was observed to be stained with a fluorescent brightener, as well as that of the cell plate region. These effects of aculeacin A are discussed as compared with effects of 2-deoxy-D-glucose.     

Immuno-electron microscopic identification of somatostatin in cells and axons of sympathetic ganglia in the guinea pig

Summary The superior cervical ganglia (SCG), celiac superior mesenteric ganglia (CMG), and splanchnic nerve of unoperated guinea pigs, as well as both proximal and distal stumps of a previously transected branch of the postganglionic plexus of the CMG, were immunostained for somatostatin (SS). In addition, the PAP technique was adapted for fine-structural visualization of SS. A greater proportion of cells were labeled for SS in the CMG than in the SCG. PAP molecules were present in one type of intraganglionic axons. Only two labeled axons were found in the splanchnic nerve. Neither proximal nor the distal stump of the transected CMG postganglionic nerve contained labeled axons. The present results support the hypothesis that the intraganglionic axons labeled for SS arise from SS-containing intraganglionic neurons.     

Growth factor requirement of Thiobacillus novellus

Thiobacillus novellus cannot be grown in mineral salts media unless supplied with yeast extract. The requirement is only for miniscule amounts of yeast extract and is not fully expressed unless cells grown in a complex medium are allowed to multiply in a mineral salts medium for four to five generations. Individual sulfur-containing organic compounds, namely biotin, coenzyme A, and lipoic acid, but not reduced inorganic sulfur compounds, can substitute for the yeast extract requirement. Biotin can fully satisfy this requirement at a concentration insufficient to fulfill the biosynthetic sulfur needs; further, the organisms continue to incorporate ³⁵SO₄ into cellular protein in the presence of yeast extract or biotin. It is concluded that biotin is required as a growth factor and not owing to an inability to obtain sulfur from sulfate; the reasons why coenzyme A and thiamine pyrophosphate can substitute for biotin are discussed.Non-standard Abbreviations MS Mineral Salts Base     

The extinction of slowly evolving dynamical systems

The time evolution of slowly evolving discrete dynamical systems x _{i + 1} = T(r _i ,x _i ), defined on an interval [0, L], where a parameter r _ichanges slowly with respect to i is considered. For certain transformations T, once r _i reaches a critical value the system faces a non-zero probability of extinction because some x _j [0, L]. Recent ergodic theory results of Ruelle, Pianigiani, and Lasota and Yorke are used to derive a simple expression for the probability of survival of these systems. The extinction process is illustrated with two examples. One is the quadratic map, T(r, x) = rx(1 – x), and the second is a simple model for the growth of a cellular population. The survival statistics for chronic myelogenous leukemia patients are discussed in light of these extinction processes. Two other dynamical processes of biological importance, to which our results are applicable, are mentioned.     

Scanning and transmission electron microscopy of the squamose gill-filament epithelium from fresh- and seawater adaptedTilapia

Synopsis The architecture of the gill structure of variousTilapia species was studied in relation to their adaptability to hypersaline media. Using SEM and EM, it was shown that the squamose epithelial cells of the gills have species-typical patterns of ridges on their outer surfaces. These have previously been misinterpreted by other authors as microvilli or stereocillia. The ridges are more dense and better developed in euryhaline species, likeT. zillii, and less so in stenohaline species likeSarotherodon niloticus. Comparing freshwater and seawater-adapted individuals ofT. zillii, S. niloticus, S. galflaeus, andTristramella sacra, it was shown that in fresh water the surface cells are slightly swollen, extending over the openings of the chloride cells. During adaptation to sea water, these ridges become higher and denser and the cell surface shrinks, exposing the underlying orifices of the apical crypts of the chloride cells. The more euryhaline the species, the less change there is in the ridge pattern of the cells during passage from fresh to sea water. This evidence implicates the gill epithelium, together with the chloride cells, in the process of osmoregulation.     

RNA Polymerase B levels during the cell cycle ofPhysarum polycephalum

Summary Tritiated -amanitin has been used as a specific and sensitive probe to estimate the number of RNA polymerase B molecules in isolated nuclei, chromatin and nucleoids, obtained from macroplasmodia ofPhysarum polycephalum. During mitosis (metaphase±10 min) there is at least 10-fold less RNA polymerase B than at all phases of the cell cycle, even if DNA replication has been blocked in vivo. It is concluded that many of the RNA polymerase B molecules leave the chromatin during decondensation of the chromosomes in telophase of the synchronous nuclear division ofPhysarum.     

The changes of nuclear position and distribution of circumferentially aligned cortical microtubules during the progression of cell cycle inAdiantum protonemata

The intracellular positions of the nucleus and of cortical, circumferentially aligned microtubules (CCAM) in filamentous, single-celled protonemata ofAdiantum capillus-veneris were determined throughout the cell cycle in the dark. When apical growth continued at G₁ phase, the nucleus migrated keeping a constant distance from the tip. When the apical growth stopped at late S or G₂ phase, the nucleus stopped moving forward and then slightly moved backward to the site of cytokinesis. The CCAM were found only in the dome of protonemal tip when growing under continuous red light; they increased in number after dark incubation for 12 hr and then decreased after 20th hr in the dark. The CCAM were usually observed in the region between the nucleus and the tip at 28 hr in the dark. They were located around the nuclear region at pre-prophase and prophase, but then totally disappeared at metaphase and thereafter.