Growth of Chlorella sorokiniana at Hyperbaric Oxygen Pressures

The growth rate of Chlorella sorokiniana decreased in a linear fashion as the partial pressure of oxygen was increased from 711 to 1,478 mm of Hg. Under two atmospheres of oxygen pressure, growth ceased after 10 to 12 hr. This cessation of growth was not due to any permanent injury, as growth resumed when oxygen partial pressure was reduced to ambient levels. The inhibition occurred under both autotrophic and heterotrophic growth conditions and was not accompanied by an increase in cell size. The results indicated that the tolerance of Chlorella cells to elevated oxygen pressures was not an absolute immunity, and that inhibition of growth at very high oxygen pressures cannot be accounted for by an inhibition of photosynthesis alone.     

A limnological comparison of two small Idaho reservoirs

Summary Some limnological aspects of two small, widely fluctuating reservoirs were studied for one year. A well defined thermocline did not form in either reservoir. Annual heat budgets were about 15,000 cal/cm² for both waters. Dissolved oxygen concentrations were low on the bottom during the summer months. Both reservoirs were alkaline with the pH ranging from 7.5 to 8.9.The mean primary production summer rates of nannoplankton were 9.9 mg C/m³/hr for Crowthers Reservoir and 6.7 mg C/m³/hr for Deep Creek Reservoir. Standing crop of zooplankton was highest in Deep Creek Reservoir. Biomass of detrital heterotrophs was highest in Crowthers.

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Resumen Algunos aspectos limnológicos de dos reservorios pequeños con extensa fluctuación se estudiaron por un año. Termocline (thermocline)bien definido no se formó en uno u otro reservorio. Las acumulaciones anuales de calor fueron más o menos 15,000 cal/cm² (calorías por centímetros cuadrados) por ambas aguas. La concentración de oxígeno disuelto fué bajo en el fondo durante los meses del verano. Ambos reservorios fueron alcalinos con el pH fluctuando desde 7.5 hasta 8.9.Les clasificaciones del pequeño plankton (nannoplankton) durante la producción en el verano fueron 9.9 mg (miligramos) C/m³/hr (carbóno por metro cúbico por hora) para el Reservorio Crowthers y 6.7 mg C/m³/hr para el Reservorio Deep Creek. La cosecha fija de zooplancton fué más fuerte en el Reservorior Deep Creek. La biomasa de heterótrofo detríticos fué más fuerte en Crowthers.

     

Length of Deoxyribonucleic Acid of PBSX-like Particles of Bacillus subtilis Induced by 4-Nitroquinoline-1-Oxide

The formation of particles resembling PBSX phages was induced by 4-nitroquinoline-1-oxide in a Marburg strain of Bacillus subtilis. All particles were homogeneous in their morphology. Physical and biological analyses revealed that the deoxyribonucleic acid (DNA) carried by these particles are fragments of host-cell DNA. The contour length of the DNA is 4.25 mum, corresponding to a molecular weight of 8.1 x 10(6) daltons.     

Changes in Extracellular Amino Acids During Soman-and Kainic Acid-Induced Seizures

Extracellular amino acid levels in the rat piriform cortex, an area highly susceptible to seizure-induced neuropathology, were determined by means of intracranial microdialysis. Seizures were induced by systemic administration of either soman (O-1,2,2-trimethylpropyl methylphosphonofluoridate), a potent inhibitor of acetylcholinesterase, or the excitotoxin kainic acid. Extracellular glutamate levels increased in animals with seizures shortly after administration of either convulsant, but this change was statistically significant only in the case of soman-treated animals. Extracellular taurine levels increased markedly, reaching two- and fourfold baseline levels during the second hour of soman- and kainic acid-induced seizures, respectively. Taurine levels did not increase in the subpopulation of soman-treated animals without seizures, a finding indicating that elevation of extracellular taurine level is seizure related. Thus, we propose that taurine efflux may be a physiological cellular response to neuronal changes produced by excitotoxic chemicals, either directly or as a consequence of seizures.     

The relative rate of synthesis and levels of single-stranded DNA binding protein during induction of SOS repair in Escherichia coli

Summary Induction of the SOS response in Escherichia coli results in an increase in the relative rate of synthesis of single-stranded DNA binding protein (SSB). In contrast to RecA protein, this increase is slow and does not lead to higher SSB levels. The significance of ssb induction to SOS repair is discussed.     

Soybean root nodule ultrastructure during dark-induced stress and recovery

Summary Root-nodules of soybean plants dark-stressed for 8 days and then allowed to recover for up to 17 days were examined by transmission electron microscopy. Control nodules possessed all the ultrastructural features characteristic of infected and uninfected nodule cells. Minimal changes in the appearance of host cells and bacteroids occurred during the first four days of dark stress. After 8 days of dark stress, damage was observed in the cellular and organelle membranes; however, very few changes were observed in the bacteroids. Nodule structure continued to degrade during the first two days of recovery after which time nodules either recovered or completely degraded. In the former case, structural integrity returned to all nodule cells. In the latter case all structural integrity of the host cell disappeared; however, bacteroids appeared intact suggesting that they remained viable.Published as Paper no. 7974, Journal Series, Nebraska Agriculture Research Division.     

Differential effect of growth factors on growth stimulation and phenotypic stability of glutamine-synthetase-positive and -negative hepatocytes in primary culture

In rat liver parenchyma, two subpopulations of hepatocytes can be distinguished by the absence or presence of the marker enzyme, glutamine synthetase (GS). Hepatocytes in the perivenous zone immediately adjacent to the hepatic venules in the liver acinus are positive for GS. Using autoradiography in combination with immunocytochemistry, the response of these two hepatocyte populations (GS positive and GS negative) to a variety of growth factors (defined compounds or complex stimuli) was investigated in vitro. Irrespective of the individual growth-promoting activity (which varied considerably), all stimuli led to much higher labeling indices in GS-negative cells as compared to GS-positive cells. In GS-negative cells, the strongest effect was exerted by serum obtained from partially hepatectomized rats (labeling index, 67%) and the conditioned media of JM1 and JM2 hepatoma cells (63%-82%), followed by a combination of insulin and either norepinephrine (46%) or epidermal growth factor (EGF; 42%). In contrast, serum had the weakest influence on GS-positive cells (0.3%), while the other potent stimuli enhanced the labeling index of these cells by between 6% and 15% within 48 h. The percentage of labeled nuclei was higher in mononucleated than in binucleated GS-positive hepatocytes. The time course of thymidine incorporation was also different for the two subpopulations. Under all growth-promoting conditions, the stimulation of GS-negative cells peaked between 72 and 96 h, while it increased continuously in GS-positive cells for at least 120 h, particularly in the case of serum. In proliferating cultures, both the absolute and the relative number of GS-positive hepatocytes decreased, while no such effect was found in various nonproliferating control cultures maintained at low and high cell density. Similar results were found for GS activity. In contrast, the hormonal induction of tyrosine aminotransferase (TAT) was not affected. It is suggested that these differences in the growth response of GS-positive and -negative cells contribute to the acinar gradient in hepatocyte proliferation that occurs during liver regeneration. Furthermore, the striking phenotypic instability of GS-positive cells that have undergone DNA synthesis and mitosis supports the hypothesis that cellular reprogramming depends on passage through the cell cycle.     

In vivo recordings of neuroendocrine cells (caudo-dorsal cells) in the pond snail

Summary Ovulation and egg-laying behavior in the pond snailLymnaea stagnalis are controlled by the neuroendocrine caudodorsal cells (CDCs), constituting two clusters — one in each cerebral ganglion — totaling about 100 cells. In vitro studies have shown that the CDCs release their products, including the ovulation hormone, during a burst of spiking activity lasting for about 30 min (CDC discharge). This burst can be initiated by repeated intracellular stimulation with depolarizing current pulses, in which case the firing pattern is termed afterdischarge.Using cuff electrodes we recorded extracellularly from the intercerebral commissure, (the neurohaemal area of the CDCs) to study the activity of these cells during spontaneous egg-laying of freely behaving snails.The cuff-implanted snails showed long-lasting spiking activity prior to every bout of egg-laying. These spontaneous long-lasting discharges had several features in common with the intracellularly recorded activity of the CDCs in vitro: the time courses of spike broadening and of firing rates in the cuff-implanted animals were very similar to the characteristic patterns found in the isolated brain. Firing rates were higher and durations were longer in the cuff-implanted animals, however. In vitro, the duration of the discharge could be prolonged appreciably by recording in blood instead of normal saline, indicating that the bathing fluid normally used causes shortening of the CDC discharge. The way in which CDC discharges are triggered is discussed as a possible explanation for the differences in firing rates.The pattern of locomotion during spontaneous egg-laying was largely similar in cuff-implanted and unoperated animals. The level of locomotion was lower in the experimental animals. In addition, the rate of locomotion only partially returned to pre-oviposition levels. This is ascribed to the effect of the operation.It is concluded that the afterdischarge is the natural firing pattern of the caudodorsal cells ofLymnaea, and that this firing pattern constitutes the central event in the egg-laying behavior of this animal.Abbreviations CDC caudodorsal cells - CDCH caudodorsal cell hormone - CDCA caudodorsal cell autotransmitter     

Segregation Analyses and Gene-Centromere Distances in Zebrafish

The gol-1, gol-2, alb-1 and spa-1 mutations affect pigment pattern in the zebrafish. We show here that these loci are unlinked to each other. In addition, gene-centromere distances were determined for these loci by analysis of half-tetrads obtained by the inhibition of the second meiotic division. The fractions of tetratype (second-division segregation) tetrads range from 0.24 (spa-1) to 0.89 (gol-1). The observation of greater than 0.67 second-division segregation indicates that the zebrafish has high chiasma interference.     

Inhibition of Synaptosomal Neurotransmitter Uptake by Hallucinogens

The effect of 13 hallucinogens on the uptake of serotonin and norepinephrine into hippocampal synaptosomes and of serotonin and dopamine into caudate synaptosomes was found to be inhibitory, except for lysergic acid diethylamide and 2-bromolysergic acid diethylamide, which were inactive. The indoleal-kylamines were generally more potent than the phenylethylamines. The reported inhibition of uptake of serotonin by 5-methoxy-N,N-dimethyltryptamine and lysergic acid diethylamide into whole brain synaptosomes was not reproducible at concentrations 10² to 10⁴ times higher than those stated in the literature.