Photoadaptation in marine Arctic diatoms

Summary Photoadaptation in some marine Arctic diatoms has been studied. Thalassiosira antarctica, Nitzschia delicatissima and Chaetoceros furcellatus were grown at-0.5°C and various irradiances and continuous light. Growth and cellular chlorophyll were followed during transitional phase after the algae had been transferred from one irradiance to another. Adaptation time for cellular chlorophyll was linearly related to the gradient in irradiance, and adaptation to transfer from high to low light was faster than from low to high light. Adaptation time was found to be species dependent, and Arctic diatoms growing at low temperature seemed to adapt as fast as temperate species.Contribution No. 243 from Trondhjem Biological Station     

Plasminogen activator inhibitor (type-1) in rat adrenal medulla

Summary Plasminogen activator inhibitor type-1 (PAI-1) was identified in extracts of rat adrenal medulla, and its immunohistochemical localization was studied together with that of tissue-type plasminogen activator (t-PA). By staining of adjacent sections and by doublestaining of the same section we demonstrate that the same cells of the adrenal medulla contain both PAI-1 and t-PA immunoreactivity in the cytoplasm. In addition a few ganglion cells of the adrenal medulla were found to contain PAI-1 but not t-PA. Neither of the components were found in the adrenal cortex. Analysis of extracts from isolated adrenal medulla using reverse zymography showed the presence of a plasminogen activator inhibitor with M _r46000. The inhibitory activity disappeared when the extract was passed through a column with sepharose-coupled anti-PAI-1 IgG, while the run-through from a similar column coupled with preimmune IgG still contained the inhibitor. The present findings suggest that PAI-1 could play a role in the regulation of t-PA activity in the rat adrenal gland medullary cells.     

Human monocytes convert leukotriene B4 to two dihydro-leukotriene B4-metabolites

Human monocytes metabolize LTB4 by an additional pathway different from omega-oxidation. Reverse-phase high performance liquid chromatography showed four metabolites: 20-COOH-LTB4, 20-OH-LTB4 and two metabolites less polar than LTB4 with an UV maximum at 232 nm. Gas-chromatography mass-spectrometry showed nearly identical mass spectra for both metabolites. The main mass fragments of the two metabolites were increased by two mass units compared to LTB4. Our findings suggest that LTB4 had been reduced to a known and a new dihydro-metabolite of LTB4. Both metabolites together amounted to 85% of total metabolites. The remaining 15% were omega-oxidation products. Thus, the major pathway of LTB4 metabolism by human monocytes is reduction to dihydro-LTB4.     

Rabbit distal colon epithelium: III. Ca2+-activated K+ channels in basolateral plasma membrane vesicles of surface and crypt cells

Summary In the mammalian distal colon, the surface epithelium is responsible for electrolyte absorption, while the crypts are the site of secretion. This study examines the properties of electrical potential-driven⁸⁶Rb⁺ fluxes through K⁺ channels in basolateral membrane vesicles of surface and crypt cells of the rabbit distal colon epithelium. We show that Ba²⁺-sensitive, Ca²⁺-activated K⁺ channels are present in both surface and crypt cell derived vesicles with half-maximal activation at 5×10^–7 m free Ca²⁺. This suggests an important role of cytoplasmic Ca²⁺ in the regulation of the bidirectional ion fluxes in the colon epithelium.The properties of K⁺ channels in the surface cell membrane fraction differ from those of the channels in the crypt cell derived membranes. The peptide toxin apamin inhibits Ca²⁺-activated K⁺ channels exclusively in surface cell vesicles, while charybdotoxin inhibits predominantely in the crypt cell membrane fraction. Titrations with H⁺ and tetraethylammonium show that both high-and low-sensitive⁸⁶Rb⁺ flux components are present in surface cell vesicles, while the high-sensitive component is absent in the crypt cell membrane fraction. The Ba²⁺-sensitive, Ca²⁺-activated K⁺ channels can be solubilized in CHAPS and reconstituted into phospholipid vesicles. This is an essential step for further characterization of channel properties and for identification of the channel proteins in purification procedures.     

Gating in iodate-modified single cardiac Na+ channels

Summary Elementary Na⁺ currents were recorded at 19°C during 220-msec lasting step depolarizations in cell-attached and inside-out patches from cultured neonatal rat cardiocytes in order to study the modifying influence of iodate, bromate and glutaraldehyde on single cardiac Na⁺ channels.Iodate (10 mmol/liter) removed Na⁺ inactivation and caused repetitive, burst-like channel activity after treating the cytoplasmic channel surface. In contrast to normal Na⁺ channels under control conditions, iodate-modified Na⁺ channels attain two conducting states, a short-lasting one with a voltage-independent lifetime close to 1 msec and, likewise tested between –50 and +10 mV, a long-lasting one being apparently exponentially dependent on voltage. Channel modification by bromate (10 mmol/liter) and glutaraldehyde (0.5 mmol/liter) also included the occurrence of two open states. Also, burst duration depended apparently exponentially on voltage and increased when shifting the membrane in the positive direction, but there was no evidence for two bursting states. Chemically modified Na⁺ channels retain an apparently normal unitary conductance (12.8±0.5 pS). Of the two substates observed, one of them is remarkable in that it is mostly attained from full-state openings and is very short living in nature; the voltage-independent lifetime was close to 2 msec. Despite removal of inactivation, open probability progressively declined during membrane depolarization. The underlying deactivation process is strongly voltage sensitive but, in contrast to slow Na⁺ inactivation, responds to a voltage shift in the positive direction with a retardation in kinetics. Chemically modified Na⁺ channels exhibit a characteristic bursting state much shorter than in DPI-modified Na⁺ channels, a difference not consistent with the hypothesis of common kinetic properties in noninactivating Na⁺ channels.     

Unbalanced translocation between chromosomes 2 and 7 with de novo deletion of band 35 on the long arm of chromosme 2

Summary Clinical and cytogenetical findings are described in an infant with a de novo deletion of the long arm of chromosome 2. The boy's karyotype is 46,XY, rec(2)delq,t(2;7) (2pter2q34::7p217pter) (7qter7p21::2q362qter). He showed developmental retardation, low-set ears, micrognathia, short neck, abundant skin of the neck, tetralogy of Fallot, bipartite labialike scrotum, clitorislike penis, cryptorchism, and deformities of the hands and feet.     

Detection of sonar signals in the presence of pulses of masking noise by the echolocating bat,Eptesicus fuscus

Summary Two big brown bats (Eptesicus fuscus) were trained to report the presence or absence of a virtual sonar target. The bats' sensitivity to transient masking was investigated by adding 5 ms pulses of white noise delayed from 0 to 16 ms relative to the target echo. When signal and masker occurred simultaneously, the bats required a signal energy to noise spectrum level ratio of 35 dB for 50% probability of detection. When the masker was delayed by 2 ms or more there was no significant masking and echo energy could be reduced by 30 dB for the same probability of detection. The average duration of the most energetic sonar signal of each trial was measured to be 1.7 ms and 2.4 ms for the two bats, but a simple relation between detection performance and pulse duration was not found.In a different experiment the masking noise pulses coincided with the echo, and the duration of the masker was varied from 2 to 37.5 ms. The duration of the masker had little or no effect on the probability of detection.The findings are consistent with an aural integration time constant of about 2 ms, which is comparable to the duration of the cries. This is an order of magnitude less than found in backward masking experiments with humans and may be an adaptation to the special constraints of echolocation. The short time of sensitivity to masking may indicate that the broad band clicks of arctiid moths produced as a countermeasure to bat predation are unlikely to function by masking the echo of the moth.Abbreviations SPL sound pressure level - SD standard deviation - SE standard error - BW bandwidth     

NADP-Utilizing Enzymes in the Matrix of Plant Mitochondria

Purified potato tuber (Solanum tuberosum L. cv Bintie) mitochondria contain soluble, highly latent NAD⁺- and NADP⁺-isocitrate dehydrogenases, NAD⁺- and NADP⁺-malate dehydrogenases, as well as an NADPH-specific glutathione reductase (160, 25, 7200, 160, and 16 nanomoles NAD(P)H per minute and milligram protein, respectively). The two isocitrate dehydrogenase activities, but not the two malate dehydrogenase activities, could be separated by ammonium sulfate precipitation. Thus, the NADP⁺-isocitrate dehydrogenase activity is due to a separate matrix enzyme, whereas the NADP⁺-malate dehydrogenase activity is probably due to unspecificity of the NAD⁺-malate dehydrogenase. NADP⁺-specific isocitrate dehydrogenase had much lower K_ms for NADP⁺ and isocitrate (5.1 and 10.7 micromolar, respectively) than the NAD⁺-specific enzyme (101 micromolar for NAD⁺ and 184 micromolar for isocitrate). A broad activity optimum at pH 7.4 to 9.0 was found for the NADP⁺-specific isocitrate dehydrogenase whereas the NAD⁺-specific enzyme had a sharp optimum at pH 7.8. Externally added NADP⁺ stimulated both isocitrate and malate oxidation by intact mitochondria under conditions where external NADPH oxidation was inhibited. This shows that (a) NADP⁺ is taken up by the mitochondria across the inner membrane and into the matrix, and (b) NADP⁺-reducing activities of malate dehydrogenase and the NADP⁺-specific isocitrate dehydrogenase in the matrix can contribute to electron transport in intact plant mitochondria. The physiological relevance of mitochondrial NADP(H) and soluble NADP(H)-consuming enzymes is discussed in relation to other known mitochondrial NADP(H)-utilizing enzymes.     

Genetic analysis of risk in clonal populations of forest trees

Summary A major concern arising from the culture of clonally propagated crops of forest trees is risk of catastrophic loss due to an agent or event not anticipated at the time of population establishment. Since danger of such a catastrophe depends to some degree on the genetic variability within clonal mixtures, attention has been focused on the number of clones needed to keep the risk of catastrophic loss below specified levels. In this paper, we describe a genetical analysis of susceptibility to a destructive agent and the effect that frequency of genes for susceptibility have on the number of clones needed to effectively manage this risk. As a part of the analysis, parameters representing the minimum unacceptable mortality rates in plantations () and acceptable levels of risk () are defined, and their effects on the number of single-pair matings needed for the production of clonal stock are evaluated. Dominance and recessive gene action models for a single two-allele genetic locus are investigated. Probabilities for plantation failure are functions of the gene frequency for the allele conferring susceptibility. These functions converge to zero for allele frequencies less than but to one for frequencies greater than or equal to . This convergence is periodic rather than monotonie, since probabilities for plantation failure increase rather than decrease over restricted ranges of increasing numbers of clones. Recessive and dominance gene actions are found to have different effects on the minimum number of clones needed to attain acceptable risk levels. For conditions in which substantial numbers of clones are required, selecting multiple clones per mating is an effective method for reducing the number of matings necessary to achieve acceptable risks.Paper No. 12480 of the Journal Series of the North Carolina Agriculture Research Service, Raleigh, NC 27695-7643, USA