THE OCCURRENCE AND STRUCTURE OF MICROBODIES : A Comparative Study

Livers from chickens, rats, mongrel dogs, Dalmatian dogs, and man have been examined in the electron microscope in order to compare the microbodies with the known content of uricase. It is concluded that microbodies with inclusion are present in rats, mongrel dogs, and, although the inclusion generally is smaller, in Dalmatian dogs. The inclusion has a characteristic structural appearance. These species (rat, dog) have uricase. Chickens and man lack both the enzyme uricase and the microbody inclusion. This evidence and that from previously published electron micrographs in the literature on microbodies support the notion of a positive correlation between uricase and microbodies with an inclusion. It is recommended that the term "uricosome" be used for such microbodies that have an inclusion of the appearance here described.     

Sandwich Embedding of Monolayers of Cells in Epoxy Resin for Ultrathin Sectioning

In this procedure for embedding monolayers of cells, the usual glass slides are replaced by plates of resin 1-1.5 mm thick. Unlike the open-face embedding technique, the present procedure uses only a few drops of unpolymerized resin, which are applied to the fixed and dehydrated cells. During polymerization this small amount of liquid resin spreads across a relative large area, leaves the cells covered by a very thin layer, and permits phase contrast observations through it. Ultrathin sections of a particular cell encircled by a rotary scriber can be obtained by sectioning the resin slide, which has been trimmed and mounted directly in the specimen holder of the ultramicrotome.     

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.     

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.     

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.