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  • 1
    Electronic Resource
    Electronic Resource
    Whistler instability in a magnetic trap (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 281-283 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The eigenvalue problem of whistler propagation in a magnetic trap is analyzed in the slab model. The plasma is comprised of three regions: (I) a≤x〈∞, (II) 0≤x≤a, and (III) −∞〈x≤0. Region II contains a hot-electron component and possesses a smaller magnetic field. The hot electrons have a temperature anisotropy and tend to destabilize the whistler mode. The dip in the magnetic field tends to confine the mode to region II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336828
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  • 2
    Electronic Resource
    Electronic Resource
    FATTY ACIDS IN FOSSIL ALGAE OF DIFFERENT GEOLOGIC AGES (1968)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 147 (1968), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1968.tb45555.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of aging on cholinephosphotransferase activity on guinea pig lung mitochondria and microsomes (1993)
    Springer
    Molecular and cellular biochemistry 121 (1993), S. 31-36 
    Details
    ISSN: 1573-4919
    Keywords: aging ; cholinephosphotransferase ; mitochondria ; microsomes ; lung ; guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract It is known that the composition of phospholipids in lung changes with age. The final step in thede novo synthesis of phosphatidylcholine, a major component of lung surfactant, by the CDP-choline pathway, requires the enzyme cholinephosphotransferase (CPT). Even though CPT has earlier been proposed to be located exclusively in the endoplasmic reticulum, we have recently demonstrated its presence also in the mitochondria. We have earlier reported a gestational variation of CPT activity in fetal mitochondria and microsomes. In the present study we examined the subcellular distribution of CPT activity in lung as a function of age. After birth, the microsomal CPT activity continued to increase until adulthood (24 wks of age), thereafter it gradually decreased. On the otherhand, the CPT activity of mitochondria continued to increase with the advancement of age and beyond 72 wks of age, it was approximately 2-fold higher than that of the microsomal fraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928697
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of calcium-dependent phospholipid-binding proteins (annexins) from guinea pig alveolar type II cells (1992)
    Springer
    Molecular and cellular biochemistry 115 (1992), S. 79-84 
    Details
    ISSN: 1573-4919
    Keywords: calcium-dependent phospholipid-binding proteins (annexins) ; lung ; alveolar type II cells ; lavage fluid ; guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A new group of calcium-regulating proteins, called annexins or Ca++-dependent phospholipid-binding proteins (PLBP), have been detected in different species, organs and cell types. In the present study, we have identified and quantitated PLBP from guinea pig lung, lavage fluid and alveolar type II cells to elucidate the possible role of PLBP in lung surfactant biogenesis and secretion. Lungs were lavaged and type II cells from lavaged lung were isolated by elastase digestion and purified by centrifugal elutriation. For the quantitative identification of PLBP, we performed ELISA assays and Western blot analysis by using an antiserum raised in guinea pigs against a pure rabbit lung 36 kDa PLBP. The lavage fluid, cytosol from lung and type II cells contained 784,167 and 435 ng per mg protein, respectively, of PLBP. The SDS-PAGE electrophoretic pattern and Western blot confirmed that all lung samples have band corresponding to a 36 kDa protein. This indicates that both alveolar type II cells and lavage fluid have higher levels of PLBP than whole lung cytosol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229099
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  • 5
    Electronic Resource
    Electronic Resource
    Heterogeneity of human red blood cell membrane: Co-existence of heavy and light membranes (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 141-149 
    Details
    ISSN: 1573-4919
    Keywords: antioxidant enzymes ; ATPases ; spectrin ; cell membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The exact chemical composition of the red blood cell (RBC) membrane may vary depending on the methods used to isolate the membrane. We provide evidence here that RBC membrane can be fractionated by differential centrifugation and/or density gradient centrifugation into two distinct types, designated as ‘heavy membrane’ (HM) and ‘light membrane’ (LM). The amount of LM is twice that of HM on a per cell basis. HM and LM differ in some biochemical and electrophoretic properties. The total activities of Na+, K+ - and Ca2+- ATPases, superoxide dismutase, glutathione peroxidase, catalase and glucose-6-phosphate and 6-phosphogluconate dehydrogenase are significantly higher in LM than HM on a per cell basis. While there is no significant difference in the specific activity of other enzymes between the two membranes, the specific activity of Ca2+-ATPase is significantly higher in HM, whereas Na+, K+-ATPase activity is higher in LM. There is a remarkable difference in the distribution of major ghost polypeptides between these two membranes. Component I of spectrin, component III and a protein with mol. wt. of 165 KDa are present in smaller amounts, whereas component II of spectrin and proteins with mol. wt. of 145, 84 and 76 KDa, respectively, are present in higher amounts in HM than LM. Some proteins such as band 4.1, 48 and 46 KDa are present only in LM, whereas some proteins with mol. wt. of 96, 78 and 43 KDa, respectively are present only in HM. It has been confirmed that these two membranes are not representatives of either (a) right side-out vs. inside out vesicles, or (b) open vs. sealed membranes. Thus HM and LM are two distinct membrane fractions. It is suggested that some part of the membrane is denser than other parts, and during hemolysis of RBCs, the rbc membrane is spliced resulting in two populations, dense and light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006932010565
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  • 6
    Electronic Resource
    Electronic Resource
    Alterations in binding characteristics of peripheral benzodiazepine receptors in testes by vitamin A deficiency in guinea pigs (2000)
    Springer
    Molecular and cellular biochemistry 211 (2000), S. 47-50 
    Details
    ISSN: 1573-4919
    Keywords: peripheral benzodiazepine receptors ; vitamin A deficiency ; testis ; guinea pigs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The correlation of vitamin A with the binding characteristics of peripheral benzodiazepine receptors (PBRs) in testes have been implicated on the basis of findings of involvement of vitamin A in testicular physiology and the abundance of PBRs in testicular tissue. Both vitamin A and PBRs are involved in the control of cell proliferation and differentiation but no data exists regarding the relationship between them. In the present study, we have examined the effects of vitamin A deficiency on the affinity and density of PBRs in testes of guinea pigs. Weanling guinea pigs were divided into three groups: control, pair-fed control and vitamin A deficient. They were fed a complete semipurified diet. The vitamin A deficient diet was similar to the control diet except vitamin A palmitate was omitted. Vitamin A deficiency status was achieved after 90 days of feeding. Binding of [3H]Ro 5-4864, a specific ligand for peripheral benzodiazepine receptors was determined in whole homogenate of testicular tissue. There was a 77% decrease in the receptor density (Bmax) in vitamin A deficient group compared to control. The Bmaxvalues for control, pair-fed control and vitamin A deficient groups were: 12.4 ± 0.4, 8.8 ± 0.2 and 3.0 ± 0.6 pmol/g, respectively. The equilibrium dissociation constant (KD) values were also 86% decreased in the vitamin A deficient group compared to the other groups. The KD values for control, pair-fed control and vitamin A deficient groups were: 3.4 ± 0.7, 2.8 ± 0.5 and 0.5 ± 0.01, respectively. The decrease in the binding characteristics of PBRs in testes due to vitamin A deficiency was accompanied with a corresponding decrease in the levels of testosterone in plasma. These results suggest a close functional relationship of vitamin A with PBRs in testes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007198330496
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  • 7
    Electronic Resource
    Electronic Resource
    β-Adrenoreceptors of multiple affinities in a clonal capillary endothelial cell line and its functional implication (1994)
    Springer
    Molecular and cellular biochemistry 140 (1994), S. 49-54 
    Details
    ISSN: 1573-4919
    Keywords: capillary endothelial cells ; β-adrenoreceptor ; cell proliferation ; endothelial cell culture ; angiogenesis ; adenylate cyclase-cAMP system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract β-Adrenoreceptor has been studied in a clonal capillary endothelial cell line established from the vascular bed of the bovine adrenal medulla. [3H]Dihydroalprenolol ([3H]DHA) binding to the isolated plasma membranes from these cells has demonstrated the presence of β-adrenoreceptors with two different affinities. the dissociation constants (Kd) have been found to be 0.27±0.09×10−9 M and 2.96±0.31×10−9 M, respectively with the corresponding Bmax of 5.1±0.05 and 70.0±0.2 pmol/mg protein, respectively. Inhibition of [3H]DHA binding to the β-receptor by atenolol (a β1-antagonist) and ICI 118,551 (a β1-antagonist) has suggested that the IC50cor (=Ki) for atenolol and ICI 118,551 for high affinity site are 0.08±0.03×10−12 M and 0.25±0.08×10−12 M, respectively. This, therefore, indicates that both atenolol and ICI 118,551 are able to displace the bound ligand effectively but the β1-selective antagonist atenolol is 3 times more potent than its β2 counterpart, ICI 118,551. Displacement of [3H]DHA binding to the endothelial cell plasma membrane by the agonists isoproterenol, epinephrine and norephinephrine has established a relative order of Ki for these agents as isoproterenol (0.56±0.19×10−9 M)〈epinephrine (0.77±0.26−9 M)〉-norepinephrine (0.71±0.24×10−9 M) for the high affinity site. The corresponding values for the low affinity site, however, are 4.62±0.64×10−9 M, 6.21±0.86×10−9 M and 5.90±0.82×10−9 M, respectively for the same agonists. Increased intracellular cAMP accompanied with cellular proliferation in the presence of isoproterenol has suggested not only the coupling of β-adrenoreceptors to the adenylate cyclase system but also its involvement in endothelial cell proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928365
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  • 8
    Electronic Resource
    Electronic Resource
    Study of properties of cholinephosphotransferase from fetal guinea pig lung mitochondria and microsomes (1991)
    Springer
    Molecular and cellular biochemistry 101 (1991), S. 157-166 
    Details
    ISSN: 1573-4919
    Keywords: cholinephosphotransferase ; mitochondria ; microsomes ; fetal lung ; guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary We have reported earlier that cholinephosphotransferase (EC 2.7.8.2) is present in both mitochondria and microsomes of fetal guinea pig lung. This study was designed to compare the properties of mitochondrial and microsomal cholinephosphotransferase in fetal guinea pig lung. Various parameters, such as substrate specificity, Km values, sensitivity to N-ethylmaleimide, dithiothreitol and trypsin were measured. Both showed significant preference for unsaturated diacylglycerols over saturated diacylglycerols. Data on Km and Vmax indicate that the affinity of this enzyme for different diacylglycerols varies between the two forms. The ID50 values for N-ethylmaleimide were 20 mM and 12.5 mM for the mitochondrial and microsomal form of the enzyme, respectively. Dithiothreitol showed an inhibitory effect on both; however, the mitochondrial form was inhibited less than the microsomal form. The effects of N-ethylmaleimide and dithiothreitol on both forms of enzyme indicated that the microsomal cholinephosphotransferase requires a higher concentration of -SH for its activity than the mitochondrial enzyme does. The enzyme was inhibited by trypsin in both mitochondria and microsome under isotonic condition suggesting that this enzyme is on the outside of the membrane in both endoplasmic reticulum and mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229532
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  • 9
    Electronic Resource
    Electronic Resource
    Role of Peripheral Benzodiazepine Receptors on Secretion of Surfactant in Guinea Pig Alveolar Type II Cells (1999)
    Springer
    Bioscience reports 19 (1999), S. 461-471 
    Details
    ISSN: 1573-4935
    Keywords: PBRs, Alveolar type II cells ; Surfactant secretion ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Granular type II cells located in the alveolar epithelium synthesize and secrete pulmonary surfactant and have specialized ion transport system. Alveolar type II cells are stimulated to secrete pulmonary surfactant by a variety of agonists. One mechanism by which extracellular signals are perceived by cells is the mobilization of intracellular Ca2+. Peripheral benzodiazepine receptors (PBRs) are present in both peripheral tissues and central nervous system. We have previously reported the presence of high density PBRs in lung and alveolar type II cells. It is known that both PBRs and beta-adrenergic receptors (beta-ARs) play an important role in cellular Ca2+ transport. Furthermore, we have suggested earlier that PBRs are someway functionally associated with the beta-ARs. The objective of the present study was to determine whether PBRs play any role in the secretion of surfactant by alveolar type II cells. Alveolar type II cells were isolated from normal weanling guinea pigs by panning method and incubated with 3H-palmitic acid in minimum essential medium to synthesize labelled dipalmitoyl phosphatidylcholine (DPPC). After washing, the cells were treated at 37°C for one hour with 10 μM isoproterenol (IP) in the presence and absence of 10 μM Ro 5-4864, an agonist for PBRs. After one hour, the release of labelled DPPC in the medium was analyzed. The control cells released DPPC without any addition of a ligand. However, the treatment of cells with IP, Ro 5-4864 and IP + Ro 5-4864 caused 24, 52 and 171% increase in the secretion of DPPC, respectively. In another experiment, type II cells were loaded with Fura-2 dye and treated with either IP or epineprine or Ro 5-4864. Both isoproterenol and epinephrine caused a significant increase in the level of cytosolic free Ca2+. However, Ro 5-4864 caused not only a decrease in the level of cytosolic free Ca2+ but also counteracted the stimulatory effect of IP. This may suggest that while ligands for ARs stimulate Ca2+ release into cytosol, the ligand for PBRs stimulates efflux of Ca2+ in alveolar type cells. Thus, the increased secretion of surfactant by the ligand of PBRs in alveolar type II cells may be mediated through its effects on increased Ca2+ efflux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020272508250
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