Phosphatidylcholine exchange protein catalyzes the net transfer of phosphatidylcholine to model membranes

2-Stearoyl spin-labeled phosphatidylcholine (PC*) has been introduced into the phosphatidylcholine exchange protein from bovine liver and its electron spin resonance (ESR) spectrum determined. The spin-labeled group in the PC*- exchange protein complex was strongly immobilized. Addition of sodium deoxycholate micelles released PC* from its binding site, producing a mobile signal. This was also observed when micelles of lysophosphatidylcholine and vesicles of phosphatidic acid were added, indicating that the exchange protein can insert its endogenous PC* into interfaces devoid of phosphatidylcholine. ESR spectroscopy was used to measure transfer of PC* from spin-labeled "donor" vesicles to unlabeled "acceptor" vesicles as described by Machida & Ohnishi [Machida, K., & Ohnishi, S. (1978) Biochim. Biophys. Acta 507, 156-164]. The donor vesicles consisted of PC* and phosphatidic acid (75:25 mol%) and the acceptor vesicles of phosphatidylethanolamine and phosphatidic acid (81:19 mol%). Addition of exchange protein catalyzed a net transfer of PC* from donor to acceptor vesicles. This transfer proceeded until the acceptor vesicles contained approximately 2 mol% of PC*. A spontaneous transfer of PC* was not observed. As for the mode of action, it appears that the exchange protein, after insertion of its endogenous PC* into the acceptor, leaves the interface without a bound phospholipid molecule yet continues to shuttle PC* from donor to acceptor.     

Effect of CO2 on short-term human lymphocyte culture in vitro

Summary There was no significant difference in the mitotic indices of the cultures maintained at different CO₂ concentrations, i.e. 0%, 5% and 10%. However, considerable variation was recorded among different individuals. Supported by National Cancer Institute Contract No. 1 CP 43251.     

Murine H-2Dd-reactive monoclonal antibodies recognize shared antigenic determinant(s) on human HLA-B7 or HLA-B27 molecules or both

We have evaluated the serological relationships between the murine H-2Dd and human HLA molecules using four H-2Dd-reactive monoclonal antibodies (mAbs) produced in the A.BY (KbIbDb) anti-A.TL (KsIkDd) combination. In the mouse, these reagents exhibited three distinct reactivity patterns: Dd, Ks, and H-2u (mAb 81.L); Dd, H-2p, and H-2u (mAb 81.R); and Dd, Kd, H-2p, H-2u, and H-2v (mAbs 97.G and 97.H). Sequential immunoprecipitation and cross-competitive mAb binding experiments revealed that these mAbs recognized determinants in two spatially distinct polymorphic domains on the H-2Dd molecule of B10.A(5R) cells (defined by mAbs 81.L and 81.R, 97.H, and 97.G, respectively). MAbs 81.R, 97.G, and 97.H, but not 81.L, also defined an HLA-linked polymorphism in the human, the main characteristics of which can be summarized as follows: (i) on B lymphoblastoid cell lines, mAbs 81.R and 97.H bound to cells expressing the HLA-B7, HL-B27 or Bw40 cross-reacting specificities, (ii) on peripheral blood lymphocyte (PBL) panel mAb 81.R exerted C dependent cytotoxicity to 118 of 400 cells tested, including almost all HLA-B7 or HLA-B27 cells or both (r: 0.952), (iii) the expression of the 81.R cross-reacting determinant segregated in an informative family with the parental haplotype carrying the HLA-B7 allele, and (iv) mAbs 81.R, 97.G, and 97.H recognized topologically related determinants on the same class I molecule(s) of the human B lymphoblastoid cells JY (HLA-A2,2, -B7,7). These data support the view that some, but not all H-2Dd allotopes have been conserved throughout evolution and are associated in the human with the HLA-B7, -B27 cross-reacting specificities.     

Epidemiology of diaphragmatic hernia in Languedoc-Roussillon.

The frequency of diaphragmatic hernia (DH) varies, according to the studies, between 1/2000 and 1/7000. In the Languedoc-Roussillon (South of France), due to the presence of a Regional Foeto-Pathology Department and Medico Surgical Paediatric Department, it was possible to itemize all of the DH over a 24 month period (June 1989----May 1991). 20 children presenting DH (10 foetuses and 10 liveborns) were examined for a total population of 49.350 foetuses and liveborns (frequency of DH: 0.40/1000). 10 DH were associated with extra-pulmonary malformations (50%). 4 chromosome abnormalities were found (20%). Prenatal chromosome analysis in cases of ultrasound malformation detection has increased the number of karyotype abnormalities diagnosed.     

Kann die ?spezifisch dynamische Wirkung“ einen Beitrag zur Thermoregulation k?rnerfressender Singv?gel leisten?

Zusammenfassung 1. Respirometrische Messungen der spezifisch-dynamischen Wirkung (SDW) bei körnerfressenden Singvögeln zeigen, daß die SDW mit sinkenden Umgebungstemperaturen relativ kleiner wird. 2. Der Existenzstoffwechsel körnerfressender Singvögel weist nahrungsspezifische Unterschiede auf. Diese Unterschiede sind durch den unterschiedlichen SDW-Effekt verschiedener Nährstoffzusammensetzungen verursacht und sind von der Umgebungstemperatur abhängig: Sinken die Umgebungstemperaturen, werden die Unterschiede relativ kleiner. Diese Ergebnisse weisen darauf hin, daß körnerfressende Singvögel in der Lage sind, mit der SDW die Thermoregulation zu unterstützen.

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Can the specific dynamic action (SDA) contribute to the thermoregulation of granivorous song birds?

Summary 1. Respirometric measurements of the specific dynamic action (SDA) of granivorous song birds show that the SDA decreases relatively with dropping temperatures. 2. The existence metabolic rates of granivorous song birds show diet-related differences. These differences are caused by the SDA of different food types and are depend on the ambient temperature: With dropping ambient temperature differences become relatively smaller. These results indicate that granivorous song birds are able to use the SDA in thermoregulation.

     

Shape changes of giant liposomes induced by an asymmetric transmembrane distribution of phospholipids.

The influence of a phospholipid transmembrane redistribution on the shape of nonspherical flaccid vesicles was investigated at a fixed temperature by optical microscopy. In a first series of experiments, a transmembrane pH gradient was imposed on egg phosphatidylcholine (EPC)-egg phosphatidylglycerol (EPG) (100:1) giant vesicles. The delta pH induced an asymmetric distribution of EPG. Simultaneously, discoid vesicles were transformed into tubular or a series of connected small vesicles. The fraction of phospholipid transfer necessary for a shape change from discoid to two connected vesicles was of the order of 0.1% of the total phospholipids. Additional lipid redistribution was accompanied by a sequence of shape changes. In a second series of experiments, lyso phosphatidylcholine (L-PC) was added to, or subtracted from, the external leaflet of giant EPC vesicles. The addition of L-PC induced a change from discoid to a two-vesicle state without further evolution, suggesting that lipid transfer and lipid addition are not equivalent. L-PC depletion from the outer leaflet generated stomatocyte-like vesicles. Whenever possible, we have determined whether the giant vesicles undergoing shape changes were unilamellar or multilamellar by measuring the elastic area compressibility modulus, K, by the micropipette assay (Kwok and Evans, 1981). Shape transformations triggered by phospholipid modification of the most external bilayer were indeed influenced by the presence of other underlying membranes that played a role comparable to that of a passive cytoskeleton layer. It appears that in real cells, invaginations of the plasma membrane or budding of organelles could be triggered by a phospholipid transfer from one leaflet to the other caused, for instance, by the aminophospholipid translocase which is present in eukaryotic membranes.     

Comparative kinetics of short and long sperm in sperm dimorphic Drosophila species

All species of the Drosophila obscura group exhibit within-ejaculate sperm length dimorphism. The present work is a contribution to the understanding of sperm competition through a comparative study of sperm kinetic parameters in four of these species. Videomicrographic observations at 200 frames per second of sperm from males and females, out of the storage organ, prior or after storage were made. Drosophila sperm display both major and minor waves. The former is analysed by measuring coiling diameter (micron) and the latter by recording both beat frequency (s-1) and wave propagation velocity (micron.s-1). Results show that the 'behaviour' of short and long spermatozoa noticeably differ: short sperm kinetics remains unaltered after storage while both major and minor waves of long spermatozoa are markedly modified. Thus, evidence is provided here of a sort of "differential activation" which is assumed to result in different survival abilities of short and long sperm within the storage organ of females.