Characterization of the Ss sialoglycoprotein and its antigens in Rhnull erythrocytes

The Ss sialoglycoprotein (glycophorin B) and its antigens in Rhnull erythrocytes, which lack the Rhesus blood group antigens, due to apparently silent (amorphic type) or independent suppressor (regulator type) genes, were investigated. The quantity of the molecule in amorphic and in regulator type red cell membranes was found to be decreased by about 60%-70%, as judged from sodium-dodecylsulfate polyacrylamide gel electrophoresis. The Ss glycoprotein content in the erythrocytes from heterozygotes (regulator type) was diminished to an extent of about 30%. Confirming and extending previous studies, the S, s, Ux, Uz and 'N' antigens were slightly weakened in Rhnull erythrocytes. The U and Duclos receptors were only slightly or not depressed in amorphic Rhnull cells, but almost absent from or not detectable in those of the regulator type. This demonstrates that an additional alteration, apart from the decreased Ss glycoprotein content of the membranes, accounts for the weakness of these receptors in regulator type cells. We propose the hypothesis that (a) protein(s) encoded by the Rhesus locus form(s) a complex with the Ss glycoprotein. Thus, it (they) might facilitate the incorporation of the Ss glycoprotein into the membrane and also contribute to the complete expression of the U and Duclos antigens in normal cells.     

Improved embryo yield and condition of donor ovaries in cows after PMSG superovulation with monoclonal anti-PMSG administered shortly after the preovulatory LH peak

Nonlactating Dutch-Friesian cows were selected from a local slaughterhouse and synchronized with Syncro-Mate B. Cows with a normal progesterone pattern were treated with PMSG (3,000 I.U. i.m.) on Day 10 followed by PG (Prosolvin 22.5 mg) 48 h later. Blood samples were collected daily and at hourly intervals from 30 h after PG. Monoclonal anti-PMSG (Neutra-PMSG) was administered i.v. at 5.8 h after the LH peak in 16 cows; controls (n = 16) did not receive Neutra-PMSG. For comparison, 16 additional cows were superovulated with FSH-P in decreasing doses, twice a day (total 32 mg), starting at Day 10. All cows were inseminated at 10 h after the LH peak. Embryos were evaluated on Days 6 and 7 after flushing upon slaughter (recovery 87%). The number of corpora lutea and follicles on the donor ovaries were counted. No significant differences in the concentrations of progesterone and LH were observed between the three superovulation groups. Upon Neutra-PMSG, PMSG in blood was completely neutralized, it was decreased to < 0.5 ug/l at AI from 7.0 ug/l at the LH peak. The number of transferable embryos was significantly higher after Neutra-PMSG (9.1 per cow) than without Neutra-PMSG (5.3). or upon FSH-superovulation (4.6). The number of cysts on the ovaries of Neutra-PMSG-treated cows was reduced similarly to that after FSH-superovulation. Treatment with Neutra-PMSG shortly after the LH peak positively affects final follicular maturation in PMSG-superovulated cows and results in a nearly two-fold increase of transferable embryos.     

Frequency dependence of the action-perception cycle for postural control in a moving visual environment: relative phase dynamics

When standing human subjects are exposed to a moving visual environment, the induced postural sway displays varying degrees of coherence with the visual information. In our experiment we varied the frequency of an oscillatory visual display and analysed the temporal relationship between visual motion and sway. We found that subjects maintain sizeable sway amplitudes even as temporal coherence with the display is lost. Postural sway tended to phase lead (for frequencies below 0.2 Hz) or phase lag (above 0.3 Hz). However, we also observed at a fixed frequency, highly variable phase relationships in which a preferred range of phase lags is prevalent, but phase jumps occur that return the system into the preferred range after phase has begun drifting out of the preferred regime. By comparing the results quantitatively with a dynamical model (the sine-circle map), we show that this effect can be understood as a form of relative coordination and arises through an instability of the dynamics of the action-perception cycle. Because such instabilities cannot arise in passively driven systems, we conclude that postural sway in this situation is actively generated as rhythmic movement which is coupled dynamically to the visual motion. Received: 7 September 1993/Accepted in revised form: 2 May 1994     

In vivo magnetic and electric recordings from nerve bundles and single motor units in mammalian skeletal muscle. Correlations with muscle force

Recent advances in the technology of recording magnetic fields associated with electric current flow in biological tissues have provided a means of examining action currents that is more direct and possibly more accurate than conventional electrical recording. Magnetic recordings are relatively insensitive to muscle movement, and, because the recording probes are not directly connected to the tissue, distortions of the data due to changes in the electrochemical interface between the probes and the tissue are eliminated. In vivo magnetic recordings of action currents of rat common peroneal nerve and extensor digitorum longus (EDL) muscle were obtained by a new magnetic probe and amplifier system that operates within the physiological temperature range. The magnetically recorded waveforms were compared with those obtained simultaneously by conventional, extracellular recording techniques. We used the amplitude of EDL twitch force (an index of stimulus strength) generated in response to graded stimulation of the common peroneal nerve to enable us to compare the amplitudes of magnetically recorded nerve and muscle compound action currents (NCACs and MCACs, respectively) with the amplitudes of electrically recorded nerve compound action potentials (NCAPs). High, positive correlations to stimulus strength were found for NCACs (r = 0.998), MCACs (r = 0.974), and NCAPs (r = 0.998). We also computed the correlations of EDL single motor unit twitch force with magnetically recorded single motor unit compound action currents (SMUCACs) and electrically recorded single motor unit compound action potentials (SMUCAPs) obtained with both a ring electrode and a straight wire serving as a point electrode. Only the SMUCACs had a relatively strong positive correlation (r = 0.768) with EDL twitch force. Correlations for ring and wire electrode-recorded SMUCAPs were 0.565 and -0.366, respectively. This study adds a relatively direct examination of action currents to the characterization of the normal biophysical properties of peripheral nerve, muscle, and muscle single motor units.     

Structure of the Ss blood group antigens, II: a methionine/threonine polymorphism within the N-terminal sequence of the Ss glycoprotein

The N-terminal amino acid sequence (residues 1--35) of the Ss sialoglycoprotein (or glycophorin B) from human erythrocyte membranes of defined Ss blood group activity was determined by manual sequencing methods, using N-terminal tryptic or chymotryptic glycopeptides and various secondary peptides. The proposed structure differs considerably from that suggested on the basis of work with glucopeptides of unknown Ss blood group activity (Furthmayr, Nature 271, 519--523, 1978). Only one difference between glycopeptides from Ss and ss erythrocytes was found, i.e. a methionine/threonine polymorphism at position 29. On the basis of previous work (Dahr et al., Hoppe-Seyler's Z. Physiol. Chem. 361, 145--152, 1980), it is concluded that this amino acid heterogeneity represents the Ss polymorphism rather than the UX or UZ polymorphisms, which are in strong genetic linkage disequilibrium with the Ss antigens. A part of the sequence (residues 9--30) of the major (MN) red cell membrane sialoglycoprotein (glycophorin A) was re-investigated and revised at positions 11 and 17. As judged from the present data, the first 26 residues of the Ss and the blood group N-specific MN glycoprotein are identical. The sequence 27--35 of the Ss glycoprotein shows a homology with the residues 56--64 and 59--67 of the MN glycoprotein. Data on the partial N-terminal sequence of glycopeptides from a third erythrocyte membrane sialoglycoprotein (component D or glycophorin C) indicate that its structure is different from those of the two other glycoproteins.     

Measurement of testosterone and dehydroepiandrosterone 16alpha-hydroxylase activities by a tritium exchange method.

A new isotopic method, based upon the stereospecific replacement of a proton (3H) by a hydroxyl group has been developed for the measurement of rat liver testosterone and dehydroepiandrosterone 16alpha-hydroxylase activity. Specifically 16-tritiated substrates were prepared by microbiological (Cylindrocarpon radicicola) transformation of the [16-3H]progesterone and [16-3H]pregnenolone. The incubation medium consists of a phosphate buffer (pH7; 150mM), NADPH (0.1 mM), nicotinamide (10mM) and magnesium chloride (4 mM). Tween 80 (1 mg/ml) is used to solubilize saturating concentrations of [16-3H]testosterone (50 micron) or [16-3H]dehydroepiandrosterone (100 micron). The enzymatically released tritium is recovered in the incubation medium as tritiated water which is distilled under reduced pressure and counted by liquid scintillation. The method is easy to perform, very sensitive (50 pmol of 16alpha-hydroxylated metabolites) and is independent of any further metabolism of the 16alpha-hydroxylated products.     

Evidence for an ancient chromosomal duplication in Arabidopsis thaliana by sequencing and analyzing a 400-kb contig at the APETALA2 locus on chromosome 4

As part of the European Scientists Sequencing Arabidopsis program, a contiguous region (396607 bp) located on chromosome 4 around the APETALA2 gene was sequenced. Analysis of the sequence and comparison to public databases predicts 103 genes in this area, which represents a gene density of one gene per 3.85 kb. Almost half of the genes show no significant homology to known database entries. In addition, the first 45 kb of the contig, which covers 11 genes, is similar to a region on chromosome 2, as far as coding sequences are concerned. This observation indicates that ancient duplications of large pieces of DNA have occurred in Arabidopsis.     

Synthesis, characterization and in vitro antitumor activity of di- and triorganotin derivatives of polyoxa- and biologically relevant carboxylic acids

An overview of the development of anti-tumor organotin derivatives, sometimes as active in vitro as doxorubicin, is presented and discussed. Solubility in water is an important issue, dominating the in vivo testing of compounds with promising in vitro properties. Several water-soluble organotin compounds gave the best in vitro activities. Novel, useful organotin anti-tumor compounds should be designed toward improved water solubility.