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Biomedical subjects

C B Lindemann

Publications and source records attributed to C B Lindemann.

28 records · Page 2Linked to original sources
PubMed1983

The interaction of cAMP with modeled bull sperm.

Demembranated and membrane disrupted bull sperm models exhibit an increase in motility when exposed to cAMP. Tritium-labeled cAMP was used to locate the initial site of action of cAMP in the modeled sperm preparations. cAMP did not bind selectively to the modeled cells, and the presence or absence of plasma membrane fragments on the models did not significantly alter this result. When suspension medium taken from modeled sperm preparations was subjected to gel filtration on Sephadex G25-150 columns, cAMP bound to a high molecular weight component that eluted with the void volume. The responsible binding factor is a soluble component that is released when the plasma membranes of the sperm are disrupted during the modeling procedure. To test the importance of the cAMP binding factor, modeled sperm were centrifuged, the supernatant solution was decanted, and the cells were resuspended in fresh medium. After this treatment the cells could be restored to motility with Mg-ATP but no longer exhibited a response to cAMP. Furthermore, addition of cAMP binding factor isolated by gel filtration partially restored the response of these sperm to cAMP. Investigation of the properties of the cAMP-binding factor have confirmed that it is specific for cAMP, with a much lower affinity for AMP and cGMP. In the presence of a large excess of unlabeled cAMP the labeled complex has a half-life of approximately 1 hour. Our results indicate that the action of cAMP on the motility of modeled sperm is mediated by its attachment to a high molecular weight, soluble component of the cell cytoplasm.

Animals↗
PubMed1980

A selective effect of Ni2+ on wave initiation in bull sperm flagella.

Bull sperm that are extracted with 0.1% Triton X-100 and restored to motility with Mg2+-ATP lose coordination and stop swimming in the presence of 0.5 mM NiSO4. Although spontaneous coordination of flagellar waves is lost after exposure to Ni2+, other functions of the flagellum remain intact. The capacity for wave propagation along the flagellum is maintained together with the capacity for microtubular sliding. Wave motility can be restored to Ni2+-inhibited sperm by inducing a permanent bend onto the flagellum by micromanipulation. In the absence of such intervention, the loss of wave coordination is complete and irreversible. Ni2+-inhibited demembranated cells that are kept active by maintaining a bend in the flagellum exhibit a normal beat frequency. Both intact and demembranated sperm can retain spontaneous wave production at considerably slower rates of motion than Ni2+-inhibited cells. Short segments from the distal tip of the flagellum contain only the 9 + 2 microtubular axoneme. These short segments are able to propagate imposed bends even in the presence of Ni2+. In addition to wave propagation Ni2+-treated sperm can be shown to exhibit a normal sliding tubule phenomenon by direct assay. Although Ni2+-treated cells have a functional sliding tubule mechanism, and consequently the axoneme can propagate bends, it appears that these retained functions are not sufficient to cause spontaneous bend initiation. Our findings show that bend initiation is inhibited by Ni2+, and therefore is an independent process separate from the sliding tubule mechanism responsible for wave propagation.

Animals↗
PubMed1975

Adenosine triphosphate-induced motility and sliding of filaments in mammalian sperm extracted with Triton X-100.

Bull sperm that had been extracted with 0.2% Triton X-100 could be reactivated with ATP, and their movement closely resembled the motion of intact live sperm. Their motility required the presence of ATP, magnesium, and a medium of suitable salt concentration and pH. When Triton-extracted bull sperm were digested breifly with trypsin at pH 9.0, they appeared to reatin most of their normal structure, but subsequent exposure of the digested sperm to ATP caused a disintegration by light microscopy, using dark-field illumination, combined with an electron microscope study of preparations of the disintegrated sperm, demonstrated the presence of an active sliding mechanism of filament interaction in bull spermatozoa. Human sperm subjected to the same procedures showed similar patterns of reactivation and of disintegration.

Adenosine Triphosphate↗
PubMed1973

The stiffness of the flagella of impaled bull sperm.

The elastic rigidity (stiffness) of impaled motionless bull sperm flagella has been determined by a manipulatory technique which permitted direct analytical treatment of the experimental system. The effects of external ATP and ADP were measured. It was found that ATP acts as a plasticizing agent, while ADP does not. The stiffness measured for flagella in a medium without ATP was 15 times greater than the value measured with 10 mM ATP present. The rigor-like stiffness measured with no ATP present is reversible with ATP and seems to be correlated to a transition in the state of the contractile system.

Adenosine Diphosphate↗
PubMed1972

Sperm flagella: autonomous oscillations of the contractile system.

Bull sperm are deactivated, losing all motility, when they are impaled or dissected with a microprobe. Loss of activity is due to the creation of a hole or break in the cell membrane. Uncoordinated contractile activity is retained if external adenosine triphosphate and adenosine diphosphate are present. When these substances are in the medium, coordinated wave motion can be initiated in impaled or dissected sperm by bending a segment of the flagellum.

Acetylcholine↗
PubMedDate not supplied

Interdoublet sliding in bovine spermatozoa: its relationship to flagellar motility and the action of inhibitory agents.

Interdoublet sliding rates were assessed in bull sperm, utilizing a freeze-thaw procedure to allow axonemal disintegration. The sliding rate of 23 degrees C increased with increasing MgATP concentrations up to 1 mM ATP, to plateau at 8 microns/sec. The analyzed interdoublet shear in both live and demembranated (Triton X-100-extracted) bull sperm reactivated with 1 mM ATP established maximal microtubule sliding rates at 6 microns/sec during flagellar beating. Therefore, in vitro sliding rates were sufficient to account for the beat in intact flagella. The effect of inhibitors of flagellar motility on in vitro sliding rates was evaluated. While 8 microM vanadate minimally reduced the sliding rate (to approximately or equal to 4 microns/sec), only 0.5 microM vanadate was sufficient to terminate reactivated bull sperm motility. Nickel ion (0.66 mM) terminated all spontaneous motility, while only reducing microtubule sliding rates to approximately or equal to 5.0 microns/sec. Exposing intact bull sperm to theophylline (1 mM), and incubating the subsequently demembranated sperm in cAMP (3 microM), improved flagellar motility, but had little impact on microtubule sliding rates as determined by axonemal disintegration. Furthermore, deactivating live sperm with 2 mM KCN and 4 mM 2-deoxy-D-glucose renders the subsequently reactivated sperm immotile (as long as exogenous cAMP is absent). Yet, this treatment only reduced the sliding rate by 38%. Paradoxically, 4 mM MgADP reduced the sliding rates most dramatically (86%), whereas demembranated sperm models retain a strong, coordinated beating pattern in the presence of MgADP. These results demonstrate that there is no direct relationship between interdoublet sliding rates and the capacity for coordinated flagellar beating.

Adenosine Diphosphate↗