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Biomedical subjects

R Cooke

Publications and source records attributed to R Cooke.

At least 181 records · Page 10Linked to original sources
PubMed1981

Electron microscopic mapping of wheat germ RNA polymerase II binding sites on cloned CaMV DNA.

The binding sites of wheat germ RNA polymerase II were mapped on the cloned CaMV genome by observation of enzyme-linear DNA complexes by electron microscopy. Twelve sites are observed. Three of them are relatively stable in the presence of heparin and are found at positions 8-9, 21-23, and 41-44 map units on the physical map of the genome. These positions correspond to AT-rich regions of the viral genome which contain potential promoter sites. These results are discussed with reference to current information on the structure and expression of the CaMV genome.

Binding Sites↗
PubMed1981

Observations on the combination of clomiphene citrate-human menopausal gonadotropin-human chorionic gonadotropin in the management of anovulation.

To study the effects of the addition of clomiphene citrate to human menopausal gonadotropin (hMG) and human chorionic gonadotropin (hCG), 23 cycles of clomiphene citrate-hMG-hCG (CHH) were administered to 10 anovulatory women. Of these 10 women, 5 also received 15 cycles of hMG-hCG (HH). Although there was a significant increase in the ovulation rate in the CHH group (p less than 0.01), there was no difference in the pregnancy rate (p less than 0.05). Patients in the CHH group required significantly less hMG for ovulation induction than the HH group (p less than 0.01). Patients receiving CHH who had low serum levels of follicle-stimulating hormone required significantly more hMG than those with normal values. The luteinizing hormone releasing hormone test may predict those patients who will require less hMG during CHH therapy. The relative safety of the CHH treatment is discussed.

Anovulation↗
PubMed1981

Ovalocytosis in Papua New Guinea -- dominantly inherited resistance to malaria.

Analysis of ovalocytosis in families has demonstrated dominant inheritance. This conclusion is based on finding ovalocytic children of ovalocytic Melanesian mothers and normocytic Caucasian fathers. Inheritance of resistance to thermal deformation and to crenation upon storage correlated with inheritance of ovalocytic erythrocyte morphology. The latter was associated with in vitro resistance to invasion by P. falciparum.

Elliptocytosis, Hereditary↗
PubMed1980

Proton nuclear magnetic resonance and electron paramagnetic resonance studies on skeletal muscle actin indicate that the metal and nucleotide binding sites are separate.

The distance separating the high-affinity binding sites of actin for a divalent metal ion and nucleotide was evaluated by using high-resolution proton NMR and EPR spectroscopy. Replacement of the Ca2+ or Mg2+ bound to the high-affinity divalent cation site of G-actin by trivalent lanthanide ions such as La3+, EU3+, or Gd3+ results in an increase in the mobility of the bound ATP as observed in the NMR spectra of G-actin monomers. Little difference was observed between the spectra obtained in the presence of the diamagnetic La3+ control and the paramagnetic ions Eu3+ and Gd3+ which respectively shift and broaden the proton resonances of amino acids in the vicinity of the binding site. Analysis of the NMR spectra indicates that the metal and nucleotide binding sites are separated by a distance of at least 16 A. In the past, the metal and ATP have been widely assumed to bind as a complex. Further verification that the two sites on actin are physically separated was obtained by using an ATP analogue with a nitroxide spin-label bound at the 6' position of the purine ring. An estimate of the distance was made between the site containing the ATP analogue and the paramagnetic ion, Mn2+, bound to the cation binding site. These EPR experiments were not affected by the state of polymerization of the actin. The data obtained by using this technique support the conclusion stated above, namely, that the cation and nucleotide sites on either G- or F-actin are well separated.

Actins↗
PubMed1980

Orientation of spin-labeled myosin heads in glycerinated muscle fibers.

We have used electron paramagnetic resonance (EPR) spectra to study spin labels selectively and rigidly attached to myosin heads in glycerinated rabbit psoas muscle fibers. Because the angle between the magnetic field and the principal axis of the probe determines the position of the EPR absorption line, spectra from labeled fibers oriented parallel to the magnetic field yielded directly the distribution of spin label orientations relative to the fiber axis. Two spin labels, having reactivities resembling iodoacetamide (IASL) and maleimide (MSL), were used. In rigor fibers with complete filament overlap, both labels displayed a narrow angular distribution, full width at half maximum approximately 15 degrees, centered at angles of 68 degrees (IASL) and 82 degrees (MSL). Myosin subfragments (heavy meromyosin and subfragment-1) were labeled and allowed to diffuse into fibers. The resulting spectra showed the same sharp angular distribution that was found for the labeled fibers. Thus is appears that virtually all myosin heads in a rigor fiber have the same orientation relative to the fiber axis, and this orientation is determined by the actomyosin bond. Experiments with stretched fibers indicated that the spin labels on the fraction of heads not interacting with actin filaments had a broad angular distribution. Addition of ATP to unstretched fibers under relaxing conditions produced orientational disorder, resulting in a spectrum almost indistinguishable from that of an isotropic distribution of probes. Addition of either an ATP analog (AMPPNP) or pyrophosphate produced partial disorder. That is a fraction of the probes remained sharply oriented as in rigor while a second fraction was in a disordered distribution similar to that of relaxed fibers.

Actins↗