bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct identification of sickle cell anemia by blot hybridization.
Authors: Geever R F , Wilson L B , Nallaseth F S , Milner P F , Bittner M , Wilson J T
Published: May 2006

Several reports have been published on the use of polymorphisms found in the human hemoglobin genes as a means for prenatal diagnosis of sickle cell anemia. The disadvantages of this approach reside in its limited application and the need for family analysis. Here we report that, by use of restriction endonuclease Dde I and diazobenzyloxymethyl-paper transfer procedures, a direct analysis can be made. Individuals with normal hemoglobin (AA) show two bands (175 and 201 base pairs) complementary to a 5'-specific beta-globin gene probe. Sickle cell trait individuals (AS) exhibit an additional band (376 base pairs). Individuals with sickle cell anemia (SS) show the band at 376 base pairs with a concomitant loss of the 175-base pair band. We interpret these changes in banding pattern to be the result of the elimination of a restriction site for Dde I in the altered codon associated with the sickle cell allele. Because an analysis can be performed on as little as 20 micrograms of cellular DNA, the application to prenatal diagnosis of sickle cell anemia should be possible.
Increased susceptibility to cytomegalovirus infection in beige mutant mice.
Authors: Shellam G R , Allan J E , Papadimitriou J M , Bancroft G J
Published: May 2006

Mice homozygous for the beige gene (bg/bg) are a homologue of the Chédiak-Higashi syndrome of man and are known to be selectively defective in natural killer (NK) cells. We have compared the susceptibility of bg/bg and bg/+ C57BL/6J mice to infection with murine cytomegalovirus (MCMV). Beige mice are more susceptible to lethal infection and develop 33- to 43-fold higher virus titers in the liver, spleen, and kidney than do bg/+ mice after a sublethal infection, although virus replication is the same in vitro in cultured fibroblasts or epithelial cells from these mice. Inoculation with a sublethal dose of virus stimulates a NK cell response, although this is lower in bg/bg mice despite higher titers of interferon type 1 than in bg/+. A dose of MCMV that is lethal only to bg/bg augments cytotoxicity within 12 hr in bg/+ mice, whereas cytotoxicity in bg/bg remains very low. In bone marrow chimeras, recipients of bg/bg marrow were more susceptible to MCMV and had lower NK cell responses after virus inoculation than did recipients of marrow from bg/+ donors. The greater susceptibility of beige mice to the virus suggests that NK cells may contribute to resistance early in McMV infection.
Periodicity in the isotope chemistry of hydrogen
Authors: Bigeleisen Jacob
Published: May 2006

Periodicities and regularities are established among the deuterium to protium isotopic reduced partition function ratios, ln(
s
/
s
′)
f
, of 39 diatomic and 19 polyatomic hydrides. It is shown that ln(
s
/
s
′)
f
for diatomic hydrides can be correlated with the position in the periodic table of the element X in the hydride HX. A similar analysis is made for the contributions from X—H stretching motion in the polyatomic hydrides H

n

X. It is shown that the contributions from stretching motions to ln(
s
/
s
′)
f
in diatomic and polyatomic molecules are a linear function of the square root of the stretching force constants. The contributions from bending coordinates to ln(
s
/
s
′)
f
depend on both the molecular structure of the hydride and the bending force constant. Simple correlations are established for the bending contributions to ln(
s
/
s
′)
f
for the hydrides of the elements belonging to a common group in the periodic table. Four periodic rules of the isotope chemistry of hydrogen summarize and classify the data on the isotopic partition function ratios and the isotopic differences in free energies of formation of hydrides.
Phosphocitrate inhibits mitochondrial and cytosolic accumulation of calcium in kidney cells in vivo.
Authors: Tew W P , Malis C D , Howard J E , Lehninger A L
Published: May 2006

Synthetic 3-phosphocitrate, an extremely potent inhibitor of calcium phosphate crystallization as determined in a nonbiological physical-chemical assay, has many similarities to a mitochondrial factor that inhibits crystallization of nondiffracting amorphous calcium phosphate. In order to determine whether phosphocitrate can prevent uptake and crystallization of calcium phosphate in mitochondria in vivo, it was administered intraperitoneally to animals given large daily doses of calcium gluconate or parathyroid hormone, a regimen that causes massive accumulation and crystallization of calcium phosphate in the mitochondria and cytosol of renal tubule cells in vivo. Administration of phosphocitrate greatly reduced the net uptake of Ca2+ by the kidneys and prevented the appearance of apatite-like crystalline structures within the mitochondrial matrix and cytosol of renal tubule cells. Phosphocitrate, which is a poor chelator of Ca2+, did not reduce the hypercalcemia induced by either agent. These in vivo observations therefore indicate that phosphocitrate acts primarily at the cellular level to prevent the extensive accumulation of calcium phosphate in kidney cells by inhibiting the mitochondrial accumulation or crystallization of calcium phosphate.
Effect of nonspecific forces and finite receptor number on rate constants of ligand--cell bound-receptor interactions.
Authors: DeLisi C , Wiegel F W
Published: May 2006

We develop a theory of ligand diffusion in the presence of a central potential toward or away from receptor patches that are uniformly distributed over a spherical cell. The current onto the receptors is reduced to less than that onto the sphere by a factor that is a nonlinear function of the number of free receptors, their size, and their potential energy. Similarly, under conditions defined by the theory, the dissociation rate from a receptor is reduced by the probability of rebinding to some other receptor on the same cell. This complicates the kinetic analysis, leading to the possibility of an occupancy-dependent dissociation rate, but has no effect on the interpretation of thermodynamic data.
Sequence of events in the transformation process in cells infected with a temperature-sensitive transformation mutant of Moloney murine sarcoma virus.
Authors: Brown R L , Horn J P , Wible L , Arlinghaus R B , Brinkley B R
Published: May 2006

Normal rat kidney cells infected with the temperature-sensitive transformation mutant of Moloney murine sarcoma virus were used to study the biochemical and morphological changes that occur during transformation. The infected cells exhibited a normal morphology at the nonpermissive temperature (39 degrees C) and a transformed morphology at the permissive temperature (33 degrees C). A new viral protein was detected 2 hr after shift to the permissive temperature as a polyprotein with an estimated Mr of 85,000 (p85). Scanning electron microscopy of the cells within 5 hr after shifting them to the permissive temperature showed that they became smaller and rounded with numerous elongated microvilli. In an earlier study, changes in hexose uptake were found to occur 8-12 hr after the shift [Horn, J. P., Wood, T. G., Blair, D. G. & Arlinghaus, R. B. (1980) Virology 105, 516-525]. By 48 hr, the cells had the morphology of a fully transformed cell. Concomitant with the changes in the morphology were alterations in the cytoplasmic microtubule complex. At the nonpermissive temperature, the complex consisted of a lacy network of microtubules. Within 5 hr at the permissive temperature, the lacy network was still present but the microtubules were more diffusely stained and less discernible. By 48 hr, the microtubules were so diffuse that the lacy network could not be recognized. Alterations in the F-actin cables did not occur until 24 hr after shifting the cells to the permissive temperature. Enucleation of the cells at the nonpermissive temperature and shifting the cytoplasts to the permissive temperature did not result in the synthesis of detectable p85 or in any alteration of the cytoplast morphology or microtubule complex, suggesting that the temperature-sensitive lesion affects some event occurring in the nucleus.
Taxol induces the assembly of free microtubules in living cells and blocks the organizing capacity of the centrosomes and kinetochores.
Authors: De Brabander M , Geuens G , Nuydens R , Willebrords R , De Mey J
Published: May 2006

Taxol, a potent promoter of microtubule polymerization in vitro, induces massive assembly of free microtubules in cultured cells as visualized by immunocytochemistry and electron microscopy. The centrosomes and kinetochores largely lost their capacity to organize microtubule assembly, as became evident by the disappearance of the cytoplasmic microtubule complex and the mitotic spindle. The taxol-induced microtubules were partially resistant to nocodazole, an inhibitor of tubulin polymerization. Moreover, taxol induced microtubule assembly in cells pretreated with nocodazole. Increasing the ratio of nocodazole to taxol restored the ability of the centrosomes and kinetochores to specifically induce microtubule assembly in their immediate vicinity. The data suggest that taxol lowers the critical tubulin concentration in vivo as well as in vitro and that the organizing capacity of the microtubule-organizing centers depends on the cytoplasmic polymerization threshold.
Cellular homologue (c-src) of the transforming gene of Rous sarcoma virus: isolation, mapping, and transcriptional analysis of c-src and flanking regions.
Authors: Parker R C , Varmus H E , Bishop J M
Published: May 2006

The tumorigenic properties of Rous sarcoma virus are attributable to a 60,000-dalton protein, pp60v--src, encoded by a single viral gene, v-src. A homologous gene, c-src, that contains the information for a 60,000-dalton protein, pp60c--src, has been identified in all tested vertebrate cells. By screening a recombinant DNA library representative of the chicken genome, we isolated two overlapping DNA fragments that contain more than 30 kilobases (kb) of DNA spanning the coding sequences for pp60c--src. This 30-kb region is devoid of moderately or highly repeated sequences and shares homology with the entire viral gene and noncoding sequences 5' of v-src. Although v-src has an uninterrupted coding sequence, c-src is interrupted by a minimum of seven intervening sequences. At least two polyadenylylated RNAs seem to be encoded within the DNA we have isolated. The larger RNA, approximately 3.9 kb, is the presumptive c-src mRNA; the smaller transcript of about 2 kb hybridizes to DNA sequences several kb from the 3' end of the v-src/c-src homology area.
Modulation of the neural control of the clasp reflex in male Xenopus laevis by androgens: a multidisciplinary study.
Authors: Erulkar S D , Kelley D B , Jurman M E , Zemlan F P , Schneider G T , Krieger N R
Published: May 2006

The neural control of the clasp reflex in male Xenopus laevis has been studied by using anatomical, electrophysiological, and biochemical techniques. Neurons in spinal segment 2 of castrated males accumulate label after injection of [3H]-dihydrotestosterone; these neurons are distributed within the rostral portions of the motoneuronal pools of the sternoradialis and flexor carpi radialis muscles. In vitro recordings from the nerve to the sternoradialis muscle in the isolated spinal cord preparation from castrated male Xenopus showed increased activation to paired dorsal root stimulation after addition of dihydrotestosterone to the bath. This increase could be prevented by prior administration of cycloheximide. The reducing enzyme testosterone 5 alpha-reductase is present and is selectively distributed in male Xenopus spinal cord. It is speculated that the androgens may alter patterns of neuronal activity leading to the "clasp" muscles and thereby influence myosin types within these muscles.
D-aspartate potentiates the effects of L-glutamate on horizontal cells in goldfish retina.
Authors: Ishida A T , Fain G L
Published: May 2006

The amino acids L-glutamate and L-aspartate depolarize H1 horizontal cells in the perfused goldfish retina but only at millimolar concentrations. The effects of L-glutamate (but not of L-aspartate) are potentiated approximately 15-fold by exposure to D-aspartate. D-Aspartate blocks acidic amino acid uptake in goldfish retina, so that the potentiation of L-glutamate may be produced by an increase in its effective concentration at the horizontal cell membrane. Because D-aspartate also augments the light responses of horizontal cells, our results are consistent with the possibility that L-glutamate is a neurotransmitter of cone photoreceptors in goldfish.
RNA intermediates in potato spindle tuber viroid replication
Authors: Owens Robert A. , Diener T. O.
Published: May 2006

Two double-stranded RNA intermediates of viroid replication have been isolated from potato spindle tuber viroid (PSTV)-infected tomato tissue and characterized by polyacrylamide gel electrophoresis and DNA-RNA hybridization techniques. These replicative intermediates contain monomeric circular or linear PSTV strands complexed with a multimeric complementary RNA strand. Synchronous synthesis of single-stranded PSTV is accompained by a simultaneous marked increase in double-stranded PSTV RNA; thus,
in vivo
precursors of the characterized double-stranded PSTV RNAs seem to be involved in PSTV replication. A “rolling circle” model for viroid replication on a circular PSTV template can accommodate the double-stranded PSTV RNA species characterized.
Varicella zoster virus DNA exists as two isomers.
Authors: Ecker J R , Hyman R W
Published: May 2006

Fragments of varicella zoster virus DNA produced by EcoRI endonuclease cleavage were cloned in vector pACYC 184 and those produced by HindIII cleavage were cloned in pBR322. Restriction enzyme cleavage maps established by double digestion and blot hybridization showed that varicella zoster virus DNA has a Mr of 80 +/- 3 x 10(6) and exists as a population of two isomers.
Mechanism of action of dichloro-beta-D-ribofuranosylbenzimidazole: effect on in vitro transcription.
Authors: Zandomeni R , Mittleman B , Bunick D , Ackerman S , Weinmann R
Published: May 2006

The adenosine analog 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) and its mono- and triphosphate derivatives inhibit RNA polymerase II-specific transcription in an extract of whole HeLa cells. The analog does not inhibit RNA polymerase III-specific adenovirus VA RNA transcription in the whole cell extract. With purified RNA polymerase II under nonspecific transcription conditions, no effect on DRB could be detected. DRB is equally effective in inhibiting in vitro transcription from several of the adenovirus promoters and the human epsilon-globin gene. The inhibitory effects are in the order DRB greater than DRB monophosphate greater than DRB triphosphate. Thus DRB acts in vitro presumably on systems in which specific RNA polymerase II initiation of transcription occurs and with no detectable effect on premature termination. This will provide a suitable model for study of the molecular mechanism of action of DRB on transcription.
Tumor induction by
Agrobacterium rhizogenes
involves the transfer of plasmid DNA to the plant genome
Authors: White Frank F. , Ghidossi Gina , Gordon Milton P. , Nester Eugene W.
Published: May 2006

The DNA from tumors of
Nicotiana glauca
initiated by strains of
Agrobacterium rhizogenes
was shown to contain sequences that are homologous to the root-inducing (Ri) plasmid of the bacterium. Two independently established tumor lines contained a similar portion of the Ri-plasmid. The Ri-plasmid also hybridized to DNA fragments from uninfected
N. glauca
. A cosmid clone of the Ri-plasmid encompassing the region containing the Ri-plasmid sequences that are stably transferred to the plant also hybridized to the Ri-plasmid-related fragments found in uninfected plants. Five of six tumor lines tested produced a tumor-specific compound that is similar to agropine.
Gap junctional communication compartments in the Drosophila wing disk.
Authors: Weir M P , Lo C W
Published: May 2006

We have examined the gap junctional communication properties of cells in the wing imaginal disk of Drosophila, using intracellular injection of the fluorescent dye tracer Lucifer Yellow. The cell-to-cell passage of Lucifer Yellow is restricted at a boundary line that divides the wing disk into halves. We refer to each half as a "communication compartment" because there is a high level of gap junctional exchange within a compartment and much lower exchange between compartments. Comparison of the positions of the compartments with developmental fate maps suggests that cells in one communication compartment give rise to cuticular structures in the anterior half of the adult dorsal mesothorax, and cells in the other compartment contribute to posterior structures. This communication-restriction line appears to be coincident with the line between the anterior and posterior developmental compartments observed in studies of cell lineage. We propose that gap junctional communication restrictions may play a general role in generating or maintaining developmental compartments.
Human neutrophil Fc gamma receptor distribution and structure.
Authors: Fleit H B , Wright S D , Unkeless J C
Published: May 2006

Fc receptors (FcR) for IgG on human cells were analyzed with two monoclonal antibodies, 3G8 and 4F7. Fab fragments of both hybridoma IgGs inhibited binding to neutrophils of soluble rabbit IgG complexes and sheep erythrocytes (E) coated with rabbit IgG. The number of sites for 3G8 Fab was 135,000 per neutrophil, roughly equivalent to the number of sites for rabbit IgG in immune complexes (112,000 per cell). We did not observe human IgG1 binding sites on neutrophils, although binding of IgG1 to FcR-bearing lines U937 and HL-60 was readily demonstrated. Other cell types bearing 3G8 binding sites were mature chronic myelogenous leukemia cells, eosinophils, 6% of E-rosetting lymphocytes, and 15% of Ig-bearing peripheral lymphocytes. No binding of 3G8 Fab was observed on the FcR-bearing cell lines U937, HL-60 Raji, Daudi, and K562 or on blood monocytes. However, 15% of monocytes cultured for 7 days and 60% of lung macrophages expressed 3G8 antigen. When analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, the neutrophil FcR immunoprecipitated with 3G8 or 4F7 Fab-Sepharose displayed a broad band extending from Mr 73,000 to 51,000; in many experiments this band was resolved into two poorly separated components, centered at Mr 66,000 and 53,000. These results show that human neutrophil FcR for IgG is different from that on monocytes, with respect to both antigenic composition and binding of monomeric IgG1.
Markedly elevated specific renin levels in the adrenal in genetically hypertensive rats.
Authors: Naruse M , Inagami T
Published: May 2006

The specific renin (EC 3.4.99.19) activity in the adrenal of spontaneously hypertensive rats was determined by a method that is capable of distinguishing renin from nonspecific renin-like activity of proteases by using specific antibody to renin. The renin level in the adrenals of adult spontaneously hypertensive rats with established hypertension was found to be 6-8 times as high as that of the normotensive control Wistar-Kyoto strain. The large difference in the adrenal renin level was observed even in 3-wk-old rats in which hypertension has not yet developed. The adrenal renin level was increased by bilateral nephrectomy in both the hypertensive and normotensive strains. A larger quantity of renin was found in the adrenal cortex than in the medulla, and the difference between the hypertensive strain and the normotensive strain was more prominent in the cortex than in the medulla. These results suggest possible involvement of adrenal renin in the development and in the early maintenance phase of hypertension in this animal mode of human essential hypertension by affecting the adrenocortical or adrenomedullary activity, or both.
On 1/
f
noise and other distributions with long tails
Authors: Montroll Elliott W. , Shlesinger Michael F.
Published: May 2006

It is shown, following Shockley [Shockley, W. (1957)
Proc. IRE
45, 279-290], that, when a population is engaged in tasks whose completion requires the successful conclusion of many independent subtasks, the distribution function for successes in the primary task is log normal. It is also shown that, when the dispersion of the log-normal distribution is large, the distribution is mimicked by a 1/
x
distribution over a wide range of
x
. This argument provides a generic set of processes that yields the much observed 1/
x
distribution, and will also lead to a 1/
f
noise spectrum. It is commonly found that distributions that seem to be log normal over a broad range (say to the 95th percentile of a population) change to an inverse fractional power (Pareto) distribution for the last few percentile. Annual income distributions are examples with this structure. The very wealthy generally achieve their superwealth through amplification processes that are not available to most. We have introduced a simple amplification model to characterize the transition from a log-normal distribution to an inverse-power Pareto tail.
Nucleotide sequence of the SUF2 frameshift suppressor gene of Saccharomyces cerevisiae.
Authors: Cummins C M , Donahue T F , Culbertson M R
Published: May 2006

To elucidate the molecular mechanism of frameshift suppression by the SUF2 gene of yeast, the sequences of DNA fragments carrying the SUF2-1 and suf2+ alleles of the gene and surrounding regions have been determined. Comparison of the suppressor and wild-type sequences indicates that the SUF2 gene product is a proline tRNA. Disregarding possible base modifications, we find that the wild-type suf2+ anticodon of the tRNA inferred from the DNA sequence is 3'-GGA-5'. The SUF2-1 mutation represents the insertion of a G-C base pair at a position in the gene that corresponds to the anticodon loop of the tRNA. Replacement of the wild-type suf2+ anticodon by a 3'-GGGA-5' fourbase anticodon enables the SUF2-1 tRNA to suppress the 5'-CCCU-3' four-base codons generated as the result of the his4-712 and his4-713 frameshift mutations. This nontriplet codon-anticodon interaction restores the correct reading frame and allows synthesis of a functional his4 protein.
Transforming genes of human bladder and lung carcinoma cell lines are homologous to the ras genes of Harvey and Kirsten sarcoma viruses.
Authors: Der C J , Krontiris T G , Cooper G M
Published: May 2006

Blot hybridization analysis indicated that NIH 3T3 mouse bladder transformed by high molecular weight DNAs of a human bladder and a human lung carcinoma cell line contained new sequences homologous, respectively, to the transforming genes of Harvey (rasH) and Kirsten (rasK) sarcoma viruses. The unique ras sequences were present in multiple independent NIH cell lines transformed in both primary and secondary transfection assays and corresponded to ras sequences normally present in human DNAs. The ras gene product was expressed in NIH cells transformed by bladder carcinoma DNAs and in the human bladder carcinoma cell lines at levels 2- to 4-fold greater than the level observed in nontransformed NIH 3T3 cells. These results indicate that the transforming genes of these human tumor cell lines are the cellular homologs of two retroviral transforming genes.
Reciprocal effects of an inhibitory factor on catalytic activity and noncatalytic cGMP binding sites of rod phosphodiesterase.
Authors: Yamazaki A , Bartucca F , Ting A , Bitensky M W
Published: May 2006

In illuminated rod outer segment membranes, GTP and guanosine 5'-[beta, gamma-imido]triphosphate (p[NH]ppG) have reciprocal effects on cGMP phosphodiesterase (PDEase; 3':5'-cyclic-nucleotide 5'-nucleotidohydrolase, EC 3.1.4.17) activity and cGMP binding to noncatalytic sites on that enzyme. Two micromolar p[NH]ppG increased PDEase activity more than 2-fold while inhibiting cGMP binding more than 40%. Reduction of noncatalytic cGMP binding, which followed addition of p[NH]ppG, was not a result of PDEase activation. Both effects of p[NH]ppG were completely dependent on the presence of bleached rhodopsin. A heat-stable factor has been found to inhibit PDEase activity and also to stimulate cGMP binding to noncatalytic cGMP binding sites. Addition of p[NH]ppG reversed the effects of this factor on both PDEase activity and cGMP binding. During purification of this material, the activity peaks for both PDEase inhibition and activation of noncatalytic cGMP binding comigrated on both Blue Sepharose CL-6B column chromatography and sucrose density gradients centrifugation, suggesting that the same factor could be responsible for both inhibition of PDEase activity and enhancement of noncatalytic cGMP binding. Limited tryptic proteolysis of PDEase, which markedly reduced cGMP binding to the noncatalytic sites, and experiments using highly purified cAMP (free of cGMP) as substrate for PDEase showed that the binding of cGMP to noncatalytic sites was not required for the heat-stable inhibitory factor to inhibit PDEase activity. We discuss possible relationships between the regulation of PDEase and the binding of cGMP to noncatalytic sites.
Inhibition of fibrinogen binding to human platelets by the tetrapeptide glycyl-L-prolyl-L-arginyl-L-proline.
Authors: Plow E F , Marguerie G
Published: May 2006

The role of fibrinogen as a cofactor in platelet aggregation is mediated by its binding to platelet receptors that are induced by stimuli such as ADP. In the present study, we demonstrate that the tetrapeptide glycyl-L-prolyl-L-arginyl-L-proline inhibits the interaction of fibrinogen with its platelet receptor. The primary effect of the peptide was on the extent rather than on the rate of fibrinogen binding. Significant inhibition occurred at a 1:1 molar ratio of peptide to fibrinogen and reached maximal levels at 100:1 ratio. The inhibition was dependent upon fibrinogen concentration and occurred in the presence of calcium or magnesium. The peptide inhibited the binding of fibrinogen to platelets with exposed receptors, suggesting that it interfered directly with the ligand-receptor interaction. Fibrinogen binding supported by epinephrine and thrombin as well as ADP was inhibited by the peptide. Fibrinogen-dependent aggregation of washed platelets by ADP was abolished by a 30-fold molar excess of the peptide. The tetrapeptide is an analog of the amino-terminal sequence of the alpha-chain of fibrin and has been shown to inhibit fibrin polymerization [Laudano, A. P. & Doolittle, R. F. (1978) Proc. Natl. Acad. Sci. USA 75, 3085-3089]. A peptide corresponding to the natural sequence, glycyl-L-prolyl-L-arginyl-L-valyl-L-valine, was also capable of inhibiting fibrinogen binding to the platelet. These results suggest that common structural features within fibrinogen may serve a dual function by permitting the molecule to participate in both platelet aggregation and fibrin formation.
Intracellular injection of protein kinase inhibitor blocks the serotonin-induced increase in K+ conductance in Aplysia neuron R15.
Authors: Adams W B , Levitan I B
Published: May 2006

Previous work has shown that serotonin induces an increase in membrane K+ conductance in Aplysia neuron R15 and that this response is mediated by cAMP. The present study examines the role of protein phosphorylation in the response to serotonin. A specific inhibitor of cAMP-dependent protein kinase was injected intracellularly into neuron R15. The injection blocked the serotonin-induced increase in K+ conductance completely for at least 4 hours. The blockage was selective because the cell's response to dopamine was not inhibited. Furthermore, the blockage was specifically produced by protein kinase inhibitor because injection of other proteins (alpha-bungarotoxin and bovine serum albumin) did not affect the serotonin response. The serotonin response recovered fully 5-13 hours after the injection, presumably as a result of intracellular proteolysis of the protein kinase inhibitor. The results indicate that protein phosphorylation is a necessary step in the process that leads to activation of K+ channels by serotonin in neuron R15.
Substance P-containing neurons of the avian suprachiasmatic nucleus project directly to the nucleus of Edinger-Westphal.
Authors: Gamlin P D , Reiner A , Karten H J
Published: May 2006

Retrograde and anterograde pathway tracing techniques were used in the pigeon to study afferent visual input from the suprachiasmatic nucleus (SCN) of the hypothalamus to the nucleus of Edinger-Westphal (EW), the parasympathetic visceral efferent component of the oculomotor complex. Horseradish peroxidase injected into the EW retrogradely labeled numerous neurons in the contralateral SCN, a retinorecipient hypothalamic nucleus, as well as a few neurons in the ipsilateral SCN. Autoradiographic orthograde pathway tracing experiments confirmed that the SCN projects heavily upon the medial subdivision of the contralateral EW and lightly upon the medial subdivision of the ipsilateral EW. Some neurons of the SCN contain substance P and a substance P-positive plexus of fibers was seen in precisely that medial portion of the EW to which the SCN was found to project in the autoradiographic experiments. This substance P-positive fiber plexus in the medial EW was eliminated by bilateral electrolytic lesions of the SCN. These results show that the avian suprachiasmatic nucleus has a heavy contralateral and a much lighter ipsilateral projection to the medial subdivision of the EW and that this projection may be largely substance P positive. Previous studies have suggested that neurons of the medial EW specifically project to the neurons of the ciliary ganglion that control the choriocapillary blood flow of the eye. Since the SCN has been implicated in the control of circadian rhythms in vertebrates, the projection of the SCN to the EW may represent a pathway by which a circadian rhythmicity is imposed on choriocapillary blood flow. Alternatively or in addition, the SCN-EW pathway described in this paper may provide the central neural substrate for a homeostatic regulatory mechanism by which choriocapillary blood flow is controlled by the intensity of retinal illumination.
Coding sequence for the pT181 repC product: a plasmid-coded protein uniquely required for replication.
Authors: Novick R P , Adler G K , Majumder S , Khan S A , Carleton S , Rosenblum W D , Iordanescu S
Published: May 2006

pT181 is a 4.4-kilobase plasmid from Staphylococcus aureus specifying tetracycline resistance and present in about 20 copies per cell. The existence of a diffusible pT181 product required for plasmid replication has been proposed on the basis of trans-complementable thermosensitive mutants defective in plasmid maintenance (phenotype Tsr). In this report, the Tsr mutants are shown to have primary replication defects, and the genetic complementation data are confirmed biochemically. All of five mutations are in a single cistron, the repC cistron; interruption of the plasmid DNA molecule at any of three neighboring restriction sites inactivates repC function. Analysis of the DNA sequence in this region reveals an open reading frame of 939 base pairs which encodes the repC product, a 313-amino acid protein. pT181 replication has been demonstrated in cell-free extracts to require specifically a pT181-coded protein of approximately the same size, and it is proposed that this protein is, indeed, the repC product. Preliminary evidence is discussed suggesting that the pT181 replication rate is controlled at the level of synthesis of the repC protein.
Pharmacokinetics of progesterone after its administration to ovariectomized rhesus monkeys by injection, infusion, or nasal spraying.
Authors: Anand Kumar T C , David G F , Sankaranarayanan A , Puri V , Sundram K R
Published: May 2006

The pharmacokinetics of progesterone (dose: 10 microgram per animal) were studied in blood and cerebrospinal fluid of adult ovariectomized rhesus monkeys after the administration of the steroid as an intravenous injection, intravenous infusion (duration of infusion: 10 min), or nasal spray. The bioavailability of progesterone, in terms of area under the time--concentration curve and the maximal concentration in the two body fluids, was significantly higher when the steroid was infused or sprayed intranasally than when it was injected intravenously. The clearance of the steroid from the serum, as estimated by its elimination rate constant, elimination half-life, and total body clearance, did not differ for the three methods of administration. These findings suggest that the bioavailability of progesterone is enhanced by extending the duration over which the steroid is delivered into the hemic circulation.
Lateral and rotational diffusion of bacteriorhodopsin in lipid bilayers: experimental test of the Saffman-Delbrück equations.
Authors: Peters R , Cherry R J
Published: May 2006

Lateral diffusion of bacteriorhodopsin and a lipid analogue has been measured in dimyristoylphosphatidylcholine bilayers as a function of temperature, phospholipid/protein (mol/mol; L/P) ratio, and aqueous phase viscosity. The protein lateral diffusion coefficients measured above the temperature at which the lipid gel-liquid/crystalline phase transition occurs (Tc) are combined with previously determined rotational diffusion coefficients to provide a test of the Saffman-Delbrück equations [Saffman, P. G. & Delbrück, M. (1975) Proc. Natl. Acad. Sci. USA 72, 3111-3113]. Insertion of the diffusion coefficients into these equations enables the protein diameter to be calculated. The value of 4.3 +/- 0.5 nm so obtained is in reasonable agreement with the known structure of bacteriorhodopsin. A 12-fold increase in the viscosity of the aqueous phase reduces protein lateral diffusion coefficients by 50%, which is also consistent with the Saffman-Delbrück equations. Both protein and lipid lateral diffusion coefficients decrease with decreasing L/P ratio above the Tc. It is argued that, at a high L/P ratio, this effect is probably due to changes in membrane viscosity while, at a low L/P ratio, "crowding" effects (steric restrictions) and protein aggregation become important. When comparing diffusion measurements made in different systems, it is important to take the effect of the L/P ratio into account. When this is done, other published measurements of freely diffusing membrane proteins are in good agreement with the present results and the predictions of the Saffman-Delbrück equations. Below the Tc, the presence of protein enhances diffusion rates. The overall effect is to smooth out the large change in diffusion coefficient that occurs at the Tc.
Exocytosis regulates urinary acidification in turtle bladder by rapid insertion of H+ pumps into the luminal membrane.
Authors: Gluck S , Cannon C , Al-Awqati Q
Published: May 2006

Urinary acidification by the turtle bladder is due to a H+-ATPase that is located in the luminal membrane. The rate of H+ transport is stimulated by an increase in the ambient CO2. Using the fluorescent dye acridine orange, we showed that the mitochondria-rich cell of this equilibrium contains vesicles whose internal pH is acidic. We measured the pH of these vesicles by using endocytosed fluorescein isothiocyanate-labeled dextran and found it to be near 5.0. The pH increased after treatment with protonophores or metabolic inhibitors, suggesting that it was due to a H+ pump rather than to a Donnan effect. In bladders preloaded with fluorescent dextran, CO2 stimulated exocytosis and H+ transport measured simultaneously in the same bladder. The increase in the H+ current correlated well with the extent of exocytosis, and both were inhibited by pretreatment with colchicine. We conclude that the turtle bladder contains an intracellular reserve of vesicles containing H+ pumps and CO2 stimulates rapid fusion of these vesicles with the luminal membrane with consequent insertion of H+ pumps, thereby stimulating H+ secretion across the whole epithelium.
Organization and evolution of immunoglobulin VH gene subgroups.
Authors: Rechavi G , Bienz B , Ram D , Ben-Neriah Y , Cohen J B , Zakut R , Givol D
Published: May 2006

The organization and evolution of immunoglobulin variable region genes was studied by comparing human and mouse heavy chain variable region (VH) genes. We show that a VH gene subgroup constitutes a physically linked multigene family separated from another VH subgroup. We mapped the VHIII gene subgroup to be 3' to the VHII gene subgroup based on deletion of VH genes after V-D-J rearrangement. The results indicate that the human VHIII gene subgroup underwent a significant gene expansion as compared to the mouse VHIII subgroup. Amino acid sequence data indicate that human VHIII genes correspond to only a small subset of mouse VHIII genes. Human VHIII genes contain a shorter intron and are two codons shorter than most BALB/c mouse VHIII genes. The nature of nucleotide substitutions between VH genes within a species (human) is similar to that between genes of different species (human/mouse). Both contain approximately 50% silent substitutions.
Regeneration of beta-adrenergic receptors in senescent rats: a study using an irreversible binding antagonist.
Authors: Pitha J , Hughes B A , Kusiak J W , Dax E M , Baker S P
Published: May 2006

The drug used in this study, bromoacetylalprenololmenthane, has the ability to bind and block irreversibly beta-adrenergic receptors. The drug was bound to membranes prepared from hearts, lungs, and brains of both senescent and young rats with a similar affinity. When this drug was injected into rats in nontoxic doses (up to 70 mg/kg), up to 90% of beta-adrenergic receptors were irreversibly blocked 4 hr after injection, whereas the injection of similar amounts of (+/-)-alprenolol was without effect on receptor number. In senescent animals this blockade lasted considerably longer than in young animals; receptor numbers in hearts and lungs of senescent rats returned to control levels only 1 month after injection. The number of beta-adrenergic receptors in brains of senescent rats was unaffected by this drug. Thus, based upon the long-lasting blockade of beta-adrenergic receptors in therapeutically important organs, it appears that irreversible binding blockers may have potential in the treatments of senescent organisms.
Agonist-induced subsensitivity of adenylate cyclase coupled with a dopamine receptor in slices from rat corpus striatum.
Authors: Memo M , Lovenberg W , Hanbauer I
Published: May 2006

Incubation, for 30 min, of striatal slices with 10 microM dopamine, 10 microM apomorphine, or 10 microM SKF 38393 decreased dopamine-stimulated adenylate cyclase activity by 50-60%. This loss in dopamine-stimulated enzyme activity appears to be mediated by a persistent occupancy of recognition sites of the D-1 receptor because: (i) at 10 microM, SKF 38393, a selective D-1 receptor agonist, facilitates desensitization and Ly 141865, a selective D-2 receptor agonist, fails to elicit desensitization of dopamine-dependent adenylate cyclase; and (ii) preincubation with dopamine in the presence of 1 microM haloperidol but not 1 microM sulpiride curtails the desensitization of dopamine-dependent adenylate cyclase. In dopamine-desensitized striatal slices of the Kd for N-propylnorapomorphine binding is increased but the content of membrane-bound calmodulin and the activation of adenylate cyclase by NaF and cholera toxin are decreased significantly. In striatal slices incubated with dopamine for prolonged time periods the coupling of the GTP-binding protein with adenylate cyclase and dopamine recognition sites may be impaired and the content of membrane-bound calmodulin is decreased.
Landscape evolution (A Review)
Authors: Sharp Robert P.
Published: May 2006

Landscapes are created by exogenic and endogenic processes acting along the interface between the lithosphere and the atmosphere and hydrosphere. Various landforms result from the attack of weathering and erosion upon the highly heterogeneous lithospheric surface. Landscapes are dynamic, acutely sensitive to natural and artificial perturbation. Undisturbed, they can evolve through a succession of stages to a plain of low relief. Often, the progression of an erosion cycle is interrupted by tectonic or environmental changes; thus, many landscapes preserve vestiges of earlier cycles useful in reconstructing the recent history of Earth's surface. Landforms are bounded by slopes, so their evolution is best understood through study of slopes and the complex of factors controlling slope character and development. The substrate, biosphere, climatic environment, and erosive processes are principal factors. Creep of the disintegrated substrate and surface wash by water are preeminent. Some slopes attain a quasisteady form and recede parallel to themselves (backwearing); others become ever gentler with time (downwearing). The lovely convex/rectilinear/concave profile of many debris-mantled slopes reflects an interplay between creep and surface wash. Landscapes of greatest scenic attraction are usually those in which one or two genetic factors have strongly dominated or those perturbed by special events. Nature has been perturbing landscapes for billions of years, so mankind can learn about landscape perturbation from natural examples.
Recent aspects of nitration: New preparative methods and mechanistic studies (A Review)
Authors: Olah George A. , Narang Subhash C. , Olah Judith A. , Lammertsma Koop
Published: May 2006

New preparative methods of electrophilic nitration and transfer nitration are reviewed, including reactions relating to the ambident reactivity of the nitronium ion. Recent aspects of the mechanism of electrophilic aromatic substitution are discussed.
Lumen formation by epithelial cell lines in response to collagen overlay: a morphogenetic model in culture.
Authors: Hall H G , Farson D A , Bissell M J
Published: May 2006

Two cell lines--Madin-Darby canine kidney (MDCK) and normal murine mammary gland (NMuMG)--growing as monolayers on collagen gels were overlaid with another collagen gel. The cells responded to the overlay by undergoing reorganization resulting in the creation of lumina. MDCK cells formed lumina that coalesced to form large cavities comparable in size with a tubule. NMuMG cells formed clusters surrounding small lumina, which appeared similar to acini of glandular tissue. The characteristic arrangements, described here by light and electron microscopy, resembled the morphology of the tissues of cell line origin. MDCK cells, grown in the presence of serum, formed lumina whether or not serum was removed at the time of overlay, whereas NMuMG cells required either a nondialyzable component of serum or hormonal supplements in serum-free defined media. Lumen formation was delayed by MDCK cells in the presence of the glutamine analog 6-diazo-5-oxo-L-norleucine, but this compound did not affect NMuMG lumen formation. In both cell lines, lumen formation was unaffected by the absence of sulfate, the presence of an inhibitor of sulfated glycosaminoglycan synthesis, or an inhibitor of collagen synthesis. DNA synthesis accompanied lumen formation but was not required.
Mitochondrial DNA polymorphism in a maternal lineage of Holstein cows.
Authors: Hauswirth W W , Laipis P J
Published: May 2006

Two mitochondrial genotypes are shown to exist within one Holstein cow maternal lineage. They were detected by the appearance of an extra Hae III recognition site in one genotype. The nucleotide sequence of this region has been determined and the genotypes are distinguished by an adenine/guanine base transition which creates the new Hae III site. This point mutation occurs within an open reading frame at the third position of a glycine codon and therefore does not alter the amino acid sequence. The present pattern of genotypes within the lineage demands that multiple shifts between genotypes must have occurred within the past 20 years with the most rapid shift taking place in no more than 4 years and indicates that mitochondrial DNA polymorphism can occur between maternally related mammals. The process that gave rise to different genotypes in one lineage is clearly of fundamental importance in understanding intraspecific mitochondrial polymorphism and evolution in mammals. Several potential mechanisms for rapid mitochondrial DNA variation are discussed in light of these results.
Development of the adrenergic phenotype: increase in adrenal messenger RNA coding for phenylethanolamine-N-methyltransferase.
Authors: Sabban E , Goldstein M , Bohn M C , Black I B
Published: May 2006

Mechanisms regulating the developmental increase in the activity of adrenal phenylethanolamine-N-methyltransferase (PNMTase), an index of the adrenergic phenotype, were examined. Immunotitration indicated that the increase in catalytic activity in rat adrenal from birth to adulthood was attributable to increased numbers of PNMTase molecules, not enzyme activation. To determine whether the ontogenetic increase in PNMTase protein was associated with elevation of mRNA coding for PNMTase, cell-free translation was performed on total cellular mRNA obtained from adrenals at different ages. Translation in wheat-germ and reticulocyte lysate systems, followed by immunoprecipitation of the PNMTase product, NaDodSO4 gel electrophoresis, and fluorography, showed an 8-fold increase in the proportion of specific PNMTase mRNA relative to total mRNA in rat adrenals from birth to adulthood. Moreover, bovine adrenal medullae exhibited a 100-fold increase in PNMTase mRNA levels between embryonic life and adulthood. Consequently, the ontogenetic increase in adrenal PNMTase appears to be due to a developmental rise in specific mRNA coding for the protein.
Refined crystal structure of the molecular complex of Streptomyces griseus protease B, a serine protease, with the third domain of the ovomucoid inhibitor from turkey.
Authors: Fujinaga M , Read R J , Sielecki A , Ardelt W , Laskowski M , James M N
Published: May 2006

We have determined the crystal structure of the molecular complex between Streptomyces griseus protease B (SGPB), a bacterial serine protease, and the third domain of the ovomucoid inhibitor from turkey. Restrained-parameter least-squares refinement of the structure with the 1.8-A intensity data set has resulted in an R factor of 0.125. The carbonyl carbon atom of the reactive bond between Leu-18 and Glu-19 in the inhibitor lies at a distance of 2.71 A from the O gamma atom of the nucleophilic Ser-195 in SGPB; this distance is 0.5 A shorter than a normal van der Waals contact. Unlike the reactive bond in the pancreatic trypsin inhibitor complexed with bovine trypsin, the Leu--Glu bond of the ovomucoid inhibitor is not distorted from planarity towards a pyramidal configuration.
Cooperative effects in water-biomolecule crystal systems.
Authors: Goodfellow J M
Published: May 2006

Monte Carlo computer simulation techniques have been used to model non-pair-additive (cooperative) effects in the water organization around several biomolecules. Although most models for water assume pair-additive potentials, both quantum mechanical calculations and experimental data indicate that cooperative effects are not negligible in hydrogen-bounded systems such as water. The many-body polarizable electropole (PE) model for water is used to examine the extent and the consequences of this cooperative behavior in several biomolecule hydrate crystals. Increases in the dipole moments of water molecules are predicted in all systems studied so far and can be as much as 50% more than the monomer value of 1.855 debyes. The average value of the individual dipole moments for any one system differs from that of another system and, therefore, should be considered a property of the system and not of the water molecule itself. When this previously calculated average value of the dipole moment for water molecules in a given system is used as a fixed parameter in the simulation, we find differences between this fixed calculation and the original unfixed simulation. An alternative procedure, which allows for a spread in dipole moments and is not dependent on a predetermined average value, has been developed to make simulations of large water-protein systems, including cooperative effects, computationally feasible.