bluuebunny/crossref_metadata_2025 huggingface dataset:
Serum iron levels and response to hepatitis B virus
Authors: Felton Craig , Lustbader Edward D. , Merten Cynthia , Blumberg Baruch S.
Published: May 2006

Response to hepatitis B virus (HBV) infection [HBV surface antigen (HBsAg) and antibody to HBsAg (anti-HBs)], serum iron, total iron-binding capacity, hematological status (erythrocytes, Hb, and hematocrit), and evidence of liver damage (serum glutamic pyruvic transaminase; aspartate aminotransferase, L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) were determined for 201 patients on chronic renal dialysis. Four factors—serum iron level, transminase level, sex, and HBV response [i.e., infected-HBsAg(+) (HBsAg positive), anti-HBs(+) (anti-HBs positive), or no response]—were analyzed simultaneously to test the hypothesis that serum iron is higher in those with HBsAg in their serum than in those without HBsAg, independent of the transaminase level. Four independent, statistically significant two-factor interactions were identified. (
i
) Serum iron is higher in those HBsAg(+). (
ii
) Serum iron is higher in those with increased transaminase. (
iii
) Transaminase is higher in those HBsAg(+). (
iv
) Males are more likely to be HbsAg(+) and females are more likely to be anti-HBs(+). Also, those who are HBsAg(+) have significantly higher percent iron saturation (serum iron/total iron-binding capacity). That is, the hypothesis was supported by the findings. Several additional biological hypotheses are suggested, including a possible role of increased iron levels in susceptibility and response to HBV infection and the possible relationship between higher iron levels and the likelihood of HBV infection progressing to primary hepatocellular carcinoma. In addition, further tests of the initial hypothesis in nonhospitalized populations with endemic HBV infection are proposed.
Release and distribution of [3H]norepinephrine in nonpigmented and pigmented rabbit iris.
Authors: Farah M B , Patil P N
Published: May 2006

Unequal accumulation of drugs in pigmented and nonpigmented iris has been known for some time. However, at low concentrations of the sympathetic neurotransmitter norepinephrine, the accumulation is equal in both types of irides. The spontaneous and potassium-induced release of 3H was studied in isolated rabbit irides labeled with 0.1 micron [3H]norepinephrine ([3H]NE). The spontaneous outflow and the tissue 3H content were similar in both types of irides, but the potassium-induced release was significantly higher in nonpigmented iris. When irides were labeled with [3H]NE in the presence of 1 micron desmethylimipramine, the potassium-induced release was still significantly higher in nonpigmented than in pigmented iris, although the tissue 3H content was higher in the latter. Subcellular distribution of [3H]NE in both types of irides is presented. The data indicate that [3H]NE is distributed unequally in both types of irides in spite of equal tissue accumulation. The binding of NE by the pigment cell suggests an additional site of loss, or site of uptake, of the transmitter in melanin-containing tissues. The physiological significance of such an unequal release in relation to the evolutionary adaptation of the eye to light is discussed.
Segments of simian virus 40 DNA spanning most of the leader sequence of the major late viral messenger RNA are dispensable.
Authors: Subramanian K N
Published: May 2006

A highly specific procedure for the isolation of deletion mutants is described. The size and location of the deletions can be predetermined. By this method a series of deletion mutants mapping within and near the untranslated 5' leader sequence of the late 16S mRNA of simian virus 40 have been isolated. The boundaries of the deletions have been accurately determined by DNA sequence analysis. The deletions range from 20 to 223 nucleotides. All these deletions mutants are viable and grow without helper virus. The largest of these deletions removes the entire leader sequence except for six nucleotides at the 3' end that are probably involved in covalent linkage with the 5' end of the body of the mRNA located 937 nucleotides away on the genome. Three of the deletion mutants remove the 5' end of the leader that normally bears the cap structure of the mRNA. A large segment immediately preceding the leader sequence is also removed in one of these mutants, ruling out the generation of the 5' end of the mRNA via initiation of transcription at this point. The circularization of linear infecting DNA producing the DNA of the deletion mutants proceeds mainly by way of blunt end ligation in vivo.
Noncovalent intermolecular crosslinks are produced by bleomycin reaction with duplex DNA.
Authors: Lloyd R S , Haidle C W , Robberson D L
Published: May 2006

Reaction of covalently closed circular PM2 bacteriophage DNA with the anticancer drug bleomycin produces nicked circular (form II) and linear duplex (form III) DNA [Lloyd, R.S., Haidle, C.W. & Robberson, D.L. (1978) Biochemistry 17, 1890-1896]. As the reaction proceeds, the frequencies of both form II and form III DNA increase and, concomitantly, an increasing fraction of the DNA mass is found to be in crosslinked structures. Approximately 16% of the PM2 DNA mass is found to be crosslinked after 30 min of reaction with bleomycin at 0.5 microgram/ml. The proportion of each form found in any given crosslinked structure is directly related to the concentration of uncrosslinked (monomeric) forms. Multiple sites of crosslinking occur, and these frequently extend over a region of approximately 500 nucleotide pairs. The intermolecular crosslinked bonds are dissociated by extensive dialysis or by the addition of salt at high concentration (0.8 M NaCl), as would be expected if the bonds were noncovalent. Because intramolecular covalent crosslinks between complementary strands are not detected, it is suggested that intermolecular crosslinks are formed by noncovalent association of bleomycin molecules bound to each of the forms of DNA.
Arachidonic acid is responsible for the smooth muscle-contracting activity of G-acid.
Authors: Bates H A , Sih C J
Published: May 2006

G-acid, a smooth-muscle-contracting substance isolated from human blood plasma, was previously identified as 3-octadecenoic acid. Synthetic cis- and trans-3-octadecenoic acid, however, are biologically inactive. G-acid actually consists of a mixture of fatty acids, characteristic of animal tissues. The biological activity is caused by arachidonic acid, which contracts smooth muscle upon in situ conversion to prostaglandins.
Insulin-stimulated protein phosphorylation in 3T3-L1 preadipocytes.
Authors: Smith C J , Wejksnora P J , Warner J R , Rubin C S , Rosen O M
Published: May 2006

A protein of molecular weight 31,000 became labeled with 32P within 5 min after addition of insulin to differentiated 3T3-L1 preadipocytes previously incubated for 55 min with 32Pi. The effect was mimicked by antisera directed against the insulin receptor and was eliminated by anti-insulin antiserum. Incorporation of 32P into this protein was more than 20-fold greater in insulin-treated cells than in cells not exposed to the hormone. At concentrations greater than required with insulin, epidermal growth factor and serum (1-5%) also stimulated phosphorylation whereas 1-isoproterenol, a beta-adrenergic agonist that increases intracellular accumulation of cyclic AMP, was without effect. The 31,000-dalton protein has been tentatively identified as ribosomal protein S6 by two-dimensional polyacrylamide gel electrophoresis. Incorporation of 32P into S6 could be detected within the same time period (5 min) and at the same insulin concentrations (0.1-1.0 nM) as are required to stimulate hexose uptake in both 3T3-L1 cells and mature mammalian adipocytes. The mechanism by which this phosphorylation either mediates or reflects the intracellular actions of insulin remains to be elucidated.
Keratin cytoskeletons in epithelial cells of internal organs
Authors: Sun Tung-Tien , Shih Chiaho , Green Howard
Published: May 2006

An antiserum against human epidermal keratins was used to detect keratins in frozen sections of various rabbit and human tissues by indirect immunofluorescence. Strong staining was observed in all stratified squamous epithelia (epidermis, cornea, conjunctiva, tongue, esophagus, vagina, and anus), in epidermal appendages (hair follicle, sebaceous gland, ductal and myoepithelial cells of sweat glands), as well as in Hassall's corpuscles of the thymus, indicating that all contain abundant keratins. No staining by the antiserum was observed in fibroblasts, muscle of any type, cartilage, blood vessel, nerve tissue, iris or lens epithelium, or the glomerular or tubular cells of the kidney. In contrast, the antiserum stained the cells of most epithelia of the intestinal tract, urinary tract (urethra, bladder, ureter, collecting ducts of kidney), female genital tract (cervix, cervical glands, uterus, and oviduct), and respiratory tract (trachea and bronchi). Epithelial cells of the fine ductal system in the pancreas and submaxillary gland also stained well. When primary cultures of epithelial cells derived from bladder, intestine, kidney, and trachea were grown on glass coverslips and stained with anti-keratin, fiber networks similar to those of cultured keratinocytes were observed. These results show that keratins constitute a cytoskeleton in epithelial cells of diverse morphology and embryological origin. The stability of keratin filaments probably confers the structural strength necessary for cells covering a free surface. Keratin staining can be used to obtain information about the origin of cell lines.
Human lymphoblastoid cell variants defective in cell-cell adhesion.
Authors: Whipple A P , Millis A J
Published: May 2006

Adhesion mutants were selected from a human lymphoblastoid cell line. Initially, cells were selected on the basis of survival in serum-free medium. Subclones that grow as single cells rather than macroscopic aggregates were selected from the serum-independent variant. The defect in cell-cell adhesion is stable over many generations and is not corrected by growth in serum or the presence of serum in the culture medium. Analysis of mixed cultures composed of adhesive cells and nonadhesive cells indicates that the two cell types do not interact to form mixed aggregations. Furthermore, those results suggest that the adhesion-deficient phenotype does not result from the production of a transferable inhibitor. In a previous study [Whipple, A.P., Dalvin, M. & Millis, A.J.T. (1978) Exp. Cell Res. 116, 457-461], we found that the growth rate in serum-containing medium is identical for the two classes of cells. This suggests that cell-cell adhesion is not a critical factor in the growth of these cells.
Structural analysis of human platelet membrane glycoprotein I complex.
Authors: Nachman R L , Kinoshita T , Ferris B
Published: May 2006

The glycoprotein I complex, consisting of two polypeptides of Mr 210,000 and 150,000, was isolated from human platelet membranes by wheat germ lectin affinity chromatography. Glycocalicin, a soluble loosely bound membrane glycoprotein of Mr 150,000 related to the glycoprotein I system, was also purified. The isolated polypeptides were radioiodinated in sodium dodecyl sulfate/polyacrylamide gels and digested with trypsin, and the labeled peptide digest was analyzed by two-dimensional high-voltage electrophoresis and thin-layer chromatography. The two polypeptides of Mr 210,000 and 150,000 in the glycoprotein I complex had essentially identical radioactive peptide maps. Glycocalicin had a completely different tryptic peptide map. These studies shed light on the molecular relationships of some of the components of the platelet membrane glycoprotein I system. The possibility is raised that the receptorlike function of the intrinsic platelet membrane glycoproteins may be related to the polymeric subunit associations of the constituent polypeptides.
Hybrid resistance to parental bone marrow transplantation: adaptive modification of hemopoietic stem cell in a nonsyngeneic environment.
Authors: Chertkov J L , Gelfand I M , Gurevitch O A , Lemeneva L N , Udalov G A
Published: May 2006

Defective growth of parental bone marrow in an F1 hybrid is associated with delay of the exponential growth phase of injected hemopoietic stem cells rather than with their rejection. This is demonstrated both by parental hemopoietic stem cell kinetics in the irradiated hybrid and by the increase in the number of spleen colonies with time after hemopoietic cell injection. After passage through an F1 hybrid the parental hemopoietic stem cells acquire ability for better growth in the same F1 host. This phenomenon, which we designated "adaptive modification of hemopoietic stem cells," is associated with the appearance, on their surface, of histocompatibility molecules carrying H-2 determinants of the recipient. Treatment of the modified cells with antiserum against the second parental strain abrogates the state of adaptive modification.
Morphine and endorphins modulate dopamine turnover in rat median eminence.
Authors: Deyo S N , Swift R M , Miller R J
Published: May 2006

The is evidence that some of the actions of both endogenous and exogenous opioids (e.g., stimulation of prolactin release) are mediated by interaction with catecholaminergic systems. Morphine (1.67, 5, and 15 mg/kg of body weight, intraperitoneally) altered dopamine turnover as measured by the alpha-methyl-p-tyrosine method in the median eminence, neostriatum, and frontal cortex of male Sprague-Dawley rats. The turnover rate of dopamine was reduced in the median eminence and frontal cortex but accelerated in the neostriatum. In the frontal cortex all doses were effective in decreasing dopamine turnover; however, in the median eminence the lowest dose of morphine did not significantly alter dopamine turnover. All three doses accelerated dopamine turnover in the neostriatum. Naloxone effectively reversed the effects of morphine at all doses in all brain areas, whereas it had no effect on turnover when given alone. In the median eminence, neostriatum, and frontal cortex, intraventricular injection of [D-Ala2,D-Leu5]-enkephalin (25 micrograms) or beta-endorphin (15 micrograms) produced the same effects on dopamine turnover as morphine. The actions of these peptides were blocked by naloxone. It is hypothesized that opiates and opioid peptides increase prolactin release by reducing the activity of the tuberoinfundibular dopaminergic system.
Dissociation of action potentials from contraction in single crab muscle fibers.
Authors: Suarez-Kurtz G , Sorenson A L
Published: May 2006

In single crab fibers (Callinectes danae) bathed in Ca2+-free media, Ba2+ action potentials did not elicit tension. In contrast, Sr2+ spikes evoked twitches similar in amplitude to those accompanying the control Ca2+ spikes. Tension development in these fibers, therefore, depends on the ionic species carrying the inward current during membrane excitation. The Ca2" or Sr2+ influx appears insufficient to evoke the observed twitch tensions, and it seems necessary to postulate mobilization of an intracellular source of Ca1+. Procaine, which suppresses release of Ca2+ from sarcoplasmic reticulum, depressed twitch tension but did not reduce the overshoot or duration of Ca2+ or Sr2+ spikes. This finding is compatible with the suggestion that the contractions results from release of Ca2+ from the sarcoplasmic reticulum initiated by signals given by the influx of Ca2+ or Sr2+, but not Ba2+.
Local convergence theorems for adaptive stochastic approximation schemes
Authors: Lai T. L. , Robbins Herbert
Published: May 2006

For the regression model
y
=
M(x)
+ ε, adaptive stochastic approximation schemes of the form
x

n
+1

=

x
n

—

y
n

/(

nb
n

) for choosing the levels
x
1
,
x
2
,... at which
y
1
,
y
2
,... are observed converge with probability 1 to the unknown root θ of the regression function
M(x)
. Certain local convergence theorems that relate the convergence rate of

x
n

— θ to the limiting behavior of the random variables

b
n

are established.
Moloney murine sarcoma virions synthesize full-genome-length double-stranded DNA in vitro.
Authors: Benz E W , Dina D
Published: May 2006

Moloney murine sarcoma virus (MSV) virions incubated under optimal conditions were shown to support extensive synthesis of double-stranded DNA. The major product, a 5950-base-pair (6-kilobase-pair DNA) double-stranded DNA, was characterized by cleavage with restriction endonucleases and shown to contain a 600-nucleotide-long direct repeat at both ends of the MSV genome. Linear DNA molecules made in vivo shortly after infection were compared to the linear double-stranded DNA synthesized in vitro. The restriction maps of both viral DNA products were indistinguishable. The 600-base-pair repeat results in a progeny DNA molecule that is longer than the parental MSV genomic RNA. The generation of this repeat must involve a mechanism that allows the viral reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) to copy 5'- and 3'-terminal genomic (+) strand sequences twice.
T lymphocyte response to H-2 mutants: cytotoxic effectors are Ly-1+2+.
Authors: Wettstein P J , Bailey D W , Mobraaten L E , Klein J , Frelinger J A
Published: May 2006

The lymphocyte differentiation (Ly) antigen phenotype of cytotoxic effector T cells specific for H-2 mutant alloantigens was determined. Cytotoxic effectors generated in primary mixed lymphocyte culture and specific for H-2Kba and H-2Dda alloantigens are sensitive to both anti-Ly-1 and anti-Ly-2 serum plus complement. Reconstitution analysis demonstrated that the mutant-specific T cells were Ly-1+2+. These observations and those previously reported, which indicated that H-2K/D mutant-specific T cells proliferating in mixed lymphocyte culture were Ly-1+2+, demonstrated that Ly-1+2+ T cells are immunocompetent. Furthermore, the nature of the stimulating H-2 complex alloantigen determines the Ly phenotype of responsive T cells.
Antigenic marker on a functional subpopulation of B cells, controlled by the I-A subregion of the H-2 complex.
Authors: Huber B T
Published: May 2006

CBA/N mice have an X-linked recessive effect that results in the absence of a subpopulation of B cells carrying the Lyb3 surface marker. It has been shown previously that this marker is present on a mature subset of B cells in all mouse strains. In this paper the Lyb3+ B cell population in C57BL/6 mice was analyzed further. This subset of B cells selectively expresses a surface marker controlled by the I-A subregion of the H-2 complex. A cytotoxic antiserum recognizing this marker was raised by immunizing defective (CBA/N X C57BL/6)F1 male mice with C57BL/6 spleen cells. This antiserum also contained noncytotoxic, non-strain-restricted anti-Lyb3 antibodies. The possible functional relevance of this surface marker is discussed.
Communication between dissimilar subunits in aspartate transcarbamoylase: Effect of inhibitor and activator on the conformation of the catalytic polypeptide chains
Authors: Hensley Preston , Schachman H. K.
Published: May 2006

Although local, direct effects of ligand binding to proteins are readily differentiated conceptually from gross, indirect conformational changes in regions of the protein remote from the site of binding, it has been difficult experimentally to distinguish between them. In oligomeric proteins, for example, the binding of ligands to one chain may cause a conformational change in the unliganded chains, but many physical chemical probes are not sufficiently discriminating to demonstrate where the change occurred. Evidence has been lacking as to whether the inhibitor, CTP, or the activator, ATP, in binding to the regulatory chains of the allosteric enzyme aspartate transcarbamoylase (aspartate carbamoyltransferase; carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) causes a conformational change that is propagated throughout the enzyme to the catalytic chains. To demonstrate this “communication” of effects of binding at one site on the conformation of other polypeptide chains, we constructed molecules containing native regulatory subunits and enzymically active nitrated catalytic subunits having one sensitive nitrotyrosyl chromophore per polypeptide chain. These hybrid molecules exhibited the characteristic regulatory properties of the native enzyme. Upon the addition of CTP the population of molecules was shifted toward the constrained or T state, as shown by the change in the sedimentation coefficient and the altered enzyme kinetics. Moreover, there was a decrease in absorbance at 430 nm due to the altered environment of the nitrated catalytic polypeptide chains. In contrast, ATP caused a shift toward the relaxed or R conformation, and the absorbance due to the nitrotyrosyl residues was increased. Different types of experiments indicated that the modified enzyme molecules are in a preexisting equilibrium that is perturbed by CTP or ATP; the resulting conformational changes in the nitrated catalytic subunits are detected by opposite alterations in their absorbance spectrum.
Synthesis of a small RNA in cells coinfected by standard and defective interfering particles of vesicular stomatitis virus.
Authors: Rao D D , Huang A S
Published: May 2006

A small RNA, containing approximately 50 nucleotides, is synthesized by cells coinfected with standard vesicular stomatitis virus and its defective interfering (DI) particles. Infection of cells by standard virus or DI particles alone does not lead to synthesis of significant amounts of small RNA. The RNA is initiated at its 5' end with (p)ppXp and is not polyadenylylated at the 3' end despite a content of 51% adenosine. It has sequences complementary to the genome of a DI particle. The synthesis of the small RNA correlates with the replication of the genome of DI particles with molar ratio small RNA/genome RNA of DI particles greater than 50. When replication of DI genomes is prevented by the addition of cycloheximide or prior UV irradiation of DI particles, small RNA is not synthesized in coinfected cells. These results indicate that the small RNA is not the result of transcriptional initiation and that it may relate to interference mediated by DI particles.
Modulation of plasminogen activator secretion by activated macrophages: influence of serum factors and correlation with tumoricidal potential.
Authors: Chapman H A , Vavrin Z , Hibbs J B
Published: May 2006

A high molecular weight fraction of human serum (Fr-1) was found to both inhibit macrophage tumoricidal activity and enhance plasminogen activator activity in supernates over activated macrophages in vitro. Conversely, a 40- to 90-kilodalton serine esterase (Fr-3) also found in normal human serum and endotoxin enhanced tumoricidal potential and suppressed the supernatant plasminogen activator activity. Inactivation of either Fr-1 or Fr-3 by 2-mercaptoethanol or diisopropyl fluorophosphate, respectively, abolished both biologic effects. Examination of cell-associated and culture medium plasminogen activator activity before and after acidification to inactivate proteinase inhibitors indicated that suppression of plasminogen activator activity by Fr-3 or endotoxin most likely represents modulation of macrophage plasminogen activator secretion. The findings demonstrate that activated macrophages are capable of highly coordinated biologic responses to alterations in their microenvironment and suggest that it is in fact the high potential for such responsiveness that reliably characterizes the activated macrophage. The results also suggest that an endogenous regulatory system dependent on the interaction of serine esterases may operate to regulate the functional capabilities of activated macrophages.
Population genetics of multigene family with special reference to decrease of genetic correlation with distance between gene members on a chromosome.
Authors: Kimura M , Ohta T
Published: May 2006

A mathematical method is developed which enables us to treat exactly the process of coincidental evolution under mutation, unequal intrachromosomal crossing-over as well as ordinary crossing-over between homologous chromosomes in a finite population of the effective size N. It makes use of finite difference equations involving two quantities denoted by fi and phi i, in which fi is the identity coefficient of two gene members that are i steps apart on the same chromosome and phi i is that of two members i steps apart on two homologous chromosomes. When the number of genes (n) per family is large, the finite difference equations can be approximately by ordinary second-order differential equations which can then be solved analytically. Results obtained by the present method are compared with the corresponding results previously obtained by one of us (T.O.) using conventional diffusion models of gene frequency changes in population genetics. It is shown that the previous results obtained by T.O. regarding second-order statistics are essentially valid, and they give good approximations particularly when N beta is small, where beta is the rate of ordinary interchromosomal crossing-over within the multigene family.
In vitro infectivity assay for mouse mammary tumor virus.
Authors: Vacquier J P , Cardiff R D
Published: May 2006

Studies of mouse mammary tumor virus (MMTV) have been impeded by the lack of an in vitro infectivity assay. We have developed a rapid, quantitative in vitro assay for MMTV infectivity based on the detection of positively staining foci by immunoperoxidase. This assay and a 50% end-point titration of MMTV infectivity gave identical virus titers. Infection of a rat hepatoma cell line, a feline kidney cell line, and a normal murine mammary gland cell line by virus from the mouse mammary tumor GR3A cell line was linear with respect to virus concentration. The infectious titers obtained in both homologous and heterologous cell lines were not significantly different, demonstrating a lack of host range specificity. Virus infectivity was inactivated by heating at 55 degrees C and by ultraviolet irradiation. Rabbit anti-MMTV serum neutralized the infectivity with a 50% neutralization end point of 1:5000. Applications of this assay to the study of the immunological, biological, and biochemical characteristics of MMTV are discussed.
Selection of variant neuroblastoma clones with missing or altered sodium channels.
Authors: West G J , Catterall W A
Published: May 2006

Neurotoxins that cause persistent activation of voltage-sensitive sodium channels are highly cytotoxic to electrically excitable neuroblastoma cells. These toxins were used as selective agents to isolate variant neuroblastoma clones with missing or altered sodium channels. Of ten resistant clones analyzed, seven lacked functional sodium channels and one had a specific 40-fold increase Kd for scorpion toxin and altered voltage dependence of scorpion toxin binding. The phenotypes of these cell clones were stable for more than 100 generations, indicating that they were the result of stable genetic change.
Earth history at the century mark of the U.S. Geological Survey
Authors: Simpson George Gaylord
Published: May 2006

Earth history involves all aspects of geological and biological evolution, especially paleontology and stratigraphy. Early paleontological exploration of the western United States by and before the U.S. Geological Survey featured the dramatic discoveries and rivalries of the great vertebrate paleontologists Leidy, Cope, Marsh, and Osborn. Invertebrate paleontology and paleobotany in the U.S. Geological Survey blossomed with emphasis on practical missions. The most illuminating and useful earth history, nevertheless, emerges where there is a high degree of interaction with academic scholars. Despite a good knowledge of its broad features, the drama of earth history remains obscure in detail. Whereas it speaks conclusively for the reality of organic evolution, it is less conclusive about mechanisms and many important transitions. Current investigations, however, especially in pre-Phanerozoic, mammalian, and human paleontology, promise improved insights. New techniques in collecting, sample preparation, and research are revealing previously unknown kinds of fossils and exquisite details of preservation. Plate tectonic theory provides a new framework for historical geography and biogeography. Emerging techniques in geochronology—matching paleopolarity sequences, for example—promise to resolve old problems of the synchroneity or heterochroneity of different biotal provinces. As it splits into subfields, the teaching and practice of paleontology expand to cover all of them. The fossils themselves, however, remain the basic objective evidence. All hypotheses about them must answer to this court of appeal. But nature rarely responds in an either-or way. The most probable hypotheses are those that have repeatedly confronted objective reality and survived all opportunity for disproof.
Cytoplasmic phase separation in formation of galactosemic cataract in lenses of young rats
Authors: Ishimoto Coe , Goalwin Patrick W. , Sun Shao-Tang , Nishio Izumi , Tanaka Toyoichi
Published: May 2006

We have determined the age dependence of the characteristics of the cytoplasmic phase separation of lenses from normal and galactosemic young rats. In the normal lens, the temperature at which the phase separation occurs decreases monotonically with age. In the lenses of rats fed with a high galactose diet, the phase separation temperature becomes increasingly higher with the development of galactosemia. When the phase separation temperature becomes higher than the ocular temperature, the nuclear opacity appears
in vivo
. The opacity is the result of light scattering by spatial fluctuations of the refractive index formed by interspersed regions of two separated phases in the fiber cell cytoplasm. This shows that the nuclear opacity that develops in the lens of galactosemic rats is the manifestation of phase separation of the lens fiber cytoplasm.
Regulation of translational initiation ina temperature-sensitive mutant of BHK cells.
Authors: Kumar A
Published: May 2006

The role of various essential components in mammalian cell protein chain initiation, such as the 40S ribosomal subunit and the initiation factors, have been studied largely in fractionated systems and little is known about the mechanisms of their regulation. The process was studied in an unfractionated system derived from temperature-sensitive (ts) 422E cells. The mutant cells fail to assemble 60S ribosomal subunits at the nonpermissive temperature with little effect on the production of 40S ribosomal subunits. Although the resulting imbalance in ribosomal subunits has little immediate effect on the overall rate of protein synthesis, the nascent 40S subunits in mutant cells appear to be markedly unstable at the nonpermissive temperature. The initial step in protein synthesis, initiation factor elF-2-promoted binding of [35S]Met-tRNAf Met to 40S ribosomal subunits, remains unimparied in ts 422E cells at the nonpermissive temperature. However, most of the nascent 40S ribosomal subunits in ts 422E cells band at a higher density, suggesting their failure to bind initiation factor elF-3. These newly synthesized 40S subunits in the mutant cells are unstable, and may be degraded before their appearance in the polysomes.
Polymorphism and loss of duplicate gene expression: a theoretical study with application of tetraploid fish.
Authors: Takahata N , Maruyama T
Published: May 2006

We studied the fixation of null alleles at independent duplicate loci, assuming that wild-type active alleles mutate irreversibly to nonfunctional null alleles and that the population is finite and panmictic. Solving the two-dimensional Kolmogorov backward equation numerically, we obtained the rate at which one of the active genes is lost and the amount of heterozygosity at specified times. Previously harmful genes, including recessive lethals, can be fixed at one of the duplicate loci, which would not happen with a single locus. Examination of data from several fish families showed that the rate of fixation of null alleles is too slow and the amount of heterozygosity too small to be compatible with complete recessivity at all loci. Our conclusion differs in this regard from that of Bailey et al. [Bailey, G.S., Poulter, R. T. M. & Stockwell, P. A. (1978) Proc. Natl. Acad. Sci. USA 75, 5575--5579]. They also reported that the time taken for 50% of the loci to be fixed for null alleles is approximately 15N + v-3/4, in which N and v are the effective population sizgote is lethal. We found that the fixation rate depends not only on N, but also on Nv.
Sigma subunit of Escherichia coli RNA polymerase affects the function of lambda N gene.
Authors: Nakamura Y , Kurihara T , Saito H , Uchida H
Published: May 2006

A new class of Escherichia coli mutants, referred to as grn, has been isolated by localized mutagenesis. These mutations affect the sigma subunit of DNA-dependent RNA polymerase (ribonucleoside 5'-triphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) by abolishing the expression of the lambda N gene, and they are closely lniked to dnaG in the order dnaG-grn-uxaA. Detailed study of one such mutant, grn1, yielded the following results: (i) grn1 is a single mutation and the mutant cell shows cold-sensitivity in growth; (ii) the Grn phenotype of the mutant can easily be suppressed by secondary mutations in the beta subunit gene of RNA polymerase; (iii) purified holoenzyme of RNA polymerase isolated from the mutant showed an altered salt-dependency in vitro, and the mixed reconstitution of the mutant with the wild-type subunits showed that the sigma subunit of the grn1 mutant is altered; (iv) lambda phage mutants (lambda grg), which overcome the grn mutation, can be classified into two groups, the "nin-deletion" and the "N-mutant" groups (both of these are also able to grow on the previously described groN mutant of Georgopoulos and nusAB of Friedman); (iv) the mutant polymerase transcribed 12S as well as 7S RNA from lambda DNA in the presence of the rho factor in vitro. These results indicate that the grn mutation alters the sigma subunit of RNA polymerase and that the sigma subunit participates in activating the N-mediated antitermination mode of lambda phage transcription.
Cholesterol homeostasis in the rat with a portacaval anastomosis.
Authors: Proia A , McNamara D J , Edwards K D , Ahrens E H
Published: May 2006

Studies were undertaken to determine the effect of portacaval anastomosis on cholesterol homeostasis in rats fed sucrose/lard under conditions of normal body growth. Four to 6 weeks after portacaval shunt surgery, we found decreases in plasma cholesterol and triglyceride concentrations, total liver weight, and hepatic microsomal protein concentration. Measurements oof hepatic 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase (EC 1.1.1.34) activity showed decreases in specific activity and total liver activity in portacaval shunt rats, but the enzyme diurnal rhythm remained. Decreased reductase activity in shunted rats was not due to an altered Km for D-HMG-COA, nor was an enzyme inhibitor found in the livers of the portacaval shunt animals. Sterol balance measurements in rats with shunts showed a 22% decrease in whole body cholesterol synthesis rate compared to controls. These metabolic studies, coupled with postmortem data, showed diminished bile acid synthesis, unchanged fecal neutral steroid excretion, and decreased net tissue accumulation of cholesterol during growth. The decreased whole body cholesterol synthesis rate ultimately led to a diminished total carcass cholesterol concentration in the rats with shunts.
"Hybrid" synapses formed by foreign innervation of parasympathetic neurons: a model for selectivity during competitive reinnervation.
Authors: Proctor W , Frenk S , Taylor B , Roper S
Published: May 2006

Selectivity of synapse formation after nerve regeneration was tested in the parasympathetic cardiac ganglion of frogs (Rana pipiens). First, we tested the ability of somatic motor axons to establish synaptic connections with denervated ganglion cells by implanting the hypoglossus nerve into the vagotomized heart. After several weeks, stimulation of the implanted hypoglossus mediated a parasympathetic-like inhibition of the heart rate, and synaptic responses produced by hypoglossal stimulation were recorded intracellularly in ganglion cells. Light and electron microscopy indicated that implanted hypoglossal nerve terminals contacted parasympathetic ganglion cells only on their axons and not on the cell body (where most vagal synapses are found in control animals). Second, we tested whether regenerating vagal preganglionic axons would complete with foreign (hypoglossal) terminals for innervation of cardiac ganglion cells. We allowed the vagus nerve to regenerate in animals in which the implanted hypoglossus had established functional contacts with the cardiac ganglion. Vagal axons were able to reinnervate the heart and reestablish synaptic connections on the cell bodies of ganglion cells. Furthermore, functional transmission at the foriegn (hypoglossal) terminals disappeared concomitant with vagal reinnervation.
Optical polarization and infrared spectrum of a possible protostar in a reflection nebula
Authors: Ney E. P. , Hatfield B. F. , Gehrz R. D.
Published: May 2006

The star HD 200775 illuminates the reflection nebula NGC 7023. This star is one of a small group of Ae and Be stars associated with nebulosity and proposed by Herbig as candidates for newly formed stars of moderately large mass. The system is a part of a large dust complex more than a degree in extent. Structural features in the nebulosity can be traced very near to the star (several are seconds away) and some of these structures are highly polarized in the sense expected for scattered light from the central object. Although the star is classified as an early spectral type (B2-B8) of moderate luminosity (class IV or V), its energy distribution does not resemble a black body characteristic of a stellar photosphere. Instead, the radiated flux has the appearance of free free radiation (thermal bremsstrahlung) usually considered to arise in astrophysical situations involving optically thin plasmas of ions and free electrons. Our observations are consistent with the belief that HD 200775 is a protostar and that the surrounding material is the cocoon from which it formed. The complex polarized structures probably originate in material ejected by radiation pressure and plasma processes as the star rose in luminosity after its gravitational collapse.
Electron spin resonance of
17
O-labeled protein-peroxide radicals: Zein and edestin
Authors: Dimmey Louis J. , Gordy Walter
Published: May 2006

Hyperfine structure due to
17
O has been measured in irradiated zein and edestin after exposure to gaseous oxygen with
17
O concentrated to 24%. The observations prove that the free radicals produced by ionizing irradiation under vacuum at 300 K are converted by the oxygen to protein-peroxide free radicals X—O
(1)
—O
(2)
, with the unpaired electron density in a π-type orbital predominantly on the peroxide group. From the observed couplings, the 2
p
π
spin densities on zein-peroxide are found to be 0.29 and 0.45 for O
(1)
and O
(2)
, respectively; those on edestin-peroxide are 0.26 and 0.48 for O
(1)
and O
(2)
, respectively.
Principles of liquids working in heat engines
Authors: Allen P. C. , Knight W. R. , Paulson D. N. , Wheatley J. C.
Published: May 2006

The thermodynamic and thermophysical properties of liquids suggest that they should be powerful working fluids in heat engines. Their use requires heat engines based conceptually on the Stirling and Malone principles. The principles are explained, and then experiments on propylene are presented that demonstrate the principles and confirm the thermodynamic analysis.
Polypeptide composition of squid neurofilaments.
Authors: Roslansky P F , Cornell-Bell A , Rice R V , Adelman W J
Published: May 2006

Neurofilaments, 10 nm in diameter, from the axoplasm of the squid Loligo pealei have been isolated by a combination of sonication and Millipore filtration. The presence of neurofilaments during the isolation procedure was confirmed by negative staining and transmission electron microscopy. By use of this technique, which results in minimal or no chemical alteration of the native neurofilament proteins, it was shown that actin (43,000 daltons) and tubulin (56,000 daltons) are physically separable from intact neurofilaments. The neurofilament-rich retentate contained two major proteins of 200,000 and 63,000 daltons and larger polypeptides.
Do energetic heavy nuclei penetrate deeply into Earth's atmosphere?
Authors: Price P. B. , Askary F. , Tarlé G.
Published: May 2006

We calculate the expected fluxes of cosmic ray nuclei with charge 5 ≤
Z
≤ 28 at various depths in the earth's atmosphere, taking into account the initial charge distribution, ionization loss, and various modes of fragmentation. The flux of surviving heavy nuclei is too low by a factor ≈10
-10
to account for the ultra-high-energy Centauro events. We describe an experiment to search for highly ionizing particles that may or may not be nuclei.
Kinetics of decay in the expression of interferon-dependent mRNAs responsible for resistance to virus.
Authors: Gordon I , Stevenson D
Published: May 2006

We used 5,6-dichloro-beta D-ribofuranosyl-benzimidazole (DRB), a selective and reversible inhibitor of mRNA production, to investigate the regulation of the pathway leading to resistance to viruses in cells treated with interferon (IF). DRB allows initiation of transcription but promotes premature termination of the nucleotide chains, so that it abolishes interferon-dependent protection against viruses. When the DRB is removed, synthesis of complete mRNAs can resume. Mouse L-929 cells were exposed to 100 microM DRB before and during a 1-hr pulse of IF followed by treatment with antibody to IF to prevent cell-to-cell spread of IF after that time. At different intervals thereafter the cells were washed and the DRB was replaced by medium; after further incubation, the cells were infected with vesicular stomatitis virus. Resistance to virus was inversely proportional to the duration of the block imposed by DRB. When the DRB was removed soon after the IF pulse, substantial protection from virus ensued, but none developed when removal of the DRB was deferred for 5-6 hr. Cells exposed to DRB for 5 hr, then pulsed with IF for 1 hr, still mounted a strong antiviral response. The data show that the ability of cells to resist viral infection decays within 5-6 hr after treatment with IF. Whether the decay is due to shutoff of transcription of mRNAs, or to their destruction or degradation, or whether regulation takes place at one or more subsequent steps in the antiviral pathway, remains to be determined.
A cytoplasmic clock with the same period as the division cycle in Xenopus eggs.
Authors: Hara K , Tydeman P , Kirschner M
Published: May 2006

In most species the cell cycle is arrested in the unfertilized egg. After fertilization the cell cycle is reestablished and a rapid series of cleavages ensues. Preceding the first cleavage in Xenopus the egg undergoes a contraction of its cortex, called the "surface contraction wave," which can be visualized by time-lapse cinematography. This wave of contraction is propagated in a circular manner from the animal pole to the equator. We have found that eggs prevented from cleaving by treatment with antimitotic drugs undergo a sequence of periodic surface contraction waves timed with the cleavage cycle in untreated eggs. In addition, artificially activated eggs, which fail to cleave presumably for lack of a functioning centriole, undergo the same periodic contractions. No nuclear material is required for the periodic waves because a separated egg fragment, produced by constricting a fertilized egg, still undergoes contraction waves with the same period as the cleaving nucleated fragment. These results demonstrate that some expression of the cell cycle persists in the absence of any nuclear material or centrioles, suggesting to us that a biological clock exists in the cytoplasm or cortex of vertebrate eggs, which may be involved in timing the cell cycle.
Monoclonal antibodies specific for carcinoembryonic antigen and produced by two hybrid cell lines.
Authors: Accolla R S , Carrel S , Mach J P
Published: May 2006

Spleen cells from mice immunized with purified carcinoembryonic antigen (CEA), an important tumor marker of human carcinomas, were fused with the mouse myeloma cell line P3-NSI/1-Ag4. Out of the 400 hybrids obtained, 2 secreted antibodies reacting specifically with two different antigenic determinants present on CEA molecules. They were cloned and established as permanent hybridoma cell lines. These antibodies, which have relatively high-affinities and can be produced in unlimited amounts, will be useful both for the immunochemical characterization of CEA and as a standard reagent for the identification of this antigen in human tissues and body fluids.
Self-fertilization and monogenic strains in natural populations of terrestrial slugs
Authors: McCracken Gary F. , Selander Robert K.
Published: May 2006

Electrophoretic studies of genetic variation in 14 species of terrestrial slugs of the families Arionidae, Philomycidae, and Limacidae in the eastern United States indicate that self-fertilization, either facultative or obligatory, is the normal breeding system in six of the species. Three of these six species are single monogenic strains; one consists of three monogenic strains; one includes a highly heterozygous form and two monogenic strains; and one has a moderate amount of polymorphism but little heterozygosity and strong linkage disequilibrium. Eight species are outcrossers, being highly polymorphic and panmictic within local populations. Niche breadth, assessed in terms of extent of geographic distribution and variety of habitats occupied and measured on an experimental plot of woodland, is greater in some monogenic strains than in highly heterozygous, outcrossing species. Colonizing success apparently is independent of the amount of genetic variation carried by a species.
Major structural proteins of type B, type C, and type D oncoviruses share interspecies antigenic determinants.
Authors: Barbacid M , Long L K , Aaronson S A
Published: May 2006

Interspecies antigenic determinants have been used as markers to study the evolution of oncoviruses. By radioimmunologic techniques, it has been possible to detect crossreactivities among the major structural proteins of prototype viruses representing each of the three major Oncovirinae genera. Two different subsets of interspecies antigenic determinants were demonstrated. One encompasses known type B and type D viruses; the other is shared by type D and mammalian type C viruses. Such determinants were also demonstrated in certain as yet unclassified oncoviruses. These findings provide experimental evidence supporting the concept of an evolutionary relationship among the three major oncovirus genera.