bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron microscopic x-ray microanalysis of normal and leukemic human lymphocytes.
Authors: Yarom R , Hall T A , Polliack A
Published: May 2006

A comparative study of the elemental content of normal and leukemic cells was undertaken on a few subjects, using electron microscopic x-ray microanalysis. Phosphorus, sulfur, chlorine, calcium, copper, and zinc were detected in intracellular loci. The concentration of some of the above elements appeared to be disease related. In leukemic lymphocytes, the nuclear zinc was significantly lower than that recorded in normal lymphocytes, while the phosphorus was only moderately decreased. This suggests a faulty zinc uptake or binding in leukemic cells. The possible consequences of intracellular zinc deficiency are discussed.
C-type virus particle formation in erythroblastic islands in spleens of C3Hf mice injected with erythropoietin.
Authors: Feldman D
Published: May 2006

Previous studies suggested a possible association between C-type virus particle formation and erythropoiesis. In this experiment, normal C3Hf mice were injected with erythropoietin in order to increase the rate of erythropoiesis. Sections of spleen from these animals revealed extensive areas of erythroblasts. C-type particles, budding from erythroblasts, were often observed in such areas of spleen from every mouse injected with erythropoietin. In contrast, in sections of spleen from control mice, zones of erythropoiesis were limited, and only a few scattered C-type virus particles were observed in some of the animals examined.
Photoreceptor pigment that induces differentiation in the slime mold Physarum polycephalum.
Authors: Wormington W M , Weaver R F
Published: May 2006

An extract of small molecules (molecular weight less than 500) of the slime mold Physarum polycephalum undergoes a shift in ultraviolet-visible absorption spectrum upon illumination. This illumination also confers on the extract the ability to induce sporulation when injected into a starved, unilluminated slime mold. The spectral shift and appearance of the sporulation-inducing activity both occur regardless of whether the illumination is carried out on an intact slime mold or on the plasmodium-free extract itself. Thin-layer chromatography resolves the slime mold extract into four major visible fractions. One of these has high sporulation-inducing activity after illumination in vitro.
Simultaneous synthesis of types I and III collagen by fibroblasts in culture.
Authors: Gay S , Martin G R , Muller P K , Timpl R , Kuhn K
Published: May 2006

Specific antibodies against types I and III collagens and procollagens were used to localize these proteins in cultured human cells. These studies indicate that the same cell makes both proteins. No type III procollagen synthesis was observed in cells from two patients with two patients with the Ehlers-Danlos type IV syndrome.
Biochemical evidence of variability in the DNA repeat length in the chromatin of higher eukaryotes.
Authors: Compton J L , Bellard M , Chambon P
Published: May 2006

Biochemical evidence is presented which confirms that the DNA repeat length in micrococcal nuclease (spleen endonuclease, nucleate 3'-oligonucleotidohydrolase, EC 3-1-4-7) digests of Chinese hamster ovary chromatin is shorter than that of rat liver chromatin [J.L. Compton, R. Hancock, P. Oudet, and P. Chambon (1976) Eur. J. Biochem., in press]. A survey of available cells has shown that the DNA repeat length of the chromatin of higher eukaryotes varies widely. A value of 196 base pairs was found for cells of all mature tissues, regardless of the source of the tissue, whereas smaller values were found for cells of actively dividing tissues and larger values were found for a genetically inactive cell. Although the DNA repeat length of the chromatin of cells in culture was usually shorter than 196 base pairs, there was no general correlation between the size of the chromatin DNA repeat length and the rate of cell division or the functional state of the cell in culture. Examination of extensive micrococcal nuclease digests suggests that the chromatin subunits of all of the higher eukaryotic cells we have studied contain a core with approximately 140 base pairs of DNA.
Hormone responsive human breast cancer in long-term tissue culture: effect of insulin.
Authors: Osborne C K , Bolan G , Monaco M E , Lippman M E
Published: May 2006

The mechanisms of steroid and peptide hormone action in human breast cancer are poorly understood. We have previously characterized a cell line of human breast cancer in long-term tissue culture that possesses various steroid hormone receptors and responses, providing a model for the study of steroid hormone action. The present studies describe a human breast cancer in vitro that responds to physiologie concentrations of insulin with an increased rate of macromolecular synthesis and growth. Thymidine and uridine incorporation in cells in serum-free medium are stimulated by 10(-11) M insulin and are maximal with 10(-8) M. Leucine incorporation is stimulated by 5 X 10(-11) M insulin and is maximal with 10(-9) M. Significant stimulation of uridine and leucine incorporation is evident by 3 hr and maximal by 10 hr. A 10-hr lag period exists for insulin stimulation of thymidine incorporation, which is maximal form 14 to 24 hr. The effect of 10(-8) M insulin on macromolecular synthesis is accompanied by a 69% increase above controls in the number of cells after 24 hr. The effect on macromolecular synthesis is observed in glucose-free medium. Insulin's effect on protein synthesis is not blocked by inhibition of RNA synthesis with actinomycin D. Glucocorticoids partially inhibit the action of insulin in these cells. This system provides a model for studying insulin action, and suggests that some human breast cancer may show growth regulation by insulin.
Structure and transformation of chitin synthetase particles (chitosomes) during microfibril synthesis in vitro.
Authors: Bracker C E , Ruiz-Herrera J , Bartnicki-Garcia S
Published: May 2006

The fine structure of isolated chitin synthetase (UDP-2-acetamido-2-deoxy-D-glucose:chitin 4-beta-acetamido-deoxyglucosyltransferase; EC 2-4-1-16) particles (chitosomes) from Mucor rouxii and the elaboration of chitin microfibrils were studied by electron microscopy. Chitosomes are spheroidal, but often polymorphic, structures, mostly 40-70 nm in diameter. Their appearance after negative staining varies. Some reveal internal granular structure enclosed by a shell measuring 6-12 nm thick; others do not show internal structure but have a pronounced depression of the external surface. In thin sections, isolated chitosomes appear as microvesicular structures with a tripartite shell 6.5-7.0 nm thick. Morphologically similar structures can be seen in intact cells of M. rouxii. Isolated chitosomes undergo a seemingly irreversible series of transformations when substrate and activators are added. The internal structure changes, and a coiled microfibril (fibroid) appears inside the chitosome. The shell of the chitosome is opened or shed, and an extended microfibril arises from the fibroid particle. During prolonged incubation, the fibroid coils become less common and extended microfibrils appear thicker. We regard the chitosome as the cytoplasmic container and conveyor of chitin synthetase en route to its destination at the cell surface. Isolated chitosomes are well suited for integrated ultrastructural-biochemical studies of microfibril biogenesis in vitro.
Possible role of nucleus-membrane interaction in capping of surface membrane receptors.
Authors: Berke G , Fishelson Z
Published: May 2006

Interaction of multivalent ligands and cell surface receptors can induce redistribution of these receptors to form patches and caps. In this study, we have investigated the role of nucleus-membrane interaction in the capping of membrane components. Mouse L cells and leukemia EL4 cells were enucleated with the aid of cytochalasin B, yielding cytoplasts and karyoplasts. Capping of surface receptors was induced by allo- and hetero-immune sera followed by fluorescein-conjugated antiglobulin serum, or by the plant lectin concanavalin A. Capping could easily be induced in intact cells, but virtually no capping was detected in the nucleus-free cytoplasts. Interestingly, karyoplasts, which posses cell-membrane components but very little cytoplasm, could be easily induced to cap their surface antigens. Hence, cap formation of membrane components seems not to be an autonomous membrane process. The data suggest that interaction of surface membranes and inner cell components associated with the nucleus is involved in the movement of surface membrane receptors.
Group selections among laboratory populations of Tribolium.
Authors: Wade M J
Published: May 2006

Selection at the population level or group selection is defined as genetic change that is brought about or maintained by the differential extinction and/or proliferation of populations. Group selection for both increased and decreased adult population size was carried out among laboratory populations of Tribolium castaneum at 37-day intervals. The effect of individual selection within populations on adult population size was evaluated in an additional control series of populations. The response in the group selection treatments occurred rapidly, within three or four generations, and was large in magnitude, at times differing from the controls by over 200%. This response to selection at the populational level occurred despite strong individual selection which caused a decline in the mean size of the control populations from over 200 adults to near 50 adults in nine 37-day intervals. "Assay" experiments indicated that selective changes in fecundity, developmental time, body weight, and cannibalism rates were responsible in part for the observed treatment differences in adult population size. These findings have implications in terms of speciation in organisms whose range is composed of many partially isolated local populations.
Defective function of a microsomal UDP-glucuronyltransferase in Gunn rats.
Authors: Nakata D , Zakim D , Vessey D A
Published: May 2006

The kinetic parameters of the p-nitrophenol-metabolizing form of UDP-glucuronyltransferase [-UDPglucuronosyltransferase; UDPglucuronate beta-glucuronosyltransferase (acceptor-unspecific), EC 2.4.1.17] have been compared in liver microsomes from the Gunn strain of rat and from normal; Wistar rats. The abnormally low rate of glucuronidation of p-nitrophenol in the Gunn rats, as compared with Wistar rats, is due to decreased affinity of UDP-glucuronyltransferase for UDP-glucuronic acid. Activities at Vmax and the Michaelis constant for p-nitrophenol, KPNP, of UDP-glucuronyltransferase are the same for enzyme from either strain of rat. Studies of the kinetic parameters of the reverse reaction catalyzed by UDP-glucuronyltransferase indicate that the enzyme from Gunn rats also has decreased affinity for UDP. Calculated values of deltaG degrees for the binding of the UDP portion of UDP-glucuronic acid suggest that the defect of UDP-glucuronyltransferase of Gunn rats appears limited to abnormal interactions between the enzyme and the UDP portion of UDP-glucuronic acid. Studies of the extent of UDP-induced inhibition of the forward reaction support this idea. Diethylnitrosamine, added to microsomes in vitro, enhances the affinity of UDP-glucuronyltransferase for the UDP portion of UDP-glucuronic acid. Despite the defective conformation of the UDP-glucuronic acid binding site of UDP-glucuronyltransferase from Gunn rats this enzyme is activated in the normal way by UDP-N-acetylglucosamine, which is a K-type effector with regard to UDP-glucuronic acid.
5'-terminal structure of poliovirus polyribosomal RNA is pUp.
Authors: Hewlett M J , Rose J K , Baltimore D
Published: May 2006

Poliovirus RNA purified from virus-specific polyribosomes does not contain m7G in a 5'-5'-pyrophosphate linkage at its 5'-end. The only potential 5'-end found in ribonuclease digests of this RNA is pUp, which is present in a yield of 1 mole/mole of poliovirus RNA. We conclude that a 5'-terminal m7G is not required for translation of at least one RNA species in animal cells.
Clustering of replicating cells in aortic endothelium.
Authors: Schwartz S M , Benditt E P
Published: May 2006

Cell division in the aortic endothelium of the rat is not randomly distributed. Maps of the aortic surface show focal areas where the daily rate of replication may be in excess of 50%. This implies the existence of focal areas of rapid cell growth or rapid cell turnover and other areas where growth or turnover is largely absent.
Diffusion frequency factors in some simple examples of transition-state rate theory.
Authors: Hill T L
Published: May 2006

In the Eyring rate theory, the rate constant is expressed as a product of a frequency factor (kT/h) and a quotient of partition functions. Continuing an earlier paper, it is shown here by means of simple examples that the Eyring formalism may be extended to include diffusion-controlled processes if a new frequency factor, D/Rlambda, is substituted for kT/h, where D = diffusion coefficient, lambda = thermal de Broglie wavelength, and R = a characteristic distance that depends on the particular case. The Eyring formalism is also applicable in hybrid cases, intermediate between diffusion (D/Rlambda) and dynamics (kT/h). Because these modified frequency factors are not "universal" (as kT/h is), their main use (other than conceptual) would appear to be in cases in which one considers a simple model (with calculable frequency factor) together with a related more complicated model. In the latter case, as an approximation, one would combine the "simple" frequency factor with the "complicated" quotient of partition functions in order to obtain the desired rate constant. Examples are given.
Simultaneous initiation of synthesis of bacteriophage T4 DNA and of deoxyribonucleotides.
Authors: Chiu C S , Tomich P K , Greenberg G R
Published: May 2006

In earlier reports we have suggested that bacteriophate T4 DNA replication occurs in a complex composed of the proteins required for polymerization and the system of enzymes synthesizing the deoxyribonucleoside triphosphate precursors of DNA. T4-induced dCMP hydroxymethylase and dTMP synthetase, though demonstrable in extracts soon after infection, are not active in vivo until about 5 min. The in vivo activities increase exponentially for approximately 15 min and then become constant. We have suggested that the exponential period represents the formation of the complexes. This paper shows that the initiation of DNA synthesis and of the two deoxyribonucleotide-synthesizing activities occurs simultaneously and with coinciding exponential kinetics. The in vivo activities of the two enzymes were tested after infection by a number of T4 amber Dna- mutants. Their activities were essentially unchanged compared to the wild-type phage, except on infection by mutants of gene 43 (T4 DNA nucleotidyltransferase or DNA polymerase). With these mutants the rate of increase of dTMP synthetase and dCMP hydroxymethylase activities was always substantially lower than after infection by wild-type phage. It is proposed that an intimate interaction occurs between T4-induced DNA polymerase and the complex of enzymes forming 5-hydroxymethyl-dCMP and dTMP.
Hemoglobin Wayne: a frameshift mutation detected in human hemoglobin alpha chains.
Authors: Seid-Akhavan M , Winter W P , Abramson R K , Rucknagel D L
Published: May 2006

Hemoglobin Wayne is an alpha chain variant which manifests itself as two minor hemoglobin (Hb) components that migrate more rapidly than Hb A on electrophoresis at pH 8.6. It has been found in a child with Fanconi's anemia and in three generations of the child's family. Each of the minor components yields an alpha chain in which the carboxyl-terminal tripeptide sequence, Lys-Tyr-Arg, has been replaced by the octapeptide sequence Asx-Thr-Val-Lys-Leu-Glu-Pro-Arg. In alpha Wayne I, the slower of the pair, Asx is asparagine, whereas in alpha Wayne II it is aspartic acid. Comparison of the alpha Wayne sequences with the amino-acid sequences of alpha A and alpha Constant Spring leads to the conclusion that Hb Wayne I is the result of a -1 frameshift mutation in the alpha chain and that Hb Wayne II is formed secondarily by spontaneous deamidation of the new asparagine residue. A frameshift is consistent with a single mRNA base sequence for the last eight codons involved and supports the view of Clegg, Weatherall, and Milner [Nature (1971) 234, 337-341] that Hb Constant Spring is the result of a terminator mutation leading to translation of 31 codons not normally translated.
An altered apurinic DNA endonuclease activity in group A and group D xeroderma pigmentosum fibroblasts.
Authors: Kuhnlein U , Penhoet E E , Linn S
Published: May 2006

Endonuclease activity upon depurinated DNA was measured in extracts of cultured fibroblasts from xeroderma pigmentosum patients. Cell lines from complementation groups A, B, C, E, and the XP-variant had slightly reduced levels of activity, but cell lines from complementation group D had one-sixth of the normal activity. An altered pH dependence and a higher apparent Km for substrate in D-cell lines indicate that the remaining activity is also qualitatively different from the activity found in normal cells. A higher Km was also found in cell lines from the A-complementation group but not in cell lines from the C-complementation group. These defects in apurinic DNase might account for the neurological disorders in patients from the D- and the A-complementation groups.
Transepithelial transport in cell culture.
Authors: Misfeldt D S , Hamamoto S T , Pitelka D R
Published: May 2006

In cell culture a kidney epithelial cell line MDCK, forms a continuous sheet of identically oriented asymmetrical cells joined by circumferential occluding junctions. The reconstructed epithelial membrane has transport and permeability qualities of in vivo transporting epithelia. The cell layer can be readily manipulated when cultured on a freely permeable membrane filter and, when placed in an Ussing chamber, electrophysiological measurements can be taken. In the absence of a chemical gradient, the cell layer generates an electrical potential of 1.42 mV, the apical surface negative. It is an effective permeability barrier and lacks significant shunting at the clamped edge, as indicated by a resistance of 84 ohms-cm2, which increased when bulk flow from basolateral to apical was induced by an osmotic gradient or electroosmosis. The MDCK cell layer is cation selective with a relative permeability ratio, PNa/PCl, of 1.7. Net water flux, apical to basolateral, was 7.3 mul cm-2 hr-1 in the absence of a chemical gradient. The morphological and functional qualities of a transporting epithelium are stable in cell culture, and the potential use of a homogeneous cell population in cell culture would enhance studies of epithelial transport at the cellular and subcellular levels.
Rates, patterns, and effectiveness of evolution in multi-level situations.
Authors: Darlington P F
Published: May 2006

Evolution is a multi-level process. Both actual evidence and theoretical considerations suggest as a first generalization that evolution both at single levels and in series of increasingly complex levels decelerates with time. Additional evidence, the expected difference between rapid nonadaptive speciation in small populations and effective adaptation in large ones, and analysis of explosive evolution suggest further that effective adaptive evolution occurs primarily in large populations, and that segments of such evolution tend to begin slowly; accelerate, sometimes explosively; and then decelerate. The segments are irregular, and do not occur at regular intervals. However, the explosive evolution of a general adaptation pre-adapts to and is often followed by an explosive radiation of derivative lineages. This description seems to fit the origin and initial radiation of mammals, and the evolutionary history of man and man's cultures.
Lifting derivations from quotients of separable
C
*
-algebras
Authors: Pedersen Gert K.
Published: May 2006

If π:
A
→
B
is a surjective morphism between separable
C
*
-algebras, then for each derivation δ of
B
there is a derivation [unk]δ of
A
such that π([unk]δ(
a
)) for each
a
in
A
.
Alpha-fetoprotein: the major high-affinity estrogen binder in rat uterine cytosols.
Authors: Uriel J , Bouillon D , Aussel C , Dupiers M
Published: May 2006

Evidence is present that alpha-fetoprotein (AFP), a serum globulin, accounts mainly, if not entirely, for the high estrogen-binding properties of uterine cytosols from immature rats. By the use of specific immunoadsorbents to AFP and by competitive assays with unlabeled steroids and pure AFP, it has been demonstrated that in hypotonic cytosols AFP is present partly as free protein with a sedimentation coefficient of about 4-5 S and partly in association with some intracellular constituent(s) to form an 8S estrogen-binding entity. The AFP leads to 8S transformation results in a loss of antigenic reactivity to antibodies against AFP and a significant change in binding specificity. This change in binding specificity is manifested by an increase in binding affinity for estradiol, estriol, diethylstillbestrol, and nafoxidine ( a non-steroidal anti-estrogen), and by a concomitant decrease in estrone binding. Both the antigenic and binding properties of native AFP are recovered after dissociation of the 8S complex in 0.4 M KC1. An AFP-mediated mechanism of early intracellular events associated with estrogen entry in target cells is suggested and discussed with regard to current views on steroid action.
An enzyme system for replication of duplex circular DNA: the replicative form of phage phi X174.
Authors: Eisenberg S , Scott J F , Kornberg A
Published: May 2006

Viral single strands (SS) are converted to the duplex from (RF) by a soluble enzyme fraction uninfected Escherichia coli [Schekman et al. (1975) J. Biol. Chem. 250, 5859-5865]. When reactions were supplemented with a soluble enzyme fraction from phi X174-infected cells, replication of phi X174 superhelical RF I DNA was observed. The activity supplied by infected cells was absent in cells treated with chloramphenicol or in cells infected with a phi X174 phage mutant in cistron A (cis A). A host function coded by the rep gene, essential in vivo for RF replication (but not for SS leads to RF), was supplied by enzyme fractions from either infected or uninfected cells. Based on complementation assays, the cisA-dependent and the rep-dependent proteins have each been purified about 1000-fold. The synthetic products of the enzymatic reaction were identified as RF I and RF II in which viral (+) and complementary (-) strands were newly synthesized.
Cell cycle analysis and X-chromosome inactivation in the developing mouse.
Authors: Mukherjee A B
Published: May 2006

The duration of different phases of the cell cycle (G1, S, G2, and M), as well as the exact time of initiation of asynchronous DNA replication pattern in one of the X-chromosomes in the female mouse during the early stages of development, have been investigated. It was found that early developmental stages in the mouse are devoid of G1 period, and from the late blastocyst stage the embryonic cells first acquire all the characteristic stages of the cell cycle (G1, S, G2, and M). Additionally, asynchronous DNA replication pattern in one of the X-chromosomes in the female embryos was found to be initiated with the appearance of the G1 period. I have established a correlation between the onset of the G1 period and the initiation of an asynchronous DNA replication pattern in one of the X-chromosomes of the female mammal during embryogenesis.
Distribution of annionic sites in glomerular basement membranes: their possible role in filtration and attachment.
Authors: Caulfield J P , Farquhar M G
Published: May 2006

Lysozyme (pI = II) has been used to identify anionic sites in the glomerular capillary wall. A solution of 1-3% lysozyme was perfused into the left kidney at varying rates. After perfusion, the kidney was fixed in situ and processed for electron microscopy. Lysozyme was seen as an electron-dense deposit which was not present when succinylated lysozyme (pI = 4.5) or myoglobin (pI = 6.9) was perfused instead of native lysozyme. First, the epithelial cell plasma membrane was outlined by a 300-400 A electron-dense layer. Second, there were discrete dense deposits in the subepithelial portions (lamina rara externa) of the basement membrane which, in normal sections, extended from the epithelial cell membrane to the lamina densa and, in grazing section, formed a continuous reticular pattern.
Effects of cholera toxin on cochlear endolymph production: model for endolymphatic hydrops.
Authors: Feldman A M , Brusilow S W
Published: May 2006

To evaluate a possible role for adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and adenosine 3':5'-cyclic monophosphate in the secretion of endolymph, we studied the effect of an intra-scala media injection of purified cholera toxin (an adenylate cyclase stimulant) on cochlear endolymph volume, endolymphatic potential, and endolymphatic Na and K concentrations.
A van der Waals-type equation of state for fluids with associating molecules
Authors: Heidemann Robert A. , Prausnitz J. M.
Published: May 2006

The basic assumptions of van der Waals theory are contained in two well-known concepts: excluded volume (repulsive forces) and a homogeneous, isotropic field potential (attractive forces). We have superimposed on these, one more well-known concept: the existence of dimers, trimers, etc., at chemical equilibrium. With reasonable simplifying assumptions, we obtain a closed-form equation of state, applicable to all fluid densities, and potentially useful for fluids containing strongly polar or hydrogen-bonded molecules. At all temperatures and at high densities, the equation of state suggests a phase transition where, because of extensive association, a new (solid-like) phase is in equilibrium with a “normal” fluid phase. The boundary between these phases has no critical point.
Alteration of polynucleotide secondary structure by ribosomal protein S1.
Authors: Bear D G , Ng R , Van Derveer D , Johnson N P , Thomas G , Schleich T , Noller H F
Published: May 2006

Ribosomal 30S protein S1 causes disruption of the secondary structure of certain pyrimidine-containing polynucleotides. Helical poly(U), poly(C, U), and neutral and acidic poly(C) are stoichiometrically converted by S1 to structures indistinguishable from their partially or completely thermally denatured forms, as revealed by circular dichroism. Of the several double- and triple-stranded helical polynucleotides tested that contain one polypurine strand and at least one polypyrimidine strand, only the conformation of the DNA.RNA hybrid, poly(A)-poly(dT), is perturbed. In the presence of S1, this hybrid undergoes a transition to a new structure that has a circular dichroism spectrum unlike either the native or thermally denatured forms. Intercalated ethidium bromide is released from poly(A)-poly(dT) by S1, confirming the occurrence of a conformational rearrangement. The translation inhibitor, autintricarboxylic acid, completely inhibits the action of S1 on polypyrimidines, but has no effect on the conformational perturbation of poly(A(-poly(dT). The possible relation between these observations and the biological function of protein S1 is discussed.
Protein-protein interaction in transport: periplasmic histidine-binding protein J interacts with P protein.
Authors: Ames G F , Spurich E N
Published: May 2006

A component of the high-affinity histidine transport system in Salmonella typhimurium, the periplasmic histidine-binding protein J, interacts with another transport component, the P protein. A mutant J protein, with a defective interaction site but intact histidine-binding site, can function in histidine transport if an appropriate compensating mutation is introduced in the P protein. The interaction between the J and P proteins is an obligatory step in transport. The significance of this interaction and of the involvement of the P protein in multiple transport functions is discussed.
Regulation of viral transciption and tumor antigen expression in cells transformed by simian virus 40.
Authors: Basilico C , Zouzias D
Published: May 2006

We have studied the expression of simian virus 40 (SV40) specific tumor antigen (T-antigen) and viral RNA in SV40-transformed mouse 3T3 cells that are temperature-sensitive for the expression of the transformed phenotype (ts SV3T3). Although transformed by wild-type SV40, ts SV3T3 cells at 32 degrees behave like standard transformants, while at 39 degrees they became arrested in G1 after reaching saturation density or under conditions of serum starvation. ts SV3T3 cells at 32 degrees or exponentially growing at 39 degrees are uniformly T-antigen positive. However, after G1 arrest at 39 degrees the majority of the cells becomes T-antigen negative. Induction of proliferation in the resting cultures results in the reappearance of T-antigen in most of the cells, concomitant with the induction of DNA synthesis. The reason for the disappearance of T-antigen from ts SV3T3 cells arrested in G1 seems to reside in a transcriptional control operating on the integrated viral DNA, since these cells contain no appreciable amounts of SV40 specific RNA. Viral RNA can be easily detected in cells growint at 32 degrees or at 39 degrees. The results suggest that transcription of the viral genome in SV40-transformed cells is cell-cycle-dependent.
Homologous inhibitors from potato tubers of serine endopeptidases and metallocarboxypeptidases.
Authors: Hass C M , Venkatakrishnan R , Ryan C A
Published: May 2006

A potent polypeptide inhibitor of chymotrypsin has been purified from Russett Burbank potatoes. The inhibitor has no effect on bovine carboxypeptidases A or B but exhibits homology with a carboxypeptidase inhibitor that is also present in potato tubers. The chymotrypsin inhibitor has a molecular weight of approximately 5400 as estimated by gel filtration, amino acid analysis, and titration with chymotrypsin. The polypeptide chain consists of 49 amino acid residues, of which six are half-cystine, forming three disulfide bonds. Its size is similar to that of the carboxypeptidase inhibitor, which contains 39 amino acid residues and also has three disulfide bridges. In immunological double diffusion assays, the chymotrypsin inhibitor and the carboxypeptidase inhibitor do not crossreact; however, automatic Edman degradation of reduced and alkylated derivatives of the chymotrypsin inhibitor, yielding a partial sequence of 18 amino acid residues at the NH2-terminus, reveals a similarity in sequence to that of the carboxypeptidase inhibitor. Thus, inhibitors directed toward two distinct classes of proteases, the serine endopeptidases and the metallocarboxypeptidases, appear to have evolved from a common ancestor.
Isolation and characterization of conditional lethal mutants of Escherichia coli defective in transcription termination factor rho.
Authors: Das A , Court D , Adhya S
Published: May 2006

Polarity suppressor mutants that are conditional lethal for growth have been isolated in E. coli K12. The mutations map between the ilv and cya loci of the E. coli chromosome. Rho factor isolated from one of these ts mutants does not show transcription termination activity at any temperature tested; however, it is found to be temperature sensitive for its poly(C)-dependent ATPase activity. Unlike the previously known polarity suppressor mutants (suA and psu), the rho mutation suppresses all types of polarity. Other interesting properties of these mutants include ultraviolet sensitivity, recombination deficiency, and decreased ability to lysogenize temperate phages lambda and P1. Our results suggest that rho has an essential function in the growth and normal physiology of cells. The rho(ts) mutant allows the growth of phage lambda defective in the N gene. This result supports the model that N gene product prevents transcription termination by antagonizing rho activity.
Induction of maturation (meiosis) in small Xenopus laevis oocytes by injection of maturation promoting factor.
Authors: Hanocq-Quertier J , Baltus E , Brachet J
Published: May 2006

Treatment of small-(stage III) or medium-sized (stage IV) Xenopus laevis oocytes with progesterone, human chorionic gonadotropin, or para-hydroxymercuriphenylsulfonate does not induce maturation. Only the full-grown oocytes (stage VI) undergo maturation when treated with either one of these three substances. In contrast, injection of maturation promoting factor into oocytes of stages III-VI invariably leads to chromosome condensation and germinal vesicle breakdown. No maturation spindle is found in oocytes smaller than 0.9 nm in diameter, and the nuclear sap does not mix with the cytoplasm in the smallest (0.45-0.55 mm in diameter) oocytes. In oocytes of 0.9 mm, maturation is identical to that of full-grown oocytes, except that the maturation spindle does not reach the cortex of the oocyte. Progesterone increases protein synthesis in medium-sized (0.8 mm in diameter) oocytes without inducing meiosis. It has little or no effect on protein synthesis in smaller oocytes.
Isolation from patients with breast cancer of antibodies specific for antigens associated with breast cancer and other malignant diseases.
Authors: Gorsky Y , Vanky F , Sulitzeanu D
Published: May 2006

Antibodies were specifically purified, with the use of pleural fluid antigens entrapped in a polyacrylamide gel as immunoadsorbent, from a pool of sera from patients with breast cancer and from the pleural effusion of an individual patient. The purified antibodies were radioiodinated and tested for capacity to bind to the pleural fluid adsorbent. Binding of the radiolabeled antibodies was inhibited by many of the sera from women with breast cancer to a much greater extent than by sera of healthy women. With purified antibodies originating from the serum, 52% of the breast cancer sera and 16% of sera from patients with other malignancies were more inhibitory than were 95% of the sera of healthy women. In the tests with antibodies eluted from pleural fluid, 24% of the breast cancer sera and 25% of the sera from patients with other neoplastic diseases were more inhibitory than were 95% of the normal sera. We concluded that sera of patients with breast cancer may contain antibodies against antigens associated with breast cancer as well as additional antibodies against antigens that are also found in patients with other neoplastic diseases or in normal individuals. Individual breast cancer sera may inhibit binding of the labeled antibodies against breast cancer owing to their content of antibodies, antigen(s), or both.
Synthesis of choline from ethanolamine in rat brain.
Authors: Kewitz H , Pleul O
Published: May 2006

Specific radioactivities of choline, acetylcholine, phosphocholine, lecithin, lysolecithin, and glycerophosphorylcholine have been measured in brain, blood, liver, and muscle after the intravenous injection of three labeled precursors: choline, methyl-labeled methionine, and ethanolamine. In relation to the specific activity of free choline in blood there was significantly more radioactivity in the free choline of brain after administration of methyl-labeled methionine and labeled ethanolamine than after labeled choline. Since the choline moiety of lipids, which returns back to the choline pool, contained less radioactivity after methyl-labeled methionine and labeled ethanolamine than after labeled choline, it is the most likely interpretation of the finding that choline, in brain can be formed by methylation of free ethanolamine. Data from liver confirm that lecithin is formed in the liver by methylation of phosphatidylethanolamine. No indication was found for the synthesis of choline in muscle. Rates of transfer and transport of choline in brain have been calculated as nmol x g-1 x min-1 as follows: turnover rate of choline, 36.5; rate of synthesis of choline by methylation and net loss of choline into the bloodstream, 6.3; inflow from the blood 6.2; outflow into the blood, 12.5; transfer into lipids and vice versa, 20; transfer to acetylcholine and vice versa, 4.
Influence of growth conditions upon the number of chloroplast DNA molecules in
Euglena gracilis
Authors: Rawson James R. Y. , Boerma Cindy
Published: May 2006

The number of chloroplast DNA molecules in
Euglena gracilis
cells was measured by determining the shift in the observed second-order rate constant for the reassociation of
125
I-labeled chloroplast DNA in the presence of unlabeled total cell DNA. Cells grown to stationary phase in the dark contained 217 molecules of chloroplast DNA. Cells grown to stationary phase in the light in either heterotrophic or autotrophic medium contained 590 and 1014 chloroplast DNA molecules, respectively. The observed second-order rate constant for the reassociation of
125
I-labeled chloroplast DNA was not significantly altered in the presence of total cell DNA from a heat-bleached mutant, ZHB, which lacks chloroplast DNA. This evidence suggests that there is less than 0.3 of a chloroplast DNA molecule present in the nucleus of
Euglena
.
Characterization of 80-million-year-old mollusk shell proteins.
Authors: Weiner S , Lowenstam H A , Hood L
Published: May 2006

Fossil glycoproteins of the soluble organic matrix are present in an 80-million-year-old mollusk shell from the Late Cretaceous Period. Discrete molecular weight components, as determined by gel electrophoresis, are preserved. The fossil organic matrix was compared with the organic matrix of a living representative species of the same superfamily. A particular repeating amino acid sequence, found in contemporary mollusk shell proteins, was identified in the fossil glycoproteins. The ultrastructure, mineralogy, and chemistry of the inorganic components of the fossil and contemporary shells provide information on the state of preservation of the fossil. The use of fossil shell proteins to further our understanding of molecular evolution is discussed.
Linking numbers and nucleosomes.
Authors: Crick F H
Published: May 2006

In considering supercoils formed by closed double-stranded molecules of DNA certain mathematical concepts, such as the linking number and the twist, are needed. The meaning of these for a closed ribbon is explained and also that of the writhing number of a closed curve. Some simple examples are given, some of which may be relevant to the structure of chromatin.
(+/-)-7alpha,8beta-dihydroxy-9beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo(a)-pyrene is an intermediate in the metabolism and binding to DNA of benzo(a)pyrene.
Authors: King H W , Osborne M R , Beland F A , Harvey R G , Brookes P
Published: May 2006

The addition of borate buffer to the aqueous methanol used to elute hydrocarbon-deoxyribonucleoside derivatives from an LH 20 Sephadex column resulted in the separation of the products of reaction with DNA of the stereoisomers, (+/-)7alpha,8beta-dihydroxy-9alpha,10alpha-epoxy- and (+/-)-7alpha,8beta-dihydroxy-9beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrenes, i.e., the syn- and anti-benzo(a)pyrene-diolepoxide, respecitvely. By this technique it was shown that the microsome-mediated binding to DNA of benzo(a)pyrene-7,8-dihydrodiol involved exclusively the anti-benzo(a)pyrene-diolepoxide. The benzo(a)pyrene binding to DNA that resulted on exposure of BHK21/C13 cells to this carcinogen was also shown to result predominantly by reaction of the anti-benzo(a)pyrene-diolepoxide. However, in this case other derivatives, including the syn-benzo(a)pyrene diolepoxide, might also be involved.
Thermodynamic fluctuations in protein molecules.
Authors: Cooper A
Published: May 2006

Apparently conflicting views of the physical nature of globular proteins, and other macromolecules, may be reconciled by consideration of the inevitable thermodynamic fluctuations inherent in microscopic systems. Discrete protein molecules, considered singly, undergo sizeable fluctuations in thermodynamic properties which are manifest in their stochastic properties. This is not incompatible with time-averaged studies of ensembles of proteins from which a more compact, rigid, and static view of these molecules may be obtained.
Aplastic anemia: presence in human bone marrow of cells that suppress myelopoiesis.
Authors: Kagan W A , Ascensão J A , Pahwa R N , Hansen J A , Goldstein G , Valera E B , Incefy G S , Moore M A , Good R A
Published: May 2006

Bone marrow from a patient with aplastic anemia was shown by multiple criteria to have a block in early myeloid differentiation. This block was overcome in vitro by elimination of marrow lymphocytes. Furthermore, this differentiation block was transferred in vitro to normal marrow by coculturing with the patient's marrow. We suggest that some cases of aplastic anemia may be due to an immunologically based suppression of marrow cell differentiation rather than to a defect in stem cells or their necessary inductive environment.
Effects of persistent selective suppression of ganglionic butyrylcholinesterase on steady state and regenerating levels of acetylcholinesterase: implications regarding function of butyrylcholinesterase and regulation of protein synthesis.
Authors: Koelle W A , Koelle G B , Smyrl E G
Published: May 2006

Persistent selective suppression of the butyrylcholinesterase (cholinesterase; acylcholine acyl-hydrolase, EC 3.1.1.8) activity of the superior cervical, stellate, and ciliary ganglia of cats by the daily administration of tetramonoisopropyl pyrophosphortetramide, 3.0 mumol/kg, intravenously, for 6 days produced a significant elevation in the levels of ganglionic acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7). When the same procedure was preceded by the inactivation of over 95% of the ganglionic acetylcholinesterase by sarin, 2.0 mumol/kg, intravenously, the rate of regeneration of acetylcholinesterase was decreased. Results are interpreted as evidence that ganglionic butyrylcholinesterase may serve as a precursor to acetylcholinesterase, and that the level of butyrylcholinesterase may regulate the rate of acetylcholinesterase synthesis.
Interferon, double-stranded RNA, and protein phosphorylation.
Authors: Lebleu B , Sen G C , Shaila S , Cabrer B , Lengyel P
Published: May 2006

We reported earlier that the addition of double-stranded RNA and ATP increases the endonuclease activity more in an extract of Ehrlich ascites tumor cells which have been treated with an interferon preparation than in a comparable extract from control cells. We report here that the addition of double-stranded RNA to an extract from Ehrlich ascites tumor cells which have been treated with an interferon preparation [or with the interferon inducer poly(I)-poly(C)] promotes the phosphorylation by [gamma-32P]ATP of at least two proteins: P1 (molecular weight of 64,000) and P2 (molecular weight of 37,000). Double-stranded RNA also promotes the phosphorylation of at least one (i.e., P1) of these two proteins in an extract from cells which have not been treated with interferon, but the extent of phosphorylation is much smaller. Double-stranded RNA which has been degraded by RNase III, or DNA, does not promote the phosphorylation.
Tolerance and dependence evoked by an endogenous opiate peptide.
Authors: Lampert A , Nirenberg M , Klee W A
Published: May 2006

Incubation of neuroblastoma X glioma hybrid cells for 12-97 hr with methionine-enkephalin results in an increase in adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] that is mediated by the opiate receptor. The results show that cells become tolerant to, and dependent upon, enkephalin.
Localization of vasoactive intestinal polypeptide (VIP) to central and peripheral neurons.
Authors: Larsson L I , Fahrenkrug J , Schaffalitzky De Muckadell O , Sundler F , Håkanson R , Rehfeld J R
Published: May 2006

The localization of the vasoactive intestinal polypeptide (VIP) has been studied with immunohistochemistry and radioimmunoanalysis. VIP immunoreactivity is present in gastrointestinal nerves, which constitute a quantitatively important nerve population that may be intrinsic to the gut wall. VIP-immunoreactive neurons are also found within the ventromedial hypothalamus and give off processes that travel latteral to the third ventricle. Results of radioimmunoanalysis strongly indicate that the immunoreactive material represents true VIP. Thus VIP, at present a gastrointestinal hormone candidate, appears to represent a new neuronal peptide occurring in both the central and peripheral nervous system.
Temperature dependence of cycloheximide-sensitive phase of circadian cycle in Acetabularia mediterranea.
Authors: Karakashian M W , Schweiger H G
Published: May 2006

The biochemical nature of the circadian regulatory system that controls many cellular activities is still unclear. Recent results obtained from the application of protein synthesis inhibitors to individual Acetabularia cells expressing circadian rhythms of photosynthesis indicate that some protein(s) must be synthesized on 80S ribosomes during a discrete part of each cycle to insure correct time-keeping. A comparative study of the effects of brief cycloheximide treatments on cells investigated at different temperature has revealed that the phase of cycloheximide sensitivity is 4-6 hr longer and occurs about 8 hr later in the cycle when cells are kept at 20 degrees rather than 25 degrees. Temperature is known to influence the function of the circadian regulatory system in Acetabularia, but the effect on frequency is small (Q10 approximately equal to 0.8) due to the existence of a temperature-compensating feature. The large effects of temperature observed here thus favor the interpretation that protein synthesis on 80S ribosomes, while providing an essential component of the circadian timing mechanism, does not itself generate the period of the photosynthesis rhythm.
Neurophysiological defects in temperature-sensitive paralytic mutants of Drosophila melanogaster.
Authors: Siddiqi O , Benzer S
Published: May 2006

A new temperature-sensitive paralytic mutant of Drosophila, comatose, is compared behaviorally and physiologically with the previously known types, para and shi. All three have different properties with respect to kinetics of paralysis at high temperature and recovery from paralysis; com is hypersensitive to paralysis by cooling. Neurophysiological experimeents indicate different mechanisms for paralysis in each of the mutants.
Significant structure theory applied to phase separation
Authors: Lee Suck-hyun , Jhon Mu Shik , Eyring Henry
Published: May 2006

The significant structure theory of liquids has been applied to the partially miscible system of the O
3
-O
2
mixture, which exhibits partial miscibility in the temperature range from -195.5°C to -179.9°C. The thermodynamic condition for phase separation is given by the following inequality: [Formula: see text] A partition function for the binary liquid mixture is developed using significant liquid structure theory. Here

X
i

is the mole fraction of either of the two components. We obtain the coexistence curve of the O
3
-O
2
system by varying the mole fractions of the components to find the temperature at which the two liquids separate. The agreement between theory and experiment is satisfactory.