bluuebunny/crossref_metadata_2025 huggingface dataset:
Drosophila
locus with gene-dosage effects on rhodopsin
Authors: Scavarda N. J. , O'Tousa J. , Pak W. L.
Published: May 2006

Mutations that decrease the amplitude of the prolonged depolarizing afterpotential (PDA) in
Drosophila melanogaster
have been shown to have reduced rhodopsin content in the rhabdomeres of photoreceptor cells. In the present study, a genetic analysis of a class of third chromosome PDA-defective mutants localized the
ninaE
locus to the salivary band region 92A-B. In flies with only one copy of this region instead of the normal two copies, and in
ninaE
heterozygotes, the rhodopsin content of the major class of photoreceptors is reduced. Three doses of this region increase the rhodopsin content of these photoreceptors. These characteristics of the
ninaE
locus are expected of the structural gene encoding the major species of opsin in the
Drosophila
compound eye.
Cell-type-specific gene expression and acatalasemic peroxisomes in a null
Cat2
catalase mutant of maize
Authors: Tsaftaris A. S. , Bosabalidis A. M. , Scandalios J. G.
Published: May 2006

Cell separation studies in conjunction with immunocytochemical studies indicate that mesophyll cells and bundle-sheath cells, the dimorphic photosynthetic cell types in the leaves of the C
4
plant
Zea mays
, differ in their catalase composition. In particular, catalase-2, the product of the
Cat2
gene, is found primarily in the bundle-sheath cells, whereas catalase-3, the product of the
Cat3
gene, is found primarily in the mesophyll cells. Electron microscopic observations reveal that bundle-sheath cells of A16, a mutant line lacking expression of the
Cat2
gene in all tissues examined, contain numerous peroxisomes, but they are acatalasemic as determined by staining with 3,3′-diaminobenzidine. The significance of this mutant in physiological studies is discussed.
The carB gene of Escherichia coli: a duplicated gene coding for the large subunit of carbamoyl-phosphate synthetase.
Authors: Nyunoya H , Lusty C J
Published: May 2006

Previous genetic and biochemical studies indicate that the carB gene of Escherichia coli codes for the large subunit of carbamoyl-phosphate synthetase (EC 6.3.5.5). We have determined the nucleotide sequence of a 4-kilobase-pair cloned fragment of E. coli DNA with genetic determinants for carB. The DNA sequence is a 3,219-nucleotide-long reading frame. The polypeptide encoded by this reading frame has been verified to be the large subunit of carbamoyl-phosphate synthetase. The gene product is similar to the large subunit in its molecular weight, amino acid composition and amino-terminal residue, and carboxyl-terminal sequence. The amino acid sequence derived from the nucleotide sequence shows a highly significant homology between the amino- and carboxyl-terminal halves of the protein. We propose that the carB gene was formed by an internal duplication of a smaller ancestral gene.
Localization of c-ras oncogene family on human germ-line chromosomes.
Authors: Jhanwar S C , Neel B G , Hayward W S , Chaganti R S
Published: May 2006

The c-ras family is a set of c-onc genes that are highly conserved in vertebrates. The genes in this family are homologous to the transforming genes of Harvey and Kirsten murine sarcoma viruses (v-Ha-ras and v-Ki-ras, respectively). Using an in situ molecular hybridization method, we detected three sites on the human pachytene chromosomes that exhibited significant hybridization to v-Ki-ras and v-Ha-ras probes. These were chromomere positions that corresponded to bands 11p14.1, 12p12.1, and 12q24.2 of somatic chromosomes. The relationship between these chromosomal sites and previously defined members of the human c-ras gene family is discussed. These chromosomal sites are known to be involved in specific chromosome changes in a variety of tumors and in several congenital disorders that predispose to neoplastic disease.
Rearrangement and amplification of c-abl sequences in the human chronic myelogenous leukemia cell line K-562.
Authors: Collins S J , Groudine M T
Published: May 2006

Structural rearrangements of specific cellular sequences (c-onc genes) homologous to acute transforming retrovirus oncogenes (v-onc genes) have been recently described in various malignancies. Here we show that human cellular sequences (c-abl) homologous to the transforming sequences of the mouse Abelson leukemia virus (v-abl) are amplified some 4- to 8-fold in K-562, a Philadelphia chromosome-positive cell line derived from a patient with chronic myelogenous leukemia in blast crisis. Restriction analysis of K-562 and other human DNA samples reveals a significant rearrangements of the c-abl sequences in this cell line. In addition, investigation of v-abl-related cytoplasmic RNA reveals relatively high levels of these sequences in K-562 compared to other normal and leukemia cells. We have also observed that lambda light chain constant region immunoglobulin genes are amplified in K-562, whereas kappa light chain sequences exhibit no amplification. These results are discussed within the context of the possibility that these Philadelphia chromosome-positive cells exhibit a reciprocal translocation involving chromosome 9 (containing c-abl) and chromosome 22 (containing the lambda light chain genes).
Viral nucleic acid synthesis and antigen accumulation in pancreas and kidney of Pekin ducks infected with duck hepatitis B virus.
Authors: Halpern M S , England J M , Deery D T , Petcu D J , Mason W S , Molnar-Kimber K L
Published: May 2006

Liver, pancreas, and kidney from Pekin ducks infected with duck hepatitis B virus (DHBV) were assayed for the presence of both viral antigen and replication-specific forms of viral nucleic acid. In young congenitally infected ducks, antigen was detectable in hepatocytes and bile duct epithelia, in kidney glomeruli and tubular epithelia, and in cells localized to pancreatic acini. In older experimentally infected ducks, antigen was detectable in hepatocytes, in glomeruli and tubular epithelia, and in cells localized to presumptive pancreatic alpha-islets. All but the glomeruli-associated viral antigen appeared to be localized to the cytoplasm of antigen-positive cells. Much of the glomeruli-associated antigen appeared to be extracellular and was detected in glomeruli that were positive for the accumulation of immunoglobulin, observations suggestive of the deposition of viral antigen-antibody complexes. As analyzed with bulk tissue, replication-specific forms of viral nucleic acid were detectable in liver and pancreas from the young congenitally infected ducks and in liver and kidney from the older experimentally infected ducks.
Reconstitution of active transport in proteoliposomes containing cytochrome o oxidase and lac carrier protein purified from Escherichia coli.
Authors: Matsushita K , Patel L , Gennis R B , Kaback H R
Published: May 2006

Most active transport across the bacterial cell membrane is driven by a proton electrochemical gradient (delta-muH+, interior negative and alkaline) generated via electron transfer through a membrane-bound respiratory chain. This phenomenon is now reproduced in vitro with proteoliposomes containing only two proteins purified from the membrane of Escherichia coli. An o-type cytochrome oxidase was extracted from membranes of a cytochrome d terminal oxidase mutant with octyl beta-D-glucopyranoside after sequential treatment with urea and cholate and was purified to homogeneity by ion-exchange chromatography. The purified oxidase contains four polypeptides (MrS 66,000, 35,000, 22,000, and 17,000), two b-type cytochromes (b558 and b563), and 16-17 nmol of heme b per mg of protein, and it catalyzes the oxidation of ubiquinol and other electron donors with specific activities 20- to 30-fold higher than crude membranes. The lac carrier protein was purified as described. Proteoliposomes were formed in the presence of the oxidase and lac carrier protein by detergent dilution, followed by freeze-thaw/sonication. The system generates a delta-muH+ (interior negative and alkaline) with ubiquinol as electron donor and the magnitude of delta-muH+ is dependent on the concentration of cytochrome o in the proteoliposomes. Furthermore, the proteoliposomes transport lactose against a concentration gradient to an extent that is commensurate with the magnitude of delta-muH+ generated. The results provide powerful additional support for the "chemiosmotic hypothesis" and demonstrate that purified lac carrier protein retains the ability to function in a physiological manner.
Primary structure of the Escherichia coli thyA gene and its thymidylate synthase product.
Authors: Belfort M , Maley G , Pedersen-Lane J , Maley F
Published: May 2006

The nucleotide sequence of a 1,163-base-pair fragment that encodes the entire thyA gene of Escherichia coli K-12 was determined. The strategy involved sequence determination of both DNA strands by using overlapping deletions that had been generated in vitro from the two ends of the fragment with BAL-31 nuclease. The amino-terminal sequence of thymidylate synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45), the product of the thyA gene, located the 792-base-pair open reading frame, which codes for the 264 amino acid residues of this enzyme. The amino acid sequence deduced from the nucleotide data was confirmed to the extent of 40% by partial sequence analysis of the enzyme purified from extracts of the amplified cloned gene. Transcriptional and translational control areas were apparent in the regions flanking the structural gene. The 5-fluorodeoxyuridylate-binding residue of the active site was identified as cysteine-146. Comparison of the E. coli and Lactobacillus casei synthase sequences reveals consistent homology (62%) over extensive regions. This homology is particularly striking in a very hydrophobic region bordering cysteine-146. In the two enzymes, this region, which probably defines the active site, is 82% homologous. However, a dramatic difference between the two sequences is reflected by the surprising finding that a 51-amino-acid stretch, present midway through the L. casei sequence, is completely absent from the E. coli enzyme.
Charged amino acids as spectroscopic determinants for chlorophyll
in vivo
Authors: Eccles Joseph , Honig Barry
Published: May 2006

In this paper we propose that the large spectroscopic red shifts observed for chlorophyll (Chl) and bacteriochlorophyll (BChl)
in vivo
may be due to charged amino acids in the binding site. Molecular orbital calculations of the transition energies of Chl in the field of external charges are carried out. The calculated wavelength shifts induced by these charges are comparable in magnitude to those observed
in vivo
. Moreover the size of the shifts increases in the order BChl
b
> BChl
a
> Chl
a
, which is the observed trend. The ability of the calculations to account for both the absolute and relative magnitudes of the wavelength shifts argues for the validity of the model. Further indirect support comes from the recent demonstration that charged amino acids are responsible for the colors of visual pigments and bacteriorhodopsin. In addition to their effects on spectra the presence of external charges induces large changes in the ionization potential of Chl molecules and thus might explain the
in vivo
alteration of the oxidation potentials in reaction centers.
Two nonallelic tRNAiMet genes are located in the p23 leads to q12 region of human chromosome 6.
Authors: Naylor S L , Sakaguchi A Y , Shows T B , Grzeschik K H , Holmes M , Zasloff M
Published: May 2006

Two nonallelic human tRNAiMet genes were assigned to chromosome 6 by filter hybridization of DNA from human-rodent somatic cell hybrids by using probes containing unique sequences from the regions flanking each tRNAiMet gene. These unique sequence probes thus allowed each tRNAiMet gene to be analyzed individually in cell hybrids. Both tRNAiMet genes segregated in the hybrid cells with the chromosome 6 enzyme markers, soluble malic enzyme and the mitochondrial form of superoxide dismutase, and also with a karyotypically normal chromosome 6. By using hybrid clones containing translocations that divide chromosome 6 into five segments, both tRNAiMet genes were assigned to the p23 leads to q12 region. These results raise the possibility that other tRNAiMet genes may be syntenic with the two described in this study and illustrate the utility of using unique flanking sequences to identify members of a multigene family.
Association of endogenous viral loci with genes encoding murine histocompatibility and lymphocyte differentiation antigens.
Authors: Meruelo D , Rossomando A , Offer M , Buxbaum J , Pellicer A
Published: May 2006

Several polymorphic DNA restriction endonuclease fragments hybridizing with xenotropic and ecotropic envelope virus probes map adjacent to minor histocompatibility and lymphocyte (H/Ly) antigen-encoding loci. Viral DNA restriction fragments are associated with Ly-17 on chromosome 1, H-30, H-3, and H-13 on chromosome 2, Ly-21 on chromosome 7, H-28 on chromosome 3, and H-38 (chromosomal location as yet undetermined). In each case no recombinant can be found between the H/Ly locus in question and the virus-related restriction fragment, suggesting that linkage is very tight. Although some viral loci map to locations where no H/Ly has yet been mapped, the frequency and tightness of linkage in the seven instances described, coupled with the large number of as yet unmapped H/Ly loci, suggests that the associations found are significant.
Antischizophrenic drugs of the diphenylbutylpiperidine type act as calcium channel antagonists.
Authors: Gould R J , Murphy K M , Reynolds I J , Snyder S H
Published: May 2006

Antischizophrenic neuroleptic drugs of the diphenylbutylpiperidine class, which includes pimozide, fluspirilene, penfluridol, and clopimozide, inhibit [3H]nitrendipine binding with IC50 values of 13-30 nM. This inhibition involves receptors for the verapamil/prenylamine class of calcium channel antagonists. These diphenylbutylpiperidines also inhibit potassium-induced calcium-dependent contractions of rat vas deferens at concentrations of 40-350 nM. Other phenothiazine and butyrophenone neuroleptics lack such potent calcium-antagonist actions. Diphenylbutylpiperidines also differ from other neuroleptics in their ability to relieve negative symptoms of schizophrenia, such as emotional withdrawal, as well as the positive symptoms which respond to all neuroleptics. We suggest that these unique antischizophrenic actions are related to a blockade by diphenylbutylpiperidines of voltage-operated calcium channels.
Proenkephalin, [Met]enkephalin, and oxytocin immunoreactivities are colocalized in bovine hypothalamic magnocellular neurons.
Authors: Vanderhaeghen J J , Lotstra F , Liston D R , Rossier J
Published: May 2006

The distribution of proenkephalin and [Met]enkephalin immunoreactivities in the bovine hypothalamo-neurohypophyseal system was studied by use of specific antisera. Proenkephalin and [Met]enkephalin immunoreactivities were found in magnocellular neuronal cell bodies in the dorsal part of the supraoptic nuclei and in the peripheral part of the paraventricular nuclei. A densely staining network of nerve terminals was found in the external part of the median eminence and in the posterior hypophysis. This general distribution is identical to that of the neurohypophyseal hormone oxytocin. The precise localization of proenkephalin and [Met]enkephalin immunoreactivities was compared to the distribution of oxytocin and vasopressin in serial 5-micron sections through the magnocellular nuclei. Oxytocin immunoreactivity was nearly always present in cells that were stained with proenkephalin and [Met]enkephalin antisera. The vasopressin-immunoreactive cells were never stained with either the proenkephalin or the [Met]enkephalin antisera.
Regulation of polyamine biosynthesis in Escherichia coli by basic proteins.
Authors: Heller J S , Rostomily R , Kyriakidis D A , Canellakis E S
Published: May 2006

In Escherichia coli, the biosynthetic ornithine and arginine decarboxylases (EC 4.1.1.17 and 4.1.1.19, respectively) are responsible for the biosynthesis of polyamines from ornithine and arginine, respectively. When E. coli cells are grown in the presence of increasing amounts of polyamines, a progressive increase in the amount of antizyme 1 and antizyme 2 occurs. The amino acid compositions of antizymes 1 and 2 show them to be basic proteins; antizyme 1 has an amino acid composition similar to that of the E. coli histone-like protein HU and of the eukaryotic histone H2B; antizyme 2 is characterized by an unusually high arginine content. We find these proteins to be specific inhibitors of both the biosynthetic ornithine decarboxylase and the biosynthetic arginine decarboxylase. They do not inhibit the corresponding biodegradative ornithine and arginine decarboxylases, nor do they inhibit lysine decarboxylase or S-adenosylmethionine decarboxylase. These properties of the antizymes favor their function in the regulation of polyamine biosynthesis in E. coli. The ability of the purified antizymes to inhibit the ornithine and arginine decarboxylases is stabilized in acidic buffers and is lost upon prolonged exposure to solutions at neutral or basic pH.
Transport of glutathione, as gamma-glutamylcysteinylglycyl ester, into liver and kidney.
Authors: Puri R N , Meister A
Published: May 2006

Administration of gamma-glutamylcysteinylglycyl monomethyl (or monoethyl) ester to mice leads to substantial increases in the levels of glutathione in the liver and kidney. Mice depleted of glutathione by treatment with buthionine sulfoximine, a potent inhibitor of gamma-glutamylcysteine synthetase, exhibited about a 4-fold increase in liver and kidney glutathione levels after administration of glutathione monomethyl ester. This ester also prevented the marked decline in liver glutathione level found after giving mice acetaminophen, and it protected mice from toxicity due to this compound. The findings indicate that the monomethyl and monoethyl esters of glutathione are transported into cells and hydrolyzed to glutathione. Such esters may be useful in experimental work on glutathione metabolism and function and may provide a relatively safe method for protecting cells against damage by toxic compounds, oxygen, and radiation.
Isolation and characterization of a highly enriched preparation of receptosomes (endosomes) from a human cell line.
Authors: Dickson R B , Beguinot L , Hanover J A , Richert N D , Willingham M C , Pastan I
Published: May 2006

Receptor-mediated endocytosis proceeds by transfer of receptor-ligand complexes from clathrin-coated pits at the cell surface to uncoated endocytic vesicles termed receptosomes (or endosomes). These vesicles have now been purified more than 37-fold based on their content of newly internalized epidermal growth factor. 125I-labeled EGF was bound to human KB carcinoma cells at 4 degrees C, and then the cells were warmed to 37 degrees C for 8 min and disrupted. The purification scheme involved density gradient centrifugation on colloidal silica and sucrose and gel filtration on Sephacryl S-1000. Relative to homogenate, receptosomes are enriched 4.3-fold in their cholesterol content and depleted in enzyme markers for plasma membranes (2- to 3-fold) and lysosomes (9-fold). Receptosomes have a polypeptide composition that is different from plasma membrane, lysosome, and other homogenate fractions. They are enriched in transferrin receptors (30-fold) and in unidentified Mr 70,000-75,000 glycoprotein(s); they contain phosphomannosyl receptors. They do not contain detectable amounts of clathrin.
Variation at the 87A heat shock locus in
Drosophila melanogaster
Authors: Brown Andrew J. Leigh
Published: May 2006

Restriction maps for 25 kilobases of DNA around the 87A7 heat shock locus have been determined in 29 chromosomes isolated from a natural population. The heterozygosity per nucleotide and the proportion of polymorphic nucleotide sites were estimated to be 0.0024 and 0.007, respectively. The mean number of insertional differences in this region between random pairs of chromosomes was 0.95. A significant amount of this variation was due to the insertion of large transposable elements. All the insertion/deletion events were found in a region less than 2 kilobases in size. This could either be due to nonrandom integration or to differences in the intensity of selection against DNA insertion at different sites.
Modification of Streptococcus faecalis sex pheromones after acquisition of plasmid DNA.
Authors: Ike Y , Craig R A , White B A , Yagi Y , Clewell D B
Published: May 2006

Recipient strains of Streptococcus faecalis excrete multiple, peptide sex pheromones that induce mating responses in donors harboring certain conjugative plasmids. Acquisition of plasmid DNA leads to a "shutting off" of pheromone excretion, and such cells become responsive to exogenous pheromone. Data are presented showing that donors excrete low levels of a modified, inactive form of the pheromone. This substance, when mixed in excess with active pheromone, inhibits pheromone activity (probably by competition for a receptor site on the donor). Modified forms of both cPD1 and cAD1 were revealed, and each appeared to have a mass about 350-400 daltons larger than the active pheromone. In both cases, pheromone activity could be regenerated by treatment with phosphodiesterase II.
Positive regulation in the general amino acid control of Saccharomyces cerevisiae.
Authors: Hinnebusch A G , Fink G R
Published: May 2006

Starvation of yeast for a single amino acid leads to derepression of enzymes in many different amino acid biosynthetic pathways. This general control is regulated by several transacting genes. Mutations in the TRA3 gene result in constitutive derepression, whereas mutations in AAS genes lead to the inability to derepress. We have isolated aas mutations as suppressors of the tra3-1 mutation. Some of these suppressors are alleles of AAS2 and others define a heretofore unidentified gene, AAS3. We have studied the regulatory behavior of strains containing both aas and tra3 mutations and strains containing the cloned AAS genes in high copy number. Either aas1- or aas2- in combination with tra3- has the Tra- phenotype, whereas aas3- in combination with tra3- has the Aas- phenotype. These interactions suggest that the AAS1 and AAS2 products act indirectly to bring about derepression by disabling the repressive effect of TRA3, whereas the AAS3 product functions more directly and is required even in the absence of the TRA3 function. When present in high copy number, the AAS3 gene complements mutations in AAS1 and AAS2, whereas AAS1 and AAS2 only complement their cognate mutations. Taken together these data suggest that AAS1 and AAS2 are negative regulators of TRA3, which in turn is a negative regulator of AAS3. AAS3 is a positive regulator, which is required for the general control response. This model of negative and positive interactions is formally identical to those proposed for the regulation of the galactose and phosphatase systems in yeast.
Ganglioside GM2 as a human tumor antigen (OFA-I-1).
Authors: Tai T , Paulson J C , Cahan L D , Irie R F
Published: May 2006

A monospecific antibody produced in vitro by a B-lymphoblastoid cell line transformed with Epstein-Barr virus has been shown to recognize a membrane antigen (OFA-I-1) on human tumors and fetal brain. This study identifies the chemical nature of OFA-I-1. The glycolipid fraction of antigen-rich spent medium of an OFA-I-1-positive melanoma cell line, M14, was extracted by chloroform/methanol/water, 4:8:3 (vol/vol), and was separated into fractions of neutral glycolipids and gangliosides by DEAE-Sephadex followed by base treatment and Bio-sil A column elution. OFA-I-1 antigens were found exclusively in the ganglioside fraction when assayed with monospecific anti-OFA-I-1 by an immune adherence inhibition test. The results obtained from thin-layer chromatography of the antigenic M14 ganglioside and sequential glycosidase digestion suggested that the antigen was a ganglioside GM2, GalNAc beta 1 leads to 4(NeuAc alpha 2 leads to 3)Gal beta 1 leads to 4Glc leads to Cer. These results were further supported by testing various authentic gangliosides and neutral glycolipids for OFA-I-1 antigenicity. Only GM2 showed positive reactivity.
A mutation in the
Escherichia coli rho
gene that inhibits the N protein activity of phage λ
Authors: Das Asis , Gottesman Max E. , Wardwell Judith , Trisler Patsy , Gottesman Susan
Published: May 2006

Certain
Escherichia coli rho
mutations, exemplified by
rho026
, block the growth of phage λ by interfering with phage gene expression. The phage gene
N
, whose product suppresses transcription termination, appears to be expressed normally in the mutants, and the functional stability of the N protein is not affected. Our data suggest that these
rho
mutations allow transcription to terminate despite the presence of N. Other
E. coli
mutants displaying a similar phenotype (Nus
-
) fail to propagate wild-type λ but permit the growth of the λ variant λ
nin5
, which has undergone a deletion of the λ terminator
t
R2
. The phenotype of the
rho026
mutant differs: the growth of λ is only marginally improved by the
nin5
deletion. Interestingly, N activity at rho-independent terminators is not inhibited by the mutations, whereas its ability to suppress rho-dependent terminators is markedly reduced. The relevance of this specificity in terms of models of N action is discussed.
Isolation and characterization of the
RAD3
gene of
Saccharomyces cerevisiae
and inviability of
rad3
deletion mutants
Authors: Higgins David R. , Prakash Satya , Reynolds Paul , Polakowska Renata , Weber Shane , Prakash Louise
Published: May 2006

The
RAD3
gene of
Saccharomyces cerevisiae
is required for nicking of DNA containing pyrimidine dimers or interstrand crosslinks. We have cloned the
RAD3
gene and physically mapped it to 2.6 kilobase of DNA. A DNA segment of the cloned
RAD3
insert was ligated into plasmid YIp5, which transforms yeast by homologous integration, and shown to integrate at the
RAD3
site in chromosome V, thus verifying the cloned DNA segment to be the
RAD3
gene and not a suppressor. The
RAD3
gene encodes a 2.5-kilobase mRNA, extending between the
Kpn
I site and the
Sau
3A1/
Bam
HI fusion junction in plasmid pSP10, and the direction of transcription has been determined. The 2.5-kilobase transcript could encode a protein of about 90,000 daltons. We also show the deletions of the
RAD3
gene to be recessive lethals, indicating that the
RAD3
gene plays an important role in other cellular processes in addition to incision of damaged DNA.
Rabbit immunoglobulin kappa genes: structure of a germline b4 allotype J-C locus and evidence for several b4-related sequences in the rabbit genome.
Authors: Emorine L , Dreher K , Kindt T J , Max E E
Published: May 2006

To investigate the genetic mechanism by which certain rabbits can express immunoglobulins unexpected on the basis of their pedigree (i.e., "latent" allotypes), we have begun a study of the rabbit immunoglobulin kappa gene locus. Here we report the structure of a germline genomic clone that encodes the b4 allotype of rabbit kappa immunoglobulin and corresponds to the kappa gene expressed by the rabbit-mouse hybridoma 12F2. The nucleotide sequences of the joining (J) and constant (C) regions reveal structures generally similar to the homologous mouse and human loci, although only one of the five J-like sequences of this rabbit gene is apparently expressed. Southern blotting analysis of DNA from several rabbit allotypic strains by using probes derived from the cloned b4 gene demonstrates that, in contrast to mouse and human, rabbits possess multiple kappa-related sequences. Rabbits of the nominal b4, b5, b6, and b9 allotypes each contain at least two b4-related sequences that are associated with their own J regions and that are highly homologous to the cloned b4 gene in both coding and flanking regions.
Specific DNA sequence amplification in human neuroblastoma cells.
Authors: Montgomery K T , Biedler J L , Spengler B A , Melera P W
Published: May 2006

Southern blot analysis of a number of EcoRI-digested human neuroblastoma DNAs has revealed the presence of a family of discrete restriction fragments, the majority of which are amplified in most, but not all, of the neuroblastoma cell lines tested. None of these sequences is abundantly present in DNA from other human tumors of different tissue origins, including several either known or presumed to contain amplified DNA. Hence, these sequences appear to be specifically amplified by neuroblastoma cells. Hybridization with metaphase chromosomes in situ has localized these sequences to either the homogeneously staining regions or double-minute chromosomes of different neuroblastoma cell lines, indicating that these chromosomal structures, although present in cell lines established from different patients, share many sequences and may have a common, but as yet unknown, function.
Shape recognition and inferior temporal neurons.
Authors: Schwartz E L , Desimone R , Albright T D , Gross C G
Published: May 2006

Inferior temporal cortex plays an important role in shape recognition. To study the shape selectivity of single inferior temporal neurons, we recorded their responses to a set of shapes systematically varying in boundary curvature. Many inferior temporal neurons were selective for stimuli of specific boundary curvature and maintained this selectivity over changes in stimulus size or position. The method of describing boundary curvature was that of Fourier descriptors.
Adaptive choice of mean or median in estimating the center of a symmetric distribution
Authors: Lai T. L. , Robbins Herbert , Yu K. F.
Published: May 2006

An adaptive choice of the sample mean

¯x
n

or the sample median

m
n

is proposed for estimating the center of a symmetric distribution. This choice becomes correct as
n
→ ∞, and in simulation results for finite
n
it is almost as good as the better of

¯x
n

and

m
n

.
Isolation of cDNA clones specific for collagen IV and laminin from mouse teratocarcinoma cells.
Authors: Wang S Y , Gudas L J
Published: May 2006

The synthesis of the proteins laminin and collagen IV is stimulated approximately equal to 20-fold in F9 mouse teratocarcinoma stem cells after treatment of the cells with retinoic acid and N6, O2'-dibutyryl-cAMP (Bt2cAMP). A cDNA library from F9 cells treated with retinoic acid, Bt2cAMP, and theophylline (F9-R + DBC cells) was constructed to isolate cDNA coding for collagen IV or laminin. The recombinant plasmids were screened by differential colony hybridization to cDNA synthesized from poly(A)+ RNA isolated from F9 stem and F9-R + DBC cells. Differentially hybridizing plasmids were then used as probes to hybridize to RNA transfer blots to determine the size of their specific mRNA. Only plasmids containing cDNA sequences specific for high molecular weight mRNA were further analyzed. Studies by hybridization-selection, in vitro translation, and immunoprecipitation showed that a plasmid clone, pc15, contains cDNA homologous to collagen IV (alpha 2) mRNA, and another plasmid clone, pc156, contains cDNA homologous to laminin B mRNA. By RNA blot analyses, the size of mRNA coding for collagen IV (alpha 2) is 7.6 kilobases; the size of mRNA for laminin is 6.8 kilobases. Using the technique of RNA blot hybridization, we studied the time course of the increase in mRNA coding for collagen IV (alpha 2) and laminin B in F9 cells after retinoic acid and Bt2cAMP treatment. Both collagen IV (alpha 2) and laminin B mRNAs are present in F9 stem cells. Collagen IV (alpha 2) mRNA and laminin B mRNA levels increase slightly at approximately 12 hr after retinoic acid and Bt2cAMP addition, with a dramatic increase between 12 and 24 hr after drug treatment.
Cyanobacterial photosystem I: Morphology and aggregation behavior
Authors: Williams Robley C. , Glazer Alexander N. , Lundell Daniel J.
Published: May 2006

A simple procedure is described for the preparation of cyanobacterial photosystem I particles with a full complement of antenna chlorophyll
a
from Triton X-100-solubilized thylakoid membranes. In the presence of ≥0.1% Triton X-100, photosystem I particles from
Synechococcus
6301 were largely monodisperse. These particles, when negatively stained, appeared to approximate prolate ellipsoids 18 × 8 nm. A value of 4-5 × 10
-19
cm
3
was estimated for the volume of the stain-exclusion envelopes of the particles. At low concentrations of Triton X-100, photosystem I particles formed linear aggregates or sheets one-layer thick. The manner of aggregation was strongly dependent on protein concentration. Shadowed preparations of the sheets indicated a thickness of 8.0-8.5 nm.
Patterns of cellular injury in myocardial ischemia determined by monoclonal antimyosin.
Authors: Nolan A C , Clark W A , Karwoski T , Zak R
Published: May 2006

The development of cellular injury in the rat left ventricle resulting from left coronary artery occlusion was examined by immunofluorescence after intravenous injection of monoclonal antimyosin. Cardiac muscle cells that bound antimyosin during ischemia were localized by staining sections with fluorescein-conjugated anti-mouse IgG. Fluorescent staining was detectable within the ischemic region of the left ventricle 3 hr after occlusion and injection of antimyosin. After 6 hr of ischemia, the highly irregular margin of the ischemic zone was clearly outlined by fluorescent cells. At 3-6 hr after occlusion, marked heterogeneity in cellular staining was observed in the epicardial half of the ischemic area, with intensely fluorescent cells intermixed with cells of markedly lower fluorescence. By 24 hr, a homogeneous pattern of staining was observed throughout the ischemic zone. In nonischemic regions of the heart and in rats treated for 24 hr with antimyosin without occlusion, there were only background levels of staining. We conclude that: (i) visualization of ischemic cells via antimyosin provides a sensitive means for examining developing patterns of injury; (ii) the heterogeneity of staining during early ischemia may reflect variation in cellular resistance to deprivation; and (iii) the pattern of fluorescence at the margin of the occluded region indicates that the "border zone" is composed of interdigitating ischemic and nonischemic tissues.
Detection and partial characterization of a chymostatin-sensitive endopeptidase in transformed fibroblasts.
Authors: O'Donnell-Tormey J , Quigley J P
Published: May 2006

A chymostatin-sensitive step in the release of plasminogen activator from transformed fibroblasts has been described recently. By using synthetic peptidyl substrates, we have detected and characterized a chymostatin-sensitive peptidase activity in chicken embryo fibroblasts transformed by Rous sarcoma virus. The activity represents a neutral endopeptidase that exhibits phenylalanine specificity and is inhibited by diisopropyl fluorophosphate. A detailed inhibitor profile of the enzyme activity shows that it is distinct from other chymotrypsin-like phenylalanine-preferring peptidases. The endopeptidase activity in transformed fibroblasts is increased over that of parallel cultures of normal fibroblasts. The mechanism of enzyme inhibition by chymostatin is indicated by these studies, and the possible role of the enzyme in modulating plasminogen activator secretion is discussed.
Expression of the beta subunit of spectrin in nonerythroid cells.
Authors: Nelson W J , Lazarides E
Published: May 2006

Antibodies raised against electrophoretically purified chicken erythrocyte beta subunit of spectrin, called "beta-spectrin," have been used to demonstrate the presence of an immunoreactive form of this polypeptide in nonerythroid tissues. Immunoautoradiography shows that, in chicken erythrocytes, this antiserum reacts with beta-spectrin (Mr 220,000) and another polypeptide (Mr 230,000) that, by two-dimensional tryptic peptide analysis, shows extensive homology with beta-spectrin but not with the alpha subunit of spectrin, called "alpha-spectrin." Immunoautoradiography and immunoprecipitation of various chicken tissues with this antiserum shows that either one variant or both variants of beta-spectrin are expressed. Indirect immunofluorescence reveals that the antiserum reacts with a plasma membrane-associated component of erythroid and some nonerythroid cells. Particularly strong fluorescence is observed in skeletal and cardiac muscle cells where beta-spectrin appears to form a grid-like network along the inner surface of the sarcolemma. The noncoordinated distribution of alpha- and beta-spectrin variants indicates that their expression may be tailored to the functional requirements of the plasma membrane in different cells.
Attenuation control of pyrBI operon expression in Escherichia coli K-12.
Authors: Turnbough C L , Hicks K L , Donahue J P
Published: May 2006

The pyrBI operon of Escherichia coli K-12 encodes the subunits of the pyrimidine biosynthetic enzyme aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2). Expression of this operon apparently is negatively regulated by the intracellular levels of UTP. To elucidate the regulatory mechanism in which UTP functions, the nucleotide sequence of the promoter-regulatory region of the pyrBI operon was determined and DNA fragments containing this region were transcribed in vitro. These experiments revealed a rho-independent transcriptional terminator (attenuator) located only 23 base pairs before the promoter-proximal end of the structural genes. Transcription initiated upstream at either of two potential pyrBI promoters was efficiently (approximately equal to 98%) terminated at this site, indicating that the regulation of pyrBI expression involves attenuation control. Additional features identified suggest a model for regulation in which the relative rates of UTP-dependent transcription within the pyrBI leader region and coupled translation of the leader transcript control transcriptional termination at the attenuator.
Mutations affecting two different steps in transcription initiation at the phage λ
P
RM
promoter
Authors: Shih Ming-Che , Gussin Gary N.
Published: May 2006

The abortive initiation assay [McClure, W. R. (1980)
Proc. Natl. Acad. Sci. USA
77, 5634-5638] was used to study the effects of mutations on the activity of the
P
RM
promoter of phage λ
in vitro
. The transcription initiation properties of four mutant promoters were compared with those of wild-type
P
RM
in the presence or absence of repressor (which activates
P
RM
). Two kinetic parameters were measured:
k
2
, the rate constant for the transition between
closed
and
open
complexes, and
K
B
, the equilibrium constant for the initial binding of RNA polymerase to DNA (formation of closed complexes). The primary effect of repressor on wild-type initiation was stimulation of the isomerization reaction:
k
2
increased about 7-fold. Both in the presence and in the absence of repressor,
prm
U31 and
prm
E104 (changes at nucleotides -33 and -38, respectively) reduced
K
B
significantly without affecting
k
2
, indicating that these mutations affect polymerase binding but not the formation of open complexes. In contrast,
prm
E37 (a change at nucleotide -14) reduced
k
2
significantly without affecting
K
B
. A fourth mutation,
prm
E93 (at nucleotide -39), is phenotypically Prm
-
primarily because it causes a defect in the
O
B
2 operator site and, therefore, the mutant promoter is unable to respond normally to repressor. These results are consistent with the idea that the two regions of
Escherichia coli
promoters in which consensus sequences have been identified, the regions at nucleotides -35 and -10, may provide information for two discrete steps in transcription initiation.
H-2-linked regulation of xenotropic murine leukemia virus expression.
Authors: Yetter R A , Hartley J W , Morse H C
Published: May 2006

A high proportion of lymphocytes from F/St mice produce infectious xenotropic murine leukemia virus (X-MuLV) and express high levels of cell surface antigens, termed XenCSA, related to the major glycoprotein of X-MuLV. In crosses of F/St with AKR, the high-virus phenotype of F/St was found to be recessive and was shown to be governed by a single locus, Cxv-1, less than 2 centimorgans from H-2K. The close association of Cxv-1 with the H-2 complex was confirmed by the observation that B10.F mice, congeneic for the H-2 region of F/St, expressed high levels of infectious X-MuLV and XenCSA, whereas C57BL/10 mice and other C57BL/10 H-2 congeneic strains did not. Studies of hybrid mice homozygous for Cxv-1s, but segregating for a chromosome 1 X-MuLV induction locus (V locus) of F/St, demonstrated that the high-virus phenotype of F/St was dependent on the interaction between Cxv-1 and the chromosome 1 V locus.
Interaction of blood platelets with a microfibrillar extract from adult bovine aorta: requirement for von Willebrand factor.
Authors: Fauvel F , Grant M E , Legrand Y J , Souchon H , Tobelem G , Jackson D S , Caen J P
Published: May 2006

Adult bovine aortic tissue was treated with 6 M guanidinium chloride in the presence of proteinase inhibitors to obtain an extract that was essentially devoid of collagenous components and appeared homogeneous by electron microscopy. When this extract was dispersed by sonication it was found to be a very potent inducer of human platelet aggregation. This interaction required the presence of von Willebrand factor and of its receptor (glycoprotein Ib) on platelet membrane. This was demonstrated by the fact that the aggregation of normal blood platelets resuspended in plasmas deficient in von Willebrand factor was significantly diminished as compared to aggregation in control plasma. Moreover, this aggregation was inhibited by a monoclonal antibody, IgG AN51, to platelet glycoprotein Ib. These studies provide direct biochemical evidence for the existence of a thrombogenic constituent of the vessel wall that is noncollagenous and von Willebrand factor-dependent.
Human papillomavirus types 6 and 11 DNA sequences in genital and laryngeal papillomas and in some cervical cancers.
Authors: Gissmann L , Wolnik L , Ikenberg H , Koldovsky U , Schnürch H G , zur Hausen H
Published: May 2006

Human genital tumors as well as recurrent laryngeal papillomas were analyzed for the presence of human papillomavirus (HPV) 6 and HPV 11 sequences. HPV 11 DNA was found in 7 of 14 laryngeal papillomas; in the 7 other tumors no HPV DNA was demonstrated. HPV 11 DNA was also found in all five atypical condylomata of the cervix included in this study. Condylomata acuminata mainly contained HPV 6 DNA. From 63 biopsy specimens, 41 clearly harbored HPV 6 DNA and 13 harbored HPV 11 DNA. In three tumors accurate typing was impossible, and in six additional ones neither HPV 6 nor HPV 11 DNA could be demonstrated. The data support a genital origin of laryngeal papillomavirus infections. In 4 of 24 malignant tumors, HPV 11 DNA or related sequences were demonstrated; 2 of the 4 were biopsy specimens from invasive cancer, and the other 2 originated from carcinomata in situ. A possible role of this or related papillomavirus types in the induction of malignant genital tumors remains to be elucidated.
Isolation of sea urchin egg microtubules with taxol and identification of mitotic spindle microtubule-associated proteins with monoclonal antibodies.
Authors: Vallee R B , Bloom G S
Published: May 2006

Microtubules were isolated from unfertilized eggs of the sea urchin with the use of the anti-tumor drug taxol. In addition to tubulin, prominent high molecular weight (Mr 205,000-350,000) microtubule-associated proteins (MAPs) were identified as well as MAP species of Mrs 77,000, 100,000, and 120,000. The microtubules were covered with both short periodic arms and longer filamentous arms, both classes of which appeared to crosslink the microtubules into bundles. Monoclonal antibodies were prepared to an unfractionated MAPs preparation. We isolated clonal hybridoma lines producing antibodies to tubulin and to four non-tubulin proteins of Mrs 235,000, 205,000, 150,000, and 37,000. All antibodies strongly and specifically stained the mitotic spindle of dividing sea urchin eggs. All four of the immunoreactive, non-tubulin species behaved as MAPs during microtubule isolation. Thus, we have identified a variety of sea urchin MAPs by biochemical, ultrastructural, and immunochemical means. The immunochemical experiments demonstrated that four of these proteins are microtubule-associated components of the mitotic spindle. We suggest that those proteins that we observed as cross-bridges between the isolated microtublules may be either structural or functional components of the spindle.
Synergy of ricin A chain-containing immunotoxins and ricin B chain-containing immunotoxins in in vitro killing of neoplastic human B cells.
Authors: Vitetta E S , Cushley W , Uhr J W
Published: May 2006

A strategy is described for improving the efficacy of ricin A chain-containing immunotoxins. Highly purified preparations of ricin A chain or ricin B chain were separately coupled to anti-human immunoglobulin antibodies and the conjugates (immunotoxins) were affinity purified to eliminate free chains. Mixtures of anti-Ig-A and anti-Ig-B immunotoxins markedly synergized in vitro in their ability to kill the Ig-bearing human lymphoma cell line Daudi. In contrast, A-chain- or B-chain-containing immunotoxins of irrelevant specificity did not synergize with anti-Ig-A or anti-Ig-B immunotoxins. This finding indicates that free A or B chains do not play a major role in the synergy and that the synergy is specific. Thus, synergy depends on the specificity of the two antibodies; the lectin binding ability of a B-chain-containing immunotoxin of irrelevant specificity does not suffice. This approach of delivering ricin A chain and B chain separately to a target cell may have significant advantages in killing cells that are not effectively killed by A-chain-containing immunotoxins alone.
Immunostimulatory mouse granuloma protein.
Authors: Fontan E , Fauve R M , Hevin B , Jusforgues H
Published: May 2006

Earlier studies have shown that from subcutaneous talc-induced granuloma in mice, a fraction could be extracted that fully protected mice against Listeria monocytogenes. Using standard biochemical procedures--i.e., ammonium sulfate fractionation, preparative electrophoresis, gel filtration chromatography, isoelectric focusing, and preparative polyacrylamide gel electrophoresis--we have now purified an active factor to homogeneity. A single band was obtained in NaDodSO4/polyacrylamide gel with an apparent Mr of 55,000. It migrated with alpha 1-globulins and the isoelectric point was 5 +/- 0.1. The biological activity was destroyed with Pronase but not with trypsin and a monospecific polyclonal rabbit antiserum was obtained. The intravenous injection of 5 micrograms of this "mouse granuloma protein" fully protects mice against a lethal inoculum of L. monocytogenes. Moreover, after their incubation with 10 nM mouse granuloma protein, mouse peritoneal cells became cytostatic against Lewis carcinoma cells.