bluuebunny/crossref_metadata_2025 huggingface dataset:
Specific estrogen-induced cell proliferation of cultured Syrian hamster renal proximal tubular cells in serum-free chemically defined media.
Authors: Oberley T D , Lauchner L J , Pugh T D , Gonzalez A , Goldfarb S , Li S A , Li J J
Published: May 2006

It has long been recognized that the renal proximal tubular epithelium of the hamster is a bona fide estrogen target tissue. The effect of estrogens on the growth of proximal tubule cell explants and dissociated single cells derived from these explant outgrowths has been studied in culture. Renal tubular cells were grown on a PF-HR-9 basement membrane under serum-free chemically defined culture conditions. The cells of tissue explant outgrowths exhibited ultrastructural features typical of proximal tubules including junctional complexes, numerous mitochondria, peroxisomes, and microvilli. At 7-14 days in culture, cell number was enhanced 3-fold in the presence of either 17 beta-estradiol or diethylstilbestrol. Maximal proliferative response was observed at hormone concentrations of 0.6-1 nM. A similar 3-fold increase in cell number was also seen at 1 nM 17 beta-estradiol in subcultured dissociated single tubular cells derived from hamster renal tubular explant outgrowths at 21 days in culture. Neither progesterone, 5 alpha-dihydrotestosterone, nor the inactive diethylstilbestrol metabolite beta-dienestrol elicited this mitogenic effect. Concomitant exposure of tamoxifen at 3-fold molar excess in culture completely abolished the increase in cell number seen with 17 beta-estradiol. Tubular cells obtained from hamster medulla did not exhibit this proliferative response when exposed similarly to 17 beta-estradiol or diethylstilbestrol. The proliferative effect of estrogens on proximal tubular cell growth appears to be species specific since 17 beta-estradiol did not alter the growth of either rat or guinea pig proximal tubules in culture. In addition, at 7-10 days in culture in the presence of 17 beta-estradiol, [3H]thymidine labeling of hamster tubular cells was enhanced 3-fold. A similar increase in mitoses was also observed in cultures containing these potent estrogens during the same time interval of estrogen exposure. These results clearly indicate that estrogens can directly induce primary epithelial cell proliferation at physiologic concentrations and provide strong additional evidence for an important hormonal role in the neoplastic transformation of the hamster kidney.
Mobility of the maize suppressor-mutator element in transgenic tobacco cells.
Authors: Masson P , Fedoroff N V
Published: May 2006

Maize Suppressor-mutator (Spm) transposable elements have been introduced into tobacco cells and a visual assay for Spm activity has been developed using a bacterial beta-glucuronidase gene. The Spm element is mobile in tobacco and can trans-activate excision of a transposition-defective Spm (dSpm) element either from a different site on the same transforming Ti plasmid or from a second plasmid. An Spm element expressed from the stronger cauliflower mosaic virus 35S promoter trans-activates transposition of a dSpm element earlier after its introduction into tobacco cells than an element expressed from its own promoter.
Exchange of terminal portions of X- and Y-chromosomal short arms in human XY females.
Authors: Levilliers J , Quack B , Weissenbach J , Petit C
Published: May 2006

Human Y(+) XX maleness has been shown to result from an abnormal terminal Xp-Yp interchange that can occur during paternal meiosis. To test whether human XY females are produced by the same mechanism, we followed the inheritance of paternal pseudoautosomal loci and Xp22.3-specific loci in two XY female patients. Y-specific sequences and the whole pseudoautosomal region of the Y chromosome of their fathers were absent in these patients. However, the entire pseudoautosomal region and the X-specific part of Xp22.3 distal to the STS locus had been inherited from the X chromosome of the respective father. This Xp transfer to Yp was established by in situ hybridization experiments showing an Xp22.3-specific locus on Yp in both cases. Such results demonstrate that an abnormal and terminal X-Y interchange generated the rearranged Y chromosome of these two XY females; they appear to be the true countertype of Y(+) XX males. In these patients, who also display some Turner stigmata, the Y gene(s) involved in this phenotype is (are) localized to interval 1 or 2. If the loss of such gene(s) affects fetal viability, their proximity to TDF would account for the underrepresentation of interchange 46,XY females compared with Y(+) XX males.
Tumor necrosis factor alpha and interleukin 1 stimulate the human immunodeficiency virus enhancer by activation of the nuclear factor kappa B.
Authors: Osborn L , Kunkel S , Nabel G J
Published: May 2006

Binding of peptide hormones to surface membrane receptors leads to the transcription of specific genes within relevant target cells. How these signals are transduced to alter gene expression is largely unknown, but this mechanism probably involves a sequence of enzymatic steps that activate factors in the nucleus that modulate transcription. We now demonstrate that two different peptide hormones, or cytokines, stimulate the human immunodeficiency virus enhancer, and this effect is mediated by nuclear factor (NF) kappa B (nuclear factor that binds the kappa immunoglobulin light chain gene enhancer). These cytokines, tumor necrosis factor alpha and interleukin 1, act on multiple cell types and represent the only naturally occurring activators of this transcription factor among eight cytokines examined. Although NF-kappa B binding can be stimulated by phorbol 12-myristate 13-acetate, tumor necrosis factor alpha acts through an independent mechanism, inducing NF-kappa B binding in HT-2 cells, which did not show increased binding in response to phorbol 12-myristate 13-acetate, and causing superinduction in Jurkat T-lymphoma cells. Tumor necrosis factor alpha is also a more selective activator of T cells than phorbol 12-myristate 13-acetate, having no effect on lymphokine production in EL-4 cells at the same time it induces NF-kappa B. These findings suggest that human immunodeficiency virus gene expression can be induced in T cells without activating lymphokine secretion and that the role of these cytokines in the activation of latent human immunodeficiency virus infection deserves further clinical evaluation. Finally, this link between binding at the surface membrane and stimulation of a specific transcription factor should help define intermediates for these cytokine activation pathways.
Purification of the migration stimulating factor produced by fetal and breast cancer patient fibroblasts.
Authors: Grey A M , Schor A M , Rushton G , Ellis I , Schor S L
Published: May 2006

We have previously shown that (i) human skin fibroblasts of fetal and adult origin display distinctive migratory phenotypes, (ii) this difference in cell behavior results from the production of a soluble "migration stimulating factor" (MSF) by fetal cells, and (iii) skin fibroblasts from breast cancer patients commonly resemble fetal fibroblasts both in migratory phenotype and in production of MSF. Data are now presented indicating that MSF present in the conditioned medium of fetal and cancer patient fibroblasts is precipitated at 10% saturation ammonium sulfate and binds to heparin and cation-exchange resins. Based on this information, we have devised a scheme for the purification of MSF involving the sequential application of ammonium sulfate precipitation, heparin affinity, gel filtration, and reverse-phase chromatography. Purified MSF has an estimated molecular mass of 70 kDa; amino acid analysis reveals a relatively high level of proline (13.34 residues per 100). Our results further suggest that skin fibroblasts from breast cancer patients produce an additional factor with migration stimulating activity; this factor is precipitated at higher concentrations of ammonium sulfate and binds to anion-exchange resins. We have previously discussed the possible direct involvement of fetal-like fibroblasts in cancer pathogenesis. The availability of MSF obtained from cancer patient fibroblasts provides a potential means with which to examine the complex cellular interactions contributing to this process as well as develop a screening regime for identifying individuals at elevated risk of developing cancer.
Regulation of neuronal oxytocin mRNA by ovarian steroids in the mature and developing hypothalamus.
Authors: Miller F D , Ozimek G , Milner R J , Bloom F E
Published: May 2006

We have examined the changes in neuronal expression of oxytocin mRNA in the perinatal and mature female rat as a function of endogenous gonadal steroids. Northern blot analysis demonstrated a significant developmental increase in the abundance of oxytocin mRNA in the female brain concomitant with puberty. Ovariectomy of adult females decreased total brain oxytocin mRNA to significantly lower levels. In contrast, lactating mothers had increased levels of neuronal oxytocin mRNA. In situ hybridization analysis of neuronal oxytocin mRNA in adolescent, mature virgin, and ovariectomized virgin female brains demonstrated that the location and number of neurons expressing oxytocin mRNA was unchanged and that total brain oxytocin mRNA differences were attributable to amounts expressed per neuron. Differences in mRNA abundance were noted in oxytocin neurons throughout the hypothalamus, including those known to project as magnocellular neurons to the neurohypophysis and those of parvocellular origin thought to make wholly intracerebral connections. This developmental and dynamic regulation of oxytocin mRNA levels during gonadal maturation may coordinate the peripheral and central effects of this peptide on the reproductive biology of the female rat.
Striatal phosphoproteins in Parkinson disease and progressive supranuclear palsy.
Authors: Girault J A , Raisman-Vozari R , Agid Y , Greengard P
Published: May 2006

This study was undertaken to evaluate the levels of cAMP-regulated phosphoproteins in the striatum of patients with neurodegenerative diseases of the dopaminergic system. Postmortem samples of caudate nucleus and putamen from 24 control subjects, 23 patients with Parkinson disease, and 13 patients with progressive supranuclear palsy were studied with immunoblotting techniques. The levels of tyrosine hydroxylase were reduced in patients with Parkinson disease (levels were 24% and 10% of controls in caudate nucleus and putamen, respectively) and with progressive supranuclear palsy (levels were 11% and 6% of controls in caudate nucleus and putamen, respectively). Five phosphoproteins, which are present in striatal neurons and are likely to play a role in the postsynaptic actions of dopamine, were measured. These included ARPP-16, ARPP-19, ARPP-21 (cAMP-regulated phosphoproteins of Mr 16,000, 19,000, and 21,000, respectively), DARPP-32 (dopamine- and cAMP-regulated phosphoprotein of Mr 32,000), and phosphatase inhibitor I. The levels of these phosphoproteins were inversely correlated with postmortem delay. In brains of patients with Parkinson disease or progressive supranuclear palsy with postmortem delays comparable to those of controls, the levels of these proteins as well as those of synaptic (synapsin I and synaptophysin) and glial (glial fibrillary acidic protein and myelin basic protein) markers were not significantly modified. We conclude that the levels of several phosphoproteins involved in signal transduction in striatal neurons are not altered in Parkinson disease and progressive supranuclear palsy. This observation supports the view that the striatal output neurons are intact in both diseases.
Puberty in monkeys is triggered by chemical stimulation of the hypothalamus.
Authors: Plant T M , Gay V L , Marshall G R , Arslan M
Published: May 2006

Gonadal quiescence prior to puberty in primates results from a diminished secretion of the pituitary gonadotropic hormones, follicle-stimulating hormone and luteinizing hormone, which, in turn, is occasioned by an interruption of pulsatile release of gonadotropin-releasing hormone (GnRH) from the hypothalamus during this phase of development. A discharge of GnRH may be provoked from the hypothalamus of prepubertal monkeys, however, by an i.v. injection of N-methyl-D-aspartate (NMDA), an analog of the putative excitatory neurotransmitter, aspartate. Since this action of NMDA is blocked by the specific NMDA receptor antagonist, DL-2-amino-5-phosphonopentanoic acid, the release of GnRH is likely mediated by NMDA receptors located either on the GnRH neurons themselves or on afferents to the GnRH cells. We report here that prolonged intermittent NMDA stimulation of GnRH neurons within the hypothalamus of the juvenile monkey for 16-30 wk results, with surprising ease, in the onset of precocious puberty with full activation of the hypothalamic-pituitary-Leydig cell axis and initiation of spermatogenesis. These findings demonstrate that, in primates, the network of hypothalamic GnRH neurons, which in adulthood provides the drive to the gonadotropin-secreting cells of the anterior pituitary gland, must now be viewed together with the pituitary and gonads as a nonlimiting component of the control system that governs the onset of puberty in these species.
Endotoxin pretreatment increases endogenous myocardial catalase activity and decreases ischemia-reperfusion injury of isolated rat hearts.
Authors: Brown J M , Grosso M A , Terada L S , Whitman G J , Banerjee A , White C W , Harken A H , Repine J E
Published: May 2006

Hearts isolated from rats pretreated 24 hr before with endotoxin had increased myocardial catalase activity, but the same superoxide dismutase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase activities, as hearts from untreated rats. Hearts isolated from rats pretreated with endotoxin 24 hr before also had increased myocardial function (decreased injury) after ischemia and reperfusion (Langendorff apparatus, 37 degrees C), as assessed by measurement of ventricular developed pressure, contractility (+dP/dt), and relaxation rate (-dP/dt), compared to control hearts. In contrast, hearts isolated from rats pretreated with endotoxin 1 hr before isolation or hearts perfused with endotoxin did not have increased catalase activity or decreased injury following ischemia and reperfusion. Aminotriazole pretreatment prevented increases in myocardial catalase activity and myocardial function after ischemia-reperfusion in hearts from endotoxin-pretreated rats. The results suggest that endotoxin pretreatment decreases cardiac ischemia-reperfusion injury and that increases in endogenous myocardial catalase activity contribute to protection.
Constitutive endocytosis of HLA class I antigens requires a specific portion of the intracytoplasmic tail that shares structural features with other endocytosed molecules.
Authors: Vega M A , Strominger J L
Published: May 2006

HLA class I antigens present in the human leukemia T-cell line HPB-ALL are shown to be endocytosed in the absence of specific antibodies. In 1 hr, approximately 10% of class I molecules initially present at the cell surface are found intracellularly. Genetically engineered mutants of the HLA-A2 gene lacking exon 6 or 7 or both were used to analyze whether the cytoplasmic region contributes to the internalization. The results indicate that amino acids encoded by exon 7 (spanning amino acid residues 323-340) are required for internalization, while deletion of exon 6 had no effect. In addition, a comparison of the cytoplasmic sequences of receptors that are known to be internalized via coated pits and the present data revealed that they share a structural feature that could constitute a specific signal required for endocytosis.
Thymidine kinase obliteration: creation of transgenic mice with controlled immune deficiency.
Authors: Heyman R A , Borrelli E , Lesley J , Anderson D , Richman D D , Baird S M , Hyman R , Evans R M
Published: May 2006

The cell-specific expression of herpes simplex virus 1 thymidine kinase (HSV-1-tk) has provided a simple and highly efficient technique to achieve conditional ablation of targeted cell types in transgenic mice. The ablation is induced by treating transgenic animals expressing HSV-1-tk with the antiherpetic drug ganciclovir. In lymphoid tissues of mice expressing HSV-1-tk from an immunoglobulin promoter, administration of ganciclovir leads to massive destruction of B- and T-cell lineages. Tissues not expressing HSV-1-tk are insensitive to drug treatment. After depletion of greater than 99% of total thymocytes, a number of progenitor cells remain that are able to repopulate all T-cell lineages within 7 days. The ability to control and direct ablation allows for creation of conditional mutant phenotypes at precise periods of development. This technique also provides a potential means to enrich stem cell populations as well as permitting the creation of animal models for particular pathological conditions.
Phagocytosis of aggregated lipoprotein by macrophages: low density lipoprotein receptor-dependent foam-cell formation.
Authors: Suits A G , Chait A , Aviram M , Heinecke J W
Published: May 2006

Low density lipoprotein (LDL) modified by incubation with phospholipase C (PLC-LDL) aggregates in solution and is rapidly taken up and degraded by human and mouse macrophages, producing foam cells in vitro. Human, mouse, and rabbit macrophages degraded 125I-labeled PLC-LDL (125I-PLC-LDL) more rapidly than native 125I-labeled LDL (125I-LDL), while nonphagocytic cells such as human fibroblasts and bovine aortic endothelial cells degraded 125I-PLC-LDL more slowly than 125I-LDL. This suggested the mechanism for internalization of PLC-LDL was phagocytosis. When examined by electron microscopy, mouse peritoneal macrophages appeared to be phagocytosing PLC-LDL. The uptake and degradation of 125I-PLC-LDL by human macrophages was inhibited greater than 80% by the monoclonal antibody C7 (IgG2b) produced by hybridoma C7, which blocks the ligand binding domain of the LDL receptor. Similarly, methylation of 125I-LDL (125I-MeLDL) prior to treatment with phospholipase C decreased its subsequent uptake and degradation by human macrophages by greater than 90%. The uptake and degradation of phospholipase C-modified 125I-MeLDL by macrophages could be restored by incubation of the methylated lipoprotein with apoprotein E, a ligand recognized by the LDL receptor. These results indicate that macrophages internalize PLC-LDL by LDL receptor-dependent phagocytosis.
Two-dimensional DNA fingerprinting of human individuals.
Authors: Uitterlinden A G , Slagboom P E , Knook D L , Vijg J
Published: May 2006

The limiting factor in the presently available techniques for the detection of DNA sequence variation in the human genome is the low resolution of Southern blot analysis. To increase the analytical power of this technique, we applied size fractionation of genomic DNA restriction fragments in conjunction with their sequence-dependent separation in denaturing gradient gels; the two-dimensional separation patterns obtained were subsequently transferred to nylon membranes. Hybridization analysis using minisatellite core sequences as probes resulted in two-dimensional genomic DNA fingerprints with a resolution of up to 625 separated spots per probe per human individual; by conventional Southern blot analysis, only 20-30 bands can be resolved. Using the two-dimensional DNA fingerprinting technique, we demonstrate in a small human pedigree the simultaneous transmission of 37 polymorphic fragments (out of 365 spots) for probe 33.15 and 105 polymorphic fragments (out of 625 spots) for probe 33.6. In addition, a mutation was detected in this pedigree by probe 33.6. We anticipate that this method will be of great use in studies aimed at (i) measuring human mutation frequencies, (ii) associating genetic variation with disease, (iii) analyzing genomic instability in relation to cancer and aging, and (iv) linkage analysis and mapping of disease genes.
The evolution of eusociality: Reproductive head starts of workers
Authors: Queller David C.
Published: May 2006

In eusocial species, many individuals forego their personal reproduction to aid the reproduction of their mother or other relatives. Kin selection can favor such behavior for any positive degree of relatedness to the individuals being helped, provided the helper gives them a sufficiently large fitness gain compared to the fitness cost of giving up its own reproduction. Yet, little attention has been given to the question of how helpers can aid relatives more than they can aid themselves, particularly in species lacking morphologically specialized castes. One answer to this question is explored here. When a potential helper is born into a colony that has immature young, its help may quickly bring those young to the age of independence. If it left to reproduce alone, it would have to bring its own offspring all the way to independence. The consequences of early mortality therefore differ: solitary reproducers that die early will fail to bring any young to independence, while helpers that die at the same age may have made substantial contributions. Published data from four polistine wasps show that high adult mortality rates and long periods of offspring dependence combine to provide a large selective advantage for worker behavior.
Evolution of mouse chromosome 17 and the origin of inversions associated with t haplotypes.
Authors: Hammer M F , Schimenti J , Silver L M
Published: May 2006

Mouse t haplotypes are variant forms of chromosome 17 that exist at high frequencies in worldwide populations of several species of house mouse. They are known to differ from wild-type chromosomes with respect to two relative inversions referred to as proximal and distal. An untested assumption has been that these two inversions originated in the chromosomal lineage leading to present-day t haplotypes. To investigate the evolutionary origins of these inversions and the possibility of additional inversions, interspecific crosses were performed between Mus spretus or Mus abbotti and laboratory strains of Mus domesticus that carried wild-type and t haplotypes forms of chromosome 17. The results provide evidence for the existence of two additional nonoverlapping inversions--one between the proximal and distal inversions and one between the centromere and the proximal inversion. These four inversions span nearly the entire region of t haplotype recombination suppression. Considering the distribution of these inversions among the species studied as well as the organization of the D17Leh66 family of DNA elements, we infer that the proximal inversion occurred on the lineage leading to the common ancestor of M. domesticus and M. abbotti, and that the other three inversions occurred on the separate lineage leading to present-day t haplotypes. Alternative models for the evolution of t haplotypes are discussed in light of these findings.
Long-term observations of autoimmune-prone mice treated for autoimmune disease by allogeneic bone marrow transplantation.
Authors: Ikehara S , Yasumizu R , Inaba M , Izui S , Hayakawa K , Sekita K , Toki J , Sugiura K , Iwai H , Nakamura T
Published: May 2006

Long-term effects of allogeneic bone marrow transplantation (ABMT) across major histocompatibility complex barriers were studied in (NZB x NZW)F1 (B/W), BXSB, and MRL/Mr-lpr-lpr (MRL/lpr) mice with established autoimmune disease at the time of ABMT. In the BXSB or B/W mice, ABMT cured all aspects of autoimmune disease. Glomerular damage, revealed by histological study was dramatically improved. Serological abnormalities and immunologic functions also were normalized. Correction of autoimmune disease and advanced renal disease in BXSB and B/W mice regularly lasted greater than 5-6 mo and even 1 yr after ABMT. In the MRL/lpr mice, however, autoimmune and renal disease at first improved but then recurred after ABMT, apparently because of intolerance of mice for high doses of irradiation and a high degree of resistance of recipient stem cells to irradiation. In this model, H-2 typing revealed that by the time of relapse, immunocompetent cells of the chimeric mice had been replaced by host (MRL/lpr; H-2k) cells. B220+ Ly-1+ cells, present in increased numbers in untreated MRL/lpr mice, initially returned to normal levels after ABMT but then reappeared in the MRL/lpr mice that had received marrow from donors having few such lymphocytes. Thus, our results show that MRL/lpr mice possess abnormal radioresistant stem cells and provide impressive evidence that the origin of autoimmune diseases in this strain, as in the several other strains studied, residues in abnormalities present in stem cells.
Unique properties of non-N-methyl-D-aspartate excitatory responses in cultured purkinje neurons.
Authors: Joels M , Yool A J , Gruol D L
Published: May 2006

Cerebellar Purkinje neurons respond to glutamate and to the agonists quisqualate (QA) and kainate (KA) with prolonged, multiphasic, voltage-dependent depolarizations. In contrast, N-methyl-D-aspartate (NMDA) at equivalent doses is not effective as an agonist for Purkinje neurons. The responses to QA and KA are reduced by extracellular Cd2+ (30 microM), by increased Mg2+ or Ca2+ (12 mM), and by the glutamate antagonist kynurenic acid (1 mM) but not by the NMDA-selective antagonist 2-amino-5-phosphonovalerate (100 microM). The short pressure application of 1 microM QA (less than or equal to 0.5 s) produces a response often exceeding 1 min in duration, which consists of several phases: rapid initial depolarization, followed by a long plateau, repolarization, and a subsequent small hyperpolarization. A similar response is evoked by glutamate and KA at higher doses (30-50 microM). The initial and plateau depolarizations are dependent on Na+, being reduced by substitution of external Na+ with sucrose or choline, but are not affected by the Na+ channel blocker tetrodotoxin. Rectification, observed at hyperpolarized potentials below -60 mV set by current clamp, is attributed in part to an intrinsic voltage sensitivity of the agonist-activated response. Both the duration and the magnitude of the excitatory responses were found to be voltage-dependent. Single-channel recordings of a Ca2+-sensitive K+ channel, activated selectively during the excitatory response, suggest that intracellular Ca2+ increases during the plateau phase. Certain properties of the excitatory responses in the Purkinje neuron resemble those associated with NMDA-receptor activation in other regions of the central nervous system, including voltage-sensitive rectification, blockade by divalent cations, and the induction of increased intracellular Ca2+ during the excitatory response. These unique properties may enable the Purkinje neuron to express both rapid and long-term effects of glutamatergic transmission with non-NMDA receptors alone.
Bacteriophage P1 cloning system for the isolation, amplification, and recovery of DNA fragments as large as 100 kilobase pairs.
Authors: Sternberg N
Published: May 2006

The development of a bacteriophage P1 cloning system capable of accepting DNA fragments as large as 100 kilobase pairs (kbp) is described. The vectors used in this system contain a P1 packaging site (pac) to package vector and cloned DNA into phage particles, two P1 loxP recombination sites to cyclize the packaged DNA once it has been injected into a strain of Escherichia coli containing the P1 Cre recombinase, a kanr gene to select bacterial clones containing the cyclized DNA, a P1 plasmid replicon to stably maintain that DNA in E. coli at one copy per cell chromosome, and a lac promoter-regulated P1 lytic replicon to amplify the DNA before it is reisolated. An essential feature of the cloning system is a two-stage in vitro packaging reaction that packages vector DNA containing cloned inserts into phage particles that can deliver their DNA to E. coli with near unit efficiency. The packaging reaction can generate 10(5) clones with high molecular weight DNA inserts per microgram of vector DNA. Using NotI fragments from E. coli DNA, it was shown that the system can clone 95- and 100-kbp fragments but not a 106-kbp fragment. Presumably, the combined size of the latter fragment and the vector DNA (13 kbp) exceeds the headful capacity of P1.
Automatic generation of primary sequence patterns from sets of related protein sequences.
Authors: Smith R F , Smith T F
Published: May 2006

We have developed a computer algorithm that can extract the pattern of conserved primary sequence elements common to all members of a homologous protein family. The method involves clustering the pairwise similarity scores among a set of related sequences to generate a binary dendrogram (tree). The tree is then reduced in a stepwise manner by progressively replacing the node connecting the two most similar termini by one common pattern until only a single common "root" pattern remains. A pattern is generated at a node by (i) performing a local optimal alignment on the sequence/pattern pair connected by the node with the use of an extended dynamic programming algorithm and then (ii) constructing a single common pattern from this alignment with a nested hierarchy of amino acid classes to identify the minimal inclusive amino acid class covering each paired set of elements in the alignment. Gaps within an alignment are created and/or extended using a "pay once" gap penalty rule, and gapped positions are converted into gap characters that function as 0 or 1 amino acid of any type during subsequent alignment. This method has been used to generate a library of covering patterns for homologous families in the National Biomedical Research Foundation/Protein Identification Resource protein sequence data base. We show that a covering pattern can be more diagnostic for sequence family membership than any of the individual sequences used to construct the pattern.
Self-tolerance to HLA focuses the response of immunized HLA-transgenic mice on production of antibody to precise polymorphic HLA alloantigens.
Authors: Hämmerling G J , Chamberlain J W , Dill O , Yang S Y , Dupont B , Khan R , Chua R , Weissman S M , Hämmerling U
Published: May 2006

HLA class I-transgenic mice express HLA antigen on their tissues and establish self-tolerance to the expressed monomorphic and polymorphic determinants. When challenged with skin grafts and lymphoid cells of a second HLA-transgenic mouse expressing a different HLA molecule, a specific immune response is elicited that is focused on the determinants specified by the allelic HLA differences between donor and recipient transgenic mice. In the studies described, this has led to the production of a number of monoclonal antibodies with specificity for the HLA-Cw3 and HLA-B7 crossreactive groups of class I antigens. These results indicate that immunization of appropriate transgenic strains of mice with murine cells expressing a different HLA allelic transgene should permit the generation of monoclonal antibodies of narrow specificity against virtually any polymorphic epitope on HLA antigens.
Mouse insulin-responsive glucose transporter gene: characterization of the gene and trans-activation by the CCAAT/enhancer binding protein.
Authors: Kaestner K H , Christy R J , Lane M D
Published: May 2006

Adipose tissue and skeletal and heart muscle, which exhibit insulin-stimulated glucose uptake, express a specific, insulin-responsive glucose transporter. Previously, a cDNA (GT2) encoding this protein was isolated from a mouse 3T3-L1 adipocyte library and was sequenced. Here we report the isolation and characterization of the corresponding mouse gene designated GLUT4. The GLUT4 gene spans 7 kilobases and consists of 11 exons and 10 introns. The start site of transcription was mapped 180 nucleotides upstream of the initial methionine codon. The GLUT4 promoter contains four potential binding sites for the nuclear transcription factor Sp1 as well as a CCAAT box. DNase I footprinting of the GLUT4 promoter with nuclear extracts from undifferentiated and differentiated 3T3-L1 cells revealed that a differentiation-specific nuclear factor binds in the region at position -258 relative to the start site of transcription. Purified CCAAT/enhancer binding protein (C/EBP) was found to bind at the same position. Transient cotransfection into 3T3-L1 preadipocytes of a GLUT4 promoter-chloramphenicol acetyltransferase gene construct that contains the C/EBP binding site, together with a C/EBP expression vector, revealed that C/EBP trans-activates the GLUT4 promoter. We suggest that C/EBP plays an important role in tissue-specific, as well as metabolic, regulation of the insulin-responsive glucose transporter gene.
Specific binding of antigenic peptides to separate alpha and beta chains of class II molecules of the major histocompatibility complex.
Authors: Rothenhäusler B , Dornmair K , McConnell H M
Published: May 2006

Class II molecules of the major histocompatibility complex bind antigenic peptides and present them to T-helper cells. Class II molecules are heterodimers consisting of one alpha and one beta chain. Here we report that each isolated alpha and beta chain binds antigenic peptides and that this binding is specific. The specificity of peptide binding was investigated by employing the murine major histocompatibility complex haplotypes I-Ad and I-Ek and fluorescence-labeled peptides of chicken ovalbumin and pigeon cytochrome c, respectively, which are known to be specific for these haplotypes. The major histocompatibility complex molecules were incubated with these peptides and subjected to SDS/PAGE under nondenaturing conditions. The gels were then scanned for the fluorescent peptides and, after silver staining, for proteins. We found that the fluorescence-labeled peptide fragment of ovalbumin bound preferentially to the isolated alpha and beta chains of I-Ad, whereas the fluorescence-labeled peptide fragment of pigeon cytochrome c bound preferentially to the isolated alpha and beta chains of I-Ek. The alpha and beta chains of each haplotype bound their specific peptides about equally well, suggesting comparable affinities. Our results indicate that in vivo the kinetic pathway for the formation of antigenic peptide complexes with the alpha/beta heterodimers may involve the initial formation of complexes of the alpha and/or beta chains with the specific antigenic peptides.
Tissue-specific expression of silkmoth chorion genes in vivo using Bombyx mori nuclear polyhedrosis virus as a transducing vector.
Authors: Iatrou K , Meidinger R G
Published: May 2006

A pair of silkmoth chorion chromosomal genes, HcA.12-HcB.12, was inserted into a baculovirus transfer vector, pBmp2, derived from the nuclear polyhedrosis virus of Bombyx mori. This vector, which permits the insertion of foreign genetic material in the vicinity of a mutationally inactivated polyhedrin gene, was used to acquire the corresponding recombinant virus. Injection of mutant silkmoth pupae that lack all Hc chorion genes with the recombinant virus resulted in the infection of all internal organs including follicular tissue. Analysis of RNA from infected tissues has demonstrated that the two chorion genes present in the viral genome are correctly transcribed under the control of their own promoter in follicular cells, the tissue in which chorion genes are normally expressed. The chorion primary transcripts are also correctly processed in the infected follicular cells and yield mature mRNAs indistinguishable from authentic chorion mRNAs present in wild-type follicles. These results demonstrate that recombinant nuclear polyhedrosis viruses can be used as transducing vectors for introducing genetic material of host origin into the cells of the organism and that the transduced genes are transiently expressed in a tissue-specific manner under the control of their resident regulatory sequences. Thus we show the in vivo expression of cloned genes under cellular promoter control in an insect other than Drosophila melanogaster. The approach should be applicable to all insect systems that are subject to nuclear polyhedrosis virus infection.
Development of a high-titer retrovirus producer cell line capable of gene transfer into rhesus monkey hematopoietic stem cells.
Authors: Bodine D M , McDonagh K T , Brandt S J , Ney P A , Agricola B , Byrne E , Nienhuis A W
Published: May 2006

Retroviral-mediated gene transfer into primitive hematopoietic cells has been difficult to achieve in large-animal models. We have developed an amphotropic producer clone that generates greater than 10(10) recombinant retroviral particles (colony-forming units) per ml of culture medium. Autologous rhesus monkey bone-marrow cells were cocultured with either high (2 x 10(10) colony-forming units/ml) or low (5 x 10(6) colony-forming units/ml) titer producer clones for 4-6 days and reinfused into sublethally irradiated animals. The proviral genome was detected in blood and bone-marrow cells from all three animals reconstituted with cells cocultured with the high-titer producer cells. In contrast, three animals reconstituted with bone marrow cocultured with the low-titer producer clone exhibited no evidence of gene transfer.
Transcriptional activation of a conserved sequence element by ras requires a nuclear factor distinct from c-fos or c-jun.
Authors: Owen R D , Ostrowski M C
Published: May 2006

The expression of transforming growth factor beta type 1 mRNA was increased by conditional expression of ras. A 31-base-pair sequence found approximately 420 base pairs upstream of the gene encoding human transforming growth factor beta 1 acted as a ras-responsive enhancer element in transient transfection assays. The human sequence contains the element TGACTCT that also is found in a murine ras-responsive enhancer. Analysis of nuclear factors present in cells stably transformed by ras indicated that both human and murine sequences were recognized by the same nuclear factor. The role of fos and jun in ras transcriptional activation was analyzed in transfection assays using murine elements that contained either TGACTCT or TGAGTAA. These experiments showed that while both elements are activated by fos/jun expression to nearly the same event, only the former element responded to ras. In addition, activation of reporters containing TGACTCT is 6-fold higher by ras than by fos/jun. Gel retention experiments revealed that the nuclear factor present in cells transformed by ras exhibited the same sequence preference as demonstrated in the transient transfection assays. UV-crosslinking experiments identify a protein of apparent molecular mass 120 kDa that recognizes the ras-responsive element. This work identifies a persistent signal transduction pathway that links ras to nuclear transcription and indicates that a 120-kDa protein is a target of this pathway.
Rat mitochondrial and cytosolic 3-hydroxy-3-methylglutaryl-CoA synthases are encoded by two different genes.
Authors: Ayté J , Gil-Gómez G , Haro D , Marrero P F , Hegardt F G
Published: May 2006

We report the isolation and characterization of a 1994-base-pair cDNA that encompasses the entire transcription unit of the mitochondrial 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase (EC 4.1.3.5.) gene from rat. Analysis of the nucleotide sequence reveals that the cDNA encodes a polypeptide of 508 residues and 56,918-Da molecular mass. Identify of the cDNA clone isolated as mitochondrial HMG-CoA synthase was confirmed by the following criteria: (i) Amino acid residues are 65% homologous with hamster cytosolic HMG-CoA synthase. (ii) A 19-amino acid sequence probably corresponding to the catalytic site is highly homologous (90%) to that reported for chicken liver mitochondrial HMG-CoA synthase. (iii) The expression product of the cDNA in Escherichia coli has HMG-CoA synthase activity. (iv) The protein includes a sequence of 37 amino acid residues at the N terminus that is not present in the cytosolic enzyme. The predominantly basic, hydrophobic, and hydroxylated nature of the residues of this sequence suggests that it is a leader peptide to target HMG-CoA synthase inside mitochondria. These data plus the hybridization pattern in genomic Southern blot analysis, the different transcript size (2.0 kilobases versus 3.4 kilobases for the cytosolic enzyme), and the different expression pattern shown in RNA blot experiments suggest the presence of two HMG-CoA synthase genes, one for the cytosolic and another for the mitochondrial enzyme.
DNA binding properties of the purified Antennapedia homeodomain.
Authors: Affolter M , Percival-Smith A , Müller M , Leupin W , Gehring W J
Published: May 2006

The in vitro DNA binding properties of a purified 68-amino acid Antennapedia homeodomain (Antp HD) peptide have been analyzed. Equilibrium and kinetic binding studies showed that stable DNA-protein complexes are formed with a Kd of 1.6 x 10(-9) M and 1.8 x 10(-10) M, respectively. Heterodimer analysis led to the conclusion that Antp HD interacts in vitro as a monomer with the DNA target sites used in our study. The results of methylation and ethylation interference studies indicated that the Antp HD closely approaches the target DNA primarily from one side in a region extending across three phosphate backbones. The DNA binding properties of the Antp HD and prokaryotic DNA binding domains that share a helix-turn-helix motif are compared.
Refolding and reassembly of separate alpha and beta chains of class II molecules of the major histocompatibility complex leads to increased peptide-binding capacity.
Authors: Dornmair K , McConnell H M
Published: May 2006

Class II molecules of the major histocompatibility complex present antigenic peptides to helper T cells. These are heterodimeric glycoproteins consisting of one alpha and one beta chain. Two different alpha/beta heterodimeric conformations as well as the separate alpha and beta chains bind specific peptides. The alpha chain is thought to have one and the beta chain two intramolecular disulfide bonds. In the present study we have reduced these disulfide bonds in the murine major histocompatibility complex molecule I-Ad, which led to the release of bound peptides from all conformations and to unfolding of the separate chains. The separate alpha and beta chains could be refolded to their native structure by reoxidation of the cysteines. Refolding was accompanied by reassembly of the separated chains to the alpha/beta heterodimer. Both the separated alpha and beta chains and the alpha/beta heterodimer bound significantly higher amounts of antigenic peptide after reduction and reoxidation, as compared to the untreated protein.
Glucose transporters are abundant in cells with "occluding" junctions at the blood-eye barriers.
Authors: Harik S I , Kalaria R N , Whitney P M , Andersson L , Lundahl P , Ledbetter S R , Perry G
Published: May 2006

We studied the distribution of the "erythroid/brain" glucose transporter protein in the human and rat eye by immunocytochemistry with monoclonal and polyclonal antibodies to the C terminus of the human erythrocyte glucose transporter. We found intense immunocytochemical staining in the endothelium of microvessels of the retina, optic nerve, and iris but not in microvessels of the choroid, ciliary body, sclera, and other retro-orbital tissues. In addition, we found marked immunocytochemical staining of retinal pigment epithelium, ciliary body epithelium, and posterior epithelium of the iris. The common feature of all those endothelial and epithelial cells that stained intensely for the glucose transporter is the presence of "occluding" intercellular junctions, which constitute the anatomical bases of the blood-eye barriers. We propose that a high density of the glucose transporter is a biochemical concomitant of epithelial and endothelial cells with barrier characteristics, at least in tissues that have a high metabolic requirement for glucose.
Molecular evidence that homologous recombination occurs in proliferating human somatic cells.
Authors: Groden J , Nakamura Y , German J
Published: May 2006

A strategy has been developed to detect and characterize certain heritable genomic alterations that occur as cells proliferate in vitro. Multiple subclones of cells were isolated from two clonal lymphoblastoid cell lines--one from a boy with Bloom's syndrome (BS), a cancer-predisposing condition known to feature excessive somatic mutation, the other from a normal man. The DNAs from the cell lines were hybridized to a panel of probes that can detect restriction fragment length polymorphisms, and the patterns of polymorphism in the primary clones were compared with that in each of the secondary clones. In one of the BS secondary clones three loci, positioned distally on the long arm of chromosome 3 and that are heterozygous in the donor and all other cell lines derived from the primary clone, had lost heterozygosity and apparently had become homozygous; in contrast, heterozygous loci more proximal on 3q had retained their heterozygosity, as had those on 3p. Taking into account the pattern of chromosome instability uniquely characteristic of BS, the most plausible explanation for the alterations in the altered clone is that somatic recombination had occurred in vitro, via homologous chromatid interchange. Such spontaneous recombinational events in nonneoplastic, nonmutagenized cells may contribute to the high cancer incidence in BS and, by analogy, to cancer that arises in the general population.
cDNA cloning of somatolactin, a pituitary protein related to growth hormone and prolactin.
Authors: Ono M , Takayama Y , Rand-Weaver M , Sakata S , Yasunaga T , Noso T , Kawauchi H
Published: May 2006

From a flounder pituitary cDNA library, cDNA clones encoding a 28-kDa glycoprotein produced by the pars intermedia of the pituitary were isolated and characterized. Nucleotide sequencing demonstrated a precursor of the 28-kDa protein, which consisted of 231 amino acid residues, to be cleaved into a signal peptide (24 amino acids) and a mature protein (207 amino acids) containing one N-glycosylation site. By comparison of amino acid sequences, the 28-kDa protein was found to be distantly and similarly related to growth hormone and prolactin. Consequently, it was named somatolactin. Somatolactin mRNAs were specifically expressed as 1.2 and 1.8 kb poly(A)+ RNAs in flounder pituitary.
Inhibition of protein kinase C induces differentiation in Neuro-2a cells.
Authors: Miñana M D , Felipo V , Grisolía S
Published: May 2006

1-(5-Isoquinolinylsulfonyl)-2-methylpiperazine (H7), a potent inhibitor of protein kinase C, induced neuritogenesis in Neuro-2a cells, whereas N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA 1004), which inhibits more efficiently cAMP- and cGMP-dependent protein kinases, did not. The effect, noticeable after 3 hr, was maximum (13-fold increase at 500 microM H7) between 1 and 3 days and was maintained over 2 months. In controls, 90% of the cells were undifferentiated, whereas after 3 hr with 500 microM H7 only 25% of the cells remained undifferentiated. DNA synthesis decreased as the number of differentiated cells increased. Differentiation is also functional since acetylcholinesterase activity increased approximately 7-fold after 48 hr with 500 microM H7. Phorbol 12-myristate 13-acetate, a specific activator of protein kinase C, prevented or reversed the induction of neuritogenesis and the inhibition of DNA synthesis by H7. There is a good correlation between the level of protein kinase C and the percentage of differentiated cells. The results indicate that protein kinase C may play a key role in the control of differentiation of neural cells. Some possible clinical implications are briefly discussed.