HSC-independent definitive hematopoiesis persists into adult life

It is widely believed that hematopoiesis after birth is established by hematopoietic stem cells (HSCs) in the bone marrow and that HSC-independent hematopoiesis is limited only to primitive erythro-myeloid cells and tissue-resident innate immune cells arising in the embryo. Here, surprisingly, we find that significant percentages of lymphocytes are not derived from HSCs, even in 1-year-old mice. Instead, multiple waves of hematopoiesis occur from embryonic day 7.5 (E7.5) to E11.5 endothelial cells, which simultaneously produce HSCs and lymphoid progenitors that constitute many layers of adaptive T and B lymphocytes in adult mice. Additionally, HSC lineage tracing reveals that the contribution of fetal liver HSCs to peritoneal B-1a cells is minimal and that the majority of B-1a cells are HSC independent. Our discovery of extensive HSC-independent lymphocytes in adult mice attests to the complex blood developmental dynamics spanning the embryo-to-adult transition and challenges the paradigm of HSCs exclusively underpinning the postnatal immune system.

Mast Cell Repopulating Ability Is Lost During the Transition From Pre-HSC to FL HSC

Recent advances in developmental immunology have revealed a hematopoietic stem cell (HSC)-independent origin for various innate immune lineages, including mast cells (MCs). It is now established that adult bone marrow (BM) long-term HSCs do not regenerate MCs but, instead, the physiological production of MCs starts before the emergence of HSCs in the aorta-gonad-mesonephros (AGM) region and is mostly completed before birth. However, while the AGM region represents a major site of MC generation during ontogeny, whether the first emerging HSCs in the AGM or fetal liver (FL) possess the potential to regenerate MCs is unknown. Here, we combined three fate-mapping mouse models with detailed HSC transplantation assays to determine the potential of AGM and FL HSCs to produce MCs. We show that HSCs from E11.5 AGM and E12.5 FL efficiently repopulated MCs in recipients. In stark contrast, HSCs from ≥E14.5 FL failed to reconstitute MCs. An Endothelial (EC) fate-mapping study confirmed the EC origin of the majority of MCs. Additionally, our HSC-labeling showed that HSCs do not produce MCs in a physiological setting. Hence, although most MCs are generated and maintained via an HSC-independent pathway, the earliest HSCs to emerge in the AGM and seed the early FL can produce MCs, but only during a minimal time window. Our results challenge the stem cell theory in hematology and EC-derived mast cells may contribute to the pathogenesis of postnatal mast cell disorders.

HSC-independent definitive lymphopoiesis persists into adult life

The stem cell theory that all blood cells are derived from hematopoietic stem cell (HSC) is a central dogma in hematology. However, exceptions are the fetal hematopoiesis in which primitive and definitive type of erythromyeloid cells are already produced from hemogenic endothelial cells (HECs) before the first HSC emergence in the mouse embryo. This early blood cell production prior to HSC emergence is called HSC-independent hematopoiesis and considered to be transient during fetus. Recent lineage-tracing studies revealed that some tissue-resident innate immune cells (e.g. brain microglia, mast cells, and certain types of γδT cells) are also produced independently of HSCs from early extra-embryonic yolk-sac (YS). Definitive T&B-lymphoid potential and multi-potent progenitor (MPP) potential have been detected in the YS and/or embryos in in vitro studies, however, the physiological presence of these cells in the embryo at pre-HSC stage remains unknown. In addition, whether HSCs in the fetal liver are the main source of innate-like B-1a cells has been controversial. Here, using complementary lineage tracing mouse models, we show that HSC-independent MPPs and HSC-independent adoptive T & B-lymphocytes persist into adult life and are gradually replaced by HSC-derived cells. Furthermore, we found that HSCs minimally contribute to the peritoneal B-1a cells, and most B-1a cells are originated directly from ECs in the YS and embryo and HSC-independent for life. Our discovery of extensive HSC-independent MPP and adoptive lymphocytes in adults attests to the complex blood developmental dynamics through embryo to adult that underpin the immune system and challenges the paradigm of HSC theory in hematology.

Supported by grant from NIH R01AI121197.

Lineage tracing and transplantation studies indicate endothelial origin of B-1a cells in the mouse embryo

Innate-immune like B-1a cells are unique in its functions and developmental origin compared to conventional adaptive immune B-cells (B-2 cells). Especially, their origin and developmental pathway have been argued over four decades between two proposed models: the lineage model and the selection model. Although many transplantation studies support the lineage model in which B-1a cells are derived from fetal progenitors, contradictory results of fetal liver transplantation studies raise a question as to whether fetal liver hematopoietic stem cells (HSCs) are the primary source of the peritoneal B-1a cells. In order to address this question, we took two approaches using transplantation assays and lineage tracing mouse models that enable us to trace Tomato+ progeny of endothelial cells (ECs, Cdh5CreERT mice) and HSCs (Fgd5CreERT2 mice) at a time of Tamoxifen (Tam) injection, respectively.

Results:

First, we transplanted HSC-precursors (pre-HSCs) from the aorta-gonad-mesonephros (AGM) region of the mouse embryo at embryonic (E) 11.5 into irradiated NSG neonates. Interestingly, we found more B-1a repopulating capacity than multi-lineage in the pre-HSC population. The lineage tracing of hemogenic ECs revealed that B-1a progenitors and HSCs were simultaneously produced from ECs during E9.5 to 10.5, but B-1a production is diminished after E11.5 while HSC were still labeled at E11.5. The HSC-tracing model demonstrated the minimal contribution of FL HSCs to the postnatal B-1a cell pool.

Conclusion:

Our data addressed the long-lasting controversy and showed HSC-independent B-1a cell development in the mouse embryo.

Dynamic chromosome reorganization in the osprey ( Pandion haliaetus , Pandionidae, Falconiformes): relationship between chromosome size and the chromosomal distribution of centromeric repetitive DNA sequences

The osprey (Pandion haliaetus) has a diploid number of 74 chromosomes, consisting of a large number of medium-sized macrochromosomes and relatively few microchromosomes; this differs greatly from the typical avian karyotype. Chromosome painting with chicken DNA probes revealed that the karyotype of P. haliaetus differs from the chicken karyotype by at least 14 fission events involving macrochromosomes (chicken chromosomes 1-9 and Z) and at most 15 fusions of microchromosomes, suggesting that considerable karyotype reorganization occurred in P. haliaetus in a similar manner previously reported for Accipitridae. A distinct difference was observed, however, between Accipitridae and Pandionidae with respect to the pattern of chromosome rearrangements that occurred after fissions of macrochromosomes. Metacentric or submetacentric chromosomes 1-5 in P. haliaetus appear to have been formed by centric fusion of chromosome segments derived from macrochromosomal fissions. By contrast, many pairs of bi-armed chromosomes in Accipitridae species seem to result from pericentric inversions that occurred in the fission-derived chromosomes. Two families of repetitive sequences were isolated; the 173-bp PHA-HaeIII sequence occurred on all chromosomes, whereas intense signals from the 742-bp PHA-NsiI sequence were localized to all acrocentric chromosomes, with weak signals on most of the bi-armed chromosomes. Two repetitive sequences cohybridized in the centromeric heterochromatin; however, the sequences differed in unit size, nucleotide sequence and GC content. The results suggest that the 2 sequence families originated from different ancestral sequences and were homogenized independently in centromeres, and that a chromosome size-dependent compartmentalization may have been lost in P. haliaetus.

Homoeologous chromosomes of Xenopus laevis are highly conserved after whole-genome duplication

It has been suggested that whole-genome duplication (WGD) occurred twice during the evolutionary process of vertebrates around 450 and 500 million years ago, which contributed to an increase in the genomic and phenotypic complexities of vertebrates. However, little is still known about the evolutionary process of homoeologous chromosomes after WGD because many duplicate genes have been lost. Therefore, Xenopus laevis (2n=36) and Xenopus (Silurana) tropicalis (2n=20) are good animal models for studying the process of genomic and chromosomal reorganization after WGD because X. laevis is an allotetraploid species that resulted from WGD after the interspecific hybridization of diploid species closely related to X. tropicalis. We constructed a comparative cytogenetic map of X. laevis using 60 complimentary DNA clones that covered the entire chromosomal regions of 10 pairs of X. tropicalis chromosomes. We consequently identified all nine homoeologous chromosome groups of X. laevis. Hybridization signals on two pairs of X. laevis homoeologous chromosomes were detected for 50 of 60 (83%) genes, and the genetic linkage is highly conserved between X. tropicalis and X. laevis chromosomes except for one fusion and one inversion and also between X. laevis homoeologous chromosomes except for two inversions. These results indicate that the loss of duplicated genes and inter- and/or intrachromosomal rearrangements occurred much less frequently in this lineage, suggesting that these events were not essential for diploidization of the allotetraploid genome in X. laevis after WGD.

Karyotype reorganization with conserved genomic compartmentalization in dot-shaped microchromosomes in the Japanese mountain hawk-eagle (Nisaetus nipalensis orientalis, Accipitridae)

The karyotype of the Japanese mountain hawk-eagle (Nisaetus nipalensis orientalis) (2n = 66) consists of a large number of medium-sized and small chromosomes but only 4 pairs of dot-shaped microchromosomes, in contrast to the typical avian karyotype with a small number of macrochromosomes and many indistinguishable microchromosomes. To investigate the drastic karyotype reorganization in this species, we performed a molecular cytogenetic characterization employing chromosome in situ hybridization and molecular cloning of centromeric heterochromatin. Cross-species chromosome painting with chicken chromosome-specific probes 1-9 and Z and a paint pool of 20 microchromosome pairs revealed that the N. n. orientalis karyotype differs from chicken by at least 13 fissions of macrochromosomes and 15 fusions between microchromosomes and between micro- and macrochromosomes. A novel family of satellite DNA sequences (NNO-ApaI) was isolated, consisting of a GC-rich 173-bp repeated sequence element. The NNO-ApaI sequence was localized to the C-positive centromeric heterochromatin of 4 pairs of microchromosomes, which evolved concertedly by homogenization between the microchromosomes. These results suggest that the 4 pairs of dot-shaped microchromosomes have retained their genomic compartmentalization from other middle-sized and small chromosomes.

Correlation of serum levels of complement C4a desArg with pathologically estimated severity of glomerular lesions and mesangial hypercellularity scores in patients with IgA nephropathy

The aim of the present study was to explore serum biomarkers for the pathology of IgA nephropathy using serum proteomics. The subjects were 57 patients with IgA nephropathy who were divided into two groups (group 1, n=25; group 2, n=32) and 14 healthy controls. Serum protein profiles were analyzed using the ProteinChip surface-enhanced laser desorption ionization (SELDI) system. Associations between signal intensities of proteins and histological findings in patients with IgA nephropathy were studied in group 1. Serum levels of a candidate biomarker protein (complement component C4a desArg) for IgA nephropathy were determined by enzyme linked-immunosorbent assay (ELISA) in group 2 and the relationships of these levels with histological findings were evaluated. There were significant differences in 93 protein signals between patients in group 1 and controls. Among these signals, 3 proteins at 8592, 8757 and 8806 m/z were significantly correlated with the severity of glomerular lesions. The protein at 8592 m/z was identified as C4a desArg and the signal intensity of 8592 m/z was strongly correlated with serum C4a levels, including C4a desArg, determined by ELISA. In addition, the serum levels of C4a (mainly C4a desArg) were significantly higher in patients in group 2 compared to controls and were correlated with the severity of glomerular lesions and with mesangial hypercellularity scores. In conclusion, the serum levels of complement C4a desArg are significantly higher in patients with IgA nephropathy compared to healthy controls and are significantly correlated with the severity of glomerular lesions and mesangial hypercellularity scores. Thus, serum C4a desArg is a potential biomarker for the severity of histological findings in patients with IgA nephropathy.

High serum thioredoxin levels are reduced after tonsillectomy in patients with IgA nephropathy

OBJECTIVE

The role of oxidative stress in IgA nephropathy (IgAN), the most common type of primary glomerulonephritis, is unknown. We evaluated the clinical significance of serum levels of oxidative stress markers, thioredoxin (TRX) and manganese superoxide dismutase (MnSOD), in patients with IgAN.

METHODS

Forty-eight patients with histologically confirmed IgAN and 14 healthy subjects were enrolled in this study. Serum samples from 14 IgAN patients were obtained after tonsillectomy, a procedure hypothesized to be an effective treatment for IgAN.

RESULTS

Serum TRX levels were significantly higher in patients with IgAN than in healthy subjects (mean [ng/mL]; 49.5 vs.14.4, p<0.001). Serum TRX levels are positively correlated with blood urea nitrogen, serum uric acid and proteinuria, and negatively with estimated glomerular filtration rate (eGFR). In addition, serum TRX levels gradually increased as the severity of renal histology increased. High levels of serum TRX were significantly decreased after tonsillectomy in patients with IgAN (mean [ng/mL]; 55.5 to 41.1, p=0.02). In contrast, serum MnSOD levels did not differ between IgAN patients and healthy subjects, and these levels did not change after tonsillectomy in IgAN patients.

CONCLUSION

Serum TRX is associated with IgAN, and tonsillectomy may decrease oxidative stress in IgAN patients, leading to clinical improvement.

Karyological characterization of the butterfly lizard (Leiolepis reevesii rubritaeniata, Agamidae, Squamata) by molecular cytogenetic approach

Karyological characterization of the butterfly lizard (Leiolepis reevesii rubritaeniata) was performed by conventional Giemsa staining, Ag-NOR banding, FISH with the 18S-28S and 5S rRNA genes and telomeric (TTAGGG)n sequences, and CGH. The karyotype was composed of 2 distinct components, macrochromosomes and microchromosomes, and the chromosomal constitution was 2n = 2x = 36 (L(4)(m) + L(2)(sm) + M(2)(m) + S(4)(m) + 24 microchromosomes). NORs and the 18S-28S rRNA genes were located at the secondary constriction of the long arm of chromosome 1, and the 5S rRNA genes were localized to the pericentromeric region of chromosome 6. Hybridization signals of (TTAGGG)n sequences were observed at the telomeric ends of all chromosomes and interstitially at the same position as the 18S-28S rRNA genes, suggesting that in the Leiolepinae tandem fusion probably occurred between chromosome 1 and a microchromosome where the 18S-28S rRNA genes were located. CGH analysis, however, failed to identify sex chromosomes, suggesting that this species may have a TSD system or exhibit GSD with morphologically undetectable cryptic sex chromosomes. Homologues of 6 chicken Z-linked genes (ACO1/IREBP, ATP5A1, CHD1, DMRT1, GHR, RPS6) were all mapped to chromosome 2p in the same order as on the snake chromosome 2p.

A multiplex PCR assay for molecular sexing of the naked mole-rat (Heterocephalus glaber)

For molecular sexing of the naked mole-rat (Heterocephalus glaber), we designed a PCR primer set to amplify part of the Y-linked DBY gene. When this primer set was applied to the samples of known sex with the 16S rRNA gene (16S rDNA) primers as control, PCR products were successfully obtained as two DNA bands in males, a male-specific 163 bp DBY band and a 446 bp band of 16S rDNA shared with females, whereas females showed only the common band. This result shows that this multiplex PCR assay is useful for sex identification of H. glaber.

Pharmacokinetic analysis of factors determining elimination pathways for sulfate and glucuronide metabolites of xenobiotics. iii: mechanisms for sinusoidal efflux of 4-methylumbelliferone sulfate

1. To elucidate the mechanisms involved in the sinusoidal efflux of sulfate and glucuronide metabolites of 4-methylumbelliferone (4MU), isolated rat liver perfusion studies were performed under several conditions. 2. The effect of sodium azide on the hepatic handling of both conjugates was examined. The net sinusoidal efflux clearance (CL(eff)) based on the unbound concentration in the liver did not change for 4MU glucuronide (4MUG) or significantly increase for 4MU sulfate (4MUS), suggesting that the sinusoidal efflux of both conjugates is not mediated by the transport systems dependent on adenosine triphosphate. 3. Under Cl(-)-depleted conditions, the CL(eff) of 4MUG significantly decreased, but the saturation of its sinusoidal efflux rather than the transport system dependent on Cl(-) might be involved because the hepatic concentration of 4MUG was extensively higher than that of the control study due to the extremely attenuated biliary excretion. The CL(eff) of 4MUS also significantly decreased, but its hepatic concentration was not different from that in the control study, suggesting that the transport system using Cl(-) is involved in the sinusoidal efflux of 4MUS. 4. The effect of glutathione was examined. CL(eff) of 4MUG was not affected by the additional glutathione, but CL(eff) of 4MUS decreased significantly, suggesting that some transport system sensitive to glutathione is involved in the sinusoidal efflux of 4MUS, but not of 4MUG. 5. Transporters such as Oatp1, Oatp2 and/or Npt1 might be involved in the sinusoidal efflux of 4MUS, but 4MUG is secreted from the sinusoidal membrane via the systems that are totally different from those for 4MUS.

[Case of multiple nodular lesions of bilateral kidneys with IgG4-related systemic disease]

A 59-year-old woman was admitted to our hospital because of a pancreatic mass lesion. Serum gamma-globulin and IgG4 levels were elevated to 2.2 g/dL and 1,310 mg/dL, respectively. Computed tomography examination revealed multiple low-density areas without enhancement by contrast in the pancreatic body and bilateral kidneys. Endoscopic retrograde cholangiopancreatography images demonstrated diffuse narrowing of the main pancreatic duct with an irregular wall from the body to the tail of the pancreas. Positron emission tomography examination revealed intense 18F-fluorodeoxyglucose uptake by the pancreas and kidneys. Accordingly, the patient was diagnosed as having IgG4-related autoimmune pancreatitis. In addition, the findings of a renal tissue specimen obtained by biopsy demonstrated IgG4-positive plasma cell infiltration in both abnormal mass lesions and normal regions by imaging, leading to the final diagnosis of IgG4-related sclerotic disease. The patient was treated with prednisolone (30 mg/day), and the size of the pancreatic and renal lesions markedly decreased four weeks later. We report here a rare case of IgG4-related autoimmune pancreatitis with multiple renal lesions, which were confirmed by renal biopsy.

A life course approach to diet, nutrition and the prevention of chronic diseases

OBJECTIVE

To briefly review the current understanding of the aetiology and prevention of chronic diseases using a life course approach, demonstrating the life-long influences on the development of disease.

DESIGN

A computer search of the relevant literature was done using Medline-'life cycle' and 'nutrition' and reviewing the articles for relevance in addressing the above objective. Articles from references dated before 1990 were followed up separately. A subsequent search using Clio updated the search and extended it by using 'life cycle', 'nutrition' and 'noncommunicable disease' (NCD), and 'life course'. Several published and unpublished WHO reports were key in developing the background and arguments.

SETTING

International and national public health and nutrition policy development in light of the global epidemic in chronic diseases, and the continuing nutrition, demographic and epidemiological transitions happening in an increasingly globalized world. RESULTS OF REVIEW: There is a global epidemic of increasing obesity, diabetes and other chronic NCDs, especially in developing and transitional economies, and in the less affluent within these, and in the developed countries. At the same time, there has been an increase in communities and households that have coincident under- and over-nutrition.

CONCLUSIONS

The epidemic will continue to increase and is due to a lifetime of exposures and influences. Genetic predisposition plays an unspecified role, and with programming during fetal life for adult disease contributing to an unknown degree. A global rise in obesity levels is contributing to a particular epidemic of type 2 diabetes as well as other NCDs. Prevention will be the most cost-effective and feasible approach for many countries and should involve three mutually reinforcing strategies throughout life, starting in the antenatal period.

Persistent hypoglossal artery associated with arteriovenous malformation: a case report

A rare case of persistent hypoglossal artery in conjunction with arteriovenous malformation was presented. MRA could delineate persistent hypoglossal artery and arteriovenous malformation very clearly. The patient suffered from intracranial hemorrhage from in the 37th week of pregnancy. MRI, MRA, angiography, and CT of this rare condition are reported.

Nitric oxide synthase structure and electron transfer

The nitric oxide synthases (NOS), although unrelated to the cytochromes P450 in terms of sequence, exhibit spectroscopic and catalytic properties strongly reminiscent of those of the P450 system. One important difference is the requirement of the NOS enzymes for tetrahydrobiopterin. The biopterin cofactor is shown by chemical studies to bind close to pyrrole ring D of the prosthetic heme group, a position confirmed recently for inducible NOS and endothelial NOS by crystal structures. The only plausible role so far for the tetrahydrobiopterin is as a transient electron donor for the activation of molecular oxygen. NADPH-derived electrons are provided to the heme by the NOS flavin domain, but the biopterin may be required to provide an electron at a faster rate than that supported by the flavin groups. Chimeras in which the reductase domains of the isoforms have been exchanged indicate that the overall rate of catalytic turnover is directly governed by the ability of the flavin domain to deliver electrons. Electron transfer from the flavin to the heme domain, and within the flavin and heme domains, is thus a critical determinant of the catalytic turnover of NOS.

Food and nutrition policy development

It has been estimated that over 700 million people still do not have enough food to eat on a daily basis and that more than 2 billion are subsisting on diets that lack the essential vitamins and minerals required for normal growth and development and to prevent premature death and disabilites such as blindness and mental retardation. At the same time, millions more suffer from chronic diseases caused by excessive and unbalanced diets. At the International Conference on Nutrition (ICN), held in Rome in 1992 and sponsored by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) of the United Nations system, 159 nations endorsed a World Declaration that included recognition of the need for national plans of action for nutrition/national food and nutrition policies. Specific objectives that the delegates agreed should be achieved were a reinforcement of earlier goals agreed to at the World Summit for Children 1990. Political will is an essential prerequisite for successful national food and nutrition policies and plans. These must also be realistic, well-conceived and effective at all levels, especially where devolution is taking place. Over the last two decades there has been an evolution in the issues that policies address, as well as changes in the expectations of them. Virtually all countries have agreed to 'establish appropriate national mechanisms to prioritize, develop, implement and monitor policies and plans to improve nutrition within designated time-frames, based on national and local needs, and to provide appropriate funds for their functioning'. Worldwide, over 120 member states of the United Nations (UN) have finalized, strengthened or have under way, national plans of action for nutrition. The policy decisions being made in order to implement more of these plans over the remainder of the decade and beyond, are already providing invaluable experience and data. Evaluation should provide even more in the future.

Tetrodecamycin and dihydrotetrodecamycin, new antimicrobial antibiotics against Pasteurella piscicida produced by Streptomyces nashvillensis MJ885-mF8. I. Taxonomy, fermentation, isolation, characterization and biological activities

The novel antimicrobial antibiotic against Pasteurella piscicida, tetrodecamycin (1) and weakly active dihydrotetrodecamycin (2) were isolated from the fermentation broth of Streptomyces nashvillensis MJ885-mF8. They were purified by adsorption on Diaion HP-20, silica gel column chromatography and crystallization. The MICs of 1 were 6.25 approximately 12.5 micrograms/liter and 1.56 approximately 6.25 micrograms/ml against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and 12 strains of P. piscicida, respectively.

Analysis of cubitus interruptus regulation in Drosophila embryos and imaginal disks

The cubitus interruptus (ci) gene of Drosophila is expressed in all anterior compartment cells in both embryos and imaginal disks where it encodes a putative zinc-finger protein related to the vertebrate Gli and C. elegans Tra-1 proteins. Using ci/lacZ fusions, we located regulatory sequences responsible for the normal pattern of ci expression, and obtained evidence that separate elements regulate its expression in embryos and imaginal disks. Mutants that delete a portion of this regulatory region express ci ectopically in the posterior compartments of their wing imaginal disks and have wings with malformed posterior compartments. Similar deletions of ci/lacZ fusion constructs also result in ectopic posterior compartment expression. Evidence that the engrailed protein normally represses ci in posterior compartments includes the expansion of ci expression into posterior compartment cells that lack engrailed function, diminution of ci expression upon overexpression of engrailed protein in anterior compartment cells, and the ability of engrailed protein to bind to the ci regulatory region in vivo and in vitro. We suggest that engrailed protein directly represses ci expression in posterior compartment cells.

Cytostatin, a novel inhibitor of cell adhesion to components of extracellular matrix produced by Streptomyces sp. MJ654-NF4. I. Taxonomy, fermentation, isolation and biological activities

Cytostatin has been identified as a novel inhibitor of cell adhesion to components of extracellular matrix (ECM) in cultured broth of Streptomyces sp. MJ654-NF4. Though cytostatin did not inhibit EL-4 cell adhesion to ECM components such as laminin and fibronectin; it inhibited the adhesion of B16 melanoma cells to laminin and collagen type IV but not to fibronectin. It exhibited antimetastatic activity on B16 melanoma cells in mice. The cytotoxicity of cytostatin are also reported.

DNA repair synthesis in human fibroblasts requires DNA polymerase delta

When UV-irradiated cultured diploid human fibroblasts were permeabilized with Brij-58 then separated from soluble material by centrifugation, conservative DNA repair synthesis could be restored by a soluble factor obtained from the supernatant of similarly treated HeLa cells. Extensive purification of this factor yielded a 10.2 S, 220,000-dalton polypeptide with the DNA polymerase and 3'- to 5'-exonuclease activities reported for DNA polymerase delta II (Crute, J. J., Wahl, A. F., and Bambara, R. A. (1986) Biochemistry 25, 26-36). Monoclonal antibody to KB cell DNA polymerase alpha, while binding to HeLa DNA polymerase alpha, did not bind to the HeLa DNA polymerase delta. Moreover, at micromolar concentrations N2-(p-n-butylphenyl)-2'-deoxyguanosine 5'-triphosphate (BuPdGTP) and 2-(p-n-butylanilino)-2'-deoxyadenosine 5'-triphosphate (BuAdATP) were potent inhibitors of DNA polymerase alpha, but did not inhibit the DNA polymerase delta. Neither purified DNA polymerase alpha nor beta could promote repair DNA synthesis in the permeabilized cells. Furthermore, under conditions which inhibited purified DNA polymerase alpha by greater than 90%, neither monoclonal antibodies to DNA polymerase alpha, BuPdGTP, nor BuAdATP was able to inhibit significantly the DNA repair synthesis mediated by the DNA polymerase delta. Thus, it appears that a major portion of DNA repair synthesis induced by UV irradiation might be catalyzed by DNA polymerase delta. When xeroderma pigmentosum human diploid fibroblasts were utilized, DNA repair synthesis dependent upon ultraviolet light could be restored by addition of both T4 endonuclease V and DNA polymerase delta, but not by addition of either one alone. This result suggests that cytosol-depleted permeabilized DNA repair-defective human fibroblasts and HeLa DNA polymerase delta might be exploited to provide a functional assay for purifying active DNA repair factors from DNA repair-proficient cells without a preknowledge of their function.

Characterization of silver-stained nucleolus organizer regions (Ag-NORs) in 16 inbred strains of the Norway rat, Rattus norvegicus

Silver-stained nucleolus organizer regions (Ag-NORs) in metaphase chromosomes of cultured fibroblasts were compared among 16 inbred strains of the Norway rat, Rattus norvegicus. Ag-NORs were located at the secondary constrictions or juxtacentromeric regions of the short arms of chromosomes 3, 11, and 12. The frequency and relative size of Ag-NORs were found to be strain-specific, providing a genetic marker system useful for characterization of inbred strains. While considerable cell-to-cell variation was observed within a given strain, the strain-specific pattern of Ag-NORs was shown to be consistent in cultured and noncultured cells obtained from different tissues of embryos, newborns, and adults, as well as in successively cultured cells examined up to the 10th subculture generation. The patterns of Ag-NORs in F1 hybrids made between some of the inbred strains were in general agreement with those expected from the parental strains; some unexpected patterns were noted in F1 hybrids of a particular cross, suggesting the possible existence of nucleolar interactions in such interstrain hybrids, although this has to be confirmed.

The sulfurtransferases

The sulfurtransferases are a group of proteins that catalyze the formation, interconversion and reactions of compounds containing sulfane sulfur atoms. Serum albumin has properties that implicate it as a major potential sulfur carrier/transferase. The relevance of the sulfane pool system as a whole to cyanide detoxication appears clear. The mechanisms of action of the various components at the molecular level are still under investigation.