Biomedical subjects

N K Egilmez

Publications and source records attributed to N K Egilmez.

At least 19 recordsLinked to original sources

PubMed2003

Comparison of human lung cancer/SCID mouse tumor xenografts and cell culture growth with patient clinical outcomes.

Leukemic cell growth in SCID mice has been reported as a predictor of disease relapse. However, there is a paucity of literature regarding xenograft growth and clinical outcomes in non-small cell lung cancer (NSCLC). Seventy-nine specimens from patients with NSCLC were either subcutaneously implanted into SCID mice and/or placed in tissue culture. Retrospective chart review was correlated with stage, histology, necrosis, disease-free interval, and survival. Tumor xenografts were successfully established with 17 of 37 (46%) tumor biopsy tissues. Thirteen of 59 (22%) specimens grew in cell culture. Patients whose tumors grew in SCID mice had no difference in survival compared to those with no growth ( n=20, p=0.42). Median survival was 36 months in 13 patients whose tumors grew in cell culture compared to 39 months in 46 patients without growth. Eight of 12 (67%) patients with metastasis showed SCID/human xenograft growth, whereas nine of 25 (36%) without metastases did so ( p=0.08). Growth of tumor cells in vitro occurred in 11 of 31 (35%) adenocarcinomas, one of 25 (4%) squamous cell carcinomas, and one of three (33%) large cell carcinomas ( p=0.02). Well or moderately differentiated tumors grew in cell culture in only two of 22 (9%), whereas poorly or undifferentiated tumors grew in 11 of 32 (34%) cases ( p=0.03). We conclude that neither the ability of a tumor to engraft and grow in SCID mice nor its ability to grow in vitro in cell culture is a reliable predictor of disease outcome or survival in patients with NSCLC. The ability to propagate tumors in vitro appears to be more dependent upon the histological type of tumor and its degree of differentiation.

Adenocarcinoma↗

PubMed2001

CD40-CD40 ligand (CD154) engagement is required but not sufficient for modulating MHC class I, ICAM-1 and Fas expression and proliferation of human non-small cell lung tumors.

To determine the possible functional significance of CD40 expression on human non-small cell lung carcinomas and to assess the potential of CD40 as a therapeutic target, 18 lung tumor cell lines were established from biopsy tissues and were monitored for phenotypic changes on the cell surface and alterations in tumor cell proliferation after the ligation of CD40 with a trimeric fusion protein complex of CD40 ligand (CD40Lt). CD40 cross-linking resulted in up to a 6-fold increase in the surface expression of major histocompatibility complex (MHC) class I, Fas and intracellular adhesion molecule (ICAM)-1 in a subset of tumors expressing the highest levels of CD40. Suppression of tumor proliferation was seen after the ligation of CD40 on CD40Lt-responsive cell lines. The suppression was dose dependent, reversible and resulted from a delay of the tumor cells entering S-phase. No change in the cell phenotype or in proliferation were observed in CD40-negative tumors or in tumors expressing moderate-to-low levels of CD40 after incubation with CD40Lt. CD40-negative tumors transfected with the CD40 gene expressed high levels of CD40 on their surface, but were also unresponsive to CD40Lt cross-linking of CD40. Our data establish that CD40 is required (but not sufficient) for transducing a signal that results in phenotypic changes in human lung tumors and suppression in their proliferation. We conclude that CD40 on non-small cell lung tumors may represent a potential therapeutic target, but only on a subset of the CD40+ tumors.

Apoptosis↗

PubMed2001

Human-SCID mouse chimeric models for the evaluation of anti-cancer therapies.

The ability to engraft human tumors and human immunocompetent cells successfully in severe combined immunodeficient (SCID) mice has spawned the development and use of human-mouse chimeric models to evaluate anti-cancer therapies. The lack of standardization and many other potential pitfalls have contributed to the current controversy surrounding the reliability of these different models. Five frequently used SCID mouse models and their specific applications are summarized with the specific aim of providing an objective discussion of the strengths and limitations of each model, together with suggestions for overcoming some of the variabilities and for improving the design and use of future models.

Animals↗

PubMed2001

Antitumor efficacy of a human interleukin-12 expression plasmid demonstrated in a human peripheral blood leukocyte/human lung tumor xenograft SCID mouse model.

Genes encoding the p35 and p40 subunits of human interleukin-12 (IL-12) and the bacterial aminoglycoside phosphotransferase were cloned into a mammalian expression plasmid. The resultant plasmid, pCMVIL-12neo, was used to transfect human lung tumor cell lines in vitro. Stably transfected subclones were generated and found to secrete human IL-12 for at least 10 days following a lethal dose of gamma-radiation. The ability of the IL-12--producing tumor cells to promote an antitumor response in vivo was evaluated in SCID mice co-engrafted subcutaneously with human peripheral blood lymphocytes (PBLs) and viable human lung tumor cells (SCID-Winn assay). Using this model system, it was established that IL-12 released locally into tumors by irradiated IL-12--transfected cells activated the human PBL and promoted their ability to suppress tumor development in a dose-dependent fashion. PBL subset depletion studies revealed that the antitumor effect promoted by the IL-12--modified cells was dependent on the presence of human CD8(+) T cells and, to a lesser extent, human CD56(+) natural killer cells within the xenograft. We conclude that (a) irradiated human lung tumor cells genetically modified with pCMVIL-12neo secrete bioactive human IL-12 at concentrations sufficient to promote a human lymphocyte-mediated antitumor response in the microenvironment of the xenograft, and (b) that the SCID-Winn assay provides a useful model for the preclinical evaluation of cytokine-based human immunotherapy protocols.

Animals↗

PubMed2001

Neoadjuvant therapy with interleukin-12-loaded polylactic acid microspheres reduces local recurrence and distant metastases.

BACKGROUND: We previously demonstrated that the intratumoral injection of biodegradable polylactic acid microspheres that were loaded with interleukin (IL)-12 can induce a systemic antitumor immunity. We sought to investigate the clinical potential as neoadjuvant therapy. METHODS: Mice were inoculated with 5 x 10(7) Line-1 cells subcutaneously. Six days later, a single intratumoral injection of IL-12- or BSA-loaded microspheres were given; 14 days later, autopsy was performed to document metastases. Mice were inoculated with 5 x 10(7) Line-1 cells and 10 days later either treated with IL-12- or BSA-loaded microspheres or resected. Treated tumors were resected 6 days after treatment. Mice were observed 45 days for local recurrence before autopsy. RESULTS: Intratumoral injection of IL-12 microspheres resulted in significant suppression of tumor growth compared with controls (599 +/- 255 mm(3) vs 1591 +/- 372 mm(3); P =.001) and pulmonary metastases (0.4 vs 3.8 nodules per mouse; P =.003). Given before the operation, IL-12-loaded microspheres both decreased the local recurrence rate (100% to 40%) and pulmonary metastases (5.2 vs 0.6 nodules per mouse; P =.06). Earlier resection did not improve local recurrence or distant metastases. CONCLUSIONS: Intratumoral injection of IL-12-loaded polylactic acid microspheres promotes the development of systemic antitumor immunity that can eradicate micrometastases. As a neoadjuvant therapy, this can result in decreased local and distant recurrence.

Adenocarcinoma↗

PubMed2000

Antibody targeting of doxorubicin-loaded liposomes suppresses the growth and metastatic spread of established human lung tumor xenografts in severe combined immunodeficient mice.

Beta1 integrins, expressed on the cell surface of human non-small cell lung carcinomas, are used here as a target for the selective delivery of anti-cancer drug-loaded liposomes. Fab' fragments of a monoclonal antibody specific for human beta1 integrins were conjugated to sterically stabilized liposomes. Confocal microscopy of beta1 integrin-positive lung tumor cells incubated with fluorescently labeled anti-beta1 Fab immunoliposomes revealed a tumor-specific binding and efficient internalization of the liposomes into the tumor cells. The ability of these liposomes to deliver cytotoxic drugs to the tumor and kill these cells was demonstrated in vitro by incubating tumor cells with doxorubicin-loaded anti-beta1 Fab' immunoliposomes. The drug-loaded immunoliposomes were >30-fold more cytotoxic to the tumor cells than drug-loaded liposomes without antibody, nonspecific Fab' control immunoliposomes with drug or immunoliposomes without drug. The therapeutic efficacy of doxorubicin-loaded immunoliposomes was also evaluated in a metastatic human lung tumor xenograft/severe combined immunodeficient (SCID) mouse model. SCID mice that received i.v. injections of human lung tumor cells developed primary tumor nodules in the lung that subsequently metastasized to the liver and adrenal gland. Treatment of SCID mice bearing established lung tumor xenografts with doxorubicin-loaded anti-beta1 Fab immunoliposomes resulted in a significant suppression of tumor growth (monitored periodically by quantifying serum levels of a tumor marker), whereas tumors grew progressively in mice treated with control formulations. In addition to suppressing the growth of the primary lung tumor nodules, the immunoliposomes prevented the metastatic spread of the tumor to the liver and adrenal glands and increased the median survival time of the tumor-bearing mice. We conclude that Fab' immunoliposomes directed to tumor-associated integrins represent a potentially viable approach clinically for the selective delivery of drugs to solid tumors and may be useful in preventing the metastatic spread of lung cancer.

Adrenal Gland Neoplasms↗

PubMed2000

In situ tumor vaccination with interleukin-12-encapsulated biodegradable microspheres: induction of tumor regression and potent antitumor immunity.

An alternative technology for the local and sustained delivery of cytokines to tumors for cancer immunotherapy was evaluated and shown here to induce tumor regression, suppression of metastasis, and development of systemic antitumor immunity. Treatment of tumor-bearing BALB/c mice with a single intratumoral injection of biodegradable polylactic acid microspheres loaded with recombinant interleukin-12 (IL-12) promoted complete regression of the primary tumor and prevented the metastatic spread to the lung. Mice that experienced tumor regression after being treated rejected a subsequent challenge with live tumor cells, which indicated the development of systemic antitumor immunity. In situ tumor vaccination, ie., injection of IL-12 microspheres into existing tumors, was superior to vaccination of mice with mixtures of tumor cells (live or irradiated) and IL-12 microspheres in inducing systemic antitumor immunity. The sustained release of IL-12 from the microspheres was superior to bolus injection of free IL-12, and intratumoral delivery of microspheres was more effective than other routes of administration. These studies establish the utility of biodegradable polymer microspheres as a clinically feasible alternative to systemic cytokine therapy and cytokine gene-modified cell vaccines for the treatment of neoplastic disease.

Absorbable Implants↗

PubMed2000

Growth of human tumor xenografts in SCID mice quantified using an immunoassay for tumor marker protein in serum.

The accurate measurement of the response of a tumor to a given treatment is critical to evaluating novel therapeutic modalities. An experimental design is reported here that can be generally applied to monitoring human tumor xenografts growing in immunodeficient mice. A human non-small cell lung tumor cell line was transfected with a mammalian expression vector containing the gene encoding human prostate specific antigen (PSA) and has been shown to grow progressively following the subcutaneous, intraperitoneal and intravenous inoculation of the tumor into severe combined immunodeficient (SCID) mice. The transfected human tumor cells produce PSA that accumulates in the sera of all tumor inoculated SCID mice. An enzyme-linked immunoassay using a rabbit polyclonal and a mouse monoclonal antibody specific for PSA was designed and tested for the detection and quantification of serum PSA in tumor-bearing mice. Over a 5-week period, the serum levels of PSA of mice inoculated subcutaneously with the tumor increased progressively, and the estimated tumor volumes correlated with the amount of PSA detected in the serum. Serum PSA levels correlated even better with total tumor mass following the intraperitoneal inoculation of tumor cells into SCID mice. Serum PSA levels fell rapidly following the surgical debulking of tumor xenograft, reaching background levels of PSA in the serum 1 week after tumor removal. Serum PSA levels were also observed in SCID mice inoculated intravenously with a PSA transfected human lung tumor cell line adapted to grow orthotopically in the lung. The transfection of human tumors with a tumor marker and the use of an immunoassay to detect this marker establish an experimental design that provides a reliable, non-invasive, accurate and simple approach to monitor and quantify the growth of human tumor xenografts in SCID mice.

Animals↗

PubMed2000

Interleukin-12 delivered by biodegradable microspheres promotes the antitumor activity of human peripheral blood lymphocytes in a human head and neck tumor xenograft/SCID mouse model.

BACKGROUND: The role of cytokines in tumor regression is now well established. The major limitation for the clinical use of cytokines is the lack of a simple and effective protocol for the local and sustained delivery of cytokines to the tumor milieu. This study reports suppression of human head and neck squamous cell carcinoma (HNSCC) by human peripheral blood lymphocytes (HuPBL) following local, sustained delivery of interleukin-12 (IL-12) to tumors with biodegradable microspheres in a human/SCID mouse chimeric model. Materials and Methods Nondisrupted biopsy pieces (120 mg) of primary HNSCC were implanted s.c. into severe combined immunodeficient (SCID) mice and were expanded by serial passage in mice. Tumors were then titrated with different doses of allogeneic HuPBL by coengraftment of tumor pieces and HuPBL into the subcutis of SCID mice to determine whether the HuPBL possessed antitumor activity (the SCID/Winn model). The lymphocyte subsets that were responsible for the suppression of tumor engraftment were identified by selective depletion of the CD4+, CD8+, and CD56+ cells from the HuPBL prior to engraftment into mice. Attempts were then made to augment the antitumor activity of the HuPBL either by repeated intralesional bolus injections of recombinant human IL-12 (0.5 microg x 10 doses) or with a single dose of IL-12-loaded microspheres ( approximately 1.65 microg IL-12/mg microspheres, 2 mg microspheres/mouse). RESULTS: Successful engraftment of HNSCC was observed in 12 of 19 different patient samples. Normal histological architecture of tumor was maintained up to four serial passages in the SCID mice. After the first tumor engraftment, but not in subsequent passages, human immunoglobulin produced by plasma cells present in the tumor infiltrating lymphocyte population was detected in the mouse sera. Allogeneic human PBL displayed antitumor cytotoxic activity in a cell dose-dependent fashion when coengrafted with the tumors passaged in SCID mice. Lymphocyte subset depletion studies established that tumor suppression was dependent on both the CD8+ T lymphocytes and the CD56+ natural killer cells. Treatment of tumors with a single intralesional injection of IL-12-loaded microspheres was highly effective, resulting in the complete suppression of tumor engraftment in 50% of the mice. In contrast, treatment of tumors with repeated bolus IL-12 injections suppressed tumor engraftment only transiently and did not result in complete tumor rejection in any of the mice. CONCLUSION: The coengraftment of HNSCC and allogeneic lymphocytes into SCID mice provides a viable model with which to evaluate immunotherapeutic strategies for human cancer. The use of biodegradable microspheres for local sustained delivery of cytokines to augment lymphocyte mediated antitumor immunity within the tumor microenvironment provides a safer and simpler alternative to current cytokine immunotherapy protocols.

Animals↗

PubMed1998

Cytokine immunotherapy of cancer with controlled release biodegradable microspheres in a human tumor xenograft/SCID mouse model.

A novel biodegradable poly(lactic acid) microsphere formulation was evaluated for in vivo cytokine immunotherapy of cancer in a human tumor xenograft/ severe combined immunodeficiency (SCID) mouse model. Co-injection of interleukin-2 (IL-2)-loaded microspheres with tumor cells into a subcutaneous site resulted in the complete suppression of tumor engraftment in 80% of animals. In contrast, bovine-serum-albumin(BSA)-loaded particles or bolus injections of poly(ethylene glycol)/IL-2 were ineffective in preventing tumor growth. The antitumor effect of IL-2 released by the microspheres was shown to be mediated by the mouse natural killer cells. This is the first evidence that the rejection of human tumor xenografts can be provoked by the sustained in vivo delivery of IL-2 from biodegradable microspheres. The use of poly(lactic acid) microspheres to deliver cytokines to the tumor environment could provide a safer and simpler alternative to gene therapy protocols in the treatment of cancer.

Animals↗

PubMed1997

Antitumor immune response of human peripheral blood lymphocytes coengrafted with tumor into severe combined immunodeficient mice.

Here, it is established that human peripheral blood lymphocytes (HuPBLs), injected s.c. with a human lung tumor into severe combined immunodeficient (SCID) mice, engraft and display antitumor cytotoxic activity. Initial studies used HuPBLs from normal donors and an allogeneic tumor cell line derived from biopsy tissue of a patient with a squamous cell carcinoma of the lung. Evidence of HuPBL antitumor activity was revealed by a cell dose-dependent suppression of the tumor xenograft. Tumor suppression was shown to be dependent upon both CD8+ T cells and CD56+ natural killer cells in the donor HuPBLs. By titrating the antitumor activity of HuPBLs in SCID mice with and without cytokines, it was established that interleukin (IL)-12 enhanced the HuPBL-mediated tumor suppression and that IL-2 had a synergistic effect upon the IL-12 enhancement of cytotoxicity. Subsequent studies revealed that a lung cancer patient's PBLs also suppress the growth of the patient's (autologous) tumor when coinjected s.c. with the tumor cells into SCID mice. The patient's antitumor immunity was shown to be mediated by CD8+ T cells and CD56+ natural killer cells. The data presented here indicate that the s.c. coengraftment of HuPBLs and tumor into SCID mice represents a viable model with which to study (and to periodically monitor) patients' immune responses to their tumors for extended periods of time and suggest that this SCID/Winn assay could be used to evaluate novel immunotherapeutic approaches, such as bolus injections of cytokines, cytokine gene therapy, or vaccination strategies for the treatment of human cancer.

Animals↗

PubMed1996

Evaluation and optimization of different cationic liposome formulations for in vivo gene transfer.

Five commonly used cationic liposome formulations were tested for their ability to deliver DNA to established subcutaneous human tumor xenografts in SCID mice. Liposomes were complexed with a mammalian expression plasmid containing the bacterial beta-galactosidase gene and delivered to tumors by direct injection. The optimal lipid to DNA ratios in vivo were markedly different than those observed in vitro for each liposome formulation. Tumor size at the time of inoculation also effected transfection efficiency significantly. Of the five liposome formulations tested, DC-Cholesterol was found to be superior to all others in vivo. Even under optimal conditions however, the efficiency of in vivo transfection was low in our system (approximately 0.3%). Implications of these results for in vivo gene therapy of tumors are discussed.

Animals↗

PubMed1996

Defining genes that govern longevity in Caenorhabditis elegans.

We previously identified five regions on the chromosomal map of Caenorhabditis elegans, containing genes that help specify life span in this species, by comparing the genotypes of young and long-lived progeny from a cross between strains Bristol-N2 and Bergerac-BO [Ebert et al. (1993): Genetics 135:1003-1010]. Analyses of additional crosses, and of putative polymorphisms for the implicated genes, are necessary to clarify the roles of naturally occurring polymorphic alleles in determining longevity. We therefore carried out a second multigenerational cross, between strains Bristol-N2 and DH424 (both nonmutators at 20 degrees C), to create a different heterogeneous recombinant-inbred population. We again found strong evidence implicating multiple genes, which differ between the parental strains, in the determination of life span. Increased variance of survival, for F2 and homozygous F25 worms relative to F1 hybrids, is consistent with such alleles assorting randomly in the cross progeny. Moreover, chromosome mapping data corroborate the polygenic nature of this quantitative trait. Genotypes of young and very long-lived adult worms from a synchronous F15 population were determined by polymerase chain reaction, to identify the parental strain of origin for each of 10 polymorphic loci. Two regions, on chromosomes II and IV, each contain at least one gene with allelic differences in associated longevity. A recombinant-inbred Bergerac-BO x Bristol-N2 population, derived from the earlier cross between those strains, was exposed to an acute toxic level of hydrogen peroxide. Genotyping of H2O2-resistant worms implicated at least one of the five chromosomal regions previously identified in the same cross progeny as harboring a longevity-determining gene. Superoxide dismutase and catalase levels, determined for the three parental strains as they aged, confirm the existence of polymorphisms in the corresponding genes (or their regulatory mechanisms) inferred from the chromosome-II mapping data, and are consistent with the hypothesis that increased longevity is conferred by high levels of these enzymes late in life.

Age Factors↗

PubMed1996

In vivo cytokine gene therapy of human tumor xenografts in SCID mice by liposome-mediated DNA delivery.

The human interleukin-2 (IL-2) gene was successfully delivered into established human tumor xenografts in SCID (severe combined immunodeficient) mice by cationic liposome-mediated DNA delivery. A bicistronic mammalian expression vector containing a reporter gene (beta-galactosidase) and human IL-2 cDNA was complexed with either lipofectin or DC-cholesterol liposomes and transferred to tumor xenografts by direct intratumoral injection. Transfection of tumors was confirmed by staining of tumor sections for beta-galactosidase activity and by reverse transcription-polymerase chain reaction (RT-PCR) for the presence of IL-2 mRNA. Growth suppression of tumor xenografts was observed in animals injected with plasmid-liposome complexes but not in animals that received liposomes or naked plasmid only. Complete tumor regression, mediated by the mouse natural killer cells, was observed in 50-80% of the mice treated with the plasmid containing the IL-2 cDNA. The effectiveness of the treatment was dependent on the transfection efficiency and the tumor size at the start of therapy. An initial IL-2 independent suppression of tumor growth was also observed with a plasmid carrying only the beta-galactosidase gene but this effect was temporary and did not lead to tumor regression. These results establish that human tumor xenografts growing in SCID mice can be transfected in vivo by liposome mediated gene delivery and that both IL-2-dependent and IL-2-independent factors may contribute to the tumor suppression observed here.

Animals↗

PubMed1995

Strain evolution in Caenorhabditis elegans: transposable elements as markers of interstrain evolutionary history.

Evolutionary relationships across taxa can be deduced from sequence divergence of proteins, RNA, or DNA; sequences which diverge rapidly, such as those of mitochondrial genes, have been especially useful for comparisons of closely related species, and--within limits--of strains within a species. We have utilized the transposable element Tc1 as a polymorphic marker to evaluate the evolutionary relationships among nine Caenorhabditis elegans strains. For five low-Tc1-copy strains, we compared patterns of restriction fragments hybridizing to a cloned Tc1 probe. Twenty of the 40 Tc1 insertion sites thus characterized were common to all five strains, and so presumably preceded strain divergence; the 20 differential bands were used to construct a maximum-parsimony tree relating these strains. In four high-copy-number stocks (three wild-type strains and a subline), we determined occupancy of 35 individual Tc1 insertion sites by a polymerase chain reaction assay. Surprisingly, the high-copy strains share a common subset of these Tc1 insertions, and the chromosomal distribution of conserved Tc1 sites is "clustered" with respect to the other elements tested. These data imply a close evolutionary relationship among the high-copy strains, such that two of these strains appear to have been derived from the highest-copy-number lineage (represented by two stocks) through crossing with a low-Tc1 strain. Abundances of Tc1 elements were also estimated for the four high-copy-number stocks, at approximately 200-500 copies per haploid genome, by quantitative dot-blot hybridization relative to two low-copy strains. Annealing with 32P-labeled probes corresponding to full-length Tc1, an oligonucleotide within the Tc1 terminal inverted repeats, and an internal Tc1 oligonucleotide, gave essentially identical results--indicating that Tc1 termini exist in the genome primarily as components of full-length Tc1 elements. A composite evolutionary tree is proposed, based on the locations and numbers of Tc1 elements in these strains, which is consistent with a four-branch intraspecific tree deduced previously by maximum-parsimony analyses of mitochondrial sequence changes; it also serves to elucidate the evolutionary history of transposon mobility.

Animals↗

PubMed1994

Age-dependent somatic excision of transposable element Tc1 in Caenorhabditis elegans.

The Tc1 element of the free-living nematode Caenorhabditis elegans is a well characterized transposon that is present in 30-500 copies per haploid genome, depending on the strain. Excision of Tc1 elements, which occurs readily in somatic tissues during larval development, has not previously been examined during aging of adult worms. We have identified a recently inserted Tc1 element in the KR1787 mutator strain of C. elegans and have found that Tc1 somatic excision at that site increases by more than 14-fold during the organism's lifespan.

Aging↗

PubMed1991

The varying frequencies of five DNA polymorphisms of X-linked coagulant factor IX in eight ethnic groups.

Five RFLPS of X-linked coagulation factor IX were evaluated in more than 500 normal persons (723-804 X chromosomes) of both sexes who belonged to eight ethnic groups: Anglo-Americans, Basques, Swedes, African-Americans, East Africans, East Indians, Chinese, and Malays. The polymorphisms, 5' to 3', were BamHI, XmnI, TaqI, MnlI, and HhaI. A PCR procedure was developed for three previously described RFLPs-XmnI, TaqI, and MnlI; a PCRP procedure was developed for BamHI, and a PCRP which had been described by others was used for HhaI. Europeans were the most polymorphic, African-Americans and East Africans were intermediate, and Orientals were the least polymorphic. Extragenic 3' HhaI was highly polymorphic in most groups, and extragenic 5' BamHI was polymorphic only in persons with African ancestry. Two major haplotypes predominated among 247 men, and the expected and observed heterozygosities were concordant among women. Allelic association was very strong between the three intragenic PCRPs; it was present but weak between 5' extragenic BamHI and XmnI. No association was found between 3' extragenic HhaI and MnlI.

Asian People↗

PubMed1990

Preparation and partial characterization of old yeast cells.

Age-synchronized populations of the binding yeast Saccharomyces cerevisiae were prepared by a combination of growth-synchronization methods and cell separation by rate-zonal sedimentation in density gradients. The procedure allowed the bulk preparation of cells of any desired age up to at least 20 generations with minimum yields of 10(8) cells per preparation, starting with 6 X 10(9) 0-generation cells. The purity of the preparations was greater than 90%, with an accuracy of +/- 2 generations. The procedure itself had no detrimental effects on the cells, as indicated by a number of physiological parameters. Cell viability and resistance to sonication remained essentially unchanged during aging. In contrast, cell size and generation time increased, providing biomarkers for the aging process. The procedure described here should help establish yeast as a useful model system for studies of cellular aging at the molecular level.

Cell Division↗