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PubMed2006

Assessing genetic effects in survival data by correlating martingale residuals with an application to age at onset of Huntington disease.

Genetic models for survival data are hard to formulate and hard to fit. For example, the popular gamma-frailty model for sib-pair data does not generalize easily to extended pedigrees and is not easy to fit. In this paper we show how martingale residuals from a (marginal) Cox model can be employed to estimate the presence of a genetic effect and to estimate genetic correlations depending on the genetic distance (kinship). The methodology is applied to age at onset of Huntington disease (HD) in carriers of the HD gene. The number of CAG repeats in the HD gene is a well-known predictor for age at onset of the disease. However, there is an indication that other genes might be involved as well; leading to unexplained familial clustering. Using our methodology, we found a clearly significant genetic association between the martingale residuals with correlations of about 0.6 for relatives that share 50 per cent of their genes (sib-pairs and parent-child) and about 0.3 for relatives that share 25 per cent of their genes (grandparent-grandchild, uncle/aunt-niece/nephew).

Adolescent↗

PubMedDate not supplied

Perceived neighbourhood correlates of walking among participants visiting the Canada on the Move website.

BACKGROUND: The purposes of this study were to: 1) explore the potential role of sex in the association between the perceived environment and walking; and 2) determine the efficacy of an Internet-based research platform for collecting population-level physical activity and correlates data. METHODS: Visitors to the Canada on the Move website were asked questions about their demographics, physical activity participation and perceptions of their neighbourhood environment. A total of 3,144 Canadians (2,036 women; 609 men) completed the survey. Level of walking was regressed on eight measures of perceived neighbourhood environment in a series of logistic regressions. RESULTS: Individuals who reported interesting scenery (OR=1.41, 95% CI 1.17-1.71) and many places to go that were within easy walking distance (OR=1.39, 95% CI 1.18-1.64) were more likely to report walking at a level sufficient to derive health benefits. For women, interesting scenery in and around their neighbourhood (OR=1.40, 95% CI 1.13-1.74) and the presence of many places to go within easy walking distance (OR=1.42, 95% CI 1.17-1.72) were associated with walking at a sufficient level. Among men, no significant associations were found between the perceived environment measures and walking. CONCLUSIONS: The results from this study provide additional support for the use of models in which sex is treated as a potential moderator of the link between the perceived environment and physical activity. Further, the results support the use of an Internet-based research platform to collect data on the correlates of physical activity.

Adolescent↗

PubMed1996

Murine interleukin-11 (IL-11) is expressed at high levels in the hippocampus and expression is developmentally regulated in the testis.

IL-11, derived from a bone marrow stromal cell line, has pleiotropic effects on both hematopoietic cells and nonhematopoietic cells. However, no previous studies have systematically addressed expression of IL-11 in primary tissues in vivo and the relationship of IL-11 tissue specific gene expression and function of IL-11 is not clear. In the present study, we examined constitutive IL-11 expression in various murine adult tissues in vivo. IL-11 mRNA is expressed in a wide range of normal tissues (including hematopoietic organs) at levels only detected by RT-PCR. IL-11 protein was detected in brain and testis by Western blot analysis. The in vivo cellular distribution of IL-11 expression was examined by in situ hybridization. In brain, IL-11 message is distributed in granular layer dentate gyrus and pyramidal cell layers of hippocampus. IL-11 is also expressed in anterior horn cells and lateral column neuronal cells of the spinal cord. In testis, IL-11 mRNA is expressed in round spermatids at stage VI-IX seminiferous tubules. IL-11 expression in testis is restricted to developing spermatogonia and is developmentally regulated, since no expression is seen in mice genetically deficient in germ cells and in mice prior to sexual maturation. These expression data correlate with functional data demonstrating that IL-11 stimulates proliferation in vitro of a hippocampus neuronal progenitor cell line and administration of IL-11 in vivo accelerates recovery of spermatogenesis after cytotoxic therapy. These studies suggest that IL-11 may be an important regulator in neural and testicular function.

Animals↗

PubMed1992

In vitro response of human small-cell lung-cancer cell lines to chemotherapeutic drugs; no correlation with clinical data.

Three cell lines derived from small-cell lung carcinoma (SCLC) tumors of patients who had no clinical response after treatment with a multi-drug regimen were compared to 3 cell lines derived from tumors of patients who, upon treatment, showed a complete clinical response. These 2 groups of cell lines were considered to represent the in vitro counterparts of the 2 extremes of the clinical spectrum of sensitivity for chemotherapeutic drugs in small-cell lung cancer. To assess whether the in vivo (in)sensitivity of a tumor to a certain drug regimen is retained in vitro, the cell lines were tested for drug sensitivity using the microtiter-well tetrazolium assay and the results were compared with the in vivo data. No correlation was found. Since in vitro models using cell lines are based on the assumption that a cell line reflects the properties of the tumor from which it is derived, several additional parameters such as MAb staining against different SCLC-associated antigens and DNA content were analyzed in the biopsies and the cell lines. The results showed that selection of discrete tumor-cell populations in vitro occurs. Results of in vitro chemosensitivity testing for individual SCLC patients should be interpreted with caution.

Antineoplastic Combined Chemotherapy Protocols↗

PubMedDate not supplied

Plasticity of the nigrostriatal system in MPTP-treated mice. A biochemical and morphological correlation.

In order to compare the recovery capacity of the nigrostriatal system between adult and old mice, MPTP hydrochloride was administered to 48 BL/C57 male mice, which were sacrificed 24 h or 10 d after the second dose. The animals were divided into four groups, based on age (adult or old) and moment of sacrifice (24 h or 10 d). The detailed morphology of the neurons and the cellular processes of the substantia nigra pars compacta and the striatum were studied using the Golgi method. Immunostaining with a polyclonal glial fibrillary acidic protein antiserum using the peroxidase-antiperoxidase technique was performed to study the glial response. Striatal catecholamines were determined to correlate the biochemical data with the morphological changes. Significant neuronal changes of cellular processes were observed in substantia nigra pars compacta from all MPTP-treated mice, consisting of swelling and distortion of cellular bodies, discontinuous thickness, and nodulations of dendrites with baded aspect. Axons showing focal swelling and nodulations were also found in the neuropil of silver impregnated striata. Marked gliosis with reactive astrocytes in substantia nigra and striatum from all the old treated mice was found. Recovery was only observed in adult mice sacrificed 10 d after withdrawal. At this time, all the old MPTP-treated mice showed marked neuronal changes and a persistent marked gliosis. As expected, 24 h after the MPTP treatment, a marked depletion of dopamine and its metabolites was found in all the animals; at 10 d, the depletion was partially reversed in the adult group. These data correlate well with the observed morphological changes. Our results suggest that, in mice, deterioration of dendritic and axonal neuropil constitutes a significant causal factor of the MPTP neurotoxicity. These features are related to the age of the animals and the integrity of the plasticity phenomena, which appear to be altered in old mice.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2006

Analytical approach for monitoring endocrine-disrupting compounds in urban waste water treatment plants.

The presence of endocrine-disrupting compounds in influent and effluent water samples from four waste water treatment plants located in Italy was studied. The estrogen-like activity of the water samples was measured using a chemiluminescent recombinant yeast assay which is based on genetically engineered yeast cells that express the human estrogen receptor. This receptor, once activated, elicits the expression of the reporter gene lac-Z and, consequently, the production of beta-galactosidase, which is then measured by chemiluminescence. To control and minimize sample matrix effects, an external control based on a modified yeast strain stably expressing beta-galactosidase was developed and also used in the assay. Rapid and sensitive chemiluminescent enzyme immunoassays were also developed and validated for the quantification of 17beta-estradiol, estrone, and estriol in waste water samples. Results from both methods were compared with a reference high-performance liquid chromatography and electrospray ionization tandem mass spectrometry (HPLC ESI-MS-MS) method developed for the quantification of natural estrogens. The recombinant yeast assay revealed a significant estrogenic activity in the influent samples, ranging from 80 to 400 pmol/L 17beta-estradiol equivalents (EEQ), which was reduced by 70-95% in the effluent samples. The yeast assay also showed a systematic 20-30% overestimation of estrogenic activity relative to the HPLC ESI-MS-MS method, suggesting the presence of other compounds in the samples with estrogenic activity. The chemiluminescent enzyme immunoassays showed the presence of estrogens in the influent samples (mean concentrations: 350-450 pmol/L for estrone, 5-100 pmol/L for 17beta-estradiol, 25-300 pmol/L for estriol), with significantly lower concentrations detected in the respective effluent samples. The waste water treatment was able to reduce natural estrogen concentrations by 40-95%, although a high variability was observed. The enzyme immunoassay data correlated well with data obtained by the HPLC ESI-MS-MS method. Although the recombinant yeast assay represents a useful tool for a first-level screening of estrogenic activity due to its simplicity and high analytical throughput, sample matrix effects observed in waste water of industrial origin were found to strongly affect the yeast cells response, even when properly corrected for using the external control, thereby limiting its use to urban waste water. Its integration with chemiluminescent enzyme immunoassays would improve its performance by reducing false negative results, thereby enabling its use in extensive studies monitoring for the presence of endocrine-disrupting compounds in urban treatment plant effluents.

Chromatography, High Pressure Liquid↗

PubMed1987

New n.m.r.-spectroscopic approaches for structural studies of polysaccharides: application to the Haemophilus influenzae type a capsular polysaccharide.

The extension of several modern nuclear magnetic resonance (n.m.r.) spectroscopic techniques to polysaccharides is discussed and illustrated, using the native Haemophilus influenzae type a capsular polysaccharide. These techniques provide for the unambiguous assignment of all n.m.r. resonances (1H, 13C, and 31P) via high-sensitivity homonuclear and 1H-detected heteronuclear correlations, and they are capable of locating the intersaccharide linkages (both O-linked and phosphoric diester-linked) and appended groups (e.g. O-acetyl groups). To illustrate the power and sensitivity of these methods, a 10-mg sample of the H. Influenzae type a polysaccharide (repeat unit mol. wt. = 376) was studied. The combined acquisition time for the two-dimensional 1H-13C correlation data (one-bond and multiple-bond), the 1H-31P correlation data, and the 1H-1H (homonuclear Hartmann-Hahn) data was approximately 18 h.

Carbohydrate Conformation↗

PubMed1993

Effect of neutral and acidic phospholipids on mitochondrial ATP synthase secondary structure.

The secondary structure of delipidated and egg phosphatidylcholine or asolectin reconstituted mitochondrial ATP synthase complex from beef heart was investigated by Fourier transform infrared spectroscopy. Upon reconstitution, the infrared spectra of ATP synthase revealed an increase in turns and a concomitant decrease in beta-sheet content which occurred to a larger extent in the presence of asolectin rather than in the presence of egg phosphatidylcholine. These data correlate with kinetic data showing a higher ATPase activity of the asolectin reconstituted enzyme protein than the egg phosphatidylcholine reconstituted or delipidated enzyme complexes.

Animals↗

PubMed1995

Definitive landmarks for reproducible tibial tunnel placement in anterior cruciate ligament reconstruction.

The purpose of this prospective study was to define constant anatomic intraarticular and extraarticular landmarks that can be used as definitive reference points to reproducibly create a tibial tunnel for anterior cruciate ligament (ACL) reconstruction that (1) results in an impingement-free graft in full extension without an intercondylar roofplasty; (2) positions the tibial tunnel's intraarticular orafice sagittally central in the original ACL insertion without visually guessing; (3) positions the tibial tunnel such that the sagittal tunnel-plateau angle is parallel with the sagittal intercondylar roof-plateau angle in full extension to minimize shear seen by the graft at the tibial tunnel inlet, and by doing so; (4) maximizes tunnel length to avoid patellar tendon graft-tunnel length mismatch allowing for endosteal interference screw fixation on both sides of the joint. Anatomic dissections in 50 knees showed the ACL sagittal central insertion point on the intercondylar floor averages 7 mm (range 7 to 8 mm) sagittally anterior to the anterior margin of the posterior cruciate ligament (PCL) with the knee flexed 90 degrees such that the PCL may be used as a reliable reference landmark for locating the ACL sagittal central insertion. This constant relationship was found to be independent of knee size. Extraarticularly, beginning the tibial tunnel sagittally 1 cm above the superior (sartorial) border of the pes anserinus insertion and coronally 1.5 cm posteromedial from the medial margin of the tibial tubercle along the superior surface of the pes, directed toward the sagittal central ACL insertion, led to a sagittal tunnel-plateau angle that averaged 68 degrees (range 64 degrees to 72 degrees) with a corresponding tunnel length that averaged 58 mm (range 50 to 65 mm) in 23 knees. This data correlated well with data obtained clinically in a series of 50 consecutive ACL reconstructions using intraarticular PCL and extraarticular pes anserine-medial tibial tubercle referenced tibial tunnels in which postoperative full extension lateral radiographs confirmed a sagittal tunnel-plateau angle parallel or near parallel with the intercondylar roof-plateau angle in all cases averaging 68 degrees +/- 3.8 degrees. Tibial tunnel length averaged 60 mm (range 52 to 66 mm) and in no case was there a patellar tendon autograft-tunnel length mismatch.

Anterior Cruciate Ligament↗

PubMed1981

Determination of diazepam and its major metabolites in man and in the cat by high-performance liquid chromatography.

A rapid, sensitive and specific high-performance liquid chromatography (HPLC) assay was developed for the determination of diazepam, and its major metabolites, oxazepam, temazepam and nordiazepam in plasma, blood, and urine of humans and cats. The assay for the compounds involves extraction into benzene--methylene chloride (90:10) from plasma, blood or urine buffered to pH 9.0. In both species the overall recovery of diazepam and its major metabolites from plasma or blood ranged from 60 +/- 3.2 to 89 +/- 13% (S.D.) and for urine from 79 +/- 7.9 to 93 +/- 10.5% (S.D.). The sensitivity limit of the assay using UV detection at 254 nm was 50 ng/ml of plasma and blood in both species except for human urine (post-Glusulase) which was 200 ng/ml. The HPLC assay was used to monitor the plasma concentration--time profile in humans following a 10-mg oral dose of diazepam and the blood concentration time profile of diazepam and nordiazepam in cats following a 10 mg/kg intravenous dose of either diazepam or nordiazepam. The HPLC assay data correlated well with data generated by an electron-capture--gas--liquid chromatography assay.

Animals↗

PubMed1998

Quantitative forced ductions in an animal model--characterization of passive forces.

PURPOSE: Our purpose was to characterize the passive tissue forces involved in ocular rotation in a controlled animal model and to evaluate the influence of manual versus mechanized ductions, repeated measurements, speed of rotation, and the influence of the nondepolarizing muscle relaxant mivacurium. METHODS: Forced ductions were performed under general anesthesia on 20 eyes of 10 pigs, with or without mivacurium, with use of a highly sensitive force gauge attached to the eye by a traction suture. The eye was moved either manually or at constant speed with a motorized platform. Eyes were rotated a total of 8 mm from their resting position under anesthesia. The force-displacement relationship was analyzed and compared between groups. RESULTS: A linear (elastic) relationship between force and displacement was noted, with a slope of 0.4 g per degree with use of the mechanized technique. Neither speed of rotation, use of mivacurium, nor repeated ductions significantly influenced the shape or slope of the relationship. Hysteresis averaged 2 to 4 g. Measurements performed with use of the motorized platform showed significantly improved reliability over those made manually. CONCLUSIONS: The passive length-tension data correlate well with data reported by others in humans. Within a wide range of eye movement, this force is elastic in nature. For relatively low angular velocities, such as might be produced in smooth pursuit, the passive forces do not change appreciably with changes in velocity. The nondepolarizing muscle relaxant mivacurium has no effect on accurate performance of passive forced ductions under general anesthesia. Studies collecting quantitative data on passive orbital forces should be performed, when feasible, with an automated duction and recording apparatus.

Anesthesia, General↗

PubMed2005

Development of two enzyme-linked immunosorbent assays for detection of endosulfan residues in agricultural products.

Two competitive immunoassays, a laboratory assay based on microwell plates and a field test based on the use of polystyrene tubes, have been developed for the detection of endosulfan in agricultural products. The limit of detection for the microwell plate format was 0.8 +/- 0.1 microg/kg, and the limit of detection for the tube format was 1.6 +/- 0.2 microg/kg. A simple, rapid, and efficient extraction method was employed, and 76-112% recoveries of spiked samples were obtained. Methanol extracts of some agricultural product samples such as grape, carrot, spinach, and tobacco could be analyzed directly by immunoassay after dilution in 0.5% fish skin gelatin-phosphate buffered saline. In contrast, extracts of green tea caused significant interference in the assay, and a number of simple cleanup methods were ineffective in removing interference. However, use of the coagulating reagent polyvinyl pyrrolidone removed the matrix effect effectively. For the validation of the enzyme-linked immunosorbent assay (ELISA) tests, samples were analyzed by ELISA and gas chromatography (GC) after solid phase extraction. The relationship between data obtained using the tube assay and microwell assay was good (the lowest r(2) value was 0.94), and also, the immunoassay assay data correlated well with data obtained from GC analysis (the lowest r(2) value was 0.93). The developed immunoassay methods are the suitable methods for the rapid quantitative and reliable determination of endosulfan residues in agricultural products.

Camellia sinensis↗

PubMed1973

Genetic control of immune responses in vitro. I. Development of primary and secondary plaque-forming cell responses to the random terpolymer 1-glutamic acid 60-1-alanine30-1-tyrosine10 (GAT) by mouse spleen cells in vitro.

In vivo, the antibody response in mice to the random terpolymer L-glutamic acid(50)-L-alanine(30)-L-tyrosine(10) (GAT) is controlled by a histocompatibility-linked immune response gene(s). We have studied antibody responses by spleen cells from responder and nonresponder mice to GAT and GAT complexed to methylated bovine serum albumin (GAT-MBSA) in vitro. Cells producing antibodies specific for GAT were enumerated in a modified Jerne plaque assay using GAT coupled to sheep erythrocytes as indicator cells. Soluble GAT stimulated development of IgG GAT-specific plaque-forming cell (PFC) responses in cultures of spleen cells from responder mice, C57Bl/6 (H-2(b)), F(1) (C57 x SJL) (H-2(b/s)), and A/J (H-2(a)). Soluble GAT did not stimulate development of GAT-specific PFC responses in cultures of spleen cells from nonresponder mice, SJL (H-2(s)), B10.S (H-2(s)), and A.SW (H-2(s)). GAT-MBSA stimulated development of IgG GAT-specific PFC responses in cultures of spleen cells from both responder and nonresponder strains of mice. These data correlate precisely with data obtained by measuring the in vivo responses of responder and nonresponder strains of mice to GAT and GAT-MBSA by serological techniques. Therefore, this in vitro system can effectively be used as a model to study the cellular events regulated by histocompatibility-linked immune response genes.

Alanine↗

PubMed2002

Architecture of a mediator for a bioinformatics database federation.

Developments in our ability to integrate and analyze data held in existing heterogeneous data resources can lead to an increase in our understanding of biological function at all levels. However, supporting ad hoc queries across multiple data resources and correlating data retrieved from these is still difficult. To address this, we are building a mediator based on the functional data model database, P/FDM, which integrates access to heterogeneous distributed biological databases. Our architecture makes use of the existing search capabilities and indexes of the underlying databases, without infringing on their autonomy. Central to our design philosophy is the use of schemas. We have adopted a federated architecture with a five-level schema, arising from the use of the ANSI-SPARC three-level schema to describe both the existing autonomous data resources and the mediator itself. We describe the use of mapping functions and list comprehensions in query splitting, producing execution plans, code generation, and result fusion. We give an example of cross-database querying involving data held locally in P/FDM systems and external data in SRS.

Algorithms↗

PubMed1991

Measurement of cell proliferation by enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody to bromodeoxyuridine.

An ELISA was developed and optimized to measure cell proliferation using a monoclonal antibody to bromodeoxyuridine (BrdUrd). Incorporation of BrdUrd into myoblast monolayers, measured as the optical density at 492 nm, increased in response to fetal calf serum, IGF-I and EGF, the ELISA data correlated closely with data obtained by BrdUrd immunocytochemistry (r = 0.984), cell counting (r = 0.972) and tritiated thymidine uptake by liquid scintillation counting (r = 0.990). The BrdUrd ELISA is a useful alternative to measurement of tritiated thymidine uptake by scintillation counting, and has the added advantages of dispensing with the use of radioactivity and of being less labour intensive.

Animals↗

PubMed2004

Construction and validation of the Rhodobacter sphaeroides 2.4.1 DNA microarray: transcriptome flexibility at diverse growth modes.

A high-density oligonucleotide DNA microarray, a genechip, representing the 4.6-Mb genome of the facultative phototrophic proteobacterium, Rhodobacter sphaeroides 2.4.1, was custom-designed and manufactured by Affymetrix, Santa Clara, Calif. The genechip contains probe sets for 4,292 open reading frames (ORFs), 47 rRNA and tRNA genes, and 394 intergenic regions. The probe set sequences were derived from the genome annotation generated by Oak Ridge National Laboratory after extensive revision, which was based primarily upon codon usage characteristic of this GC-rich bacterium. As a result of the revision, numerous missing ORFs were uncovered, nonexistent ORFs were deleted, and misidentified start codons were corrected. To evaluate R. sphaeroides transcriptome flexibility, expression profiles for three diverse growth modes--aerobic respiration, anaerobic respiration in the dark, and anaerobic photosynthesis--were generated. Expression levels of one-fifth to one-third of the R. sphaeroides ORFs were significantly different in cells under any two growth modes. Pathways involved in energy generation and redox balance maintenance under three growth modes were reconstructed. Expression patterns of genes involved in these pathways mirrored known functional changes, suggesting that massive changes in gene expression are the major means used by R. sphaeroides in adaptation to diverse conditions. Differential expression was observed for genes encoding putative new participants in these pathways (additional photosystem genes, duplicate NADH dehydrogenase, ATP synthases), whose functionality has yet to be investigated. The DNA microarray data correlated well with data derived from quantitative reverse transcription-PCR, as well as with data from the literature, thus validating the R. sphaeroides genechip as a powerful and reliable tool for studying unprecedented metabolic versatility of this bacterium.

Adaptation, Physiological↗

PubMed2003

A locus-driven mechanism for rapid and automated atlas-assisted analysis of functional images by using the Brain Atlas for Functional Imaging.

OBJECT: Functional imaging is an established neurosurgical modality for studying the brain in health and disease. Identifying numerous activation loci on many functional images and reading their underlying cortical and subcortical anatomy, coordinates, and anatomical and functional values is a tedious, time-consuming, and error-prone task. In this study the authors propose a novel approach to this problem by using an electronic brain atlas in conjunction with a locus-driven mechanism. METHODS: The Brain Atlas for Functional Imaging containing an enhanced and extended electronic version of the Talairach-Tournoux brain atlas was used for analysis. It enables loading of anatomical and functional data, correlation of these data, identification of activation loci, and their labeling with Brodmann areas, gyri, and subcortical structures by means of the atlas. The Talairach proportional grid system transformation is used to register the anatomical and functional data with the atlas. The availability of numerous tools supports this process. A locus-driven mechanism for analysis of activation loci is implemented. Locus placement within the activation region is supported by thresholding, and its location can be further edited in three dimensions on any orthogonal plane. Once all loci are identified and edited, their labels, coordinates, and anatomical/functional values are read automatically and saved in an external file. This mechanism enables the analysis to be performed in an automated, rapid, explicit, three-dimensionally consistent, and user-friendly way. CONCLUSIONS: The electronic brain atlas with locus-driven mechanism is a useful tool for localization analysis of functional images.

Anatomy, Artistic↗

PubMed1991

Amplification by the polymerase chain reaction of hypervariable regions of the human genome for evaluation of chimerism after bone marrow transplantation.

We combined the polymerase chain reaction (PCR) with oligonucleotide hybridization as a novel and sensitive technique to evaluate posttransplant chimerism. Specific oligonucleotides for hybridization were synthesized homologous to tandemly repetitive core sequences of regions with a variable number of tandem repeats (VNTRs). Polymorphisms at such loci result from allelic differences in the number of repeats. Primers flanking the repeat region of each of the corresponding VNTRs were used for amplification. Recipient and donor pretransplant DNA and recipient posttransplant DNA were amplified. The resultant fragments were analyzed after gel electrophoresis either by hybridization in-gel or after Southern transfer. To confirm our findings, we also performed standard assays of restriction fragment length polymorphisms (RFLPs). Evaluation of 13 selected cases indicated mixed chimerism (4), complete chimerism (5), recurrence of leukemia (2), and endogenous repopulation of hematopoiesis (2) after marrow transplantation. Sensitivity of the method was determined by mixing various proportions of recipient and donor DNA; the limit of detection of the minor component in a mixture was 0.1%. PCR data correlated with RFLP data in all cases except two in which PCR proved more sensitive than RFLP. PCR amplification of VNTRs combined with oligonucleotide hybridization is a novel technique for documenting posttransplant chimerism and has advantages over RFLP analysis: high sensitivity, use of small amounts of DNA (250 ng), ease of preparation of DNA, elimination of need for restriction enzymes, and the ability to complete studies in 2 days.

Base Sequence↗