272 OOCYTE SPONTANEOUS ACTIVATION IN DIFFERENT RAT STRAINS

Oocyte spontaneous activation (OSA) has been reported to occur during in vitro culture of ovulated rat eggs. Approximately 1.5 h after isolation and culture, unfertilized oocytes extrude the second polar body and enter a metaphase arrest, and by 3 h individual chromatids separate and scatter throughout the egg's cytoplasm. The objective of this study was to compare the proportion of OSA and the level of maturation promoting factor (MPF) activity in oocytes from different strains. Twelve strains were selected from two commercial sources based on litter size. Mature female rats (9 to 12 weeks old) were superovulated using 20 IU eCG s.c. followed by 30 IU eCG s.c. 5 h later. After 48 h, a dose of 50 IU hCG was administered intraperitonealy and females were mated with vasectomized males. Oocytes were collected 17 h after hCG injection and cumulus cells were removed by transfer to M2 medium containing hyaluronidase (1 mg mL−1). Denuded oocytes were cultured in 50 μ­L drops of M16 medium under oil at 37°C and 5% CO2 in air. In order to assess OSA, oocytes were mounted in glycerol containing Hoechst 33342 (10 μg mL−1) on a glass slide after 6 h of in vitro culture. The proportion of activated oocytes was determined by epifluorescence microscopy. Oocytes were considered to be in metaphase II if they presented a compact group of chromosomes at the metaphase plate, and were considered activated when chromosome dispersion at different degrees was observed. Data were analyzed by ANOVA, considering each animal as an experimental unit. Significant differences were observed between strains (P < 0.01, Table). In order to determine MPF activity of each strain, 10 oocytes were removed from culture at 0, 1.5, and 3 h after oocyte collection and immediately stored in kinase buffer in LN2 for posterior analysis using an ELISA based kit (MESACUP cdc2 Kinase Assay Kit, MBL, Nagoya, Japan). The log ratio of the MPF activity at 1.5 and 3 h relative to 0 h for each animal (5 per strain) was analyzed by ANOVA. There were no MPF differences between or within strains (P > 0.3 and P > 0.05, respectively). We did not observe the expected decrease in MPF activity that allows for the exit of metaphase II arrest. This could imply that OSA is not associated with a decrease in MPF, or that MPF decreased rapidly and returned to metaphase levels by 1.5 h after culture. In conclusion, different levels of OSA were observed between strains, however, no differences in MPF activity were detected at the analyzed time points.

95 EFFECT OF ESTROUS COW SERUM ON SURVIVAL OF IN VITRO-PRODUCED BOVINE EMBRYOS AFTER SLOW FREEZING OR VITRIFICATION

Until now, the major obstacle associated with the extensive use of in vitro-produced bovine embryos is the lack of suitable methods to cryopreserve them. At least two approaches exist for overcoming this problem. One is to adjust cryopreservation methods to the requirements of these embryos, and the other is to improve embryo quality by using an appropriate in vitro environment for embryo production. The objective of this study was to determine the effect of estrous cow serum (ECS) during in vitro culture on embryo survival after cryopreservation by slow freezing or vitrification. Cumulus-oocytes complexes were in vitro-matured and fertilized as previously described (Ferre et al. 2003 Theriogenology 59, 301 abst). Presumptive zygotes were denuded from cumulus cells and cultured in groups of 50 in 400 μL drops of CR1aa medium. Seventy-two hour post-insemination (PI) embryos were randomly separated into three groups. Each group was then cultured in CR1aa + 5% ECS (without BSA; CR1-ECS), CR1aa + 3 mg/mL BSA (CR1-BSA), or CR1aa + 5% ECS + 3 mg/mL BSA (CR1-ECS-BSA). Embryos were cultured under 38.5°C, 5% CO2, 5% O2, and 90% N2. At 7.5 days PI, blastocysts from each group were double stained using propidium iodide and bisbenzimide (Hoechst 33342) to determine damaged cells and total cell number. The remaining embryos were randomly cryopreserved by freezing (1.5 M ethylene glycol; cooled at 0.5°C/min to −35°C) or vitrification (open pulled straw, Vajta et al. 1998 Mol. Reprod. Dev. 51, 53–58). After thawing or warming, embryos were cultured in CR1-ECS-BSA to evaluate embryo survival (hatching rate). Data were analyzed by χ2, ANOVA and Student's t-test (SAS Institute, Inc., Cary, NC, USA). Total cell number was higher in embryos cultured in CR1-ECS than in CR1-BSA or CR1-ECS-BSA (CR1-ECS: 142.1 ± 4.7, n = 23 vs. CR1-BSA 124.7 ± 4.9, n = 21, and CR1-ECS-BSA 125.8 ± 4.5, n = 25; t-test, P < 0.05). No differences were found in percent of damaged cells (CR1-ECS: 0.7%; CR1-BSA: 1.8%; CR1-ECS-BSA: 0.7%). Blastocyst survival after thawing was affected by cryopreservation methods and culture media (P < 0.01, Table 1). No interaction was found between both factors. In conclusion, under our experimental conditions elimination of ECS from CR1aa medium improves embryo cryotolerance. Vitrification allows for higher survival rates, regardless of the presence of serum during embryo culture. Table 1. Effect of cryopreservation method and serum supplementation during embryo culture on survival rate of in vitro-produced bovine embryos

Sixty-day all-cause mortality rates in patients treated for gastrointestinal cancers, in randomised trials, at the Royal Marsden Hospital

The aim of this study was to determine the 60-day all-cause mortality rate, during chemotherapy, for patients with oesophagogastric, pancreatic, and colorectal cancer. We analysed 1720 patients that were treated within randomised trials. The minimum follow-up period was > 60 days. Sixty-day mortality and 95% Confidence Intervals (CI) were calculated from the Kaplan-Meier survival curves. Causes of death were classified as treatment-related, disease-related or vascular syndrome-induced deaths. Patients with oesophagogastric cancer that could not tolerate a cis-platinum-containing regimens were treated with infused 5-fluorouracil (5FU)+/-mitomycin-C (MMC). The 60-day mortality rate depends upon the site of the primary tumour and the disease status (adjuvant versus advanced). The rate of treatment- and vascular syndrome-induced deaths was </=1.8%. For patients with advanced disease, most of the early deaths were disease-related. In adjuvant colorectal cancer, one patient died within 60 days (myocardial infarction). This study provides a benchmark for assessing the safety of regimens used in these disease settings.

Suppression of α-Cyano-4-hydroxycinnamic Acid Matrix Clusters and Reduction of Chemical Noise in MALDI-TOF Mass Spectrometry

Progress in high-throughput MALDI-TOFMS analysis, especially in proteome applications, requires development of practical and efficient procedures for the preparation of proteins and peptides in a form suitable for high acquisition rates. These methods should improve successful identification of peptides, which depends on the signal intensity and the absence of interfering signals. Contamination of MALDI samples with alkali salts results in reduced MALDI peptide sensitivity and causes matrix cluster formation (widely reported for CHCA matrix) observed as signals dominating in the range below m/z 1200 in MALDI spectra. One way to remove these background signals, especially for concentrations of peptides lower than 10 fmol/microL, is to wash matrix/sample spots after peptide cocrystallization on the MALDI plate with deionized water prior to analysis. This method takes advantage of the low water solubility of the CHCA compared to its alkali salts. We report here that the application of some ammonium salt solutions, such as citrates and phosphates, instead of deionized water greatly improves the efficiency of this washing approach. Another way to reduce matrix cluster formation is to add ammonium salts as a part of the MALDI matrix. The best results were obtained with monoammonium phosphate, which successfully suppressed matrix clusters and improved sensitivity. Combining both of these approaches-the addition of ammonium salts in the CHCA matrix followed by one postcrystallization washing step with ammonium buffer-provided a substantial ( approximately 3-5-fold) improvement in the sensitivity of MALDI-MS detection compared to unwashed sample spots. This sample preparation method resulted in improved spectral quality and was essential for successful database searching for subnanomolar concentrations of protein digests.

Commissioning and clinical results utilizing the Gildenberg-Laitinen Adapter Device for X-ray in fractionated stereotactic radiotherapy

BACKGROUND

The Gildenberg-Laitinen Adapter Device for X-Ray (GLAD-X/LS) frame is a positioning device that allows the use of the same fiducial points as the Brown-Robert-Wells (BRW) system. Thus it permits treatment planning to be accomplished by the Radionics X-knife Radiosurgery Program. We investigated the commissioning and clinical benefits of the GLAD-X/LS for fractionated stereotactic radiotherapy (FSRT) in patients who were unable to tolerate the Gill-Thomas-Cosman (GTC) frame.

METHODS AND MATERIALS

Commissioning of the GLAD-X/LS system was done via use of a Rando Phantom. A target volume of 2 x 2 x 2 cm was drilled into the phantom head. An ion chamber and thermoluminescence dosimetric chips (TLDs) were implanted in the target. A simulated treatment course consisting of 5 stereotactic radiotherapy fractions (300 cGy, 30 mm collimator) was delivered to the phantom head. A total of 27 patients who could not tolerate the GTC frame were treated using the GLAD-X/LS system. A total of 35 isocenters were used; the median number of treatment fractions was eight. Reproducibility of the x, y, and z coordinates was examined and correlated to the same determined using orthogonal port films. Relocation accuracy and reproducibility were further assessed comparing the x, y, and z coordinates of the target center with multiplanar reconstructed coronal and sagittal images. Patient tolerance of the device was also evaluated daily throughout the treatment.

RESULTS

The measured TLD and ion chamber doses were within 3% of the prescribed dose at the isocenter. The same dose accuracy was also found at incremental distances of 5 mm, 10 mm, and 15 mm from the isocenter. All patients tolerated the treatment and the device well. Six patients experienced mild ear canal pain, and softer or smaller earpieces were substituted. The mean relocation accuracy was 1.5 mm +/- 0.8.

CONCLUSIONS

The GLAD-X/LS system has excellent accuracy and reproducibility with the mean relocation accuracy of 1.5 mm +/- 0.8. The device is well-tolerated by patients, with no significant complications. Larger scale studies are necessary before routine use can be recommended for the administration of FSRT.

Hyperfractionated radiotherapy and paclitaxel for locally advanced/unresectable pancreatic cancer

PURPOSE

To determine prospectively the maximal tolerated dose and potential antitumor activity of weekly paclitaxel with concurrent hyperfractionated radiotherapy in patients with locally advanced and/or unresectable pancreatic cancer.

METHODS AND MATERIALS

We embarked on Phase I-II study of hyperfractionated radiotherapy using a concomitant in-field boost to a total dose of 63.80 Gy in 6 weeks at 1.1 Gy/fraction. Paclitaxel was administered weekly on Days 1, 8, 15, 22, 29, and 36 as a 3-h infusion. Paclitaxel doses were escalated from 20 mg/m(2)/wk to 70 mg/m(2)/wk. Twenty patients were studied, 14 women and 6 men (mean age 64 years). Some patients presented with one or more symptoms. Obstructive jaundice was the main presenting symptom in 10 patients and epigastric pain in 14. All patients had unresectable histologically proven adenocarcinoma of the pancreas (15 head, 4 body, and 1 tail). Reasons for unresectability were involvement of the portal vein, and/or superior mesenteric artery (n = 14), paraaortic nodes (n = 8), and medically inoperable (n = 1). Fourteen patients underwent a biliary bypass procedure before treatment (four endoscopic stenting, five choledochojejunostomy, and five cholecystojejunostomy). The follow-up period ranged from 14 to 66 months (median 44).

RESULTS

The dose-limiting toxicity was observed at 70 mg/m(2)/wk. Grade IV Radiation Therapy Oncology Group late GI toxicity was seen in 1 patient in the form of duodenal stricture and hemorrhage. Grade II gastrointestinal adverse effects occurred in 13 patients and Grade 3 in 1 patient. No neurologic morbidity was encountered. Eight patients required cytokine support for Grade 2 and 3 neutropenia. The treatment course was delivered within the planned time in 80% of the patients. Complete relief of pain occurred in 10 of 14 patients. The CA 19-9 level was either stable or decreasing in 12 of 15 patients. Of 17 assessable patients, stable disease was seen in 10, regression in 2, a partial response in 3, and a complete response in 2.

CONCLUSION

The use of hyperfractionated radiotherapy to a dose of 63.80 Gy with concomitant weekly paclitaxel is tolerated. The maximal tolerated dose of paclitaxel for this study was 60 mg/m(2)/wk. The preliminary objective responses denote activity of the regimen. We recommend testing this regimen in larger scale studies.

Global distribution of halogenated dimethyl bipyrroles in marine mammal blubber

Four halogenated dimethyl bipyrroles (HDBPs), hypothesized to be naturally produced, were quantitated in marine mammal blubber from a number of species obtained from various locations worldwide. HDBPs were found in samples from all locations studied. Concentrations of total HDBPs (SigmaHDBPs) ranged from 0.4 ng/g lipid weight in ringed seals (Phoca hispida) from the White Sea to 2,540 ng/g lipid weight in Dall's porpoise (Phocoenoides dalli) from the northwestern North Pacific Ocean. At their highest levels, SigmaHDBPs made up 11% of the total quantitated organohalogen body burden of adult male Dall's porpoises. In two beluga (Delphinapterus leucas) data subsets, it was found that males contained significantly higher concentrations of SigmaHDBPs than females. No significant effects of age or sex on SigmaHDBPs were observed in harbor seal (Phoca vitulina) and bowhead whale (Balaena mysticetus) data subsets. The geographical distribution of concentrations did not resemble that of the ubiquitous anthropogenic organohalogen, polychlorinated biphenyl congener CB-153. Higher concentrations of HDBPs and different patterns of congeners were observed in samples from Pacific as opposed to non-Pacific Ocean influenced environments. Concentrations of HDBPs in beluga from the Arctic and St. Lawrence River were similar. Their high abundance in north Pacific Ocean biota and widespread occurrence suggest that HDBPs undergo extensive transport from a source located primarily in the Pacific Ocean. Evidence from HDBP congener patterns indicates that both ocean currents and atmospheric transport likely play a role in the movement of HDBPs. These results imply that HDBPs and anthropogenic organohalogens have different sources and support the natural production hypothesis.

Prospective randomized trial comparing mitomycin, cisplatin, and protracted venous-infusion fluorouracil (PVI 5-FU) With epirubicin, cisplatin, and PVI 5-FU in advanced esophagogastric cancer

PURPOSE

We report the results of a prospectively randomized study that compared the combination of epirubicin, cisplatin, and protracted venous-infusion fluorouracil (PVI 5-FU) (ECF) with the combination of mitomycin, cisplatin, and PVI 5-FU (MCF) in previously untreated patients with advanced esophagogastric cancer.

PATIENTS AND METHODS

Five hundred eighty patients with adenocarcinoma, squamous carcinoma, or undifferentiated carcinoma were randomized to receive either ECF (epirubicin 50 mg/m(2) every 3 weeks, cisplatin 60 mg/m(2) every 3 weeks and PVI 5-FU 200 mg/m(2)/d) or MCF (mitomycin 7 mg/m(2) every 6 weeks, cisplatin 60 mg/m(2) every 3 weeks, and PVI 5-FU 300 mg/m(2)/d) and analyzed for survival, response, toxicity, and quality of life (QOL).

RESULTS

The overall response rate was 42.4% (95% confidence interval [CI], 37% to 48%) with ECF and 44.1% (95% CI, 38% to 50%) with MCF (P =.692). Toxicity was tolerable, and there were only two toxic deaths. ECF resulted in more grade 3/4 neutropenia and grade 2 alopecia, but MCF caused more thrombocytopenia and plantar-palmar erythema. Median survival was 9.4 months with ECF and 8.7 months with MCF (P =.315); at 1 year, 40.2% (95% CI, 34% to 46%) of ECF and 32.7% (95% CI, 27% to 38%) of MCF patients were alive. Median failure-free survival was 7 months with both regimens. Global QOL scores were better with ECF at 3 and 6 months.

CONCLUSION

This study confirms response, survival, and QOL benefits of ECF observed in a previous randomized study. The equivalent efficacy of MCF was demonstrated, but QOL was superior with ECF. ECF remains one of the reference treatments for advanced esophagogastric cancer.

Process Evaluation of An Internet Career Fair

This evaluation describes the development of an internet version of a career fair. The ‘internet career fair’ was developed in response to the growing demand for e-recruitment in the graduate employment market, and the need to provide employment-related career services to external university students. In order to conserve resources and to assess what could be achieved with limited resources, the development process took a ‘minimalist’ approach based on static web pages, rather than a virtual chat-room approach. Twenty major employers registered with the internet career fair. The site attracted over 61,000 hits from the student body. It was recommended that the minimalist approach be retained for future internet career fairs.

The use of AEDs by police officers in the City of London. Automated external defibrillators

The Guidelines 2000 for cardiopulmonary resuscitation recommend shock delivery to victims in ventricular fibrillation within 5 min of call receipt by the Emergency Medical Services. In an effort to achieve this goal, in some parts of the United States, police officers have been trained to use automated external defibrillators (AEDs). We undertook a 3-year pilot evaluation of the use of AEDs by City of London police (CPOL) officers. Over a period of 3 years, 147 CPOL officers were trained in the use of an AED. Four AEDs were placed on rapid response vehicles covering the City of London. An overall call-response interval target was set at 8 min. The CPOL attended 1103 (90%) of the total of 1232 calls to which they were summoned. The mean interval between the first call received and arrival of the CPOL on scene was 8.9+/-4.0 min. The CPOL applied AEDs to 25 victims, 13 of whom were initially in ventricular fibrillation; at least one shock was delivered to all 13. The interval between call reception and delivery of the first shock was 5.5+/-2.5 min. The mean interval between switching on the AED and delivery of the first shock was 24+/-12 s. Two (15%) of these victims survived to hospital discharge. This study has confirmed the feasibility of training police officers in the UK to use AEDs as first responders. The call received to arrival on scene interval should be reduced by improvements in communication between LAS and CPOL.

Effects of acid treatment on the trace metal content of chromatographic silica: bulk analysis, surface analysis and chromatographic performance of bonded phases

A series of studies has been carried out on the effect of refluxing silica chromatography particles for 0.5 h and 18 h in water, dilute hydrochloric acid and dilute hydrofluoric acid. The bulk and surface trace metal concentrations were measured by inductively-coupled plasma atomic emission spectroscopy, static secondary ion mass spectrometry (SSIMS) and X-ray photoelectron spectroscopy. Diffuse reflectance Fourier transform infrared spectroscopy was used to determine changes in 'isolated" and "bonded" silanol groups. The chromatographic behaviour of a series of weakly basic analytes was investigated on C8 and C18 bonded phases manufactured from the acid-treated silicas. The different reflux treatments all resulted in a reduction in the numbers of isolated silanols compared with the untreated silica and SSIMS analysis suggested that the HF-treated silicas had undergone a more efficient surface rehydroxylation. Bulk trace metals were removed most effectively by the HF treatment, with the multivalent elements (Ti and Al) being the most difficult to remove. Surface specific analysis suggested that trace metals were removed more rapidly from the surface of the silica compared to the bulk matrix and that the acid treatments resulted in halide contamination of the silica surface. Evidence is presented to suggest that the bulk metal content of the silica is not representative of the concentration of metals at the chromatographic surface. The chromatographic investigations showed that the HF-treated silica gave substantially better performance towards weak bases than the HCl-treated silicas.

Smooth muscle tumor of the pleura. A case report and review of the literature

Smooth muscle tumors of the serosal membranes are extremely rare and have received little attention in the literature. To the best of our knowledge, only 1 published series of 5 pleural smooth muscle neoplasms has been published to date. We describe a primary pleural neoplasm with smooth muscle differentiation documented by light microscopy, immunohistochemistry, and electron microscopy. This tumor originated in the parietal pleura in a 32-year-old white man and was diagnosed incidentally by chest radiography; the diagnosis was confirmed by magnetic resonance imaging and biopsy. Four years later, the tumor was noted to have increased in size and disseminated into the chest wall as a separate circumscribed mass located in the pectoral muscle. Both masses were resected and diagnosed as smooth muscle tumors. We conclude that smooth muscle tumor of the pleura is a well-defined entity with a low, but definite malignant potential; therefore, we recommend complete resection and long-term follow-up for all patients.

Detection of unwanted residues of ivermectin in bovine milk by dissociation-enhanced lanthanide fluoroimmunoassay

Avermectins are frequently used to control parasitic infestations in many animal species. Previous studies have shown the long-term persistence of unwanted residues of these drugs in animal tissues and fluids. An immunoassay screening test for the detection and quantification of ivermectin residues in bovine milk has been developed. After an extensive extraction procedure, milk samples were applied to a competitive dissociation-enhanced lanthanide fluoroimmunoassay using a monoclonal antibody against an ivermectin-transferrin conjugate. The monoclonal antibody, raised in Balb C mice, showed cross-reactivity with eprinomectin (92%), abamectin (82%) and doramectin (16%). The limit of detection of the assay (mean + 3 SD), calculated from the analysis of 17 known negative samples, was calculated as 4.6 ng/mL. Intra- and inter-assay RSDs were determined as 11.6% and 15.8%, respectively, using a negative bovine milk sample fortified with 25 ng/mL ivermectin. Six Friesian milking cows were treated with ivermectin, three with a pour-on formulation of the drug and three with an injectable solution at the manufacturer's recommended dose rate. An initial mean peak in ivermectin residue concentration was detected at day 4 (mean level = 47.5 ng/mL) and day 5 post-treatment (mean level = 26.4 ng/mL) with the injectable form and pour-on treatment, respectively. A second peak in residue concentration was observed using the DELFIA procedure 28 days post-treatment in both treatment groups (23.1 ng/mL injectable and 51.9 ng/mL pour-on). These second peaks were not confirmed by HPLC and must at this time be considered to be false-positive results. By day 35 after treatment the mean ivermectin residue concentration of both groups fell below the limit of detection of the assay.

A clinical nomogram for predicting long-term survival in advanced colorectal cancer

From our prospectively accrued database of patients with gastrointestinal cancer, 1057 patients with advanced colorectal cancer were identified with the aim of determining predictive factors for survival of greater than 2 years and to use this information to develop a predictive nomogram. Patient's baseline characteristics, type and number of chemotherapy regimens received, and response to chemotherapy were assessed by univariate and multivariate logistic regression comparing those who survived greater than or less than 2 years. A total of 161 (15.2%) patients survived more than 2 years, so-called long survivors (LS). In multivariate analysis, positive predictive factors for LS were: good performance status (PS), normal serum carcinoembryonic antigen (CEA), rectal primary, Dukes' stage A-B, well or moderate differentiation, two or less disease sites, response to chemotherapy and treatment used protracted venous infusion (PVI) 5-fluorouracil (5-FU) in first-line chemotherapy, and the increasing number of chemotherapy treatments received. From these PS, CEA, number of sites and response to first-line chemotherapy were used to develop a nomogram capable of predicting the probability of survival beyond 2 years for an individual patient. This large study confirmed the relevance of known prognostic factors in metastatic colorectal cancer and demonstrated the importance of response to chemotherapy as an independent factor to predict LS. By combining these, we developed a nomogram which provides information which is likely to prove useful in the management of patients with advanced colorectal cancer.

Effects of growth hormone treatment on red cell plasma membrane fatty acid constituents in hypopituitary adults

The effects of replacement with recombinant human GH (hGH) on red cell plasma membrane fatty acid and cholesterol constituents were assessed in nine adult patients with growth hormone deficiency. They were treated with hGH in a dose of 0.125 U.kg-1.wk-1 for four weeks and at 0.25 U.kg-1.wk-1 thereafter for an overall mean duration 13.5 +/- 3.9 months (mean +/- SD). The relative proportions of the various phospholipid fatty acid constituents and the proportion of cholesterol in the phospholipid bilayer were assayed every six months. At the end of the study, the percentage of arachadonic acid (20:4) in membrane phospholipid was found to rise by an average of 3.7% (P < 0.05) and there appeared to be a nonsignificant trend showing an increase in highly unsaturated fatty acids, namely linoleate (18:2) and gamma linolenic acid (18:3) and a corresponding decrease in unsaturated fatty acids, namely palmitate (16:0) and stearate (18:0) and monounsaturated fatty acids such as palmitoleic acid (16:1), oleic acid (18:1) and oleic acid isomer (18:1 iso). In addition, the proportion of cholesterol in the plasma membrane i.e. the cholesterol/phospholipid ratio was found to decrease by 0.84% (P < 0.05). There was a significant increase in HbAlc from 4.85 +/- 0.51 to 4.94 +/- 0.45% (P < 0.01) by the end of the study.

Quantitative approach to single-nucleotide polymorphism analysis using MALDI-TOF mass spectrometry

Pooling of DNA samples before genotyping is a valuable means of streamlining large-scale genotyping efforts in disease association studies, single-nucleotide polymorphism (SNP) validation or mutant allele screening programs. In this report, we explore the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to quantitative analysis of SNPs. The measurements are based on MALDI-TOF MS analysis of primer extension assays performed on standard mixtures of pooled PCR products at several test loci. The inherent high molecular weight resolution of MALDI-TOF MS conveys high specificity and good signal-to-noise ratio for performing accurate quantitation. The methods described maximize the sensitivity and quantitative capacity of MALDI-TOF MS while preserving the throughput and economic advantages of the MALDI-TOF platform. Using the format described, we demonstrate that allele frequencies as low as 5% can be detected quantitatively and unambiguously.