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At least 433 records · Page 24Linked to original sources
PubMed2002

Lack of standardization in performance of the semen analysis among laboratories in the United States.

OBJECTIVE: To determine the level of standardization in performance of the semen analysis among clinical laboratories in the United States. DESIGN: A survey was mailed to laboratories requesting information about the laboratory and performance of the semen analysis. Responses were received from 536 laboratories. SETTING: Clinical laboratories enrolled in the American Association of Bioanalysts Andrology Proficiency Testing Program. PATIENT(S): None. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Agreement among laboratories. RESULT(S): Sixty-one percent of respondent laboratories were part of an assisted reproductive technology program. The laboratories perform less than 50 (53%), less than 10 (25%), or less than 5 (16%) andrology laboratory procedures per month. The laboratories routinely report sperm count (94% of laboratories), motility (95%), morphology (85%) and forward progression (69%), and semen volume (96%) as part of the semen analysis. Only 64% of laboratories routinely report abstinence, and 60% of laboratories indicate the criteria used for sperm morphology on the report form. The most common lower limits of normality for sperm count and motility were >20 x 10(6)/mL (77% of laboratories) and >50% (59% of laboratories), respectively. Few laboratories performed quality control for sperm counts (29%), motility (41%), and morphology (41%). CONCLUSION(S): These data indicate a significant lack of standardization in the performance and reporting of semen analyses among laboratories in the United States.

Humans↗
PubMed1999

Electrical activation and in vitro development of human oocytes that fail to fertilize after intracytoplasmic sperm injection.

OBJECTIVE: To determine whether electrically stimulated Ca2+ influx can "rescue" fertilization and early embryogenesis in human oocytes that fail to fertilize after intracytoplasmic sperm injection (ICSI). DESIGN: Prospective, randomized trial of a laboratory procedure. SETTING: A research laboratory at a university medical center. PATIENT(S): Discarded oocytes from ICSI-IVF cycles. INTERVENTION(S): Oocytes (n = 104) that showed no evidence of fertilization 16-24 hours after ICSI were assigned to three treatment groups: group 1 (one direct current electrical pulse at 1.36-1.50 kV/cm for 40-60 micros), group 2 (three pulses every 15-20 minutes), or group 3 (treated the same as group 2 but with no electrical stimulation). MAIN OUTCOME MEASURE(S): After stimulation, the oocytes were cultured in vitro for 3-5 days. Oocytes that displayed two pronuclei and a second polar body within 16 hours were considered to have fertilized normally. Fertilization and embryo cleavage rates were compared between groups. RESULT(S): Fertilization occurred in 26 (70%) of 37 and 38 (78%) of 49 group 1 and 2 oocytes, respectively, but in only 5 (27%) of 18 group 3 oocytes. Within 3 days, group 2 embryos routinely developed beyond the two-cell to four-cell stage (61% versus 13% in group 1); 11% of these oocytes developed to the morula or early blastocyst stage. Sex chromosome analyses indicated 10 male and 8 female embryos. CONCLUSION(S): Oocytes that fail to fertilize by 24 hours after ICSI can resume apparently normal fertilization and early embryonic development in response to electrical stimulation. Moreover, the degree of cytoplasmic activation as determined by the number of pulses applied affects fertilization efficiency and early embryonic development.

Adult↗
PubMed1999

Thermal cycling procedures for laboratory testing of dental restorations.

OBJECTIVES: Exposure of restorations in extracted teeth to cyclic thermal fluctuations to simulate one of the many factors in the oral environment has been common in many tracer penetration, marginal gap and bond strength laboratory tests. Temperature changes used have rarely been substantiated with temperature measurements made in vivo and vary considerably between reports. Justification and standardization of regimen are required. DATA, SOURCES AND STUDY SELECTION: An assessment of reports describing temperature changes of teeth in vivo is followed by an analysis of 130 studies of laboratory thermal cycling of teeth by 99 first authors selected from 25 journals. A clinically relevant thermal cycling regimen was derived from the in vivo information, and is suggested as a benchmark standard. CONCLUSIONS: Variation of regimens used was large, making comparison of reports difficult. Reports of testing the effects of thermal cycling were often contradictory, but generally leakage increased with thermal stress, although it has never been demonstrated that cyclic testing is relevant to clinical failures. However, should this be done, the standard cyclic regimen defined is: 35 degrees C (28 s), 15 degrees C (2 s), 35 degrees C (28 s), 45 degrees C (2 s). No evidence of the number of cycles likely to be experienced in vivo was found and this requires investigation, but a provisional estimate of approximately 10,000 cycles per year is suggested. Thermal stressing of restoration interfaces is only of value when the initial bond is already known to be reliable. This is not the case for most current restorative materials.

Benchmarking↗
PubMed2004

Progressing toward the reduction, refinement and replacement of laboratory animal procedures: thoughts on some encounters with Dr Iain Purchase.

A variety of encounters with Dr Iain Purchase over the last 25 years are reviewed in relation to their significance in terms of progress toward the reduction, refinement and replacement of animal procedures in toxicology and toxicity testing. Included are the work of the first FRAME Toxicity Committee and the FRAME International Alternatives Validation Scheme, the International Conferences on Practical In Vitro Toxicology and the foundation of Toxicology in Vitro, the work of an Institute of Medical Ethics working party on issues raised by animal experimentation and alternative approaches, the need for in vitro assays for chemical carcinogenesis based on the transformation of human cells, the problem presented by the human hazard potential of thousands of chemicals already in use before modern regulations for the registration of new chemicals came into force, and the importance of testing strategies with a focus on the integrated use of non-animal computer-based and in vitro test systems.

Animal Experimentation↗
PubMed1994

Absorbed-dose calibrations in high-energy photon beams at the National Physical Laboratory: conversion procedure.

The absorbed-dose calibration service from NPL is based on a primary-standard calorimeter that measures absorbed dose to graphite. Secondary-standard dosemeters are calibrated in absorbed dose to water in a 60Co gamma-ray beam and in x-ray beams over a range of generating potentials from 4 MV to 19 MV. Two methods were used to convert the calibrations of working-standard ionization chambers from absorbed dose to graphite into absorbed dose to water. One method involved the use of published interaction data for photons and secondary electrons, and required a knowledge of the chamber construction. The second method involved the calculation of the ratio of absorbed dose in graphite and water phantoms irradiated consecutively in the same photon beam using the photon-fluence scaling theorem. The two methods were in agreement to 0.1%.

Algorithms↗