Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MICROMANIPULATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed1994

Monozygotic twinning in the human is associated with the zona pellucida architecture.

Six cases of identical twin pregnancies which occurred in 2163 cycles of in-vitro fertilization during a 3 year period are reported. Monozygosity was confirmed when the number of fetuses exceeded the number of embryos replaced (n = 4) or when two concepti were observed in a single amniotic sac (n = 2). Each of the reported pregnancies resulted from replacement of embryos either with naturally thin zonae pellucidae or embryos whose zonae had been breached during micromanipulation for assisted fertilization (subzonal sperm insertion) or assisted hatching. That such cases exclusively gave rise to monozygosity suggests a link between the physical state of the zona pellucida, hatching, and generation of identical twins.

Blastocyst↗
PubMed2003

Production of cloned pigs by whole-cell intracytoplasmic microinjection.

Cloning by somatic cell nuclear transfer has been successfully achieved by both fusing of a donor cell with and injecting an isolated donor cell nucleus into an enucleated oocyte. However, each of the above methods involves extended manipulation of either the oocytes (fusion) or the donor cells (nucleus isolation). Additionally, cloning efficiency can be reduced by low fusion rate of the cell fusion method, and specialized micromanipulation equipment and exacting nucleus isolation techniques are required for the nucleus injection method. Here we report a whole-cell injection technique for nuclear transfer in pigs and the production of cloned piglets with comparable, if not higher, efficiency than the other two nuclear transfer procedures. First, we tested the feasibility of this technique with three types of frequently used donor cells (cumulus, mural granulosa, and fibroblasts) and obtained the optimal nuclear reprogramming conditions for these cells. We further improved our protocol by avoiding ultraviolet exposure during enucleation and achieved a 37% blastocyst rate. We then conducted whole-cell injection using skin fibroblasts from the ear of a sow transgenic for two genes, the porcine lactoferrin and the human factor IX, and produced four live-born cloned transgenic piglets from three recipients. The present study demonstrated the applicability of producing normal, cloned piglets by the simple and less labor-intensive whole-cell intracytoplasmic injection.

Animals↗
PubMed1984

Visualization of pronuclei in living bovine zygotes.

Bovine embryos were surgically collected from the oviducts of superovulated crossbred heifers 48 h postonset of estrus. The one-celled ova were treated with 4'-6'-diamidino-2-phenylindole (DAPI) and observed under ultraviolet light by fluorescence microscopy. Both male and female pronuclei were visualized, identified and subjected to micromanipulation.

Animals↗
PubMed1987

Nuclear transplantation in the bovine embryo: assessment of donor nuclei and recipient oocyte.

Blastomeres from 2- to 32-cell bovine embryos were transferred to enucleated oocytes matured either in vivo or in vitro by micromanipulation and electrofusion. The percentage of donor cells fusing with the recipient oocytes was dependent on relative cell size or stage of development. Therefore, when smaller donor karyoplasts (17- to 32-cell vs. 2- to 8-cell) were transferred, the rate of fusion was significantly less (p less than 0.01). After fusion, nuclear transfer embryos were cultured either in vitro or in vivo (in a ligated ovine oviduct). Nuclear transfer embryos cultured in vitro developed to the 4- to 6-cell stage after 72 h (4-cell, 71%; 8-cell, 33%, 16-cell, 33%; p less than 0.30), whereas nuclear transfer embryos cultured in vivo developed to the morula or blastocyst stage (2- to 8-cell, 11.7%; 9- to 16-cell, 16.0%; 17- to 32-cell, 8.3%; p greater than 0.30) after 4 or 5 days. Freshly ovulated oocytes (collected 36 h after the onset of estrus), when used as recipients, resulted in morula/blastocyst-stage embryos more often than in vitro-matured oocytes or in vivo-matured oocytes collected 48 h after the onset of estrus (20% vs. 7.8% and 6.7%, respectively; p less than 0.02). After in vivo culture, nuclear transfer embryos were mounted and fixed or transferred nonsurgically to the uteri of 6- to 8-day postestrus heifers. Seven pregnancies resulted from the transfer of 19 embryos into 13 heifers; 2 heifers completed pregnancy with the birth of live calves.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Multiple generational bovine embryo cloning.

Repeated cycles (multiple generations) of nuclear transfer procedures have the potential of producing a large number of identical offspring from the micromanipulation of one mammalian embryo. This paper outlines the differences in nuclear transfer procedure efficiencies and developmental rates for the various stages and generations of embryos. We report the production of 54 genetically identical embryos that developed to the morula stage from one parent embryo. When a limited number of nuclear transfer embryos (clones) were transferred to recipient females, first, second, and third generation calves were born. Clones cultured for 5 days in the sheep oviduct had a greater number of cells (28.1 +/- 1.7) than clones cultured for 4 days (17.8 +/- 1.7). However, fusion rates were lower for Day 5 clones (Day 5, 57% vs. Day 4, 68%; p < 0.001) used as donors for the next generation of cloning. Different generations of clones also varied in fusion rates. Fusion rates generally declined with each additional generation and ranged from 66% for the parent-donor embryos to 52% for second generation donors (p < 0.01). Developmental rates were highest for first and third generation donors (20% and 19%) and lowest for second generation donors (10%; p < 0.001). Further understanding of the factors that are conducive to high developmental rates and nuclear reprogramming may make it possible to produce an unlimited number of genetically identical animals.

Animals↗
PubMed1994

Removal of cytoplasmic lipid enhances the tolerance of porcine embryos to chilling.

The lipid content of porcine 1-cell stage embryos was reduced (delipated) through the use of micromanipulation to remove the lipid layer formed after centrifugation. Of 94 delipated embryos chilled to 4 degrees C for 1 h at the 1-cell or 2- to 4-cell stage, 60 (64%) cleaved in culture with development to the morula-blastocyst stage, whereas all of the control embryos lysed within 24 h. Significantly more embryos developed beyond the 8-cell stage when they were chilled at the 2- to 4-cell stage compared with chilling at the 1-cell stage (44%, 20 of 45 vs. 18%, 9 of 49). Fewer embryos developed after chilling if they were only partially rather than fully delipated. Developmental rates of partially delipated embryos to the 8-cell and blastocyst stages were 33% (13 of 40) and 8% (3 of 40), rates significantly (p < 0.001 and 0.05) lower than the rate for fully delipated embryos (73%, 38 of 52 and 27%, 14 of 52, respectively). The in vitro developmental competence of the unchilled fully delipated embryos was comparable to that of intact zygotes (cleavage: 94%, 45 of 48 vs. 87%, 26 of 30; > or = blastocyst: 40%, 19 of 48 vs. 57%, 17 of 30). These data demonstrate that the sensitivity of porcine embryos to chilling is related to their high lipid content and that they can become tolerant to chilling if their lipid content is reduced.

Animals↗
PubMed1999

Transmembrane regulation of intracellular calcium by a plasma membrane sodium/calcium exchanger in mouse ova.

Regulation of cytoplasmic free calcium concentration ([Ca2+)]i) is a key factor for maintenance of viability of cells, including oocytes. Indeed, during fertilization of an ovum, [Ca2+]i is known to undergo oscillations, but it is unknown how basal [Ca2+]i or calcium oscillations are regulated. In the present study we investigated the role of the plasma membrane in regulating [Ca2+]i of metaphase II-arrested mouse oocytes (ova). Ova were collected from B6C3F1 mice treated with eCG (10 IU) and hCG (5 IU), and intracellular calcium was determined by means of fura-2. Extracellular calcium flux across the zona pellucida was detected noninvasively by a calcium ion-selective, self-referencing microelectrode that was positioned by a computer-controlled micromanipulator. Under basal conditions ova exhibited a calcium net efflux of 20.6 +/- 5.2 fmol/cm2 per sec (n = 69). Treatment of ova with ethanol (7%) or thapsigargin (25 nM-2.5 microM) transiently increased intracellular calcium and stimulated calcium efflux that paralleled levels of [Ca2+]i. The presence of a Na+/Ca2+ exchanger was indicated by experiments employing both bepridil, an inhibitor of Na+/Ca2+ exchange, and sodium-depleted media. In the presence of bepridil, a net influx of calcium was revealed across the zona pellucida, which was reflected by an increase in the [Ca2+]i. In addition, replenishment of extracellular sodium to ova that had been incubated in sodium-depleted media induced a large calcium efflux, consistent with the actions of Na+/Ca2+ exchange. Sodium/calcium exchange in mouse ova may be an important mechanism that regulates [Ca2+]i.

Adenosine Triphosphatases↗
PubMed2000

Epigenetic modifications necessary for normal development are established during oocyte growth in mice.

The ability of maternal chromatin to support full-term development is attained during oocyte growth. The aim of this study was to identify when during the growth phase the maternal chromatin developed the capacity to support term development. Mature metaphase II-arrested oocytes that contained chromatin from oocytes at different stages of oocyte growth were constructed by micromanipulation. The oocytes were fertilized in vitro, developed to the blastocyst stage in vitro, and transferred to recipients to assay developmental potential. The results demonstrate, firstly, that the origin of the maternal chromatin has no effect on the rate of oocyte maturation, fertilization, or development to the blastocyst in vitro. Secondly we demonstrate that maternal chromatin is first competent to support development to term during the latter half of oocyte growth when oocytes are 60-69 microm in diameter in juvenile mice or 50-59 microm in diameter in adult mice. These data show that epigenetic modifications necessary for postimplantation development occur during a specific phase of oocyte growth.

Animals↗
PubMed2002

Sequential development of Hodgkin's disease and CD30+ diffuse large B-cell lymphoma in a patient with MALT-type lymphoma: evidence of different clonal origin of single microdissected Reed-Sternberg cells.

We observed in the same patient the development of a tonsil mucosa-associated lymphoid tissue-type lymphoma in 1994, a mediastinal Hodgkin's disease in 1998, and a colonic CD30+ anaplastic diffuse large B-cell lymphoma in 2000. A same-sized FR3-JH fragment was demonstrated by polymerase chain reaction, both at the level of total DNA and of single micromanipulated cells, showing monocytoid, Reed-Sternberg, or anaplastic morphology. Moreover, an identical IgH nucleotide sequence was detected in mucosa-associated lymphoid tissue-type lymphoma and colonic CD30+ anaplastic diffuse large B-cell lymphoma, whereas mediastinal Hodgkin's disease IgH rearrangement involved different VH and JH genes. CD30+ Reed-Sternberg and diffuse large B-cell lymphoma cells contained Epstein-Barr virus EBER sequences that were not observed at the level of mucosa-associated lymphoid tissue-type lymphoma. Therefore, Epstein-Barr virus infection may have played a role in diffuse large B-cell lymphoma transformation of mucosa-associated lymphoid tissue-type lymphoma and in the lymphomagenesis of Hodgkin's disease. In addition to their different clonal origin, Reed-Sternberg cells of Hodgkin's disease expressed a CD15+, CD20+ (rare cells), CD30+, Oct-2-, EBNA2-, LMP1+ phenotype, whereas anaplastic and Reed-Sternberg-like cells of diffuse large B-cell lymphoma were CD15-, CD20+, CD30+, Oct-2+, EBNA2+, and LMP1+. Interestingly, we also detected scattered CD30+ Epstein-Barr virus- large cells with prominent nucleoli in the initial tonsil mucosa-associated lymphoid tissue-type lymphoma, suggesting that these cells could be prone to Epstein-Barr virus infection and/or large cell transformation.

DNA, Neoplasm↗
PubMed2003

Dural tissue trauma and cerebrospinal fluid leak after epidural needle puncture: effect of needle design, angle, and bevel orientation.

BACKGROUND: The effects of epidural needle design, angle, and bevel orientation on cerebrospinal fluid leak after puncture have not been reported. The impact of these factors on leak rate was examined using a dural sac model. Dural trauma was examined using scanning electron microscopy. METHODS: Human cadaveric dura, mounted on a cylindrical model, was punctured with epidural needles using a micromanipulator. Tissue was punctured at 15 cm H2O (left lateral decubitus) system pressure, and leak was measured at 25 cm H2O (semisitting) pressure. Leak rates and trauma were compared for the following: (1) six different epidural needles at 90 degrees, bevel parallel to the dural long axis; (2) 18-gauge Tuohy and 18-gauge Special Sprotte epidural needles, 30 degrees versus 90 degrees; (3) 18-gauge Tuohy, bevel perpendicular versus parallel to the dural long axis. RESULTS: With the 90 degrees puncture, bevel parallel, the greatest leak occurred with a 17-gauge Hustead (516 +/- 319 ml/15 min), and the smallest leak occurred with a 20-gauge Tuohy (100 +/- 112 ml/15 min; P = 0.0018). A 20-gauge Tuohy puncture led to statistically significant reductions in leak (P value range, 0.0001-0.0024) compared with all needles except the Special Sprotte. With the 30 degrees versus 90 degrees angle, 30 degrees punctures with an 18-gauge Tuohy produced nonstatistically significant leak reductions compared with the 18-gauge Tuohy at 90 degrees. The puncture angle made no difference for the Special Sprotte. Nonsignificant reductions were found for the Special Sprotte compared with the Tuohy. With the 18-gauge Tuohy bevel orientation, perpendicular orientation produced nonstatistically significant reductions in leak compared with parallel orientation. CONCLUSIONS: Cerebrospinal fluid leak after puncture was influenced most by epidural needle gauge. Leak rate was significantly less for the 20-gauge Tuohy needle.

Anesthesia, Spinal↗
PubMed2004

Epidural catheter penetration of human dural tissue: in vitro investigation.

BACKGROUND: Factors contributing to subarachnoid catheter passage after epidural placement are not well understood. This study explored mechanisms that might explain its occurrence. METHODS: Human cadaveric dura was mounted on a model and pressurized to physiologic levels. In a standardized fashion, a 20-gauge Portex three-port, closed end (nonflexible) tip catheter was passed through an epidural needle mounted on a micromanipulator at a 90 degree angle, attempting to penetrate dura with the catheter. Attempts then followed with a 19-gauge Arrow Flex Tip Plus single-port catheter. Subarachnoid catheter passage was compared in (1) intact dura, (2) clinically occult versus obvious epidural needle punctures, and (3) single 25-gauge Whitacre spinal needle punctures after combined spinal-epidural placement. RESULTS: Neither catheter penetrated intact dura: Portex, 0 of 300 attempts (0.0000; 95% confidence interval [CI]: 0.0000, 0.0158); Arrow, 0 of 300 attempts (0.0000; 95% CI: 0.0000, 0.0158). In clinically occult epidural needle punctures, the 20-gauge Portex catheter penetrated 1 of 3 specimens in 1 of 14 attempts (0.0714; 95% CI: 0.0021, 0.3583). The 19-gauge Arrow did not pass (0 of 15 attempts, 0.0000; 95% CI: 0.0000, 0.2535). In clinically obvious epidural needle punctures, the Portex passed in 6 of 33 attempts (0.1818; 95% CI: 0.0760, 0.3608) and the Arrow passed in 1 of 35 attempts (0.0286; 95% CI: 0.0012, 0.1662). Neither catheter passed through a single 25-gauge spinal needle puncture after an uncomplicated combined spinal-epidural: Portex, 0 of 90 attempts (0.0000; 95% CI: 0.0000, 0.0510); Arrow, 0 of 90 attempts (0.0000; 95% CI: 0.0000, 0.0510). CONCLUSIONS: Catheter passage is unlikely in the presence of intact dura or after an uncomplicated combined spinal-epidural. Unintentional subarachnoid passage suggests dural damage with the epidural needle.

Adult↗
PubMed1998

Rat cardiac neurons express the non-coding R-exon (exon 1) of the cholinergic gene locus.

Choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (VAChT) are both encoded by the cholinergic gene locus from which, in the rat, five different species of ChAT mRNA and three different species of VAChT mRNA are produced. So far, discrimination between mRNA subtypes has been possible only in CNS homogenates or in cell cultures. In this study, cardiac neurons were microdissected from frozen sections of rat heart using a u.v. laser and harvested using a micromanipulator. RT-PCR demonstrated the expression of the non-coding R-exon and splicing to R1-type mRNA in the majority of cardiac neurons. The technique presented here is the first to allow subtype analysis of cholinergic locus mRNA species in neurons in situ.

Animals↗
PubMed2001

Identifying the origin of single corneal cells by DNA fingerprinting: part I--implications for corneal limbal allografting.

PURPOSE: To demonstrate that the combination of impression cytology and single cell DNA fingerprinting represents a powerful tool that is suitable for detecting transplanted cells after corneal limbal allografting. METHODS: Fifty single cells were obtained by corneal impression cytology from 12 patients undergoing cataract surgery. Individual cells were isolated from samples by micromanipulation. Polymerase chain reaction and short tandem repeat profiling was used to obtain forensic standard "DNA fingerprints" from single cells. Blood samples taken at the time of impression cytology provided control "fingerprints." RESULTS: Informative DNA fingerprints were obtained from all corneal samples and 66% (33 of 50 cells) of isolated single cells. Of all fingerprints obtained, most (91%, 30 of 33 fingerprints) corneal fingerprints matched corresponding blood sample fingerprints. At least one corneal fingerprint matched the corresponding blood sample fingerprint in 83% (10 of 12 patients) of the patients in the study. CONCLUSIONS: This extremely specific single cell DNA fingerprinting system permits accurate identification of individual corneal epithelial cells, allowing very reliable determination of their origin, which will enable host and donor cells to be distinguished from each other after keratolimbal allografting procedures, even if the host and donor are the same sex or siblings. These DNA fingerprinting methods allow assessment of quality and quantity of donor cell survival, as well as survival time. The extreme sensitivity and accuracy of the technique means that should contamination occur, it would be identified, thus ensuring meaningful results.

Cell Transplantation↗
PubMed2001

Identifying the origin of single corneal cells by DNA fingerprinting: part II-- application to limbal allografting.

PURPOSE: Successful limbal allotransplantation allows regression of limbal stem cell deficiency features. Transplant survival is presumed if clinical improvement occurs. However, positive proof of surviving transplanted stem cells remains difficult. This follow-up study attempted to prove donor cell survival 5 years after limbal stem cell allograft in one woman with aniridia. METHODS: Impression cytology and single-cell DNA fingerprinting were used to investigate a previously studied patient. Corneal epithelial cells were harvested from five sites and isolated by micromanipulation. Polymerase chain reaction and short tandem repeat profiling were used to obtain forensic standard "DNA fingerprints" from single cells. (The technique is described in the preceding article, Part I.) Blood samples yielded host and donor DNA for comparison. Negative controls were performed for impression cytology and polymerase chain reaction. Simultaneous micro-scrape samples were also taken. RESULTS: Impression cytology samples permitted informative DNA fingerprints from all corneal sites and represented 76% (23/30) of tested cells. Fifty percent (15/30) of the fingerprints were "specific" but 83% (19/23) matched the host DNA fingerprint. The remaining 17% (4/23) represented contamination from various sources. Specific fingerprints were obtained in 55% (10/18) of the cells from micro-scrape samples. All samples giving sufficient information matched the host DNA fingerprint. All tested blood samples gave specific fingerprints. None of the sampled corneal cells gave a donor DNA fingerprint. CONCLUSIONS: In a single patient, no detectable long-term donor cell survival exists at 5 years. Positive identification would have provided unequivocal proof of donor cell survival. This technique gives useful information even if contamination occurs.

Aniridia↗
PubMed1994

Effects of two low-osmolar contrast media, ioxaglate and iopamidol, on erythrocyte membrane elasticity.

RATIONALE AND OBJECTIVES: The effect of ioxaglate and iopamidol, two recently developed low-osmolality contrast media, on the shear elasticity of erythrocyte membranes was studied at an iodine concentration of 300 mg/mL and at a 20% volume concentration and compared with that obtained for control solutions matched in osmolality. METHODS: The authors used a micromanipulation technique, which consists of visualizing deformations of individual erythrocytes when gently aspirated into the tip of a glass micropipette by an accurately controlled pressure. An erythrocyte membrane shear elasticity modulus mu was then deduced. An increase in mu corresponded to an increase in erythrocyte membrane rigidity. RESULTS: In all cases, the erythrocytes remained discocytic. The shear elasticity modulus of the erythrocyte membrane is found to be (1) in the presence of ioxaglate (4.3 +/- 0.9 microN/m) lower (P < .001) than in the presence of hyperosmolar saline (6.2 +/- 1.3 microN/m) and lower (P < .02) than in the presence of iso-osmolar control (4.7 +/- 0.7 microN/m); (2) in the presence of iopamidol (5.4 +/- 0.7 microN/m) lower (P < .001) than in the presence of hyperosmolar sucrose (6.4 +/- 1.2 microN/m) and higher (P < .001) than in the presence of iso-osmolar control (4.7 +/- 0.7 microN/m); and (3) lower (P < .001) in the presence of ioxaglate (4.3 +/- 0.9 microN/m) than in the presence of iopamidol (5.4 +/- 0.7 microN/m). CONCLUSIONS: Under the experimental conditions used, both contrast media (ioxaglate and iopamidol) modify the erythrocyte membrane shear elasticity modulus less than do the matched hyperosmolar controls. Moreover, ioxaglate makes the erythrocyte membrane less rigid, and iopamidol makes the erythrocyte membrane more rigid than does the iso-osmolar control.

Elasticity↗
PubMed1997

Thermal effects of laser stapedectomy in an animal model: CO2 versus KTP.

Although use of the laser for stapedectomy has become common in recent years, controversy remains regarding whether the CO2 or visible-spectrum lasers (argon and KTP) are best suited for this operation. The main concern has been the potential for thermal injury to the inner ear with the visible-spectrum lasers attributable to their absorption characteristics. To further investigate this issue, the author performed 20 laser stapedectomies on adult chinchillas. Following placement of a 0.127-mm-diameter copper/constantan thermocouple (sampling at 12 Hz) beneath the footplate on the medial wall of the vestibule via a distant fenestration site, thermal changes with a micromanipulator-based CO2 and fiberoptic KTP system were compared. This was the first live animal model comparison of these two lasers. There was no statistical difference in the mean temperature elevation between the two systems (P = 0.395).

Animals↗
PubMed1998

A 585-nanometer pulsed dye laser treatment of laryngeal papillomas: preliminary report.

OBJECTIVES/HYPOTHESIS: Standard management of recurrent respiratory papillomatosis (RRP) currently consists of CO2 laser microsurgical ablation of papillomas. Because of the recurrent nature of this viral disease, patients are often faced with significant cumulative risk of soft tissue complications. As a minimally traumatic alternative to management of RRP, we have investigated the use of the 585-nm pulsed dye laser (PDL) to cause regression of papillomas by selective eradication of the tumor microvasculature. STUDY DESIGN: Nonrandomized prospective pilot study. METHODS: Patients with laryngeal papillomas were treated with the PDL at fluences of 6 J/cm2 (double pulses per irradiated site), 8 J/cm2 (single pulses), and 10 J/cm2 (single pulses), at noncritical areas within the larynx, using a specially designed micromanipulator. Lesions on the true cords were treated with the CO2 laser, using standard methodology. RESULTS: Clinical examination of three patients treated to date showed that PDL treatment appeared to produce complete regression of papillomas. Unlike the sites of lesions treated by the CO2 laser, the epithelial surface at the PDL treatment sites was preserved intact. CONCLUSIONS: These preliminary results suggest the PDL may eradicate respiratory papillomas with minimal damage to normal laryngeal tissue. Further analysis of the ongoing study is required to demonstrate potential benefits of the technique.

Adult↗
PubMed1998

Pretreatment and midtreatment measurement of oxygen tension levels in head and neck cancers.

OBJECTIVE: Considerable evidence exists to suggest that tumor hypoxia results in radioresistance. Historically, it has been difficult to assess tumor oxygen tension levels reliably. These levels can now be assessed in head and neck malignancies using the Eppendorf pO2 histograph, which uses a fine-needle electrode and a computerized micromanipulator. This technology was used to compare the pretreatment tumor oxygen tension level in lymph node metastases of patients with head and neck cancer to measurements taken during nonsurgical treatment after a partial response had been achieved. STUDY DESIGN: Prospective study. METHODS: Oxygen tension levels were measured in the cervical lymph nodes of 10 patients with biopsy-proven head and neck squamous cell carcinoma and cervical metastases who were being treated with nonsurgical management. These levels were obtained using the Eppendorf pO2 histograph system. Measurements were taken before the start of treatment and were repeated when the size of the cervical metastatic node had decreased by 50%. Normal subcutaneous tissue was measured during the same session. The mean and median pO2 levels, as well as the percentage of measurements with pO2 less than 5 mm Hg were determined. RESULTS: A mean of 72.6 measurements per session was taken from each lymph node. The median tumor pO2 measurement fell from a mean (+/-SD) of 13.9+/-8.0 mm Hg to 7.3+/-9.9 mm Hg. Even more dramatic, however, was the substantial increase in the percentage of values less than 5 mm Hg, a rise from 29% to 52%. CONCLUSIONS: While there is variability both in the pretreatment oxygenation of head and neck cervical metastases and in the change in tumor oxygen tension during treatment, there appears to be a decrease in the overall oxygenation of the tumors. The dramatic increase in very low oxygen measurements may reflect selective survival of radioresistant or chemoresistant hypoxic tumor cells. Cells at the very low level would be expected to be radiobiologically hypoxic (resistant to radiation-induced cell kill).

Aged↗