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At least 1,153 records · Page 64Linked to original sources
PubMed2002

Vitamin D(3) receptor ablation sensitizes skin to chemically induced tumorigenesis.

1,25-Dihydroxyvitamin D(3) (1,25D(3)) is the biologically active form of vitamin D(3) that interacts with the nuclear vitamin D(3) receptor (VDR) to modulate gene expression in a tissue-specific fashion. 1,25D(3) is a potent regulator of cell proliferation, differentiation and apoptosis in a variety of cell types, including keratinocytes. In these studies, we assessed the sensitivity of mice homozygous for a null allele of the VDR (VDR(-/-) mice) and their wild-type counterparts (VDR(+/+) mice) to oral administration of the carcinogen 7,12-dimethylbenzanthracene (DMBA). Although the protocol was optimized for the induction of mammary tumors, 85% of VDR(-/-) mice developed persistent skin tumors within 60 days of carcinogen exposure. In VDR(-/-) mice exposed to DMBA, papillomas arose on all areas of the body, with an average tumor burden of 5.3 papillomas/mouse. No papillomas or any other skin lesions were observed in age- and sex-matched VDR(+/+) mice dosed with DMBA and followed for 6 months. The majority (80%) of skin tumors that developed in VDR(-/-) mice were classified histologically as sebaceous, squamous or follicular papillomas. Other types of lesions, including basal cell carcinoma, hemangioma and melanotic foci, were occasionally observed in VDR(-/-) mice (but not in VDR(+/+) mice) exposed to DMBA. Quantification of epidermal thickness and BrdU incorporation indicated that skin from VDR(-/-) mice exhibited hyperproliferation beginning at 7 weeks of age, which was exacerbated by DMBA treatment. Untreated aging VDR(-/-) mice did not exhibit tumor formation, but did develop a progressive skin phenotype characterized by thickened wrinkled skin, dermoid cysts and long curly nails. Together with previous reports that 1,25D(3) inhibits papilloma formation induced by topical DMBA-TPA regimens, our observation of enhanced sensitivity of VDR(-/-) mice to chemically induced skin carcinogenesis offers compelling evidence that disruption of VDR signaling predisposes to neoplasia.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

Mutagenicity of azo dyes in the Salmonella/activation test.

The detection of certain bis-azo biphenyl dyes (Trypan blue, Evans blue and Congo red) by a modification of the standard Ames test protocol is reported. Detection of a mutagenic response required both the inclusion of FMN in S-9 mix and use of a static pre-incubation step prior to addition of top-agar and pouring in the usual manner. Evidence is presented to substantiate the proposal that use of this protocol provides optimal conditions for the two stages of activation required for the production of mutagenic metabolites from these dyes. These are (i) initial flavin-mediated (hepatic) azo reduction resulting in the formation of proximate mutagenic metabolites followed by (ii) the oxidative metabolism by S-9 resulting in the formation of ultimately mutagenic products.

Animals↗
PubMed1985

Mouse cell clones for improved quantitation of carcinogen-induced altered differentiation.

Two new mouse epidermal cell lines have been isolated and characterized as target cells for three chemical carcinogens. The ability to grow these cells at low density (approximately 5 clonogenic cells/cm2) has permitted more precise quantitation of chemical carcinogen-induced changes in epidermal differentiation. The cell lines, designated 291 and 271c, retain the property previously observed in primary cultures of mouse epidermal cells, that is the regulation of terminal differentiation by extracellular Ca2+ ion. Altered response to extracellular Ca2+ after carcinogen treatment of these cells is the basis of the assay endpoint. Other normal properties demonstrated by these cells are keratin immunofluorescence patterns, ability to form cornified envelopes in response to Ca2+ and a lack of tumorigenicity. Both of the lines have high cloning efficiencies (up to 20%) and characteristic epidermal morphology. Their chromosome number, however, is near tetraploid. Dose response studies indicated an increase in colonies with altered response to Ca2+ proportional to the dose of three chemical carcinogens: DMBA 0.001-0.5 microgram/ml X 24 h, MCA 0.01-5 micrograms/ml X 24 h and MNNG 0.01-0.2 micrograms/ml X 1 h. The optimized assay protocol has provided a reproducible means of quantitating carcinogen-altered epidermal cells relative to carcinogen dose, and of isolating cell clones for studies of altered differentiation in carcinogenesis and chemotherapy.

Animals↗
PubMed2000

Embryo implantation and GnRH antagonists: GnRH antagonists do not activate the GnRH receptor.

Recent suggestions that gonadotrophin-releasing hormone (GnRH) antagonists activate the GnRH receptor are discussed. Most of the studies cited in support of this suggestion are in-vitro studies, testing supra-pharmacological doses of GnRH analogues in cancer cell lines, whereas GnRH antagonists, e.g. ganirelix or cetrorelix, do not affect the steroidogenesis of human granulosa cells in vitro. In patients treated with GnRH antagonists prior to IVF or intracytoplasmic sperm injection (ICSI), oocyte maturity and fertilization rates are equal to those achieved following a long protocol of GnRH agonists. Although there is a tendency towards a lower pregnancy rate (not statistically significant) in the initial trials using GnRH antagonist with either recombinant FSH or human menopausal gonadotrophin (HMG) for ovarian stimulation, this new treatment option of GnRH antagonists facilitates short and simple treatment and improves the convenience and safety for the patient. As with GnRH agonists in the past, the clinical outcome of GnRH antagonist treatment will improve with time as more clinical experience is gained (learning curve) and the treatment protocol is optimized. Moreover, a GnRH agonist instead of human chorionic gonadotrophin (HCG) may be used for triggering ovulation and will decrease the cancellation rate and minimize the risk for developing ovarian hyperstimulation syndrome (OHSS).

Female↗
PubMed2002

Morphological appearance of the cryopreserved mouse blastocyst as a tool to identify the type of cryoinjury.

BACKGROUND: If it were possible to deduce the mechanism of injury in cryopreserved embryos by their appearance, it would help to optimize cryopreservation protocols. METHODS: Mouse blastocysts were treated so that they were damaged by the six types of cryoinjuries listed below, and their appearance was observed at recovery in sucrose solution and a modified phosphate-buffered saline (PB1), and after culture for 1 and 24 h. RESULTS: (i) Intracellular ice: the embryos shrank normally in sucrose solution, but swelled in PB1 and collapsed after culture. (ii) Chemical toxicity of the cryoprotectant: the embryos looked normal in sucrose solution and PB1. After 1 h of culture, however, the blastomeres showed decompaction and degenerated thereafter. If the toxicity was extremely high, embryos looked nearly normal in PB1, but the surface of the cytoplasm was wrinkled as if they were "fixed". (iii) Osmotic swelling: the embryos looked normal in PB1, but after culture they shrank. (iv) Osmotic shrinkage: the embryos swelled in PB1, and then collapsed. (v) Fracture damage: the zona pellucida of the embryos was dissected. (vi) Extracellular ice: the zona of the embryos was elongated. CONCLUSIONS: It was often possible to deduce the type of injury that had occurred in cryopreserved embryos from their appearance at recovery and during subsequent culture. This may help to improve cryopreservation protocols for embryos of many species, including man.

Animals↗
PubMed2005

Need for optimal body composition data analysis using air-displacement plethysmography in children and adolescents.

Air-displacement plethysmography (ADP) is now widely used for body composition measurement in pediatric populations. However, the manufacturer's software developed for adults leaves a potential bias for application in children and adolescents, and recent publications do not consistently use child-specific corrections. Therefore we analyzed child-specific ADP corrections with respect to quantity and etiology of bias compared with adult formulas. An optimal correction protocol is provided giving step-by-step instructions for calculations. In this study, 258 children and adolescents (143 girls and 115 boys ranging from 5 to 18 y) with a high prevalence of overweight or obesity (28.0% in girls and 22.6% in boys) were examined by ADP applying the manufacturer's software as well as published equations for child-specific corrections for surface area artifact (SAA), thoracic gas volume (TGV), and density of fat-free mass (FFM). Compared with child-specific equations for SAA, TGV, and density of FFM, the mean overestimation of the percentage of fat mass using the manufacturer's software was 10% in children and adolescents. Half of the bias derived from the use of Siri's equation not corrected for age-dependent differences in FFM density. An additional 3 and 2% of bias resulted from the application of adult equations for prediction of SAA and TGV, respectively. Different child-specific equations used to predict TGV did not differ in the percentage of fat mass. We conclude that there is a need for child-specific equations in ADP raw data analysis considering SAA, TGV, and density of FFM.

Adolescent↗
PubMed2000

Rapid determination of short DNA sequences by the use of MALDI-MS.

We have developed a protocol for rapid sequencing of short DNA stretches (15-20 nt) using MALDI-TOF-MS. The protocol is based on the Sanger concept with the modification that double-stranded template DNA is used and all four sequencing reactions are performed in one reaction vial. The sequencing products are separated and detected by MALDI-TOF-MS and the sequence is determined by comparing measured molecular mass differences to expected values. The protocol is optimized for low costs and broad applicability. One reaction typically includes 300 fmol template, 10 pmol primer and 200 pmol each nucleotide monomer. Neither the primer nor any of the nucleotide monomers are labeled. Solid phase purification, concentration and mass spectrometric sample preparation of the sequencing products are accomplished in a few minutes and parallel processing of 96 samples is possible. The mass spectrometric analyses and subsequent sequence read-out require only a few seconds per template.

Alleles↗
PubMed1997

Assessment of coronary reserve by transoesophageal Doppler echocardiography. Direct comparison between different modalities of dipyridamole and adenosine administration.

BACKGROUND: This study was undertaken to compare the coronary vasodilator response to different application modalities of intravenous vasodilators, in order to identify the optimal pharmacological protocol for the evaluation of coronary reserve by means of transoesophageal Doppler echocardiography. METHODS: Blood flow velocity in the left anterior descending artery, coronary vascular resistance and left main coronary artery cross-sectional area were assessed by transoesophageal echo-Doppler during an i.v. adenosine bolus (5 mg), a 5-min adenosine infusion (infusion rate 140 micrograms. kg-1 min-1), and low (0.56 mg.kg-1. 4 min-1), and high-dose (0.84 mg.kg-1.9 min-1) dipyridamole infusions in 10 healthy normals (Group 1) and in 20 patients (Group 2) with either coronary microvascular disease (11 patients) or coronary artery disease (nine patients). RESULTS: In both groups, the highest flow velocity and the lowest coronary vascular resistance were observed during the adenosine infusion. Flow velocity values and indices of coronary vasodilator capacity observed after the adenosine bolus and the high-dose dipyridamole infusion were very close to those obtained during the adenosine infusion, especially in Group 1. Coronary flow velocity was lower and coronary vascular resistance higher after low-dose dipyridamole, significantly in Group 2. The maximal flow response to the adenosine bolus was observed within a few seconds after the injection, and was very short. The peak response to the adenosine infusion was observed 57 +/- 27 s after its start. The coronary flow velocity response to dipyridamole was dose dependent and differed between Groups 1 and 2. CONCLUSION: In combination with transoesophageal Doppler echocardiography, a short-lasting adenosine infusion at a rate of 140 micrograms.kg-1.min-1 seems to be preferable to an adenosine bolus and dipyridamole infusion. The effect of the bolus is too short for an accurate measurement of coronary flow velocity, while the dipyridamole infusion, especially at a low dose, induces a submaximal vasodilator response.

Adenosine↗
PubMed2005

Effective dose calculations in conventional diagnostic X-ray examinations for adult and paediatric patients in a large Italian hospital.

The effective dose E is an efficient and powerful parameter to study the radioprotection of the patient. In our hospital, eight radiological departments and more than 100 radiological X-ray tubes are present. The effective doses were calculated for adults and paediatric patients in 10 standard projections. To calculate E, first the entrance skin dose (ESD) was evaluated by a mathematical model that was validated by >400 direct measurements taken with an ionisation chamber on four different phantoms: the overall accuracy of the model was better than 12%. Second, to relate ESD to E, conversion coefficients calculated by Monte Carlo techniques were used. The E-values obtained were of the same order as those presented in the literature. Finally, we analysed how the study of E distributions among the various radiological departments can help to optimise the procedures, by identifying the most critical examinations or sub-optimal clinical protocols.

Adult↗
PubMed1996

Changes in membrane integrity, cytoskeletal structure, and developmental potential of murine oocytes after vitrification in ethylene glycol.

A systematic approach was taken to assess and optimize a protocol for intracellular vitrification by introducing high concentrations of the cryoprotectant agent (CPA) ethylene glycol (EG) into unfertilized murine oocytes. The effects of EG on membrane integrity, microfilament organization, and developmental potential were evaluated. During exposure to 0.5-2 M EG, oocytes showed maximum shrinkage to 55.5% of the isotonic volume within the first minute and reexpanded to their initial volume within 15 min. Transferral of oocytes to higher concentrations of EG (4-8 M EG) for 1-5 min after 15 min of equilibration at 2 M EG was tolerated well. Microfilament organization appeared normal after this equilibration period. During prolonged exposure (> 5 min) to high concentrations of EG (> 4 M), membrane blebs were noticed on the surface of the cells, and microfilament distribution was disturbed. After treatment with 6 M EG and vitrification with 6 M EG + f2p40.5 M sucrose, there were no significant differences in development to the two-cell and blastocyst stages between CPA-treated, vitrified, and control oocytes. These results indicate that EG is an effective CPA for mouse oocyte vitrification protocols without any observed compromise in morphology and developmental functions.

Actin Cytoskeleton↗
PubMed1998

Corticosteroids in the treatment of rheumatologic diseases.

As understanding of the role of endogenous corticosteroid production by the adrenal glands in rheumatologic diseases has increased, attempts to refine their use in accordance with this knowledge have been reported. Similarly, as understanding of the induction of bone loss by corticosteroids increases, trials of agents designed to antagonize these actions are reported. The lack of large-scale comparative studies means that the optimal method of use of corticosteroids and the optimal antiresorptive protocols have yet to be defined.

Adrenal Cortex Hormones↗
PubMed1999

Effective contrast use in CT angiography and dual-phase hepatic CT performed with a subsecond scanner.

OBJECTIVE: To deduce an optimal injection protocol for CT angiography and fast dual-phase hepatic CT. METHODS: Fifty-two patients underwent fast dual-phase hepatic CT using one of three different injection protocols: A (0.9 g/sec iodine injection rate, 36 g dose); B (1.35 g/sec, 30 g); C (1.6 g/sec, 40 g). Aortic attenuation time curves as well as aorta-to-liver contrast and hepatic enhancement time curves obtained by region of interest measurements along the helical axis were analyzed. RESULTS: Protocol C revealed a significantly higher peak in aortic attenuation and hepatic enhancement than the other protocols. Approximately 50 seconds after the bolus injection, hepatic enhancement declined to a plateau similar to that seen with the other protocols. In terms of the areas under the curves of the aorta-to-liver contrast and hepatic enhancement dynamics, protocol C was significantly superior to the other protocols. CONCLUSIONS: A high iodine injection rate realized by a high iodine concentration in conjunction with fast dual-phase scanning (total scan time < 50 seconds) promises to enhance CT angiography and contrast of liver lesions.

Angiography↗
PubMedDate not supplied

Parameters affecting bolus geometry in CTA: a review.

CT angiography (CTA) is based on acquisition of data during the arterial phase of contrast material passage. CTA needs timing of the contrast bolus, which should be based on accurate knowledge of bolus geometry. Experimental and human studies on bolus geometry and bolus timing in CTA were reviewed. Important parameters of bolus geometry and methods of bolus timing (test bolus and bolus tracking) are described. Recommendations are given for an optimal CTA protocol.

Angiography↗
PubMed1999

Efficacy of intraoperative monitoring for pediatric patients with spinal cord pathology undergoing spinal deformity surgery.

STUDY DESIGN: A retrospective study of 38 pediatric patients with spinal cord pathology who underwent corrective spinal deformity surgery from January 1989 through June 1998. OBJECTIVES: To report reliability and specificity in obtaining intraoperative data in this population. These data were compared with monitoring results obtained in a group of pediatric patients with idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Reports in the literature suggest intraoperative monitoring for patients with spinal cord pathology may be of limited value. No optimal monitoring protocol has been suggested for this population. METHODS: The study group consisted of 38 pediatric patients with a diagnosis of spinal cord pathology who underwent corrective spinal deformity surgery from January 1989 through June 1998. All patients had lower extremity function. Somatosensory and neurogenic motor evoked potentials were used to monitor neurologic status during surgery. These data were compared with data obtained in 429 pediatric patients with idiopathic scoliosis. Study patients were divided into Group I, those who had had spinal cord surgery (n = 20), and Group II, those who had not (n = 18). RESULTS: Somatosensory evoked potentials were obtained in 93.2% and remained consistent with baselines in 87.2% of the study group patients. Neurogenic motor evoked potentials were obtained in 50.8% of the study subjects and remained consistent in 76.6% of those cases. The false-positive rate was 27.1% in the study group, compared with 1.4% in the group with idiopathic scoliosis. The study group had no true-positive or false-negative findings. Group I data differed from Group II data. CONCLUSIONS: Intraoperative monitoring should be used in patients with spinal cord pathology who undergo surgery for spinal deformity. Monitoring should not miss a neurologic deficit but demonstrates greater variability, resulting in more frequent use of an intraoperative wake-up test.

Adolescent↗
PubMed1994

Variations in serum OKT3 concentration based upon age, sex, transplanted organ, treatment regimen, and anti-OKT3 antibody status.

An essential parameter of the efficacy of OKT3 therapy is serial determinations of serum OKT3 levels. We hypothesized that precise monitoring of these levels would optimize treatment protocols. Therefore, enzyme-linked immunosorbent assay (ELISA) technology was utilized to measure OKT3 serum concentrations daily during 263 OKT3 treatment courses in recipients of solid organ grafts. Patient characteristics were: mean age 33 years (0.1-71), 147 male/116 female, 134 kidney/82 liver/47 heart, 122 prophylaxis/141 rejection, and 213 conventional dosing/50 increased dosing. Mean OKT3 levels were higher in women than in men at all time points from day 1 to day 14, reaching the greatest difference between groups on day 7 (849 versus 598 ng/ml, p = 0.004). Patients receiving OKT3 as a component of a prophylactic protocol had higher levels than those receiving the drug for treatment of rejection from day 1 to day 6, with the greatest difference between groups occurring on day 1 (678 versus 333 ng/ml, p < 0.00001). However, from day 7 to day 14 patients receiving OKT3 prophylactically had lower mean OKT3 levels than did those receiving OKT3 for rejection, with the greatest difference between groups occurring on day 11 (555 versus 784 ng/ml, p < 0.05). Liver transplant recipients had significantly higher OKT3 levels than did kidney or heart transplants at all time points. However, more liver patients required increased OKT3 doses to modulate peripheral blood CD3+ cells to < 25/mm3. Kidney recipients had higher levels than did heart recipients. Children < 10 years of age had higher OKT3 levels than did older patients at all time points.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Suppression of B cell immunity to DNP by serotherapy with monoclonal anti-DNP antibodies. Effect of the treatment schedule on the magnitude of specific suppression and its duration.

The effect of prior administration of anti-DNP (N-[2,4-dinitrophenyl]-B-alanylglycylglycine) monoclonal antibodies on the humoral immune response of BALB/c mice was examined. One-time administration of a "cocktail" of two anti-DNP monoclonals resulted in suppression of the IgM anti-DNP response for one week after challenge but not longer. Maximal suppression of anti-DNP IgM plaque-forming cells was achieved by administration of antibody 1-2 weeks before challenge with DNP. Maximal suppression of serum IgM antibody was seen by administration of antibody 2-3 weeks before challenge with antigen. Following one-time administration of suppressive monoclonal antibody, the serum IgG antibody response to DNP was suppressed beginning 2 weeks after immunization and remained so for up to 241 days despite continual booster injections of antigen. Although most effective suppression of the humoral anti-DNP response was seen in animals receiving their single dose of suppressive antibody 2 weeks before first exposure to antigen, suppression of the IgG response was evident at all intervals examined up to 232 days in mice given monoclonal antibody between 0.1 day and 30 days before antigen, but not at earlier times. These findings suggest that regulatory networks, rather than the masking of antigenic determinants by passively administered antibody, play a role in antibody-mediated immunoregulation. They may be of use in designing strategies for optimizing immunosuppression protocols in clinical studies.

Animals↗
PubMed1997

Immunologic and patient selection strategies for successful utilization of less than 15 kg pediatric donor kidneys--long term experiences with 40 transplants.

Renal transplantation using infant donors is associated with significantly less graft survival (GS) and increased morbidity, especially from very young and small donors. We report our results using specific strategies to determine which age and size donor require en bloc renal transplant reconstruction and associated immunologic protocols for optimization of subsequent GS. Forty cadaveric pediatric en bloc renal transplants were performed. Mean donor age was 23.6+/-18.4 months with subgroups: 2-12 months, n=14; 13-24 months, n=19; and 25-60 months, n=7. Mean donor weight was 14.4+/-4.5 kg. All kidneys were placed in primary, nonsensitized (peak PRA = 7.9+/-5.6%) adult (41.6+/-16 years) recipients. Low weight was preferred (62.4+/-12.8 kg). Mean cold ischemia time was 26.9+/-8.6 hr. Immunosuppression consisted of quadruple immunosuppression (QI) with OKT3 induction. All patients had ureteral stents placed intraoperatively. Mean follow-up was 16.9 months. Actuarial GS at 12, 24, and 33 months were 100% (n=13), 85% (n=20), and 71% (n=7), respectively. Total GS was 35/40=88%. All grafts functioned immediately and there were no technical losses. Biopsy proven rejections occurred in 12 (30%) patients, developing at 16-167 days postoperatively (mean = 50.3 days). Mean serum creatinine at one week and 1, 6, 12, and 18 months were 2.1+/-2.0, 1.5+/-0.8, 1.3+/-0.5, 1.1+/-0.4, and 0.9+/-0.4 mg/dl, respectively. Functional isotopic renography, as well as sonographic monitoring reflected rapid initial and continued growth in these kidneys. Mean BP at 12 and 24 months postoperatively were 145/83+/-18/13 and 122/76+/-20/10 mmHg, respectively, with no significant proteinuria noted. Excellent results with minimal complications utilizing very small and young infant donors can be achieved with QI immunosuppression, and selection of low immune reactive and noncomplicated adult recipients. Additionally, maximal renal dosing by minimizing recipient weight may prevent future hyperfiltration damage.

Actuarial Analysis↗