Left-right difference in fetal liver oxygenation during hypoxia estimated by BOLD MRI in a fetal sheep model

OBJECTIVE

The purpose of this study was to measure differences in oxygenation between the left and right sides of the fetal liver during varying oxygenation levels.

METHODS

Eight ewes carrying singleton fetuses at gestational age 125 days (term, 145 days) were included in the study. Under anesthesia the ewes were ventilated with gas containing different levels of oxygen, thereby subjecting the fetuses to hyperoxia (mean ± SD maternal arterial partial pressure of oxygen (pO2), 23.2 ± 8.2 kPa) and hypoxia (mean maternal arterial pO2, 7.1 ± 0.5 kPa). Changes in oxygenation within the fetal liver were assessed by blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI).

RESULTS

During hyperoxia there was no difference between the BOLD signal in the left and right sides of the fetal liver; mean change in BOLD (ΔBOLD)(hyperox), -0.9 ± 3.7%. During hypoxia, however, the decrease in the BOLD signal was more pronounced in the right side as compared with the left side, thereby creating a significant increase in the left-right difference in the BOLD signal; mean ΔBOLD(hypox), 5.2 ± 2.2% (P = 0.002, paired t-test). The left-right difference was directly proportional to the degree of hypoxia (R2 = 0.86, P = 0.007).

CONCLUSIONS

To our knowledge, this is the first study demonstrating differences in oxygenation between the left and right sides of the fetal liver during hypoxia, a difference that can be explained by increased ductus venosus shunting. Thus, the BOLD MRI technique is a promising non-invasive tool that might be useful for the future monitoring of the human fetus.

De novo identification of cell-type specific antibody-antigen pairs by phage display subtraction

The aim of this study was to identify novel antibodies directed against cytosolic keratinocyte-specific antigens from a phage display antibody repertoire by using phage display subtraction. Phage display is a method of displaying foreign molecules on the surface of filamentous bacteriophage particles. It allows the interaction between two cognate molecules to be analysed through affinity selections. Recently, large repertoires of phage displayed human antibody fragments have been constructed. From such repertoires, antibodies can be obtained in vitro without the need for immunization or the hybridoma technology. A novel subtractive strategy for selecting antibodies from phage libraries was applied. Phage antibodies were selected against immobilized crude lysates of cultured human keratinocytes, the target antigens being unknown beforehand. A competing cell lysate was used to reduce retrieval of phage antibodies with specificities to commonly non-differentially expressed antigens. A monoclonal single chain fragment variable (scFv) with specificity for crude lysates of cultured human keratinocytes was identified as demonstrated by ELISA assays and immunoblotting analysis. The cognate keratinocyte antigen was shown to be keratin 14 (K14) by using immunoblotting based on 2D PAGE and a corresponding 2D PAGE protein database. In accordance with the expected tissue localization of K14, the identified scFv stained the basal layer of human epidermis by indirect immunofluorescence analysis. Starting with crude cell lysates, phage display subtraction in combination with 2D PAGE and 2D PAGE protein databases can be used to identify antibody-antigen pairs that characterize a specific cell type.

Characterization and radiosensitivity of fibroblasts derived from squamous cell carcinomas of the head and neck, and the surrounding oral mucosa

Recently, extensive stromal fibroblast contamination has been reported in the modified Courtenay-Mills soft agar clonogenic assay for cellular in vitro radiosensitivity in tumour biopsies. The aim of the present study was to evaluate the hypothesis that an immunocytochemical analysis added to the modified Courtenay-Mills soft agar clonogenic assay provides a measure of both fibroblast and tumour cell radiosensitivity. Therefore, fibroblasts derived from squamous cell carcinomas of the head and neck, and from the surrounding oral mucosa were compared for immunocytochemistry, DNA ploidy, plating efficiency and surviving fraction of cells after a radiation dose of 2 Gy. The results of our study suggest that the stromal fibroblasts derived from tumour biopsies are representative of normal fibroblasts with respect to the characteristics examined using mucosal fibroblasts as normal controls.

In vitro radiosensitivity of tumour cells and fibroblasts derived from head and neck carcinomas: mutual relationship and correlation with clinical data

The aim was to characterize the variation in the cellular in vitro radiosensitivities in squamous cell carcinomas of the head and neck, and to test for a possible correlation between different measures of radiosensitivity and the clinical and histopathological data. Cellular in vitro radiosensitivities were assessed in tumour biopsies from 71 patients using the modified Courtenay-Mills soft agar clonogenic assay combined with an immunocytochemical analysis. Radiosensitivity was quantified as the surviving fraction after a radiation dose of 2 Gy irrespective of cell type (overall SF2), or based on identification of cell type (tumour cell SF2, fibroblast SF2). Sixty-three biopsies were from primary tumours, and eight were from recurrences. Overall plating efficiency ranged from 0.005 to 1.60% with a median of 0.052%. The majority of the colonies obtained from the biopsies were fibroblast marker-positive; the proportion of tumour marker-positive colonies ranged from 1 to 88% with a median of 15%. The median overall SF2 was 0.47 (range 0.24-0.96), the median tumour cell SF2 was 0.50 (range 0.11-1.0) and the median fibroblast SF2 was 0.49 (range 0.24-1.0). Comparing data from independent experiments, the overall SF2 was significantly correlated with the SF2 of fibroblasts (2P = 0.006) but not with the tumour cell SF2. The tumour cell and fibroblast radiosensitivities measured in the same individuals were not correlated (r= 0.06, 95% CI [-0.19, 0.30]):This finding seems to preclude a strong correlation between the radiosensitivity of tumour cells and fibroblasts. Concerning the clinical characteristics, neither of the measures of tumour radiosensitivity was correlated with T- and N-category, stage, tumour size, sex and age. However, the tumour cell radiosensitivity decreased with increasing grade of histopathological differentiation (2P = 0.012). The same tendency was found in two independent analyses of the same patient material. This correlation was not significant in case of the overall SF2 or the fibroblast SF2.

Relationship between tumour cell in vitro radiosensitivity and clinical outcome after curative radiotherapy for squamous cell carcinoma of the head and neck

BACKGROUND AND PURPOSE

Clinically, it is recognized that individual tumours respond differently to radiation treatment. Variation in tumour cell radiosensitivity is believed to be an important underlying factor. In the current study, cellular in vitro radiosensitivity was estimated as the fraction of surviving cells after a radiation dose of 2 Gy (SF2) and related to clinical outcome after curative radiotherapy.

PATIENTS AND METHODS

Thirty-eight patients with squamous cell carcinoma of the head and neck were treated with curative radiotherapy alone. Pre-treatment biopsies were disaggregated to form a single-cell suspension and cells were cultured in the modified Courtenay-Mills soft agar clonogenic assay. Directly from this assay and with no respect to cell type, overall SF2 was assessed. By collecting the obtained colonies on a preparation slide using a colony-filter technique, and with immunocytochemical staining, it was possible to measure the surviving fraction of tumour cells selectively as tumour cell SF2.

RESULTS

Experimentally, a broad inter-tumour variation was found for both tumour cell SF2 and overall SF2. Using weighted linear regression, it was demonstrated that tumour cell SF2 and overall SF2 were two independent measures of tumour radiosensitivity. In general, the measures of tumour radiosensitivity were independent of patient sex and age, T- and N-category, disease stage, tumour size and plating efficiency. Among the 38 patients grouped in loco-regional failures and patients with loco-regional control, respectively, sex, age, total radiation dose, overall treatment time and tumour grade were equally distributed. Advanced stage, lymph node involvement and tumour size correlated statistically significantly with poor loco-regional control. Neither tumour cell SF2, overall SF2, nor plating efficiency predicted loco-regional tumour control probability. In a multivariate analysis with respect to the risk of loco-regional tumour failure, only disease stage yielded independent prognostic significance. This significance suggests that this patient sample was representative for the patient population with head and neck cancer.

CONCLUSION

In 38 patients with squamous cell carcinoma of the head and neck, the estimated tumour radiosensitivities were not statistically related to clinical outcome after curative radiotherapy alone.

Immunohistochemical BCL-2 and Ki-67 expression predict survival in prostate cancer patients followed expectantly

The prognostic value of BCL-2 expression, solely and combined with Ki-67 expression, was determined in prostate cancer patients followed expectantly. Furthermore, associations with well established prognostic markers were tested. Formalin fixed, paraffin-embedded tumour tissue obtained at diagnosis was immunohistochemically investigated in 221 patients with a 15 y median follow-up time. BCL-2 protein was expressed in 114 (52%) tumours and was significantly associated with tumour stage (P=0.01). The prognostic value of BCL-2 expression was significant, using both disease-specific (P=0.0015) and overall survival (P=0.005) as endpoint. Patients with a combined BCL-2 negative/Ki-67 'low' tumour had the most favourable prognosis. This combined BCL-2/Ki-67 variable was of independently prognostic value in both the entire population (P=0.0001) and in the clinically localized subpopulation (P=0.035).

Glycerol diversifies phage repertoire selections and lowers non-specific phage absorption

Using a semi-synthetic phage displayed antibody repertoire, isoform-specific and cross-reactive phage-antibodies to eukaryotic elongation factor 1A (eEF1A) have been selected. Enrichment of specific antibodies was found to depend on the presence of glycerol. Further selections against lactate dehydrogenase (LDH) revealed that the dominance of a phage-antibody clone to LDH was inhibited by glycerol, a notable feature for selection strategies where a broad variety of binding clones is desired. The impact of glycerol in distinct steps of the selection protocol was examined and glycerol found to affect certain antibody-antigen interactions. Furthermore, the nonspecific phage binding was lowered by three orders of magnitude at a 20% (v/v) glycerol concentration.

Radiosensitivity of normal fibroblasts from breast cancer patients assessed by the micronucleus and colony assays

PURPOSE

To investigate whether radiation-induced micronucleus formation as expressed by the cytochalasin-blocked Mn-assay correlates with cellular radiosensitivity measured by a colony assay in primary fibroblast cultures from cancer patients.

MATERIALS AND METHODS

Studies were made on skin fibroblasts from 36 breast cancer patients. The micronucleus assay was performed using treatment with cytochalasin-B to create binucleate cells. Response was scored in terms of the percentage of binucleate cells with micronuclei, also as the number of micronuclei per binucleate cell. The data were related to previously published results of cell survival measurements on these cell lines.

RESULTS

Neither endpoint for micronucleus formation showed a correlation with radiosensitivity by the colony assay. The fraction of fibroblasts that reach mitosis without micronuclei also failed to correlate with cell survival.

CONCLUSIONS

Among these primary fibroblast cell lines radiation-induced micronucleus formation was not associated with radiosensitivity as measured by a colony assay.

Retrieval of phage displayed scFv fragments using direct bacterial elution

Phage displayed repertoires of antibody fragments, either single chain Fv (scFv) or Fab, have become a real alternative to traditional hybridoma technology in the generation of monoclonal antibodies. The steps usually taken in the selection from such repertoires were analysed and the necessity of chemical elution of bound phage-Abs and precipitation of amplified phage particles questioned. By using a semi-synthetic scFv library as a source, phage antibodies recognising a panel of seven antigens were isolated utilising direct bacterial elution of bound phage. Selections against two antigens were subsequently performed with bacterial or chemical elution in parallel and the resulting pools of phage antibodies compared. It is demonstrated that direct bacterial elution can be used when selecting from phage displayed antibody repertoires but that the enrichment of high affinity binders might be jeopardised. In addition, a simplified and more rapid scheme for amplification and use of phage displayed repertoires is described.

A model phage display subtraction method with potential for analysis of differential gene expression

In order to establish a subtractive procedure that makes it possible to enrich selectively phage displayed antibodies directed against proteins constituting a difference between two populations of cells, a competitive selection strategy utilising two solid phases was developed and tested. Antibodies recognising a defined difference between two otherwise identical protein mixtures were isolated and their specificity confirmed. To test further the efficacy of selection inhibition during the competitive selections, selections towards a total cell extract were performed with and without competition from the same extract. An analysis of the resulting phage antibodies confirmed the subtractive nature of the system described.

Increase by lysophosphatidylcholines of smooth muscle Ca2+ sensitivity in alpha-toxin-permeabilized small mesenteric artery from the rat

1. Pharmacological characterization of different lysophosphatidylcholines was performed based on their effect on the Ca2+ sensitivity of contraction in alpha-toxin-permeabilized rat mesenteric arteries. Furthermore, the effect of noradrenaline on [3H]-myristate-labelled lysophosphatidylcholine levels was assessed, to investigate whether lysophosphatidylcholines could be second messengers. 2. Palmitoyl or myristoyl L-alpha-lysophosphatidylcholine increased the sensitivity to Ca2+, whereas lysophosphatidylcholines containing other fatty acids had less or no effect. 3. L-alpha-phosphatidylcholine, L-alpha-glycerophosphorylcholine, palmitic acid, myristic acid and choline, potential metabolites of lysophosphatidylcholines, did not affect contractions. 4. Noradrenaline (GTP was required) and GTP gamma S increased the sensitivity to Ca2+, and GDP-beta-S inhibited the effect of noradrenaline. Lysophosphatidylcholines, however, had no requirement for GTP and caused sensitization in the presence of GDP-beta-S. 5. Calphostin C, a relatively specific protein kinase C inhibitor, did not affect contraction induced by Ca2+, but abolished the sensitizing effect of lysophosphatidylcholine. 6. Noradrenaline caused no measurable changes in the levels of [3H]-myristate-labelled phosphatidylcholine and lysophosphatidylcholine at 30 s and 5 min stimulation. 7. These results suggest that lysophosphatidylcholines can increase Ca2+ sensitivity through a G-protein-independent, but a protein kinase C-dependent mechanism. However, the role for lysophosphatidylcholines as messengers causing Ca2+ sensitization during stimulation with noradrenaline remains uncertain because no increase in [3H]-myristate labelled lysophosphatidylcholine could be measured during noradrenaline stimulation.

Selective assessment of in vitro radiosensitivity of tumour cells and fibroblasts from single tumour biopsies using immunocytochemical identification of colonies in the soft agar clonogenic assay

The assumed selective growth of tumour cells has formed the basis for the use of the soft agar clonogenic assay to test in vitro radio- and chemosensitivity of tumours. However, recent studies have demonstrated that fibroblasts proliferate in soft agar in addition to tumour cells. The present study was initiated to quantify the contaminating growth of non-malignant cells in the modified form of the Courtenay-Mills soft agar assay, in order to establish a reliable assay for estimating tumour cell radiosensitivity in squamous cell carcinomas of the head and neck. DNA flow cytometry analysis confirmed that 'tumour fibroblasts' (fibroblasts obtained from tumour biopsies) grow in soft agar. In contrast, white blood cells did not form colonies. Different media were tested with soft agar, but a selective medium for tumour cells was not found. Therefore, a colony filter-technique combined with an immunocytochemical analysis was developed to quantify the number of tumour cell and fibroblast colonies. In 12 tumour biopsies, 2-33% of the colonies were Cytokeratin AE1-3 positive, whereas 83-100% of the colonies were 5B5 fibroblast antibody positive. The parameter normally reported, the overall SF2 (surviving cell fraction at 2 Gy) based on colonies in agar, was found to be statistically significantly correlated to the fibroblast SF2, but not to the tumour cell SF2. The overall SF2 was significantly different from the tumour cell SF2 in half of the tumours. Furthermore, the tumour cell SF2 was not correlated to fibroblast SF2. In consequence of our findings, correcting for fibroblast contamination is a necessity, when studying in vitro sensitivity of tumour cells. Combining the soft agar clonogenic assay with the new colony filter-technique and the immunocytochemical analysis appear to be useful for making this routine correction and for measuring the in vitro radiosensitivity of both tumour cells and fibroblasts from single tumour biopsies, which is of interest in future clinical studies on predictive assays.