Radiation-induced enhanced proliferation of human squamous cancer cells in vitro: a release from inhibition by epidermal growth factor

Ionizing radiation is believed to stimulate the repopulation of squamous carcinoma cells that survive the early portion of a fractionated course of radiotherapy. To characterize any intrinsic radiation-induced adaptive response and to examine whether epidermal growth factor (EGF) influences this response, A431 and 183A cells were irradiated with repeated daily exposures of 0.5-0.75 Gy and then grown in monolayer culture for 7 days with or without EGF at a 1 ng/ml concentration. Cell numbers were quantified using a microtiter dye-reduction assay. EGF alone caused approximately 70% and 30% growth inhibition of human SC A431 and 183A cells, respectively. Although radiation alone did not affect proliferative rates in these conditions, radiation eliminated the EGF-related growth inhibition in both cell lines. This effect was dose dependent in single radiation exposure experiments. Cell cycle analyses indicated that EGF initially promoted entry into S-phase 3 days after treatment but caused a G1-S block after 7 days. Treatment with radiation recruited cells into S-phase and G2-M, an effect which was sustained 7 days after treatment, overriding the influence of EGF. Radiation-induced modulation of the response of human squamous carcinoma cells to EGF in vitro after single and repeated radiation exposures suggests a proliferation response that may underlie enhanced repopulation of tumor clonogens in vivo.     

Solid-state NMR studies of the prion protein H1 fragment

Conformational changes in the prion protein (PrP) seem to be responsible for prion diseases. We have used conformation-dependent chemical-shift measurements and rotational-resonance distance measurements to analyze the conformation of solid-state peptides lacking long-range order, corresponding to a region of PrP designated H1. This region is predicted to undergo a transformation of secondary structure in generating the infectious form of the protein. Solid-state NMR spectra of specifically 13C-enriched samples of H1, residues 109-122 (MKHMAGAAAAGAVV) of Syrian hamster PrP, have been acquired under cross-polarization and magic-angle spinning conditions. Samples lyophilized from 50% acetonitrile/50% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117. Complete conversion to the helical conformation was not observed and conversion from alpha-helix back to beta-sheet, as inferred from the solid-state NMR spectra, occurred when samples were exposed to water. Rotational-resonance experiments were performed on seven doubly 13C-labeled H1 samples dried from water. Measured distances suggest that the peptide is in an extended, possibly beta-strand, conformation. These results are consistent with the experimental observation that PrP can exist in different conformational states and with structural predictions based on biological data and theoretical modeling that suggest that H1 may play a key role in the conformational transition involved in the development of prion diseases.     

BiP maintains the permeability barrier of the ER membrane by sealing the lumenal end of the translocon pore before and early in translocation

Secretory proteins are cotranslationally translocated across the mammalian ER membrane through an aqueous pore in the translocon while the permeability barrier is maintained by a tight ribosome-membrane junction. The lumenal end of the pore is also blocked early in translocation. Extraction of soluble lumenal proteins from microsomes and reconstitution with purified proteins demonstrate, by fluorescence collisional quenching, that BiP seals the lumenal end of this pore. BiP also seals translocons that are assembled but are not engaged in translocation. These ribosome-free translocons have smaller pores (9-15 A diameter versus 40-60 A in functioning translocons) and are generated when ribosomes dissociate from functioning translocons with large pores. BiP therefore maintains the permeability barrier by sealing both nontranslocating and newly targeted translocons.     

Comparison between enzyme-linked immunosorbent assay and cytotoxic cross-match procedures for detecting IgG anti-donor antibodies

BACKGROUND: Disadvantages inherent to complement-dependent cytotoxicity cross-match (CDC XM) methods are the requirements for complement and viable target cells, detection of antibodies (Abs) against non-HLA antigens, and subjective scoring. Cross-Stat (SangStat Medical Corp., Menlo Park, CA), a recently developed enzyme-linked immunosorbent assay XM procedure for the detection of IgG anti-donor HLA Abs, is theoretically devoid of these flaws. METHODS: We compared results of Cross-Stat and our standard anti-human globulin (AHG)-enhanced CDC XM procedure on 524 sera from 230 transplant candidates, which were evaluated against 51 cadaveric donors. RESULTS: There was a significant correlation between AHG-CDC IgG XM and Cross-Stat results (P<0.001). For false negative sera, repeat AHG-CDC IgG XMs were still positive after platelet absorption, indicating that the Abs present were either non-HLA Abs or anti-HLA class II. Flow cytometry testing of false positive sera usually (42/62) substantiated Cross-Stat results, indicating that the discrepancy with AHG-CDC IgG XM is caused by greater sensitivity of Cross-Stat. Relative to the AHG-CDC XM, the sensitivity of Cross-Stat was 100%, the specificity was 93%, the positive predictive value was 73%, and the negative predictive value was 100%. A technical shortcoming of the Cross-Stat assay is that the frequency of indeterminate samples in the assays was 15%. Among 49 Cross-Stat negative vs. 13 Cross-Stat positive primary cadaveric renal allograft recipients (all AHG-CDC IgG-XM negative), there was no statistical difference in overall graft survival. CONCLUSION: Given the important theoretical advantages of enzyme-linked immunosorbent assay-based XM methods over the CDC XM, however, further testing of the clinical relevance of the Cross-Stat is warranted.     

Synergistic interaction of 3 M KCl-extracted donor antigens (e-HAg) with cyclosporine or cyclosporine/sirolimus for prolongation of rat heart allograft survival

This article examines the attaching and detaching experience of a mother encountering the perinatal death of a twin. Her experience is related to the relevant theoretical and research literature pertaining to prebirth and postbirth maternal-infant attachment and detachment (grieving). Literature for both single infants and twins is considered. The experience of this mother suggests that elements of postbirth attachment may have been accelerated into the prebirth period. In addition, her postbirth attaching and detaching experience suggests that an attachment and detachment to the twins as a unit preceded detachment from the twin who died. The health care provider's role in promoting maternal well-being, and indirectly the well-being of the surviving infant, is described.     

Bacterial and Ureaplasma colonization of the airway: radiologic findings in infants with bronchopulmonary dysplasia

OBJECTIVE: We designed this retrospective study to compare radiologic findings in premature infants with bronchopulmonary dysplasia (BPD) in whom gram-positive cocci (GPC), gram-negative bacilli (GNB), or Ureaplasma urealyticum were colonized. Another objective was to correlate the radiologic findings of these patients with the clinical severity of BPD. STUDY DESIGN: We correlated serial tracheal aspirates with radiographic findings from 183 infants whose birth weight was < or = 1250 gm. BPD severity was assessed by oxygen dependency at 36 weeks of postconceptional age (36 w PCA) and at the time of discharge. Two radiologists independently scored films taken at birth and 1, 7, 14, 21, 28, and 35 days of life. RESULTS: Of the study population, 55% were male and 35% were black; 80% received surfactant and 69% received dexamethasone; 91% survived. GPC isolates from throat cultures were mainly Staphylococcus [corrected] epidermidis and Streptococcus haemolyticus. A superimposed GNB colonization was present in 37% of these infants. Most common isolates were Klebsiella pneumoniae, Enterobacter cloacae, and Escherichia coli. Sepsis caused by GPC developed in 16% of all patients; 7% had sepsis caused by GNB. Infants infected with GNB remained receiving oxygen at 36 w PCA and at the time of discharge twice as often as those noninfected. RADIOLOGIC FINDINGS: Hyperinflation, interstitial changes, and generalized or localized emphysema were prominent features throughout. Mean radiologic scores increased over time in a pattern similar among GPC, GNB, and U. urealyticum infected and noninfected infants. High radiologic scores were not predictive at any time of infants who needed supplemental oxygen at 28 days and at 36 w PCA. Infants infected with U. urealyticum were neither clinically nor radiologically different than noncolonized neonates. CONCLUSION: GPC, GNB, and U. urealyticum airway colonization is not associated with particular radiographic changes at any time. GNB-infected infants had the most severe BPD course, and yet they were radiologically indistinguishable from the other patients. U. urealyticum colonization does not result in more clinically severe BPD or demonstrate a unique radiologic course.     

Structural features of thyroid hormone response elements that increase susceptibility to inhibition by an RTH mutant thyroid hormone receptor

The chicken lysozyme silencer F2 (F2) thyroid hormone response element (TRE) contains an unusual everted palindromic arrangement, has a high affinity for thyroid hormone receptor (TR) homodimers, and is especially sensitive to dominant negative inhibition by, the T3 resistance (RTH) mutant TR beta P453H. We used various TREs and TR mutations to determine the mechanisms for this sensitivity. Changing the F2 orientation from an everted palindrome to a direct repeat with a 4-bp gap (DR+4) (F2-DR) decreased the sensitivity to inhibition at high T3 concentrations, while a loss of this sensitivity occurred with a palindromic arrangement of these same half-sites. F2 contains the dinucleotide TG 5' to each consensus half-site conforming to the optimal TR-binding octamer, YRRGGTCA. A T to A change in position 1 of both F2 half-sites markedly reduced T3-induction, yet only slightly reduced TR homodimer or TR-retinoid X receptor (RXR) heterodimer binding. The TR beta ninth heptad mutation, L428R, prevents TR heterodimerization with RXR and eliminates the inhibitory effect of the P453H mutant TR on the F2-DR, but not the F2 element. Structural features of a TRE that favor strong TR binding of both TR homodimers and TR-RXR heterodimers containing the mutant TR, such as the everted palindromic conformation or the optimal TR-binding consensus octamer, enhance the sensitivity of a TRE to inhibition by the mutant TR. Thus, both half-site orientation and sequence contribute to the sensitivity of a given TRE to dominant negative inhibition by a mutant TR.     

Novel monoclonal antibodies to putative selectin carbohydrate ligands that inhibit selectin binding to myeloid cells

Four newly developed monoclonal antibodies (MAbs) are characterized using flowcytometry, enzyme-linked immunoadsorbent assay (ELISA), immunoprecipitation and Western blots, carbohydrate epitope mapping, glycosidase cleavage, and competition binding assays. Their effects on selectin binding to myeloid cells was tested. These MAbs react only with myeloid cells. MAbs CI-1, BU60, and HIM95 recognize epitopes expressed by CD11/CD18 (beta2) integrins, while HI247 and CSLEX1 do not. The epitopes require Lewis x [Galbeta1-4 (Fucalpha1-3)GlcNAc] based on reactivity with oligosaccharide-polyacrylamide-biotin or oligosaccharide-BSA conjugates. MAb HI247 recognizes a related structure, sialyl-Lewis x, NeuAcalpha2-3GaLbeta1-4(Fucalpha1-3)GlcNAc. The three MAbs against Lewis x show some minor differences in their reactivity such as recognizing their antigens on CD11/CD18 integrins after endo-beta-galactosidase treatment and recognizing free Lewis x. The hydroxyl group on C-3 of the terminal galactose is important for recognition by MAb CI-1, BU60, and HIM95 as its substitution with sulfo group of sialic acid abolishes the binding of these MAbs. The C-3 sialic acid is crucial for the binding of MAb HI247. Its replacement by sulphate or its cleavage by sialidase eliminates recognition by this MAb. MAbs HI247 and CSLEX-1 did not react in ELISA with immobilized CD11/CD18, suggesting that the majority of sialyl Lewis x on CD11/CD18 molecules may have sialic acid 6-linked rather than 3-linked to galactose. Unexpectedly, MAb BU60 inhibited binding of P-selectin mu chain chimera to HL-60 or U937 cells, while CI-1, HIM95 and three other defined anti-Lewis x MAbs (6C7, M6-1 and LeuM1) did not. MAb HI247 inhibited binding of both E- and P-selectin chimeras to these cell lines more effectively than several characterized MAbs (CSLEX-1, FH6, HECA-452) to sialyl Lewis x and related oligosaccharides. Certain combinations of these anticarbohydrate MAbs had additive inhibitory effects on selectin binding, suggesting a potential application of these new MAbs in cell adhesion/migration and tumor metastasis studies.