A novel technique to optimise the length of a linear accelerator treatment room maze without compromising radiation protection

Simulations with the FLUktuierende KAskade (FLUKA) Monte Carlo code were used to establish the possibility of introducing lead to cover the existing concrete walls of a linear accelerator treatment room maze, in order to reduce the dose of the scattered photons at the maze entrance. In the present work, a pilot study performed at Singleton Hospital in Swansea was used to pioneer the use of lead sheets of various thicknesses to absorb scattered low energy photons in the maze. The dose reduction was considered to be due to the strong effect of the photoelectric interaction in lead resulting in attenuation of the back-scattered photons. Calculations using FLUKA with mono-energetic photons were used to represent the main components of the x-ray spectrum up to 10 MV. Mono-energetic photons were used to enable the study of the behaviour of each energy component from the associated interaction processes. The results showed that adding lead of 1 to 4 mm thickness to the walls and floor of the maze reduced the dose at the maze entrance by up to 80%. Subsequent scatter dose measurements performed at the maze entrance of an existing treatment room with lead sheet of 1.3 mm thickness added to the maze walls and floor supported the results from the simulations. The dose reduction at the maze entrance with the lead in place was up to 50%. The variation between simulation and measurement was attributed to the fact that insufficient lead was available to completely cover the maze walls and floor. This novel proposal of partly, or entirely, covering the maze walls with lead a few millimetres in thickness has implications for the design of linear accelerator treatment rooms since it has the potential to provide savings, in terms of space and costs, when an existing maze requires upgrading in an environment where space is limited and the maze length cannot be extended sufficiently to reduce the dose.

Not re-inventing the wheel: the adaptive implementation of the meeting centres support programme in four European countries

OBJECTIVES

The implementation of new health services is a complex process. This study investigated the first phase of the adaptive implementation of the Dutch Meeting Centres Support Programme (MCSP) for people with dementia and their carers in three European countries (Italy, Poland, the UK) within the JPND-MEETINGDEM project. Anticipated and experienced factors influencing the implementation, and the efficacy of the implementation process, were investigated. Findings were compared with previous research in the Netherlands.

METHOD

A qualitative multiple case study design was applied. Checklist on anticipated facilitators and barriers to the implementation and semi-structured interview were completed by stakeholders, respectively at the end and at the beginning of the preparation phase.

RESULTS

Overall, few differences between countries were founded. Facilitators for all countries were: added value of MCSP matching needs of the target group, evidence of effectiveness of MCSP, enthusiasm of stakeholders. General barriers were: competition with existing care and welfare organizations and scarce funding. Some countries experienced improved collaborations, others had difficulties finding a socially integrated location for MCSP. The step-by-step implementation method proved efficacious.

CONCLUSION

These insights into factors influencing the implementation of MCSP in three European countries and the efficacy of the step-by-step preparation may aid further implementation of MCSP in Europe.

Characterizing the sphingomyelinase pathway triggered by PRIMA-1 derivatives in lung cancer cells with differing p53 status

BACKGROUND/AIM

Derivatives of PRIMA-1 compound, 8a and 8b have been shown to increase cytotoxicity in lung cancer cells through sphingomyelinase pathways in IR and 8a or 8b co-treated lung cancer cells. The goal of the present study was to further elaborate the molecular mechanism of 8a- or 8b-treated lung cancer cells in order to understand their potential as anti-cancer drugs.

MATERIALS AND METHODS

Biochemical assays, western blot, flow cytometry and gene array analyses were employed to distinguish these mechanisms.

RESULTS

Herein we demonstrated that 8a and 8b cause apoptosis with S-phase arrest in lung cancer cells by activating neutral sphingomyelinase with ceramide production. 8a induces expression of TNF family genes while 8b induces p53-mediated apoptosis genes. Protein analysis shows an increased expression in caspase 8, bcl-2, bax, caspase 9 and cytochrome c.

CONCLUSION

PRIMA-1 derivatives provoke cytotoxicity in lung cancer cells mainly through the neutral sphingomyelinase-dependent apoptosis pathway.

The impact of ingested potato type II inhibitors on the production of the major serine proteases in the gut of Helicoverpa armigera

The flowers of the ornamental tobacco produce high levels of a series of 6 kDa serine protease inhibitors (NaPIs) that are effective inhibitors of trypsins and chymotrypsins from lepidopteran species. These inhibitors have a negative impact on the growth and development of lepidopteran larvae and have a potential role in plant protection. Here we investigate the effect of NaPIs on the activity and levels of serine proteases in the gut of Helicoverpa armigera larvae and explore the adaptive mechanisms larvae employ to overcome the negative effects of NaPIs in the diet. Polyclonal antibodies were raised against a Helicoverpa punctigera trypsin that is a target for NaPIs and two H. punctigera chymotrypsins; one that is resistant and one that is susceptible to inhibition by NaPIs. The antibodies were used to optimize procedures for extraction of proteases for immunoblot analysis and to assess the effect of NaPIs on the relative levels of the proteases in the gut and frass. We discovered that consumption of NaPIs did not lead to over-production of trypsins or chymotrypsins but did result in excessive loss of proteases to the frass.

Mach-Zehnder recording systems for pulsed power diagnostics

Fiber-optic transmission and recording systems, based on Mach-Zehnder modulators, have been developed and installed at the National Ignition Facility (NIF), and are being developed for other pulsed-power facilities such as the Z accelerator at Sandia, with different requirements. We present the design and performance characteristics for the mature analog links, based on the system developed for the Gamma Reaction History diagnostic at the OMEGA laser and at NIF. For a single detector channel, two Mach-Zehnders are used to provide high dynamic range at the full recording bandwidth with no gaps in the coverage. We present laboratory and shot data to estimate upper limits on the radiation effects as they impact recorded data quality. Finally, we will assess the technology readiness level for mature and developing implementations of Mach-Zehnder links for these environments.

Mutations in a novel serine protease PRSS56 in families with nanophthalmos

PURPOSE

Nanophthalmos is a rare genetic ocular disorder in which the eyes of affected individuals are abnormally small. Patients suffer from severe hyperopia as a result of their markedly reduced axial lengths, but otherwise are capable of seeing well unlike other more general forms of microphthalmia. To date one gene for nanophthalmos has been identified, encoding the membrane-type frizzled related protein MFRP. Identification of additional genes for nanophthalmos will improve our understanding of normal developmental regulation of eye growth.

METHODS

We ascertained a cohort of families from eastern Canada and Mexico with familial nanophthalmos. We performed high density microsatellite and high density single nucleotide polymorphism (SNP) genotyping to identify potential chromosomal regions of linkage. We sequenced coding regions of genes in the linked interval by traditional PCR-based Sanger capillary electrophoresis methods. We cloned and sequenced a novel cDNA from a putative causal gene to verify gene structure.

RESULTS

We identified a linked locus on chromosome 2q37 with a peak logarithm (base 10) of odds (LOD) score of 4.7. Sequencing of coding exons of all genes in the region identified multiple segregating variants in one gene, recently annotated as serine protease gene (PRSS56), coding for a predicted trypsin serine protease-like protein. One of our families was homozygous for a predicted pathogenic missense mutation, one family was compound heterozygous for two predicted pathogenic missense mutations, and one family was compound heterozygous for a predicted pathogenic missense mutation plus a frameshift leading to obligatory truncation of the predicted protein. The PRSS56 gene structure in public databases is based on a virtual transcript assembled from overlapping incomplete cDNA clones; we have now validated the structure of a full-length transcript from embryonic mouse brain RNA.

CONCLUSIONS

PRSS56 is a good candidate for the causal gene for nanophthalmos in our families.

GEANT4 simulations of Cherenkov reaction history diagnostics

This paper compares the results from a GEANT4 simulation of the gas Cherenkov detector 1 (GCD1) with previous simulations and experimental data from the Omega laser facility. The GCD1 collects gammas emitted during a deuterium-tritium capsule implosion and converts them, through several processes, to Cherenkov light. Photon signals are recorded using subnanosecond photomultiplier tubes, producing burn reaction histories. The GEANT4 GCD1 simulation is first benchmarked against ACCEPT, an integrated tiger series code, with good agreement. The simulation is subsequently compared with data from the Omega laser facility, where experiments have been performed to measure the effects of Hohlraum materials on reaction history signals, in preparation for experiments at the National Ignition Facility.

Development and characterization of sub-100 ps photomultiplier tubes

We describe the evaluation of a microchannel plate (MCP) photomultiplier tube (PMT), incorporating a 3 μm pore MCP and constant voltage anode and cathode gaps. The use of the small pore size results in PMTs with response functions of the order of 85 ps full-width-half-maximum, while the constant electric field across the anode and cathode gaps produces a uniform response function over the entire operating range of the device. The PMT was characterized on a number of facilities and employed on gas Cherenkov detectors fielded on various deuterium tritium fuel (DT) implosions on the Omega Laser Facility at the University of Rochester. The Cherenkov detectors are part of diagnostic development to measure Gamma ray reaction history for DT implosions on the National Ignition Facility.

Mutation in the gene encoding ubiquitin ligase LRSAM1 in patients with Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease (CMT) represents a family of related sensorimotor neuropathies. We studied a large family from a rural eastern Canadian community, with multiple individuals suffering from a condition clinically most similar to autosomal recessive axonal CMT, or AR-CMT2. Homozygosity mapping with high-density SNP genotyping of six affected individuals from the family excluded 23 known genes for various subtypes of CMT and instead identified a single homozygous region on chromosome 9, at 122,423,730–129,841,977 Mbp, shared identical by state in all six affected individuals. A homozygous pathogenic variant was identified in the gene encoding leucine rich repeat and sterile alpha motif 1 (LRSAM1) by direct DNA sequencing of genes within the region in affected DNA samples. The single nucleotide change mutates an intronic consensus acceptor splicing site from AG to AA. Direct analysis of RNA from patient blood demonstrated aberrant splicing of the affected exon, causing an obligatory frameshift and premature truncation of the protein. Western blotting of immortalized cells from a homozygous patient showed complete absence of detectable protein, consistent with the splice site defect. LRSAM1 plays a role in membrane vesicle fusion during viral maturation and for proper adhesion of neuronal cells in culture. Other ubiquitin ligases play documented roles in neurodegenerative diseases. LRSAM1 is a strong candidate for the causal gene for the genetic disorder in our kindred.

Sensory motor neuropathies are diseases of the peripheral nervous system, involving primarily the nerves which control our muscles. These can result from either genetic or non-genetic causes, with genetic causes usually referred to as Charcot-Marie-Tooth (CMT) disease after the three clinicians who first described the key diagnostic markers. CMT patients lose muscle function, mainly in their arms and legs, with increasing severity during their lives. There are almost two dozen known genes that can mutate to cause CMT, and these fall into a wide variety of biochemical cellular pathways. We identified a group of patients with CMT from a small rural community, with good reason to suspect a genetic basis for their disease. Using high-throughput mapping and DNA sequencing technologies developed as part of the Human Genome Project, we were able to find the likely mutated gene, which was not any of the previously known CMT genes. Based on its sequence, the gene, called LRSAM1, probably plays a role in the correct metabolism of other proteins in the cell. Among the known CMT genes, some are also involved in protein metabolism, suggesting that this is a generally important pathway in the neurons that control muscle activity.

A common intracellular allosteric binding site for antagonists of the CXCR2 receptor

BACKGROUND AND PURPOSE

We have previously shown that SB265610 (1-(2-bromo-phenyl)-3-(7-cyano-3H-benzotriazol-4-yl)-urea) behaves as an allosteric, inverse agonist at the C-X-C chemokine (CXCR)2 receptor. The aim of this study was to determine whether SB265610, in addition to two other known antagonists, bind to either of the two putative, topographically distinct, allosteric binding sites previously reported in the Literature.

EXPERIMENTAL APPROACH

Ten single point mutations were introduced into the CXCR2 receptor using site-directed mutagenesis. Three CXCR2 antagonists were investigated, SB265610, Pteridone-1 (2-(2,3 difluoro-benzylsulphanyl)-4-((R)-2-hydroxy-1-methyl-ethylamino)-8H-pteridin-7-one) and Sch527123 (2-hydroxy-N,N-dimethyl-3-{2-[[(R)-1-(5-methyl-furan-2-yl)-propyl]amino]-3,4-dioxo-cyclobut-1enylamino}-benzamide), and the effect of these mutations on their binding affinity and ability to inhibit interleukin-8-stimulated binding of [(35)S]GTPgammaS was examined.

KEY RESULTS

Seven of the nine mutations introduced into the C-terminal domain and intracellular loops of the receptor produced a significant reduction in affinity at least one of the antagonists tested. Of those seven mutations, three produced a significant reduction in the affinity of all three antagonists, namely K320A, Y314A and D84N. In all but one mutation, the changes observed on antagonist affinity were matched with effects on inhibition of interleukin-8-stimulated [(35)S]GTPgammaS binding.

CONCLUSIONS AND IMPLICATIONS

These antagonists bind to a common intracellular, allosteric, binding site of the CXCR2 receptor, which has been further delineated. As many of these mutations are close to the site of G protein coupling or to a region of the receptor that is responsible for the transduction of the activation signal, our results suggest a molecular mechanism for the inhibition of receptor activation.

Mutation in pyrroline-5-carboxylate reductase 1 gene in families with cutis laxa type 2

Autosomal-recessive cutis laxa type 2 (ARCL2) is a multisystem disorder characterized by the appearance of premature aging, wrinkled and lax skin, joint laxity, and a general developmental delay. Cutis laxa includes a family of clinically overlapping conditions with confusing nomenclature, generally requiring molecular analyses for definitive diagnosis. Six genes are currently known to mutate to yield one of these related conditions. We ascertained a cohort of typical ARCL2 patients from a subpopulation isolate within eastern Canada. Homozygosity mapping with high-density SNP genotyping excluded all six known genes, and instead identified a single homozygous region near the telomere of chromosome 17, shared identically by state by all genotyped affected individuals from the families. A putative pathogenic variant was identified by direct DNA sequencing of genes within the region. The single nucleotide change leads to a missense mutation adjacent to a splice junction in the gene encoding pyrroline-5-carboxylate reductase 1 (PYCR1). Bioinformatic analysis predicted a pathogenic effect of the variant on splice donor site function. Skipping of the associated exon was confirmed in RNA from blood lymphocytes of affected homozygotes and heterozygous mutation carriers. Exon skipping leads to deletion of the reductase functional domain-coding region and an obligatory downstream frameshift. PYCR1 plays a critical role in proline biosynthesis. Pathogenicity of the genetic variant in PYCR1 is likely, given that a similar clinical phenotype has been documented for mutation carriers of another proline biosynthetic enzyme, pyrroline-5-carboxylate synthase. Our results support a significant role for proline in normal development.

Ovca1, a candidate gene of the genetic modifier of Tp53, Mop2, affects mouse embryonic lethality

In this study, we show genetic modifier genes of Tp53 that can exacerbate embryonic abnormalities. Using a mouse model in which CE/J mice were crossed with the Tp53-null 129/Sv (129-Trp53(tm1 Tyj)) mice, a subset of Tp53+/- and -/- male and female embryos died during gestation. Our hypothesis, based on the genotypes of survivors, is that two genetic modifiers and a Tp53 null allele lead to an increase in embryonic lethality. We previously identified a recessive modifier (Mop1) from CE/J mice on chromosome 11 centromeric to Tp53. We have uncovered a dominant modifier (Mop2) from 129/Sv mice telomeric to Tp53. We discovered a polymorphic change (321P-->321S) of Ovca1 within the Mop2 locus of CE/J mice. This polymorphism increased both mRNA and protein levels of OVCA1 in various tissues. CE/J primary cells cultured from different tissues proliferated more rapidly than 129/Sv cells. In addition, CE/J cells cycled while 129/Sv cells had a higher arrest in the G1 phase. Transfection of Ovca1 containing the 321P polymorphism into CE/J cells caused a higher G1 arrest. The pattern of OVCA1 expression also changed from being diffuse throughout the cytoplasm in 129/Sv cells to being punctuate in the cytoplasm of CE/J cells. Tp53+/- abnormal embryos had more proliferating cells than normal embryos, but no obvious difference in differentiated neuronal cells. Tp53-/- small embryos had less differentiated neuronal cells and proliferating cells than normal embryos. Thus, a polymorphism of Ovca1, combined with Mop1, genetically modifies embryonic lethality in Tp53 deficient mice.

Regulation of hdm2 by stress-induced hdm2alt1 in tumor and nontumorigenic cell lines correlating with p53 stability

Alternative and aberrant splicing of hdm2 occurs in tumor and normal tissues. However, the factors that induce these splice variants and whether they are translated to protein products in vivo is unknown, making it difficult to decipher which of these hdm2 transcripts have a normal physiologic function or contribute to carcinogenesis. We investigated the conditions that induce this post-transcriptional modification of hdm2 in tumor and nontumorigenic cell lines. We showed that UV and gamma radiation as well as cisplatin treatment induced alternative splicing of hdm2, which resulted in a single splice variant, hdm2(alt1), irrespective of the cell type. Interestingly, the mechanism of UV-induced splicing is independent of p53 status. Immunoanalysis revealed that, after UV radiation, HDM2(ALT1) protein was expressed and interacted with HDM2 that correlated to increased p53 protein levels and its accumulation in the nucleus, whereas HDM2 localized more to the cytoplasm with a decrease in its RNA and protein level. We propose that stress-induced HDM2(ALT1) regulates HDM2 at two levels, RNA and protein, further modulating the p53-HDM2 interaction or interactions of HDM2 with other cell cycle regulatory proteins. This kind of regulation may possibly restrict oncogenic functions of HDM2 and contribute to the many protective responses triggered by certain stress signals. Our data imply that HDM2(ALT1) possesses a normal physiologic function in damaged cells, perhaps facilitating cellular defense.

Optimisation of imaging technique used in direct digital radiography

The purpose of the study was to optimise the technique employed for AP shoulder and lateral cervical spine examinations following an investigation into image quality, based on clinical assessment, and effective dose, calculated from patient entrance surface dose measurements. A study was therefore conducted in an attempt to determine whether the increased radiation dose to the patient following the introduction of an anti-scatter grid was justified by the level of improvement in image quality. The study, involving 100 patients, was able to demonstrate that the increase in radiation dose to the patient when using an anti-scatter grid for AP shoulder examinations is not justified by the improved image quality. A poor level of inter-rater reliability between the consultants scoring the lateral cervical spine images prevented a firm conclusion from being reached. The fact that all images were of diagnostic quality, however, suggested that the use of the anti-scatter grid was unnecessary. Following completion of the project the hospital involved was informed of all findings.

Genetic mapping of a putative tumor suppressor locus that influences tumorigenesis and metastasis in mice

The tumor suppressor TP53 is mutated in approximately 70% of Li-Fraumeni syndrome (LFS) families; however, other genes may lead to the predisposition to tumors in other families. We developed a mouse model to search for other tumor suppressors that may be involved in the syndrome. Inbred CE/J mice, which succumb to multiple types of tumors similar to those found in LFS, were crossed with the Trp53-null 129-Trp53tm1Tyj mouse. We monitored the tumor onset and type and found a significant earlier tumor onset in the CE/J:129-Trp53tm1Tyj mice compared with 129-Trp53tm1Tyj mice with a Trp53-null allele. Additionally, in CE/J:129-Trp53tm1Tyj-Trp53+/- mice, the tumors metastasize, which does not occur in other strains of mice. Using simple-sequence length polymorphism analysis for loss of heterozygosity in tumors, we identified a putative tumor suppressor locus within 1 cM on mouse chromosome 11, which encompasses 12 mapped genes.

Differential effect of selected methylxanthine derivatives on radiosensitization of lung carcinoma cells

AIM

Using caffeine as a reference derivative, this study was performed to investigate how other methylxanthine derivatives, theophylline, 3-isobutyl-methylxanthine and 1,3-dipropyl-7-methylxanthine, sensitize cells to radiation by modifying cell cycle checkpoints and inducing the apoptotic response. The effect of the methylxanthine derivatives was studied in response to gamma and ultraviolet radiation in a human large cell lung carcinoma cell line, null for p53, a normal lung epithelial cell line and the large cell lung carcinoma cell line stably transfected with p53.

METHODS

Effects of theophylline, 3-isobutyl-methylxanthine and 1,3-dipropyl 7-methylxanthine on cell-radiosensitization in comparison to caffeine tested by clonogenic survival assay, MTT assay, ELISA based apoptotic assay, flow cytometry, caspase-3 activity, TUNEL assay, and western blot analysis.

RESULTS

All the derivatives, except 3-isobutyl-methylxanthine, increased tumor cell sensitization to radiation by inducing apoptosis in the p53-null lung cancer cell line. The pattern of cell cycle progression revealed that these derivatives increased the number of cells in G1 phase by abrogating the G2/M checkpoint, directing the cells to apoptose through a p53-independent mechanism. In contrast, 3-isobutyl-methylxanthine was more potent than the other derivatives in radiosensitization of normal lung epithelial cells and the lung carcinoma cells stably transfected with wild-type p53. IBMX increased p53 protein level more than caffeine in lung carcinoma cells stably transfected with wild-type p53.

CONCLUSION

Our results suggest that 3-isobutyl-methylxanthine might function through a p53-dependent mechanism.

Structure–activity studies of quinuclidinone analogs as anti-proliferative agents in lung cancer cell lines

We have synthesized and tested novel quinuclidinone analogs to assay the effects on H1299 lung cancer cell lines alone or with gamma-radiation. We have found two series of quinuclidinone analogs that act as anti-cancer agents. Of these, four interesting analogs significantly decreased cell viability in H1299 lung cancer cell lines. Two derivatives decreased cell proliferation in a dose-dependent fashion alone or in the presence of gamma-radiation. Radiosensitization increased when derivative treatment preceded radiation treatment for both derivatives. These preliminary studies show an evidence for both additive and synergistic cytotoxicity for treatment of lung cancer by these novel quinuclidinone analogs.

Cyclin D1 polymorphism (G870A) and risk for esophageal adenocarcinoma

BACKGROUND

To investigate individual susceptibility to gastroesophageal reflux disease, Barrett esophagus, and esophageal adenocarcinoma, the authors studied the frequency of the common G870A polymorphism of CCND1, which encodes cyclin D1, a key cell cycle regulatory protein.

METHODS

The study population included 307 patients who were enrolled in a prospective case-control study to evaluate lifestyle risk factors and molecular alterations in gastroesophageal reflux disease (n = 126 patients), Barrett esophagus (n = 125 patients), and esophageal adenocarcinoma (n = 56 patients). A control group included 95 strictly asymptomatic individuals. Genomic DNA was extracted from cases and controls, and polymerase chain reaction was used to amplify exon 4 of CCND1. After digestion with BsrI, acrylamide gel electrophoresis was used to identify the wild type and common G870A polymorphic alleles. The frequency of alleles (G/G, G/A, A/A) was compared between cases and controls. Immunohistochemistry was used to study cyclin D1 distribution in among patients in the case group.

RESULTS

Compared with the asymptomatic control group, and adjusted for age and gender, increasing frequencies were seen for the A/A genotype in patients with gastroesophageal reflux disease (odds ratio [OR], 2.83; 95% confidence interval [95% CI], 1.09-7.34), Barrett esophagus (OR, 3.69; 95% CI, 1.46-9.29), and esophageal adenocarcinoma (OR, 5.99; 95% CI, 1.86-18.96). No association was seen between genotype and cyclin D1 overexpression.

CONCLUSIONS

The CCND1 A/A genotype was associated with increased risk for gastroesophageal reflux disease, Barrett esophagus, and esophageal adenocarcinoma. The contribution of this polymorphism to susceptibility of defined stages of progression to esophageal adenocarcinoma suggested potential application in endoscopic Barrett surveillance programs.

Polymorphisms in DNA repair genes in the molecular pathogenesis of esophageal (Barrett) adenocarcinoma

To test the hypothesis that aberrations of DNA repair contribute to susceptibility for the progression of gastroesophageal reflux disease (GERD) into Barrett esophagus (BE) and esophageal adenocarcinoma (EADC), we studied the frequency of polymorphisms of selected DNA repair genes in patients with GERD (n = 126), BE (n = 125) and EADC (n = 56) enrolled in a 2-year prospective case-control study. Controls comprised 95 strictly asymptomatic healthy individuals. Using genomic DNA extracted from blood samples, we identified wild-type and polymorphic variants of XPD (Arg156Arg and Lys751Gln), XRCC1 (Arg194Trp and Arg399Gln) and XRCC3 (Thr241Met), and the poly (AT) insertion/deletion of XPC (PAT). Allelic frequencies were compared between cases and controls using logistic regression to calculate age, gender, smoking and alcohol-adjusted odds ratios (OR) and 95% confidence intervals (CI). Patients with EADC demonstrated a significantly higher frequency of the XPC PAT homozygous variant genotype compared with asymptomatic controls (OR = 3.82; 95% CI = 1.05-13.93). Significantly reduced frequencies were seen for the XPD Lys751Gln homozygous variant genotype in patients with EADC (OR = 0.24; 95% CI = 0.07-0.88), and for the XRCC1 Arg399Gln homozygous variant genotype in patients with BE (OR = 0.38; 95% CI = 0.12-0.64) and GERD (OR = 0.29; 95% CI = 0.12-0.66). We conclude that the malignant phenotype probably results from a summation of polymorphic nucleotide excision repair genes showing opposing effects (an increased risk of XPC versus a protective effect of XPD). The protective effect of the homozygous variant of XRCC1 Arg399Gln for GERD and BE suggests that base excision repair alterations may occur early in progression to EADC, likely in response to GERD-induced endogenous oxidative or inflammatory DNA damage. As GERD and BE are highly prevalent in the general population, this protective effect may well explain why only a fraction of individuals with GERD and BE progress into invasive EADC.

Effect of reduced EGFR function on the radiosensitivity and proliferative capacity of mouse jejunal crypt clonogens

BACKGROUND AND PURPOSE

Previous data indicate that the EGFR pathway is involved in the response of tumor cell lines to irradiation. To determine if this receptor plays a role in the response of the intestinal mucosa, the effect of a spontaneous mutation in EGFR (B6C3-a-wa-2) on radiosensitivity and proliferative capacity was investigated using in vivo clonogenic assays and immunohistochemistry.

PATIENTS AND METHODS

EGFR mutant mice were compared with wild-type mice using the in vivo jejunal microcolony assay using single and split doses to measure the radiosensitivity and repopulation of clonogenic jejunal mucosal cells. In addition, paraffin-embedded tissue sections were assessed for proliferation (PCNA), DNA repair (Ku70 and gamma H2AX), and apoptosis (TUNEL) by immunofluorescent staining (wild-type vs. heterozygous only) at various times after 5 Gy single dose.

RESULTS

After the high doses used in the split-dose experiments, EGFR heterozygous and homozygous mutant mice were significantly more radiosensitive than their wild-type littermates. There was no clear difference in split-dose repair based on EGFR function. After 5 Gy single dose there were significantly more apoptotic cells within the crypts of heterozygous mice than of wild-type mice, beginning at 3h post irradiation. Decreased proliferation was observed only in the homozygous mutant mice. PCNA staining was lower in the heterozygous mice than in wild-type mice at 1 and 3 h post-5 Gy.

CONCLUSION

The results indicate that after high doses the radiosensitivity of EGFR mutant mice is significantly higher than that of wild-type, and that this could be the result of an increase in apoptosis rather than reduced DNA repair. Proliferative capacity was modestly reduced, but only in the homozygous mutants.

A novel genetic modifier of p53, mop1, results in embryonic lethality

The heterogeneity that occurs in the tumor spectrum and latency in Li-Fraumeni syndrome (LFS) patients with inherited mutations in p53 suggest risk modifiers at loci other than the major gene. We developed a mouse model to investigate these risk modifiers. Inbred CE/J mice, which succumb to multiple types of tumors similar to those found in LFS, were crossed with the p53-null 129/Sv (129-Trp53(tm1Tyj)) mouse. In this cross, we uncovered evidence for a genetic modifier of p53, mop1, based on an unexpected mix of genotypes in the F2 progeny from Mendelian expectations. A model in which a recessive CE/J allele in combination with p53 heterozygosity or homozygosity results in lethality most closely fits the data. Using simple-sequence length polymorphism analysis of the entire genome, we identified a putative chromosomal region for this modifier of p53 on mouse chromosome 11 centromeric to p53.

Microsatellite instability in esophageal adenocarcinoma

The frequency of microsatellite instability (MSI), a result of defective mismatch repair during DNA replication, has been reported inconsistently in primary esophageal adenocarcinoma (EADC). Using a panel of 15 markers, the primary aim of this study was to analyze the frequency of MSI in a well-characterized series of 27 primary EADCs, defined according to strict clinicopathologic criteria. Polymerase chain reaction was used to amplify the following microsatellite repeat loci: D2S123, D10S197, D2S119, D11S904, D2S147, D3S1764, D7S1830, D7S1805, D2S434, D9S299, BAT25, BAT26, D5S346, D17S250, and TGF-beta-RII. Tumors were classified as microsatellite-stable (MSS) when no alterations were seen in tumor DNA compared to matched normal tissues, low-level MSI (MSI-L) when 1-5 of 15 markers were altered, and high-level MSI (MSI-H) when more than five markers were altered. Using these stringent criteria, 9/27 (33%) tumors were MSS, 18/27 (67%) tumors were MSI-L, and no tumor was MSI-H. Immunohistochemistry demonstrated cell nuclear expression of DNA mismatch repair proteins (both hMLH1 and hMSH2) in 78% (21/27) of tumors. No associations were seen between MSI and immunohistochemical expression of hMLH1, hMSH2, alterations in p53 or MBD4, tumor grade, pathologic stage, or patient survival. In conclusion, the finding of low levels of MSI in most tumors suggests an inherent baseline genomic instability, and potentially increased susceptibility to mutations during the progression of esophageal adenocarcinoma.

Mutational analysis of the cytoplasmic domain of beta1,4-galactosyltransferase I: influence of phosphorylation on cell surface expression

Beta1,4-galactosyltransferase I (GalT I) exists in two subcellular compartments where it performs two distinct functions. The majority of GalT I is localized in the Golgi complex where it participates in glycoprotein biosynthesis; however, a small portion of GalT I is expressed on the cell surface where it functions as a matrix receptor by binding terminal N-acetylglucosamine residues on extracellular glycoside ligands. The GalT I polypeptide occurs in two alternate forms that differ only in the length of their cytoplasmic domains. It is thought that the longer cytoplasmic domain is responsible for GalT I function as a cell surface receptor because of its ability to associate with the detergent-insoluble cytoskeleton. In this study, we demonstrate that the long GalT I cytoplasmic and transmembrane domains are capable of targeting a reporter protein to the plasma membrane, whereas the short cytoplasmic and transmembrane domains do not have this property. The surface-localized GalT I reporter protein partitions with the detergent-insoluble pool, a portion of which co-fractionates with caveolin-containing lipid rafts. Site-directed mutagenesis of the cytoplasmic domain identified a requirement for serine and threonine residues for cell surface expression and function. Replacing either the serine or threonine with aspartic acid reduces surface expression and function, whereas substitution with neutral alanine has no effect on surface expression or function. These results suggest that phosphorylation negatively regulates GalT I function as a surface receptor. Consistent with this, phosphorylation of the endogenous, full-length GalT I inhibits its stable expression on the cell surface. Thus, the 13 amino acid extension unique to the long GalT I isoform is required for GalT I expression on the cell surface, the function of which is regulated by phosphorylation.

Clinical implications of p53 tumor suppressor gene mutation and protein expression in esophageal adenocarcinomas: results of a ten-year prospective study

OBJECTIVE

This study was undertaken to characterize the spectrum of p53 alterations (mutations and protein expression) in surgically resected esophageal adenocarcinomas, and to correlate molecular alterations with clinicopathologic findings and outcome.

METHODS

Between 1991 and 2001, 91 consecutive patients with esophageal adenocarcinomas underwent subtotal esophagectomy. No patient received induction therapy. Strict clinicopathologic criteria were used to define primary esophageal adenocarcinomas. Genomic DNA was extracted from esophageal tumors, each matched with histologically normal esophageal epithelium (internal control) from the resection margin. Polymerase chain reaction was used to amplify p53 exons 4 through 10. Mutations were studied by single-strand conformation polymorphism analysis and direct DNA sequencing. Immunohistochemical testing (monoclonal antibody DO7) was used to evaluate p53 protein distribution.

RESULTS

Five-year overall survival was 27.3%. No p53 alterations (mutations and/or protein overexpression) were found in normal esophageal epithelium. A total of 57.1% (n = 52) of tumors had p53 alterations (mutations and/or protein overexpression), which on univariate analysis were associated with poor tumor differentiation (P =.001), advanced pTNM stage (P =.009), and number of involved lymph nodes (0, 1-3, >3; P =.04). Patients with p53 alterations had significantly reduced 5-year overall survival relative to patients with wild-type p53 (15% vs 46%; P =.004). The p53 mutations were predominantly G:C to A:T transitions at CpG dinucleotides (52.2%, 24/46)

CONCLUSIONS

We conclude that p53 alterations (mutations and/or protein overexpression) are a predictor of reduced postoperative survival after surgical resection of esophageal adenocarcinomas and that p53 may be a clinically useful molecular marker for stratifying patients in future clinical trials. Patterns of p53 mutations suggest endogenous mutational mechanisms.

ING1 and p53 tumor suppressor gene alterations in adenocarcinomas of the esophagogastric junction

The aim of this study was to characterize molecular alterations of the recently reported candidate tumor suppressor gene, ING1, and to explore the relationship between ING1 and p53 in a well-defined series of adenocarcinomas of the esophagogastric junction (AdEGJ). Polymerase chain reaction (PCR)-based assays were used to characterize ING1 and p53 alterations, relative to histologically normal esophageal mucosa. Two tumors were found to have ING1 mutations: one novel missense mutation (AGC(Ser)-->ATC(Ile)) at codon 147, and one silent mutation (TCG(Ser)-->TCA(Ser)) at codon 173. Reduced expression of the two major alternatively spliced ING1 messenger RNA variants, p47(ING1a) and p33(ING1b) was variable, but was reduced (1.2-10-fold) in 12 of 19 AdEGJs compared to normal esophageal epithelium. No association between p53 and ING1 alterations was apparent. We conclude that reduced ING1 expression is frequently associated with AdEGJ tumorigenesis, further supporting its role as a tumor suppressor gene, and that ING1 expression is independent of p53 status.

Activation of protein kinase C increases acetylcholine release from frog motor nerves by a direct action on L-type Ca(2+) channels and apparently not by depolarisation of the terminal

The effects of the dihydropyridine Ca(2+) channel antagonist nimodipine and the protein kinase C inhibitors staurosporine and calphostin C on the changes in the electrophysiological indices of quantal acetylcholine release induced by a 4-beta-phorbol ester were studied at the frog neuromuscular junction. 4-beta-Phorbol 12-myristate 13-acetate (200 nM) caused an increase in the frequency of miniature endplate potentials and miniature endplate currents and in the quantal content of endplate potentials and endplate currents. These effects were not replicated by 4-alpha-phorbol 12,13-didecanoate (200 nM). Nimodipine (1 microM) itself had no effect on the frequency of miniature endplate potentials and miniature endplate currents and it had no effect on the quantal content. Nimodipine inhibited by 83-98% the increase in these parameters induced by 4-beta-phorbol 12-myristate 13-acetate. The increase in the frequency of miniature endplate potentials and currents caused by KCl (12 mM) matched the increase caused by 20 min exposure to 4-beta-phorbol 12-myristate 13-acetate. Nimodipine did not reduce the increase in frequency caused by KCl. Unlike 4-beta-phorbol 12-myristate 13-acetate, KCl (12 mM) prevented neuromuscular transmission. The effects of prior exposure of muscles to staurosporine (5 microM) on 4-beta-phorbol 12-myristate 13-acetate-induced increases in quantal acetylcholine release were inconsistent. In some pretreated fibres, 4-beta-phorbol 12-myristate 13-acetate caused increases in miniature endplate potential frequency and quantal content which were as great as the largest values encountered in fibres that had not been pretreated. In others, 4-beta-phorbol 12-myristate 13-acetate did not have a marked effect; the frequency of the spontaneous potentials and the quantal content of endplate potentials recorded in the presence of 4-beta-phorbol 12-myristate 13-acetate were sometimes less than their respective control values. Pretreatment with calphostin C (500 nM) was more consistent; it prevented by 93-100% the 4-beta-phorbol 12-myristate 13-acetate-induced increases in the frequency of miniature endplate potentials and quantal content.Overall, from these results we suggest that activation of protein kinase C increases quantal acetylcholine release by opening quiescent L-type Ca(2+) channels in motor nerve terminals at resting potential and apparently not by depolarisation.

An alternatively spliced HDM2 product increases p53 activity by inhibiting HDM2

The human counterpart hdm2 of the murine double-minute 2 (mdm2) gene encodes a 90-kD protein (HDM2) that inhibits the function of the p53 tumor suppressor. Hdm2 is amplified in approximately 30% of sarcomas, leading to overproduction of HDM2 and inactivation of p53. Using immunohistochemistry to screen a panel of human tumors for HDM2 overproduction, we detected high levels of HDM2 in the cytoplasm in 25% of lung tumors as opposed to its normal localization in the nucleus. These samples contained full-length hdm2 and several alternate-splice forms of hdm2 mRNA. Sequence analysis revealed deletions in the alternate-splice forms of the p53 binding domain and absence of a nuclear localization signal. In transient transfection assays, one of the alternate-splice forms, HDM2(ALT1), bound and sequestered full-length HDM2 in the cytoplasm. In addition, the binding of HDM2(ALT1) to HDM2 inhibited the interaction of HDM2 with p53, thus enhancing p53 transcriptional activity. These data suggest the existence of another level of regulation of HDM2 which increases the activity of p53.

The proliferative response of mouse jejunal crypt cells to radiation-induced cell depletion is not mediated exclusively by transforming growth factor alpha

Several lines of correlative evidence link transforming growth factor alpha (Tgfa, also known as TGF-alpha) to proliferative activity in jejunal crypt cells. It is therefore tempting to hypothesize that, as a ligand of the epidermal growth factor, it mediates the compensatory proliferative burst in the crypts after radiation-induced cell killing. We have tested this hypothesis by comparing the repopulation response of wild-type and Tgfa-null mice, using the microcolony assay. Mice were exposed whole-body to (137)Cs gamma rays at a dose of approximately 1.6 Gy/min. Single doses and equal doses separated by 4 and 54 h were given. The rightward shift of the dose-response curves for 54 h was identical for wild-type and Tgfa-null mice, and there was no indication of a difference in radiosensitivity. This result indicates that Tgfa is not an essential component of the proliferative response of tissue to radiation-induced cell killing.

Progress toward ignition with noncryogenic double-shell capsules

Inertial confinement fusion implosions using capsules with two concentric shells separated by a low density region (double shells) are reported which closely follow one dimensional (1D) radiatively driven hydrodynamics simulations. Capsule designs which mitigate Au M-band radiation asymmetries appear to correspond more closely to 1D simulations than targets lacking mitigation of hohlraum drive M-band nonuniformities. One capsule design achieves over 50% of the unperturbed 1D calculated yield at a convergence ratio of 25.5, comparable to that of a double-shell design for an ignition capsule at the National Ignition Facility.

Antegrade intramedullary fixation of displaced fifth metacarpal fractures

We report a new and simple modification for antegrade insertion of intramedullary K-wires used in the treatment of displaced fifth metacarpal fractures. This method of fixation was performed on six patients all of whom had excellent results when reviewed clinically and radiologically with a mean follow-up of 9 months.

Exclusion of a p53 germline mutation in a classic Li-Fraumeni syndrome family

Li-Fraumeni syndrome (LFS) is characterized by a high risk of sarcomas, early onset of breast cancer, and a diversity of other cancers occurring as multiple primary tumors in multiple family members. In many families with LFS, germline mutations within the tumor-suppressor gene p53 have been identified. However, mutations in p53 have not been detected in approximately 30% of LFS families. To address the possibility either that p53 mutations were being missed or that another predisposing gene is altered in LFS, we used a variety of methods to accurately determine the p53 status in a large LFS kindred. A transcriptional activation assay on exons 4-10 of p53 excluded a mutation within the DNA-binding domain of p53. Single-stranded conformational-polymorphism analysis, using intronic primers and sequencing of all the coding exons and intron/exon junctions, also yielded no mutations. Finally, linkage analysis excluded potential mutations in the noncoding regions of p53. Our findings exclude the presence of a p53 germline mutation in a classic LFS family.

Isolation of the Aspergillus nidulans sudD gene and its human homologue

We have been studying the heat-sensitive bimD6 mutation of Aspergillus nidulans. At a restrictive temperature, the chromosomes of bimD6 mutant strains fail to attach properly to the spindle microtubules, and the mutant also displays a high rate of chromosome loss. We previously cloned the sudA gene, an extragenic suppressor of the heat-sensitive bimD6 mutation and showed that it coded for a DA-box or SMC protein. SMC proteins have been demonstrated to function in chromosome condensation, segregation and global gene regulation. We have now cloned the sudD gene, another of the extragenic suppressor genes of the bimD6 mutation. The predicted SUDD protein is the founding member of a widely expressed protein family. Similar proteins are found in sequence databases for Saccharomyces cerevisiae, Caenorhabditis elegans, mammals and four species of archaebacteria. We have also cloned and sequenced a human cDNA that encodes the human homologue of SUDD and mapped the gene to 18q11.2. The predicted SUDD proteins from A. nidulans, Homo sapiens and S. cerevisiae all share a variety of features. The predicted proteins are approximately 60000Da in mass and have a serine-plus-threonine content of about 11%. The evolutionary conservation of the proteins suggests an ancient origin and conserved function for these proteins.

The Li-Fraumeni syndrome: an inherited susceptibility to cancer

The Li-Fraumeni syndrome is a rare autosomal-dominant disease whose hallmark is a predisposition to a wide range of cancers among members of a family. Many of these families have a germline mutation within the tumor suppressor gene TP53, which encodes the p53 protein. The inheritance of a mutant TP53 allele results in a 25-fold increase in the chance of developing cancer by 50 years of age, compared with the general population. TP53 mutations are also very common in the development of somatic tumors. This article reviews the biological and biochemical role of p53 in the susceptibility to cancer in Li-Fraumeni syndrome.

MRI of 'idiopathic' juvenile scoliosis. A prospective study

In a prospective trial we performed MRI of the spine and hind brain in 31 patients with scoliosis of onset between the ages of four and 12 years. In eight patients (26%) there was a significant neuroanatomical abnormality; there were six cases of Chiari-1 malformation associated with a syrinx, one isolated Chiari-1 malformation and one astrocytoma of the cervical spine. Four of these patients had left-sided curves. There were no clinical features which could reliably identify those patients with abnormalities on MRI. In particular, the unilateral absence of abdominal reflexes was found to be non-specific (1 of 8 of patients with neuroanatomical abnormalities (12.5%) v 2 of 23 with normal scans (8.7%). In view of the established risks of surgical correction of scoliosis in the presence of undecompressed syringomyelia and the possible improvement that may follow decompression of the foramen magnum, we feel that MRI of all patients with scoliosis of juvenile onset should be obligatory.

Altering the expression of cell surface beta 1,4-galactosyltransferase modulates cell growth

beta 1,4-Galactosyltransferase (GalTase) is unusual among the glycosyltransferases in that it is localized both in the Golgi complex and on the cell surface. Most studies of surface GalTase function have focused on its role in cellular interactions; however, surface GalTase has also been suggested to function during cellular proliferation. Consistent with this hypothesis, a variety of GalTase-specific perturbants inhibit cell growth in vitro and in vivo. However, all of these studies have been limited to the use of exogenous reagents to perturb GalTase function. Furthermore, all of these perturbants inhibit cell growth, irrespective of whether they stimulate or inhibit GalTase enzyme activity. Therefore, it remains unclear whether surface GalTase delivers a growth inhibitory or growth stimulatory signal. In this study, we took a more direct approach to defining surface GalTase function during growth by examining its expression during the cell cycle and by molecularly altering its expression in stably transfected cell lines. The expression of GalTase was shown to be cell cycle specific, with the cell surface and intracellular GalTase pools displaying independent expression patterns. Furthermore, multiple, independent, stably transfected cell lines with reduced levels of cytoskeletally associated surface GalTase grew faster than control cells, whereas cell lines that over-expressed surface GalTase grew slower than controls. These observations directly support the concept that surface GalTase delivers a growth inhibitory signal. Evidence is presented suggesting that surface GalTase interacts with the epidermal growth factor (EGF) receptor, as suggested by others. The activity of the EGF receptor was shown to be directly proportional to the growth rate of the various GalTase-transfected cell lines. Thus, the expression of surface GalTase directly affects cell proliferation rate and may do so by modulating the ability of the EGF receptor to transduce EGF-dependent signals.

Biological consequences of targeting beta 1,4-galactosyltransferase to two different subcellular compartments

beta 1,4-galactosyltransferase is unusual among the glycosyltransferases in that it is found in two subcellular compartments where it performs two distinct functions. In the trans-Golgi complex, galactosyltransferase participates in oligosaccharide biosynthesis, as do the other glycosyltransferases. On the cell surface, however, galactosyltransferase associates with the cytoskeleton and functions as a receptor for extracellular oligosaccharide ligands. Although we now know much regarding galactosyltransferase function in these two compartments, little is known about how it is targeted to these different sites. By cloning the galactosyltransferase gene products, certain features of the protein have been identified that may be critical for its expression on the cell surface or retention within the Golgi complex. This article discusses recent studies which suggest that a cytoplasmic sequence unique to one galactosyltransferase isoform is required for targeting a portion of this protein to the plasma membrane, enabling it to function as a cell adhesion molecule. These findings allow one to manipulate surface galactosyltransferase expression, either positively or negatively, and perturb galactosyltransferase-dependent cellular interactions during fertilization and development.

Airport metal detectors and orthopedic implants. The responses of arch and hand-held devices

8 subjects with a variety of orthopedic implants were examined by the security staff at an international airport using arch and hand-held metal detectors. None of the subjects caused activation of the alarm on the arch, although the presence of metal was registered in 2 at a level below the alarm threshold. The hand-held detectors alarmed over the larger superficial implants. A substantial tissue screening effect was noted.

Dominant negative mutation in cell surface beta 1,4-galactosyltransferase inhibits cell-cell and cell-matrix interactions

In addition to its traditional location within the Golgi complex, beta 1,4-galactosyltransferase (GalTase) is also present on the cell surface, where it is thought to function as a cell adhesion molecule by binding to extracellular oligosaccharide ligands. Recent studies suggest that cells contain two forms of GalTase with distinct cytoplasmic domains. The longer form of GalTase contains a 13-amino acid cytoplasmic extension and is preferentially targeted to the plasma membrane, relative to the shorter GalTase protein that is confined primarily to the Golgi compartment. In this study, we created a dominant negative mutation that interferes with the function of cell surface GalTase by transfecting into cells cDNAs encoding truncated versions of the long form of GalTase containing the complete cytoplasmic and transmembrane domains, but devoid of the catalytic domain. In both F9 embryonal carcinoma cells and Swiss 3T3 fibroblasts, overexpressing the truncated long GalTase (TLGT) protein displaced the endogenous cell surface GalTase from its association with the cytoskeleton, resulting in a loss of intercellular adhesion and cell spreading specifically on matrices that use GalTase as a cell surface receptor. In contrast, overexpressing the analogous truncated short GalTase (TSGT) protein did not affect cell morphology or GalTase activity. In control assays, inducing the TLGT protein had no effect on cell interactions with fibronectin (which is independent of GalTase), or on the cytoskeleton attachment of another matrix receptor (beta 1 integrin), or on overall glycoprotein synthesis, thus eliminating nonspecific effects of the TLGT protein on cellular adhesion and metabolism. These results represent the first molecular manipulation of cell surface GalTase expression and confirm its function as a cell adhesion molecule. These studies further suggest that the cytoskeleton contains a defined, saturable number of binding sites for GalTase, which enables it to function as an adhesion molecule.

The Victoria bomb: a report from the Westminster Hospital

On 18 February 1991 a bomb exploded on Victoria station, London. A total of 51 people were injured including one fatally. Of the most seriously wounded, 30 were treated at The Westminster Hospital. The majority of injuries were to the lower limbs, but serious wounds were also sustained to the chest, abdomen, forearm, orbit and cranium. Almost all injuries were caused by shrapnel. The low incidence of infection was attributed to thorough early surgical débridement. The administration of antibiotics was varied and uncoordinated, reflecting a lack of a common policy. The exhaustion of common external fixators necessitated the use of equipment unfamiliar to the surgeons and underlined the need for the rapid transfer of equipment between hospitals at the time of major incidents.

Evidence for a molecular distinction between Golgi and cell surface forms of beta 1,4-galactosyltransferase

beta 1,4-Galactosyltransferase (GalTase) is present on the plasma membrane of many cell types in addition to its traditional location within the Golgi compartment. Recently, the GalTase gene has been shown to encode two proteins that are identical throughout their length except that one has an additional 13-amino acid extension in its amino-terminal cytoplasmic domain. We present evidence here suggesting that the longer GalTase protein, containing this unique 13-amino acid peptide, is preferentially targeted to the plasma membrane, and the shorter GalTase protein resides primarily within the Golgi compartment. S1 nuclease protection assays of RNA from a variety of cells and tissues show that the relative abundance of the short and long GalTase mRNAs correlates with GalTase-specific activities in the Golgi and plasma membranes, respectively. Furthermore, transfection of cDNAs encoding either the long or short GalTase protein into F9 embryonal carcinoma cells suggests that the long GalTase protein is preferentially expressed on the cell surface. These results propose a molecular distinction between the Golgi and cell surface forms of GalTase as well as a novel mechanism for targeting glycoproteins to the cell surface.