Fertility in seasonal-calving pasture-based lactating dairy cows following timed artificial insemination or timed embryo transfer with fresh or frozen in vitro-produced embryos.

The objective was to compare pregnancy per service event (P/S) in lactating dairy cows following timed artificial insemination (AI) or timed embryo transfer (ET) using either fresh or frozen in vitro-produced embryos. Oocytes were collected once per week for up to 9 wk using transvaginal ovum pick-up from elite dairy donors (ET-DAIRY; n = 40; Holstein-Friesian and Jersey) and elite beef donors (ET-ELITE-BEEF; n = 21; Angus). Both ET-DAIRY and ET-ELITE-BEEF donors consisted of heifers and cows. In addition, oocytes were collected from the ovaries of beef heifers of known pedigree following slaughter at a commercial abattoir (ET-COMM-BEEF; n = 119). Following in vitro maturation and fertilization, presumptive zygotes were cultured in vitro to the blastocyst stage. Grade 1 blastocysts were either transferred fresh or frozen for on-farm thawing and direct transfer. A total of 1,106 recipient cows (all lactating, predominantly Holstein-Friesian) located on 16 herdlets were blocked based on parity, calving date, and Economic Breeding Index, and randomly assigned to receive AI (n = 243) or ET (n = 863) after estrous synchronization with a 10-d Progesterone-synch protocol. Cows assigned to ET were further randomized to receive fresh (n = 187) or frozen (n = 178) ET-ELITE-BEEF embryos, fresh (n = 169) or frozen (n = 162) ET-DAIRY embryos, or fresh (n = 80) or frozen (n = 87) ET-COMM-BEEF embryos. Pregnancy was diagnosed using transrectal ultrasound on d 32 to 35 after synchronized ovulation and confirmed on d 62 to 65, at which time fetal sex was determined. Pregnancy per service event at d 32 was not different between AI (48.8%) and ET (48.9%) and did not differ between dairy and beef embryos (50.3% vs. 48.1%, respectively). However, P/S was less on d 32 following transfer of frozen embryos (41.6%) compared with fresh embryos (56.1%). Pregnancy loss between d 32 and 62 was greater for ET (15.1%) compared with AI (4.7%), with greater losses observed for frozen beef (18.5%), fresh beef (17.3%), and frozen dairy (19.2%) compared with fresh dairy (6.0%) embryos. Serum progesterone (P4) concentration on d 7 was associated with P/S at d 32 and 62. Cows in the quartile with the least serum P4 concentrations (quartile 1) had less probability of being pregnant on d 32 (33.4%) compared with cows in the 3 upper quartiles for serum P4 (45.7%, 55.6%, and 61.2% for quartile 2, quartile 3, and quartile 4, respectively). Sex ratio (male:female) at d 62 was skewed toward more male fetuses following ET (61.1:38.9) compared with AI (43.2:56.8) and was consistent with the sex ratio among in vitro blastocysts (61.2:38.8). In conclusion, P/S was similar for AI and ET, although pregnancy loss between d 32 and 62 was greater for ET than for AI.

Association Between Minimum Inhibitory Concentration, Beta-lactamase Genes and Mortality for Patients Treated With Piperacillin/Tazobactam or Meropenem From the MERINO Study.

INTRODUCTION: This study aims to assess the association of piperacillin/tazobactam and meropenem minimum inhibitory concentration (MIC) and beta-lactam resistance genes with mortality in the MERINO trial. METHODS: Blood culture isolates from enrolled patients were tested by broth microdilution and whole genome sequencing at a central laboratory. Multivariate logistic regression was performed to account for confounders. Absolute risk increase for 30-day mortality between treatment groups was calculated for the primary analysis (PA) and the microbiologic assessable (MA) populations. RESULTS: In total, 320 isolates from 379 enrolled patients were available with susceptibility to piperacillin/tazobactam 94% and meropenem 100%. The piperacillin/tazobactam nonsusceptible breakpoint (MIC >16 mg/L) best predicted 30-day mortality after accounting for confounders (odds ratio 14.9, 95% confidence interval [CI] 2.8-87.2). The absolute risk increase for 30-day mortality for patients treated with piperacillin/tazobactam compared with meropenem was 9% (95% CI 3%-15%) and 8% (95% CI 2%-15%) for the original PA population and the post hoc MA populations, which reduced to 5% (95% CI -1% to 10%) after excluding strains with piperacillin/tazobactam MIC values >16 mg/L. Isolates coharboring extended spectrum ß-lactamase (ESBL) and OXA-1 genes were associated with elevated piperacillin/tazobactam MICs and the highest risk increase in 30-day mortality of 14% (95% CI 2%-28%). CONCLUSIONS: After excluding nonsusceptible strains, the 30-day mortality difference from the MERINO trial was less pronounced for piperacillin/tazobactam. Poor reliability in susceptibility testing performance for piperacillin/tazobactam and the high prevalence of OXA coharboring ESBLs suggests that meropenem remains the preferred choice for definitive treatment of ceftriaxone nonsusceptible Escherichia coli and Klebsiella.

Putting CYP2C19 genotyping to the test: utility of pharmacogenomic evaluation in a voriconazole-treated haematology cohort.

OBJECTIVES: The clinical utility of pharmacogenomic testing in haematology patients with invasive fungal disease (IFD) receiving azole therapy has not been defined. We report our experience with CYP2C19 testing in haematological patients requiring voriconazole therapy for IFD. METHODS: As a single-centre pilot study, 19 consecutive patients with a haematological malignancy undergoing active chemotherapy with a possible, probable or proven IFD requiring voriconazole therapy underwent CYP2C19 testing from 2013 to 2014. Baseline patient demographics, concurrent medications, voriconazole levels and IFD history were captured. RESULTS: The median voriconazole levels for intermediate metabolizer (IM) (CYP2C19*2 or 3/*1 or 17), extensive metabolizer (EM) (CYP2C19*1/*1) and heterozygote ultrarapid metabolizer (HUM)/ultrarapid metabolizer (UM) (UM, CYP2C19*17/*17; HUM, CYP2C19*1/*17) patients were 5.23, 3.3 and 1.25 mg/L, respectively. Time to therapeutic voriconazole levels was longest in the IM group, whilst voriconazole levels <1 mg/L were only seen in UM, HUM and EM phenotypes. The highest rates of clinical toxicity were seen in the IM group (3/5, 60%). CONCLUSIONS: Voriconazole exposure and toxicity was highest for IM and lowest for HUM/UM phenotypes. Time to therapeutic voriconazole level was longest in IM, whilst refractory subtherapeutic levels requiring CYP2C19 inhibition were only seen in the EM, HUM and UM phenotypes. CYP2C19 genotyping may predict those likely to have supratherapeutic or subtherapeutic levels and/or toxicity. Prospective evaluation of clinical pathways incorporating genotyping and voriconazole dose-titrating algorithms is required.

Diverticular disease in Scotland: 2000-2010.

AIM: Symptomatic diverticular disease (DD) may be increasing in incidence in western society particularly in younger age groups. This study aimed to describe hospital admission rates and management for DD in Scotland between 2000 and 2010. METHOD: Data were obtained from the Scottish Morbidity Records (SMR01). The study cohort included all patients with a hospital admission and a primary diagnosis of DD of the large intestine (ICD-10 primary code K57). RESULTS: Scottish NHS hospitals reported 90 990 admissions for DD (in 87 314 patients) from 2000 to 2010. The annual number of admissions increased by 55.2% from 6591 in 2000 to 10,228 in 2010, an average annual increase per year of 4.5%. Most of the increase attributable to DD was due to elective day cases (3618 in 2000; 6925 in 2010) a likely consequence of a greater proportion of the population accessing colonoscopy over that time period. There was an 11% increase in inpatient admissions (2973-3303), 60% of these patients being women. Admissions in younger age groups increased proportionally in the later years of the study, and there was an association between DD admissions and greater deprivation. Despite an increase in complicated DD from 22.9% in 2000 to 27.1% in 2010 and a 16.8% increase in emergency inpatient admissions, the rate of surgery fell during the period of study. CONCLUSION: This report supports findings of other population-based studies of western countries indicating that DD is an increasing burden on health service resources, particularly in younger age groups.

The influence of passage number for Caco2 cell models when evaluating P-gp mediated drug transport.

Caco2 cells are a human adenocarcinoma cell line that forms tight junctions and are widely used to examine bidirectional drug transport as well as P-glycoprotein mediated efflux. Unfortunately Caco2 cell lines can be very heterogeneous in nature. Our aim was to improve the Caco2 cell model for determination of P-glycoprotein mediated drug transport. Young passage Caco2 from ATCC had inadequate expression of P-glycoprotein, therefore three approaches were adopted to upregulate Caco2 P-glycoprotein expression to mimic that in vivo; a) incubation of mature Caco2 monolayer with rifampicin, b) prolonged exposure of Caco2 cells to vinblastine (generating the Caco2 VIN line), and c) splitting cells every 7 to 9 days until late passage numbers (over P80) were available. Upon development of the models, P-gp expression and activity was determined using western blotting and bidirectional transport studies of rhodamine123. All four models exhibited P-gp mediated efflux transport for rhodamine123. Incubation with rifampicin did not alter bidirectional transport compared to passage 44 cells. Increased passage number altered P-glycoprotein expression and the efflux ratio increased to 4.7 for passage 80 from 1.4 of passage 44. The highest basolateral to apical transport was observed for both passage 89 Caco2 and the Caco2 VIN model with an efflux ratio of 13 to 14. Western blot images confirmed the increased P-glycoprotein expression of late passage and Caco2 VIN. Caco2 cells are not ready for P-gp related research when first acquired from ATCC (Passage 18). Late passage Caco2 cell monolayers or Caco2 VIN models are needed to determine P-gp mediated efflux transport.

Rothia aeria mitral valve endocarditis complicated by multiple mycotic aneurysms: laboratory identification expedited using MALDI-TOF MS.

Rothia aeria has only rarely been described as a human pathogen. We describe a case of Rothia aeria causing mitral valve endocarditis and multiple mycotic aneurysms, including cerebral mycotic aneurysms. In the case described, early identification of Rothia aeria was achieved using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS).

A nitric oxide-releasing solution as a potential treatment for fungi associated with tinea pedis.

AIMS: To test a nitric oxide-releasing solution (NORS) as a potential antifungal footbath therapy against Trichophyton mentagrophytes and Trichophyton rubrum during the mycelial and conidial phases. METHODS AND RESULTS: NORS (sodium nitrite citric acid) produces nitric oxide verified by gas chromatography and mass spectrometry (GC-MS). Antifungal activity of this solution was tested against mycelia and conidia of T. mentagrophytes and T. rubrum, using 1-20 mmol l(-1) nitrites and 10-30 min exposure times. The direct effect of the gas released from the solution on the viability of those fungi was tested. NORS demonstrated strong antifungal activity and was found to be dose and time dependent. NO and nitrogen dioxide (NO(2) ) were the only gases detected from this reaction and are likely responsible for the antifungal effect. CONCLUSIONS: This in vitro research suggests that a single 20-min exposure to NORS could potentially be used as an effective single-dose treatment against fungi that are associated with tinea pedis in both mycelia and spore phase. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides the background for developing a user-friendly footbath treatment for Athlete's Foot that will kill both vegetative fungi and its spores.

Effect of delayed timing of artificial insemination with sex-sorted semen on pregnancy per artificial insemination in synchronized dairy heifers managed in a seasonal-calving pasture-based system.

The objective of this study was to evaluate the timing of artificial insemination (AI) with frozen-thawed sex-sorted semen on pregnancy per AI (P/AI) in dairy heifers. A 6-d progesterone Co-Synch protocol was used for ovulation synchronization of dairy heifers, with timed AI (TAI) coincident with (TAI-0) or 8 h (TAI-8) after the second injection of GnRH, corresponding to either 48 h or 56 h after removal of the progesterone-releasing intravaginal device. Pregnancy diagnosis was conducted by transrectal ultrasound scanning of the uterus 34 d after TAI (n = 816 records available for analysis). Generalized linear mixed models were used to examine the effects of treatment on P/AI. Treatment (n = 2), herd (n = 11), and treatment × herd were included as categorical fixed effects. Heifer body weight and Economic Breeding Index values for milk production, fertility, calving performance, beef carcass, cow maintenance, cow management, and health were included as continuous fixed effects. Heifer ID was included as a random effect. Pregnancy per AI was greater for TAI-8 heifers (59%) compared with TAI-0 heifers (50%). Pregnancy per AI ranged from 38% to 75% between herds but there was no treatment × herd interaction. The fertility subindex (positive) and the cow management subindex (negative) were the only continuous animal variables associated with P/AI. Delaying the timing of AI with frozen-thawed sex-sorted semen by 8 h in dairy heifers enrolled on a 6-d progesterone Co-Synch protocol improved P/AI.

Measuring stock and change in the GB countryside for policy--key findings and developments from the Countryside Survey 2007 field survey.

Countryside Survey is a unique large scale long-term monitoring programme investigating stock and change of habitats, landscape features, vegetation, soil and freshwaters of Great Britain. Repeat field surveys combine policy and scientific objectives to provide evidence on how multiple aspects of the environment are changing over time, a key goal of international science in the face of profound human impacts on ecosystems. Countryside Survey 2007 (CS2007), the fifth survey since 1978, retained consistency with previous surveys, whilst evolving in line with technological and conceptual advances in the collection and integration of data to understand landscape change. This paper outlines approaches taken in the 2007 survey and its subsequent analysis and presents some of the headline results of the survey and their relevance for national and international policy objectives. Key changes between 1998 and 2007 included: a) significant shifts in agricultural land cover from arable to grassland, accompanied by increases in the area of broadleaved woodland, b) decreases in the length of managed hedges associated with agricultural land, as a proportion deteriorated to lines of trees and c) increases in the areas and numbers of wet habitats (standing open water, ponds) and species preferring wetter conditions (1998-2007 and 1978-2007). Despite international policy directed at maintaining and enhancing biodiversity, there were widespread decreases in species richness in all linear and area habitats, except on arable land, consistent with an increase in competitive and late successional species between 1998 and 2007 and 1978 and 2007. Late successional and competitive species: Stinging nettle (Urtica dioica), Hawthorn (Cratageous monogyna) and Bramble (Rubus fruticosus), in the top ten recorded species recorded in 2007, all increased between 1998 and 2007. The most commonly recorded species in CS (1990, 1998 and 2007) was agricultural Ryegrass (Lolium perenne). Increases in both water quality and soil pH were in line with policy aimed at addressing previous deterioration of both. Headwater streams broadly showed continued improvements in biological quality from 1998 to 2007, continuing trends seen since 1990. In soils, there were significant increases in soil pH between 1998 and 2007 consistent with recovery from acidification.

Gynaecological endoscopic evaluation of 4% icodextrin solution: a European, multicentre, double-blind, randomized study of the efficacy and safety in the reduction of de novo adhesions after laparoscopic gynaecological surgery.

BACKGROUND: Gynaecological laparoscopic surgery outcomes can be compromised by the formation of de novo adhesions. This randomized, double-blind study was designed to assess the efficacy and safety of 4% icodextrin solution (Adept(®)) in the reduction of de novo adhesion incidence compared to lactated Ringer's solution (LRS). METHODS: Patients undergoing laparoscopic surgery for removal of myomas or endometriotic cysts were treated with randomized solution as an intra-operative irrigant and 1l post-operative instillate. De novo adhesion incidence (number of sites with adhesions), severity and extent were independently scored at a second-look procedure and the efficacy of the two solutions compared. The effect of surgical covariates on adhesion formation was also investigated. Initial exploratory analysis of individual anatomical sites of clinical importance was progressed. RESULTS Of 498 patients randomized, 330 were evaluable (160 LRS--75% myomectomy/25% endometriotic cysts; 170 Adept--79% myomectomy/21% endometriotic cysts). At study completion, 76.2% LRS and 77.6% Adept had ≥ 1 de novo adhesion. The mean (SD) number of de novo adhesions was 2.58 (2.11) for Adept and 2.58 (2.38) for LRS. The treatment effect difference was not significant (P = 0.909). Assessment of surgical covariates identified significant influences on the mean number of de novo adhesions regardless of treatment, including surgery duration (P = 0.048), blood loss in myomectomy patients (P = 0.019), length of uterine incision in myomectomy patients (P < 0.001) and number of suture knots (P < 0.001). There were 15 adverse events considered treatment-related in the LRS patients (7.2%) and 18 in the Adept group (8.3%). Of 17 reported serious adverse events (9 LRS; 8 Adept) none were considered treatment-related. CONCLUSIONS: The study confirmed the safety of Adept in laparoscopic surgery. The proportion of patients with de novo adhesion formation was considerably higher than previous literature suggested. Overall there was no evidence of a clinical effect but various surgical covariates including surgery duration, blood loss, number and size of incisions, suturing and number of knots were found to influence de novo adhesion formation. The study provides direction for future research into adhesion reduction strategies in site specific surgery.

Dental nurses as trainers and assessors: vocational dental trainer attitudes.

AIM: To explore the attitudes of vocational dental trainers (VDTs) working in general dental practice to the role of dental nurses as trainers and assessors of trainee dental nurses (tDNs), vocational dental practitioners (VDPs) and vocational dental hygienist/therapists (VDHTs). METHOD: This research was conducted within the context of the development of a training and assessment qualification for dental nurses. A survey was sent to all 148 VDTs in Scotland. The survey assessed VDT attitudes as to the appropriateness of dental nurses to train and assess tDNs, VDPs, VDHTs with regard to their clinical, communication-based and administrative duties. The three sets of attitudes for tDNS, VDPS and VDHTs were assessed on a five-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). The data were subjected to one way and repeated measures of ANOVA. RESULTS: A total of 126 VDTs responded giving an 85% response rate. For clinical, communication-based and administrative activities, VDTs had significantly greater mean scores for the appropriateness of DNs to train [F(1,57) = 45.69, P < 0.001] and assess [F(1,57) = 76.94, P < 0.001] tDNs compared with VDPs and VDHTs. CONCLUSION: Vocational dental trainers felt it was more appropriate for DNs to train and assess tDNs' clinical, communication-based and administrative activities compared with VDPs and VDHTs. Over 80% of dental trainers, however, indicated there would be benefit to their practice in having a dental nurse educated in the principles and application of training and assessment.

The effect of 4% icodextrin solution on adhesiolysis surgery time at the Hartmann's reversal: a pilot, multicentre, randomized control trial vs lactated Ringer's solution.

OBJECTIVE: A pilot randomized controlled clinical multicentre trail was established to compare intraperitoneal 4% icodextrin (ID) solution with lactated Ringer's solution (LRS) on adhesion formation after Hartmann's procedure. The adhesiolysis surgery time during Hartman's reversal was used as a marker of the severity of adhesions. METHOD: Patients scheduled for Hartmann's resection were randomized at surgery to either of the two study solutions used as an irrigant during the operation and instilled (1000 ml) at the end of surgery. During the reversal procedure, the time for small bowel adhesiolysis was recorded. RESULTS: On completion of 17 eligible patients, an interim analysis was performed. There were no complications following the use of 4% ID solution. The mean (SD) total adhesiolysis times in patients treated with 4% ID solution and LRS were 30.8 (18.0) min and 47.6 (45.7) min, respectively. The mean reduction of 16.8 min, although greater than expected, was not statistically significant (P = 0.33) because of the large variance in adhesiolysis times. Further statistical analysis showed that to achieve significance for the observed differences and variance, a minimum of 240 patients in each group would be required. CONCLUSION: Icodextrin treatment resulted in a decreasing trend in adhesiolysis time. The use of 4% ID solution in peritonitis patients seemed to be safe. Because of larger than expected variations in adhesiolysis times, this pilot study was underpowered to meet the study end-point and further statistical modelling estimated that significance cannot be reached within a reasonable time scale. Other models should be used to evaluate the efficacy of anti-adhesive agents.

p53-mediated repression of alpha-fetoprotein gene expression by specific DNA binding.

Aberrant expression of the alpha-fetoprotein (AFP) gene is characteristic of a majority of hepatocellular carcinoma cases and serves as a diagnostic tumor-specific marker. By dissecting regulatory mechanisms through electromobility gel shift, transient-transfection, Western blot, and in vitro transcription analyses, we find that AFP gene expression is controlled in part by mutually exclusive binding of two trans-acting factors, p53 and hepatic nuclear factor 3 (HNF-3). HNF-3 protein activates while p53 represses AFP transcription through sequence-specific binding within the previously identified AFP developmental repressor domain. A single mutation within the DNA binding domain of p53 protein or a mutation of the p53 DNA binding element within the AFP developmental repressor eliminates p53-repressive effects in both transient-transfection and cell-free expression systems. Coexpression of p300 histone acetyltransferase, which has been shown to acetylate p53 and increase specific DNA binding, amplifies the p53-mediated repression. Western blot analysis of proteins present in developmentally staged, liver nuclear extracts reveal a one-to-one correlation between activation of p53 protein and repression of AFP during hepatic development. Induction of p53 in response to actinomycin D or hypoxic stress decreases AFP expression. Studies in fibroblast cells lacking HNF-3 further support a model for p53-mediated repression that is both passive through displacement of a tissue-specific activating factor and active in the presence of tissue-specific corepressors. This mechanism for p53-mediated repression of AFP gene expression may be active during hepatic differentiation and lost in the process of tumorigenesis.

S-Phase progression mediates activation of a silenced gene in synthetic nuclei.

Aberrant expression of developmentally silenced genes, characteristic of tumor cells and regenerating tissue, is highly correlated with increased cell proliferation. By modeling this process in vitro in synthetic nuclei, we find that DNA replication leads to deregulation of established developmental expression patterns. Chromatin assembly in the presence of adult mouse liver nuclear extract mediates developmental stage-specific silencing of the tumor marker gene alpha-fetoprotein (AFP). Replication of silenced AFP chromatin in synthetic nuclei depletes sequence-specific transcription repressors, thereby disrupting developmentally regulated repression. Hepatoma-derived factors can target partial derepression of AFP, but full transcription activation requires DNA replication. Thus, unscheduled entry into S phase directly mediates activation of a developmentally silenced gene by (i) depleting developmental stage-specific transcription repressors and (ii) facilitating binding of transactivators.

A mutation in the second largest subunit of TFIIIC increases a rate-limiting step in transcription by RNA polymerase III.

In previous studies, we have shown that the PCF1-1 mutation of Saccharomyces cerevisiae suppresses the negative effect of a tRNA gene A block promoter mutation in vivo and increases the transcription of a variety of RNA polymerase III genes in vitro. Here, we report that PCF1 encodes the second largest subunit of transcription factor IIIC (TFIIIC) and that the PCF1-1 mutation causes an amino acid substitution in a novel protein structural motif, a tetratricopeptide repeat, in this subunit. In agreement with the nature of the mutation, in vitro transcription studies with crude extracts indicate that PCF1-1 facilitates the rate-limiting step in transcription, namely, the recruitment of TFIIIB to the template. Additionally, biochemical fractionation of wild-type and mutant cell extracts shows that PCF1-1 increases the amount of the 70-kDa TFIIIB subunit detectable by Western (immunoblot) analysis in purified TFIIIB fractions and the transcription activity of a TFIIIB" fraction containing the 90-kDa subunit of this factor. We suggest that the effect of PCF1-1 on TFIIIB activity in vitro is a consequence of its increased rate of recruitment in vivo.

Post-translational modifications of the env-sea oncogene product: the role of proteolytic processing in transformation.

The transforming gene product of the S13 avian erythroblastosis virus, env-sea, is a member of the growth factor receptor class of tyrosine kinases. The env-sea precursor protein gp155env-sea is proteolytically processed into the mature cleavage products gp85env-sea and gp70env-sea which are subsequently terminally glycosylated. Previous studies have shown that the abnormal glycosylation of gp155env-sea which takes place in the presence of the inhibitor castanospermine inhibits the proteolytic cleavage of gp155env-sea and blocks its transforming ability. To define a role for proteolytic processing of env-sea in transformation, we have introduced mutations at the protease recognition site which efficiently block cleavage without affecting the biosynthesis or transport of the resulting uncleaved protein. We show here that an uncleaved but fully glycosylated sea-encoded protein retains the ability to transform chicken embryo fibroblasts, indicating that proteolytic processing is not essential for transformation by the env-sea tyrosine kinase.

Chromatin alteration, transcription and replication: What's the opening line to the story?

Polymerase accessibility to chromatin is a limiting step in both RNA and DNA synthesis. Unwinding DNA and nucleosomes during polymerase complex binding and processing likely requires priming by chromatin restructuring. The initiating step in these processes remains an area of speculation. This review focuses on the physical handling of chromatin during transcription and replication, the fate of nucleosomes assembled on DNA during unwinding and processing the chromatin substrate, and how these alterations in chromatin structure may affect gene expression. Transcription or replication may alter chromatin structure during synthesis, enabling regulatory factor binding and, potentially, future rounds of transcription. As chromatin remodeling and transcription factor binding augment transcription and replication, and are themselves increased by these processes, a temporal model of structural alterations and gene activation is built that may be more circular than linear.

Phosphorylation of the SHC proteins on tyrosine correlates with the transformation of fibroblasts and erythroblasts by the v-sea tyrosine kinase.

The S13 avian erythroblastosis viral genome encodes an oncogenic tyrosine kinase, termed env-sea, that is capable of transforming fibroblasts and erythroblasts. Although the tyrosine kinase activity of the env-sea protein has been shown to be necessary for transformation, no substrates for this enzyme have been detected in vivo. Here we demonstrate that the recently described shc proteins are phosphorylated on tyrosine residues in both S13 transformed fibroblasts and erythroblasts. Furthermore, using an S13 temperature sensitive mutant, we show that the phosphorylation of the shc proteins occurs concomitantly with the activation of the tyrosine kinase activity of the env-sea protein. These observations make the phosphorylation of the shc proteins a good candidate for being involved in oncogenic signaling by the env-sea oncoprotein.