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Biomedical subjects

John Nicholls

Publications and source records attributed to John Nicholls.

11 recordsLinked to original sources
PubMed2005

Differential expression of genes at stages when regeneration can and cannot occur after injury to immature mammalian spinal cord.

Comprehensive screens were made for genes that change their expression during a brief critical period in development when neonatal mammalian central nervous system (CNS) loses its capacity to regenerate. In newly born opossums older than 12 days regeneration ceases to occur in the cervical spinal cord. It continues for 5 more days in lumbar regions. The mRNA's expressed in cords that do and do not regenerate were analyzed by polymerase chain reaction-based subtractive hybridization. The mRNAs extracted from cervical cords of animals aged 9 and 12 days were subtracted reciprocally, old from young and young from old. Additional subtractions were made between lumbar regions of 12 day-old cords (which can regenerate) and cervical regions (which cannot). Mini libraries of approximately 2000 opossum cDNA clones resulted from each subtraction. Many sequences were novel. Others that were expressed differentially were related to cell growth, proliferation, differentiation, motility, adhesion, cytoskeleton and extracellular matrix. A major task was to narrow the search and to eliminate genes that were not associated with regeneration. Clones from different subtractions were cross-hybridized. After those common to regenerating and nonregenerating cords were rejected, approximately 284 sequences of interest remained. Our results revealed novel sequences, as well as genes involved in transcription, cell signaling, myelin formation, growth cone motility, liver regeneration, and nucleic acid and protein management as the candidates important for neuroregeneration. For selected genes of potential interest for regeneration (for example cadherin, catenin, myelin basic protein), their temporal and spatial distributions and levels of expression in the CNS were measured by Northern blots, semiquantitative and real-time RT-PCR, and in situ hybridization. Our experiments set the stage for testing the efficacy of candidate genes in turning on or off the capacity for spinal cord regeneration. Opossum spinal cords in vitro provide a reliable and rapid assay for axon outgrowth and synapse formation.

Animals↗
PubMed2004

Laboratory markers of tumor burden in nasopharyngeal carcinoma: a comparison of viral load and serologic tests for Epstein-Barr virus.

Epstein-Barr virus (EBV) is present within the tumor cells of most cases of nasopharyngeal carcinoma (NPC). Recent studies suggest that tumor burden is proportional to the level of EBV DNA in blood and that rapid blood testing can be used to guide therapeutic intervention. The relative utility of viral load vs. serology has been insufficiently studied. In our study, EBV viral load was measured by quantitative PCR using either real-time or end-point detection systems in serum samples from 124 NPC patients (93 pretreatment, 13 relapsed, 18 in remission) and 40 controls. Serologic titers against EBV early antigen were measured in the same serum samples. EBV DNA was detectable in 64 of 93 untreated NPC patients (69%; mean viral load 11,211 copies/ml), 11 of 13 relapsed NPC patients (85%; mean 53,039 copies/ml) and 0 of 18 remission patients. EBV DNA was detectable in only 1 of 40 non-NPC controls (3%). In 34 instances where paired plasma and serum samples were available for testing, both were effective sample types, and there was no significant difference between end-point and real-time methods for measuring viral load. Early antigen (EA) IgA and IgG titers were elevated in most NPC patients regardless of whether their disease was active or in remission. EBV viral load was more informative than was EA serology for distinguishing remission from relapsed disease. EBV DNA measurement appears to be a noninvasive way to monitor tumor burden after therapy.

Antibodies, Viral↗
PubMed2004

Upregulation of macrophage migration inhibitory factor contributes to induced N-Myc expression by the activation of ERK signaling pathway and increased expression of interleukin-8 and VEGF in neuroblastoma.

Macrophage migration inhibitory factor (MIF) has been linked to fundamental processes such as control of cell proliferation, cell survival, angiogenesis, and tumor progression. The expression of MIF has been reported in several tumors. However, the precise role of MIF in tumor cells remains unclear. In the present study, we investigated the expression pattern and the function of MIF in neuroblastoma. Our results showed that intracellular MIF was upregulated in neuroblastoma tumor tissues and cell lines. MIF protein expression significantly correlated with the grade of tumor differentiation. In addition, we found that MIF induced a significant dose-dependent increase of vascular endothelial growth factor and interleukin-8 secretion. We also observed that an increased MIF expression level correlated with N-Myc protein (the N-myc oncogene product) expression in neuroblastoma tissues. MIF increased the expression of N-myc mRNA and N-Myc protein and induced N-Myc translocation from the cytoplasm to nucleus in neuroblastoma cell lines. MIF-induced N-Myc expression was found to be dependent on ERK signaling pathways. The inhibition of ERK activation reduced MIF-mediated N-Myc expression. These results suggest that MIF may contribute to the progression of neuroblastoma by (a) inducing N-Myc expression and (b) upregulating the expression of angiogenic factors.

Adolescent↗
PubMed2004

Results of surgical removal of the pouch after failed restorative proctocolectomy.

PURPOSE: Restorative proctocolectomy is the elective surgical procedure of choice for ulcerative colitis and familial adenomatous polyposis. Most patients have a satisfactory outcome, but at ten years 15 percent or more will have failed, needing indefinite defunctioning or excision of the pouch. There is little information on the morbidity of pouch excision. The study was designed to present the early results of surgical removal of the pouch after failed restorative proctocolectomy with reference to the indications and intermediate complications, particularly of the perineal wound. METHODS: Between 1977 and 2002, 996 patients underwent a restorative proctocolectomy at our hospital and 245 patients were referred for potential salvage. The pouch was excised in 58 and 10 patients respectively. There were 40 females and 28 males (median age, 34 (14-65) years) including 47 with ulcerative colitis, 10 with Crohn's disease, and 11 with familial adenomatous polyposis. The median follow-up was 79 (range, 3-312) months from excision. RESULTS: There was one (1.4 percent) postoperative death. The overall morbidity rate was 62.3 percent (immediate 30 days (25 percent), late (53.7 percent)). Thirty-six patients (53.7 percent) were readmitted on 67 occasions for a late complication. The risk of readmission from the time of pouch excision was 38 and 58 percent at one and five years, respectively. Surgical treatment was required during 48 of these readmissions. A persistent perineal sinus was the most common late complication. The perineal wound was not healed at 6 months in 27 patients (40 percent) and at 12 months in 7 patients (10 percent). No factor, including age at the time of pouch excision, gender, indication for excision, or final histologic diagnosis, was associated with an unhealed perineal wound. Two males (7 percent) had impotence. One female suffered from short-bowel syndrome with the need of permanent parenteral nutrition. The median overall hospital stay for all admissions was 20 (range, 8-220) days. CONCLUSIONS: Pouch excision is associated with high morbidity. Perineal wound-delayed healing is the commonest late complication and often requires further surgery.

Adenomatous Polyposis Coli↗
PubMed2004

Detection of wild type and deleted latent membrane protein 1 (LMP1) of Epstein-Barr virus in clinical biopsy material.

The latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) is one of two postulated viral oncogenic proteins. Sequence variations, and in particular a 30 base pair deletion variant called CAO, may define different disease populations. We developed a panel of rat monoclonal antibodies (MAb) specific for the non-wild type LMP1 and compared the presence of the antibody staining with LMP1 DNA sequence analysis on clinical samples of nasopharyngeal carcinoma, peripheral T-cell lymphoma (PTCL), Hodgkin's disease, lymphoblastoid cell lines (LCL) from normal volunteers, and patients with nasopharyngeal carcinoma. The results demonstrate specificity of the monoclonal cocktail for detecting the non-wild type LMP1 and the ability to sub-differentiate between the mediterranean type of LMP1 and the CAO-LMP1. Double immunofluorescence on paraffin material using the traditional CS1-4 monoclonal antibodies and the CAO-cocktail revealed no dual population of cells in the biopsy material from the Asian region.

Amino Acid Sequence↗
PubMed2003

SARS: clinical virology and pathogenesis.

Severe acute respiratory syndrome (SARS) is caused by a novel coronavirus, called the SARS coronavirus (SARS-CoV). Over 95% of well characterized cohorts of SARS have evidence of recent SARS-CoV infection. The genome of SARS-CoV has been sequenced and it is not related to any of the previously known human or animal coronaviruses. It is probable that SARS-CoV was an animal virus that adapted to human-human transmission in the recent past. The virus can be found in nasopharyngeal aspirate, urine and stools of SARS patients. Second generation reverse transcriptase polymerase chain reaction assays are able to detect SARS-CoV in nasopharyngeal aspirates of approximately 80% of patients with SARS within the first 3 days of illness. Seroconversion for SARS-CoV using immunofluorescence on infected cells is an excellent method of confirming the diagnosis, but antibody responses only appear around day 10 of the illness. Within the first 10 days the histological picture is that of acute phase diffuse alveolar damage (DAD) with a mixture of inflammatory infiltrate, oedema and hyaline membrane formation. Desquamation of pneumocytes is prominent and consistent. After 10 days of illness the picture changes to one of organizing DAD with increased fibrosis, squamous metaplasia and multinucleated giant cells. The role of cytokines in the pathogenesis of SARS is still unclear.

Histological Techniques↗
PubMed2003

Long-term failure after restorative proctocolectomy for ulcerative colitis.

OBJECTIVE: To establish the incidence and causes of late failure in patients undergoing restorative proctocolectomy for a preoperative diagnosis of ulcerative colitis was the objective of this investigation. SUMMARY BACKGROUND DATA: Restorative proctocolectomy is the elective surgical procedure of choice for ulcerative colitis. Most patients have a satisfactory outcome but failures occur. The reasons and rates of early failure are well documented, but there is little information on long-term failure. METHODS: A series of 634 patients (298 females, 336 males) underwent restorative proctocolectomy for inflammatory bowel disease between 1976-1997, with a mean follow-up of 85 +/- 58 months. Failure was defined as removal of the pouch or the need for an indefinite ileostomy. It was divided into early and late, occurring within 1 year or more than 1 year postoperatively. RESULTS There were 3 (0.5%) postoperative deaths, leaving 631 patients for analysis. Of these, 23 subsequently died (disseminated large bowel cancer, 12; unrelated causes, 9; related causes, 2). There were 61 (9.7%) failures (15 early [25%], 46 late [75%]) due to pelvic sepsis (32 [52%]: 7 early, 25 late), poor function (18 [30%]: 2 early, 16 late), pouchitis (7 [11%]: 2 early, 5 late) and miscellaneous (4, all early). A final diagnosis of Crohn's disease, type of reservoir (J,S), female gender, postoperative pelvic sepsis and a one-stage procedure were significantly associated with failure. Failure rate rose with time of follow-up from 9% at 5 years to 13% at 10 years. CONCLUSIONS: Pelvic sepsis and poor function were the main reasons for later failure. Failure rates should be reported based on the duration of follow-up.

Adolescent↗
PubMed2002

Evidence of increased Id-1 expression and its role in cell proliferation in nasopharyngeal carcinoma cells.

Inhibitor of differentiation or DNA binding (Id-1), a helix-loop-helix transcription factor, has recently been shown to inactivate the retinoblastoma (RB)/p16(INK4a) pathway through down-regulation of p16(INK4a) and increasing phosphorylation of RB in certain cell types. Nasopharyngeal carcinoma (NPC) is a common cancer in Hong Kong, and inactivation of the tumor suppressor RB at transcription level is a rare event in NPC. The objective of this study was to investigate the role of Id-1 in NPC cell proliferation and its expression in NPC samples. An NPC cell line, CNE1, was transfected with a retroviral vector containing a full-length Id-1 cDNA, and six stable transfectant clones were isolated with differential Id-1 expression levels. The effect of ectopic Id-1 expression on serum-independent cell growth, cell-cycle distribution, and expression of proteins associated with RB pathway was studied. The Id-1 expression in five NPC samples was also investigated using immunohistochemistry. Ectopic Id-1 expression in CNE1 cells resulted in an increase in serum-independent cell growth, percentage of cells in S phase, and phosphorylation of RB and cyclin-dependent kinase 2 proteins. In addition, immunohistochemical studies on NPC samples showed that expression of Id-1 was present in NPC cells but absent in normal tissues. This study demonstrates that Id-1 plays an important role in cell proliferation in NPC cells, and our results provide evidence for the first time of the significance of Id-1 expression in NPC cells and suggest a possible role of Id-1 expression in the inactivation of RB and development of NPC.

CDC2-CDC28 Kinases↗