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Biomedical subjects

N Harris

Publications and source records attributed to N Harris.

At least 37 records · Page 2Linked to original sources
PubMed2001

Endosperm-specific activity of a storage protein gene promoter in transgenic wheat seed.

The characterization of the promoter of a wheat (Triticum aestivum) cv. Cheyenne high molecular weight glutenin subunit (HMW subunit) gene, Glu-1D-1 is reported. The nucleotide sequence of the promoter from position -1191 to -650 with respect to the transcription start site was determined, to add to that already determined. Analysis of this region of the promoter revealed the presence of an additional copy of part of the primary enhancer sequence and sequences related to regulatory elements present in other wheat seed protein genes. A chimaeric gene was constructed comprising the 5' flanking region of the Glu-1D-1 gene from position -1191 to +58, the coding region of the UID:A (Gus) gene, and the nopaline synthase (Nos) gene terminator. This chimaeric gene was introduced into wheat (Triticum durum cv. Ofanto) by particle bombardment of inflorescence explants. Two independent transgenic lines were produced, and both showed expression of the Gus gene specifically in the endosperm during mid-development (first detected 10-12 d after anthesis). Histochemical analysis of homozygous T(2) seed confirmed this pattern of expression, and showed that expression was initiated first in the central lobes of the starchy endosperm, and then spread throughout the endosperm tissue, while no expression was detected in the aleurone layer. Native HMW subunit protein was detectable by Western analysis 12-14 d after anthesis, consistent with concurrent onset of activity of the native and introduced HMW subunit gene promoters.

Base Sequence↗
PubMed2000

A valence bond study of the Bergman cyclization: geometric features, resonance energy, and nucleus-independent chemical shift (NICS) values

The Bergman cyclization of (Z)-hex-3-ene-1,5-diynes (1, enediynes), which produces pharmacologically important DNA-cleaving biradicals (1,4-benzyne, 2), was studied by using Hartree-Fock (HF) and density-functional theory (DFT) based valence bond (VB) methods (VB-HF and VB-DFT, respectively). We found that only three VB configurations are needed to arrive at results not too far from complete active space [CASSCF(6 x 6)] computations, while the quality of VB-DTF utilizing the same three configurations improves upon CASSCF(6 x 6) analogous to CASPT2. The dominant VB configuration in 1 contributes little to 2, while the most important biradical configuration in 2 plays a negligible role in 1. The avoided crossing of the energy curves of these two configurations along the reaction coordinate leads to the transition state (TS). As a consequence of the shape and position of the crossing section, the changes in geometry and in the electronic wavefunction along the reaction coordinate are non-synchronous; the TS is geometrically approximately 80% product-like and electronically approximately 70% reactant-like. While the pi resonance in the TS is very small, it is large (64.4 kcal mol(-1)) for 2 (cf. benzene=61.5 kcal mol(-1)). As a consequence, substituents operating on the sigma electrons should be much more effective in changing the Bergman reaction cyclization barrier. Furthermore, additional sigma resonance in 2 results in unusually high values for the nucleus-independent chemical shift (NICS, a direct measure for aromaticity). Similarly, the high NICS value of the TS is due mostly to sigma resonance to which the NICS procedure is relatively sensitive.

Journal Article↗
PubMed2000

Stage III thymoma: pattern of failure after surgery and postoperative radiotherapy and its implication for future study.

PURPOSE: With the conventional approach of surgery and postoperative radiotherapy for patients with Masaoka Stage III thymoma, progress has been slow for an improvement in the long-term survival rate over the past 20 years. The objective of this study was to evaluate the pattern of failure and survival after surgery and postoperative radiotherapy in Stage III thymoma and search for a new direction for better therapy outcome. METHODS AND MATERIALS: Between 1975 and 1993, 111 patients with thymoma were treated at Massachusetts General Hospital. Of these, 32 patients were determined to have Masaoka Stage III thymoma. The initial treatment included surgery for clinically resectable disease in 25 patients and preoperative therapy for unresectable disease in 7 patients. Surgical procedure consisted of thymectomy plus resection of involved tissues. For postoperative radiotherapy (n = 23), radiation dose consisted of 45-50 Gy for close resection margins, 54 Gy for microscopically positive resection margins, and 60 Gy for grossly positive margins administered in 1.8 to 2.0 Gy of daily dose fractions, 5 fractions a week, over a period of 5 to 6.6 weeks. In preoperative radiotherapy, a dose of 40 Gy was administered in 2.0 Gy of daily dose fractions, 5 days a week. For patients with large tumor requiring more than 30% of total lung volume included in the target volume (n = 3), a preoperative radiation dose of 30 Gy was administered and an additional dose of 24-30 Gy was given to the tumor bed region after surgery for positive resection margins. RESULTS: Patients with Stage III thymoma accounted for 29% (32/111 patients) of all patients. The median age was 57 years with a range from 27 to 81 years; gender ratio was 10:22 for male to female. The median follow-up time was 6 years. Histologic subtypes included well-differentiated thymic carcinoma in 19 (59%), high-grade carcinoma in 6 (19%), organoid thymoma in 4 (13%), and cortical thymoma in 3 (9%) according to the Marino and Müller-Hermelink classification. The overall survival rates were 71% and 54% at 5 and 10 years, respectively. Ten of the 25 patients who were subjected to surgery as initial treatment were found to have incomplete resection by histopathologic evaluation. The 5- and 10-year survival rates were 86% and 69% for patients (n = 15) with clear resection margins as compared with 28% and 14% for those (n = 10) with incomplete resection margins even after postoperative therapy, p = 0.002. Survival rates at 5 and 10 years were 100% and 67% for those with unresectable disease treated with preoperative radiation (n = 6) and subsequent surgery (n = 3). Recurrence was noted in 12 of 32 patients and 11 of these died of recurrent thymoma. Recurrences at pleura and tumor bed accounted for 77% of all relapses, and all pleural recurrences were observed among the patients who were treated with surgery initially. CONCLUSION: Incomplete resection leads to poor results even with postoperative radiotherapy or chemoradiotherapy in Stage III thymoma. Pleural recurrence is also observed more often among patients treated with surgery first. These findings suggest that preoperative radiotherapy or chemoradiotherapy may result in an increase in survival by improving the rate of complete resection and reducing local and pleural recurrences.

Adult↗
PubMed2000

The effect of arcelin-1 on the structure of the midgut of bruchid larvae and immunolocalization of the arcelin protein.

Some wild accessions of the common bean (Phaseolus vulgaris) contain a family of proteins called arcelins, that are toxic to the larvae of certain bruchid species. Among the six allelic variants of arcelin tested so far, arcelin-5 and arcelin-1 confer the highest level of resistance against the Mexican bean weevil, Zabrotes subfasciatus. The same proteins are not toxic to the bean weevil, Acanthoscelides obtectus, which is also a serious pest of cultivated beans. Arcelins belong to the bean lectin family that includes phytohemaggutinins and alpha-amylase inhibitors. Although homologous to lectins, arcelins are themselves only very weak lectins, and their binding properties have not been clearly established. The toxic properties of arcelins may be related to their recognition of and interaction with the glycoproteins and other constituents of the membranes along the digestive tract of insects. Since arcelin-1 was shown to have growth inhibitory effects for the larvae of Z. subfasciatus but not of A. obtectus, we examined the effect of an arcelin-1 containing diet on the structure of the cells that line the intestinal tract of the larvae of these two bruchid species, and used antibodies against arcelin to examine the distribution of arcelin within the cells and tissues. Here we show that dietary arcelin-1 caused an alteration of the gut structure and the penetration of arcelin into the haemolymph in Z. subfasciatus but not in A. obtectus. These results lead us to suggest that arcelins exert their toxic effect by severely damaging the epithelial cells.

Journal Article↗
PubMed2000

Two cDNAs representing alleles of the nitrate reductase gene of potato (Solanum tuberosum L. cv. Desirée): sequence analysis, genomic organization and expression.

Two, different, full-length cDNAs, StNR2 and StNR3, of 3049 and 3066 nucleotides, respectively, were isolated from a Solanum tuberosum L. cv. Desirée leaf cDNA library by an RT-PCR approach. Conceptual translation of the longest open reading frame of each cDNA showed that they could encode a protein of 911 amino acids in each case with an M(r) of 102.6 and 102.5 kDa, respectively, and with 99.7% identity with each other. The cDNAs have a high degree of sequence similarity with all higher plant nitrate reductases (NRs) and possess structural characteristics expected of NADH-NR proteins, consistent with enzyme activity data. Southern analysis of genomic DNA suggested the presence of a single NR gene in the potato genome whilst studies using the mapping population F1840, and the full-length StNR2 cDNA as hybridization probe, identified a single NR locus within the potato genome that is located on chromosome XI. The two cDNAs identified here are probably derived from two transcribing alleles of this single gene. Distribution of total NR transcript and of NADH-NR activity, in different organs of compost-grown plants, depended on the level of nitrate supplied: at low nitrate level transcript and activity were detected only in leaf and stem tissue whilst at high nitrate level they could also be detected in root and stolon. An RT-PCR approach was used to differentiate between the transcripts derived from the two identified alleles and to show that the pattern of transcription of the two identified alleles of the potato nia gene, in the organs studied, is the same.

Amino Acid Sequence↗
PubMed2000

Dependence of anticancer activity of camptothecins on maintaining their lactone function.

Camptothecins contain a lactone ring that exists in the closed form below ph 7. Above 7, the open (CPT+) and the closed (CPT) form coexist in a 50-50 ratio in mouse plasma and in a 90-10 ratio in human plasma due to the high affinity of human serum albumin (HSA) for CPT+. CPT+ is much less toxic than CPT and it is excreted much faster. In complete RPMI 1640 culture medium, the equilibrium CPT(+)-CPT is 50-50. If 4% HSA is added, it moves to 90-10 modeling for the human physiological situation.

Animals↗
PubMed2000

Structure-activity relationship of alkyl camptothecin esters.

The cytotoxicity of camptothecin (CPT) esters 1-6 was measured. Like parental camptothecin, esters 2 and 3, but not 1, 4, 5, and 6, inhibited proliferation of human leukemia cells in culture and induced programmed cell death as assessed by flow cytometry studies. Exhibition of similar levels of antiproliferative activities of CPT 2 and 3 required different incubation time periods in cell cultures, with CPT and 3 requiring the shortest and longest periods, respectively. Both 2 and 3 were inactive against cells resistant to the semisynthetic CPT derivative 9-nitrocamptothecin and unable to stabilize DNA-topoisomerase I (Topo I) "cleavable complexes" in a cell-free system, suggesting that Topo I activity was required but insufficient for the mechanism of action of 2 and 3. Mouse liver homogenate converted esters to parental CPT, but the conversion rates were different with different esters. Of four tested esters in this experiment, ester 2 had the fastest conversion rate. In vivo studies showed that ester 2 had an exceptional lack of toxicity in nude mice, even at enormous doses, and demonstrated extensive activity against human breast and colon tumors grown as xenografts in immunodeficient nude mice, whereas no antitumor activity was observed for the other esters. In conclusion, ester 2 is a prodrug of the antitumor compound CPT, and it can be administered at very high doses in mice with no appearance of toxicity. This study provides a basis for further evaluation of CPT ester 2 as an investigational anticancer agent.

Animals↗
PubMed2000

[Low prevalence of autoimmune antiphospholipid antibodies in hepatic diseases].

Antiphospholipid antibodies (aPL) have been associated with different diseases. They are defined as a large family of immunoglobulins (Ig) of either alloantibodies or autoantibodies. The autoimmune antibodies are associated with venous and/or arterial thrombosis, thrombocytopenia and recurrent fetal loss in the so-called antiphospholipid syndrome or in systemic lupus erythematosus. These antibodies are directed against proteins or phospholipid-protein complexes. On the contrary, antiphospholipid antibodies (alloantibodies) which are found in infectious diseases sera (syphilis, HIV, and other viral diseases), disappear with illness remission and are directed to phospholipids alone (particularly cardiolipin) and are not associated with thrombosis or recurrent fetal loss. However, the role and type of aPL found during hepatic diseases is still unclear. To investigate the prevalence of autoimmune aPL (IgG and IgM) during different hepatic diseases, we have studied 128 patients with hepatitis C virus, hepatitis B virus and hepatic autoimmune diseases without treatment as well as 40 healthy control subjects. We have used a specific ELISA kit, that uses a mixture of phospholipid instead of cardiolipin alone, and allows a better detection of aPL of the autoimmune type. Our results show that autoimmune aPL are not significantly increased in viral hepatic diseases (2%) or autoimmune diseases of the liver (3%) when compared to the control group (0%).

Antibodies, Antiphospholipid↗
PubMed1999

On the "Rebound" Mechanism of Alkane Hydroxylation by Cytochrome P450: Electronic Structure of the Intermediate and the Electron Transfer Character in the Rebound Step.

Two electromeric forms, a and b (a is the ground state in a solvent) exist for the hydroxo-iron complex 1, an intermediate in the rebound mechanism of alkane hydroxylation by cytochrome P450. Results of density functional and model solvent calculations of various species are in agreement with experimental findings, and imply the role of 1 a in the rebound mechanism.

Journal Article↗
PubMed1999

Effect of conductive hearing loss on the vestibulo-collic reflex.

The vestibulo-collic reflex represents a promising test for evaluating the integrity of otolith function. We have investigated the threshold of this response in a group of normal subjects, and the effect of a conductive hearing loss. A positive response was recorded in 31 of 32 normal subjects. The threshold of the vestibulo-collic reflex varied from 80 to 97 dBHL in these subjects with a 95% response rate at a threshold at 96 dBHL. A total of 23 ears with a conductive hearing loss in 17 patients were also investigated. The average conductive hearing loss (at 0.5, 1, 2 and 4 kHz) ranged from 8.75 to 40 dBHL (average 24.46 dBHL). A positive response was recorded in only two ears. Therefore, the vestibulo-collic reflex has a high stimulus threshold which is dependant on reliable transmission of the click stimulus to the inner ear thus limiting is clinical use.

Adult↗
PubMed1999

An exploration of the sequence of a 2.9-Mb region of the genome of Drosophila melanogaster: the Adh region.

A contiguous sequence of nearly 3 Mb from the genome of Drosophila melanogaster has been sequenced from a series of overlapping P1 and BAC clones. This region covers 69 chromosome polytene bands on chromosome arm 2L, including the genetically well-characterized "Adh region." A computational analysis of the sequence predicts 218 protein-coding genes, 11 tRNAs, and 17 transposable element sequences. At least 38 of the protein-coding genes are arranged in clusters of from 2 to 6 closely related genes, suggesting extensive tandem duplication. The gene density is one protein-coding gene every 13 kb; the transposable element density is one element every 171 kb. Of 73 genes in this region identified by genetic analysis, 49 have been located on the sequence; P-element insertions have been mapped to 43 genes. Ninety-five (44%) of the known and predicted genes match a Drosophila EST, and 144 (66%) have clear similarities to proteins in other organisms. Genes known to have mutant phenotypes are more likely to be represented in cDNA libraries, and far more likely to have products similar to proteins of other organisms, than are genes with no known mutant phenotype. Over 650 chromosome aberration breakpoints map to this chromosome region, and their nonrandom distribution on the genetic map reflects variation in gene spacing on the DNA. This is the first large-scale analysis of the genome of D. melanogaster at the sequence level. In addition to the direct results obtained, this analysis has allowed us to develop and test methods that will be needed to interpret the complete sequence of the genome of this species. Before beginning a Hunt, it is wise to ask someone what you are looking for before you begin looking for it. Milne 1926

Alcohol Dehydrogenase↗
PubMed1999

A phase II clinical and pharmacological study of oral 9-nitrocamptothecin in patients with refractory epithelial ovarian, tubal or peritoneal cancer.

9-Nitrocamptothecin (9-NC) is a water-insoluble topoisomerase I inhibitor with a broad antitumor activity in animal models. A phase II study was performed in patients with heavily refractory ovarian, tubal or peritoneal cancer (median number of previous chemotherapy regimens > 3) to determine the activity of a daily oral dose of 9-NC. 9-NC dose was 1.5 mg/m2/day for four consecutive days every week. Increments of 0.25 mg/day were authorized in patients without significant side effects. Of 29 evaluable patients, a 7% remission rate was observed. Thirty-four percent of patients had stable disease. The median survival was 8 months. Toxicity was evaluated in 31 patients. Grade 3 or 4 hematologic toxicity consisted of anemia in 10 patients (32%), neutropenia in eight (26%) and thrombocytopenia in three (10%). Grade > or = 2 non-hematologic toxic effects were nausea and vomiting in 26 (84%), diarrhea in 12 (39%), weight loss in seven (22%), chemical cystitis in six (19%) and neutropenic sepsis in six (19%). 9-NC was tolerated for sustained periods of time in some patients (up to 47 weeks). The observed 8-month survival in such a refractory patient population is noteworthy. Further clinical research of prolonged exposure to less toxic analogs of 9-NC is warranted.

Administration, Oral↗
PubMed1999

Clinical presentation, course, and prognostic factors in lymphocyte-predominant Hodgkin's disease and lymphocyte-rich classical Hodgkin's disease: report from the European Task Force on Lymphoma Project on Lymphocyte-Predominant Hodgkin's Disease.

PURPOSE: Recent studies have suggested that lymphocyte-predominant Hodgkin's disease (LPHD) is both clinically and pathologically distinct from other forms of Hodgkin's disease, including classical Hodgkin's disease (CHD). However, large-scale clinical studies were lacking. This multicenter, retrospective study investigated the clinical characteristics and course of LPHD patients and lymphocyte-rich classical Hodgkin's disease (LRCHD) patients classified according to morphologic and immunophenotypic criteria. MATERIALS AND METHODS: Clinical data and biopsy material of all available cases initially submitted as LPHD were collected from 17 European and American centers, stained, and reclassified by expert pathologists. RESULTS: The 426 assessable cases were reclassified as LPHD (51%), LRCHD (27%), CHD (5%), non-Hodgkin's lymphoma (3%), and reactive lesion (3%); 11% of cases were not assessable. Patients with LPHD and LRCHD were predominantly male, with early-stage disease and few risk factors. Patients with LRCHD were significantly older. Survival and failure-free survival rates with adequate therapy were similar for patients with LPHD and LRCHD, and were stage-dependent and not significantly better than stage-comparable results for CHD (German trial data). Twenty-seven percent of relapsing LPHD patients had multiple relapses, which is significantly more than the 5% of relapsing LRCHD patients who had multiple relapses. Lymphocyte-predominant Hodgkin's disease patients had significantly superior survival after relapse compared with LRCHD or CHD patients; however, this was partly due to the younger average age of LPHD patients. CONCLUSION: The two subgroups of LPHD and LRCHD bore a close clinical resemblance that was distinct from CHD; the course was similar to that of comparable nodular sclerosis and mixed cellularity patients. Thorough staging is necessary to detect advanced disease in LPHD and LRCHD patients. The question of how to treat such patients, either by reducing treatment intensity or following a "watch and wait" approach, remains unanswered.

Adult↗
PubMed1998

Lipid interactions with human antiphospholipid antibody, beta 2-glycoprotein 1, and normal human IgG using the fluorescent probes NBD-PE and DPH.

Recurrent venous thrombosis, arterial thrombosis and pregnancy losses are clinical manifestation associated with antiphospholipid antibody (aPL) that recognizes negatively charged phospholipid antigens. Enzyme-linked immunosorbent assays (ELISA) are generally used to determine the presence and specificity of aPL. In this paper, a fluorescence spectroscopy method has been applied, through monitoring the alteration of fluorescence intensity and anisotropy of a fluorophore that was incorporated in liposomes to explore the changes of molecular structure or configuration elicited by the binding aPL with phospholipid antigens. The bilayer surface was markedly ordered by aPL binding as indicated by the surface-sensitive probe NBD-PE. The binding of aPL on the bilayer surface is saturable. The saturation concentration of aPL is 40% (w/w, aPL/lipid) for cardiolipin membranes. The binding of aPL on cardiolipin took place in the absence of beta 2-GP1. The addition of beta 2-GP1 further increased the anisotropy and decreased the intensity of fluorescence. The binding of aPL is predominantly attributed to electrostatic interaction, but the configuration of the acyl chains of phospholipid also plays a role. It is found that the thermal history is important for aPL binding. The incubation at 37 degrees C is more favorable for aPL binding than ambient temperature. Normal human serine (IgG-NHS) did not elicit any distinct change of NBD-PE fluorescence, which indicates it does not interact with the lipid.

Animals↗