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R J Howard

Publications and source records attributed to R J Howard.

At least 19 recordsLinked to original sources
PubMed2001

Ring-closing metathesis of olefinic peptides: design, synthesis, and structural characterization of macrocyclic helical peptides.

Heptapeptides containing residues with terminal olefin-derivatized side chains (3 and 4) have been treated with ruthenium alkylidene 1 and undergone facile ring-closing olefin metathesis (RCM) to give 21- and 23-membered macrocyclic peptides (5 and 6). The primary structures of peptides 3 and 4 were based upon a previously studied heptapeptide (2), which was shown to adopt a predominantly 3(10)-helical conformation in CDCl(3) solution and an alpha-helical conformation in the solid state. Circular dichroism, IR, and solution-phase (1)H NMR studies strongly suggested that acyclic precursors 3 and 4 and the fully saturated macrocyclic products 7 and 8 also adopted helical conformations in apolar organic solvents. Single-crystal X-ray diffraction of cyclic peptide 8 showed it to exist as a right-handed 3(10)-helix up to the fifth residue. Solution-phase NMR structures of both acyclic peptide 4 and cyclic peptide 8 in CD(2)Cl(2) indicated that the acyclic diene assumes a loosely 3(10)-helical conformation, which is considerably rigidified upon macrocyclization. The relative ease of introducing carbon-carbon bonds into peptide secondary structures by RCM and the predicted metabolic stability of these bonds renders olefin metathesis an exceptional methodology for the synthesis of rigidified peptide architectures.

Alkenes↗
PubMed2001

Tomato Ve disease resistance genes encode cell surface-like receptors.

In tomato, Ve is implicated in race-specific resistance to infection by Verticillium species causing crop disease. Characterization of the Ve locus involved positional cloning and isolation of two closely linked inverted genes. Expression of individual Ve genes in susceptible potato plants conferred resistance to an aggressive race 1 isolate of Verticillium albo-atrum. The deduced primary structure of Ve1 and Ve2 included a hydrophobic N-terminal signal peptide, leucine-rich repeats containing 28 or 35 potential glycosylation sites, a hydrophobic membrane-spanning domain, and a C-terminal domain with the mammalian E/DXXXLphi or YXXphi endocytosis signals (phi is an amino acid with a hydrophobic side chain). A leucine zipper-like sequence occurs in the hydrophobic N-terminal signal peptide of Ve1 and a Pro-Glu-Ser-Thr (PEST)-like sequence resides in the C-terminal domain of Ve2. These structures suggest that the Ve genes encode a class of cell-surface glycoproteins with receptor-mediated endocytosis-like signals and leucine zipper or PEST sequences.

Amino Acid Sequence↗
PubMed2001

Outcome of kidney transplants in patients known to be flow cytometry crossmatch positive.

BACKGROUND: The clinical significance of the flow cytometry crossmatch has been addressed in several retrospective studies, but the results have been controversial. There are no prospective studies in which patients known to be antibody positive underwent transplantation. METHODS: The flow cytometry crossmatch was performed prospectively in 1130 renal transplant recipients. A decision to perform transplantation was based on whether the positive results were on T or B cells, in the current or peak specimen, and taking into account the presence or absence of other immunological risk factors. One hundred antibody-positive patients received a transplant. Graft survival and rejection episodes were analyzed in this group and compared with 100 crossmatch-negative patients matched for age, sex, race, and time of transplantation. RESULTS: The incidence of rejection at 1 month was higher in antibody-positive patients (26%) than in antibody-negative patients (12%, P<0.01). Early rejection seemed to be more frequent in antibody-positive patients regardless of whether the antibodies were current or historic, or against T or B cells. There were more steroid-resistant rejections in antibody-positive than in antibody-negative patients. However, biopsy specimens showed that vascular lesions that can be associated with humoral rejection were not more frequent in the antibody-positive patients than in the controls. There were no differences in graft survival between the two groups. CONCLUSIONS: Low-level preformed alloantibodies detected by flow cytometry represent a risk of rejection even for patients purposely selected for having no additional immunological risk factors. The risk seems to be due to donor-specific memory rather than to a direct effect of the antibodies. The results indicate that flow cytometry provides useful information to assess donor-recipient compatibility.

B-Lymphocytes↗
PubMed2001

Cytology of fungal pathogens and plant-host interactions.

Imaging plays a unique role in fungal cell biology and phytopathology by allowing for the documentation of molecular structure in individual fixed and living cells. Advances in fluorescence laser techniques, including confocal and multiphoton microscopy, are opening new avenues for cellular exploration. These techniques hold tremendous potential for studies of host-pathogen interactions including the use of genetically encoded markers such as green fluorescent protein, in situ hybridization and fluorescence resonance energy transfer.

Fungi↗
PubMed2001

Randomized study of vaginal misoprostol (PGE(1)) and dinoprostone gel (PGE(2)) for induction of labor at term.

OBJECTIVES: To investigate the efficacy and safety of misoprostol in the induction of labor at term by comparing this agent with the commonly used dinoprostone gel. PATIENTS AND METHODS: A randomized clinical trial of vaginal misoprostol, 50 microg 6-hourly, and dinoprostone gel, 1-2 mg 6-hourly, in 435 women undergoing induction of labor at term. The women, 210 in the misoprostol group and 225 in the dinoprostone group, were compared to determine whether there was a significant difference in achieving vaginal delivery within 24 h, the incidence of hyperstimulation syndrome, Cesarean section rate and adverse neonatal outcome. They were also offered the option of preinduction sonographic cervical assessment. RESULTS: Misoprostol, compared to dinoprostone gel, was associated with a significantly shorter median induction-to-delivery interval (14.6 h vs. 19.0 h; P = 0.0014), a higher incidence of vaginal delivery within 24 h of induction (65.7% vs. 54.2%; P = 0.019) and a reduced need for oxytocin augmentation during labor (20.5% vs. 29.8%; P = 0.034). The groups did not differ significantly in the rates of Cesarean section (18.1% vs. 19.1%; P = 0.88) and hyperstimulation syndrome (2.4% vs. 0.9%; P = 0.27). None of the cases of hyperstimulation required treatment with tocolysis. All nine cases of excessive uterine contractility occurred after the first dose of the drug. There were no significant differences in maternal and neonatal morbidity between the two groups. There was a significant association between preinduction cervical length and the induction-to-delivery interval in both those receiving misoprostol and those treated with dinoprostone. CONCLUSIONS: The use of misoprostol is associated with a shorter duration of labor and a higher rate of vaginal delivery within 24 h from induction without an increase in maternal and neonatal morbidity. Transvaginal sonographic measurement of cervical length is useful in the prediction of the likelihood of vaginal delivery within 24 h of induction and of the induction-to-delivery interval and may be useful in the stratification of patients participating in randomized studies that examine the effectiveness of inducing agents.

Administration, Intravaginal↗
PubMed2001

What happens to renal transplant recipients who lose their grafts?

Little attention has been given to the fate of patients who lose their grafts. We reviewed outcomes of 438 recipients of first renal allografts who underwent transplantation at our institution between January 1, 1988, and December 31, 1997, and lost their grafts or died with a functioning transplant. Of the 438 patients, 168 patients died with a functioning transplant. The most common causes of death were cardiac disease, infection, and cancer. Patients who died with a functioning graft were older (>49 years, 64.3%) than patients who died after returning to dialysis therapy or who are still alive (>49 years, 25.9%). Eighty-six patients (39%) who returned to dialysis therapy were again placed on a cadaveric waiting list. Only 44 patients received a second transplant, of which 30 transplants (68.2%) are still functioning. Our study shows that relatively few patients who lose kidney transplants are returned to the cadaveric waiting list and even fewer undergo retransplantation.

Adolescent↗
PubMed2001

Graft survival in pediatric liver transplantation.

BACKGROUND/PURPOSE: Liver transplantation is standard therapy for children with a variety of liver diseases. The current shortage of organ donors has led to aggressive use of reduced or split grafts and living-related donors to provide timely liver transplants to these children. The purpose of this study is to examine the impact of these techniques on graft survival in children currently treated with liver transplantation. METHODS: Data were obtained on all patients less than 21 years of age treated with isolated liver transplants performed after January 1, 1996 in an integrated statewide pediatric liver transplant program, which encompasses 2 high-volume centers. Nonparametric tests of association and life table analysis were used to analyze these data (SAS v 6.12). RESULTS: One hundred twenty-three children received 147 grafts (62 at the University of Florida, 85 at the University of Miami). Fifty-two (36%) children were less than 1 year of age at time of transplant, and 80 (55%) were less than 2 years of age. Patient survival rate was identical in the 2 centers (1-year actuarial survival rate, 88.4% and 87.1%). Twenty-five (17%) grafts were reduced, 28 (19%) were split, 6 were from living donors (4%), and 88 (60%) were whole organs. One-year graft survival rate was 80% for whole grafts, 71.6% for reduced grafts, and 64.3% for split grafts (P =.06). Children who received whole organs (mean age, 6.1 years) were older than those who received segmental grafts (mean age, 2.5 years; P <.01). Multifactorial analysis suggested that patient age, gender, and use of the graft for retransplant did not influence graft survival, nor did the type of graft used influence patient survival. CONCLUSIONS: The survival rate of children after liver transplantation is excellent independent of graft type. Use of current techniques to split grafts between 2 recipients is associated with an increased graft loss and need for retransplantation. Improvement in graft survival of these organs could reduce the morbidity and cost of liver transplantation significantly in children.

Age Distribution↗
PubMed2001

Detection of aster yellows phytoplasma in false flax based on PCR and RFLP.

False flax (Camelina sativa L.) plants were found to be infected with a yellows-type disease caused by a phytoplasma in experimental plots at the Edmonton Research station. Alberta, Canada. Typical phytoplasmas were detected in the phloem cells in ultrathin sections from leaf midrib tissues examined by electron microscopy. These observations were supported by polymerase chain reaction (PCR) using two primer pairs, R16 F2n/R2 and R16(1)F1/R1, derived from phytoplasma rDNA sequences. Aster yellows (AY) and potato witches'-broom (PWB) phytoplasma DNA samples served as controls and were used to study group relatedness. In a direct PCR assay, DNA amplification with universal primer pair R16F2n/R2 gave the expected PCR products of 1.2 kb. Based on a nested-PCR assay using the latter PCR products as templates, and a specific primer pair, R16(1)F1/R1, designed on the basis of AY phytoplasma rDNA sequences, a PCR product of 1.1 kb was obtained from each phytoplasma-infected false flax and AY sample, but not from PWB phytoplasma and healthy controls. DNA amplification with specific primer pair R16(1)F1/R1 and restriction fragment length polymorphism indicated the presence of AY phytoplasma in the infected false flax sample. This is the first reported characterization of AY phytoplasma in false flax.

Acholeplasmataceae↗
PubMed2001

Liver transplantation for hepatocellular carcinoma.

OBJECTIVE: To analyze patient and tumor characteristics that influence patient survival to select patients who would most benefit from liver transplantation. SUMMARY BACKGROUND DATA: The selection of patients with hepatocellular carcinoma (HCC) for liver transplantation remains controversial. METHODS: One hundred twelve patients with nonfibrolamellar HCC who underwent a liver transplant from 1985 to 2000 were reviewed. Survival was calculated using the Kaplan-Meier method, with differences in outcome assessed using the log-rank procedure. Multivariate analysis was then performed using a Cox regression model. RESULTS: Overall patient survival rates were 78%, 63%, and 57% at 1, 3, and 5 years, respectively. Patients infected with the hepatitis B virus had a worse 5-year survival than those who were not (43% vs. 64%), with most deaths being attributed to recurrent hepatitis B. However, patients with hepatitis B virus who underwent more recent transplants using antiviral therapy fared as well as those who were negative for the virus, showing a 5-year survival rate of 77%. Patients with vascular invasion by tumor had a worse 5-year survival than patients without vascular invasion (33% vs. 68%). Vascular invasion, tumor size greater than 5 cm, and poorly differentiated tumor grade were predictors of tumor recurrence by univariate analysis; however, only vascular invasion remained significant on multivariate analysis: the rate of tumor recurrence at 5 years was 65% in patients with vascular invasion and only 4% for patients without vascular invasion. CONCLUSIONS: For well-selected patients with HCC, liver transplantation in the current era can achieve equivalent results to transplantation for nonmalignant indications. Vascular invasion is an indicator of high risk of tumor recurrence but is difficult to detect before transplantation.

Adolescent↗
PubMed2001

Cognitive neuropsychiatric models of persecutory delusions.

OBJECTIVE: The major cognitive theories of persecutory delusion formation and maintenance are critically examined in this article. METHOD: The authors present a comprehensive review of the literature, citing results of relevant functional neuroimaging and neural network studies. RESULTS: People with persecutory delusions selectively attend to threatening information, jump to conclusions on the basis of insufficient information, attribute negative events to external personal causes, and have difficulty in envisaging others' intentions, motivations, or states of mind. Presence of the "reality distortion" cluster of psychotic symptoms correlates with cerebral blood flow in the left lateral prefrontal cortex, ventral striatum, superior temporal gyrus, and parahippocampal region. Social cognitive processing (selective attention to threat, attribution of causation or mental states) in normal subjects involves similar areas. Neural network models of persecutory delusions highlight the importance of disordered neuromodulation in their formation and of disordered neuroplasticity in their maintenance. CONCLUSIONS: Further studies examining the interaction of these cognitive processes, cross-sectionally and longitudinally, at cognitive psychological, neural network, and functional neuroanatomical levels are warranted to establish a comprehensive cognitive neuropsychiatric model of the persecutory delusion.

Attention↗
PubMed2001

Increased first-contact rates for very-late-onset schizophrenia-like psychosis in African- and Caribbean-born elders.

BACKGROUND: Studies have consistently shown a higher incidence of schizophrenia with onset in early adult life in African and Caribbean migrants to the UK. AIMS: To establish the incidence (first-contact rates) of very-late-onset (>60 years) schizophrenia-like psychosis (SLP) in south London and to test the hypothesis that this is higher among African- and Caribbean-born than indigenous elders. METHOD: We identified all new referrals of SLP to the Maudsley Hospital between 1995 and 2000. Demographic details, including age, ethnicity and electoral ward (address), were obtained from case notes. Incidence was estimated using 1997 census data to determine the denominator population for each ethnic group. RESULTS: The incidence of SLP was significantly higher in African- and Caribbean-born than indigenous elders: 172.4 per 100,000 population (95% CI=57.9--286.8) in African- and Caribbean-born males and 323.5 per 100,000 population (95% CI 167.8--479.1) in African- and Caribbean-born females. Rates also were increased in elders from other immigrant groups, but the numbers involved were too small to reach accepted levels of significance. CONCLUSIONS: Large-scale epidemiological studies are needed to determine both the incidence of and the coexistent risk factors for SLP among all elderly migrants, who may constitute a group with high service needs.

Africa↗
PubMed2001

Resection of the inferior vena cava for hepatic malignancy.

Involvement of the inferior vena cava (IVC) by hepatic tumors, although uncommon, is considered to be unresectable by standard surgical techniques. Recent advances in hepatic surgery have made combined hepatic and vena caval resection possible. The purpose of this study is to describe the surgical techniques and early results of combined resection of the liver and IVC. From 1997 to 2000, 11 patients underwent resection of the IVC along with four to seven liver segments. Resections were carried out for hepatocellular carcinoma (four); colorectal metastases (four); and hepatoblastoma, gastrointestinal stromal tumor metastases, and squamous cell carcinoma in one patient each. Ex vivo procedures were performed twice, and total vascular isolation was used in the nine other cases. The IVC was reconstructed with ringed Gore-Tex tube graft (five), primarily (five), or with Gore-Tex patches (one). There were two early deaths: one from liver failure at 3 weeks and one from sepsis secondary to a perforated segment of small bowel 4 months postresection. One patient with a gastrointestinal stromal tumor died at 32 months of recurrent tumor and one patient with hepatocellular carcinoma is alive with recurrent tumor at 16 months. The remaining patients are alive and disease free with follow-up ranging from 3 to 40 months without evidence of IVC occlusion. Combined resection of the liver and IVC is a formidable undertaking with substantial surgical risk. However, this aggressive surgical approach offers a chance for cure in patients with tumors involving the IVC that would otherwise have a dismal prognosis.

Adolescent↗
PubMed2000

Reconstitution of higher plant chloroplast chaperonin 60 tetradecamers active in protein folding.

Unlike the GroEL homologs of eubacteria and mitochondria, oligomer preparations of the higher plant chloroplast chaperonin 60 (cpn60) consist of roughly equal amounts of two divergent subunits, alpha and beta. The functional significance of these isoforms, their structural organization into tetradecamers, and their interactions with the unique binary chloroplast chaperonin 10 (cpn10) have not been elucidated. Toward this goal, we have cloned the alpha and beta subunits of the ch-cpn60 of pea (Pisum sativum), expressed them individually in Escherichia coli, and subjected the purified monomers to in vitro reconstitution experiments. In the absence of other factors, neither subunit (alone or in combination) spontaneously assembles into a higher order structure. However, in the presence of MgATP, the beta subunits form tetradecamers in a cooperative reaction that is potentiated by cpn10. In contrast, alpha subunits only assemble in the presence of beta subunits. Although beta and alpha/beta 14-mers are indistinguishable by electron microscopy and can both assist protein folding, their specificities for cpn10 are entirely different. Similar to the authentic chloroplast protein, the reconstituted alpha/beta 14-mers are functionally compatible with bacterial, mitochondrial, and chloroplast cpn10. In contrast, the folding reaction mediated by the reconstituted beta 14-mers is only efficient with mitochondrial cpn10. The ability to reconstitute two types of functional oligomer in vitro provides a unique tool, which will allow us to investigate the mechanism of this unusual chaperonin system.

Adenosine Triphosphate↗
PubMed2000

Cortical activity during rotational and linear transformations.

Neuroimaging studies of cortical activation during image transformation tasks have shown that mental rotation may rely on similar brain regions as those underlying visual perceptual mechanisms. The V5 complex, which is specialised for visual motion, is one region that has been implicated. We used functional magnetic resonance imaging (fMRI) to investigate rotational and linear transformation of stimuli. Areas of significant brain activation were identified for each of the primary mental transformation tasks in contrast to its own perceptual reference task which was cognitively matched in all respects except for the variable of interest. Analysis of group data for perception of rotational and linear motion showed activation in areas corresponding to V5 as defined in earlier studies. Both rotational and linear mental transformations activated Brodman Area (BA) 19 but did not activate V5. An area within the inferior temporal gyrus, representing an inferior satellite area of V5, was activated by both the rotational perception and rotational transformation tasks, but showed no activation in response to linear motion perception or transformation. The findings demonstrate the extent to which neural substrates for image transformation and perception overlap and are distinct as well as revealing functional specialisation within perception and transformation processing systems.

Adult↗
PubMed2000

Imaging attentional and attributional bias: an fMRI approach to the paranoid delusion.

BACKGROUND: The pathophysiology of auditory hallucinations and delusions of control has been elucidated using functional imaging. Despite their clinical importance, there have been few similar attempts to investigate paranoid delusions. We have examined two components of social cognition (attentional and attributional biases) that contribute to the formation and maintenance of paranoid delusions, using functional magnetic resonance imaging (fMRI). METHOD: Normal subjects performed tasks requiring attentional and attributional judgements. We investigated the neural response particularly associated with attention to threatening material relevant to self and with the 'self-serving' attributional bias. RESULTS: The determination of relevance to self of verbal statements of differing emotional valence involved left ventrolateral prefrontal cortex (left inferior frontal gyrus, BA 47), right caudate and right cingulate gyrus (BA 24). Attention to threatening material relevant to self differentially activated a more dorsal region of the left inferior frontal gyrus (BA 44). Internal attributions of events, where the self was viewed as an active intentional agent, involved left precentral gyrus (BA 6) and left middle temporal gyrus (BA 39). Attribution of events in a non 'self-serving' manner required activation of the left precentral gyrus (BA 6). CONCLUSIONS: Anomalous activity or connectivity within these defined regions may account for the attentional or attributional biases subserving paranoid delusion formation. This provides a simple model for paranoid delusion formation that can be tested in patients.

Adult↗
PubMed2000

Infusion of donor spleen cells and rejection in liver transplant recipients.

Intact or inactivated donor lymphoid cells have been found to downregulate the alloimmune response in a number of experimental models. We conducted a randomized, prospective, double blind, and placebo-controlled trial to determine whether heat-treated donor spleen cells would affect early rejection after liver transplantation. Donor spleen was obtained during organ procurement for 40 patients undergoing liver transplantation. All patients were treated with cyclosporine, azathioprine and steroids. The patients were randomized after surgery to receive either heat-treated (45 degrees C for 1 h) spleen cells or placebo. Patients underwent protocol biopsies at 1 wk, 4 and 12 months, or as needed. Biopsies were reviewed in a blind fashion and scored according to the Banff consensus criteria. Randomization resulted in 19 patients in the spleen cell group and 21 in the placebo group. One-yr graft survival was 94 and 100%, respectively. Early rejection was more frequent in the spleen cell group (61 vs. 35%, p, not significant). The histopathological rejection activity index at 7 d was also higher for the patients in the spleen cell group: 39% of spleen cell treated patients had a score of 4 or higher as opposed to 5% in the placebo group (p < 0.01). The mean score was 2.9 +/- 2.8 for the spleen cell group versus 1.3 + 1.7 for the placebo group (p = 0.034). It is concluded that heat-treated donor spleen cells given within 24 h after liver transplantation were not clinically beneficial and increased the intensity of rejection in 7-d protocol liver biopsies.

Cell Transplantation↗
PubMed2000

Visual hallucinatory syndromes and the anatomy of the visual brain.

We have set out to identify phenomenological correlates of cerebral functional architecture within Charles Bonnet syndrome (CBS) hallucinations by looking for associations between specific hallucination categories. Thirty-four CBS patients were examined with a structured interview/questionnaire to establish the presence of 28 different pathological visual experiences. Associations between categories of pathological experience were investigated by an exploratory factor analysis. Twelve of the pathological experiences partitioned into three segregated syndromic clusters. The first cluster consisted of hallucinations of extended landscape scenes and small figures in costumes with hats; the second, hallucinations of grotesque, disembodied and distorted faces with prominent eyes and teeth; and the third, visual perseveration and delayed palinopsia. The three visual psycho-syndromes mirror the segregation of hierarchical visual pathways into streams and suggest a novel theoretical framework for future research into the pathophysiology of neuropsychiatric syndromes.

Aged↗