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D Lambert

Publications and source records attributed to D Lambert.

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

Functional involvement of G8 in the hairpin ribozyme cleavage mechanism.

The catalytic determinants for the cleavage and ligation reactions mediated by the hairpin ribozyme are integral to the polyribonucleotide chain. We describe experiments that place G8, a critical guanosine, at the active site, and point to an essential role in catalysis. Cross-linking and modeling show that formation of a catalytic complex is accompanied by a conformational change in which N1 and O6 of G8 become closely apposed to the scissile phosphodiester. UV cross-linking, hydroxyl-radical footprinting and native gel electrophoresis indicate that G8 variants inhibit the reaction at a step following domain association, and that the tertiary structure of the inactive complex is not measurably altered. Rate-pH profiles and fluorescence spectroscopy show that protonation at the N1 position of G8 is required for catalysis, and that modification of O6 can inhibit the reaction. Kinetic solvent isotope analysis suggests that two protons are transferred during the rate-limiting step, consistent with rate-limiting cleavage chemistry involving concerted deprotonation of the attacking 2'-OH and protonation of the 5'-O leaving group. We propose mechanistic models that are consistent with these data, including some that invoke a novel keto-enol tautomerization.

Base Sequence↗
PubMed2001

The hairpin ribozyme substrate binding-domain: a highly constrained D-shaped conformation.

The two domains of the hairpin ribozyme-substrate complex, usually depicted as straight structural elements, must interact with one another in order to form an active conformation. Little is known about the internal geometry of the individual domains in an active docked complex. Using various crosslinking and structural approaches in conjunction with molecular modeling (constraint-satisfaction program MC-SYM), we have investigated the conformation of the substrate-binding domain in the context of the active docked ribozyme-substrate complex. The model generated by MC-SYM showed that the domain is not straight but adopts a bent conformation (D-shaped) in the docked state of the ribozyme, indicating that the two helices bounding the internal loop are closer than was previously assumed. This arrangement rationalizes the observed ability of hairpin ribozymes with a circularized substrate-binding strand to cleave a circular substrate, and provides essential information concerning the organization of the substrate in the active conformation. The internal geometry of the substrate-binding strand places G8 of the substrate-binding strand near the cleavage site, which has allowed us to predict the crucial role played by this nucleotide in the reaction chemistry.

Base Sequence↗
PubMed2001

Detection of moderate hyperhomocysteinemia: comparison of the Abbott fluorescence polarization immunoassay with the Bio-Rad and SBD-F high-performance liquid chromatographic assays.

The importance of accurate methods for homocysteine measurement has been emphasized. We compared the results obtained with the most commonly used high-performance liquid chromatography (HPLC) assay, and two recently commercially available methods: another HPLC and a fluorescence polarization immunoassay, in plasmas from normo- or hyperhomocysteinemic patients. A significant agreement between the different methods in classifying the results as hyper or normal-homocysteinemia was observed. However, a significant difference between the results was found. Standardization is urgently necessary to improve the concordance of homocysteine determination.

Chemistry, Clinical↗
PubMed2001

Leadzyme.

Explore the source record for details and available documents.

Base Sequence↗
PubMed2001

[Bullous cutaneous mastocytosis revealed by acute disease secondary to morphine administration].

UNLABELLED: Mastocytosis in children shows in three clinical forms. The rarest is the diffuse or bullous form. CASE REPORT: Since one month of age an infant showed a diffuse erythema and vesicle rash. At four months of age, serious discomfort after morphinic absorption led to the diagnosis of bullous cutaneous mastocytosis. Histologic examination confirmed this diagnosis. The clinical severity led to intravenous corticosteroid and antihistamine therapy. COMMENTS: Bullous cutaneous mastocytosis is unusual in children. However, it should be considered if there are any doubts because of its serious complications and iatrogenic therapeutic risks. Some serious cases require intravenous corticosteroid therapy. Appropriate care enables a normal development with a disappearance of the disease before the teenage years.

Acute Disease↗
PubMed2001

[Acute osteomyelitis. A rare erysipelas differential diagnosis].

INTRODUCTION: Acute haematogenous osteomyelitis, whose clinical features may mimic erysipelas, is an uncommon disease in adults. OBSERVATION: A 56 year-old man was hospitalized for a suspicion of leg erysipelas. Oral and intravenous antibiotic therapy was inefficient. Magnetic Resonance Imaging (MRI) of the leg revealed osteomyelitis with subperiosteal abscess. Change of antibiotics and surgical debridement improved the patient's condition. DISCUSSION: Erysipela is a common disease which most often responds to anti-streptococcal therapy. Unfavourable evolution under antibiotherapy must lead to consider necrotizing fasciitis but also acute osteomyelitis. In these cases MRI is necessary. In our observation, the leg pain which preceded other signs of local inflammation, suggested the existence of primitive bone infection which further diffused in soft tissues, thus explaining the erysipelatoid aspect.

Abscess↗
PubMed2000

A polymorphism (80G->A) in the reduced folate carrier gene and its associations with folate status and homocysteinemia.

5-methyltetrahydrofolate is the predominant form of folate in plasma. It may be the preferred substrate for transport via the reduced-folate carrier (RFC). We isolated a cDNA for the reduced folate carrier (RFC-1) from human skin fibroblasts. A common polymorphism at position 80 in exon 2 of RFC-1 was identified. This polymorphism changes a guanine (G) to an adenine (A), abolishing a CfoI restriction site. Using genomic DNA samples from 169 healthy subjects, we identified 27.1% GG homozygotes, 21.9% AA homozygotes, and 50.9% GA heterozygotes. We explored the impact of this polymorphism, separately and in combination with the 677C->T polymorphism in the methylenetetrahydrofolate reductase gene, on folate status and total homocysteine levels. We found a moderate, but significant, increase in total homocysteine levels in doubly homozygous 80GG/677TT subjects as compared to 80GG/677CC (P = 0.01) or 80GG/677CT (P = 0.04) subjects. In addition, individuals who were 80AA/677CT had higher plasma folate levels than those who were 80GG/677CT (P = 0.02).

Base Sequence↗
PubMed2000

ASW: a gene with conserved avian W-linkage and female specific expression in chick embryonic gonad.

Vertebrates exhibit a variety of sex determining mechanisms which fall broadly into two classes: environmental or genetic. In birds and mammals sex is determined by a genetic mechanism. In mammals males are the heterogametic sex (XY) with the Y chromosome acting as a dominant determiner of sex due to the action of the testis-determining factor, SRY. In birds females are the heterogametic sex (ZW); however, it is not known whether the W chromosome carries a dominant ovary-determining gene, or whether Z chromosome dosage determines sex. Using an experimental approach, which assumes only that the sex-determining event in birds is accompanied by sex-specific changes in gene expression, we have identified a novel gene, ASW (Avian Sex-specific W-linked). The putative protein for ASW is related to the HIT (histidine triad) family of proteins. ASW shows female-specific expression in genital ridges and maps to the chicken W chromosome. In addition, we show that, with the exception of ratites, ASW is linked to the W chromosome in each of 17 bird species from nine different families of the class Aves.

Amino Acid Sequence↗
PubMed2000

Homocysteine, vitamins B6, B12, folate, and risk of coronary artery disease in patients undergoing diagnostic coronary angiography.

Homocysteine and vitamins B were correlated with coronary artery disease in patients undergoing diagnostic coronary angiography. 160 patients having > or =1 stenosis (G1), 55 patients having normal coronary arteries (G2) and 171 healthy volunteers (G3) were prospectively recruited. Homocysteine levels were significantly higher in patients, particularly in those with normal coronary angiograms, than in healthy subjects (13.8 +/-6.3 micromol/L in G1 (p < 0.0001) and 15.2 +/- 8.8 micromol/L in G2 (p < 0.0001) versus 10.1 +/- 3.1 micromol/L in G3). Homocysteine levels were not related to the extent of coronary artery disease. In patients with normal angiogram, vitamin B12 and folate levels were significantly higher compared with the other groups (p < 0.05 and p < 0.001, respectively) showing that vitamin B deficiency was not involved in the hyperhomocysteinemia. In conclusion, homocysteine and vitamins B levels do not contribute to discriminate for the presence of coronary artery disease in patients undergoing diagnostic coronary angiography. Homocysteine levels, however, were higher in patients referred for coronary angiography than in healthy controls.

Aged↗
PubMed2000

Radiotherapy of advanced mycosis fungoides: indications and results of total skin electron beam and photon beam irradiation.

BACKGROUND: The goals of this retrospective study of advanced mycosis fungoides are (1) to describe the indications of a combination of total skin electron beam and photon beam irradiation and (2) to analyze the results of total body or segmental photon irradiation for patients with extension beyond the skin. METHODS: From January 1975 to December 1995, 45 patients with pathologically-confirmed mycosis fungoides or Sézary syndrome received a combination of TSEB and photon beam irradiation for advanced disease: 34 males and 11 females, mean age 61 years (range 27-87 years). The mean follow-up was 111 months (range 18-244 months, median 85 months). Whole-skin irradiation treatment to a depth of 3-5 mm with a 6-MeV electron beam was produced by a linear accelerator to a total dose of 24-30 Gy in 8-15 fractions, 3-4 times a week. In cases of thick plaques or tumors that were beyond the scope of low energy electron beams or for treating nodal areas (especially in the head and neck area or axilla involvement), regional irradiation (RRT) with Co-60 photon beams was followed by whole-skin electron beam irradiation (15 patients). In cases of diffuse erythrodermia, Sézary syndrome, nodal or visceral involvement, total body irradiation was delivered with a 25-MV photon beam using a split-course regimen to prevent hematological toxicity (22 patients). The first course consisted of 1.25 Gy delivered in ten fractions and 10 days. Subsequently, patients received TSEB. Four to 6 weeks after TSEB, they received a second course of 1.25 Gy. The cumulative TBI dose ranged from 2.5 to 3 Gy in about 3 months. Hemi-body irradiation (HB) with Co-60 (and a bolus) was given in cases of multiple regional tumors with large and thick infiltration of the skin to a dose of 9-12 Gy (using fractions of 1-1.5 Gy/day) which, once flattened, were boosted with whole-skin electron beam therapy (8 patients). RESULTS: At 3 months, the overall response rate was 75% with 23/45 (51%) patients in complete response and 24% in partial response; one patient had stable lesions and 1 patient presented progressive disease. The overall response rate was 81% for T3 patients, 61% for T4, 79% for N1 and 70% for N3. The complete response rate was 67% for T3 and 28% for T4. Sixty-four percent of N1 patients and 41% of N3 had a complete response. The 5-year actuarial overall survival was 37% for T3 and 44% for T4 (P = 0.84). Patients with clinically abnormal lymph nodes that were pathologically negative (N1) presented a 5-year survival of 63%. Patients with pathologically positive lymph nodes (N3) experienced a 5-year survival rate of 32% (P = 0.040). CONCLUSIONS: TSEB provides an excellent quality of life by reducing itching and discharge from the skin. Patients with more advanced disease may be treated and cured by the addition of photon beams in combination with TSEB. A selection of patients with advanced skin disease and regional extension may be cured by a combination of TSEB and photon beam irradiation. The regional treatment allows the use of electrons after the reduction of the plaques or thick tumors and a prophylactic irradiation of the adjacent nodal area.

Adult↗
PubMed2000

[Umbilical cutaneous metastasis (or Sister Mary Joseph's nodule) disclosing an ovarian adenocarcinoma].

In this study, the case is described of an umbilical metastasis as the presenting symptom of an ovarian adenosarcoma. The overall frequency of cutaneous metastases has been estimated at between 5 and 9%. Umbilical metastases are a rare occurrence: it is estimated that between 1 and 3% of patients with abdomino-pelvic disease present with an umbilical nodule. Epidemiological studies have shown the female predominance of this disease. The clinical characteristics of umbilical metastases cannot be visually distinguished from those of primary lesions. The clinical appearance is often that of a nodule of varying size, more or less painful, and sometimes ulcerated or suppurating as in the present case. The nodule may be indicative of cancer, or of cancer recurrence. The most frequently encountered histological type is adenocarcinoma (about 75% of cases), and is more rarely epidermoid, undifferentiated, or carcinoid. Etiological findings have indicated a digestive origin in over 55% of cases (stomach, colon, rectum, pancreas, in decreasing order of frequency), with a clear male predominance; cancers of gynecological origin are the second most frequent etiology, with ovarian cancers being the most common (34% of cases). Sister Mary Joseph nodule accounts for 60% of all malignant umbilical tumors (primary or secondary), and is usually associated with a poor prognosis (mean survival: 10-12 months). However, patient survival time could be lengthened by aggressive therapy, i.e., surgery combined with chemotherapy.

Adenocarcinoma↗
PubMed2000

The effect of 677C-->T and 1298A-->C mutations on plasma homocysteine and 5,10-methylenetetrahydrofolate reductase activity in healthy subjects.

We have studied the effect of common mutations (677C-->T and 1298A-->C) of the methylenetetrahydrofolate reductase (MTHFR) gene in sixty-six healthy French subjects, aged 27-47 years. Serum folate, vitamin B12, and plasma total homocysteine were measured as well as the specific activity of MTHFR in lymphocytes. The frequency of subjects homozygous for the 677TT genotype was 18%, and that of those homozygous for the 1298CC genotype was 12.5%. The frequency of individuals heterozygous for both mutations was 23.5%. The 1298A-->C mutation was associated with decreased MTHFR specific activity in subjects with both 677CC and 677CT genotypes. This activity was 60% for the 677CC/1298AC genotype and 52% for the 677CC/1298CC genotype when compared with the MTHFR specific activity of the 677CC/1298AA genotype. Heterozygotes for both mutations (677CT/1298AC genotype) had 36% of the reference specific activity. Although homocysteine levels in 677TT and 1298CC genotype subjects were higher than for other genotypes, no significant differences were observed among different genotypes. This may be due to high serum folate level in our samples, and suggests that folate therapy may be useful to prevent hyperhomocysteinaemia in homozygous mutant subjects.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗
PubMed2000

Transcytosis and coenzymatic conversion of [(57)Co]cobalamin bound to either endogenous transcobalamin II or exogenous intrinsic factor in caco-2 cells.

We have examined the intracellular route, coenzyme conversion and transcytosis rate of [(57) Co]-labeled cobalamin (Cbl) in function of its presentation to the apical side of Caco-2 cells, either free or bound to intrinsic factor (IF). The free-presented Cbl was progressively bound to endogenous transcobalamin II (TCII) which may stem, in part, from a basolateral to apical passage. Its transcytosis was TCII-mediated as it was abolished when antibodies to TCII were added to the apical medium. The apparent permeability coefficient (P(app)) was estimated at 20.8+/-3.6, 103.5+/-17.7, 0.9+/-0.3 x 10(-5) cm/h for TCII-Cbl, IF-Cbl and haptocorrin-Cbl, respectively. Chloroquine inhibited the transcytosis rate of both TCII and IF-bound Cbl in a dose-dependent manner. Approximately 80% of apical Cbl, bound to either exogenous IF or endogenous TCII, was transported to the basolateral side as intact cyano[(57)Co]Cbl whereas the remainder was converted into Ado-Cbl and CH(3)-Cbl within the cells, as shown by HPLC analyses of a 1,000-g pellet and a 12,000-g supernatant. Coenzymatic conversion was virtually abolished by chloroquine. In conclusion, we suggest that apically presented free Cbl is internalized via TCII-dependent transport. The apically internalized CN-Cbl, bound to either IF or TCII, is processed via an acidic vesicle and part of it is converted to coenzymes, whereas bulk of CN-Cbl is transcytosed intact.

Biological Transport↗
PubMed2000

Comparative tolerability of the newer generation antiparkinsonian agents.

In recent years, the treatment of Parkinson's disease has undergone an immense amount of research, resulting in the development of multiple new medications. This has largely been fuelled by dissatisfaction over the development of motor complications secondary to long term levodopa therapy. Different treatment approaches are applied depending on the stage of Parkinson's disease. In early and mild Parkinson's disease, selegiline offers a limited symptomatic effect. Its neuroprotective effect, although at present theoretical, has questionable clinical relevance. Increased mortality associated with selegiline has been reported, although a meta-analysis of 5 different trials did not support this finding. The newer, non-ergoline dopamine agonists, pramipexole and ropinirole, have undergone extensive studies to evaluate their efficacy as monotherapy in early Parkinson's disease. These newer agonists are ideal initial symptomatic medications, primarily because they delay the onset of levodopa-induced motor fluctuations. Efficacy of the newer dopamine agonists in advanced disease seems to be comparable to that of the older agents, bromocriptine and pergolide. Adverse effects can be reduced by starting the medication at a very low dose and then slowly titrating upward. Catechol-O-methyl transferase (COMT) inhibitors are indicated for the treatment of motor fluctuations in advanced disease, particularly the 'wearing-off' phenomenon. Tolcapone, a peripheral and central COMT inhibitor, appears to be quite effective, producing a 47% reduction in 'off' time. Unfortunately, 3 deaths have been observed, which are presumably secondary to tolcapone therapy. The drug has been withdrawn in many countries, and liver enzyme testing is mandatory in the US. Entacapone, a purely peripheral COMT inhibitor with a lower potency than tolcapone, has also proved to be effective and has not been associated with liver damage, obviating the need for testing.

Aged↗
PubMed2000

[Melanoma in organ transplant patients].

OBJECTIVE: The incidence of cutaneous melanoma has rapidly increased in the white population over the last decades. It has been estimated that the incidence doubles world-wide every 10 years. Different risk factors have been identified, including immunosuppression. The aim of our study-was to determine the relative risk of developing melanoma in the organ transplant population and the clinical and histological features of their melanomas. PATIENTS AND METHODS: This retrospective study was conducted with the collaboration of 9 University Hospital Centers: Besançon, Brest, Caen, Dijon, Lille, Lyon, Nantes, Paris (Pitié-Salpétrière) and Rennes. A questionnaire was sent to the different departments of dermatology of these hospitals to obtain information on patients who had presented a melanoma after a transplantation between 1971 and 1997. During this period, there were 12,477 organ transplant recipients in the transplantation units of these 9 hospitals. Average follow-up for these patients was about 5 years and the average duration of immunosuppressive therapy was about 4.5 years. RESULTS: Among 12,477 organ transplant recipients, we found 17 cases of melanoma but no data could be obtain on one case: 14 occurred in renal transplant recipients and 3 in cardiac transplant recipients. Clinical and histological data were only available in 16 patients. The average time between transplantation and diagnosis of melanoma was 63 months, but it was 5 times shorter for 2 patients who had a past history of melanoma before transplantation. Two patients had a mucosal melanoma; for the cutaneous melanomas, 2 appeared on Dubreuilh melanosis, 2 were in situ melanomas, 7 were superficial spreading melanomas and 3 were nodular melanomas. The histological review of 11 cutaneous melanomas revealed a precursor nevus in 6 cases and a weak or no stroma reaction in 7/7 cases. Complete excision of the melanoma was performed in all patients except one with anorectal melanoma. Four patients died of visceral metastasis within a mean 15 months. The other 12 patients are still alive with a mean 3 year course since tumor treatment. We tried to determine the relative risk of developing melanoma in the renal transplant population (14 cases). The number of expected cases of melanoma was 5.54, giving a relative risk of 2.5. DISCUSSION: Only 4 studies have shown an increase in the incidence of melanoma in the renal transplant population: approximately 2 to 5-fold. In our study, the 2.5-fold increase in melanoma was estimated with an average 5 year follow-up and an average 5 year immunosuppressive therapy. This is probably an underestimation of risk because we were unable to make an exhaustive collection of cases of melanomas even though transplant recipients undergo more physical examinations than a reference population. The mean latency period from transplantation to melanoma diagnosis was 63 months, as in other studies. Histological examination showed that a precursor nevus is frequent with weak host cellular response to the tumor. The prognosis of these melanomas remains difficult to predict, but in our study, it would not appear to be as poor as expected. Discontinuation of immunosuppressive therapy would not appear to be necessary except in the presence of metastasis. Finally, our study demonstrates the importance of good patient follow-up, even after graft rejection due to the persistent risk of melanoma.

Adult↗