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D Martin

Publications and source records attributed to D Martin.

At least 145 records · Page 8Linked to original sources
PubMed2001

Nifedipine-activated Ca(2+) permeability in newborn rat cortical collecting duct cells in primary culture.

To characterize Ca(2+) transport in newborn rat cortical collecting duct (CCD) cells, we used nifedipine, which in adult rat distal tubules inhibits the intracellular Ca(2+) concentration ([Ca(2+)](i)) increase in response to hormonal activation. We found that the dihydropyridine (DHP) nifedipine (20 microM) produced an increase in [Ca(2+)](i) from 87.6 +/- 3.3 nM to 389.9 +/- 29.0 nM in 65% of the cells. Similar effects of other DHP (BAY K 8644, isradipine) were also observed. Conversely, DHPs did not induce any increase in [Ca(2+)](i) in cells obtained from proximal convoluted tubule. In CCD cells, neither verapamil nor diltiazem induced any rise in [Ca(2+)](i). Experiments in the presence of EGTA showed that external Ca(2+) was required for the nifedipine effect, while lanthanum (20 microM), gadolinium (100 microM), and diltiazem (20 microM) inhibited the effect. Experiments done in the presence of valinomycin resulted in the same nifedipine effect, showing that K(+) channels were not involved in the nifedipine-induced [Ca(2+)](i) rise. H(2)O(2) also triggered [Ca(2+)](i) rise. However, nifedipine-induced [Ca(2+)](i) increase was not affected by protamine. In conclusion, the present results indicate that 1) primary cultures of cells from terminal nephron of newborn rats are a useful tool for investigating Ca(2+) transport mechanisms during growth, and 2) newborn rat CCD cells in primary culture exhibit a new apical nifedipine-activated Ca(2+) channel of capacitive type (either transient receptor potential or leak channel).

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2001

Exhaled nitric oxide correlated with induced sputum findings in COPD.

STUDY OBJECTIVES: Neutrophilic airway inflammation may underlie the pathogenesis of COPD. We examined repeated measurements of the fractional concentration of exhaled nitric oxide (FENO) and the correlation with cells and mediators in induced sputum (IS) from patients with COPD. PARTICIPANTS: Eleven COPD subjects (9 men and 2 women, aged 46 to 69 years) with predicted FEV(1) of 45 to 70%. SETTING: A hospital research laboratory. DESIGN: Single-cohort, prospective study with four visits at two weekly intervals. INTERVENTIONS: FENO and spirometry were assessed at all visits, and IS for differential cell count, leukotriene-B(4) (LTB(4)) and interleukin (IL)-8, nitrite, and nitrate at visit 1, visit 3, and visit 4. RESULTS: During the study, there were significant declines in mean percent predicted FEV(1), from 55.2 to 51.6% (p = 0.029), and mean FEV(1)/FVC ratio, from 50.4 to 45.4% (p = 0.001), accompanied by a significant increase in FENO geometric mean (95% confidence limits), from 15.2 (10.9 to 21.2) to 23.6 (17.1 to 32.4) parts per billion (p = 0.037), and sputum LTB(4), from 1.79 (1.03 to 3.11) to 3.57 (1.95 to 6.53) ng/mL (p = 0.033), but no significant change in other sputum parameters. From visits 1 to 4, the change in percent neutrophils correlated with the changes in FENO and IL-8 (r = 0.648, p = 0.028; r = 0.60, p = 0.05, respectively). Hypertonic saline solution induction of sputum caused a fall in FEV(1), from 1.83 +/- 0.44 to 1.46 +/- 0.44 L (p = 0.049). CONCLUSIONS: The worsening spirometry results were accompanied by significant increases in FENO and sputum LTB(4). FENO may be related to neutrophilic inflammation driven by the chemoattractant IL-8. FENO and IS may be useful markers of airway inflammation in COPD patients. Sputum induction with hypertonic saline solution causes a significant fall in FEV(1) requiring appropriate caution.

Aged↗
PubMed2001

A comparative statistical analysis of neuronavigation systems in a clinical setting.

The use of neuronavigation (NN) in neurosurgery has become ubiquitous. A growing number of neurosurgeons are utilizing NN for a wide variety of purposes, including optimizing the surgical approach (macrosurgery) and locating small areas of interest (microsurgery). The goal of our team is to apply rapid advances in hardware and software technology to the field of NN, challenging and ultimately updating current NN assumptions. To identify possible areas in which new technology may improve the surgical applications of NN, we have assessed the accuracy of neuronavigational measurements in the Radionics and BrainLab systems. Using a phantom skull, we measured how accurate the visualization of a navigational probe's tip was in these systems, taking a total of 2180 measurements. We found that, despite current NN tenets, error is maximal at the six marker count and minimal in the spreaded marker setting; that is, placing less markers around the area of interest maximizes accuracy and active tracking does not necessarily increase accuracy. Comparing the two systems, we also found that accuracy of NN machines differs both overall and in different axes. As researchers continue to apply technological advances to the NN field, an increasing number of currently held tenets will be revised, making NN an even more useful tool in neurosurgery.

Factor Analysis, Statistical↗
PubMed2001

Neuronavigational epilepsy focus mapping.

The localization of a seizure focus for resective surgery often requires invasive monitoring for precise localization of the target as well as structures to avoid. We report on the use of intra-operative surgical navigation to precisely localize and co-register subdural electrodes to regions of know radiographic pathology. Additionally, the navigation system was used to develop intra-operative electrode maps. These maps were subsequently used in the sub-acute recording phase to assign electrographic pathology and function (e.g. speech) to a specific cortical surface anatomy. This permitted for more precise planning of surgery and better assessment of potential risk, based on functional as well as anatomical criterion.

Artificial Intelligence↗
PubMed2001

The submental flap: its uses as a pedicled or free flap for facial reconstruction.

The submental flap is an alternative to microsurgical flaps for facial and intraoral defects. The submental flap is simple and can be raised rapidly. It produces good color, texture, and contour match without a conspicuous site. Its versatility and its rotational arc explains its large application in facial surgery. The pedicle is reliable when the flap is not used with a reverse flow. The surgeon must know the possible presence of valves in the venous system of the face and plan to perform a venous microsurgical anastomosis if venous congestion jeopardizes the flap's survival. The location of the flap in a lymph node area restricts its uses for traumatic cases, and for benign and malignant tumors, to reduce the potential of cancer spreading to the lymph nodes (e.g., basal cell carcinoma).

Aged↗
PubMed2001

[Comparison of MRA and angiography in the follow-up of intracranial aneurysms treated with GDC].

OBJECTIVE: Evaluation of TOF 3D MRA compared to angiography in the follow-up of intracranial aneurysms treated by Guglielmi detachable coils (GDC). MATERIAL: and method: Prospective analysis of follow-up MRA and angiographies for 20 patients with 22 aneurysms. There were 2 MRAs for 3 aneurysms giving a total of 25 cases. RESULTS: A poor correlation between MRA and angiography was observed in 21 cases of 25. For 9 cases, stable exclusion (95-100%) visible on MRA was confirmed by angiography. For 12 other cases, a residual flow within the aneurysmal neck or a residual flow between coils was detected by MRA and confirmed by angiography. A poor correlation was found in 4 cases out of 25: 3 residual flows within the aneurysmal neck and 1 residual flow within the coil mass not visible on MRA. MRA has a sensibility of 75% for the detection of an anomaly, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 69.2%. MRA is able to detect a large residual flow within aneurysmal neck and a re-growth, which would need a second embolization. Anomalies not visible on MRA as observed in our study, residual flow within the coil mass and the aneurysmal neck, do not require complementary treatment. CONCLUSION: A normal TOF 3D MRA can avoid an angiography in the follow-up of an intracranial aneurysm treated by GDC.

Adult↗
PubMed2001

[MRI screening of vestibular schwannomas without gadolinium: usefulness of the turbo gradient spin echo T2-weighted pulse sequence].

The purpose of this retrospective MRI work was to evaluate the use of turbo gradient spin echo (TGSE) high resolution imaging for the detection of eighth nerve schwannomas, without injection of gadolinium. The TGSE sequence (slice thickness: 3 mm with 1.5 mm interleaving; matrix: 512) was compared with a reference sequence: T1-weighted spin echo (SE) after gadolinium injection (slice thickness: 3 mm, matrix: 256). Among 380 internal auditory meatus (IAM) explored, 34 abnormalities were detected on T2-weighted TGSE images compared with 19 on contrast-enhanced T1-weighted SE images. This new sequence has a 100% sensitivity, a 96% specificity and a 100% negative predictive value. Using a rigorous protocol for IAM analysis with the TGSE sequence, gadolinium injection may no longer be needed systematically for vestibular schwannoma screening, but might only be necessary when an abnormality or a doubt persists after TGSE. This approach allows about 20% cost reduction for each patient, a savings of 11,433 euros considering only the true negatives observed in this study.

Adolescent↗
PubMed2001

Proinflammatory cytokine expression contributes to brain injury provoked by chronic monocyte activation.

BACKGROUND: We have proposed that an increased interaction between monocyte/macrophages and blood vessel endothelium predisposes subjects to strokes. The effect of chronic monocyte activation on the development of cerebral infarcts was thus studied in rats after provocation of a modified local Swartzman reaction, in brain vasculature. MATERIALS AND METHODS: Two weeks after an IV bolus of bacillus Calmette-Guérin (BCG), we studied spontaneous superoxide production, integrin expression, endothelial adhesion of monocytes and the neurological symptoms, brain histology, and cytokine immunoreactivity after a provocative dose of LPS (30-300 microg/rat i.c.v.). RESULTS: Monocyte migration into the brain was stimulated by BCG priming. The incidence of paralysis and death in response to LPS was markedly increased in BCG-primed rats. Histological evaluation of the brains of neurologically impaired and moribund animals revealed intravascular thrombosis and pale and hemorrhagic infarcts. Infiltrates of leukocytes expressing immunoreactive IL-1:, IL-6, and TNF-alpha were found around blood vessels, cerebral ventricles, and meninges, and were accompanied by a profound microglial expression of IL1P, endothelial expression of IL-6, and expression of TNF-alpha and TNF-R 1 in glia and neurons of cortex and hippocampus. Treatment (2 x 100 microg/10 ,I, i.c.v.) with recombinant human (rh-)TNF 55kDa receptor completely prevented, and treatment with rh-IL- I receptor antagonist significantly decreased the incidence of paralysis and death in response to BCG + LPS. The improvement of neurological symptoms was accompanied by reduced histological damage and supppression of IL-1P/ expression in the brain tissue. CONCLUSIONS: The data demonstrate that chronic monocyte activation predisposes subjects to thrombosis and hemorrhage via an exaggerated release of proinflammatory cytokines.

Adjuvants, Immunologic↗
PubMed2001

[How I treat ... refractory epilepsy by vagal nerve stimulation].

Intermittent left vagus nerve stimulation is a novel therapeutic modality that can be proposed to patients with a refractory epilepsy and for whom resective surgery is not an option. Its precise mechanism of action is not known. Controlled studies have shown that its efficacy is similar to that of antiepileptic drugs: 50% decrease in seizure frequency in 40% patients after two years. Side effects which are generally mild to moderate are the result of a diffusion of the stimulation to the larynx. No CNS side effect has been reported.

Drug Resistance↗
PubMed2001

Moulds, moisture and microbial contamination of First Nations housing in British Columbia, Canada.

This paper reviews the difficulties experienced with mould growth in First Nations homes in British Columbia and to describe the team approach used in dealing with this problem. Humid, damp conditions promote the growth of bacteria, moulds, and dust mites. These organisms contribute to poor air quality and causes serious health problems. There is increasing evidence indicating an association between mould, particularly toxigenic moulds, and some diseases, notably asthma. These health problems usually improve when families are relocated to more suitable accommodation. Those particularly at risk include atopic, immunocompromised, very young and elderly individuals and those with chronic health conditions. Our experience suggests that substandard housing is a major contributor to poor health in First Nations communities.

Air Pollution, Indoor↗
PubMed2001

Adolescent premarital sexual activity, cohabitation, and attitudes toward marriage.

Societal trends indicate ambivalent attitudes about marriage. Specifically, there is greater acceptance of divorce and nontraditional living arrangements such as cohabitation, as well as acceptance and prevalence of premarital sex, than in the past. The authors examine adolescent attitudes toward marriage and their association with premarital sexual activity and cohabitation. Recommendations for helping adolescents understand the realities of marriage and family life are shared.

Adolescent↗
PubMed2000

Peripheral nerve regeneration using bioresorbable macroporous polylactide scaffolds.

The ability of DRG-derived neurons to survive and attach onto macroporous polylactide (PLA) foams was assessed in vitro. The foams were fabricated using a thermally induced polymer-solvent phase separation. Two types of pore structures, namely oriented or interconnected pores, can be produced, depending on the mechanism of phase separation, which in turn can be predicted by the thermodynamics of the polymer-solvent pair. Coating of the porous foams with polyvinylalcohol (PVA) considerably improved the wettability of the foams and allowed for cell culture. The in vitro biocompatibility of the PVA-coated supports was demonstrated by measuring cell viability and neuritogenesis. Microscopic observations of the cells seeded onto the polymer foams showed that the interconnected pore networks were more favorable to cell attachment than the anisotropic ones. The capacity of highly oriented foams to support in vivo peripheral nerve regeneration was studied in rats. A sciatic nerve gap of 5-mm length was bridged with a polymer implant showing macrotubes of 100 microm diameter. At 4 weeks postoperatively, the polymer implant was still present. It was well integrated and had restored an anatomic continuity. An abundant cell migration was observed at the outer surface of the polymer implant, but not within the macrotubes. This dense cellular microenvironment was found to be favorable for axogenesis.

Animals↗
PubMed2000

Candidate Neisseria meningitidis NspA vaccine.

The highly conserved NspA protein has been found in the outer membrane of every Neisseria meningitidis strain tested so far. Two monoclonal antibodies (MAbs) directed against this protein were used to demonstrate that biologically important epitopes of the NspA protein are exposed at the surface of serologically distinct meningococcal strains. Analysis of sera collected from mice that survived a deadly meningococcal challenge following immunization with recombinant NspA protein (rNspA) revealed the presence of cross-reactive antibodies which efficiently attached to and killed the four serogroup B strains tested. These data are additional proof that the NspA protein is exposed at the surface of intact meningococcal cells, which is an important characteristic for a vaccine candidate.

Amino Acid Sequence↗
PubMed2000

Intranasal immunization with gonococcal outer membrane preparations reduces the duration of vaginal colonization of mice by Neisseria gonorrhoeae.

Nasal immunization was studied to determine if it could elicit an immune response capable of preventing vaginal colonization by Neisseria gonorrhoeae or of reducing its duration in the estradiol-treated mouse model. Nasal administration of gonococcal outer membrane (OM) preparations induced the development of systemic and vaginal immune responses that were directed mainly against a limited number of gonococcal OM proteins. The impact of nasal immunization on vaginal colonization by N. gonorrhoeae was evaluated by use of an experimental model, in which mice were treated with estradiol to prolong the infection. Bacterial clearance was significantly faster for mice immunized intranasally with N. gonorrhoeae OM preparations (4.0+/-2.5 days) than for control mice (8.5+/-4.3 days). The estradiol-treated mouse model may serve as a useful tool for the evaluation of potential gonococcal vaccine candidates.

Administration, Intranasal↗
PubMed2000

Response of macrophage/microglial cells to experimental neuronal degeneration in the avian isthmo-optic nucleus during development.

Blockade of the retrograde axonal transport of isthmo-optic nucleus (ION) neurons in the avian embryo results in their massive degeneration. We used this system to investigate the response of macrophage/microglial cells to neuronal degeneration in the embryonic brain. Colchicine was injected into the right eye of quail or chick embryos at a time when the survival of ION neurons depends on retrograde trophic support from the retina, and the chronology of the subsequent macrophage/microglial response in the ION was analyzed. This response was restricted to the ION contralateral to the injected eye; no modifications of the normal state were observed in the surrounding parenchyma or in the opposite ION, used as control. The response was first detected 18 hours after the colchicine injection (18 hours pi), when an increase of the macrophage/microglial cell number was evident. The number of these cells in the affected ION increased, peaking at 40-48 hours pi. At later survival times, macrophage/microglial cells were progressively less abundant in the affected ION, which gradually diminished in size. At 120 hours pi the only remnant of the ION was a small cluster of macrophage/microglial cells, surrounded by a clear area with scarce nonmicroglial cells, in the region formerly occupied by the ION. This study reveals that a strong macrophage/microglial response occurs in the embryonic brain in response to neuronal degeneration but that these cells do not trigger the neuronal death, as they only appear after pyknotic fragments are already observable.

Animals↗