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Biomedical subjects

M L Weber

Publications and source records attributed to M L Weber.

At least 37 records · Page 2Linked to original sources
PubMed1990

Hypoxic neuronal injury in tissue culture is associated with delayed calcium accumulation.

Calcium accumulation and neuronal injury were studied after hypoxia in cerebrocortical cell cultures in vitro. Neuronal injury was associated with a delayed calcium accumulation, which was greatest 5-7 hours after hypoxic exposure. Antiexcitotoxic treatments with tetrodotoxin and magnesium chloride or the selective N-methyl-D-aspartate antagonist (+/-)-4-(3-phosphonopropyl)-2-piperazinecarboxylic acid prevented hypoxic calcium accumulation and neuronal injury even when added 3 hours after hypoxia, during reoxygenation. Rescue of the neurons after hypoxia by blocking the delayed calcium accumulation in this cell culture preparation suggests a "therapeutic window" determined by calcium entry.

Animals↗
PubMed1989

A model of subretinal neovascularization in the pigmented rat.

We produced krypton laser photocoagulation lesions of mild to moderate whiteness in the posterior retinas of one eye of 23 pigmented rats, and identical appearing argon laser burns in the fellow eyes. We observed foci of subretinal neovascularization, histopathologically markedly similar to that which occurs in several human retinal diseases, in the krypton laser treated eyes of 6 of the 14 rats that were followed for one to three months after photocoagulation. No such lesions were observed in the argon laser treated fellow eyes, nor in krypton or argon laser treated eyes examined earlier than one month after photocoagulation. The photocoagulation damaged only the choriocapillaris, the retinal pigment epithelium (RPE), and the photoreceptor layer. In the acute lesions, we did not observe ruptures in Bruch's membrane. The neovascularization was surrounded by multiple layers of RPE cells, a histopathologic finding that has also been reported in some human eyes with subretinal neovascularization in age-related macular degeneration. These observations suggest that the RPE cells may be modifying the proliferative behavior of adjacent choroidal capillaries. This model differs from previous models of subretinal neovascularization in primates, and may be useful for additional studies of this important pathological process.

Animals↗
PubMed1989

Retinovitreal neovascularization in the Royal College of Surgeons rat.

Retinovitreal blood vessels, which we have previously reported in the dystrophic retinas of approximately 20% of older (greater than 15 months of age) spontaneously hypertensive (SHR) rats, also occur in about 20% of retinal dystrophic Royal College of Surgeons (RCS) rats greater than 1 year of age. We have demonstrated previously that these vessels, in the SHR rat, have the anatomic characteristics of retinovitreal neovascularization as it has been described in vasoproliferative retinopathies in humans (1). We now provide strong evidence that the endothelial cells and pericytes of the retinovitreal vessels that occur in RCS rats are proliferating, since they demonstrate by autoradiography significantly increased nuclear labeling with [3H]-thymidine over intra-retinal or choroidal vessels, or the abnormal vessels that grow within the retinal pigment epithelium in these dystrophic retinas. One important difference between the neovascularization that occurs in these rats and that which is observed in various human retinal vascular diseases is the frequent association of the new vessels in dystrophic rat retinas with surrounding cords of proliferating retinal pigment epithelium. The retinovitreal vessels in these strains of dystrophic rats represent a new animal model that may be useful for studying the fundamental processes underlying new blood vessel growth in the retina.

Animals↗
PubMed1988

ATP causes retinal pericytes to contract in vitro.

We evaluated the contractility of bovine retinal microvascular pericytes in culture by permeabilizing the cells with 0.1% Triton X-100 and measuring their response to MgATP. Sequential photographs of the cells were taken over 20 min and their surface areas were measured. Our study directly demonstrates that pericytes are contractile cells, which respond to MgATP in a dose-dependent fashion over a relatively short time course (minutes). Pericytes did not contract in response to GTP, pyrophosphate or beta, gamma-methylene ATP. Immunofluorescence study showed the presence of muscle actin in Triton X-100-treated cells before and after contraction, indicating preservation of this cytoskeletal protein even after treatment with the detergent. Similar experiments on human umbilical vein endothelial cells, bovine lens epithelial cells and human retinal pigment epithelial cells showed that these cells were significantly less contractile than retinal pericytes. That pericytes show substantial contraction over a short time course indicates that these cells may play a major role in regulating blood flow in the microcirculation.

Actins↗
PubMed1987

Myeloperoxidase deficiency with extensive candidal osteomyelitis of the base of the skull.

A 6-year-old girl had a 7-month history of headaches and painful torticollis. A CT scan of the mastoids showed extensive bone destruction of the base of the skull and C-1. Biopsies of the retropharyngeal area and of the anterior aspect of C-1 were performed: histopathologic findings were suggestive of mycotic infection and cultures were positive for Candida albicans. The child was treated successfully with amphotericin B. The immunologic evaluation demonstrated the absence of myeloperoxidase in the neutrophils.

Candidiasis↗
PubMed1986

Knowledge of medical students, pediatric residents, and pediatricians about the cost of some medications.

Medical students, pediatric residents, and pediatricians were asked to evaluate the cost of commonly prescribed medications. Their estimations varied considerably and were considered as adequate in 40%, 52%, and 62% of the cases, respectively. In most situations, the adequacy of their estimations did not seem to improve significantly with the length of training and practice. Since the cost of medications may influence compliance, it should probably be discussed more often during the course of medical and pediatric training.

Asthma↗
PubMed1983

[Teaching rounds].

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Education, Medical, Continuing↗
PubMed1980

[Trichopoliodystrophy or Menkes disease].

Trichopoliodystrophy (also known as Menkes' kinky or steely hair disease), a recessive sex-linked syndrome, is characterized by severely retarded mental and physical development, convulsions, a particular phenotype and abnormalities of the hair, bones and arteries. Very low levels of copper and ceruloplasmin in the serum confirm the diagnosis. This rare disorder is caused by an inborn error of copper metabolism whose nature is not yet clear. Recent hypotheses favour either an abnormality in the transport of copper across the cell membrane or increased affinity for copper of the intracellular binding protein. Because the metabolic abnormality is expressed autonomously and irregularly in various tissues, the distribution of copper within the body is disordered. Up to now none of the many forms of copper therapy has succeeded in modifying the fatal course of the disease in humans. This article presents a new case, the first in Canada, and a review of the other 69 cases described in the literature. The new case illustrates, in addition to the classic picture, less well known features, such as diverticula of the bladder mucosa and serosa, as well as cortical atrophy and malformed cerebral vessels demonstrated by computer-assisted tomography.

Angiography↗
PubMed1979

The microbiology of serous and mucoid otitis media.

One hundred forty-four serous and mucoid effusions were cultured for aerobic bacteria, Mycoplasma pneumoniae, and virus. Thirty percent of all effusions yielded an unequivocally positive culture for aerobic bacteria. Although serous effusions were culture positive as often as mucoid effusions, Haemophilus influenzae was isolated predominantly from serous effusions and Staphylococcus epidermidis predominantly from mucoid samples. Only one of 73 effusions yielded a viral isolate (Herpesvirus hominis). None of 33 effusions yielded M pneumoniae, and only one of 17 effusions yielded an anaerobe (Propionibacterium). These findings suggest that aerobic bacteria may play a role in the pathogensis of serous and mucoid otitis media.

Bacterial Infections↗
PubMed1978

[Nasotracheal intubation and tracheostomy in acute epiglottitis and laryngotracheal bronchitis].

Acute infectious respiratory distress in children has known different modalities of treatment during these past few years, but controversy remains between tracheostomy and naso-tracheal intubation as ways to cope with the problem. This study, which was undertaken at St. Justine's Hospital in Montreal, reports our complications with the two methods and shows that non-fatal complications are about the same but less serious with naso-tracheal intubation, whereas mortality was 3.2% with tracheostomy and 0% with naso-tracheal intubation. These results entitle us to think that naso-tracheal intubation is the treatment which should be used. This study also reviews different incidence in regards to age, sex, and seasonal prevalence between croup and epiglottitis and also compares the duration of hospital care between the two modalities.

Acute Disease↗
PubMed1978

Evaluation of disc diffusion susceptibility testing performed from a four-hour subculture of positive blood culture bottles.

Disc diffusion susceptibility tests were performed on standardized broth suspensions inoculated from a four-hour subculture of a positive blood culture bottle as well as from an agar plate subculture of the same positive blood culture bottle. The zone sizes and interpretative results of both methods were compared. Of 101 isolates tested, only one organism exhibited a very major difference between the two methods (one Staphylococcus epidermidis was interpreted as susceptible to methicillin by the four-hour subculture method and resistant by the agar plate subculture method). Thirteen other isolates showed minor changes from susceptible or resistant to intermediate or from intermediate to either susceptible or resistant with only one antibiotic each. The data indicates that disc diffusion susceptibilities may be performed easily and accurately from a four-hour subculture of positive blood culture bottles.

Evaluation Studies as Topic↗