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Biomedical subjects

R Cormier

Publications and source records attributed to R Cormier.

9 recordsLinked to original sources
PubMed2001

Phase-shifting effects of dusklike and dawnlike light pulses on the circadian activity rhythms of Syrian hamsters.

This study tested whether light pulses with a dusklike offset or a dawnlike onset caused phase shifts of different sizes in the circadian wheel-running activity of Syrian hamsters, Mesocricetus auratus. Six experiments were conducted, each with 30 hamsters; the hamsters received first one type of pulse and then the other type a few weeks later, allowing a paired comparison. The six experiments represented the combination of two maximum light intensities (150 and 250 lux) and three zeitgeber times (ZTs) at which the pulses were given (ZT13.5, ZT14.5, and ZT20). Pulses were 30 minutes long, a relatively short duration to minimize circadian time effects. Aschoff's type II method of measuring phase shifts was used. In none of the six experiments did a two-tailed paired t test detect a significant difference in the size of phase shifts caused by dusklike versus dawnlike pulses. A three-way analysis of variance (ANOVA) on the combined data from all six experiments (with pulse type, pulse intensity, and ZT as factors) also failed to detect a significant effect of pulse type. Statistical power was calculated and found to be reasonably good. These negative results are in line with those of a previous study in which a different methodology was used.

Analysis of Variance↗
PubMed2000

Slow death of postnatal hippocampal neurons by GABA(A) receptor overactivation.

Neurotransmitters can have both toxic and trophic functions in addition to their role in neural signaling. Surprisingly, chronic blockade of GABA(A) receptor activity for 5-8 d in vitro enhanced survival of hippocampal neurons, suggesting that GABA(A) receptor overactivation may be neurotoxic. Potentiating GABA(A) receptor activity by chronic treatment with the endogenous neurosteroid (3alpha,5alpha)-3-hydroxypregnan-20-one caused massive cell loss over 1 week in culture. Other potentiators of GABA(A) receptors, including benzodiazepines, mimicked the cell loss, suggesting that potentiating endogenous GABA activity is sufficient to produce neuronal death. Neurosteroid-treated neurons had lower resting intracellular calcium levels than control cells and produced smaller calcium rises in response to depolarizing challenges. Manipulating intracellular calcium levels with chronic elevated extracellular potassium or with the calcium channel agonist Bay K 8644 protected neurons. The results may have implications for the mechanisms of programmed cell death in the developing CNS as well as implications for the long-term consequences of chronic GABAmimetic drug use during development.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1997

Radar detection of the nucleus and coma of comet hyakutake

Radar observations of comet Hyakutake (C/1996 B2) made at the Goldstone Deep Space Communications Complex in California have detected echoes from the nucleus and from large grains in the inner coma. The nucleus of this bright comet was estimated to be only 2 to 3 kilometers in diameter. Models of the coma echo indicate backscatter from porous, centimeter-size grains ejected anisotropically at velocities of tens of meters per second. The radar observations suggest that a comet's activity may be a poor indicator of its size and provide evidence that large grains constitute an important component of the mass loss from a typical active comet.

Journal Article↗
PubMed1992

The coronal forehead lift--modifications and results.

The coronal forehead lift has produced excellent results in the rejuvenation of the upper face. The problem of brow and glabellar ptosis, as well as the problem of frontoglabellar rhytids, are directly addressed with this procedure while producing no visible scars. In addition, the pretrichial modification of it can be used without alteration in the hairline. The success and low morbidity of the coronal forehead lift has made it the procedure of choice for upper facial rejuvenation in females, and many male patients. A review of 41 coronal forehead lifts performed by the senior author is presented, with emphasis placed on the results and the refinements brought to the surgical technique. A discussion comparing this procedure to other brow lift procedures is also presented, outlining their respective advantages and disadvantages.

Adult↗
PubMed1990

Cervicofacial liposuction: results and controversies.

Obtaining ideal results with cervicofacial rhytidectomy has long frustrated facial plastic surgeons due to the difficulty of removing local excesses of adipose tissue in the parotid, melolabial, submental and submandibular areas. Open and closed liposuction techniques are being developed in conjunction with the facelift to improve definition of the facial, mandibular and cervical contours. A review of the senior author's (PAA) cases of cervicofacial liposuction and rhytidectomy is presented with emphasis placed on surgical techniques and results. Current literature is reviewed. Recommendations are made regarding analysis, surgical techniques and postoperative management of patients presenting for rejuvenation of the lower face.

Face↗
PubMed1987

Assessment of the guinea pig's middle ear cell-mediated response using the mixed lymphocyte response (MLR).

The mixed lymphocyte response (MLR) of the guinea pig was assessed using skin allografts placed in the tympanic cavity, in comparison to the MLR obtained with allografts sutured on the backs of these animals. The MLR obtained from middle ear stimulation was transient. It was not altered by previous systemic immunization, nor did it alter the subsequent MLR obtained when the allografts were implanted on the backs of the guinea pigs. Immunoperoxidase and hematoxylin/eosin stainings of the tympanic allografts were also attempted to make a pathological correlation. Our findings are compatible with other observations of mucosal immune systems.

Animals↗
PubMed1986

The cell-mediated response of the guinea pig's middle ear.

In this project, we studied the cell-mediated response of guinea pig's middle ear. The specific objective was to characterize rejection of skin grafts on the back (allo- and iso-grafts) after primary stimulation (iso- or allo-) in the ear or on the back. The method used was the mixed lymphocyte response with and without phytohemagglutinin (PHA). Preliminary results showed that the middle ear is able to mount a normal immune response, both locally and systemically. Such basic studies will help us to understand the otologic immune response as a whole and may shed some light on the immune phenomena observed in middle ear transplantations.

Animals↗
PubMed1986

Nosocomial gram-negative parotitis.

Nosocomial parotitis is an uncommon postoperative complication, usually affecting elderly, debilitated, dehydrated patients. The preponderance of gram-positive pathogens has been emphasized. The authors present two cases of gram-negative parotitis and review the literature on this condition. Because the organisms producing nosocomial infection in patients receiving intensive care are commonly gram-negative bacilli, treatment should be based on the findings of Gram's staining of the pus obtained from Stensen's duct, altered when necessary by the final culture results.

Cross Infection↗