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Biomedical subjects

J Schoonmaker

Publications and source records attributed to J Schoonmaker.

11 recordsLinked to original sources
PubMed1999

Gelfoam as a barrier to prevent polymethylmethacrylate-induced thermal injury of the spinal cord: in vitro and in vivo studies in pigs.

Gelatin sponge (Gelfoam; Upjohn, Kalamazoo, MI, U.S.A.) is commonly used as an interpositional barrier to shield the spinal cord from thermal injury during vertebral reconstruction with polymethylmethacrylate bone cement. The aim of this study was to record epidural and intradural temperatures during polymethylmethacrylate reconstruction of vertebral corpectomy defects. Three surgical techniques (subtotal corpectomy, total corpectomy with insertion of a Gelfoam barrier, and total corpectomy with no barrier) were compared in vivo and in vitro in a porcine model. As expected, total corpectomy defects cemented without a Gelfoam barrier produced the highest epidural temperatures in vivo (52.8 degrees C) and in vitro (58 +/- 2 degrees C). The Gelfoam barrier provided some protection against heat transfer, but peak temperatures and absolute temperature increases were significantly higher than in defects with an intact posterior cortex (p < 0.05). These results indicate that an intact posterior cortex provides the best protection against heat transfer, whereas the use of a Gelfoam barrier appears to provide only partial protection against thermal injury.

Animals↗
PubMed1998

Morphological and neurochemical correlates of vestibular compensation.

Morphometric analysis of the cat's superior vestibulo-ocular neurons (SVON) 8 weeks, and 1 and 2 years following vestibular neurectomy or labyrinthectomy revealed similar changes which indicate that an excitatory mode of input to the denervated SVON is responsible for the behavioral recovery. These changes include an increased proportion of strong asymmetric synapses, somal spines surrounding the SP, increased size of and number of SP at long (> 1 year) survival periods. There is a parallel decrease < 1 year and increase > 1 year of contralateral vestibular nerve SP on SVON which matches in timing and magnitude the number of ipsilateral vestibular nerve SP after surgical ablation. These unexpected SVON are consistent with the hypothesis that neurotrophins regulate symmetry in the adult vestibular system. This hypothesis was tested in a series of 13 heterozygous brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4) knockout mice. Following unilateral surgical labyrinthectomy the BDNF and NT4 knockout mice demonstrated no delay in behavioral recovery compared to their normal littermate controls. However, the NT3 knockout mice required twice the time to recover from balance deficits as their littermate controls. These results indicate that NT3 protein is important for normal vestibular function.

Animals↗
PubMed1996

Morphologic changes in contralateral superior vestibulo-ocular neurons following labyrinthectomy in the cat.

Ultrastructural changes were measured in 22 contralateral superior vestibulo-ocular neurons (SVONs) from four cats painlessly sacrificed at 8 weeks and 25 contralateral SVONs from four cats sacrificed at 1 year following unilateral labyrinthectomy. The SVONs at 8 weeks showed a 43% decrease in somal size, a 34% loss in rough endoplasmic reticulum (RER), a 48% loss of ribosomes, and a 47% decrease in the number of synaptic profiles (SPs) contacting the soma. At 1 year the SVONs had a 31% decrease in size, a 43% decrease in RER, a 50% loss of ribosomes, and a 71% decrease in SPs. Synaptic vesicles (SVs) in both groups of SVONs showed no change in size or shape compared to control SVs. These findings resemble the contralateral SVON changes that occur following excision of the vestibular ganglion.

Animals↗
PubMed1995

Morphologic changes in superior vestibulo-ocular neurons and vestibular nerve following labyrinthectomy in the cat.

Morphologic changes in ipsilateral superior vestibulo-ocular neurons (SVON) and the vestibular nerve were measured in 4 cats 8 weeks after labyrinthectomy and 4 cats 1 year after labyrinthectomy. There is a 20% decrease in SVON size and 30% decrease in rough endoplasmic reticulum and ribosomes with no change in the volume fractions of Golgi apparatus or mitochondria. In the central nervous system degeneration of the vestibular nerve terminals ipsilateral to the labyrinthectomy was represented by a 25% loss of synaptic profiles (SP) on SVON at 8 weeks and 57% loss of SP at 1 year after labyrinthectomy. There was no significant loss of fiber number in the vestibular nerve at 8 weeks post lesion but a 35% loss of fibers primarily of the large size at 1 year post lesion.

Animals↗
PubMed1992

Ultrastructural changes in contralateral superior vestibulo-ocular neurons one year after vestibular neurectomy in the cat.

Twenty contralateral superior vestibulo-ocular neurons (SVON) from 3 cats were studied morphologically one year after a right vestibular neurectomy. Eighteen SVON contained a smooth or slightly crenated nuclear membrane, a 63% loss of synaptic profiles (SP) and a 22% decrease in size compared to control SVON. Two cells contained nuclear membrane invaginations, a 40% loss of SP and a 31% size decrease compared to control SVON. The volume fractions of rough endoplasmic reticulum and ribosomes were decreased in these two cell groups but no change was noted in Golgi apparatus and mitochondria. These contralateral SVON reached a size, innervation density and content of organelles similar to ipsilateral SVON at one year following vestibular neurectomy.

Animals↗
PubMed1991

Ultrastructural changes in contralateral vestibulo-ocular neurons following vestibular neurectomy in the cat.

Twenty contralateral superior vestibular vestibulo-ocular neurons (SVON) from 4 cats were studied morphologically 8 weeks after a right vestibular neurectomy. Nine SVON demonstrated a 35% loss of somal synaptic profiles (SP), normal nuclear and cytoplasmic size, but a slight decrease in organelles responsible for protein synthesis (rough endoplasmic reticulum and polyribosomes). Eleven SVON showed an 82% loss of SP, decrease in cell and nuclear size, and significant reduction in rough endoplasmic reticulum (RER) and polyribosomes. These transneuronal SVON changes are presumed to be the result of commissural pathway degeneration caused by the vestibular neurectomy.

Animals↗
PubMed1990

Cervicovaginal microflora and pregnancy outcome: results of a double-blind, placebo-controlled trial of erythromycin treatment.

Available information suggests that some instances of preterm birth or premature rupture of membranes are associated with clinically unrecognized infection and inflammation of the lower uterine segment, decidua, and fetal membranes. Various cervicovaginal microorganisms have been recovered from these sites. Many of these microorganisms produce factors that may lead to weakening of the fetal membranes, release of prostaglandins, or both. This study evaluated the presence of various lower genital tract microflora and bacterial conditions in 229 women enrolled in a double-blind, placebo-controlled trial of short-course erythromycin treatment at 26 to 30 weeks' gestation to prevent preterm birth. Demographic, obstetric, and microbiologic parameters were prospectively evaluated. Premature rupture of membranes occurred less frequently (p less than 0.01) among women who received erythromycin (6%) versus placebo (16%). Preterm premature rupture of membranes also occurred less frequently, although not significantly (p = 0.3) in patients who received erythromycin (2%) versus placebo (5%). Erythromycin treatment significantly decreased the occurrence of premature rupture of membranes among women who were initially positive for Chlamydia trachomatis infection. Logistic regression analysis demonstrated that C. trachomatis (p = 0.05; odds ratio, 9), vaginal wash phospholipase C (p = 0.08; odds ratio, 6) and prior preterm birth (p = 0.007; odds ratio 17) were associated with increased risk of preterm birth. Bacterial vaginosis, Mycoplasma hominis, Ureaplasma urealyticum were not significantly associated with increased risk of preterm birth or preterm rupture of membranes. These findings support a role for selected lower genital tract microflora in preterm birth and premature rupture. Large controlled treatment trials of specific infections or conditions associated with preterm birth and premature rupture of membranes are required to confirm the value of antimicrobial treatments in prevention of microbial-associated preterm birth.

Adolescent↗
PubMedDate not supplied

Ultrastructural changes in vestibulo-ocular neurons following vestibular neurectomy in the cat.

Vestibulo-ocular (VO) neurons in the superior vestibular nucleus were labeled retrogradely with horseradish peroxidase and studied quantitatively using electron microscopy to determine the morphologic correlates of vestibular compensation. Eleven VO neurons from three normal cats were compared to 26 VO neurons in four animals killed 8 weeks after vestibular neurectomy and 13 VO cells from two animals killed 1 year after vestibular neurectomy. The results demonstrated a marked reduction (74%) in the number of synaptic profiles (SPs) on the VO cell soma in both experimental groups. Synaptic vesicles in the remaining SPs on VO neurons were fewer, smaller, and rounder than vesicles in control animals. The residual SPs also were associated with more asymmetric synapses. The experimental VO neuron showed a significant decrease in soma and organelles associated with protein synthesis.

Animals↗