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S Coons

Publications and source records attributed to S Coons.

15 recordsLinked to original sources
PubMed1995

Comparative anatomy of the baboon and the human cervical spine.

STUDY DESIGN: The anatomy of baboon and human cervical spines were compared by measuring adult, cadaveric specimens. OBJECTIVE: The objective of the study was to compare human and baboon cervical motion segments to determine whether the baboon provides a suitable model for spinal research. SUMMARY OF BACKGROUND DATA: Several studies have examined the quantitative anatomy of the human cervical bones and ligaments. Several animal species have been used for cervical spine research; however, no studies have validated whether the animal models resemble the human cervical spine closely enough to provide generalizable data. METHODS: Multiple morphologic parameters were measured directly from nine baboon and six human adult cadaveric cervical spine specimens. The bone structure and geometry of each of the seven cervical vertebrae were analyzed; the structure and histology of the ligaments were measured; and histomorphometry of the vertebrae was performed. RESULTS: The architectural composition and geometry of individual cervical vertebrae of baboons and humans were similar at each level. The proportional relationship of bone and ligament structures in the two species was almost identical. There were, however, several differences: 1) The baboon spine was about half the size of the human spine; 2) its vertebral arteries were encased fully within the C1 lateral mass; 3) its uncovertebral joints were more prominent; 4) its vertebral endplates were more concave; 5) its pedicles were thinner; 6) its transverse processes were longer; and 7) its spinous processes were horizontal and nonbifid. CONCLUSIONS: The geometry and anatomy of the baboon cervical spine closely resemble that of the human cervical spine. It therefore provides an excellent model for in vivo and in vitro research.

Adult↗
PubMed1994

Morphology and kinematics of the baboon upper cervical spine. A model of the atlantoaxial complex.

STUDY DESIGN: Quantitative and qualitative analyses were performed to compare the anatomy and biomechanics of baboon and human upper cervical spines. OBJECTIVES: This study examined the baboon as a potential model for in vivo and in vitro atlantoaxial research. SUMMARY OF BACKGROUND DATA: A variety of animal models have been used for spine research; however, no species have been used for C1-C2 research. Most species have remarkably different C1-C2 morphology compared with that of humans. METHODS: Twenty baboon and seven human normal adult cadaveric upper cervical spines were studied morphologically. C1-C2 motion segments were analyzed biomechanically using a flexibility method of testing with physiologic range, nondestructive loading. Motion and load-deformation relationships were studied during flexion, extension, bilateral lateral bending, and bilateral axial rotation. RESULTS: The bones and ligaments of the baboon and human upper cervical vertebrae have similarly proportioned structures, identical individual components, and similar geometric configurations. The average size of the baboon vertebrae was 50% to 60% of the human specimens. There were several minor anatomical differences. Baboons had more horizontal C2-C3 facet joints and more vertical C1-C2 articular surfaces; the vertebral arteries were encased in a continuous bony canal in C1. Biomechanical testing demonstrated that baboons and humans had similarly proportioned neutral zones and elastic zones. Compared with humans, baboons had a 2 degrees to 9 degrees wider range of motion in all directions. CONCLUSIONS: The baboon and human upper cervical anatomy and biomechanics are similar. The baboon may be useful to study atlantoaxial biomechanics and pathology.

Adult↗
PubMed1989

Choroid plexus carcinoma in siblings: a study by light and electron microscopy with Ki-67 immunocytochemistry.

Choroid plexus carcinomas in siblings aged 11 months and 10 years were examined by light microscopy and immunocytochemistry. One case was studied by electron microscopy. Choroid plexus carcinoma is rare, with approximately 24 reported cases in children. Predicting the behavior of choroid plexus tumors from the histology can be difficult. Neither mitoses nor necrosis were seen in one case, but evaluation of proliferation using Ki-67 monoclonal antibody showed 9% of the cells to be in proliferative phases of the cell cycle, a high value for a glial-derived neoplasm. Ki-67 activity may be a more sensitive measure of proliferation in malignant choroid plexus tumors than the presence of mitoses and necrosis, and additional studies may establish its role in distinguishing between choroid plexus carcinoma and papilloma when histologic classification is equivocal. Both tumors were immunoreactive for keratin, which confirmed previous studies. Both were nonreactive for glial fibrillary acidic protein, S-100, and carcinoembryonic antigen (CEA), unlike a previous study which reported that choroid plexus carcinoma, compared to papilloma, was uniquely S-100-negative and CEA-positive. Choroid plexus carcinoma in siblings has not been reported. Chance occurrence in siblings is extremely unlikely; thus a genetic basis for the neoplasms is likely, although environmental influences cannot be excluded.

Antibodies, Monoclonal↗
PubMed1988

A second DNA methyltransferase repair enzyme in Escherichia coli.

The Escherichia coli ada-alkB operon encodes a 39-kDa protein (Ada) that is a DNA-repair methyltransferase and a 27-kDa protein (AlkB) of unknown function. By DNA blot hybridization analysis we show that the alkylation-sensitive E. coli mutant BS23 [Sedgwick, B. & Lindahl, T. (1982) J. Mol. Biol. 154, 169-175] is a deletion mutant lacking the entire ada-alkB operon. Despite the absence of the ada gene and its product, the cells contain detectable levels of a DNA-repair methyltransferase activity. We conclude that the methyltransferase in BS23 cells is the product of a gene other than ada. A similar activity was detected in extracts of an ada-10::Tn10 insertion mutant of E. coli AB1157. This DNA methyltransferase has a molecular mass of about 19 kDa and transfers the methyl groups from O6-methylguanine and O4-methylthymine in DNA, but not those from methyl phosphotriester lesions. This enzyme was not induced by low doses of alkylating agent and is expressed at low levels in ada+ and a number of ada- E. coli strains.

DNA Repair↗
PubMed1988

Myelopathy due to epidural varicose veins of the cervicothoracic junction. Case report.

A 30-year-old man presented with a subacute course of myelopathic signs and symptoms. Magnetic resonance imaging demonstrated an epidural mass lesion of the spinal canal at the cervicothoracic junction causing compression of the spinal cord. Laminectomy with resection of this lesion revealed a large varix with acute and chronic thrombus. Postoperatively, an improvement in neurological function occurred. Spinal epidural varicosities have been reported as an etiological factor in lumbar and sacral radiculopathies. This is the first reported case of spinal cord compression in association with spinal epidural varices. The diagnosis, pathophysiology, and management of this disorder are presented.

Adult↗
PubMed1985

Motility and arousal in near miss sudden infant death syndrome.

Developmental sleep patterns were compared in infants at known risk for "near-miss" sudden infant death syndrome and age-matched normal infants. Near-miss SIDS infants had significant differences suggestive of a temporary developmental delay. They retained rapid eye movement (REM) sleep at neonatal proportions, and stage 2 non-REM sleep appeared later. They also had a significantly increased apnea index. Twenty-four-hour recordings of sleep and respiratory patterns in near-miss SIDS infants from 3 weeks through 6 months of age showed a significant reduction in number of body movements in REM, non-REM, and total sleep time and in percentage of movement time at 3 weeks through 3 months of age. These findings can be used to address the role of arousal threshold in infants at risk for SIDS.

Arousal↗
PubMed1985

Near-miss sudden infant death syndrome in eight infants with sleep apnea-related cardiac arrhythmias.

Eight full-term infants between 3 and 8 weeks of age, who had had 24 to 48 hours of vague problems involving a congested upper airway and/or irritability, had a life-threatening respiratory episode at home, called a near-miss for sudden infant death syndrome event. Polygraphically monitored mixed apneas occurred in clusters during non-rapid eye movement (NREM) sleep with significant cardiac arrhythmias, predominantly sinus arrest. The cardiorespiratory problems continued during sleep in the following 8 to 12 weeks but did not recur after that time, and there were no long-term sequelae when the children were studied again 4 to 7 years later.

Arrhythmias, Cardiac↗
PubMed1984

Apnea and bradycardia during feeding in infants weighing greater than 2000 gm.

One full-term and nine premature infants who had been or were about to be discharged from the hospital were studied to identify any breathing problems. While awake and when sucking and swallowing, the infants had central apnea accompanied by significant bradycardia and significant drops in transcutaneous oxygen values. These events occurred whether infants were breast-fed or ingested human milk, formula, or water by bottle, and were not associated with falls in esophageal pH. While awake, after occlusion of both nostrils, the infants responded with mouth breathing. Sleep-related apneic episodes were also found but were less significant. The long apneic events were related to poorly coordinated sucking and breathing while awake.

Bottle Feeding↗
PubMed1984

Development of consolidated sleep and wakeful periods in relation to the day/night cycle in infancy.

Periods of sustained sleep were analyzed to assess the development of sleep-state organization and structure during the first six months of life. Infants first establish consolidated sleep and wakeful periods, which then become oriented to the 24-hour day/night cycle. As infants mature they gradually show greater sleep 'efficiency', and at onset of sleep, REM periods become less likely. The longest sleep period progressively becomes associated with the dark period of the 24-hour cycle. This study also assessed the sequences of NREM-REM sleep-cycle organization during the first six months of life. Although individual infants may have a significant correlation between duration of sleep and latency at onset of sleep, the over-all direction is not constant, nor is an 'age effect' apparent during the first six months. The data support the hypothesis that states of alterness , which develop independently in the perinatal period, become integrated in early infancy.

Child Development↗
PubMed1982

Development of sleep-wake patterns and non-rapid eye movement sleep stages during the first six months of life in normal infants.

Thirty-one normal infants were selected for 24-hour polygraphic monitoring at different ages during the first six months of life. The development of sleep-wake distribution patterns during day and night was observed. Qualitative changes in non-rapid eye movement (NREM) sleep as it becomes differentiated in stages 1, 2, and 3-4 were measured. Sustained periods of wake are present by 6 weeks of age. After 3 months of age, wake is predictably distributed in late afternoon and early evening. REM sleep is disproportionately distributed within sleep in 24 hours, presenting a higher percent of total sleep during the night. At 4.5 and 6 months of age, stages 2 and 3-4 NREM are coincident during the nocturnal hours and 3-4 NREM sleep peaks in the early period of the night. The decreasing proportion of REM sleep, particularly in its daytime distribution, suggests a reciprocal relationship to the developing of wakefulness.

Child Development↗
PubMed1981

Sleep parameters and respiratory variables in "near miss' sudden infant death syndrome infants.

Twenty-nine near miss for sudden infant death syndrome and thirty normal infants between the ages of 3 weeks and 6 months were monitored polygraphically for 24 hours. The distribution of sleep and abnormal respiratory events were analyzed for both groups. On the basis of mixed and obstructive apnea, 12-hour nocturnal segments (8 PM to 8 AM) consistently distinguished near miss from normal infant groups between the ages of 3 weeks and 4.5 months. Daytime naps do not provide statistical differences sufficient to differentiate between the two groups. During sleep, abnormal respiratory events are more likely to occur between 1 AM and 6 AM, at least 40 minutes after sleep onset. Respiratory pauses show a significant increase just prior to waking (a strong respiratory stimulus). Any impairment of the arousal threshold during sleep will place near miss infants at increased risk.

Monitoring, Physiologic↗
PubMed1979

Mixed and obstructive sleep apnea and near miss for sudden infant death syndrome: 2. Comparison of near miss and normal control infants by age.

Twenty-nine full-term near miss for sudden infant death syndrome (SIDS) and 30 normal control infants underwent 24-hour polygraphic monitoring. Several types of respiratory events during sleep (eg, central, mixed, and obstructive apnea, periodic breathing) were defined and tabulated. Analysis of these respiratory variables and comparison of groups of near miss and control infants indicated that between 3 weeks and 4 1/2 months of age only one variable was consistently different at a statistically significant level: the number of mixed and obstructive apnea greater than 3 seconds during total sleep time. This study also showed an increase in mixed and obstructive respiratory events during sleep at 6 weeks of age in control as well as in near miss infants.

Female↗
PubMedDate not supplied

MR characteristics of meningioma subtypes at 1.5 tesla.

Analysis of MR signal characteristics and histopathologic findings confirms the strong correlation between meningioma subtype and observed signal intensity (SI) changes in 24 patients imaged at 1.5 T. On T2-weighted images, 90% of fibroblastic and transitional tumors were hypointense relative to cerebral cortex (SI intermediate greater than SI T2-weighted images); conversely, 66% of meningothelial subtypes displayed persistent hyperintensity (SI intermediate less than or equal to SI T2-weighted images), and the remaining one-third demonstrated mixed high-signal changes. Subtype specific differences in collagen distribution and cellularity, i.e., tumor geometry, appeared to account for these signal trends. Based solely on SI characteristics, correct histologic subgrouping of tumors as either fibroblastic/transitional or meningothelial/angioblastic was possible in 80% (19 of 24) of patients. Utilization of adjunctive imaging features (i.e., mass effect, peritumoral edema, intratumoral cyst formation) in conjunction with signal changes permitted a correct histologic pattern in 96% (23 of 24) of patients.

Adult↗