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Biomedical subjects

M Ramsey

Publications and source records attributed to M Ramsey.

At least 19 recordsLinked to original sources
PubMed2001

The parachute technique: valgus impaction osteotomy for two-part fractures of the surgical neck of the humerus.

Fourteen elderly patients with a two-part fracture, in osteopenic bone, of the surgical neck of the humerus were treated with a valgus impaction osteotomy and tension band fixation--that is, the parachute technique. Thirteen patients were followed, and all were able to perform activities of daily living without difficulty and were satisfied with the result of the surgery. The average age of these thirteen patients was sixty-eight years, and the average duration of follow-up was 18.5 months. Union was achieved in all patients, at an average of 45.5 days. No patient demonstrated osteonecrosis of the humeral head. This technique of valgus impaction osteotomy with Dacron-tape tension band fixation leads to rapid union. Patient satisfaction and function were excellent.

Aged↗
PubMed2001

The floating shoulder: a biomechanical basis for classification and management.

BACKGROUND: The floating shoulder (ipsilateral fractures of the clavicular shaft and the scapular neck) is thought to be an unstable injury pattern requiring operative stabilization in most instances. This recommendation has been made with little biomechanical data to support it. The purpose of this study was to determine the osseous and ligamentous contributions to the stability of experimentally created scapular neck fractures in a cadaver model. METHODS: Standardized scapular neck fractures were made in twelve fresh-frozen human cadaveric shoulders. Each specimen was mounted in a specially designed testing apparatus and secured to a standard materials testing device. In group 1 (six shoulders), resistance to medial displacement was determined following sequential creation of an ipsilateral clavicular fracture, coracoacromial ligament disruption, and acromioclavicular capsular disruption. In group 2 (six shoulders), resistance to medial displacement was determined following sequential sectioning of the coracoacromial and coracoclavicular ligaments. RESULTS: The average measured force for all specimens (groups 1 and 2) after scapular neck fracture was 183 +/- 3.3 N (range, 166 to 203 N). The addition of a clavicular fracture (group 1) resulted in an average measured force of 128 +/- 10.5 N (range, 83 to 153 N), which corresponds to only a 30% loss of stability. Subsequent sectioning of the coracoacromial and acromioclavicular capsular ligaments yielded an average force of 126 +/- 9.1 N (range, 114 to 144 N), a 31% loss of stability, and 0 N, a complete loss of stability, respectively. Sectioning of the coracoacromial and coracoclavicular ligaments after scapular neck fracture (group 2) resulted in an average force of 103 +/- 8.4 N (range, 89 to 118 N), a 44% loss of stability, and 0 N, a complete loss of stability, respectively. CONCLUSIONS: Ipsilateral fractures of the scapular neck and the clavicular shaft do not produce a floating shoulder without additional disruption of the coracoacromial and acromioclavicular capsular ligaments. These and other unstable combined injury patterns are likely to be accompanied by substantial medial displacement of the glenoid fragment.

Aged↗
PubMed2001

Variation in summer dormancy in the lilioid geophyte Burchardia umbellata (Colchicaceae).

Plant dormancy is a form of phenotypic plasticity that minimizes exposure to seasonally stressful conditions. We examined variation in summer dormancy in two highland and two lowland populations of the lilioid geophyte Burchardia umbellata to test the prediction that facultative dormancy is advantageous in habitats with variable summer conditions. Consistent with this prediction fewer highland plants than lowland plants became dormant under wet common garden conditions. Also, significant among-family variance occurred within highland but not lowland populations, indicating genetic differences among and within populations. Most lowland plants became dormant when exposed to wet or dry conditions (∼92%), indicating that dormancy was primarily obligate. In contrast, dormancy in highland plants increased from 44% under wet conditions to 93% under dry conditions, indicating that dormancy of some highland plants was facultative and induced by drought. Survival, growth, and flowering were reduced in lowland populations, and in dormant vs. nondormant highland plants, indicating costs of dormancy that could negate the advantages of dormancy under variable summer conditions. Summers in lowland populations are predictably hot and dry, favoring a phenotype that responds invariably to environmental cues that are correlated to future dry conditions. In highland populations, variable summer conditions probably maintain polymorphism in dormancy.

Journal Article↗
PubMed2000

Saline irrigation in the prevention of otorrhea after tympanostomy tube placement.

OBJECTIVES: Comparison of intraoperative saline irrigation to otic drops in the prevention of postoperative otorrhea in children with middle ear effusion undergoing bilateral myringotomy with ventilation tubes. STUDY DESIGN: This study was designed as a blinded, controlled, prospectively randomized trial. METHODS: Study children were randomly assigned to receive either otic drops for 3 days postoperatively or saline irrigation of the middle ear space at the time of myringotomy. Only children with effusion present at the time of surgery were included. All children were evaluated for drainage 7 to 14 days postoperatively, and the degree of drainage was graded from 0 to 4. RESULTS: Of the 84 patients entered into the study, 62 patients were eligible for data analysis (16 failed follow-up, 6 records were lost). Of the patients who completed the study, not all had bilateral effusions, resulting in 111 ears for inclusion in the study. Fifty-two ears underwent irrigation, and 10 were noted to have otorrhea (19.2%). Fifty-nine ears received otic drops, resulting in 21 ears with otorrhea (35.6%). Evaluating the degree of otorrhea with a five-point Leichert scale, the average score per ear was 0.42 for the saline irrigation group and 1.07 for the control group. The rate and degree of drainage were both statistically reduced in the saline irrigation group (P < .05). CONCLUSIONS: Using middle ear irrigation at the time of tympanostomy may be more effective than antibiotic drops in preventing postoperative otorrhea.

Anti-Bacterial Agents↗
PubMed2000

Rotation of the clavicular portion of the pectoralis major for soft-tissue coverage of the clavicle. An anatomical study and case report.

BACKGROUND: The purposes of this study were to describe the anatomical features of a rotational flap consisting of the clavicular portion of the pectoralis major and to report the surgical technique and the outcome of use of this flap in a patient with poor soft-tissue coverage following multiple operations for a clavicular fracture complicated by nonunion and infection. METHODS: Ten shoulders from five cadavera were dissected to isolate the clavicular portion of the pectoralis major. The vascular pedicle, thoracoacromial artery, and axillary artery were identified, and the length of the vascular pedicle from the axillary artery to the muscle was measured. The angle of rotation of the flap about its intact clavicular origin was measured before and after division of the acromial branch of the thoracoacromial artery. The clavicular origin was then incised, and the overall length, width, and thickness of the muscle as well as the distance from each end of the muscle to the vascular pedicle were measured. RESULTS: The average length of the vascular pedicle from the axillary artery to the pectoralis muscle belly was 5.3 centimeters (range, 3.7 to 6.5 centimeters). The average maximum angle of rotation with the clavicular origin intact was 60 degrees (range, 55 to 67 degrees) before division of the acromial branch and 73 degrees (range, 65 to 82 degrees) after division. The average total length of the clavicular head was 20.2 centimeters (range, 18.0 to 23.0 centimeters). The average width of the clavicular head was 2.9 centimeters (range, 2.0 to 4.0 centimeters), and the average thickness was 0.5 centimeter (range, 0.2 to 0.7 centimeter). The vascular pedicle entered the muscle an average of 8.7 centimeters (range, 5.2 to 10.7 centimeters) lateral to the most medial extent of the muscle and an average of 11.5 centimeters (range, 9.5 to 14.0 centimeters) medial to the most lateral extent of the muscle. The rotational flap was successfully used clinically to provide soft-tissue coverage after bone-grafting and internal fixation of a clavicular nonunion that had been complicated by infection. CONCLUSIONS: The clavicular head of the pectoralis major may be used as a local rotational flap to cover soft-tissue deficiencies over the clavicle. It can be harvested with relative ease without damaging the sternocostal head.

Aged↗
PubMed2000

Pollen quality limits seed set in Burchardia umbellata (Colchicaceae).

In self-incompatible plants, interference by self pollen or genetically related pollen can potentially exacerbate pollen limitation, although this has rarely been demonstrated. We examined the breeding system, pollen limitation, and pollen interference using self- and cross- pollinations and pollen supplementations in Burchardia umbellata, an insect-pollinated lilioid monocot. Ovule fertilization and seed set were less following selfing than crossing (22 vs. 78% and 4 vs. 73%, respectively), indicating partial self-incompatibility. Flowers were partially protandrous, and flowers opened concurrently on plants potentially allowing self pollen interference. Natural seed set was pollen limited and varied within and among years, probably due to variation in flowering plant density. Interference by self or genetically related pollen caused pollen limitation as evidenced by increased seed set of bagged cross-pollinated plants compared to unbagged pollen-supplemented plants in two years. In 1996, both fertilization and seed set increased in response to cross-pollination, indicating that interference occurred in the style and ovary. In 1997, only seed set increased after cross-pollination indicating that interference occurred in the ovary. Inappropriate pollen deposition may contribute to pollen limitation more often than previously recognized and should select for floral traits that decrease deposition of self or related pollen.

Journal Article↗
PubMed1997

A role for the Ras signalling pathway in synaptic transmission and long-term memory.

Members of the Ras subfamily of small guanine-nucleotide-binding proteins are essential for controlling normal and malignant cell proliferation as well as cell differentiation. The neuronal-specific guanine-nucleotide-exchange factor, Ras-GRF/CDC25Mm, induces Ras signalling in response to Ca2+ influx and activation of G-protein-coupled receptors in vitro, suggesting that it plays a role in neurotransmission and plasticity in vivo. Here we report that mice lacking Ras-GRF are impaired in the process of memory consolidation, as revealed by emotional conditioning tasks that require the function of the amygdala; learning and short-term memory are intact. Electrophysiological measurements in the basolateral amygdala reveal that long-term plasticity is abnormal in mutant mice. In contrast, Ras-GRF mutants do not reveal major deficits in spatial learning tasks such as the Morris water maze, a test that requires hippocampal function. Consistent with apparently normal hippocampal functions, Ras-GRF mutants show normal NMDA (N-methyl-D-aspartate) receptor-dependent long-term potentiation in this structure. These results implicate Ras-GRF signalling via the Ras/MAP kinase pathway in synaptic events leading to formation of long-term memories.

3T3 Cells↗
PubMed1995

Placement of pedicle screws in the thoracic spine. Part I: Morphometric analysis of the thoracic vertebrae.

We studied the morphology of the thoracic vertebrae in the spines of seventeen human cadavera in order to define parameters that could be used as guidelines for the placement of hooks and screws in the pedicles to obtain internal fixation. We also reviewed computerized tomographic scans of nineteen thoracic spines in living patients who had no evidence of any vertebral deformity. The transverse diameter of the pedicle, which helps to determine the size of the screw, ranged from a mean (and standard deviation) of 4.5 +/- 1.2 millimeters in the fourth thoracic vertebra to a mean of 7.8 +/- 2.0 millimeters in the twelfth thoracic vertebra. The pedicles were inclined anteromedially throughout the thoracic spine, and the angle ranged from 0.3 degree toward the midline in the twelfth thoracic vertebra to 13.9 degrees in the fourth thoracic vertebra. The morphometric data revealed wide variations in the dimensions of the pedicles, demonstrating the importance of accurate preoperative imaging with transaxial computerized tomographic scans to visualize the precise osseous margins and angles of insertion of the thoracic pedicles.

Bone Screws↗
PubMed1994

Further characterisation of forms of haemosiderin in iron-overloaded tissues.

The biochemical and biophysical properties of isolated haemosiderins have been compared to that of another iron-containing protein, termed prehaemosiderin, which sediments through chaotropic potassium iodide only after 20 h of ultracentrifugation, in contrast to that of haemosiderin which is recovered after 2 h of ultracentrifugation. The iron/protein ratio and iron/phosphate ratio were less that that of the corresponding haemosiderin, while the elemental composition was also reduced in many of the prehaemosiderin samples. Mossbauer spectroscopy and electron diffraction identified the predominant presence of ferrihydrite in prehaemosiderin species even though the secondary haemochromatosis haemosiderin iron cores were essentially goethite-like. The majority of the prehaemosiderins isolated showed the presence of an additional peptide band at 17 kDa in addition to that at 21 kDa. Further Mossbauer studies of haemosiderin isolated from untreated secondary haemochromatosis patients showed that goethite was the predominant form of iron present, thereby indicating that the presence of this form of ferrihydrite was not wholly attributable to chelation therapy.

Animals↗