Determinants of ovine compact bone viscoelastic properties: effects of architecture, mineralization, and remodeling.

Significant decreases in ovine compact bone viscoelastic properties (specifically, stress-rate sensitivity, and damping efficiency) are associated with three years of ovariectomy and are particularly evident at higher frequencies [Proc. Orthop. Res. Soc. 27 (2002) 89]. It is unclear what materials or architectural features of bone are responsible for either the viscoelastic properties themselves, or for the changes in those properties that were observed with estrogen depletion. In this study, we examined the relationship between these viscoelastic mechanical properties and features involving bone architecture (BV/TV), materials parameters (ash density, %mineralization), and histologic evidence of remodeling (%remodeled, cement line interface). The extent of mineralization was inversely proportional to the material's efficiency in damping stress oscillations. The damping characteristics of bone material from ovariectomized animals were significantly more sensitive to variation in mineralization than was bone from control animals. At low frequencies (6 Hz or less), increased histologic evidence of remodeling was positively correlated with increased damping efficiency. However, the dramatic decreases in stress-rate sensitivity that accompanied 3-year ovariectomy were seen throughout the bone structure and occurred even in areas with little or no secondary Haversian remodeling as well as in areas of complete remodeling. Taken together, these data suggest that, while the mineral component may modify the viscoelastic behavior of bone, the basic mechanism underlying bone viscoelastic behavior, and of the changes in that behavior with estrogen depletion, reside in a non-mineral component of the bone that can be significantly altered in the absence of secondary remodeling.

Microvessels that predict axillary lymph node metastases in patients with breast cancer.

HYPOTHESIS: The density of vasoactive endothelial growth factor receptor 3-immunostained microvessels in primary breast cancers correlates with the incidence of axillary lymph node metastasis. DESIGN: Breast cancer microvessel clusters ("hot spots") were sequentially immunostained for factor VIII, type IV collagen, and vasoactive endothelial growth factor receptor 3. Microvessels were counted under light microscopy at a magnification of x 200. Axillary lymph nodes were evaluated for metastases by light microscopy. SETTING: A multidisciplinary breast cancer clinic and laboratory. PATIENTS: Sixty patients with T2 breast cancers treated by lumpectomy (or mastectomy) and axillary lymphadenectomy. MAIN OUTCOME MEASURES: Putative lymphatic microvessel density compared with axillary metastases. RESULTS: There were 16% (SE, 1.4%) vs 4% (SE, 0.8%) vasoactive endothelial growth factor receptor 3-immunostained microvessels (P<.001), 38% (SE, 3.9%) vs 65% (SE, 3.1%) type IV collagen-immunostained microvessels (P<.001), and 46% (SE, 4.1%) vs 31% (SE, 3.2%) unstained microvessels (P = .004) in node-positive vs node-negative patients, respectively. A fitted logistic model based on the relative percentage of putative lymphatic microvessels to blood microvessels correctly predicted that 23 (96%) of 24 patients would have a low risk and that 26 (96%) of 27 patients would have a high risk of lymph node metastases. Six (67%) of 9 patients predicted to have an intermediate risk had lymph node metastases. CONCLUSION: The odds of a patient with breast cancer having axillary lymph node metastasis increased substantially as the proportion of putative lymphatic microvessels increased and the relative proportion of blood microvessels in angiogenic hot spots decreased (log likelihood = 14.6; chi2 = 53.4; P<.001; area under the receiver operation characteristic curve = 0.97).

Ophthalmoplegia resulting from an intraorbital hematoma.

BACKGROUND: A case is described in which an intraorbital hematoma was found to complicate recovery from attempted aneurysm clipping 5 days into the postoperative period. The etiology, management, and complication avoidance are discussed. CASE DESCRIPTION: Five days after attempted surgical clipping of an internal carotid artery aneurysm via a frontotemporal craniotomy with orbital osteotomy, a patient underwent coiling of the aneurysm. Shortly after the endovascular procedure, the patient developed exophthalmos and ophthalmoplegia involving the right side followed by decline in her level of consciousness. An emergency computed tomography (CT) scan revealed an epidural hematoma with intraorbital extension. After evacuation of the hematoma, the patient recovered extraocular function and returned to her baseline mental status. CONCLUSION: Exophthalmos and ophthalmoplegia in a patient recovering from cranial surgery using skull base techniques warrants immediate attention, especially after endovascular procedures. Delay in intervention may result in loss of neurologic function or life. The authors discuss the relevant literature and management of this uncommon complication.

The role of spinal fusion in surgery for lumbar spinal stenosis: a review.

The authors undertook a review of the literature and analysis of the local surgical experience for lumbar stenosis to define the role of simultaneous arthrodesis in the treatment of patients undergoing decompression for spinal stenosis. The restrained use of spinal fusion is recommended in spinal stenosis surgery because of the coexisting medical problems in the elderly patient population and the higher associated complication rate with spinal fusion and instrumentation. A spinal fusion is recommended when decompression is performed in an area of segmental instability as manifested by gross movement on flexion--extension radiographs; when the decompression coincides with an area of degenerative instability, as with scoliosis or spondylolisthesis; or when the decompression creates an iatrogenic instability by the disruption of the posterior elements. The use of spine instrumentation as an adjunct to fusion is recommended when an area of degenerative instability shows evident gross instability or has had additional destabilizing procedures, such as a discectomy or a facetectomy. Spinal fusion is not recommended for a routine decompressive laminectomy for lumbar stenosis or in the case of stable degenerative deformities. New fusion techniques may improve the outcome and decrease the morbidity associated with contemporary methods of spinal fusion and instrumentation.

Effect of 1,3-butanediol and short chain acids in sow gestation diets on maternal plasma metabolites and fetal energy storage.

Gestating sows were fed diets in which 15% of the metabolizable energy was in the form of glucose monohydrate (control), 1,3-butanediol (BD) or an equimolar mixture of acetate and lactate (AL) in order to study the effects of ketogenic, glucogenic and lipogenic substrates on fetal energy storage. Diets were initiated on d 90 of gestation. Blood plasma was obtained from sows 2 and 8 h after feeding on d 102 of gestation. Sows receiving BD had a higher (P less than .001) concentration of beta-hydroxybutyrate (.54 vs .12, .14 mM) and a lower (P less than .05) concentration of glucose (72 vs 82, 86 mg/dl) after 8 h than sows in control or AL groups, respectively. Sows in the AL group had a higher (P less than .10) acetate concentration at 2 h, but no difference was observed by 8 h. Lactate concentration was lower (P less than .10) in AL sows when compared with those in the control group (69 vs 101 mg/dl). Two pigs/litter were killed at birth and two/litter were fasted for 36 h with blood samples obtained at 12-h intervals. Newborn pigs from AL and BS sows had more total liver glycogen than pigs derived from control sows (4.18, 4.07 vs 3.09 g, respectively); however, this difference was significant only for pigs from AL sows (P less than .10). Pigs in BD and AL groups had a higher (17 to 25%), though not significantly different, glucose concentration than controls after 24 and 36 h of fasting.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the chemical and biochemical composition of thirteen muscles of the rat after dietary protein restriction.

1. The objective of this study was to determine whether the chemical and biochemical changes induced by muscle wasting caused by dietary protein restriction are different in various skeletal muscles. 2. Rats were fasted for 3 d and then fed on a 10 g protein/kg diet for 21 d. Thirteen muscles from the trunk, forelimb, and hind-limb regions were analysed for muscle weight, and the content of water, fat, cellular and extracellular protein, DNA and RNA. Results were compared to values for an 'initial' control group killed at the start of the experiment. 3. Weight loss was greatest in trunk muscles and least in the distal forelimb muscles. Water content decreased in most muscles, but increased in three forelimb muscles. A significant loss of lipid was found in the gastrocnemius, while the biceps brachii gained lipid. Changes in lipid content of the muscles did not form a distinctive pattern. 4. All muscles except the distal forelimb muscles lost a significant amount of cellular protein, while all muscles except the diaphragm gained extracellular protein. 5. DNA content was unchanged in all muscles. The value for cellular protein:DNA was significantly reduced in the rectus abdominis and the diaphragm. A significant loss of RNA was found in all muscles; the percentage change was greatest in trunk muscles and least in the distal forelimb muscles. The values for RNA:protein and RNA:DNA were significantly lower in all muscles except two distal forelimb muscles. 6. With the exception of the water and lipid content of the muscles, the directions of the changes in the experimental animals were the same for all muscles. The results suggested, however, that the magnitude of changes in certain chemical and biochemical indices of composition may depend to some extent on the anatomical location of the muscle: trunk muscles tended to show the greatest percentage change, while the distal forelimbs changed the least.