Decreased blood perfusion in canine tibial diaphysis after filling with acrylic bone cement compared with inert bone wax

Sixteen dogs had one tibia filled with acrylic PMMA bone cement and the opposite, control tibia filled with inert bone wax. After 1, 4, and 12 weeks, the blood perfusion in diaphyses was measured with Sc-46 labeled microspheres. The blood flow rates increased from 1 to 4 weeks and dropped to about the 1-week level after 12 weeks on both sides, with the acrylic side lower than the control side. On both sides, Disulphine Blue staining of the bones showed severe endosteal avascularity after 1 and 4 weeks and massive periosteal apposition after 4 and 12 weeks. The initial increase in blood flow is considered due to periosteal apposition, and the differences in blood flow rates are attributed to avascularity caused by the polymerization heat and toxicity of the acrylic cement.     

Simultaneous assessment of cardiac perfusion and function using 5-dimensional imaging with Tc-99m teboroxime

BACKGROUND: Dynamic single photon emission computed tomography (SPECT) acquisition and reconstruction of early poststress technetium 99m teboroxime washout images has been shown to be useful in the detection of coronary disease. Assessment of poststress regional wall motion may offer additional use in assessing coronary disease. Our goal was to investigate the feasibility of simultaneously imaging myocardial ischemia and transient poststress akinesis using gated-dynamic SPECT. METHODS AND RESULTS: A gated-dynamic mathematical cardiac torso (MCAT) phantom was developed to model both teboroxime kinetics and cardiac regional wall motion. A lesion was simulated as having delayed poststress teboroxime washout together with a transient poststress wall motion abnormality. Gated projection data were created to represent a 3-headed SPECT system undergoing a total rotation of 480 degrees . The dynamic expectation-maximization reconstruction algorithm with postsmoothing across gating intervals by Wiener filtering, and the ordered-subset expectation maximization reconstruction algorithm with 3-point smoothing across gating intervals were compared. Compared with the ordered-subset expectation maximization with 3-point smoothing, the dynamic expectation-maximization algorithm with Wiener filtering was able to produce visually higher-quality images and more accurate left ventricular ejection fraction estimates. CONCLUSION: From simulations, we conclude that changing cardiac function and tracer localization possibly can be assessed by using a gated-dynamic acquisition protocol combined with a 5-dimensional reconstruction strategy.     

Genotype prevalence and risk factors for severe clinical adenovirus infection, United States 2004-2006.

BACKGROUND: Recently, epidemiological and clinical data have revealed important changes with regard to clinical adenovirus infection, including alterations in antigenic presentation, geographical distribution, and virulence of the virus. METHODS: In an effort to better understand the epidemiology of clinical adenovirus infection in the United States, we adopted a new molecular adenovirus typing technique to study clinical adenovirus isolates collected from 22 medical facilities over a 25-month period during 2004-2006. A hexon gene sequence typing method was used to characterize 2237 clinical adenovirus-positive specimens, comparing their sequences with those of the 51 currently recognized prototype human adenovirus strains. In a blinded comparison, this method performed well and was much faster than the classic serologic typing method. RESULTS: Among civilians, the most prevalent adenovirus types were types 3 (prevalence, 34.6%), 2 (24.3%), 1 (17.7%), and 5 (5.3%). Among military trainees, the most prevalent types were types 4 (prevalence, 92.8%), 3 (2.6%), and 21 (2.4%). CONCLUSIONS: For both populations, we observed a statistically significant increasing trend of adenovirus type 21 detection over time. Among adenovirus isolates recovered from specimens from civilians, 50% were associated with hospitalization, 19.6% with a chronic disease condition, 11% with a bone marrow or solid organ transplantation, 7.4% with intensive care unit stay, and 4.2% with a cancer diagnosis. Multivariable risk factor modeling for adenovirus disease severity found that age <7 years (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.4-7.4), chronic disease (OR, 3.6; 95% CI, 2.6-5.1), recent transplantation (OR, 2.7; 95% CI, 1.3-5.2), and adenovirus type 5 (OR, 2.7; 95% CI, 1.5-4.7) or type 21 infection (OR, 7.6; 95% CI, 2.6-22.3) increased the risk of severe disease.     

Experimental verification of a model for predicting transient temperature distributions by focused ultrasound

A thermal model for predicting time-dependent temperature distributions during ultrasound heating was tested quantitatively. The relevant thermal processes incorporated in the model are heat conduction and ultrasound power absorption, and the required input parameters include the absolute ultrasound power, the shape and frequency of the ultrasound transducer, and the thermal and acoustical properties of the medium. Testing was done by heating an ultrasonically tissue-mimicking phantom with a 525 kHz, single element, focused source. The phantom has muscle-like acoustical properties and contains an array of copper-constantan thermocouples. Time-dependent temperature changes predicted with the thermal model were in very good agreement with those measured in the phantom, verifying the validity of the model for use in optimizing an ultrasound applicator design for a specific treatment situation.     

Channges in regional cerebral blood flow after hyperventilation in the pig with an induced focal cerebral contusion

Summary Changes in regional cerebral blood flow in anaesthetized pigs with an induced focal cerebral contusion were studied before and after two grades of hyperventilation. A reduction in arterial tension of CO₂ with 0.70mmHg and a further reduction of 0.55mmHg did not change the CO₂ reactivity. Reactivity in both injured and macroscopically normal regions was the same, revealing an average of 39.3% flow change per kPa change in CO₂ tension. Regions with low flow after the contusion had an equally big reduction apparently leading to hypoxia because global metabolic rate was unchanged.     

DIALLELIC POLYMORPHISM MAY EXPLAIN VARIATIONS OF THE BLOOD CONCENTRATION OF MANNAN-BINDING PROTEIN IN ESKIMOS,BUT NOT IN BLACK AFRICANS

Mannan-binding protein (MBP) is a lectin which, upon binding to certain carbohydrates, activates the classical pathway of complement without the involvement of antibody or C1q. Deficiency of the MBP is associated with an opsonic defect and recurrent infections during early life. An amino acid substitution in the exon 1 at codon 54 in the MBP gene (GGC [glycine] to GAC [aspartic acid]) has been shown to be closely associated with low MBP concentration in Caucasoids. The gene frequency of the mutant allele in this population has been estimated at 0.13. In the study described here, we investigated the association between the mutant allele and MBP protein concentration in Eskimos from East-Greenland and black Africans from the Baringo District in Kenya. The frequency of the GAC allele was identical in Eskimos and Caucasoids (0.13). No overlap with regard to MBP concentration between the genotypes was found in the Eskimos. In contrast, the Africans revealed a low frequency of the GAC allele (0.009). However, the median MBP protein concentration was approximately 5 times lower among the Africans than the Eskimos. In 12.6% of the Africans and in 2.5% of the Eskimos, MBP was undetectable. Thus, MBP deficiency is the most frequent immunodeficiency so far described. The high prevalence of MBP deficiency among healthy individuals indicates that MBP deficiency also confers some selective advantages. We advance the hypothesis that MBP deficiency is maintained in populations because MBP deficiency decreases the infectivity of some intracellular micro-organisms which are dependent on opsonization.     

A simple mechanical model using a piston to produce localized cerebral contusions in pigs

Summary A simple mechanical model using a piston to produce localized cerebral contusions in pigs, is presented.The precision and reproducibility of the method are described by the biomechanical and pathological results.There are only pathological changes with haemorrhage and laceration close to the place of entry of the piston. The changes in the physiological parameters also indicate that the damage is focal.In this model, when kept intact, the dura mater offers considerable protection as no pathological changes in the brain are observed even when the energy at the time of the contusion is increased to twice the values which, when the dura is open, cause considerable damage.     

Effects of Clodronate on Cortical and Trabecular Bone in Ovariectomized Rats on a Low Calcium Diet

The aim of this study was to evaluate the contribution of a low calcium diet to the cortical and trabecular osteoporosis seen in ovariectomized rats after 7 weeks on a low calcium diet and to investigate the effects of the bisphosphonate clodronate on this development of osteoporosis. Thirty-six mature, female Wistar rats were randomized into four groups: Ovx−B (bisphosphonate) and Ovx−C (control) were ovariectomized, and Sham−Ca (low calcium) and Sham+Ca (normal calcium) were sham operated. The first three groups were fed a low calcium diet (0.01%) and Sham+Ca normal rat chow (Ca 1.1%). The Ovx−B received 10 mg/kg s.c. clodronate daily for nine weeks, and Ovx−C, Sham−Ca, and Sham+Ca received the same volumes of saline. Bone mineral turnover measured as ⁸⁵Sr-uptake was increased in all low calcium groups compared to Sham+Ca. The Sham+Ca femora had higher dry weight and ash weight than the other groups, and Ovx−C had higher dry weight compared with Ovx−B and Sham−Ca. Calcium content was lower in both Ovx groups compared to both Sham groups. Magnesium was lower in all groups compared to Sham+Ca and higher in Ovx−B compared with Ovx−C. In the femoral shaft, Sham+Ca had significantly higher ultimate bending moment, energy absorption, and deflection compared to the other three groups. Ultimate bending moment was higher in Sham−Ca than in Ovx−C. Stiffness was increased in both Sham+Ca and Ovx−B compared to Ovx−C. The maximum stress in the femoral midshaft was higher in Sham+Ca than in the other groups, and higher in Ovx−B than in Ovx−C. Histomorphometry showed increased medullary area in all low calcium groups compared to Sham+Ca and larger cortical area in Sham+Ca and Ovx−B compared to Ovx−C. Compared to Sham+Ca the trabecular bone volume was decreased to 30% in Sham−Ca and to 9% in Ovx−C, but was unchanged in Ovx−B. The low calcium diet generally increased bone mineral turnover and reduced the tibial bone volume. Femoral changes led to a reduction of cortical fracture strength and maximal stress. Ovariectomy in addition to a low calcium diet reduced femoral strength even more. Daily injections of clodronate to ovariectomized rats on a low calcium diet increased femoral shaft stiffness and maximum stress, and clodronate preserved both trabecular and cortical tibial bone volume completely. Received: 11 June 1996 / Accepted: 5 March 1997     

Diving physiology and pathophysiology

Summary. Divers have worked at 500 m depth in the sea and have reached 700 m in simulated chamber dives. A prerequisite for this has been extensive physiological studies of the body's reactions to pressure and pressure changes. This paper reviews such physiological and pathophysiological studies with emphasis on recent developments.