Hydrostatic pressure and aquatic plant growth: a laboratory study

A method was tested for growing aquatic vascular plants at elevated hydrostatic pressure so that the influence of other factors will not mask the specific plant-pressure interaction. Eighteen species of submersed vascular plants, belonging to twelve families and several distinct growth forms, were subjected to series of hydrostatic pressures including those well in excess of those encountered by the species when growing at its normal depths in lakes. Under no circumstances was the form of the plant altered even at the highest pressures, equivalent to that at a water depth of 23 m. The removal of confounding extraneous factors depends upon controlling competing algae, on raising the pressure in a series of steps, on maintaining the pressure without fluctuations during the growing period, on suiting the light and temperature conditions to the species and maintaining aquasoil air spaces or allowing them to develop. These preliminary data suggest that the level of hydrostatic pressure in the depth distribution of aquatic plants cannot be either a necessary or a sufficient controlling factor.     

Vibratory sensory testing in acute compartment syndromes: a clinical and experimental study

Invasive and noninvasive diagnostic testing was correlated in 11 patients with acute compartmental syndromes of the forearm. The excellent correlation between diminished perception of vibration and increasing compartmental pressure suggested that 256 cycle per second (cps) vibratory stimuli may be useful clinically in determining the appropriate time for surgical intervention in the acute compartmental syndrome. In 12 adult male volunteers, elevated compartment pressures were created in the anterior tibial compartment of the leg. A decrease in perception to 256 cycle per second (cps) vibratory stimulus was the earliest sensory abnormality to occur with elevated tissue compartment pressures. Analysis of variance showed significantly that 256-cps vibration was the most reliable and earliest sensory modality to change at pressures of 35 to 40 mmHg. These clinical and experimental findings support the use of the 256-cps tuning fork as a noninvasive diagnostic test in the evaluation of the patient with suspected acute compartment syndrome.     

Intraocular pressure changes: an important determinant of the biocompatibility of intravitreous implants

Background

In recent years, research efforts exploring the possibility of using biomaterial nanoparticles for intravitreous drug delivery has increased significantly. However, little is known about the effect of material properties on intravitreous tissue responses.

Principal Findings

To find the answer, nanoparticles made of hyaluronic acid (HA), poly (l-lactic acid) (PLLA), polystyrene (PS), and Poly N-isopropyl acrylamide (PNIPAM) were tested using intravitreous rabbit implantation model. Shortly after implantation, we found that most of the implants accumulated in the trabecular meshwork area followed by clearance from the vitreous. Interestingly, substantial reduction of intraocular pressure (IOP) was observed in eyes implanted with particles made of PS, PNIPAM and PLLA, but not HA nanoparticles and buffered salt solution control. On the other hand, based on histology, we found that the particle implantation had no influence on cornea, iris and even retina. Surprisingly, substantial CD11b+ inflammatory cells were found to accumulate in the trabecular meshwork area in some animals. In addition, there was a good relationship between recruited CD11b+ cells and IOP reduction.

Conclusions

Overall, the results reveal the potential influence of nanoparticle material properties on IOP reduction and inflammatory responses in trabecular meshwork. Such interactions may be critical for the development of future ocular nanodevices with improved safety and perhaps efficacy.     

Hepatocyte polarity and the peroxisomal compartment: a comparative study

In search of factors that regulate the phenotype of the peroxisomal compartment in wild-type liver parenchymal cells, we compared hepatocyte polarity to peroxisome differentiation, using adult liver as the standard. Differentiation parameters were evaluated in a three-dimensional culture model (spheroid), in 'sandwich' and monolayer primary hepatocyte cultures, and in 15.5 and 18.5-day-old foetal rat liver.Peroxisomes, studied by immunohistochemistry, enzyme histochemistry, and catalase specific activity, were better differentiated depending on foetal age (day 18.5 > day 15.5) and culture type (spheroid > sandwich > monolayer). The hepatocyte polarity markers ATP-, ADP-, and AMP-hydrolysing activities were, in all models, mislocalized at the lateral plasma membrane, whereas in contrast the multidrug resistance-associated protein 2 (mrp2) antigen was always correctly immunolocalized at the apical membrane domain. In cultures, the correct secretion of fluorescein (mrp2-mediated) into bile canaliculi was observed. Bile canaliculi (branching, ultrastructure and immunolocalization of the tight-junction associated protein ZO-1), were better differentiated in 18.5 than in 15.5-day-old foetal liver and in spheroid > sandwich > monolayer cultures.Our results show a parallelism between changes of the peroxisomal compartment and bile canalicular structure together with mrp2-mediated secretory function. Distinct polarization characteristics do not necessarily change simultaneously, suggesting different regulatory mechanisms.     

Liver development and regeneration: from laboratory study to clinical therapy

The liver has an unusual capacity to regenerate after a loss of mass and function caused by surgical resection or toxic liver injury. Over the last 10 years there have been major advances in our understanding of the molecular and cellular mechanisms underlying liver development and regeneration. The numerous factors crucial to these phenomena have been identified mainly by using knockout mice. Forward-genetics studies using zebrafish and medaka have also generated many mutants with liver disorders or defects in liver formation. Our goal is to translate knowledge gained from laboratory work and animal models into novel therapies for human liver diseases. Exciting progress has been achieved using human partial liver transplantation and autologous cell therapy.     

Coenzyme Q: a molecular orbital study.

The molecular structure and electronic properties of coenzyme Q, also known as ubiquinone, have been studied with the methods of semiempirical molecular orbital theory. It is found that the preferred conformation of the isoprene unit is such that formation of the chroman is favorable. The methoxy groups then assume a nonplanar configuration. Orbital energies, dipole moments, and spectra for the coenzyme Q₁ molecule and some of its chroman intermediates are also given in the calculations. The possibility of charge-transfer complex formation of chroman intermediate with inorganic phosphate is discussed.     

Radiographic changes in alveolar bone height on overdenture abutments: a longitudinal study

Objective: Stabilisation of partial dentures is an important part of prosthodontic treatment, particularly in patients with an excessive reduction in alveolar bone supporting their abutment teeth. In these cases, overdenture prostheses are one possible treatment choice. Background: The aim of this study was to evaluate the effects of overdentures on the condition of alveolar bone of the remaining teeth, and to evaluate the overdenture concept in the prosthetic treatment of partially edentulous patients. Materials and methods: The investigation was conducted on 22 patients during observation periods of 6 and 10 years. After preparation, all abutment teeth were provided with either amalgam restorations or gold copings. An overdenture in the lower jaw was fabricated for every patient. A special film holder was used to repeat the X‐ray procedure in every patient in the same manner. The radiographs were evaluated using the grid scale. The alveolar bone level of all remaining teeth was evaluated on dental films by measuring the distance between the root apex and coronal border of the alveolar bone. Results: A statistically significant difference (p < 0.01) was calculated 6 years after delivery stage between distal alveolar bone levels of experimental abutments under overdentures and the remaining teeth of the control group. Alveolar bone of abutment teeth was considerably preserved, particularly in seven patients observed 10 years after provision of their dentures. Conclusion: Within the limitation of this study, the validity of the overdenture treatment in partially edentulous patients is concluded. Good oral hygiene was crucial for the success of treatment with overdentures.     

Intraocular pressure in genetically distinct mice: an update and strain survey

Background  

Little is known about genetic factors affecting intraocular pressure (IOP) in mice and other mammals. The purpose of this study was to determine the IOPs of genetically distinct mouse strains, assess the effects of factors such as age, sex and time of day on IOP in specific strain backgrounds, and to assess the effects of specific candidate gene mutations on IOP.     

Bacterial and phosphorus dynamics in profundal Lake Erken sediments following the deposition of diatoms: a laboratory study

The benthic microbial response to the deposition of naturalseston and the microbial impact on nutrient dynamics wasstudied in an experimental system using whole sediment coresequipped with flow-through systems for the overlying water. For20 days, changes in sediment bacterial activity, totalmetabolic activity (heat production), bacterial biomass,phosphorus fractions and basic chemistry were followed, as wellas the exchange of nutrients between sediment and water.Microbial activity and biomass increased immediately inresponse to the deposition of seston, peaked after seven daysand then decreased linearly over the remaining time of theexperiment. Co-settled bacteria were suggested to play animportant role in the microbial response. Changes in bacterialbiomass production, bacterial biomass and the NaOH-nrPextractable phosphorus fraction were concurrent in response toseston additions. The sediment acted as a trap for SRP from theoverlying water when bacterial activity was high and as asource when the bacterial activity decreased. Altogether, theresults suggest an important role of bacteria in theregeneration of seston P. Mineralization rates estimated fromsediment heat production showed that ca. 11% of the addedseston carbon was oxidized in the sediments during theexperiment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparative bacterial clearances of muscle and skin/subcutaneous tissues with and without dead bone: a laboratory study

Seventeen New Zealand White rabbits underwent implantation of three different concentrations of bacteria and a sterile saline control solution with and without dead autologous bone in eight separate muscular and eight separate subcutaneous sites. Following a period of 1 week, each site was surgically explored and samples of tissue were taken for histology and quantitative culture. Results reveal that final bacterial concentrations in the subcutaneous sites were significantly lower than in the muscle sites (p less than or equal to 0.0001) for each concentration of bacteria, with and without dead bone. Dead bone resulted in very significantly greater bacterial concentrations in both subcutaneous and muscle sites. Clinically, these results indicate that a thorough bony wound debridement is more important than the type of tissue used to close the wound. Flap tissue should be selected with regard to the perfusion, contour, and appearance of the recipient site.     

Maxillofacial growth in children with unilateral cleft lip and palate following secondary alveolar bone grafting: an interim evaluation

This study evaluates the effect of alveolar bone grafting on the maxillofacial growth in children of mixed dentition with unilateral complete cleft lip-cleft palate. Twenty patients received an iliac crest alveolar bone graft between the ages of 6 years 10 months and 10 years 10 months, whereas 20 matched controls between the ages of 6 years 11 months and 10 years 6 months did not. Geometric morphometric assessments were used to localize alterations between the initial and final cephalographs in the two groups of cleft children, using Procrustes analysis and thin-plate spline analysis, in addition to conventional cephalometric techniques. It is concluded that no statistically significant difference in maxillofacial growth was found between the cleft children having received secondary alveolar bone grafting and the nongraft controls in general during the first to third postoperative years. Further investigation will be undertaken to determine the long-term effects after the age of skeletal maturity.     

Material changes in osteoporotic human cancellous bone following infiltration with acrylic bone cement for a vertebral cement augmentation

Bone cement infiltration can be effective at mechanically augmenting osteoporotic vertebrae. While most published literature describes the gain in mechanical strength of augmented vertebrae, we report the first measurements of viscoelastic material changes of cancellous bone due to cement infiltration. We infiltrated cancellous core specimen harvested from osteoporotic cadaveric spines with acrylic bone cement. Bone specimen before and after cement infiltration were subjected to identical quasi-static and relaxation loading in confined and free compression. Testing data were fitted to a linear viscoelastic model of compressible material and the model parameters for cement, native cancellous bone, and cancellous bone infiltrated (composite) with cement were identified. The fitting demonstrated that the linear viscoelastic model presented in this paper accurately describes the mechanical behaviour of cement and bone, before and after infiltration. Although the composite specimen did not completely adopt the properties of bulk bone cement, the stiffening of cancellous bone due to cement infiltration is considerable. The composite was, for example, 8.5 times stiffer than native bone. The local stiffening of cancellous bone in patients may alter the load transfer of the augmented motion segment and may be the cause of subsequent fractures in the vertebrae adjacent to the ones infiltrated with cement. The material model and parameters in this paper, together with an adequate finite-element model, can be helpful to investigate the load shift, the mechanism for subsequent fractures, and filling patterns for ideal cement infiltration.     

Effect of bleeding site on clinical laboratory testing of rats: orbital venous plexus versus posterior vena cava.

We sought to determine if there were any differences in the results of clinical laboratory tests between blood samples collected from the orbital venous plexus and the posterior vena cava of adult male rats. Thirty healthy adult male Sprague Dawley rats were anesthetized by ether inhalation, and blood samples were collected successively from the orbital venous plexus (OVP) and the posterior vena cava (PVC) for hematologic (n = 10), serum chemistry (n = 10), and coagulation (n = 10) analyses. The prothrombin and partial thromboplastin times of samples from the OVP were prolonged (17% and 288%, respectively) when compared with samples from the PVC. Respective hematologic biases were as follows: red blood cell count (7%), hemoglobin (6%), hematocrit (5%), mean corpuscular volume (-3%), mean corpuscular hemoglobin (-1%), mean corpuscular hemoglobin content (1%), white blood cell count (13%), and platelet count (-7%). Respective serum chemistry biases were as follows: sorbitol dehydrogenase (-7%), glucose (-7%), blood urea nitrogen (-10%), creatinine (-2%), total protein (4%), albumin (2%), globulin (9%), alkaline phosphatase (5%), lactate dehydrogenase (-6%), aspartate aminotransferase (-5%), alanine aminotransferase (-2%), total bilirubin (0%), direct bilirubin (0%), magnesium (-17%), sodium (4%), potassium (0), chloride (4%), calcium (-2%), phosphorous (-17%), cholesterol (3%), triglycerides (24%), creatinine kinase (-8%), 5'nucleotidase (0%), and total bile acids (4%). For hematologic testing, there were no biologically significant differences between samples collected from the OVP and PVC. The coagulation times and serum Mg and P showed biologically significant differences between samples collected from the OVP and PVC.(ABSTRACT TRUNCATED AT 250 WORDS)     

Platelet concentrate as an additive to bone allografts: a laboratory study using an uniaxial compression test

Chemical cleaning procedures of allografts are destroying viable bone cells and denaturing osteoconductive and osteoinductive proteins present in the graft. The aim of the study was to investigate the mechanical differences of chemical cleaned allografts by adding blood, clotted blood; platelet concentrate and platelet gel using a uniaxial compression test. The allografts were chemically cleaned, dried and standardized according to their grain size distribution. Uniaxial compression test was carried out for the four groups before and after compacting the allografts. No statistically significant difference was found between native allografts, allografts mixed with blood, clotted blood, platelet concentrate and platelet concentrate gel regarding their yield limit after compaction. The authors recommend to chemical clean allografts for large defects, optimize their grain size distribution and add platelet concentrate or platelet rich plasma for enhancing as well primary stability as well bone ingrowth.