An analytical model for the prediction of the local concentration of cryophylactic agents in perfused organs.

An analytical model has been developed for the prediction of the spatial and temporal distribution of the concentration of cryophylactic agent (CPA) in perfused tissues and organs. Perfusate concentration of the CPA is allowed to change according to a protocol in which the concentration increases linearly from zero during a time interval t₀. Between time t₀ and t_f, the concentration is constant.The numerical results of this analysis show that the typical time required to reach an appropriate CPA concentration by simple diffusion alone is sufficiently long that the natural vascular network must be employed as a means of introducing the CPA. The results of this analysis also demonstrate the importance of careful protocol design with the aid of this model. There is evidence to show that protocols previously reported in the literature failed to achieve the appropriate CPA concentration.Further work in this area requires more detailed information concerning the diffusion coefficients of the various CPA's in biological tissues. With the aid of this information and the present model, optimum protocols can be designed so that the CPA concentration can be increased to the desired level without inducing osmotic shock.     

A comparison of chemical pretreatment methods for improving saccharification of cotton stalks

The effectiveness of sulfuric acid (H(2)SO(4)), sodium hydroxide (NaOH), hydrogen peroxide (H(2)O(2)), and ozone pretreatments for conversion of cotton stalks to ethanol was investigated. Ground cotton stalks at a solid loading of 10% (w/v) were pretreated with H(2)SO(4), NaOH, and H(2)O(2) at concentrations of 0.5%, 1%, and 2% (w/v). Treatment temperatures of 90 degrees C and 121 degrees C at 15 psi were investigated for residence times of 30, 60, and 90 min. Ozone pretreatment was performed at 4 degrees C with constant sparging of stalks in water. Solids from H(2)SO(4), NaOH, and H(2)O(2) pretreatments (at 2%, 60 min, 121 degrees C/15 psi) showed significant lignin degradation and/or high sugar availability and hence were hydrolyzed by Celluclast 1.5L and Novozym 188 at 50 degrees C. Sulfuric acid pretreatment resulted in the highest xylan reduction (95.23% for 2% acid, 90 min, 121 degrees C/15 psi) but the lowest cellulose to glucose conversion during hydrolysis (23.85%). Sodium hydroxide pretreatment resulted in the highest level of delignification (65.63% for 2% NaOH, 90 min, 121 degrees C/15 psi) and cellulose conversion (60.8%). Hydrogen peroxide pretreatment resulted in significantly lower (p相似文献   

A clinical comparison of bone imaging agents

This study compares the six commercially available kits for preparing methylene diphosphonate. The kits were randomly assigned to 134 bone examinations such that neither the physicians nor the technologists knew which brand of tracer was used. Thigh activity quantitatively varied significantly among the kits (P = 0.019). Detectable gastric activity also varied by brand. Other qualitative and quantitative measures of bone and soft tissue uptake showed no significant differences among the kits but consistently favored the Squibb product.     

Cryoprotective agents for frozen concentrated starters from non-bitterStreptococcus lactis strains

Summary Six cryoprotective agents were tested on cells harvested from 4 pH-regulated fermentations of a non-bitterS. lactis strain. Addition of 5% lactose or 5% sucrose to centrifugation pellets and a storage temperature of –40 C or –70 C resulted in the highest viability and acid-producing activity of frozen concentrated starters.     

A comparison of skin temperature and EMG training for primary dysmenorrhea

Eleven female volunteers completed a 6-month treatment program consisting of a 2-month baseline phase, 2 months of biofeedback training ( number of sessions=12.9), and 2 months of follow-up data collection. Subjects were assigned to one of two treatment groups: skin temperature training or EMG training of the frontalis muscle. Self-report data were gathered by means of the Symptom Severity Scale. Results, which were analyzed according to a 2×3 (treatment×phase) split-plot factorial design, indicate a highly significant overall treatment effect (F=19.32,p<.001). There was no significant difference between treatments (F=.47) and no significant interaction effect (F=1.74).     

Lignocellulose pretreatment: A comparison of wet and dry ball attrition

Summary A comparison of wet and dry ball attrition of various lignocellulosic substrates indicates that terminal crystallinity index following enzymatic hydrolysis usually decreases after wet attrition and increases after dry attrition. Particle size was reduced to a greater extent in dry attrition in accordance with increased friability. Conversions favored neither wet nor dry pretreatment, indicating substrate specific requirements.     

A comparison of radiolabelled agents for thrombus imaging using a rabbit model

The quantitative uptakes of five potential thrombus-localizing radiopharmaceuticals in experimental thrombi of the rabbit jugular vein have been compared to assist with the selection of a thrombus imaging agent for clinical use. Three hours after injection, ¹¹¹In-platelets were clearly the agent of choice but at 18 h ^99mTc-fibrinogen had more favourable characteristics. Both agents were superior to ^99mTc-plasmin or its acyl derivatives, including ^99mTc-streptokinase-activated anisoylplasminogen. The ease of preparation coupled with favourable biological properties suggest that ^99mTc-fibrinogen should be of value in the clinical situation.     

A technique for unilateral instillation of agents into the rat lung

We describe a technique for unilateral instillation of agents into the right lung of rats. We intubated rats perorally with a 16-gauge flexible polyethylene catheter and through it introduced narrow-bore (less than 1 mm diam) polyethylene tubing into the trachea and beyond the carina into the right main-stem bronchus. This maneuver was facilitated by placing the animal supine with the cephalad end tilted up and the right side tilted down. We tested the effectiveness of our technique by instilling Evans blue dye into the right lung of 14 rats and spectrophotometrically quantitating the amount of dye present in homogenates from each lobe of the right and left lungs. Ninety-seven percent of the instilled dye was recovered from the right lung, and distribution of dye per gram of tissue was uniform among the four lobes. The technique described should be useful in producing severe degrees of unilateral lung injury and fibrosis in rodents without the high mortality that can be associated with bilateral lung injury.     

A comparison of absorbable and nonabsorbable suture materials for skin repair.

This prospective clinical study was conducted to compare the outcome of elective surgical wound repair in the occipital region during rhytidectomy using absorbable and nonabsorbable suture materials. On an alternative basis, 6-0 polypropylene and 6-0 plain catgut were used to repair the incisions on the upper and lower half of the surgical wounds in 80 sites. These sites were then compared for stitch marks, erythema, hypertrophic scars, infection, and wound necrosis. This study revealed slightly visible stitch marks in 4 of 40 (10 percent) sites repaired with catgut and in 10 of 40 (25 percent) sites repaired with polypropylene material (p less than 0.10); however, this was not statistically significant. There were five incidences of suture-site erythema (12.5 percent) noted in the group of catgut repairs in comparison with three incidences (7.5 percent) in the group repaired using polypropylene. Furthermore, there was no statistically significant difference in hypertrophic scarring or infection rate between these groups. The incidence of erythema following repair with catgut was higher, but this was also not statistically significant. Considering these findings, coupled with the avoidance of patient discomfort, suture removal, and time spared for the surgeon and staff when absorbable suture material is used, the superiority of plain catgut over nonabsorbable material becomes evident.     

Cyclophosphamide pretreatment in tumor cryotherapy: A comparison with alternative drugs

The method of Turk and Lagrange for modulating immune responses in favor of the cell-mediated effector arm by using single high doses of cyclophosphamide 3 days before antigen has previously been shown to cause decreased rates of local tumor recurrence when adapted as an adjunctive therapy to cryosurgery in a murine model. This series of experiments compares cyclophosphamide, azathioprine, and methotrexate against cryosurgery alone in the same therapeutic protocol. Only cyclophosphamide gave enhanced numbers of cures; azathioprine caused an increase in metastases arising concurrently with local tumor recrudescence.     

Mixed glycosidase pretreatment reduces nonspecific binding of antibodies to frozen tissue sections

Indirect immunohistochemical studies of frozen mouse tissues with mouse monoclonal antibodies yield, in general, suboptimal results primarily because of indiscriminate binding of secondary antibody to all mouse immunoglobulins, i.e., to the monoclonal reagent and to endogenous immunoglobulin nonspecifically trapped in the tissue. To reduce this nonspecific staining, frozen sections of mouse kidney were treated enzymatically. Optimal results were obtained following a 2 hr treatment with 20 mg/ml of mixed glycosidases (MG). This treatment reduced the nonspecific background staining of the interstitial spaces and blood vessels, but did not affect the reactivity of structurally bound immunoglobulin G (IgG) in the glomeruli or alter the reactivity of mouse renal tissue to the monoclonal antibody that recognizes an oligosaccharide antigenic determinant (SSEA-1). Eluates from enzyme-treated frozen tissue sections contained normally immunoreactive IgG in the form of dimers. These data indicate that MG treatment of frozen sections could be safely used to reduce the content of nonstructurally bound immunoglobulins in frozen tissues and thus improve the visualization of specific monoclonal antibody binding.     

Physical changes in specimens of five species of Cyprinidae preserved in ethanol and frozen

Preservation in 30% ethanol and freezing to a temperature of ?20 ± 2° C is an appropriate method for measurement of fish eggs, larvae and juveniles. Egg diameter of the common carp Cyprinus carpio increased insignificantly by 1·32% after preservation compared with live size. The total length (L_T) of 1 day post‐hatching (dph) larvae as well as the standard length (LS) of 16 dph larvae of C. carpio increased significantly (2·95 and 1·50%, respectively) after preservation. Egg diameter as well as the L_T of 1 dph larvae of barbel Barbus barbus increased significantly after preservation, by 1·74 and 1·96%, respectively over their original size. The standard length (L_S) of 14 dph larvae of B. barbus as well as juveniles of B. barbus, crucian carp Carassius carassius, common nase Chondrostoma nasus and tench Tinca tinca decreased significantly after preservation (?0·56 to ?5·54%), whereas their body mass increased significantly (11·46–18·57%). Preserved eggs of C. carpio and B. barbus were hard, round and transparent. The larvae and juveniles of examined fishes, preserved in frozen ethanol, were straight, flexible and easily measurable after 60 days. Integrity of body surface and fins, as well as preservation of colours were much better in larvae or juveniles frozen and thawed only once than in specimens frozen and thawed thrice. Cooling in 30% ethanol to a temperature of 6 ± 2° C and freezing in water to a temperature of ?20 ± 2° C are not appropriate preservation methods for eggs and larvae of C. carpio (1 and 16 dph).