Inkjet printing of bioadhesives

Over the past century, synthetic adhesives have largely displaced their natural counterparts in medical applications. However, rising concerns over the environmental and toxicological effects of the solvents, monomers, and additives used in synthetic adhesives have recently led the scientific community to seek natural substitutes. Marine mussel adhesive protein is a formaldehyde-free natural adhesive that demonstrates excellent adhesion to several classes of materials, including glasses, metals, metal oxides, and polymers. In this study, we have demonstrated computer aided design (CAD) patterning of various biological adhesives using piezoelectric inkjet technology. A MEMS-based piezoelectric actuator was used to control the flow of the mussel adhesive protein solution through the ink jet nozzles. Fourier transform infrared spectroscopy (FTIR), microscopy, and adhesion studies were performed to examine the chemical, structural, and functional properties of these patterns, respectively. FTIR revealed the piezoelectric inkjet technology technique to be nondestructive. Atomic force microscopy was used to determine the extent of chelation caused by Fe(III). The adhesive strength in these materials was correlated with the extent of chelation by Fe(III). Piezoelectric inkjet printing of naturally-derived biological adhesives may overcome several problems associated with conventional tissue bonding materials. This technique may significantly improve wound repair in next generation eye repair, fracture fixation, wound closure, and drug delivery devices.     

Development of a fully implantable wireless pressure monitoring system

A fully implantable wireless pressure sensor system was developed to monitor bladder pressures in vivo. The system comprises a small commercial pressure die connected via catheter to amplifying electronics, a microcontroller, wireless transmitter, battery, and a personal digital assistant (PDA) or computer to receive the wireless data. The sensor is fully implantable and transmits pressure data once every second with a pressure detection range of 1.5 psi gauge and a resolution of 0.02 psi. In vitro calibration measurements of the device showed a high degree of linearity and excellent temporal response. The implanted device performed continuously in vivo in several porcine studies lasting over 3 days. This system can be adapted for other pressure readings, as well as other vital sign measurements; it represents the first step in developing a ubiquitous sensing platform for telemedicine and remote patient monitoring.     

Assessing Human Immunodeficiency Virus Type 1 Tropism: Comparison of Assays Using Replication-Competent Virus versus Plasma-Derived Pseudotyped Virions

Detection of CXCR4-using human immunodeficiency virus by the Trofile assay was compared to that by assays using virus isolates or replication-competent recombinants. Concordance with the Trofile assay was good, but assays using replicating viruses did not increase substantially the ability to detect the presence of CXCR4-using virus.Human immunodeficiency virus type 1 (HIV-1) can be assigned to one of three classes based on its ability to utilize the CCR5 and CXCR4 coreceptors: viruses that use CCR5 but not CXCR4 (R5 virus), those that use CXCR4 but not CCR5 (X4 virus), and those that can use either coreceptor (dualtropic virus). HIV-1 also can be classified according to its ability to replicate and induce syncytia in MT-2 cells (8, 12). The use of CXCR4 is a defining feature of syncytium-inducing (SI) viruses in MT-2 cells; most but not all non-SI (NSI) viruses are R5 (1, 13, 16).Testing to determine coreceptor usage of HIV-1 isolates is essential to identify patients who are suitable candidates for treatment with CCR5 antagonists. The tropism assay (Trofile; Monogram BioSciences, South San Francisco, CA) used in clinical trials of CCR5 antagonists to date is a validated single-cycle assay performed in a Clinical Laboratory Improvement Amendments/College of American Pathologists-certified laboratory; the assay is based on pseudotyped virus and sensitively detects the presence of CXCR4-using virus (14). However, up to 10% of subjects identified as having exclusively R5 virus at screening had evidence of dualtropic or mixed-tropic (D/M) virus at the time treatment with maraviroc or vicriviroc (VCV) was begun (3, 4). To test the hypothesis that the sensitivity of tropism testing could be improved by use of replicating viruses instead of pseudotyped viruses, we compared the results of tropism testing with the Trofile assay to those of assays using replication-competent viruses using clinical samples from AIDS Clinical Trials Group (ACTG) protocol A5211, a phase 2b trial of the investigational CCR5 antagonist VCV (SCH-D; SCH417690; Schering-Plough, Kenilworth, NJ) (4).(This work was presented in part at the 14th Conference on Retroviruses and Opportunistic Infections, Los Angeles, CA, 25-28 February 2007 [5a].)     

Skeletal muscle buffering capacity and endurance performance after high-intensity interval training by well-trained cyclists

Skeletal muscle buffering capacity (βm), enzyme activities and exercise performance were measured before and after 4 weeks of high-intensity, sub maximal?interval training (HIT) undertaken by six well-trained competitive cyclists [mean maximal oxygen consumption ( O_2max)?=?66.2 ml?·?kg^?1?·?min^?1]. HIT replaced a portion of habitual endurance training and consisted of six sessions, each of six to eight repetitions of 5 min duration at 80% of peak sustained power output (PPO) separated by 1 min of recovery. βm increased from 206.6 (17.9) to 240.4 (34.1) μmol H⁺?·?g muscle dw^?1?·?pH^?1 after HIT (P?=?0.05). PPO, time to fatigue at 150% PPO (TF₁₅₀) and 40-km cycle time trial performance (TT₄₀) all significantly improved after HIT (P?40 performance before HIT (r?=??0.82, P?40 was close to significance (r?=??0.74). βm did not correlate with TF₁₅₀. These results indicate that βm may be an important determinant of relatively short-duration (相似文献   

Age-related changes in brain proDynorphin gene expression in the rat

Dynorphin has a well-established role in feeding and gustation. Alterations in taste perception and feeding behavior are common with age. We hypothesized that proDynorphin gene expression in brain areas involved in taste and feeding declines with age. Male Sprague-Dawley rats were housed individually with ad libitum access to food and water. Brain punches of the selected regions were dissected out in groups of rats aged 4–6, 12–14 and 18–21 months. ProDynorphin mRNA (measured using a cDNA probe) decreased significantly with age in arcuate nucleus and amygdala; increased significantly with age in hippocampus; and was not significantly affected in nucleus of the solitary tract, cortex, caudate putamen or hypothalamic paraventricular nucleus. These data suggest an age-related decrease in the synthesis of dynorphin in two brain regions strongly associated with feeding behavior, and an increase in dynorphin synthesis in a brain region associated with learning and memory.     

Hypohydration effects on thermoregulation during moderate exercise in the cold

Hyperosmotic hypovolemia impairs vasoconstriction during sedentary cold exposure. The purpose of this study was to determine whether hypohydration alters thermoregulation and cardiovascular responses to exercise in cold air. On four occasions, eight males [35.1 (2.7) years, 175.5 (3.1) cm, 73.3 (2.6) kg, 57.2 (2.6) ml kg^–1 min^–1 maximal oxygen uptake (O_2max), 19.6 (2.4)% fat] walked, in t-shirt, shorts, and shoes, at 50% O_2max, for 60 min in either a 4°C (Cold) or a 25°C (Temperate) environment in both hypohydrated state (HYPO, –4% body mass) and euhydrated state (EU). During exercise–cold stress, rectal temperature (T_re), mean weighted skin temperature, heart rate (HR), cardiac output (CO), and stroke volume (SV) were measured every 20 min. Mean weighted skin temperature values were not different between HYPO and EU but were lower (P<0.05) in Cold versus Temperate trials. T_re was not different (P>0.05) between HYPO–Cold and EU–Cold. CO and SV were not different within hydration states and were not different between Cold and Temperate trials (P<0.05). HR was not different between HYPO–Cold and EU–Cold. These data demonstrate that moderate intensity exercise in the cold while hypohydrated does not alter metabolic heat production, skin temperatures and heat loss, nor does it increase thermoregulatory and cardiovascular strain.     

A wide range of baroreflex stimulation does not alter forearm blood flow

The contribution to the regulation of forearm blood flow (FBF) by different baroreceptor populations has previously only been studied over a limited range of stimuli. Therefore, FBF and R-R interval were recorded during neck suctions and neck pressures ranging from –60 to +40 mmHg. The change in R-R interval (R-R) during neck suction was significantly increased at each stage when compared to the control (P<0.05). R-R did not show any significant change during any of the neck pressure stages (P>0.05). Suction or pressure applied to the neck did not elicit any significant changes in FBF when compared to the control (P>0.05). These data show that widening the range of applied stimuli to carotid sinus baroreceptors does not induce a change in FBF. However, the small transient changes reported previously cannot be discounted.     

Activity-driven synaptic and axonal degeneration in canine motor neuron disease

The role of neuronal activity in the pathogenesis of neurodegenerative disease is largely unknown. In this study, we examined the effects of increasing motor neuron activity on the pathogenesis of a canine version of inherited motor neuron disease (hereditary canine spinal muscular atrophy). Activity of motor neurons innervating the ankle extensor muscle medial gastrocnemius (MG) was increased by denervating close synergist muscles. In affected animals, 4 wk of synergist denervation accelerated loss of motor-unit function relative to control muscles and decreased motor axon conduction velocities. Slowing of axon conduction was greatest in the most distal portions of motor axons. Morphological analysis of neuromuscular junctions (NMJs) showed that these functional changes were associated with increased loss of intact innervation and with the appearance of significant motor axon and motor terminal sprouting. These effects were not observed in the MG muscles of age-matched, normal animals with synergist denervation for 5 wk. The results indicate that motor neuron action potential activity is a major contributing factor to the loss of motor-unit function and degeneration in inherited canine motor neuron disease.