Ionoprinted Multi-Responsive Hydrogel Actuators

We report multi-responsive and double-folding bilayer hydrogel sheet actuators, whose directional bending response is tuned by modulating the solvent quality and temperature and where locally crosslinked regions, induced by ionoprinting, enable the actuators to invert their bending axis. The sheets are made multi-responsive by combining two stimuli responsive gels that incur opposing and complementary swelling and shrinking responses to the same stimulus. The lower critical solution temperature (LCST) can be tuned to specific temperatures depending on the EtOH concentration, enabling the actuators to change direction isothermally. Higher EtOH concentrations cause upper critical solution temperature (UCST) behavior in the poly(N-isopropylacrylamide) (pNIPAAm) gel networks, which can induce an amplifying effect during bilayer bending. External ionoprints reliably and repeatedly invert the gel bilayer bending axis between water and EtOH. Placing the ionoprint at the gel/gel interface can lead to opposite shape conformations, but with no clear trend in the bending behavior. We hypothesize that this is due to the ionoprint passing through the neutral axis of the bilayer during shrinking in hot water. Finally, we demonstrate the ability of the actuators to achieve shapes unique to the specific external conditions towards developing more responsive and adaptive soft actuator devices.

Plant growth during the Greenhouse II experiment on the Mir orbital station

We carried out three experiments with Super Dwarf wheat in the Bulgarian/Russian growth chamber Svet (0.1 m2 growing area) on the Space Station Mir. This paper mostly describes the first of these NASA-supported trials, began on Aug. 13, 1995. Plants were sampled five times and harvested on Nov. 9 after 90 days. Equipment failures led to low irradiance (3, then 4 of 6 lamp sets failed), instances of high temperatures (ca. 37 degrees C), and sometimes excessive substrate moisture. Although plants grew for the 90 d, no wheat heads were produced. Considering the low light levels, plants were surprisingly green, but of course biomass production was low. Plants were highly disoriented (low light, mirror walls?). Fixed and dried samples and the root module were returned on the U.S. Shuttle Atlantis on Nov. 20, 1995. Samples of the substrate, a nutrient-charged zeolite called Balkanine, were taken from the root module, carefully examined for roots, weighed, dried, and reweighed. The Svet control unit and the light bank were shipped to Moscow. An experiment validation test (EVT) of plant growth and experimental procedures, carried out in Moscow, was highly successful. Equipment built in Utah to measure CO2, H2O vapor, irradiance, air and leaf (IR) temperature, O2, pressure, and substrate moisture worked well in the EVT and in space. After this manuscript was first prepared, plants were grown in Mir with a new light bank and controller for 123 d in late 1996 and 39 days in 1996/1997. Plants grew exceptionally well with higher biomass production than in any previous space experiment, but the ca. 280 wheat heads that were produced in 1996 contained no seeds. Ethylene in the cabin atmosphere was responsible.

Induced abnormality in Mir- and Earth grown Super Dwarf wheat

Super-dwarf wheat grown on the Mir space station using the Svet "Greenhouse" exhibited morphological, metabolic and reproductive abnormalities compared with Earth-grown wheat. Of prominent importance were the abnormalities associated with reproductive ontogeny and the total absence of seed formation on Mir. Changes in the apical meristem associated with transition from the vegetative phase to floral initiation and development of the reproductive spike were all typical of 'Super-Dwarf' wheat up to the point of anthesis. Observation of ruptured anthers from the Mir-grown plants revealed what appeared to be normally developed pollen. These pollen gains, however, contained only one nuclei, while normal viable pollen is tri-nucleate. A potentially important difference in the flight experiment, compared with ground reference studies, was the presence of a high level of atmospheric ethylene (1,200 ppb). Ground studies conducted by exposing 'Super-Dwarf' wheat to ethylene just prior to anthesis resulted in manifestation of the same abnormalities observed in the space flight samples.

Silica deposition on the leaves of Mir- and Earth-grown Super Dwarf wheat

Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) microanalysis were used to investigate the nature of crystals deposited on leaves of Mir- and Earth-grown Super Dwarf wheat (Triticum aestivum L.) plants. Leaves from these plants exhibited dense and uniformly distributed crystals on leaf abaxial surfaces when viewed by SEM. Young leaves showed that crystals initially accumulated around the stomata on the adaxial surface, but became more dense and uniformly distributed as the leaves aged. EDX microanalyses of the Balkanine (a nutrient charged clinoptilolite zeolite) medium in which the wheat plants were grown showed an elemental pattern similar to that observed on the wheat leaves. The absence of N and P in the Balkanine suggests that they were completely utilized by the plants. Only Si and O were evident in the drying agent, Sorb-it-Silica (TM), and perhaps could have accounted for some of the Si observed on the plant tissue. Grant numbers: NCC2-831, 84322-4810

Comparative floral development of Mir-grown and ethylene-treated, earth-grown Super Dwarf wheat

To study plant growth in microgravity, we grew Super Dwarf wheat (Triticum aestivum L.) in the Svet growth chamber onboard the orbiting Russian space station, Mir, and in identical ground control units at the Institute of BioMedical Problems in Moscow, Russia. Seedling emergence was 56% and 73% in the two root-module compartments on Mir and 75% and 90% on earth. Growth was vigorous (produced ca. 1 kg dry mass), and individual plants produced 5 to 8 tillers on Mir compared with 3 to 5 on earth-grown controls. Upon harvest in space and return to earth, however, all inflorescences of the flight-grown plants were sterile. To ascertain if Super Dwarf wheat responded to the 1.1 to 1.7 micromoles mol-1 atmospheric levels of ethylene measured on the Mir prior to and during flowering, plants on earth were exposed to 0, 1, 3, 10, and 20 micromoles mol-1 of ethylene gas and 1200 micromoles mol-1 CO2 from 7 d after emergence to maturity. As in our Mir wheat, plant height, awn length, and the flag leaf were significantly shorter in the ethylene-exposed plants than in controls; inflorescences also exhibited 100% sterility. Scanning-electron-microscopic (SEM) examination of florets from Mir-grown and ethylene-treated, earth-grown plants showed that development ceased prior to anthesis, and the anthers did not dehisce. Laser scanning confocal microscopic (LSCM) examination of pollen grains from Mir and ethylene-treated plants on earth exhibited zero, one, and occasionally two, but rarely three nuclei; pollen produced in the absence of ethylene was always trinucleate, the normal condition. The scarcity of trinucleate pollen, abrupt cessation of floret development prior to anthesis, and excess tillering in wheat plants on Mir and in ethylene-containing atmospheres on earth build a strong case for the ethylene on Mir as the agent for the induced male sterility and other symptoms, rather than microgravity.

Canopy photosynthesis and transpiration in microgravity: gas exchange measurements aboard Mir

The SVET Greenhouse on-board the Orbital Station Mir was used to measure canopy photosynthesis and transpiration rates for the first time in space. During the Greenhouse IIB experiment on Mir (June-January 1997), carbon and water vapor fluxes from two wheat (cv. Superdwarf) canopies were measured using the US developed Gas Exchange Measurement System (GEMS). Gas analyzers capable of resolving CO2 concentration differences of 5 micromoles mol-1 against a background of 0.9% CO2, are necessary to measure photosynthetic and respiratory rates on Mir. The ability of the GEMS gas analyzers to measure these CO2 concentration differences was determined during extensive ground calibrations. Similarly, the sensitivity of the analyzers to water vapor was sufficient to accurately measure canopy evapotranspiration. Evapotranspiration, which accounted for over 90% of the water added to the root zone, was estimated using gas exchange and used to estimate substrate moisture content. This paper presents canopy photosynthesis and transpiration data during the peak vegetative phase of development in microgravity.

[Doxycycline-induced esophageal ulcers]

Tetracycline is known as one of the antibiotics that induce esophageal ulcers.

PURPOSE

Understand how these ulcers may behave and respond to treatment with sucralfate.

METHOD

During the last two years we studied all patients complaining of dysphagia and odinophagia with an upper GI endoscopy, who were taking doxycycline in the last few days. All of them discontinued the drug once the diagnosis was done and most of them were treated also with sucralfate, 1 g tid.

RESULTS

Eleven patients took doxycycline prescribed for: pelvic inflammatory disease, acne, urinary tract and pulmonary infections. Odinophagia was the most common symptom over the next few days of treatment with some risk factors previously documented, such as taking pills just before bedtime and with a small amount of water. The esophageal ulcers were multiple and located mainly in the middle esophageal third. Symptoms disappeared 3.7 days after the medication was stopped, while those taking sucralfate did not change the period of symptoms.

CONCLUSIONS

Physicians must be aware of the doxycycline induced esophageal ulcers and discontinuation of the antibiotic as the main treatment, while sucralfate even though has shown to cover these ulcers, does not change the outcome. Therefore, they must encourage then patients to take the pills with enough liquid, in supine position and have special attention to the elderly and those with any kind of esophageal disease.

Peculiarities of moisture transfer in capillary-porous soil substitutes during space flight

Aboard the orbital stations, "Salyut-7" and "Mir", investigations on the peculiarities of moisture transfer in capillary-porous bodies (CPB; that is, soil substitutes) in microgravity were conducted by the authors with a specially designed device and an original method. Water distribution in CPB-perlite (fractions 1.5... 2.5 mm) was studied, and theoretical dependances for linear capillary impregnation of CPB were determined.

Effects of aspirin on gastric mucosal prostaglandin E2 and F2 alpha content and on gastric mucosal injury in humans receiving fish oil or olive oil

Gastric mucosal prostaglandin E2 and F2 alpha content was evaluated in healthy human subjects who received either fish oil or olive oil (control) daily for 3 wk before exposure to aspirin or no aspirin. Two hours after aspirin administration, when mean serum salicylate concentration was approximately 12 mg/dl, gastric mucosal prostaglandin E2 and F2 alpha content was reduced by greater than 95% in the fundus and antrum (p less than 0.001) and there was endoscopic evidence of gastric mucosal damage (erosions, submucosal hemorrhages). Fish oil feeding had no significant effect on mucosal prostaglandin E2 or F2 alpha content or on the damaging effect of aspirin on the stomach, despite the fact that fish oil reduced serum triglyceride concentrations significantly. These studies indicate that the damaging effects of aspirin on the gastric mucosa are not influenced by dietary fish oil.

Endoscopic sphincterotomy in outpatients

We retrospectively reviewed 137 cases of outpatient endoscopic sphincterotomy (ES) performed over a 4-year period in a single center and compared them with an equal number of inpatient ES. The indications for ES in outpatients as compared with inpatients were, respectively: choledocholithiasis, 60% and 70%; papillary stenosis, 35% and 15% (p less than 0.001); stent insertion, 3.6% and 14% (p less than 0.01); and ampullary tumor, 1.4% and 0.7%. Complications were noted within 2 to 4 hours of ES in 6.6% of outpatients, a rate similar to that of inpatients--7.3%. Outpatients with complications were immediately admitted and stayed in the hospital for a mean of 5 days. No delayed complications were noted and no deaths occurred. Thus, a policy whereby selected individuals undergo ES as outpatients, with hospitalization reserved only for those in whom a complication develops, is reasonable and safe.

Gastric adenocarcinoma masquerading endoscopically as benign gastric ulcer. A five-year experience

The pathologic features and five-year survival of patients in whom gastric cancer masquerades at endoscopy as a benign gastric ulcer has been poorly characterized. We reviewed retrospectively all cases of gastric adenocarcinoma in three hospitals for a five-year period. Of 266 patients with gastric adenocarcinoma, 169 (63.5%) had endoscopy with biopsy prior to diagnosis of cancer. In 159 of these 169 patients (94.1%), the endoscopic findings suggested cancer, while in the remaining 10 patients (5.9%) the endoscopic appearance suggested benign ulcer. In six of these 10 patients, the initial endoscopic biopsies did not reveal cancer and correct diagnosis was delayed for as long as 14 months. Three of the 10 patients had "early gastric cancer" by pathologic criteria at gastrectomy, although one had lymph node metastasis. The other seven patients had pathologic criteria for advanced gastric cancer, and three had lymph node metastasis. In spite of advanced cancer and/or lymph node metastasis in eight of our 10 patients, five-year survival in these patients with benign-appearing ulcers was 70%, as compared to 17% in patients whose gastric lesions appeared malignant at endoscopy.