Capillarity-Driven Enrichment and Hydrodynamic Trapping of Trace Nucleic Acids by Plasmonic Cavity Membrane for Rapid and Sensitive Detections

Small-reactor-based polymerase chain reaction (PCR) has attracted considerable attention. A significant number of tiny reactors must be prepared in parallel to capture, amplify, and accurately quantify few target genes in clinically relevant large volume, which, however, requires sophisticated microfabrication and longer sample-to-answer time. Here, single plasmonic cavity membrane is reported that not only enriches and captures few nucleic acids by taking advantage of both capillarity and hydrodynamic trapping but also quickly amplifies them for sensitive plasmonic detection. The plasmonic cavity membrane with few nanoliters in a void volume is fabricated by self-assembling gold nanorods with SiO2 tips. Simulations reveal that hydrodynamic stagnation between the SiO2 tips is mainly responsible for the trapping of the nucleic acid in the membrane. Finally, it is shown that the plasmonic cavity membrane is capable of enriching severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genes up to 20 000-fold within 1 min, amplifying within 3 min, and detecting the trace genes as low as a single copy µL-1. It is anticipated that this work not only expands the utility of PCR but also provides an innovative way of the enrichment and detection of trace biomolecules in a variety of point-of-care testing applications.

Bubble-free diatoms polymerase chain reaction

Polymerase chain reaction (PCR) in small fluidic systems not only improves speed and sensitivity of deoxyribonucleic acid (DNA) amplification but also achieves high-throughput quantitative analyses. However, air bubble trapping and growth during PCR has been considered as a critical problem since it causes the failure of DNA amplification. Here we report bubble-free diatom PCR by exploiting a hierarchically porous silica structure of single-celled algae. We show that femtoliters of PCR solution can be spontaneously loaded into the diatom interior without air bubble trapping due to the surface hydrophilicity and pore structure of the diatom. We discover that a large pressure gradient between air bubbles and nanopores rapidly removes residual air bubbles through the periodically arrayed nanopores during thermal cycling. We demonstrate the DNA amplification by diatom PCR without air bubble trapping and growth. Finally, we successfully detect DNA fragments of SARS-CoV-2 with as low as 10 copies/μl by devising a microfluidic device integrated with diatoms assembly. We believe that our work can be applied to many PCR applications for innovative molecular diagnostics and provides new opportunities for naturally abundant diatoms to create innovative biomaterials in real-world applications.

Quantum Electrodynamic Behavior of Chlorophyll in a Plasmonic Nanocavity

Plasmonic nanocavities have been used as a novel platform for studying strong light-matter coupling, opening access to quantum chemistry, material science, and enhanced sensing. However, the biomolecular study of cavity quantum electrodynamics (QED) is lacking. Here, we report the quantum electrodynamic behavior of chlorophyll-a in a plasmonic nanocavity. We construct an extreme plasmonic nanocavity using Au nanocages with various linker molecules and Au mirrors to obtain a strong coupling regime. Plasmon resonance energy transfer (PRET)-based hyperspectral imaging is applied to study the electrodynamic behaviors of chlorophyll-a in the nanocavity. Furthermore, we observe the energy level splitting of chlorophyll-a, similar to the cavity QED effects due to the light-matter interactions in the cavity. Our study will provide insight for further studies in quantum biological electron or energy transfer, electrodynamics, the electron transport chain of mitochondria, and energy harvesting, sensing, and conversion in both biological and biophysical systems.

Water-Wettable Open Plasmonic Nanocavities for Ultrasensitive Molecular Detections in Multiple Phases

Plasmonic nanocavities between metal nanoparticles on metal films are either hydrophobic or fully occupied by nonmetallic spacers, preventing molecular diffusion into electromagnetic hotspots. Here we realize water-wettable open plasmonic cavities by devising gold nanoparticle with site-selectively grown ultrathin dielectric layer-on-gold film structures. We directly confirm that hydrophilic dielectric layers of SiO₂ or TiO₂, which are formed only at the tips of gold nanorod via precise temperature control, render sub-10 nm cavities open to the surroundings and completely water-wettable. Simulations reveal that spontaneous wetting in our cavities is driven by the presence of tip-selective hydrophilic layer and tendency of minimizing high energy air/water interface inside the cavities. Our plasmonic cavities show significant Raman enhancement of up to 4 orders of magnitude higher than those of conventional ones for molecules in various media. Our findings will offer new opportunities for sensing applications of plasmonic nanocavities and have huge impacts on cavity plasmonics.

Sensitive and Direct Optical Monitoring of Release and Cellular Uptake of Aqueous CO from CO-Releasing Molecules

Dynamics of release and cellular uptake of aqueous CO from CO-releasing molecules (CORMs) significantly affect signaling and cell viability. So far, it has been mainly observed by IR, UV-visible, and fluorescence techniques, which suffer from poor sensitivity and slow response time. Here, we show how to directly probe the mass transfer of aqueous CO from CORMs to cells using a fluidic chamber integrated with live cells and Raman reporters of large-area Au@Pd core-shell nanoparticle assembly to emulate a physiologically relevant microenvironment. We sensitively and directly detect CO release from trace CORMs of as low as 100 nM by measuring the Raman transitions of CO via rapid chemisorption onto the surface of the Au@Pd nanoparticles. By using our method, we successfully observe the dynamics of CO release from CORM-2 despite its very short half-life. We also reveal that the initial rate of CO release from CORM-3 is dramatically decreased by tens to hundreds of times when exposed to physiologically relevant pH variations from 7.4 to 2.5, which can be attributed to the acid hydrolysis of the CO ligand. CORM-2 tends to quickly release CO regardless of pH, probably because of its rapid cleavage into two monomeric Ru complexes by the co-solvent. The decrease in the initial rate at lower temperatures is more significant for CORM-3 than for CORM-2. Finally, we observe that the cellular uptake of aqueous CO from CORM-3 by lung cancer cells is approximately 2 times higher than that of normal lung cells.

Optical Detection of Small Metabolites for Biological Gas Conversion by using Metal Nanoparticle Monolayers Produced by Capillary-Assisted Transfer

Detection of small metabolites is essential for monitoring and optimizing biological gas conversion. Currently, such detection is typically done by liquid chromatography with offline sampling. However, this method often requires large equipment with multiple separation columns and is at risk of serious microbial contamination during sampling. Here we propose real-time optical detection of small metabolites using uniform plasmonic nanoparticles monolayers produced by capillary-assisted transfer. We reproducibly fabricate metal nanoparticles monolayers with a diameter of ∼1 mm for the detection of acetate, butyrate, and glucose by a glass capillary tube. Metal nanoparticles monolayers are not only uniform in terms of average interparticle distance but also structurally stable under dynamic fluidic conditions. The monolayers resistant to fluid shear stress with surface-enhanced Raman scattering are able to reversibly monitor the concentration of acetate and sensitively detect acetate and glucose at levels as low as 10 μM, which is more than 2 orders of magnitude lower than the concentration range of typical biological gas conversion. In addition, structurally similar metabolites such as acetate and butyrate, when mixed, become distinguishable by our method.

Plasmonic bacteria on a nanoporous mirror via hydrodynamic trapping for rapid identification of waterborne pathogens

A rapid, precise method for identifying waterborne pathogens is critically needed for effective disinfection and better treatment. However, conventional methods, such as culture-based counting, generally suffer from slow detection times and low sensitivities. Here, we developed a rapid detection method for tracing waterborne pathogens by an innovative optofluidic platform, a plasmonic bacteria on a nanoporous mirror, that allows effective hydrodynamic cell trapping, enrichment of pathogens, and optical signal amplifications. We designed and simulated the integrated optofluidic platform to maximize the enrichment of the bacteria and to align bacteria on the nanopores and plasmonic mirror via hydrodynamic cell trapping. Gold nanoparticles are self-assembled to form antenna arrays on the surface of bacteria, such as Escherichia coli and Pseudomonas aeruginosa, by replacing citrate with hydroxylamine hydrochloride in order to amplify the signal of the plasmonic optical array. Owing to the synergistic contributions of focused light via the nanopore geometry, self-assembled nanoplasmonic optical antennas on the surface of bacteria, and plasmonic mirror, we obtain a sensitivity of detecting E. coli as low as 10² cells/ml via surface-enhanced Raman spectroscopy. We believe that our label-free strategy via an integrated optofluidic platform will pave the way for the rapid, precise identification of various pathogens.

General and programmable synthesis of hybrid liposome/metal nanoparticles

Hybrid liposome/metal nanoparticles are promising candidate materials for biomedical applications. However, the poor selectivity and low yield of the desired hybrid during synthesis pose a challenge. We designed a programmable liposome by selective encoding of a reducing agent, which allows self-crystallization of metal nanoparticles within the liposome to produce stable liposome/metal nanoparticles alone. We synthesized seven types of liposome/monometallic and more complex liposome/bimetallic hybrids. The resulting nanoparticles are tunable in size and metal composition, and their surface plasmon resonance bands are controllable in visible and near infrared. Owing to outer lipid bilayer, our liposome/Au nanoparticle shows better colloidal stability in biologically relevant solutions as well as higher endocytosis efficiency than gold nanoparticles without the liposome. We used this hybrid in intracellular imaging of living cells via surface-enhanced Raman spectroscopy, taking advantage of its improved physicochemical properties. We believe that our method greatly increases the utility of metal nanoparticles in in vivo applications.

Laparoscopic adrenalectomy for malignancy

Background

Controversy exists as to whether laparoscopic adrenalectomy should be performed for malignant or potentially malignant tumours affecting the adrenals.

Methods

This was a retrospective analysis of all patients undergoing laparoscopic adrenalectomy at this institution from 1993 to 1999. Patients were classified by their preoperative diagnosis and analysed with respect to their final pathological diagnosis, operation and postoperative course.

Results

Some 121 patients underwent 133 laparoscopic adrenalectomies. Preoperative classification was type I (benign disease; 67 patients), type II (possibly malignant disease; 46 patients) and type III (malignant disease; eight patients). After operation, 11 patients had malignancy on pathological diagnosis including all eight patients with known preoperative malignancy (one adrenocortical carcinoma (3 × 3 cm) presenting as a virilizing tumour, two neuroblastomas, one lymphoma, one bilateral staged adrenalectomy for metastatic colon cancer, two metastatic lung cancers and one metastatic renal cell carcinoma). One patient with adrenocortical cancer (8 × 6 cm) had incorrect preoperative classification by cytology (type I; oncocytoma). Two of 14 patients with Cushing's adrenal tumour (type II) had adrenocortical cancer (12 × 9 cm and 3 × 3 cm). Mean length of stay was 1·8 days in patients with malignancy. No procedure was converted to open adrenalectomy and no significant complications were encountered. Only the four patients with adrenocortical carcinoma had a recurrence (two required open re-resection 3 months and 2 years after initial operation, one had laparoscopic re-resection 2 years after operation for local recurrence and one presented with recurrence 1 year after operation).

Conclusion

Forty-five per cent of patients undergoing laparoscopic adrenalectomy may be classified as having potentially malignant disease (type II or III). Most malignant tumours of the adrenals can be treated laparoscopically, but adrenocortical carcinomas are at high risk of recurrence after laparoscopic adrenalectomy.

Functional, dynamic, and anatomic MR urography: feasibility and preliminary findings

RATIONALE AND OBJECTIVES

The authors assessed the feasibility of using magnetic resonance (MR) urography to acquire functional, dynamic, and anatomic information in human subjects with normal and hydronephrotic kidneys.

MATERIALS AND METHODS

In subjects known to have or suspected of having hydronephrosis, split renal filtration fractions were measured with a customized magnetization-prepared, inversion-prepared gradient-recalled echo sequence to determine the T1 of flowing blood in the inferior vena cava and aorta before and after contrast medium administration and in the renal veins and arteries after contrast medium administration. Multiple timed sets of coronal fast spoiled gradient-echo 70 degrees flip-angle images were acquired before and after contrast medium administration to derive MR renograms from changes in the signal intensity of the cortex and medulla. Precontrast T2-weighted images were obtained with a three-dimensional fast spoiled gradient-echo maximum intensity projection pulse sequence, and postcontrast T1 maximum intensity projection images were also obtained to depict the renal anatomy.

RESULTS

Split filtration fraction differentiated normal from hydronephrotic kidneys. MR renograms depicted vascular, tubular, and ductal phases and differentiated between normal and hydronephrotic kidneys (P < .05, n = 20). Contrast medium dose correlated with the peak of the cortical signal intensity curves on the renogram (r = 0.7, P < .0005; n = 20). The sensitivities for the visual determination of hydronephrosis and unilateral delayed excretion of contrast material were both 100%, and the specificities were 64% and 85%, respectively.

CONCLUSION

The preliminary findings show promise for the use of MR urography in the comprehensive assessment of renal function, dynamics, and anatomy.

Laparoscopic Heller myotomy and Dor fundoplication for achalasia: analysis of successes and failures

BACKGROUND

In the treatment of achalasia, surgery has been traditionally reserved for patients with residual dysphagia after pneumatic dilatation. The results of laparoscopic Heller myotomy have proven to be so good, however, that most experts now consider surgery the primary treatment.

HYPOTHESIS

The outcome of laparoscopic myotomy and fundoplication for achalasia is dictated by technical factors.

SETTING

University hospital tertiary care center.

DESIGN

Retrospective study.

PATIENTS AND METHODS

One hundred two patients with esophageal achalasia underwent laparoscopic Heller myotomy and Dor fundoplication. Fifty-seven patients had been previously treated by pneumatic dilatation or botulinum toxin. The design of the operation involved a 7-cm myotomy, which extended 1.5 cm onto the gastric wall, and a Dor fundoplication. Esophagrams, esophageal manometric findings, and video records of the procedure were analyzed to determine the technical factors that contributed to the clinical success or failure of the operation.

MAIN OUTCOME MEASURE

Swallowing status.

RESULTS

In 91 (89%) of the 102 patients, good or excellent results were obtained after the first operation. A second operation was performed in 5 patients to either lengthen the myotomy (3 patients) or take down the fundoplication (2 patients). Dysphagia resolved in 4 of these patients. The remaining 6 patients were treated by pneumatic dilatation, but dysphagia improved in only 1. At the conclusion of treatment, excellent or good results had been obtained in 96 (94%) of the 102 patients.

CONCLUSIONS

These data show that a Heller myotomy was unsuccessful in patients with an esophageal stricture; a short myotomy and a constricting Dor fundoplication were the avoidable causes of residual dysphagia; a second operation, but not pneumatic dilatation, was able to correct most failures; and that the identified technical flaws were eliminated from the last half of the patients in the series.

Clinical usefulness of magnetic resonance cisternography in patients having hemifacial spasm

To evaluate the usefulness of MR cisternography fourteen patients that had hemifacial spasm and 20 control patients underwent MR cisternography. All the patients with hemifacial spasm had a confirmed vascular compression after surgery. MR cisternography was performed using a 1.5-tesla superconducting MR magnet in which a 3D (dimensional) heavily T2-weighted turbo spin-echo sequence was used. In 34 randomly selected individuals, we retrospectively determined whether MR cisternography images could be used to evaluate symptoms, and what the benefits of obtaining this image was. The results were correlated with the surgical findings. The sensitivity was 100% and the specificity was 94% in all patients having a hemifacial spasm. The offending vessels were the anterior inferior cerebellar artery (AICA) in six patients cases, the posterior inferior cerebellar artery (PICA) in six, both the vertebral artery and PICA in one, and the vertebral artery in one. All the images showed good resolution and contrast, and also showed the exact correlation between the facial nerve and intracranial vessels in the multiplaner image. The findings of neurovascular compression were well correlated with the surgical findings. We believe that high-resolution 3D MR cisternography is a very useful method for evaluating the neurovascular compression in patients that have hemifacial spasm.

Laparoscopic Heller myotomy relieves dysphagia in patients with achalasia and low LES pressure following pneumatic dilatation

BACKGROUND

Although pneumatic dilatation is said to relieve dysphagia in achalasia if it decreases lower esophageal sphincter (LES) pressure to 10 mmHg (n = 23); group C, no previous balloon dilatation and LES pressure >10 mmHg (n = 25). All patients underwent a laparoscopic Heller myotomy and Dor fundoplication. The severity of dysphagia was gauged on a scale of 0-4.

RESULTS

In group A, LES pressure was 7 +/- 2 mmHg preoperatively and 8 +/- 3 mmHg postoperatively; the dysphagia score was 3.3 +/- 0.7 preoperatively and 0.9 +/- 1.1 postoperatively. Eighty-nine percent of patients had excellent or good results. In group B, LES pressure was 23 +/- 8 mmHg preoperatively and 10 +/- 1 mmHg postoperatively; the dysphagia score was 3.3 +/- 0.7 preoperatively and 0.3 +/- 0.5 postoperatively. All patients had excellent or good results. In group C, LES pressure was 23 +/- 11 mmHg preoperatively and 14 +/- 12 mmHg postoperatively; the dysphagia score was 3.6 +/- 0.6 preoperatively and 0.2 +/- 0.5 postoperatively. All patients had excellent or good results.

CONCLUSIONS

These results show that (a) a LES pressure of <10 mmHg after pneumatic dilatation does not guarantee relief of dysphagia, and (b) laparoscopic Heller myotomy relieves dysphagia in most patients with a postdilatation LES pressure <10 mmHg. Thus, a laparoscopic Heller myotomy is indicated if dilatation does not relieve dysphagia, even if LES pressure has been decreased to <10 mmHg. Esophagectomy should be reserved for the occasional failure of this simpler operation.

Tic convulsif caused by cerebellopontine angle schwannoma

A case is presented of painful tic convulsif caused by schwannoma in the cerebellopontine angle (CPA), with right trigeminal neuralgia and ipsilateral hemifacial spasm. Magnetic resonance images showed a 4 cm round mass displacing the 4th ventricle and distorting the brain stem in the right CPA. The schwannoma, which compressed the fifth and seventh cranial nerves directly, was subtotally removed by a suboccipital craniectomy. Postoperatively, the patient had a complete relief from the hemifacial spasm and marked improvement from trigeminal neuralgia. The painful tic convulsif in this case was probably produced by the tumor compressing and displacing the anterior cerebellar artery directly.

Functional magnetic resonance imaging of visual object construction and shape discrimination : relations among task, hemispheric lateralization, and gender

We studied the brain activation patterns in two visual image processing tasks requiring judgements on object construction (FIT task) or object sameness (SAME task). Eight right-handed healthy human subjects (four women and four men) performed the two tasks in a randomized block design while 5-mm, multislice functional images of the whole brain were acquired using a 4-tesla system using blood oxygenation dependent (BOLD) activation. Pairs of objects were picked randomly from a set of 25 oriented fragments of a square and presented to the subjects approximately every 5 sec. In the FIT task, subjects had to indicate, by pushing one of two buttons, whether the two fragments could match to form a perfect square, whereas in the SAME task they had to decide whether they were the same or not. In a control task, preceding and following each of the two tasks above, a single square was presented at the same rate and subjects pushed any of the two keys at random. Functional activation maps were constructed based on a combination of conservative criteria. The areas with activated pixels were identified using Talairach coordinates and anatomical landmarks, and the number of activated pixels was determined for each area. Altogether, 379 pixels were activated. The counts of activated pixels did not differ significantly between the two tasks or between the two genders. However, there were significantly more activated pixels in the left (n = 218) than the right side of the brain (n = 161). Of the 379 activated pixels, 371 were located in the cerebral cortex. The Talairach coordinates of these pixels were analyzed with respect to their overall distribution in the two tasks. These distributions differed significantly between the two tasks. With respect to individual dimensions, the two tasks differed significantly in the anterior--posterior and superior--inferior distributions but not in the left--right (including mediolateral, within the left or right side) distribution. Specifically, the FIT distribution was, overall, more anterior and inferior than that of the SAME task. A detailed analysis of the counts and spatial distributions of activated pixels was carried out for 15 brain areas (all in the cerebral cortex) in which a consistent activation (in > or = 3 subjects) was observed (n = 323 activated pixels). We found the following. Except for the inferior temporal gyrus, which was activated exclusively in the FIT task, all other areas showed activation in both tasks but to different extents. Based on the extent of activation, areas fell within two distinct groups (FIT or SAME) depending on which pixel count (i.e., FIT or SAME) was greater. The FIT group consisted of the following areas, in decreasing FIT/SAME order (brackets indicate ties): GTi, GTs, GC, GFi, GFd, [GTm, GF], GO. The SAME group consisted of the following areas, in decreasing SAME/FIT order : GOi, LPs, Sca, GPrC, GPoC, [GFs, GFm]. These results indicate that there are distributed, graded, and partially overlapping patterns of activation during performance of the two tasks. We attribute these overlapping patterns of activation to the engagement of partially shared processes. Activated pixels clustered to three types of clusters : FIT-only (111 pixels), SAME-only (97 pixels), and FIT + SAME (115 pixels). Pixels contained in FIT-only and SAME-only clusters were distributed approximately equally between the left and right hemispheres, whereas pixels in the SAME + FIT clusters were located mostly in the left hemisphere. With respect to gender, the left-right distribution of activated pixels was very similar in women and men for the SAME-only and FIT + SAME clusters but differed for the FIT-only case in which there was a prominent left side preponderance for women, in contrast to a right side preponderance for men. We conclude that (a) cortical mechanisms common for processing visual object construction and discrimination involve mostly the left hemisphere, (b) cortical mechanisms specific for these tasks engage both hemispheres, and (c) in object construction only, men engage predominantly the right hemisphere whereas women show a left-hemisphere preponderance.

A biodegradable polymer scaffold for delivery of osteotropic factors

Despite discoveries and developments in osteotropic factors, therapies exploiting these macromolecules have been limited due to a lack of suitable delivery vehicles and three dimensional (3D) scaffolds that promote bone regeneration. To address this limitation, an emulsion freeze-drying process was developed to fabricate biodegradable scaffolds with controlled microarchitecture, and the ability to incorporate and deliver bioactive macromolecules for bone regeneration. The effect of median pore size and protein loading on protein release kinetics was investigated using scaffolds with different protein loading and median pore sizes ranging from 7 to 70 microm. Graphs of protein release from scaffolds showed an initial burst followed by a slower sustained release. Release kinetics were characterized using an unsteady-state, diffusion-controlled model with an effective diffusivity that took tortuosity (tau) and partition coefficient for protein adsorption (Kp) onto the scaffold walls into account. Tortuosity and partition coefficient significantly reduced the protein diffusivity by a factor of 41 +/- 43 and 105 +/- 51 for 60 and 30-microm median pore-sized scaffolds, respectively. The activity of the protein released from these scaffolds was demonstrated by delivering rhBMP 2 and [A-4] (an amelogenin derived polypeptide) proteins from the scaffold and regenerating bone in a rat ectopic bone induction assay [Whang et al. J Biomed Mater Res 1998;42:491-9, Veis et al. J Bone Mineral Res, Submitted].

Engineering bone regeneration with bioabsorbable scaffolds with novel microarchitecture

Critical-sized defects (CSDs) were introduced into rat calvaria to test the hypothesis that absorption of surrounding blood, marrow, and fluid from the osseous wound into a bioabsorbable polymer matrix with unique microarchitecture can induce bone formation via hematoma stabilization. Scaffolds with 90% porosity, specific surface areas of approximately 10 m2/g, and median pore sizes of 16 and 32 microm, respectively, were fabricated using an emulsion freeze-drying process. Contact radiography and radiomorphometry revealed the size of the initial defects (50 mm2) were reduced to 27 +/- 11 mm2 and 34 +/- 17 mm2 for CSDs treated with poly(D,L-lactide-co-glycolide). Histology and histomorphometry revealed scaffolds filled with significantly more de novo bone than negative controls (p < 0. 007), more osteoid than both the negative and autograft controls (p < 0.002), and small masses of mineralized tissue (< 15 mm in diameter) observed within the scaffolds. Based on these findings, we propose a change in the current paradigm regarding the microarchitecture of scaffolds for in vivo bone regeneration to include mechanisms based on hematoma stabilization.

Vibrotactile stimulus order effects in somatosensory cortical areas of rhesus monkeys

This study demonstrated effects of stimulus order on single-cell responses in the macaque primary and secondary somatosensory and 7b cortical areas. As part of a study of tactile attention, two monkeys (Macaca mulatta) received similar constant amplitude, sinusoidal tactile vibration patterns (125 Hz) at two glabrous skin, hand locations. The stimuli started asynchronously with offsets of 150 or 300 ms. In cells with bilateral receptive fields and increased firing to a stimulus, we observed an average lowering of 30% in the firing rates to the contralateral stimulus when preceded by stimulation of the ipsilateral hand. Some cells with only contralateral receptive fields showed similar depressed responses to a contralateral stimulus when preceded by an ipsilateral stimulus. Stimulus order effects were more prominent during dual stimulation of the receptive field on one hand. In six cells whose background activity was inhibited by the first stimulus, higher rates appeared at the onset of the second stimulus. These results suggest a possible substrate for psychophysical findings of stimulus masking in which a preceding stimulus depresses detection thresholds. The spatial and temporal characteristics of in-field inhibitory mechanisms best account for the observed stimulus order effects.

Ectopic bone formation via rhBMP-2 delivery from porous bioabsorbable polymer scaffolds

Drug delivery devices have received considerable interest in the field of tissue engineering due to the advent of proteins that can induce proliferation and differentiation of various cells to form specific tissues and organs, for example, bone morphogenetic protein (BMP-2) for osteogenesis. In this work the delivery of a clinically relevant bioactive factor, recombinant human rhBMP-2, was tested in vivo in a rat ectopic bone induction assay. Contact radiography and radiomorphometry showed significantly more radiopacity (1798+/-183 mm2 versus. 784+/-570 mm2 radiopaque area/g scaffold) in the BMP scaffolds than controls (p < 0.002). De novo woven bone and abundant osteoid formation were confirmed from histological sections while controls contained minimal amounts of tissue. Histomorphometry revealed significantly more bone (124+/-93 mm2 versus 7+/-12 mm2) and osteoid (72+/-43 mm2 versus 20+/-21 mm2) in the BMP implants (p < 0.001). These scaffolds demonstrated the ability to deliver viable rhBMP-2 and to induce bone formation in an ectopic site.

The effects of serial stretch loading on stretch work and stretch-shorten cycle performance in the knee musculature

Training methods to optimize stretch-shorten cycle performance and an active muscle's ability to resist a sudden stretch (stretch work) and the relationship between the two have not been fully explored. The purpose of this study was to examine the effects of an 8-week strengthening program of serial stretch loading on stretch work and stretch-shorten cycle performance in the quadriceps and hamstring muscles. Thirty-one asymptomatic subjects participated in pre- and post-tests of maximum voluntary isometric contractions, stretch work and stretch-shorten cycle trials, and single-leg vertical jumps. The training portion consisted of progressively resisted isotonic single-leg squats. One leg exercised against an isotonic load with serial stretch loading, while the other leg exercised against isotonic load alone. Training resulted in strength gains in both legs indicated by the increase in weight lifted during training, but not by maximum voluntary isometric contractions. Vertical jump height increased in both legs. In the hamstring, stretch work decreased and stretch-shorten cycle performance increased in both legs. In the quadriceps, serial stretch loading intervention resulted in increased stretch-shorten cycle performance and no significant change in stretch work. The correlation between stretch-shorten cycle and stretch work was weak but significant. These findings suggest that the use of serial stretch loading could improve muscular performance and enhance a muscle's potential for dynamic stabilization.

Human keratinocytes maintain reversible anti-apoptotic defenses in vivo and in vitro

Human keratinocytes proliferate and differentiate in an epidermal environment where induction of apoptosis can be triggered by ultraviolet radiation (UVR), activated lymphocytes and cytokines. The purpose of this study was to determine whether keratinocytes were susceptible to apoptosis induced by ionophore, ultra-violet radiation, cytokines or crosslinking of CD95 (Fas/APO-1). In normal human skin exposed to two minimal erythema doses of ultraviolet radiation, suprabasal cells were the first keratinocytes to demonstrate apoptotic nuclei, and by 48 h apoptotic cells were identified throughout the mid to upper epidermis. However, most keratinocytes resisted apoptosis and UVR-induced apoptosis was not observed in basal cells, or in the most differentiated epidermis. Human keratinocytes and keratinocyte cell lines cultured in vitro developed maximal apoptosis 48 h after radiation. Human keratinocytes cultured in full growth factor supplements were resistant to UVR-induced apoptosis compared to keratinocyte cell lines or to a lymphoid cell line (HL60) susceptible to apoptosis. Keratinocyte cell lines were completely resistant to apoptosis induced by interferon-gamma, interferon-alpha, IL-2, IL-6, TNF-alpha, IL-1Ra, and GM-CSF. A subset of the cells in cultures of keratinocytes and transformed keratinocyte cell lines died by apoptosis in response to anti-Fas, IL-1alpha and TNF-alpha plus IFN-gamma and ionophore. Second passage freshly isolated human keratinocytes were much more resistant to apoptosis induced by ionophore, anti-Fas and cytokines than were transformed keratinocyte cell lines. Calcium shift to induce differentiation in second-passage keratinocyte cultures made keratinocytes even more resistant to UVR-induced apoptosis. This parallels the lack of UVR-induced apoptosis observed in the most differentiated keratinocytes in irradiated human skin. Both keratinocytes and keratinocyte cell lines express rather low levels of the anti-apoptotic proteins bcl-2 and bcl-x compared to other apoptosis-resistant cell types. The differences between keratinocytes and keratinocyte cell lines in susceptibility to apoptosis are not explained by difference in expression of bcl-2 or bcl-x. Finally, withdrawal of growth factors from keratinocytes decreased cell survival following UVR and increased the induction of apoptosis. Inhibition of protein synthesis with cyclo-heximide also made keratinocytes more susceptible to UVR-induced apoptosis, indicating that anti-apoptotic defences in cultured keratinocytes are dependent on active protein synthesis. These experiments show that the strong keratinocyte defences against apoptosis are stratified within the epidermis, and can be altered by differentiation and growth factor withdrawal.

Oligotrophic bacteria from rendzina forest soil

Oligotrophic bacteria were shown to exist abundantly in all layers of a rendzina forest soil throughout the year. Two-hundred-three oligotrophic bacteria were isolated from forest soil (Aoba, Sendai) at different layers (L, F, H and A layers) throughout the year, and their morphological and physiological characteristics were examined. A high proportion (95%) of the isolated oligotrophs were Gram-negative, non-spore forming bacteria. Based on the cell shape, the isolates were divided into four groups: regular rods, curved/spiral bacteria, irregular rods, and buddin and/or prosthecate bacteria. Each group of bacteria is discussed in relation to the physiological characteristics. Notably oligotrophic bacteria of different cell types showed a marked zonal distribution in respect to profile depth.