Mechanical properties and structure of the biological multilayered material system, Atractosteus spatula scales.

During recent decades, research on biological systems such as abalone shell and fish armor has revealed that these biological systems employ carefully arranged hierarchical multilayered structures to achieve properties of high strength, high ductility and light weight. Knowledge of such structures may enable pathways to design bio-inspired materials for various applications. This study was conducted to investigate the spatial distribution of structure, chemical composition and mechanical properties in mineralized fish scales of the species Atractosteus spatula. Microindentation tests were conducted, and cracking patterns and damage sites in the scales were examined to investigate the underlying protective mechanisms of fish scales under impact and penetration loads. A difference in nanomechanical properties was observed, with a thinner, stiffer and harder outer layer (indentation modulus ∼69 GPa and hardness ∼3.3 GPa) on a more compliant and thicker inner layer (indentation modulus ∼14.3 GPa and hardness ∼0.5 GPa). High-resolution scanning electron microscopy imaging of a fracture surface revealed that the outer layer contained oriented nanorods embedded in a matrix, and that the nanostructure of the inner layer contained fiber-like structures organized in a complex layered pattern. Damage patterns formed during microindentation show complex deformation mechanisms. Images of cracks identify growth through the outer layer, then deflection along the interface before growing and arresting in the inner layer. High-magnification images of the crack tip in the inner layer show void-linking and fiber-bridging exhibiting inelastic behavior. The observed difference in mechanical properties and unique nanostructures of different layers may have contributed to the resistance of fish scales to failure by impact and penetration loading.

The effect of delayed visual feedback on telerobotic surgery.

BACKGROUND: Telerobotic surgery is ideally suited for remote applications in which the instrument control console is stationed separately from the end-effectors at the patient's bedside. However, if the distance between the console and the patient is great enough, a lag effect or latency between end-effector manipulation and the depicted image leads to alterations in movement patterns. The purpose of this study was to determine the effect of visual delay on surgical task performance. METHODS: At an endoscopic skill station, an analogue delay device was interposed between the surgical field and monitor to delay the transmission of visual information, thus mimicking the distance effect of data transmission. Three surgeons with similar laparoscopic experience participated in the laparoscopic knot tying portion of the study, and seven residents participated in the accuracy and dexterity tasks. The time to complete a single throw was recorded in seconds after adding consecutively increasingly time delay in 50 ms increments. Similar time delay increments were added for the accuracy and dexterity tasks, which involved passing a needle through two adjacent circles and passing a small cylinder through a larger one to reproduce two-handed coordination and spatial resolution. Data were presented as the median time to complete each task. RESULTS: For all three tasks, an incremental increase in time delay was associated with a significant (p < 0.001) increase in the time to complete the task. For dexterity, a statistically significant (p

The treatment of pancreatic pseudocysts by laparoscopic drainage: endoluminal and lesser sac techniques.

A variety of approaches are now available to drain pancreatic pseudocysts (PP) when indicated. In addition to open surgery, endoscopic, laparoscopic, intra-luminal, and percutaneous techniques are available as therapeutic options to facilitate drainage of mature symptomatic PP. The laparoscopic lesser sac technique is appealing since it • relies on a secure stapled anastomosis, • provides an adequate sized cystgastrostomy to facilitate drainage, and • utilizes minimally invasive techniques to diminish operative morbidity and expedite return to normal activities. Short-term follow-up data suggest that this approach is feasible, effective and reproducible, Long-term studies demonstrating the efficacy of laparoscopic drainage of PP using the lesser sac technique are needed to validate these early favorable outcomes.

Bactericidal and endotoxin neutralizing activity of a peptide derived from Limulus antilipopolysaccharide factor.

BACKGROUND: Release of lipopolysaccharide (endotoxin, LPS) is a critical inciting event in the development of sepsis syndrome due to gram-negative bacteria, and mortality associated with this entity remains approximately 40%. Limulus anti-LPS factor (LALF) is a naturally occurring horseshoe crab derived protein that, unlike antibiotics, is both bactericidal for gram-negative bacteria and capable of neutralizing LPS. We hypothesized that a peptide derived from the active domain of LALF (LALF #28-54) would exhibit potent biologic activity similar to that of LALF itself and could potentially be useful as a therapeutic agent. METHODS: The effects of LALF, synthetic peptide LALF #28-54, polymyxin B (PmB), and a biologically inactive synthetic peptide were examined in several models. In vitro bactericidal activity was determined against Pseudomonas aeruginosa, and LPS-neutralizing capacity was determined via inhibition of LPS-induced tumor necrosis factor-alpha (TNF-alpha) secretion by RAW 264.7 cells. In vivo biologic activity was determined via pretreatment following which P aeruginosa endotoxemia or bacteremia was induced; serum TNF-alpha levels, bacterial clearance, and survival were assessed. RESULTS: LALF and LALF #28-54 exhibited potent in vitro bactericidal and LPS-neutralizing activity comparable to PmB (P <.01). However, although LALF #28-54 diminished systemic TNF-alpha production and aided bacterial clearance similar to that observed for LALF (P <.01), it did not provide significant protective capacity (P >.1). CONCLUSIONS: These data demonstrate that peptide LALF #28-54 retained the LPS-neutralizing and bactericidal biologic activity of LALF but failed to protect during overwhelming P aeruginosa bacteremia, perhaps due to short serum half-life.

Six years of surgical wound infection surveillance at a tertiary care center: review of the microbiologic and epidemiological aspects of 20,007 wounds.

HYPOTHESES: (1) Antibiotic restriction policies result in alteration of microbiologic features of surgical site infections (SSIs) and (2) reported SSI rates are underestimated when postdischarge surveillance is not included in SSI surveillance efforts. DESIGN: Retrospective analysis of prospectively collected SSI surveillance data. PATIENTS AND METHODS: We compared initial microbial isolates from SSIs between (1) January 1, 1993, and December 31, 1995, and (2) January; 1, 1996, and December 31, 1998. Antibiotic restriction policies were implemented at Fairview-University Medical Center, Minneapolis, Minn, on March 1, 1995. For the combined periods (January 1, 1993, to December 31, 1998), we determined SSI rates for 20007 operations according to the extent of bacterial contamination at surgery (wound class). Then, we analyzed SSI rates for 10559 of these operations (selected based on availability of Anesthesia Society of America score and type of procedure) using the surgical wound risk index (wound class, Anesthesia Society of America score, and length of operation). We categorized SSI rates by 17 procedures for comparison with SSI rates reported by 286 hospitals that contributed data confidentially and voluntarily to the National Nosocomial Infections Surveillance System in 1998. We compared SSI rates with and without postdischarge surveillance. RESULTS: Coagulase-negative staphylococcus and group D enterococcus were the 2 most frequent isolates before and after antibiotic restriction policies were implemented. Candida albicans isolates decreased from 7.9% (1993-1995) to 6.5% (1996-1998; P=.46). Methicillin-resistant Staphylococcus aureus (1.8% of isolates) and vancomycin-resistant enterococcus (2.4% of isolates) organisms were first identified between 1996 and 1998. Our SSI rates were 2.6% for class I wounds, 3.6% for class II wounds, and 10.5% for class III/IV wounds; 53.9% of SSIs were identified after hospital discharge. CONCLUSIONS: Antibiotic restriction policies did not alter the microbial spectrum of SSIs during the observation period. Reporting SSI rates in the absence of postdischarge surveillance dramatically underestimates actual SSI rates, especially in tertiary care hospitals that provide care for large populations of elderly and immunosuppressed patients.

Surgical treatment and long-term outcome of ferrets with bilateral adrenal tumors or adrenal hyperplasia: 56 cases (1994-1997).

OBJECTIVE: To determine signalment, clinical signs, concurrent diseases, response to surgical treatment, and long-term outcome of ferrets with bilateral adrenal tumors or adrenal hyperplasia. DESIGN: Retrospective study. ANIMALS: 56 ferrets with bilateral adrenal tumors or adrenal hyperplasia confirmed histologically following subtotal bilateral adrenalectomy. PROCEDURE: Medical records of all ferrets with bilateral adrenal tumors or hyperplasia examined between 1994 and 1997 were reviewed. Ferrets underwent a subtotal bilateral adrenalectomy or a unilateral adrenalectomy initially, followed by a unilateral subtotal adrenalectomy when tumors or hyperplasia later developed on the contralateral adrenal gland. A long-term follow-up of a minimum of 18 months after final adrenal gland surgery was obtained by examination of medical records and follow-up telephone conversations. RESULTS: Clinical signs of hyperadrenocorticism included bilaterally symmetric alopecia, return to male sexual behavior in castrated male ferrets, or swollen vulva in spayed female ferrets. Surgical treatment of bilateral adrenal disease by subtotal bilateral adrenalectomy (or unilateral adrenalectomy followed by contralateral unilateral subtotal adrenalectomy) was effective with a mortality rate of < 2%. Only 3 (5%) ferrets required glucocorticoid or mineralocorticoid replacement following subtotal bilateral adrenalectomy. Recurrence after bilateral adrenalectomy was 15% with a mean long-term follow-up period of 30 months. CONCLUSIONS AND CLINICAL RELEVANCE: Bilaterally symmetric alopecia, return to male sexual behavior in castrated male ferrets, or swollen vulva in spayed female ferrets are indicative of adrenal tumors or adrenal hyperplasia in ferrets. Surgical treatment of bilateral adrenal disease by subtotal bilateral adrenalectomy is effective, with a low rate of complications and postoperative recurrence rate.

Antiendotoxin agents share molecular homology within their lipopolysaccharide binding domains.

BACKGROUND: The purpose of this study was to determine whether antiendotoxin agents exhibit molecular homology within their lipopolysaccharide (LPS) binding domains, suggesting a common mechanism of action. We hypothesized that the presence of positively charged basic amino acids or a paucity of negatively charged acidic amino acids, or both, would be a critical characteristic of that portion of the molecule that binds to the highly negatively charged deep core/lipid A (DCLA) region of LPS. MATERIALS AND METHODS: We analyzed the amino acid sequences of the variable light (VL) and heavy (VH) chain complementarity-determining regions (CDRs) of anti-DCLA monoclonal antibodies (mAbs) 1B6, 5A5, and 7C5 and compared them with (1) the CDRs of three irrelevant control mAbs and (2) the LPS binding region of bactericidal permeability-increasing protein (BPI). We purified and amplified the specific nucleotide sequences of the variable regions using reverse transcriptase polymerase chain reaction. DNA was sequenced by dideoxy termination, and protein sequences were deduced and analyzed. The percentages of acidic, basic, polar, and hydrophobic amino acids within VH and VL chain CDRs were determined. RESULTS: We identified a paucity of negatively charged acidic amino acids exclusively within VL chain CDRs of anti-DCLA mAbs (P < 0.005). Although increased, the number of positively charged basic residues was not statistically significantly different; neither was the number of polar or hydrophobic amino acids. Conclusions. Our data suggest that the near absence of negatively charged acidic residues is critical for LPS binding. This characteristic appears to reside exclusively in the VL chain CDRs of anti-DCLA mAbs.

Insulinoma in the ferret: clinical findings and treatment comparison of 66 cases.

The clinical signs and surgical findings were reported for 66 ferrets with insulinomas confirmed histologically. All of the ferrets were treated with one of three modalities, and disease-free intervals and survival times were gathered to determine the most effective treatment. The three treatment groups included 10 ferrets treated medically, 27 ferrets treated with pancreatic nodulectomy, and 29 ferrets treated with pancreatic nodulectomy combined with a partial pancreatectomy. The mean disease-free intervals for each group were 22, 234, and 365 days, respectively. The mean survival times for each group were 186, 456, and 668 days, respectively. Based upon the data, recommendations were made for treating insulinoma in the ferret.

Clinical aspects and surgical treatment of hyperadrenocorticism in the domestic ferret: 94 cases (1994-1996).

The signalment, clinical findings, laboratory values, and histopathological results of 96 ferrets with signs (i.e., bilaterally symmetrical alopecia, return to male sexual behavior, or an enlarged vulva) suggestive of hyperadrenocorticism were evaluated retrospectively. Of these 96 ferrets, 94 (98%) were diagnosed with hyperadrenocorticism histologically. Treatment consisted of unilateral adrenalectomy for unilateral tumors (84%) and subtotal bilateral adrenalectomy for bilateral adrenal tumors (16%). The histopathological diagnosis included nodular hyperplasia (56%), adrenocortical carcinoma (26%), and adrenocortical adenoma (16%). Common concurrent diseases included splenomegaly (87%), islet-cell tumor (27%), and cardiomyopathy (10%).

The G protein alpha subunit (GP alpha1) is associated with the ER and the plasma membrane in meristematic cells of Arabidopsis and cauliflower.

Towards the elucidation of the cellular function(s) of GP alpha1, we have characterized its subcellular localization using immunofluorescence and cell fractionation. GP alpha1 is not present in nuclei or chloroplasts. It is a membrane-bound protein, and analysis of isolated endoplasmic and plasma membranes indicates a good correlation between GP alpha1 in both the plasma membrane and the ER compartment. Interestingly, these results may suggest more different functions for GP alpha1: it might be involved in transmission of extracellular signals across the plasma membrane and in the cytoplasm, and/or it may also be involved in regulating some aspects of the ER functions or membrane trafficking between both membranes.

The Arabidopsis MADS-box gene AGL3 is widely expressed and encodes a sequence-specific DNA-binding protein.

The Arabidopsis AGL3 gene was previously identified on the basis of sequence similarity to the floral homeotic gene AGAMOUS (AG), which encodes a protein with a conserved MADS domain that is also found in human and yeast transcription factors (SRF and MCM1, respectively). Analysis of newly isolated full-length cDNA clones as well as genomic clones indicates that AGL3 is indeed a MADS-box gene with a general intron-exon structure similar to other plant MADS-box genes. However, unlike the others, which are expressed specifically in flowers, AGL3 is expressed in all above-ground vegetative organs, as well as in flowers, but not in roots. Furthermore, since AGL3 is MADS-domain protein, it is likely that it is also a DNA-binding protein regulating transcription. To characterize AGL3 as a DNA-binding protein in vitro, we expressed the AGL3 protein in Escherichia coli, and characterized its DNA-binding properties. We show that AGL3 binds to sequences which resemble the target sequences of SRF and MCM1, and have determined the consensus sequence to which AGL3 binds using random oligonucleotides. These results suggest that AGL3 is a widely distributed DNA-binding protein, which may be involved the transcriptional regulation of genes in many cells.

Isolation of cDNAs encoding guanine nucleotide-binding protein beta-subunit homologues from maize (ZGB1) and Arabidopsis (AGB1).

We have isolated cDNAs from maize (ZGB1) and Arabidopsis (AGB1) encoding proteins homologous to beta subunits of guanine nucleotide-binding protein (G protein). The predicted ZGB1 and AGB1 gene products are 76% identical to each other and 41% or more identical to animal G protein beta subunits. Both predicted proteins contain seven repeats of the so-called "WD-40" motif, where WD is Trp-Asp. RNA blot analysis indicates that ZGB1 mRNA is present in the root, leaf, and tassel and that AGB1 mRNA is expressed in the root, leaf, and flower. DNA blot hybridizations indicate that maize and Arabidopsis genomes contain no other genes that are highly similar to ZGB1 and AGB1, respectively, suggesting that the newly isolated G protein beta-subunit homologues are likely to have unique functions. Furthermore, these G protein beta-subunit homologues are conserved among other plant species and may play important role(s) in plant signaling.

Immunolocalization of the G protein alpha subunit encoded by the GPA1 gene in Arabidopsis.

Heterotrimeric GTP binding proteins (G proteins) are important signal transducers in lower eukaryotes and in animal cells. In plants, the occurrence of GTP binding proteins has been reported, but their biological function remains unclear. Two genes coding for G protein alpha subunits have been cloned: GPA1 in Arabidopsis and TGA1 in tomato. To gain some insights into the function of GPA1, we describe an extensive immunolocalization of GPalpha1, the gene product of GPA1, during Arabidopsis development. Our results show that the GPalpha1 is present through all stages of development and in all organs examined, with the exception of mature seeds. It is expressed in roots, floral stem, rosette leaves, cauline leaves, flowers, and seed pods. Interestingly, the level of GPalpha1 protein is higher in immature organs than in mature organs. GPalpha1 is present at a high level in the root meristem and elongation zone, in the shoot and floral meristems, and in the leaf primordium and floral organ (sepal, petal, stamen, and gynoecium) primordia. During flower development, dividing microspores, but not mature pollen, show high levels of GPalpha1. During pollination, GPalpha1 is present in the growing pollen tubes. The protein is also present in nectaries and developing ovules and, after fertilization, in developing embryos. In mature tissue, GPalpha1 is preferentially found in the vascular system but is also present in other cell types. The complexity of the GPalpha1 localization pattern suggests that GPalpha1 might be involved in different signaling pathways depending on the developmental stage.

Rotator cuff sonography: a reassessment.

This study is both a retrospective and prospective evaluation of the clinical usefulness of shoulder sonography. Ninety-eight patients suspected of having rotator cuff tears underwent sonography of both shoulders. Sixty-two patients underwent double-contrast arthrography performed on the same day as sonography, and 38 patients underwent surgery after sonography. A comparison of the results from ultrasound and arthrography, using published diagnostic criteria, demonstrated a sensitivity of 75% and a specificity of 43% for detection of a rotator cuff tear. In this study, use of more restricted criteria, a subset of the published criteria, yielded a sensitivity of 68% and a specificity of 90%. A comparison of sonography with surgery, using this study's criteria, demonstrated a sensitivity of 57% and a specificity of 76%. This report shows that shoulder sonography is less reliable than previously reported and appears to have a very limited role in the evaluation of rotator cuff injuries.

Transcatheter embolization with sodium tetradecyl sulfate. Experimental and clinical results.

Sodium tetradecyl sulfate (Sotradecol), which has been employed for sclerotherapy of varicose veins, was evaluated in dogs and humans as an agent for selective arterial embolization. In dogs, intraarterial injection of Sotradecol 3% into the proximally occluded renal, hepatic, splenic, and deep femoral arteries produced arterial occlusion and tissue destruction. Transcatheter embolization with Sotradecol was performed in 11 patients and was successful in 10; in the remaining patient, failure was attributed to rapid dilution by unobstructed blood flow in arteriovenous malformations of the neck. The authors conclude that Sotradecol is a safe and efficient agent for selective arterial embolization.