Enzyme-functionalized alginate microparticles enable anaerobic culture under ambient oxygen.

Methods for culturing oxygen-sensitive cells and organisms under anaerobic conditions are vital to biotechnology research. Here, we report a biomaterial-based platform for anaerobic culture that consists of glucose oxidase (GOX) functionalized alginate microparticles (ALG-GOX), which are designed to deplete dissolved [O2 ] through enzymatic activity. ALG-GOX microparticles were synthesized via a water-in-oil emulsion and had a size of 132.0 ± 51.4 µm. Despite having a low storage modulus, the microparticles remained stable under aqueous conditions due to covalent crosslinking through amide bonds. Enzyme activity was tunable based on the loaded GOX concentration, with a maximum activity of 3.6 ± 0.3 units/mg of microparticles being achieved at an initial loading concentration of 5 mg/mL of GOX in alginate precursor solution. High enzyme activity in ALG-GOX microparticles resulted in rapid oxygen depletion, producing a suitable environment for anaerobic culture. Microparticles loaded with both GOX and catalase (ALG-GOX-CAT) to reduce H2 O2 buildup exhibited sustained activity for potential long-term anaerobic culture. ALG-GOX-CAT microparticles were highly effective for the anaerobic culture of Bacteroides thetaiotaomicron, with 10 mg/mL of ALG-GOX-CAT microparticles supporting the same level of growth in an aerobic environment compared to an anaerobic chamber after 16 h (8.70 ± 0.96 and 10.03 ± 1.03 million CFU, respectively; N.S. p = 0.07). These microparticles could be a valuable tool for research and development in biotechnology.

COURAGE-ALS: a randomized, double-blind phase 3 study designed to improve participant experience and increase the probability of success.

Objective: To determine the target population and optimize the study design of the phase 3 clinical trial evaluating reldesemtiv in participants with amyotrophic lateral sclerosis (ALS).Methods: We evaluated the phase 2 study of reldesemtiv, FORTITUDE-ALS, to inform eligibility criteria and design features that would increase trial efficiency and reduce participant burden of the phase 3 trial.Results: In FORTITUDE-ALS, the effect of reldesemtiv was particularly evident among participants in the intermediate- and fast-progressing tertiles for pre-study disease progression. These participants most often had symptom onset ≤24 months and an ALS Functional Rating Scale-Revised (ALSFRS-R) total score ≤44 at baseline. Compared with the overall FORTITUDE-ALS population, the subgroup meeting these criteria declined by fewer ALSFRS-R points at 12 weeks (difference of least-squares mean [SE] versus placebo 1.84 [0.49] and 0.87 [0.35] for the overall population). These inclusion criteria will be used for the phase 3 clinical trial, COURAGE-ALS, in which the primary outcome is the change in ALSFRS-R total score at week 24. We also measure durable medical equipment use and evaluate strength in muscles expected to change rapidly. To reduce participant burden, study visits are often remote, and strength evaluation is simplified to reduce time and effort.Conclusions: In COURAGE-ALS, the phase 3 clinical trial to evaluate reldesemtiv, the sensitivity of detecting a potential treatment effect may be increased by defining eligibility criteria that limit the proportion of participants who have slower disease progression. Implementing remote visits and simplifying strength measurements will reduce both site and participant burden.ClinicalTrials.gov identifiers: NCT03160898 (FORTITUDE-ALS) and NCT04944784 (COURAGE-ALS).

Glucose biosensors based on Michael addition crosslinked poly(ethylene glycol) hydrogels with chemo-optical sensing microdomains.

Continuous glucose monitoring (CGM) devices have the potential to lead to better disease management and improved outcomes in patients with diabetes. Chemo-optical glucose sensors offer a promising, accurate, long-term alternative to the current CGMs that require frequent calibration and replacement. Recently, we have proposed glucose sensor designs using phosphorescence lifetime-based measurement of chemo-optical glucose sensing microdomains embedded within alginate hydrogels. Due to the poor long-term stability of calcium-crosslinked alginate, we propose poly(ethylene glycol) (PEG) hydrogels synthesized via thiol-Michael addition chemistry as an alternative hydrogel carrier. The objective of this study was to evaluate the suitability of Michael addition crosslinked PEG hydrogels compared to calcium crosslinked alginate hydrogels for encapsulating glucose-sensing microdomains. PEG hydrogels crosslinked via thiol-vinyl sulfone addition achieved gelation in under 5 minutes, resulting in an even distribution of sensing microdomains. The shear storage modulus of the PEG hydrogels was tunable from 2.2 ± 0.1 kPa to 9.5 ± 1.8 kPa, which was comparable to the alginate hydrogels (10.5 ± 0.8 kPa), and the inclusion of microdomains did not significantly impact stiffness. The high water content of PEG hydrogels resulted in high glucose permeability that closely corresponded to the glucose permeability of alginate (D = 0.09 and 0.12 cm2 s-1, respectively; p = 0.47), but the PEG hydrogels exhibited superior stability. Both PEG and alginate-embedded sensors exhibited a sensing range up to ∼200 mg dL-1 glucose. The lower limits of detection (LOD) for PEG and alginate-based glucose sensors were 19.8 and 20.6 mg dL-1 with a difference of just 4.2% variation. The small difference between PEG and alginate embedded sensors indicates that their sensing properties are primarily determined by the glucose sensing microdomains rather than the hydrogel matrix. Overall, the results of this study indicate that Michael addition-crosslinked PEG hydrogels are a promising platform for encapsulation of chemo-optical glucose sensing microdomains.

Autoimmune disease of head and neck, imaging, and clinical review.

Autoimmune disease of the head and neck (H&N) could be primary or secondary to systemic diseases, medications, or malignancies. Immune-mediated diseases of the H&N are not common in daily practice of radiologists; the diagnosis is frequently delayed because of the non-specific initial presentation and lack of familiarity with some of the specific imaging and clinical features. In this review, we aim to provide a practical diagnostic approach based on the specific radiological findings for each disease. We hope that our review will help radiologists expand their understanding of the spectrum of the discussed disease entities, help them narrow the differential diagnosis, and avoid unnecessary tissue biopsy when appropriate based on the specific clinical scenarios.

Autoimmune diseases of the brain, imaging and clinical review.

There is an extensive spectrum of autoimmune entities that can involve the central nervous system, which has expanded with the emergence of new imaging modalities and several clinicopathologic entities. Clinical presentation is usually non-specific, and imaging has a critical role in the workup of these diseases. Immune-mediated diseases of the brain are not common in daily practice for radiologists and, except for a few of them such as multiple sclerosis, there is a vague understanding about differentiating them from each other based on the radiological findings. In this review, we aim to provide a practical diagnostic approach based on the unique radiological findings for each disease. We hope our diagnostic approach will help radiologists expand their basic understanding of the discussed disease entities and narrow the differential diagnosis in specific clinical scenarios. An understanding of unique imaging features of these disorders, along with laboratory evaluation, may enable clinicians to decrease the need for tissue biopsy.

A clinical decision rule predicting outcomes of emergency department patients with altered mental status.

STUDY OBJECTIVE: Approximately 5% of emergency department patients present with altered mental status (AMS). AMS is diagnostically challenging because of the wide range of causes and is associated with high mortality. We sought to develop a clinical decision rule predicting admission risk among emergency department (ED) patients with AMS. METHODS: Using retrospective chart review of ED encounters for AMS over a 2-month period, we recorded causes of AMS and numerous clinical variables. Encounters were split into those admitted to the hospital ("cases") and those discharged from the ED ("controls"). Using the first month's data, variables correlated with hospital admission were identified and narrowed using univariate and multivariate statistics, including recursive partitioning. These variables were then organized into a clinical decision rule and validated on the second month's data. The decision rule results were also compared to 1-year mortality. RESULTS: We identified 351 encounters for AMS over a 2-month period. Significant contributors to AMS included intoxication and chronic disorder decompensation. ED data predicting hospital admission included vital sign abnormalities, select lab studies, and psychiatric/intoxicant history. The decision rule sorted patients into low, moderate, or high risk of admission (11.1%, 44.3%, and 89.1% admitted, respectively) and was predictive of 1-year mortality (low-risk group 1.8%, high-risk group 34.3%). CONCLUSIONS: We catalogued common causes for AMS among patients presenting to the ED, and our data-driven decision tool triaged these patients for risk of admission with good predictive accuracy. These methods for creating clinical decision rules might be further studied and improved to optimize ED patient care.

Chronic Demyelination and Axonal Degeneration in Multiple Sclerosis: Pathogenesis and Therapeutic Implications.

PURPOSE OF REVIEW: Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system (CNS). Inflammatory attacks in MS lead to both demyelination and axonal damage. However, due to incomplete remyelination most MS lesions remain chronically demyelinated. In parallel, there is axonal degeneration in the CNS of MS patients, contributing to progressive disability. There are currently no approved therapies that adequately restore myelin or protect axons from degeneration. In this review, we will discuss the pathophysiology of axonal loss and chronic demyelination in MS and how understanding this pathophysiology is leading to the development of new MS therapeutics. RECENT FINDINGS: Ongoing research into the function of oligodendrocytes and myelin has revealed the importance of their relationship with neuronal health. Demyelination in MS leads to a number of pathophysiologic changes contributing to axonal generation. Among these are mitochondrial dysfunction, persistent neuroinflammation, and the effects of reactive oxygen and nitrogen species. With this information, we review currently approved and investigational therapies designed to restore lost or damaged myelin and protect against neuronal degeneration. The development of therapies to restore lost myelin and protect neurons is a promising avenue of investigation for the benefit of patients with MS.

Neuron-Oligodendrocyte Interactions in the Structure and Integrity of Axons.

The myelination of axons by oligodendrocytes is a highly complex cell-to-cell interaction. Oligodendrocytes and axons have a reciprocal signaling relationship in which oligodendrocytes receive cues from axons that direct their myelination, and oligodendrocytes subsequently shape axonal structure and conduction. Oligodendrocytes are necessary for the maturation of excitatory domains on the axon including nodes of Ranvier, help buffer potassium, and support neuronal energy metabolism. Disruption of the oligodendrocyte-axon unit in traumatic injuries, Alzheimer's disease and demyelinating diseases such as multiple sclerosis results in axonal dysfunction and can culminate in neurodegeneration. In this review, we discuss the mechanisms by which demyelination and loss of oligodendrocytes compromise axons. We highlight the intra-axonal cascades initiated by demyelination that can result in irreversible axonal damage. Both the restoration of oligodendrocyte myelination or neuroprotective therapies targeting these intra-axonal cascades are likely to have therapeutic potential in disorders in which oligodendrocyte support of axons is disrupted.

In situ printing of scaffolds for reconstruction of bone defects.

Bone defects are commonly caused by traumatic injuries and tumor removal and critically sized defects overwhelm the regenerative capacity of the native tissue. Reparative strategies such as auto, xeno, and allografts have proven to be insufficient to reconstruct and regenerate these defects. For the first time, we introduce the use of handheld melt spun three dimensional printers that can deposit materials directly within the defect site to properly fill the cavity and form free-standing scaffolds. Engineered composite filaments were generated from poly(caprolactone) (PCL) doped with zinc oxide nanoparticles and hydroxyapatite microparticles. The use of PCL-based materials allowed low-temperature printing to avoid overheating of the surrounding tissues. The in situ printed scaffolds showed moderate adhesion to wet bone tissue, which can prevent scaffold dislocation. The printed scaffolds showed to be osteoconductive and supported the osteodifferentiation of mesenchymal stem cells. Biocompatibility of the scaffolds upon in vivo printing subcutaneously in mice showed promising results. STATEMENT OF SIGNIFICANCE.

In Situ Printing of Adhesive Hydrogel Scaffolds for the Treatment of Skeletal Muscle Injuries.

Reconstructive surgery remains inadequate for the treatment of volumetric muscle loss (VML). The geometry of skeletal muscle defects in VML injuries varies on a case-by-case basis. Three-dimensional (3D) printing has emerged as one strategy that enables the fabrication of scaffolds that match the geometry of the defect site. However, the time and facilities needed for imaging the defect site, processing to render computer models, and printing a suitable scaffold prevent immediate reconstructive interventions post-traumatic injuries. In addition, the proper implantation of hydrogel-based scaffolds, which have generated promising results in vitro, is a major challenge. To overcome these challenges, a paradigm is proposed in which gelatin-based hydrogels are printed directly into the defect area and cross-linked in situ. The adhesiveness of the bioink hydrogel to the skeletal muscles was assessed ex vivo. The suitability of the in situ printed bioink for the delivery of cells is successfully assessed in vitro. Acellular scaffolds are directly printed into the defect site of mice with VML injury, exhibiting proper adhesion to the surrounding tissue and promoting remnant skeletal muscle hypertrophy. The developed handheld printer capable of 3D in situ printing of adhesive scaffolds is a paradigm shift in the rapid yet precise filling of complex skeletal muscle tissue defects.

Soft-Nanoparticle Functionalization of Natural Hydrogels for Tissue Engineering Applications.

Tissue engineering has emerged as an important research area that provides numerous research tools for the fabrication of biologically functional constructs that can be used in drug discovery, disease modeling, and the treatment of diseased or injured organs. From a materials point of view, scaffolds have become an important part of tissue engineering activities and are usually used to form an environment supporting cellular growth, differentiation, and maturation. Among various materials used as scaffolds, hydrogels based on natural polymers are considered one of the most suitable groups of materials for creating tissue engineering scaffolds. Natural hydrogels, however, do not always provide the physicochemical and biological characteristics and properties required for optimal cell growth. This review discusses the properties and tissue engineering applications of widely used natural hydrogels. In addition, methods of modulation of their physicochemical and biological properties using soft nanoparticles as fillers or reinforcing agents are presented.

Reduced Noradrenergic Signaling in the Spleen Capsule in the Absence of CB1 and CB2 Cannabinoid Receptors.

The spleen is a visceral organ that contracts during hypoxia to expel erythrocytes and immune cells into the circulation. Spleen contraction is under the control of noradrenergic sympathetic innervation. The activity of noradrenergic neurons terminating in the spleen capsule is regulated by α2-adrenergic receptors (AR). Interactions between endogenous cannabinoid signaling and noradrenergic signaling in other organ systems suggest endocannabinoids might also regulate spleen contraction. Spleens from mice congenitally lacking both CB1 and CB2 cannabinoid receptors (Cnr1 -/- /Cnr2 -/- mice) were used to explore the role of endocannabinoids in spleen contraction. Spleen contraction in response to exogenous norepinephrine (NE) was found to be significantly lower in Cnr1 -/- /Cnr2 -/- mouse spleens, likely due to decreased expression of capsular α1AR. The majority of splenic Cnr1 mRNA expression is by cells of the spleen capsule, suggestive of post-synaptic CB1 receptor signaling. Thus, these studies demonstrate a role for CB1 and/or CB2 in noradrenergic splenic contraction.

Differences Between Bilateral Adrenal Incidentalomas and Unilateral Lesions.

IMPORTANCE: Adrenal incidentalomas are found in 1% to 5% of abdominal cross-sectional imaging studies. Although the workup and management of unilateral lesions are well established, limited information exists for bilateral incidentalomas. OBJECTIVE: To compare the natural history of patients having bilateral incidentalomas with those having unilateral incidentalomas. DESIGN, SETTING, AND PARTICIPANTS: Retrospective analysis of a prospective database of consecutive patients referred to an academic multidisciplinary adrenal conference. The setting was a tertiary care university hospital among a cohort of 500 patients with adrenal lesions between July 1, 2009, and July 1, 2014. MAIN OUTCOMES AND MEASURES: Prevalence, age, imaging characteristics, biochemical workup, any intervention, and final diagnosis. RESULTS: Twenty-three patients with bilateral incidentalomas and 112 patients with unilateral incidentalomas were identified. The mean age at diagnosis of bilateral lesions was 58.7 years. The mean lesion size was 2.4 cm on the right side and 2.8 cm on the left side. Bilateral incidentalomas were associated with a significantly higher prevalence of subclinical Cushing syndrome (21.7% [5 of 23] vs 6.2% [7 of 112]) (P = .009) and a significantly lower prevalence of pheochromocytoma (4.3% [1 of 23] vs 19.6% [22 of 112]) (P = .003) compared with unilateral lesions, while rates of hyperaldosteronism were similar in both groups (4.3% [1 of 23] vs 5.4% [6 of 112]) (P > .99). Only one patient with bilateral incidentalomas underwent unilateral resection. The mean follow-up was 4 years (range, 1.2-13.0 years). There were no occult adrenocortical carcinomas. CONCLUSIONS AND RELEVANCE: Bilateral incidentalomas are more likely to be associated with subclinical Cushing syndrome and less likely to be pheochromocytomas. Although patients with bilateral incidentalomas undergo a workup similar to that in patients with unilateral lesions, differences in their natural history warrant a greater index of suspicion for subclinical Cushing syndrome.

Comparison of the D2 receptor regulation and neurotoxicant susceptibility of nigrostriatal dopamine neurons in wild-type and CB1/CB2 receptor knockout mice.

Motor dysfunctions of Parkinson Disease (PD) are due to the progressive loss of midbrain nigrostriatal dopamine (NSDA) neurons. Evidence suggests a role for cannabinoid receptors in the neurodegeneration of these neurons following neurotoxicant-induced injury. This work evaluates NSDA neurons in CB1/CB2 knockout (KO) mice and tests the hypothesis that CB1/CB2 KO mice are more susceptible to neurotoxicant exposure. NSDA neuronal indices were assessed using unbiased stereological cell counting, high pressure liquid chromatography coupled with electrochemical detection or mass spectrometry, and Western blot. Results reveal that CB1 and CB2 cannabinoid receptor signaling is not necessary for the maintenance of a normally functioning NSDA neuronal system. Mice lacking CB1 and CB2 receptors were found to be equally susceptible to the neurotoxicant 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP). These studies support the use of CB1/CB2 KO mice for investigating the cannabinoid receptor-mediated regulation of the NSDA neuronal system in models of PD.

Pre-operative dopamine agonist therapy improves post-operative tumor control following prolactinoma resection.

OBJECTIVE: Normalization of serum prolactin concentrations in patients with prolactinomas is an accepted endpoint of therapy. Clinical signs and symptoms of hyperprolactinemia are usually resolved when prolactin levels are lowered to within the normal range. While most patients are treated with dopamine agonist drugs, some patients require surgical resection of their tumors. We sought to determine whether preoperative treatment with dopamine agonists alters the outcome of surgical intervention. METHODS AND RESULTS: We present an analysis of 253 patients with prolactinomas treated surgically during the period of time when dopamine agonist therapy was first introduced and prior to its widespread use as first-line therapy. We compared both short- and long-term outcomes of patients treated with dopamine agonists prior to surgery with those undergoing surgery as their initial treatment modality. Our data showed that that patients treated with dopamine agonists prior to surgery experienced greater reductions in prolactin levels, had lower prolactin levels, were more likely to have normal prolactin levels at long term follow-up, and were less likely to require additional therapy to control their prolactin levels. CONCLUSION: Our study provides strong evidence suggesting that, regardless of initial prolactin level, preoperative dopamine agonist therapy is not detrimental. In fact, pretreatment with dopamine agonist drugs, possibly by inducing tumor regression, seemed to improve the surgeon's ability to resect a greater percentage of the tumor and led to better control of the prolactin level.

Relationship between venous and arterial carboxyhemoglobin levels in patients with suspected carbon monoxide poisoning.

STUDY OBJECTIVE: To test the hypothesis that venous carboxyhemoglobin (V-COHb) levels accurately predict arterial (A-COHb) levels. DESIGN: Prospective comparison of A-COHb and V-COHb levels in patients with suspected carbon monoxide (CO) poisoning. SETTING: Municipal hospital emergency department with contiguous multiplace hyperbaric chamber staffed 24 hours a day. PARTICIPANTS: Unselected convenience sample of 61 adults with suspected CO toxicity. INTERVENTION: Simultaneous sampling of arterial and venous blood. RESULTS: Correlation between V-COHb and A-COHb showed an r value of .99 (95%CI, .99 to .99), and an r2 value of .98. Agreement between V-COHb and A-COHb levels was examined by use of a plot of arteriovenous differences against the mean of the two measurements. The mean arteriovenous difference was .15% COHb (95%CI, .13% to .45%), with 95% of the differences ranging from 2.4% COHb to -2.1% COHb. CONCLUSION: Venous COHb levels predict arterial levels with a high degree of accuracy. Patients with suspected CO poisoning can be screened with the use of venous blood, without the need for arterial puncture.

Thrombosis of abdominal aortic aneurysms.

The usual complication of abdominal aortic aneurysms is rupture. Although thrombosis of peripheral aneurysms is common, thrombosis of abdominal aortic aneurysms is rare. Sudden thrombosis of abdominal aortic aneurysms constitutes a surgical emergency, with a mortality of 50 percent. The patient often presents with cool and mottled skin, and with severe pain from the umbilicus to the lower extremities. Femoral pulses are rarely present, and neurologic deficits below the level of occlusion are common. We reviewed four recent patients with thrombosed abdominal aortic aneurysms. They presented with a range of symptoms that included impotence, abdominal pain, lower extremity pain, coolness, and weakness. Angiography in three of the patients revealed complete occlusion of the aorta. The fourth patient did not undergo angiography because of hemodynamic instability. Three of the four patients underwent thrombectomy, aneurysmectomy, and bypass grafting. The other patient underwent axillofemoral bypass grafting in lieu of aneurysmectomy because of severe coronary arteriosclerotic heart disease. All patients did well postoperatively. Our limited experience suggests that prompt diagnosis and surgical management of patients with thrombosed aortic aneurysms can lead to a successful outcome.

Small bowel cancer: a 30-year review.

BACKGROUND: Small bowel cancer is a relatively rare tumor with an incidence of 2,700 new cases and 900 deaths per year. The influence of stage on survival has been reported only once previously. Patterns of recurrence are unreported. METHODS: All cases of small bowel cancer treated at our hospital over a 30-year period (1960-1989) were reviewed. RESULTS: The site of most cancers was the duodenum (46%), followed in frequency by the jejunum (33%) and the ileum (21%). Adenocarcinoma was the most common histology (63%), followed in frequency by lymphoma (15%), leiomyosarcoma (13%), carcinoid tumors (6%), and miscellaneous (3%). Analysis of stage distribution by site showed a decrease in stages I and II with more distal locations. Associated cancers occurred in 11%, but none were seen in the group with carcinoid tumors. Actuarial 10-year survival rates were 24% for those with adenocarcinoma (all stages) 75% for stage I, 25% for those with stage II, and 0% for stage III. A subgroup of 10 patients who underwent a pancreaticoduodenectomy (one stage I, seven stage II, two stage III) had a 30% 10-year survival rate. Those patients with lymphoma had a 12% 10-year survival rate, and those with leiomyosarcoma had a 20% 10-year survival rate. A 100% 10-year survival rate was observed in those with carcinoid tumors. Peritoneal carcinomatosis was the most common failure pattern (33%), followed in frequency by local recurrence in 23% and abdominal wall recurrence in 15%. CONCLUSIONS: A correlation exists between the pathologic stage and the survival rate for adenocarcinoma. The most common recurrence pattern for adenocarcinoma was carcinomatosis, followed in frequency by abdominal wall recurrence. Leiomyosarcoma preferentially metastasizes to the liver.

Iodine125 interstitial brachytherapy in the treatment of carcinoma of the lung.

In a prospective study, 14 patients with primary non-oat cell lung carcinoma were treated with intraoperative Iodine125 (I125) implantation of the lung tumor via lateral thoracotomy or median sternotomy. Staging mediastinal node dissection was performed in each case. Patients were selected when wedge or segmental resections were not technically feasible, such that lobectomy or completion pneumonectomy would have been required or pulmonary function studies were poor. Doses ranged from 8,000 cGy at the periphery to 20,000 cGy at the center. With a minimum 12 month follow-up, mean and median survivals were 16.7 and 15.1 months, respectively. Local control was achieved in 10 of 14 patients (71%) with all local failures occurring in pathologic stage III patients. When separated according to tumor size, local control was obtained in six of seven tumors of less than 3 cm and four of five tumors of 3-5 cm. Both cases with masses greater than 5 cm failed locally. There was one operative mortality and two postoperative complications. All other patients were discharged within one week of surgery. There was no radiation pneumonitis. I125 lung brachytherapy is an excellent alternative treatment for T1 and T2 tumors when medical conditions preclude curative resection.

Absorbable versus permanent mesh in abdominal operations.

Because previous studies evaluating prosthetic mesh have yielded conflicting results, we compared two permanent (polypropylene and polytetrafluoroethylene) and two absorbable (polyglactin and polyglycolic acid) meshes with respect to histologic appearance, development of adhesions, tensile strength and occurrence of hernias in rabbits in which defects of the abdominal wall measuring 2 by 3 centimeters were repaired with one of the meshes. Twenty experiments were performed with each material, and observations were made at two, five, seven and ten weeks. The inflammatory response was minimal with all products. Adhesions were more marked with polypropylene (Marlex) than with polytetrafluoroethylene (Gore-tex); there was no difference between the absorbable meshes. In vitro tensile strength measurements at ten weeks indicated that Marlex was superior to the other materials, and between the absorbable products, polyglactin (Vicryl) was superior to polyglycolic acid (Dexon). No hernias were observed with the nonabsorbable meshes, but all of the rabbits repaired with absorbable meshes had ventral hernias by the tenth week. Thus, absorbable meshes are not indicated when prolonged tensile strength is required, but they may be useful for other purposes, including the temporary repair of fascial defects, since evisceration was not observed.