Topical Drug Delivery in the Treatment of Skin Wounds and Ocular Trauma Using the Platform Wound Device

Topical treatment of injuries such as skin wounds and ocular trauma is the favored route of administration. Local drug delivery systems can be applied directly to the injured area, and their properties for releasing therapeutics can be tailored. Topical treatment also reduces the risk of adverse systemic effects while providing very high therapeutic concentrations at the target site. This review article highlights the Platform Wound Device (PWD) (Applied Tissue Technologies LLC, Hingham, MA, USA) for topical drug delivery in the treatment of skin wounds and eye injuries. The PWD is a unique, single-component, impermeable, polyurethane dressing that can be applied immediately after injury to provide a protective dressing and a tool for precise topical delivery of drugs such as analgesics and antibiotics. The use of the PWD as a topical drug delivery platform has been extensively validated in the treatment of skin and eye injuries. The purpose of this article is to summarize the findings from these preclinical and clinical studies.

Human platelet lysate delivered via an ocular wound chamber for the treatment of corneal epithelial injuries

Current strategies to address corneal surface defects are insufficient to successfully resolve damage caused by injury and/or disease. To address this issue, we have developed an ocular wound chamber (OWC) that creates a fluid-filled environment by encompassing damaged ocular and periocular tissues allowing for the continuous delivery of therapeutics. This study tested human platelet lysate (hPL) as a treatment for corneal epithelial defects when used with the OWC. Corneal epithelial injuries were created in anesthetized guinea pigs by debridement of the central cornea. An OWC was placed over the injured eye and animals randomly grouped followed by injection of either 20% hPL, 100% hPL, or vehicle (balanced salt solution, BSS) into the chamber. Eyes were assessed at 0, 24, 48, and 72 h using intraocular pressure (IOP), optical coherence tomography (OCT), and fluorescein imaging. Whole globes were histologically processed, and hematoxylin and eosin (H&E) stained. No differences in IOP were recorded as a result of corneal wounding, chamber placement, and/or therapeutic application. OCT images demonstrated increased corneal swelling at 48 h and 72 h in the vehicle group compared to 20% hPL. Fluorescein staining showed increased corneal re-epithelialization in the 20% and 100% hPL groups at 48 h compared to vehicle only. H&E staining revealed increased stromal cellular infiltrate in the BSS group. This study demonstrates the delivery of hPL via the OWC improves corneal re-epithelialization and supports the expanded usage of the chamber in combination with hPL to manage a variety of corneal surface injuries, diseases and/or periocular conditions.

Treatment of Corneal Infections Utilizing an Ocular Wound Chamber

Purpose

To demonstrate that the ocular wound chamber (OWC) can be used for the treatment of bacterial keratitis (BK).

Methods

A blepharotomy was performed on anesthetized, hairless guinea pigs to induce exposure keratopathy 72 hours before corneal wound creation and Pseudomonas aeruginosa inoculation. Twenty-four hours postinoculation, eyes were treated with an OWC filled with 500 µL 0.5% moxifloxacin hydrochloride ophthalmic solution (OWC), 10 µL 0.5% moxifloxacin hydrochloride drops (DROPS) four times daily, or not treated (NT). White light, fluorescein, and spectral domain optical coherence tomography (SD-OCT) images; ocular and periocular tissues samples for colony-forming units (CFU) quantification; and plasma samples were collected at 24 and 72 hours posttreatment.

Results

White light, fluorescein, and SD-OCT imaging suggests OWC-treated eyes are qualitatively healthier than those in DROPS or NT groups. At 24 hours, the median number of CFUs (interquartile range) measured was 0 (0-8750), 150,000 (106,750-181,250), and 8750 (2525-16,000) CFU/mL for OWC, NT, and DROPS, respectively. While 100% of NT and DROPS animals remained infected at 24 hours, only 25% of OWC-treated animals showed infection. Skin samples at 24 hours showed infection percentages of 50%, 75%, and 0% in DROPS, NT, and OWC groups, respectively. OWC-treated animals had higher moxifloxacin plasma concentrations at 24 and 72 hours than those treated with drops.

Conclusions

OWC use resulted in a more rapid decrease of CFUs when compared to DROPS or NT groups and was associated with qualitatively healthier ocular and periocular tissue.

Translational Relevance

The OWC could be used clinically to continuously and rapidly deliver antimicrobials to infected ocular and periocular tissues, effectively lowering bacterial bioburdens and mitigating long-term complications.

The utilization of an ocular wound chamber on corneal epithelial wounds

Purpose

Currently available ocular moisture chambers are not adequate to manage the treatment of periocular burns, corneal injuries, and infection. The purpose of these studies was to demonstrate that a flexible, semi-transparent ocular wound chamber device adapted from technology currently used on dermal wounds is safe for use on corneal epithelial injuries.

Materials and methods

A depilatory cream (Nair™, 30 seconds) was utilized to remove the excess hair surrounding the left eyes of anesthetized Institute Armand Frappier (IAF) hairless, female guinea pigs (Crl:HA-Hrhr). A 4 mm corneal epithelium defect was created using a corneal rust ring remover (Algerbrush^®II). Epithelial defects were either left untreated or the eyes were fitted with an ocular wound chamber and 0.5 mL of hydroxypropyl methylcellulose (HPMC) gel (GenTeal^®) or HPMC liquid (GenTeal^®) was injected into each chamber (N=5 per group). At 0, 24, 48, and 72 hours fluorescein and optical coherence tomography imaging was collected and the intraocular pressure (IOP) was measured. H&E staining was performed on corneal and eyelid skin samples and evaluated by a veterinary pathologist.

Results

Corneal epithelial wounds demonstrated 100% closure rates when left untreated or treated with an ocular wound chamber containing HPMC gel at 72 hours while wounds treated with an ocular wound chamber containing HPMC liquid were 98% healed. No significant differences were found in corneal thickness and wound healing, IOP, or eyelid skin pathology in any treatment group when compared to controls.

Conclusions

This study indicates that adapted wound chamber technology can be safely used on sterile, corneal epithelial wounds without adverse effects on periocular or ocular tissue when filled with a liquid or gel.

Treatment of corneal chemical alkali burns with a crosslinked thiolated hyaluronic acid film

PURPOSE

The study objective was to test the utilization of a crosslinked, thiolated hyaluronic acid (CMHA-S) film for treating corneal chemical burns.

METHODS

Burns 5.5mm in diameter were created on 10 anesthetized, male New Zealand white rabbits by placing a 1N NaOH soaked circular filter paper onto the cornea for 30s. Wounds were immediately rinsed with balanced salt solution (BSS). CMHA-S films were placed in the left inferior fornix of five injured and five uninjured animals. Five animals received no treatment. At 0h, 48h, 96h, and on day 14 post chemical burn creation, eyes were evaluated by white light imaging, fluorescein staining, and optical coherence tomography (OCT). Corneal histology was performed using H&E and Masson's Trichrome stains.

RESULTS

Image analysis indicated biocompatible CMHA-S treatment resulted in significant decreases in the areas of corneal opacity at 48h, 96h, and on day 14 postoperatively. A significant increase in re-epithelialization was seen 14days post injury. CMHA-S treated corneas showed significantly less edema than untreated burns. No pathological differences were observed in corneal histological samples as a result of CMHA-S treatment.

CONCLUSIONS

CMHA-S films facilitate re-epithelialization and decrease the area of corneal opacity in our corneal alkali burn rabbit model.

Bioactive Antimicrobial Peptides as Therapeutics for Corneal Wounds and Infections

Significance: More than 2 million eye injuries and infections occur each year in the United States that leave civilians and military members with reduced or complete vision loss due to the lack of effective therapeutics. Severe ocular injuries and infections occur in varied settings including the home, workplace, and battlefields. In this review, we discuss the potential of developing antimicrobial peptides (AMPs) as therapeutics for the treatment of corneal wounds and infections for which the current treatment options are inadequate.

Recent Advances: Standard-of-care employs the use of fluorescein dye for the diagnosis of ocular defects and is followed by the use of antibiotics and/or steroids to treat the infection and reduce inflammation. Recent advances for treating corneal wounds include the development of amniotic membrane therapies, wound chambers, and drug-loaded hydrogels. In this review, we will discuss an innovative approach using AMPs with the dual effect of promoting corneal wound healing and clearing infections.

Critical Issues: An important aspect of treating ocular injuries is that treatments need to be effective and administered expeditiously. This is especially important for injuries that occur during combat and in individuals who demonstrate delayed wound healing. To overcome gaps in current treatment modalities, bioactive peptides based on naturally occurring cationic antimicrobial proteins are being investigated as new therapeutics.

Future Directions: The development of new therapeutics that can treat ocular infections and promote corneal wound healing, including the healing of persistent corneal epithelial defects, would be of great clinical benefit.

Effect of Cationic Antimicrobial Protein CAP37 on Cytokine Profile during Corneal Wound Healing

The cationic antimicrobial protein of 37 kDa (CAP37) mediates proliferation, migration, and adhesion of human corneal epithelial cells and promotes corneal re-epithelialization in mouse. The purpose of this study was to investigate the cytokine profile following abrasion of the corneal epithelium, and to identify the cytokines modulated by topical treatment with CAP37 to determine the mechanism by which CAP37 contributes to the recruitment of inflammatory cells and healing of the cornea. The corneal epithelium in mouse eyes was removed and wounds were treated with a saline vehicle or human recombinant CAP37. Wounds were visualized with fluoresce in staining at 0, 16, 24 and 48 h. Mouse corneas were excised at 0, 6, 16, 24 and 48 h post corneal abrasion. The excised corneas were analyzed by immunohistochemistry for re-epithelialization and infiltration of inflammatory cells while the expression profiles of thirty-two cytokines were investigated by multiplex analysis. Results corroborating previous studies showed accelerated wound closure in corneas treated with CAP37 compared to those treated with the saline vehicle. Immunohistochemistry revealed less neutrophil infiltration in CAP37-treated corneas when compared to controls at 24 h. By 48 h post-wounding, histological analysis revealed more staining for neutrophils than the staining observed in the controls. Modulation of cytokine expression occurred for the majority of the cytokines tested at the time of corneal abrasion, during re-epithelialization, and/or by CAP37 treatment. Cytokines monocyte chemoattractant protein-1 (MCP-1) and regulated on activation, normal T cell expressed and secreted (RANTES) were induced during re-epithelialization, at the early 16 h time point. Interleukin 6 (IL-6), leukemia inhibitory factor (LIF), granulocyte colony-stimulating factor (G-CSF), IL-12p70, macrophage inflammatory protein 1 beta (MIP-1β), and interferon gamma-induced protein 10 (IP-10) were induced at 24 h and unchanged during CAP37 treatment. By contrast, IL-15, monokine induced by gamma interferon (MIG), keratinocyte-derived cytokine (KC), tumor necrosis factor alpha (TNF-α), MIP-1α, IL-1β, and macrophage colony-stimulating factor (M-CSF) were modulated by CAP37 treatment. In general, CAP37 appeared to decrease pro-inflammatory cytokines at 24 h and increase them at 48 h when compared to the control group. These data demonstrate that CAP37 modulates the production of cytokines in the cornea and suggest that limiting the number of neutrophils recruited during the early inflammatory phase may support corneal re-epithelialization.

A multifunctional peptide based on the neutrophil immune defense molecule, CAP37, has antibacterial and wound-healing properties

CAP37, a protein constitutively expressed in human neutrophils and induced in response to infection in corneal epithelial cells, plays a significant role in host defense against infection. Initially identified through its potent bactericidal activity for Gram-negative bacteria, it is now known that CAP37 regulates numerous host cell functions, including corneal epithelial cell chemotaxis. Our long-term goal is to delineate the domains of CAP37 that define these functions and synthesize bioactive peptides for therapeutic use. We report the novel finding of a multifunctional domain between aa 120 and 146. Peptide analogs 120-146 QR, 120-146 QH, 120-146 WR, and 120-146 WH were synthesized and screened for induction of corneal epithelial cell migration by use of the modified Boyden chamber assay, antibacterial activity, and LPS-binding activity. In vivo activity was demonstrated by use of mouse models of sterile and infected corneal wounds. The identity of the amino acid at position 132 (H vs. R) was important for cell migration and in vivo corneal wound healing. All analogs demonstrated antimicrobial activity. However, analogs containing a W at position 131 showed significantly greater antibacterial activity against the Gram-negative pathogen Pseudomonas aeruginosa. All analogs bound P. aeruginosa LPS. Topical administration of analog 120-146 WH, in addition to accelerating corneal wound healing, effectively cleared a corneal infection as a result of P. aeruginosa. In conclusion, we have identified a multifunctional bioactive peptide, based on CAP37, that induces cell migration, possesses antibacterial and LPS-binding activity, and is effective at healing infected and noninfected corneal wounds in vivo.

Corneal wound healing, a newly identified function of CAP37, is mediated by protein kinase C delta (PKCδ)

PURPOSE

The neutrophil-derived granular protein, CAP37, an innate immune system molecule, has antibiotic and immunomodulatory effects on host cells, including corneal epithelial cells. We previously showed that CAP37 modulates corneal epithelial cell migration, adhesion, and proliferation, and that protein kinase C delta (PKCδ) mediates CAP37-induced chemotaxis of these cells. The objective of this study was to investigate the hypothesis that CAP37 facilitates corneal wound healing through the PKC signaling pathway.

METHODS

The standard "scratch" assay performed on monolayers of corneal epithelial cells was used to measure the in vitro effect of CAP37 on wound closure. In vivo wound healing in response to CAP37 was measured using a mouse corneal epithelium abrasion model. In vitro and in vivo wound closure were monitored over 48 hours. The PKCδ was visualized during wound closure in cell monolayers and corneal epithelium by immunohistochemistry. The importance of PKCδ in CAP37-induced corneal wound healing was assessed by siRNA.

RESULTS

We found that CAP37 accelerated wound closure in vitro and in vivo. Maximal closure occurred with concentrations of CAP37 between 250 and 500 ng/mL. Topical applications on mouse cornea led to re-epithelialization of the cornea by 24 hours. Immunohistochemistry of in vitro and in vivo wounds revealed a local increase of PKCδ along the wound edge in CAP37-treated cell monolayers and corneas, compared to untreated controls. CAP37-induced corneal wound healing was significantly reduced in vivo upon treatment with PKCδ siRNA.

CONCLUSIONS

These findings support the hypothesis that CAP37 facilitates corneal wound healing through the activation of PKCδ.

CAP37 activation of PKC promotes human corneal epithelial cell chemotaxis

PURPOSE

The objective of this study was to elucidate the signaling pathway through which cationic antimicrobial protein of 37 kDa (CAP37) mediates human corneal epithelial cell (HCEC) chemotaxis.

METHODS

Immortalized HCECs were treated with pertussis toxin (10 and 1000 ng/mL), protein kinase C (PKC) inhibitors (calphostin c, 50 nM and Ro-31-8220, 100 nM), phorbol esters (phorbol 12,13-dibutyrate, 200 nM and phorbol 12-myristate 13-acetate, 1 μM) known to deplete PKC isoforms, and siRNAs (400 nM) before a modified Boyden chamber assay was used to determine the effect of these inhibitors and siRNAs on CAP37-directed HCEC migration. PKCδ protein levels, PKCδ-Thr(505) phosphorylation, and PKCδ kinase activity was assessed in CAP37-treated HCECs using immunohistochemistry, Western blotting, and a kinase activity assay, respectively.

RESULTS

Chemotaxis studies revealed that treatment with pertussis toxin, PKC inhibitors, phorbol esters, and siRNAs significantly inhibited CAP37-mediated chemotaxis compared with untreated controls. CAP37 treatment increased PKCδ protein levels and led to PKCδ phosphorylation on residue Thr(505). Direct activation of PKCδ by CAP37 was demonstrated using a kinase activity assay.

CONCLUSIONS

These findings lead us to conclude that CAP37 is an important regulator of corneal epithelial cell migration and mediates its effects through PKCδ.

A micro costing of NHS cancer genetic services

This paper presents the first full micro costing of a commonly used cancer genetic counselling and testing protocol used in the UK. Costs were estimated for the Cardiff clinic of the Cancer Genetics Service in Wales by issuing a questionnaire to all staff, conducting an audit of clinic rooms and equipment and obtaining gross unit costs from the finance department. A total of 22 distinct event pathways were identified for patients at risk of developing breast, ovarian, breast and ovarian or colorectal cancer. The mean cost per patient were pound sterling 97- pound sterling 151 for patients at moderate risk, pound sterling 975- pound sterling 3072 for patients at high risk of developing colorectal cancer and pound sterling 675- pound sterling 2909 for patients at high risk of developing breast or ovarian cancer. The most expensive element of cancer genetic services was labour. Labour costs were dependent upon the amount of labour, staff grade, number of counsellors used and the proportion of staff time devoted to indirect patient contact. With the growing demand for cancer genetic services and the growing number of national and regional cancer genetic centers, there is a need for the different protocols being used to be thoroughly evaluated in terms of costs and outcomes.

Cancer genetics services: a systematic review of the economic evidence and issues

This paper systematically reviews the published economic research upon cancer genetics services for families at risk of having familial breast, ovarian or colorectal cancer. A structured search was made of 15 electronic databases. The search identified 1030 papers, of which 31 fulfilled the inclusion criteria, two were cost–benefit studies, five were cost consequences, four were cost-effectiveness studies, one was a cost analysis, two were cost-minimisation studies, one was a cost–utility study, 10 modelled life years and six were reviews. Modelling studies indicate that surveillance, prophylactic and chemoprevention techniques extend survival for carriers of identified mutations. Genetic testing has been estimated to cost $70–2400 [£48^*–1591] and genetic counselling $129–800 [£89–£551]. The technology of genetic testing has been found to be cost effective. Cost effectiveness was particularly influenced by targeting genetic services for patients with a strong family history of cancer rather than screening the entire population. Future economic evaluation must go beyond merely assessing health outcomes and mutation identification, and account for the impact of genetic services upon the individual, the family and society, establish the value of services to these groups and determine the most effective ways of delivering genetic services.

Estimating the survival benefits gained from providing national cancer genetic services to women with a family history of breast cancer

The aim of this paper is to compare a service offering genetic testing and presymptomatic surveillance to women at increased risk of developing breast cancer with its predecessor of no service at all in terms of survival and quality-adjusted survival (QALYs) by means of a Markov cohort chain simulation model. Genetic assessment and presymptomatic care provided between 0.07 – 1.61 mean additional life years and 0.05 – 1.67 mean QALYs over no services. Prophylactic surgery and surveillance extended mean life expectancy by 0.41 – 1.61 and 0.32 – 0.99 years, respectively over no services for high-risk women. Model outcomes were sensitive to all the parameters varied in the sensitivity analysis. Providing cancer genetic services increase survival and as long as services do not induce adverse psychological effects they also provide more QALYs. The greatest survival and QALY benefits were found for women with identified mutations. As more cancer genes are identified, the survival and cost-effectiveness of genetic services will improve. Although mastectomy provided most additional life years, when quality of life was accounted for oophorectomy was the optimal strategy. Delayed entry into coordinated genetic services was found to diminish the average survival and QALY gains for a woman utilising these services.

Risk factors for leg wound complications following endoscopic versus traditional saphenous vein harvesting

BACKGROUND

Risk factors for leg wound complications following traditional saphenectomy have included: obesity, diabetes, female gender, anemia, age, and peripheral vascular disease. Use of an endoscopic saphenectomy technique may modify the risk factor profile associated with a traditional longitudinal incision.

METHODS

From September 1996 to May 1999, 276 consecutive patients who underwent elective isolated coronary artery bypass grafting performed by a single surgeon (K.B.A.) had their greater saphenous vein harvested endoscopically. During the period from January 1999 to May 1999, the surgical records of 643 patients who underwent the same operation and had a traditional longitudinal saphenectomy were reviewed for postoperative leg wound complications. Group demographics were similar regarding preoperative risk stratification and traditionally identified wound complication risk factors (diabetes, gender, obesity, preoperative anemia, and peripheral vascular disease). Leg wound complications were defined as: hematoma, dehiscence, cellulitis, necrosis, or abscess requiring dressing changes, antibiotics and/or debridement prior to complete epithelialization. Follow-up was 100% at six weeks.

RESULTS

Leg wound complications following endoscopic harvest occurred in 3% (9/276) of patients versus 17% (110/643) of traditional harvest patients (p < 0.0001). No univariate risk factors for wound complications were associated with endoscopic saphenectomy. Univariate predictors of wound complications following traditional saphenectomy included: diabetes (p = 0.001), obesity (p = 0.0005), and female gender (p = 0.005). Multivariable risk factors for leg wound complications following saphenectomy were traditional harvest technique (OR 7.56, CI 3.8-17.2, p < 0.0001), diabetes (OR 2.10, CI 1.4-3.2, p = 0.0006) and obesity (OR 1.82, CI 1.2-2.8, p = 0.007).

CONCLUSIONS

Traditional longitudinal saphenectomy is a multivariable risk factor for development of leg wound complications. Endoscopic saphenectomy modifies the risk factor profile for wound complications and should be the standard of care, particularly for obese and/or diabetic patients who require venous conduit during coronary artery bypass grafting.

Endoscopic and traditional saphenous vein harvest: a histologic comparison

BACKGROUND

Vein trauma after saphenectomy by endoscopic or longitudinal techniques may influence the progression of medial and intimal hyperplasia and ultimately affect graft patency. This study compared the histologic characteristics of saphenous veins after endoscopic and longitudinal harvest.

METHODS

One hundred seventy patients who underwent elective coronary artery bypass grafting had saphenectomy performed endoscopically (n = 88) or by a longitudinal incision (n = 82). Cross-sectional specimens from endoscopically (n = 151) and longitudinally (n = 158) harvested veins were submitted for hematoxylin-eosin, trichrome, and elastin staining. Blinded histologic evaluation involved graded analysis of endothelial, smooth muscle, and elastic lamina continuity in addition to medial and adventitial connective tissue uniformity.

RESULTS

Regardless of harvest technique, endothelial, elastic lamina, and smooth muscle continuity as well as medial and adventitial connective tissue uniformity were not significantly different.

CONCLUSIONS

Minor histologic alterations occur during saphenectomy, however, endoscopically and longitudinally harvested saphenous veins are histologically similar.

Endoscopic versus traditional saphenous vein harvesting: a prospective, randomized trial

BACKGROUND

Saphenous vein harvested with a traditional longitudinal technique often results in leg wound complications. An alternative endoscopic harvest technique may decrease these complications.

METHODS

One hundred twelve patients scheduled for elective coronary artery bypass grafting were prospectively randomized to have vein harvested using either an endoscopic (group A, n = 54) or traditional technique (group B, n = 58). Groups A and B, respectively, were similar with regard to length of vein harvested (41 +/- 8 cm versus 40 +/- 14 cm), bypasses done (4.1 +/- 1.1 versus 4.2 +/- 1.4), age, preoperative risk stratification, and risks for wound complication (diabetes, sex, obesity, preoperative anemia, hypoalbuminemia, and peripheral vascular disease).

RESULTS

Leg wound complications were significantly (p < or = 0.02) reduced in group A (4% [2 of 51] versus 19% [11 of 58]). Univariate analysis identified traditional incision (p < or = 0.02) and diabetes (p < or = 0.05) as wound complication risk factors. Multiple logistic regression analysis identified only the traditional harvest technique as a risk factor for leg wound complications with no significant interaction between harvest technique and any preoperative risk factor (p < or = 0.03). Harvest rate (0.9 +/- 0.4 cm/min versus 1.2 +/- 0.5 cm/min) was slower for group A (p < or = 0.02) and conversion from endoscopic to a traditional harvest occurred in 5.6% (3 of 54) of patients.

CONCLUSIONS

In a prospective, randomized trial, saphenous vein harvested endoscopically was associated with fewer wound complications than the traditional longitudinal method.

2H NMR studies of isomeric omega 3 and omega 6 polyunsaturated phospholipid membranes

The properties of aqueous multilamellar dispersions of [2H31]16:0-alpha 18:3 PC (1-[2H31]palmitoyl-2-cis,cis,cis-octa-9,12,15- trienoylphosphatidylcholine) and of [2H31]16:0-gamma 18:3 PC (1-[2H31]palmitoyl-2-cis,cis,cis-octa-6,9,12-trienoylphosphatid ylcholine) were compared by broadline 2H NMR spectroscopy. These isomeric phospholipids differ only in the location of the unsaturations in the sn-2 chain. The alpha 18:3 chain has double bonds at delta 9, 12, and 15 positions whereas in the gamma 18:3 chain they are at positions delta 6, 9, and 12. Moment analysis of spectra recorded as a function of temperature reveals dramatically distinct phase behavior for the two isomers. The gel to liquid crystalline transition for [2H31]16:0-alpha 18:3 PC membranes exhibits broad hysteresis which is characterized by a mid point temperature of -9 degrees C and -20 degrees C on heating and cooling, respectively. In contrast, the phase transition of [2H31]16:0-gamma 18:3 PC membranes does not exhibit hysteresis and occurs over a lower temperature range centred on -27 degrees C. Appreciably different molecular ordering also exists within the membranes in the liquid crystalline state. Average order parameters SCD are smaller in [2H31] 16:0-alpha 18:3 PC than in [2H31]16:0-gamma 18:3 PC by 10% at the same temperature and by 20% at equal reduced temperature. Smoothed order parameter profiles generated from depaked spectra clarify the nature of the difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute aortic dissection

Disease processes affecting the aorta are gaining increasing attention as average longevity of the population in this country increases and as awareness of conditions such as hypertension and atherosclerotic cardiovascular disease improves. Aortic dissection is commonly seen as a manifestation of these processes in the aging population and is the most common catastrophic illness affecting the aorta. Familiarity with its pathogenesis, diagnosis, and therapy is mandatory to prevent almost certain death if left untreated.

Right atrial rupture due to blunt chest trauma

Violent injury currently accounts for the majority of deaths among young people. Cardiac trauma is responsible for 15% of deaths from thoracic injury, and the incidence of cardiac injury in blunt chest trauma is as high as 76% in some clinical series. Many of these cardiac injuries consist of myocardial contusions. Recently, however, there has been increasing recognition of chamber disruption caused by blunt chest trauma. Cardiac injury is usually the result of direct compression of the heart between the sternum and the dorsal spine. These patients are frequently in extremis, with signs of pericardial tamponade, hypotension, and/or massive hemothorax. Successful management is dependent upon prompt diagnosis and surgical repair. To date there have been only 28 survivors (including the three patients in this report) of this catastrophic and frequently unrecognized injury.

Umbilical anomalies

During intrauterine development the primordia of the developing gastrointestinal and urinary tract come into close proximity in the umbilicus where the communication of these structures with the external environment is usually obliterated. In a small percentage of patients the omphalomesenteric duct and/or urachus may remain completely or partially patent. When complete patency is present, drainage of mucus, stool, or urine may occur. Partial patency may be manifest by an abdominal mass or by no symptoms at all. Definitive treatment includes total excision of the omphalomesenteric duct and/or urachus, lest recanalization of remnant tissue or carcinoma in later life occur.

Massive skin necrosis in Rocky Mountain spotted fever

The occurrence of massive skin necrosis of approximately 50% of the body surface area in an 8-year-old girl with Rocky Mountain spotted fever is reported. Although the surgeon will not often be confronted with the management of Rocky Mountain spotted fever or its complications, certain therapeutic corollaries can be outlined, based upon the observed similarity between this particular complication of severe skin loss and the syndrome of purpura fulminans: (1) heparinization for the consumptive coagulopathy and disseminated intravascular clotting; (2) correction of hypovolemia and hypoproteinemia; (3) decompression by escharotomy and/or fasciotomy if indicated; (4) topical chemotherapeutic coverage of necrotic skin; (5) full-thickness eschar excision combined with biologic dressings directed toward autograft wound closure; and (6) appropriate extremity splinting and physiotherapy.

Acute traumatic hemothorax

Over the past 5 years, 107 patients have been evaluated for acute traumatic hemothorax at the University of Kentucky Medical Center. Immediate tube thoracostomy was performed on 90 patients for evacuation of blood and air. Only 2 patients died. Thoracotomy was performed as part of the initial therapy in 9 patients. Thoracotomy for continued hemorrhage from a pulmonary parenchymal injury was required in 3 patients from the entire group. Thoracentesis or observation was the initial therapy for limited hemothorax in 8 stable patients. Three of these patients subsequently required tube thoracostomy 2 to 23 days following injury due to expanding effusions, and 1 patient required multiple thoracotomies for sepsis, fibrothorax, and empyema. These observations indicate that early evacuation of blood by means of a tube thoracostomy is essential to minimize morbidity in acute traumatic hemothorax. If continuing hemorrhage after tube thoracostomy occurs, there is a higher association of injury to additional vital structures.

Septic pulmonary embolization

Septic pulmonary embolization occurs when an infected thrombus lodges in the pulmonary arterial tree. Pulmonary abscess, empyema, bronchopleural fistula, shock and death may follow. During the preantibiotic era, septic pulmonary embolization was a dread complication of septic thrombophlebitis occurring in the pelvis and after infections of the head and neck. More recently, the multiplicity of long term indwelling catheters has changed the epidemiologic aspect of this disease, pointing toward iatrogenic causes in many instances. The drug addict, however, remains the person at greatest risk of having septic pulmonary embolization develop. A clinical evaluation seeking drug abuse and related stigmata is extremely helpful in suggesting the proper cause, establishing the presence of right-sided endocarditis and directing appropriate therapy. Staphylococcus aureus is the most common offending organism in all patient populations except for the patient with thermal injury in which gram-negative organisms predominate. Early diagnosis and proper therapy, which includes high doses of parenteral antibiotics and control of the inciting septic focus in all instances, are prerequisites for a favorable outcome.