Increased Tissue Pressure Research Articles

The context-dependent role of the Na+/Ca2+-exchanger (NCX) in pancreatic stellate cell migration

Pancreatic stellate cells (PSCs) that can co-metastasize with cancer cells shape the tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC) by producing an excessive amount of extracellular matrix. This leads to a TME characterized by increased tissue pressure, hypoxia, and acidity. Moreover, cells within the tumor secrete growth factors. The stimuli of the TME trigger Ca2+ signaling and cellular Na+ loading. The Na+/Ca2+ exchanger (NCX) connects the cellular Ca2+ and Na+ homeostasis. The NCX is an electrogenic transporter, which shuffles 1 Ca2+ against 3 Na+ ions over the plasma membrane in a forward or reverse mode. Here, we studied how the impact of NCX activity on PSC migration is modulated by cues from the TME. NCX expression was revealed with qPCR and Western blot. [Ca2+]i, [Na+]i, and the cell membrane potential were determined with the fluorescent indicators Fura-2, Asante NaTRIUM Green-2, and DiBAC4(3), respectively. PSC migration was quantified with live-cell imaging. To mimic the TME, PSCs were exposed to hypoxia, pressure, acidic pH (pH 6.6), and PDGF. NCX-dependent signaling was determined with Western blot analyses. PSCs express NCX1.3 and NCX1.9. [Ca2+]i, [Na+]i, and the cell membrane potential are 94.4 nmol/l, 7.4 mmol/l, and − 39.8 mV, respectively. Thus, NCX1 usually operates in the forward (Ca2+ export) mode. NCX1 plays a differential role in translating cues from the TME into an altered migratory behavior. When NCX1 is operating in the forward mode, its inhibition accelerates PSC migration. Thus, NCX1-mediated extrusion of Ca2+ contributes to a slow mode of migration of PSCs.

Intramuscular Pressure following Compartment of Limbs by Electric Measuring Instrument of Tissue Pressure

Background and Aim: Muscular compartment syndrome that is surgical disease at high risk of morbidity and disability causes intra-compartment bleeding as injury of muscle tissue with fracture and luxation in limbs. Increasing pressure of compartment makes small veins exhausted and migration of humor difficult in that compartment, finally it causes arterial ischemic block of blood circulation and muscular necrosis by increasing tissue pressure that is just opposite of systolic pressure. That is why it is really important to diagnose and treat this disease earlier than irreversible ischemic changes, so we can reduce permanent disability. Methods: We used electric measuring instrument of tissue pressure and obtained some basic results to diagnose those disease that causes increasing disability earlier by measuring intramuscular pressure following compartment in healthy people and patients with closed fracture in their limbs. Results and Conclusion: The difference between every muscles following compartment, sex, age in healthy people was not statistically significant and difference between sports men and officers or workers reached statistical significance. Intramuscular pressure in fracture region of patients with closed fracture in limbs was statistically significant than normal region of them.

Pressure distribution and flow characteristics during negative pressure wound therapy

Aim of the studyNegative pressure wound therapy is thought to improve wound healing by altering capillary perfusion. However, despite many theories, the underlying mechanism of action remains controversial. Recent evidence suggests an increased tissue pressure and a temporary decreased microvascular blood flow as the main reasons for the good clinical results [1]. In an attempt to further explain the mechanism of action, we investigated the pressure distribution on the foam interface, and the influence on perfusion in a pre-experimental design. Materials and methodsPressure distribution was measured using a sensor based on a capacitive dielectric elastomer with flexible electrodes. In vitro flow measurements were done with vessel imitations in a block of 300 bloom ballistic gel to simulate soft tissue. ResultsA peak pressure of up to 187 mmHg (255 g/cm2) within the foam interface, as well as decreased perfusion, were found using a standard negative pressure wound therapy setup. In conclusion, negative pressure wound therapy applies positive pressure to adjacent tissue and decreases local flow. The amount of suction applied is proportional to the pressure on the foam interface and reduction in flow. ConclusionIn line with previous studies investigating the underlying mechanism of action, these findings may contribute to possible alterations in the use of negative pressure wound therapy, e.g. lowering suction pressure in patients with diminished peripheral blood flow.

Defining a Taxonomy of Intracranial Hypertension: Is ICP More Than Just a Number?

Intracranial pressure (ICP) monitoring and control is a cornerstone of neuroanesthesia and neurocritical care. However, because elevated ICP can be due to multiple pathophysiological processes, its interpretation is not straightforward. We propose a formal taxonomy of intracranial hypertension, which defines ICP elevations into 3 major pathophysiological subsets: increased cerebral blood volume, masses and edema, and hydrocephalus. (1) Increased cerebral blood volume increases ICP and arises secondary to arterial or venous hypervolemia. Arterial hypervolemia is produced by autoregulated or dysregulated vasodilation, both of which are importantly and disparately affected by systemic blood pressure. Dysregulated vasodilation tends to be worsened by arterial hypertension. In contrast, autoregulated vasodilation contributes to intracranial hypertension during decreases in cerebral perfusion pressure that occur within the normal range of cerebral autoregulation. Venous hypervolemia is produced by Starling resistor outflow obstruction, venous occlusion, and very high extracranial venous pressure. Starling resistor outflow obstruction tends to arise when cerebrospinal fluid pressure causes venous compression to thus increase tissue pressure and worsen tissue edema (and ICP elevation), producing a positive feedback ICP cycle. (2) Masses and edema are conditions that increase brain tissue volume and ICP, causing both vascular compression and decrease in cerebral perfusion pressure leading to oligemia. Brain edema is either vasogenic or cytotoxic, each with disparate causes and often linked to cerebral blood flow or blood volume abnormalities. Masses may arise from hematoma or neoplasia. (3) Hydrocephalus can also increase ICP, and is either communicating or noncommunicating. Further research is warranted to ascertain whether ICP therapy should be tailored to these physiological subsets of intracranial hypertension.

Is Complex Decongestive Physical Therapy Safe for Median Nerve at the Level of Carpal Tunnel in Breast Cancer Related Lymphedema?

Multilayer bandaging used in complex decongestive therapy (CDT) may increase tissue pressure resulting in nerve entrapments. The aim of this study was to discover if median nerve damage is a consequence of CDT in patients with breast cancer-related lymphedema (BCRL). Eighty-two arms of 41 patients with BCRL were included. Mean age was 56.05 (8.16) years and all stages of lymphedema were equally included. Fifteen sessions of CDT was applied to all patients. The calculated volume of extremities, the quality of life (cancer adaptation of Ferrans-Powell), neuropathic pain (NP; Douleur Neuropathique 4), and disability (quick disabilities of arm, shoulder, and hand [Q-DASH]) tests were recorded before and after therapy. Skin and subcutaneous tissue thicknesses of volar and dorsal sides and median nerve cross-sectional area (CSA) at the level of carpal tunnel were measured using ultrasonography (US), before and after therapy. Carpal tunnel syndrome (CTS; 41.37%) and polyneuropathy (10.34%) were common findings confirmed by electromyography. Neuropathic pain profile was also found in 34.14% of patients. The arm volume of affected side, quality of life, and skin and subcutaneous tissue thicknesses were improved after therapy (p < 0.05). However, median nerve CSA, the NP, and Q-DASH scores were not changed after therapy. Although lymphedema is a painless condition, NP and CTS should not be ignored in patients with BCRL. US is an alternative, precise, and high technological method for evaluating treatment response. CDT is an effective and safe treatment according to volumetric calculations, US measurements of tissue thicknesses, and median nerve size.

Acute effect of wearing compression stockings on lower leg swelling and muscle stiffness in healthy young women.

Compression stockings are known to be effective in reducing peripheral oedema or leg swelling by increasing tissue pressure and venous blood flow. While previous studies on compression stockings have focused on its prolonged, preventive effect on leg swelling, the aim of this study was to investigate an acute effect of wearing compression stockings on lower leg swelling and muscle stiffness. Twenty healthy women aged 18-23years participated in the experiment conducted in the evening, in which they wore below-knee graduated compression stockings and rested in a seated position for 30min. Before and after the application of stockings, maximum calf circumference, volume, extracellular water resistance (RECW ) and muscle stiffness of the right lower leg were determined by tape measure, water displacement volumetry, segmental bioelectrical impedance spectroscopy and ultrasound shear-wave elastography, respectively. The maximum calf circumference and the reciprocal of RECW (an index of extracellular fluid volume) significantly decreased after the application of stockings, whereas the total lower leg volume and the stiffness (shear modulus) of the medial gastrocnemius muscle tended to decrease. These changes, except for that in the medial gastrocnemius muscle stiffness, were opposite to those from morning to evening studied in the subgroup of participants (n=8). However, partial correlation analysis failed to detect significant associations among these changes. These results suggest that even for a short period of application, compression stockings have some positive effects against lower leg swelling.

Simulation education for lower limb fasciotomy: improving surgical trainee confidence in executing a time-critical limb-saving procedure.

Acute extremity compartment syndrome is a relatively rare but well-recognised complication seen in a wide variety of clinical situations from acute trauma to snakebites. Local swelling within a muscle compartment results in increasing tissue pressure resulting in critical ischaemia, severe pain and altered sensation. There is only one effective treatment and that is timely surgical decompression of the osteofascial compartments involved.1 Failure to do so results in crippling ischaemic muscle contractures and in extreme cases, death. The surgical treatment is technically simple, however the stumbling blocks to success lie in recognition along with the speed and completeness of the surgery. Each of the four osteofascial compartments in the leg (anterior, peroneal, deep and superficial posterior) must be fully decompressed.1 The development of the Management of Surgical Emergencies (MSE) course was supported by the Department for International Development with the International Federation of Surgical Colleges, Association of Surgeons of Great Britain and Ireland, and College of Surgeons of East, Central and Southern Africa.2 Following an initial pilot course, the need for integration of compartment syndrome education was identified by one of the authors (YN). In Africa, although a huge proportion of the clinical workload is obstetrics and general surgery, a surgeon is expected to deal with all conditions requiring surgery. There are parallels between this truly time-critical emergency and cardiac arrest for which simulation training is well established, as it is …

Blood vessel tortuosity selects against evolution of aggressive tumor cells in confined tissue environments: A modeling approach.

Cancer is a disease of cellular regulation, often initiated by genetic mutation within cells, and leading to a heterogeneous cell population within tissues. In the competition for nutrients and growth space within the tumors the phenotype of each cell determines its success. Selection in this process is imposed by both the microenvironment (neighboring cells, extracellular matrix, and diffusing substances), and the whole of the organism through for example the blood supply. In this view, the development of tumor cells is in close interaction with their increasingly changing environment: the more cells can change, the more their environment will change. Furthermore, instabilities are also introduced on the organism level: blood supply can be blocked by increased tissue pressure or the tortuosity of the tumor-neovascular vessels. This coupling between cell, microenvironment, and organism results in behavior that is hard to predict. Here we introduce a cell-based computational model to study the effect of blood flow obstruction on the micro-evolution of cells within a cancerous tissue. We demonstrate that stages of tumor development emerge naturally, without the need for sequential mutation of specific genes. Secondly, we show that instabilities in blood supply can impact the overall development of tumors and lead to the extinction of the dominant aggressive phenotype, showing a clear distinction between the fitness at the cell level and survival of the population. This provides new insights into potential side effects of recent tumor vasculature normalization approaches.

Reply: Effects of Negative-Pressure Wound Therapy on Primary Closed Defects after Superficial Circumflex Iliac Artery Perforator Flap Harvest: Randomized Controlled Study

Sir: We thank the authors for their interest in our article.1 Recently, incisional negative-pressure wound therapy has been used to enhance healing for surgical incisions in patients with a high risk of wound dehiscence. As shown in this article, the application of negative-pressure wound therapy has many benefits. However, before applying negative-pressure wound therapy to patients, clinicians need to know the limited benefits and possible complications by understanding the physics and physiology of the therapy. The following are answers to your questions. First, it became a common belief that when using negative-pressure wound therapy dressing, tissue pressure increases proportional to the amount of negative pressure applied.2,3 The additional tissue pressure, with a pressure setting of −150 mmHg with continuous pressure mode, was +2 to 10 mmHg in noncircumferential wounds. This increased tissue pressure has a minimal effect on healthy tissues. However, in ischemic wounds and tissues with compromised perfusion, tissue perfusion might be jeopardized. There are many clinical reports of minimizing the tissue pressure increase by using a lower pressure setting.4–6 In these cases, lowering the pressure to −50 mmHg over the incisional wound can be an option. However, our series involves healthy donor sites and furthermore uses the cyclic mode to minimize the chance of possible tissue ischemia caused by the compression effect. This compression, in our hands, is enough to give the tie-over bolster fixation effect. This will minimize shearing of the skin and thus allow faster healing and reduce seroma/hematoma formation as shown in the article. Second, using the Jackson-Pratt drain is within good practice when closing a wound with dead space. By maintaining the negative pressure of the drain, hematoma collection will be minimized. One cannot compare the effect of the drain to the negative-pressure wound therapy applied on the skin because it is used for different purposes. The negative-pressure wound therapy over the skin will improve perfusion of the skin and play a role in fixation. If one were to see the fluid drain to the negative-pressure wound therapy system, it would mean that either the Jackson-Pratt drain was not functioning or secure closure of the skin was not performed. Third, the PeriScan PIM 3 System does not use a probe but rather uses a 785-nm, 70-mW laser (Perimed AB, Stockholm, Sweden) to calculate the blood perfusion of the closed margin. The measurement is performed immediately after the dressing is removed. DISCLOSURE Dr. Hong and Dr. Suh are consultants for Daewoong Pharmaceutical Company. No financial support was received regarding this study. Hyunsuk Peter Suh, M.D., Ph.D.Min Young Jang, R.N.Joon Pio (Jp) Hong, M.D., Ph.D., M.M.M.Seoul Asan Medical CenterUniversity of Ulsan College of MedicineSeoul, Republic of Korea

Demyelinating diseases as a result of cerebral edema?

Due to the elastic properties of the human organs, tissue edema causes an increased tissue pressure. This phenomenon leads to a reduction of blood circulation or ischemia, and thus leads to the hypothesis that tissue edema can be the cause of demyelinating lesions. Even though brain edema occurs in the whole brain, the authors assume that the characteristically focal appearance of demyelinated lesions, for instance of multiple sclerosis plaques, are attributable to anatomical and structural characteristics of the brain. In an experimental section, a balloon inserted into the brain and other organs removed during autopsies produces an increased tissue pressure. This model shows tissue pressure in the vicinity of the balloon up to 80mmHg. The height of the produced pressure varies in different organs and special regions of the brain.The verified pressures in the pons cerebri show that stretched myelinated fiber bundles in outer regions can induce strong pressures in enclosed edematous tissue, as seen in central pontine myelinolysis.The presented experimental results support the hypothesis that demyelinated lesions, as seen in multiple sclerosis, may be caused by increased tissue pressure, or respectively, brain edema.

Morphogenesis of the demyelinating lesions in Baló’s concentric sclerosis

In tissues with elastic properties, an edema causes a raised tissue pressure and therefore a diminished blood flow. The authors assume that an increased tissue pressure due to local and/or relapsing edema may be the cause for incomplete necrosis (e.g. demyelinated lesions) or seldom complete necrosis in the brain.Newly forming demyelinating lesions seldom show small tissue bands with normal appearing myelin sheaths in the immediate vicinity of precursor lesions (Baló type of MS). The small myelinated bands are the result of a “protected zone” on the edge of previous demyelinated lesions. The authors explain this protected zone with two arguments.Firstly, the resorptive granulation tissue of more or less older lesions is relatively rich in capillaries. These capillaries may act as an energy reservoir that can nourish not only the plaque, but also a narrow adjacent myelinated tissue band by diffusion, even if the capillary blood flow in this tissue band is limited due to the greater tissue pressure of a new developing lesion in the neighborhood.Secondly, another protective mechanism may act simultaneously: older or more sclerosed lesions and small adherent bands of myelinated tissue with them may swell less in cases of an edema than in normal tissue. The hardening of the older lesions is caused by proliferated fiber-forming astrocytes in the sense of scarring. In an area with an increased tissue pressure, the capillaries are less compressed in a sclerosed lesion than in regions of normal grey and white matter. In addition, the adherent myelinated tissue band closest to the edge of a hardened plaque is better protected against swelling and compression than the further away tissue. Theoretically, this protection zone is comparable with protected blood vessels in the Haversian canals or the medullary spaces of bones.Both theses of protecting mechanisms at the edges of demyelinated lesions support the assumption of a hypoxic causation principle of demyelinating lesions in Baló’s concentric sclerosis and multiple sclerosis.

Face Masks for Noninvasive Ventilation: Fit, Excess Skin Hydration, and Pressure Ulcers

Pressure ulcers (stages III and IV) are serious safety events (ie, never events). Healthcare institutions are no longer reimbursed for costs to care for affected patients. Medical devices are the leading cause of pediatric pressure ulcers. Face masks for noninvasive ventilation were associated with a high percentage of pressure ulcers at our institution. A prospective cohort study investigated factors contributing to pressure ulcer development in 50 subjects using face masks for noninvasive ventilation. Color imaging, 3-dimensional surface imaging, and skin hydration measurements were used to identify early skin compromise and evaluate 3 interventions to reduce trauma: (1) a silicone foam dressing, (2) a water/polyethylene oxide hydrogel dressing, and (3) a flexible cloth mask. A novel mask fit technique was used to examine the impact of fit on the potential for skin compromise. Fifty subjects age 10.4 ± 9.1 y participated with color images for 22, hydration for 34, and mask fit analysis for 16. Of these, 69% had diagnoses associated with craniofacial anomalies. Stage I pressure ulcers were the most common injury. Skin hydration difference was 317 ± 29 for sites with erythema versus 75 ± 28 for sites without erythema (P < .05) and smallest for the cloth mask (P < .05). Fit distance metrics differed for the nasal, oronasal, and face shield interfaces, with threshold distances being higher for the oronasal mask than the others (P < .05). Areas of high contact were associated with skin erythema and pressure ulcers. This fit method is currently being utilized to select best-fit masks from available options, to identify the potential areas of increased tissue pressure, and to prevent skin injuries and their complications. Improvement of mask fit is an important priority for improving respiratory outcomes. Strategies to maintain normal skin hydration are important for protecting tissue integrity.

The effect of fluid overload by saline infusion on heart rate variability in men during sleep.

Fluid shift from the legs and into the neck during sleep has been shown to increase tissue pressure around the upper airway and increase sleep apnea severity. Recently, acute fluid overload via saline infusion during sleep was shown to increase sleep apnea severity in an older men (≥ 40 years of age) but not the younger men (<;40 years of age). The purpose of this study was to estimate the changes in the autonomic nervous system response to saline infusion in the younger and older men using well studied time- and frequency domain heart rate variability metrics (HRV). Eighteen healthy men (10 in the younger group and 8 in the older group) slept for up to 3 hours during the day while ≈ 2L of saline was intravenously injected during sleep. An electrocardiogram was collected continuously during the sleep period. Two five minute segments of stage 1 or 2 sleep were selected for analysis of HRV: one before saline infusion and one after completion of saline infusion. Time- and frequency domain metrics of HRV were used to characterize autonomic nervous system response. Results generally showed increased HRV as measured by time-domain statistical measures in the younger men after saline infusion. In the frequency domain, the change in high frequency power from pre- to post-saline infusion was significantly greater in the younger compared to the older men. In addition, there was a borderline significant trend showing an increase in HF power from pre- to post-saline infusion in the younger, but not the older men. These results suggest that only in the younger men and not the older men, parasympathetic nervous activity increased in response to acute fluid overload. This might be one of the mechanisms that increased the severity of OSA in older and not the younger men.

Increased Tissue Pressure Induces Demyelinated Lesions and Necroses in the Brain

A general brain edema increases the size of the brain tissue and stretches the elastic neuronal and glial fibers. Myelinated fibers are more elastic than unmyelinated fibers. The stretching of the neuronal fibers leads particular in regions of the white matter or areas surrounded by myelinated fiber tracts to an increased tissue pressure. This physical principle can be the reason for demyelination and tissue necrosis. The higher the tissue pressure, the lower the blood perfusion. We support the pressure-hypothesis by comparison with well-known pressure related pathologies of the nervous system and other organs. One convincing example is the central pontine myelinolysis. A general or local tissue edema may lead especially in the periventricular and the deep white matter, but also in the cerebellum, the brain stem and the spinal cord to the formation of hypoxemic lesions. In consequence, this could result in diseases like leukoaraiosis, Binswanger encephalopathy, idiopathic intracranial hypertension and Multiple Sclerosis (MS). In cases of brain tissue swelling, capsula-like structures may lead to a rapid increase in tissue pressure within the enclosed areas. This may occur particularly at the optic nerve. A reduced reabsorption of Cerebrospinal Fluid (CSF) can also lead to an increase of the pressure in the Central Nervous System (CNS).

Does a Zone of Increased Perfusion Exist around Negative-Pressure Dressings?

Although recent work has demonstrated that perfusion adjacent to a negative-pressure wound therapy dressing is decreased, laser Doppler studies have indicated that there is a zone of increased perfusion a couple of centimeters away. The existence of such a zone of increased perfusion is counterintuitive to the fact that negative-pressure wound therapy has been shown to increase tissue pressure. This study, using an alternative to laser Doppler, evaluated whether such a zone exists. Six volunteers were randomized into three groups to test different suction pressures (-75, -125, and -400 mmHg). Each volunteer would have two dressings applied on either side of the lower back. A thermal imaging camera was used to assess perfusion around the dressing during different phases (e.g., "Suction on" and "Suction off"). The mean area under the curve for each phase was compared with those of other phases by means of one-way analysis of variance. Each condition (phase) was compared in a systematic manner with every other by means of Fisher's least significant difference for post hoc comparisons. A Pearson's correlation was determined to test the effects of the different suction pressure groups. No significant difference could be demonstrated for the area under the curve for the different phases. There was no significant correlation between the three suction pressures tested and the difference between the mean area under the curve for "Dressing on, no suction" and the two "Suction on" periods (Pearson correlation = 0.24; p > 0.4). Thermographic evaluation of tissue around a negative-pressure dressing did not demonstrate a zone of increased perfusion, contrary to other studies, which used laser Doppler. This is in keeping with recent work demonstrating that negative-pressure wound therapy increases tissue pressure while the dressing is applying suction. Therapeutic, V.

Case Scenario: Compartment Syndrome of the Forearm in Patient with an Infraclavicular Catheter

Case Scenario: Compartment Syndrome of the Forearm in Patient with an Infraclavicular Catheter

Role of nocturnal rostral fluid shift in the pathogenesis of obstructive and central sleep apnoea.

Obstructive sleep apnoea (OSA) is common in the general population and increases the risk of motor vehicle accidents due to hypersomnolence from sleep disruption, and risk of cardiovascular diseases owing to repetitive hypoxia, sympathetic nervous system activation, and systemic inflammation. In contrast, central sleep apnoea (CSA) is rare in the general population. Although their pathogenesis is multifactorial, the prevalence of both OSA and CSA is increased in patients with fluid retaining states, especially heart failure, where they are associated with increased mortality risk. This observation suggests that fluid retention may contribute to the pathogenesis of both OSA and CSA. According to this hypothesis, during the day fluid accumulates in the intravascular and interstitial spaces of the legs due to gravity, and upon lying down at night redistributes rostrally, again owing to gravity. Some of this fluid may accumulate in the neck, increasing tissue pressure and causing the upper airway to narrow, thereby increasing its collapsibility and predisposing to OSA. In heart failure patients, with increased rostral fluid shift, fluid may additionally accumulate in the lungs, provoking hyperventilation and hypocapnia, driving below the apnoea threshold, leading to CSA. This review article will explore mechanisms by which overnight rostral fluid shift, and its prevention, can contribute to the pathogenesis and therapy of sleep apnoea.

Role of increased tissue pressure in the pathophysiology of osteoarthritis

Osteoarthritis is characterized by increased internal pressure in the subchondral bone tissue as well as in the joint capsule. In analogy to the pathophysiological mechanism of venous compartment syndrome it is demonstrated that the increased pressure is maintained by high protein edema and initiates a vicious circle. Drug-induced resorption of the osmotically active proteins leads to elimination of the high protein edema and is able to interrupt the pathophysiological process.

Gas-Producing Cellulitis from Injection of Spot Remover Fluid (n-Hexane)

BackgroundSubcutaneous administration of hydrocarbons, categorized according to their toxicological profiles, is rare compared to oral, inhalational, and cutaneous routes of exposure. Furthermore, injection of n-hexane in humans has not been described. ObjectivesThis report demonstrates a singular case of subcutaneous administration of n-hexane. Case ReportA 21-year-old man presented to the Emergency Department (ED) 7 h after injecting his left antecubital fossa with approximately 5 cc of spot remover fluid, which contained more than 95% n-hexane, in a suicide attempt. There was redness in the left forearm, but no apparent swelling was observed. He was administered tetanus prophylaxis and discharged with follow-up. However, the patient returned to the ED 14 h later, complaining of progression of the swelling around the injection site extending to the axilla. Significant volume of air in the soft tissue of the affected extremity was noted on both the radiograph and computed tomography scan; therefore, an immediate extensive incision and debridement of the diseased limb was performed. The postoperative course was uneventful, and a complete resolution of emphysema without any functional deficits was obtained for 5 months of follow-up. ConclusionIn patients suffering from n-hexane injection, initial physical examination findings may not be apparent. Thus, the patient must be monitored closely for evidence of a spread of subcutaneous gas with elevation and immobilization. If increase in tissue pressure or spread of gas is not prevented, as in our case, immediate incision and removal of the toxic substances should be planned.

Structure, function and evolution of somatic musculature in Dasydytidae (Paucitubulatina, Gastrotricha)

The musculature of two species of the gastrotrich taxon Dasydytidae, Dasydytes (Dasydytes) goniathrix and Haltidytes crassus, was investigated and described using phalloidin staining, confocal microscopy and computer-aided three-dimensional data analysis. Dasydytidae is a peculiar taxon of freshwater Gastrotricha, containing species that are characterized by different adaptations to a semiplanktonic lifestyle, a rather uncommon feature among primarily benthic Gastrotricha. Like other dasydytid species studied so far, D. goniathrix and H. crassus possess a system of movable cuticular spines with an associated system of somatic oblique and segmented lateral muscles. The presence of other somatic (dorsodermal muscles R1 and R2) and visceral muscles (musculi ventrales, m. ventrolaterales, m. dorsales, m. helicoidales) known from a wide range of gastrotrich species was confirmed. Regarded from a functional perspective, the earlier proposed antagonistic role of oblique muscles (as spine abductors) and segmented lateral muscles (as adductors) is questioned for the species studied herein. Alternatively, our structural and behavioral observations suggest that muscular spine abduction in D. goniathrix is brought about by synergistic contraction of the musculi obliqua and m. laterales, and a passive adduction due to muscle relaxation and elastic recoil of the trunk and cuticle. For H. crassus, we hypothesize active muscular spine abduction by contraction of the musculi obliqua plus the last segment of m. laterales accompanied by severe cuticle deformations close to the spine insertions. Adduction is achieved by cuticle reformation due to elasticity and increase in tissue pressure brought about by muscle action, possibly of enforced dorsodermal muscles. The newly obtained and published muscular data of further gastrotrich species were gathered in a species-character matrix. Based on this data set, a maximum parsimony analysis of representatives of the Dasydytidae has been conducted. According to this analysis, there are three well-supported monophyletic lineages within likewise monophyletic Dasydytidae. The first lineage comprises the taxa Anacanthoderma, Stylochaeta and Chitonodytes, the second comprises Dasydytes, Setopus and Ornamentula, and the third represents the taxon Haltidytes. Relationships between these clades could be resolved but are only weakly supported. The new phylogenetic hypothesis is used to reconstruct the ancestral character pattern and to infer possible evolutionary transformations within the Dasydytidae.