Point-of-Care Echocardiography Unveils Misclassification of Acute Kidney Injury as Hepatorenal Syndrome.

INTRODUCTION: Fulfillment of the diagnostic criteria for -hepatorenal syndrome type 1 (HRS-1) requires prior failure of 2 days of intravenous volume expansion and/or diuretic withdrawal. However, no parameter of volume status is used to guide the need for volume expansion in patients with suspected HRS-1. We hypothesized that point-of-care echocardiography (POCE) may better characterize the volume status in patients with acute kidney injury (AKI) and cirrhosis to ascertain or disprove the diagnosis of HRS-1. METHODS: A pilot observational study was conducted to determine the clinical utility of POCE-based examination of inferior vena cava diameter (IVCD) and collapsibility index (IVCCI) to assess intravascular volume status in patients with cirrhosis and AKI who had been deemed adequately volume-repleted and thereby assigned a clinical diagnosis of HRS-1. Early improvement in kidney function was defined as ≥20% decrease in serum creatinine (sCr) at 48-72 h. RESULTS: A total of 53 patients were included. The mean sCr at the time of volume assessment was 3.2 ± 1.5 mg/dL, and the mean Model for End-Stage Liver Disease score was 29 ± 8. Fifteen (23%) patients had an IVCD <1.3 cm and IVCCI >40% and were reclassified as fluid-depleted, 11 (21%) had an IVCD >2 cm and IVCCI <40% and were reclassified as fluid-expanded, and 8 (15%) had and IVCD <1.3 cm and IVCCI <40% and were reclassified as having intra-abdominal hypertension (IAH). Twelve (23%) patients exhibited early improvement in kidney function following a POCE-guided therapeutic maneuver, that is, volume expansion, diuresis, or paracentesis for those deemed fluid-depleted, fluid-expanded or having IAH, respectively. CONCLUSION: POCE-based assessment of volume status in cirrhotic individuals with AKI reveals marked heterogeneity. Unguided volume expansion in these patients may lead to premature or delayed diagnosis of HRS-1.

Self-management and adherence in childhood-onset systemic lupus erythematosus: what are we missing?

OBJECTIVES: The aims of this study are (1) to characterize factors influencing self-management behaviors and quality of life in adolescent and young adult (AYA) patients with childhood-onset systemic lupus erythematosus (cSLE) and (2) to identify barriers and facilitators of treatment adherence via focus groups. METHODS: AYAs with cSLE ages 12-24 years and primary caregivers of the adolescents participated in this study. Recruitment occurred during pediatric rheumatology clinic visits at a Midwestern children's hospital or the hospital's cSLE active clinic registry. Information about disease severity was obtained from patient health records. Pain and fatigue questionnaires were administered. Descriptive statistics were used to analyze data. RESULTS: Thirty-one AYA patients and caregivers participated in six focus groups. Ten major themes emerged from sessions; four were expressed both by the AYA and caregiver groups: knowledge deficits about cSLE, symptoms limiting daily function, specifically mood and cognition/learning, barriers and facilitators of adherence, and worry about the future. Themes unique to AYA participants included symptoms limiting daily functioning-pain/fatigue, self-care and management, impact on personal relationships, and health care provider communication/relationship. For caregiver groups unique themes included need for school advocacy, disruption of family schedule, and sense of normalcy for their adolescent. CONCLUSION: AYAs with cSLE face a lifelong disease characterized by pervasive pain, fatigue, organ damage, isolation-social and/or physical-and psycho-socioeducational challenges. This study confirmed that continued psychosocial support, health information education, adherence interventions, and personalized treatment plans are necessary to increase self-management and autonomy in AYAs with cSLE.

Utility of lacrimal caruncle infrared thermography when monitoring alterations in autonomic activity in healthy humans.

PURPOSE: Physiological markers that estimate sympathetic activation may be used to infer pain and stress in humans. To date, effective reproducible methods are invasive and pose an undesired risk to participants. Previous work in animal models has used infrared thermography to measure the temperature of the lacrimal caruncle region and may be a promising method for measuring stress and pain non-invasively. The current study aimed to determine whether this method is useful in humans. METHODS: Sixteen young healthy participants (age: 18-35) were recruited and underwent sympathetic activation using a cold pressor test (CPT) and a muscle chemoreflex (MCR), and completed a control trial. Throughout all trials, infrared thermographic imaging of the lacrimal caruncle, heart rate, heart rate variability, mean arterial blood pressure and pulse transit time were measured. RESULTS: Heart rate (MCR: 4 ± 3 bpm, CPT: 17 ± 4 bpm p < 0.01) and mean arterial pressure increased (MCR: 6 ± 2, CPT: 5 ± 2 mmHg, p < 0.01) and pulse transit time decreased (p = 0.03) with both sympathetic activation interventions. However, lacrimal caruncle temperature did not vary under any condition remaining at 35.2 ± 0.2 °C which was similar to baseline. CONCLUSIONS: Our findings suggest infrared thermographic monitoring of eye temperature in humans does not reliably relate to sympathetic activation. This could be due to hemodynamic responses at the lacrimal caruncle that may be more complex than previously proposed with sympathetic activation. Alternatively, pulse transit time seems like a promising non-invasive measure of changes in sympathetic activation in humans.

Safety of nintedanib added to pirfenidone treatment for idiopathic pulmonary fibrosis.

We assessed safety and tolerability of treatment with pirfenidone (1602-2403 mg·day-1) and nintedanib (200-300 mg·day-1) in patients with idiopathic pulmonary fibrosis (IPF).This 24-week, single-arm, open-label, phase IV study (ClinicalTrials.gov identifier NCT02598193) enrolled patients with IPF with forced vital capacity % pred ≥50% and diffusing capacity of the lung for carbon monoxide % pred ≥30%. Before initiating nintedanib, patients had received pirfenidone for ≥16 weeks and tolerated a stable dose of ≥1602 mg·day-1 for ≥28 days. The primary end-point was the proportion of patients who completed 24 weeks of combination treatment on pirfenidone (1602-2403 mg·day-1) and nintedanib (200-300 mg·day-1). Investigators recorded treatment-emergent adverse events (TEAEs), attributing them to pirfenidone, nintedanib, both or neither.89 patients were enrolled; 73 completed 24 weeks of treatment (69 meeting the primary end-point) and 16 discontinued treatment prematurely (13 due to TEAEs). 74 patients had 418 treatment-related TEAEs, of which diarrhoea, nausea and vomiting were the most common. Two patients had serious treatment-related TEAEs.Combined pirfenidone and nintedanib use for 24 weeks was tolerated by the majority of patients with IPF and associated with a similar pattern of TEAEs expected for either treatment alone. These results encourage further study of combination treatment with pirfenidone and nintedanib in patients with IPF.

Disambiguating pharmacological mechanisms from placebo in neuropathic pain using functional neuroimaging.

BACKGROUND: A lack of objective outcome measures and overreliance on subjective pain reports in early proof-of-concept studies contribute to the high attrition of potentially effective new analgesics. We studied the utility of neuroimaging in providing objective evidence of neural activity related to drug modulation or a placebo effect in a double-blind, randomized, placebo-controlled, three-way crossover trial. METHODS: We chronically administered pregabalin or tramadol (first-line and second-line analgesics, respectively), recommended for neuropathic pain, in 16 post-traumatic neuropathic pain patients. We measured subjective pain reports, allodynia-evoked neural activity, and brain resting state functional connectivity from patients during the three sessions and resting state data at baseline from patients after washout of their current medication. All data were collected using a 3 T MRI scanner. RESULTS: When compared with placebo only, pregabalin significantly suppressed allodynia-evoked neural activity in several nociceptive and pain-processing areas of the brain, despite the absence of behavioural analgesia. Furthermore, placebo significantly increased functional connectivity between the rostral anterior cingulate and the brainstem, a core component of the placebo neural network. CONCLUSIONS: Functional neuroimaging provided objective evidence of pharmacodynamic efficacy in a proof-of-concept study setting where subjective pain outcome measures are often unreliable. Additionally, we provide evidence confirming the neural mechanism underpinning placebo analgesia as identified in acute experimental imaging studies in patients during the placebo arm of a clinical trial. We explore how brain penetrant active drugs potentially interact with this mechanism. CLINICAL TRIAL REGISTRATION: NCT0061015.

Organ involvement other than lupus nephritis in childhood-onset systemic lupus erythematosus.

In this review we critically analyze pulmonary, gastrointestinal and cardiac manifestations of childhood-onset systemic lupus erythematosus (cSLE). Clinical manifestations of these organ systems may be the initial manifestation of cSLE; frequently occur with very active cSLE; and are potential life-threatening manifestations often presenting to the emergency department and requiring admission to the intensive care unit. Early recognition and treatment of the pulmonary, gastrointestinal and cardiac manifestations of cSLE will result in improved prognosis and better outcomes.

Why do two procedures when one will do? Thoracic ultrasound guiding management of complex pleural space infections.

Complicated parapneumonic effusions and empyemas are associated with significant morbidity and mortality. When managing a potentially infected pleural space, current guidelines support performing diagnostic thoracentesis prior to consideration of chest tube insertion. We present a case demonstrating our clinical approach to the management of complicated parapneumonic effusions and empyemas, with patient presentation and initial point-of-care thoracic ultrasound assessment guiding consideration of immediate insertion of small-bore (14 F) chest tube.

Utility of point-of-care ultrasound for guidance of ultrafiltration goal in a patient with end stage renal disease and acute hypoxic respiratory failure following 2 weeks on mechanical ventilation.

Point-of-care ultrasound is a bedside tool that is increasingly being used as part of the physical examination to evaluate fluid status. Cardiac ultrasound for assessment of volume status focuses on evaluating left ventricular ejection fraction, presence of pericardial effusion, right ventricular size, inferior vena cava size and collapsibility, and stroke volume measurement at the left ventricular outflow tract. Another way in which POCUS can be used to assess for fluid overload is the use of mitral inflow doppler to measure early diastolic transmitral flow velocity (E) and tissue doppler to measure early diastolic mitral annular velocity (e'). The ratio of E/e' is then used as an estimation of left ventricular filling pressure. This is a case where a 54-year-old female with end stage renal disease presents with hypoxic respiratory failure and is found to have diffuse bilateral airspace opacities on chest radiograph. E/e' was used to determine the etiology of the patient's undifferentiated pulmonary infiltrates and guide fluid removal through ultrafiltration. Ultrafiltration was performed with subsequent improvement in E/e' and the patient was successfully weaned off mechanical ventilation.

Intrapleural therapy.

Numerous intrapleural therapies have been adopted to treat a vast array of pleural diseases. The first intrapleural therapies proposed focused on the use of fibrinolytics and DNase to promote fluid drainage in empyema. Numerous case series and five randomized controlled trials have been published to determine the outcomes of fibrinolytics in empyema treatment. In the largest randomized trial, the use of streptokinase had no reduction in mortality, decortication rates or hospital days compared with placebo in the treatment of empyema. Criticism over study design and patient selection may have potentially affected the outcomes in this study. The development of dyspnoea is common in the setting of malignant pleural effusions. Pleural fluid evacuation followed by pleurodesis is often attempted. Numerous sclerosing agents have been studied, with talc emerging as the most effective agent. Small particle size of talc should be avoided because of increased systemic absorption potentiating toxicity, such as acute lung injury. Over the past several years, the use of chronic indwelling pleural catheters have emerged as the preferred modality in the treating a symptomatic malignant pleural effusion. For patients with malignant-related lung entrapment, pleurodesis often fails due to the presence of visceral pleural restriction; however, chronic indwelling pleural catheters are effective in palliation of dyspnoea. Finally, the use of staphylococcal superantigens has been proposed as a therapeutic model for the treatment of non-small lung cancer. Intrapleural instillation of staphylococcal superantigens increased median survival by 5 months in patients with non-small cell lung cancer with a malignant pleural effusion.

Management of complex pleural disease in the critically ill patient.

Disorders of the pleural space are quite common in the critically ill patient. They are generally associated with the underlying illness. It is sometimes difficult to assess for pleural space disorders in the ICU given the instability of some patients. Although the portable chest X-ray remains the primary modality of diagnosis for pleural disorders in the ICU. It can be nonspecific and may miss subtle findings. Ultrasound has become a useful tool to the bedside clinician to aid in diagnosis and management of pleural disease. The majority of pleural space disorders resolve as the patient's illness improves. There remain a few pleural processes that need specific therapies. While uncomplicated parapneumonic effusions do not have their own treatments. Those that progress to become a complex infected pleural space can have its individual complexity in therapy. Chest tube drainage remains the cornerstone in therapy. The use of intrapleural fibrinolytics has decreased the need for surgical referral. A large hemothorax or pneumothorax in patients admitted to the ICU represent medical emergencies and require emergent action. In this review we focus on the management of commonly encountered complex pleural space disorders in critically ill patients such as complicated pleural space infections, hemothoraces and pneumothoraces.

Systemic sclerosis with associated interstitial lung disease: management considerations and future directions.

Systemic sclerosis (SSc), also referred to as scleroderma, is a rare autoimmune disease associated with vasculopathy, inflammation, and fibrosis of the skin and/or internal organs. Interstitial lung disease (ILD) is a frequent complication and is the leading cause of death in patients with SSc. Although economic data are limited, available data suggest that SSc-ILD is associated with significant cost implications. Treatment of SSc-ILD has historically been with immunosuppressive agents. In 2019, however, the treatment landscape expanded with the FDA approval of the tyrosine kinase inhibitor nintedanib. A lack of codified treatment guidelines for patients with SSc-ILD creates significant challenges in improving outcomes at the patient level and, more generally, in reducing disease burden to the health care system. As the treatment landscape continues to evolve, it is likely that to reduce lung volume loss in patients, a combination of immunosuppressive and antifibrotic approaches will need to be used. Additionally, a greater emphasis on risk-stratification strategies may allow for more efficient follow-up, monitoring, and assessment of treatment response.

Chylothorax and cholesterol pleural effusion.

A chylothorax and a cholesterol pleural effusion represent the two forms of lipid effusions encountered. Traditionally, a lipid pleural effusion is characterized by the presence of milky fluid. Although these two effusions often share a similar pleural fluid appearance due to the high lipid concentration, they have major differences in the pathogenesis, clinical presentation, diagnosis, predisposing conditions, and management of these effusions. A chylothorax is defined by the presence of chyle in the pleural space resulting from obstruction or disruption of the thoracic duct or one of its major tributaries. A triglyceride concentration > 110 mg/dL is virtually diagnostic, but the presence of chylomicrons confirms the diagnosis. However, a chylothorax defined by these criteria represents a heterogeneous group of clinical entities. The presence of chylomicrons or triglyceride levels > 110 mg/dL in a pleural effusion should be considered evidence of chyle leakage of indeterminate clinical significance. Many cases of a chylous effusion may be associated with other causes of pleural fluid formation. In the case of an acute or chronic chylothorax due to recent or remote thoracic duct injury, this assessment is essential, as surgical ligation of the thoracic duct is often entertained. In other cases, especially lymphoma or chylous ascites, treatment of the underlying condition is indicated regardless, and the assessment of the response to treatment is a reasonable initial approach. In contrast, a cholesterol effusion is typically the result of long-standing pleurisy with elevated cholesterol levels in the pleural space; however, this paradigm has been challenged. Lung entrapment with thickened parietal and visceral pleural membranes is the typical radiographic findings of a cholesterol effusion. Most cases of cholesterol pleural effusions are attributed to tuberculous or rheumatoid pleurisy. Decortication is the mainstay of treatment for a cholesterol effusion in symptomatic patients with restrictive lung function.

Effects of cytoskeletal perturbant drugs on ecto 5'-nucleotidase, a concanavalin A receptor.

Differences in cell morphology, concanavalin A-induced receptor redistributions, and the cooperativity of the inhibition of 5'-nucleotidase (AMPase) by concanavalin A (Con A) have been investigated in ascites sublines of the 13762 rat mammary adenocarcinoma cells treated with microfilament- and microtubule-perturbing drugs. By scanning electron microscopy MAT-C1 cells exhibit a highly irregular surface, covered with microvilli extending as branched structures from the cell body. MAT-A, MAT-B, and MAT-B1 cells have a more normal appearance, with unbranched microvilli, ruffles, ridges, and blebs associated closely with the cell body. MAT-C cells have an intermediate morphology. Treatment of MAT-A, MAT-B, or MAT-B1 cells with Con A causes rapid redistribution of Con A receptors. Both cytochalasins and colchicine cause alternations in the receptor redistributions. Receptors on MAT-C1 cells are highly resistant to redistribution, even in the presence of cytoskeletal perturbant drugs. The cooperativity of the inhibition of AMPase by Con A was investigated in MAT-A and MAT-C1 cells. Untreated cells exhibit no cooperativity. If either subline is treated with colchicine, cytochalasin B or D, or dibucaine, cooperativity is observed. Lumicolchicine has no effect. Theophylline or dibutyryl cyclic AMP prevents the effects of either colchicine or cytochalasin. The concentration required for half-maximal induction of cooperativity is 0.3--0.4 microM for both colchicine and cytochalasin D, which is in the appropriate range for specific microtubule and microfilament disruptions. The effectiveness of the cytochalasins (E greater than D greater than B) is consistent with their known effects on microfilaments. No direct correlation was observed between the induction of cooperativity and drug-induced changes in Con A receptor redistribution or cell morphology. The morphology of MAT-A cells is grossly altered by cytochalasins or dibucaine and somewhat less by colchicine. MAT-C1 cells exhibit more minor alterations in morphology as a result of these drug treatments. The results of this study indicate that the inhibition of AMPase, which is a Con A receptor, is a different process from the redistribution of the bulk of the Con A receptors, possibly short range membrane interactions rather than global effects on the cell.

Serious adverse events in patients with idiopathic pulmonary fibrosis in the placebo arms of 6 clinical trials.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease characterized by irreversible loss of lung function and an unpredictable course of disease progression. METHODS: The safety data for patients with IPF who received placebo in 6 clinical trials were pooled to examine the categories and frequencies of serious adverse events (SAEs) in this population. RESULTS: In 1082 patients with IPF who received placebo, 673 SAEs were reported. Of these, 93 SAEs resulted in death (8.6% of patients). Respiratory-related conditions were the most frequently reported SAE (225 events, 16.33 per 100 patient-exposure years [PEY]), followed by infections and infestations (136 events, 9.87 per 100 PEY) and cardiac disorders (79 events, 5.73 per 100 PEY); these categories also had the most fatal outcomes (60, 10, and 10 deaths, respectively). The most frequently reported fatal respiratory-related SAEs were IPF and respiratory failure (38 and 11 patients, respectively), and the most frequently reported fatal infections and infestations and cardiac disorders were pneumonia (5 patients) and myocardial infarction (3 patients), respectively. CONCLUSIONS: This pooled analysis has value as a comparator for safety in future studies of IPF and provides insights in the natural evolution of both IPF and common comorbidities.

Safety and Tolerability of Thrombin Inhibition in Scleroderma-Associated Interstitial Lung Disease.

OBJECTIVE: Interstitial lung disease (ILD) is a frequent complication of systemic sclerosis (SSc) (scleroderma) and the leading cause of scleroderma-related deaths. There exists an unmet need for a new drug therapy for ILD-complicated SSc. Substantial evidence supports an important role for thrombin in the pathogenesis of SSc-associated ILD (hereafter SSc-ILD), and targeting thrombin with a direct thrombin inhibitor could prove to be a novel and effective treatment strategy. As a first step toward designing a clinical trial to test the efficacy of thrombin inhibition in SSc-ILD, we conducted this study to test the safety and tolerability of dabigatran in patients with SSc-ILD. METHODS: We performed a prospective, single-center, open-label treatment trial with the direct thrombin inhibitor, dabigatran, in patients with SSc-ILD. Any patient with a history of gastrointestinal hemorrhage or gastric antral vascular ectasia was excluded. Blood monitoring was performed monthly, and patient-reported outcomes, pulmonary function tests, and skin scores were obtained at baseline and at 3- and 6-month visits. Bronchoscopy with bronchoalveolar lavage (BAL) was performed at baseline and at 6 months for measurement of lung thrombin activity. RESULTS: Of 15 patients with SSc-ILD, 14 completed 6 months of treatment with dabigatran at 75 mg taken orally twice daily. Adverse events were uncommon and usually mild or unrelated to the study medication. No serious adverse event was observed. Dabigatran was well tolerated, and we observed no significant gastrointestinal, pulmonary, or other safety issues or intolerability. BAL fluid thrombin activity decreased or remained stable in 13 of 14 (92.8%) subjects. CONCLUSION: Dabigatran appears to be safe and well tolerated in patients with SSc-ILD. A larger randomized controlled trial to test the efficacy of direct thrombin inhibition with dabigatran can be considered.

Asynchronous brain-computer interface for cognitive assessment in people with cerebral palsy.

OBJECTIVE: Typically, clinical measures of cognition require motor or speech responses. Thus, a significant percentage of people with disabilities are not able to complete standardized assessments. This situation could be resolved by employing a more accessible test administration method, such as a brain-computer interface (BCI). A BCI can circumvent motor and speech requirements by translating brain activity to identify a subject's response. By eliminating the need for motor or speech input, one could use a BCI to assess an individual who previously did not have access to clinical tests. APPROACH: We developed an asynchronous, event-related potential BCI-facilitated administration procedure for the peabody picture vocabulary test (PPVT-IV). We then tested our system in typically developing individuals (N = 11), as well as people with cerebral palsy (N = 19) to compare results to the standardized PPVT-IV format and administration. MAIN RESULTS: Standard scores on the BCI-facilitated PPVT-IV, and the standard PPVT-IV were highly correlated (r = 0.95, p < 0.001), with a mean difference of 2.0 ± 6.4 points, which is within the standard error of the PPVT-IV. SIGNIFICANCE: Thus, our BCI-facilitated PPVT-IV provided comparable results to the standard PPVT-IV, suggesting that populations for whom standardized cognitive tests are not accessible could benefit from our BCI-facilitated approach.

Management of pneumothorax in lymphangioleiomyomatosis: effects on recurrence and lung transplantation complications.

STUDY OBJECTIVES: Pneumothorax is a common complication of lymphangioleiomyomatosis (LAM), and the optimal approach to its treatment and prevention is unknown. Chemical or surgical pleurodesis are often required to prevent recurrence. However, their efficacy in LAM is unclear, and whether they contribute to perioperative complications during lung transplantation is uncertain. SETTING: The LAM Foundation database of registered patients. DESIGN: A questionnaire was sent to all registered patients who had at least one pneumothorax to determine rates and patterns of recurrence and efficacy of interventions. A second questionnaire was sent to registered LAM patients who received a lung transplant. PATIENTS OR PARTICIPANTS: Of 395 registered patients, 260 patients (66%) reported at least one pneumothorax during their lifetime, 193 of whom (74%) completed the questionnaire. Of the 85 lung transplant patients who were sent a separate questionnaire, 80 patients (94%) responded. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Of the 193 respondents to the pneumothorax questionnaire, data on 676 episodes of pneumothorax were collected. Eighty-two percent (158 of 193 patients) had their first pneumothorax prior to a diagnosis of LAM. One hundred forty patients (73%) had at least one additional pneumothorax, either an ipsilateral recurrence (99 of 140 patients, 71%) or a contralateral pneumothorax (104 of 140 patients, 74%). Recurrence rates were 66% after conservative therapy, 27% after chemical pleurodesis, and 32% after surgery. In patients who had undergone lung transplantation, prior chemical or surgical pleurodesis was performed in 45 of 80 patients (56%). Fourteen of 80 patients (18%) reported pleural-related postoperative bleeding, 13 of whom (93%) had prior pleurodesis. CONCLUSIONS: Chemical pleurodesis or surgery are equally effective and better than conservative therapy in preventing recurrence of pneumothorax in LAM. Due to the high recurrence rate, either procedure should be considered for the initial pneumothorax in these patients. However, both contribute to increased perioperative bleeding following lung transplantation, with no effect on length of hospital stay.

Relationship between xenotransplantability and cell surface properties of ascites sublines of a rat mammary adenocarcinoma.

Cell surface properties of several ascites sublines of the 13762 rat mammary adenocarcinoma were compared in an effort to understand factors important to the xenotransplantability of these tumors into C57BL/6J mice. MAT-C, MAT-C1, and MAT-cMR6-S ascites sublines were xenotransplantable; MAT-B1, MAT-C2, and MAT-MR2-S were not. All of these sublines contained a large mucin-type sialoglycoprotein (ASGP-1) as a major cell surface component. Mat-B1 and MAT-cMR6-S ASGP-1 molecules were sulfated, but MAT-C1 and MAT-MR2-S incorporated little sulfate. The major oligosaccharide of MAT-C1 ASGP-1, a disialo-oligosaccharide, was present in very low amounts in the other sublines. ASGP-1 was detected readily in the plasma of animals with MAT-C1 or MAT-MR2-S tumors, but it was not detected readily in animals with MAT-B1 or MAT-cMR6-S tumors. Thus none of these significant features of ASGP-1 that differed among the sublines correlated with xenotransplantation. However, both MAT-C1 and MAT-cMR6-S sublines had branched cell surface microvilli. Moreover, MAT-C grown in mice after xenotransplantation had extensive, branched microvilli, even though only about 10% of the population of the cells grown in the rat had them. These results suggest that the branched microvilli may provide a protective mechanism, possibly by acting as a barrier to the approach of cytotoxic cells.

The effects of calcium, temperature and phospholamban phosphorylation on the dynamics of the calcium-stimulated ATPase of canine cardiac sarcoplasmic reticulum.

Highly purified sarcoplasmic reticulum (SR) has been prepared from dog hearts and has been incubated with the triplet probe erythrosinyl isothiocyanate to specifically label the Ca2+-stimulated ATPase (Ca2+-ATPase) of the SR. The rotational mobility of the Ca2+-ATPase has been studied in this erythrosin-labelled SR using time-resolved phosphorescence polarization. Qualitatively, the mobility of the cardiac Ca2+-ATPase resembles that of skeletal muscle SR Ca2+-ATPase. Addition of Ca2+ to SR affects the mobility of the Ca2+-ATPase in a way consistent with a segment of the ATPase altering its orientation relative to the plane of the membrane. Phosphorylation of phospholamban in cardiac SR by the purified catalytic subunit of cAMP-dependent protein kinase, which is known to increase the activity of the Ca2+-ATPase by deinhibition, also alters measured anisotropy. The changes observed are not compatible with dissociation of the Ca2+-ATPase from phospholamban after the latter is phosphorylated. The data are more consistent with phospholamban associating with the Ca2+-ATPase following phosphorylation, or more complex models in which only the hydrophilic domain of phospholamban binds with and dissociates from the Ca2+-ATPase.

Molecular changes in cell surface membranes resulting from trypsinization of sarcoma 180 tumor cells.

Sarcoma-180 tumor cells in culture or grown as an ascites form in the CD-1 mouse have been subjected to mild trypsinization procedures in order to study morphological and molecular changes resulting from proteolysis. The cells attached to a substratum become rounded within 20 min. and most undergo cell division, but they do not detach from the substratum. Removal of trypsin permits the cells to go back to their original spindle shape over an 8-20 h period. Surface membranes were isolated from trypsinized ascites and cultured cells and subjected to dodecyl sulfate-acrylamide gel electrophoresis. Both cell types showed the same two kinds of changes in electrophoretic patterns. First, there was a loss of glycoproteins from both cell types even though they show different complements of cell surface glycoproteins. Second, there is a loss of high molecular weight polypeptides, which have previously been suggested to play a role in membrane stabilization and cell shape. These results further implicate these polypeptides in the control of cell morphology and offer circumstanital evidence for transmembrane interactions of surface glycoproteins with the high molecular weight polypeptides as a factor in controlling cell morphology.