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The article examines the early influences that have contributed to what is now football in the United States. Men have played different forms of football games since earliest times. Football is not ordinarily associated with the Chinese people, because intellectual excellence rather than physical prowess has been their dominant goal in education. However, the harmonious development of mind and body was their ideal during their early culture. A well organized school system, that is thought to exist in the Chou dynasty, cultivated the physical, intellectual, moral and esthetic capacities of the youth. Ceremonial dances and sports were an integral part of formal education.

The article focuses on intuitionist free abelian groups. It states that the intuitionist free abelian groups are different with projective groups and there is no need for their subgroups to be free. It presents an intuitionistic construction of the groups that, aside from natural numbers, does not use constructive principles.

Background: During the first lockdown of the COVID-19 pandemic, an exponential increase in video consultations replacing in-person outpatient visits was observed in hospitals. Insight into patients' experiences with this type of consultation is helpful for a broad, sustainable, and patient-centered implementation of video consultation., Objective: This study aims to examine patients' experiences with video consultation during the COVID-19 pandemic and identify discriminative patient and consultation characteristics to determine when video consultation is most feasible., Methods: A cross-sectional survey study was conducted. Patients aged ≥18 years and scheduled for a video consultation at the outpatient clinic of a Dutch university medical center from August 2020 to December 2020 for all medical specialties were eligible. Patients' experiences were explored through a study-specific survey using descriptive quantitative statistics. Open-ended questions were qualitatively analyzed and thematically categorized into appreciated aspects and aspects for improvement. Discriminative patient and consultation characteristics were identified using 3 distinctive survey items. Characteristics of patients who scored and those who did not score all 3 items positively were analyzed using binary logistic regression., Results: A total of 1054 patients were included in the analysis. Most patients (964/1054, 91.46%) were satisfied with their video consultation, with a mean overall grade of 8.6 (SD 1.3) of 10. In the qualitative analyses, 70.02% (738/1054) of the patients cited aspects they appreciated and 44.97% (474/1054) mentioned aspects for improvement during their consultation. Patients with better self-rated health reported a positive evaluation significantly more often (P=.001), which also held true for other medical specialties (vs surgical and nonsurgical specialties; P<.001)., Conclusions: Video consultation was perceived as highly satisfactory by patients during the COVID-19 pandemic, with the best experience reported by healthy participants and those undergoing their first consultation. Appreciated aspects are mainly at the individual professional level, organizational level, and innovation level itself. The aspects that were mentioned for improvement can be changed for the better., (©Stefanie C van den Bosch, Demi Van Dalen, Marjan Meinders, Harry van Goor, Stefaan Bergé, Martijn Stommel, Sandra van Dulmen. Originally published in the Journal of Medical Internet Research (https://www.jmir.org), 27.03.2024.)

Introduction: Accelerated by the coronavirus pandemic, the healthcare landscape is rapidly evolving, with a shift towards hybrid care models combining in-person and online care. To support this shift, the Radboudumc, an academic hospital in the Netherlands, decided to redesign an existing space facilitating the conduction of video consultations., Method: The design process involved participation of end-users to ensure that the physical space met their needs. The look and feel of the area was based on evidence-based design guidelines. Two prototype setups were built and tested, and the feedback informed the final design of the Garden Room., Results: Identified end-user needs were divided into 3 major categories entailing consultation room setup, optimal use of technology and practical issues involving room availability. Combined with the look and feel of the hospital, final design requirements were developed. The Garden Room consists of 18 video consultation rooms, 4 shared workspaces, relaxation area with kitchen, and meeting rooms. Specific attention is given to the ergonomics, technology and privacy in the rooms to facilitate optimal video conversations between patients and healthcare providers. In the Garden Room, natural elements and an open design supports working in a healing environment., Discussion: Next challenge will be optimizing the use of the Garden Room, which may be hindered by various barriers like resistance to change, existing work processes, and lack of skills training. To address these barriers and support use of the Garden Room, the hospital should focus on the implementation of education, changes in work processes, and the presence of advocates for telehealth., Competing Interests: MS is employed by PBLQ. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Smits, van Dalen, Popping, Bleeker, Stommel and van Goor.)

Regulatory T cells (T regs ) are major drivers behind immunosuppressive mechanisms and present a major hurdle for cancer therapy. T regs are characterized by a high expression of CD25, which is a potentially valuable target for T reg depletion to alleviate immune suppression. The preclinical anti-CD25 (αCD25) antibody, clone PC-61, has met with modest anti-tumor activity due to its capacity to clear T regs from the circulation and lymph nodes, but not those that reside in the tumor. The optimization of the Fc domain of this antibody clone has been shown to enhance the intratumoral T reg depletion capacity. Here, we generated a stable cell line that produced optimized recombinant T reg -depleting antibodies. A genome engineering strategy in which CRISPR-Cas9 was combined with homology-directed repair (CRISPR-HDR) was utilized to optimize the Fc domain of the hybridoma PC-61 for effector functions by switching it from its original rat IgG1 to a mouse IgG2a isotype. In a syngeneic tumor mouse model, the resulting αCD25-m2a (mouse IgG2a isotype) antibody mediated the effective depletion of tumor-resident T regs , leading to a high effector T cell (T eff ) to T reg ratio. Moreover, a combination of αCD25-m2a and an αPD-L1 treatment augmented tumor eradication in mice, demonstrating the potential for αCD25 as a cancer immunotherapy.

The proteasome recognizes ubiquitinated proteins and can also edit ubiquitin marks, allowing substrates to be rejected based on ubiquitin chain topology. In yeast, editing is mediated by deubiquitinating enzyme Ubp6. The proteasome activates Ubp6, whereas Ubp6 inhibits the proteasome through deubiquitination and a noncatalytic effect. Here, we report cryo-EM structures of the proteasome bound to Ubp6, based on which we identify mutants in Ubp6 and proteasome subunit Rpt1 that abrogate Ubp6 activation. The Ubp6 mutations define a conserved region that we term the ILR element. The ILR is found within the BL1 loop, which obstructs the catalytic groove in free Ubp6. Rpt1-ILR interaction opens the groove by rearranging not only BL1 but also a previously undescribed network of three interconnected active-site-blocking loops. Ubp6 activation and noncatalytic proteasome inhibition are linked in that they are eliminated by the same mutations. Ubp6 and ubiquitin together drive proteasomes into a unique conformation associated with proteasome inhibition. Thus, a multicomponent allosteric switch exerts simultaneous control over both Ubp6 and the proteasome., (© 2022. The Author(s).)

Background: While immune checkpoint inhibitors such as anti-PD-L1 antibodies have revolutionized cancer treatment, only subgroups of patients show durable responses. Insight in the relation between clinical response, PD-L1 expression and intratumoral localization of PD-L1 therapeutics could improve patient stratification. Therefore, we present the modular synthesis of multimodal antibody-based imaging tools for multiscale imaging of PD-L1 to study intratumoral distribution of PD-L1 therapeutics., Results: To introduce imaging modalities, a peptide containing a near-infrared dye (sulfo-Cy5), a chelator (DTPA), an azide, and a sortase-recognition motif was synthesized. This peptide and a non-fluorescent intermediate were used for site-specific functionalization of c-terminally sortaggable mouse IgG1 (mIgG1) and Fab anti-PD-L1. To increase the half-life of the Fab fragment, a 20 kDa PEG chain was attached via strain-promoted azide-alkyne cycloaddition (SPAAC). Biodistribution and imaging studies were performed with 111 In-labeled constructs in 4T1 tumor-bearing mice. Comparing our site-specific antibody-conjugates with randomly conjugated antibodies, we found that antibody clone, isotype and method of DTPA conjugation did not change tumor uptake. Furthermore, addition of sulfo-Cy5 did not affect the biodistribution. PEGylated Fab fragment displayed a significantly longer half-life compared to unPEGylated Fab and demonstrated the highest overall tumor uptake of all constructs. PD-L1 in tumors was clearly visualized by SPECT/CT, as well as whole body fluorescence imaging. Immunohistochemistry staining of tumor sections demonstrated that PD-L1 co-localized with the fluorescent and autoradiographic signal. Intratumoral localization of the imaging agent could be determined with cellular resolution using fluorescent microscopy., Conclusions: A set of molecularly defined multimodal antibody-based PD-L1 imaging agents were synthesized and validated for multiscale monitoring of PD-L1 expression and localization. Our modular approach for site-specific functionalization could easily be adapted to other targets., (© 2022. The Author(s).)

Aim: Up to 50% of the patients experience complications after colorectal cancer (CRC) surgery. Improved preoperative physical and nutritional status can enhance clinical outcomes and reduce postoperative complications. This retrospective, single-center, observational cohort study assessed the impact of a four-week multimodal prehabilitation program on postoperative complications, unplanned readmissions, length of stay, and mortality in elective high-risk CRC patients., Method: Elective high-risk CRC patients, defined as ASA ≥3 or ≥65yr, who attended the multimodal prehabilitation program (prehabilitation-group) were compared to a historical cohort receiving standard care (control-group). Differences in outcomes between these groups were tested using Fisher's Exact and Mann-Whitney U test. To adjust for confounding, multivariate logistic regression analysis was performed. The main study outcome was the occurrence of postoperative complications. Secondary outcomes included unplanned readmissions, length of hospital stay, and mortality., Results: 351 patients were included (n = 275 control-group, n = 76 prehabilitation-group). The complication rate was lower in the prehabilitation group compared to the control group, 26.3% (n = 20) versus 40% (n = 110) (p = .032). There were fewer unplanned readmissions in the prehabilitation group compared to the control group, 5.3% (n = 4) versus 16.4% (n = 45), p = .014. Median hospital days of stay was 1 day shorter for the prehabilitation-group (p = .004), mortality did not significantly differ between the groups., Conclusion: This study shows that the used multimodal prehabilitation program leads to a reduction of medical postoperative complications, unplanned readmissions, and shortens the median hospital stay compared with standard care in high-risk CRC patients undergoing elective CRC surgery., Competing Interests: Declaration of competing interest None., (Copyright © 2021 Elsevier Ltd, BASO ~ The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.)

Introduction: Whereas neoadjuvant chemo(radio)therapy is increasingly used in pancreatic cancer, it is currently not recommended for other periampullary (non-pancreatic) cancers. This has important implications for the relevance of the preoperative diagnosis for pancreatoduodenectomy. This retrospective multicentre cohort study aimed to determine the frequency of clinically relevant misdiagnoses in patients undergoing pancreatoduodenectomy for pancreatic or other periampullary cancer., Methods: Data from all consecutive patients who underwent a pancreatoduodenectomy between 2014 and 2018 were obtained from the prospective Dutch Pancreatic Cancer Audit. The preoperative diagnosis as concluded by the multidisciplinary team (MDT) meeting was compared with the final postoperative diagnosis at pathology to determine the rate of clinically relevant misdiagnosis (defined as missed pancreatic cancer or incorrect diagnosis of pancreatic cancer)., Results: In total, 1244 patients underwent pancreatoduodenectomy of whom 203 (16%) had a clinically relevant misdiagnosis preoperatively. Of all patients with a final diagnosis of pancreatic cancer, 13% (87/679) were preoperatively misdiagnosed as distal cholangiocarcinoma (n = 41, 6.0%), ampullary cancer (n = 27, 4.0%) duodenal cancer (n = 16, 2.4%), or other (n = 3, 0.4%). Of all patients with a final diagnosis of periampullary (non-pancreatic) cancer, 21% (116/565) were preoperatively incorrectly diagnosed as pancreatic cancer. Accuracy of preoperative diagnosis was 84% for pancreatic cancer, 71% for distal cholangiocarcinoma, 73% for ampullary cancer and 73% for duodenal cancer. A prediction model for the preoperative likelihood of pancreatic cancer (versus other periampullary cancer) prior to pancreatoduodenectomy demonstrated an AUC of 0.88., Discussion: This retrospective multicentre cohort study showed that 16% of patients have a clinically relevant misdiagnosis that could result in either missing the opportunity of neoadjuvant chemotherapy in patients with pancreatic cancer or inappropriate administration of neoadjuvant chemotherapy in patients with non-pancreatic periampullary cancer. A preoperative prediction model is available on www.pancreascalculator.com., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: The gut microbiota are the main source of infections in necrotising pancreatitis. We investigated the effect of disruption of the intestinal microbiota by a Western-type diet on mortality and bacterial dissemination in necrotising pancreatitis and its reversal by butyrate supplementation., Design: C57BL/6 mice were fed either standard chow or a Western-type diet for 4 weeks and were then subjected to taurocholate-induced necrotising pancreatitis. Blood and pancreas were collected for bacteriology and immune analysis. The cecum microbiota composition of mice was analysed using 16S rRNA gene amplicon sequencing and cecal content metabolites were analysed by targeted (ie, butyrate) and untargeted metabolomics. Prevention of necrotising pancreatitis in this model was compared between faecal microbiota transplantation (FMT) from healthy mice, antibiotic decontamination against Gram-negative bacteria and oral or systemic butyrate administration. Additionally, the faecal microbiota of patients with pancreatitis and healthy subjects were analysed., Results: Mortality, systemic inflammation and bacterial dissemination were increased in mice fed Western diet and their gut microbiota were characterised by a loss of diversity, a bloom of Escherichia coli and an altered metabolic profile with butyrate depletion. While antibiotic decontamination decreased mortality, Gram-positive dissemination was increased. Both oral and systemic butyrate supplementation decreased mortality, bacterial dissemination, and reversed the microbiota alterations. Paradoxically, mortality and bacterial dissemination were increased with FMT administration. Finally, patients with acute pancreatitis demonstrated an increase in Proteobacteria and a decrease of butyrate producers compared with healthy subjects., Conclusion: Butyrate depletion and its repletion appear to play a central role in disease progression towards necrotising pancreatitis., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.)

Functionalized antibodies and antibody fragments have found applications in the fields of biomedical imaging, theranostics, and antibody-drug conjugates (ADC). In addition, therapeutic and theranostic approaches benefit from the possibility to deliver more than one type of cargo to target cells, further challenging stochastic labeling strategies. Thus, bioconjugation methods to reproducibly obtain defined homogeneous conjugates bearing multiple different cargo molecules, without compromising target affinity, are in demand. Here, we describe a straightforward CRISPR/Cas9-based strategy to rapidly engineer hybridoma cells to secrete Fab' fragments bearing two distinct site-specific labeling motifs, which can be separately modified by two different sortase A mutants. We show that sequential genetic editing of the heavy chain (HC) and light chain (LC) loci enables the generation of a stable cell line that secretes a dual tagged Fab' molecule (DTFab'), which can be easily isolated. To demonstrate feasibility, we functionalized the DTFab' with two distinct cargos in a site-specific manner. This technology platform will be valuable in the development of multimodal imaging agents, theranostics, and next-generation ADCs.

Background: Both obesity and the presence of collagenolytic bacterial strains (Enterococcus faecalis) can increase the risk of anastomotic leak. The aim of this study was to determine whether mice chronically fed a high-fat Western-type diet (WD) develop anastomotic leak in association with altered microbiota, and whether this can be mitigated by a short course of standard chow diet (SD; low fat/high fibre) before surgery., Methods: Male C57BL/6 mice were assigned to either SD or an obesogenic WD for 6 weeks followed by preoperative antibiotics and colonic anastomosis. Microbiota were analysed longitudinally after operation and correlated with healing using an established anastomotic healing score. In reiterative experiments, mice fed a WD for 6 weeks were exposed to a SD for 2, 4 and 6 days before colonic surgery, and anastomotic healing and colonic microbiota analysed., Results: Compared with SD-fed mice, WD-fed mice demonstrated an increased risk of anastomotic leak, with a bloom in the abundance of Enterococcus in lumen and expelled stool (65-90 per cent for WD versus 4-15 per cent for SD; P = 0·010 for lumen, P = 0·013 for stool). Microbiota of SD-fed mice, but not those fed WD, were restored to their preoperative composition after surgery. Anastomotic healing was significantly improved when WD-fed mice were exposed to a SD diet for 2 days before antibiotics and surgery (P < 0·001)., Conclusion: The adverse effects of chronic feeding of a WD on the microbiota and anastomotic healing can be prevented by a short course of SD in mice. Surgical relevance Worldwide, enhanced recovery programmes have developed into standards of care that reduce major complications after surgery, such as surgical-site infections and anastomotic leak. A complementary effort termed prehabilitation includes preoperative approaches such as smoking cessation, exercise and dietary modification. This study investigated whether a short course of dietary prehabilitation in the form of a low-fat/high-fibre composition can reverse the adverse effect of a high-fat Western-type diet on anastomotic healing in mice. Intake of a Western-type diet had a major adverse effect on both the intestinal microbiome and anastomotic healing following colonic anastomosis in mice. This could be reversed when mice received a low-fat/high-fibre diet before operation. Taken together, these data suggest that dietary modifications before major surgery can improve surgical outcomes via their effects on the intestinal microbiome., (© 2019 BJS Society Ltd Published by John Wiley & Sons Ltd.)

Background: For several purposes, skin parameters like thickness and elasticity can be measured. However, little is known about the accuracy of those measurements., Aim: The aim of this study was to determine the intrarater and test-retest reliability of skin thickness and elasticity measurements performed with the DermaLab Combo®., Methods: A total of 49 participants were included in this study. Skin thickness and elasticity were measured at six defined locations on the dominant arm. Measurements were repeated two times by the same observer to determine the test-retest reliability. To determine the inter-rater reliability, a second observer repeated the measurements once., Results: Inter-rater and test-retest reliability for elasticity measurements fluctuates per location and per parameter: Inter-rater intraclass correlation coefficient (ICC) ranged from 0.23 to 0.80, and test-retest ICC ranged from 0.25 to 0.84. Skin thickness was measured reliable by every observer on every location, with a test-retest ICC ranging from 0.71 to 0.83 and an inter-rater ICC ranging from 0.69 to 0.80., Conclusion: The DermaLab Combo® showed a good inter-rater reliability when measuring skin thickness and elasticity. Not all locations are suitable for reliable inter-rater or test-retest measurements. The device is difficult to use by inexperienced users, as the echo probe is sensitive to small movements., (© 2019 The Authors. Skin Research and Technology Published by John Wiley & Sons Ltd.)

Hybridoma technology is instrumental for the development of novel antibody therapeutics and diagnostics. Recent preclinical and clinical studies highlight the importance of antibody isotype for therapeutic efficacy. However, since the sequence encoding the constant domains is fixed, tuning antibody function in hybridomas has been restricted. Here, we demonstrate a versatile CRISPR/HDR platform to rapidly engineer the constant immunoglobulin domains to obtain recombinant hybridomas, which secrete antibodies in the preferred format, species, and isotype. Using this platform, we obtained recombinant hybridomas secreting Fab' fragments, isotype-switched chimeric antibodies, and Fc-silent mutants. These antibody products are stable, retain their antigen specificity, and display their intrinsic Fc-effector functions in vitro and in vivo. Furthermore, we can site-specifically attach cargo to these antibody products via chemoenzymatic modification. We believe that this versatile platform facilitates antibody engineering for the entire scientific community, empowering preclinical antibody research.

Background: Hyperammonemia can result in hepatic encephalopathy, which in severe cases eventually can lead to coma and death. In dogs, congenital portosystemic shunts (CPSS) are the most common cause for hyperammonemia. Conservative treatment consists of a protein modified diet, nonabsorbable disaccharides, antibiotics, or some combinations of these. Sodium benzoate (SB) and sodium phenylbutyrate (SPB) both are used in the acute and long-term treatment of humans with hyperammonemia caused by urea cycle enzyme deficiencies. Both treatments are believed to lower blood ammonia concentrations by promoting excretion of excess nitrogen via alternative pathways., Objectives: To evaluate the efficacy and safety of PO treatment with SB and SPB on hyperammonemia and clinical signs in CPSS dogs., Methods: Randomized, double-blind, placebo-controlled crossover trial. Concentrations of blood ammonia and bile acids were measured in CPSS dogs before and after a 5-day treatment with SB, SPB, and placebo. A wash-out period of 3 days was used between treatments. A standard questionnaire was developed and distributed to owners to evaluate clinical signs before and after each treatment., Results: Blood ammonia concentrations were not influenced by any of the treatments and were comparable to those observed during placebo treatment. In addition, SB and SPB treatment did not result in improvement of clinical signs. Adverse effects during treatment included anorexia, vomiting, and lethargy., Conclusions and Clinical Importance: Based on our results, we conclude that SB or SPB are not useful in the conservative treatment of hyperammonemia in dogs with CPSS., (© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

USP7 is a highly abundant deubiquitinating enzyme (DUB), involved in cellular processes including DNA damage response and apoptosis. USP7 has an unusual catalytic mechanism, where the low intrinsic activity of the catalytic domain (CD) increases when the C-terminal Ubl domains (Ubl45) fold onto the CD, allowing binding of the activating C-terminal tail near the catalytic site. Here we delineate how the target protein promotes the activation of USP7. Using NMR analysis and biochemistry we describe the order of activation steps, showing that ubiquitin binding is an instrumental step in USP7 activation. Using chemically synthesised p53-peptides we also demonstrate how the correct ubiquitinated substrate increases catalytic activity. We then used transient reaction kinetic modelling to define how the USP7 multistep mechanism is driven by target recognition. Our data show how this pleiotropic DUB can gain specificity for its cellular targets.

The enzyme-mediated construction of poly-ubiquitin (Ub) chains on target proteins leads to a variety of cellular responses and is involved in processes ranging from protein degradation to cell cycle control and immune responses. This complex post-translational modification system is under intense investigation, but generation of specific Ub chains and tools made thereof is not always trivial. We discovered that native methionine-1-linked polymeric ubiquitin chains can be constructed in a single chemical reaction. We validate correct folding and regioselective attachment of such chains using linkage specific proteases and further demonstrate that these poly-Ub chains can be converted into thioesters by the activating E1-enzyme. Subsequent ligation reactions using these in situ prepared thioesters leads to poly-ubiquitinated peptides., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Deubiquitinating enzymes (DUBs) are proteases that fulfill crucial roles in the ubiquitin (Ub) system, by deconjugation of Ub from its targets and disassembly of polyUb chains. The specificity of a DUB towards one of the polyUb chain linkages largely determines the ultimate signaling function. We present a novel set of diubiquitin FRET probes, comprising all seven isopeptide linkages, for the absolute quantification of chain cleavage specificity of DUBs by means of Michaelis-Menten kinetics. Each probe is equipped with a FRET pair consisting of Rhodamine110 and tetramethylrhodamine to allow the fully synthetic preparation of the probes by SPPS and NCL. Our synthetic strategy includes the introduction of N,N'-Boc-protected 5-carboxyrhodamine as a convenient building block in peptide chemistry. We demonstrate the value of our probes by quantifying the linkage specificities of a panel of nine DUBs in a high-throughput manner., (© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The capacity of rat liver Kupffer and endothelial cells to endocytose glycoproteins with N-acetylglucosamine- or mannose-terminated oligosaccharide chains was studied. For this purpose, agalactoorosomucoid, ahexosaminoorosomucoid and horseradish peroxidase were used as ligands. A reliable determination of the amount of ligand endocytosed in vivo or in vitro was made possible by using the recently developed cold pronase method for the isolation and purification of Kupffer and endothelial cells. Both cell types participated in the uptake of the ligands in vivo as well as in vitro, but their endocytic capacity was several times greater in vivo than in vitro. Under both conditions, endothelial cells possessed a greater capacity to endocytose the ligands than did Kupffer cells. Since the total number of endothelial cells in the liver is at least twice the number of Kupffer cells, the contribution of endothelial cells to the liver uptake of N-acetylglucosamine-terminated glycoproteins in vivo was estimated to be 3 to 7 times higher than that of the Kupffer cells. In vitro experiments showed that the uptake of the glycoproteins followed saturation kinetics and was strongly inhibited at 4 degrees C and in the presence of mannan. Ultrastructural investigations revealed that horseradish peroxidase was taken up by all Kupffer and endothelial cells. These results emphasize the important role liver endothelial cells play in the clearance of specific glycoproteins from the circulation.

The clearance of five radioactively labeled test substances--polyvinylpyrrolidone, colloidal albumin, antimony sulfur colloid, endotoxin, and heparin--by the reticuloendothelial system was studied after i.v. injection of these substances into rats. The participation of parenchymal, Kupffer, and endothelial liver cells could be determined after isolation and purification of these cell classes. Only endotoxin was almost exclusively taken up by Kupffer cells. All other substances were also taken up by both endothelial and parenchymal cells. From the rate of uptake, expressed as the endocytic index, it appeared that all substances, with the exception of polyvinylpyrrolidone, were taken up by adsorptive endocytosis. Although the specific rate of uptake by parenchymal cells was always slower than that shown by both Kupffer and endothelial cells, the total contribution of parenchymal cells to the clearance of polyvinylpyrrolidone, antimony sulfur colloid, and heparin by the liver was even greater than that of the other two cell classes. The results demonstrate that nonphagocytosing parenchymal and endothelial cells make an important contribution to the clearance of the various test substances which, in addition, is highly dependent on the nature of the substance used. This necessitates a revision of present concepts of clearance by the reticuloendothelial system.