bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring university students’ perceptions and engagement in game-based learning
Authors: Hamadneh Burhan , Fikry Amr , Talaat Mohammed , Abbas Ahmed , Ghanem Reham , Ramzy Samah , Aly Mohamed , Elkilani Ahmed , Mabrouk Sherin , Aloqlah Reema
Published: November 2024

Students in academia are facing serious challenges such as engagement, which causes academicians to question the quality and effectiveness of the teaching pedagogy. As such, new adapted innovative technological tools such as gamifications have been introduced to learning activities experiences and skills acquisition. However, little is known about the implementation of such technologies, which have been relatively underexplored in education literature. The primary objective of this study is to identify the perceptions of students and evaluate their engagement considering the use of gamification in the learning process. There were 210 respondents enrolled in the private university in Jordan were surveyed using a quantitative questionnaire. The study used descriptive statistics and independent sample t-test analyses on the data. The results indicated that the students have positive perceptions of game-based technology in both learning and classroom activity engagement. In addition, student perceptions and engagement did not differ significantly based on age or gender, but significant differences based on user experience were identified. These findings provide insight into the dynamic interaction between students and gamified technology to enhance student perceptions and promote meaningful learning. This research also provides implications on gamification literacy education and the pedagogically rich design of educational games to enhance student engagement. The recommendations are enumerated based on the obtained findings.
Perceive social support, academic self-efficacy, and learning engagement among high school students in China
Authors: Yang Liu , Hooi Lian Lim
Published: November 2024

The aim of this study was to analyze the mediating role of academic self-efficacy in the relationship between perceive social support and learning engagement among Chinese senior high school students. A quantitative research method was adopted, and 572 Chinese senior high school students from Inner Mongolia Autonomous Region in China completed three self-report questionnaires. Correlation analysis revealed that senior high school students perceive social support, academic self-efficacy, and learning engagement were significantly correlated with each other. In addition, structural equation modeling analysis showed that perceive social support exerted its indirect effect on learning engagement through the mediation of academic self-efficacy. These findings have practical implication for government policymakers, education administrators, teachers, students, and parents, informing evidence-based policies, interventions, and strategies to enhance learning engagement and academic success.
Malay essay writing module based on thematic approach for non-native speaker: a need analysis in primary schools
Authors: Austrus Edmund , Mahamod Zamri , Adnan Nor Hafizah
Published: November 2024

The challenges faced by non-native speaking pupils in primary schools, characterized by diverse backgrounds, highlight the difficulty in teaching and learning essay writing. This study was conducted to identify the needs for the development of a Malay language essay writing module based on a thematic approach through the needs analysis phase. This qualitative study was conducted among Malay language teachers in Sarawak. Eight teachers were purposively sampled, and thematic analysis was employed for data analysis. The findings found that there are six themes that have been identified, namely: i) relevant form of teaching and learning in essay writing; ii) relevant teaching and learning resources; iii) relevant teaching and learning activities; iv) relevant teaching and learning strategies; and v) the needs of the thematic approach in essay writing; vi) the needs for the development of thematic-based essay writing module. The findings underscore the imperative development of a Malay essay writing module based on a thematic approach to enhance the essay writing proficiency of non-native-speaking pupils. Furthermore, the study's insights offer valuable guidance for researchers in designing and developing modules during the subsequent phases, contributing to the refinement of essay writing pedagogy in primary schools.
Dicionário Etno-Histórico da Amazônia Colonial
Authors:   Universidade de São Paulo. Instituto de Estudos Brasileiros, Porro Antonio
Published: November 2024

Este pequeno dicionário, com todas as limitações que aqui serão assinaladas, espera vir ao encontro de uma demanda que já se faz sentir há anos, resultante do crescente interesse, não só nos meios acadêmicos e não só em nosso país, pela história indígena ou etno-história. No Brasil e demais países da América, assim como em grande parte da África e da Oceania, a ausência de registros nativos que atendessem aos requisitos da historiografia tradicional fez com que, na própria literatura antropológica, uma aparente atemporalidade e ausência de suceder histórico permitissem que até os anos 70 do século XX, se falasse em sociedades frias ou sem história. Esta concepção já não se sustenta. Com graus variáveis de recuperação da auto-estima e da consciência étnica, graças especialmente a condições políticas e ideológicas mais favoráveis, diversos grupos indígenas estão redescobrindo e vocalizando conhecimentos, memórias e tradições que antropólogos e historiadores estão agora mais motivados e preparados a entender e interpretar. Começam então a ser conhecidos capítulos esparsos de uma história oral que, embora situando-se por vezes numa escala temporal presumivelmente reduzida, têm dado legitimidade e sentido à busca das raízes históricas de diferentes etnias. A publicação deste Dicionário Etno-Histórico da Amazônia Colonial dá continuidade aos objetivos e propósitos que levaram à edição dos Cadernos do IEB. Sua publicação, além da relevância do conteúdo, marca mais uma etapa da reafirmação do compromisso do IEB com a produção e difusão do conhecimento, sempre em perspectiva multidisciplinar, sobre a sociedade brasileira.
Mechanisms and Screening for Atherosclerosis in Adults With Vasculitis
Authors: Hendrickson Michael J. , Wallace Zachary S.
Published: November 2024

Vascular inflammation is a hallmark of both primary systemic vasculitis and atherosclerosis. As such, cardiovascular events are common in patients with vasculitis and likely due to both direct vascular inflammation and accelerated atherosclerosis. Direct cardiac involvement is possible in all vasculitides, though more commonly described in Takayasu arteritis, polyarteritis nodosa, and eosinophilic granulomatosis with polyangiitis. Accelerated atherosclerosis has been described in Takayasu arteritis and antineutrophil cytoplasmic antibody–associated vasculitis, though there remains a paucity of data in other forms of vasculitis. Multiple screening and management approaches for cardiovascular risk in people with vasculitis have been proposed, though evidence-based guidelines are lacking. In this review, we discuss the latest evidence in epidemiology, mechanisms, and screening for atherosclerosis in patients with primary systemic vasculitides.
Andexanet Alfa–Associated Heparin Resistance in Cardiac Surgery: Mechanism and In Vitro Perspectives
Authors: Chabata Charlene V. , Yu Haixiang , Ke Lei , Frederiksen James W. , Patel Prakash A. , Sullenger Bruce A. , Thalji Nabil K.
Published: November 2024

BACKGROUND:

Andexanet alfa (andexanet) is the only Food and Drug Administration–approved antidote for direct FXa (factor Xa) inhibitors but has been reported to cause resistance to unfractionated heparin (UFH). This has delayed anticoagulation for procedures requiring cardiopulmonary bypass. The mechanism, andexanet and UFH dose dependence, and thrombotic risk of andexanet-associated heparin resistance are unknown.

METHODS:

The effect of andexanet in vitro was determined using activated clotting times and thromboelastography. Ex vivo cardiopulmonary bypass circuits were used to determine whether andexanet impaired anticoagulation for extracorporeal circulation. Kinetics of AT (antithrombin) inhibition of FXa and thrombin were measured in the presence of andexanet. Equilibrium modeling and thrombin generation assay validation were used to predict the role of andexanet, AT, and UFH concentrations in andexanet-associated heparin resistance.

RESULTS:

Andexanet prevented UFH-mediated prolongation of activated clotting times and thromboelastography times. At lower concentrations of andexanet, heparin resistance could be overcome with suprapharmacologic doses of UFH, but not at higher andexanet concentrations. Andexanet rendered standard doses of UFH inadequate to prevent circuit thrombosis, and suprapharmacologic UFH doses were only partially able to overcome this. Scanning electron microscopy demonstrated coagulation activation in circuits. Andexanet prevented UFH enhancement of AT-mediated inhibition of FXa and thrombin. Equilibrium modeling and thrombin generation assay validation demonstrated that andexanet creates a triphasic equilibrium with UFH and AT: initial UFH unresponsiveness, normal UFH responsiveness when andexanet is depleted, and finally AT depletion. Sufficient cardiopulmonary bypass heparinization can only occur at low therapeutic andexanet doses and normal AT levels. Higher andexanet doses or AT deficiency may require high UFH doses and potentially AT supplementation.

CONCLUSIONS:

Andexanet causes heparin resistance due to redistribution of UFH-bound AT. If andexanet cannot be avoided before heparinization and direct thrombin inhibitors are undesirable, our in vitro study suggests excess UFH should be considered as a potential strategy before AT supplementation.
Cerebral Blood Flow Dynamics in Neurogenic Orthostatic Hypotension: A Systematic Review and Meta-Analysis
Authors: Baker Jacquie R. , Beach Paul A. , Ranada Shaun I. , Patel Aishani , Gewandter Jennifer , Tan Can Ozan , Freeman Roy , Raj Satish R.
Published: November 2024

BACKGROUND:

Neurogenic orthostatic hypotension (nOH) causes pathological falls in standing blood pressure that may or may not be symptomatic. nOH also raises the risk of poor neurological outcomes irrespective of symptom presence, possibly reflecting subclinical cerebral hypoperfusion. Dynamic changes in cerebral blood flow velocity (CBFv) help infer how blood pressure fluctuations influence CBFv and cerebral autoregulation. Whether CBFv is impacted in nOH relative to related conditions without nOH and healthy controls (HC) remains unresolved. Whether nOH symptoms reflect greater CBFv falls is also unclear. This review aimed to compare CBFv between nOH and HC, nOH and disease-matched controls (eg, Parkinson disease±nOH), and between symptomatic and asymptomatic nOH.

METHODS:

Embase and MEDLINE were searched up to April 2024. Means, SDs, and sample sizes for supine and upright CBFv were extracted to generate standardized effect sizes (Hedge g). Random-effects modeling compared postintervention between-group effect sizes.

RESULTS:

Seventeen studies were included for review. Thirteen studies were suitable for meta-analysis comparing nOH to HC, 2 comparing disease-matched controls to nOH and to HC, and 3 for symptomatic comparisons. Compared with HC, nOH had larger drops in CBFv (Hedge g, −0.64 [95% CI, −0.85 to −0.44];
P
<0.001). CBFv falls between nOH and disease-matched controls were similar (
P
=0.17). Symptomatic nOH had larger CBFv drops (Hedge g, 0.84 [95% CI, 0.212–1.461];
P
=0.009) than asymptomatic nOH.

CONCLUSIONS:

nOH causes significant orthostatic reductions in CBFv compared with HC, and symptomatic patients experience greater falls in CBFv than asymptomatic patients. Recognizing the clinical implications of CBFv in nOH is crucial for mitigating adverse outcomes.
Conformal Prediction for Natural Language Processing: A Survey
Authors: Campos Margarida , Farinhas António , Zerva Chrysoula , Figueiredo Mário A. T. , Martins André F. T.
Published: November 2024

The rapid proliferation of large language models and natural language processing (NLP) applications creates a crucial need for uncertainty quantification to mitigate risks such as Hallucinations and to enhance decision-making reliability in critical applications. Conformal prediction is emerging as a theoretically sound and practically useful framework, combining flexibility with strong statistical guarantees. Its model-agnostic and distribution-free nature makes it particularly promising to address the current shortcomings of NLP systems that stem from the absence of uncertainty quantification. This paper provides a comprehensive survey of conformal prediction techniques, their guarantees, and existing applications in NLP, pointing to directions for future research and open challenges.
The Supreme Court of Uganda’s Powers to Depart from or Reopen (Review) Its Decisions Under Article 132(4) of the Constitution
Authors: Mujuzi Jamil Ddamulira
Published: November 2024

Article 132(4) of Uganda’s Constitution (1995) states that the Supreme Court may generally consider its decisions binding but can depart from them when necessary. Unlike some other African constitutions, Uganda’s does not explicitly authorise the Supreme Court to review its own rulings. The drafters intended for Article 132(4) to permit only departure, not review. However, this Article does not explicitly forbid review, and Rule 2(2) of the Supreme Court Rules (1996) allows the Court to set aside judgments found to be ‘null and void’. This article relies on the drafting history of the Constitution and contends that Rule 2(2) aligns with the Constitution since Article 132(4) does not expressly bar review. Drawing on practices in countries like Kenya, Ghana, and Tanzania, it argues that the Court could invoke its inherent powers to broaden the grounds for review when justice so requires, even beyond cases deemed null and void.
L’insurgée et le Calife. Une voix féminine au service du panislamisme
Authors: Blili Leïla
Published: November 2024

Nazli Hanem, a member of Egypt’s ruling family (1853-1913), was an unlikely woman. Affected by her father’s ouster from the throne and forced into exile with her family in Istanbul, she never ceased to harbor an aversion to the despotism of the Caliphate Sultans. She spent many years in Paris as a diplomat’s wife, before returning to Cairo and opening a cultural salon where she entertained the local intelligentsia as well as representatives of the colonial authorities. A freedom-loving, westernized woman, she was approached by Sultan-Caliph Abdülhamid II, and from 1898 became the spokeswoman for his pan-Islamist ideology. Unofficially, she became the first female diplomat, helping the Sultan-Caliph to heal his battered image.
4. Knowledge
Authors: Weatherson Brian
Published: November 2024

This chapter sets out how the moves from the previous two chapters combine to generate a constraint on any plausible theory of knowledge. A person has knowledge that p only if it makes sense to use p as a starting point into what they are actually inquiring into. A central focus of this chapter is how this constraint meshes with the idea that we can extend our knowledge by logical deduction.
Retrieval of Parameters of Constrained Gamma Raindrop Size Distribution in South China
Authors: Liu Xiantong , Huang Hao , Hu Sheng , Xia Feng , Lai Ruize , Feng Lu , Xiao Hui , Li Huiqi , Rao Xiaona
Published: November 2024

Raindrop size distributions (RSDs) retrieved from polarimetric radar observations have proven to be effective for understanding precipitation microphysics. However, the current RSD retrieval scheme from polarimetric radar observations (using radar reflectivity ZHH and differential reflectivity ZDR) in South China has been established for monsoon precipitation only. Using abundant RSD observations from 2D video disdrometers (2DVDs), this study constructs the high-precision shape–slope (μ–Λ) relationships of the constrained gamma (C-G) model for subgroups of ZHH and ZDR for not only monsoon but also premonsoon, typhoon, and dry seasons. The current RSD retrieval is only applicable for precipitation with rain rate: R > 5.0 mm h−1, and total raindrop number concentration: Nt > 1000 m−3. This study expanded the applicability of rain rate and number concentration with R > 0.5 mm h−1 and Nt > 100 m−3. The new retrieval scheme was tested in four typical rainfall cases and provided better accuracy in estimating mass-weighted mean diameters and normalized intercept parameters. The new scheme was also better suited for analyzing precipitation microphysics in South China, which helps to gain a better understanding of microphysics in various types of precipitation in this region.
Ceftazidime-Cefazolin Empiric Therapy for Pediatric Gradenigo Syndrome
Authors: Tao Brendan K. , Alotaibi Fahad , McAlpine Alastair
Published: November 2024

Objective:

Gradenigo Syndrome (GS), a rare complication of petrous apicitis secondary to acute otitis media, is characterized by (an often incomplete) triad of otorrhea, abducens nerve palsy, and facial pain along the trigeminal nerve distribution. There are several causative pathogens of petrous apicitis, including Streptococcus and Staphylococcus species, while Pseudomonas aeruginosa is the most common. However, the case report literature often describes antibiotic management of GS with antibiotics that do not cover Pseudomonas, potentially predisposing to further intracranial complications or mortality. The purpose of this work was to describe a case of pediatric Gradenigo Syndrome, successfully treated with sufficiently broad-spectrum antibiotics.

Methods:

This is case report.

Results:

A previously healthy 5-year-old boy with a history of swimming presented with esotropia and acute otitis media. Initial symptoms included otorrhea, otalgia, and pruritis, which were refractory to ciprofloxacin-dexamethasone drops. He subsequently developed a right sixth nerve palsy, suggestive of Gradenigo Syndrome, and neuroimaging showed evidence of petrous apicitis, clival osteomyelitis, and internal carotid artery stenosis. The causative organism was not elucidated to laboratory error. Given this uncertainty, he was successfully treated with empiric intravenous ceftazidime and cefazolin. After 16 weeks, he recovered fully without the need for surgery.

Conclusions:

In the setting of delayed or absent culture results with suspicion of skull-base infection, our case supports the use of empiric antibiotic therapy with sufficient coverage of all common pathogens including Streptococcus/ Staphylococcus and Pseudomonas aeruginosa species, the latter of which is often not adequately covered by antibiotic regimens described in the literature.
Electrostatic repulsion among erythrocytes in tube flow, demonstrated by the thickness of marginal cell‐free layer
Authors: Suzuki Y. , Tateishi N. , Maeda N.
Published: November 2024

Electrostatic repulsion among erythrocytes in flow was evaluated through measurement of the thickness of the marginal cell‐free layer in narrow glass tubes of 20–50 $\mu$ m in inner diameter. To reduce the electrostatic repulsive force, due mainly to sialic acid of the membrane glycoproteins, human erythrocytes were treated with neuraminidase. The surface negative charge of the erythrocytes, as determined from the electrophoretic mobility using free‐flow electrophoresis, was found to be proportional to the sialic acid content. When erythrocytes with decreased sialic acid content flowed through narrow tubes, the thickness of cell‐free layer determined using an image processor increased even in the absence of erythrocyte aggregation in the suspension. The effect was more pronounced at acidic pH. The addition of Dextran T‐70 (70,400 Mol. Wt.) further increased the cell‐free layer thickness due to erythrocyte aggregation. Thus, reducing the negative charge density on the erythrocyte surface by itself accelerates the axial accumulation of erythrocytes in flow due to the decreased electrostatic repulsive force between the cells, even in the absence of erythrocyte aggregation.
Shear stress gradient over endothelial cells in a curved microchannel system
Authors: Frame Mary D.S. , Chapman Gary B. , Makino Yoshia , Sarelius Ingrid H.
Published: November 2024

Our purpose was to test a scale model of the microcirculation by measuring the shear forces to which endothelial cells were exposed, and comparing this to computer simulations. In vitro experiments were performed to measure the 2‐dimensional projected velocity profile along endothelial cell lined microchannels (D‐shaped, 10–30 $\mu$ m radius, $n=15$ ), or in microchannels without endothelial cells ( $n=18$ ). Microchannels were perfused with fluorescently labeled microspheres (0.5 $\mu$ m dia., $<$ 1%) suspended in cell culture media. The velocity of individual microspheres was obtained off‐line (videorecording), using an interactive software program; velocity was determined as the distance traveled in one video field (1/60 s). Mass balance was verified in the microchannels by comparing the microsphere velocities to the perfusion pump rate. In confluent endothelial cell lined microchannels, a velocity profile was obtained as microspheres passed an endothelial cell nucleus (identified by fluorescent dye), and again, for a paired region 100 $\mu$ m away without nuclei (cytoplasm region). The velocity profile was significantly shifted and sharpened by the endothelial cell nucleus, as anticipated. Over the nucleus, data are consistent with a normal sized nucleus extending into the lumen, further confirming that this scale model can be used to determine the wall shear stress to which endothelial cells are exposed. Using the experimental bulk phase fluid parameters as boundary conditions, we used computational fluid dynamics (CFD) to predict the expected wall shear stress gradient along an endothelial cell lined D‐shaped tube. The wall shear stress gradient over the nucleus was 2‐fold greater in the radial versus axial directions, and was sensitive to lateral versus midline positioned nuclei.
Computational study of the effect of geometric and flow parameters on the steady flow field at the rabbit aorto‐celiac bifurcation
Authors: Cheer A.Y. , Dwyer H.A. , Barakat A.I. , Sy E. , Bice M.
Published: November 2024

Arterial hemodynamic forces may play a role in the localization of early atherosclerotic lesions. We have been developing numerical techniques based on overset or “Chimera” type formulations to solve the Navier–Stokes equations in complex geometries simulating arterial bifurcations. This paper presents three‐dimensional steady flow computations in a model of the rabbit aorto‐celiac bifurcation. The computational methods were validated by comparing the numerical results to previously‐obtained flow visualization data. Once validated, the numerical algorithms were used to investigate the sensitivity of the computed flow field and resulting wall shear stress distribution to various geometric and hemodynamic parameters. The results demonstrated that a decrease in the extent of aortic taper downstream of the celiac artery induced looping fluid motion along the lateral walls of the aorta and shifted the peak wall shear stress from downstream of the celiac artery to upstream. Increasing the flow Reynolds number led to a sharp increase in spatial gradients of wall shear stress. The flow field was highly sensitive to the flow division ratio, i.e., the fraction of total flow rate that enters the celiac artery, with larger values of this ratio leading to the occurrence of flow separation along the dorsal wall of the aorta. Finally, skewness of the inlet velocity profile had a profound impact on the wall shear stress distribution near the celiac artery. While not physiological due to the assumption of steady flow, these results provide valuable insight into the fluid physics at geometries simulating arterial bifurcations.
Effects of the glycocalyx on the electrophoretic mobility of red cells and on streaming potentials in blood vessels: predictions of a structurally‐based model
Authors: Mestel A.J. , Mokady A.J. , Parker K.H. , Winlove C.P.
Published: November 2024

The polyelectrolyte layer coating mammalian cells, known as the glycocalyx, may be important in communicating flow information to the cell. In this paper, the layer is modelled as a semi‐infinite, doubly periodic array of parallel charged cylinders. The electric potential and ion distributions surrounding such an array are found using the linearised Poisson–Boltzmann equation and an iterative domain decomposition technique. Similar methods are used to calculate Stokes flows, driven either by a shear at infinity or by an electric field, parallel or transverse to the cylinders. The resulting electric streaming currents due to flow over endothelial cells, and the electrophoretic mobilities of red blood cells are deduced as functions of polymer concentration and electrolyte molarity. It is shown that only the top portion of the layer is important in these effects.
Distributions of rheological parameters in populations of human erythrocytes
Authors: Lisovskaya I.L. , Shurkhina E.S. , Yakovenko E.E. , Tsvetaeva N.V. , Kolodei S.V. , Shcherbinina S.P. , Ataullakhanov F.I.
Published: November 2024

We have previously proposed the osmofiltration method based on a modified Hanss hemorheometer to analyze distributions of erythrocytes in their ability to pass through membrane filters with 3 $\mu$ m pores. Upon decrease in medium osmolality ( $u$ ) the erythrocyte volume increases. When cell volume becomes $V=V_{\mathrm{cr}}$ at $u=u_{\mathrm{cr}}$ , such cell loses its ability to pass through a 3 $\mu$ m pore. The flow rate of erythrocyte suspension containing cells with different $u_{\mathrm{cr}}$ through a filter gradually decreases with decreasing medium osmolality. This rate becomes zero at some $u=\Omega$ , when the number of non‐filterable cells in the applied sample approaches the number of pores in filter. Experimental determination of the dependencies of the filtration rate on medium osmolality for various hematocrit values allows to obtain $\Omega$ for each hematocrit and, thereby, to assess the distribution of erythrocytes in $u_{\mathrm{cr}}$ . Here, we propose a simplified version of this method, which allows screening of the erythrocytes in heterogeneous suspensions for the distribution in $u_{\mathrm{cr}}$ by measuring $\Omega$ for only two hematocrit values, 0.1% and 1%. Applications of the proposed method are exemplified by analysing the erythrocyte populations of healthy donors, of patients with microspherocytosis, hemochromatosis and normal erythrocyte populations in an acidic environment.
Swelling and flow properties of tubular poly(vinyl alcohol) gels
Authors: Takigawa Toshikazu , Uchida Koichi , Takahashi Katsunori , Masuda Toshiro
Published: November 2024

Swelling and flow properties of tubular poly(vinyl alcohol) (PVA) hydrogels prepared with the cooling method were investigated using an inflation testing method. When the tubular hydrogel in liquid paraffin was inflated by using liquid paraffin as a pressure transmitting medium, namely in the case that the liquids inside and outside the gel are both liquid paraffin (P/P combination), the gel showed a slight volume change determined by Poisson’s ratio of the gel. When the gel in water was inflated by liquid paraffin (P/W combination), the gel swelled to large extent compared with the case of P/P. The hydrogel in W/W combination, namely in the situation that the gel was immersed in water and also inflated by water, showed a very large volume change if the comparison was done at the same pressure. The origin of the volume change in P/P, P/W and W/W combinations is discussed. The volume change in P/P was governed by the Poisson ratio as a material constant (µ $_{0}$ ) of the PVA gels, and the gels swelled by the change in the application of pressure (or deformation) in P/W. The volume change in W/W was closely related to the flow of solvent in the gel.
Loading‐induced changes in synovial fluid affect cartilage metabolism
Authors: van de Lest C.H.A. , van den Hoogen B.M. , van Weeren P.R.
Published: November 2024

The object of this study was to determine whether changes in the synovial fluid (SF) induced by in vivo loading can alter the metabolic activity of chondrocytes in vitro, and, if so, whether insulin‐like growth factor‐I (IGF‐I) is responsible for this effect. Therefore, SF was collected from ponies after a period of box rest and after they had been exercised for a week. Normal, unloaded articular cartilage explants were cultured in 20% solutions of these SFs for 4 days and chondrocyte bioactivity was determined by glycosaminoglycan (GAG) turnover (i.e., the incorporation of ${}^{35}$ SO $_4$ into GAG and the release of GAG into the medium). Furthermore, the extent to which the bioactivity is IGF‐I‐dependent was determined in a cartilage explant culture in 20% SF, in the presence and absence of anti‐IGF‐I antibodies.

In explants cultured in post‐exercise SF, GAG synthesis was enhanced and GAG release was diminished when compared to cultures in pre‐exercise SF. SF analysis showed that IGF‐I and IGFBP‐3 levels were increased in post‐exercise SF. There was a positive correlation between IGF‐I levels and proteoglycan synthesis, but no correlation between IGF‐I levels and proteoglycan release. Addition of anti‐IGF‐I antibodies significantly inhibited stimulation of proteoglycan synthesis in explants cultured in SF with 40%. However, there was no difference in inhibition of proteoglycan synthesis between pre‐ and post‐exercise SF which indicated that the relative contribution of IGF‐I in the stimulating effect of SF did not change. Proteoglycan release was not influenced by the presence of anti‐IGF‐I antibodies.

It is concluded that chondrocyte metabolic activity is at least partially regulated by changes in the SF induced by in vivo loading. Exercise altered the SF in a way that it had a favourable effect on cartilage PG content by enhancing the PG synthesis and reducing the PG breakdown. IGF‐I is an important contributor to the overall stimulating effect of SF on cartilage metabolism. It is, however, unlikely that IGF‐I is the only mediator in the exercise‐induced increase in this stimulating effect.
Chondrocyte regulation by mechanical load
Authors: Wilkins Robert J. , Browning Joseph A. , Urban Jill P.G.
Published: November 2024

The effects of load on articular cartilage are complex. Dynamic loading of cartilage is associated with slight cell and tissue deformation as well as cyclical fluctuations in the hydrostatic pressure of cartilage and in fluid movement. Static loading results in expression of fluid from the tissue, concentrating extracellular matrix macromolecules and consequently increasing the concentrations of cations, reducing extracellular pH and increasing extracellular osmolarity. Each of these alterations is implicated in regulating the synthetic response of chondrocytes to load. However, the mechanisms by which these changes affect matrix turnover are poorly understood. In this review we consider how load may affect chondrocyte behaviour through its influence on membrane transport processes and thus on the intracellular environment.
Transcriptional activation in chondrocytes submitted to hydrostatic pressure
Authors: Sironen Reijo , Elo Mika , Kaarniranta Kai , Helminen Heikki J. , Lammi Mikko J.
Published: November 2024

At present, only a little is known about the transcriptional regulation in chondrocytes submitted to various physicomechanical factors known to exist in articular cartilage. Recently, we have investigated the effects of hydrostatic pressure on transcriptional control in chondrocytes using human chondrosarcoma and immortalized chondrocyte cell lines for the experiments. Hydrostatic pressure was applied on the cells in a special computer‐controlled, water‐filled pressure chamber, where cyclic and static pressures up to 32 MPa can be created. Differential display RT‐PCR and probing of cDNA arrays are the methods we have used to study differential gene expression due to hydrostatic pressure. By differential display RT‐PCR experiments, we have observed several differentially expressed cDNA bands under continuous 30 MPa hydrostatic pressure, while 30 MPa cyclic pressure at 1 Hz produced much fewer changes. In the first phase of our studies, we have focused on the effects of 30 MPa hydrostatic pressure because it causes a unique hsp70‐mediated stress response in immortalized chondrocytes. Differential display RT‐PCR screening provided us with several clones that derive from low‐abundance mRNAs, such as death‐associated protein 3 (DAP3), a nucleotide‐binding protein which increases due to interferon‐gamma induced cell death; PTZ‐17 (or p311), a seizure‐related protein; H‐NUC, a nuclear DNA binding protein; and one new gene of unknown function. In Northern blots, an induction was confirmed for the new gene, DAP3 and PTZ‐17 were down‐regulated in some but not in all parallel experiments; however, basal level of H‐NUC mRNA was too low to be detected in Northern blots. We then chose to widen our screening to a number of known genes arrayed as cDNA blots. Under 30 MPa continuous hydrostatic pressure, four different time points were chosen (0, 3, 6 and 24 h) for the experiments. The screening of 588 cDNAs showed 15 up‐regulated and 6 down‐regulated genes. Consistently with our previous results hsp70 was highly induced, as well as hsp40, a chaperone protein functioning together with hsp70. Gadd45 and to a lesser extent Gadd153 (stress genes induced by, e.g., ionizing radiation and ischaemia) were up‐regulated, as well as p21 $^\mathrm{waf1,cip1}$ , a protein participating in cell cycle regulation that can interact with Gadd45. Northern blots confirmed Gadd45 induction. Down‐regulated transcripts included, e.g., DAD‐1, glutathione S‐transferase pI, DNA‐binding inhibitor ID‐1H, and cytoplasmic dynein light chain.
Chondrocyte integrin expression and function
Authors: Loeser Richard F.
Published: November 2024

The extracellular matrix (ECM) is an “information rich” environment and interactions between the chondrocyte and ECM regulate many biological processes important to cartilage homeostasis and repair including cell attachment, growth, differentiation, and survival. The integrin family of cell surface receptors appears to play a major role in mediating cell‐matrix interactions that are important in regulating these processes. Chondrocytes have been found to express several members of the integrin family which can serve as receptors for fibronectin (α5β1), types II and VI collagen (α1β1, α2β1, α10β1), laminin (α6β1), and vitronectin and osteopontin (αVβ3). Integrin expression can be regulated by growth factors including IGF‐I and TGF‐β. By providing a link between the ECM and the cytoskeleton, integrins may be important transducers of mechanical stimuli. Integrin binding stimulates intracellular signaling which can affect gene expression and regulate chondrocyte function. Further studies are needed to more clearly define the role of integrins in cartilage.
Phenotypic modulation of nasal septal chondrocytes by cytoskeleton modification
Authors: Loty S. , Sautier J.M. , Forest N.
Published: November 2024

The reversion to the initial round shape of chondrocytes in monolayer cultures is one of the initial events required for the expression of cartilage‐specific macromolecules. Thus, considerable research efforts have focused on developing reliable procedures to maintain a round morphology of cultured chondrocytes. Our study focuses on evaluating the response of dedifferentiated fetal rat chondrocytes to cytochalasin D, an actin‐disrupting agent, with special emphasis on the morphological events. Immediately after exposure to the drug, cells round up but flatten again after removing the agent. However, immunocytochemical procedures revealed a disorganization of microfilaments and intermediate filaments. Phase‐contrast and scanning electron microscopic observations revealed that on day 6 of culture, cells located at the top of the cell layer adopted a spherical morphology. Prominent differences were noted in control cultures where cells had to aggregate prior to overt chondrogenesis. These morphological changes occurred parallel to the expression of type II collagen, marker of the chondrocytes phenotype, strongly expressed in experimental cultures, but relatively weak in control cultures, and only restricted on areas of polygonal cellular aggregates. Furthermore, [ $^{35}$ S]‐sulphate incorporation into sulphated glycosaminoglycans increased rapidly with the period of culture to a maximum after 7 days and was then two‐fold in treated cultures. Taken together, these findings indicated that cytochalasin‐D stimulates chondrogenesis in response to modification of cytoskeleton architecture and the subsequent rounding up of the cells.
The influence of temperature and length of time of storage of frog mucus samples
Authors: Gastaldi Ada C. , Jardim José R. , King Malcolm
Published: November 2024

Frozen, stored mucus has been extensively used for transport studies but there is no clear evidence of the influence that the temperature and length of time of storage may have on the results. We stored frog mucus samples at –20 and –80°C and analysed them on days zero, 2, 10, 30 and 90. At each temperature, a sample was thawed, studied and refrozen on each of the study days, at the same time that one sample was thawed only on the study day. Displacement in a simulated cough machine and on the frog palate, as well as contact angle measurements, were determined for the mucus samples on each study day. Mucus cytologic analyses on each of the study days were done with special regard to neutrophil counts and cell integrity. Friedman analysis of variance did not show any difference between the different periods of storage and the two temperatures for any of the parameters studied. The medians for the relative transport velocity on the frog palate varied between 0.88 and 1.03, for the contact angle between 21 and 28°, and for the displacement in the simulated cough machine between 58 and 95 mm over the 90 days of the experiment. There were no cytologic alterations compatible with cell degeneration. We conclude that the storage of frog mucus either at –20 or -80°C for periods up to 90 days does not lead to any significant differences in mucus transportability.
Dielectric approach to investigation of erythrocyte aggregation. II. Kinetics of erythrocyte aggregation–disaggregation in quiescent and flowing blood
Authors: Pribush A. , Meiselman H.J. , Meyerstein D. , Meyerstein N.
Published: November 2024

A method based on dielectric properties of dispersed systems was applied to investigate the kinetics of RBC aggregation and the break‐up of the aggregates. Experimentally, this method consists of measuring the capacitance at a frequency in the beginning of the β‐dispersion. Two experimental protocols were used to investigate the aggregation process. In the first case, blood samples were fully dispersed and then the flow was decreased or stopped to promote RBC aggregation. It was found that the initial phases of RBC aggregation are not affected by the shear rate. This finding indicates that RBC aggregation is a slow coagulation process. In the second case, RBCs aggregated under flow conditions at different shear rates and after the capacitance reached plateau levels, the flow was ceased. The steady‐state capacitance of the quiescent blood and the kinetics of RBC aggregation after stoppage of shearing depend on the prior shear rate. To clarify the reasons for this effect, the kinetics of the disaggregation process was studied. In these experiments, time courses of the capacitance were recorded under different flow conditions and then a higher shear stress was applied to break up RBC aggregates. It was found that the kinetics of the disaggregation process depend on both the prior and current shear stresses. Results obtained in this study and their analysis show that the kinetics of RBC aggregation in stasis consists of two consecutive phases: At the onset, red blood cells interact face‐to‐face to form linear aggregates and then, after an accumulation of an appropriate concentration of these aggregates, branched rouleaux are formed via reactions of ends of the linear rouleaux with sides of other rouleaux (face‐to‐side interactions). Branching points are broken by low shear stresses whereas dispersion of the linear rouleaux requires significantly higher energy.
Electrophoretic and aggregation behavior of bovine, horse and human red blood cells in plasma and in polymer solutions
Authors: Bäumler Hans , Neu Björn , Mitlöhner Rita , Georgieva Radostina , Meiselman Herbert J. , Kiesewetter Holger
Published: November 2024

The electrophoretic mobility of native and glutaraldehyde‐fixed bovine, human, and horse red blood cells (RBC) was investigated as a function of ionic strength (5–150 mM) and concentration of 464 kDa dextran (2 and 3 g/dl); RBC aggregation in autologous plasma and in dextran solutions was also measured. In agreement with previous observations, human and horse RBC form stable rouleaux whereas bovine RBC do not aggregate in either plasma or in dextran 464 kDa solutions. Electrophoretic measurements showed a species‐dependent adsorption and depletion of dextran that can be theoretically evaluated. Adsorption of polymer is not a prerequisite for RBC aggregation (bovine RBC show the highest amount of adsorbed dextran yet do not aggregate). Aggregate formation thus occurs as long as the Gibbs free energy difference, given by the osmotic pressure difference between the bulk phase and the polymer‐depleted region between two RBC, is larger than the steric and electrostatic repulsive energy contributed by the macromolecules present on the RBC surface. With increasing bulk‐phase polymer concentration the depletion layer thickness decreases and the amount of adsorbed macromolecules increases, thereby resulting in an increase of the repulsive component of the interaction energy and decreased aggregation. We thus view electrophoretic measurements of RBC in various media as an important tool for understanding polymer behavior near the red cell surface and hence the mechanisms involved in RBC aggregation.
Modulation of red blood cell aggregation and blood viscosity by the covalent attachment of Pluronic copolymers
Authors: Armstrong Jonathan K. , Meiselman Herbert J. , Wenby Rosalinda B. , Fisher Timothy C.
Published: November 2024

Despite many years of research, the physiologic or possible pathologic significance of RBC aggregation remains to be clearly determined. As a new approach to address an old question, we have recently developed a technique to vary the aggregation tendency of RBCs in a predictable and reproducible fashion by the covalent attachment of nonionic polymers to the RBC membrane. A reactive derivative of each polymer of interest is prepared by substitution of the terminal hydroxyl group with a reactive moiety, dichlorotriazine (DT), which covalently bonds the polymer molecule to membrane proteins. Pluronics are block copolymers of particular interest as these copolymers can enhance or inhibit RBC aggregation. Pluronics exhibit a critical micellization temperature (CMT): a phase transition from predominantly single, fully hydrated copolymer chains to micelle‐like structures. The CMT is a function of both copolymer molecular mass and concentration. This micellization property of Pluronics has been utilized to enhance or inhibit RBC aggregation and hence to vary low‐shear blood viscosity. Pluronic‐coated RBCs were prepared using reactive DT derivatives of a range of Pluronics (F68, F88, F98 and F108) and resuspended in autologous plasma at 40% hematocrit. Blood viscosity was measured at a range of shear rates (0.1–94.5 s−1) and at 25 and 37°C using a Contraves LS‐30 couette low shear viscometer. RBC aggregation and whole blood viscosity was modified in a predictable manner depending upon the CMT of the attached Pluronic and the measurement temperature: below the CMT, RBC aggregation was diminished; above the CMT it was enhanced. This technique provides a novel tool to probe some basic research questions. While certainly of value for in vitro mechanistic studies, perhaps the most interesting application may be for in vivo studies: typically, intravital experiments designed to examine the role of RBC aggregation in microvascular flow require perturbation of the suspending plasma to promote or reduce aggregation (e.g., by the addition of dextran). By binding specific Pluronics to the surface, we can produce RBCs that intrinsically have any desired degree of increased or decreased aggregation when suspended in normal plasma, thereby eliminating many potential artifacts for in vivo studies. The copolymer coating technique is simple and reproducible, and we believe it will prove to be a useful tool to help address some of the longstanding questions in the field of hemorheology.
Modulation of A‐NK cell rigidity: In vitro characterization and in vivo implications for cell delivery
Authors: Melder Robert J. , Kristensen Claus A. , Munn Lance L. , Jain Rakesh K.
Published: November 2024

The delivery of cells to specific regions of the vasculature is a critical step in many therapeutic strategies. These include the packaging of DNA or RNA in cell “vehicles” for delivery to tissues, the reconstitution of differentiated cells to an organ using embryonic stem cells, and the enhancement of the immune response using effector lymphocytes. In most cases, these cells must be injected systemically. Unfortunately, ex vivo manipulation or activation can affect cell visco‐elastic properties, making it difficult for the injected cells to traverse capillary beds. Compounding the problem is the fact that common agents used in the laboratory for increasing cell deformability generally have adverse side effects on the therapeutic potential of the cells. Using micropipet aspiration techniques, cytotoxicity assays and in vivo trafficking studies we show that: (1) the rigidity of injected effector cells directly affects resistance to passage through tissue; (2) modulation of cytoskeletal organization can be used to decrease cell rigidity, but can also compromise therapeutic efficacy; and (3) thioglycollate, an agent which does not influence effector lymphocyte cytotoxic activity, reduces cell rigidity and entrapment in the lungs.
Effect of secondary flow on biological experiments in the cone‐plate viscometer: Methods for estimating collision frequency, wall shear stress and inter‐particle interactions in non‐linear flow
Authors: Shankaran Harish , Neelamegham Sriram
Published: November 2024

We present a theoretical analysis of fluid flow and particle interactions in the cone‐plate viscometer under conditions typically applied in biological studies. The analysis demonstrates that at higher shear rates, besides linear primary flow in the rotational direction, prominent non‐linear secondary flow causes additional fluid circulation in the radial direction. Two parameters, the cone angle and Reynolds number, characterize flow in the viscometer over all ranges of shear rate. Our results indicate that secondary flow causes positional variations in: (i) the velocity gradient, (ii) the direction and magnitude of the wall shear stress at the plate surface, (iii) inter‐particle collision frequency, (iv) magnitude and periodicity of normal and shear forces applied during particle–particle interactions, and (v) inter‐particle attachment times. Thus, secondary flow may significantly influence cellular aggregation, platelet activation and endothelial cell mechanotransduction measurements. Besides cone‐plate viscometers, this analysis methodology can also be extended to other experimental systems with complex non‐linear flows.