[Effects of individual factors and labor organization on neck pain in auto assembler]

Objective: To investigate the influence of individual factors and labor organization on the prevalence of neck pain (hereinafter referred to as neck pain) in automotive assemblers, and to provide a basis for enterprises to optimize neck pain interventions. Methods: A cluster random sampling method was taken in January 2021, at an automobile manufacturing plant in Shiyan, 656 assemblers with ≥1.0 years of service were selected, the "Musculoskeletal Disorder Questionnaire" was used to investigate the incidence and influencing factors of neck pain. Pearson χ(2) test or trend χ(2) test was used to compare the data rates. The influencing factors of neck pain were analyzed by multivariate logistic regression. Results: The prevalence rate of neck pain (hereinafter referred to as the prevalence rate of neck pain) of automobile assemblers within one year was 53.94% (342/634) . The prevalence of neck pain in women was higher than that in men (69.1% vs 48.6%, P<0.01) . The prevalence of neck pain was related to length of service, self-assessment of fatigue, working hours per week, working in the same workshop, rest days per shift, and accumulated rest time per shift (P<0.05) . Multivariate logistic regression analysis showed that the risk of neck pain in women was 2.434 times higher than that in men; The risk of neck pain increased by 18.9% for each hour of work per week; Rest during work was a protective factor for neck pain. The number of rest per shift increased and the risk of neck pain decreased (r=0.405, 0.311, 0.302, 95%CI=0.205~0.803, 0.169~0.572, 0.142~0.642, P<0.05) . Conclusion: The annual prevalence of neck pain was higher in automobile assemblers. Enterprises should fully consider the influencing factors such as gender, working hours per week and the number of breaks when arranging production.

Emerging role of air pollution in chronic kidney disease

Chronic kidney disease (CKD), a global disease burden related to high rates of incidence and mortality, manifests as progressive and irretrievable nephron loss and decreased kidney regeneration capacity. Emerging studies have suggested that exposure to air pollution is closely relevant to increased risk of CKD, CKD progression and end-stage kidney disease (ESKD). Inhaled airborne particles may cause vascular injury, intraglomerular hypertension, or glomerulosclerosis through non-hemodynamic and hemodynamic factors with multiple complex interactions. The mechanisms linking air pollutants exposure to CKD include elevated blood pressure, worsening oxidative stress and inflammatory response, DNA damage and abnormal metabolic changes to aggravate kidney damage. In the present review, we will discuss the epidemiologic observations linking air pollutants exposure to the incidence and progression of CKD. Then, we elaborate the potential roles of several air pollutants including particulate matter and gaseous co-pollutants, environmental tobacco smoke, and gaseous heavy metals in its pathogenesis. Finally, this review outlines the latent effect of air pollution in ESKD patients undergoing dialysis or renal transplant, kidney cancer and other kidney diseases. The information obtained may be beneficial for further elucidating the pathogenesis of CKD and making proper preventive strategies for this disease.

[Investigation on high-frequency hearing loss of noise workers in an automobile factory]

Objective: To investigate the high-frequency hearing loss (HFHL) of workers in an automobile factory and its influencing factors, so as to provide a scientific basis for occupational health management of noise workers. Methods: From March to July 2019, 2647 workers from an automobile factory were selected as the research objects by cluster sampling method. The basic personal information (such as gender, age, education level, height, weight, etc.) , history of ear disease, the history of detonation, history of exposure to ototoxic drugs, history of exposure to occupational noise, etc., were investigated by questionnaire and occupational health examination. Chi-square test was used to compare the detection rates of HFHL in different populations, and multivariate logistic regression model was used to analyze the influencing factors of HFHL. Results: The noise level of 2647 individual workers ranged from 75.0 dB (A) to 92.0 dB (A) , with an average of (84.14±2.47) dB (A) . The detection rate of HFHL was 17.2% (456/2647) . There were significant differences in the the detection rate of HFHL among workers of different gender, age, educational level, working age, noise exposure level, diabetes history, detonation history, smoking and drinking workers (P<0.05) . Multivariate logistic regression analysis showed that male, age ≥30 years old, smoking and noise exposure were risk factors for HFHL (P<0.05) . Conclusion: The detection rate of HFHL in automobile factory workers is high. Gender, age, smoking and noise are the influencing factors of HFHL. It is necessary to strengthen the noise control in the workplace and guide workers to choose healthy lifestyle.

Circadian clock genes as promising therapeutic targets for autoimmune diseases

Circadian rhythm is a natural, endogenous process whose physiological functions are controlled by a set of clock genes. Disturbance of the clock genes have detrimental effects on both innate and adaptive immunity, which significantly enhance pro-inflammatory responses and susceptibility to autoimmune diseases via strictly controlling the individual cellular components of the immune system that initiate and perpetuate the inflammation pathways. Autoimmune diseases, especially rheumatoid arthritis (RA), often exhibit substantial circadian oscillations, and circadian rhythm is involved in the onset and progression of autoimmune diseases. Mounting evidence indicate that the synthetic ligands of circadian clock genes have the property of reducing the susceptibility and clinical severity of subjects. This review supplies an overview of the roles of circadian clock genes in the pathology of autoimmune diseases, including BMAL1, CLOCK, PER, CRY, REV-ERBα, and ROR. Furthermore, summarized some circadian clock genes as candidate genes for autoimmune diseases and current advancement on therapy of autoimmune diseases with synthetic ligands of circadian clock genes. The existing body of knowledge demonstrates that circadian clock genes are inextricably linked to autoimmune diseases. Future research should pay attention to improve the quality of life of patients with autoimmune diseases and reduce the effects of drug preparation on the normal circadian rhythms.

Structural Diversity in Oxadiazole-Containing Silver Complexes Dependent on the Anions

Two coordination polymers, namely [Ag2(L)(SO3CF3)(H2O)](SO3CF3)•CH2Cl2 (1) and [Ag5(L)4(H2O)2](SbF6)5•5THF (2), were obtained by reacting oxadiazole-containing tri-armed ligand 1,3,5-tri(2-methylthio-1,3,4-oxadiazole-5yl) ben-zene (L) and silver salts in CH2Cl2/THF medium. The two complexes crystallized in the tetragonal space group I41/a and orthorhombic space group Fdd2, respectively. The Single-crystal X-ray diffraction revealed that the two complexes ex-hibit strikingly different 3D polymeric structures, which can be ascribed to the different counter anions. L in compound 1 acted as a hexa-dentate ligand, binding to two types of Ag+ atoms to form a 3D polymeric structure. L in compound 2acted as a hexa- and penta-dentate ligand, binding to three types of Ag+ atoms to form the 3D polymeric structure. The antibacterial activity of the complexes was also investigated.

[Study on the effects of noise on hypertension and hyperglycemia among occupational workers]

Objective: To study the effect of noise on hypertension and hyperglycemia among occupational workers. Methods: Total 670 workers in an automobile manufacturing company were selected as the subjects of physical examination in 2017. According to the noise exposure or not, the subjects were divided into control group (no noise exposure) 143 and contact group (noise exposure) 527. Questionnaire survey and physical examination were conducted. The measurement data were analyzed by t-test, and the count data and grade data were analyzed by χ(2) test. The influence of noise on blood glucose, heart rate, blood pressure and other indicators was analyzed by logistic regression, and the OR and 95%CI of each risk factor were calculated. Results: The average age of the control group and the contact group was no significant difference (P>0.05) . There were 139 (20.7%) cases of high systolic pressure, 154 (23.0%) cases of high diastolic pressure, 63 (9.4%) cases of hyperglycemia, 29 (4.3%) cases of tachycardia. Compared with the control group, there were significant differences in systolic blood pressure, diastolic blood pressure and blood glucose in the contact group (P<0.05) . Compared with the control group, the systolic blood pressure, diastolic blood pressure and blood glucose of the subjects in the corresponding age contact group increased significantly (P<0.05) . The years of noise exposure were protective factors for systolic and diastolic blood pressure (OR=0.970, 0.973) . Conclusion: Noise exposure may increase blood pressure and blood sugar of occupational workers, but the effect on heart rate can not be determined.

Epigenetic alterations contribute to promoter activity of imprinting gene IGF2

The expression of insulin-like growth factor 2 (IGF2), a classical imprinting gene, didn't completely correlate with its imprinting profiles in hepatocellular carcinoma (HCC). The mechanistic importance of promoter activity in regulation of IGF2 has not been fully clarified. Here we show that histone 3 lysine 4 trimethylation (H3K4me3) modified by menin-MLL complex of IGF2 promoter contributes to promoter activity of IGF2. The strong binding of menin and abundant H3K4me3 at the DNA demethylated P3/4 promoters were observed in Hep3B cells with the robust expression of IGF2. In IGF2-low-expressing HepG2 cells, menin didn't bind to DNA hypermethylated P3/4 regions; however, menin overexpression inhibited DNA methylation and promoted H3K4me3 at the P3/4 as well as IGF2 expression in HepG2. In addition, the H3K4me3 at P3/4 locus was activated in primary HCC specimens with high IGF2 expression. Furthermore, inhibition of the menin/MLL interaction via MI-2/3 reduced IGF2 expression, inhibited the IGF1R-AKT pathway, and significantly repressed HCC with robust expression of IGF2. Taken together, we conclude that H3K4me3 of P3/4 locus mediated by the menin-MLL complex is a novel epigenetic mechanism for releasing IGF2.

TLR2-MyD88-NF-κB pathway is involved in tubulointerstitial inflammation caused by proteinuria

Proteinuria is an important risk factor for chronic kidney diseases (CKD). Several studies have suggested that proteinuria initiates tubulointerstitial inflammation, while the mechanisms have not been fully understood. In this study, we hypothesized whether the activation of the TLR2-MyD88-NF-κB pathway is involved in tubulointerstitial inflammation induced by proteinuria. We observed expression of TLR2, MyD88, NF-κB, as well as TNF-α and IL-6 detected by immunohistostaining, Western blotting and real-time PCR in albumin-overloaded (AO) nephropathy rats. In vitro, we observed these markers in HK-2 cells stimulated by albumin. We used TLR2 siRNA or the NF-κB inhibitor BAY 11-7082 to observe the influence of TNF-α and IL-6 expression caused by albumin overload. Finally, we studied these markers in non-IgA mesangioproliferative glomerulonephritis (MsPGN) patients with different levels of proteinuria. It was demonstrated that expression of TLR2, MyD88 and NF-κB were significantly increased in AO rats and in non-IgA MsPGN patients with high levels of proteinuria, and TNF-α and IL-6 expressions were increased after NF-κB activation. Furthermore, TNF-α and IL-6 expression was positively correlated with the level of proteinuria. Albumin-overload induced TNF-α and IL-6 secretions by the TLR2-MyD88-NF-κB pathway activation, which could be attenuated by the TLR2 siRNA or BAY 11-7082 in HK-2 cells. In summary, we demonstrated that proteinuria may exhibit an endogenous danger-associated molecular pattern (DAMP) that induces tubulointerstitial inflammation via the TLR2-MyD88-NF-κB pathway activation.

Urinary vimentin mRNA as a potential novel biomarker of renal fibrosis

Renal fibrosis is a histological outcome of chronic kidney disease (CKD) progression. However, the noninvasive detection of renal fibrosis remains a challenge. Here we constructed a renal fibrosis target mRNA array and used it to detect urinary mRNAs of CKD patients for investigating potential noninvasive biomarkers of renal fibrosis. We collected urine samples from 39 biopsy-proven CKD patients and 11 healthy controls in the training set. Urinary mRNA profiles of 86 genes showed a total of 21 mRNAs that were differentially expressed between CKD patients and controls ( P < 0.05), and vimentin (VIM) mRNA demonstrated the highest change fold of 9.99 in CKD vs. controls with robust correlations with decline of renal function and severity of tubulointerstitial fibrosis. Additionally, VIM mRNA further differentiated patients with moderate-to-severe fibrosis from none-to-mild fibrosis group with an area of the curve of 0.796 ( P = 0.008). A verification of VIM mRNA in the urine of an additional 96 patients and 20 controls showed that VIM is not only well correlated with renal function parameters but also correlated with proteinuria and renal fibrosis scores. Multiple logistic regression and receiver-operating characteristics analysis further showed that urine VIM mRNA is the best predictive parameter of renal fibrosis compared with estimated glomerular filtration rate, serum creatinine, and blood urea nitrogen. In addition, there is no improved predictive performance for the composite biomarkers to predict renal fibrosis severity compared with a single gene of VIM. Overall, urinary VIM mRNA might serve as a novel independent noninvasive biomarker to monitor the progression of kidney fibrosis.

Activation of the Nlrp3 inflammasome by mitochondrial reactive oxygen species: a novel mechanism of albumin-induced tubulointerstitial inflammation

Albuminuria is not only an important marker of chronic kidney disease but also a crucial contributor to tubulointerstitial inflammation (TIF). In this study, we determined whether activation of the Nlrp3 inflammasome is involved in albuminuria induced-TIF and the underlying mechanisms of inflammasome activation by mitochondrial reactive oxygen species (mROS). We established an albumin-overload induced rat nephropathy model characterised by albuminuria, renal infiltration of inflammatory cells, tubular dilation and atrophy. The renal expression levels of the Nlrp3 inflammasome, IL-1β and IL-18 were significantly increased in this animal model. In vitro, albumin time- and dose-dependently increased the expression levels of the Nlrp3 inflammasome, IL-1β and IL18. Moreover, the silencing of the Nlrp3 gene or the use of the caspase-1 inhibitor Z-VAD-fmk significantly attenuated the albumin-induced increase in IL-1β and IL-18 expression in HK2 cells. In addition, mROS generation was elevated by albumin stimulation, whereas the ROS scavenger N-acetyl-l-cysteine (NAC) inhibited Nlrp3 expression and the release of IL-1β and IL-18. In kidney biopsy specimens obtained from patients with IgA nephropathy, Nlrp3 expression was localised to the proximal tubular epithelial cells, and this result is closely correlated with the extent of proteinuria and TIF. In summary, this study demonstrates that albuminuria may serve as an endogenous danger-associated molecular pattern (DAMP) that stimulates TIF via the mROS-mediated activation of the cytoplasmic Nlrp3 inflammasome.

The functional and mechanistic relatedness of EZH2 and menin in hepatocellular carcinoma

BACKGROUND & AIMS

The alterations of histone modification may serve as a promising diagnostic biomarker of hepatocellular carcinoma (HCC), but the clinical and mechanistic relatedness of the histone H3 lysine 27 and 4 trimethylation (H3K27me3 and H3K4me3) in HCC remains poorly understood. Here we propose that the combination of H3K27me3 and H3K4me3 is a more precise predictive/prognostic value for outcome of HCC patients.

METHODS

We used chromatin immunoprecipitation (ChIP) assays and a ChIP-on-chip screen to analyse HCC.

RESULTS

We found that the EZH2 occupancy coincides with the H3K27me3 at promoters and directly silences the transcription of target genes in HCC. The H3K27me3-related gene network of EZH2 contains well-established genes, such as CDKN2A, as well as previously unappreciated genes, including FOXO3, E2F1, and NOTCH2, among others. We further observed independently increasing profiles of H3K27me3 and H3K4me3 at the promoters of certain target genes in HCC specimens. Importantly, Kaplan-Meier analysis reveals that 3-year overall and tumour-free survival rates are dramatically reduced in patients that simultaneously express EZH2 and menin, compared to rates in the EZH2 or menin under expressing patients. Furthermore, an inhibitor of H3K27me3 alone, or in combination with an H3K4me3 inhibitor, effectively blocked the aggressive phenotype of HCC cells.

CONCLUSIONS

Our results indicate that a combined analysis of both H3K27me3 and H3K4me3 may serve as powerful diagnostic biomarkers of HCC, and targeting both might benefit anti-HCC therapy.

Diet folate, DNA methylation and polymorphisms in methylenetetrahydrofolate reductase in association with the susceptibility to gastric cancer

Methylenetetrahydrofolate reductase (MTHFR) has been reported to be associated with DNA methylation, an epigenetic feature frequently found in gastric cancer. We conducted a case-control study to explore the association of MTHFR C677T polymorphisms with gastric cancer risk and its relation with the DNA methylation of COX-2, MGMT, and hMLH1 genes. Genotyping of P16, MGMT and HMLH1 was determined by methylation-specific PCR after sodium bisulfate modification of DNA, and genotyping of MTHFR C677T was conducted by TaqMan assays using the ABI Prism 7911HT Sequence Detection System. Folate intake was calculated with the aid of a questionnaire. Compared with the MTHFR 677CC genotype, the TT genotype was significantly associated with 2.08 fold risk of gastric cancer when adjusting for potential risk factors. Individuals who had an intake of folate above 310 μg/day showed protective effects against gastric cancer risk. The effect of MTHFR C677T polymorphisms on the risk of gastric cancer was modified by folate intake and methylation status of MGMT (P for interaction <0.05).

Microfiltration and ultrafiltration of polysaccharides produced by fermentation using a rotating disk dynamic filtration system

The recovery of exopolysaccharides (EPS) produced by Sinorhizobium meliloti bacteria by dynamic microfiltration was investigated using a rotating disk device designed in our laboratory, equipped with a 0.2 microm nylon membrane. This system differs from commercially available systems by the presence of vanes on the disk which produce a very important increase in permeate flux while yielding excellent EPS transmission. For polymers produced under standard fermentation conditions (70 h at 30 degrees C), the mass flux rose to 650 g h(-1) m(-2) using a disk equipped with 2 mm vanes rotating at 2000 rpm against 380 g h(-1) m(-2) with a smooth disk at the same speed. The maximum flux observed was 1560 g h(-1) m(-2) with a 6-mm vanes disk rotating at 3000 rpm and a 36 degrees C broth. An interesting finding was that the permeate flux J(f) for various disks can be correlated by the same function of the mean shear stress at the membrane tau(wm) according to J(f) = 4.6 tau(wm) (0.717) for a 30 degrees C broth, showing that the effect of vanes is merely to increase the shear stress by raising the fluid core velocity between the membrane and the disk. With 6-mm vanes the core angular velocity was found to be 84% of disk velocity vs. 45% for a smooth disk. When the fermentation temperature was increased to 36 degrees C to produce a lower molecular weight polymer, the permeate flux rose by about 250%, much more than what could be expected from the reduction in permeate viscosity and followed the same power law with membrane shear stress as for 30 degrees C. The same device was equipped with a PES 50 kDa membrane to concentrate EPS by ultrafiltration. Permeate fluxes were of the order of 160 L h(-1) m(-2) at 2000 rpm and 30 degrees C with nearly complete EPS rejection. Finally, the net electrical power consumed by the disk was measured by subtracting the power consumed without fluid from the power during filtration at the same speed. This power increases with speed and with the presence of vanes, but since the gain provided by the vanes is very high, the specific energy per m(3) of permeate is minimal with the highest vanes tested (6 mm) and maximal for smooth disks.

Hemolysis reduction in plasmapheresis by module design: operating with pulsed flow filtration enhancement

This study is an investigation into the effects of module design on hemolysis levels during the filtration enhancement of plasmapheresis using pulsed blood flow. Two polypropylene hollow fiber modules (F1 and F2) were compared under steady and pulsed flow conditions. The fiber lengths and membrane areas of the respective filters were 136 mm, 0.1 m2 and 226 mm, 0.25 m2 and were used at wall shear rates of 400 and 600 s-1. Fresh citrated bovine blood was circulated at 90 ml/min through their fibers with permate and retentate being recirculated. Plasma samples were analysed by the Cripps method to obtain the mean free hemoglobin concentration. A comparison of the average hemoglobin released with time per fiber, and per unit length allowed an assessment of the effects of fiber length and shear rate on hemolysis levels. It was concluded that a reduction in area and fiber length would reduce hemolysis levels and design equations are suggested to find the optimum length.

Effects of naloxone on tissue oxygen supply and somatosensory evoked potentials in cat brain during focal cerebral ischemia

The effects of naloxone on local tissue oxygen partial pressure (pO2) and on the somatosensory evoked potentials (SEP) were studied in the brain of cat during focal cerebral ischemia. Ischemia, produced by clamping of the middle cerebral artery (MCA) by a transorbital approach, was performed in two series of cats for 3 h. In one group of cats (n = 5), naloxone 5 mg.kg-1 was injected i.v. 0.5 h after clamping. The pO2 was continuously recorded on different depths (0-5000 microns) of the median gyrus by a polarographic oxygen microelectrode. After MCA clamping, pO2 (depth of 0-1000 microns) decreased markedly and hypoxia occurred in the ischemic area. But in the deeper brain (1001-5000 microns) pO2 did not change significantly. The amplitude of SEP decreased after MCA clamping, while the conduction time of SEP did not significantly decrease. The mean pO2 values in the ischemic area were increased as compared to the control group after naloxone, especially at the depths of 0-1000 microns, and the hypoxia was improved. The amplitude of SEP was increased after naloxone in comparison to the situation of ischemia without naloxone. The conduction time of SEP was not improved significantly. We conclude that naloxone can improve the oxygen supply and the electrical activity of neurons in the ischemic region of the brain.

Plasma fractionation by dead-end membrane filtration: effects of membrane properties and plasma flux

Plasma fractionation by membrane filtration permits the reinfusion of the patient with his own albumin. In this study, the influence of membrane nature and plasma flux on plasma fractionation in dead-end mode is investigated with acetate hollow fiber filters. It is found that transmembrane pressure TMP rises exponentially with time, the rate of increase being proportional to plasma flux. The faster TMP rises, the faster the drop in sieving coefficient SC. It is also found that albumin SC is a function of TMP and not of plasma flux. Theoretical analysis of the dead-end filtration was performed. This theoretical model indicates that the observed variation of TMP with time is consistent with the assumptions that pore volume decreases proportionally to the filtrate plasma volume.

Comparison of polyamide and polypropylene membranes for plasma separation

Plasma separation experiments were made with polyamide experimental prototype hollow-fiber plasma filters with surface areas between 0.025 m2 and 0.1090 m2 using bovine blood collected in acid citrate dextrose (ACD). The maximum filtration velocity rose with the wall shear rate gamma w as gamma w 0.72 +/- 0.02 and decreased with the length of fiber L as L-0.41 with a correlation coefficient of 0.97 +/- 0.02. The results were similar to those with polypropylene fibers. We also investigated the occurrence of hemolysis as a function of shear rate and transmembrane pressure. The free hemoglobin concentration of filtered plasma was checked using a U.V. spectrophotometer. It was concluded that polyamide membrane filters can be safely used for plasma separation from blood.

Simultaneous convective and diffusive mass transfers in a hemodialyser

The mass transfer in a hemodialyser in the presence of combined dialysis and ultrafiltration has been calculated by integration of mass fluxes across the boundary layers in blood and dialysate phase taking into account the partial rejection of solute as well as changes in local blood flow and ultrafiltration flux along the membrane. Clearances of creatinin, vitamin B12, and myoglobin have been calculated as a function of blood and ultrafiltrate flow rate and were found to be in good agreement with in vitro measurements. The data suggest the following empirical correlation for the hemodiafiltration clearance.

Effect of membrane characteristics on the performance of Couette rotating plasma separation devices

The concept of a cylindrical membrane rotating at high speed inside a concentric cylinder (Couette flow device) has proved to be very efficient for plasma separation from whole blood. The authors show that its high filtration velocity (about 0.5-0.6 cm/min) is due to the presence of Taylor vortices in the blood-filled annular gap, which greatly increase the shear rates, but not radial migration of formed elements under centrifugal forces. The variation of filtrate velocity with transmembrane pressure (ptm) markedly depends upon the type of membrane. With a 0.8 micron polycarbonate membrane and bovine blood at 40% hematocrit, the filtration velocity reaches a peak equal to 0.6 cm/min at 3,000 rpm, then decreases to 80 mmHg, reaching a plateau of 0.35 cm/min independent of ptm. With a nylon membrane of 0.5 micron pores under the same conditions, the filtration velocity does not present a peak, but rises continuously to reach a 90 mmHg plateau equal to 0.5 cm/min. Similar behavior, but with lower plateaus, is also obtained with polycarbonate membranes at pore sizes below 0.4 microns. At 3,000 rpm, hemolysis occurs if ptm exceeds 750 mmHg, far above the operating range.

High shear rate hemofiltration: influence of fiber dimensions and shear rates

The variation of ultrafiltration flow rate (QF) at high transmembrane pressure with inlet wall shear rate (gamma w) was found to be proportional to gamma wn, with n ranging from 0.45 to 0.55, when gamma w increases up to 4,500 s-1. To test whether long filters operated at high shear rates were more efficient than shorter ones for the same inlet blood flow, we made experiments with 10- and 20-cm filters with same number of fibers (550) at various shear rates from 700 to 3,000 s-1. The filtration rates provided by the 20-cm filter were found to be 5-15% larger than those provided by two 10-cm filters arranged in parallel and 10-20% smaller than those provided by two 10-cm filters arranged in a series. The explanation lies in the rapid decay of QF with distance from the inlet due to the developing concentration boundary layer. When pulsations are imposed on the inlet blood flow, the filtration rate was seen to increase by 10-20%, and the effect of plugging was seen to decrease in small-area hemofilters.

Modelling of plasma-separation through microporous membranes

Available mathematical models of ultrafiltration have been used to predict changes in maximum plasma filtration rate with wall shear rate for given filters and blood properties. We have done many plasmapheresis experiments in vitro, using hollow-fiber filters (500-1000 cm2) and fresh bovine blood collected on ACD or heparin. The comparison between predicted and experimentally obtained filtration rates was good for models based on the concentration polarization theory and lift velocity theory. In other experiments with pulsatile inlet flow we found that plasma filtration rate increased by 20 to 50% compared to non-pulsatile conditions. These results are in good agreement with the modified model of ultrafiltration incorporating pulsating flow. This paper presents relationships between plasma filtration velocity (steady and pulsating flow) and hemolysis limit as a function of wall shear rate and filter size.

Rationale of filtration enhancement in membrane plasmapheresis by pulsatile blood flow

It has been demonstrated in our laboratory that blood flow pulsations enhance plasma filtration rate by 30-60 per cent. The increase in plasmafiltration over the steady flow value is found to be a function of the parameter F. delta V'/QB where F denotes the pulsation frequency, delta V' the volume amplitude of pulsed blood in the filter and QB is the time mean blood flow. The increment in plasma filtration may be related to the increase in time-mean absolute value of shear rate.

Membrane plasma separation through small-area, hollow-fiber filters

The filtration capabilities of small polypropylene hollow-fiber plasma filters with membrane areas ranging from 100 to 1,000 cm2 have been investigated. It is found that the filtration flux per unit membrane area is approximately proportional to the wall shear rate gamma w at least up to gamma w = 7,500 s-1. As a result, the total filtration flow rate increases very little when the number of fibers is increased as the increase in membrane area is offset by the decrease in shear rate, but it increases with the fiber length L as L 2/3. Hemolysis occurs when the transmembrane pressure exceeds a certain threshold, but this threshold is itself an increasing function of shear rate. As a result, it is possible to circulate high blood flow rates even in very small filters (100 cm2) without hemolysis, provided the fiber length is below a critical value.