1.Acute Inflammatory Pain Induces Sex-different Brain Alpha Activity in Anesthetized Rats Through Optically Pumped Magnetometer Magnetoencephalography
Meng-Meng MIAO ; Yu-Xuan REN ; Wen-Wei WU ; Yu ZHANG ; Chen PAN ; Xiang-Hong LIN ; Hui-Dan LIN ; Xiao-Wei CHEN
Progress in Biochemistry and Biophysics 2025;52(1):244-257
ObjectiveMagnetoencephalography (MEG), a non-invasive neuroimaging technique, meticulously captures the magnetic fields emanating from brain electrical activity. Compared with MEG based on superconducting quantum interference devices (SQUID), MEG based on optically pump magnetometer (OPM) has the advantages of higher sensitivity, better spatial resolution and lower cost. However, most of the current studies are clinical studies, and there is a lack of animal studies on MEG based on OPM technology. Pain, a multifaceted sensory and emotional phenomenon, induces intricate alterations in brain activity, exhibiting notable sex differences. Despite clinical revelations of pain-related neuronal activity through MEG, specific properties remain elusive, and comprehensive laboratory studies on pain-associated brain activity alterations are lacking. The aim of this study was to investigate the effects of inflammatory pain (induced by Complete Freund’s Adjuvant (CFA)) on brain activity in a rat model using the MEG technique, to analysis changes in brain activity during pain perception, and to explore sex differences in pain-related MEG signaling. MethodsThis study utilized adult male and female Sprague-Dawley rats. Inflammatory pain was induced via intraplantar injection of CFA (100 μl, 50% in saline) in the left hind paw, with control groups receiving saline. Pain behavior was assessed using von Frey filaments at baseline and 1 h post-injection. For MEG recording, anesthetized rats had an OPM positioned on their head within a magnetic shield, undergoing two 15-minute sessions: a 5-minute baseline followed by a 10-minute mechanical stimulation phase. Data analysis included artifact removal and time-frequency analysis of spontaneous brain activity using accumulated spectrograms, generating spectrograms focused on the 4-30 Hz frequency range. ResultsMEG recordings in anesthetized rats during resting states and hind paw mechanical stimulation were compared, before and after saline/CFA injections. Mechanical stimulation elevated alpha activity in both male and female rats pre- and post-saline/CFA injections. Saline/CFA injections augmented average power in both sexes compared to pre-injection states. Remarkably, female rats exhibited higher average spectral power 1 h after CFA injection than after saline injection during resting states. Furthermore, despite comparable pain thresholds measured by classical pain behavioral tests post-CFA treatment, female rats displayed higher average power than males in the resting state after CFA injection. ConclusionThese results imply an enhanced perception of inflammatory pain in female rats compared to their male counterparts. Our study exhibits sex differences in alpha activities following CFA injection, highlighting heightened brain alpha activity in female rats during acute inflammatory pain in the resting state. Our study provides a method for OPM-based MEG recordings to be used to study brain activity in anaesthetized animals. In addition, the findings of this study contribute to a deeper understanding of pain-related neural activity and pain sex differences.
2.Cell-of-origin for heterotopic ossification induced by bone morphogenetic protein 4 in skeletal muscle
Yangyi YU ; Qiang LIAN ; Jianqun WU ; Xuan ZHANG ; Jinke REN ; Guangheng LI
Chinese Journal of Tissue Engineering Research 2024;28(25):4034-4040
BACKGROUND:Heterotopic ossification of skeletal muscle is a clinically serious complication.For heterotopic ossification of skeletal muscles,the cells involved in the process of heterotopic ossification remain unclear. OBJECTIVE:To investigate the involvement of myocytes,fascia cells,and endothelial cells in the process of heterotopic ossification in skeletal muscle and to observe the cell origin of heterotopic ossification in skeletal muscle induced by bone morphogenetic protein 4. METHODS:Both C2C12 cells and the myotubes formed by the C2C12 cells in the induction medium were cultured,and 500 ng/mL bone morphogenetic protein 4 was added to the medium respectively,and whether the C2C12 cells and myotubes continued to proliferate within 10 days under the treatment were observed under a microscope.Myogenic cells(L6,derived from rats)and fibroblast-derived cells(derived from human)were co-cultured.After treatment with 500 ng/mL bone morphogenetic protein 4 and 10 ng/mL transforming growth factor-β,osteogenic and chondrogenic differentiation potential within 21 days were observed using Safranine O staining and Alcian blue staining.Using transgenic animal FVB/N-TgN(TIE2-LacZ)182Sato mice,15 μL of adeno-associated virus-bone morphogenetic protein 4(5×1010 PFU/mL)were implanted in the thigh muscle space of genetic mice for 10 and 14 days.X-gal staining was used to observe the formation of new blood vessel endothelium in the differentiated bone. RESULTS AND CONCLUSION:(1)Bone morphogenetic protein 4 caused myotube breakdown and increased C2C12 cell proliferation.Compared with other groups,the pure fibroblast-derived cell group had a higher area of positive alcian blue and safarin O staining(P<0.05)and a lower area of alkaline phosphatase staining(P<0.05),while the pure L6 group had a bigger area of alkaline phosphatase staining(P<0.05)but a smaller area of positive alcian blue and safarin O staining(P<0.05).(2)Transplantation of adeno-associated virus-bone morphogenetic protein 4-adsorbed gelatin sponge into FVB/N-TgN(TIE2-LacZ)182Sato mice resulted in heterotopic ossification.(3)X-gal staining results demonstrated that there was no obvious staining in chondrocytes and differentiated bones and Tie2+ endothelial cells did not participate in the formation of the alienated bone.(4)These findings verify that fibroblasts are the primary source of osteoblasts during the adeno-associated virus-bone morphogenetic protein 4-induced ectopic endochondral ossification in skeletal muscle,but myogenic cells are the main source of osteoblasts.Tie2+ endothelial cells might not be the cell source for cartilage and bone.
3.Expert consensus on surgical treatment of oropharyngeal cancer
China Anti-Cancer Association Head and Neck Oncology Committee ; China Anti-Cancer Association Holistic Integrative Oral Cancer on Preventing and Screen-ing Committee ; Min RUAN ; Nannan HAN ; Changming AN ; Chao CHEN ; Chuanjun CHEN ; Minjun DONG ; Wei HAN ; Jinsong HOU ; Jun HOU ; Zhiquan HUANG ; Chao LI ; Siyi LI ; Bing LIU ; Fayu LIU ; Xiaozhi LV ; Zheng-Hua LV ; Guoxin REN ; Xiaofeng SHAN ; Zhengjun SHANG ; Shuyang SUN ; Tong JI ; Chuanzheng SUN ; Guowen SUN ; Hao TIAN ; Yuanyin WANG ; Yueping WANG ; Shuxin WEN ; Wei WU ; Jinhai YE ; Di YU ; Chunye ZHANG ; Kai ZHANG ; Ming ZHANG ; Sheng ZHANG ; Jiawei ZHENG ; Xuan ZHOU ; Yu ZHOU ; Guopei ZHU ; Ling ZHU ; Susheng MIAO ; Yue HE ; Jugao FANG ; Chenping ZHANG ; Zhiyuan ZHANG
Journal of Prevention and Treatment for Stomatological Diseases 2024;32(11):821-833
With the increasing proportion of human papilloma virus(HPV)infection in the pathogenic factors of oro-pharyngeal cancer,a series of changes have occurred in the surgical treatment.While the treatment mode has been im-proved,there are still many problems,including the inconsistency between diagnosis and treatment modes,the lack of popularization of reconstruction technology,the imperfect post-treatment rehabilitation system,and the lack of effective preventive measures.Especially in terms of treatment mode for early oropharyngeal cancer,there is no unified conclu-sion whether it is surgery alone or radiotherapy alone,and whether robotic minimally invasive surgery has better func-tional protection than radiotherapy.For advanced oropharyngeal cancer,there is greater controversy over the treatment mode.It is still unclear whether to adopt a non-surgical treatment mode of synchronous chemoradiotherapy or induction chemotherapy combined with synchronous chemoradiotherapy,or a treatment mode of surgery combined with postopera-tive chemoradiotherapy.In order to standardize the surgical treatment of oropharyngeal cancer in China and clarify the indications for surgical treatment of oropharyngeal cancer,this expert consensus,based on the characteristics and treat-ment status of oropharyngeal cancer in China and combined with the international latest theories and practices,forms consensus opinions in multiple aspects of preoperative evaluation,surgical indication determination,primary tumor re-section,neck lymph node dissection,postoperative defect repair,postoperative complication management prognosis and follow-up of oropharyngeal cancer patients.The key points include:① Before the treatment of oropharyngeal cancer,the expression of P16 protein should be detected to clarify HPV status;② Perform enhanced magnetic resonance imaging of the maxillofacial region before surgery to evaluate the invasion of oropharyngeal cancer and guide precise surgical resec-tion of oropharyngeal cancer.Evaluating mouth opening and airway status is crucial for surgical approach decisions and postoperative risk prediction;③ For oropharyngeal cancer patients who have to undergo major surgery and cannot eat for one to two months,it is recommended to undergo percutaneous endoscopic gastrostomy before surgery to effectively improve their nutritional intake during treatment;④ Early-stage oropharyngeal cancer patients may opt for either sur-gery alone or radiation therapy alone.For intermediate and advanced stages,HPV-related oropharyngeal cancer general-ly prioritizes radiation therapy,with concurrent chemotherapy considered based on tumor staging.Surgical treatment is recommended as the first choice for HPV unrelated oropharyngeal squamous cell carcinoma(including primary and re-current)and recurrent HPV related oropharyngeal squamous cell carcinoma after radiotherapy and chemotherapy;⑤ For primary exogenous T1-2 oropharyngeal cancer,direct surgery through the oral approach or da Vinci robotic sur-gery is preferred.For T3-4 patients with advanced oropharyngeal cancer,it is recommended to use temporary mandibu-lectomy approach and lateral pharyngotomy approach for surgery as appropriate;⑥ For cT1-2N0 oropharyngeal cancer patients with tumor invasion depth>3 mm and cT3-4N0 HPV unrelated oropharyngeal cancer patients,selective neck dissection of levels ⅠB to Ⅳ is recommended.For cN+HPV unrelated oropharyngeal cancer patients,therapeutic neck dissection in regions Ⅰ-Ⅴ is advised;⑦ If PET-CT scan at 12 or more weeks after completion of radiation shows intense FDG uptake in any node,or imaging suggests continuous enlargement of lymph nodes,the patient should undergo neck dissection;⑧ For patients with suspected extracapsular invasion preoperatively,lymph node dissection should include removal of surrounding muscle and adipose connective tissue;⑨ The reconstruction of oropharyngeal cancer defects should follow the principle of reconstruction steps,with priority given to adjacent flaps,followed by distal pedicled flaps,and finally free flaps.The anterolateral thigh flap with abundant tissue can be used as the preferred flap for large-scale postoperative defects.
4.Effect of JAK2/STAT3 pathway on chemotherapy sensitivity in head and neck squamous cell carcinoma
Sun MENGYU ; Liu CHAO ; Xing BOFAN ; Wu HAN ; Ren YU ; Zhou XUAN
Chinese Journal of Clinical Oncology 2024;51(19):1009-1015
Objective:We examined the levels of Janus kinase 2(JAK2)/signal transducer and activator of transcription 3(STAT3)signaling in head and neck squamous cell carcinoma(HNSCC)and their influence on chemotherapy sensitization.Methods:Sixty patients with HNSCC who were treated at Tianjin Medical University Cancer Institute&Hospital,between January 2018 and December 2022,were included in the study.Levels of expressed JAK2,p-STAT3Y705,c-Myc,and Ki-67 in HNSCC tissues were evaluated using immunohistochemical staining,and correlation analysis was performed.The viability of UM-SCC1 cells treated with fedratinib,a JAK2 inhibitor,combined with cisplatin(DDP)and paclitaxel(PTX)was determined using the CCK8 assay.Western blot was performed to detect p-STAT3Y705 expression in tumor tissues and HNSCC cell lines.SCC15 and UM-SCC1 cell lines stably transfected with JAK2 or STAT3 vectors were constructed and verified.Cell activity and cell proliferation capacity were measured to evaluate the detrimental impact of STAT3 overexpression on chemotherapy with fedratinib using Western blot,CCK8,and plate cloning assays.Results:JAK2 expression in HNSCC positively correlated with p-STAT3Y705(r=0.43,P<0.000 1)and c-Myc(r=0.48,P<0.01)expression.High p-STAT3Y705 expression positively correlated with AJCC stage(P<0.000 1)and Ki-67 expression(P<0.05).High STAT3 and p-STAT3 levels were associated with poor prognosis in patients with HNSCC.In vitro,the JAK2 inhibitor fedratinib inhibited HNSCC cell proliferation and enhanced tumor cell sensitivity to DDP and PTX.JAK2 activation promotes STAT3 phosphorylation,and STAT3 overexpression reverses the effects of fedratinib on HNSCC sensitivity to chemotherapy.Conclusions:JAK2/STAT3 signaling is elev-ated in patients with HNSCC.Targeting the JAK2/STAT3 pathway is a potential method for increasing the sensitivity of HNSCC to chemotherapy.
5.Research progress on antiviral effects of immunosuppressants
Xi-Li FENG ; Xuan-Ye YANG ; Xin-Yan HU ; Ming-Yang GAO ; Yu-Hu WU ; Zhong-Ren MA ; Jian-Hua ZHOU
Chinese Journal of Infection Control 2024;23(9):1184-1191
Immmunosuppressants are mainly used to reduce rejection after solid organ transplantation,so as to improve the success rate of organ transplantation.However,long-term use of immunosuppressants can also serious-ly impair the immune function of patients,thereby increasing the risk of viral infection and postoperative complica-tions,leading to transplant failure.Therefore,patients need to use both immunosuppressants and antiviral agents.If some immunosuppressants with antiviral effects are found,the patient's burden of taking medicines will be greatly reduced.Currently,the immunosuppressants with antiviral effect have been focused by researchers.The gradual re-vealing of the antiviral mechanism of these immunosuppressants will help to optimize the treatment plan of postope-rative rehabilitation of organ transplant recipients.Based on the mechanism of rejection of transplanted organ,this paper systematically describes the types of viruses which closely related to infection of organ transplant patients and the molecular mechanism of some immunosuppressants in antiviral aspects,which further provides a new idea for clinical prevention and treatment of viral infection due to organ transplantation.
6.Establishment of a Rat Model of Hypotension Induced by Reserpine.
Xuan ZHANG ; Ci WANG ; Ze-Yu ZHANG ; Pei-Pei ZHANG ; Qiu'an REN ; Xian-Liang WANG ; Jing-Yuan MAO
Acta Academiae Medicinae Sinicae 2023;45(4):533-540
Objective To determine the optimal dosage and intervention duration of reserpine to establish a rat model of hypotension.Methods According to the body weight and systolic blood pressure (SBP),60 male Wistar rats were assigned to six groups (n=10),including a control group and five observation groups with different doses.The control group was administrated with 10 ml/kg 0.5% sodium carboxymethyl cellulose solution,and the observation groups with 0.016,0.032,0.064,0.128,and 0.160 mg/kg reserpine suspensions,respectively.All the groups were administrated by gavage twice a day,and the body weights of rats were monitored daily.SBP and heart rate (HR) were measured before modeling and 1-6 weeks after administration.After 6 weeks of administration,the blood samples of inner canthus were collected.The levels of lactate dehydrogenase (LDH),creatine kinase MB isoenzyme (CK-MB),alanine aminotransferase,aspartate aminotransferase (AST),serum creatinine,and blood urea nitrogen (BUN) were measured by an autoanalyzer.Three rats in each group were randomly selected for observation of the changes in SBP after drug withdrawal and the rest rats were sacrificed for measurement of the levels of norepinephrine and dopamine in the brain.Results Compared with the control group,different doses of reserpine lowered the SBP of rats (F=28.492,P<0.001).The decline in SBP increased in a concentration-dependent manner.SBP reached the lowest value after 1 week,rose slightly later,and was stable after 3 weeks of administration.There was no significant difference in SBP between 0.016 mg/kg reserpine group and the control group after the 5th week (P>0.05).The SBP levels of rats in 0.032,0.064,0.128,and 0.160 mg/kg reserpine groups showed no significant difference between each other (P=0.204) and were lower than that in the control group (all P<0.001).One week after drug withdrawal,the SBP of rats in the observation groups rose to the baseline level and remained stable.HR showed similar changes among groups,first increasing and then decreasing.There was no significant difference in HR among different groups at the same time point (F=0.922,P=0.475).Compared with the control group,reserpine of different doses reduced the norepinephrine content in the hippocampus (all P<0.001),and 0.128 mg/kg (P=0.045) and 0.160 mg/kg (P=0.042) reserpine lowered the dopamine level in the striatum,which showed no significant differences between different reserpine groups(P=0.343,P=0.301).The levels of LDH,CK-MB,and BUN in the serum increased with the increase in reserpine concentration,and the levels of LDH (P=0.001),CK-MB (P=0.020),AST (P=0.007),and BUN (P=0.001) in the 0.160 mg/kg reserpine group were significantly different from those in the control group.Conclusions The rat model of hypotension can be induced by gavage with reserpine.The gavage with reserpine at a dose of 0.032 mg/kg,twice a day for three consecutive weeks is the optimal scheme for the modeling.After the model establishment,continuous administration is essential to maintain the hypotension.
Male
;
Rats
;
Animals
;
Reserpine
;
Dopamine
;
Rats, Wistar
;
Hypotension/chemically induced*
;
Norepinephrine
7.Microsurgical thinned anterolateral thigh perforator flap to repair soft tissue defects of foot and ankle.
Rong-Yu LAN ; Ji-Yong JIANG ; Tian YU ; Wei-Hua ZHANG ; Lin-Xuan HAN ; Xiao-Ping REN
China Journal of Orthopaedics and Traumatology 2023;36(8):701-707
OBJECTIVE:
To explore method and clinical effect of microsurgical thinned anterolateral thigh perforator flap to repair soft tissue defects of foot and ankle.
METHODS:
From March 2017 to January 2022, totally 20 patients with soft tissue defects of ankle joint were treated with micro-thinning anterolateral perforator flap for free transplantation, included 13 males and 7 females, aged from 22 to 58 years old with an average of (36.45±12.36) years old. The size of flap ranged from 8.0 cm×5.0 cm to 20.0 cm×12.0 cm. Before operation, perforating vessels on the anterolateral thigh region were detected and marked with a portable Doppler detector. For the defect width less than 8 cm, 11 patients were repaired with a single flap. For the defect width more than 8 cm, the wound could not be sutured directly, and the lobulated flap technique was used in 9 patients, the width was converted to length, and the donor site was closed directly. Under the microscope, all flaps were thinened in a stepwise manner from the center of the pedicle to the periphery. After operation, survival of the flap, the shape, texture, sensory function recovery were observes, and recovery of foot function was evaluated by Maryland foot function evaluation standard.
RESULTS:
All 20 patients with microsurgical thinned anterolateral thigh perforator flaps were survived. Venous crisis occurred in 1 patient due to subcutaneous hematoma, after removal of the hematoma, the crisis was relieved and the flap survived successfully. The wounds in the donor and recipient sites healed well, and only linear scars left in the donor sites. Twenty patients were followed up for 3 to 26 months after operation, good shape of flaps without bloated, and good texture. The two-point discrimination of free flaps ranged from 9.0 to 16.0 mm, and the protective sensation was restored. The ankle flexion and extension function recovered well and patients could walk normally. According to Maryland foot function evaluation standard, 8 patients got excellent result, 10 patients good and 2 middle.
CONCLUSION
Microsurgical thinned anterolateral thigh perforator flap is an ideal method to repair soft tissue defects in functional area of foot and ankle, with good appearance and texture of the flap, no need for re-plastic surgery, reduced hospitalization costs, and less donor site damage.
Female
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Male
;
Humans
;
Young Adult
;
Adult
;
Middle Aged
;
Ankle/surgery*
;
Thigh/surgery*
;
Ankle Joint
;
Perforator Flap
;
Hematoma
8. GPER inhibitor increases tamoxifen-induced apoptosis in T-47DTR-resistant cells
Min-Qin ZHANG ; Min ZHANG ; Min-Qin ZHANG ; Yu-Xuan SONG ; Shuang-Qin FAN ; Shuang REN ; Yue ZHANG ; Yan CHEN ; Xiang-Chun SHEN ; Tong-Zheng LIU ; Min ZHANG
Chinese Pharmacological Bulletin 2023;39(1):96-100
Aim To study the effect of G protein-coupled estrogen receptor(GPER)inhibitor G15 on the sensitivity of breast cancer tamoxifen-resistant cells to T-47DTR. Methods Experiments were carried out with 4-hydroxytamoxifen(4-OHT),the active form of tamoxifen in vivo. The sensitivity of tamoxifen-resistant breast cancer cell line T-47DTR and its parental cell line T-47D to tamoxifen was detected by MTT assay; the expression of GPER protein was analyzed by plasma separation of inhibitor G15; the effect of 4-OHT combined with G15 on the apoptosis of T-47DTR cells was analyzed by flow cytometry AnnexinV-FITC/PI double staining; the expression levels of apoptosis-related proteins Bax,Bcl-2,caspase-3,cleaved caspase-3,caspase-9,cleaved caspase-9 were analysed by Western blot. Results(1)Compared with the parental cell T-47D,the resistance of T-47DTR-resistant cells to 4-OHT was significantly enhanced.(2)When 4-OHT(2 μmol·L-1)was administered,the membrane distribution of GPER increased,indicating that GPER was activated in T-47DTR-resistant cells compared with the control group; Compared with OHT,the use of G15(5 μmol·L-1)and OHT significantly reduced the expression of GPER.(3)GPER inhibitor G15 could increase the apoptotic rate of T-47DTR-resistant cells while down-regulating the anti-apoptotic protein Bcl-2 and up-regulating the expression of pro-apoptotic proteins Bax,cleaved caspase-3,cleaved caspase-9. Conclusions The GPER inhibitor G15 increases the apoptosis of T-47DTR cells and restores the sensitivity of drug-resistant cells to tamoxifen.
9.A case report on irritable bowel syndrome treated with low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet
Yutang REN ; Ruifeng WANG ; Xutong YU ; Xuan JIANG ; Xiaojuan GUO ; Xueru HUO ; Xiaofang YING ; Qiuxiang LU ; Bo JIANG
Chinese Journal of Clinical Nutrition 2023;31(2):113-116
Irritable bowel syndrome (IBS) is characterized by abdominal pain associated with changes in defecation frequency and blood folate level. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. High-FODMAP diet could elicit or exacerbate IBS-associated bowel symptoms, which is inadequately recognized among gastroenterologists in China. Here we report an IBS case, focusing on the association between high-FODMAP diet and bowel symptoms and the intervention of low-FODMAP diet.
10.Investigation on 90Sr and 137Cs activity concentrations in water in Hangzhou urban area from 2012 to 2020
Peng WANG ; Yiyao CAO ; Hong REN ; Lei ZHOU ; Hua ZOU ; Shunfei YU ; Yaoxian ZHAO ; Zhongjun LAI ; Zhiqiang XUAN
Chinese Journal of Radiological Medicine and Protection 2023;43(8):627-632
Objective:To investigate the activity concentrations of 90Sr and 137Cs in water in Hangzhou urban area. Methods:From 2012 to 2020, Qiantang River water as an important drinking water source, tap water as direct drinking water for residents, and West Lake water in tourists crowded area were selected forwater quality monitoring with respect to conctnts of 90Sr and 137Cs. The activity concentrations of 90Sr and 137Cs in water samples, as collected in wet and dry seasons resepectively, were determined by radiochemical analysis, with the 137Cs to 90Sr activity ratios obtained. Results:From 2012 to 2020, the activity concentrations of 90Sr and 137Cs in tap water were (2.0±1.1) - (7.4±0.4) mBq/L and (0.45±0.06) - (7.1±0.6) mBq/L, respectively. The 137Cs to 90Sr activity ratios ranged from 0.07 to 2.40. The activity concentrations of 90Sr and 137Cs in Qiantang River were (3.7±1.1) - (17.0±4.4) mBq/L and (0.28±0.01) - (15.0±4.5) mBq/L, respectively. The 137Cs to 90Sr activity ratios ranged from 0.03 to 0.90. The activity concentrations of 90Sr and 137Cs in West Lake water were (2.2±0.5) - (11.0±2.0) mBq/L and (0.32±0.04) - (7.9±1.9) mBq/L, respectively. The 137Cs to 90Sr activity ratios ranged from 0.05 to 1.20. Conclusions:The activity concentrations of 90Sr and 137Cs in water in Hangzhou urban area were at the background levels, lower than the concentration limits, 10 Bq/L both for 90Sr and 137Cs recommended by WHO in the 4 th edition of Guidelines for Drinking Water Quality.


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