The effect of dibromo-dulcitol,diepoxy-dulcitol and various new cytostatic hexitol derivatives on the metabolic activities of nucleic acids and proteins—II

The effects of nine antiblastic, 1,6-disubstituted hexitol derivatives were compared on DNA, RNA and protein synthesis. Each compound reduced ¹⁴C-thymidine incorporation into the DNA in surviving rabbit bone marrow cell culture, in vitro. The rate of inhibition increased as a function of incubation time with the compounds and of their concentration. Among the hexitol skeletons carrying identical substituents dulcitol (galactitol) proved to be the most effective, D-mannitol was less and D-sorbitol the least effective. Comparing the reactive functional groups carried by identical hexitol skeletons, the dianhydride (diepoxide) derivatives were the most effective, dibromo derivatives were less and dimethanesulphonyloxy (dimesyl) derivatives the least effective. The inhibition of DNA synthesis by diiodo-D-sorbitol was anomalously strong. At higher concentrations the hexitols reduced precursor incorporation into RNA and protein of human tonsillar cells, in vitro. At relatively low concentration and short incubation times, however, enhancement could be observed. A good correlation was established between the rate of inhibition of DNA synthesis and the cytotoxic effect. Since the dianhydride derivative of hexitol was always more effective than its corresponding dibromo-or dimethane-sulphonyloxy derivative, the anhydrides may have formed from the latter in vivo and these are probably responsible for a large portion of the cytotoxic effect. The various hexitols, especially, dibromodulcitol and dianhydro-dulcitol, used with success in clinical practice have different properties in vivo (transport, transformation, target). In addition to DNA, the nuclear proteins may also be an important target site.     

Detailed sorption isotherms of pentachlorophenol on soils and its correlation with soil properties

Insight into the sorption mechanism of pentachlorophenol (PCP) was gained by constructing highly detailed isotherms over the widest possible concentration range. Using the dual-mode model, sorption isotherms of PCP were accurately predicted, the sorption capacities were determined, and the mechanisms of adsorption (hole-filling) and partitioning were elucidated. Sorption-desorption hysteresis in the present study was manifested to some significant degree in 10 soils with different properties. Such hysteresis might result from the pore deformation and entrapment of PCP molecules within organic matter. Total nitrogen in soils also has its contribution in these kinds of processes. Correlations of stepwise regression equations obtained confirm that pH, soil organic carbon and organic carbon fractions, and particle size distribution are the main factors responsible for the sorption and desorption hysteresis processes. These factors worked in concert in influencing the fate of PCP sorption-desorption in soil. The empirical models developed in this study accurately predict PCP sorption and desorption hysteresis phenomena for the soils that were investigated.     

Human dental plaque microcosm biofilms: effect of nutrient variation on calcium phosphate deposition and growth

Plaque mineralisation is a multi-factorial process involving plaque pH, nucleation, inhibitors and promotors. It is poorly understood because of its complexity. OBJECTIVE: To establish the effects of amino acids and peptones in the simulated oral fluid BMM, a saliva analogue DMM and modifications of these on mineral deposition into dental plaque biofilm microcosms. METHODS: Microcosms were cultured for up to 35 days in an Artificial Mouth pulsed with sucrose, followed by 10 days periodic treatment with a pH 5.0 calcium-phosphate-monofluorophosphate-urea solution (CPMU). RESULTS: Initial biofilm doubling times were 3-7h, which then slowed and varied under the different nutrient conditions although their pH behaviour was similar. In BMM, mineral deposition was 20% that of DMM, but removal of BMM peptones increased deposition 12-fold. Substitution of the amino acids in DMM by casein did not affect deposition levels, but their removal leaving mucin the sole macronutrient, increased mineral deposition three-fold, reaching 40 mmol Ca/g protein. CONCLUSIONS: These substantial increases in mineral deposition when the macronutrient concentration is reduced indicates probable changes in the nucleating, inhibitory and Ca-binding properties of the simulated oral fluids themselves and/or changes in the plaque microbiota and their crystal nucleators and inhibitors.     

Mechanisms of permanent loss of olfactory receptor neurons induced by the herbicide 2,6-dichlorobenzonitrile: Effects on stem cells and noninvolvement of acute induction of the inflammatory cytokine IL-6

We explored the mechanisms underlying the differential effects of two olfactory toxicants, the herbicide 2,6-dichlorobenzonitrile (DCBN) and the anti-thyroid drug methimazole (MMZ), on olfactory receptor neuron (ORN) regeneration in mouse olfactory epithelium (OE). DCBN, but not MMZ, induced inflammation-like pathological changes in OE, and DCBN increased interleukin IL-6 levels in nasal-wash fluid to much greater magnitude and duration than did MMZ. At 24 h after DCBN injection, the population of horizontal basal cells (HBCs; reserve, normally quiescent OE stem cells) lining the DMM became severely depleted as some of them detached from the basal lamina, and sloughed into the nasal cavity along with the globose basal cells (GBCs; heterogeneous population of stem and progenitor cells), neurons, and sustentacular cells of the neuroepithelium. In contrast, the layer of HBCs remained intact in MMZ-treated mice, as only the mature elements of the neuroepithelium were shed. Despite the respiratory metaplasia accompanying the greater severity of the DCBN lesion, residual HBCs that survived intoxication were activated by the injury and contributed to the metaplastic respiratory epithelium, as shown by tracing their descendants in a K5CreEr^T2::fl(stop)TdTomato strain of mice in which recombination causes HBCs to express TdTomato in advance of the lesion. But, contrary to published observations with MMZ, the HBCs failed to form ORNs. A role for IL-6 in suppressing ORN regeneration in DCBN-treated mice was rejected by the failure of the anti-inflammatory drug dexamethasone to prevent the subsequent respiratory metaplasia in the DMM, suggesting that other factors lead to HBC neuro-incompetence.     

四川省2家二甲氧基甲烷生产企业职业流行病学调查及职业接触限值的验证

目的了解工作场所中二甲氧基甲烷（DMM）暴露情况与职业人群健康状况,验证美国政府工业卫生学家协会（ACGIH）推荐的DMM职业接触限值是否适用于我国的用人单位。方法对生产企业进行职业流行病学调查,并检测工作场所空气中DMM的浓度,同时对两组人群（暴露组与对照组）进行职业健康检查、自觉症状问卷调查,分析暴露人群的健康危害。结果采集的165份空气样品中,有14份样品高于拟引进限值（3100mg／m2）,主要分布在灌装岗位。企业现有的职业防护措施可以保护大多数职业人群健康,但有8．33％的接触者存在不同程度呼吸道和皮肤黏膜刺激症状,高暴露组异常检出率高于对照组。结论建议工作场所空气中DMM的时间加权平均容许浓度（PC-TWA）定为3100mg／m2,在此阈值工作环境下,我国的DMM作业人群可以得到有效、可行的健康保护。     

Effective knock down of matrix metalloproteinase‐13 by an intra‐articular injection of small interfering RNA (siRNA) in a murine surgically‐induced osteoarthritis model

This study investigated the effect of MMP‐13 gene knock down on cartilage degradation by injecting small interfering RNA (siRNA) into knee joints in a mouse model of osteoarthritis (OA). OA was induced in male C57BL/6 mice by destabilization of medial meniscus (DMM) surgery. Change of Mmp13 expression over time was determined by qPCR analysis from 3 days to 6 weeks after surgery. Mmp13 and control chemically modified siRNA were injected into the knee joint 1 week after surgery and expression levels were assessed in synovium by qPCR 48 h later. Cartilage degradation was histologically assessed 8 weeks after DMM surgery according to OARSI recommendations. Mmp13 expression levels were elevated 1 week after surgery and peaked at 77 fold at 2 weeks compared to expression at 3 days. A 55% decrease of Mmp13 levels in cartilage was observed 48 h after injection of Mmp13 siRNA (p = 0.05). Significant reduction in the histological score at 8 weeks after surgery was observed in the Mmp13 siRNA‐treated group compared to the control siRNA group (p < 0.001). Intra‐articular injection of Mmp13 siRNA at the early phase of OA development resulted in effective knock down of Mmp13 expression and delay in cartilage degradation in vivo. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1175–1180, 2014.     

EGFR Signaling Is Required for Maintaining Adult Cartilage Homeostasis and Attenuating Osteoarthritis Progression

The uppermost superficial zone of articular cartilage is the first line of defense against the initiation of osteoarthritis (OA). We previously used Col2-Cre to demonstrate that epidermal growth factor receptor (EGFR), a tyrosine kinase receptor, plays an essential role in maintaining superficial chondrocytes during articular cartilage development. Here, we showed that EGFR activity in the articular cartilage decreased as mice age. In mouse and human OA samples, EGFR activity was initially reduced at the superficial layer and then resurged in cell clusters within the middle and deep zone in late OA. To investigate the role of EGFR signaling in postnatal and adult cartilage, we constructed an inducible mouse model with cartilage-specific EGFR inactivation (Aggrecan-CreER Egfr^Wa5/flox, Egfr iCKO). EdU incorporation revealed that postnatal Egfr iCKO mice contained fewer slow-cycling cells than controls. EGFR deficiency induced at 3 months of age reduced cartilage thickness and diminished superficial chondrocytes, in parallel to alterations in lubricin production, cell proliferation, and survival. Furthermore, male Egfr iCKO mice developed much more severe OA phenotypes, including cartilage erosion, subchondral bone plate thickening, cartilage degeneration at the lateral site, and mechanical allodynia, after receiving destabilization of the medial meniscus (DMM) surgery. Similar OA phenotypes were also observed in female iCKO mice. Moreover, tamoxifen injections of iCKO mice at 1 month post-surgery accelerated OA development 2 months later. In summary, our data demonstrated that chondrogenic EGFR signaling maintains postnatal slow-cycling cells and plays a critical role in adult cartilage homeostasis and OA progression. © 2022 American Society for Bone and Mineral Research (ASBMR).     

Platelet-derived growth factor receptor-β (PDGFRβ) lineage tracing highlights perivascular cell to myofibroblast transdifferentiation during post-traumatic osteoarthritis

Pericytes ubiquitously surround capillaries and microvessels within vascularized tissues and have diverse functions after tissue injury. In addition to regulation of angiogenesis and tissue regeneration after injury, pericytes also contribute to organ fibrosis. Destabilization of the medial meniscus (DMM) phenocopies post-traumatic osteoarthritis, yet little is known regarding the impact of DMM surgery on knee joint-associated pericytes and their cellular descendants. Here, inducible platelet-derived growth factor receptor-β (PDGFRβ)-CreER^T2 reporter mice were subjected to DMM surgery, and lineage tracing studies performed over an 8-week period. Results showed that at baseline PDGFRβ reporter activity highlights abluminal perivascular cells within synovial and infrapatellar fat pad (IFP) tissues. DMM induces a temporospatially patterned increase in vascular density within synovial and subsynovial tissues. Marked vasculogenesis within IFP was accompanied by expansion of PDGFRβ reporter⁺ perivascular cell numbers, detachment of mGFP⁺ descendants from vessel walls, and aberrant adoption of myofibroblastic markers among mGFP⁺ cells including α-SMA, ED-A, and TGF-β1. At later timepoints, fibrotic changes and vascular maturation occurred within subsynovial tissues, with the redistribution of PDGFRβ⁺ cellular descendants back to their perivascular niche. In sum, PDGFRβ lineage tracing allows for tracing of perivascular cell fate within the diarthrodial joint. Further, destabilization of the joint induces vascular and fibrogenic changes of the IFP accompanied by perivascular to myofibroblast transdifferentiation.