Mammalian growth plate, also known as epiphyseal plate or physis, is highly specialized mesodermderived cartilaginous structure. It develops in the bone bud, secondary to presence of the primary ossification centers and is responsible for bone elongation. The plates are formed by numerous cells that rapidly divide and mature. Post puberty, the epiphyseal cartilage cell division decreases, bone completely replaces cartilage, and the epiphyseal plates fuse together with primary and secondary ossification centers [1,2]. Cartilage differentiation processPresently, four major stages of chondrocyte differentiation are known, i.a., mesenchymal precursor cells (MPCs), prechondrocytes, early chondroblasts and terminally differentiated chondrocytes [1][2][3][4]. Abstract: The epiphyseal growth plate develops from the cartilaginous-orientated mesenchymal cells that express SOX family genes. This multilayer structure is formed by the proliferation and hypertrophy of cells that synthesize the extracellular matrix composed of collagen (mainly type II, IX, X, XI) and proteoglycans (aggrecan, decorin, annexin II, V and VI). The resting zone is responsible for protein synthesis and maintaining a germinal structure. In the proliferative zone, cells rapidly duplicate. The subsequent morphological changes take place in the transformation zone, divided into the upper and lower hypertrophic layers. In the degenerative zone, the mineralization process becomes intensive due to increased release of alkaline phosphate, calcium and matrix vesicles by terminally differentiated chondrocytes and some other factors e.g., metaphyseal ingrowth vessels. At this level, as well as in the primary and secondary spongiosa zones, chondrocytes undergo apoptosis and are physiologically eliminated. Unlike adult cartilage, in fetal and early formed growth plates, unusual forms such as autophagal bodies, paralysis and dark chondrocytes are also observed. Their ultrastructure differs greatly from apoptotic and normal cartilage cells. Chondrocyte proliferation and differentiation are regulated by various endocrine, paracrine, and autocrine agents such as growth, thyroid and sex hormones, beta-catenin, bone morphogenetic proteins, insulin-like growth factor, iodothyronine deiodinase, leptin, nitric oxide, transforming growth factor beta and vitamin D metabolites. However, the most significant factor is parathyroid hormone-related protein (PTHrP) which is synthesized in the perichondrium by terminally differentiated chondrocytes. Secondary to activation of PTH/PTHrP receptors, PTHrP stimulates cell proliferation by G protein activation and delays their transformation into prehypertrophic and hypertrophic chondrocytes. When proliferation is completed, chondrocytes release Indian hedgehog (Ihh), which stimulates PTHrP synthesis via a feedback loop. Any disturbances of the epiphyseal development and its physiology result in various skeletal abnormalities known as dysplasia.
NADPH-cytochrome P-450 reductase (P-450 reductase) plays a crucial role in the metabolism of many endogenic compounds and xenobiotics detoxication. The enzyme is also involved in the toxicity of some clinically important antitumour drugs (doxorubicin) and pesticides (paraquat). P-450 reductase activates them to their more toxic metabolites via one electron reduction which triggers free radical cascade. In some cases however, such transformation is essential to produce therapeutic effect in anticancer drugs. The main purpose of the paper was to evaluate the effect of three natural compounds found in human diet: (-)-epigallocatechin gallate (EGCG), quercetin and resveratrol on P-450 reductase activity. The activity of the enzyme was determined spectrophotometrically by measurement of the rate of cytochrome c reduction at 550 nm, in vitro, using human heart, liver and lung microsomes. It was found that quercetin increased the P-450 reductase activity in human organs at all tested doses. The activity of microcosms in all organs was enhanced according to the concentrations of quercetin, which increased the activity in the order lungϾheartϾliver. Addition of EGCG to the reaction mixture enhanced the P-450 reductase activity in the following order: liverϾheartϾlung. However, no significant effect of resveratrol on P-450 reductase activity was observed. It seems that the presence of quercetin and EGCG in the diet may increase P-450 reductase activity during doxorubicin therapy with subsequent increased risk of toxicity. A beneficial effect may be obtained in anticancer therapy with bioreductive agents like tirapazamine.
Ventricular septal defects (VSDs) are common congenital abnormalities which have been reported to be associated with maternal fever and various environmental factors. The aim of the present study was to evaluate the effect of prenatal exposure to cyclooxygenase (COX) inhibitors on heart defects. A retrospective statistical analysis was performed using data collected in our laboratory during various teratological studies carried out on albino CRL:(WI)WUBR Wistar strain rats from 1997 to 2004. The observations were compared with concurrent and historic control data, as well as findings from other developmental toxicological studies with selective and nonselective COX-2 inhibitors. Despite the lack of significant differences in the frequency of VSDs between drug-exposed and control groups, statistical analysis by the two-sided Mantel-Haenszel test and historical control data showed a higher incidence of heart defects in offspring exposed to nonselective COX inhibitors (30.06/10,000). Unlike other specific inhibitors, aspirin (46.26/10,000) and ibuprofen (106.95/ 10,000) significantly increased the incidence of the VSD when compared with various control groups (5. 38-19.72/10,000). No significant differences in length or weight were detected between fetuses exposed to COX inhibitors and born with VSD and non-malformed offsprings. However, a statistically significant increase of fetal body length and decrease of body mass index were found in fetuses exposed to COX inhibitors when compared with untreated control. We conclude that prenatal exposure to COX inhibitors, especially aspirin and ibuprofen, increased the incidence of VSDs in rat offspring but was not related to fetal growth retardation.
Methanol, ethylene glycol and other alcohol intoxications are complicated by severe acidosis which could be caused by formation of metabolic acids and additionally lactic acid production. An increasing nicotinamide adenine dinucleotide reduced/nicotinamide adenine dinucleotide oxidized (NADH/NAD) ratio during alcohol biotransformation is responsible for the induction of lactic acidosis. The main purpose of the present paper was to evaluate the effect of 4-methylpyrazole, cimetidine, ethylenediaminetetraacetic acid disodium salt, ethanol and methanol on lactate dehydrogenase (E.C. 1.1.1.27) activity and to discuss this issue. The activity of the enzyme was determined spectrophotometrically, in vitro using human enzyme skeletal muscle homogenates. 4-Methylpyrazole, cimetidine and ethylenediaminetetraacetic acid disodium salt at concentrations 0.01, 0.1, 1.0 mM and 12.5, 25.0, 50.0 mM of ethanol and methanol were studied. Our results showed that cimetidine increased lactate dehydrogenase activity as compared to the control at all tested concentrations. Such activity was noted for 4-methylpyrazole at 0.1 mM and higher concentration. By contrast, no significant effect on lactate dehydrogenase activity in the presence of ethylenediaminetetraacetic acid disodium salt, methanol and ethanol was observed.
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