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Carrier Screening For Inherited Genetic Conditions
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
Whitney Bender, Lorraine Dugoff
Clinical features: This disorder is caused by a deficiency of 7-dehydrocholesterol reductase. Smith-Lemli-Opitz syndrome has been associated with low maternal serum unconjugated estriol levels less than 0.25 MoM on second-trimester maternal serum screening. The clinical manifestations of this disorder include intellectual disability, poor growth, and characteristic phenotypic abnormalities, including microcephaly, characteristic facies, hypospadias, and polysyndactyly.
Diagnosis and Treatment Model of the COVID-19 Rehabilitation Unit
Published in Wenguang Xia, Xiaolin Huang, Rehabilitation from COVID-19, 2021
Osteoporosis (OP) is a bone metabolism disease caused by the loss of bone matrix and minerals. It causes a decrease in bone strength and an increase in brittleness. Even minor trauma can cause fractures. COVID-19 patients believe that long-term bed rest is the best way for recovering from the disease due to the reduced space for activities in the isolation ward or the lack of understanding of the disease. This misunderstanding causes patients to stay in bed for a long time. Patients’ bones lack stimulations, such as weight-bearing, center of gravity, and muscle activity, which gradually leads to bone loss and degeneration of the fibrous structure of bone tissue. Due to the long-term lack of sunlight in the isolation ward, 7-dehydrocholesterol in the human body cannot be converted into vitamin D3, which affects calcium absorption and bone mineralization disorders. Moreover, long-term inactivity affects the patient’s endocrine system and increases calcium excretion in the urine. All of the above further aggravate the patient’s osteoporosis. Patients with disuse osteoporosis caused by immobilization can lose 30%–40% of their total bone mass in a relatively short period. Therefore, prevention is more important than treatment for OP.
Basic Principles in Photomedicine and Photochemistry
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
Skin contains many chromophores absorbing in the visible and UV range. Some, but not all, initiate photobiological responses after absorbing a photon of light. DNA is most important chromophore for photobiological responses in the UVB range (Fig. 3). Aromatic amino acids in proteins, especially tryptophan, also absorb UVB radiation but usually do not initiate biological responses. However, absorption of photons by aromatic amino acids in the stratum corneum is important in photomedicine because this process removes a large amount of the UVB radiation before it reaches the DNA in viable cells. Thus, absorption by the stratum corneum is an important protective factor against UVB effects on skin. Carbohydrates do not absorb above about 240 nm and, therefore, are not chromophores in cutaneous responses to biologically relevant wavelengths. The double bonds in unsaturated fatty acids such as arachidonic acid are not conjugated and do not absorb in the UVB range. 7-Dehydrocholesterol contains conjugated double bonds and, after absorbing UVB radiation, is converted to previtamin D3. Urocanic acid in the epidermis absorbs in the UVB range and is a possible chromophore for certain effects of UV radiation on the immune system. The crosslinking amino acid derivatives, pyridinoline (in collagen) and desmosine (in elastin) in the dermis, also absorb UVB radiation but are not known to initiate photobiological responses. The cofactors nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD) absorb in the UVA range and may be chromophores for certain responses to UVA.
1,25-Dihydroxvitamin D3 attenuates the damage of human immortalised keratinocytes caused by Ultraviolet-B
Published in Cutaneous and Ocular Toxicology, 2023
Pingwei Wang, Dongge Liu, Jiajing Cui, Shuqi Yan, Yujun Liang, Qianqian Chen, Yanping Liu, Shuping Ren, Peng Chen
Vitamin D is initially produced in the skin from 7-dehydrocholesterol conversion mediated by UVB radiation. The product of that conversion, cholecalciferol (vitamin D3) requires further stepwise hydroxylations-first in the liver, where it is converted to 25(OH)D [25,26], and then in the kidney to produce 1,25(OH)2D3 [27–29]. Vitamin D has a variety of physiological functions in the skin, regulating cell growth, differentiation and immune response, as well as having a protective effect on skin cells [30]. The active metabolites of vitamin D modulate the proliferation and differentiation of keratinocytes, thereby skin physiology is closely associated with the production of vitamin D and its activities [31]. HaCaT cells maintain intact epidermal differentiation and are non-tumorigenic, making them a good model for studying skin cell damage because of their similarity to the differentiation of normal keratin-forming cells [32,33].
Overview of gene expression techniques with an emphasis on vitamin D related studies
Published in Current Medical Research and Opinion, 2023
Jeffrey Justin Margret, Sushil K. Jain
Vitamin D, often called the sunshine vitamin, is a vital nutrient required for maintaining healthy bones and teeth; in addition, it reduces the risk of various chronic diseases. Vitamin D, which belongs to the family of fat-soluble vitamins, can be synthesized in skin exposed to sunlight and can also be acquired from the diet56. Vitamin D2 (ergocalciferol) can be obtained from plant food sources and vitamin D3 (cholecalciferol) from animal sources. UVB rays from sunlight stimulate the photolytic reaction that converts 7-dehydrocholesterol to pre-vitamin D3 and through subsequent thermal isomerization to vitamin D357. Both vitamin D2 and vitamin D3 are biologically inactive; in the liver, they undergo 25-hydrozylation to form 25-hydroxyvitamin D3 [25(OH)D]. This major storage form has a half-life of 2–3 weeks. Further 25(OH)D is converted into 1,25-dihydroxyvitamin D [1,25(OH)2D] in the proximal tubules of the kidney by the enzyme 1-α-hydroxylase58. 1,25(OH)2D (calcitriol), the active form of vitamin D, utilizes its physiologic functions in the target tissue by regulating gene expression59.
Effects of Vitamin D Analogs Alfacalcidol and Calcitriol on Cell Proliferation and Migration of HEC1A Endometrial Adenocarcinoma Cells
Published in Nutrition and Cancer, 2021
İbrahim Duman, R. Nalan Tiftik, İsmail Ün
Vitamin D is actually a secosteroid hormone and its classically known effects are on the mechanism of calcium and phosphate (9, 10). Besides this basic function, vitamin D also regulates cell growth and neuromuscular functions (11, 12). Vitamin D could be taken both as diet and produce endogenously in the body. As a result of exposure of the epidermis to the ultraviolet B rays in sunlight, 7-dehydrocholesterol, the precursor of the skin, is converted into cholecalciferol. Then cholecalciferol is hydroxylated to 25-dihydroxyvitamin D in the liver. This form goes to the kidney via the bloodstream and is re-hydroxylated to 1.25(OH)2D calcitriol that is known as the active form of vitamin D (13, 14). It has been shown that vitamin D receptor is expressed in the ovarian tissue, endometrium, fallopian epithelial cells, decidua and placenta (11, 15).