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1.
OBJECTIVE: To use karyometric analysis methods to compare actinic keratoses (AKs) to squamous cell carcinomas (SCCs) to determine if SCCs showed a logical progression beyond that seen in AKs and to explore variability within and between lesion types to better understand distinctions between the 2. STUDY DESIGN: Biopsies from 31 subjects with AKs were obtained from upper inner arm skin, forearm skin and AK lesions. Biopsies from 23 different subjects in a related subproject provided SCC biopsies for comparison. RESULTS: Karyometric measures of nuclear abnormality and sun damage were derived. Mean actinic damage levels progressed logically from inner arm to sun-exposed skin, to AK, to SCC. Considerable heterogeneity existed at the case level. Unsupervised learning methods revealed 2 distinct clusters of progressed lesions with different nuclear signatures, reflecting differing levels of actinic damage. Number of AKs and SCCs and invasiveness and differentiation of SCCs were distributed across both clusters in roughly equivalent proportions. CONCLUSION: Karyometric methods, shown previously to be capable of sensitively detecting subtle nuclear changes, revealed the possibility of 2 progression pathways, each containing AKs and SCCs. This finding may have prognostic implications.  相似文献   

2.
Actinic keratosis (AK) corresponds to the earliest stage of in situ squamous cell carcinoma and arises on chronically sun‐exposed skin. Around the clinically evident AKs, the apparently healthy epidermis may contain different grades of atypia that can be detected by noninvasive imaging techniques such as reflectance confocal microscopy (RCM) and optical coherence tomography (OCT). Subclinical actinic keratosis (sAK) has captured increasing interest as a potential target of field therapies. The aim of this study was to evaluate in vivo the changes in the field cancerization undergoing treatment with topical ingenol mebutate by combining RCM and OCT. Twenty patients with field cancerization of the face and scalp were treated with ingenol mebutate gel (150 mcg/g) for three consecutive days on an area of 25 cm2 containing at least two AKs, two sAKs and two apparently healthy sites. About 120 lesions were evaluated through clinical investigation and clinical, dermoscopical, RCM and OCT images at day 0, 4, 14 and 56 based on the diagnostic criteria for AKs. Main pathological features improved in both AKs and sAKs, in particular the epidermal thickness measured by OCT and the epidermal atypia graded by RCM. Local skin reactions (LSR) arose predominantly in the lesional area compared with healthy skin. A complete clearance was detected in 58% for AKs, and in 55% and 72% for sAKs measured by RCM and OCT, respectively. Both OCT and RCM allow the morphological representation of field cancerization including subclinical lesions and provide complementary information. Ingenol mebutate is effective not only in clinically evident but also in sAKs. The differences in LSR highlight the potential selectivity of the treatment.   相似文献   

3.
Merkel cell polyomavirus (MCPyV) has recently been identified in Merkel cell carcinoma (MCC), an aggressive cancer that occurs in sun-exposed skin. Conventional technologies, such as polymerase chain reaction (PCR) and immunohistochemistry, have produced conflicting results for MCPyV infections in non-MCC tumors. Therefore, we performed quantitative analyses of the MCPyV copy number in various skin tumor tissues, including MCC (n?=?9) and other sun exposure-related skin tumors (basal cell carcinoma [BCC, n?=?45], actinic keratosis [AK, n?=?52], Bowen's disease [n?=?34], seborrheic keratosis [n?=?5], primary cutaneous anaplastic large-cell lymphoma [n?=?5], malignant melanoma [n?=?5], and melanocytic nevus [n?=?6]). In a conventional PCR analysis, MCPyV DNA was detected in MCC (9 cases; 100%), BCC (1 case; 2%), and AK (3 cases; 6%). We then used digital PCR technology to estimate the absolute viral copy number per haploid human genome in these tissues. The viral copy number per haploid genome was estimated to be around 1 in most MCC tissues, and there were marked differences between the MCC (0.119-42.8) and AK (0.02-0.07) groups. PCR-positive BCC tissue showed a similar viral load as MCC tissue (0.662). Immunohistochemistry with a monoclonal antibody against the MCPyV T antigen (CM2B4) demonstrated positive nuclear localization in most of the high-viral-load tumor groups (8 of 9 MCC and 1 BCC), but not in the low-viral-load or PCR-negative tumor groups. These results demonstrated that MCPyV infection is possibly involved in a minority of sun-exposed skin tumors, including BCC and AK, and that these tumors display different modes of infection.  相似文献   

4.
OBJECTIVE: To develop numeric, statistically secured measures of chemopreventive efficacy and to derive procedures with high sensitivity of detection. STUDY DESIGN: Karyometric features were computed for nuclei from the basal cell layer of biopsies taken from sun-exposed but histologically "normal" skin. Biopsies were collected from placebo-treated subjects and subjects treated for one year with daily, oral doses of 25,000, 50,000 and 75,000 IU of vitamin A. A total of 22,600 nuclei were recorded from 113 cases, at baseline and after one year. RESULTS: Two numeric measures of chemopreventive efficacy were applied: a measure of nuclear abnormality and a measure based on discriminant function scores. Both showed statistically significant chemopreventive effects of vitamin A. Dose-response curves were derived. A novel procedure, second order discriminant analysis, resulted in very high sensitivity for the detection of change in nuclear chromatin patterns. CONCLUSION: Karyometric analysis has increased in sensitivity such that changes on the order of 10%, found in only a low percentage of nuclei in a biopsy specimen, can be reliably documented. The methodology lends itself to cost-efficient screening of compounds for chemopreventive efficacy.  相似文献   

5.
OBJECTIVE: To explore methods suitable for quantitative assessment of the efficacy of chemopreventive intervention. STUDY DESIGN: High-resolution imagery of nuclei from the suprabasal and basal cell layers of sun-damaged skin were recorded. There were 10 cases. A shave biopsy was taken from an area of clearly evident solar keratosis before and after treatment with 2-difluoromethyl-dlornithine (DFMO) and from the colateral forearm, treated with a placebo. A number of karyometric variables were computed and combined to derive marker features that provided a numeric measure of the degree of nuclear deviation from normal. RESULTS: DFMO treatment was effective overall in reducing the degree of nuclear abnormality seen in the biopsies; in 8 of the 10 cases there was a significant improvement. The placebo-treated arm did not show a statistically different abnormality from the untreated arm. CONCLUSION: Karyometric analysis can provide numeric measures that allow documentation of statistically significant regression of actinic keratotic lesions following treatment with DFMO.  相似文献   

6.
Objective:  Cytology may become the diagnostic method of choice with the advent of new non-invasive treatments for non-melanoma skin cancer, as the sampling technique for cytology entails little tissue disfiguration. The aim of this study was to compare and evaluate the diagnostic performance of scrape cytology using two different cytological staining techniques, and to evaluate additional touch imprint cytology, with that of histopathology of basal cell carcinoma (BCC) and actinic keratosis (AK).
Methods:  We investigated 50 BCC and 28 AK histologically verified lesions, from 41 and 25 patients, respectively. Two separate skin scrape samples and one touch imprint sample were taken from each lesion. The smears were stained with Papanicolaou (Pap) or May–Grünwald–Giemsa (MGG) stains. All cytological specimens were examined in random order by pathologists without knowledge of the histology. Cytodiagnostic results were compared with the histopathological report.
Results:  Scrape cytodiagnosis agreed with histopathology in 48 (Pap) and 47 (MGG) of the 50 BCC cases, and in 26 of 28 (Pap) and 21 of 26 (MGG) AK cases, yielding sensitivities of 96%, 94%, 93% and 81%, respectively. No significant difference in sensitivity between the two staining methods was found but a trend towards higher Pap sensitivity for AK was noted ( P  =   0.10). Touch imprint cytology confirmed histopathology in 38 of the 77 cases of BCC and AK.
Conclusion:  Cytological diagnosis with either Pap or MGG stain for BCC and AK is reliable, and differentiates well between BCC and AK. Imprint cytology proved to be non-diagnostic in half of the examined cases.  相似文献   

7.
Sun exposure is causal for melanoma but is subject to bias of recall so that it is difficult to dissect the role of particular patterns of sun exposure. In this hospital-based case-control study (n = 1991), we aimed to analyze pigmentation traits and signs of actinic damage at different anatomic locations as markers of melanoma risk in central European patients. Although all signs of actinic damage (freckling, wrinkling and solar lentigos) were significantly associated with melanoma risk in multivariate logistic regression models adjusting for age and sex, the strongest associations were observed for the dorsal parts of the body: adjusted odds ratios [OR] were 4.22 for wrinkling on the neck, 3.43 for solar lentigos and 3.37 for freckling on the back (all P < 0.001), respectively. These associations were independent of age, sex and pigmentation traits. Our results indicate that signs of actinic damage are predictors of melanoma risk, particularly on the back.  相似文献   

8.
Cryosurgery with liquid nitrogen is one of the most used treatments for actinic keratosis. We aimed to study the effectiveness of two consecutive sessions of cryosurgery for actinic keratosis and investigate factors associated with its therapeutic success. Hence, we conducted a longitudinal study including 92 patients of both sexes, aged 50–75 years with 5–50 actinic keratosis on the face and forearms, who underwent cryosurgery and treatment with sunscreen SPF 30, at baseline and after 120 days. The lesions were counted in duplicate by the same examiner before the start of treatment and after 120 (N = 92) and 300 days (N = 33), represented by their medians and quartiles and compared using the generalized linear mixed effects model (negative binomial). Treatment behavior was investigated in relation to sex, age, education, skin type, smoking, sun exposure at work and the use of aspirin, anti-inflammatory and angiotensin-converting enzyme inhibitors. There was a significant reduction in the actinic keratosis count on the face and forearms (p < 0.05). Our results confirmed the effectiveness of cryosurgery for actinic keratosis, with a 57% reduction in the number, and size of the lesions. Higher education levels (p = 0.02) and less sun exposure at work (p = 0.02) independently promoted a significant reduction in the actinic keratosis count. Different population groups showed characteristic responses to the treatment, which may be explained by the degree of adherence to the use of photoprotection. In two sessions, cryosurgery with liquid nitrogen reduced the actinic keratosis count.  相似文献   

9.
OBJECTIVE: To develop a reliable and valid scoring system for grading skin biopsies from actinic keratosis (AK) and sun-damaged skin for use in evaluating the efficacy of skin cancer chemopreventive agents. STUDY DESIGN: A panel of dermatopathologists developed histologic criteria and diagnostic definitions for the progression of lesions from early AK to AK. The criteria were then applied to a sample of 335 histologic slides from an ongoing chemoprevention study. A 10% sample of 35 slides was reread in order to assess intrarater reliability. RESULTS: Six of the 7 criteria demonstrated high reliability (> 85%). The total histologic score, calculated using the 6 criteria, was found to significantly differentiate between (blinded) biopsy location (normal, pre-AK, AK and adjacent to squamous cell carcinoma) and histologic diagnosis (normal, pre- or early AK, AK and squamous cell carcinoma). CONCLUSION: The total histologic score, having demonstrated reliability on repeated readings and validity in its association with biopsy location and histologic score, is a reliable and valid end point for judging the efficacy of agents in skin cancer chemoprevention studies. Additional interrater reliability tests utilizing larger test sets and a rigorous statistical design should be undertaken to establish its portability.  相似文献   

10.
BackgroundAging and sun exposure are the leading causes of skin cancer. It has been shown that epigenetic changes, such as DNA methylation, are well established mechanisms for cancer, and also have emerging roles in aging and common disease. Here, we directly ask whether DNA methylation is altered following skin aging and/or chronic sun exposure in humans.ResultsWe compare epidermis and dermis of both sun-protected and sun-exposed skin derived from younger subjects (under 35 years old) and older subjects (over 60 years old), using the Infinium HumanMethylation450 array and whole genome bisulfite sequencing. We observe large blocks of the genome that are hypomethylated in older, sun-exposed epidermal samples, with the degree of hypomethylation associated with clinical measures of photo-aging. We replicate these findings using whole genome bisulfite sequencing, comparing epidermis from an additional set of younger and older subjects. These blocks largely overlap known hypomethylated blocks in colon cancer and we observe that these same regions are similarly hypomethylated in squamous cell carcinoma samples.ConclusionsThese data implicate large scale epigenomic change in mediating the effects of environmental damage with photo-aging.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-015-0644-y) contains supplementary material, which is available to authorized users.  相似文献   

11.
Chronically sun-exposed facial skin of three females aged 68, 71, and 78 years, and of a male aged 78, was examined by electron microscopy in order to study the condition of the epidermal melanocytes. Considerable heterogeneity of morphological and functional characteristics of the cells was observed. The majority of melanocytes were large, active, with occasionally lobulated or double nuclei, an appearance indicative of hyperstimulation. Some cells exhibited an appearance of having reached the end of an active life cycle and were labelled "aged." Others, in the upper end of the outer root sheath of hair follicles and adjacent interfollicular epidermis, presented a typically inactive appearance, indistinguishable from that of fetal melanocytes, or of those in unexposed skin of younger subjects. A cell with indented nucleus, fully melanised melanosomes, and hypertrophic Golgi apparatus was sporadically seen. Minute foci of dissociation of keratocytes were present, and melanocytes included in these were frequently disrupted. Swelling of mitochondria and cytoplasmic lipid droplets occurred sporadically within all the above variants of melanocytes. It proved difficult to establish criteria of specific sun damage of melanocytes. It is suggested that either the melanocytes exhibiting stimulation or the relatively inactive ones could be the precursors of the proliferating cells of lentigo maligna.  相似文献   

12.
Arginine kinase (AK), which catalyzes the reversible transfer of phosphate from ATP to arginine to yield phosphoarginine and ADP, is widely distributed throughout the invertebrates. We determined the cDNA sequence of AK from the tardigrade (water bear) Macrobiotus occidentalis, cloned the sequence into pET30b plasmid, and expressed it in Escherichia coli as a 6x His-tag—fused protein. The cDNA is 1377 bp, has an open reading frame of 1080 bp, and has 5′- and 3′-untranslated regions of 116 and 297 bp, respectively. The open reading frame encodes a 359-amino acid protein containing the 12 residues considered necessary for substrate binding in Limulus AK. This is the first AK sequence from a tardigrade. From fragmented and non-annotated sequences available from DNA databases, we assembled 46 complete AK sequences: 26 from arthropods (including 19 from Insecta), 11 from nematodes, 4 from mollusks, 2 from cnidarians and 2 from onychophorans. No onychophoran sequences have been reported previously. The phylogenetic trees of 104 AKs indicated clearly that Macrobiotus AK (from the phylum Tardigrada) shows close affinity with Epiperipatus and Euperipatoides AKs (from the phylum Onychophora), and therefore forms a sister group with the arthropod AKs. Recombinant 6x His-tagged Macrobiotus AK was successfully expressed as a soluble protein, and the kinetic constants (K(m), K(d), V(ma) and k(cat)) were determined for the forward reaction. Comparison of these kinetic constants with those of AKs from other sources (arthropods, mollusks and nematodes) indicated that Macrobiotus AK is unique in that it has the highest values for k(cat) and K(d)K(m) (indicative of synergistic substrate binding) of all characterized AKs.  相似文献   

13.
Here, we report the PCR amplification and cloning of a cDNA for arginine kinase (AK) from the beetle Cissites cephalotes (Olivier). The cDNA is 1210bp and has an open reading frame of 1125bp and 5' and 3'-untranslated regions of 30 and 55bp, respectively. The open reading frame encodes a 374 amino acid protein with most of the residues considered necessary for AK function: five residues predicted to interact with the substrate arginine (S77, Y82, E239, C285 and E328), and five residues predicted to interact with the substrate ADP (R138, R140, R243, R294 and R323). A phylogenetic tree of arthropod AKs indicated clearly that insect AKs can be separated into typical AKs from various insect species (group 1) and putative AK sequences deduced from genomic sequences (group 2). Cissites AK clustered in group 2 and provides the first evidence that a group-2 gene is indeed expressed in insects. Moreover, we expressed Cissites AK protein in Escherichia coli as a fusion with maltose-binding protein, and kinetic constants (K(m), K(d), V(max) and k(cat)) were determined for the forward reaction. Comparison of kinetic constants with those of AKs from other sources (insects, mollusks and echinoderms) indicated that insect AKs from Cissites and Periplaneta have two very unique features, the lowest k(cat) (and k(cat)/K(m)(arg)) among AKs, and a lack of synergistic substrate binding (K(d)/K(m) approximately 1).  相似文献   

14.
The genome of the choanoflagellate Monosiga brevicollis contains at least three genes for the phosphoryl transfer enzyme, arginine kinase (AK; EC 2.7.3.3). Bioinformatic analyses of the deduced amino acid sequences of the proteins coded for by two of these genes showed that one of these AKs is cytoplasmic (denoted AK1) while the other appears to have an N-terminal mitochondrial targeting peptide (denoted AK2). Cloning and expression of the cDNA for AK1 yielded considerable soluble AK activity. Three AK2 constructs were expressed - one corresponding to the full length protein and two corresponding to truncated versions in which the signal peptide had been deleted. Expression of the former construct yielded minimal soluble activity. In contrast, significant AK activity was found in both truncated constructs confirming the importance of removal of the targeting peptide for proper folding and catalytic activity. Both AK1 and AK2 are functional oligomers unlike typical AKs which are monomeric. A phylogenetic analysis showed that these choanoflagellate AKs group more closely with a supercluster consisting of cytoplasmic and mitochondrial CKs and invertebrate AKs that evolved secondarily from a CK-like ancestor. Reaction-diffusion constraints in choanoflagellates are likely mitigated by the presence of AK isoforms which facilitate energy transport in these highly polarized cells.  相似文献   

15.
The recovery, after inhibition by u.v.-irradiation, of phytohaemagglutinin-stimulated DNA synthesis is impaired in lymphocytes from patients with multiple actinic keratoses (AK) compared to the recovery in lymphocytes from age-matched, control individuals. This shows that the reduced level (50%) of DNA repair activity in AK ceils is sufficiently different from that in normal cells to significantly affect cellular activity.  相似文献   

16.
OBJECTIVE: To characterize nuclei from well-differentiated, moderately differentiated and poorly differentiated lesions of invasive breast cancer by karyometry and to test the hypothesis that these diagnostic categories form homogeneous sets. STUDY DESIGN: Histopathologic sections from 6 cases of well-differentiated, 11 cases of moderately differentiated and 17 cases of poorly differentiated ductal carcinomas were digitally recorded. From each case 100 nuclei were segmented and analyzed by karyometry. A discriminant analysis was performed, and nuclear and lesion signatures were computed. The nonsupervised learning algorithm P-index was applied. A progression curve per diagnostic category based on mean nuclear abnormality and a discriminant function score was derived. RESULTS: The well-differentiated lesions formed a homogeneous set, but both the moderately and poorly differentiated lesions showed 2 significantly different subpopulations with nuclei of substantially different nuclear abnormality and progression. CONCLUSION: The visual histopathologic diagnostic assessment of these lesions was based on an evaluation of both tissue architectural criteria and nuclear criteria. Here, only the pattern of nuclear chromatin was evaluated. Cases belonging to the same diagnostic category as assessed by their differentiation may be further characterized by the extent to which the nuclei deviate from normal. There was substantial case-to-case heterogeneity in these invasive lesions.  相似文献   

17.
To assess presence of virus DNA in skin lesions, swab samples from 82 squamous cell carcinomas of the skin (SCCs), 60 actinic keratoses (AKs), paraffin-embedded biopsies from 28 SCCs and 72 kerathoacanthomas (KAs) and fresh-frozen biopsies from 92 KAs, 85 SCCs and 92 AKs were analyzed by high throughput sequencing (HTS) using 454 or Ion Torrent technology. We found total of 4,284 viral reads, out of which 4,168 were Human Papillomavirus (HPV)-related, belonging to 15 known (HPV8, HPV12, HPV20, HPV36, HPV38, HPV45, HPV57, HPV59, HPV104, HPV105, HPV107, HPV109, HPV124, HPV138, HPV147), four previously described putative (HPV 915 F 06 007 FD1, FA73, FA101, SE42) and two putatively new HPV types (SE46, SE47). SE42 was cloned, sequenced, designated as HPV155 and found to have 76% similarity to the most closely related known HPV type. In conclusion, an unbiased approach for viral DNA detection in skin tumors has found that, although some new putative HPVs were found, known HPV types constituted most of the viral DNA.  相似文献   

18.
OBJECTIVE: To derive an objective, numeric measure for the progression of intraepithelial and invasive squamous cell cervical lesions. STUDY DESIGN: Thin-layer cervical cytology preparations from colposcopically confirmed normal cervix, low grade squamous intraepithelial lesions, high grade squamous intraepithelial lesions and carcinoma were identified from a cross-sectional study. Fifty-nine cases representing 4 diagnostic categories were selected, and 2,375 nuclei from epithelial cells representative of the diagnostic category were randomly selected for imaging and measurement from these cases. Additionally, 1,378 visually normal appearing intermediate cells from low and high grade squamous intraepithelial lesions, as well as from carcinoma cases, were identified for analysis. The nuclei were quantitatively characterized, and discriminant analyses were performed to derive a progression curve from normal cytology to carcinoma. RESULTS: The lesion signatures show a clear increase in nuclear abnormality with increasing progression. A progression curve was derived based on mean discriminant function scores for each diagnostic category and on the mean nuclear abnormality values for the nuclei in each category, as expressed by their deviation in feature values from normal reference nuclei. CONCLUSION: A numeric assessment of lesion progression for cervical precancerous and cancerous lesions based on karyometric measurements is possible and may provide an objective, precise characterization of each lesion as well as a basis for improved performance in automated cytology-based cervical cancer screening.  相似文献   

19.
OBJECTIVE: To test whether histologically normal epithelium within ovarian inclusion cysts and stroma exhibit changes in nuclear chromatin pattern that indicate the presence of occult ovarian lesions. STUDY DESIGN: Ovaries were collected from 10 low-risk women,from 7 high-risk women and from 3 women with ovarian cancer. Histologic sections were cut at 5 microm and hematoxylin and eosin stained. High-resolution images were recorded from the epithelium lining inclusion cysts and from the underlying stroma of ovaries from these 20 subjects. A total of 2860 epithelial nuclei and 3610 stromal nuclei were recorded. Karyometric features and nuclear abnormality were computed. Discriminant analyses and unsupervised learning algorithms defined deviations from normal that were designated "above threshold" and used to compute average nuclear abnormality of a second nuclear phenotype. RESULTS: Histologically normal epithelium from inclusion cysts of ovaries harboring a malignant lesion was shown to exhibit changes in the nuclear chromatin pattern that were statistically significant using quantitative image analysis procedures. Similar changes were seen in the inclusion cyst epithelia of high-risk ovaries. A subpopulation of cells representing a new phenotype was detected in the underlying stroma of women harboring a malignant ovarian lesion and in women at high risk of ovarian cancer. CONCLUSION: The karyometric changes observed in the epithelia lining inclusion cysts and in the underlying stroma of ovaries either with ovarian cancer or at high risk of ovarian cancer suggest the presence of preneoplastic changes in histologically normal tissue.  相似文献   

20.
He W  Zhu F  Ma X  Zhao X  Zheng M  Chen Z  Heymsfield SB  Zhu S 《PloS one》2011,6(5):e19907

Background

Exposure to sunlight may decrease the risk of several diseases through the synthesis of vitamin D, whereas solar radiation is the main cause of some skin and eye diseases. However, to the best of our knowledge, the association of sun-induced skin damage with mortality remains unknown.

Methodology/Principal Findings

Subjects were 8472 white participants aged 25–74 years in the First National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. Cardiovascular disease mortality, cancer mortality, and all-cause mortality were obtained by either a death certificate or a proxy interview, or both. Actinic skin damage was examined and recorded by the presence and severity (absent, minimal, moderate, or severe) of overall actinic skin damage and its components (i.e., fine telangiectasia, solar elastosis, and actinic keratoses). Cox regression and Kaplan-Meier methods were applied to explore the associations. A total of 672 cancer deaths, 1500 cardiovascular disease deaths, and 2969 deaths from all causes were documented through the follow-up between 1971 and 1992. After controlling for potential confounding variables, severe overall actinic skin damage was associated with a 45% higher risk for all-cause mortality (95% CI: 1.22, 1.72; P<0.001), moderate overall skin damage with a 20% higher risk (95% CI: 1.08., 1.32; P<0.001), and minimal overall skin damage with no significant mortality difference, when compared to those with no skin damage. Similar results were obtained for all-cause mortality with fine telangiectasia, solar elastosis, and actinic keratoses. The results were similar for cancer and cardiovascular disease mortality.

Conclusions

The present study gives an indication of an association of actinic skin damage with cardiovascular disease, cancer and all-cause mortality in white subjects. Given the lack of support in the scientific literature and potential unmeasured confounding factors, this finding should be interpreted with caution. More independent studies are needed before any practical recommendations can be made.  相似文献   

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