Subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and fat beneath the dermis layer were investigated using a ball lens top hollow optical fiber Raman probe (BHRP). Hamsters were fed with trilinolein (TL) and tricaprin (TC) for six weeks and measurements were carried out every two weeks. The BHRP with an 800 μm diameter fused-silica ball lens was able to obtain information on the subcutaneous fat in a totally non-invasive manner. Changes in the concentration of TL and TC during the treatment were analyzed, and the relationship between fat accumulation and dietary fat was studied. It was found that SAT had, in general, a higher degree of unsaturation than VAT. The accumulation rate of TC found in SAT and VAT was 0.52 ± 0.38 and 0.58 ± 0.4%, respectively, while the TL accumulation rate was 4.45 ± 1.6 and 4.37 ± 2.4%, respectively. The results suggest different metabolic pathways for TC, a typical medium-chain fatty acid, and TL, a long-chain unsaturated fatty acid. Raman subsurface spectra were successfully obtained and used to analyze the subcutaneous fat layer. The accumulation rates of TL and TC found in skin fat were 5.01 ± 3.53% and 0.45 ± 0.36%, respectively. The results demonstrate the high feasibility of Raman spectroscopy for non-invasive analysis of adipose tissue.
Virus infection of a human cell was determined only 3 h after invagination. We used viral vector Ad-CMV-control (AdC), which lacks the E1 gene coding for early polypeptide 1 (E1). AdC can replicate in human embryonic kidney 293 (HEK293) cells into which the E1 gene has been transfected. According to partial least-square regression discriminant analysis, it was assumed that two kinds of reaction take place in the cell during viral invasion. The first response of the cell was determined 3 h after the virus invasion, and the second one was determined ∼9 h later. The first one seems to be due to compositional changes in DNA. Analysis of large-scale datasets strongly indicated that the second reaction can be attributed to a reduction in protein concentration or uptake of phenylalanine into the nucleus.
A miniaturized Raman endoscope (mRE) system was employed to study the effects of anticancer treatment on colorectal tumors in a live murine model. The endoscope is narrow enough to observe the inside of the mouse colon under anesthesia. It has a channel for a ball lens mounted on a hollow fiber Raman probe (BHRP) to measure any targeted point under the visual control of the endoscope. Colorectal cancer tissue was observed to study the alterations of the tissue in response to anticancer drug treatment. Three anticancer drugs, 5-fluorouracil (5-FU), cisplatin (CDDP), and docetaxel, were employed. Although no alteration was recognized in the endoscopic visual observations at 2 weeks after the drug treatment, the Raman spectra obtained in the live mouse colon indicated that molecular changes of lipids and proteins were observed. This study demonstrates that in situ Raman analysis is highly sensitive for detecting the effects of anticancer drugs.
We have succeeded in discriminating between intact excitatory and inhibitory neuronal cells with Raman analysis. Excitatory and inhibitory neurons have several differences in their electric activities, but it can be difficult to determine their types based only on visual appearances. As Raman spectroscopy does not require any staining or labeling, its use in live neuronal cells is possible. In the present study, we used primary neurons obtained from rat cerebral cortexes, which we cultured on a glial feeder layered culturing dish for 15 days. The Raman spectra of the intact neurons on the dish were obtained; the neurons were then immunostained and their types determined. Partial least squares regression-discriminant analysis (PLSR-DA) was employed for classification of the excitatory and inhibitory neurons. The results demonstrated a high feasibility for use of Raman spectroscopy for discrimination analysis of inhibitory and excitatory neurons in a nondestructive manner.
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