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Biomedical subjects

Shozo Yokoyama

Publications and source records attributed to Shozo Yokoyama.

10 recordsLinked to original sources
PubMed2003

The cone visual pigments of an Australian marsupial, the tammar wallaby (Macropus eugenii): sequence, spectral tuning, and evolution.

Studies on marsupial color vision have been limited to very few species. There is evidence from behavioral, electroretinographic (ERG), and microspectrophotometric (MSP) measurements for the existence of both dichromatic and trichromatic color vision. No studies have yet investigated the molecular mechanisms of spectral tuning in the visual pigments of marsupials. Our study is the first to determine the mRNA sequence, infer the amino acid sequence, and determine, by in vitro expression, the spectra of the cone opsins of a marsupial, the tammar wallaby (Macropus eugenii). This yielded some information on mechanisms and evolution of spectral tuning of these pigments. The tammar wallaby retina contains only short-wavelength sensitive (SWS) and middle-wavelength sensitive (MWS) pigment mRNAs. This predicts dichromatic color vision, which is consistent with conclusions from previous behavioral studies ( Hemmi 1999). We found that the wallaby has a SWS1 class pigment of 346 amino acids. Sequence comparison with eutherian SWS pigments predicts that this SWS1 pigment absorbs maximally (lambdamax) at 424 nm and, therefore, is a blue rather than a UV pigment. This (lambdamax) is close to that of the in vitro-expressed wallaby SWS pigment (lambdamax of 420 +/- 2 nm) and to that determined behaviorally (420 nm). The difference from the mouse UV pigment (lambdamax of 359 nm) is largely accounted for by the F86Y substitution, in agreement with in vitro results comparing a variety of other SWS pigments. This suggests that spectral tuning employing F86Y substitution most likely arose independently in the marsupials and ungulates as a result of convergent evolution. An apparently different mechanism of spectral tuning of the SWS1 pigments, involving five amino acid positions, evolved in primates. The wallaby MWS pigment has 363 amino acids. Species comparisons at positions critical to spectral tuning predict a lambdamax near 530 nm, which is close to that of the in vitro-expressed pigment (529 +/- 1 nm), but quite different from the value of 539 nm determined by microspectrophotometry. Introns interrupt the coding sequences of the wallaby, mouse, and human MWS pigment sequences at the same corresponding nucleotide positions. However, the length of introns varies widely among these species.

Amino Acid Sequence↗
PubMed2003

Molecular analysis of the evolutionary significance of ultraviolet vision in vertebrates.

Many fish, amphibians, reptiles, birds, and some mammals use UV vision for such basic activities as foraging, mate selection, and communication. UV vision is mediated by UV pigments in the short wavelength-sensitive type 1 (SWS1) group that absorb light maximally (lambda max) at approximately 360 nm. Reconstructed SWS1 pigments of most vertebrate ancestors have lambda max values of approximately 360 nm, whereas the ancestral avian pigment has a lambda max value of 393 nm. In the nonavian lineage, UV vision in many modern species is inherited directly from the vertebrate ancestor, whereas violet vision in others has evolved by different amino acid replacements at approximately 10 specific sites. In the avian lineage, the origin of the violet pigment and the subsequent restoration of UV pigments in some species are caused by amino acid replacements F49V/F86S/L116V/S118A and S90C, respectively. The use of UV vision is associated strongly with UV-dependent behaviors of organisms. When UV light is not available or is unimportant to organisms, the SWS1 gene can become nonfunctional, as exemplified by coelacanth and dolphin.

Amino Acid Sequence↗
PubMed2003

The spectral tuning in the short wavelength-sensitive type 2 pigments.

Using site-directed mutagenesis and multiple regression analysis, we have studied the molecular genetics and evolution of short wavelength-sensitive (SWS2) pigments in vertebrates. These analyses suggest that the SWS2 pigment in the vertebrate ancestor had the wavelength of maximum absorption (lambda(max)) of approximately 440 nm and that various lambda(max)'s of the contemporary SWS2 pigments in vertebrates are caused mainly by additive effects of amino acid replacements at ten sites.

Animals↗
PubMed2002

Molecular evolution of color vision in vertebrates.

Visual systems of vertebrates exhibit a striking level of diversity, reflecting their adaptive responses to various color environments. The photosensitive molecules, visual pigments, can be synthesized in vitro and their absorption spectra can be determined. Comparing the amino acid sequences and absorption spectra of various visual pigments, we can identify amino acid changes that have modified the absorption spectra of visual pigments. These hypotheses can then be tested using the in vitro assay. This approach has been a powerful tool in elucidating not only the molecular bases of color vision, but the processes of adaptive evolution at the molecular level.

Animals↗
PubMed2002

Prediction of distant metastasis by using reverse transcriptase-polymerase chain reaction for epithelial and variant CD44 mRNA in the peripheral blood of patients with colorectal cancer.

BACKGROUND: Reverse transcriptase-polymerase chain reaction (RT-PCR) has been used to identify small numbers of tumor cells. Molecular detection is thought to provide useful information for the clinical management of postoperative adjuvant therapy regimens. OBJECTIVE: To use RT-PCR to identify messenger RNA (mRNA) coding for carcinoembryonic antigen, epithelial and variant CD44, and matrix metalloproteinase 7 in the portal venous and peripheral blood of patients with colorectal carcinoma to predict live or distant metastasis. DESIGN: Prospective consecutive series. SETTING: University hospital. PATIENTS AND METHODS: Portal venous and peripheral blood samples were obtained from 22 patients with colorectal cancer during surgical manipulation. Using complementary DNA primers specific for carcinoembryonic antigen, CD44, and matrix metalloproteinase 7, RT-PCR was performed to detect tumor cells. MAIN OUTCOME MEASURE: The clinical significance of RT-PCR for epithelial and variant CD44 mRNA in peripheral blood. RESULTS: During 3 years of follow-up, 2 patients whose peripheral blood had carcinoembryonic antigen and CD44 variant mRNA also had distant metastases (lung or spleen). Expression of epithelial and variant CD44 mRNA in peripheral blood was more highly correlated with the clinical cancer stage than with expression of carcinoembryonic antigen and matrix metalloproteinase 7. CONCLUSIONS: Molecular detection of epithelial and variant CD44 mRNA in the peripheral blood may help determine distant metastases in patients with colorectal carcinoma. Molecular detection in the peripheral blood at surgical treatment suggests that systemic hematogenic tumor cell dissemination is an early event of distant metastasis.

Carcinoembryonic Antigen↗
PubMed2002

So-called carcinosarcoma of the gallbladder; spindle cell carcinoma of the gallbladder: report of a case.

We report a so-called carcinosarcoma of the gallbladder in a 53-year-old man. The findings of ultrasonography, computed tomography, endoscopic retrograde cholangiopancreatography, and angiography revealed a large mass of the gallbladder with a cholesterol stone. He underwent three operations, and died from liver failure with multiple liver metastasis immediately after the third operation. A pathological examination revealed neoplastic tissue composed of sarcomatous and glandular components. Hematoxylin-eosin stain proved the presence of carcinosarcoma in the gallbladder, but an immunohistochemical study proved that the sarcomatous component was stained by antivimentin and also anticytokeratin antibodies, which thus proved it to be so-called carcinosarcoma of the gallbladder. As a result, an immunohistochemical study is considered to provide valuable information regarding the identification of sarcomatous elements in such cases.

Carcinoma↗
PubMed2002

Locoregional chemotherapy for patients with pancreatic cancer intra-arterial adjuvant chemotherapy after pancreatectomy with portal vein resection.

INTRODUCTION AND AIMS: The survival of pancreatic cancer patients with portal vein resection is extremely poor due to the high incidence of liver metastasis. The occurrence of liver metastasis is decreased by locoregional arterial infusion after pancreatic surgery. Chemosensitivity tests can provide the basis for individualized chemotherapy in each patient and predict the clinical response. Therefore, the current study was designed to clarify whether locoregional chemotherapy based on the results of chemosensitivity tests has the clinical effects of preventing liver metastasis and improving survival for patients with portal vein resection. METHODOLOGY: The resected specimens from 40 of 47 patients with resection of pancreatic cancer were assessed for chemosensitivity to various anticancer drugs. Fourteen patients underwent portal vein resection due to direct invasion, and nine of these patients received intra-arterial adjuvant chemotherapy on the basis of the results of MTT assay to prevent liver metastasis. The remaining five patients received no chemotherapy. RESULTS: None of the patients who received intra-arterial chemotherapy had liver metastasis, and this group of patients had improved survival. The mean survival of patients with intra-arterial chemotherapy was significantly longer than that of patients without chemotherapy (25.6 months with chemotherapy versus 9.4 months without chemotherapy). CONCLUSION: A pilot study of postoperative intra-arterial chemotherapy showed the reduction of liver metastasis and improvement of survival among pancreatic cancer patients with portal vein resection.

Antineoplastic Agents↗