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Biomedical subjects

S Yuasa

Publications and source records attributed to S Yuasa.

At least 235 records · Page 13Linked to original sources
PubMed1970

Lactation and cancer of the breast. A summary of an international study.

An international collaborative study has been carried out to test the hypothesis that prolonged lactation protects women against cancer of the breast. While pregnancy itself seemed to confer some protection against breast cancer in all areas studied, no consistent differences in duration of lactation were found between breast cancer patients and unaffected women, once the fact that breast cancer patients have fewer pregnancies had been allowed for. Even in areas where some women had lactated for a total of 5 years or more, such women occurred proportionately no less frequently among breast cancer patients than among unaffected women. In the light of this and other recent evidence, it is unlikely that lactation has any protective effect against breast cancer in women, and other explanations must be sought for the remarkable international differences in the frequency of this disease.

Adult↗
PubMed1970

Lactation and reproductive histories of breast cancer patients in Tokyo, Japan.

Epidemiological characteristics of breast cancer have been studied in Tokyo, an area of relatively low breast cancer rates, as part of an international collaborative study. Breast feeding of infants is customary for Japanese women, but even very prolonged lactation did not appear to be associated with a reduction in breast cancer risk. Late age at menarche and early age at first pregnancy were both associated with reduced breast cancer risk. The protective effect of early pregnancy seems much greater than has previously been recognized, and may indeed be greater in Japan than in other areas. However, the average age at first pregnancy is not lower in Tokyo than in areas than in areas where breast cancer rates are high.

Adult↗
PubMed1970

Age at first birth and breast cancer risk.

An international collaborative study of breast cancer and reproductive experience has been carried out in 7 areas of the world. In all areas studied, a striking relation between age at first birth and breast cancer risk was observed. It is estimated that women having their first child when aged under 18 years have only about one-third the breast cancer risk of those whose first birth is delayed until the age of 35 years or more. Births after the first, even if they occur at an early age, have no, or very little, protective effect. The reduced risk of breast cancer in women having their first child at an early age explains the previously observed inverse relationship between total parity and breast cancer risk, since women having their first birth early tend to become ultimately of high parity. The association with age at first birth requires different kinds of etiological hypotheses from those that have been invoked in the past to explain the association between breast cancer risk and reproductive experience.

Adolescent↗
PubMedDate not supplied

Resolution of DL-amino acids on a native cellulose column and a plausible mechanism for their resolution.

We have studied the resolution of DL-amino acids on a native cellulose column. All the DL-amino acids related to protein and their 16 DNP-DL-amino acids were separated. The resolution capability depends mainly upon the bulkiness of the side group attached to the alpha-carbon, but also on structural and functional interaction of amino acid with cellulose. We propose a plausible resolution mechanism that is thought to be governed by a so-called key and lock relation between an amino acid and cellulose. Then, the affinity of each enantiomer for cellulose was calculated based on the resolution factor, which was known to be some 10(-2) -10(-3) eV.

Amino Acids↗
PubMedDate not supplied

High frequency discharge experiment. I: Formation of organic compounds from methane and ammonia.

Investigations of the synthesis of organic compounds from methane and ammonia were carried out by using high frequency discharges. The radical of CN was observed in the early phase of the discharge. Therefore it is considered that the CN radical contributes to the successive reaction steps. An important intermediate, a tetramer of hydrogen cyanide was observed to be formed at room temperature. The amounts of this compound progressively increased with time. It was speculated that the purines which were identified in the refluxed sample were synthesized through the above tetramer. Compounds which are thought to be heterocyclic (max:250-265nm) were initially formed in the sample trapped at liquid nitrogen temperature. After hydrolysis with hydrochloric acid, Gly, Asp Ala, etc. were observed in the sample. Overall yield of organic compounds was estimates at 5-6% based on input carbon of methane.

Ammonia↗