Given a passage with a question and an answer to that question, classify if the answer actually answers the question into 'yes' or 'no'. Output 'yes' if the answer answers the question and output 'no' if the answer does not answer the question.

Q: Question: Is the dorsal motor nucleus of the vagus an obligatory trigger site of Parkinson 's disease : a critical analysis of alpha-synuclein staging?
Answer: Our results demonstrate a predominant involvement of the SN and NBM in PD but do not support the existence of a medullary induction site of alpha Syn pathology in all PD brains.

A: no
****
Q: Question: Is tumor differentiation a risk factor for lymph node metastasis in elderly patients with early gastric cancer?
Answer: Elderly patients with undifferentiated type histology early gastric cancer without other risk factors for lymph node metastasis may be candidates for endoscopic resection.

A: no
****
Q: Question: Does glial cell line-derived neurotrophic factor promote β-catenin phosphorylation and nuclear translocation in glioma cells?
Answer: The results of our study demonstrate that GDNF increases the intracellular phosphorylation level of β-catenin through N-cadherin/Src signaling, which subsequently stimulates the nuclear translocation of β-catenin. This study provides a theoretical basis for us to reveal the role of biological mechanisms on glioma cell by GDNF.

A:
yes
****