Welcome
Research Team
Highly experienced investigators in California
Research Team
Dr. Jay Guan has extensive training in a broad range of GI disorders and procedures. His clinical focus includes Inflammatory Bowel Disease, Barret’s Esophagus, NASH, GI motility disorders, Hepatitis B/C, and Eosinophilic Esophagitis. He is passionate about applying the latest and evidence-based care to help improve patients’ quality of life.
In his free time, he enjoys cooking, hiking, traveling, reading, and spending time with his son and wife. He is fluent in English, Mandarin, and Medical Spanish.
Dr. Justin Marasigan was raised in the Los Angeles area. He earned his undergraduate degree from the University of Southern California and his medical degree from Kirksville College of Osteopathic Medicine in Missouri. Dr. Marasigan went on to complete his Internal Medicine Residency in the Detroit area and his Gastroenterology specialty training in Erie, Pennsylvania. He applied a variety of experiences from rural offices to large academic centers throughout Western Pennsylvania and Eastern Ohio. Prior to joining the team in Ventura County, Dr. Marasigan practiced Gastroenterology for 7 years in Washington State.
When he is not at work, Dr. Marasigan enjoys spending time with his wife, twin son and daughter, and dog Sadie.
Dr. Micha Rojany was born and raised in Southern California. He received his undergraduate degree from the University of California, Berkeley. After, he attended USC Medical School and completed his internship and residency at Cedars-Sinai Medical Center in Los Angeles. Additionally, he completed a fellowship in Gastroenterology at the University of California, Davis.
Dr. Rojany has practiced in Ventura County since 2006 and is an active member of the local medical community and hospital staff at St. John’s Regional Medical Center in Oxnard, and Pleasant Valley Hospital, in Camarillo. He enjoys practicing as a Gastroenterologist with special interests in inflammatory bowel disease and biliary tract diseases.
When not in the office, Dr. Rojany enjoys spending time with his wife and three daughters and mountain hiking on the local trails.
Dr. Karen Simon, M.D. is board certified in Gastroenterology and Hepatology. She received her B.A. from Stanford University in 1996. She then attended Northwestern University in Illinois for medical school. Dr. Simon completed her residency at Cedars-Sinai Medical Center in 2004 and her fellowship in gastroenterology at UCLA and Cedars, California, in 2008. Dr. Simon has been serving patients in Ventura County in her private practice for over 16 years. In addition, she is a speaker for Exact Sciences on behalf of Cologuard and is actively associated in research.
Alia Jamison-Dinowitz knew that she would always have a career that would involve helping others and support people in their health and well-being. She earned a Bachelors of Science in psychology at UCLA with a minor in anthropology and went on to complete her nursing training and Masters of Science in nursing at Western University of Health Sciences in Pomona, California along with her Public Health Nursing license. She began her career working as a nurse in obstetrics specifically working in postpartum and nursery while attending classes in a post-masters Family Nurse Practitioner program at Western University of Health Sciences. Educating and caring for new mothers and their babies was incredibly rewarding, however as she continued with her classes, she transitioned into working as a nurse in an urgent care setting. This new assignment provided direct experience in patient care and conditions she was learning about in her academic program. Shortly after starting in the urgent care setting she assumed the role of lead nurse in which she served in for three years, training new nurses and ensuring high level of patient care and follow-up.
Alia is a member of the American Nurses Association, California Association of Nurse Practitioners, and American Association of Nurse Practitioners. While not working as a Family Nurse Practitioner Alia enjoys hiking, spending time with her husband Bryan, and capturing the beauty of nature as an amateur nature photographer.
Lori Rodriguez has been in medicine since she was 15 years old when she started her medical journey as a candy striper at Little Company of Mary Hospital in Torrance, CA. A native of Manhattan Beach she continued in medicine as a medical assistant for many years until she decided to become a physician assistant. She graduated with honors from San Joaquin College in Visalia in 2005, and has practiced in internal medicine ever since. She also specializes in women’s health and urgent care medicine. She has her bachelor’s degree in healthcare administration and her masters degree in health care ethics.
She has been married to her husband Peter, who is also a PA, for the past 12 years. They love to spend time with family and friends and enjoy going to the beach for relaxing weekends. Lori is well known in the Antelope Valley as a knowledgeable and compassionate clinician who cares deeply for her patients.
Nitin A. Shah, M.D. is a board-certified orthopedic surgeon. Dr. Shah received his medical degree from The Maharaja Sayajirao University of Baroda in India. He then completed an internship in general surgery at Elyria Memorial Hospital in Ohio which lasted for a year and a half. Dr. Shah performed his residency in general surgery at Maimonides Medical Center in New York and returned to Elyria Memorial Hospital where he performed his orthopedic surgery residency. He has over 45 years of experience as he operates his private practice in Lancaster, CA. In addition, Dr. Shah has been involved in clinical research since 2022, partnering with Om Research.
Dr. Raj Bhatia, M.D. is board certified in Internal Medicine, Critical Care Medicine, Pulmonary Disease and Sleep Medicine.
He received his Bachelor of Medicine and surgery from the University of Poona, India. Dr. Bhatia completed his residency in internal medicine at Morristown Memorial Hospital in New Jersey preceded by a rotating internship.
In addition, he completed his pulmonary/critical care fellowship at Mount Sinai in New York, followed by an additional fellowship at UCI Medical Center in Orange, CA. He has served Ventura County for over 20 years. Furthermore, Dr. Bhatia has been involved in clinical research in partnership with Om Research for over two years.
Physician Assistant
Laura Craver, PA-C, a long-standing resident of Ventura County, completed her training as a Physician Assistant at Touro University in Henderson, NV. She comes from a family of healthcare providers, and after living across the country in Virginia, she is excited to be back and providing care for patients in her home community. Laura is accepting referrals for our Oxnard location.
Medical Education
Dr. Movses Hayrabedian is board certified in Internal Medicine, Critical Care Medicine and Pulmonary Disease. He recently finished his Critical Care fellowship from Southern Illinois University in Springfield, Illinois. Dr. Hayrabedian is accepting referrals for all aspects of Pulmonary Medicine for our Oxnard and Camarillo locations.
Medical School
Internship/Residency
Fellowship(s)
Board Certification
Professional Affiliation
Physician
Dr. Darren Maehara is board certified in Internal Medicine, Pulmonary Disease and Critical Care Medicine. During his time in Medical School at LAC+USC Medical Center in Los Angeles, CA, he volunteered at a rural health clinic in Africa providing basic medical care to local residents. He was the Chief Fellow during his Pulmonary and Critical Care Medicine Fellowship at LAC+USC Medical Center. Dr. Maehara is fluent in medical Spanish, and is accepting referrals for all aspects of Pulmonary Medicine in our Oxnard and Camarillo locations.
Medical School
Internship/Residency
Fellowship
Board Certification
Professional Affiliation
Physician
Dr. Sofia Nelson is board certified in Internal Medicine and Pulmonary Disease. During Medical School, she received the Internal Medicine Chief’s Research Fellowship at UCLA David Geffen School of Medicine in Los Angeles, CA. Dr. Nelson is accepting referrals for all aspects of Pulmonary Medicine for our Oxnard and Camarillo locations.
Medical School
Internship/Residency
Fellowship
Board Certification
Professional Affiliation
Physician
Dr. Seze Obilor is board certified in Internal Medicine and Sleep Medicine. She completed her Residency in Internal and Primary Care Medicine at Rush University Medical Center/John Stroger Hospital of Cook County, Chicago, IL. She completed her Fellowship in Sleep Medicine at Keck School of Medicine, University of Southern California, Los Angeles, CA. Dr. Obilor is accepting referrals for Sleep Medicine for our Camarillo location.
Medical School
Internship/Residency
Fellowship
Board Certification
Professional Affiliation
Dr. Zachary Taich is board certified in Internal Medicine, Pulmonary Disease Sleep Medicine and Critical Care Medicine. He completed his Critical Care, Pulmonary and Sleep Medicine fellowship from the University of California, Los Angeles. Dr. Taich is accepting referrals for all aspects of Pulmonary and Sleep Medicine for our Oxnard and Camarillo locations.
Medical School
Internship/Residency
Fellowship(s)
Board Certification
Professional Affiliation
Physician
Dr. Andrew Weymer is board certified in Internal Medicine, Pulmonary Disease, and Critical Care Medicine. He has served Ventura County for over 25 years. During Medical School at St. Louis University School of Medicine in St. Louis, MO, he was awarded the American Gastroenterology Research Fellowship. Dr. Weymer is accepting referrals for all aspects of Pulmonary Medicine for our Oxnard and Camarillo locations.
Medical School
Internship/Residency
Fellowship
Board Certifications
Professional Affiliation
Family Nurse Practitioner
Allison Wastak, MSN, FNP, AGACNP received dual Master of Nursing degrees from the University of South Alabama in Mobile, Alabama and is certified in both Family Nurse Practitioner and in Adult-Gerontology Acute Care Nurse Practitioner. She has over six years of experience as a Pulmonary, Sleep Medicine, and Critical Care Nurse Practitioner and eighteen years as a critical care registered nurse. She has recently moved to Ventura County and is excited to join the West Coast Pulmonary team.
Medical Education
Bachelor of Science in Nursing – University of Central Missouri (Warrensburg, MO)
Education
EDUCATION
Gastroenterology and Hepatology
Pennsylvania State University Milton S. Hershey Medical Center
ABIM Board Certified, American Board of Internal Medicine – Gastroenterology
Trained in Diagnostic, Therapeutic and Interventional Endoscopic Procedures
INTERNSHIP AND RESIDENCY
Internal Medicine
Pennsylvania State University Milton S. Hershey Medical Center
Board Certified, American Board of Internal Medicine
POSTGRADUATE
Doctor of Osteopathic Medicine
Des Moines University College of Osteopathic Medicine (Des Moines, Iowa)
UNDERGRADUATE
Bachelor of Science in Biochemistry
University of California, Los Angeles (UCLA)
EDUCATION
Loma Linda University Medical Center 2019-2022
Gastroenterology/Hepatology Fellowship
Los Angeles County/University of Southern California Medical Center 2016-2019
Resident Physician – Internal Medicine
Thomas Jefferson University 2012-2016
M.D. Degree
University of Southern California 2007-2011
Bachelor of Arts Biological Sciences; Popular Music Minor
Cum Laude
Madrid, Spain Study Abroad Semester
EDUCATION
Gastroenterology
University of California, Irvine
Trained in Diagnostic, Therapeutic and Interventional Endoscopic Procedures
Board Certified, American Board of Internal Medicine-Gastroenterology Subspecialty
INTERNSHIP AND RESIDENCY
Internal Medicine
University of California, Irvine
Board Certified, American Board of Internal Medicine
POSTGRADUATE
Doctor of Medicine
University of California, Irvine, School of Medicine
UNDERGRADUATE
Bachelor of Science in Biology, cum laude
California State University, Los Angeles
Education
Bachelor of Science, Nursing
2005 California State University, Dominguez Hills
Master of Science, Nursing
2007 California State University, Long Beach
Family Nurse Practitioner Certificate, Board of Nursing California 2007
National Certification Family Nurse Practitioner, American Nurses Credentialing Center 2015
Education
Associates in Math and Science Physician Assistant Studies
Moreno Valley college August 2014
Board Certified through NCCPA December 2021
Education
Gastroenterology
University of California, Irvine, Medical Center
Gastroenterology Fellowship
Trained in Diagnostic, Therapeutic and Interventional Endoscopy.University of California, Irvine, Medical Center
Internal Medicine Internship and Residency
University of Massachusetts School of Medicine
Doctor of Medicine
Boston University School of Medicine
Master of Arts
Research thesis on skeletal muscle cell differentiation under Dr. Nadia Rosenthal.
Bowdoin College
Bachelor of Arts degree, cum laude
Dual major in Biology and Religion
Education
Education
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