Section 3 Medical Literature 第三部分 医学文献
Part 1.
There are a couple of situations that would mandate1) a liver transplant.First，patients with acute liver failure.Those are patients that have no history of any type of liver disease.Out of the blue，their liver would fail.There are multiple causes for that，including viruses or Tylenol overdoses.Those patients usually require transplantation very urgently.
The second group of patients are patients that have chronic liver disease.Chronic liver disease can be caused by a variety of etiologies,including viral hepatitis，hepatitis-B，hepatitis-C，alcohol，and cholestatic diseases，primary biliary cirrhosis，sclerosing cholangitis.There are pages and pages of possible causes for chronic liver disease.
In those patients,they progress to chronic liver disease and then develop complications of chronic liver disease.These might include bleeding varices，they might include ascites，fluid build-up in the abdomen.They might include liver cancer.
Once patients develop these complications of chronic liver disease,then they would need a liver transplant.However，a liver transplant is not considered an option when the patient is too far gone and has developed complications that are not reversible2) with liver transplantation，or when the patients have other medical conditions that would preempt3) them from getting a liver transplant.For example，advanced heart disease，advanced lung disease.If a patient has metastatic cancer，for example，they would not be a candidate for a liver transplant.
In evaluating when a liver transplant is no longer an option，we would look at the whole patient to try to decide if there are other medical conditions that would contraindicate4) a liver transplant.
Other potential contraindications would include psychosocial contraindications.If the patient,for example,is an active alcoholic or an active intravenous drug abuser5) or any type of recreational6) drug user,then those patients are typically not considered for a liver transplantation.
When a patient is evaluated at a transplant center and deemed to be a potential recipient for liver transplantation，then that transplant center will list the patient with a national organization called UNOS，United Network for Organ Sharing.The patient will be listed with this national organization，but they will be listed at a local level.There are 60-odd organ procurement organizations in the country that divide up the country.There are 11 regions.So the 60-odd OPOs，as they are called，would be within these 11 regions.
From the time a patient signs up until the actual time that he gets a liver transplant，how much time are we talking about here on average?The waiting time is a major problem.It depends on a lot of factors，which include the blood type，the severity of illness.To a certain extent，it includes the size of the recipient.
One of the biggest controversies today has to do with the federal government requiring that geography should not be a part of it,and that it should be entirely based on severity of illness.That has been a raging controversy between the transplant community and the federal government.
So to get back to the question about what happens when a patient gets listed.The patient gets listed with UNOS，and then depending on the level of severity，will get an organ allocated whenever their name comes up on this national，computerized list.
If the patient is moribund7) in the intensive care unit and has less than a week to live，then that patient may get a liver allocated within that week.Oftentimes，the patients will die before a liver becomes available.So in that status，for example，waiting times could be as long as a month.But if patients are stable and have no real need for an urgent liver transplant，the waiting time could be as long as two or three years.
注释：
1）mandadate 命令，托管、授权
2）reversible 可逆的
3）preempt 以优先购买权取得，抢先占有，霸占
4）contraindicate 禁忌
5）drug abuse 药物滥用
6）recreational 休养的，消遣的、疗养的
7）moribund 濒死的
Part 2.
The challenges that face us in liver transplantation today are very,very different from where they were a decade ago.A decade ago，we worried about technical considerations.We worried about the types of drugs to prevent rejection and worried about success rates.Liver transplantation today is extremely successful.As a result，it has become a victim of its success，and the major hurdle that we face today is that there are not enough organs to go around，and so patients die waiting for transplantation.
The challenges have led to very innovative techniques to allow us to expand the donor pool1).The ways that we have attacked that have been to first of all accept what are called marginal donors，and we keep pushing the envelope on what is a usable liver.The second way that we’ve done that is，as I mentioned，split livers.So one liver can be enough for two patients，and we do that routinely here.(https://www.daowen.com)
The third way that we’ve expanded the donor pool is to use live donors.Now，live donors have been used for about ten years for pediatric recipients2)，and we certainly perform a large number of these at Children’s Memorial.The newest technology has been to use live donor liver transplantation for adult recipients,and the reason that that is trickier is that we have to take a much bigger piece of liver in order to do that.We roughly take between 50 and 60% of the donor’s liver to accommodate a recipient，and that is a risky proposition，and that is an operation that cannot be taken lightly.And we have assessed the situation，and are presently one of the leaders in adult-to-adult living donor transplantation.
Liver transplantation is extremely successful.The one-year survival，which is what we use as a measure of long-term survival is in the range of 85 to 90%.When you compare that to the survival of not having a transplant in these patients being zero percent，that is very successful by definition.The complication rate is very low，and in general these patients have a normal lifestyle，with the exception of having to take lifetime medications.
As far as being able to go back to work，being able to go back to school，our goal is to get every patient that we transplant back to either school or work，and we’re very successful at doing that.
注释：
1）donor pool 捐赠者
2）recipients 接受者，受体
Part 3.
The enzymes of the pancreatic juice1) are secreted entirely by the acini2) of the pancreatic glands.Pancreatic juice contains enzymes for digesting all three major types of food.
(1)Proteolytic enzymes3) The pancreatic enzymes that digest protein are trypsin4),chymotrypsin5),carboxypolypeptidase6),ribonuclease7),and deoxyribonuclease8).By far the most abundant of these is trypsin.The tryspin and chymotrypsin split whole and partially digested proteins into peptides of various sizes.Carboxypolypeptidase splits individual amino acids from the carboxyl ends of the peptides,thus completing the digestion of much of the proteins all the way to the amino acid state.The nucleases split the two types of nucleic acids:ribonucleic and deoxyribonucleic acids.
When synthesized in the pancreatic cells,the proteolytic enzymes are in the forms of trypsinogen,chymotrypsinogen,and procarboxypeptidase9)，which are all enzymatically inactive.They become activated only after being secreted into the intestinal tract.Trypsinogen is activated by an enzyme called enterokinase，which is secreted by the intestinal mucosa.Trypsinogen can also be autocatalytically activated by trypsin that has already been formed.Chymotrypsinogen is activated by trypsin to form chymotrypsin,and procarboxypolypeptidase is activated in a similar manner.
(2)Carbohydrate digestive enzyme10) The pancreatic enzyme for digesting carbohydrates is amylase which hydrolyzes starches，glycogen，and most other carbohydrates except cellulose into disaccharides and some trisaccharides.
(3)Fat digestive enzymes The main enzymes for fat digestion are pancreatic lipase capable of hydrolyzing neutral fat into fatty acids and monoglyceride11),cholesterol esterase capable of hydrolyzing cholesterol esters,and phospholipase which splits fatty acids from phospholipids12).
注释：
1）pancreatic juice 胰液
2）acini 腺泡（acinus的复数）
3）Proteolytic enzymes 蛋白酶，蛋白水解酶，解朊酶
4）trypsin 胰蛋白酶
5）chymotrypsin 糜蛋白酶，胰凝乳蛋白酶
6）carboxypolypeptidase 羧基多肽酶
7）ribonuclease 核糖核酸酶，核糖核苷酸酶
8）deoxyribonuclease 去氧核糖核酸酶，脱氧核糖核酸酶
9）procarboxypeptidase 羧肽酶原
10）Carbohydrate digestive enzyme 碳水化合物消化酶
11）monoglycerides 单甘油酯，单酸甘油酯，甘油一酸酯
12）phospholipids 磷脂，磷脂质