Preface

The stomach is one of the most critical organ in our body and is also the one that suffers most, because it carries many burdens in addition to its own duty. Our biological body relies on two sources of supply from the environment: oxygen taken in through the respiratory system and food through the digestive tract. While breathing is an involuntary action, meaning that the body does it automatically without our effort, eating is not. If we do not eat actively, we will die of starvation. The Chinese has an old saying, "Living is for eating and wearing," and another one goes like this, "Eating and sleeping are essential for life." They both recognize the importance of eating. In modern civilization, eating is no longer just a way to provide nutritional supply to the body. It has become an entertainment activity as well. We like to entertain our taste buds with various food, all sorts of flavors, and some‐ times even try some exotics just for fun. We eat French cuisine today and perhaps Italian tomorrow; Kentucky fried chicken for lunch, and perhaps Korean barbecue for dinner. As a result, our stomach has to learn to deal with all of these frequent changes. One might say, "That's a duty for being a digestive organ. What else do you expect?" Well, let's say this is true. We must eat when we are hungry, but what about drinking? Every time when we are thirsty, we will let the stomach carry a load of liquid. If it is just water, that would be fine too. But, a lot of people are carelessly pouring whisky or vodka down the throat. These bev‐ erages contain at least 40% ethanol and can damage the stomach lining and cause gastritis, ulceration, or even gastric malignancy. What is even worse is smoking. Supposedly smoking ought to be a job for the respiratory system, but part of our digestive system (mouth and esophagus at least) has to suffer from it as well. Smoking can not only weaken the lower esophageal sphincter and allow acid reflux to happen but can also reduce mucus secretion in the stomach and elevate the risk of gastric ulcers or even cancer. That's not all. Every time when we are sick, we feed the stomach with all kinds of drugs regardless whether it is a stomach problem. Moreover, some people have no self-control over food. They keep eating and eating and eventually become obese, but they blame the stomach for it. They either have their stomachs tightened up with a band (gastric band) or have a slice cut off (sleeve gastrec‐ tomy). Even after all these, our stomach still keeps doing its job day and night dutifully and makes sure our body gets the best quality supplies that this organ can possibly provide.

The stomach is commonly known as a digestive organ; however, as pointed out in Chapter 1, its functions are far beyond simple digestion. First, the stomach is a place for food storage, and for this reason, we do not need to eat frequently in order to maintain health. This allows us to be able to concentrate on our work for hours without being distracted by food con‐ sumption. The stomach can also act as the first line of defense for our body by sterilizing the food that we have swallowed. Although the food has been passing through the mouth and the esophagus before reaching the stomach, these two parts of the digestive system do not

have sophisticated defense mechanisms, and the food only stays in there briefly. The true interface between our internal biological machinery and the external world is our stomach. Once the food gets into the stomach, the stomach keeps the food inside for several hours and washes the food with its highly acidic juice up and down, back and forth, making sure there is no chance for any pathogens to go further into the rest of our body.

Among all the cancers known so far, gastric cancer is ranked globally as number five by its prevalence and number three by its mortality. Like other digestive disorders, gastric cancer is more common in developing countries, particularly in East Asia and Eastern Europe. Among all the risk factors, *Helicobacter pylori* infection has been found to be the predominant one. Considering the fact that more than half of the world population is carrying this bacte‐ rium, we can imagine the risk of stomach cancer. Over 90% of gastric malignancies are ade‐ nocarcinoma, which develops from the glandular epithelial cells. Chapter 2, "Molecular Pathogenesis of Gastric Adenocarcinoma," written by scholars from the Chinese University of Hong Kong, gives us an update about this disease from molecular perspective and raises several interesting questions about molecules involved in the cancer development and their therapeutic potential. It opens up some urgent areas for us to dig deeper.

There are many disorders associated with the stomach, but gastric ulcer is the most common chronic infection in the entire human population. Although it mainly affects the developing countries, it can be found in other regions of the world as well. *Helicobacter pylori* infection has been blamed for the majority of cases; therefore, eradication of the bacterium has helped to control the disease significantly. However, the stomach lumen contains some powerful harsh agents (such as hydrochloric acid and pepsin) that can cause ulceration whenever there is a chance for them to make a direct contact with the gastric epithelium. For this reason, any damages to the mucous layer of the stomach can be opportunities for ulcers to develop. The long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) creates such opportunities. NSAIDs function as pain relievers by inhibiting cyclooxygenase (COX), which is responsible for the synthesis of prostaglandin. Without adequate prostaglandin, the mucous layer cannot be renewed as it is needed periodically, and as a consequence, the gastric mucosa becomes vulnerable for any harsh agents. People have a long history of using various plants or their derivatives to treat stomach ulcers. Chapter 3, "The Purview of Phytotherapy in the Manage‐ ment of Gastric Ulcer," contributed by our African colleagues, broadens the topic further by reviewing nearly 70 species of plants that have been reported for their antiulcer effects. This is an excellent reference for people who are interested in some further studies on these plants, such as molecular mechanisms of their actions in gastric protection, etc.

Portal hypertensive gastropathy (PHG) and gastric antral vascular ectasia (GAVE) are two poorly studied conditions, basically referring to two types of gastritis in patients with portal hypertension. However, their pathophysiology and treatment options are different. It should be clear that not all portal hypertension patients will develop PHG or GAVE defi‐ nitely. PHG only happens to 20–75% of portal hypertension patients. They both can cause gastric bleeding and other complications. As portal hypertension is mainly caused by cirrho‐ sis, both PHG and GAVE are frequently found in association with liver cirrhosis. In Chap‐ ters 4 and 5, Dr. Ramai, Linn, and Reddy (Brooklyn Hospital Center, USA, and St George's University School of Medicine, Grenada) and Dr. Gamie (Helwan University, Egypt) update us with a detailed review on these rare diseases. Reading through these papers gives you an urgent feeling for more study, because the available data are just too inconclusive.

Gastroenteritis, commonly known as the "stomach flu," is an infectious disease, although it has nothing to do with influenza. It is mainly caused by viruses, especially rotavirus, which is responsible for about 70% of the patients, but other pathogens like bacteria, parasites, and even fungi can induce gastroenteritis as well. Children are the main targets, especially in de‐ veloping countries. In the United States, gastroenteritis represents the second most common infection after the common cold. Among 2 billion cases worldwide in the year 2015, 1.3 million were dead, and most of them were children under five. Although we were unable to include an essay on human gastroenteritis in this book, Chapter 6, "Application of Transmission Elec‐ tron Microscopy Techniques in the Veterinary Diagnosis of Viral Gastroenteritis in Livestock Animals," contributed by Catroxo and Martins, introduces the disease in livestock and gives a detailed description on how to use electron microscope to identify the pathogens. Coincident‐ ly, rotavirus was also found as the main cause of animal gastroenteritis. Therefore, this work remains valuable to our human studies. Besides, electron microscopic technique is universal. In order to make the best vaccines for this disease, identification of the pathogens is critical. Transmission electron microscopy has been proved to be a reliable method to do the job.

have sophisticated defense mechanisms, and the food only stays in there briefly. The true interface between our internal biological machinery and the external world is our stomach. Once the food gets into the stomach, the stomach keeps the food inside for several hours and washes the food with its highly acidic juice up and down, back and forth, making sure

Among all the cancers known so far, gastric cancer is ranked globally as number five by its prevalence and number three by its mortality. Like other digestive disorders, gastric cancer is more common in developing countries, particularly in East Asia and Eastern Europe. Among all the risk factors, *Helicobacter pylori* infection has been found to be the predominant one. Considering the fact that more than half of the world population is carrying this bacte‐ rium, we can imagine the risk of stomach cancer. Over 90% of gastric malignancies are ade‐ nocarcinoma, which develops from the glandular epithelial cells. Chapter 2, "Molecular Pathogenesis of Gastric Adenocarcinoma," written by scholars from the Chinese University of Hong Kong, gives us an update about this disease from molecular perspective and raises several interesting questions about molecules involved in the cancer development and their

There are many disorders associated with the stomach, but gastric ulcer is the most common chronic infection in the entire human population. Although it mainly affects the developing countries, it can be found in other regions of the world as well. *Helicobacter pylori* infection has been blamed for the majority of cases; therefore, eradication of the bacterium has helped to control the disease significantly. However, the stomach lumen contains some powerful harsh agents (such as hydrochloric acid and pepsin) that can cause ulceration whenever there is a chance for them to make a direct contact with the gastric epithelium. For this reason, any damages to the mucous layer of the stomach can be opportunities for ulcers to develop. The long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) creates such opportunities. NSAIDs function as pain relievers by inhibiting cyclooxygenase (COX), which is responsible for the synthesis of prostaglandin. Without adequate prostaglandin, the mucous layer cannot be renewed as it is needed periodically, and as a consequence, the gastric mucosa becomes vulnerable for any harsh agents. People have a long history of using various plants or their derivatives to treat stomach ulcers. Chapter 3, "The Purview of Phytotherapy in the Manage‐ ment of Gastric Ulcer," contributed by our African colleagues, broadens the topic further by reviewing nearly 70 species of plants that have been reported for their antiulcer effects. This is an excellent reference for people who are interested in some further studies on these plants,

Portal hypertensive gastropathy (PHG) and gastric antral vascular ectasia (GAVE) are two poorly studied conditions, basically referring to two types of gastritis in patients with portal hypertension. However, their pathophysiology and treatment options are different. It should be clear that not all portal hypertension patients will develop PHG or GAVE defi‐ nitely. PHG only happens to 20–75% of portal hypertension patients. They both can cause gastric bleeding and other complications. As portal hypertension is mainly caused by cirrho‐ sis, both PHG and GAVE are frequently found in association with liver cirrhosis. In Chap‐ ters 4 and 5, Dr. Ramai, Linn, and Reddy (Brooklyn Hospital Center, USA, and St George's University School of Medicine, Grenada) and Dr. Gamie (Helwan University, Egypt) update us with a detailed review on these rare diseases. Reading through these papers gives you an

urgent feeling for more study, because the available data are just too inconclusive.

there is no chance for any pathogens to go further into the rest of our body.

VIII Preface

therapeutic potential. It opens up some urgent areas for us to dig deeper.

such as molecular mechanisms of their actions in gastric protection, etc.

We can choose what to eat, when to eat, and how to eat. However, whatever we eat, the stomach is the first station to store it, to inspect it, to process it, and finally to issue a pass for its next journey. Without a healthy stomach, we cannot have a happy life. So, please take good care of it.

> **Jianyuan Chai, PhD** Baotou Medical College, China University of California, USA

**Provisional chapter**
