Fluorescence Microscopy Digital Image Gallery
Rat Stomach Tissue Sections
The stomach of the rat is divided into only two main sections: the forestomach and the corpus, or body. The contents of the esophagus empty into the forestomach, the walls of which are thin and similar to the esophageal walls. Non-glandular, the forestomach chiefly serves as a temporary storage location for ingested material before it enters the corpus of the stomach, from which it is divided by a fold of tissue known as the limiting ridge. Secretory glands located in the thick walls of the corpus supply mucus and enzymes that facilitate the beginning of the digestive process. From the corpus ingesta passes through the pyloric sphincter to the duodenum.
The barrier between the rat stomach and esophagus is very strong. This fact, along with the inability of the rodent’s diaphragm muscles to contract independently and the lack of certain nervous system connections, renders the rat nonemetic. Animals that are nonemetic are never able to involuntarily expel the contents of the stomach, an act commonly known as vomiting. One of the main purposes of vomiting is to protect the body by quickly eliminating any ingested toxins. Since they cannot vomit, rats must protect themselves from toxic substances via other means. One of the methods they employ is to taste new items they encounter in very small quantities so that if they are toxic they are likely to only become sick rather than to be more seriously harmed. If illness does develop, they learn to avoid that food in the future. Another way rats handle toxins is to consume clay or other nonfood substances if they become nauseous. Such materials can combine with toxins in the stomach in order to mitigate their effects.
The cytoskeletal F-actin network was targeted in a sample of the pylorus region of a rat stomach (presented above) with phalloidin conjugated to Alexa Fluor 488. Phalloidin is a member of the phallotoxin group of bicyclic peptides isolated from the deadly Amanita phalloides mushroom. The tissue section was also labeled for nuclear DNA with Hoechst 33342 and the Golgi complex with Texas Red conjugated to wheat germ agglutinin (WGA). Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.
Additional Widefield Fluorescence Images of Rat Stomach Tissue Sections
Section of Rat Pylorus Skeletal Muscle Tissue Labeled with Wheat Germ Agglutinin and Phalloidin - Epithelial cells located inside the stomach are specialized for secretory activity. The four major kinds of the cells include mucus cells, chief cells, parietal cells, and G cells. Mucus cells, which secrete alkaline mucus that protects the stomach from self-digestion, are the most abundant gastric epithelial cells. They line the entire lumenal surface, even reaching into the necks of gastric glands, where they are referred to as mucus neck cells.
Localizing Fluorescent Tags to the Golgi Complex and the F-Actin Cytoskeleton in Rat Stomach Samples - In cows, goats, sheep, and other ruminants the stomach is composed of multiple chambers: the rumen, reticulum, omasum, and abomasum. This design facilitates the break down of the thick cell walls of plants and the digestion of cellulose in a multi-step process involving the formation of regurgitation of cud. Ruminant digestion is also heavily dependent on symbiotic bacteria and protozoa that inhabit the stomach. Rodents are not ruminants, but similar to those species usually reingest material that was already partially digested.
Pylorus Region of Rat Stomach with Alexa Fluor 488, Texas Red, and Hoechst 33342 - The stomach and other parts of the gastrointestinal system are layered structures. In the stomach, the innermost stratum (nearest the lumen) is the mucosa, which is comprised of an epithelial lining, a loose layer of connective tissue called the lamina propria, and the muscularis mucosa, which consists of smooth muscle tissue. The next division of the stomach is the submucosa, a stratum of connective tissue interspersed with many blood and lymphatic vessels. Surrounding the submucosa is the muscularis externa, which is composed of three layers of muscle rather than only two layers, as it is in other sections off the gastrointestinal tract. The outermost stratum of the stomach is a covering of connective tissue called the serosa or adventitia.
Sialic Acid Residues, Filamentous Actin, and Nuclear DNA in Rat Fundus Tissue - The gastric mucosa secretes a number of substances, including acid, mucus, hormones, and proteases. Parietal cells are responsible for the release of hydrochloric acid into the deep plasma membrane invaginations known as canaliculi. The acid, which helps break down ingested material, is so strong that it could easily eat through wood. Gastrin, a hormone secreted by the g-cells of the mucosa, is primarily responsible for the regulation of the parietal cells’ acid secretion.
Rat Stomach Fundus Region Tissue Section Labeled with Fluorescent Probes Conjugated to Phallotoxins and Lectins - Most cells in the gastric epithelium are linked to neighboring cells via tight junctions, as are intestinal epithelial cells. Tight junctions not only seal adjacent cells together, but also separate apical membranes from basolateral membranes. These cell-cell junctions are important as a critical part of the gastrointestinal barrier that shields the body from ingested materials until they can be broken down and absorbed or eliminated.
Triple Staining of Stomach Tissue Sample with Alexa Fluor 568, Oregon Green 488, and Hoechst 33342 - The stomach does not absorb many substances. One of the few macronutrients that the stomach is able to absorb is ethanol, the intoxicating substance in fermented and distilled liquors. Only a small amount of ethanol passing through the stomach is absorbed, and this absorption is facilitated by an enzyme, alcohol dehydrogenase, which is secreted by the gastric wall, and by the liver in significantly larger amounts. Alcohol dehydrogenase converts ethanol into acetaldehyde, which is then further modified to produce acetate and other molecules utilizable by cells.
Targeting Sialic Acid Residues, Filamentous Actin, and Nuclei in Rat Gastric Tissue - The stomach is a sac-like organ that in humans exhibits a J-shape and can be considered to be divided into several different sections. The small gastric region adjacent to the esophagus is called the proximal stomach or the cardia. Neighboring this section is the main body of the organ and along the upper part of the body is the fundus. The lower region located next to the small intestine is the distal stomach, which includes the antrum and the pylorus.
Probing Golgi Networks and Filamentous Actin Networks in a Sample of Rat Stomach Tissue - The best-known constituent of gastric juice is hydrochloric acid, which is produced by parietal cells. The secretion of hydrochloric acid is triggered by at least three different stimuli: gastrin, histamine (H2), and acetylcholine. Receptors for these molecules are located on the surface of parietal cells. The extent of hydrochloric acid secretion appears to be a function of a complicated additive or multiplicative interaction of receptor signals of each sort.
Rat Pylorus Region Labeled with Alexa Fluor 568, Oregon Green 488, and Hoechst 33342 - When material first reaches the stomach, it has already been through the initial stages of digestion involving mastication and exposure to saliva. The digestive process continues in the stomach, where secreted chemicals and enzymes, as well as the strong contractions of gastric muscles, help to further breakdown foodstuffs. Solids are liquefied in the stomach before they are gradually moved into the small intestine for the next stage of digestion.
Localizing Fluorescent Tags to Filamentous Actin and Golgi Complexes in Gastric Tissue - While many types of cancer have increased in incidence over the last several decades, stomach cancer has declined significantly in the United States and many other parts of the world. It is widely thought that this decline may be related to the widespread use of refrigeration and a decreased dependence on smoked, salted, and pickled foods. Some researchers have also suggested that the decrease in stomach cancer is largely attributable to the prevalent dispensation of antibiotics to children with infections.
Rat Stomach Section Treated with Wheat Germ Agglutinin and Phalloidin Conjugates - Even when the stomach is empty, the organ is not entirely inactive. A cycle of electromechanical activity, known as the migrating motor complex, occurs in humans about once every one and a half to two hours throughout the gastrointestinal tract. There are four phases of the cycle, which is thought to help clear out any residual material in the digestive system. In the first phase, gastrointestinal smooth muscle is largely quiescent, very few contractions taking place for nearly an hour.
Labeling Gastric Tissue with Fluorescent Probes Conjugated to Phallotoxins and Lectins - Gastric cancers most commonly develop in the mucosa of the stomach over long periods of time. The vast majority (90 to 95 percent) of cases are adenocarcinomas, which originate in the epithelial cells of glandular tissue. Other tumor types that can develop in the stomach, though much less often, include carcinoid tumors, gastrointestinal stromal tumors, and lymphoma. Typically pre-cancerous lesions form prior to the onset of gastric cancers, but these are rarely detected because they tend to be nonsymptomatic.
Pylorus Tissue Sample Probed with Texas Red, Alexa Fluor 488, and Hoechst 33342 - The stomach’s chief cells synthesize the enzyme chymosin, also known as rennin, which is important in the digestion of milk. Most liquids pass very quickly through the stomach to the small intestine because they do not need to be broken down to the same extent as solids. Milk, however, is partially coagulated in the stomach due to the proteolytic action of chymosin. In its semisolid form, milk is retained in the stomach for a longer period of time than it would be as a liquid. Consequently, there is greater opportunity for proteins in milk to be digested in the stomach.
Stomach Tissue Labeled with Oregon Green 488 Conjugated to Wheat Germ Agglutinin - A number of risk factors have been identified that increase the likelihood that someone will develop cancer of the stomach. Age is a particularly notable risk factor, prevalence of the disease increasing sharply among individuals over the age of 50. Stomach cancer is also twice as common among men as women, and is more prevalent among African American, Asian, and Hispanic peoples than white Americans. Differences in customary diet and eating habits are thought to at least partially underlie ethnicity and gender differences in stomach cancer rates.
Probing Rat Tissue Sections with Alexa Fluor 488 Conjugated to a Lectin Isolated from the Red Kidney Bean - Due to the design of the rodent digestive system, most rodents must consume their food twice before nutrients can be efficiently absorbed. Rodents are primarily herbivores that consume large amounts of plant cellulose that is difficult to digest. When food is initially ingested by a rodent, it is softened in the stomach and is carried to the small intestine and then a large, post-digestive cecum that houses a dense collection of bacteria.