Category: My Classroom Material

Gastric Bacteria

 

The Nobel Prize in Physiology or Medicine for 2005

jointly to

Barry J. Marshall and J. Robin Warren

for their discovery of

“the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease”

 

 Introduction

This year’s Nobel Laureates in Physiology or Medicine made the remarkable and unexpected discovery that inflammation in the stomach (gastritis) as well as ulceration of the stomach or duodenum (peptic ulcer disease) is the result of an infection of the stomach caused by the bacterium Helicobacter pylori.

Robin Warren (born 1937), a pathologist from Perth, Australia, observed small curved bacteria colonizing the lower part of the stomach (antrum) in about 50% of patients from which biopsies had been taken. He made the crucial observation that signs of inflammation were always present in the gastric mucosa close to where the bacteria were seen.

Barry Marshall (born 1951), a young clinical fellow, became interested in Warren’s findings and together they initiated a study of biopsies from 100 patients. After several attempts, Marshall succeeded in cultivating a hitherto unknown bacterial species (later denoted Helicobacter pylori) from several of these biopsies. Together they found that the organism was present in almost all patients with gastric inflammation, duodenal ulcer or gastric ulcer. Based on these results, they proposed that Helicobacter pylori is involved in the aetiology of these diseases.

Even though peptic ulcers could be healed by inhibiting gastric acid production, they frequently relapsed, since bacteria and chronic inflammation of the stomach remained. In treatment studies, Marshall and Warren as well as others showed that patients could be cured from their peptic ulcer disease only when the bacteria were eradicated from the stomach. Thanks to the pioneering discovery by Marshall and Warren, peptic ulcer disease is no longer a chronic, frequently disabling condition, but a disease that can be cured by a short regimen of antibiotics and acid secretion inhibitors.

Peptic ulcer – an infectious disease!

This year’s Nobel Prize in Physiology or Medicine goes to Barry Marshall and Robin Warren, who with tenacity and a prepared mind challenged prevailing dogmas. By using technologies generally available (fibre endoscopy, silver staining of histological sections and culture techniques for microaerophilic bacteria), they made an irrefutable case that the bacterium Helicobacter pylori is causing disease. By culturing the bacteria they made them amenable to scientific study.

In 1982, when this bacterium was discovered by Marshall and Warren, stress and lifestyle were considered the major causes of peptic ulcer disease. It is now firmly established that Helicobacter pylori causes more than 90% of duodenal ulcers and up to 80% of gastric ulcers. The link between Helicobacter pylori infection and subsequent gastritis and peptic ulcer disease has been established through studies of human volunteers, antibiotic treatment studies and epidemiological studies.

Helicobacter pylori causes life-long infection

Helicobacter pylori is a spiral-shaped Gram-negative bacterium that colonizes the stomach in about 50% of all humans. In countries with high socio-economic standards infection is considerably less common than in developing countries where virtually everyone may be infected.

Infection is typically contracted in early childhood, frequently by transmission from mother to child, and the bacteria may remain in the stomach for the rest of the person’s life. This chronic infection is initiated in the lower part of the stomach (antrum). As first reported by Robin Warren, the presence of Helicobacter pylori is always associated with an inflammation of the underlying gastric mucosa as evidenced by an infiltration of inflammatory cells.

The infection is usually asymptomatic but can cause peptic ulcer!

The severity of this inflammation and its location in the stomach is of crucial importance for the diseases that can result from Helicobacter pylori infection. In most individuals Helicobacter pylori infection is asymptomatic. However, about 10-15% of infected individuals will some time experience peptic ulcer disease. Such ulcers are more common in the duodenum than in the stomach itself. Severe complications include bleeding and perforation.

The current view is that the chronic inflammation in the distal part of the stomach caused by Helicobacter pylori infection results in an increased acid production from the non-infected upper corpus region of the stomach. This will predispose for ulcer development in the more vulnerable duodenum.

Malignancies associated with Helicobacter pylori infection

In some individuals Helicobacter pylori also infects the corpus region of the stomach. This results in a more widespread inflammation that predisposes not only to ulcer in the corpus region, but also to stomach cancer. This cancer has decreased in incidence in many countries during the last half-century but still ranks as number two in the world in terms of cancer deaths.

Inflammation in the stomach mucosa is also a risk factor for a special type of lymphatic neoplasm in the stomach, MALT (mucosa associated lymphoid tissue) lymphoma. Since such lymphomas may regress when Helicobacter pylori is eradicated by antibiotics, the bacterium plays an important role in perpetuating this tumour.

 Disease or not – interaction between the bacterium and the human host

Helicobacter pylori is present only in humans and has adapted to the stomach environment. Only a minority of infected individuals develop stomach disease. After Marshall’s and Warren’s discovery, research has been intense. Details underlying the exact pathogenetic mechanisms are continuously being unravelled.

The bacterium itself is extremely variable, and strains differ markedly in many aspects, such as adherence to the gastric mucosa and ability to provoke inflammation. Even in a single infected individual all bacteria are not identical, and during the course of chronic infection bacteria adapt to the changing conditions in the stomach with time.

Likewise, genetic variations among humans may affect their susceptibility to Helicobacter pylori. Not until recently has an animal model been established, the Mongolian gerbil. In this animal, studies of peptic ulcer disease and malignant transformation promise to give more detailed information on disease mechanisms.

Antibiotics cure but can lead to resistance

Helicobacter pylori infection can be diagnosed by antibody tests, by identifying the organism in biopsies taken during endoscopy, or by the non-invasive breath test that identifies bacterial production of an enzyme in the stomach.

An indiscriminate use of antibiotics to eradicate Helicobacter pylori also from healthy carriers would lead to severe problems with bacterial resistance against these important drugs. Therefore, treatment against Helicobacter pylori should be used restrictively in patients without documented gastric or duodenal ulcer disease.

Microbial origin of other chronic inflammatory conditions?

Many diseases in humans such as Crohn’s disease, ulcerative colitis, rheumatoid arthritis and atherosclerosis are due to chronic inflammation. The discovery that one of the most common diseases of mankind, peptic ulcer disease, has a microbial cause, has stimulated the search for microbes as possible causes of other chronic inflammatory conditions.

Even though no definite answers are at hand, recent data clearly suggest that a dysfunction in the recognition of microbial products by the human immune system can result in disease development. The discovery of Helicobacter pylori has led to an increased understanding of the connection between chronic infection, inflammation and cancer.

Source: http://nobelprize.org/nobel_prizes/medicine/laureates/2005/press.html

 

Graphing Practice

Graphing Practice

Introduction

  • Graphing is an important procedure used by scientists to display the data that is collected during a controlled experiment
  • Line graphs must be constructed correctly to accurately portray the data collected
  • Many times the wrong construction of a graph detracts from the acceptance of an individual’s hypothesis
  • A graph contains five major parts:
    a. Title
    b. The independent variable
    c. The dependent variable
    d. The scales for each variable
    e. A legend
  • The title: depicts what the graph is about. By reading the title, the reader should get an idea about the graph. It should be a concise statement placed above the graph.
  • The Independent Variable: is the variable that can be controlled by the experimenter. It usually includes time (dates, minutes, hours), depth (feet, meters), temperature (Celsius). This variable is placed on the X axis (horizontal axis).
  • The Dependent Variable: is the variable that is directly affected by the independent variable. It is the result of what happens because of the independent variable. Example: How many oxygen bubbles are produced by a plant located five meters below the surface of the water? The oxygen bubbles are dependent on the depth of the water. This variable is placed on the Y-axis or vertical axis.
  • The Scales for each Variable: In constructing a graph one needs to know where to plot the points representing the data. In order to do this a scale must be employed to include all the data points. This must also take up a conservative amount of space. It is not suggested to have a run on scale making the graph too hard to manage. The scales should start with 0 and climb based on intervals such as: multiples of 2, 5, 10, 20, 25, 50, or 100. The scale of numbers will be dictated by your data values.
  • The Legend: is a short descriptive narrative concerning the graph’s data. It should be short and concise and placed under the graph.
  • The Mean for a group of variables: To determine the mean for a group of variables, divide the sum of the variables by the total number of variables to get an average.
  • The median for a group of variables: To determine median or “middle” for an even number of values, put the values in ascending order and take the average of the two middle values.    e.g.    2, 3, 4, 5, 9, 10     Add 4+5 (2 middle values) and divide by 2 to get 4.5
  • The mode for a group of variables: The mode for a group of values is the number that occurs most frequently.     e.g.   2, 5,  8, 2,  6,  11    The number 2 is the mode because it occurred most often (twice)  

Procedure 1:
Using the following data, answer the questions below and then construct a line graph.

 

Depth in meters Number of Bubbles / minute Plant A Number of Bubbles / minute Plant B
2 29 21
5 36 27
10 45 40
16 32 50
25 20 34
30 10 20

 

 

1. What is the dependent variable and why?  

2. What is the independent variable and why?

3. What title would you give the graph? .

4. What are the mean, median, and mode of all 3 columns of data? 

a). Depth :                      Mean____________Median__________Mode________ 

b). Bubble Plant A.:        Mean ____________Median_________Mode________ 

c). Bubbles Plant B:        Mean ____________Median_________Mode________

Graph Title: _________________________________________________________

Legend: ______________________________________________________________ 

Procedure 2:
Diabetes is a disease affecting the insulin producing glands of the pancreas. If there is not enough insulin being produced by these cells, the amount of glucose in the blood will remain high. A blood glucose level above 140 for an extended period of time is not considered normal. This disease, if not brought under control, can lead to severe complications and even death. 

Answer the following questions concerning the data below and then graph it.  

 

Time After Eating hours Glucose mg /dL of Blood Person A Glucose mg /dL of Blood Person B
0.5 170 180
1 155 195
1.5 140 230
2 135 245
2.5 140 235
3 135 225
4 130 200

 

 1. What is the dependent variable and why?

2. What is the independent variable and why?

3. What title would you give the graph?

4. Which, if any, of the above individuals (A or B) has diabetes? 

5. What data do you have to support your hypothesis? 

6. If the time period were extended to 6 hours, what would the expected blood glucose level for Person B? 

Title: ________________________________________________________________

Legend: ______________________________________________________________

Summary:
1. What conclusions can be determined from the data in graph 1?

2. What conclusions can be determined from the data in graph 2?

3. Can the data in each of these graphs be used to construct other types of graphs?

4. If so, what other graph types can be constructed?

 
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Gene Expression

 

Gene Expression [18,787 bytes]

 

 

Section 11-1     Control of Gene Expression

 

1. Cells use ______________________ to build hundreds of different________________each with a unique ____________________________.

2. Are all proteins used by a cell at any one time? If not, how do cells control this?

3. Define gene expression.

4. When are proteins produced?

5. What is the genome?

6. What are the 2 steps of gene expression?

7. What 2 scientists determined how genes are expressed in prokaryotes?

8. What gene & in what organism did Jacob & Monod make their discoveries about gene expression?

9. Name the 3 regulatory elements on the DNA of the E. coli bacterium and tell the function of each.

10. What is an operon & what 3 things is it made up of?

11. What name did Jacob & Monod give their gene & why?

12. If lactose is not present, what attaches to the operator?

13. Define repressor protein and give its function.

14. Define repression.

15. What occurs if lactose is present in the E. coli in lactose metabolism?

16. What is an inducer?

17. What is an inducer for E. coli in lactose metabolism?

18. How does the genome of eukaryotes compare with that of prokaryotes?

19. Are operons found in eukaryotes?

20. Each eukaryotic cell contains a ___________________ set of genes, but only some genes

are ______________________ at a given time.

21. What controls much of the gene expression in eukaryotes?

22. What is euchromatin?

23. Some sections of chromatin always remain coiled preventing what process?

24. Name & define the 2 kinds of segments found behind the promoter in eukaryotes.

25. Where do the processes of transcription & translation take place in prokaryotes?

26. Where do these processes take place in eukaryotes?

27. Are introns and/or exons transcribed?

28. What is pre-mRNA and how is mRNA formed from this?

 

Section 11-2     Gene Expression and Development

 

29. Multicellular, sexually reproducing organisms begin life as a _____________________with all cells containing the same _______________________.

30. Genes may be turned ______________ and _____________as various ___________________ are needed by the cells.

31. What is cell differentiation?

32. Define morphogenesis.

33. What genes determine what anatomical structures an organism will develop during morphogenesis?

34. What is a tumor and what are the 2 main types?

35. Define benign tumor.

36. Are benign tumors dangerous? Explain.

37. What treatment do doctors use with benign tumors?

38. Define malignant tumor.

39. Malignant tumors are commonly known as ____________________________.

40. What is metastasis & what happens to the body when this occurs?

41. How are malignant tumors categorized?

42. Name & describe 4 types of malignant tumors.

43. Lung cancer & breast cancer are what type of tumors?

44. When do normal cells stop dividing? Do cancer cells respond the same way? Explain.

45. What trait of cancer cells facilitates the spread of cancer cells in the body?

46. What is a carcinogen & give 5 examples?

47. What causes most lung cancer?

48. What is the effect of mutagens on cells?

49. What are oncogenes?

50. Certain ____________________ can cause cancer in plants & animals.

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Grasshopper Dissection

 

Grasshopper Dissection

 

Introduction:

Insects are arthropods with jointed appendages, segmented bodies, and an exoskeleton composed of chitin. Insects are in the class Insecta, & are the largest and most diverse group of animals on earth. The genus Romalea is a large grasshopper common in the southeastern United States. Insects have three body regions (head, thorax, & abdomen), 3 pairs of legs attached to the thorax, a single pair of antenna attached to the head, mouthparts adapted for chewing or sucking, and two pairs of wings. Some insects may have a single pair of wings or be wingless. Insect legs are often adapted for digging, crawling, jumping, or swimming. The insects are mostly terrestrial, they breathe air which enters small lateral openings on the body called spiracles and circulates in a system of ducts to all organs and tissues. Their chewing or sucking mouth parts are adapted  for  feeding on plant or animal materials.

Classification:

Kingdom – Animalia
Phylum – Arthropoda
Class – Insecta
Order – Orthoptera

Objective:

Identify & label the internal & external anatomy of a grasshopper.

Materials:

Lab apron, gloves, eyeglasses, dissecting pan, dissecting kit with forceps & scalpel, t-pins, magnifying glass, preserved grasshopper, paper, pencil.

Procedure (External Anatomy): Examine the entire grasshopper and identify the major subdivisions and parts of the body.  

  1. Obtain a preserved grasshopper & rinse off any preservative with water. Place grasshopper in the dissecting pan.

  1. Observe that the body of the grasshopper is divided into 3 regions — the head, the thorax, and abdomen. Label these on Figure 2.
  2. Examine the head and locate the following parts:
    HEAD
    Antennae (two, slender appendages)
    Compound eyes (2, large lateral)
    Ocelli (or simple eyes) – 3, small, between compound eyes
    Mouth parts – Labrum (upper lip), mandibles (jaws) below the labrum, maxillae located behind the mandibles to help cut & hold food, and the lower lip or labium

 

 

          1. Labrum          4. Labium
          2. Mandibles          5. Maxillary Palps
          3. Labial Palps          6. Maxillae
          7. compound eye          8. ocelli

 

 

  1. Label the mouthparts, eyes, and antenna on Figure 1.
  2. Using forceps, remove each of the appendages from the head, and attached them to table 1.
  3. Examine the following appendages on the thorax (middle section of the grasshopper’s body):

   THORAX
Legs (first 2 pairs are for walking & the last pair are for jumping)
Wings (forewings have a leathery appearance & protect the hind wings)

  1. Using forceps, remove one of the walking legs and identify these parts — the coxa connects the femur (the thickest part of the leg) to the grasshopper’s body; a slender, spiny tibia connects the femur to the tarsal segments (lowest part of the leg). Label these on Figure 2.
  2. Remove a jumping leg and attach the walking leg & jumping leg to Table 1.
  3. Raise both pairs of wings and locate the first abdominal segment.
  4. Locate the tympanic membrane or eardrum on the first abdominal segment. Label this on Figure 2.

  1. Using a magnifying glass, locate the spiracles or tiny pores for respiration on each side of the abdominal segments.  Label these on Figure 2.
  2. Determine if your grasshopper is a male or female by looking at the end of the abdomen. Females have a tapered abdomen that ends in a pointed egg laying tube called the ovipositor. Male have a more rounded abdomen that turns upward.

  1. Label the ovipositor on Figure 2.

ABDOMEN
Spiracles (small openings on the side of somites or body segments)
Auditory Organs (two located laterally on the 1st body somite or segment)
Ovipositor (on female)

Observations & Conclusion:

Figure 1 – Grasshopper Head (Label ALL parts.)

 

Figure 2 – External Grasshopper anatomy (Label ALL parts.)

Table 1 – External Appendages of the Grasshopper (Attach ALL parts.)

 

Antenna

 
Labrum

 
Mandible

 
Maxilla

 
Labium

 
Forewing

 
Hindwing

 
Walking Leg

 
Jumping Leg

 
Sex of Grasshopper

 

 

1. Which region of the insect’s body is specialized for sensory functions? Explain your answer.

 

2. Which region of the insect’s body is specialized for movement & explain why?

 

3. What is the purpose of compound eyes? of simple eyes?

4. List the grasshopper’s mouthparts & their functions.

 

 

5. How are the ends of the legs adapted for holding onto plants?

 

6. How is the third pair of legs adapted for jumping?

 

7. Describe the differences between the two pairs of wings (appearance & function).

 

8. How does the tympanic membrane help a grasshopper?

9. What system do spiracles open into on a grasshopper?

10. Do all abdominal segments have spiracles? Are there any spiracles on the thoraic segments?

11. How did you determine the sex of your grasshopper?

 

12. Explain how grasshoppers dig holes to lay their eggs.