Exercise A The Blackworm Model to Test Bioactive Drugs

To test the actions of bioactive drugs derived from plants, you will work with a segmented worm, or annelid. In dicsc worms, the body is organized into repeated rings or segments. Annelids can be found in terrestrial, freshwater, and marine environments. There are three classes of annelids, based on the relative number of bristles, or setae on the body wall. You will be studying a spccics within the oligochaetes, annelids that have few bristles—in this case, only four per segment.

Our experimental animal is the California blackworm, or mudworm (l.umbricttlus varicgnttis) (fig. 17.1). It is found throughout North America at die edge of freshwater ponds, lakes, and marshes. This free living animal survives by ingesting organic debris and microscopic algae. It is a small worm, only 2.5-5.0 cm in total length. It has a closed circulatory system, much like our own in that the blood is contained within blood vessels. Two major blood vessels, the ventral and dorsal vessels, run lengthwise from head to tail, and several lateral vessels connect the two in the anterior segments. The dorsal (along the backside) blood vessel acts as die heart, pumping the blood through wavelikc contractions of its

California Blackworms

FIGURE 17.1 THE CALIFORNIA BLACKWORM (LUMBRICULUS VARIEGATUS).

muscular walls. The blood of the worm is also like ours in that it is bright red due to the presence of a hemoglobin like pigment (crythrocuruorin) that transports oxygen. Unlike our circulator) system, this pigment is not contained in red blood cells but is dissolved in the plasma.

Since the body wall of the worm is transparent, you will be able to observe the blood directly as it pulses through the dorsal vessel. By immersing the worms in \ar-ious plant extracts, you will observe the bioactivc effects of these drugs on the worms' circulatory systems. It is expected that the pulse rate of the California blackworm will be affected by the plant drugs just as our circulatory system is affcctcd by these same drugs. Please note that the worms will not be harmed by this testing.

The plant extracts or plant derived drugs available for testing are listed in table 17.1.

Materials Needed for Exercise A

California blackworms (Lumbriculus varicjjartts) Compound light microscope

Kimwipcs

Marker pen

Observation chamber

Paper cups, 5-oz si/e

Pan of spring water for fresh worms

Pan of spring water for used worms

Pasteur pipct, large bore l est solutions of nicotine, caffeine, kava kava, digitoxin, ephedrine, or pscudocphcdrine

Spring water

Worm w rangling tools

Watch or clock with second hand

Procedure for Exercise A

  1. You will need a lab partner for this exercise. One student observes and counts the pulsation rates of the test worms, while the other student acts as a timer and recorder of the data.
  2. Decide upon a bioactivc plant extract or drug to test. Label one paper cup as the control and three other paper cups with the appropriate concentrations of the drug or extract solutions. Obtain a compound microscope, observation chamber, Pasteur pipets (one for each solution and concentration», and a worm wrangling tool.
  3. With die Pasteur pipct. select four worms from the culture pan and place them in a cup of spring water. Make sure the worms arc approximately the same length. Do not pick worms that have recently regenerated tail scg mcnts. Regenerated segments will be unpigmentcd.
  4. The next step is to determine the baseline pulse rate in spring water (before treatment) for each of the four worms. Using the pipct, place one worm in the observation chamber (fig. 17.2). Add enough spring water so that the worm will not dry out, but do not overfill or the worm will leave the confines of the trough. The water level should just till the trough. Absorb any
TA B L E 17.1 BIOACTIVE PLANTS AND THEIR PRINCIPLES

COMMON NAME

SCIENTIFIC NAME

PART USED

ACTIVE PRINCIPLE

DRUG CLASSIFICATION

Coffee tree, tea bush, and other species

Coffee spp., Ccmelho sinensis.

Leaves

Caffeine

Alkaloid

Ephedra, ma huang

Ephedra sintca

Stem

Ephedrine, pseudoephedrine

Alkaloid

Foxglove

Digaalis purporeo

Leaves

Digitoxin

Glycoside

Kava

Piper meifiysuum

Rhizome

Kawaic »

Lactone

Tobacco

Nfcovona spp.

Leaves

Nicotine

Alkaloid

How Check Pulsation Rate Blackworm

FIGURE 17.2 OBSERVATION CHAMBER

  1. After each drug treatment. rinse the worm briefly in spring water and then place the worm in the pan marked "used worms." It is very important to prevent contamination by rinsing the observation chamber thoroughly with spring water after a pulse reading is taken on a drug-treated worm.
  2. Calculate the means for both before and after treatment, and analyze the data in worksheet 17 1

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Responses

  • hana abel
    How to check pulsation rate blackworm?
    8 years ago

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