School Biology Teachers Research Articles

Some aspects of catalase induction in baker's yeast (Saccharomyces cerevisiae)

Yeasts grown in anaerobic liquid media produced catalase in response to the presence of H2O2 in the growth medium. The fact that some of the induced enzyme was active at the cell surface, bound either to the cell wall or cell-surface membrane, eliminated the need to crush cells in order to release the enzyme complement. Instead, catalase production was monitored by using H2O2-reagent strips to detect changes in the level of H2O2, in the growth medium. In addition, catalase induction in yeasts was found to be temperature-sensitive. It is suggested that biology teachers in schools might find the following experiments useful for demonstrating essential features of substrate-induced enzyme synthesis, based on the Jacob-Monod model, and for showing that the activity of certain genes can be modified by environmental temperature.

The Use of Balsa Wood in the Preparation of Skins of Small Mammals

Many biology teachers in high schools and colleges maintain a small collection of mammal skins for teaching use. These collections are subject to much unskilled handling and as a result there is likely to be considerable damage to even the best-made specimens. Legs and tails are frequently lost, so that replacements are constantly needed. In the case of common species this is no more than a nuisance, but specimens which cannot be

A Simple Method of Mounting Small Exhibit Specimens of Mammals and Birds

At regular intervals, biology teachers are confronted with the problem of presenting their work graphically to boards, patrons and laity. Biology teachers in high schools and colleges are frequently charged with the task of preparing such exhibits in order to found or expand the Museum of the Biological Department as a teaching adjunct. Because an expense acount seldom envisages the preparation of these demonstrations, professional assistance cannot be readily procured. It is for the above reasons that I believe my simple method of mounting small mammals is worth placing on record. This technique was first applied to mouse specimens exhibited at the Harvard Tercentenary in 1936, and more recently it has been employed on rats for the museum collections of the Wistar Institute, where they will be pointed out upon request. There is no reason why this method can not be readily extended with modifications to small birds and mammals generally. For the sake of simplicity I shall here describe the method as applied to the rat. First, kill the rat with a lethal dose of ether, or chloroform or by some other method that will not harm the anatomy. Inject 10 cc of 40 per cent. formaldehyde into the thoradie cavity and another 10 cc into the abdominal cavity, massaging the animal to distribute the injection fluid within the body cavities. Inject smliall amounts into the legs and subcutaneously over the body. Within 15 minutes to half an hour subsequent to this injection the body will stiffen. When fairly rigid, place the rat upon a small temporary base-block of wood in the position desired for the finished specimen. Brad the rat's tail to the block. Then brad the four feet to their proper positions bending the body into the pose desired. The hips may be prevented from moving laterally by hammering several 7-penny nails into the block adjacent to the hips. The head may be held up by resting the teeth on a block of proper dimensions. See Fig. A. When the animal is in the position desired, allow it to stand an hour or so until it has completely hardened. Invert the specimen and wash it thoroughly under a faucet so water will wet the whole outer surface of the skin. Place the inverted specimen, block and all, into a jar of formalin and allow it to stand 24 hours. The previous washing removes all air caught in the fur that might prevent areas of the skin from coming in contact with formalin. After the specimen has cured 24 hours in formalin, wash under the faucet for a few minutes to remove all traces of formalin, which will attack the skin of the operator 's hands, unless they are otherwise protected. Lay the specimen on its back, and with a sharp razor blade cut the skin along the mid-ventral line from throat to geni1 Reprinted in part from Science.

A Simple Method of Mounting Small Exhibit Specimens of Mammals and Birds

At regular intervals, biology teachers are confronted with the problem of presenting their work graphically to boards, patrons and laity. Biology teachers in high schools and colleges are frequently charged with the task of preparing such exhibits in order to found or expand the Museum of the Biological Department as a teaching adjunct. Because an expense acount seldom envisages the preparation of these demonstrations, professional assistance cannot be readily procured. It is for the above reasons that I believe my simple method of mounting small mammals is worth placing on record. This technique was first applied to mouse specimens exhibited at the Harvard Tercentenary in 1936, and more recently it has been employed on rats for the museum collections of the Wistar Institute, where they will be pointed out upon request. There is no reason why this method can not be readily extended with modifications to small birds and mammals generally. For the sake of simplicity I shall here describe the method as applied to the rat. First, kill the rat with a lethal dose of ether, or chloroform or by some other method that will not harm the anatomy. Inject 10 cc of 40 per cent. formaldehyde into the thoradie cavity and another 10 cc into the abdominal cavity, massaging the animal to distribute the injection fluid within the body cavities. Inject smliall amounts into the legs and subcutaneously over the body. Within 15 minutes to half an hour subsequent to this injection the body will stiffen. When fairly rigid, place the rat upon a small temporary base-block of wood in the position desired for the finished specimen. Brad the rat's tail to the block. Then brad the four feet to their proper positions bending the body into the pose desired. The hips may be prevented from moving laterally by hammering several 7-penny nails into the block adjacent to the hips. The head may be held up by resting the teeth on a block of proper dimensions. See Fig. A. When the animal is in the position desired, allow it to stand an hour or so until it has completely hardened. Invert the specimen and wash it thoroughly under a faucet so water will wet the whole outer surface of the skin. Place the inverted specimen, block and all, into a jar of formalin and allow it to stand 24 hours. The previous washing removes all air caught in the fur that might prevent areas of the skin from coming in contact with formalin. After the specimen has cured 24 hours in formalin, wash under the faucet for a few minutes to remove all traces of formalin, which will attack the skin of the operator 's hands, unless they are otherwise protected. Lay the specimen on its back, and with a sharp razor blade cut the skin along the mid-ventral line from throat to geni1 Reprinted in part from Science.