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GIEMSA BANDING OF CHROMOSOMES
1285 cular development of the fetus is just sufficient to maintain life at 28-weeks gestation (1000 g.). Therefore, these infants require 100% of their alveoli to survive. A 10% loss of lung tissue due to atelectasis, caused by aspiration of amniotic fluid and its contents, will cause considerable respiratory distress in the premature infant, who may not survive. However, in a more mature infant much more atelectasis may be tolerated. In a full-term infant 50% or more of the lung may be atelectatic and the infant may still survive. The reason for the high incidence of R.D.S. in cxsarean section is probably, as Dr. Liu says, the lack of thoracicThis compression is important not cage compression. because it squeezes out innocuous tracheal fluid, but because it prevents aspiration of amniotic fluid and its contents.
Therefore, I believe that any factor, such as improper fundal pressure, that may lead to aspiration must be identified and, if possible, avoided. Newborn Nurseries, Hôtel Dieu and Cornwall General Hospitals,
Cornwall, Ontario, Canada.
CHARLES B. PENDER.
with a solution which is deficient in the divalent cations, Ca++ and Mg++. Trypsin itself is known to bind calcium ions.44 We have therefore tested the hypothesis that elimination of such cations plays a decisive role in the production of Giemsa banding. The usual glacial-acetic-acid/methanol (1/3) fixed chromosomes were treated with Hanks’ balanced salt solution (B.s.s.) minus calcium and magnesium for 15-120 seconds before staining with Giemsa (Fisher Scientific Co., 1% solution in Tris maleate buffer at pH 5-6). This pretreat-
technique produces chromosome banding (see accomPretreatment with B.S.S. containing Mg++ and Ca++ also produces some chromosome banding, but only after more prolonged treatment. The addition of 0.25% trypsin-0-025% E.D.T.A. (GIBCO) to both types of B.s.s. greatly speeds the banding process. Pretreatment with the chelating agent, E.D.T.A., which is often a component of trypsin solutions, also produces some banding. It seems likely that Giemsa banding of chromosomes can be produced by any pretreatment which removes divalent ment
panying figure).
cations from the chromosomes. relative
experiments, and of the Mg++, is in preparation.
Departments of Human Genetics and Development and Obstetrics and Gynecology, College of Physicians and Surgeons, Columbia University,
GIEMSA BANDING OF CHROMOSOMES
SIR,-Dr. Miiller and Professor Rosenkranz (April 22, p. 898) have reported that Giemsa staining produces a characteristic pattern of chromosomal banding after treatment of fixed metaphase chromosomes with Pancreatin ’, a mixture of the enzymes protease, amylase, and lipase. Similar results have been obtained with solutions of trypsin,l «-chymotrypsin,2and pronase.3 However, in none of these reports was any evidence presented to show that the chromosome banding effect is related to the proteolytic activity of the enzyme preparations. We have been led to question the importance of the enzyme activity of these solutions because excellent bandings can be obtained by pretreatment with trypsin-containing solutions even at 4°C and a pH of 6-8 for no more than 30 seconds. In view of the narrow pH and temperature optima of trypsin, this effect is not likely to be due to enzyme reaction. A common factor in all the Giemsa-banding methods seems to be pretreatment of fixed metaphase chromosomes 1. Seabright, M. Lancet, 1971, ii, 971. 2. Finaz, C., de Grouchy, J. Ann. Genet. 1971, 14, 309. 3. Dutrillaux, B., Finaz, C., de Grouchy, J., Lejeune, J. Cytogenetics, 1972, 11, 113.
A full report of these Ca++ and
importance of
New York 10032, U.S.A.
V. G. DEV D. WARBURTON O. J. MILLER.
CLINICS FOR THE TREATMENT OF EPILEPSY AND CONVULSIONS
SIR,-Epilepsy can be a symptom of disease affecting almost every organ of the body. It may be due to metabolic disorders, cardiovascular disorders, cerebral disorders, and so on; and this seems to be the main cause of confusion when special clinics for epilepsy are discussed. Dr. Meinardi (May 27, p. 1181) states that there is agreement over centres for the diagnosis of epilepsy, as well as for treatment and rehabilitation. To be true diagnostic centres they would need the complete resources of a wellequipped general hospital. Even if this was desirable for the diagnosis of a symptom it would be impracticable. However, there does seem to be general agreement that when the initial assessment has been made, in whichever 4.
Gorini,
L. Biochem.
biophys. Acta, 1951, 7,
Chromosome banding produced by pretreatment technique described in
text.
318.
Therefore, I believe that any factor, such as improper fundal pressure, that may lead to aspiration must be identified and, if possible, avoided. Newborn Nurseries, Hôtel Dieu and Cornwall General Hospitals,
Cornwall, Ontario, Canada.
CHARLES B. PENDER.
with a solution which is deficient in the divalent cations, Ca++ and Mg++. Trypsin itself is known to bind calcium ions.44 We have therefore tested the hypothesis that elimination of such cations plays a decisive role in the production of Giemsa banding. The usual glacial-acetic-acid/methanol (1/3) fixed chromosomes were treated with Hanks’ balanced salt solution (B.s.s.) minus calcium and magnesium for 15-120 seconds before staining with Giemsa (Fisher Scientific Co., 1% solution in Tris maleate buffer at pH 5-6). This pretreat-
technique produces chromosome banding (see accomPretreatment with B.S.S. containing Mg++ and Ca++ also produces some chromosome banding, but only after more prolonged treatment. The addition of 0.25% trypsin-0-025% E.D.T.A. (GIBCO) to both types of B.s.s. greatly speeds the banding process. Pretreatment with the chelating agent, E.D.T.A., which is often a component of trypsin solutions, also produces some banding. It seems likely that Giemsa banding of chromosomes can be produced by any pretreatment which removes divalent ment
panying figure).
cations from the chromosomes. relative
experiments, and of the Mg++, is in preparation.
Departments of Human Genetics and Development and Obstetrics and Gynecology, College of Physicians and Surgeons, Columbia University,
GIEMSA BANDING OF CHROMOSOMES
SIR,-Dr. Miiller and Professor Rosenkranz (April 22, p. 898) have reported that Giemsa staining produces a characteristic pattern of chromosomal banding after treatment of fixed metaphase chromosomes with Pancreatin ’, a mixture of the enzymes protease, amylase, and lipase. Similar results have been obtained with solutions of trypsin,l «-chymotrypsin,2and pronase.3 However, in none of these reports was any evidence presented to show that the chromosome banding effect is related to the proteolytic activity of the enzyme preparations. We have been led to question the importance of the enzyme activity of these solutions because excellent bandings can be obtained by pretreatment with trypsin-containing solutions even at 4°C and a pH of 6-8 for no more than 30 seconds. In view of the narrow pH and temperature optima of trypsin, this effect is not likely to be due to enzyme reaction. A common factor in all the Giemsa-banding methods seems to be pretreatment of fixed metaphase chromosomes 1. Seabright, M. Lancet, 1971, ii, 971. 2. Finaz, C., de Grouchy, J. Ann. Genet. 1971, 14, 309. 3. Dutrillaux, B., Finaz, C., de Grouchy, J., Lejeune, J. Cytogenetics, 1972, 11, 113.
A full report of these Ca++ and
importance of
New York 10032, U.S.A.
V. G. DEV D. WARBURTON O. J. MILLER.
CLINICS FOR THE TREATMENT OF EPILEPSY AND CONVULSIONS
SIR,-Epilepsy can be a symptom of disease affecting almost every organ of the body. It may be due to metabolic disorders, cardiovascular disorders, cerebral disorders, and so on; and this seems to be the main cause of confusion when special clinics for epilepsy are discussed. Dr. Meinardi (May 27, p. 1181) states that there is agreement over centres for the diagnosis of epilepsy, as well as for treatment and rehabilitation. To be true diagnostic centres they would need the complete resources of a wellequipped general hospital. Even if this was desirable for the diagnosis of a symptom it would be impracticable. However, there does seem to be general agreement that when the initial assessment has been made, in whichever 4.
Gorini,
L. Biochem.
biophys. Acta, 1951, 7,
Chromosome banding produced by pretreatment technique described in
text.
318.