A cytochemical kinetic investigation of the Feulgen hydrolysis of fixed chromatin

Hydrolysis optimum of TCA Feulgen reaction on lymphocytes, liver cells, and Ehrlich ascites tumour cells

For simultaneous cytophotometric measurements of DNA and protein the Feulgen hydrolysis must be performed with trichloracetic acid (TCA) at room temperature because of the preservation of nuclear proteins. Already after 10 h of hydrolysis, a good discrimination between the frequency peaks in the histogram is obtained. The best results are achieved after a hydrolysis time in the range of the maximum of the hydrolysis curve (20 h). At this time, little variations of hydrolysis duration scarcely influence the cytophotometric data.

Cytophotometric evidence of variation in genome size of desmognathine salamanders

The amount of DNA per haploid genome, the C-value, is often directly correlated with nuclear and cell volume, but inversely correlated with cell replication rate. Also, rates of cellular growth sometimes appear to be correlated with organismal developmental rates and life history patterns. Among vertebrates, salamanders exhibit the greatest variation in genome size. In the present study we have examined interspecific and intraspecific variation in blood cell DNA levels in the genus Desmognathus, which shows greater variation in life history traits than any other salamander genus. Specimens of Desmognathus quadramaculatus, D. monticola, D. ochrophaeus and D. wrighti were collected from nature at two localities in the southern Appalachian Mountains. Estimates of genome size in pg of DNA were obtained from blood smears by DNA-Feulgen cytophotometry, using erythrocyte nuclei of Xenopus laevis as an internal reference standard of 6.35 pg DNA per cell. C-values of Desmognathus are the smallest in the order Caudata. Although significant variation in DNA levels was found among the four species, the differences were small, and do not support previously proposed relationships between C-value and life-history variation.

Lability to acid hydrolysis in some different DNA-protein complexes of spermatozoa

The Feulgen hydrolysis kinetics was investigated in spermatozoa with different composition in DNA-protein complexes. The species used were: Bos taurus (arginine rich nuclear protein also containing cystine residues), Pichroplus bergi, Triatoma infestans (arginine-rich nuclear protein), Lytechinus variegatus and Apis mellifera (lysine-rich nuclear protein). The spermatozoa were subjected to Feulgen's reaction, after varying the fixative type and the hydrolysis times. Feulgen-DNA values were obtained with an automatic scanning cytophotometric procedure. Differences were demonstrated in the hydrolysis kinetics as a function of differences in composition of the DNA-protein complexes being present in the spermatozoon chromatin. Differences in the profiles of Feulgen hydrolysis curves, having for basis the fixation, were rather clear for bull, grasshopper, and blood-sucking insect spermatozoa than for the sea-urchin and bee spermatozoa. The different hydrolysis kinetics of chromatin of blood-sucking insect spermatozoa compared to that of grasshopper, sea-urchin, and bee sperm cells suggests that, although the first 2 materials contain an arginine-rich "germinative" protein and the latter 2 ones contain a lysine-rich protein, these differ to each other. The DNA depurination was obtained more quickly for T. infestans (20 min) and P. bergi (10 min) spermatozoa when they were fixed in the ethanol-acetic acid (EA) mixture. Morphologically anomalous bull spermatozoa fixed in the EA mixture presented a quicker depurination (30 min) as compared to the normal cells (1 h). The fast lability to acid hydrolysis in the abnormal cells is certainly due to anomalies in their basic nuclear "germinative" protein. In the formalin fixed materials the maximal depurination was obtained earlier in bull spermatozoa (30 min) followed by sperm cells of P. bergi, T. infestans, L. variegatus (all of them one-hour hydrolysis) and finally Apis mellifera (2 h hydrolysis). The presence of secondary peaks at the descending branch of the hydrolysis curves of grasshopper and sea-urchin spermatozoa, indicates for these, more than 1 kind of apurinic-acid protein complexes. The spermatozoa bearing arginine-and/or cystine-rich nuclear protein contain a more easily soluble apurinic acid protein complex. Due to the differences in hydrolysis kinetics of chromatin in spermatozoa containing different nuclear "germinative" proteins, this cellular type does not appear indicated as a haploid control for evaluation of Feulgen-DNA contents of diploid and polyploid somatic cells.

Computer analysis of Feulgen hydrolysis kinetics

A least squares fit of Feulgen hydrolysis time curves to the Bateman function is performed using an especially adapted parameter transformation together with a standard conjugate gradients iteration procedure. The method has been applied to a large number of measured data, and the use and limits of the computer evaluation are discussed.

A study of DNA depolymerisation during Feulgen acid hydrolysis

The binding of Schiff dye molecules after acid hydrolysis (1 M HCl) for varying lengths of time was studied in ascites tumour cells. The amount of dye bound to the tumour cells closely followed the number of aldehyde groups, calculated from the extraction of radioactive nucleotides. This constant dye to aldehyde ratio did not change when the hydrolysis was performed at a lower acid concentration (0.3 M HCl). The conclusion drawn is that Feulgen dye measurements represent, in a constant way, the number of aldehydes on DNA at any given time during hydrolysis. The alteration of the hydrolysis pattern of chromatin fixed in formalin was found to be due to a slower extraction of DNA depolymerisation products, the purine liberation being unaffected. A similar explanation is offered for the extreme pattern obtained from hydrolysis of bull spermatozoa chromatin.