Histochemical studies on the skin. I. The activity of phosphatases during the histogenesis of the skin in the rat

Localization and quantification of intact, undamaged right-handed double-stranded B-DNA, and denatured single-stranded DNA in normal human epidermis and its effects on apoptosis and terminal differentiation (denucleation)

Quantification of two types of nucleic acids [double-stranded (ds-) and single-stranded (ss-) DNA] was performed to understand the distribution of DNA within the epidermal strata and to examine the effects of DNA structure on gene expression, viz., apoptosis and terminal differentiation. In addition, we examined the precise starting point of cell death within the epidermis (suprabasal layer); examined how DNA structure affects gene expression of melanocytes; and characterized the "transitional cells" located between the stratum granulosum and stratum corneum, viz., epidermal phase transition zone (EPTZ). Ultrasensitive anti-DNA antibody probes (ds-DNA, ss-DNA), the Feulgen reaction, histological stains (morphological characterization) and the terminal deoxyribonucleotidyl transferase (TUNEL) assay (apoptosis) were used to characterize cell death in normal human epidermis. This study characterized, for the first time, the deterioration of right-handed ds-B-DNA and the increase in denatured ss-DNA during epidermal maturation. For the first time, this approach also allowed for the quantitative and qualitative characterization of DNA content and structure in all epidermal strata, using anti-ds-B-DNA and anti-ss-DNA antibodies. In order to improve the retention and quality of DNA, a novel histotechnological processing procedure was used. The results indicate that the largest decline in DNA occurred within the stratum granulosum, followed by the EPTZ, and the stratum spinosum. Not all epidermal nuclei lost DNA, indicating two differentiating keratinocyte pathways, viz., apoptotic and non-apoptotic. Both pathways united in the stratum granulosum. These results suggest that keratinocyte terminal differentiation and apoptosis are distinct cellular events, cell death begins earlier than expected, and molecular epidermal events take place in a gradual and orderly manner within keratinocytes. During maturation, ds-B-DNA decreases as ss-DNA increases. Therefore, during differentiation of keratinocytes, both DNA content and DNA structure are altered.

Identification of a phosphotyrosyl-protein phosphatase in mouse epidermis

Binding of epidermal growth factor (EGF) stimulates tyrosyl protein kinase activity of its receptor in the epidermis. This tyrosine residue phosphorylation is thought to be one mechanism by which EGF mediates its effects such as growth stimulation. To modulate a cellular response to EGF, an enzyme which dephosphorylates phosphotyrosyl residues should be present to oppose the effect of the tyrosyl kinase activity of the EGF receptor. We have identified an enzyme in the neonatal mouse epidermis which has the ability to dephosphorylate tyrosyl residues in vitro on EGF receptors. This phosphatase is a soluble protein with a molecular weight greater than 10,000 daltons and shows optimum activity at neutral pH. This epidermal tyrosyl protein phosphatase is not inhibited by tartrate, ATP, and micromolar levels of zinc, but is inhibited by millimolar levels of zinc, magnesium, manganese, and fluoride. Unlike other well-known phosphotyrosyl phosphatases, alkaline phosphatase, and calcineurin, this enzyme is not inhibited by EDTA. Thus, we have identified and partially characterized a possibly unique phosphotyrosyl phosphatase from the epidermis.

Acid hydrolases of the epidermis: subcellular localization and relationship to cornification

Three lysosomal-type acid hydrolases were examined in subcellular fractions of the developing epidermis of fetal rats to assess the relationship of degradative enzymes to cornification. As the granular layer developed and cornified between 18 and 20 days (D) of gestation, epidermal acid phosphatase increased, acid phospholipase A remained constant, and beta-glucuronidase activity declined. The enzymes were present in 3,000, 17,000, and 100,000 g particulate fractions and soluble cytoplasm. However distribution differed: acid phosphatase and phospholipase A were more preferentially localized than was glucuronidase in the 17,000 g fraction which excluded mitochondria and ribosomes and was enriched in lamellar granules. The findings suggested that acid phosphatase and phospholipase were present in membrane-bound organelles (e.g., lamellar granules) in the granular layer. Particulate acid phosphatase increased with granular layers on days 19 and 20 while a 7-fold increase in soluble enzyme coincided with cornification on day 20. As shown by isoelectric focusing, the enzyme became more heterogeneous at day 20 than at day 18, suggesting increased glycosylation. The particulate fraction displayed lysosomal characteristics with respect to release of acid phosphatase, which was inhibited by hydrocortisone and enhanced by retinol. When fetal epidermis was allowed to cornify in organ cultures, similar increases in acid phosphatase occurred. The presence of hydrocortisone did not affect increase in total enzyme but a greater proportion remained in the particulate fraction. The findings suggest that particulate acid phosphatase and phospholipase are compartmentalized in organelles with lysosomal characteristics during development of granular cells and that release of phosphatase is coincident with cornification. This may reflect not only exocytosis of lamellar granules but also intracellular release of the hydrolytic enzyme.

Purification and properties of a neutral endodeoxyribonuclease from guinea pig epidermis

Guinea pig epidermal DNAase I was purified from an epidermal extract by a procedure including DEAE-cellulose chromatography, Sephadex G-100 gel filtration and Con A-Sepharose affinity chromatography. The purified enzyme contained no detectable activities of acid DNAase, alkaline RNAase, phosphodiesterase or acid or alkaline phosphatase, but was contaminated with acid RNAase activity. The molecular weight of the enzyme was estimated to be 33 000 by sucrose density gradient centrifugation and Sephadex G-100 gel filtration. Its isoelectric point is 5.2 +/- 0.1. The enzyme requires divalent cations and exhibits two pH optima that are dependent on divalent cations: in the presence of Mn2+, the optimum pH is about 7.5 in 50 mM Tris-HCl buffer and in the presence of Mn2+, the pH is 6.4 in 50 mM cacodylate-HCl buffer. The enzyme hydrolyzes native DNA about 6-times faster than denatured DNA, producing 5'-phosphoryl and 3'-hydroxyl terminated oligonucleotides with an average chain length of about eight nucleotides, and converts double-stranded and circular DNA to relaxed and linear forms. The enzyme is inhibited by G-actin and antiserum against bovine pancreatic DNAase A. Thus this enzyme is classified as DNAase I.

Purification and characterization of guinea-pig epidermal acid phosphatase

Guinea-pig epidermal acid phosphatase has been purified approximately 120-fold by a procedure including acid treatment, CM-cellulose and DEAE-cellulose chromatography, and gel filtration on Sephadex G-100. The enzyme had a pH optimum at 5-0 and the optimal temperature for activity was approximately 50 degrees C. The enzyme was not activated by divalent cations or 2-mercaptoethanol, but it was inhibited by p-chloromercuribenzoate and by fluoride. The km value for p-nitrophenyl phosphate was 1-31x10-4 M, the molecular weight was about 73,000 as determined by Sephadex G-100 gel filtration and the isoelectric point was 6.1. The enzyme hydrolyzed deoxyribonucleoside monophosphates to deoxyribonucleosides.

Histochemical study of the distribution of a few enzymes in the digestive system of Indian parrot

Acid-and alkaline phosphatase, 5-nucleotidase and lipase have been localized histochemically in the gizzard, intestine liver and pancreas of Indian parrot, Psittacula krameri. In the gizzard and intestine, the mucosal epithelial cells are the main sites for the enzyme production. The tubular glands of the gizzard show intense reaction for all the enzymes tested. The hepatic sinusoid cells of the liver and the acinii of pancreas give positive reaction. Like pancreas, the intestine has also been found responsible for the production and secretion of lipase. Functional significance of phosphatases in the tissues tested has been discussed.

On the distribution and role of acid phosphatase in the sub-pharyngeal ganglia of Indian cattle leech, Poecilobdella granulosa

Histoenzymatic studies on the sub-pharyngeal ganglia have shown two types of neurons, enclosed in a packet-glial-cell. One of these kinds of cells is larger than the other and vesiculated, while the other is non-vesiculated. Interestingly, all the neurons have reacted very violently for acid phosphatase. The reaction is predominently cytoplasmic, masking the cellular organelles in most of the cells. Smaller cells are more in number and of two kinds. The neuronal processes (axons) have manifested mild enzymatic activity. The neuropile shows predominently granular reaction, each dot probably representing a synaptic site. Intersegmental tracts have provided intense enzymatic activity. Possible physiological significance has been discussed.

Degradation of deoxyribonucleic acid by guinea pig epidermal extracts

The capability of guinea pig epidermal extracts to hydrolyze deoxyribonucleic acid has been studied. The results of investigation by gel filtration on Sephadex G-75 column and by viscometry on the mode of hydrolysis of deoxyribonucleic acid by epidermal extracts revealed that deoxyribonucleic acid was degraded by both endonuclease and exonuclease activities. The exhaustive digestion by epidermal extracts yielded the complete degradation of deoxyribonucleic acid to mononucleosides or further metabolites. The enzyme systems involved in the deoxyribonucleic acid degradation include at least an endonuclease, an exonuclease and a phosphatase.