A quantitative study of N-acetyl-beta-glucosaminidase activity in unfixed tissue sections of the guinea-pig thyroid gland

Tissue stabilizer methods in histochemistry

Quantitative studies in the 1960s established that the tissue disruption and enzyme loss which occurs when unfixed cryostat sections are incubated could be prevented with high concentrations of polyvinyl alcohol without inhibition of enzyme activity. This use of polymeric stabilizers has been largely confined to studies of 'soluble' dehydrogenases in tissue sections. However, optimum conditions for 'soluble' enzymes in cut sections may not be ideal for membrane-bound enzymes or for whole cells, where an over-stabilization of membranes can lead to restricted entry of reagents and thereby low activities. Lower concentrations, or other stabilizers such as Ficoll (a synthetic polysucrose) and collagen polypeptides, have been used in such cases. Suggested criteria for a tissue stabilizer are: (i) The stabilizer should be chemically inert, of defined and constant composition, and generally available; (ii) The tissue must remain structurally intact during the incubation, and the final preparation should look 'clean' and have the proper morphology; (iii) The component being assayed must remain inside the section, and not diffuse into the incubation medium. Ideally, it and any reaction product should remain at their original loci, although it may not always be possible to verify this; (iv) Recorded activities should be comparable to those found in biochemical systems under similar conditions.

Hexosaminidase-altered aberrant crypts, carrying decreased hexosaminidase alpha and beta subunit mRNAs, in colon of 1,2-dimethylhydrazine-treated rats

Aberrant crypt foci (ACF), consisting of morphologically irregular crypts, are thought to be precancerous lesions for colon cancers. For their molecular analysis, it is necessary to avoid contamination with adjacent normal crypts and stromal cells. Decreased hexosaminidase activity in ACF, which has been histochemically demonstrated, was used in the present study to classify isolated crypts in combination with morphological changes. The length, rim diameter, and width (average SD, microm) of hexosaminidase-positive (Hex + ) crypts were 238.6 +/- 40.4, 89.5 +/- 22.9, and 57.6 +/- 14.0, respectively. For hexosaminidase-negative (Hex - ) crypts, the values were 314.4 +/- 77.8, 140.3 +/- 45.7, and 97.3 +/- 34.7, the width being 1.69 times greater (P < 0.0001). Crypts wider than 115 microm (approximately 2 times the average size of Hex + crypts) were all from ACF, judging from hexosaminidase staining. To analyze transcription levels of Hex alpha and beta subunits (Hexa and Hexb, respectively), real-time relative quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis was performed using the LightCycler system. In aberrant crypts, both Hexa and Hexb were significantly down-regulated to 0.266 (P < 0.002) and 0.131 (P < 0.001) units, respectively, compared with those in morphologically normal crypts, with beta-actin as the internal standard. This decrease could be a molecular marker for precancerous enzyme-altered ACF.

Organ culture of benign, aging, and hyperplastic human prostate

Organ culture of the human prostate began in the 1970s and was modeled after the work of Lasnitzki and her collaborators in the mouse two decades earlier. In organ culture of human prostates, one sees a rapid increase in epithelial cells and decrease in stromal cells during the first 3-5 days of culture. While modulation of many phenotypic properties occurs, these cultures provide a simple and rapid way to achieve large numbers of human prostatic epithelial cells in cultured tissues that are markedly depleted of stromal cells. There is some evidence that organ cultures are maintained in slightly better functional states in the presence of androgens; however, most of this evidence is less than quantitative. Most organ culture of prostates has been accomplished with tissues from unspecified locations within the prostate; interpretation of cultures carried out in this fashion has been less complete than would have been possible if they had been carried out from specific anatomic locations within the prostate. Careful pathological characterization of locations contiguous to the cultured tissue is mandatory if cultures are to be interpreted meaningfully.

Acute in vitro thyrotropin regulation of lysosomal enzyme activity in the thyroid follicular cell

The acute effect of a physiological concentration (1 mU/l) of thyrotropin (TSH) on the activity of four lysosomal enzymes in the thyroid follicular lining cell has been studied by quantitative cytochemical techniques. N-acetyl-beta-glucosaminidase (NAG) activity was increased by 14% after 10 min TSH stimulation and NAG and beta-galactosidase activities were increased by 24% and 25% respectively (P less than 0.05) after 20 min stimulation and by 40% and 45% (P less than 0.05) respectively after 30 min stimulation with TSH, indicating an early processing of these carbohydrate residues in thyroglobulin. Acid phosphatase activity, an acid hydrolase unrelated to the hydrolysis of thyroglobulin, was unchanged 30 min after TSH stimulation. Leucyl-beta-naphthylaminidase (LNA) activity changed biphasically with peak activities of 7 and 25 min possibly representing an early fusion of endocytotic vesicles and lysosomes and later the release process of the thyroid hormones. The changes in LNA activity and thus membrane permeability were not reflected in the other enzyme activities studied. This may indicate that the TSH regulation of lysosomal enzyme activities could be independent to the endocytotic process, which is known to involve fusion of lysosomes and endocytotic vesicles. In conclusion we have demonstrated for the first time with physiological concentrations of TSH a specific acute regulation of some lysosomal enzyme activities which may be involved in thyroglobulin processing. Further, these effects may be independent of the changes in lysosomal membrane permeability due to formation of secondary lysosomes.

In situ localization of enzymes and mucin in normal rat colon embedded in plastic

Several enzymes were investigated histochemically in the colons of normal male F344 rats in order to understand the function of different types of cells in this tissue. Serial methacrylate-embedded sections (2-4 microns) allowed the precise localizations of several enzymes including acid phosphatase, alkaline phosphatase, gamma-glutamyl transpeptidase, N-acetyl-beta-D-glucosaminidase (hexosaminidase), alpha-naphthyl butyrate esterase and 5'-nucleotidase. Sites reactive with periodic acid-Schiff were also localized. Gradients of enzyme activity were observed between caecum and rectum and/or from the luminal surfaces to the bases of the crypts for hexosaminidase, esterase and gamma-glutamyl transpeptidase. To our knowledge this is the first histochemical demonstration of gamma-glutamyl transpeptidase in normal rat colonic epithelial cells. The utilization of the methacrylate-embedding technique has revealed previously undescribed gradients of enzyme activity and has allowed the localization of enzyme activities not previously reported in normal rat colonic mucosa.

A quantitative cytochemical assay for osteoclast acid phosphatase activity in foetal rat calvaria

Acid phosphatase activity is prominent in osteoclasts (bone resorbing cells) and has been implicated in the process of bone resorption, although its precise role is not understood. To study the distribution and activity of this enzyme, a quantitative cytochemical method has been developed using undecalcified fresh frozen sections of foetal rat calvariae. Sections were allowed to react with 3 mM naphthol ASBI phosphate at pH 5.0, and the reaction was stopped by rinsing in ice-cold tap water containing 50 mM sodium fluoride. The reaction product was post-coupled to Fast Garnet at 4 degrees C. The absorbance of areas of reaction product in the cytoplasm was measured using scanning and integrating microdensitometry. The initial velocity rate was maintained for up to 2 min at pH 5.0 with a substrate concentration of 3 mM and a section thickness of 5 micron. Under these conditions reaction product was localized to osteoclasts and the surface of bone matrix beneath these cells. Activities in osteoblasts and chondrocytes were negligible. Osteoclastic acid phosphatase was almost totally inhibited by 10 mM fluoride and reduced by 70% by 100 mM tartrate.

A quantitative cytochemical assay of beta-galactosidase in single cultured human skin fibroblasts

A quantitative cytochemical method for the measurement of beta-galactosidase activity in cultured human skin fibroblasts has been developed using 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside as the indigogenic substrate. The method relies upon the oxidation of the primary reaction product by ferro/ferricyanide during which an insoluble indigo dye is generated as the final reaction product. The reaction was linear with time up to 60 min using the final cytochemical standard procedure. The enzyme showed maximum activity at pH 4.0 to 4.1. The concentration optima of indigogenic substrate and potassium ferro/ferricyanide were 3.67 mM and 3.13 mM respectively. The presence of sodium chloride activated beta-galactosidase up to 100 mM, but was inhibitory above that concentration. The enzyme was inhibited by N-ethylmaleimide, N-acetyl-D-galactosamine and heparin. The enzyme molecules were shown to diffuse out of the cells using media without a suitable inert colloid stabilizer. However, diffusion was completely prevented by using polyvinyl alcohol (PVA) grade G18/140. Air-drying of cells was essential to make the cell membrane permeabel to the substrate and, thereby, to avoid a pronounced lag phase. However, in a biochemical analysis, air-drying itself caused a decrease in enzyme activity to 43% of the control. Even after air-drying lysosomal latency could still be demonstrated by using PVA grade G04/140. Control persons, one carrier of and two patients with beta-galactosidase deficiency were easily identified as belonging to three separate groups by using the cytochemical assay. It is proposed that the quantitative cytochemical approach may also be applied to cultured human amniotic fluid cells or chorion biopsies giving a rapid prenatal diagnosis of beta-galactosidase deficiency due to the small number of cells needed in the analysis.

The influence on enzyme activity of storage of tissue blocks at -70 degrees C

Blocks of tissue from various organs of the rat have been chilled by precipitate immersion in n-hexane cooled to -70 degrees C, and then stored at -70 degrees C. At various intervals (up to 14 days) after chilling, cryostat sections were prepared from these blocks and assayed for the activity of a variety of enzymes. Enzyme activity was measured by scanning and integration microdensitometry. With the exception of acid phosphatase and cytochrome oxidase, all enzymes assayed were stable for at least 7 days after storage at -70 degrees C and most were stable for 14 days, Storage of fresh-frozen sections at -30 degrees C in the cabinet of the cryostat, for up to 24 h, had little effect on enzyme activity.

The use of an inexpensive, general purpose microcomputer in quantitative cytochemistry

A 32K Commodore Pet microcomputer has been interfaced with two Vickers microdensitometers. This system allows for the simultaneous logging of data from two densitometers being operated independently of each other. Software for the statistical analysis of data generated by the densitometers, and for use with the cytochemical bioassay of hormones, is described. The densitometer/Pet system is relatively cheap, reliable, and readily adaptable to other applications.