Histochemistry of hydrolytic enzymes in resting submandibular glands of rabbits

Comparative histochemistry of posterior lingual salivary glands of mouse

Normal posterior deep and superficial salivary glands of tongue were examined in male mice by means of light microscopical histochemistry and neurohistology. Both glands showed acini and simple ducts. Demilunes were present in the superficial gland. Disulphides and neutral mucosubstances occurred in acini and demilunes. Tryptophan staining was seen in acini of the deep gland and demilunes, whereas acid mucosubstances were exclusively localised in the superficial gland. Dehydrogenase activities were widespread. Strong esterase activity occurred throughout the parenchyma of the deep gland and in demilunes; it was variably inhibited by E600, apart from acinar apical regions in the deep gland. Lipase was confined to acini of the deep gland and demilunes. Acid phosphatase staining was similarly localised; it was also seen in periluminal ductal rims of the deep gland, in which ouabain-sensitive Na,K-ATPase was localised basolaterally. Staining for alkaline phosphatase decorated occasional myoepithelial-like arrangements and interstitial capillaries. Acetylcholinesterase was associated with nerve fibres embracing glandular parenchyma. Adrenergic fibres were not seen. The results suggest that the acini of the posterior deep lingual gland secrete neutral glycoproteins, whereas the ducts transport ions and absorb luminal material. The posterior superficial lingual gland mainly secretes acid glycoproteins. Both glands produce lingual lipase, receive cholinergic-type innervation and have inconspicuous myoepithelium.

Organic secretory products, adaptive responses and innervation in the parotid gland of ferret: A histochemical study

To qualify cellular events of possible pathophysiological significance in the parotid of ferret, tissue obtained post-mortem from mature animals of either sex was examined by light microscopical histochemistry for calcium, protein, amino acids, mucosubstances and hydrolases, and by neurohistology. Calcium was localised in acinar cells replete with granules containing protein, disulphides and usually carboxylated mucosubstances. Acid phosphatase activity was basally concentrated in the acinar cells. The granular luminal region of striated ductal cells showed protein, tryptophan, disulphides, neutral mucosubstances, and E600-sensitive esterase and Naphthol AS-D chloroacetate esterase activities, whereas their basal region showed acid phosphatase activity. Strong periluminal activity of acid phosphatase and E600-resistant esterase characterised the collecting ducts. Cholinesterase activity was associated with an extensive network of nerve fibres embracing parenchyma. Catecholamine fluorescence was not seen. beta-glucuronidase reactive macrophages abounded in the interstices. The results suggest that while the acini in the parotid of ferret secrete polyionic glycoproteins, shielded by calcium, the striated ducts secrete tryptophan-rich products comprising neutral glycoproteins and showing proteolytic activity. Innervation is of the cholinergic type and parenchymal lysosomal activity, possibly related to autophagy of stored secretory products and heterophagy of luminal material, is brisk. Macrophages contribute to maintaining the glandular microenvironment, wherein secretory activity appears to be lethargic.

Screening of stimulatory effects of dietary risk factors on mouse intestinal cell kinetics

AIM

Although epidemiological and experimental studies validate influence of genetic, environmental and dietary factors in the causation of various types of cancers including colon, results from all these sources are inconclusive. Hypothesizing that high fat diet and obesity are among the major predisposing factors in the incidence of colon cancer, we evaluated the role of diet constituted with food material derived from a tropical plant, Tamarindus indica Linn (TI).

METHODS

A two part randomized double-blind study was conducted employing inbred Swiss albino mice from a single generation for the whole investigation. One day-old neonates (n = 12) were subcutaneously administered with monosodium glutamate (MSG) to induce obesity (OB). At weaning these animals were maintained on modified AIN-76 diet supplemented with 10% TI and 10% fat bolus (w/w, TIFB) for 8 wk. Subsequently, in the second part of study, four groups of animals belonging to the same generation, age and gender (n = 12 per group), were maintained on: AIN-76 control diet (CD); AIN-76 mixed with 10% TI extract (TI); and, mixed with 10% TI and 10% FB (TIFB) for 8 wk, to determine intestinal crypt cell proliferation, functionally-specific enzyme activities, fermentation profile, and energy preferences.

RESULTS

We observed a significant increase in the crypt cell production rate in distal colonic segment of experimental animals when compared with the controls. This segment also contained significantly low butyrate levels compared to control and TIFB groups. All the experimental groups showed a gross decrease in the enzyme activities viz., succinate dehydrogenase, acid-galactosidase and dipeptidyl amino peptidase IV demonstrating pathological stress caused by the test regimens, and an altered metabolic flux in the cellular environment.

CONCLUSION

We have demonstrated a cumulative response to the three dietary factors, one of which (TI) is reported, herein, for the first time to modulate kinetics of large intestinal mucosa, contributing to total risk posed by these test agents.

Structure and function of human sweat glands studied with histochemistry and cytochemistry

The basic structure and the physiological function of human sweat glands were reviewed. Histochemical and cytochemical techniques greatly contributed the elucidation of the ionic mechanism of sweat secretion. X-ray microanalysis using freeze-dried cryosections clarified the level of Na, K, and Cl in each secretory cell of the human sweat gland. Enzyme cytochemistry, immunohistochemistry and autoradiography elucidated the localization of Na,K-ATPase. These data supported the idea that human eccrine sweat is produced by the model of N-K-2Cl cotransport. Cationic colloidal gold localizes anionic sites on histological sections. Human eccrine and apocrine sweat glands showed completely different localization and enzyme sensitivity of anionic sites studied with cationic gold. Human sweat glands have many immunohistochemical markers. Some of them are specific to apocrine sweat glands, although many of them stain both eccrine and apocrine sweat glands. Histochemical techniques, especially immunohistochemistry using a confocal laser scanning microscope and in situ hybridization, will further clarify the relationship of the structure and function in human sweat glands.

Histochemical phenotypes of von Ebner's gland of ferret and their functional implications

Von Ebner's gland of ferret was examined by means of light microscopy, protein, mucosubstance and enzyme histochemistry, and neurohistology. Acinar cells were replete with granules containing neutral mucosubstances and disulphides, and showed strong diffuse acid phosphatase activity and weak granular staining for peroxidase. Staining for cytochrome oxidase, succinate dehydrogenase, and NADH and NAD(P)H dehydrogenases was also seen. Basolateral plasmalemma of acinar cells showed weak, ouabain-sensitive Na+,K+-ATPase activity. Ductal cells were of a simple appearance, contained thiols and showed variable staining for acid phosphatase, dehydrogenases and cytochrome oxidase. Variable amounts of beta-glucuronidase reaction product were localized in the glandular parenchyma, being marked in atrophic areas. Prominent stellate myoepithelial cells embracing acini and also basal ductal cells were demonstrated by alkaline phosphatase. Thiamine pyrophosphatase reaction product was concentrated in blood vessels around parenchyma, with little Golgi-like staining in acinar cells. Acetylcholinesterase activity was associated with an extensive network of nerve fibres embracing parenchyma, whereas catecholamine fluorescence was not seen. The results suggest that the acini of von Ebner's gland of ferret synthesise neutral secretory glycoproteins and peroxidase. Water mobilization is inconspicuous. Lysosomal activities feature in the parenchyma, possibly a consequence of processing secretory products in acini, absorption in ducts and/or adaptation atrophy. The gland receives a rich cholinergic-type innervation, and has extensive myoepithelial and microvascular networks.

Influence of different fixation procedures on the quantification of infarction and oedema in a rat model of stroke

In pharmacodynamic studies using focal ischaemia models, the size of the infarct measured by quantitative histology is the most important outcome measure. Precise, unbiased and reproducible assessment of infarct volume is of foremost importance. A frequent problem in interventional stroke models is the evaluation of infarcts in animals found dead, where instant post-mortem fixation of the brain cannot be performed. The purpose of this study was to investigate possible bias from perfusion, immediate and 3-h post-mortem delayed immersion fixation on the measured volumes of cerebral infarction, oedema and hemispheres in a rat embolic stroke model. Thirty-six male Sprague-Dawley rats were thromboembolized into the internal carotid artery. After survival for 24 h, the animals were divided into three groups: group 1 - immediate perfusion fixation; group 2 - immediate immersion fixation of the brain; and group 3 - animals left dead for 3 h at room temperature before removal of the brain for immersion fixation. Following histological preparation and evaluation, the volumes of the hemispheres and infarction were measured by quantitative histology and planimetry. Brains fixed by immersion were 7% larger than the perfusion-fixed brains. Delaying the immersion fixation for 3 h may increase hemisphere volume by a further 12%. Independent of the fixation procedure, the size of infarction was approximately 40% of the ipsilateral hemisphere, and the oedema was approximately 11% of the size of the infarct. The used planimetric technique was accurate with measured values within +/- 2% of the factual value. In conclusion, sizes of hemispheres, infarction and oedema in absolute volume measures are influenced by the effect of unwanted variation of brain size caused by biological factors and artificial shrinkage caused by fixation, dehydration and heat treatment of the specimens. Infarction and oedema expressed relatively in per cent of hemisphere and infarct, respectively, are robust measures independent of the investigated fixation procedures.

Morphological phenotypes and functional capabilities of submandibular parenchymal cells of the ferret investigated by protein, mucosubstance and enzyme histochemistry

Submandibular glands obtained post-mortem from mature ferrets of both sexes were examined with the use of light microscopical histochemical methods for proteins, mucosubstances and enzymes associated with cell functions or organelles. Demilunar cells showed carboxylated mucosubstances that were mainly non-sulphated, and diffuse activity for peroxidase, E600-sensitive esterase and acid phosphatase. Thiol groups were also detected in these cells. Central acinar cells showed sulphated mucosubstances, disulphides and reticular staining for thiamine pyrophosphatase. Intercalary ducts showed diffuse activity for NADH and NAD(P)H dehydrogenases. Striated ducts contained protein, tryptophan, disulphides, neutral mucosubstances and E600-sensitive esterase periluminally. Basally, the striated ductal cells showed variable activity for peroxidase, cytochrome oxidase, succinate dehydrogenase and acid phosphatase. Basolateral plasma membranes of these cells exhibited ouabain-sensitive Na,K-ATPase activity. The collecting ducts were characterized by variable periluminal staining for acid phosphatase, beta-glucuronidase, acid beta-galactosidase and E600-resistant esterase. The results suggest that the histological appearances of the acini of the submandibular gland of the ferret are dependent on the synthesis of secretory acid glycoproteins, that the striated ducts are involved with the secretion of tryptophan-rich product comprising neutral glycoproteins and showing esterase activity and with marked transport of ions and that the collecting ducts are involved with absorption.

Advantages of backscatter electron imaging scanning electron microscopy for intracellular localization of cardiac analytes by gold conjugated antibody

Myoglobin and myosin light chain 1 (MLC1) are intracellular human cardiac marker proteins which are released as a consequence of ischemia. Human cardiomyocytes were isolated from fresh biopsies and also maintained for several passages in cell culture. The cardiomyocytes were fixed in 100% methanol at -20 degrees C, and labeled. The immunolocalization of intracellular antigen by fluorescence conjugated imaging was compared with scanning electron microscopy (SEM) backscatter electron (BSE) imaging of gold conjugated antibody. Ultra-violet light microscopy showed the intracellular distribution of both proteins to be mainly in the nuclear envelope, the cytoplasm immediately surrounding the nucleus and along portions of the cell membrane. To confirm this observed distribution of myoglobin and MLC1, labeling was repeated with antimyoglobin and anti-MLC1 monoclonal antibodies conjugated to colloidal gold particles. The advantage of colloidal gold labeling is that the intracellular antigen-antibody complexes may be more precisely located because of the significant improvement in resolution provided by BSE imaging in the SEM. BSE imaging confirmed the presence and subsarcolemma localization of myoglobin in cardiomyocytes directly isolated from fresh biopsies. The distribution of colloidal gold-conjugated antibodies did not coincide with the intracellular distribution of the two proteins in the cardiomyocytes grown in cell culture as indicated by immunofluorescence. A relatively random, intracellular gold particle distribution was confirmed by x-ray microanalysis. BSE imaging resulted in consistent auto-backscatter labeling patterns very similar to the labeling patterns obtained with immunofluorescent labeling. X-ray microanalysis confirmed that these auto-backscatter labeling patterns were formed by concentrations of intracellular phosphate. Sodium dodecyl sulfate-poly-acrylamide gel electrophoresis (SDS-PAGE) and subsequent Western blotting indicated that myoglobin and MLC1 were no longer present in detectable quantities in these cells after several passages. Polymerase chain reaction (PCR) amplification of mRNA for human myoglobin and cardiac MLC1 confirmed the absence of their transcripts. Electrophoretic analysis of proteins in cardiomyocytes grown in cell culture confirmed an increasing presence of alkaline phosphatase. Staining of this enzyme with 5-bromo-4-chloro-3-indolyl phosphate and nitroblue tetrazolium showed that alkaline phosphatase was distributed in the same intracellular pattern as the fluorescence conjugated anti-body and the phosphatase auto-backscatter. These results indicate that high-resolution backscatter SEM imaging may be used as necessary control to confirm fluorescence light microscope intracellular labeling of antigens.

A comparison between activities for non-specific esterases and esterproteases

Electrophoretic separation of non-specific esterases and esterproteases from kidney, lung, and liver have been carried out in polyacrylamide gels. By use of zone electrophoresis, isoelectric focusing, and 2-dimensional electrophoresis it was found that most of the esterprotease bands had the same localization in the gels as non-specific esterase bands. A number of esterase bands showed no activity towards the esterprotease substrates and a single kidney band possessed esterprotease activity only. Isozymes of the ES-6 and ES-9 zones showed sex dependent esterprotease reactions. In sections esterase activity was located to all parts of the proximal tubule. In male kidneys, esterprotease activity was present in the 2nd segment of the convoluted tubule which is not connected to glomeruli and in the descending part of the proximal tubule. In female kidney only the descending part of the proximal tubule showed esterprotease activity.

Morphological changes in the rabbit submandibular gland after parasympathetic or sympathetic denervation

Selective denervation was used to obtain further information about the relative roles of the nerves supplying the gland. Parasympathetic denervation soon caused atrophy in both acinar and granular tubule cells, and a substantial reduction in gland wet weight. The secretory cells had several unusual features, and striated duct cells tended to accumulate glycogen. Three to four weeks after pre-ganglionic parasympathectomy, the parenchymal cells were less abnormal but still smaller than in the control, unoperated gland. Thus, parasympathetic impulses are required to maintain normal parenchymal cells. Chronic sympathectomy caused little or no detectable changes in the secretory cells, and there was no significant change in wet weight. Nevertheless, pre-ganglionic sympathetic axotomy reduced the reflex secretion of acinar mucosubstances in response to feeding. Thus, sympathetic impulses normally contribute to the reflex secretion of acinar mucosubstance from these glands.

Structural and functional studies of the effects of sympathetic nerve stimulation on rabbit submandibular salivary glands

Continuous sympathetic stimulation at 8-10 Hz caused intense vasoconstriction in the gland, so stimulation was generally given in an interrupted pattern to minimize this detrimental effect on secretion. Only a small increase in fluid secretion occurred; it became thick and tended to block the cannula; therefore in later experiments the main duct was not cannulated. After sympathetic stimulation there was substantial degranulation of acinar cells. However, as this was accompanied by little movement of water, the secreted mucosubstance distended the ductal lumina. The granular tubule cells were unchanged by sympathetic stimulation. Use of selective blocking agents revealed that the sympathetically-evoked secretion of acinar mucin was mediated mainly via beta-adrenoreceptor activation. As stimulation of the sympathetic nerves alone caused little additional formation of fluid, the effects of superimposing continuous low frequency sympathetic stimulation onto a background of low parasympathetic secretion were compared with similar parasympathetic stimulation alone of the contralateral gland. These double nerve stimulations did not augment the volume of fluid secreted, or cause morphological changes additional to those from parasympathetic stimulation alone. Nevertheless, it is likely that, under natural reflex conditions, sympathetic impulses can increase the amount of acinar mucosubstance secreted.