Ultrastructural and cytochemical observations on the granulocytes of the sturgeon, Acipenser brevirostrum (Chondrostei)

Granulocytes from cranial granulopoietic tissue were studied under the electron microscope, and cytochemistry carried out oncranial and peripheral blood granulocytes of two sturgeons, Acipenser brevirostrum . Ultrastructurally, eosinophils and basophils had homogeneous electron-dense granules similar to those of teleosts and some higher vertebrates. Neutrophils contained two granule types: small elongated fibrillar granules and large (<3.8μm long) usually homogeneous granules.
Neutrophil fibrillar granules were positive for alkaline phosphatase (ALP), acid phosphatase (ACP), α-naphthyl acetate esterase (ANAE), acetyl-l-tyrosine-α-naphthyl esterase (ATNE) and periodic acid Schiff (PAS) reaction. The large homogeneous granules were negative for all enzymes, and were only PAS positive. Eosinophils had granular, cyanide-, azide- and aminotriazole-resistant peroxidase (PO) and were ACP, ATNE, tosyl-l-lysine-α-naphthyl esterase (TLNE) and Luxol fast blue positive.
Ultrastructure and cytochemistry are discussed in relation to other vertebrates, and eosinophils identified as the main phagocytic leucocyte.     

Granulation staining and cytochemistry of peripheral blood leucocytes in healthy carp (Cyprinus carpio L.) II: Monocytes

Granulation staining and cytochemistry of peripheral blood monocytes in healthy carp ( Cyprinus carpio L.) are described. Blood smears were stained for periodic acid-Schiff (PAS), peroxidase, oxidase, alkaline and acid phosphatase, α-naphthyl acetate esterase, α-naphthyl-butyrate esterase, naphthol-AS-chloroacetate esterase (AS-D), naphthol-AS-acetate esterase and β-glucuronidase. For representation of different granulations triazide-staining for eosinophil and neutrophil granules and aqueous methylere-blue staining for basophil granules were used. Lipids were shown by sudan-black-reaction. Monocytes showed only basophil granulation and weak lipid reaction. All tested enzymes were detected, with the exception of peroxidase. The PAS reaction for glycogen proof was negative.     

Cytochemical, immunocytochemical and ultrastructural observations on leukocytes and thrombocytes of fat snook (Centropomus parallelus)

The cytochemical, immunocytochemical and ultrastructural characteristics of leukocytes and thrombocytes in the peripheral blood of the fat snook (Centropomus paralellus) - a fish occurring in Brazil - were investigated. The cytochemical methods were performed to demonstrate four enzymatic reactions - o-toluidine-hydrogen peroxide, naphtol AS-MX phosphate, naphtol AS-BI phosphate and alpha-naphtil acetate to detect myeloperoxidase (MPO), alkaline phosphatase (ALP), acid phosphatase (ACP) and non-specific esterase (α-NAE), respectively - and two non-enzymatic ones - Periodic-Acid Schiff (PAS) and Sudan black B (SBB) to detect the occurrence of glycogen and phospholipids, respectively. Immunocytochemical method utilizing polyclonal rabbit antibody against mammal metalloproteinases (MMPs) 2 and 9 were done. Standard method for Electron Microscopy (EM) was applied for the ultrastructural study. The cytochemical reactions were positive in neutrophils for MPO, ACP, α-NAE, glycogen and phospholipids; in lymphocytes for ACP and α-NAE; in monocytes for ACP and α-NAE and in thrombocytes for ACP, α-NAE and glycogen. Only neutrophils were positive for MMPs 2 and 9, and none of the cells studied were positive for ALP. Ultrastructurally: 1) neutrophil showed a spherical shape with a spherical, indented or lobulated euchromatic nucleus, and cytoplasm containing granules of varied sizes and mitochondria of varied shapes and sizes. The nucleus/cytoplasm relation and the size of granules suggest neutrophil maturation in peripheral blood; 2) lymphocytes showed partially heterochromatic nucleus and minimal cytoplasm; 3) monocytes had long cytoplasmic projections, an indented nucleus, evident nucleolus and cytoplasm with granules of varied sizes and vacuoles; 4) thrombocytes were predominantly elliptical or roughly spherical in shape, had a partially heterochromatic nucleus and cytoplasm containing electron-dense granules, intricate canalicular system and vacuoles occasionally holding phagocytic material.     

C. I. Acid Red 52: A New Stain for Cells of Granulocytic Origin

Using the xanthene dye C.I. acid red 52 (CI. 45100) as a single agent stain applied to coverslip preparations of blood and bone marrow, primary and secondary granules in cells of neutrophilic origin stained brilliant pink. In eosinophils, granules stained dark red. In leukemic myeloblasts that also stained with Sudan black B and demonstrated myeloperoxidase and specific esterase activity, a few bright red staining granules were visualized with acid red 52- In some leukemic promyelocytes, Auer rods stained bright red. In leukemic lymphoblasts, no red granules were seen. Of a wide variety of dyes tested so far, acid red 52 is the most sensitive stain for primary and secondary granules of granulocytes in blood and bone marrow.     

C. I. acid red 52: a new stain for cells of granulocytic origin

Using the xanthene dye C.I. acid red 52 (C.I. 45100) as a single agent stain applied to coverslip preparations of blood and bone marrow, primary and secondary granules in cells of neutrophilic origin stained brilliant pink. In eosinophils, granules stained dark red. In leukemic myeloblasts that also stained with Sudan black B and demonstrated myeloperoxidase and specific esterase activity, a few bright red staining granules were visualized with acid red 52. In some leukemic promyelocytes, Auer rods stained bright red. In leukemic lymphoblasts, no red granules were seen. Of a wide variety of dyes tested so far, acid red 52 is the most sensitive stain for primary and secondary granules of granulocytes in blood and bone marrow.     

Comparative distribution of four lysosomal enzymes within various structures of the human placenta

The histochemical activity of 4 lysosomal enzymes, acid phosphatase (AP), nonspecific esterase (NE), aryl sulphatase (AS), and beta-glucuronidase (BG), was compared in following structures of the human placenta: syncytiotrophoblast, villous stromal cells, fetal capillaries and larger blood vessels, cells of basal plate, macrophages, and Hofbauer cells. In spite of a general similarity in distribution of the investigated enzymes, differences concerning particular structures were found. Thus positively stained granules in endothelia of capillary vessels were revealed only in the reaction for BG, although contours of capillaries were also outlined by the diffuse reaction product for AS. The muscular layer of larger vessels reacted strongly for AS and weakly for NE with the remaining reactions being negative. In syncytiotrophoblast, BG appeared much less active than the other 3 enzymes. The possible significance of the BG positive granules in endothelial of capillaries and of the occasional divergence in distribution of the classical lysosomal markers (AP and BG) is discussed.     

The enzyme cytochemistry and composition of elasmobranch granulocytes

Peroxidase, alkaline phosphatase, acid phosphatase, β-glucuronidase, α-naphthyl acetate esterase (ANAE), α-naphthyl butyrate esterase, naphthol AS-D chloroacetate esterase, acetyl-L-tyrosine-α-naphthyl esterase (ATNE), tosyl-L-lysine-α-naphthyl esterase (TLNE) and periodic acid-Schiff (PAS) were studied in 17 species of elasmobranchs in which granulocytes had previously been identified at the ultrastructural level.
Eosinophils, eosinophilic and neutrophilic granulocytes contained variable acid phosphatase, esterases and PAS, but they were strongest in neutrophilic granulocytes; particularly ANAE. Esterases were released into surrounding plasma and therefore probably function as ectoenzymes. In eosinophils and some neutrophilic granulocytes there were indications of weak peroxidase, but this could not be conclusively demonstrated. Alkaline phosphatase was diffuse between granules in some eosinophils of Pavoraja , and (β-glucuronidase was diffuse in neutrophilic granulocytes of Etmopterus baxteri , otherwise granulocytes lacked these enzymes. Neutrophilic granulocytes stained moderately to strongly for ATNE and weakly and inconsistently for TLNE in Squalus acanthias and Dalatias licha . with a similar reaction in granular lymphocytoid and thrombocytoid cells of Galeorhinus ausiralis and Raja nasuta . The enzyme composition of these granulocytes is discussed.     

Cytochemical profile of immunoregulatory T-lymphocyte subsets defined by monoclonal antibodies

Immunogold staining in combination with enzyme cytochemistry was used to determine the cytochemical profile of the immunoregulatory T-lymphocyte subpopulations defined by the monoclonal antibodies OKT3, OKT4, OKT8, and OKM1 in normal peripheral blood. Leukocyte suspensions were first incubated with the monoclonal mouse antibodies and then with colloidal gold-labeled goat antimouse antibodies. The cells were fixed and cytocentrifuge preparations were made. Cytochemical reactions for the detection of peroxidase, acid alpha-naphthyl acetate esterase, acid phosphatase, and beta-glucuronidase were performed on these preparations. Under light microscopy, lymphocytes reacting with the monoclonal antibodies had numerous dark granules around their surface membrane. In the cytoplasm the intracellular enzymatic activities were stained. The T-lymphocytes were characterized by a dot-like activity for the three enzymes. No significant difference could be found between the cytochemical profile of the T-helper (OKT4 positive) and T-cytotoxic suppressor cell populations (OKT8 positive). A few cells with lymphocyte morphology reacted with the OKM1 monoclonal antibody. Their cytochemical characteristics were different from those of mature T-cells (OKT3 population) or mature monocytes. From the comparison of their cytochemical characteristics, we can conclude that there is little correlation between the immunoregulatory T-lymphocyte subsets defined by these monoclonal antibodies and those defined by Fc receptors.     

Fine structure of the mandibular gland of the Djungarian hamster (Phodopus sungarus)

The mandibular gland of the Djungarian hamster was examined by light microscopy, and transmission and scanning electron microscopies. Its acinar cells reacted with periodic acid-Schiff (PAS) and were weakly stained with alcian blue (AB). There were intercellular canaliculi between the acinar cells. These cells therefore appeared to be seromucous. The acinar epithelium was composed of light cells containing various spherical secretory granules. The granular cells of the mandibular gland possessed many acidophilic granules exhibiting a positive reaction to PAS stain. They were frequently observed at the junction of the acini and intercalated ducts in all mandibular glands examined. All of these cells were light and contained secretory granules of varying size and density. The intercalated ducts consisted exclusively of light cells possessing a few round granules of high density in the apical region. The striated ducts were comprised of two portions--a secretory portion and a typical striated portion without secretory granules. The secretory portion consisted of light, dark and specifically light epithelial cells containing acidophilic granules, which exhibited a strongly positive PAS reaction. The epithelium of typically striated portions was composed of light and dark cells containing fine vacuoles in the apical region. The mandibular gland of the Djungarian hamster revealed no histological differences between sexes.     

Localization and characterization of carbohydrates in adrenal medullary cells

The localization and characterization of carbohydrates in adrenal medullary cells were studied by histochemical and cytochemical methods. Adrenaline (A)-and noradrenaline (N)-storing granules were argentaphobic when ultrathin sections of Araldite-embedded medullae were stained according to the periodic acid-thiocarbohydrazide-silver proteinate technique of Thiery. A small amount of glycogen in the form of single beta-particles as well as lysosomes were, however, visualized by this technique. The entire core of the A granules was markedly positive after ultrathin sections of glutaraldehyde-fixed, glycol methacrylate (GMA)-embedded medullae were stained with phosphotungstic acid (PTA) at low pH (0.3). The N granules, in contrast, were mostly unreactive. In the A cells, PTA stained a large part of the Golgi complex, whereas in the N cells the Golgi complex was mostly unstained. In both cell types, the cell coat, lysosomes, and multivesticular bodies reacted to PTA. The periodic acid-Schiff (PAS) technique showed A but not N granules in semithin sections of GMA- or Araldite-embedded medullae. The PTA and PAS stains were abolished by acetylation, restored by saponification, unchanged by methylation, and greatly diminished by sulfation. In ultrathin sections of GMA- or Araldite-embedded medullae incubated with colloidal iron according to various techniques, the cell coat and lysosomes of both cell types were stained, unlike all the other cytoplasmic organelles. These results indicate that A granules and the Golgi complex of A cells, unlike the same structures in N cells, are rich in glycoproteins which are probably not acidic.     

Adipose conversion of mouse bone marrow fibroblasts in vitro: their alkaline phosphatase activity

By an in vitro colony assay and cytochemical staining, we investigated the capacity of mouse bone marrow fibroblasts to differentiate into adipocytes and to express alkaline phosphatase (ALP) activity. Glucocorticoids enhanced colony formation of the fibroblasts, and stimulated their adipose conversion (55-65% of the colonies became adipocyte-positive), but they did not affect ALP activity. The fibroblasts became heterogeneous in size and morphology after growing in vitro then differentiated into adipocytes. All the cell types had ALP activity, and more than 95% of the colonies contained ALP-positive cells. ALP staining was strongest in cells in the early stage of adipose conversion, gradually decreasing with maturation. Our results indicate that the majority of the mouse bone marrow fibroblasts that formed colonies under our culture conditions are preadipocytes. We conclude that these fibroblasts originate from adventitial reticular cells present in bone marrow stroma because reticular cells have been reported to possess high ALP activity and have been suggested to differentiate into adipocytes.     

A comparative study of primary and secondary granules in monocytopoiesis and myelopoiesis of mouse bone marrow

Summary The differentiation and maturation of monocytes and neutrophil granulocytes were studied in bone marrow of normal mice by electron microscopy and cytochemical assessment of peroxidatic activity. The granule populations of the mature cells of bone marrow were identified and investigated to obtain a basis for the analysis of the earlier stages of maturation. Mature monocytes and neutrophils showed primary and secondary granules, and mature neutrophils had more of both kinds. The size, shape, and number of primary granules proved to offer the most reliable criteria for distinguishing promonocytes and promyelocytes. The primary granules of monocytes were smaller than those of mature neutrophils and were either spherical (smallest diameter 50–200 nm) or elongate (100×400 nm). Both granules had a homogeneous matrix. The granules of the granulocytes were either spherical (smallest diameter 200–300 nm) or elongate (150–200×300–500 nm), and some of them had a crystalline inclusion.     

Ultrastructural cytochemistry of the human adrenal medulla

Summary A cytochemical study of the human adrenal medulla showed that it is made up of two cell types, the adrenaline (A-) and noradrenaline (N-) storing cells. A- and N-storing granules were argentaphobic when ultrathin sections of Araldite-embedded medullae were stained according to the periodic acid-thiocarbohydrazide silver proteinate technique of Thiery. A small amount of glycogen (which disappeared after digestion with alpha amylase) in the form of B-particles, as well as lysosomes were, however, visualized by this technique. The entire core of A granules was markedly positive after ultrathin sections of glutaraldehyde-fixed, glycol methacrylate-(GMA-) embedded medullae were stained with phosphotungstic acid (PTA) at a low pH (0.3). The N granules, in contrast, were mostly unreactive. PTA stained a large part of the Golgi complex of A cells, whereas it generally had no such effect on that of the N cells. In both cell types, the cell coat, lysosomes and multivesicular bodies reacted to PTA. The periodic acid —schiff (PAS) technique showed A but not N granules in semithin sections of GMA- or Araldite-embedded medullae. The PTA and PAS stains were abolished by acetylation, restored by saponification, unchanged by methylation and greatly diminished by sulfation or by digestion with beta glucuronidase after oxidation by perchloric acid. These results indicate that in man the A granules and the Golgi complex of A cells, unlike the same structures in N cells, are rich in glycoproteins.     

Cytochemical reactions of human hematopoietic cells in liquid culture.

Growth of human bone marrow in liquid suspension cultures has been used to study normal hematopoietic cell differentiation and abnormalities in blood diseases. A variety of cytochemical stains were applied to human marrow cells cultured in vitro for up to 14 days. AS-D- CHLOROACETATE ESTERASE AND ALPHA-NAPHYHYL BUTYrate esterase were most useful in distinguishing different cell lines in culture. Peroxidase activity disappeared with mononuclear phagocyte morphogenesis and diminished with culture in intermediate and mature granulocytes. Acid phosphatase activity and methyl greed pyronin staining intensity increased with macrophage maturation.     

Morphological,cytochemical, and culture study of normal human bone marrow frozen at −196 °C

A morphological, cytochemical, and agar culture study was carried out on samples of bone marrow that had been taken from 13 normal individuals and frozen at ?196 °C. The cryoprotective agent (DMSO) was removed by slow or rapid dilution. A large number of the thawed cells appeared to have been destroyed or exhibited vacuoles in the nucleus and cytoplasm, as well as numerous short cytoplasmic evaginations. The few mature cells of the neutrophilic line that had survived contained only rare, if any, specific granules; only the lymphocytes were apparently unaffected. There was a reduction in, or an irregular distribution of, the positive reactions to PAS, peroxidase, naphthol-ASD-chloro-acetate esterase, and Sudan black exhibited by cells of the neutrophilic line, and the lysozyme activity of the neutrophils and the monocytes was affected. Where the DMSO had been removed by slow dilution these changes were less severe and diffuse, the percentage of trypan blue-negative cells was higher, and a much larger number of the colony-forming cells were recovered, this number being constantly reproducible. Similar results were obtained by comparing the two dilution methods on thawed-out specimens of peripheral blood from five patients with chronic myeloid leukaemia. With both types of dilution very few cluster-forming cells were recovered and no spontaneous formation of clusters or colonies was observed. The results suggest that marrow frozen at ?196 °C and treated after thawing by slow dilution is suitable for marrow-transplant experiments, as a control for the agar culture of fresh marrow samples and for the stimulating activity of the feeder layers of peripheral blood leucocytes.     

Cytochemistry of normal and leukaemic lymphocytes: a review.

Findings with six cytochemical reactions demonstrable in normal and leukaemic lymphocytes were reviewed. The two methods which are presently of greater diagnostic value are the acid phosphatase (AP) and alpha-naphthyl acetate esterase (ANAE) reactions. AP has a definitive role in the diagnosis of acute and chronic T-cell leukaemias, where a strong positive reaction helps to distinguish them from most B-cell lymphoproliferative disorders. New findings concerning the ultrastructural localization of this enzyme are presented. ANAE is of value in distinguishing T-lymphocytes (positive localized reaction) from B lymphocytes (negative reaction) and the T micron from the T gamma subpopulation of T-lymphocytes, a positive reaction demonstrable only in the T micron cells. Other reactions reviewed were PAS, beta-glucoronidase, hexosaminidase and alkaline phosphatase.     

Atypical micromegakaryocytes, promegakaryoblasts and megakaryoblasts: a critical evaluation by immunohistochemistry, cytochemistry and morphometry of bone marrow trephines in chronic myeloid leukemia and myelodysplastic syndromes.

A morphometric analysis of bone marrow trephine biopsies has been performed to study the frequency and planimetric characteristics of so-called atypical micromegakaryocytes in chronic myeloid leukemia (CML) and myelodysplastic syndromes (MDS). In addition, an attempt was made to discriminate this particular cell population from small immature elements of megakaryocytopoiesis, such as promegakaryoblasts and megakaryoblasts. The staining reactions employed included periodic acid-Schiff (PAS), alpha-naphthyl acetate esterase (ANAE) and immunohistochemistry with a monoclonal antibody against platelet glycoprotein IIIa (Y2/51-CD61). Comparison of the various staining reactions applied to the different megakaryocytic elements together with morphometric measurements resulted in a clearcut identification of promegakaryoblasts. These were defined as the earliest immature and exclusively CD61-positive precursors. Atypical micromegakaryocytes were characterized by their dysplastic features and strong ANAE reactivity in addition to their positive CD61 staining. When stringent diagnostic criteria (diameter ranging between 10 to 15 microns, mean size about 12 microns) were applied, this abnormal cell population comprised less than 10% of total megakaryocytopoiesis in CML and MDS. It may be assumed that dysmegakaryocytic features in the latter disorders are partially generated by small to medium-sized megakaryocytes (diameter less than 30 microns). In conclusion, the relative frequency of promegakaryoblasts in the normal bone marrow (range 6-8%) is confirmed by evaluation of the immunohistochemical and cytochemical staining methods (CD61 and ANAE). Furthermore, the ANAE reaction facilitates the recognition of atypical micromegakaryocytes as well as small megakaryocytes. Thus cytochemistry provides a better insight into alterations of these cell lineages in various pathological conditions.     

团头鲂外周血细胞的显微结构及细胞化学特征

采用常规瑞氏染色和细胞化学染色方法对团头鲂(Megalobrama amblycephala)外周血细胞的显微结构及细胞化学特征进行了观察。在团头鲂外周血细胞中可区分出六类细胞: 红细胞、淋巴细胞、单核细胞、嗜中性粒细胞、嗜酸性粒细胞和血栓细胞。其中淋巴细胞是除红细胞外含量最多的细胞, 其次分别为血栓细胞、单核细胞、嗜中性粒细胞、嗜酸性粒细胞。成熟红细胞多为卵圆形, 表面光滑, 胞核呈椭圆形或圆形, 染色质较为致密; 淋巴细胞多呈圆形, 胞质较少, 胞核常偏位; 单核细胞多为圆形, 胞核呈圆形或椭圆形, 胞质内可见空泡状结构; 嗜中性粒细胞近似圆形, 胞核常偏于细胞一侧, 呈分叶状、肾形或椭圆形, 核质界限清晰; 嗜酸性粒细胞一般为圆形, 胞核为肾形或椭圆形, 胞质中充满紫红色颗粒; 血栓细胞形态多样, 主要有椭圆形、纺锤形、长杆状和泪滴形, 核质比较大。淋巴细胞呈α-醋酸萘酚酯酶(ANAE)阳性, 呈过碘酸-雪夫(PAS)、氯乙酸AS-D萘酚酯酶(AS-DCE)弱阳性, 呈苏丹黑B(SBB)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)及过氧化物酶(POX)阴性; 单核细胞呈POX、ACP强阳性, PAS、SBB、AS-DCE和ANAE为阳性, 呈AKP阴性; 嗜中性粒细胞除PAS和ANAE为弱阳性外, 其他染色结果和单核细胞相同; 嗜酸性粒细胞呈POX、ANAE强阳性, SBB、ACP阳性, PAS及AS-DCE则为弱阳性, 呈AKP阴性; 血栓细胞呈PAS、AS-DCE及ANAE弱阳性, 呈SBB、ACP、AKP及POX阴性。团头鲂外周血细胞的显微结构及细胞化学特征与其他鱼类具有相似之处, 但亦有其明显的物种特异性。该研究结果可作为监测团头鲂健康状态的依据, 为其养殖及病理诊断提供基础资料。     

The influence of fixation on the carbohydrate cytochemistry of rat salivary gland secretory granules

Synopsis A series of studies was performed to assess the optimum fixation conditions for staining of carbohydrate-containing constituents of rat salivary gland secretory granules. In the parotid and submandibular salivary glands of the rat, the reactivity of secretory granules, at both the light and electron microscopic level, with routine stains and with cytochemical reagents was highly dependent upon the nature of the fixative employed. At the light microscopic level, secretory granules in rat parotid gland were periodic acid-Schiff (PAS) positive if fixed with buffered formalin fixatives. However, if the gland was fixed with lipid-solvent-containing fixatives, or with formalin at a very acid pH (as in Bouin's fixative), the PAS reactivity of the granules was lost. In the submandibular gland of rats, the acinar cells and granular tubules behaved similarly after such fixation in terms of their PAS reactivity, particularly in males; acinar cells of the female submandibular gland stained only lightly with PAS. At the fine structural level, the morphology of secretory granule constituents depended on the buffer used (cacodylate, phosphate or collidine) and on whether or not tissue was post-osmicated. Post-osmication considerably reduced the reaction of secretory granule components with stains for carbohydrates.The experimental evidence indicated that the carbohydrate-containing components of both parotid and submandibular gland secretory granules were not typical long-chain neutral or acidic mucins, but were rather glycolipids or lipophilic glycoproteins that were solubilized by lipid solvents or at acidic pH and were lost or destroyed in the presence of strong oxidants.     

Fine structure of the mandibular gland in Japanese field vole (Microtus montebelli)

The mandibular glands of the Japanese field vole were examined by light microscopy, and transmission and scanning electron microscopies. The acinar cells contained light and coarse secretory granules, and reacted with PAS and stained slightly with AB; they were considered to be seromucous in nature. The acinar epithelium was composed of light and dark cells containing many secretory granules. The intercalated duct cells consisted of light cells possessing a few dense granules. A few cytoplasmic crystalloides of moderate density were observed in occasional light cells. The striated ducts were comprized of two distinct portions, a secretory portion and a typical striated portion without secretory granules. The epithelium secretory portion consisted of light and dark cells containing acidophilic granules and exhibited a sexual dimorphism in these granules: The male epithelia contained the granules of low to high densities, while the female epithelia had only dense granules being smaller than those in the males. The epithelium of typical striated portion was composed of light and dark cells containing fine vacuoles and vesicles.