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The aim of this study, was to observe the effects of KH-1060, a new vitamin D3 analogue, on the dermis of hairless mice by electron microscopy. KH-1060 (0.2 micrograms/ml in isopropanol) or KH-1060 following betamethasone 17-valerate (2 mg/ml in isopropanol) was applied topically to the backs of hairless mice for 4 weeks. KH-1060 increased the number of dermal fibroblasts, the cytoplasm of which was dominated by secretory components. Mast cells contained normal mature granules and degranulated after disintegration. No extrusion of non-disintegrated granules was seen. Collagen fibrils were thickened and increased in number; however the content of type I collagen in the fibrils did not increase. Glycosaminoglycan figures appeared distinct. KH-1060 prevents betamethasone-induced changes in collagen fibrils and glycosaminoglycans, while no prevention was seen for mast cells.

A new highly potent analogue (KH-1060) of vitamin D3 has been recently shown to stimulate the growth and differentiation of keratinocytes. This study was intended to determine the effects of this new analogue on epidermis at the ultrastructural level. KH-1060 was applied topically on the backs of hairless mice for 4 weeks; the skin was then studied by routine electron microscopy. The effects were compared with those of betamethasone-17-valerate and with concomitant treatment of KH-1060 following betamethasone. KH-1060 stimulated normal function of keratinocytes and formed a thick epidermis. The ultrastructure of the thick epidermis represents an enhanced normal process of keratinization and proliferation. Moreover, KH-1060 diminished the atrophogenic effects of betamethasone.

We report on a newborn boy with junctional epidermolysis bullosa and pyloric atresia. Blisters were found on his skin at birth, especially in places exposed to pressure, and appeared later on his mucous membranes. Epidermolysis bullosa was confirmed by electron microscopy. Radiography revealed pyloric atresia, and a gastroduodenostomy was carried out at 7 days of age. A connective tissue septum was found between his ventricle and duodenum. The skin changes were mild, and the clinical course was determined by his protein-losing enteropathy. He died at 66 days of age from pseudomonas sepsis.

A patient suffering from generalized morphea developed blisters in the morpheic plaques on her buttocks. The plaques had an increased concentration of serum aminoterminal propertice of type III procollagen, an echo response and thickened skin on ultrasound scanning, and compact bundles of collagen fibrils with bimodal distribution of the diameters. The blisters appeared as an echo-free band in the subepidermal zone by ultrasound scanning. Electron microscopy revealed blisters in the upper papillary dermis, surrounded by degraded collagen fibrils.

Amyloid masses were found in the dermis of two brothers suffering from primary amyloidosis. The masses consisted of fibrils, composed in turn of twin hollow filaments of amyloid. An amyloid filament appeared as a 3 nm thick lucent core with a 2 nm thick wall. Occasionally 4--6 filaments were packed together in one fibril. The twin filaments were slightly twisted, with a twisting angle of 2.5 degrees and a coiling pitch of 1 160 nm. Wavy shapes of amyloid fibrils were also seen in elastic fibres. Amyloid fibrils were found in elastic fibres, under the basal lamina of the epidermis, sweat gland epithelium and Schwann cells; also around perineural cells, perivascular cells and, in one of the brothers, in collagen fibril bundles. No amyloid fibrils were found under the endothelial basal lamina. It would appear that amyloid fibrils are pathological fibrils belonging to the elastic fibre-basal lamina system.

A case of vulvar angiokeratoma studied by electron microscopy is described. The patient, a 51-year-old woman, had noticed eruptions for the last 15 years, though without symptoms. Osmiophilic bodies with myelin-like figures were found in the vascular endothelial cells. The findings support previous opinion that vulvar angiokeratoma is a variant of scrotal angiokeratoma.

A 5 1/2-year-old girl with idiopathic intestinal pseudo-obstruction became severely depleted of zinc during total parenteral nutrition and developed a vesico-bullous rash on face, hands and feet such as is seen in acrodermatitis enteropathica. Light and electron microscopy of a bullous lesion on one foot revealed a pronounced extracellular edema with cyst and cleft formation in the deep part of the epidermis. A few acantholytic cells were seen. In the electron microscope degenerate keratinocytes showed multiple vacuoles in the dark cytoplasm and slender, finger-like protrusions. Desmosomes were few. The basal lamina was well-preserved forming deep invaginations, which may serve to distinguish the condition from other bullous diseases of the skin.

A case of juvenile xanthogranuloma in a female newborn infant is reported. Red-brown, flat, well-demarcated lesions were present at birth on her scalp, face and trunk. During the following year of observation the eruptions regressed slowly and spontaneously. Light and electron microscopy revealed histiocytes and Touton giant cells dominating the dermal cell infiltrate. The Touton cells contained bizarre invaginated nuclei, lysosomes, a granular endoplasmic reticulum, and cholesterol clefts in their cytoplasm. No fat droplets were seen.

Fabry's disease is a recessive X-linked inborn error of metabolism due to deficiency of the lysosomal enzyme alpha-galactosidase. The large variety of symptoms may make the diagnosis difficult. A severely afflicted female patient is presented. For several years she had been treated under the diagnosis polyarteritis nodosa until the characteristic cutaneous lesions of Fabry's disease were recognized. Enzymatic studies and electronmicroscopic examinations confirmed the diagnosis. A symptomatic effect of corticosteroid treatment was proven. The grave prognosis, the recent attempts at enzyme substitution therapy and the possibility of preventing new cases by prenatal diagnosis should stimulate the efforts of the clinician to diagnose the disease.

In an attempt to induce acantholysis in cultivated normal human epidermis, porcine pancreatic elastase was used. After 30 minutes, the intercellular contact layers of desmosomes appeared discontinuous. Following the disappearance of the intercellular filamentous structures, desmosomes ruptured into two, and in 3 hours, typical acantholysis was observed. After 15 minutes, prior to the desmosomal changes, dermo-epidermal separation started at the subepidermal space. After 2 hours of elastase influence, anchoring filaments and the basal lamina were degraded. Five hours from the start of culture, the anchoring fibrils remained undigested by elastase. The mechanism of elastase influence on epidermis is assumed to depend rather on its proteolytic activity than on its elastolytic activity.

Application of suction blister transplants to leg ulcers is an alternative symptomatic treatment to split-skin grafting, i.e. "pinch-grafting". Blisters are produced by the suction device Dermovac at a suction pressure of 250-300 mmHg for 1-2 hours. The blister-roofs are cut off at the periphery and placed on the granulation tissue of the ulcer. The healing time for leg ulcers was 10-14 days. Excellent epithelialization was seen in 10 out of 12 ulcers. The advantages of the method are, that it is easy to perform, no scarring is produced, and the procedure is painless.

Biopsies for electron microscopy were obtained from syphilitic chancres of 7 patients, 6 males and one female. In 4 of the patients, Treponemata pallida were seen gathering around peripheral nerves and invading the spaces between Schwann cells and their basal lamina. No definite degenerative changes were seen in the axons. In all patients, Treponemata pallida were gathering around the small blood vessels. The fine structure of Treponema pallidum in the lesions included a twined cytoplasmic cylinder with an inner and an outer lamina, an axial fibril consisting of three to five parallel filaments, each consisting of six microtubules, and a covering, outpouching periplastic membrane.

A 48-year-old woman with generalized scleroderma of the acrosclerosis type developed several lesions clinically, histologically and ultrastructurally, which were characteristic of necrobiosis lipoidica. The lesions were located to scar tissue. An increased collagen synthesis is suggested as a possible explanation.

Vascular changes in morphea were studied in skin biopsies from 14 patients. Small vessels with pericytes present the changes in three different patterns. The first was the endothelial cells in a stimulated condition and thickened vascular wall with infiltrating macrophages and mast cells. The second was characterized by thick basal lamina of pericytes and the third by activated pericytes with infiltrating lymphocytes and plasma cells. Otherwise, all patterns showed altered endothelial cells and infiltrating macrophages and mast cells similar to the first pattern. The first pattern was mostly found in uninvolved skin. The second and the third were found in the inflammatory and sclerotic areas. It seems, therefore, that activated pericytes are the most essential changes in vessels of morphea. Probably, muscular vessels are simply involved in the fibrotic process.

During cultivation, the collagen fibrils of skin explants are broken down. The cells of the explants participate in this resorption. The ultrastructure of the intracellular degradation of collagen fibrils of cultured human skin has been examined. Intracellular collagen fibrils occur in fibroblasts, macrophages, smooth muscle cells and unidentifiable cells. Normal collagen fibrils are engulfed and appear within membrane-bounded tubes of the cytoplasm. Primary lysosomes fuse with the tubes. Degraded intracellular collagen fibrils are frequently present in secondary lysosomes and show decreasing diameters, filamentous splitting, loss of axial periodicity, variable stainability and cross-banded filamentous aggregates. The changes in the intracellular collagen fibrils are identical with those seen in the extracellular space. The present study demonstrates that various cell types in dermis are involved in collagen fibril degradation and that the lysosomes play an important part in the intracellular resorption.

Routine electron microscopy was carried out on biopsy material taken in an active stage from cutaneous sarcoid granulomas of 5 patients. In addition, mononuclear cells isolated from the peripheral blood of 2 patients and 2 controls were studied prior to and after culture with phytohemagglutinin. The infiltrating cells of the sarcoid granulomas varied only slightly from patient to patient. The dominant cell types were macrophages and epithelioid cells rich in endoplasmic reticulum. Epithelioid cells with numerous secondary lysosomes were frequently seen. Typical as well as atypical lymphocytes, giant cells and epithelioid cells with many primary lysosomes were less frequent. No atypical lymphocytes were seen among the mononuclear cells from the peripheral blood, either before or after culture with phytohemagglutinin.

Five biopsies from three patients with localized myxedema were studied by electron microscopy. The dermis showed an overwhelming accumulation of microfibrils with knobs (acid glycosaminoglycans) and an amorphous material containing glycoprotein. Furthermore, evidence of degradation without new formation of collagen fibrils was found. Considerable numbers of mast cells with various types of granules, fibroblasts with dilated granular endoplasmic reticulum, and macrophages were seen in the mucinous areas.

The ultrastructure of treponema pallidum obtained directly from human chancres by biopsy was studied by electron microscopy. The treponemes were enveloped by a trilaminar cytoplasmic membrane and a trilaminar periplastic membrane. The central part of the periplastic membrane corresponds to the protective mucoid layer. In undamaged organisms bunches of axial filaments were seen to entwine the whole cytoplasmic body without any disruption or overlapping. The number of axial filaments varied between three and four. Identical nose pieces were demonstrable in both ends of the treponemes. Axial filaments and nose pieces seem to differ from those of Nichols' strain.

Trichophyton mentagrophytes produces three enzyme fractions of molecular weight 65,000, 92,000 and 18,000, respectively. Normal human skin was cultivated and the specimens were subjected to electron microscopy. Enzyme fraction I showed the capacity to induce epidermal acantholysis and dermo-epidermal separation, while the other two fractions showed no proteolytic nor keratinolytic action in cultivated skin.

Dermal cells maintained in cultured human skin explants for up to 10 weeks were studied by electron microscopy. Common findings in the cell organelles were: 1) altered nuclear shapes and numerous nuclear bodies; 2) reduced rough endoplasmic reticulum; 3) a prominent Golgi complex; and 4) an increasing number of free ribosomes, mitochondria, glycogen granules, lysosomes and lipid droplets. The individual types of dermal cells showed various cytoplasmic changes according to duration of the culture. The fibroblasts displayed a moderately developed rough endoplasmic reticulum. The macrophages were filled up with lysosomes and residual bodies. The mast cells showed typical as well as atypical granules. The smooth muscle cells had a variable content of myofilaments. The pericytes and the smooth muscle cells, both surrounded by a basal lamina, became increasingly difficult to discern from each other as a consequence of the decreasing number of myofilaments in the latter. The endothelial cells were recognized because of the preserved blood vessel architecture. Besides the above-mentioned cell types, two other types appeared with the culture time. The unidentifiable cells were characterized by dense zones of the cell membrane and an adjacent extracellular basal lamina-like material. This cell type may be derived from the pericytes of the small blood vessels. The primitive cells had a large rounded nucleus and a cytoplasm with few organelles. This cell type is assumed to represent a precursor cell common to various cell types.

Desmosomes of a patient suffering from pemphigus vegetans were studied by electron microscopy and analysed by morphometry, The desmosomes were fewer in the patient's skin than in healthy individuals. The desmosomes of the patient were thin and short, showing pathological ultrastructures, viz. lack of median lines, single-sided attachment plaques and direct cell contact with some thickened cell membranes. These desmosomal changes were more manifest in the involved than in the uninvolved skin. The changes suggest deterioration or defective formation of desmosomes in pemphigus vegetans.

A case of pseudo-Kaposi sarcoma of the feet (acroangiodermatitis) is reported. The patient showed clinical and light-microscopic signs closely resembling Kaposi's sarcoma, but by electron microscopy of skin biopsies definite signs of degeneration of vascular walls and infiltrating cells were demonstrated. Electron microscopy should be applied when conventional histology is inconclusive or fits poorly to the anamnestic information and/or clinical appearance of the lesions.

Clostridial collagenase, elastase, medium material of human skin culture, dithioerythritol and citrate buffer, pH 3.5, were applied to fresh human skin specimens. Phenomena of degradation of dermal fibrils were observed by electron microscopy.

Thirty-nine peripheral nerves in dermis of 12 morphea patients were analysed for ultrastructural changes. Changes found in the mesenchymal parts of the nerves, i.e. epi-, peri- and endoneurium, were myxedematous changes, collagen fibril degradation, cell infiltration and abnormal fibrosis. The infiltrating cells were lymphocytes and plasma cells as well as mast cells and myofibroblast. Perineural cells were assumed to be one of the origins of myofibroblasts. The axons and the Schwann cells showed slight signs of degeneration.

Punch biopsies from syphilitic leukoderma lesions and from unaffected skin in 3 patients with secondary syphilis were studies in the transmission electron microscope. In one of the patients the pigment disorder was not preceded by any visible syphilids, and in the biopsy from the leukodermal skin in this patient Treponemata pallidium were demonstrated around vessels and inside nerve fibres in which the myelin sheaths of the axons showed evidence of degeneration. In the other 2 patients the depigmented areas appeared while macular and papular syphilitic lesions were healing. In the biopsies from the leukodermal lesions of these 2 patients and from unaffected skin of all 3 patients, no treponemes were demonstrated. The study indicates that syphilitic leukoderma is not invariably a post-inflammatory phenomenon, but the pigmented skin lesions may themselves represent stigmata of an active syphilitic infection.

Adenyl cyclase activity in normal human epidermis was detected by an electron microscopic cytochemical technique. The sodium fluoride sensitive receptors were demonstrated on the outer sheath of the cell membranes. Adenyl cyclase activity was demonstrated in the basal cells and in the 4-5 lower layers of the Malpighian cells, while the superficial layers, stratum granulosum and stratum corneum showed no activity. The findings confirm and extend previous biochemical studies and provide a clue to the conception of the adenyl cyclase enzyme as a transmembrane arranged system.

A young female with local panatrophy of the right-side extremities affecting all mesodermal layers--dermis, subcutaneous tissue, muscles, and bone--is described. The atrophies were strictly linear. Ultrastructurally, collagen fibrils of the reticular dermis from the atrophic area consisted of two types, a large population of fibrils with decreased diameter and round cut-surface, and a small population with increased diameter and a "flower-like" cut-surface. Collagen analysis revealed a reduced hydroxyproline concentration and content per mm2 skin in atrophic area as compared with the perilesional and regional control. Urinary excretion of hydroxyproline was normal. Glycosaminoglycan analysis showed a less reduced content of hexosamine and uronic acid in the atrophic area per mm2 skin, but no differences in the concentrations. Consistently, the gel/fibre ratio (uronic acid/hydroxyproline) was found slightly elevated in atrophic skin. The proportions of the individual glycosaminoglycans heparin, dermatan sulphate, hyaluronic acid and chondroitin sulphates were not affected. It is concluded that reduced collagen and ultrastructural changes of collagen fibrils are significant features in local panatrophy. The significance of local foetal factors affecting the somatic mesoderm is discussed.

A 15-month-old boy with pachyonychia congenita is described. The patient also had follicular keratosis, leukokeratosis of the tongue, and blisters on the soles. Histopathological examination of the follicular keratosis showed hyperkeratosis and acanthosis. Horny plugs were located in sweat pores. By electron microscopy abnormal keratinization was demonstrated.

Keratinocytes were dissociated from normal human adult epidermis with clostridial collagenase, dithio-erythritol and trypsin, and cultured. Immediately after this, no connection was seen between contiguous cells. Ruptured desmosomes, with masses of tonofilaments and distinct attachment plaques were still left on the cell surface. As culture proceeded, however, they became internalized into cytoplasm. As soon as culture was started and the cells established contact with each other, forming conglomerates, they began to form desmosomes. The cell membranes of a limited area which were in contact with neighbouring cells became thicker and formed attachment plaques. In the intercellular space of the desmosomal portion, fine filaments developed and a midline formed. The progress of desmosome formation was classified into six types.

The dimensions of desmosomes and hemidesmosomes in normal human epidermis, i.e. their length and thickness, were studied in ordinary ultrathin sections. The length of desmosomes in the inner and middle squamous cell layer was 310 nm and 300 nm, while the thickness was 31 nm and 30 nm, respectively. In the outer squamous cell layer the values increased to 340 nm and 35 nm, respectively. The percentage total desmosomal length in relation to the perimeter of a cell showed the same tendency.

Lichen aureus (LA) is a distinctive, rare disease occurring predominantly in males, characterized by solitary rust- or copper-coloured patches of lichenoid micropapules, often present on fingers and calves. A case of LA in a 41-year-old male is presented. Biopsy revealed the characteristic pattern of LA, including a dense dermal infiltrate of lymphocytes and histiocytes containing haemosiderin. No epidermal changes were present.

Salpeter-induced calcium deposits in ten patients showed a close clinical and histopathological similarity to the lesions of pseudoxanthoma elasticum. By electron microscopy and selected area diffraction analyses of the calcium deposits we find the changes indistinguishable from the changes previously described in involved skin of patients suffering from PXE. Clinically our patients were compared with the fourteen patients with traumatic calcification previously described.

The ultrastructure of dermal connective tissue in two patients suffering from fibrodysplasia ossificans progressiva (syn myositis o.p.) was studied. The disorder starts with soft tissue swelling which subsequently ossify. The connective tissue of various organs may be affected. No defects in calcium metabolism have been discovered. It was intended to study the primary event which initiates the ossification. The present ultrastructural study demonstrates an accumulation of proteoglycan microfibrils as well as glycoprotein material in dermal connective tissue. Both substances are prerequisites of calcification resulting from the binding of calcium and phosphorus ions. A subsequent release of proteolytic enzymes in the tissues may be set free the bound iones and, thus, initiate mineralization.

The ultrastructure of biopsies from dry macular and papular secondary syphilitic skin lesions of 10 patients were studied by electron microscopy. In all biopsies few diffusely distributed treponemes were observed. This may explain the difficulties in demonstrating treponemes by darkfield examination of tissue fluid from dry secondary syphilitic skin lesions. The outlines of treponemes were less distinct as compared to those of primary syphilis. The periplastic membranes were almost invariably absent and the cytoplasmic membranes appeared in close contact with an enclosing layer of irregularly demarcated, electron dense amorphous substance. This substance may be a manifestation of the immune reaction of the host cells to the treponemes. Degenerations were noted in both unmyelinated and myelinated nerve tissue. This accounts for the fact that skin lesions in secondary syphilis are usually without symptoms. Also in the vessel walls treponemes were demonstrated. The vascular endothelial cells were proliferating and the basement membranes were multilaminated and split.

A new technique which detects the presence of DNA-polymerase and primer-template DNA by measuring the incorporation of 3H-thymidine-5'-triphosphate (3H-TTP) showed nuclear labelling of enzymatically liberated epidermal cells of human skin.

Treponema pallidum was isolated from various types of secondary syphilitic skin lesions. From moist genital papules and from condylomata lata several treponemes were isolated whereas few were isolated from dry papules of the trunk. One third of the observed treponemes were morphologically different from treponemes isolated from human chancres. Especially the nose-piece structures of the terminal parts of the treponemes were deviating. Some nose-pieces were coated by a fuzzily outlined electron dense substance, whereas others were degenerated or nearly separated from the cytoplasmic body. Other treponemes were missing their nose-piece as avirulent saprophytic treponemes. Recent studies have indicated that the nose-pieces are essential for the tissue attachment of treponemes and the treponemal virulence. The significance of the altered nose-piece structure observed is discussed.

Skin biopsy specimens from a patient with disseminated connective tissue nevi and from her son and daughter who had no such clinical alterations were studied with the electron microscope. The nevi showed increased amounts of thick elastic fibres, which were composed of irregularly arranged, often finger-like, subunits surrounded by a thready material. Both structures probably represent malformed components of elastic fibres, the thready material representing malformed elastic fibrils. Many of the collagen fibrils showed increased diameters and twistings, which alterations are believed to represent malformation of collagen. The fibroblasts showed changes which might be related to a pathological protein synthesis. Examination of biopsy specimens from normal skin of the patient and from the skin of her son and daughter failed to demonstrate similar alterations. The present case is regarded as an entity, distinct from dermatofibrosis lenticularis disseminata and from shagreen patch.

Zinc deficiency was produced in rats by feeding them a diet containing 0.5 mg zinc per kg. After 2 weeks the zinc-deficient rats showed markedly stunted growth as compared with control rats receiving an identical diet supplemented with 50 mg zinc per kg. After about 3 weeks all rats in the zinc-deficient group developed a greasy, coarse and scaly coat with dispersed, denuded, eczematous patches. After 32 days the animals were sacrificed and skin specimens were obtained from the abdominal area. Electron microscopy showed two different patterns of epidermal changes: (A) edematous cell bodies and cell organelles, degenerate nuclei, while desmosomes were well preserved: (B) parakeratotic and dyskeratotic cells with sparse keratohyalin granules, abnormal keratinosomes, poorly developed desmosomes, and disintegrated mitochondria in the upper part of the epidermis. In the lower part, keratinocytes contained numerous ribosomes and thick chromatin aggregates in the nuclei. Dendritic cells were disintegrated in pattern A, while they appeared normal in pattern B. In both patterns mitochondria showed vacuoles and a lack of DNA granules. A transient form of type A and B changes was also observed.

Skin biopsy specimens from a 60-year-old patient with paraproteinemia and generalized changes of the skin typical of scleromyxedema were studied with the electron microscope. The dermis was dominated by collagen fibrils and accumulations of peculiar connective tissue cells, while elastic tissue was sparse and in some areas completely absent. Large, sharply demarcated areas of a filamentous material were occasionally observed. The collagen fibrils were often surrounded by thin filaments with a periodic segmentation and by many glycosaminoglycan (mucopolysaccharide) filaments. The elastic fibres contained large amounts of elastic fibrils and small amounts of a homogenous matrix. The cytoplasm of the above-mentioned cells was dominated by lysosomes in different stages of development, often occupying almost all the cytoplasmic area. The collagen fibrils were found in close relation to these cells, frequently inside invaginations of the cells. Furthermore, collagen fibrils were observed free in the cytoplasmic area and inside the lysosomes, indicating lysosomal degradation of collagen.

In biopsies obtained from syphilitic chancres of varying ages in 10 patients, a total of 766 ultrathin sections of Treponema pallidum were studied by electron microscopy. The course and number of axial filaments observed reveal that one bunch of 3-4 filaments without interruption entwine the whole cytoplasmic body. In 9.2% of the sections a trilaminar or a fragmentary trilaminar periplastic membrane was observed outside the cytoplasmic membrane and the axial filaments. The occurrence of the periplastic membrane decreased with advancing ages of the chancres. A protective function of the membrane is discussed. A peritreponemal fine reticular halo demonstrable in most fragments is supposed to be due to fixation induced shrinkage of treponemal hyaluronidase-influenced semifluid glycosaminoglycans. Peritreponemal reticular halos were also observed in collagen tissue. A destructive effect of the treponemes on collagen fibres could explain how the organisms penetrate through the collagen rich meninges into the central nervous system. A surface associated narrow border of electron dense amorphous substance, probably originating from the host organism, yields to tangentially cut treponemes a spiny caterpillar-like appearance.

To obtain viable cells from normal human skin, clostridial collagenase was used. Crude collagenase digestion of collagen fibres and basal lamina results in free dermal cells and sheets of epidermis. The collagenase was tested at various concentrations, solvents and incubation periods. The specimens digested were either split or full thickness skin of varying size. The optimal result was obtained by using small (3mm across) split skin pieces incubated in 2 mg/ml collagenase. The choice of solvent MEM, MEM supplemented with serum, and Tris buffer, was less important. 3 hours' incubation the epidermis was peeled off in sheets and finally dissociated by trypsin-EDTA. The corium was completely digested after 6 hours. After 6 hours' incubation no viable cells could be seen. The epidermal cells appeared mainly as polygonal cells of various sizes and a few little dendritic cells. The dermal cells had a heterogeneous morphology during the first weeks of cultivation. After 2 weeks the cells appeared as fibroblast-like cells.

Primary cultures of epidermal cells from human adult skin were dissociated by dithiothreitol (DTT) with subsequent trypsinization. After treatment with disulfide reducing agents, the desmosomes were either destroyed or showed a homogeneous ultrastructure. Trypsin separated the homogeneous desmosomes, whereas cell membranes, organelles, and nuclei remained undamaged. Trypsin did not influence normal desmosomes. A suspension of human epidermal cells was recultivated in new flasks. Two types of cells grew in the cultures--polygonal and spindle-shaped. The polygonal cells were maintained for 30 to 60 days and grew slowly. The spindle-shaped cells were leucine-amino-peptidase negative, grew actively, and were subcultured.

Collagenolytic enzymes are produced by cultured skin explants. During cultivation the acellular compartment of the dermal connective tissues is digested away. The ultrastructure of the connective tissue resorption has been studied in human skin maintained in organ culture for 2--10 weeks. The connective tissue changes are: (1) Collagen fibrils with normal axial periodicity but decreasing diameters. On cross sections these fibrils have irregular outlines, while the longitudinal sections show fibrils separated into thin bundles of filaments 40--80 A thick with preserved normal axial periodicity. (2) Cross-banded filamentous aggregations (CBFA) consisting of fine parallel filaments 25 A thick and without axial periodicity. The CBFA has 350 A thick bands at 525 A intervals. At the end of the cultivation, the CBFA are replaced by solitary filaments 25 A thick. (3) The elastic fibres show no marked changes of the amorphous matrix, while the fibrils disappear. The loss of collagen and elastic fibrils during cultivation of the skin gives direct evidence of connective tissue degradation. The described changes are discussed in relation to previous ultrastructural studies on connective tissue resorption of various tissues.