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Head injury in the child
Published in Helen Whitwell, Christopher Milroy, Daniel du Plessis, Forensic Neuropathology, 2021
Helen Whitwell, Christopher Milroy
This has become increasingly recognizsed as the major pathology in the infant. It is identifiable by neuropathological criteria of widespread neuronal eosinophilia and shrinkage (Figure 15.12). It is usually widespread throughout the brain, see Chapter 12. However, it is possible in some cases to identify changes earlier. Differentiation from the so-called dark cell change may be difficult. The usual cause of death is brain swelling related to the hypoxic damage. Apnoea is a frequent presentation in head injury (Johnson et al. 1995) and it is thought that this, rather than the mechanism of injury, has the major role in prognosis (Prasad et al. 2002).
Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Dark cells are also found among the basal keratinocytes. A dark cell is elongated and lies perpendicular to the basement membrane, has numerous tonofilaments, an indented nucleus, and has cytoplasm which is more electron dense than the adjacent keratinocytes. Dark cells have an increase in the number of melanosomes, filaments, and membrane-bound organelles, a higher surface density of nuclear membrane, and a larger number of desmosomes. The significance of dark cells is not known and has been the object of controversy. Some workers have interpreted them as being differentiating cells prior to migrating up through the epidermal cell layers.38,39 Dark cells have been reported in both normal and abnormal tissues and their relevance to tumor promotion is not clear.40,41 However, there is a good correlation to the induction of dark cells with some tumor promoters.42,43 Dark basal keratinocytes have been observed in the mouse epidermis treated with one tumor promoter TPA (12-o-tetradecanoylphorbol-13-acetate).42,44 Dark cells are not limited solely to the epidermis, but have been noted in other squamous epithelia such as the respiratory epithelium.45,46
The Pineal Gland
Published in Nate F. Cardarelli, The Thymus in Health and Senescence, 2019
Dense-cored vesicles are found in the polar processes and the cytoplasm.96 They may be part of a lysosomal system97 or perhaps represent a secretory product. They are generally seen in the Type I cell and in the termini of cytoplasmic processes.78,95 Cultured cells, at least from neonatal rats, lack the dense granules seen in vivo.98 Also, the separation into light- and dark-cell population types does not appear.
Physiology of sweat gland function: The roles of sweating and sweat composition in human health
Published in Temperature, 2019
The anatomical structure of the eccrine sweat gland, illustrated in Figure 2, consists of a secretory coil and duct made up of a simple tubular epithelium. The secretory tubule is continuous with and tightly coiled with the proximal duct. The distal segment of the duct is relatively straight and connects with the acrosyringium in the epidermis [5]. The secretory coil has three types of cells: clear, dark, and myoepithelial. As shown in Figure 2(c), clear cells are responsible for the secretion of primary sweat, which is nearly isotonic with blood plasma [6–8]. The clear cells contain a system of intercellular canaliculi, glycogen, and a large amount of mitochondria and Na-K-ATPase activity [5]. The dark cells are distinguishable by the abundance of dark cell granules in the cytoplasm. Their function is poorly understood, but thought to potentially act as a repository for various bioactive materials involved in regulation of clear cell and duct cell function [9,10]. The function of the myoepithelial cells is provision of structural support for the gland against the hydrostatic pressure generated during sweat production [5]. The duct has two cell layers: basal and luminal cells. Its primary function is reabsorption of Na and Cl ions as sweat flows through the duct, as shown in Figure 2(d). Most of the NaCl reabsorption occurs in the proximal duct, as these cells contain more mitochondria and Na-K-ATPase activity than that of the distal segment of the eccrine duct [5]. The result is a hypotonic final sweat excreted onto the skin surface [6,9].
Vestibular findings in patients with schwannoma of the 8th cranial nerve: a survey of nine cases and review of the literature
Published in Hearing, Balance and Communication, 2018
Silvia Palma, Paola Boldrini, Elisabetta Genovese, Gennaro Auletta, Alessandro Martini, Giovanna Cenacchi
Few ultrastructural studies have addressed the morphology of the human vestibular labyrinth as it is difficult to obtain well-conserved samples (in vivo), especially from patients without middle-inner ear pathologies [15,16]. The results of this study confirm the absence of specific structural alterations of vestibular receptors and the dark cell area in patients with VS [17,18]. The degenerative features seen in the neurosensory epithelium, including the loss of stereocilia, with vacuoles and laminated structures in the cytoplasm, were interpreted as artefacts linked to the epithelium and to the high mean age of the patients in our sample [19–21]. Indeed, a loss of sensory cells and degeneration of the vestibular nerve have been demonstrated to begin in the human inner ear after 40 years of age and these same features were identified in specimens from patients surgically treated for Menière’s disease or delayed endolymphatic hydrops [22–24]. As VS incidence is rising in patients older than 50 years [9] and considering the functions of Schwann cells, age could be a factor in inducing the first proliferation of these cells in an attempt to repair damaged nerve fibres.
Melanin in human vestibular organs: what do we know now? An ultrastructural study and review of the literature
Published in Hearing, Balance and Communication, 2018
Silvia Palma, Paola Boldrini, Raul Nucci, Rita Adriana Fano, Giovanna Cenacchi, Alessandro Martini
The samples examined were sections of the semicircular canals of the dark cell area. The images show the basal membrane and epithelium made up of dark cells, light cells and transitional cells (Figure 1). The dark cells, assembled in one or two layers close to the sensory epithelium and in a single layer close to the canal wall, had a cube-like or slightly flattened shape with numerous microvilli. The cytoplasm contained the endoplasmic reticulum and was mitochondria-rich with basolateral invaginations that appeared piled on top of one another or in a sagittal section depending on the direction of the cut (Figure 2). Light cells also contained high quantities of mitochondria, while numerous cytoplasmic processes were found next to the dark cells. Tight junctions were evident in the dark cells, whereas gap junctions were not noted.