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R J Pack

Publications and source records attributed to R J Pack.

28 records · Page 2Linked to original sources
PubMed1982

The Clara cell.

The Clara cells are a group of cells, sometimes called "nonciliated bronchiolar secretory cells", found in the bronchiolar epithelium of mammals including man, and in the upper airways of some species such as mice. Their secretory function is assumed from their ultrastructural appearance, that usually includes copious smooth endoplasmic reticulum, many apical mitochondria and scanty secretory-like dense vesicles near the luminal membrane. An apical cap of the cell usually bulges into the airway lumen, and secretion may be by shedding this cap, or by diffusion secretion or by merocrine secretion in individual granules. The chemical nature of the secretion probably includes protein, glycoprotein and lipids. The secretion may contain enzymes. Its function is presumably to determine the chemical and physical properties of the lining of small airways, and it could behave as a kind of bronchiolar surfactant, limiting lung collapse. The Clara cells also contain much cytochrome P450 dependent mixed-function oxidases, which presumably play a detoxifying role. It is not known whether these oxidases can be secreted or whether they have a lipid-synthesizing function. Clara cells may be important in human disease, both by giving rise to tumours and by taking part in metaplastic changes in bronchiolar disease.

Animals↗
PubMed1981

Arterial chemoreceptor-like activity in the abdominal vagus of the rat.

1. Centripetal activity in fibres in the ventral abdominal vagus nerve of the rat has been studied by recording from fine strands of the divided nerve within the abdomen. 2. In the starved animal, few spontaneously active fibres were located. A proportion of these, however, showed changes in activity in response to changes in F1 oxygen which were typical of arterial chemoreceptor afferent nerves. The resting discharge in these preparations was 0.8-8.0 impulses/sec. In response to extreme hypoxic hypoxia, histotoxic hypoxia or acetylcholine, this discharge increased markedly, with a maximum mean activity of up to 25 impulses/sec. 3. Both the mean/S.D. ratio and statistical comparison with a 'noise' equation were used to assess the apparent random nature of the spike intervals. The former indicated that the spike intervals were random but the latter test was inconclusive. 4. We suggest that this chemoreceptor-like activity originates from the abdominal vagal paraganglia and that these structures may be part of a more generally distributed chemoreceptor system.

Abdomen↗
PubMed1981

The cells of the tracheobronchial epithelium of the mouse: a quantitative light and electron microscope study.

The epithelium of the conducting airways of the mouse consists of a single layer of cells. The number, type and form of these cells have been investigated at five airway levels from the trachea to the distal conducting bronchi with both light and electron microscopes. Contrary to what is found in other species, the majority (50-60%) of cells in the murine airway epithelium are Clara cells. Mucus-producing tissue was infrequent throughout the airways, though epithelial mucous cells occurred in increased numbers at the carina and in the primary bronchus. No mucous or serous cells or submucosal glands were seen in intralobular airways. On a morphological basis, three distinct forms of Clara cell were recognized. On occasion, cells were observed which were apparently transitional types between these and also between Clara cells and mucous or ciliated cells. It is suggested that the 'transforming' cells may indicate a role for the Clara cell as a developmental cell involved in the epithelial cell turnover. Evidence is also provided that Clara cells may undergo both apocrine and merocrine secretion and, it is argued that the latter may be of a PAS + ve material. Free nerve endings were not seen in the epithelium. This may be related to athe restricted ability of mice to cough. It is suggested that the lack of mucus-producing tissue and of cough reflex may be due to the small diameter of the mouse airways.

Animals↗
PubMed1980

The distribution and structure of cells in the tracheal epithelium of the mouse.

The tracheal epithelium of the mouse is a single layer of columnar cells resting on a basement membrane. Many of the cell types resemble those of other species. However, goblet cells are rare and ciliated cells occur only in scattered patches. Submucosal glands are absent from all but the highest reaches of the airway. The major proportion of the epithelial cells are non-ciliated. These usually project into the lumen of the trachea. Large amounts of smooth endoplasmic reticulum and many secretory vesicles occur within the cytoplasm. Secretory activity of these cells may be either apocrine or merocrine and these cells may transform into other cell types. It is suggested that these non-ciliated cells are Clara cells and that the mouse tracheal epithelium may make a useful model for the study of this type of cell.

Animals↗
PubMed1976

Structure of cells and nerve endings in abdominal vagal paraganglia of the rat.

The abdominal vagal paraganglia of the rat consist of small groups of cells, interspersed by blood vessels and nerve bundles and lying close to, or within, the vagus nerve or its branches. Each cell group consists of 2-10 Type I cells incompletely invested by 1-3 satellite cells. Type I cells are characterised by the presence of numerous dense-cored vesicles in their cytoplasm and may exhibit 'synaptic'-like contact with each other. Small efferent nerve endings make synaptic contacts with Type I cells. Larger cup-shaped afferent nerve endings also make synaptic contacts of two kinds with Type I cells. Nerve-nerve synapses are often seen within or close to paraganglia. Attention is drawn to the close similarity of fine structure of abdominal vagal paraganglia, carotid body and small intensely fluorescent cells of the superior cervical ganglion in rats. Possible functional implications of this morphological similarity are discussed.

Animals↗
PubMed1975

Nerve endings in rat carotid body.

The carotid body of the rat consists of "glomera" interspersed by blood vessels and nerve bundles. Each "glomus" consists of 2-12 Type I cells, incompletely invested by 1-3 Type II cells. Type I cells are characterised by the presence of numerous dense cored vesicles in their cytoplasm and may exhibit "synaptic" -like contacts with each other. Small efferent nerve endings make synaptic contact with one or more Type I cells. Large cup-shaped afferent nerve endings make multiple synaptic contacts of two kinds with one or more Type I cells. A second kind of efferent nerve ending is occasionally seen in synaptic contact with one of these afferent nerve endings. A model for the mode of operation of the glomus as a chemoreceptor is proposed.

Animals↗