Biomedical subjects

A L Patra

Publications and source records attributed to A L Patra.

9 recordsLinked to original sources

PubMed1991

Studies of inspiratory airflow patterns in the nasal passages of the F344 rat and rhesus monkey using nasal molds: relevance to formaldehyde toxicity.

For highly water soluble and reactive gases, such as formaldehyde, the reported distribution of nasal lesions in rats and rhesus monkeys following inhalation exposure may be attributable, at least in part, to regional gas uptake patterns that are a consequence of nasal airflow characteristics. Inspiratory nasal airflow was studied at flow rates across the physiologic range using a unidirectional dynamically similar water-dye siphon system in clear acrylic molds of the nasal airways of F344 rats and rhesus monkeys. In both species there were complex and inspiratory flow streams, exhibiting regions of simple laminar, complex secondary (vortices, eddies, swirling), and turbulent flows, with only minor effects of the volumetric flow rates studied on these flow patterns. There was a precise association between points of dye intake at the nostril with complex but generally coherent streaklines throughout the nose, indicating the potential for sensitive dependence of nasal airflow on nostril geometry. On the basis of these studies, a classification for the major airways (meatuses) in the nasal passages of rats and rhesus monkeys was proposed. The spiral shape of the anterior nasal airway of the rat was considered to play an important role in local mixing of inspired airstreams. In the rhesus monkey, the complex geometry of the nasal vestibule contributed to the formation of secondary flows and turbulence in the anterior nose, which represents a potentially important difference between rheusus monkeys and humans. There was a good correlation between routes of flow, regional secondary flows, turbulence, and impaction of airstreams on the airway wall, with the reported distribution of formaldehyde-induced nasal lesions in rats and rhesus monkeys. These studies support the proposal that nasal airflow patterns play an important role in the distribution of lesions induced by formaldehyde.

Administration, Inhalation↗

PubMed1991

Airway structure variability in the Long-Evans rat lung.

Mathematical models used to study deposition of inhaled toxicants require morphometric data to represent the tracheobronchial airways of laboratory animals. Because of the difficulty and cost of obtaining detailed measurements, morphometric models are generally based on measurements from a small number of specimens. To determine the degree of interanimal variability among laboratory animals of the same strain and size, lengths and diameters of the same 200 airways were measured in solid casts in each of 10 male Long-Evans rats. Intraanimal variability was substantially greater than interanimal variability for airway lengths and diameters. Intraanimal variability was reduced when the airways were grouped so that airway generations were adjusted for lobar position. The study results suggest that detailed measurements of the conducting airways in a small number of casts with summarization techniques that retain lobar information will provide a less variable estimate of lung geometry than a smaller number of measurements made in several casts.

Animals↗

PubMed1987

A morphometric study of nasal-pharyngeal growth for particle deposition in the rat.

Animal studies frequently are used in assessing potential human health effects from exposure to inhaled toxicants. Such studies also are used to investigate sensitive subpopulations such as children. Among other factors that influence the degree to which animal models are predictive of human effects in the delivered dose of the toxicant to the various regions of the respiratory tract. Because the rat is an obligatory nose breather, an understanding of the rat nasal-pharyngeal airway geometry is needed to relate exposures to delivered doses. In this study, the growth and development of the rat nasal-pharyngeal airway was studied at one-week intervals in male Fischer-344 rats from one to five weeks. Casts of an adult (60 day) and an aging (441 day) rat were included for comparison. Replica casts of the nasal-pharyngeal airway were made by injecting silicone rubber through the trachea, and sections in anterior-posterior positions were made for morphometric study. A simple structure of the nasal-pharyngeal airway was found in the young rats. While the percentage of the airway composed of turbinates was similar at all ages, the surface area of the turbinates increased 7.7-fold between 7 and 60 days. Because of the simpler structure and smaller surface area in the young rat, extrathoracic clearance is probably less efficient, resulting in a higher delivered dose to the lung of a young rat than to that of an adult rat exposed to the same toxicant concentration.

Aging↗

PubMed1986

A morphometric comparison of the nasopharyngeal airway of laboratory animals and humans.

Solid silicone rubber casts of the nasopharyngeal and laryngeal regions of a human cadaver (child, 3 years old) and a laboratory primate (baboon, 10 years old) were made, and cross-sectional areas were measured in detail. Cross-sectional areas of other species reported in the published literature were used for comparison. In the child's nose cast, the frontal nasal duct (frontonasal duct), which enters the anterior part of the middle meatus, and the sphenoidal recess were almost absent. The ethmoidal turbinates (superior and middle concha) and the maxillary turbinates (inferior concha) were present but were not fully developed. In the baboon nose, the different turbinates were well defined and smooth but of a less complex nature than the child's nose. Of the species compared, the baboon's upper airways had the greatest similarity to the human child's. The present study shows that for the species investigated and for those from the literature, the cross-sectional area increases from the external nares to the maxilloturbinate region (inferior concha). There is a relatively sudden drop in cross-sectional area about halfway through the nose. The present study suggests a functional relationship between nasal structure and cross-sectional area across species.

Animals↗

PubMed1986

Comparative anatomy of mammalian respiratory tracts: the nasopharyngeal region and the tracheobronchial region.

Silicone rubber casts of the respiratory tract were used in morphological studies of the human, baboon, rhesus monkey, dog, rabbit, guinea pig, rat, hamster, and mouse. In these studies, the trachea of the specimen was opened by tracheotomy, and silicone rubber (734 RTV) was introduced through the trachea to form nasopharyngeal and tracheobronchial casts. Measurements were made on the nasal structures, and the lungs were observed for species variation in branching pattern and number of lobes per lung. While species differences in respiratory tract anatomy are known to exist, the present study provides a focus for toxicologists when extrapolating toxicological results from one species to another.

Adult↗

PubMed1986

Airflow characteristics in a baboon nasal passage cast.

Airflow patterns in the nasal passages influence the distribution of air-pollutant-induced lesions in the airway mucosa. Little is known about airflow characteristics of the complex nasopharyngeal airway of humans and experimental animals. Airflow characteristics in the nasopharyngeal airways of an adult male baboon (13.9 kg body wt) were investigated with thermistor probes and the findings compared with flow visualization, using a cinephotographic technique. A clear, acrylic, hollow cast of a baboon nose was made, and thermistor probes were inserted to record air velocity in the cast lumen using a wind tunnel to propel air through the cast. An identical cast was studied by passing water through the cast, with pulses of dye to reveal flow, and cinephotography was used for determination of flow velocities and flow patterns. Flow rates adjusted on the basis of a Reynolds conversion showed good correlations between the two methods, whereas cinephotography revealed areas of turbulence and vortex-like flow not detected by thermistor probes. These results suggest that water flow may provide useful information in complex airways where airflow cannot be determined by other methods.

Animals↗

PubMed1986

Airway branching patterns influence asbestos fiber location and the extent of tissue injury in the pulmonary parenchyma.

The degree to which various anatomic components of the lung influence the distribution of inhaled particles is not entirely clear. Therefore, we have studied the role intrapulmonary airways play in the localization of respired asbestos fibers and have correlated local asbestos fiber burden with tissue injury in rats following exposure to aerosolized chrysotile asbestos for 7 hours per day, 5 days per week for 12 months. Tissues arising from anatomically distinct pathways of the tracheobronchial tree were isolated by using microdissection. Adjacent tissue blocks from regions immediately distal to the last dissected airway were prepared for light microscopic evaluation or digested in hypochlorite solution to determine alveolar septal tissue density and asbestos fiber concentration respectively. These studies demonstrated regional differences in asbestos fiber number, size, and mass which were inversely related to airway pathlength and to bifurcation number along each airway path. Fiber burden within each region was found to be proportional to the relative degree of tissue injury present. These findings suggest that differences in tissue injury from region to region in the lungs following exposure to asbestos are a result of regional differences in the deposition and retention of these substances in the lungs. These airway characteristics which influence fiber deposition may also play an important role in the deposition and subsequent lung injury caused by other particulates and environmental pollutants.

Animals↗

PubMed1984

Identification system for airways in lung models: a note.

A lobar notational system for the identification of airways in the mammalian lung is presented. This system was developed to identify uniquely the location of morphometric and deposition data within a lobe as well as within the lung, and to provide for easy and efficient data reduction. In addition, this notational system can be used to identify main stems like those found in the monopodial lung, and incorporates identification of terminal bronchioles in the airway identifier. The lobar notational system is composed of a two-character lobe code, followed by a third character identifying the branching structure as monopodial or symmetric. The fourth digit identifies the relative position of a branch within the lobe. Subsequent digits identify the airway's relative location within the branching.

Animals↗

PubMed1983

An experimental study of velocity distribution in a human lung cast.

A mechanical lung model with branching up to five generations, developed from an actual human lung, is used to study experimentally the velocity profiles in the trachea and the main branches. Three different flow rates representing light, medium, and heavy breathings have been simulated for both inhalation and exhalation. The velocity profiles, except for the one in the trachea in the frontal direction due to exhalation, are in good agreement with the velocity profiles in simplified models of published literature.

Biomechanical Phenomena↗