Quantitative deposition of ultrafine stable particles in the human respiratory tract

Theoretical models of particle deposition in the respiratory tract predict high fractional deposition for particles of less than 0.1 micron, but there are few confirming experimental data for those predictions. We have measured the deposition fraction of a nonhygroscopic aerosol in the human respiratory tract. The aerosol had a count mean diameter of 0.044 micron SD of 1.93, as measured with an electrical aerosol analyzer, and was produced from a 0.01% solution of bis(2-ethylhexyl) sebacate using a condensation generator. Subjects inhaled the aerosol using a controlled respiratory pattern of 1 liter tidal volume, 12/min. Deposition was calculated as the difference in concentration between inhaled and exhaled aerosol of five size fractions corrected for system deposition and dead-space constants. Three deposition studies were done on each of five normal male volunteers. Means (+/- SE) for the five size fractions were 0.024 micron, 0.71 +/- 0.06; 0.043 micron, 0.62 +/- 0.06; 0.075 micron, 0.53 +/- 0.05; 0.13 micron, 0.44 +/- 0.04; and 0.24 micron, 0.37 +/- 0.06. These data demonstrate that deposition of inhaled particles in the 0.024- to 0.24-micron size range is high and increases with decreasing size. These observations agree with and validate predictions of mathematical models.     

Distributions of specific energy in sensitive layers of the human respiratory tract.

The purpose of the present work was to calculate the specific energy distribution in sensitive cells of the human lung. Specific energy distributions were calculated by applying Monte Carlo methods and the ICRP 66 model of the human respiratory tract. Specific energies were calculated at various depths in the epithelium and combined according to the relative cell abundance. Distributions are given for various combinations of sources, alpha-particle energies, targets and regions of the lung. The chord length does not follow the triangular distribution when the particle range is comparable to the diameter of the target. The notion of "effective volume" is introduced and defined, which is needed for estimation of hit frequency in some particular targets. It has been shown that basal cells are subjected to a larger proportion of alpha-particle hits with small energy transfer than secretory cells. Small energy transfer events that lead to minor damage of the DNA are more efficient in cancer induction than are hits with large energy deposition that lead to cell killing.     

Biomarkers of human gastrointestinal tract regions

Dysregulation of intestinal epithelial cell performance is associated with an array of pathologies whose onset mechanisms are incompletely understood. While whole-genomics approaches have been valuable for studying the molecular basis of several intestinal diseases, a thorough analysis of gene expression along the healthy gastrointestinal tract is still lacking. The aim of this study was to map gene expression in gastrointestinal regions of healthy human adults and to implement a procedure for microarray data analysis that would allow its use as a reference when screening for pathological deviations. We analyzed the gene expression signature of antrum, duodenum, jejunum, ileum, and transverse colon biopsies using a biostatistical method based on a multivariate and univariate approach to identify region-selective genes. One hundred sixty-six genes were found responsible for distinguishing the five regions considered. Nineteen had never been described in the GI tract, including a semaphorin probably implicated in pathogen invasion and six novel genes. Moreover, by crossing these genes with those retrieved from an existing data set of gene expression in the intestine of ulcerative colitis and Crohn’s disease patients, we identified genes that might be biomarkers of Crohn’s and/or ulcerative colitis in ileum and/or colon. These include CLCA4 and SLC26A2, both implicated in ion transport. This study furnishes the first map of gene expression along the healthy human gastrointestinal tract. Furthermore, the approach implemented here, and validated by retrieving known gene profiles, allowed the identification of promising new leads in both healthy and disease states.     

Absorbed fraction of alpha-particles emitted in bifurcation regions of the human tracheo-bronchial tree

A model for bifurcation regions of the human tracheo-bronchial tree was developed. Equations for the surfaces are given to enable calculations of doses from alpha-particles emitted in these regions. It has been found that a bifurcation region is well approximated by a quasi-ellipsoid. The absorbed fractions of alpha-particles emitted in bifurcation regions were calculated by the Monte Carlo method. The average absorbed fraction under the bifurcation geometry is close to that found under the cylindrical geometry in the bronchial region. In the bronchiolar region, the absorbed fractions under the bifurcation geometry are up to 20% larger than those under the cylindrical geometry.     

Preferential breakage of sensitive regions of human chromosomes

Summary Whilst studying the chromosomes of the peripheral blood lymphocytes of normal controls and patients with lymphoproliferative disorders, two examples of preferential breakage of a sensitive chromosomal region were found. A patient with lymphocytic lymphoma had a sensitive region in a C9 chromosome coinciding with the secondary constriction. A healthy woman had one A2 chromosome showing an unusually located secondary constriction in which breakage sometimes occurred.     

Catecholamine- and acetylcholinesterase-containing nerves in human lower respiratory tract

Summary The innervation of human lower respiratory tract was studied with special emphasis on airways with sodium-potassium glyoxylic acid (SPG) and acetylcholinesterase (AChE) methods to demonstrate catecholamine-containing and acetylcholinesterase-containing nerve fibers. AChE-method revealed a rich network of cholinesterase positive nerves both inside the bronchial glands where they run around and between the acini, and the airway smooth muscle from secondary bronchi to terminal bronchioli. No AChE-positive fibers were found in connection with the blood vessels or within the epithelium of bronchi or bonchioli. The AChE-positive nerve fibers in bronchial smooth muscle greatly outnumbered those containing catecholamine. The SPG-method revealed the presence of adrenergic nerves from the level of secondary bronchi to that of terminal bronchioli. These nerve fibers were most abundant in bronchial glands, where their amount was equal and distribution similar to those of AChE-containing nerve fibers. Outside the glands adrenergic fibers were constantly seen in connection with the bronchial blood vessels in connective tissues surrounding bronchi. A few nerve fibers were also present in airway smooth muscle from the secondary bronchi to terminal bronchioli.     

Flow simulation in the human upper respiratory tract

Computer simulations of airflow patterns within the human upper respiratory tract (URT) are presented. The URT model includes airways of the head (nasal and oral), throat (pharyngeal and laryngeal), and lungs (trachea and main bronchi). The head and throat morphology was based on a cast of a medical school teaching model; tracheobronchial airways were defined mathematically. A body-fitted three-dimensional curvilinear grid system and a multiblock method were employed to graphically represent the surface geometries of the respective airways and to generate the corresponding mesh for computational fluid dynamics simulations. Our results suggest that for a prescribed phase of breath (i.e., inspiration or expiration), convective respiratory airflow patterns are highly dependent on flow rate values. Moreover, velocity profiles were quite different during inhalation and exhalation, both in terms of the sizes, strengths, and locations of localized features such as recirculation zones and air jets. Pressure losses during inhalation were 30-35% higher than for exhalation and were proportional to the square of the flow rate. Because particles are entrained and transported within airstreams, these results may have important applications to the targeted delivery of inhaled drugs.     

Regulation of proliferation and differentiation of respiratory tract epithelial cells by TGF beta

In this paper we examined the effects of transforming growth factor beta (TGF beta) on the proliferation and differentiation of rabbit tracheal epithelial cells in primary culture. Treatment of these cells with TGF beta inhibits cell proliferation in a time- and dose-dependent manner; concentrations as low as 1 pM are able to inhibit cell growth. Concomitantly, TGF beta causes cells to accumulate in the G0/G1 phase of the cell cycle and a sharp reduction in the ability of the cells to form colonies after subculture at clonal density. These results indicate that TGF beta induces terminal cell division in these cells. The inhibition of cell growth is accompanied by changes in cell morphology and a stimulation of the formation of cross-linked envelopes. TGF beta enhances the levels of transglutaminase activity and cholesterol sulfate, two markers of squamous differentiation. Our results indicate that TGF beta induces terminal squamous cell differentiation in rabbit tracheal epithelial cells. Retinoic acid (RA) does not affect the commitment to terminal cell division induced by TGF beta, but inhibits the expression of the squamous phenotype. Growth of normal human bronchial epithelial cells was affected by TGF beta in a way similar to that of rabbit tracheal epithelial cells. Several carcinoma cell lines tested were quite resistant to TGF beta, whereas growth of one carcinoma cell line was stimulated by TGF beta. These results indicate that a modified response to TGF beta could be one mechanism involved in the aberrant growth control of malignant cells.     

Mathematical modeling of heat and water transport in human respiratory tract

Excessive heat and water losses from the airways are stimuli to asthma. To study heat and water vapor transport in the human respiratory tract, a time-dependent model, based on a single differential equation with an analytical solution, was developed that could predict the intra-airway temperatures and water vapor contents. The key feature is the dependence of the temperature and water vapor along the respiratory tract as a function of the air residence time at each location. The model assumes disturbed laminar flow leading to enhanced transport mechanisms and wall temperature profiles modeled according to experimental data (E. R. McFadden, Jr., B. M. Pichurko, H. F. Bowman, E. Ingenito, S. Burns, N. Dowling, and J. Soloway. J. Appl. Physiol. 58: 564-570, 1985). It predicts that 1) the air equilibrates with the wall before it reaches body conditions (37 degrees C, 99.5% relative humidity); 2) conditioning of the inspired air involves several generations, with the number depending on the respiratory conditions; and 3) the walls of the upper airways are unsaturated, although it is difficult to judge at this state the depth of the respiratory tract affected.     

Immunoreactivity of thymosin beta 4 in human foetal and adult genitourinary tract

Thymosins beta 4 (Tβ4) is a member of the beta-thymosins family, a family of peptides playing essential roles in many cellular functions. Our recent studies suggested Tβ4 plays a key role in the development of human salivary glands and the gastrointestinal tract. The aim of this study was to analyse the presence of Tβ4 in the human adult and foetal genitourinary tract. Immunolocalization of Tβ4 was studied in autoptic samples of kidney, bladder, uterus, ovary, testicle and prostate obtained from four human foetuses and four adults. Presence of the peptide was observed in cells of different origin: in surface epithelium, in gland epithelial cells and in the interstitial cells. Tβ4 was mainly found in adult and foetal bladder in the transitional epithelial cells; in the adult endometrium, glands and stromal cells were immunoreactive for the peptide; Tβ4 was mainly localized in the glands of foetal prostate while, in the adults a weak Tβ4 reactivity was restricted to the stroma. In adult and foetal kidney, Tβ4 reactivity was restricted to ducts and tubules with completely spared glomeruli; a weak positivity was observed in adult and foetal oocytes; immunoreactivity was mainly localized in the interstitial cells of foetal and adult testis. In this study, we confirm that Tβ4 could play a relevant role during human development, even in the genitourinary tract, and reveal that immunoreactivity for this peptide may change during postnatal and adult life.     

Growth of respiratory syncytial virus in primary epithelial cells from the human respiratory tract

Respiratory syncytial virus (RSV) is the most important cause of lower respiratory tract disease in infants and children. To study RSV replication, we have developed an in vitro model of human nasopharyngeal mucosa, human airway epithelium (HAE). RSV grows to moderate titers in HAE, though they are significantly lower than those in a continuous epithelial cell line, HEp-2. In HAE, RSV spreads over time to form focal collections of infected cells causing minimal cytopathic effect. Unlike HEp-2 cells, in which wild-type and live-attenuated vaccine candidate viruses grow equally well, the vaccine candidates exhibit growth in HAE that parallels their level of attenuation in children.     

Assembly of human severe acute respiratory syndrome coronavirus-like particles

Viral particles of human severe acute respiratory syndrome coronavirus (SARS CoV) consist of three virion structural proteins, including spike protein, membrane protein, and envelope protein. In this report, virus-like particles were assembled in insect cells by the co-infection with recombinant baculoviruses, which separately express one of these three virion proteins. We found that the membrane and envelope proteins are sufficient for the efficient formation of virus-like particles and could be visualized by electron microscopy. Sucrose gradient purification followed by Western blot analysis and immunogold labeling showed that the spike protein could be incorporated into the virus like particle also. The construction of engineered virus-like particles bearing resemblance to the authentic one is an important step towards the development of an effective vaccine against infection of SARS CoV.