Mucus Film Research Articles

Adaptations of Anomopoda crustaceans (Cladocera) to the benthic mode of life

Crustaceans of the order Anomopoda inhabit both pelagic and littoral zones of fresh water bodies. Different adaptations to the benthic mode of life in representatives of different families and genera of this order are described. They include incomplete molting, the presence of a mucous film on the body surface, protection of the head from frontal damage, large lateral projections on the valves and additional sculpture on the head and valves, well-developed lateral armature of the postabdomen, the presence of projections on the postabdomen preanal margin, specialization of setae and spines of the second antenna, especially large exopodites on limbs IV and V, a reduced compound eye, and a large, well-developed ocellus. Similar adaptations to the benthic mode of life in the Anomopoda and Ostracoda are discussed.

109 Ventilation non invasive dans le SDRA : étude prospective randomisée controlée

The surface of the airways is coated with a thin film of mucus composed primarily of mucin, which is under continuous motion via ciliary action. Mucin not only serves to lubricate the airways epithelia, but also functions as a trap for foreign particles and pathogens, thereby assisting in keeping the airways clean and free of particulate matter and infections. Altered mucin secretion especially increased mucin viscosity, results in mucin stagnation due to the inability of the cilia to propel them, leading to infections and diseases such as cystic fibrosis (CF). Since porosomes have been demonstrated to be the secretory portals at the cell plasma membrane in cells, their presence, structure, and composition in the mucin-secreting human airway epithelial cell line Calu-3 expressing CF transmembrane receptor (CFTR), were investigated. Atomic force microscopy (AFM) of Calu-3 cells demonstrates the presence of approximately 100 nm in diameter porosome openings at the plasma membrane surface. Electron microscopy confirms the AFM results, and tandem mass spectrometry and immunoanalysis performed on isolated Calu-3 porosomes, reveal the association of CFTR with the porosome complex. These new findings will facilitate understanding of CFTR–porosome interactions influencing mucous secretion, and provide critical insights into the etiology of CF disease.In the present study, the porosome proteome in human airway epithelia has been determined. The interaction between the cystic fibrosis transmembrane conductance regulator (CFTR) and the porosome complex in the human airway epithelia is further demonstrated. The possible regulation by CFTR on the quality of mucus secretion via the porosome complex at the cell plasma membrane is hypothesized. These new findings will facilitate understanding of CFTR–porosome interactions influencing mucous secretion, and provide critical insights into the etiology of CF disease.

Surfactant driven flows overlying a hydrophobic epithelium: film rupture in the presence of slip

Both for tear films and along the airways within the lung, one has an extremely thin fluid layer overlying a biological substrate; in both cases surfactants either of natural origin, or artificially introduced, are important in driving fluid flows. There is evidence that slip can occur when hydrophilic liquids, similar to mucus or aqueous tear films, overlie hydrophobic epithelium. Utilizing results from recent experimental findings we examine the possible influence of slip upon tear film rupture, important in so-called dry eye, and upon surfactant-induced flows within the lung, used in surfactant replacement therapy.

Microbial taphonomic processes in the fossilization of insects and plants in the late Eocene Florissant Formation, Colorado

The remarkably well-preserved fossils in the Florissant Formation (Eocene) at Florissant, Colorado occur in a lacustrine shale consisting of numerous couplets of millimeter-thin, alternating laminae of diatomite and volcanic debris of ash and smectite clay. The results of this study indicate the importance of microbial processes in fossilization. The plant and insect fossils are found within the diatomite layers and are covered with a mucus film produced by diatoms. The laminated shale sequence represents cyclic sedimentation during which ash-clay sedimentation alternated with intervals of abundant diatom growth (blooming?). During each proliferation of diatoms, a mat of diatom mucus formed. Additional mucus came from secretions of bacteria lying on the diatom mat. Bodies of organisms blown or washed into the lake became entangled in the sticky mucus mat that later settled to the lake bottom. The mucus retarded decomposition of the plants and insect bodies while sinking through the water column and during the interval before burial on the lake floor. The fossil-containing diatomite layer was then buried under an ash-clay layer. The organisms escaped decomposition and were fossilized mainly because of the protective mucus covering.

A new medical microrobot for minimal invasive surgery.

A new medical microrobot to drive endoscopes into endocoeles is presented. The structure of the microrobot is very simple; it consists of a right spirally grooved micromotor, a left spirally grooved cylinder and a flexible coupling. When the micromotor rotates, a hydrodynamic mucus film is formed because highly viscous mucus exists in endocoeles. The mucus film can prevent direct contact between the microrobot and the endocoele, and the injury to organic tissues may be avoided. The locomotion speed and the hydrodynamic mucus film thickness formed when the microrobot drives endoscopes into endocoeles have been calculated according to hydrodynamic lubrication theory. The results indicate that the microrobot can be suspended to drive endoscopes quickly into endocoeles. This has been confirmed by experiments.

Helicobacter pylori vacuolating cytotoxin: cell intoxication and anion-specific channel activity.

The entire sequence of the circular genome of two Helicobacter pylori strains is presently available (Tomb et al. 1997; Alm et al. 1999), together with portions of the genome of several other strains. These genomes are predicted to contain about 1,500 coding genes, most of which encode proteins necessary for the formation, growth and division of the bacterial cell (Doig et al. 1999; Ge and Taylor 1999; Marais et al. 1999). Fewer genes, including those for urease and the proteins involved in its biosynthesis, are necessary for the colonization, binding and survival of H. pylori in its particular ecological niche, i.e., the apical surface of stomach epithelial cells and the protective mucus layer covering them. H. pylori can survive the acidic conditions of the stomach lumen by buffering the pH around itself through the action of the cytosolic urease, which catalyzes the hydrolysis of urea to produce ammonia (Weeks et al. 2000). H. pylori then rapidly enters the mucus layer which covers and protects the mucosa from the gastric fluid, preventing its ulceration. This layer has unique barrier properties, being rather impermeable even to small molecules. In addition, hydrogen ions can freely diffuse from the apical portion of the mucosal epithelial cells into the gastric lumen, but not vice-versa. In contrast, bicarbonate anions are poorly permeable, as is thought to be the case for iron and nickel ions, which are necessary for H. pylori growth. Thus, a pH gradient exists inside the mucus film, with the apical cell membrane being almost neutral under normal conditions, but becoming acid if the thickness of the protective layer is reduced.KeywordsLate EndosomePlanar Lipid BilayerStomach LumenToxin ChannelLate Endosomal CompartmentThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Surfactant transport on mucus films

Motivated by the non-Newtonian properties of mucus and the bilayer nature of fluid lining in the pulmonary airways, we investigate surfactant transport on both single and bilayer fluid systems; the aim is twofold. First, we explore the influence of two principle rheological properties of mucus, yield stress and shear thinning, on the surfactant spreading behaviour. Secondly, in these airways, mucus, which has substantial non-Newtonian properties, overlies the periciliary liquid layer (PCL) which is primarily Newtonian, and we incorporate this bilayer structure into the analysis. This consists of the derivation of coupled spatio-temporal evolution equations describing the layer thicknesses and surfactant concentration. Subsequent analytical methods examine limiting cases where similarity variables can be usefully employed, and more generally numerical simulations are performed.

Where are the receptors for Streptococcus pyogenes located on the tonsillar surface epithelium?

Streptococcus pyogenes is the most frequent causative agent of acute pharyngotonsillitis (AT). The first events in the etiopathogenesis of an AT infection caused by these bacterial pathogens are their penetration through the mucus film covering the oropharyngeal mucosa, and their attachment to the surface epithelium. Adherence of S. pyogenes to tonsillar epithelial cells is a precondition for bacterial colonisation, for triggering off cell activation, internalising of bacteria into the epithelial cells and cytokine release from the epithelial cells with subsequent induction of an inflammatory reaction in underlying tissues. Scanning and transmission electron microscopic studies revealed that the surface epithelium of the human palatine tonsils consisted of a weakly keratinized, stratified squamous epithelium built up of pentangular cells where the apical cell surface formed an irregular pattern of microridges. The distance between two adjacent microridges was roughly one-third of the diameter of a S. pyogenes bacterium. By using gold-labelled antiserum to S. pyogenes, we showed that the target region for these pathogens on the epithelial cells during an on-going AT infection was located on the crests of the microridges where bacterial pili made adhesin-receptor contact with the tonsillar surface epithelium.

Developmental mucin gene expression in the human respiratory tract.

The epithelial surface of the respiratory tract is coated with a protective film of mucus secreted by epithelial goblet and submucosal gland cells. Histology of the airway mucosa and composition of secretions during the second trimester of fetal life are known to differ from the normal adult in that these secretions show similarities with those of hypersecretory disorders. To provide information regarding cell-specific expression of mucin genes and their relation to developmental patterns of epithelial cytodifferentiation, we studied the expression of eight different mucin genes (MUC1-MUC4, MUC5AC, MUC5B, MUC6, MUC7) in human embryonic and fetal respiratory tract using in situ hybridization. These investigations demonstrated that MUC4 is the earliest gene expressed in the foregut at 6.5 wk, followed by MUC1 and MUC2 from 9. 5 wk of gestation in trachea, bronchi, epithelial tubules, and terminal sacs before epithelial cytodifferentiation. In contrast, MUC5AC, MUC5B, and MUC7 are expressed at later gestational ages concomitant with epithelial cytodifferentiation. During this developmental stage, MUC1 and MUC4 mRNAs are located in goblet and ciliated cells, whereas MUC2 mRNAs are located in basal and goblet cells. MUC5AC expression is confined to goblet cells. In the submucosal glands, MUC2 mRNAs are located in both mucous and serous cells, whereas MUC5B and MUC7 mRNAs are expressed in mucous and in serous cells, respectively. These data suggest distinct developmental roles for MUC1, MUC2, MUC4, MUC5AC, MUC5B, and MUC7 in the elongation, branching, and epithelial cytodifferentiation of the respiratory tract during ontogenesis. Distinct patterns of mucin gene expression are also likely to play an important role in regulating appropriate epithelial cell proliferation and cytodifferentiation in adult airway mucosa as it is indicated by aberrant expression in hypersecretory disorders.

A Prospective Study of Pathogenesis of Catheter-Associated Urinary Tract Infections

To determine the pathogenesis of catheter-associated urinary tract infection (CAUTI) and the relative importance of each of the possible mechanisms of entry of infecting microorganisms to the catheterized urinary tract. We conducted a prospective study of 1,497 newly catheterized patients. Paired quantitative urine cultures were obtained daily, from the catheter specimen port and from the collection bag, using a technique that could detect 1 colony-forming unit/mL. We assumed that with extraluminal infections, caused by microorganisms ascending from the perineum in the mucous film contiguous to the external surface of the catheter, the organisms would be detected first in bladder urine or in far higher concentrations in urine from the specimen port than from the collection bag. With intraluminal CAUTIs, caused by microorganisms gaining access to the catheter lumen because of failure of closed drainage or contamination of collection bag urine, the organisms would be detected first or in far larger numbers in a collection bag specimen. The probable mechanism of infection could be determined for 173 of 250 organisms (69.2 %) identified in 235 new-onset CAUTIs. Among these 173 cases, 115 (66%) were extraluminally acquired, and 58 (34%) were derived from intraluminal contaminants. For these determinable cases, CAUTIs caused by gram-positive cocci (enterococci and staphylococci) and yeasts were far more likely to be extraluminally acquired (extraluminal:intraluminal, 2.9) than were gram-negative bacilli, which caused CAUTIs by both routes equally (extraluminal: intraluminal, 1.2; P = 0.007). Surprisingly, no significant differences were noted in pathogenetic mechanisms between men and women. We conclude that, in both men and women, CAUTIs occur by both extraluminal and intraluminal portals of entry but derive preponderantly from organisms that gain access extraluminally. Strategies for prevention of CAUTIs must focus on new technologies to prevent access of organisms by all possible routes.

Induction of larval attachment and metamorphosis in the abalone Haliotis diversicolor (Reeve)

The attachment and metamorphic responses of veliger larvae of the abalone, Haliotis diversicolor (Reeve) to potassium chloride (KCl), gamma-aminobutyric acid (GABA) and natural cues were determined. Attachment and metamorphosis of H. diversicolor were two distinctly different responses. Attachment was characterized by larval contact with a substratum followed by crawling with the larval foot firmly attached to the surface of the substratum. This behavior began approximately 48 h post-fertilization at 22°C. Larvae could detach from the substratum and continue to swim for over 96 h after attachment behavior began. Metamorphosis was irreversible and could occur in larvae that were 96 h post-fertilization. The neurotransmitter GABA, stimulated attachment behavior and induced low levels of normal metamorphosis at a concentration of 10 −5 M, but was toxic to larvae at concentrations of 10 −3 and 10 −4 M. KCl at 10, 20 and 30 mM concentrations above normal seawater salinity stimulated attachment behavior, but became toxic at 30 and 40 mM. Low levels of metamorphosis were induced at excess KCl concentrations of 20 and 30 mM. Single films of mucus, diatoms and three species of bacteria were not as stimulatory as a combination film of diatoms and mucus in dish assays. Survival of larvae settled in dishes coated with a film of diatoms and mucus was higher than that in dishes containing either diatom or mucus films alone. The combination of diatom film and conspecific mucus may produce a novel cue that is not present in either film alone. Observations suggest that the condition of the adults may influence cues present in mucus. Moreover, when given a choice of vertical attachment sites, H. diversicolor larvae attached more frequently to slides filmed with both diatoms and mucus than to clean or diatom-filmed slides. A combination film may increase numbers of attached larvae and reduce mortality in commercial aquaculture facilities.

ACID-BASE INTERACTIONS IN THE CORNEA-TEAR FILM SYSTEM: SURFACE CHEMISTRY OF CORNEAL WETTING, CLEANING, LUBRICATION, HYDRATION AND DEFENSE

ABSTRACT Various surface-chemical interactions among the corneal epithelium, ocular mucous gel, tear film and tear film contaminants (e.g., cellular debris, lipids, bacteria) are characterized based on their apolar and polar (acid-base) surface properties. Based on this approach, the surface-chemical pathways of the tear film breakup and of the corneal epithelial lubrication, cleansing, wetting and defense are proposed. A strong monopolar repulsion keeps mucus in the form of a highly hydrated gel, which cannot adhere to the normal glycocalix carrying epithelial surface, but forms an effective surface-chemical trap for the apolar and weakly polar hydrophobic contaminants. However, mucus-deficiency and/or a host of epithelial surface abnormalities (e.g., increased cell loss, chemical or morphologic changes, damage) can initiate a vicious cycle comprising of factors such as: increased mucus contamination, loss of mucus and epithelial hydrophilicity, abnormal adhesion and aggregation of mucus, reduced mucus mobility and faulty surface cleansing. All of these factors can conspire to produce a chronically unstable tear film secondary to the loss of corneal surface wettability.

Response of frog and toad skin to norepinephrine

Maintenance of a hydrated integument is essential to the normal function of amphibian skin, and amphibians have developed mechanisms to minimize cutaneous dessication. The present work was conducted on skins of amphibians exhibiting a clear preference for either of two such mechanisms to study the influence of such mechanisms on the characteristics of epithelial transport. The response to norepinephrine (NE) was studied in isolated skins of a semiaquatic frog ( Leptodactylus chaquensis), known to maintain indispensable skin moisture by secreting a superficial film of mucus via sympathetic stimulation of skin glands, and a terrestrial toad ( Bufoarenarum), which replenishes a superficial film of fluid by drawing soil water upward by capillarity. In L. chaquensis skin, NE 5.0 × 10 −7 M, induced slow onset, sustained increases in short-circuit current (SCC) and transepithelial conductance, which were abolished by amiloride, a specific sodium transport inhibitor. At 1.2 × 10 −5 M, the response to NE exhibited a faster onset and a shorter time course. The SCC response also became insensitive to amiloride and could thus be induced by exposing the skin to NE in the presence of the inhibitor. The response was also greatly reduced in the absence of chloride, strongly suggesting a greater dependence on the glandular secretory response. In B. arenarum skin, the response to NE was far more sensitive to amiloride, regardless of the concentration of NE used. Induction of a response in the amiloride-blocked skin required a 10-fold higher concentration of NE, and the resulting effect was still considerably smaller than that observed in the skin of L. chaquensis after the same treatment. The number of mucous glands per unit area in B. arenarum skin was found to be around one-fifth of that observed in L. chaquensis, thus in part explaining the difference in the magnitude of the responses. The response of the skin of L. chaquensis to NE in the presence of sulfate was found to be consistent with the postulated involvement of frog skin glands in sulfate excretion. In contrast, this function was not evident in the skin of B. arenarum. The pattern of response of B. arenarum skin to all concentrations of NE tested closely resembles that seen after exposure to agents known to activate a cyclic AMP-dependent, high-permeability Cl − pathway previously described by us in the skin of the toad. Our observations underscore the physiological differences existing in skins from different species, particularly regarding the relative importance of the glandular component of transport.

Effects of acid aerosol exposure on the surface properties of airway mucus.

It was hypothesized that the mucous layer lining the tracheas of rats and guinea pigs contains surfactant material capable of lowering the air/mucus surface tension, gamma, and that exposure to an irritant aerosol would raise the gamma. The gamma of the surface film was measured directly by a spreading droplet technique and indirectly by displacement of polymethyl methacrylate particles into the aqueous layer. The morphology of the mucous film was examined by electron microscopy after nonaqueous fixation. gamma was 33.3 +/- 0.70 (SE) mN/m and 32.3 +/- 0.68 (SE) mN/m for the normal rat and guinea pig trachea, respectively. Exposure for 4 h to aerosols of sulfuric acid (94.1 +/- 18.68 (SD) and 43.3 +/- 4.57 (SD) mg/m3) caused a several-fold increase in thickness of the mucous layer with exudation of protein-like material. The osmiophilic surfactant film at the air/mucus interface became irregularly thickened and multilayered. Despite these morphological changes gamma remained low, 33.2 +/- 0.43 (SE) mN/m and 32.6 +/- 0.60 (SE) mN/m for rats and guinea pigs, respectively, and displacement of particles into the subphase was not compromised. The results indicate that rodent tracheas are able to maintain a low surface tension in the presence of injury.

Electrophoretic patterns of human denatured tear proteins and glycoproteins from normal subjects and soft contact lens wearers.

The biological reactivity of soft contact lenses (SCL) is influenced by a variety of factors. The composition of the tear fluid contacting the SCL is one of the most important factors affecting biocompatibility. Maintenance of adequate tear functions seems to be an important way to control SCL deposits1. Two major mechanisms lead to an abnormal protein deposition on SCL: abnormal protein denaturation and instability of the mucous tear film.

Design of an apparatus incorporating a linear variable differential transformer for the measurement of type III bioadhesion to cervical tissue

The design and initial evaluation of a bioadhesive strength testing apparatus are reported. Measurement of adhesive strength is mediated via a linear variable differential transformer (LVDT). The apparatus, constructed from Perspex, consists of a movable platform with a pedestal to which the bioadhesive formulation is attached. Tissue is secured to a second, upper pedestal linked to the LVDT via a sensor. During the test procedure the platform is moved downwards at a predetermined rate controlled by the motor drive logic board. As movement occurs to the upper pedestal this can be detected by the output from the LVDT which is recorded potentiometrically. The force generated is measured by a previously calibrated spring contained within the sensor housing. Different calibrated springs can be used to increase OT decrease the sensitivity of the apparatus. Initial evaluation of the testing device was performed on a range of candidate bioadhesive film formulations. The effects on bioadhesion of varying the initial applied weight, mucus surface density, film thickness and film hydration were investigated. Excellent bioadhesion was achieved with the application of a dry sodium carboxymethylcellulose/ sodium carbopol film to cervical tissue with a surface mucus layer.

Mucociliary clearance following tracheal resection and end-to-end anastomosis.

Mucociliary clearance is an important cleaning system of the bronchial tree. The complex transport system reacts sensitively to medicinal stimuli and inhaled substances. A disturbance causes secretion retention which encourages the development of acute and chronic pulmonary diseases. It is not yet known in which way sectional resection of the central airway effects mucociliary clearance. A large number of the surgical failures are attributable to septic complications in the area of the anastomosis. In order to study the transportation process over the anastomosis, ten dogs underwent a tracheal resection with end-to-end anastomosis, and the mucociliary activity was recorded using a bronchoscopic video-technical method. Recommencement of mucous transport was observed on the third, and transport over the anastomosis from the sixth to tenth, postoperative days. The mucociliary clearance had completely recovered on the twenty-first day in the majority of dogs. Histological examination of the anastomoses nine months postoperatively showed a flat substitute epithelium without cilia-bearing cells in all dogs. This contrasts with the quick restitution of the transport function. In case of undamaged respiratory mucosa, a good adaptation of the resection margins suffices for the mucous film to slide over the anastomosis.

Toxicity of Crude Oil to the Survival of the Fresh Water Fish Puntius sophore (HAM.)

AbstractThe exposure of Puntius sophore to different concentrations of crude oil (200… 4000 ppm) revealed that 4000 ppm was acutely lethal to the fish and mortality did not occur at <500 ppm at 21±1 °C for up to 15 days. The increase in the opercular frequency during exposure to crude oil has been recorded almost parallel to toxicant concentrations. The objectionable odour of the crude oil and the formation of coagulated mucous film over the body and gills were the main factors causing mortality among the experimental fish.The 24, 48, 78 and 96‐h TL 50 values have been 3275, 1750, 1650 and 1450 ppm. The corresponding regression coefficients b were –1.8056, –1.5849, –1.6037 and –1.6497.

The interaction between benthic diatom films and sediment transport

Field and laboratory flume studies were used to examine the stabilization of intertidal sands by diatom mucus films. Films were delineated by analyzing colloid carbohydrates, chlorophyll, and by scanning electron microscopy on intact sediment samples. In the field, diatom films were patchy on a scale of centimetres, corresponding to the structure of sand ripples. Films were present on the sediment surface after calm weather and absent after storms. Extracellular polysaccharides accounted for a maximum of 20% of microalgal carbon. Erosion of intact cores in the flume showed that although films stabilized local areas of the bed, portions of the film were also washed away or buried. Stabilized areas of the bed were transposed to new ripple locations as the bedform moved ‘through’ the film. This observation explained the heterogeneous distribution of films with respect to ripple topography in the field. SEM showed diatom cells attached between sand grains with mucus strands, particularly in samples from the films. Mucus attachment due to protozoa, fungi, and other organisms was also observed. In the flume, diatom cells were washed away leaving mucus strands behind. A flume core with diatom films lost smaller amounts of chlorophyll than a core without films, under similar stages of erosion. At the highest flow, many grains were cleaned of mucus coatings; the grains appeared similar to those from sites of active transport (crests) in the field. We conclude that sediment stabilization by biofilms must be studied on a spatial scale of centimetres, and a temporal scale of days to weeks. The most important effect of microbial binding of sediments may be their role in the transfer of organic matter between the sediment and the water column.

Physical, chemical and physiological factors influencing entry of xenobiotics into the body via the pulmonary system

The respiratory system has an extremely large surface area covered with a thin aqueous film of either mucus or a lipoprotein surfactant-containing fluid. The large total surface area and minute separation between the air space and the blood make the lung an efficient organ for the rapid, systemic absorption of xenobiotics with a variety of physicochemical characteristics. Gases are absorbed throughout the entire respiratory system, the dominant driving force being diffusion. Highly water soluble gases are rapidly absorbed and may be cleared significantly through the surfaces of the upper respiratory tract before penetrating the deeper recesses of the lung. Inhaled particles are deposited in the respiratory system according to their size. Particles with aerodynamic diameters of 5 to 30 μm are similarly trapped in the nasopharyngeal region; those from 1 to 5 μm are largely deposited in the tracheal and bronchiolar regions, the major portion of particles smaller than 1 μm penetrate to the alveoli. Solute absorption studies indicate that the respiratory epithelium behaves like a lipoid–pore type membrane. Lipid soluble compounds are most rapidly absorbed at rates roughly related to their lipid/water partition coefficient at pH 7.4. Lipid insoluble substances are absorbed by nonsaturable diffusion with absorption rates related to the size of the molecules, i.e., the higher the molecular weight, the slower is the absorption. Organic ions can be absorbed by diffusion and by saturable, carrier-mediated processes. Pulmonary exposure to substances known to produce lung damage, i.e., ozone, silica, or acids, can alter carrier-mediated absorption of solutes and increase the passive absorption of lipid insoluble compounds alone or of both lipid soluble and lipid insoluble compounds. Age appears to be an important factor in absorption rate of lipid insoluble compounds. The lungs of 3- to 12-day-old rats absorb lipid insoluble compounds twice as rapidly as those of 18- to 27-day-old or adult animals. Age is unimportant, however, in the absorption of lipid soluble compounds. Species differences also exist for the absorption rates of lipid insoluble compounds but not for those of lipid soluble compounds. Mice will absorb lipid insoluble compounds 2 to 3 times more rapidly than rats, while rats absorb 1.3 to 3 times more rapidly than the rabbit.