Quality and freezing qualities of first and second ejaculates collected from endangered Gulf Coast Native rams

The Gulf Coast Native sheep, or Louisiana Native sheep, is an endangered previously feral domestic sheep population of European origin that has been under natural selection pressure for reproductive survival in their transplanted range while roaming in the southern Gulf Coast Region of the United States. This sheep population has an increased natural resistance to internal parasites, breeds year-around and has a greater percentage of live lambs as compared with other breeds of sheep raised in similar environments. To preserve the genetic diversity of this important feral sheep population, semen was collected by electro-ejaculation and subjected to cryopreservation for subsequent storage in a genome resource bank. Unrelated rams (n=5) were collected 3 days-a-week, allowing at least 2 days of rest between collections. Two ejaculates were obtained from each ram per collection day, with the second collection conducted 10min after the first ejaculation. Semen was processed using the standard Salamon cryopreservation procedure in a Tris-yolk-glycerol extender, frozen in 0.5ml plastic straws using liquid nitrogen (LN(2)) vapor and stored in LN(2). Each ejaculate was evaluated for volume, sperm concentration/ml (x10(9)/ml), number of spermatozoa/ejaculate (x10(9)), sperm progressive motility (%) for pre-cooled semen, cooled semen and semen after thawing. For the five rams, each semen variable for the first ejaculate was compared with that of the second ejaculate collected 10min later. The mean semen volume, sperm concentration and number of spermatozoa per ejaculate obtained from the first ejaculate were significantly greater (P< or =0.01) than those of the second ejaculate (comparisons being 1.62 and 1.06; 3.2 and 1.5; 5.4 and 1.8, respectively). Overall, the mean motility of pre-cooled (22 degrees Celsius), cooled (5 degrees Celsius) and frozen (-196 degrees Celsius) post-thawed spermatozoa was less (P< or =0.01) in the first ejaculate (71.5, 64.8 and 34.1%, respectively) compared with that of the second ejaculate (75, 72.4 and 44.1%, respectively). Conversely, no differences were detected in loss in the percent progressive motility of sperm from cooled sperm to post-thaw sperm from the first and second ejaculates. In summary, our findings suggest sperm collected during the second ejaculate 10min after the first ejaculate of rams survives thawing with a greater rate of progressive motility than that of the first ejaculate. The ability to collect two consecutive ejaculates in a short period by electro-ejaculation could be valuable for gamete resource banking and preserving genetic diversity of the Gulf Coast Native sheep.

Occupational radiation doses in interventional cardiology: a 15-year follow-up

This report describes occupational radiation doses of interventional cardiologists over 15 years and assesses action undertaken to optimize radiation protection. Personal dosimetry records of nine staff cardiologists and eight interventional cardiology fellows were recorded using personal dosemeters worn over and under their lead aprons. The hospital in which this study was conducted currently performs 5000 cardiology procedures per year. The hospital has improved its facilities since 1989, when it had two old-fashioned theatres, to include four rooms with more advanced and safer equipment. Intensive radiation protection training was also implemented since 1989. Initially, some individual dose values in the range of 100-300 mSv month(-1), which risked exceeding some regulatory dose limits, were measured over the lead apron. Several doses in the range of 5-11 mSv month(-1) were recorded under the apron (mean = 10.2 mSv year(-1)). During the last 5 years of the study, after the implementation of the radiation protection actions and a programme of patient-dose optimization, the mean dose under the apron was reduced to 1.2 mSv year(-1). Current mean occupational doses recorded under the lead apron are 14% of those recorded during 1989-1992 and those recorded over the apron are 14-fold less than those recorded during 1989-1992. The regulatory dose limits and the threshold for lens injuries might have been exceeded if radiation protection facilities had not been used systematically. The most effective actions involved in reducing the radiation risk were training in radiation protection, a programme of patient-dose reduction and the systematic use of radiation protection facilities, specifically ceiling-suspended protective screens.

Force-dependent chemical kinetics of disulfide bond reduction observed with single-molecule techniques

The mechanism by which mechanical force regulates the kinetics of a chemical reaction is unknown. Here, we use single-molecule force-clamp spectroscopy and protein engineering to study the effect of force on the kinetics of thiol/disulfide exchange. Reduction of disulfide bonds through the thiol/disulfide exchange chemical reaction is crucial in regulating protein function and is known to occur in mechanically stressed proteins. We apply a constant stretching force to single engineered disulfide bonds and measure their rate of reduction by DTT. Although the reduction rate is linearly dependent on the concentration of DTT, it is exponentially dependent on the applied force, increasing 10-fold over a 300-pN range. This result predicts that the disulfide bond lengthens by 0.34 A at the transition state of the thiol/disulfide exchange reaction. Our work at the single bond level directly demonstrates that thiol/disulfide exchange in proteins is a force-dependent chemical reaction. Our findings suggest that mechanical force plays a role in disulfide reduction in vivo, a property that has never been explored by traditional biochemistry. Furthermore, our work also indicates that the kinetics of any chemical reaction that results in bond lengthening will be force-dependent.

Forty years of 90Sr in situ migration: importance of soil characterization in modeling transport phenomena

In 1960 experiments were carried out on the transfer of (90)Sr between soil, grapes and wine. The experiments were conducted in situ on a piece of land limited by two control strips. The (90)Sr migration over the last 40 years was studied by performing radiological and physico-chemical characterizations of the soil on eight 70 cm deep cores. The vertical migration modeling of (90)Sr required the definition of a triple layer conceptual model integrating the rainwater infiltration at constant flux as the only external factor of influence. Afterwards the importance of a detailed soil characterization for modeling was discussed and satisfactory simulation of the (90)Sr vertical transport was obtained and showed a calculated migration rate of about 1.0 cm year(-1) in full agreement with the in situ measured values. The discussion was regarding some of the key parameters such as granulometry, organic matter content (in the Van Genuchten parameter determination), Kd and the efficient rainwater infiltration. Besides the experimental data, simplifying assumptions in modeling such as water-soil redistribution calculation and factual discontinuities in conceptual model were examined.

Influence of patient thickness and operation modes on occupational and patient radiation doses in interventional cardiology

Patient and staff dose values in an interventional cardiology laboratory for different operational modes and several patient thicknesses (from 16 to 28 cm, simulated using polymethylmethacrylate) are presented. When increasing patient thicknesses and depending on fluoroscopy and cine modes, occupational doses can increase >30 times the baseline level. Scatter dose rates at the cardiologist's position with no radiation protective tools ranged from 1 to 14 mSv h(-1) for fluoroscopy, and from 10 to 47 mSv h(-1) during cine acquisition. Patient entrance surface air kerma rates increased by nearly 3 and staff dose rates by up to 2.6 when fluoroscopy was moved from the low to the high mode, for a typical 20 cm thickness. The respective increase factors were 6 and 4.2 when patient thickness rose from 16 to 28 cm, and by 10 and 8.3, when comparing cine acquisition with the low fluoroscopy mode. The knowledge of typical dose rates for each X-ray system in use in catheterisation laboratories is essential in order to optimise protection of patients and staff.

Stepwise unfolding of ankyrin repeats in a single protein revealed by atomic force microscopy

Using single-molecule atomic force microscopy, we find that a protein consisting of six identical ankyrin repeat units flanked by N- and C-terminal modules (N6C) unfolds in a stepwise, unit-by-unit fashion under a mechanical force. Stretching a N6C molecule results in a sawtooth pattern fingerprint, with as many as six peaks separated by approximately 10 nm and an average unfolding force of 50 +/- 20 pN. Our results demonstrate that a stretching force can unfold multiple repeat units individually in a single protein molecule, despite extensive hydrophobic interactions between adjacent units.

Comparison of the protein-unfolding pathways between mitochondrial protein import and atomic-force microscopy measurements

Many newly synthesized proteins have to become unfolded during translocation across biological membranes. We have analyzed the effects of various stabilization/destabilization mutations in the Ig-like module of the muscle protein titin upon its import from the N terminus or C terminus into mitochondria. The effects of mutations on the import of the titin module from the C terminus correlate well with those on forced mechanical unfolding in atomic-force microscopy (AFM) measurements. On the other hand, as long as turnover of the mitochondrial Hsp70 system is not rate-limiting for the import, import of the titin module from the N terminus is sensitive to mutations in the N-terminal region but not the ones in the C-terminal region that affect resistance to global unfolding in AFM experiments. We propose that the mitochondrial-import system can catalyze precursor-unfolding by reducing the stability of unfolding intermediates.

Effects of Dietary Cation-Anion Difference on Intake, Milk Yield, and Blood Components of the Early Lactation Cow

Early lactation Holsteins cows (15 primiparous and 18 multiparous) were offered rations with dietary cation-anion difference, calculated as mEq (Na + K - Cl - S)/100 g of feed dry matter (DCAD:S), of 20, 35, or 50 mEq from d 0 (calving) to 42 d postpartum (August 20, 2000 to January 9, 2001) to determine the effects of increasing DCAD:S on dry matter intake (DMI), milk yield, and blood metabolites. For DCAD:S of 20, 35, and 50, DMI was 3.30, 3.38, 2.96 kg/100 kg of body weight (BW); milk yield was 25.5, 24.2, and 22.4 kg/d, respectively. No differences were observed for concentration or yield of milk fat or milk protein. Serum Ca, P, Mg, Na, K, Cl, cation-anion difference, insulin, and glucose did not differ with DCAD. Serum HCO3- was 26.07, 25.88, and 27.64 mEq/L for 20, 35, and 50 DCAD:S. Serum Ca, Mg, Na, and K concentrations were greater for primiparous cows (9.52 mg/dL, 2.35 mg/dL, 140.03 mEq/L, 4.66 mEq/L, respectively) than for multiparous cows (9.27 mg/dL, 2.12 mg/dL, 137.63 mEq/L, 4.46 mEq/ L, respectively). A DCAD:S between 23 and 33 mEq/100 g of dry matter (DM) appears to be adequate during cool weather for the milk yield that occurred in the present study based on DMI (kg/100 kg of BW), whereas DCAD:S of 50 mEq/100 g of DM may be excessive and could be too alkaline or unpalatable, resulting in decreased DMI (kg/100 kg of BW).

Ligand binding modulates the mechanical stability of dihydrofolate reductase

We use single-molecule force spectroscopy to demonstrate that the mechanical stability of the enzyme dihydrofolate reductase (DHFR) is modulated by ligand binding. In the absence of bound ligands, DHFR extends at very low forces, averaging 27 pN, without any characteristic mechanical fingerprint. By contrast, in the presence of micromolar concentrations of the ligands methotrexate, nicotinamide adenine dihydrogen phosphate, or dihydrofolate, much higher forces are required (82 +/- 18 pN, 98 +/- 15 pN, and 83 +/- 16 pN, respectively) and a characteristic fingerprint is observed in the force-extension curves. The increased mechanical stability triggered by these ligands is not additive. Our results explain the large reduction in the degradation rate of DHFR, in the presence of its ligands. Our observations support the view that the rate-limiting step in protein degradation by adenosine triphosphate-dependent proteases is the mechanical unfolding of the target protein.

L-Carnitine Supplementation does not Promote Weight Loss in Ovariectomized Rats Despite Endurance Exercise

In this five-week study, we tested the hypotheses that free access to a maintenance diet supplemented with L-carnitine (L-C) would reduce body fat in adult, sedentary, ovariectomized (OVX) rats, and that there would be an additive effect of L-C on weight reduction in swim-trained animals. As expected, serum carnitine was higher in rats fed the L-C diet, and the OVX-induced weight gain and abdominal fat were counteracted by swimming. L-C supplementation did not reduce the weight gain or abdominal fat in these adult female rats. Moreover, though not reaching statistical significance, rats that were fed L-C demonstrated a tendency for greater weight gain than their basal-fed counterparts despite no difference in energy intake. If the results of this study on ovariectomized rats can be translated to postmenopausal women, moderate intensity exercise may be recommended, but L-C supplementation, with no energy restriction, may be contraindicated as a weight loss method in this cohort.

The elasticity of individual titin PEVK exons measured by single molecule atomic force microscopy

The I-band region of the giant muscle protein titin contains a large domain enriched for the amino acids proline, glutamate, valine, and lysine and is denoted the PEVK domain. The PEVK domain of titin encodes a random coil shown to be an important factor in the passive elasticity of titin. Muscle-specific splicing of 116 PEVK exons encodes this domain. It has been proposed that proline contents determine the elasticity of the PEVK polypeptide, where the individual exons code for "flexibility cassettes." To test this hypothesis, we have measured the elasticity of three distinct polypeptides encoded by individual PEVK exons (161, 120 and 184) that varied greatly in their proline contents (7, 14, and 37% respectively) and total PEVK contents (55, 70, and 87%). We used single molecule atomic force microscopy techniques to measure the persistence length, p, of the engineered PEVK proteins. Surprisingly, all three exons 161, 120, and 184 coded for proteins with similar values of persistence length, p = 0.92 +/- 0.38, 0.89 +/- 0.42, and 0.98 +/- 0.4 nm, respectively. We conclude that the PEVK exons encode polypeptides of similar elastic properties, unrelated to their total PEVK contents. Hence, alternative splicing solely adjusts the length of the PEVK domain of titin.

Patient dosimetry and image quality in digital radiology from online audit of the X-ray system

The present work describes an online patient dosimetry and an image quality system in digital radiology. For the patient dosimetry audit, current mean values of entrance surface dose (ESD) were compared with local and national reference values (RVs) for the specific examination type evaluated. Mean values exceeding the RV trigger an alarm signal and then an evaluation of the technical parameters, operational practice and image quality was begun, using data available in the DICOM header to derive any abnormal settings or performance to obtain the image. The X-ray tube output for different kVp values is measured periodically, to allow for the automatic calculation of ESD. The system allows also for image audit, linking the dose imparted, the image quality and the alarm condition, if produced. Results and the benefits derived from this online quality control are discussed here.

Mechanical Unfolding Intermediates Observed by Single-molecule Force Spectroscopy in a Fibronectin Type III Module

Domain 10 of type III fibronectin (10FNIII) is known to play a pivotal role in the mechanical interactions between cell surface integrins and the extracellular matrix. Recent molecular dynamics simulations have predicted that 10FNIII, when exposed to a stretching force, unfolds along two pathways, each with a distinct, mechanically stable intermediate. Here, we use single-molecule force spectroscopy combined with protein engineering to test these predictions by probing the mechanical unfolding pathway of 10FNIII. Stretching single polyproteins containing the 10FNIII module resulted in sawtooth patterns where 10FNIII was seen unfolding in two consecutive steps. The native state unfolded at 100(+/-20) pN, elongating (10)FNIII by 12(+/-2) nm and reaching a clearly marked intermediate that unfolded at 50(+/-20) pN. Unfolding of the intermediate completed the elongation of the molecule by extending another 19(+/-2) nm. Site-directed mutagenesis of residues in the A and B beta-strands (E9P and L19P) resulted in sawtooth patterns with all-or-none unfolding events that elongated the molecule by 19(+/-2) nm. In contrast, mutating residues in the G beta-strand gave results that were dependent on amino acid position. The mutation I88P in the middle of the G beta-strand resulted in native like unfolding sawtooth patterns showing an intact intermediate state. The mutation Y92P, which is near the end of G beta-strand, produced sawtooth patterns with all-or-none unfolding events that lengthened the molecule by 17(+/-2) nm. These results are consistent with the view that 10FNIII can unfold in two different ways. Along one pathway, the detachment of the A and B beta-strands from the body of the folded module constitute the first unfolding event, followed by the unfolding of the remaining beta-sandwich structure. Along the second pathway, the detachment of the G beta-strands is involved in the first unfolding event. These results are in excellent agreement with the sequence of events predicted by molecular dynamics simulations of the 10FNIII module.

Evaluation of risk of deterministic effects in fluoroscopically guided procedures

A methodology for the evaluation of skin dose distribution and possible skin injuries on patients undergoing interventional procedures has been developed as part of the European DIMOND programme. Relevant dosimetric data from the procedures are recorded and other specific measurements for skin dose evaluation (slow films for therapy, radiochromic films, thermoluminescence dosemeters and optically stimulated luminescence dosemeters) have been carried out. For non-cardiac and for some cardiac procedures, dose-area product values of 200 and 300 Gy cm2 were proposed, respectively, as a trigger level for further detailed skin dose investigation and possible clinical follow-up. Results from a survey of 191 selected complex procedures are reported. Out of all the patients included in the trial, 16% received skin doses > or =1.5 Gy. No skin injuries were found in any of the patients followed.

Beta-sarcoglycanopathy (LGMD 2E) in a Spanish family

Out of 10 autosomal recessive limb-girdle muscular dystrophies reported, 4 are caused by mutations in the genes encoding for sarcoglycans (alpha-, beta-, gamma- and delta-SG). Beta-sarcoglycanopathy (limb-girdle muscular dystrophy 2E) is a genetically heterogeneous disorder which usually presents a severe progressive clinical course. A complete immunohistochemical evaluation of the sarcoglycan complex should be carried out to direct the mutation analysis approach. The present report concerns a Spanish family with a genetically confirmed beta-sarcoglycanopathy. The patient, a 16-year-old female, offspring of a consanguineous marriage, developed a severe limb-girdle muscular dystrophy with a Duchenne-like phenotype. Muscle biopsy showed dystrophic changes and complete absence of the four sarcoglycans. Genetic analysis demonstrated homozygosis for the M100K missense mutation in exon 3, encoding for the proximal extracellular domain. The parents and one sister were found to be carriers. Missense mutations affecting this domain result in the instability of the entire sarcoglycan complex and lead to severe phenotypes as seen in non-sense mutations.

Simultaneous atomic force microscope and fluorescence measurements of protein unfolding using a calibrated evanescent wave

Fluorescence techniques for monitoring single-molecule dynamics in the vertical dimension currently do not exist. Here we use an atomic force microscope to calibrate the distance-dependent intensity decay of an evanescent wave. The measured evanescent wave transfer function was then used to convert the vertical motions of a fluorescent particle into displacement (SD = < 1 nm). We demonstrate the use of the calibrated evanescent wave to resolve the 20.1 +/- 0.5-nm step increases in the length of the small protein ubiquitin during forced unfolding. The experiments that we report here make an important contribution to fluorescence microscopy by demonstrating the unambiguous optical tracking of a single molecule with a resolution comparable to that of an atomic force microscope.

The force-driven conformations of heparin studied with single molecule force microscopy

Using single molecule force spectroscopy we examine the response of heparin chains to mechanical stretching. We find that at forces below 200 pN heparin behaves as a simple entropic spring. At approximately 200 pN heparin displays a large enthalpic elasticity, which is evident as a pronounced plateau in the force-extension relationship. We determine that this enthalpic elasticity is produced by sugar rings of heparin flipping to more energetic and more extended conformations. We estimate that in vivo, the forces which stretch heparin are comparable to the forces that trigger conformational transitions in our single molecule atomic force microscopy measurements. We hypothesize that these conformational transitions have biological significance in that they provide a mechanism to finely regulate the affinity of various ligands toward heparin, for example, in secretory granules undergoing exocytosis and during the mechanical interactions between cells and the extracellular matrix.

Effect of nonwaxy and waxy sorghum on growth, carcass traits, and glucose and insulin kinetics of growing-finishing barrows and gilts12

Two experiments were conducted to determine the effect of nonwaxy (amylose and amylopectin starch) or waxy (amylopectin starch) sorghum on growth, carcass traits, and glucose and insulin kinetics of pigs. In Exp. 1 (95-d), 60 crossbred barrows or gilts (initial and final BW of 24 and 104 kg) were allotted to three treatments with five replications of four pigs per replicate pen in a randomized complete block design. The dietary treatments for Exp. 1 were 1) corn-soybean meal (C-SBM) diet, 2) sorghum-SBM (red pericarp, non-waxy), and 3) sorghum-SBM (red pericarp, waxy). In Exp. 2, 28 crossbred barrows (initial and final BW of 24 and 64 kg) were allotted to two treatments with three replications of four or five pigs per replicate pen in a randomized complete block design. Growth data were collected for 49 d, and then 20 barrows were fitted with jugular catheters, and then a glucose tolerance test (500 mg glucose/kg BW), an insulin challenge test (0.1 IU of porcine insulin/kg BW), and a feeding challenge were conducted. The dietary treatments for Exp. 2 were 1) sorghum-SBM (white pericarp, nonwaxy) and 2) sorghum-SBM (white pericarp, waxy). In Exp. 1, ADG (P = 0.10) and ADFI (as-fed basis; P = 0.02) were increased (P = 0.10) and gain:feed was decreased (P = 0.04) in pigs fed the sorghum-SBM diets relative to those fed the C-SBM diet. These responses may have resulted from the lower energy content of sorghum relative to corn. Plasma NEFA concentration (collected after a 16-h fast on d 77) was decreased (P = 0.08) in pigs fed the waxy sorghum-SBM diet relative to those fed the nonwaxy sorghum-SBM diet. Kilograms of carcass fat was decreased (P = 0.07) in pigs fed the waxy sorghum-SBM diet relative to those fed the nonwaxy sorghum-SBM diet. In Exp. 2, there was no effect (P = 0.57 to 0.93) of sorghum starch type on growth performance by pigs. During the glucose tolerance and insulin challenge tests, there were no effects (P = 0.16 to 0.98) of diet on glucose or insulin kinetics. During the feeding challenge, glucose (P = 0.02) and plasma urea N (P = 0.06) area under the response curves from 0 to 90 min were decreased in pigs fed the waxy sorghum-SBM diet. Feeding waxy sorghum had minimal effects on growth and carcass traits relative to pigs fed corn or nonwaxy sorghum. Waxy sorghum vs. nonwaxy sorghum had no effect on glucose or insulin kinetics in pigs.

The unfolding kinetics of ubiquitin captured with single-molecule force-clamp techniques

We use single-molecule force spectroscopy to study the kinetics of unfolding of the small protein ubiquitin. Upon a step increase in the stretching force, a ubiquitin polyprotein extends in discrete steps of 20.3 +/- 0.9 nm marking each unfolding event. An average of the time course of these unfolding events was well described by a single exponential, which is a necessary condition for a memoryless Markovian process. Similar ensemble averages done at different forces showed that the unfolding rate was exponentially dependent on the stretching force. Stretching a ubiquitin polyprotein with a force that increased at a constant rate (force-ramp) directly measured the distribution of unfolding forces. This distribution was accurately reproduced by the simple kinetics of an all-or-none unfolding process. Our force-clamp experiments directly demonstrate that an ensemble average of ubiquitin unfolding events is well described by a two-state Markovian process that obeys the Arrhenius equation. However, at the single-molecule level, deviant behavior that is not well represented in the ensemble average is readily observed. Our experiments make an important addition to protein spectroscopy by demonstrating an unambiguous method of analysis of the kinetics of protein unfolding by a stretching force.

Force-Clamp Spectroscopy Monitors the Folding Trajectory of a Single Protein

We used force-clamp atomic force microscopy to measure the end-to-end length of the small protein ubiquitin during its folding reaction at the single-molecule level. Ubiquitin was first unfolded and extended at a high force, then the stretching force was quenched and protein folding was observed. The folding trajectories were continuous and marked by several distinct stages. The time taken to fold was dependent on the contour length of the unfolded protein and the stretching force applied during folding. The folding collapse was marked by large fluctuations in the end-to-end length of the protein, but these fluctuations vanished upon the final folding contraction. These direct observations of the complete folding trajectory of a protein provide a benchmark to determine the physical basis of the folding reaction.

Flow paths of plant tissue residues and digesta through gastrointestinal segments in Spanish goats and methodological considerations1

A sequence of eight twice-daily meals, each marked with different rare earth elements, was fed to 24 Spanish goats (BW = 20.6 +/- 1.94 kg) to produce meal-based profiles of rare earth markers within segments of the gastrointestinal digesta on subsequent slaughter. Accumulative mean residence time and time delay of rare earths and segmental and accumulative mean residence times of indigestible NDF (IDF) were estimated for each sampled segment. Diets consisted of ad libitum access to bermudagrass hay with a limit feeding of one of four supplements: 1) minerals (basal, B); 2) B + energy (E); 3) B + CP (CP); or 4) B + E + CP for 84 d. Mean daily intake (g/kg of BW) during the 5 d before slaughter differed (P < 0.05) via diet for DM but not for IDF (8.0 +/- 0.35 g/kg of BW). Larger estimates of cumulative mean residence time for IDF vs. rare earths were suggested to be the consequence of a meal-induced bias in the single measurement of IDF pool size by anatomical site. The rare earth compartment method was considered more reliable than the IDF pool dilution method because it yielded flow estimates based on the flux of eight meal-dosed rare earth markers over 4 d and was independent of anatomical definitions of pool size. Statistically indistinguishable estimates for gastrointestinal mean residence times for IDF and rare earths conform to assumed indelibility for the specifically applied rare earths and indigestibility of IDF. The potentially digestible NDF (PDF):IDF ratio of dietary fragments (0.8) progressively decreased in the following order: caudodorsal reticulorumen (0.390) > crainodorsal reticulorumen (0.357) approximately reticulum (0.354) > mid-dorsal reticulorumen (0.291) approximately ventral reticulorumen (0.286), to that within the omasal folds and in the abomasum (0.259). Such a gradient of progressively aging mixture of plant tissue fragments is consistent with age-dependent flow paths established in the reticulorumen and flowing to the omasum and abomasum. Such heterogeneity of fragment ages within the reticulorumen is also indicated by the superior fit of marker dose site double dagger marker sampling site model assumptions. Additionally, cyclic meal- and rumination-induced variations in escape rate occur. Estimates of mean escape rates over days, needed for the practice of ruminant nutrition, must consider the complex interactions among plant tissues and the dynamics of their ruminal digestion of PDF.